Developmental androgen excess programs sympathetic tone and adipose tissue dysfunction and predisposes to a cardiometabolic syndrome in female mice

Sex- and Gender-Related Differences in Obesity: From Pathophysiological Mechanisms to Clinical Implications

Obesity, primarily characterized by excessive fat accumulation, is a multifactorial chronic disease with an increasing global prevalence. Despite the well-documented epidemiology and significant advances in understanding its pathophysiology and clinical implications, the impact of sex is typically overlooked in obesity research. Worldwide, women have a higher likelihood to become obese compared to men. Although women are offered weight loss interventions more often and at earlier stages than men, they are more vulnerable to psychopathology. Men, on the other hand, are less likely to pursue weight loss intervention and are more susceptible to the metabolic implications of obesity. In this narrative review, we comprehensively explored sex- and gender-specific differences in the development of obesity, focusing on a variety of biological variables, such as body composition, fat distribution and energy partitioning, the impact of sex steroid hormones and gut microbiota diversity, chromosomal and genetic variables, and behavioural and sociocultural variables influencing obesity development in men and women. Sex differences in obesity-related comorbidities and varying effectiveness of different weight loss interventions are also extensively discussed.

Neonatal inhibition of androgen activity alters the programming of body weight and orexinergic peptides differentially in male and female rats

The involvement of androgens in the regulation of energy metabolism has been demonstrated. The main objective of the present research was to study the involvement of androgens in both the programming of energy metabolism and the regulatory peptides associated with feeding. For this purpose, androgen receptors and the main metabolic pathways of testosterone were inhibited during the first five days of postnatal life in male and female Wistar rats. Pups received a daily s.c. injection from the day of birth, postnatal day (P) 1, to P5 of Flutamide (a competitive inhibitor of androgen receptors), Letrozole (an aromatase inhibitor), Finasteride (a 5-alpha-reductase inhibitor) or vehicle. Body weight, food intake and fat pads were measured. Moreover, hypothalamic Agouti-related peptide (AgRP), neuropeptide Y (NPY), orexin, and proopiomelanocortin (POMC) were analyzed by quantitative real-time polymerase chain reaction assay. The inhibition of androgenic activity during the first five days of life produced a significant decrease in body weight in females at P90 but did not affect this parameter in males. Moreover, the inhibition of aromatase decreased hypothalamic AgRP mRNA levels in males while the inhibition of 5α-reductase decreased hypothalamic AgRP and orexin mRNA levels in female rats. Finally, food intake and visceral fat, but not subcutaneous fat, were affected in both males and females depending on which testosterone metabolic pathway was inhibited. Our results highlight the differential involvement of androgens in the programming of energy metabolism as well as the AgRP and orexin systems during development in male and female rats.

Sex differences in energy metabolism: natural selection, mechanisms and consequences

Metabolic homeostasis operates differently in men and women. This sex asymmetry is the result of evolutionary adaptations that enable women to resist loss of energy stores and protein mass while remaining fertile in times of energy deficit. During starvation or prolonged exercise, women rely on oxidation of lipids, which are a more efficient energy source than carbohydrates, to preserve glucose for neuronal and placental function and spare proteins necessary for organ function. Carbohydrate reliance in men could be an evolutionary adaptation related to defence and hunting, as glucose, unlike lipids, can be used as a fuel for anaerobic high-exertion muscle activity. The larger subcutaneous adipose tissue depots in healthy women than in healthy men provide a mechanism for lipid storage. As female mitochondria have higher functional capacity and greater resistance to oxidative damage than male mitochondria, uniparental inheritance of female mitochondria may reduce the transmission of metabolic disorders. However, in women, starvation resistance and propensity to obesity have evolved in tandem, and the current prevalence of obesity is greater in women than in men. The combination of genetic sex, programming by developmental testosterone in males, and pubertal sex hormones defines sex-specific biological systems in adults that produce phenotypic sex differences in energy homeostasis, metabolic disease and drug responses.

Polycystic Ovary Syndrome Fuels Cardiovascular Inflammation and Aggravates Ischemic Cardiac Injury

BACKGROUND

Reducing cardiovascular disease burden among women remains challenging. Epidemiologic studies have indicated that polycystic ovary syndrome (PCOS), the most common endocrine disease in women of reproductive age, is associated with an increased prevalence and extent of coronary artery disease. However, the mechanism through which PCOS affects cardiac health in women remains unclear.

METHODS

Prenatal anti-Müllerian hormone treatment or peripubertal letrozole infusion was used to establish mouse models of PCOS. RNA sequencing was performed to determine global transcriptomic changes in the hearts of PCOS mice. Flow cytometry and immunofluorescence staining were performed to detect myocardial macrophage accumulation in multiple PCOS models. Parabiosis models, cell-tracking experiments, and in vivo gene silencing approaches were used to explore the mechanisms underlying increased macrophage infiltration in PCOS mouse hearts. Permanent coronary ligation was performed to establish myocardial infarction (MI). Histologic analysis and small-animal imaging modalities (eg, magnetic resonance imaging and echocardiography) were performed to evaluate the effects of PCOS on injury after MI. Women with PCOS and control participants (n=200) were recruited to confirm findings observed in animal models.

RESULTS

Transcriptomic profiling and immunostaining revealed that hearts from PCOS mice were characterized by increased macrophage accumulation. Parabiosis studies revealed that monocyte-derived macrophages were significantly increased in the hearts of PCOS mice because of enhanced circulating Ly6C+ monocyte supply. Compared with control mice, PCOS mice showed a significant increase in splenic Ly6C+ monocyte output, associated with elevated hematopoietic progenitors in the spleen and sympathetic tone. Plasma norepinephrine (a sympathetic neurotransmitter) levels and spleen size were consistently increased in women with PCOS when compared with those in control participants, and norepinephrine levels were significantly correlated with circulating CD14++CD16- monocyte counts. Compared with animals without PCOS, PCOS animals showed significantly exacerbated atherosclerotic plaque development and post-MI cardiac remodeling. Conditional Vcam1 silencing in PCOS mice significantly suppressed cardiac inflammation and improved cardiac injury after MI.

CONCLUSIONS

Our data documented previously unrecognized mechanisms through which PCOS could affect cardiovascular health in women. PCOS may promote myocardial macrophage accumulation and post-MI cardiac remodeling because of augmented splenic myelopoiesis.

