Hypothalamic Estrogen Signaling and Adipose Tissue Metabolism in Energy Homeostasis

MASLD: Prevalence, Mechanisms, and Sex-Based Therapies in Postmenopausal Women

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common chronic liver disease influenced by genetic, lifestyle, and environmental factors. While MASLD is more prevalent in men, women are at increased risk after menopause, highlighting the critical pathogenetic role of sex hormones. The complex interplay between estrogen deficiency, visceral fat accumulation, metabolic syndrome (MetS), and inflammation accelerates disease progression, increases cardiovascular (CV) risk, and triggers a cycle of worsening adiposity, metabolic dysfunction, and psychological problems, including eating disorders. Weight loss in postmenopausal women can significantly improve both metabolic and psychological outcomes, helping to prevent MASLD and related conditions. This review examines the prevalence of MASLD, its comorbidities (type 2 diabetes T2D, CV, mental disorders), pathogenetic mechanisms, and pharmacological treatment with GLP-1 receptor agonists (GLP1-RAs), with a focus on postmenopausal women. Given the use of GLP1-RAs in the treatment of obesity and T2D in MASLD patients, and the increase in MetS and MASLD after menopause, this review analyzes the potential of a stable GLP-1-estrogen conjugate as a therapeutic approach in this subgroup. By combining the synergistic effects of both hormones, this dual agonist has been shown to increase food intake and food reward suppression, resulting in greater weight loss and improved insulin sensitivity, glucose, and lipid metabolism. Therefore, we hypothesize that this pharmacotherapy may provide more targeted therapeutic benefits than either hormone alone by protecting the liver, β-cells, and overall metabolic health. As these effects are only supported by preclinical data, this review highlights the critical need for future research to evaluate and confirm the mechanisms and efficacy in clinical settings, particularly in postmenopausal women.

The methyl-CpG-binding protein 2 (Mecp2) regulates the hypothalamic mitochondrial function and white adipose tissue lipid metabolism

OBJECTIVE

The neuroepigenetic factor Mecp2 regulates gene expression and is thought to play a crucial role in energy homeostasis. Body weight is regulated at the hypothalamic level, where mitochondrial energy metabolism is necessary for its proper functioning, allowing the hypothalamus to respond to peripheral signals to maintain energy balance and modulate energy expenditure through the sympathetic nervous system. Since the mechanism by which genetic and environmental factors contribute to regulating energy balance is unclear, this study aims to understand the contribution of gene-environment interaction to maintaining energy balance and how its disruption alters hypothalamic cellular energy production, impacting the control of systemic metabolism.

METHODS

We used a mouse model of epigenetic disruption (Mecp2-null) to evaluate the impact of Mecp2 deletion on systemic and hypothalamic metabolism using physiological and cellular approaches.

RESULTS

Our study shows that the previously reported body weight gain in mice lacking the expression of Mecp2 is preceded by a hypothalamic mitochondrial dysfunction that disrupts hypothalamic function, leading to a dysfunctional communication between the hypothalamus and adipose tissue, thus impairing lipid metabolism. Our study has revealed three crucial aspects of the contribution of this critical epigenetic factor pivotal for a proper gene-environment interaction: i) Mecp2 drives a molecular mechanism to maintain cellular energy homeostasis, which is necessary for the proper functioning of the hypothalamus. ii) Mecp2 is necessary to maintain lipid metabolism in adipose tissue. iii) Mecp2 is a molecular bridge linking hypothalamic cellular energy metabolism and adipose tissue lipid metabolism.

CONCLUSIONS

Our results show that Mecp2 regulates the hypothalamic mitochondrial function and white adipose tissue lipid metabolism and probably alters the communication between these two tissues, which is critical for corporal energy homeostasis maintenance.

