- Review
- Open access
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Interaction between gut microbiota and sex hormones and their relation to sexual dimorphism in metabolic diseases
Biology of Sex Differences volume 14, Article number: 4 (2023)
Abstract
Metabolic diseases, such as obesity, metabolic syndrome (MetS) and type 2 diabetes (T2D), are now a widespread pandemic in the developed world. These pathologies show sex differences in their development and prevalence, and sex steroids, mainly estrogen and testosterone, are thought to play a prominent role in this sexual dimorphism. The influence of sex hormones on these pathologies is not only reflected in differences between men and women, but also between women themselves, depending on the hormonal changes associated with the menopause. The observed sex differences in gut microbiota composition have led to multiple studies highlighting the interaction between steroid hormones and the gut microbiota and its influence on metabolic diseases, ultimately pointing to a new therapy for these diseases based on the manipulation of the gut microbiota. This review aims to shed light on the role of sexual hormones in sex differences in the development and prevalence of metabolic diseases, focusing on obesity, MetS and T2D. We focus also the interaction between sex hormones and the gut microbiota, and in particular the role of microbiota in aspects such as gut barrier integrity, inflammatory status, and the gut–brain axis, given the relevance of these factors in the development of metabolic diseases.
Highlights
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Accumulating evidences show that the alterations in the gut microbiota associated to metabolic diseases are different in men and women, and these differences may influence sex differences in the development and prevalence of metabolic diseases.
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The key aspects involved in these pathologies include lipopolysaccharide-inflammation, gut barrier integrity, gut microbiota-derived metabolites and gut–brain axis.
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Sex steroids, mainly estrogen and testosterone, are thought to play a prominent role in the sexual dimorphism of gut microbiota.
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The influence of sex hormones is reflected both in men and women, and among women themselves due to hormonal changes associated with the menopause.
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The interaction between sex steroids and the gut microbiota plays a prominent role in the development of metabolic diseases.
Introduction
The increasing incidence of metabolic diseases, and in particular obesity, MetS, and T2D, in the world population, has made these pathologies a serious health, social, and economic problem [1,2,3]. Interestingly, these pathologies show a marked sexual dimorphism in their development and prevalence, with a clear influence of sex hormones [4]. The overall prevalence of obesity is higher in women than in men, as women are more likely to gain abdominal fat with age. In fact, the prevalence of visceral obesity associated with MetS is currently much higher in women in many regions of the world. Moreover, the prevalence of T2D is reversed by life stage, with more men having diabetes before puberty and more women having diabetes after menopause. It is interesting, in this regard, to observe the pattern of body fat distribution, given its key role in metabolic diseases. Two patterns of fat distribution have been described, an abdominal (visceral) pattern, typical of men and postmenopausal women, and a peripheral (subcutaneous) pattern, typical of premenopausal women [5, 6]. Both patterns, which have a genetic basis and are regulated by sex steroid hormones [7], are related to the development of metabolic diseases, with central fat distribution showing a pathological profile [8] versus a protective profile of peripheral fat [9].
The influence of sex hormones on metabolic diseases is supported by conditions in which their normal level is altered. Both transgender men and women show fat redistribution after sex steroid treatment [10]. The hormonal changes of menopause also lead to fat redistribution [11], as well as an increased risk of T2D [12], while hormone therapy with estrogens and progestogens in postmenopausal women reduces its incidence [13]. Androgen deprivation therapy in men with prostate cancer results in increased fat mass [14], higher prevalence of MetS [15] and elevated risk of T2D [16], while testosterone treatment decreases visceral fat in nonobese aging men with symptoms of androgen deficiency and low-normal serum testosterone levels [17]. In addition, testosterone replacement improves insulin sensitivity and glycemic control, patients with hypogonadism suffering T2D and MetS, partially through reducing central obesity [18]. Polycystic ovary syndrome (PCOS) is a multifactorial disorder with various genetic, endocrine and environmental abnormalities [19]. Considerable genetic heterogeneity underlies PCOS, as several genes’ variants have been linked to this disorder. Moreover, women with PCOS present hyperandrogenism which has been associated to increased central adiposity [20] and increased risk of MetS [21]. Oophorectomy-induced estrogen depletion in postmenopausal women increases the risk of T2D [22].
In recent years, a sexual dimorphism in the composition of the gut microbiota has also been highlighted [23] in which sex hormones seem to play a prominent role [24]. In fact, a growing body of scientific evidence indicates that the interaction between the gut microbiota and its host is key to the development of metabolic diseases [25]. The alteration or protection of the intestinal mucosa by the gut microbiota is a key factor in the maintenance of the so-called gut barrier [26], which limits the access of microorganisms to the bloodstream and thus influences the inflammatory state described in processes such as obesity and MetS [27]. However, the action of the microbiota is not restricted to the gut, as its action extends to the central nervous system to influence food intake, via the gut–brain axis [28], and even to the liver to regulate nutrient metabolism, via the gut–liver axis [29]. This new scientific knowledge has made it possible to approach the treatment of metabolic diseases from a different angle, and offers a new therapy based on the modification of the microbiota through the use of probiotics [30].
Methods
PubMed databases were used to search for reviews and research studies published in English using the search terms: sex steroids (testosterone and estrogen) and microbiota, sex steroids (testosterone and estrogen) and obesity, sex steroids (testosterone and estrogen) and metabolic syndrome, sex steroids (testosterone and estrogen) and diabetes, microbiota and gut barrier, microbiota and inflammation, microbiota and short chain fatty acids, microbiota and bile acids, microbiota and phytoestrogens, gut–brain axis. Publication dates were not limited in order to fully review the available literature. Following this search, an initial selection of articles was made according to their titles and abstracts. Subsequently, a second selection was made based on a critical reading of the articles.
Interaction between gut microbiota and sex hormones
Evidence for interaction between gut microbiota and sex hormones
The composition of the gut microbiota has been found to be sex-dependent [23] and may in turn influence sex hormone levels, influencing, for example, non-ovarian estrogen levels in men and postmenopausal women via the enterohepatic circulation (Fig. 1) [31].
Studies in rodents
Studies in mice have shown a change in estradiol and testosterone levels following microbial colonization [32, 33]. Regarding hormonal changes associated with puberty, no differences in microbial alpha-diversity have been observed in prepubertal mice, while the microbiota of post-pubertal mice shows a sex bias [34]. In this latter study, after reducing androgen levels by castration, the microbiota of castrated males showed more similarities with the microbiota of females than with the microbiota of gonadal-intact males.
Furthermore, gonadectomy has demonstrated the influence of sex hormones on the observed sexual bias in gut microbiota composition [35]. This study showed that testosterone treatment prevented the observed changes in gut microbiota composition in gonadectomized males. Along the same lines, we have described that gonadal hormone depletion in rats by gonadectomy, alone or combined with postnatal overfeeding, modified the gut microbiota towards a more deleterious profile, with a greater effect in females than in males, and mainly in the presence of an overfeeding condition [36]. In this study, we have identified several gut microRNAs (miRNAs) as potential mediators of the impact of changes in the gut microbiota on host physiology. We have also observed that exposure of female rats to high doses of androgens in early postnatal life not only persistently altered the sex steroid profile and several anthropometric and physiological parameters when subjected to obesogenic manipulations, but also impacted on the gut microbiota, with higher abundance of Bacteroidetes and lower Firmicutes in early adulthood, which disappeared after overfeeding in adulthood [37]. These changes in the microbiota were also related to the intestinal expression of several miRNAs. In view of the results presented here, it seems plausible that sex hormones may contribute to defining sex-dependent differences in the gut microbiota and that the interaction between microbiota and the host may be mediated by intestinal-derived miRNAs.
Human studies
Men and women with elevated serum testosterone and estradiol levels, respectively, harbored a more diverse gut microbiota, with a number of bacterial genera correlated with testosterone (Acinetobacter, Dorea, Ruminococcus and Megamonas) and estradiol (Slackia and Butyricimonas) levels [24]. In humans, it has been shown that the gut microbiota is influenced by changes in estrogen and androgen levels due to factors such as pregnancy, puberty, menopause, or PCOS. In this regard, women with PCOS (hyperandrogenic) show a markedly altered microbiota [38,39,40], as it changes from first to third trimester of pregnancy, with an overall increase in Proteobacteria and Actinobacteria and reduced richness [41].
Sex differences in gut microbiota composition increase at puberty, with girls' gut microbiota becoming more similar to that of adults with pubertal progression. These results might also suggest that gut microbiota may affect the timing of puberty, possibly by regulating host sex hormone levels [42,43,44].
In men and postmenopausal women, urinary estrogen levels have shown a strong association with gut microbiota richness and alpha-diversity, whereas premenopausal female estrogen levels, highly variable when collected during menstrual cycles, did not show this association [31, 45]. Recently, it has been reported that the gut microbiota of postmenopausal women is more similar to that of men than that of premenopausal women, with no significant differences actually observed between postmenopausal women and men of equivalent age [46, 47]. This study also showed an association between gonadal steroids and differences in microbiota, with steroid biosynthesis and degradation pathways being enriched in premenopausal women and significantly associated with plasma testosterone levels. In addition, the microbiota allowed prediction of circulating testosterone levels in both humans and (antibiotic-treated) male mice after transfer of human fecal material.
We have previously described in several studies a series of differences in the composition of the microbiota according to sex. In this regard, when studying the patterns of gut microbiota associated with obesity in men and postmenopausal women, according to sex and body mass index (BMI), we have observed a lower abundance of the genera Bacteroides (for a BMI over 33) and Bilophila in men, as well as a greater presence of the genera Veillonella and Methanobrevibacter [48]. In another study on differences in gut microbiota associated with sex and hormonal status conducted in premenopausal and postmenopausal women, together with their respective groups of control men, a higher proportion of Firmicutes/Bacteroidetes and the genera Lachnospira and Roseburia was observed in postmenopausal women, whose levels were similar to those of men. In contrast, the genera Prevotella, Parabacteroides and Bilophila showed lower levels in premenopausal women, whose levels were similar to those of men [47]. Another study on sex differences in the gut microbiota of patients with MetS showed a higher abundance of the genera Collinsella, Alistipes, Anaerotruncus and Phascolarctobacterium, as well as a lower abundance of the genera Faecalibacterium and Prevotella in women with MetS than in men with MetS [49]. Taken together, these results suggest that the sexual dimorphism observed in the incidence of metabolic diseases and their comorbidities might be, at least partially, related to differences in the composition of the gut microbiota between sexes and among women with different hormonal status.
Mechanism of interaction between gut microbiota and sex hormones
Bile acids
It has recently been suggested that part of the sex bias of the gut microbiota may depend on bile acids, as the bile acid pool is larger in males than in females [50, 51]. After being synthesized in the liver from cholesterol, they are metabolized by the gut microbiota into secondary bile acids, which in turn can modify the structure of the microbiota and lead to various pathologies [52,53,54]. Thus, gut microbiota regulates the secondary metabolism of bile acids and inhibits their synthesis in the liver by regulating the expression of fibroblast growth factor 15 (FGF15) in the ileum and cholesterol 7α-hydroxylase (CYP7A1) in the liver through mechanisms dependent on the farnesoid X receptor (FXR) [55, 56], a nuclear receptor for bile acids. FGF15 represses the expression of CYP7A1 in the liver [57], the enzyme that catalyzes and regulates the first step of bile acid synthesis [58]. Furthermore, it has been observed that a reduction of bile acids leads to bacterial proliferation and that FXR inhibits bacterial overgrowth [59].
Several studies have confirmed the relationship between bile acids, sex hormones and the composition of the gut microbiota. In this way, administration of cholic acid to rats induced changes in the microbiota similar to those induced by high-fat diets, increasing levels of Firmicutes at the expense of Bacteroidetes [60]. In addition, transplantation of fecal microbiota (from a lean donor) produced changes in the gut microbiome and bile acid profiles similar to those of the lean donor [61], while gonadectomy in mice altered the bile acid pattern [35], as in germ-free (GF) and antibiotic-treated rats [62]. Since testosterone is synthesized from bile acids [63], and as described above, bile acid levels are altered by the microbiota, it is tenable that the microbiota might indirectly influence the level of testosterone.
Enzymatic action
The commensal microbial community can affect sex hormone levels through the activity of its enzymes. In this way, the term “strobolome” has been coined to define as the set of genes in the gut microbiota capable of activating estrogens from their inactive glucuronides, notably thanks to the enzymes β-glucuronidases, which deconjugate estrogens into their active forms [64,65,66]. These active estrogens pass into the bloodstream and act on estrogen receptors alpha (ERα) and beta (ERβ) [67]. Similarly, a recent study has concluded that the gut microbiota is involved in the metabolism and intestinal deglucuronidation of dihydrotestosterone (DHT) and testosterone, resulting in extremely high levels of the most potent androgen, DHT [68].
Another possible mechanism of action of the gut microbiota in sex bias could be found in its hydroxysteroid dehydrogenase (HSD) enzymes, which are involved in the metabolism of steroid hormones and control the binding of steroids to their nuclear receptors, making them act as activators or inhibitors [69, 70].
Phytoestrogens
In addition to the three main forms of estrogens (cholesterol-derived steroid hormones), estradiol (E2, predominant in non-pregnant women before menopause), estrone (E1, predominant after menopause) and estriol (E3, predominant during pregnancy), there are plant compounds, called phytoestrogens, which show structural and functional similarities to estrogens [71]. Phytoestrogens include isoflavones, such as genistein and daidzein, which are mainly abundant in soya and are activated after being metabolized by the gut microbiota [72]. In this sense, the intestinal microbiota allows O-desmethylangolensin (ODMA) and equol to be obtained from daidzein, both of which have estrogenic activity [73,74,75,76].
Similar to estrogens, phytoestrogens cause physiological effects by affecting cell signaling, as they can induce or inhibit estrogen action by activating or inhibiting ERα or ERβ, and may trigger also epigenetic effects and intracellular signaling cascades [77,78,79]. Related to this, several human studies suggest that phytoestrogens can ameliorate various pathologies by modulating the endocrine system, including menopausal symptoms [72], and can reverse symptoms of metabolic endotoxemia [80]. In this regard, the phytoestrogen metabolite, equol, has been associated with a reduced risk of female hormone-related diseases by promoting urinary excretion of estrogen and modifying its blood levels in women [81, 82], while non-production of ODMA has been associated with obesity [73, 74].