Protective Effects of Coumestrol on Metabolic Dysfunction and Its Estrogen Receptor-Mediated Action in Ovariectomized Mice

Coumestrol, a phytoestrogen compound found in various plants, has been shown to act as a potent estrogen receptor (ER) agonist, with a higher binding affinity for ERβ than for ERα. However, there is currently limited information regarding its beneficial effects in postmenopausal disorders and its ER-mediated mechanisms. Herein, we investigated the effects of coumestrol (subcutaneous or oral treatment) on metabolic dysfunction in ovariectomized (OVX) mice fed a high-fat diet, in comparison with the effects of 17β-estradiol (E2) replacement. Coumestrol was administered daily at a dose of 5 mg/kg for 10 weeks. Coumestrol treatment through the subcutaneous route stimulated uterine growth in OVX mice at a level lower than that of E2. E2 and coumestrol prevented body fat accumulation, adipocyte hypertrophy, and hepatic steatosis, and enhanced voluntary physical activity. Coumestrol showed estrogen-mimetic effects in the regulation of the protein expressions involved in browning of white fat and insulin signaling, including increased hepatic expression of fibroblast growth factor 21. Importantly, the metabolic effects of coumestrol (oral administration at 10 mg/kg for 7 weeks) were mostly abolished following co-treatment with an ERβ-selective antagonist but not with an ERα-selective antagonist, indicating that the metabolic actions of coumestrol in OVX mice are primarily mediated by ERβ. These findings provide important insights into the beneficial effects of coumestrol as a phytoestrogen supplement for the prevention and treatment of postmenopausal symptoms.

Polycystic ovary syndrome and obesity: a modern paradigm

Polycystic ovary syndrome is a heterogeneous endocrine disease that affects women of childbearing age. The pathogenesis of polycystic ovary syndrome has not been fully studied to date, its paradigm considers the genetic determinism of the manifestation of hormonal and metabolic disorders, which are considered to be criteria for the verification of the disease (hyperandrogenism, oligo/anovulation and/or polycystic ovarian transformation during ultrasound examination (ultrasound). This review discusses the main ways of interaction between hyperandrogenism, insulin resistance and obesity and their role in the pathogenesis of polycystic ovary syndrome, as well as possible methods of treatment for this category of patients. The review analyzes the role of hyperandrogenism and insulin resistance in the implementation of the genetic scenario of polycystic ovary syndrome and finds out the reasons why women with polycystic ovary syndrome often demonstrate the presence of a «metabolic trio» - hyperinsulinemia, insulin resistance and type 2 diabetes mellitus. It is noted that obesity is not included in the criteria for the diagnosis of polycystic ovary syndrome, but epidemiological data confirm the existence of a relationship between these diseases. Obesity, especially visceral, which is often found in women with polycystic ovary syndrome, enhances and worsens metabolic and reproductive outcomes with polycystic ovary syndrome, as well as increases insulin resistance and compensatory hyperinsulinemia, which, in turn, stimulates adipogenesis and suppresses lipolysis. Obesity increases the sensitivity of tech cells to luteinizing hormone stimulation and enhances functional hyperandrogenism of the ovaries, increasing the production of androgens by the ovaries. Excess body weight is associated with a large number of inflammatory adipokines, which, in turn, contribute to the growth of insulin resistance and adipogenesis. Obesity and insulin resistance exacerbate the symptoms of hyperandrogenism, forming a vicious circle that contributes to the development of polycystic ovary syndrome. These data allow us to conclude that bariatric surgery can become an alternative to drugs (metformin, thiazolidinedione analogs of glucagon-like peptide-1), which has shown positive results in the treatment of patients with polycystic ovary syndrome and obesity.

Androgen signaling in adipose tissue, but less likely skeletal muscle, mediates development of metabolic traits in a PCOS mouse model

Polycystic ovary syndrome (PCOS) is a common, multifactorial disorder characterized by endocrine, reproductive, and metabolic dysfunction. As the etiology of PCOS is unknown, there is no cure and symptom-oriented treatments are suboptimal. Hyperandrogenism is a key diagnostic trait, and evidence suggests that androgen receptor (AR)-mediated actions are critical to PCOS pathogenesis. However, the key AR target sites involved remain to be fully defined. Adipocyte and muscle dysfunction are proposed as important sites involved in the manifestation of PCOS traits. We investigated the role of AR signaling in white adipose tissue (WAT), brown adipose tissue (BAT), and skeletal muscle in the development of PCOS in a hyperandrogenic PCOS mouse model. As expected, dihydrotestosterone (DHT) exposure induced key reproductive and metabolic PCOS traits in wild-type (WT) females. Transplantation of AR-insensitive (AR^-/-) WAT or BAT from AR knockout females (ARKO) into DHT-treated WT mice ameliorated some metabolic PCOS features, including increased body weight, adiposity, and adipocyte hypertrophy, but not reproductive PCOS traits. In contrast, DHT-treated ARKO female mice transplanted with AR-responsive (AR^+/+) WAT or BAT continued to resist developing PCOS traits. DHT-treated skeletal muscle-specific AR knockout females (SkMARKO) displayed a comparable phenotype with that of DHT-treated WT females, with full development of PCOS traits. Taken together, these findings infer that both WAT and BAT, but less likely skeletal muscle, are key sites of AR-mediated actions involved in the experimental pathogenesis of metabolic PCOS traits. These data further support targeting adipocyte AR-driven pathways in future research aimed at developing novel therapeutic interventions for PCOS.NEW & NOTEWORTHY Hyperandrogenism is a key feature in the pathogenesis of polycystic ovary syndrome (PCOS); however, the tissue sites of androgen receptor (AR) signaling are unclear. In this study, AR signaling in white and brown adipose tissue, but less likely in skeletal muscle, was found to be involved in the development of metabolic PCOS traits, highlighting the importance of androgen actions in adipose tissue and obesity in the manifestation of metabolic disturbances.

Sexual Dimorphism in Adipose-Hypothalamic Crosstalk and the Contribution of Aryl Hydrocarbon Receptor to Regulate Energy Homeostasis

There are fundamental sex differences in the regulation of energy homeostasis. Better understanding of the underlying mechanisms of energy balance that account for this asymmetry will assist in developing sex-specific therapies for sexually dimorphic diseases such as obesity. Multiple organs, including the hypothalamus and adipose tissue, play vital roles in the regulation of energy homeostasis, which are regulated differently in males and females. Various neuronal populations, particularly within the hypothalamus, such as arcuate nucleus (ARC), can sense nutrient content of the body by the help of peripheral hormones such leptin, derived from adipocytes, to regulate energy homeostasis. This review summarizes how adipose tissue crosstalk with homeostatic network control systems in the brain, which includes energy regulatory regions and the hypothalamic–pituitary axis, contribute to energy regulation in a sex-specific manner. Moreover, development of obesity is contingent upon diet and environmental factors. Substances from diet and environmental contaminants can exert insidious effects on energy metabolism, acting peripherally through the aryl hydrocarbon receptor (AhR). Developmental AhR activation can impart permanent alterations of neuronal development that can manifest a number of sex-specific physiological changes, which sometimes become evident only in adulthood. AhR is currently being investigated as a potential target for treating obesity. The consensus is that impaired function of the receptor protects from obesity in mice. AhR also modulates sex steroid receptors, and hence, one of the objectives of this review is to explain why investigating sex differences while examining this receptor is crucial. Overall, this review summarizes sex differences in the regulation of energy homeostasis imparted by the adipose–hypothalamic axis and examines how this axis can be affected by xenobiotics that signal through AhR.