Thermogenesis and Energy Metabolism in Brown Adipose Tissue in Animals Experiencing Cold Stress

Cold exposure is a regulatory biological functions in animals. The interaction of thermogenesis and energy metabolism in brown adipose tissue (BAT) is important for metabolic regulation in cold stress. Brown adipocytes (BAs) produce uncoupling protein 1 (UCP1) in mitochondria, activating non-shivering thermogenesis (NST) by uncoupling fuel combustion from ATP production in response to cold stimuli. To elucidate the mechanisms underlying thermogenesis and energy metabolism in BAT under cold stress, we explored how cold exposure triggers the activation of BAT thermogenesis and regulates overall energy metabolism. First, we briefly outline the precursor composition and function of BA. Second, we explore the roles of the cAMP- protein kinase A (PKA) and adenosine monophosphate-activated protein kinase (AMPK) signaling pathways in thermogenesis and energy metabolism in BA during cold stress. Then, we analyze the mechanism by which BA regulates mitochondria homeostasis and energy balance during cold stress. This research reveals potential therapeutic targets, such as PKA, AMPK, UCP1 and PGC-1α, which can be used to develop innovative strategies for treating metabolic diseases. Furthermore, it provides theoretical support for optimizing cold stress response strategies, including the pharmacological activation of BAT and the genetic modulation of thermogenic pathways, to improve energy homeostasis in livestock.

Depot-specific adiposity changes in ovariectomized mice on high-fat diet

Ovariectomized (OVX) mice serve as a key model for studying postmenopausal metabolic changes, particularly obesity, as they mimic the hormonal state of postmenopausal women. However, our understanding remains limited regarding how hormonal and dietary factors affect different adipose tissues. Furthermore, precise documentation of experimental procedures and their effects on specific adipose tissue depots is essential for reproducible translational research. This study investigated depot-specific adiposity development in OVX mice fed a high-fat diet (HFD), focusing on how reduced estrogen levels and dietary intervention affect distinct fat depots. We composed subcutaneous and visceral white adipose tissue (WAT) depots from sham-operated (Sham) and OVX female C57BL/6JJcl mice on a regular diet (RD) and high-fat diet (HFD) for 20 weeks. OVX mice on HFD gained significantly more weight than Sham controls. Adiposity increased in abdominal subcutaneous WAT (sWAT) and perirenal WAT (prWAT) of OVX mice, but not in mesenteric WAT (mWAT). Analysis of adipose tissue morphology revealed that OVX mice exhibited enlarged adipocyte cross-sectional areas under low estrogen (E2) conditions, suggesting enhanced adipogenesis in an estrogen-deficient state. These findings suggest that low estrogen condition accelerated adiposity, in a tissue site-dependent manner.

Exploring the association between exposure to pesticides, polycyclic aromatic hydrocarbons, and phthalates and metabolic syndrome in National Health and Nutrition Examination Survey in the USA, 2007-2012: utilizing a multi-step statistical strategy

BACKGROUND

Pesticides, polycyclic aromatic hydrocarbons (PAHs), and phthalates are recognized as potential contributors to metabolic disorders. Nevertheless, the combined effect of simultaneous exposure to these chemicals on the metabolic syndrome (MetS) remains elusive.

OBJECTIVES

To explore the impacts of simultaneous exposure to pesticides, PAHs and phthalates and identify critical chemicals on MetS.

METHODS

Based on the National Health and Nutrition Examination Survey (NHANES) database from 2007-2012, our study included 4030 non-pregnant individuals aged 20 years or older. We used the weighted linear regression model, variable selection models (including LASSO regression and BMA models), as well as a mixture exposure model (WQS model) to investigate the correlation between chemicals and MetS. Additionally, stratified analyses were performed based on gender and age.

RESULTS

The weighted generalized linear regression model revealed a positive correlation of 2-hydroxyphenanthrene (2-PHEN) with MetS (OR: 1.37, 95% CI: 1.19-1.59, P < 0.001). Both the LASSO regression and BMA models identified 2-PHEN as a significant chemical positively associated with MetS. Additionally, the WQS model showed a positive association between overall exposure to the three chemical categories and MetS, with the highest weighted chemicals being 2-PHEN. Stratified analyses demonstrated a significant correlation between 2-PHEN and MetS between different subgroups. Notably, the WQS regression model revealed a significant association in the subgroup of female (OR = 1.40, 95% CI: 1.08-1.83, P < 0.05), with 2-PHEN, 2,5-dichlorophenol (2,5-DCP), 2-hydroxynaphthalene (2-NAP), and mono-ethyl phthalate (MEP) identified as the primary contributions to MetS.