Phytoestrogens are consumed in the diet, as they appear in fruits, veggies, legumes, and some grains. Indeed, dietary composition has an acute effect on the gut microbiota ecosystem [83]. A plant-based diet appears to be beneficial for human health by promoting the development of more diverse and stable microbial systems [84]. From the three basics bacterial enterotypes [85], the one rich in Prevotella is associated to those individuals who consume less animal products and more plant-based foods [84]. In contrast, the enterotype rich in Bacteroides has been positively correlated with consumption of diets rich in animal protein and saturated fat. This is likely due to their ability to tolerate bile, which is common in the intestinal environments of those who consume animal products [86, 87]. Finally, the third enterotype is the one rich in Ruminococcus, whose biological significance is less evident [88].
Key aspects of gut microbiota action in metabolic diseases
Since the discovery in 2005 of an increased Firmicutes/Bacteroidetes ratio in obese compared to lean mice [89], many studies have addressed the role of the gut microbiota in obesity and associated pathologies, such as MetS and T2D [90]. The putative mechanisms whereby the microbiota contribute to these processes lies especially in the actions of lipopolysaccharide (LPS), the maintenance of the intestinal barrier, the by-products of its metabolism, and its intervention in the gut–brain axis (Fig. 2).
Inflammation
Gut microbiota has been linked to diseases characterized by chronic low-level inflammation, such as obesity and T2D. Specifically, the inflammatory state is mainly influenced by LPS, the intestinal barrier, and several metabolites derived from bacterial metabolism.
Lipopolysaccharide
The LPS, an endotoxin from the outer membrane of Gram-negative bacteria, is involved in chronic low-grade inflammation by inducing the secretion of potentially diabetogenic pro-inflammatory cytokines and key components of the innate immune response in adipose tissue [91]. In addition, a high concentration of LPS in the bloodstream, defined as metabolic endotoxemia, has been linked to insulin resistance, adipocyte hyperplasia and reduced pancreatic beta-cell function [92]. Related to this, the genus Prevotella, which is in principle beneficial by producing short-chain fatty acids (SCFAs) [93], using a wide variety of polysaccharides [94], has also been described as detrimental by inducing tumor necrosis factor alpha (TNF-α) production by a LPS-induced mechanism [95] and producing phosphorylated dihydroceramide lipids, which in turn lead to the secretion of pro-inflammatory cytokines, as IL-6 [96].
The link between elevated levels of circulating LPS and metabolic diseases has been proven by chronic infusion of LPS in mice, which resulted in increased fasting blood glucose, hyper-insulinemia, and insulin resistance, as well as increased macrophage infiltration in adipose tissue [97]. In addition, the above study showed that ablation of the LPS co-receptor, CD14, reversed LPS-induced metabolic diseases.
Two non-exclusive mechanisms of LPS absorption from the gut into the circulatory system have been proposed [98]: (1) chylomicron-facilitated transport (lipoproteins that transport dietary lipids to peripheral tissues), supported by the fact that LPS secretion increases when cells are stimulated with fatty acids that promote chylomicron formation, while inhibition of chylomicron formation blocks LPS uptake; and (2) extracellular transport through the epithelial tight junctions, supported by the fact that reducing intestinal permeability and improving tight junction integrity reduces plasma LPS levels, circulating inflammatory cytokine concentrations, and hepatic inflammation.
Gut barrier integrity
The small intestine has an unattached mucus layer, while the colon has two layers, the inner, attached layer, and the outer, less dense and unattached layer [99]. The mucus layer of the intestinal epithelium, which is composed of glycans, or mucins (highly glycosylated proteins secreted by goblet cells, most notably the MUC2 protein), and forms the so-called intestinal barrier, represents a barrier to intestinal bacteria, providing protection against inflammation [27] involved in the pathogenesis of insulin resistance, which in turn is linked to obesity and T2D [100]. In this regard, the gut microbiota is known to influence the integrity and permeability of the intestinal barrier and thus the inflammatory state, due to its interaction with mucin-type O-glycans [25, 26], which in turn may lead to the development of metabolic diseases, such as insulin resistance. Related to this, increased intestinal permeability has been associated with T2D risk [101], and the low-grade inflammation and insulin resistance that characterize both obesity and T2D are mediated by bacterial LPS (metabolic endotoxemia) [25, 97]. Indeed, in GF mice the presence of gut microbiota is necessary for the maintenance of the gut mucosal structure [102, 103] and this structure can be modified by the transfer of fecal microbiota [104].
Akkermansia muciniphila and representatives of the genera Bifidobacterium and Lactobacillus are among the bacterial species that improve intestinal barrier integrity and inflammation, which is why they have long been used as probiotics [30]. In general, probiotic administration leads to an improvement in several factors related to obesity and MetS, such as increased intestinal permeability, and therefore a reduction in LPS translocation and low-grade systemic inflammation, while also improving hypothalamic insulin resistance and glucose tolerance [105, 106].
Specifically, Akkermansia muciniphila is able to degrade mucin [107], and plays a prominent role in intestinal barrier integrity and inflammatory processes. In terms of intestinal barrier integrity, this bacterium is able to restore the thickness of the mucous layer by increasing mucin-producing goblet cells [108, 109] and restore its integrity by inducing intestinal expression of occludin (intercellular junction proteins) [110, 111]. Moreover, the Amuc_1100 protein, specific to the outer membrane of this bacterium, improves the intestinal barrier and various processes of intestinal physiology by interacting with Toll-like receptors (TLR) 2 and 4 [112,113,114], while inducing the production of the anti-inflammatory cytokine, IL-10. This bacterium also contributes to the decrease in adipose tissue inflammation by reducing macrophage infiltration, restoring regulatory T cells (Treg cells), reducing pro-inflammatory cytokines (such as IL 6 and IL-1β), and increasing anti-inflammatory factors (such as α-tocopherol and β-sitosterol) [109, 111, 115].
Different species of Lactobacillus genus are able to ameliorate damage to the intestinal barrier caused by other bacteria [116]. L. plantarum is widely cited as enhancing intestinal barrier integrity by improving epithelial tight junctions [117,118,119], while inhibiting the inflammatory response by reducing the expression of pro-inflammatory cytokines through modulation of TLR, nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways [120, 121], and inducing the secretion of human β-defensin 2, a peptide involved in host defense [122]. Similar effects have also been observed with L. fructosus, L. acidophilus, L. fermentum, L. casei and L. rhamnosus [123,124,125,126,127,128,129].
Bifidobacterium genus improves the intestinal barrier by increasing tight junction proteins [130] and modulating goblet cell function by secreting metabolites, thereby increasing the production of MUC2 [131]. In addition, this genus also induces an increase in intestinal Reg I proteins [132], which play a prominent role in the villous structure of the small intestine [133]. Moreover, these bacteria reduce inflammation by several mechanisms: (1) decreasing pro-inflammatory cytokines (IL-6 and IL-17) and increasing anti-inflammatory cytokines (IL-4 and IL-10) [130, 134]; (2) decreasing bacterial translocation [135,136,137]; (3) preventing LPS uptake into the bloodstream [130]; and (4) enhancing macrophage and dendritic cell function in relation to phagocytosis, cytokine production and induction of T-lymphocyte proliferation [134].
Gut microbiota-derived metabolites
SCFAs (mainly acetic, propionic and butyric acids) from bacterial fermentation of dietary fiber have been linked to a decrease in inflammation [138, 139], as well as improved glucose homeostasis and insulin sensitivity [140]. These compounds improve gut barrier function and inflammatory status through several mechanisms: (1) upregulation of intestinal tight junction proteins [141,142,143]; (2) regulation of tight junction assembly via an activation-dependent mechanism of AMP-activated protein kinase (AMPK) [144,145,146]; (3) increase in Treg cells [141, 147]; and (4) increase in anti-inflammatory cytokines and decrease in inflammatory cytokines [147, 148].
The inflammatory state is highly dependent on the balance between Treg cells producing the anti-inflammatory cytokine, IL-10, and T-helper (Th) 17 cells producing the inflammatory cytokine, IL-17, so that an increase in the Treg/Th17 ratio reduces the inflammatory state. In this sense, treatment of inflammatory bowel disease with parthenolide (a sesquiterpene lactone originally extracted from the shoots of the plant, Tanacetum balsamita) reduces inflammation in a gut microbiota-dependent manner, as it improves the Treg/Th17 balance in the intestinal mucosa through increased production of SCFAs [149]. Related to this, butyrate plays a key role in regulating the Treg/Th17 balance by inducing intestinal Treg cells differentiation in a histone acetylation-dependent mechanism in the promoter regions of certain genes, via inhibition of histone deacetylase [150, 151]. This increase in Treg cells translates into increased levels of anti-Th17 cytokines (IL-10 and IL-12) and reduced levels of IL-17 [152].
In addition to the increase of the anti-inflammatory cytokine IL-10 and the reduction of the pro-inflammatory cytokine IL-17 cited above, SCFAs also appear to be involved in the reduction of other pro-inflammatory factors, such as TNF-α, IL-1β, IL-6, and NO [153, 154], and in the inhibition of NF-κB activity [155, 156], which has been linked to inflammatory processes [157].
In addition, bacterial metabolites other than SCFAs, such as 4-hydroxyphenylpropionic acid, 4-hydroxyphenylacetic acid and caffeic acid, may mediate inflammation, possibly by mediating the aryl hydrocarbon receptor (AHR) and modulating the Treg/Th17 ratio [158]. In line with this, secondary bile acids resulting from bacterial deconjugation of bile acids have been reported to enhance Treg cells differentiation in the gut [159, 160].
Gut–brain axis
It is widely reported that the influence of microbiota on the development of obesity and related pathologies may be due in part to altered levels of intestinal hormones involved in the gut–brain axis, so that the central nervous system regulates food intake through the products of gut microbiota activity, including SCFAs [28]. Interestingly, the absence of gut microbiota may induce the consumption of obesogenic nutrients, such as fats and sugars, due to increased expression of their receptors [161, 162]. Together, these latter compounds appear to mediate the control of gastrointestinal motor function and food intake [163, 164]. Interestingly, the gut–brain axis activated by GLP-1 for the control of insulin secretion and gastric emptying has been reported to be affected by a set of ileum bacteria [165]. More specifically, microbially derived SCFAs have been found to induce an increase in GLP-1 levels [127, 166, 167]. Conversely, both peptide tyrosine tyrosine (PYY) and cholecystokinin (CCK), produced by intestinal L-cells, are considered anorectic hormones that inhibit food intake and reduce weight gain [168, 169].
GLP-1 is an incretin hormone whose action on insulin release from pancreatic b-cells to maintain normoglycemia has been described [170, 171]. Moreover, GLP-1 reduces the entry of nutrients into the circulation by increasing satiety and reducing the rate of gastric emptying [172, 173]. More specifically, GLP-1 has been shown to modulate central mechanisms of food intake in the hypothalamus by stimulating the activity of proopiomelanocortin (POMC) anorexigenic neurons and inhibiting the activity of agouti-related protein (AgRP)/neuropeptide Y (NpY) orexigenic neurons [174].
Both the orexigenic hormone, ghrelin, and the anorexigenic hormone, leptin, play a key role via the gut–brain axis in metabolic regulation and energy homeostasis and thus in the development of obesity [163, 175, 176]. Ghrelin is linked to adiposity and excessive weight gain by inducing an increase in gastric emptying rate and a decrease in energy expenditure [177,178,179], while increasing food intake by stimulating orexigenic AgRP/NpY neurons and inhibiting anorexigenic POMC neurons in the hypothalamus [180]. It is important to note that ghrelin is also involved in GH secretion [181, 182], which plays a key role in sexually dimorphic gene expression. In this sense, the sexual dimorphism observed in metabolic diseases could be due, at least in part, to the influence of the microbiota on ghrelin levels and thus on GH release. Regarding leptin, it is known to reduce food intake, body weight and circulating insulin, elevate circulating concentrations of n-octanoyl ghrelin, and promote the release of GH [183,184,185].
As an additional component of this gut–brain axis, there is solid evidence for the impact of conditions of stress and chronic activation of the hypothalamic–pituitary–adrenal (HPA) axis on the composition of the gut microbiota, as well as on intestinal permeability [186]. Considering that glucocorticoid stress responses are sexually distinct [187], this might represent an additional mechanism for sex divergences in gut microbiota composition, and its influence on metabolic health. Furthermore, since chronic activation of the HPA axis is linked to suppression of gonadal function [188], stress may also indirectly alter the microbiome by inhibiting sex steroid levels in both sexes. However, the actual contribution of this adrenal pathway to setting the physiological sex differences in gut microbiota and, thereby, in metabolic disease remains largely unexplored.
Obesity
Obesity, established for a BMI of 30 kg/m2 or higher, has increased in prevalence in the developed world in both adults and children. This pathology, which is the result of complex genetic, socio-economic and cultural relationships, leads to serious health, economic, and social problems [1]. Scientific evidence has shown that the development of some metabolic disorders is related to the distribution of body fat, and that this distribution shows sexual dimorphism. In this sense, fat tends to accumulate around the trunk and abdomen in men (android distribution) and around the hips and thighs in women (gynoid distribution) [5]. Abdominal adiposity, and especially visceral adiposity, has been associated with increased metabolic complications in both men and women [8, 189, 190] by causing an increase in blood glucose and triglycerides, a decrease in high-density lipoproteins (HDL) cholesterol and an increase in low-density lipoproteins (LDL) particles, as well as an increase in inflammatory markers [191]. On the contrary, gluteo-femoral fat is associated with a protective lipid and glucose profile and decreased metabolic risk, appearing to exert its protective effect through long-term fatty acid storage and a beneficial adipokine profile (positive association with leptin and adiponectin levels and negative association with the level of inflammatory cytokines) [9] (Table 1).
Role of sex hormones in obesity
A body of evidence supports the view that sex steroids modulate body fat distribution. In this regard, pubertal hormonal changes have been associated with different body weight gain between the sexes, due to increased lean mass in boys and increased fat mass in girls, and with android and gynoid fat distribution [6]. Furthermore, several studies have shown the involvement of some genes in the sexual dimorphism observed in body fat distribution, as well as the potential role of sex steroid hormones in the regulation of these genes [7, 192, 193].
In men, testosterone inhibits the uptake of triglycerides in the intra-abdominal region and appears to promote their accumulation in the subcutaneous region [194], while causing a reduction in catecholamine-stimulated lipolysis in subcutaneous but not in visceral fat [195]. These processes appear to be influenced by the androgen receptor (AR) gene, as in AR knockout mouse models, deletion of the AR causes an increase in adiposity, and especially late adiposity, by decreasing lipolysis [196, 197]. Furthermore, it appears that protein caveolin-1 (CAV1) plays an important role in fat accumulation and that it is regulated differently by estrogens (estradiol) and androgens (DHT) [198].