The hypothalamus for whole-body physiology: from metabolism to aging

Obesity and aging are two important epidemic factors for metabolic syndrome and many other health issues, which contribute to devastating diseases such as cardiovascular diseases, stroke and cancers. The brain plays a central role in controlling metabolic physiology in that it integrates information from other metabolic organs, sends regulatory projections and orchestrates the whole-body function. Emerging studies suggest that brain dysfunction in sensing various internal cues or processing external cues may have profound effects on metabolic and other physiological functions. This review highlights brain dysfunction linked to genetic mutations, sex, brain inflammation, microbiota, stress as causes for whole-body pathophysiology, arguing brain dysfunction as a root cause for the epidemic of aging and obesity-related disorders. We also speculate key issues that need to be addressed on how to reveal relevant brain dysfunction that underlines the development of these disorders and diseases in order to develop new treatment strategies against these health problems.

Brown Adipose Tissue and Novel Management Strategies for Polycystic Ovary Syndrome Therapy

Brown adipose tissue (BAT), a unique tissue, plays a key role in metabolism and energy expenditure through adaptive nonshivering thermogenesis. It has recently become a therapeutic target in the treatment of obesity and metabolic diseases. The thermogenic effect of BAT occurs through uncoupling protein-1 by uncoupling adenosine triphosphate (ATP) synthesis from energy substrate oxidation. The review discusses the recent developments and progress associated with the biology, function, and activation of BAT, with a focus on its therapeutic potential for the treatment of polycystic ovary syndrome (PCOS). The endocrine activity of brown adipocytes affects the energy balance and homeostasis of glucose and lipids, thereby affecting the association of BAT activity and the metabolic profile. PCOS is a complex reproductive and metabolic disorder of reproductive-age women. Functional abnormalities of adipose tissue (AT) have been reported in patients with PCOS. Numerous studies have shown that BAT could regulate the features of PCOS and that increases in BAT mass or activity were effective in the treatment of PCOS through approaches including cold stimulation, BAT transplantation and compound activation in various animal models. Therefore, BAT may be used as a novel management strategy for the patients with PCOS to improve women's health clinically. It is highly important to identify key brown adipokines for the discovery and development of novel candidates to establish an efficacious therapeutic strategy for patients with PCOS in the future.

Heart Rate Variability and Cardiovascular Fitness: What We Know so Far

Fluctuation analysis in intervals between heartbeats provides important indices related to autonomic modulation of heart rate variability (HRV). These indices are considered predictors of morbidity and mortality as they are frequently altered in patients with chronic degenerative diseases, especially in those with cardiovascular and metabolic diseases. Similarly, a reduction in HRV is common with aging. In all cases, cardiovascular fitness is often reduced to below the predicted values. In turn, increases in cardiovascular fitness through regular physical exercise, especially aerobic exercise, represent an important therapeutic tool capable of promoting positive adjustments in cardiac autonomic modulation. These adjustments are characterized by reduced sympathetic modulatory influence and/or increased vagal modulatory influence on the heart, increasing the HRV. Therefore, several methodological tools have been used to assess the degree of impairment of autonomic modulation and the therapeutic effects of physical exercise. In contrast, establishment of strict protocols in experimental design is a main challenge in establishing HRV analysis as a robust parameter for evaluating cardiovascular homeostasis. Thus, this review aimed to contribute to the understanding of autonomic modulation of HRV and its relationship with cardiovascular fitness, highlighting the advances made thus far, the applicability of analysis tools, and the confounding factors observed frequently.

Tamoxifen Treatment in the Neonatal Period Affects Glucose Homeostasis in Adult Mice in a Sex-Dependent Manner

Tamoxifen is a selective estrogen receptor modulator used to activate the CREERT2 recombinase, allowing tissue-specific and temporal control of the somatic mutagenesis to generate transgenic mice. Studies integrating development and metabolism require a genetic modification induced by a neonatal tamoxifen administration. Here, we investigate the effects of a neonatal tamoxifen administration on energy homeostasis in adult male and female C57BL/6J mice. C57BL/6J male and female mouse pups received a single injection of tamoxifen 1 day after birth (NTT) and were fed a high-fat/high-sucrose diet at 6 weeks of age. We measured weight, body composition, glucose and insulin tolerance, basal metabolism, and tibia length and weight in adult mice. The neonatal tamoxifen administration exerted long-term, sex-dependent effects on energy homeostasis. NTT female mice became overweight and developed impaired glucose control in comparison to vehicle-treated littermates. NTT females exhibited 60% increased fat mass, increased food intake, decreased physical activity and energy expenditure, impaired glucose and insulin tolerance, and fasting hyperglycemia and hyperinsulinemia. In contrast, NTT male mice exhibited a modest amelioration of glucose and insulin tolerance and long-term decreased lean mass linked to decreased bone weight. These results suggest that the neonatal tamoxifen administration exerted a marked and sex-dependent influence on adult energy homeostasis and bone weight and must therefore be used with caution for the development of transgenic mouse models regarding studies on energy homeostasis and bone biology.

Developmental programming of offspring adipose tissue biology and obesity risk

Obesity is reaching epidemic proportions and imposes major negative health crises and an economic burden in both high and low income countries. The multifaceted nature of obesity represents a major health challenge, with obesity affecting a variety of different organs and increases the risk of many other noncommunicable diseases, such as type 2 diabetes, fatty liver disease, dementia, cardiovascular diseases, and even cancer. The defining organ of obesity is the adipose tissue, highlighting the need to more comprehensively understand the development and biology of this tissue to understand the pathogenesis of obesity. Adipose tissue is a miscellaneous and highly plastic endocrine organ. It comes in many different sizes and shades and is distributed throughout many different locations in the body. Though its development begins prenatally, quite uniquely, it has the capacity for unlimited growth throughout adulthood. Adipose tissue is also a highly sexually dimorphic tissue, patterning men and women in different ways, which means the risks associated with obesity are also sexually dimorphic. Recent studies show that environmental factors during prenatal and early stages of postnatal development have the capacity to programme the structure and function of adipose tissue, with implications for the development of obesity. This review summarizes the evidence for a role for early environmental factors, such as maternal malnutrition, hypoxia, and exposure to excess hormones and endocrine disruptors during gestation in the programming of adipose tissue and obesity in the offspring. We will also discuss the complexity of studying adipose tissue biology and the importance of appreciating nuances in adipose tissue, such as sexual dimorphism and divergent responses to metabolic and endocrine stimuli. Given the rising levels of obesity worldwide, understanding how environmental conditions in early life affects adipose tissue phenotype and the subsequent development of obesity is of absolute importance.

Developmental exposure to DDT or DDE alters sympathetic innervation of brown adipose in adult female mice

BACKGROUND

Exposure to the bioaccumulative pesticide dichlorodiphenyltrichloroethane (DDT) and its metabolite dichlorodiphenyldichloroethylene (DDE) has been associated with increased risk of insulin resistance and obesity in humans and experimental animals. These effects appear to be mediated by reduced brown adipose tissue (BAT) thermogenesis, which is regulated by the sympathetic nervous system. Although the neurotoxicity of DDT is well-established, whether DDT alters sympathetic innervation of BAT is unknown. We hypothesized that perinatal exposure to DDT or DDE promotes thermogenic dysfunction by interfering with sympathetic regulation of BAT thermogenesis.