CONCLUSION

Combined exposure to the three chemical groups was associated with an increased risk of MetS, with the PAHs group exhibiting the most pronounced effect and 2-PHEN emerging as a key chemical, underscoring significant public health concerns regarding the potential health risks of endocrine-disrupting chemicals (EDCs) exposure to metabolic diseases.

Protein-coding mutation in Adcy3 increases adiposity and alters emotional behaviors sex-dependently in rats

OBJECTIVE

Adenylate cyclase 3 (Adcy3) has been linked to both obesity and major depressive disorder. We identified a protein-coding variant in the transmembrane (TM) helix of Adcy3 in rats; similar obesity variants have been identified in humans. This study investigates the role of a TM variant in adiposity and behavior.

METHODS

We mutated the TM domain of Adcy3 (Adcy3mut/mut) and created a heterozygous knockout (Adcy3+/-) in Wistar Kyoto (WKY) rats. Wild-type, Adcy3+/-, and Adcy3mut/mut rats were fed a high-fat diet for 12 weeks. We measured body weight, fat mass, glucose tolerance, food intake, metabolism, emotion-like behaviors, memory, and downstream proteins.

RESULTS

Adcy3+/- and Adcy3mut/mut rats weighed more than wild-type rats due to increased fat mass. There were key sex differences: adiposity was driven by increased food intake in males but by decreased energy expenditure in females. Adcy3mut/mut males displayed increased passive coping and decreased memory, whereas Adcy3mut/mut females displayed increased anxiety-like behavior. Adcy3mut/mut males had decreased hypothalamic cAMP-response element binding protein (CREB) signaling, with decreased phospho-AMP-activated protein kinase (p-AMPK) signaling in both sexes.

CONCLUSIONS

The ADCY3 TM domain plays a role in protein function via p-AMPK and CREB signaling. Adcy3 may contribute to the relationship between obesity and major depressive disorder, and sex influences the relationships between Adcy3, metabolism, and behavior.

Exploring the effects of estrogen deficiency and aging on organismal homeostasis during menopause

Sex hormone signaling declines during aging, from early midlife through menopause, as a consequence of reduced circulating estrogens and decreased receptiveness to these hormones in target tissues. Estrogens preserve energy homeostasis and promote metabolic health via coordinated and simultaneous effects throughout the brain and body. Age-associated loss of estrogen production during menopause has been implicated in a higher risk for metabolic diseases and increased mortality. However, it remains unclear whether age-associated changes in homeostasis are dependent on reduced estrogen signaling during menopause. Although menopausal hormone therapies containing estrogens can alleviate symptoms, concerns about the risks involved have contributed to a broad decline in the use of these approaches. Non-hormonal therapies have emerged that target tissues or pathways with varying levels of selectivity, reducing risk. We summarize here the broad effects of estrogen loss on homeostasis during menopause, current and emerging therapies and opportunities for understanding homeostatic disruptions associated with menopause.

Immunisation of the somatostatin gene alters hypothalamic-pituitary-liver gene expressions and enhances growth in Dazu black goats

OBJECTIVE

Somatostatin (SS) plays important regulatory roles in animal growth and reproduction by affecting the synthesis and secretion of growth hormone (GH). However, the mechanism by which SS regulates growth and development in goats is still unclear.

METHODS

In this study, we randomly selected eight 7-month-old Dazu black goats (DBGs) of similar body weight and equally assigned four bucks as the immunised and negative control groups. The immunised group received the Salmonella typhi attenuated vaccine X9241 (ptCS/2SS-asd) orally, whilst the negative control group received the empty vector vaccine X9241 (pVAX-asd) orally.