At the cellular level, differences in the effect of sex steroids (androgens and estrogens) on adipocyte function in white adipose tissue have been observed, regarding key aspects such as adipocyte differentiation, lipolysis/lipogenesis, insulin sensitivity, and adipokine production/secretion [199]. In this context, testosterone and DHT regulate the differentiation of pluripotent mouse mesenchymal cells, promoting and inhibiting their differentiation into myocytes and adipocytes, respectively, in an AR-dependent manner [200]. Similarly, in an in vitro study with human cells, DHT inhibited adipogenic differentiation of human mesenchymal stem cells and human preadipocytes in an AR-dependent manner, increased lipolysis and reduced lipid accumulation [201]. In castrated mice (a model of male hypogonadism), fat mass increased through adipocyte hypertrophy and adipogenesis [202], whereas when these mice were subjected to hormone replacement therapy, testosterone prevented the expansion of visceral and subcutaneous fat mass. In addition, obesogenic adipogenesis was also elevated by inhibiting AR activity. This study also showed differential regulation of fat distribution, with testosterone-derived estradiol and DHT blocking the increase in visceral and subcutaneous fat, respectively.
At the enzymatic level, the action of lipoprotein lipase (LPL), a key enzyme in lipid uptake and storage by adipocytes [203], appears to be suppressed by estradiol in the adipose tissue of obese women [204] and by testosterone in the adipose tissue of obese men [205], with this suppression being greater in the thigh than in the abdomen in the case of men, and could therefore be a key element in their central fat accumulation. Furthermore, testosterone deficiency in men increases LPL and acyl-CoA synthetase (ACS) activity and induces fatty acid accumulation in femoral adipose tissue [206, 207], and testosterone replacement reduces abdominal LPL activity and triglyceride uptake in this area [208]. As for the influence of female steroids, in women, sex steroid deficiency after menopause influences ACS and diacylglycerol acyltransferase (DGAT) activity and promotes increased storage of fatty acids in subcutaneous adipose tissue [209]. In addition, in premenopausal women, femoral adipogenic factors respond to acute sex hormone suppression to a greater extent than abdominal ones, and estrogen and progesterone appear to have different effects on the regulation of fatty acid metabolism [210].
Obesity in men
Testosterone concentrations have been negatively correlated with central obesity [211, 212], and testosterone treatment has been found to decrease visceral fat in men with symptoms of androgen deficiency and low-normal serum testosterone levels [17]. In this context, oxandrolone, an artificial steroid similar to testosterone, reduced total, abdominal and peripheral fat, but mainly total and abdominal fat, in elderly men [213]. In this study, visceral adipose tissue decreased to a greater extent than subcutaneous adipose tissue in the abdominal region. In addition, testosterone replacement therapy improved glycemic control, insulin resistance, and dyslipidemia in patients with hypogonadism, partly by reducing central obesity [18, 214, 215]. On the other hand, androgen deprivation therapy in men with prostate cancer leads to an increase in fat mass [14, 216, 217]. In relation to this, and contrary to what might be assumed, it has been described that the increase in abdominal fat is due to the accumulation of subcutaneous fat rather than intra-abdominal fat [218, 219]. Furthermore, the decline in testosterone with aging is accompanied by increased adiposity, with a preferential accumulation of abdominal fat and a greater accumulation of visceral adipose tissue [220]. It has also been reported that visceral adipose tissue correlates inversely with bioavailable and free testosterone, and that subcutaneous adipose tissue correlates negatively with sex hormone binding globulin (SHBG) [221]. A more recent study in male twins has shown an inverse correlation between the amount of subcutaneous fat and serum concentrations of total and free testosterone, DHT and SHBG, as well as between intra-abdominal fat and total testosterone and SHBG [222]. However, it has also been pointed out that low testosterone concentration might be linked with an increase in total body fat rather than with an excess of visceral fat; observations that underline the importance of adrenal steroids in body composition in men [223]. Finally, fat redistribution after sex steroid treatment is also observed in transsexual men [10, 224, 225].
Obesity in women
In women, central obesity has been correlated with increased testosterone levels and decreased estradiol [211]. The hormonal changes of menopause lead to a redistribution of fat, independent of total fat and age, towards a more central and android phenotype [11, 226, 227]; yet, some studies have suggested that the distribution of upper body fat after menopause may be due to ageing rather than menopause per se [228, 229]. Recently, body or trunk fat mass has been associated with lower total estradiol and higher calculated free estradiol concentrations in premenopausal women, as well as higher concentrations of total and calculated free testosterone and lower concentrations of SHBG and insulin-like growth factor-I (IGF-I) in both premenopausal and postmenopausal women [230]. Related to this, the shift towards central and android fat distribution observed in perimenopausal and postmenopausal women may be counteracted by hormone replacement therapy [231]. In addition, women with hyperandrogenism due to PCOS show increased central adiposity [20, 232, 233]. Also remarkably, fat redistribution is observed in transgender women after sex steroid treatment [10, 224, 225].
Metabolic syndrome
MetS is a pathological condition characterized by abdominal obesity, insulin resistance, hypertension and hyperlipidemia, which has spread across the globe and contributes to the rising prevalence of diseases, such as T2D, coronary heart disease, and stroke [3] (Table 1).
Role of sex hormones in metabolic syndrome
There is a large body of scientific evidence confirming the role of sex hormones in the development of MetS. An inverse association between serum SHBG levels and the prevalence of MetS has been observed in children aged 12–16 years, with SHBG being a more sensitive marker of MetS in boys, but not in girls, indicating sexual dimorphism already at an early age [234]. At older ages, an association between lower SHBG levels and MetS is still observed in both males and females, while total and free testosterone levels are lower in males and higher in females with MetS [235,236,237]. However, it has been suggested that low SHBG level would be associated with a higher prevalence of MetS in both men and premenopausal women, but not in postmenopausal women, so that plasma SHBG level could be a significant predictor of MetS only in men and women before menopause [238].
The sexual dimorphism observed in the influence of testosterone on MetS appears to be AR-dependent, and several mechanisms have been suggested to explain the association between testosterone level and MetS [239]. In men, there is evidence of an inverse correlation between testosterone and the development of visceral obesity, insulin resistance and MetS [240, 241]. Along these lines, the AR-mediated anti-obesity effect of testosterone has been reported in both men [242] and rodents [196, 243]. In women, elevated testosterone levels have been reported to be associated with insulin resistance and glucose intolerance by decreasing whole-body glucose uptake [244,245,246]. Regarding the action of testosterone on the pancreas, a study in mice has shown that the AR regulates male pancreatic beta-cell physiology, so that a deficiency of this receptor decreases glucose-stimulated insulin secretion and leads to glucose intolerance [247]. Conversely, it has been proposed that an excess testosterone could lead to pancreatic beta-cell dysfunction in women by an AR-dependent mechanism [248], with impaired insulin secretion [249].
At the central nervous system level, studies in rodents have confirmed that AR expression is higher in the brains of males than in females, where this receptor favors the central action of leptin [250]. Another study has shown that androgen excess in female mice prevents the activation of brown adipose tissue thermogenesis by leptin, which is associated with lower energy expenditure and visceral obesity, while hypothalamic expression of POMC decreases [251], suggesting that the increase in visceral adiposity in hyperandrogenic women may have a central origin.
Metabolic syndrome in men
In men, MetS appears to be related to testosterone, but not to estradiol [252, 253]. In this regard, testosterone levels have been negatively associated with MetS risk [254], while testosterone replacement therapy appears to improve most MetS parameters (glycemia, triglyceride levels, waist circumference, and high-density lipoprotein cholesterol) [255]. In addition, a recent study has shown that the negative association between testosterone and MetS holds true for all MetS components [256].
Moreover, several articles specify that MetS is inversely associated with both total testosterone and SHBG [257,258,259], and that both testosterone and SHBG show an inverse association with insulin, glucose and triglyceride concentrations, as well as a positive association with HDL cholesterol [260,261,262]. Moreover, numerous articles point to SHBG levels as the most influential in the development of MetS [263, 264] and as an independent and dominant risk factor [265,266,267] and a good early marker of MetS [257, 258].
As for free testosterone, although its inverse association with MetS has also been reported, most articles indicate that this association is smaller than in the case of total testosterone and SHBG [268,269,270], and it has even been reported that this relationship does not exist [267] or that it may be positive [264].
In relation to the above, men with hypogonadism (testosterone deficiency), resulting from androgen deprivation therapy for prostate cancer, show lower levels of total and free testosterone, as well as a higher prevalence of MetS [15]. Within the MetS parameters, these men had a higher prevalence of abdominal obesity and hyperglycemia, as well as elevated triglyceride levels compared to controls. In line with this, testosterone treatment in men with hypogonadism restores physiological testosterone levels and improves MetS components, increasing HDL and reducing total cholesterol, LDL cholesterol, triglycerides, and glucose [18, 214, 271].
Metabolic syndrome in women
The level of estrogen also appears to influence the prevalence of MetS. Thus, oophorectomy-induced estrogen depletion in rats induces a worsening of most MetS components (lipids, glucose, HDL, and LDL) [272, 273], while in women under 50 years of age, i.e., undergoing menopause, its prevalence increases [274, 275]. Furthermore, in women who have suffered hysterectomy (often accompanied by bilateral oophorectomy to prevent subsequent ovarian cancer) an increase in blood glucose level [276] and hypertension [277] has been reported.
Menopause causes a decrease in the level of SHBG, at least partially due to a decrease in estrogen, while the level of testosterone is not altered during the menopausal years [278]. In this sense, menopause can be considered a predictor (risk factor) of MetS and all its individual components independent of age [279, 280]. Furthermore, an inverse association between SHBG and MetS has been described, especially among postmenopausal women [281].
As for testosterone, its excess (hyperandrogenism) in women with PCOS is a powerful predictor of the metabolic disorders characteristic of MetS, with this pathology being more prevalent in patients with PCOS than in healthy women [21, 282]. However, although the scientific literature widely gives hyperandrogenism a prominent role in the metabolic disturbances associated with PCOS [283], a recent review and meta-analysis study has shown that the higher prevalence of MetS in women with PCOS is associated with obesity and metabolic characteristics, but not with the hyperandrogenism index [284].
Type 2 diabetes
The term diabetes encompasses a group of diseases, differentiated by their mechanisms of development, that reduce the ability to regulate the level of glucose in the blood stream and lead to prolonged hyperglycemia. There are two primary forms of diabetes, insulin-dependent diabetes (type 1 diabetes, T1D) and non-insulin-dependent diabetes (type 2 diabetes, T2D), due to autoimmune and metabolic processes, respectively. T2D is characterized by insufficient insulin production by pancreatic b-cells and impaired hepatic glucose metabolism, as well as insulin resistance, leading to reduced tissue responsiveness to insulin [285, 286]. The emergence of this pathology, which has become a pandemic, affecting approximately 9% of the world's population [2], is conditioned by several factors, such as genetics, sedentary lifestyle, physical inactivity, smoking, alcohol consumption, oxidative stress, and diet [287]. However, obesity is considered to be the major risk factor for T2D, which influences both the development of insulin resistance and the course of the disease [288]. In the present review, we have considered only T2D because of its metabolic disease character (Table 1).
Role of sex hormones in diabetes
Impaired fasting glucose (IFG) and impaired glucose tolerance (IGT), which occur as a preliminary step to T2D, show sexual dimorphism, with IGT being more frequent in women and IFG in men [289,290,291]. It has been suggested that sex hormones may be responsible for this dimorphism. Indeed, estrogen treatment of menopause lowers fasting glucose and worsens glucose tolerance [290]. Moreover, it has been confirmed that the incidence of T2D is higher in men than in women [292, 293], which further supports the involvement of sex hormones in the development of this pathology. In addition, menopause implies an increased risk of T2D, whereas hormone therapy for menopause may delay the onset of T2D [12].
Diabetes in men
Men with T2D have lower levels of total testosterone and free testosterone [294,295,296]. Related to this, it has been suggested that low levels of testosterone and SHBG are linked to the development of insulin resistance and subsequent T2D in men [8, 254]. In addition, the combination of high levels of SHBG and low levels of testosterone has been associated with increased mortality in men with T2D [297, 298]. Furthermore, other studies have shown that in men with T2D, low testosterone levels per se are associated with increased mortality, whereas testosterone replacement may improve survival in these men [299, 300]. In the same way, it has been reported that the proportion of men with T2D was reduced after 2 years of testosterone treatment [18, 301]. In addition, androgen deprivation therapy in prostate cancer has been found to induce an increased risk of diabetes [16, 302, 303].
In line with the above, men with T2D tend to have low testosterone levels, and most of them have hypogonadism [304]. Indeed, numerous studies have confirmed that obese T2D patients with hypogonadism and low testosterone levels show improved insulin resistance and glycemic control after undergoing testosterone replacement therapy (TRT) [18, 271, 305].
With regard to female hormones, men with high estradiol levels have an increased risk of T2D, and this high estradiol concentration, together with a low SHBH concentration, carries an additive detrimental effect on the risk of T2D in men [8, 306].
Diabetes in women
In contrast to men, high testosterone levels in women are linked to insulin resistance and T2D [254, 307, 308]. However, one study has shown that although elevated SHBG values in Chinese women are associated with a lower likelihood of T2D, estradiol and testosterone levels show no association with T2D in this ethnic group [306]. These contradictory results regarding the relationship between testosterone and the incidence of T2D may be due to the measurement of testosterone, with some authors using total testosterone and others using free testosterone, and according to a recent study, the method of analysis may differ between studies [309]. In addition, the free androgen index (FAI) is not a reliable indicator of free testosterone when the SHBG concentration is below 30 nmol/L, which would lead to possible research errors in women with low SHBG levels [310]. Accordingly, it has been reported that in women there is no association between total testosterone and T2D, although a higher level of free testosterone is associated with an increased risk of T2D [311].
As in men, the level of SHBG has also been inversely associated with the risk of T2D in women [254, 281, 295, 312]. In fact, in women, the association between low SHBG and T2D appears to be stronger than in men [307, 308]. Although this inverse association between SHBG and T2D is persistent in different ethnic groups [313], according to a study in postmenopausal Hispanic women with and without T2D, mean SHBG levels were not significantly different in the two groups [314]. These contradictory results may be due to the fact that sex hormone and SHBG levels may vary in postmenopausal women according to racial/ethnic differences [315, 316].