METHODS

Pregnant C57BL/6 J mice were administered environmentally relevant concentrations of DDTs (p,p'-DDT and o,p'-DDT) or DDE (p,p'-DDE), 1.7 mg/kg and 1.31 mg/kg, respectively, from gestational day 11.5 to postnatal day 5 by oral gavage, and longitudinal body temperature was recorded in male and female offspring. At 4 months of age, metabolic parameters were measured in female offspring via indirect calorimetry with or without the β3 adrenergic receptor agonist, CL 316,243. Immunohistochemical and neurochemical analyses of sympathetic neurons innervating BAT were evaluated.

RESULTS

We observed persistent thermogenic impairment in adult female, but not male, mice perinatally exposed to DDTs or p,p'-DDE. Perinatal DDTs exposure significantly impaired metabolism in adult female mice, an effect rescued by treatment with CL 316,243 immediately prior to calorimetry experiments. Neither DDTs nor p,p'-DDE significantly altered BAT morphology or the concentrations of norepinephrine and its metabolite DHPG in the BAT of DDTs-exposed mice. However, quantitative immunohistochemistry revealed a 20% decrease in sympathetic axons innervating BAT in adult female mice perinatally exposed to DDTs, but not p,p'-DDE, and 48 and 43% fewer synapses in stellate ganglia of mice exposed to either DDTs or p,p'-DDE, respectively, compared to control.

CONCLUSIONS

These data demonstrate that perinatal exposure to DDTs or p,p'-DDE impairs thermogenesis by interfering with patterns of connectivity in sympathetic circuits that regulate BAT.

Sex- and Gender-Based Pharmacological Response to Drugs

In humans, the combination of all sex-specific genetic, epigenetic, and hormonal influences of biologic sex produces different in vivo environments for male and female cells. We dissect how these influences of sex modify the pharmacokinetics and pharmacodynamics of multiple drugs and provide examples for common drugs acting on specific organ systems. We also discuss how gender of physicians and patients may influence the therapeutic response to drugs. We aim to highlight sex as a genetic modifier of the pharmacological response to drugs, which should be considered as a necessary step toward precision medicine that will benefit men and women. SIGNIFICANCE STATEMENT: This study discusses the influences of biologic sex on the pharmacokinetics and pharmacodynamics of drugs and provides examples for common drugs acting on specific organ systems. This study also discusses how gender of physicians and patients influence the therapeutic response to drugs.

Deletion of Orphan G Protein-Coupled Receptor GPR37L1 in Mice Alters Cardiovascular Homeostasis in a Sex-Specific Manner

GPR37L1 is a family A orphan G protein-coupled receptor (GPCR) with a putative role in blood pressure regulation and cardioprotection. In mice, genetic ablation of Gpr37l1 causes sex-dependent effects; female mice lacking Gpr37l1 (GPR37L1^-/-) have a modest but significant elevation in blood pressure, while male GPR37L1^-/- mice are more susceptible to cardiovascular dysfunction following angiotensin II-induced hypertension. Given that this receptor is highly expressed in the brain, we hypothesize that the cardiovascular phenotype of GPR37L1^-/- mice is due to changes in autonomic regulation of blood pressure and heart rate. To investigate this, radiotelemetry was employed to characterize baseline cardiovascular variables in GPR37L1^-/- mice of both sexes compared to wildtype controls, followed by power spectral analysis to quantify short-term fluctuations in blood pressure and heart rate attributable to alterations in autonomic homeostatic mechanisms. Additionally, pharmacological ganglionic blockade was performed to determine vasomotor tone, and environmental stress tests were used to assess whether cardiovascular reactivity was altered in GPR37L1^-/- mice. We observed that mean arterial pressure was significantly lower in female GPR37L1^-/- mice compared to wildtype counterparts, but was unchanged in male GPR37L1^-/- mice. GPR37L1^-/- genotype had a statistically significant positive chronotropic effect on heart rate across both sexes when analyzed by two-way ANOVA. Power spectral analysis of these data revealed a reduction in power in the heart rate spectrum between 0.5 and 3 Hz in female GPR37L1^-/- mice during the diurnal active period, which indicates that GPR37L1^-/- mice may have impaired cardiac vagal drive. GPR37L1^-/- mice of both sexes also exhibited attenuated depressor responses to ganglionic blockade with pentolinium, indicating that GPR37L1 is involved in maintaining sympathetic vasomotor tone. Interestingly, when these mice were subjected to aversive and appetitive behavioral stressors, the female GPR37L1^-/- mice exhibited an attenuation of cardiovascular reactivity to aversive, but not appetitive, environmental stimuli. Together, these results suggest that loss of GPR37L1 affects autonomic maintenance of blood pressure, giving rise to sex-specific cardiovascular changes in GPR37L1^-/- mice.

White, brown, and bone marrow adipose tissue behavior in DHEA-induced PCOS mice

METHODS

Thirty-one female C57BL/6J mice were divided into four groups: two were treated with subcutaneous dehydroepiandrosterone (DHEA) implants and divided into normal and hypercaloric diet (HFD). Two were control and divided into normal and HFD. Presence of insulin resistance, growth, and adipocyte markers expression of white and brown adipose tissues and growth and inflammatory cytokines expression of bone marrow adipose tissue were evaluated.

RESULTS

Hypercaloric diet groups presented higher total weight gain and huge growth in all fat sites, except bone marrow. They also demonstrated greater expression of adipocyte markers in sites of white adipose tissue. DHEA + HFD group showed more insulin intolerance than all other groups. DHEA shows to abrogate AdipoQ expression in all fatty tissues.

CONCLUSIONS

DHEA alone does not influence adipose tissue growth, but contributes to increased insulin resistance and influences the expression of adipokines. Proximal MAT showed different behavior from the other fat depot.

Sex-Bias in Irritable Bowel Syndrome: Linking Steroids to the Gut-Brain Axis

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder that is more common in females. Despite its high global incidence, the disease mechanism is still unclear and therapeutic options remain limited. The sexual dimorphism in IBS incidence suggests that sex steroids play a role in disease onset and symptoms severity. This review considers sex steroids and their involvement in IBS symptoms and the underlying disease mechanisms. Estrogens and androgens play important regulatory roles in IBS symptomology, including visceral sensitivity, gut motility and psychological conditions, possibly through modulating the gut-brain axis. Steroids are regulators of hypothalamic-pituitary-adrenal activity and autonomic nervous system function. They also modulate gut microbiota and enteric nervous systems, impacting serotonin and mast cell signaling. Sex steroids also facilitate bidirectional cross-talk between the microbiota and host following bacterial transformation and recycling of steroids by the intestine. The sex-specific interplay between sex steroids and the host provides neuroendocrinology insight into the pathophysiology, epigenetics and treatment of IBS patients.