RESULTS

The SS concentration in the serum of goats in the immunised group was significantly lower than that in the negative control group, and the daily gain was significantly higher (p<0.05). SS-14 DNA vaccine immunisation resulted in significantly higher concentrations of growth-related hormones such as GH-releasing hormone and insulin growth factor 1 (IGF-1) in the serum of goats (p<0.05). RNA-seq analysis of hypothalamus of oral SS-14 DNA vaccine and negative control DBGs identified 31 differentially expressed genes (DEGs). Pituitary gland identified 164 DEGs. A total of 246 DEGs were detected in the liver by RNA-seq. Gene ontology of DEGs was enriched in mitochondrial envelope, extracellular region, receptor binding and cell proliferation. The biological metabolic pathways associated with DEGs were explored by Kyoto encyclopedia of genes and genomes analysis. DEGs were associated with metabolic pathways, oxidative phosphorylation, vitamin digestion and absorption and galactose metabolism. These candidate genes (e.g. DGKK, CYTB, DUSP1, and LRAT) may provide references for exploring the molecular mechanisms by which SS promotes growth and development.

CONCLUSION

Overall, these results demonstrated that the SS DNA vaccine enhanced the growth of DBGs by altering growth-related hormone concentrations and regulating the expression of growth-related genes in the hypothalamic-pituitary-liver axis.

Risk factors for postoperative hepatic dysfunction in overweight patients with acute type A aortic dissection

BACKGROUND

Acute hepatic dysfunction (AHD) is a common postoperative complication in patients with acute type A aortic dissection. The aim of this study was to identify risk factors for acute hepatic dysfunction after surgery for acute type A aortic dissection.

METHODS

We performed a retrospective study from March 1, 2019, to February 28, 2021. The primary endpoints of this study were morbidity due to AHD and risk factors for incidence. Univariate analysis and multivariate logistic regression analysis were used to analyse the related factors, and receiver operating characteristic (ROC) curves were plotted to evaluate their predictive value.

RESULTS

Among 147 patients, 29 (19.73%) developed postoperative acute hepatic dysfunction, and 9 (6.12%) died. Univariate analysis revealed that the ALT (P = 0.042), Cr (P < 0.001), and BUN (P = 0.008) levels were significantly different between the two groups. Multivariate logistic regression analysis revealed that Cr (OR = 1.013, 95% CI = 1.003-1.023, P = 0.008) was an independent risk factor for postoperative hepatic dysfunction in overweight (BMI > 24) patients with ATAAD. The area under the ROC curve (AUC) for Cr was 0.745 > 0.7, indicating good predictive value.

CONCLUSION

A high Cr concentration is an independent risk factor for postoperative AHD in overweight (BMI > 24) patients with ATAAD.

Transcriptome dataset of mouse adipose tissue across estrous cycles

Adipose tissue is crucial for energy storage and release, ensuring energy homeostasis within the body. Disturbances in the physiology of adipose tissue have been associated with various health disorders, such as obesity and diabetes. The reproductive cycle represents a fundamental biological pattern in female physiology. Although previous research has highlighted the substantial regulatory influence of ovarian hormones on adipose tissue, our understanding of the comprehensive changes in adipose tissue throughout the reproductive cycle remains limited. In this study, we examined the transcriptomic profile of female mouse-adipose tissue across their complete estrous cycles. The findings provided detailed descriptions of the datasets generated, including information on data collection, processing, and quality control. The study also demonstrated the robustness of these data through various validation steps. These findings serve as crucial resources for investigating the role of estrous cycle rhythmicity in important adipose tissue processes in the future.

Beyond reproduction: unraveling the impact of sex hormones on cardiometabolic health

This review thoroughly explores the multifaceted roles of sexual hormones, emphasizing their impact beyond reproductive functions and underscoring their significant influence on cardiometabolic regulation. It analyzes the broader physiological implications of estrogen, testosterone, and progesterone, highlighting their effects on metabolic syndrome, lipid metabolism, glucose homeostasis, and cardiovascular health. Drawing from diverse molecular, clinical, and therapeutic studies, the paper delves into the intricate interplay between these hormones and cardiometabolic processes. By presenting a comprehensive analysis that goes beyond traditional perspectives, and recognizing sexual hormones as more than reproductive agents, the review sheds light on their broader significance in health and disease management, advocating for holistic and personalized medical approaches.