With respect to estradiol, postmenopausal women with T2D have been reported to have higher estradiol levels than healthy women [307, 312, 314]. However, data from a body of evidence based on earlier menarche or menopause and the practice of hysterectomy and oophorectomy suggest that non-physiological estradiol levels (higher or lower than normal values) may be responsible for an increased incidence of T2D. In this respect, early onset of menarche appears to increase the risk of T2D [317,318,319]. Nevertheless, some studies suggest that part of the risk of T2D due to early menarche may be due to the increased adiposity [22, 320, 321], as early menarche has been shown to be associated also with an increase in BMI in adulthood [322, 323]. On the other hand, early menopause or premature ovarian insufficiency leads to an increased risk of developing T2D [324,325,326]. Similar results have been observed in postmenopausal women with bilateral oophorectomy [22, 327]. Finally, hysterectomy accompanied by bilateral salpingo-oophorectomy (BSO) showed a higher risk of T2D than hysterectomy per se [327]. However, other studies have associated hysterectomy with an increased risk of T2D, while BSO per se or together with hysterectomy did not increase the risk of T2D [328, 329]. Pandeya et al. indicated that women who underwent hysterectomy or oophorectomy show an increased risk of developing T2D, but does not differentiate whether the two conditions occurred separately or together [22]. Another study showed that, relative to intact women, hysterectomized women with bilateral oophorectomy had lower levels of both total and bioavailable testosterone, while hysterectomized women with ovarian preservation had intermediate levels [330]. This study also revealed that hysterectomized women with bilateral oophorectomy tended to have lower total estradiol levels, while bioavailable estradiol and SHBG levels did not differ between hysterectomy and oophorectomy status. Related to this, hormone therapy with estrogen and progestin in postmenopausal women (both with intact uterus and hysterectomized) reduced the incidence of diabetes [13, 331, 332].
Perspectives and significance
In this review, we focused the role of sexual hormones in the development and prevalence of metabolic diseases such as obesity, metabolic syndrome and type 2 diabetes. Sex steroids, mainly estrogens and testosterone, are implicated in the sexual dimorphism in the structure and composition of the gut microbiota. Taking into account this relationship, it is plausible the contribution of their interconnections in the development of disease, and the subsequent differences between sexes. This influence is reflected both between men and women, and among women themselves due to hormonal changes associated with the menopause. The mutual interaction between sex steroids and the gut microbiota plays a prominent role in the development of metabolic diseases, highlighting the role of the microbiota in key aspects, such as gut barrier integrity, inflammatory status and the gut–brain axis.
The relevance of this field lies in the fact that fecal transfer and modification of the composition of the microbiota with specific diets, prebiotics, probiotics or synbiotics has attracted considerable interest in recent years as a potential alternative therapeutic tool for the treatment of metabolic diseases. In fact, the intestinal microbiome is currently considered an important therapeutic target, since specific changes in the bacterial community could help alleviate associated metabolic diseases.
Moreover, the identification of the mechanisms responsible for sexual dimorphism in the incidence of metabolic diseases has special importance when developing effective strategies and therapies aimed at reducing their incidence. The composition of the gut microbiota depends on the interaction with sex hormones in addition to other factors, such as the nutritional habits of the host organism, so the therapies to treat the dysbiosis of the gut microbiota associated with these diseases may have sex-specific effects.
Availability of data and materials
Not applicable.
Abbreviations
- AgRP:
-
Agouti-related protein
- ACS:
-
Acyl-CoA synthetase
- AR:
-
Androgen receptor
- BMI:
-
Body mass index
- BSO:
-
Bilateral salpingo-oophorectomy
- CCK:
-
Cholecystokinin
- CYP7A1:
-
Cholesterol 7α-hydroxylase
- DHT:
-
Dihydrotestosterone
- ERα:
-
Estrogen receptor alpha
- ERβ:
-
Estrogen receptor beta
- FGF15:
-
Fibroblast growth factor
- FXR:
-
Farnesoid X receptor
- GF:
-
Germ-free
- GH:
-
Growth hormone
- GLP-1:
-
Glucagon-like peptide-1
- HDL:
-
High-density lipoproteins
- HPA:
-
Hypothalamic–pituitary–adrenal
- IFG:
-
Impaired fasting glucose tolerance
- IGT:
-
Impaired glucose tolerance
- LDL:
-
Low-density lipoproteins
- LPL:
-
Lipoprotein lipase
- LPS:
-
Lipopolysaccharide
- MetS:
-
Metabolic syndrome
- miRNA:
-
MicroRNA
- NF-κB:
-
Nuclear factor kappa B
- NpY:
-
Neuropeptide Y
- ODMA:
-
O-Desmethylangolensin
- PCOS:
-
Polycystic ovary syndrome
- POMC:
-
Proopiomelanocortin
- PYY:
-
Peptide tyrosine tyrosine
- SHBG:
-
Sex hormone binding globulin
- SCFAs:
-
Short-chain fatty acids
- TNF-α:
-
Tumor necrosis factor alpha
- TLR:
-
Toll-like receptor
- Treg cells:
-
Regulatory T cells
- T2D:
-
Type 2 diabetes
References
Apovian CM. Obesity: definition, comorbidities, causes, and burden. Am J Manage Care. 2016;22(Suppl):176–85.
Jaacks LM, Siegel KR, Gujral UP, Narayan KM. Type 2 diabetes: a 21st century epidemic. Best Pract Res Clin Endocrinol Metab. 2016;30(3):331–43. https://doi.org/10.1016/j.beem.2016.05.003.
Saklayen MG. The global epidemic of the metabolic syndrome. Curr Hypertens Rep. 2018;20(2):12. https://doi.org/10.1007/s11906-018-0812-z.
Mauvais-Jarvis F. Sex differences in metabolic homeostasis, diabetes, and obesity. Biol Sex Differ. 2015;6:14. https://doi.org/10.1186/s13293-015-0033-y.
Bredella MA. Sex differences in body composition. Adv Exp Med Biol. 2017;1043:9–27. https://doi.org/10.1007/978-3-319-70178-3_2.
Wells JC. Sexual dimorphism of body composition. Best Pract Res Clin Endocrinol Metab. 2007;21(3):415–30. https://doi.org/10.1016/j.beem.2007.04.007.
van Nas A, Guhathakurta D, Wang SS, Yehya N, Horvath S, Zhang B, et al. Elucidating the role of gonadal hormones in sexually dimorphic gene coexpression networks. Endocrinology. 2009;150(3):1235–49. https://doi.org/10.1210/en.2008-0563.
Li J, Lai H, Chen S, Zhu H, Lai S. Interaction of sex steroid hormones and obesity on insulin resistance and type 2 diabetes in men: the Third National Health and Nutrition Examination Survey. J Diabetes Complicat. 2017;31(2):318–27. https://doi.org/10.1016/j.jdiacomp.2016.10.022.
Manolopoulos KN, Karpe F, Frayn KN. Gluteofemoral body fat as a determinant of metabolic health. Int J Obes (Lond). 2010;34(6):949–59. https://doi.org/10.1038/ijo.2009.286.
Wierckx K, Van Caenegem E, Schreiner T, Haraldsen I, Fisher AD, Toye K, et al. Cross-sex hormone therapy in trans persons is safe and effective at short-time follow-up: results from the European network for the investigation of gender incongruence. J Sex Med. 2014;11(8):1999–2011. https://doi.org/10.1111/jsm.12571.
Lovejoy JC, Champagne CM, de Jonge L, Xie H, Smith SR. Increased visceral fat and decreased energy expenditure during the menopausal transition. Int J Obes (Lond). 2008;32(6):949–58. https://doi.org/10.1038/ijo.2008.25.
Paschou SA, Papanas N. Type 2 diabetes mellitus and menopausal hormone therapy: an update. Diabetes Ther. 2019;10(6):2313–20. https://doi.org/10.1007/s13300-019-00695-y.
Bonds DE, Lasser N, Qi L, Brzyski R, Caan B, Heiss G, et al. The effect of conjugated equine oestrogen on diabetes incidence: the Women’s Health Initiative randomised trial. Diabetologia. 2006;49(3):459–68. https://doi.org/10.1007/s00125-005-0096-0.
van Londen GJ, Levy ME, Perera S, Nelson JB, Greenspan SL. Body composition changes during androgen deprivation therapy for prostate cancer: a 2-year prospective study. Crit Rev Oncol Hematol. 2008;68(2):172–7. https://doi.org/10.1016/j.critrevonc.2008.06.006.
Braga-Basaria M, Dobs AS, Muller DC, Carducci MA, John M, Egan J, et al. Metabolic syndrome in men with prostate cancer undergoing long-term androgen-deprivation therapy. J Clin Oncol. 2006;24(24):3979–83. https://doi.org/10.1200/JCO.2006.05.9741.
Chi JT, Lin PH, Tolstikov V, Oyekunle T, Chen EY, Bussberg V, et al. Metabolomic effects of androgen deprivation therapy treatment for prostate cancer. Cancer Med. 2020;9(11):3691–702. https://doi.org/10.1002/cam4.3016.
Allan CA, Strauss BJ, Burger HG, Forbes EA, McLachlan RI. Testosterone therapy prevents gain in visceral adipose tissue and loss of skeletal muscle in nonobese aging men. J Clin Endocrinol Metab. 2008;93(1):139–46. https://doi.org/10.1210/jc.2007-1291.
Li SY, Zhao YL, Yang YF, Wang X, Nie M, Wu XY, et al. Metabolic effects of testosterone replacement therapy in patients with type 2 diabetes mellitus or metabolic syndrome: a meta-analysis. Int J Endocrinol. 2020;2020:4732021. https://doi.org/10.1155/2020/4732021.
De Leo V, Musacchio MC, Cappelli V, Massaro MG, Morgante G, Petraglia F. Genetic, hormonal and metabolic aspects of PCOS: an update. Reprod Biol Endocrinol. 2016;14(1):38. https://doi.org/10.1186/s12958-016-0173-x.
Glintborg D, Petersen MH, Ravn P, Hermann AP, Andersen M. Comparison of regional fat mass measurement by whole body DXA scans and anthropometric measures to predict insulin resistance in women with polycystic ovary syndrome and controls. Acta Obstet Gynecol Scand. 2016;95(11):1235–43. https://doi.org/10.1111/aogs.12964.
Krentowska A, Lebkowska A, Jacewicz-Swiecka M, Hryniewicka J, Lesniewska M, Adamska A, et al. Metabolic syndrome and the risk of cardiovascular complications in young patients with different phenotypes of polycystic ovary syndrome. Endocrine. 2021;72(2):400–10. https://doi.org/10.1007/s12020-020-02596-8.
Pandeya N, Huxley RR, Chung HF, Dobson AJ, Kuh D, Hardy R, et al. Female reproductive history and risk of type 2 diabetes: a prospective analysis of 126 721 women. Diabetes Obes Metab. 2018;20(9):2103–12. https://doi.org/10.1111/dom.13336.
Dominianni C, Sinha R, Goedert JJ, Pei Z, Yang L, Hayes RB, et al. Sex, body mass index, and dietary fiber intake influence the human gut microbiome. PLoS ONE. 2015;10(4):e0124599. https://doi.org/10.1371/journal.pone.0124599.
Shin JH, Park YH, Sim M, Kim SA, Joung H, Shin DM. Serum level of sex steroid hormone is associated with diversity and profiles of human gut microbiome. Res Microbiol. 2019;170(4–5):192–201. https://doi.org/10.1016/j.resmic.2019.03.003.
Cani PD, Bibiloni R, Knauf C, Waget A, Neyrinck AM, Delzenne NM, et al. Changes in gut microbiota control metabolic endotoxemia-induced inflammation in high-fat diet-induced obesity and diabetes in mice. Diabetes. 2008;57(6):1470–81. https://doi.org/10.2337/db07-1403.
Zhang Y, Wang L, Ocansey DKW, Wang B, Wang L, Xu Z. Mucin-type O-glycans: barrier, microbiota, and immune anchors in inflammatory bowel disease. J Inflamm Res. 2021;14:5939–53. https://doi.org/10.2147/JIR.S327609.
Johansson ME, Phillipson M, Petersson J, Velcich A, Holm L, Hansson GC. The inner of the two Muc2 mucin-dependent mucus layers in colon is devoid of bacteria. Proc Natl Acad Sci USA. 2008;105(39):15064–9. https://doi.org/10.1073/pnas.0803124105.
Frost G, Sleeth ML, Sahuri-Arisoylu M, Lizarbe B, Cerdan S, Brody L, et al. The short-chain fatty acid acetate reduces appetite via a central homeostatic mechanism. Nat Commun. 2014;5:3611. https://doi.org/10.1038/ncomms4611.
Wang SZ, Yu YJ, Adeli K. Role of gut microbiota in neuroendocrine regulation of carbohydrate and lipid metabolism via the microbiota-gut-brain-liver axis. Microorganisms. 2020;8:4. https://doi.org/10.3390/microorganisms8040527.
Santos-Marcos JA, Perez-Jimenez F, Camargo A. The role of diet and intestinal microbiota in the development of metabolic syndrome. J Nutr Biochem. 2019;70:1–27. https://doi.org/10.1016/j.jnutbio.2019.03.017.
Flores R, Shi J, Fuhrman B, Xu X, Veenstra TD, Gail MH, et al. Fecal microbial determinants of fecal and systemic estrogens and estrogen metabolites: a cross-sectional study. J Transl Med. 2012;10:253. https://doi.org/10.1186/1479-5876-10-253.
Kamimura I, Watarai A, Takamura T, Takeo A, Miura K, Morita H, et al. Gonadal steroid hormone secretion during the juvenile period depends on host-specific microbiota and contributes to the development of odor preference. Dev Psychobiol. 2019;61(5):670–8. https://doi.org/10.1002/dev.21827.
Markle JG, Frank DN, Mortin-Toth S, Robertson CE, Feazel LM, Rolle-Kampczyk U, et al. Sex differences in the gut microbiome drive hormone-dependent regulation of autoimmunity. Science. 2013;339(6123):1084–8. https://doi.org/10.1126/science.1233521.
Yurkovetskiy L, Burrows M, Khan AA, Graham L, Volchkov P, Becker L, et al. Gender bias in autoimmunity is influenced by microbiota. Immunity. 2013;39(2):400–12. https://doi.org/10.1016/j.immuni.2013.08.013.
Org E, Mehrabian M, Parks BW, Shipkova P, Liu X, Drake TA, et al. Sex differences and hormonal effects on gut microbiota composition in mice. Gut Microbes. 2016;7(4):313–22. https://doi.org/10.1080/19490976.2016.1203502.