Increased Skeletal Muscle Fiber Cross-Sectional Area, Muscle Phenotype Shift, and Altered Insulin Signaling in Rat Hindlimb Muscles in a Prenatally Androgenized Rat Model for Polycystic Ovary Syndrome

Women with polycystic ovary syndrome (PCOS) are reported to have greater lean mass and insulin resistance. To examine muscular changes in a prenatally androgenized (PNA) rat model for PCOS, Sprague-Dawley rats were exposed to 5 mg testosterone or vehicle daily on gestational days 16-19. At 15 weeks of age, endurance on a rota-rod treadmill was measured. At 16 weeks of age, fasting blood glucose and insulin, hindlimb skeletal muscle mass, muscle fiber cross-sectional area (CSA) and composition, and intra- and peri-muscular lipid droplets were examined. Expression of mitochondrial marker ATP synthase and insulin signaling proteins were also investigated. Compared with controls, PNA female rats demonstrated greater total body and hindlimb muscle weights, greater muscle fiber CSA, and trending reduced time on the rota-rod. An increase in fibers co-expressing the slow and fast isoforms of myosin (90 vs. 86%, p < 0.05) and greater expression of ATP synthase (6-fold, p < 0.005) were observed in the gastrocnemius (GN) muscle. More lipid content was observed in GN and tibialis anterior (TA) muscles. PNA rats had elevated fasting serum insulin (1.9 vs. 1.2 ng/mL, p < 0.005) but comparable fasting glucose. Expression of total and Ser^636/9-phosphorylated IRS1 were altered in PNA rat hindlimb muscles. Together, skeletal muscle alterations in hindlimb muscles of a PNA rat model for PCOS may represent consequences of, or adaptations to, insulin resistance in this model.

Androstenedione changes steroidogenic activity of SGBS cells

The rapid increase of obesity during the last decades and its future prospects are alarming. Besides the general discussed causes of obesity, the 'Developmental Origins of Health and Disease' (DOHaD) hypothesis received more attention in recent years. This hypothesis postulates an adverse influence during early development that programs the unborn child for metabolic dysfunctions later in life. Childhood obesity - an as much increasing problem - can be predisposed by maternal overweight and diabetes. Both, obesity and hyperinsulinemia are major causes of female hyperandrogenemia. As predicted by the DOHaD hypothesis and shown in animal models, developmental androgen excess can lead to metabolic abnormalities in offspring. In this study, we investigated, if androgen exposure adversely affects the adipogenic differentiation of preadipocytes and the endocrine function of adult adipocytes. The human SGBS preadipocyte model was used to affirm the de novo biosynthesis of steroid hormones under normal adipogenesis conditions. Normal adipogenesis was paralleled by an increase of corticosteroids and androgens, whereas estrogen remained at a steady level. Treatment with androstenedione had no effect on SGBS proliferation and differentiation, but adult adipocytes exhibited a significant higher accumulation of triglycerides. Progesterone (up to 2-fold), testosterone (up to 38-fold) and cortisone (up to 1.4-fold) - but not cortisol - were elevated by androstenedione administration in adult adipocytes. Estrogen was not altered. Data suggest that androgen does not negatively influence adipogenic differentiation, but steroidogenic function of SGBS adipocytes.

Weekly Osteopathic Manipulative Treatment to Improve Measures of Sympathetic Tone in Women With Polycystic Ovary Syndrome: A Randomized, Controlled Pilot Study

Background

Polycystic ovary syndrome (PCOS), a common hormone disorder affecting reproductive and metabolic health of reproductive-age women, was shown in a previous study from these authors to be associated with increased sympathetic tone. Increased sympathetic tone contributes to long-term health risks for cardiovascular disease and promotes PCOS pathogenesis.

Objective

To determine whether weekly osteopathic manipulative treatment (OMT) improves physiologic measures of sympathetic tone in women with PCOS.

Methods

In the second phase of a larger study from this author group, 25 women with PCOS, aged 22 to 43 years, living in Erie, Pennsylvania, were recruited to participate in a randomized, controlled evaluation of OMT intervention. Participants were randomly assigned to either an OMT intervention or control group. The OMT group received weekly manipulation of Chapman points and rib-raising for viscerosomatic reflexes associated with the ovaries, adrenal glands, and heart for 12 consecutive weeks. Physiologic measures of sympathetic tone were collected, along with metabolic, endocrine, and reproductive measurements, both before the 3-month intervention and within 1 week of completing the intervention. Measurements included heart rate and blood pressure at rest and after 15 minutes of aerobic exercise, heart rate recovery after exercise, resting heart rate variability, serum androgen levels, body mass index, fasting blood glucose and insulin levels, and menstrual cycle length.

Results

Nineteen women completed the study. Comparing pre- and postintervention parameters, women with PCOS in the OMT intervention group experienced an improvement in postexercise systolic blood pressure (135.8 vs 129.1 mm Hg) and a trend toward heart rate recovery (23.2 vs 29.4 seconds). No significant improvements were found in the control group or in any other physiologic parameters measured. No significant improvements were found in the endocrine, metabolic, or reproductive parameters measured, although free testosterone was slightly lower after 3 months of weekly OMT (5.69 vs 4.64 pg/mL).

Conclusion

Improvements in sympathetic tone after OMT suggest that weekly manipulation of Chapman points and viscerosomatic reflexes can be a useful adjunctive therapeutic option for women with PCOS. (ClinicalTrials.gov No. NCT03383484).

CMKLR1 deficiency attenuates androgen-induced lipid accumulation in mice

Excess androgen-induced obesity has become a public health problem, and its prevalence has increased substantially in recent years. Chemokine-like receptor 1 (CMKLR1), a receptor of chemerin secreted by adipose tissue, is linked to adipocyte differentiation, adipose tissue development, and obesity. However, the effect of CMKLR1 signaling on androgen-mediated adiposity in vivo remains unclear. Using CMKLR1-knockout mice, we constructed an androgen-excess female mouse model through 5α-dihydrotestosterone (DHT) treatment and an androgen-deficient male mouse model by orchidectomy (ORX). For mechanism investigation, we used 2-(α-Naphthoyl) ethyltrimethylammonium iodide (α-NETA), an antagonist of CMKLR1, to suppress CMKLR1 in vivo and wortmannin, a PI3K signaling antagonist, to treat brown adipose tissue (BAT) explant cultures in vitro. Furthermore, we used histological examination and quantitative PCR, as well as Western blot analysis, glucose tolerance tests, and biochemical analysis of serum, to describe the phenotypes and the changes in gene expression. We demonstrated that excess androgen in the female mice resulted in larger cells in the white adipose tissue (WAT) and the BAT, whereas androgen deprivation in the male mice induced a reduction in cell size. Both of these adipocyte size effects could be attenuated in the CMKLR1-knockout mice. CMKLR1 deficiency influenced the effect of androgen treatment on adipose tissue by regulating the mRNA expression of the androgen receptor (AR) and adipocyte markers (such as Fabp4 and Cidea). Moreover, suppression of CMKLR1 by α-NETA could also reduce the extent of the adipocyte cell enlargement caused by DHT. Furthermore, we found that DHT could reduce the levels of phosphorylated ERK (pERK) in the BAT, while CMKLR1 inactivation inhibited this effect, which had been induced by DHT, through the PI3K signaling pathway. These findings reveal an antiobesity role of CMKLR1 deficiency in regulating lipid accumulation, highlighting the scientific importance for the further development of small-molecule CMKLR1 antagonists as fundamental research tools and/or as potential drugs for use in the treatment of adiposity.