27-Hydroxycholesterol acts on estrogen receptor α expressed by POMC neurons in the arcuate nucleus to modulate feeding behavior

Oxysterols are metabolites of cholesterol that regulate cholesterol homeostasis. Among these, the most abundant oxysterol is 27-hydroxycholesterol (27HC), which can cross the blood-brain barrier. Because 27HC functions as an endogenous selective estrogen receptor modulator, we hypothesize that 27HC binds to the estrogen receptor α (ERα) in the brain to regulate energy balance. Supporting this view, we found that delivering 27HC to the brain reduced food intake and activated proopiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus (POMCARH) in an ERα-dependent manner. In addition, we observed that inhibiting brain ERα, deleting ERα in POMC neurons, or chemogenetic inhibition of POMCARH neurons blocked the anorexigenic effects of 27HC. Mechanistically, we further revealed that 27HC stimulates POMCARH neurons by inhibiting the small conductance of the calcium-activated potassium (SK) channel. Together, our findings suggest that 27HC, through its interaction with ERα and modulation of the SK channel, inhibits food intake as a negative feedback mechanism against a surge in circulating cholesterol.

Protein-coding mutation in Adcy3 increases adiposity and alters emotional behaviors sex-dependently in rats

Objective

Adenylate cyclase 3 (Adcy3) has been linked to both obesity and major depressive disorder (MDD). Our lab identified a protein-coding variant in the 2nd transmembrane (TM) helix of Adcy3 in rats, and similar obesity variants have been identified in humans. The current study investigates the role of a TM variant in adiposity and behavior.

Methods

We used CRISPR-SpCas9 to mutate the TM domain of Adcy3 in WKY rats (Adcy3mut/mut). We also created a heterozygous knockout rat in the same strain (Adcy3+/-). Wild-type (WT), Adcy3+/-, and Adcy3mut/mut rats were fed a high-fat diet for 12 weeks. We measured body weight, fat mass, glucose tolerance, food intake, metabolism, emotion-like behaviors, and memory.

Results

Adcy3+/- and Adcy3mut/mut rats weighed more than WT rats due to increased fat mass. There were key sex differences: adiposity was driven by increased food intake in males but by decreased energy expenditure in females. Adcy3mut/mut males displayed increased passive coping and decreased memory while Adcy3mut/mut females displayed increased anxiety-like behavior.

Conclusions

These studies show that the ADCY3 TM domain plays a role in protein function, that Adcy3 may contribute to the relationship between obesity and MDD, and that sex influences the relationships between Adcy3, metabolism, and behavior.

Knockdown of Esr1 from DRD1-Rich Brain Regions Affects Adipose Tissue Metabolism: Potential Crosstalk between Nucleus Accumbens and Adipose Tissue

Declining estrogen (E2) leads to physical inactivity and adipose tissue (AT) dysfunction. Mechanisms are not fully understood, but E2's effects on dopamine (DA) activity in the nucleus accumbens (NAc) brain region may mediate changes in mood and voluntary physical activity (PA). Our prior work revealed that loss of E2 robustly affected NAc DA-related gene expression, and the pattern correlated with sedentary behavior and visceral fat. The current study used a new transgenic mouse model (D1ERKO) to determine whether the abolishment of E2 receptor alpha (ERα) signaling within DA-rich brain regions affects PA and AT metabolism. Adult male and female wild-type (WT) and D1ERKO (KD) mice were assessed for body composition, energy intake (EE), spontaneous PA (SPA), and energy expenditure (EE); underwent glucose tolerance testing; and were assessed for blood biochemistry. Perigonadal white AT (PGAT), brown AT (BAT), and NAc brain regions were assessed for genes and proteins associated with DA, E2 signaling, and metabolism; AT sections were also assessed for uncoupling protein (UCP1). KD mice had greater lean mass and EE (genotype effects) and a visible change in BAT phenotype characterized by increased UCP1 staining and lipid depletion, an effect seen only among females. Female KD had higher NAc Oprm1 transcript levels and greater PGAT UCP1. This group tended to have improved glucose tolerance (p = 0.07). NAc suppression of Esr1 does not appear to affect PA, yet it may directly affect metabolism. This work may lead to novel targets to improve metabolic dysfunction following E2 loss, possibly by targeting the NAc.