Santos-Marcos JA, Barroso A, Rangel-Zuniga OA, Perdices-Lopez C, Haro C, Sanchez-Garrido MA, et al. Interplay between gonadal hormones and postnatal overfeeding in defining sex-dependent differences in gut microbiota architecture. Aging (Albany NY). 2020;12(20):19979–20000. https://doi.org/10.18632/aging.104140.
Barroso A, Santos-Marcos JA, Perdices-Lopez C, Vega-Rojas A, Sanchez-Garrido MA, Krylova Y, et al. Neonatal exposure to androgens dynamically alters gut microbiota architecture. J Endocrinol. 2020;247(1):69–85. https://doi.org/10.1530/JOE-20-0277.
Insenser M, Murri M, Del Campo R, Martinez-Garcia MA, Fernandez-Duran E, Escobar-Morreale HF. Gut microbiota and the polycystic ovary syndrome: influence of sex, sex hormones, and obesity. J Clin Endocrinol Metab. 2018;103(7):2552–62. https://doi.org/10.1210/jc.2017-02799.
Liang Y, Ming Q, Liang J, Zhang Y, Zhang H, Shen T. Gut microbiota dysbiosis in polycystic ovary syndrome: association with obesity—a preliminary report. Can J Physiol Pharmacol. 2020;98(11):803–9. https://doi.org/10.1139/cjpp-2019-0413.
Zhou L, Ni Z, Yu J, Cheng W, Cai Z, Yu C. Correlation between fecal metabolomics and gut microbiota in obesity and polycystic ovary syndrome. Front Endocrinol (Lausanne). 2020;11:628. https://doi.org/10.3389/fendo.2020.00628.
Koren O, Goodrich JK, Cullender TC, Spor A, Laitinen K, Backhed HK, et al. Host remodeling of the gut microbiome and metabolic changes during pregnancy. Cell. 2012;150(3):470–80. https://doi.org/10.1016/j.cell.2012.07.008.
Korpela K, Kallio S, Salonen A, Hero M, Kukkonen AK, Miettinen PJ, et al. Gut microbiota develop towards an adult profile in a sex-specific manner during puberty. Sci Rep. 2021;11(1):23297. https://doi.org/10.1038/s41598-021-02375-z.
Yuan X, Chen R, Zhang Y, Lin X, Yang X. Sexual dimorphism of gut microbiota at different pubertal status. Microb Cell Fact. 2020;19(1):152. https://doi.org/10.1186/s12934-020-01412-2.
Yuan X, Chen R, Zhang Y, Lin X, Yang X. Gut microbiota: effect of pubertal status. BMC Microbiol. 2020;20(1):334. https://doi.org/10.1186/s12866-020-02021-0.
Fuhrman BJ, Feigelson HS, Flores R, Gail MH, Xu X, Ravel J, et al. Associations of the fecal microbiome with urinary estrogens and estrogen metabolites in postmenopausal women. J Clin Endocrinol Metab. 2014;99(12):4632–40. https://doi.org/10.1210/jc.2014-2222.
Mayneris-Perxachs J, Arnoriaga-Rodriguez M, Luque-Cordoba D, Priego-Capote F, Perez-Brocal V, Moya A, et al. Gut microbiota steroid sexual dimorphism and its impact on gonadal steroids: influences of obesity and menopausal status. Microbiome. 2020;8(1):136. https://doi.org/10.1186/s40168-020-00913-x.
Santos-Marcos JA, Rangel-Zuniga OA, Jimenez-Lucena R, Quintana-Navarro GM, Garcia-Carpintero S, Malagon MM, et al. Influence of gender and menopausal status on gut microbiota. Maturitas. 2018;116:43–53. https://doi.org/10.1016/j.maturitas.2018.07.008.
Haro C, Rangel-Zuniga OA, Alcala-Diaz JF, Gomez-Delgado F, Perez-Martinez P, Delgado-Lista J, et al. Intestinal microbiota is influenced by gender and body mass index. PLoS ONE. 2016;11(5):e0154090. https://doi.org/10.1371/journal.pone.0154090.
Santos-Marcos JA, Haro C, Vega-Rojas A, Alcala-Diaz JF, Molina-Abril H, Leon-Acuna A, et al. Sex differences in the gut microbiota as potential determinants of gender predisposition to disease. Mol Nutr Food Res. 2019;63(7):e1800870. https://doi.org/10.1002/mnfr.201800870.
Frommherz L, Bub A, Hummel E, Rist MJ, Roth A, Watzl B, et al. Age-related changes of plasma bile acid concentrations in healthy adults-results from the cross-sectional KarMeN study. PLoS ONE. 2016;11(4):e0153959. https://doi.org/10.1371/journal.pone.0153959.
Xiang X, Backman JT, Neuvonen PJ, Niemi M. Gender, but not CYP7A1 or SLCO1B1 polymorphism, affects the fasting plasma concentrations of bile acids in human beings. Basic Clin Pharmacol Toxicol. 2012;110(3):245–52. https://doi.org/10.1111/j.1742-7843.2011.00792.x.
Guzior DV, Quinn RA. Review: microbial transformations of human bile acids. Microbiome. 2021;9(1):140. https://doi.org/10.1186/s40168-021-01101-1.
Ridlon JM, Harris SC, Bhowmik S, Kang DJ, Hylemon PB. Consequences of bile salt biotransformations by intestinal bacteria. Gut Microbes. 2016;7(1):22–39. https://doi.org/10.1080/19490976.2015.1127483.
Ridlon JM, Kang DJ, Hylemon PB. Bile salt biotransformations by human intestinal bacteria. J Lipid Res. 2006;47(2):241–59. https://doi.org/10.1194/jlr.R500013-JLR200.
Li F, Jiang C, Krausz KW, Li Y, Albert I, Hao H, et al. Microbiome remodelling leads to inhibition of intestinal farnesoid X receptor signalling and decreased obesity. Nat Commun. 2013;4:2384. https://doi.org/10.1038/ncomms3384.
Sayin SI, Wahlstrom A, Felin J, Jantti S, Marschall HU, Bamberg K, et al. Gut microbiota regulates bile acid metabolism by reducing the levels of tauro-beta-muricholic acid, a naturally occurring FXR antagonist. Cell Metab. 2013;17(2):225–35. https://doi.org/10.1016/j.cmet.2013.01.003.
Inagaki T, Choi M, Moschetta A, Peng L, Cummins CL, McDonald JG, et al. Fibroblast growth factor 15 functions as an enterohepatic signal to regulate bile acid homeostasis. Cell Metab. 2005;2(4):217–25. https://doi.org/10.1016/j.cmet.2005.09.001.
Jelinek DF, Andersson S, Slaughter CA, Russell DW. Cloning and regulation of cholesterol 7 alpha-hydroxylase, the rate-limiting enzyme in bile acid biosynthesis. J Biol Chem. 1990;265(14):8190–7.
Inagaki T, Moschetta A, Lee YK, Peng L, Zhao G, Downes M, et al. Regulation of antibacterial defense in the small intestine by the nuclear bile acid receptor. Proc Natl Acad Sci USA. 2006;103(10):3920–5. https://doi.org/10.1073/pnas.0509592103.
Islam KB, Fukiya S, Hagio M, Fujii N, Ishizuka S, Ooka T, et al. Bile acid is a host factor that regulates the composition of the cecal microbiota in rats. Gastroenterology. 2011;141(5):1773–81. https://doi.org/10.1053/j.gastro.2011.07.046.
Allegretti JR, Kassam Z, Mullish BH, Chiang A, Carrellas M, Hurtado J, et al. Effects of fecal microbiota transplantation with oral capsules in obese patients. Clin Gastroenterol Hepatol. 2020;18(4):855-63e2. https://doi.org/10.1016/j.cgh.2019.07.006.
Swann JR, Want EJ, Geier FM, Spagou K, Wilson ID, Sidaway JE, et al. Systemic gut microbial modulation of bile acid metabolism in host tissue compartments. Proc Natl Acad Sci USA. 2011;108(Suppl 1):4523–30. https://doi.org/10.1073/pnas.1006734107.
Kuhajda K, Kevresan S, Kandrac J, Fawcett JP, Mikov M. Chemical and metabolic transformations of selected bile acids. Eur J Drug Metab Pharmacokinet. 2006;31(3):179–235. https://doi.org/10.1007/BF03190713.
Dabek M, McCrae SI, Stevens VJ, Duncan SH, Louis P. Distribution of beta-glucosidase and beta-glucuronidase activity and of beta-glucuronidase gene gus in human colonic bacteria. FEMS Microbiol Ecol. 2008;66(3):487–95. https://doi.org/10.1111/j.1574-6941.2008.00520.x.
Ervin SM, Li H, Lim L, Roberts LR, Liang X, Mani S, et al. Gut microbial beta-glucuronidases reactivate estrogens as components of the estrobolome that reactivate estrogens. J Biol Chem. 2019;294(49):18586–99. https://doi.org/10.1074/jbc.RA119.010950.
Gloux K, Berteau O, El Oumami H, Beguet F, Leclerc M, Dore J. A metagenomic beta-glucuronidase uncovers a core adaptive function of the human intestinal microbiome. Proc Natl Acad Sci USA. 2011;108(Suppl 1):4539–46. https://doi.org/10.1073/pnas.1000066107.
Plottel CS, Blaser MJ. Microbiome and malignancy. Cell Host Microbe. 2011;10(4):324–35. https://doi.org/10.1016/j.chom.2011.10.003.
Collden H, Landin A, Wallenius V, Elebring E, Fandriks L, Nilsson ME, et al. The gut microbiota is a major regulator of androgen metabolism in intestinal contents. Am J Physiol Endocrinol Metab. 2019;317(6):E1182–92. https://doi.org/10.1152/ajpendo.00338.2019.
Doden HL, Ridlon JM. Microbial hydroxysteroid dehydrogenases: from alpha to omega. Microorganisms. 2021;9:3. https://doi.org/10.3390/microorganisms9030469.
Kisiela M, Skarka A, Ebert B, Maser E. Hydroxysteroid dehydrogenases (HSDs) in bacteria: a bioinformatic perspective. J Steroid Biochem Mol Biol. 2012;129(1–2):31–46. https://doi.org/10.1016/j.jsbmb.2011.08.002.
Gruber CJ, Tschugguel W, Schneeberger C, Huber JC. Production and actions of estrogens. N Engl J Med. 2002;346(5):340–52. https://doi.org/10.1056/NEJMra000471.
Dominguez-Lopez I, Yago-Aragon M, Salas-Huetos A, Tresserra-Rimbau A, Hurtado-Barroso S. Effects of dietary phytoestrogens on hormones throughout a human lifespan: a review. Nutrients. 2020;12:8. https://doi.org/10.3390/nu12082456.
Frankenfeld CL, Atkinson C, Wahala K, Lampe JW. Obesity prevalence in relation to gut microbial environments capable of producing equal or O-desmethylangolensin from the isoflavone daidzein. Eur J Clin Nutr. 2014;68(4):526–30. https://doi.org/10.1038/ejcn.2014.23.
Miller LM, Lampe JW, Newton KM, Gundersen G, Fuller S, Reed SD, et al. Being overweight or obese is associated with harboring a gut microbial community not capable of metabolizing the soy isoflavone daidzein to O-desmethylangolensin in peri- and post-menopausal women. Maturitas. 2017;99:37–42. https://doi.org/10.1016/j.maturitas.2017.02.006.
Nakatsu CH, Armstrong A, Clavijo AP, Martin BR, Barnes S, Weaver CM. Fecal bacterial community changes associated with isoflavone metabolites in postmenopausal women after soy bar consumption. PLoS ONE. 2014;9(10):e108924. https://doi.org/10.1371/journal.pone.0108924.
Soukup ST, Stoll DA, Danylec N, Schoepf A, Kulling SE, Huch M. Metabolism of daidzein and genistein by gut bacteria of the class coriobacteriia. Foods. 2021;10:11. https://doi.org/10.3390/foods10112741.
Kostelac D, Rechkemmer G, Briviba K. Phytoestrogens modulate binding response of estrogen receptors alpha and beta to the estrogen response element. J Agric Food Chem. 2003;51(26):7632–5. https://doi.org/10.1021/jf034427b.
Mueller SO, Simon S, Chae K, Metzler M, Korach KS. Phytoestrogens and their human metabolites show distinct agonistic and antagonistic properties on estrogen receptor alpha (ERalpha) and ERbeta in human cells. Toxicol Sci. 2004;80(1):14–25. https://doi.org/10.1093/toxsci/kfh147.
Rietjens I, Louisse J, Beekmann K. The potential health effects of dietary phytoestrogens. Br J Pharmacol. 2017;174(11):1263–80. https://doi.org/10.1111/bph.13622.
Kaliannan K, Robertson RC, Murphy K, Stanton C, Kang C, Wang B, et al. Estrogen-mediated gut microbiome alterations influence sexual dimorphism in metabolic syndrome in mice. Microbiome. 2018;6(1):205. https://doi.org/10.1186/s40168-018-0587-0.
Fujitani T, Fujii Y, Lyu Z, Harada Sassa M, Harada KH. Urinary equol levels are positively associated with urinary estradiol excretion in women. Sci Rep. 2021;11(1):19532. https://doi.org/10.1038/s41598-021-98872-2.
Mayo B, Vazquez L, Florez AB. Equol: a bacterial metabolite from the daidzein isoflavone and its presumed beneficial health effects. Nutrients. 2019;11:9. https://doi.org/10.3390/nu11092231.
Sonnenburg JL, Backhed F. Diet-microbiota interactions as moderators of human metabolism. Nature. 2016;535(7610):56–64. https://doi.org/10.1038/nature18846.
Tomova A, Bukovsky I, Rembert E, Yonas W, Alwarith J, Barnard ND, et al. The effects of vegetarian and vegan diets on gut microbiota. Front Nutr. 2019;6:47. https://doi.org/10.3389/fnut.2019.00047.
Arumugam M, Raes J, Pelletier E, Le Paslier D, Yamada T, Mende DR, et al. Enterotypes of the human gut microbiome. Nature. 2011;473(7346):174–80. https://doi.org/10.1038/nature09944.
Klimenko NS, Tyakht AV, Popenko AS, Vasiliev AS, Altukhov IA, Ischenko DS, et al. Microbiome responses to an uncontrolled short-term diet intervention in the frame of the citizen science project. Nutrients. 2018;10:5. https://doi.org/10.3390/nu10050576.