Metabolic dysfunction in polycystic ovary syndrome: Pathogenic role of androgen excess and potential therapeutic strategies

Background

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy among reproductive age women. Although its cardinal manifestations include hyperandrogenism, oligo/anovulation, and/or polycystic ovarian morphology, PCOS women often display also notable metabolic comorbidities. An array of pathogenic mechanisms have been implicated in the etiology of this heterogeneous endocrine disorder; hyperandrogenism at various developmental periods is proposed as a major driver of the metabolic and reproductive perturbations associated with PCOS. However, the current understanding of the pathophysiology of PCOS-associated metabolic disease is incomplete, and therapeutic strategies used to manage this syndrome's metabolic complications remain limited.

Scope of review

This study is a systematic review of the potential etiopathogenic mechanisms of metabolic dysfunction frequently associated with PCOS, with special emphasis on the metabolic impact of androgen excess on different metabolic tissues and the brain. We also briefly summarize the therapeutic approaches currently available to manage metabolic perturbations linked to PCOS, highlighting current weaknesses and future directions.

Major conclusions

Androgen excess plays a prominent role in the development of metabolic disturbances associated with PCOS, with a discernible impact on key peripheral metabolic tissues, including the adipose, liver, pancreas, and muscle, and very prominently the brain, contributing to the constellation of metabolic complications of PCOS, from obesity to insulin resistance. However, the current understanding of the pathogenic roles of hyperandrogenism in metabolic dysfunction of PCOS and the underlying mechanisms remain largely incomplete. In addition, the development of more efficient, even personalized therapeutic strategies for the metabolic management of PCOS patients persists as an unmet need that will certainly benefit from a better comprehension of the molecular basis of this heterogeneous syndrome.

Synergistic Effects of Hyperandrogenemia and Obesogenic Western-style Diet on Transcription and DNA Methylation in Visceral Adipose Tissue of Nonhuman Primates

Polycystic ovary syndrome (PCOS) is a major reproductive disorder that is responsible for 80% of anovulatory infertility and that is associated with hyperandrogenemia, increased risk of obesity, and white adipose tissue (WAT) dysfunction. We have previously demonstrated that the combination of chronic testosterone (T) treatment and an obesogenic Western-style diet (WSD) exerts synergistic functional effects on WAT, leading to increased lipid accumulation in visceral adipocytes by an unknown mechanism. In this study, we examined the whole-genome transcriptional response in visceral WAT to T and WSD, alone and in combination. We observed a synergistic effect of T and WSD on gene expression, resulting in upregulation of lipid storage genes concomitant with adipocyte hypertrophy. Because DNA methylation is known to be associated with body fat distribution and the etiology of PCOS, we conducted whole-genome DNA methylation analysis of visceral WAT. While only a fraction of differentially expressed genes also exhibited differential DNA methylation, in silico analysis showed that differentially methylated regions were enriched in transcription factor binding motifs, suggesting a potential gene regulatory role for these regions. In summary, this study demonstrates that hyperandrogenemia alone does not induce global transcriptional and epigenetic response in young female macaques unless combined with an obesogenic diet.

Correlation Between Physiologic and Osteopathic Measures of Sympathetic Activity in Women With Polycystic Ovary Syndrome

Background

Polycystic ovary syndrome (PCOS) is a common hormone disorder that affects the reproductive, metabolic, and psychological health of reproductive-aged females, with a number of long-term health risks, including type 2 diabetes mellitus and cardiovascular sequelae. Sympathetic hyperactivity in affected persons may be involved in the pathogenesis of the disorder.

Objective

To determine whether physiologic and osteopathic measures of increased sympathetic tone correlate in a population of women with PCOS.

Methods

For this descriptive observational study, women with PCOS between the ages of 20 and 44 years were recruited. Physiologic measures of sympathetic tone (resting heart rate and blood pressure, resting heart rate variability, and postexercise heart rate recovery and blood pressure) were compared with osteopathic measures of sympathetic tone (Chapman points and viscerosomatic reflexes) for the heart, adrenal glands, and ovaries.

Results

Twenty-four women participated in the study. Overall, the participants exhibited both physiologic and osteopathic signs of increased sympathetic tone compared with reference values. In some participants, the number of osteopathic findings were greater than the number of physiologic findings of increased sympathetic tone.

Conclusions

Women with PCOS exhibit increased sympathetic tone by physiologic and osteopathic measures, indicating the utility of assessing sympathetic hyperactivity in these patients by osteopathic methods. Osteopathic structural examination is a valuable diagnostic tool that may allow detection of sympathetic hyperactivity in women with PCOS even before physiologic symptoms manifest. The osteopathic indicators of increased sympathetic tone may represent potential therapeutic targets to improve health in this population. (ClinicalTrials.gov NCT03383484).

The blood pressure variability and baroreflex sensitivity in healthy participants are not determined by sex or cardiorespiratory fitness

BACKGROUND

Heart rate (HR) and blood pressure (BP) autonomic modulation and baroreflex sensitivity (BRS) are important indexes of cardiovascular homeostasis. However, methodological errors are often observed, such as joint analysis of men and women. Another important aspect is that we still do not know whether cardiorespiratory fitness influences these autonomic parameters in healthy individuals.

OBJECTIVES

This study aimed to investigate whether sex can affect BRS, autonomic modulation of HR and BP variabilities (HRV and BPV, respectively), as well as the influence of cardiorespiratory fitness on these autonomic parameters.

METHODS

Healthy men and women (N=120) were assigned to groups according to the peak oxygen consumption (VO2 peak) obtained in the cardiorespiratory test: low cardiorespiratory fitness (VO2 peak: 22-38 ml/kg/min), moderate cardiorespiratory fitness (VO2 peak: 38-48 ml/kg/min), and high cardiorespiratory fitness (VO2 peak>48 ml/kg/min). HRV and BPV evaluations were performed for all groups in the frequency domain by spectral analysis. Spontaneous BRS was assessed using the sequence method.

RESULTS

Women presented lower BP values compared with men. HR did not differ between sexes, but showed an inverse relationship with cardiorespiratory performance. The HRV analysis showed greater sympathetic modulation for men and greater vagal modulation for women. Men and women presented similar results for systolic BPV and BRS, and cardiorespiratory performance did not influence any of the autonomic parameters evaluated.

CONCLUSION

Cardiorespiratory fitness does not interfere with HRV and BPV autonomic modulation or BRS. However, the cardiac modulatory balance differs between sexes, with a greater influence of the autonomic vagal component in women and the sympathetic component in men.