Estrogen counteracts age-related decline in beige adipogenesis through the NAMPT-regulated ER stress response

Thermogenic beige adipocytes are recognized as potential therapeutic targets for combating metabolic diseases. However, the metabolic advantages that they offer are compromised with aging. Here we show that treating mice with estrogen (E2), a hormone that decreases with age, can counteract the age-related decline in beige adipogenesis when exposed to cold temperature while concurrently enhancing energy expenditure and improving glucose tolerance in mice. Mechanistically, we found that nicotinamide phosphoribosyl transferase (NAMPT) plays a pivotal role in facilitating the formation of E2-induced beige adipocytes, which subsequently suppresses the onset of age-related endoplasmic reticulum (ER) stress. Furthermore, we found that targeting NAMPT signaling, either genetically or pharmacologically, can restore the formation of beige adipocytes by increasing the number of perivascular adipocyte progenitor cells. Conversely, the absence of NAMPT signaling prevents this process. Together, our findings shed light on the mechanisms regulating the age-dependent impairment of beige adipocyte formation and underscore the E2-NAMPT-controlled ER stress pathway as a key regulator of this process.

Periovarian Adipose Tissue - an Impact on Ovarian Functions

Periovarian adipose tissue (POAT) is a type of gonadal white adipose tissue that surrounds the ovary. POAT is a source of various bioactive molecules, such as adipokines, cytokines, chemokines, growth factors and hormones. Thereby it could influence crucial ovarian functions. Recent findings showed that removal of POAT affects folliculogenesis and steroidogenesis in the ovary. Furthermore, changes in the morphology and function of POAT were observed in women during menopause or polycystic ovary syndrome. Although the relationship between the body's energy status and fertility in females is generally well known, the contribution of POAT remains still elusive. Therefore, the objective of this review is summarizing the actual state of knowledge about POAT function in physiological and pathological processes within the ovary.

Unraveling Adipose Tissue Dysfunction: Molecular Mechanisms, Novel Biomarkers, and Therapeutic Targets for Liver Fat Deposition

Adipose tissue (AT), once considered a mere fat storage organ, is now recognized as a dynamic and complex entity crucial for regulating human physiology, including metabolic processes, energy balance, and immune responses. It comprises mainly two types: white adipose tissue (WAT) for energy storage and brown adipose tissue (BAT) for thermogenesis, with beige adipocytes demonstrating the plasticity of these cells. WAT, beyond lipid storage, is involved in various metabolic activities, notably lipogenesis and lipolysis, critical for maintaining energy homeostasis. It also functions as an endocrine organ, secreting adipokines that influence metabolic, inflammatory, and immune processes. However, dysfunction in WAT, especially related to obesity, leads to metabolic disturbances, including the inability to properly store excess lipids, resulting in ectopic fat deposition in organs like the liver, contributing to non-alcoholic fatty liver disease (NAFLD). This narrative review delves into the multifaceted roles of WAT, its composition, metabolic functions, and the pathophysiology of WAT dysfunction. It also explores diagnostic approaches for adipose-related disorders, emphasizing the importance of accurately assessing AT distribution and understanding the complex relationships between fat compartments and metabolic health. Furthermore, it discusses various therapeutic strategies, including innovative therapeutics like adipose-derived mesenchymal stem cells (ADMSCs)-based treatments and gene therapy, highlighting the potential of precision medicine in targeting obesity and its associated complications.