Wu GD, Chen J, Hoffmann C, Bittinger K, Chen YY, Keilbaugh SA, et al. Linking long-term dietary patterns with gut microbial enterotypes. Science. 2011;334(6052):105–8. https://doi.org/10.1126/science.1208344.
Roager HM, Licht TR, Poulsen SK, Larsen TM, Bahl MI. Microbial enterotypes, inferred by the prevotella-to-bacteroides ratio, remained stable during a 6-month randomized controlled diet intervention with the new nordic diet. Appl Environ Microbiol. 2014;80(3):1142–9. https://doi.org/10.1128/AEM.03549-13.
Ley RE, Backhed F, Turnbaugh P, Lozupone CA, Knight RD, Gordon JI. Obesity alters gut microbial ecology. Proc Natl Acad Sci USA. 2005;102(31):11070–5. https://doi.org/10.1073/pnas.0504978102.
Cani PD, Delzenne NM, Amar J, Burcelin R. Role of gut microflora in the development of obesity and insulin resistance following high-fat diet feeding. Pathol Biol (Paris). 2008;56(5):305–9. https://doi.org/10.1016/j.patbio.2007.09.008.
Creely SJ, McTernan PG, Kusminski CM, Fisher FM, Da Silva NF, Khanolkar M, et al. Lipopolysaccharide activates an innate immune system response in human adipose tissue in obesity and type 2 diabetes. Am J Physiol Endocrinol Metab. 2007;292(3):E740–7. https://doi.org/10.1152/ajpendo.00302.2006.
Krajmalnik-Brown R, Ilhan ZE, Kang DW, DiBaise JK. Effects of gut microbes on nutrient absorption and energy regulation. Nutr Clin Pract. 2012;27(2):201–14. https://doi.org/10.1177/0884533611436116.
Strobel HJ. Vitamin B12-dependent propionate production by the ruminal bacterium Prevotella ruminicola 23. Appl Environ Microbiol. 1992;58(7):2331–3. https://doi.org/10.1128/aem.58.7.2331-2333.1992.
Accetto T, Avgustin G. Polysaccharide utilization locus and CAZYme genome repertoires reveal diverse ecological adaptation of Prevotella species. Syst Appl Microbiol. 2015;38(7):453–61. https://doi.org/10.1016/j.syapm.2015.07.007.
Kim SJ. Leptin potentiates Prevotella intermedia lipopolysaccharide-induced production of TNF-alpha in monocyte-derived macrophages. J Periodontal Implant Sci. 2010;40(3):119–24. https://doi.org/10.5051/jpis.2010.40.3.119.
Nichols FC, Yao X, Bajrami B, Downes J, Finegold SM, Knee E, et al. Phosphorylated dihydroceramides from common human bacteria are recovered in human tissues. PLoS ONE. 2011;6(2):e16771. https://doi.org/10.1371/journal.pone.0016771.
Cani PD, Amar J, Iglesias MA, Poggi M, Knauf C, Bastelica D, et al. Metabolic endotoxemia initiates obesity and insulin resistance. Diabetes. 2007;56(7):1761–72. https://doi.org/10.2337/db06-1491.
Caesar R, Fak F, Backhed F. Effects of gut microbiota on obesity and atherosclerosis via modulation of inflammation and lipid metabolism. J Intern Med. 2010;268(4):320–8. https://doi.org/10.1111/j.1365-2796.2010.02270.x.
Johansson ME, Sjovall H, Hansson GC. The gastrointestinal mucus system in health and disease. Nat Rev Gastroenterol Hepatol. 2013;10(6):352–61. https://doi.org/10.1038/nrgastro.2013.35.
Esser N, Legrand-Poels S, Piette J, Scheen AJ, Paquot N. Inflammation as a link between obesity, metabolic syndrome and type 2 diabetes. Diabetes Res Clin Pract. 2014;105(2):141–50. https://doi.org/10.1016/j.diabres.2014.04.006.
Cox AJ, Zhang P, Bowden DW, Devereaux B, Davoren PM, Cripps AW, et al. Increased intestinal permeability as a risk factor for type 2 diabetes. Diabetes Metab. 2017;43(2):163–6. https://doi.org/10.1016/j.diabet.2016.09.004.
Arike L, Holmen-Larsson J, Hansson GC. Intestinal Muc2 mucin O-glycosylation is affected by microbiota and regulated by differential expression of glycosyltranferases. Glycobiology. 2017;27(4):318–28. https://doi.org/10.1093/glycob/cww134.
Johansson ME, Jakobsson HE, Holmen-Larsson J, Schutte A, Ermund A, Rodriguez-Pineiro AM, et al. Normalization of host intestinal mucus layers requires long-term microbial colonization. Cell Host Microbe. 2015;18(5):582–92. https://doi.org/10.1016/j.chom.2015.10.007.
Jakobsson HE, Rodriguez-Pineiro AM, Schutte A, Ermund A, Boysen P, Bemark M, et al. The composition of the gut microbiota shapes the colon mucus barrier. EMBO Rep. 2015;16(2):164–77. https://doi.org/10.15252/embr.201439263.
Alard J, Lehrter V, Rhimi M, Mangin I, Peucelle V, Abraham AL, et al. Beneficial metabolic effects of selected probiotics on diet-induced obesity and insulin resistance in mice are associated with improvement of dysbiotic gut microbiota. Environ Microbiol. 2016;18(5):1484–97. https://doi.org/10.1111/1462-2920.13181.
Bagarolli RA, Tobar N, Oliveira AG, Araujo TG, Carvalho BM, Rocha GZ, et al. Probiotics modulate gut microbiota and improve insulin sensitivity in DIO mice. J Nutr Biochem. 2017;50:16–25. https://doi.org/10.1016/j.jnutbio.2017.08.006.
Derrien M, Vaughan EE, Plugge CM, de Vos WM. Akkermansia muciniphila gen. nov., sp. nov., a human intestinal mucin-degrading bacterium. Int J Syst Evol Microbiol. 2004;54(Pt 5):1469–76. https://doi.org/10.1099/ijs.0.02873-0.
Everard A, Belzer C, Geurts L, Ouwerkerk JP, Druart C, Bindels LB, et al. Cross-talk between Akkermansia muciniphila and intestinal epithelium controls diet-induced obesity. Proc Natl Acad Sci USA. 2013;110(22):9066–71. https://doi.org/10.1073/pnas.1219451110.
Shin NR, Lee JC, Lee HY, Kim MS, Whon TW, Lee MS, et al. An increase in the Akkermansia spp. population induced by metformin treatment improves glucose homeostasis in diet-induced obese mice. Gut. 2014;63(5):727–35. https://doi.org/10.1136/gutjnl-2012-303839.
Chelakkot C, Choi Y, Kim DK, Park HT, Ghim J, Kwon Y, et al. Akkermansia muciniphila-derived extracellular vesicles influence gut permeability through the regulation of tight junctions. Exp Mol Med. 2018;50(2):e450. https://doi.org/10.1038/emm.2017.282.
Li J, Lin S, Vanhoutte PM, Woo CW, Xu A. Akkermansia muciniphila protects against atherosclerosis by preventing metabolic endotoxemia-induced inflammation in Apoe−/− mice. Circulation. 2016;133(24):2434–46. https://doi.org/10.1161/CIRCULATIONAHA.115.019645.
Ottman N, Reunanen J, Meijerink M, Pietila TE, Kainulainen V, Klievink J, et al. Pili-like proteins of Akkermansia muciniphila modulate host immune responses and gut barrier function. PLoS ONE. 2017;12(3):e0173004. https://doi.org/10.1371/journal.pone.0173004.
Plovier H, Everard A, Druart C, Depommier C, Van Hul M, Geurts L, et al. A purified membrane protein from Akkermansia muciniphila or the pasteurized bacterium improves metabolism in obese and diabetic mice. Nat Med. 2017;23(1):107–13. https://doi.org/10.1038/nm.4236.
Wang J, Xu W, Wang R, Cheng R, Tang Z, Zhang M. The outer membrane protein Amuc_1100 of Akkermansia muciniphila promotes intestinal 5-HT biosynthesis and extracellular availability through TLR2 signalling. Food Funct. 2021;12(8):3597–610. https://doi.org/10.1039/d1fo00115a.
Zhao S, Liu W, Wang J, Shi J, Sun Y, Wang W, et al. Akkermansia muciniphila improves metabolic profiles by reducing inflammation in chow diet-fed mice. J Mol Endocrinol. 2017;58(1):1–14. https://doi.org/10.1530/JME-16-0054.
Jariwala R, Mandal H, Bagchi T. Indigenous lactobacilli strains of food and human sources reverse enteropathogenic E. coli O26:H11-induced damage in intestinal epithelial cell lines: effect on redistribution of tight junction proteins. Microbiology (Reading). 2017;163(9):1263–72. https://doi.org/10.1099/mic.0.000507.
Anderson RC, Cookson AL, McNabb WC, Park Z, McCann MJ, Kelly WJ, et al. Lactobacillus plantarum MB452 enhances the function of the intestinal barrier by increasing the expression levels of genes involved in tight junction formation. BMC Microbiol. 2010;10:316. https://doi.org/10.1186/1471-2180-10-316.
Karczewski J, Troost FJ, Konings I, Dekker J, Kleerebezem M, Brummer RJ, et al. Regulation of human epithelial tight junction proteins by Lactobacillus plantarum in vivo and protective effects on the epithelial barrier. Am J Physiol Gastrointest Liver Physiol. 2010;298(6):G851–9. https://doi.org/10.1152/ajpgi.00327.2009.
Zhou Y, Qin H, Zhang M, Shen T, Chen H, Ma Y, et al. Lactobacillus plantarum inhibits intestinal epithelial barrier dysfunction induced by unconjugated bilirubin. Br J Nutr. 2010;104(3):390–401. https://doi.org/10.1017/S0007114510000474.
Wu Y, Zhu C, Chen Z, Chen Z, Zhang W, Ma X, et al. Protective effects of Lactobacillus plantarum on epithelial barrier disruption caused by enterotoxigenic Escherichia coli in intestinal porcine epithelial cells. Vet Immunol Immunopathol. 2016;172:55–63. https://doi.org/10.1016/j.vetimm.2016.03.005.
Yang J, Qiu Y, Hu S, Zhu C, Wang L, Wen X, et al. Lactobacillus plantarum inhibited the inflammatory response induced by enterotoxigenic Escherichia coli K88 via modulating MAPK and NF-kappaB signalling in intestinal porcine epithelial cells. J Appl Microbiol. 2021;130(5):1684–94. https://doi.org/10.1111/jam.14835.
Paolillo R, Romano Carratelli C, Sorrentino S, Mazzola N, Rizzo A. Immunomodulatory effects of Lactobacillus plantarum on human colon cancer cells. Int Immunopharmacol. 2009;9(11):1265–71. https://doi.org/10.1016/j.intimp.2009.07.008.
Jang YJ, Kim WK, Han DH, Lee K, Ko G. Lactobacillus fermentum species ameliorate dextran sulfate sodium-induced colitis by regulating the immune response and altering gut microbiota. Gut Microbes. 2019;10(6):696–711. https://doi.org/10.1080/19490976.2019.1589281.
Li H, Zhang L, Chen L, Zhu Q, Wang W, Qiao J. Lactobacillus acidophilus alleviates the inflammatory response to enterotoxigenic Escherichia coli K88 via inhibition of the NF-kappaB and p38 mitogen-activated protein kinase signaling pathways in piglets. BMC Microbiol. 2016;16(1):273. https://doi.org/10.1186/s12866-016-0862-9.
Li Y, Yang S, Lun J, Gao J, Gao X, Gong Z, et al. Inhibitory Effects of the Lactobacillus rhamnosus GG effector protein HM0539 on inflammatory response through the TLR4/MyD88/NF-small ka, CyrillicB Axis. Front Immunol. 2020;11:551449. https://doi.org/10.3389/fimmu.2020.551449.
Song X, Pi S, Gao Y, Zhou F, Yan S, Chen Y, et al. The role of vasoactive intestinal peptide and mast cells in the regulatory effect of Lactobacillus casei ATCC 393 on intestinal mucosal immune barrier. Front Immunol. 2021;12:723173. https://doi.org/10.3389/fimmu.2021.723173.
Wang G, Li X, Zhao J, Zhang H, Chen W. Lactobacillus casei CCFM419 attenuates type 2 diabetes via a gut microbiota dependent mechanism. Food Funct. 2017;8(9):3155–64. https://doi.org/10.1039/c7fo00593h.
Xu C, Yan S, Guo Y, Qiao L, Ma L, Dou X, et al. Lactobacillus casei ATCC 393 alleviates Enterotoxigenic Escherichia coli K88-induced intestinal barrier dysfunction via TLRs/mast cells pathway. Life Sci. 2020;244:117281. https://doi.org/10.1016/j.lfs.2020.117281.
Yu Q, Yuan L, Deng J, Yang Q. Lactobacillus protects the integrity of intestinal epithelial barrier damaged by pathogenic bacteria. Front Cell Infect Microbiol. 2015;5:26. https://doi.org/10.3389/fcimb.2015.00026.
Lim SM, Kim DH. Bifidobacterium adolescentis IM38 ameliorates high-fat diet-induced colitis in mice by inhibiting NF-kappaB activation and lipopolysaccharide production by gut microbiota. Nutr Res. 2017;41:86–96. https://doi.org/10.1016/j.nutres.2017.04.003.
Engevik MA, Luk B, Chang-Graham AL, Hall A, Herrmann B, Ruan W, et al. Bifidobacterium dentium fortifies the intestinal mucus layer via autophagy and calcium signaling pathways. MBio. 2019;10:3. https://doi.org/10.1128/mBio.01087-19.
Chen JJ, Wang R, Li XF, Wang RL. Bifidobacterium longum supplementation improved high-fat-fed-induced metabolic syndrome and promoted intestinal Reg I gene expression. Exp Biol Med (Maywood). 2011;236(7):823–31. https://doi.org/10.1258/ebm.2011.010399.
Ose T, Kadowaki Y, Fukuhara H, Kazumori H, Ishihara S, Udagawa J, et al. Reg I-knockout mice reveal its role in regulation of cell growth that is required in generation and maintenance of the villous structure of small intestine. Oncogene. 2007;26(3):349–59. https://doi.org/10.1038/sj.onc.1209799.