Mechanisms for Sex Differences in Energy Homeostasis

Sex differences exist in the regulation of energy homeostasis. Better understanding of the underlying mechanisms for sexual dimorphism in energy balance may facilitate development of gender-specific therapies for human diseases, e.g. obesity. Multiple organs, including the brain, liver, fat and muscle, play important roles in the regulations of feeding behavior, energy expenditure and physical activity, which therefore contribute to the maintenance of energy balance. It has been increasingly appreciated that this multi-organ system is under different regulations in male vs. female animals. Much of effort has been focused on roles of sex hormones (including androgens, estrogens and progesterone) and sex chromosomes in this sex-specific regulation of energy balance. Emerging evidence also indicates that other factors (not sex hormones/receptors and not encoded by the sex chromosomes) exist to regulate energy homeostasis differentially in males vs. females. In this review, we summarize factors and signals that have been shown to regulate energy homeostasis in a sexually dimorphic fashion and propose a framework where these factors and signals may be integrated to mediate sex differences in energy homeostasis.

How to choose the suitable animal model of polycystic ovary syndrome?

Polycystic ovary syndrome (PCOS) is a gynecological metabolic and endocrine disorder with uncertain etiology. To understand the etiology of PCOS or the evaluation of various therapeutic agents, different animal models have been introduced. Considering this fact that is difficult to develop an animal model that mimics all aspects of this syndrome, but, similarity of biological, anatomical, and/or biochemical features of animal model to the human PCOS phenotypes can increase its application. This review paper evaluates the recently researched animal models and introduced the best models for different research purposes in PCOS studies. During January 2013 to January 2017, 162 studies were identified which applied various kinds of animal models of PCOS including rodent, primate, ruminant and fish. Between these models, prenatal and pre-pubertal androgen rat models and then prenatal androgen mouse model have been studied in detail than others. The comparison of main features of these models with women PCOS demonstrates higher similarity of these three models to human conditions. Thereafter, letrozole models can be recommended for the investigation of various aspects of PCOS. Interestingly, similarity of PCOS features of post-pubertal insulin and human chorionic gonadotropin rat models with women PCOS were considerable which can make it as a good choice for future investigations.

Prenatal androgen exposure causes hypertension and gut microbiota dysbiosis

BACKGROUND

Conditions of excess androgen in women, such as polycystic ovary syndrome (PCOS), often exhibit intergenerational transmission. One way in which the risk for PCOS may be increased in daughters of affected women is through exposure to elevated androgens in utero. Hyperandrogenemic conditions have serious health consequences, including increased risk for hypertension and cardiovascular disease. Recently, gut dysbiosis has been found to induce hypertension in rats, such that blood pressure can be normalized through fecal microbial transplant. Therefore, we hypothesized that the hypertension seen in PCOS has early origins in gut dysbiosis caused by in utero exposure to excess androgen. We investigated this hypothesis with a model of prenatal androgen (PNA) exposure and maternal hyperandrogenemia by single-injection of testosterone cypionate or sesame oil vehicle (VEH) to pregnant dams in late gestation. We then completed a gut microbiota and cardiometabolic profile of the adult female offspring.

RESULTS

The metabolic assessment revealed that adult PNA rats had increased body weight and increased mRNA expression of adipokines: adipocyte binding protein 2, adiponectin, and leptin in inguinal white adipose tissue. Radiotelemetry analysis revealed hypertension with decreased heart rate in PNA animals. The fecal microbiota profile of PNA animals contained higher relative abundance of bacteria associated with steroid hormone synthesis, Nocardiaceae and Clostridiaceae, and lower abundance of Akkermansia, Bacteroides, Lactobacillus, Clostridium. The PNA animals also had an increased relative abundance of bacteria associated with biosynthesis and elongation of unsaturated short chain fatty acids (SCFAs).

CONCLUSIONS

We found that prenatal exposure to excess androgen negatively impacted cardiovascular function by increasing systolic and diastolic blood pressure and decreasing heart rate. Prenatal androgen was also associated with gut microbial dysbiosis and altered abundance of bacteria involved in metabolite production of short chain fatty acids. These results suggest that early-life exposure to hyperandrogenemia in daughters of women with PCOS may lead to long-term alterations in gut microbiota and cardiometabolic function.

Combined androgen excess and Western-style diet accelerates adipose tissue dysfunction in young adult, female nonhuman primates

STUDY QUESTION

What are the separate and combined effects of mild hyperandrogenemia and consumption of a high-fat Western-style diet (WSD) on white adipose tissue (WAT) morphology and function in young adult female nonhuman primates?

SUMMARY ANSWER

Combined exposure to mild hyperandrogenemia and WSD induces visceral omental (OM-WAT) but not subcutaneous (SC-WAT) adipocyte hypertrophy that is associated with increased uptake and reduced mobilization of free fatty acids.

WHAT IS KNOWN ALREADY

Mild hyperandrogenemia in females, principally in the context of polycystic ovary syndrome, is often associated with adipocyte hypertrophy, but the mechanisms of associated WAT dysfunction and depot specificity remain poorly understood.

STUDY DESIGN, SIZE AND DURATION

Female rhesus macaques were randomly assigned at 2.5 years of age (near menarche) to receive either cholesterol (C; n = 20) or testosterone (T; n = 20)-containing silastic implants to elevate T levels 5-fold above baseline. Half of each of these groups was then fed either a low-fat monkey chow diet or WSD, resulting in four treatment groups (C, control diet; T alone; WSD alone; T + WSD; n = 10/group) that were maintained until the current analyses were performed at 5.5 years of age (3 years of treatment, young adults).

PARTICIPANTS/MATERIALS, SETTING AND METHODS

OM and SC-WAT biopsies were collected and analyzed longitudinally for in vivo changes in adipocyte area and blood vessel density, and ex vivo basal and insulin-stimulated fatty acid uptake and basal and isoproterenol-stimulated lipolysis.

MAIN RESULTS AND THE ROLE OF CHANCE

In years 2 and 3 of treatment, the T + WSD group exhibited a significantly greater increase in OM adipocyte size compared to all other groups (P < 0.05), while the size of SC adipocytes measured at the end of the study was not significantly different between groups. In year 3, both WAT depots from the WSD and T + WSD groups displayed a significant reduction in local capillary length and vessel junction density (P < 0.05). In year 3, insulin-stimulated fatty acid uptake in OM-WAT was increased in the T + WSD group compared to year 2 (P < 0.05). In year 3, basal lipolysis was blunted in the T and T + WSD groups in both WAT depots (P < 0.01), while isoproterenol-stimulated lipolysis was significantly blunted in the T and T + WSD groups only in SC-WAT (P < 0.01).

LIMITATIONS, REASONS FOR CAUTION

At this stage of the study, subjects were still relatively young adults, so that the effects of mild hyperandrogenemia and WSD may become more apparent with increasing age.

WIDER IMPLICATIONS OF THE FINDINGS

The combination of mild hyperandrogenemia and WSD accelerates the development of WAT dysfunction through T-specific (suppression of lipolytic response by T), WSD-dependent (reduced capillary density) and combined T + WSD (increased fatty acid uptake) mechanisms. These data support the idea that combined hyperandrogenemia and WSD increases the risk of developing obesity in females.