Unravelling the Crosstalk between Estrogen Deficiency and Gut-biotaDysbiosis in the Development of Diabetes Mellitus

Estrogens are classically considered essential hormonal signals, but they exert profound effects in a number of physiological and pathological states, including glucose homeostasis and insulin resistance. Estrogen deficiency after menopause in most women leads to increased androgenicity and changes in body composition, and it is recommended to manipulate the β-cell function of the pancreas, insulin-induced glucose transport, and hepatic glucose output, hence, the increasing incidence of type 2 diabetes mellitus. Recently, studies have reported that gut biota alteration due to estrogen deficiency contributes to altered energy metabolism and, hence, accentuates the pathology of diabetes mellitus. Emerging research suggests estrogen deficiency via genetic disposition or failure of ovaries to function in old age modulates the insulin resistance and glucose secretion workload on pancreatic beta cells by decreasing the levels of good bacteria such as Akkermansia muciniphila, Bifidobacterium spp., Lactobacillus spp., Faecalibacterium prausnitzii, Roseburia spp., and Prevotella spp., and increasing the levels of bad bacteria's such as Bacteroides spp., Clostridium difficile, Escherichia coli, and Enterococcus spp. Alteration in these bacteria's concentrations in the gut further leads to the development of impaired glucose uptake by the muscles, increased gluconeogenesis in the liver, and increased lipolysis and inflammation in the adipose tissues. Thus, the present review paper aims to clarify the intricate interactions between estrogen deficiency, gut microbiota regulation, and the development of diabetes mellitus.

The role of the thyroid in polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrine and metabolic disease in women of childbearing age and can cause metabolic disorder, infertility, and increased anxiety and depression; as a result, it can seriously affect the physical and mental health of fertile women. PCOS is a highly clinically heterogeneous disease with unclear etiology and pathogenesis, which increases the difficulty of treatment. The thyroid gland has complex regulatory effects on metabolism, reproduction, and emotion, and produces hormones that act on almost all cells of the human body. The clinical manifestations of PCOS are similar to some thyroid diseases. Furthermore, some thyroid diseases, such as subclinical hypothyroidism (SCH), not only increase the incidence rate of PCOS, but also exacerbate its associated metabolic abnormalities and reproductive disorders. Interestingly, PCOS also increases the incidence of some thyroid diseases. However, the role of the thyroid in PCOS remains unclear. This review is intended to thoroughly explore the critical role of the thyroid in PCOS by summarizing the comorbidity of PCOS and thyroid diseases and their combined role in metabolic disorders, related metabolic diseases, and reproductive disorders; and by analyzing the potential mechanism through which the thyroid influences the development and progression of PCOS and its symptoms. We hope this review will provide a valuable reference for the role of the thyroid in PCOS.

The evolutionary impact and influence of oestrogens on adipose tissue structure and function

Oestrogens are sex steroid hormones that have gained prominence over the years owing to their crucial roles in human health and reproduction functions which have been preserved throughout evolution. One of oestrogens actions, and the focus of this review, is their ability to determine adipose tissue distribution, function and adipose tissue 'health'. Body fat distribution is sexually dimorphic, affecting males and females differently. These differences are also apparent in the development of the metabolic syndrome and other chronic conditions where oestrogens are critical. In this review, we summarize the different molecular mechanisms, pathways and resulting pathophysiology which are a result of oestrogens actions in and on adipose tissues. This article is part of a discussion meeting issue 'Causes of obesity: theories, conjectures and evidence (Part I)'.