Cano PG, Santacruz A, Trejo FM, Sanz Y. Bifidobacterium CECT 7765 improves metabolic and immunological alterations associated with obesity in high-fat diet-fed mice. Obesity (Silver Spring). 2013;21(11):2310–21. https://doi.org/10.1002/oby.20330.
Amar J, Chabo C, Waget A, Klopp P, Vachoux C, Bermudez-Humaran LG, et al. Intestinal mucosal adherence and translocation of commensal bacteria at the early onset of type 2 diabetes: molecular mechanisms and probiotic treatment. EMBO Mol Med. 2011;3(9):559–72. https://doi.org/10.1002/emmm.201100159.
Wang Z, Xiao G, Yao Y, Guo S, Lu K, Sheng Z. The role of bifidobacteria in gut barrier function after thermal injury in rats. J Trauma. 2006;61(3):650–7. https://doi.org/10.1097/01.ta.0000196574.70614.27.
Wang ZT, Yao YM, Xiao GX, Sheng ZY. Risk factors of development of gut-derived bacterial translocation in thermally injured rats. World J Gastroenterol. 2004;10(11):1619–24. https://doi.org/10.3748/wjg.v10.i11.1619.
Higashimura Y, Hirabayashi M, Nishikawa H, Inoue R, Nagai E, Matsumoto K, et al. Dietary intake of yacon roots (Smallanthus sonchifolius) affects gut microbiota and fecal mucin and prevents intestinal inflammation in mice. J Clin Biochem Nutr. 2021;69(3):272–9. https://doi.org/10.3164/jcbn.20-203.
Zhong Y, Marungruang N, Fak F, Nyman M. Effects of two whole-grain barley varieties on caecal SCFA, gut microbiota and plasma inflammatory markers in rats consuming low- and high-fat diets. Br J Nutr. 2015;113(10):1558–70. https://doi.org/10.1017/S0007114515000793.
Canfora EE, Jocken JW, Blaak EE. Short-chain fatty acids in control of body weight and insulin sensitivity. Nat Rev Endocrinol. 2015;11(10):577–91. https://doi.org/10.1038/nrendo.2015.128.
Hu ED, Chen DZ, Wu JL, Lu FB, Chen L, Zheng MH, et al. High fiber dietary and sodium butyrate attenuate experimental autoimmune hepatitis through regulation of immune regulatory cells and intestinal barrier. Cell Immunol. 2018;328:24–32. https://doi.org/10.1016/j.cellimm.2018.03.003.
Hung TV, Suzuki T. Dietary fermentable fiber reduces intestinal barrier defects and inflammation in colitic mice. J Nutr. 2016;146(10):1970–9. https://doi.org/10.3945/jn.116.232538.
Hung TV, Suzuki T. Dietary fermentable fibers attenuate chronic kidney disease in mice by protecting the intestinal barrier. J Nutr. 2018;148(4):552–61. https://doi.org/10.1093/jn/nxy008.
Miao W, Wu X, Wang K, Wang W, Wang Y, Li Z, et al. Sodium butyrate promotes reassembly of tight junctions in Caco-2 monolayers involving inhibition of MLCK/MLC2 pathway and phosphorylation of PKCbeta2. Int J Mol Sci. 2016;17:10. https://doi.org/10.3390/ijms17101696.
Olivier S, Leclerc J, Grenier A, Foretz M, Tamburini J, Viollet B. AMPK activation promotes tight junction assembly in intestinal epithelial Caco-2 cells. Int J Mol Sci. 2019;20:20. https://doi.org/10.3390/ijms20205171.
Peng L, Li ZR, Green RS, Holzman IR, Lin J. Butyrate enhances the intestinal barrier by facilitating tight junction assembly via activation of AMP-activated protein kinase in Caco-2 cell monolayers. J Nutr. 2009;139(9):1619–25. https://doi.org/10.3945/jn.109.104638.
Hartog A, Belle FN, Bastiaans J, de Graaff P, Garssen J, Harthoorn LF, et al. A potential role for regulatory T-cells in the amelioration of DSS induced colitis by dietary non-digestible polysaccharides. J Nutr Biochem. 2015;26(3):227–33. https://doi.org/10.1016/j.jnutbio.2014.10.011.
Wang S, Zhang S, Huang S, Wu Z, Pang J, Wu Y, et al. Resistant maltodextrin alleviates dextran sulfate sodium-induced intestinal inflammatory injury by increasing butyric acid to inhibit proinflammatory cytokine levels. Biomed Res Int. 2020;2020:7694734. https://doi.org/10.1155/2020/7694734.
Liu YJ, Tang B, Wang FC, Tang L, Lei YY, Luo Y, et al. Parthenolide ameliorates colon inflammation through regulating Treg/Th17 balance in a gut microbiota-dependent manner. Theranostics. 2020;10(12):5225–41. https://doi.org/10.7150/thno.43716.
Furusawa Y, Obata Y, Fukuda S, Endo TA, Nakato G, Takahashi D, et al. Commensal microbe-derived butyrate induces the differentiation of colonic regulatory T cells. Nature. 2013;504(7480):446–50. https://doi.org/10.1038/nature12721.
Takahashi D, Hoshina N, Kabumoto Y, Maeda Y, Suzuki A, Tanabe H, et al. Microbiota-derived butyrate limits the autoimmune response by promoting the differentiation of follicular regulatory T cells. EBioMedicine. 2020;58:102913. https://doi.org/10.1016/j.ebiom.2020.102913.
Zhang M, Zhou Q, Dorfman RG, Huang X, Fan T, Zhang H, et al. Butyrate inhibits interleukin-17 and generates Tregs to ameliorate colorectal colitis in rats. BMC Gastroenterol. 2016;16(1):84. https://doi.org/10.1186/s12876-016-0500-x.
Liu T, Li J, Liu Y, Xiao N, Suo H, Xie K, et al. Short-chain fatty acids suppress lipopolysaccharide-induced production of nitric oxide and proinflammatory cytokines through inhibition of NF-kappaB pathway in RAW264.7 cells. Inflammation. 2012;35(5):1676–84. https://doi.org/10.1007/s10753-012-9484-z.
Wang F, Liu J, Weng T, Shen K, Chen Z, Yu Y, et al. The inflammation induced by lipopolysaccharide can be mitigated by short-chain fatty acid, butyrate, through upregulation of IL-10 in septic shock. Scand J Immunol. 2017;85(4):258–63. https://doi.org/10.1111/sji.12515.
Luhrs H, Gerke T, Muller JG, Melcher R, Schauber J, Boxberge F, et al. Butyrate inhibits NF-kappaB activation in lamina propria macrophages of patients with ulcerative colitis. Scand J Gastroenterol. 2002;37(4):458–66. https://doi.org/10.1080/003655202317316105.
Tedelind S, Westberg F, Kjerrulf M, Vidal A. Anti-inflammatory properties of the short-chain fatty acids acetate and propionate: a study with relevance to inflammatory bowel disease. World J Gastroenterol. 2007;13(20):2826–32. https://doi.org/10.3748/wjg.v13.i20.2826.
Sun SC. The non-canonical NF-kappaB pathway in immunity and inflammation. Nat Rev Immunol. 2017;17(9):545–58. https://doi.org/10.1038/nri.2017.52.
Westfall S, Caracci F, Zhao D, Wu QL, Frolinger T, Simon J, et al. Microbiota metabolites modulate the T helper 17 to regulatory T cell (Th17/Treg) imbalance promoting resilience to stress-induced anxiety- and depressive-like behaviors. Brain Behav Immun. 2021;91:350–68. https://doi.org/10.1016/j.bbi.2020.10.013.
Campbell C, McKenney PT, Konstantinovsky D, Isaeva OI, Schizas M, Verter J, et al. Bacterial metabolism of bile acids promotes generation of peripheral regulatory T cells. Nature. 2020;581(7809):475–9. https://doi.org/10.1038/s41586-020-2193-0.
Song X, Sun X, Oh SF, Wu M, Zhang Y, Zheng W, et al. Microbial bile acid metabolites modulate gut RORgamma(+) regulatory T cell homeostasis. Nature. 2020;577(7790):410–5. https://doi.org/10.1038/s41586-019-1865-0.
Duca FA, Swartz TD, Sakar Y, Covasa M. Increased oral detection, but decreased intestinal signaling for fats in mice lacking gut microbiota. PLoS ONE. 2012;7(6):e39748. https://doi.org/10.1371/journal.pone.0039748.
Swartz TD, Duca FA, de Wouters T, Sakar Y, Covasa M. Up-regulation of intestinal type 1 taste receptor 3 and sodium glucose luminal transporter-1 expression and increased sucrose intake in mice lacking gut microbiota. Br J Nutr. 2012;107(5):621–30. https://doi.org/10.1017/S0007114511003412.
Konturek SJ, Konturek JW, Pawlik T, Brzozowski T. Brain-gut axis and its role in the control of food intake. J Physiol Pharmacol. 2004;55(Pt 2):137–54.
Steinert RE, Feinle-Bisset C, Asarian L, Horowitz M, Beglinger C, Geary N. Ghrelin, CCK, GLP-1, and PYY(3–36): secretory controls and physiological roles in eating and glycemia in health, obesity, and after RYGB. Physiol Rev. 2017;97(1):411–63. https://doi.org/10.1152/physrev.00031.2014.
Grasset E, Puel A, Charpentier J, Collet X, Christensen JE, Terce F, et al. A specific gut microbiota dysbiosis of type 2 diabetic mice induces GLP-1 resistance through an enteric NO-dependent and gut–brain axis mechanism. Cell Metab. 2017;25(5):1075–905. https://doi.org/10.1016/j.cmet.2017.04.013.
Aoki R, Kamikado K, Suda W, Takii H, Mikami Y, Suganuma N, et al. A proliferative probiotic Bifidobacterium strain in the gut ameliorates progression of metabolic disorders via microbiota modulation and acetate elevation. Sci Rep. 2017;7:43522. https://doi.org/10.1038/srep43522.
Yadav H, Lee JH, Lloyd J, Walter P, Rane SG. Beneficial metabolic effects of a probiotic via butyrate-induced GLP-1 hormone secretion. J Biol Chem. 2013;288(35):25088–97. https://doi.org/10.1074/jbc.M113.452516.
Batterham RL, Cowley MA, Small CJ, Herzog H, Cohen MA, Dakin CL, et al. Gut hormone PYY(3–36) physiologically inhibits food intake. Nature. 2002;418(6898):650–4. https://doi.org/10.1038/nature00887.
Sullivan CN, Raboin SJ, Gulley S, Sinzobahamvya NT, Green GM, Reeve JR Jr, et al. Endogenous cholecystokinin reduces food intake and increases Fos-like immunoreactivity in the dorsal vagal complex but not in the myenteric plexus by CCK1 receptor in the adult rat. Am J Physiol Regul Integr Comp Physiol. 2007;292(3):R1071–80. https://doi.org/10.1152/ajpregu.00490.2006.
Hodson DJ, Mitchell RK, Bellomo EA, Sun G, Vinet L, Meda P, et al. Lipotoxicity disrupts incretin-regulated human beta cell connectivity. J Clin Invest. 2013;123(10):4182–94. https://doi.org/10.1172/JCI68459.
Wang Y, Dilidaxi D, Wu Y, Sailike J, Sun X, Nabi XH. Composite probiotics alleviate type 2 diabetes by regulating intestinal microbiota and inducing GLP-1 secretion in db/db mice. Biomed Pharmacother. 2020;125:109914. https://doi.org/10.1016/j.biopha.2020.109914.
Flint A, Raben A, Ersboll AK, Holst JJ, Astrup A. The effect of physiological levels of glucagon-like peptide-1 on appetite, gastric emptying, energy and substrate metabolism in obesity. Int J Obes Relat Metab Disord. 2001;25(6):781–92. https://doi.org/10.1038/sj.ijo.0801627.
Gutzwiller JP, Drewe J, Goke B, Schmidt H, Rohrer B, Lareida J, et al. Glucagon-like peptide-1 promotes satiety and reduces food intake in patients with diabetes mellitus type 2. Am J Physiol. 1999;276(5):R1541–4. https://doi.org/10.1152/ajpregu.1999.276.5.R1541.
Secher A, Jelsing J, Baquero AF, Hecksher-Sorensen J, Cowley MA, Dalboge LS, et al. The arcuate nucleus mediates GLP-1 receptor agonist liraglutide-dependent weight loss. J Clin Invest. 2014;124(10):4473–88. https://doi.org/10.1172/JCI75276.
Cui H, Lopez M, Rahmouni K. The cellular and molecular bases of leptin and ghrelin resistance in obesity. Nat Rev Endocrinol. 2017;13(6):338–51. https://doi.org/10.1038/nrendo.2016.222.
Klok MD, Jakobsdottir S, Drent ML. The role of leptin and ghrelin in the regulation of food intake and body weight in humans: a review. Obes Rev. 2007;8(1):21–34. https://doi.org/10.1111/j.1467-789X.2006.00270.x.
Druce MR, Wren AM, Park AJ, Milton JE, Patterson M, Frost G, et al. Ghrelin increases food intake in obese as well as lean subjects. Int J Obes (Lond). 2005;29(9):1130–6. https://doi.org/10.1038/sj.ijo.0803001.
Levin F, Edholm T, Schmidt PT, Gryback P, Jacobsson H, Degerblad M, et al. Ghrelin stimulates gastric emptying and hunger in normal-weight humans. J Clin Endocrinol Metab. 2006;91(9):3296–302. https://doi.org/10.1210/jc.2005-2638.
Wren AM, Seal LJ, Cohen MA, Brynes AE, Frost GS, Murphy KG, et al. Ghrelin enhances appetite and increases food intake in humans. J Clin Endocrinol Metab. 2001;86(12):5992. https://doi.org/10.1210/jcem.86.12.8111.
Chen SR, Chen H, Zhou JJ, Pradhan G, Sun Y, Pan HL, et al. Ghrelin receptors mediate ghrelin-induced excitation of agouti-related protein/neuropeptide Y but not pro-opiomelanocortin neurons. J Neurochem. 2017;142(4):512–20. https://doi.org/10.1111/jnc.14080.
Carreira MC, Crujeiras AB, Andrade S, Monteiro MP, Casanueva FF. Ghrelin as a GH-releasing factor. Endocr Dev. 2013;25:49–58. https://doi.org/10.1159/000346052.
Nass R, Gaylinn BD, Thorner MO. The role of ghrelin in GH secretion and GH disorders. Mol Cell Endocrinol. 2011;340(1):10–4. https://doi.org/10.1016/j.mce.2011.03.021.
Hukshorn CJ, Westerterp-Plantenga MS, Saris WH. Pegylated human recombinant leptin (PEG-OB) causes additional weight loss in severely energy-restricted, overweight men. Am J Clin Nutr. 2003;77(4):771–6. https://doi.org/10.1093/ajcn/77.4.771.
Luque RM, Huang ZH, Shah B, Mazzone T, Kineman RD. Effects of leptin replacement on hypothalamic–pituitary growth hormone axis function and circulating ghrelin levels in ob/ob mice. Am J Physiol Endocrinol Metab. 2007;292(3):E891–9. https://doi.org/10.1152/ajpendo.00258.2006.
Vong L, Ye C, Yang Z, Choi B, Chua S Jr, Lowell BB. Leptin action on GABAergic neurons prevents obesity and reduces inhibitory tone to POMC neurons. Neuron. 2011;71(1):142–54. https://doi.org/10.1016/j.neuron.2011.05.028.
Farzi A, Frohlich EE, Holzer P. Gut microbiota and the neuroendocrine system. Neurotherapeutics. 2018;15(1):5–22. https://doi.org/10.1007/s13311-017-0600-5.
Moisan MP. Sexual dimorphism in glucocorticoid stress response. Int J Mol Sci. 2021;22:6. https://doi.org/10.3390/ijms22063139.
Toufexis D, Rivarola MA, Lara H, Viau V. Stress and the reproductive axis. J Neuroendocrinol. 2014;26(9):573–86. https://doi.org/10.1111/jne.12179.
Neeland IJ, Ayers CR, Rohatgi AK, Turer AT, Berry JD, Das SR, et al. Associations of visceral and abdominal subcutaneous adipose tissue with markers of cardiac and metabolic risk in obese adults. Obesity (Silver Spring). 2013;21(9):E439–47. https://doi.org/10.1002/oby.20135.
Sam S, Haffner S, Davidson MH, D’Agostino RB Sr, Feinstein S, Kondos G, et al. Relationship of abdominal visceral and subcutaneous adipose tissue with lipoprotein particle number and size in type 2 diabetes. Diabetes. 2008;57(8):2022–7. https://doi.org/10.2337/db08-0157.
Pi-Sunyer FX. The epidemiology of central fat distribution in relation to disease. Nutr Rev. 2004;62(7 Pt 2):S120–6. https://doi.org/10.1111/j.1753-4887.2004.tb00081.x.
Gesta S, Bluher M, Yamamoto Y, Norris AW, Berndt J, Kralisch S, et al. Evidence for a role of developmental genes in the origin of obesity and body fat distribution. Proc Natl Acad Sci USA. 2006;103(17):6676–81. https://doi.org/10.1073/pnas.0601752103.
Grove KL, Fried SK, Greenberg AS, Xiao XQ, Clegg DJ. A microarray analysis of sexual dimorphism of adipose tissues in high-fat-diet-induced obese mice. Int J Obes (Lond). 2010;34(6):989–1000. https://doi.org/10.1038/ijo.2010.12.
Marin P, Lonn L, Andersson B, Oden B, Olbe L, Bengtsson BA, et al. Assimilation of triglycerides in subcutaneous and intraabdominal adipose tissues in vivo in men: effects of testosterone. J Clin Endocrinol Metab. 1996;81(3):1018–22. https://doi.org/10.1210/jcem.81.3.8772568.
Dicker A, Ryden M, Naslund E, Muehlen IE, Wiren M, Lafontan M, et al. Effect of testosterone on lipolysis in human pre-adipocytes from different fat depots. Diabetologia. 2004;47(3):420–8. https://doi.org/10.1007/s00125-003-1324-0.
Fan W, Yanase T, Nomura M, Okabe T, Goto K, Sato T, et al. Androgen receptor null male mice develop late-onset obesity caused by decreased energy expenditure and lipolytic activity but show normal insulin sensitivity with high adiponectin secretion. Diabetes. 2005;54(4):1000–8. https://doi.org/10.2337/diabetes.54.4.1000.
Yanase T, Fan W, Kyoya K, Min L, Takayanagi R, Kato S, et al. Androgens and metabolic syndrome: lessons from androgen receptor knock out (ARKO) mice. J Steroid Biochem Mol Biol. 2008;109(3–5):254–7. https://doi.org/10.1016/j.jsbmb.2008.03.017.
Mukherjee R, Kim SW, Choi MS, Yun JW. Sex-dependent expression of caveolin 1 in response to sex steroid hormones is closely associated with development of obesity in rats. PLoS ONE. 2014;9(3):e90918. https://doi.org/10.1371/journal.pone.0090918.
Newell-Fugate AE. The role of sex steroids in white adipose tissue adipocyte function. Reproduction. 2017;153(4):R133–49. https://doi.org/10.1530/REP-16-0417.
Singh R, Artaza JN, Taylor WE, Gonzalez-Cadavid NF, Bhasin S. Androgens stimulate myogenic differentiation and inhibit adipogenesis in C3H 10T1/2 pluripotent cells through an androgen receptor-mediated pathway. Endocrinology. 2003;144(11):5081–8. https://doi.org/10.1210/en.2003-0741.
Gupta V, Bhasin S, Guo W, Singh R, Miki R, Chauhan P, et al. Effects of dihydrotestosterone on differentiation and proliferation of human mesenchymal stem cells and preadipocytes. Mol Cell Endocrinol. 2008;296(1–2):32–40. https://doi.org/10.1016/j.mce.2008.08.019.
Sebo ZL, Rodeheffer MS. Testosterone metabolites differentially regulate obesogenesis and fat distribution. Mol Metab. 2021;44:101141. https://doi.org/10.1016/j.molmet.2020.101141.
Goldberg IJ, Merkel M. Lipoprotein lipase: physiology, biochemistry, and molecular biology. Front Biosci. 2001;6:388–405. https://doi.org/10.2741/goldberg.
Iverius PH, Brunzell JD. Relationship between lipoprotein lipase activity and plasma sex steroid level in obese women. J Clin Invest. 1988;82(3):1106–12. https://doi.org/10.1172/JCI113667.
Ramirez ME, McMurry MP, Wiebke GA, Felten KJ, Ren K, Meikle AW, et al. Evidence for sex steroid inhibition of lipoprotein lipase in men: comparison of abdominal and femoral adipose tissue. Metabolism. 1997;46(2):179–85. https://doi.org/10.1016/s0026-0495(97)90299-7.
Santosa S, Bush NC, Jensen MD. Acute testosterone deficiency alters adipose tissue fatty acid storage. J Clin Endocrinol Metab. 2017;102(8):3056–64. https://doi.org/10.1210/jc.2017-00757.
Santosa S, Jensen MD. Effects of male hypogonadism on regional adipose tissue fatty acid storage and lipogenic proteins. PLoS ONE. 2012;7(2):e31473. https://doi.org/10.1371/journal.pone.0031473.
Marin P, Oden B, Bjorntorp P. Assimilation and mobilization of triglycerides in subcutaneous abdominal and femoral adipose tissue in vivo in men: effects of androgens. J Clin Endocrinol Metab. 1995;80(1):239–43. https://doi.org/10.1210/jcem.80.1.7829619.
Santosa S, Jensen MD. Adipocyte fatty acid storage factors enhance subcutaneous fat storage in postmenopausal women. Diabetes. 2013;62(3):775–82. https://doi.org/10.2337/db12-0912.
Santosa S, Bonnes SL, Jensen MD. Acute female hypogonadism alters adipose tissue fatty acid storage factors and chylomicronemia. J Clin Endocrinol Metab. 2016;101(5):2089–98. https://doi.org/10.1210/jc.2015-4065.
Garaulet M, Perex-Llamas F, Fuente T, Zamora S, Tebar FJ. Anthropometric, computed tomography and fat cell data in an obese population: relationship with insulin, leptin, tumor necrosis factor-alpha, sex hormone-binding globulin and sex hormones. Eur J Endocrinol. 2000;143(5):657–66. https://doi.org/10.1530/eje.0.1430657.
Tsai EC, Boyko EJ, Leonetti DL, Fujimoto WY. Low serum testosterone level as a predictor of increased visceral fat in Japanese–American men. Int J Obes Relat Metab Disord. 2000;24(4):485–91. https://doi.org/10.1038/sj.ijo.0801183.
Schroeder ET, Zheng L, Ong MD, Martinez C, Flores C, Stewart Y, et al. Effects of androgen therapy on adipose tissue and metabolism in older men. J Clin Endocrinol Metab. 2004;89(10):4863–72. https://doi.org/10.1210/jc.2004-0784.
Shigehara K, Konaka H, Nohara T, Izumi K, Kitagawa Y, Kadono Y, et al. Effects of testosterone replacement therapy on metabolic syndrome among Japanese hypogonadal men: a subanalysis of a prospective randomised controlled trial (EARTH study). Andrologia. 2018;50:1. https://doi.org/10.1111/and.12815.
Yassin DJ, Doros G, Hammerer PG, Yassin AA. Long-term testosterone treatment in elderly men with hypogonadism and erectile dysfunction reduces obesity parameters and improves metabolic syndrome and health-related quality of life. J Sex Med. 2014;11(6):1567–76. https://doi.org/10.1111/jsm.12523.
Galvao DA, Spry NA, Taaffe DR, Newton RU, Stanley J, Shannon T, et al. Changes in muscle, fat and bone mass after 36 weeks of maximal androgen blockade for prostate cancer. BJU Int. 2008;102(1):44–7. https://doi.org/10.1111/j.1464-410X.2008.07539.x.
Smith MR. Changes in fat and lean body mass during androgen-deprivation therapy for prostate cancer. Urology. 2004;63(4):742–5. https://doi.org/10.1016/j.urology.2003.10.063.
Smith MR, Finkelstein JS, McGovern FJ, Zietman AL, Fallon MA, Schoenfeld DA, et al. Changes in body composition during androgen deprivation therapy for prostate cancer. J Clin Endocrinol Metab. 2002;87(2):599–603. https://doi.org/10.1210/jcem.87.2.8299.
Smith MR, Lee H, McGovern F, Fallon MA, Goode M, Zietman AL, et al. Metabolic changes during gonadotropin-releasing hormone agonist therapy for prostate cancer: differences from the classic metabolic syndrome. Cancer. 2008;112(10):2188–94. https://doi.org/10.1002/cncr.23440.
Couillard C, Gagnon J, Bergeron J, Leon AS, Rao DC, Skinner JS, et al. Contribution of body fatness and adipose tissue distribution to the age variation in plasma steroid hormone concentrations in men: the HERITAGE Family Study. J Clin Endocrinol Metab. 2000;85(3):1026–31. https://doi.org/10.1210/jcem.85.3.6427.
Nielsen TL, Hagen C, Wraae K, Brixen K, Petersen PH, Haug E, et al. Visceral and subcutaneous adipose tissue assessed by magnetic resonance imaging in relation to circulating androgens, sex hormone-binding globulin, and luteinizing hormone in young men. J Clin Endocrinol Metab. 2007;92(7):2696–705. https://doi.org/10.1210/jc.2006-1847.
Vihma V, Naukkarinen J, Turpeinen U, Hamalainen E, Kaprio J, Rissanen A, et al. Metabolism of sex steroids is influenced by acquired adiposity—a study of young adult male monozygotic twin pairs. J Steroid Biochem Mol Biol. 2017;172:98–105. https://doi.org/10.1016/j.jsbmb.2017.06.007.
Tchernof A, Despres JP, Belanger A, Dupont A, Prud’homme D, Moorjani S, et al. Reduced testosterone and adrenal C19 steroid levels in obese men. Metabolism. 1995;44(4):513–9. https://doi.org/10.1016/0026-0495(95)90060-8.
Elbers JM, Asscheman H, Seidell JC, Gooren LJ. Effects of sex steroid hormones on regional fat depots as assessed by magnetic resonance imaging in transsexuals. Am J Physiol. 1999;276(2):E317–25. https://doi.org/10.1152/ajpendo.1999.276.2.E317.
Elbers JM, de Jong S, Teerlink T, Asscheman H, Seidell JC, Gooren LJ. Changes in fat cell size and in vitro lipolytic activity of abdominal and gluteal adipocytes after a one-year cross-sex hormone administration in transsexuals. Metabolism. 1999;48(11):1371–7. https://doi.org/10.1016/s0026-0495(99)90146-4.
Ijuin H, Douchi T, Oki T, Maruta K, Nagata Y. The contribution of menopause to changes in body-fat distribution. J Obstet Gynaecol Res. 1999;25(5):367–72. https://doi.org/10.1111/j.1447-0756.1999.tb01178.x.
Toth MJ, Tchernof A, Sites CK, Poehlman ET. Effect of menopausal status on body composition and abdominal fat distribution. Int J Obes Relat Metab Disord. 2000;24(2):226–31. https://doi.org/10.1038/sj.ijo.0801118.
Douchi T, Yamamoto S, Yoshimitsu N, Andoh T, Matsuo T, Nagata Y. Relative contribution of aging and menopause to changes in lean and fat mass in segmental regions. Maturitas. 2002;42(4):301–6. https://doi.org/10.1016/s0378-5122(02)00161-5.
Douchi T, Yonehara Y, Kawamura Y, Kuwahata A, Kuwahata T, Iwamoto I. Difference in segmental lean and fat mass components between pre- and postmenopausal women. Menopause. 2007;14(5):875–8. https://doi.org/10.1097/GME.0b013e318032b2f9.
Tin Tin S, Reeves GK, Key TJ. Body size and composition, physical activity and sedentary time in relation to endogenous hormones in premenopausal and postmenopausal women: findings from the UK Biobank. Int J Cancer. 2020;147(8):2101–15. https://doi.org/10.1002/ijc.33010.
Genazzani AR, Gambacciani M. Effect of climacteric transition and hormone replacement therapy on body weight and body fat distribution. Gynecol Endocrinol. 2006;22(3):145–50. https://doi.org/10.1080/09513590600629092.
Ezeh U, Pall M, Mathur R, Azziz R. Association of fat to lean mass ratio with metabolic dysfunction in women with polycystic ovary syndrome. Hum Reprod. 2014;29(7):1508–17. https://doi.org/10.1093/humrep/deu096.
Huang ZH, Manickam B, Ryvkin V, Zhou XJ, Fantuzzi G, Mazzone T, et al. PCOS is associated with increased CD11c expression and crown-like structures in adipose tissue and increased central abdominal fat depots independent of obesity. J Clin Endocrinol Metab. 2013;98(1):E17-24. https://doi.org/10.1210/jc.2012-2697.