Estrogen prevents age-dependent beige adipogenesis failure through NAMPT-controlled ER stress pathway

Thermogenic beige adipocytes are recognized as potential therapeutic targets for combating metabolic diseases. However, the metabolic advantages they offer are compromised with aging. Here, we show that treating mice with estrogen (E2), a hormone that decreases with age, to mice can counteract the aging- related decline in beige adipocyte formation when subjected to cold, while concurrently enhancing energy expenditure and improving glucose tolerance. Mechanistically, we find that nicotinamide phosphoribosyltranferase (NAMPT) plays a pivotal role in facilitating the formation of E2-induced beige adipocytes, which subsequently suppresses the onset of age-related ER stress. Furthermore, we found that targeting NAMPT signaling, either genetically or pharmacologically, can restore the formation of beige adipocytes by increasing the number of perivascular adipocyte progenitor cells. Conversely, the absence of NAMPT signaling prevents this process. In conclusion, our findings shed light on the mechanisms governing the age-dependent impairment of beige adipocyte formation and underscore the E2-NAMPT controlled ER stress as a key regulator of this process.

Highlights

Estrogen restores beige adipocyte failure along with improved energy metabolism in old mice.Estrogen enhances the thermogenic gene program by mitigating age-induced ER stress.Estrogen enhances the beige adipogenesis derived from SMA+ APCs.Inhibiting the NAMPT signaling pathway abolishes estrogen-promoted beige adipogenesis.

Gut Microbiota and Acylcarnitine Metabolites Connect the Beneficial Association between Estrogen and Lipid Metabolism Disorders in Ovariectomized Mice

Decreased estrogen level is one of the main causes of lipid metabolism disorders and coronary heart disease in women after menopause. Exogenous estradiol benzoate is effective to some extent in alleviating lipid metabolism disorders caused by estrogen deficiency. However, the role of gut microbes in the regulation process is not yet appreciated. The objective of this study was to investigate the effects of estradiol benzoate supplementation on lipid metabolism, gut microbiota, and metabolites in ovariectomized (OVX) mice and to reveal the importance of gut microbes and metabolites in the regulation of lipid metabolism disorders. This study found that high doses of estradiol benzoate supplementation effectively attenuated fat accumulation in OVX mice. There was a significant increase in the expression of genes enriched in hepatic cholesterol metabolism and a concomitant decrease in the expression of genes enriched in unsaturated fatty acid metabolism pathways. Further screening of the gut for characteristic metabolites associated with improved lipid metabolism revealed that estradiol benzoate supplementation influenced major subsets of acylcarnitine metabolites. Ovariectomy significantly increased the abundance of characteristic microbes that are significantly negatively associated with acylcarnitine synthesis, such as Lactobacillus and Eubacterium ruminantium group bacteria, while estradiol benzoate supplementation significantly increased the abundance of characteristic microbes that are significantly positively associated with acylcarnitine synthesis, such as Ileibacterium and Bifidobacterium spp. The use of pseudosterile mice with gut microbial deficiency greatly facilitated the synthesis of acylcarnitine due to estradiol benzoate supplementation and also alleviated lipid metabolism disorders to a greater extent in OVX mice. IMPORTANCE Our findings establish a role for gut microbes in the progression of estrogen deficiency-induced lipid metabolism disorders and reveal key target bacteria that may have the potential to regulate acylcarnitine synthesis. These findings suggest a possible route for the use of microbes or acylcarnitine to regulate disorders of lipid metabolism induced by estrogen deficiency.

Neuregulin 4 as a novel adipokine in energy metabolism

Adipose tissue has been shown to play a key role in energy metabolism and it has been shown to regulate metabolic homeostasis through the secretion of adipokines. Neuregulin 4 (Nrg4), a novel adipokine secreted mainly by brown adipose tissue (BAT), has recently been characterized as having an important effect on the regulation of energy homeostasis and glucolipid metabolism. Nrg4 can modulate BAT-related thermogenesis by increasing sympathetic innervation of adipose tissue and therefore has potential metabolic benefits. Nrg4 improves metabolic dysregulation in various metabolic diseases such as insulin resistance, obesity, non-alcoholic fatty liver disease, and diabetes through several mechanisms such as anti-inflammation, autophagy regulation, pro-angiogenesis, and lipid metabolism normalization. However, inconsistent findings are found regarding the effects of Nrg4 on metabolic diseases in clinical settings, and this heterogeneity needs to be further clarified by future studies. The potential metabolic protective effect of Nrg4 suggests that it may be a promising endocrine therapeutic target.