STUDY FUNDING/COMPETING INTEREST(S)

Research reported in this publication was supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health under award number P50 HD071836 to C.T.R. and award number OD 011092 from the Office of the Director, National Institutes of Health, for operation of the Oregon National Primate Research Center. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Elevated androstenedione in young adult but not early adolescent prenatally androgenized female rats

Background

Elevated testosterone (T) is routinely reported as a marker of hyperandrogenemia in rodent models for polycystic ovary syndrome (PCOS). In women with PCOS, elevated serum androstenedione (A4) is associated with more severe phenotypes, including a positive correlation with serum T, DHEAS, free androgen index (FAI), LH, and LH/FSH ratio. Furthermore, A4, along with calculated free T and FAI, was identified as one of the best predictors of PCOS in adult women of all ages (18 to > 50 y).

Objective

The objective of this study was to investigate serum A4 levels in early adolescent and young adult prenatally androgenized (PNA) female rats, a model for PCOS.

Methods

Pregnant rats were injected with 5 mg T daily during gestational days 16–19 (PNA rats, experimental group) or an equal volume of vehicle (control group). Female offspring of both groups had tail vein blood drawn for serum analysis at 8 and 16 weeks of age. ELISAs were used to quantify serum A4 and T levels.

Results

Serum A4 and T were elevated in 16-week-old PNA rats compared to controls. There was no significant difference in either hormone at 8 weeks of age.

Conclusions

The PNA rats demonstrated elevated serum A4 and T in young adulthood, as has been observed in women with PCOS, further validating this as a model for PCOS and underscoring the importance of serum A4 elevation as a parameter inherent to PCOS and a rodent model for the disorder. Significant A4 elevation develops between early adolescence and early adulthood in this PNA rat model.

The impact of androgen actions in neurons on metabolic health and disease

The male hormone testosterone exerts different effects on glucose and energy homeostasis in males and females. Testosterone deficiency predisposes males to visceral obesity, insulin resistance and type 2 diabetes. However, testosterone excess predisposes females to similar metabolic dysfunction. Here, we review the effects of testosterone actions in the central nervous system on metabolic function in males and females. In particular, we highlight changes within the hypothalamus that control glucose and energy homeostasis. We distinguish the organizational effects of testosterone in the programming of neural circuitry during development from the activational effects of testosterone during adulthood. Finally, we explore potential sites where androgen might be acting to impact metabolism within the central nervous system.

Acupuncture does not ameliorate metabolic disturbances in the P450 aromatase inhibitor-induced rat model of polycystic ovary syndrome

NEW FINDINGS

What is the central question of this study? The effectiveness of low-frequency electroacupuncture in the treatment of metabolic disorders associated with polycystic ovary syndrome (PCOS), an endocrine-metabolic disorder characterized by an imbalance in sex steroid production, is controversial. What is the main finding and its importance? In a rat model of PCOS induced by the inhibition of P450 aromatase, low-frequency electroacupuncture increased low-density lipoprotein-cholesterol but did not improve the insulin resistance or the adipose tissue dysfunction, suggesting that a balance of sex steroids is needed to restore the metabolic function in this rat model of PCOS. Low-frequency electroacupuncture restores sex steroid synthesis and sympathetic activity in women with polycystic ovary syndrome, which may ameliorate its metabolic disturbances, probably by modulating sympathetic nerve activity or sex steroid synthesis. We investigated whether low-frequency electroacupuncture regulates the metabolic function to the same extent as treatment with estradiol or β-adrenergic blocking in a rat model of polycystic ovary syndrome induced by a P450 aromatase inhibitor (letrozole). Letrozole (200 μg day^-1 ) or placebo pellets were implanted in prepubertal Wistar rats. Six weeks thereafter, rats were treated for 5-6 weeks with the following: low-frequency electroacupuncture (5 days per week); a β-adrenergic blocker (propranolol hydrochloride, 0.1 mg kg^-1 , 5 days per week); or 17β-estradiol (2.0 μg) every fourth day. Body weight development, body composition, locomotor activity, insulin sensitivity, tissue-specific glucose uptake, lipid profile, adipocyte size, serum concentrations of adiponectin and insulin, and gene expression in inguinal fat were measured. All treatments increased circulating levels of low-density lipoprotein-cholesterol. Estradiol treatment restored locomotor activity and increased insulin sensitivity but did not modify the glucose uptake in muscle and fat. An upregulation of genes related to insulin sensitivity and downregulation of genes related to adipogenesis were observed in subcutaneous adipose tissue from rats exposed to letrozole. Only estradiol treatment normalized the expression of these genes. In conclusion, low-frequency electroacupuncture increased low-density lipoprotein-cholesterol without affecting insulin sensitivity or adipose tissue function, which could suggest effects on hepatic lipid regulation, probably mediated by the action of estradiol or the β-adrenergic pathway.

Sex differences in the effects of androgens acting in the central nervous system on metabolism

One of the most sexually dimorphic aspects of metabolic regulation is the bidirectional modulation of glucose and energy homeostasis by testosterone in males and females. Testosterone deficiency predisposes men to metabolic dysfunction, with excess adiposity, insulin resistance, and type 2 diabetes, whereas androgen excess predisposes women to insulin resistance, adiposity, and type 2 diabetes. This review discusses how testosterone acts in the central nervous system, and especially the hypothalamus, to promote metabolic homeostasis or dysfunction in a sexually dimorphic manner. We compare the organizational actions of testosterone, which program the hypothalamic control of metabolic homeostasis during development, and the activational actions of testosterone, which affect metabolic function after puberty. We also discuss how the metabolic effect of testosterone is centrally mediated via the androgen receptor.

Hyperandrogenemia Induced by Letrozole Treatment of Pubertal Female Mice Results in Hyperinsulinemia Prior to Weight Gain and Insulin Resistance

Women with polycystic ovary syndrome (PCOS) diagnosed with hyperandrogenism and ovulatory dysfunction have an increased risk of developing metabolic disorders, including type 2 diabetes and cardiovascular disease. We previously developed a model that uses letrozole to elevate endogenous testosterone levels in female mice. This model has hallmarks of PCOS, including hyperandrogenism, anovulation, and polycystic ovaries, as well as increased abdominal adiposity and glucose intolerance. In the current study, we further characterized the metabolic dysfunction that occurs after letrozole treatment to determine whether this model represents a PCOS-like metabolic phenotype. We focused on whether letrozole treatment results in altered pancreatic or liver function as well as insulin resistance. We also investigated whether hyperinsulinemia occurs secondary to weight gain and insulin resistance in this model or if it can occur independently. Our study demonstrated that letrozole-treated mice developed hyperinsulinemia after 1 week of treatment and without evidence of insulin resistance. After 2 weeks of letrozole treatment, mice became significantly heavier than placebo mice, demonstrating that weight gain was not required to develop hyperinsulinemia. After 5 weeks of letrozole treatment, mice exhibited blunted glucose-stimulated insulin secretion, insulin resistance, and impaired insulin-induced phosphorylation of AKT in skeletal muscle. Moreover, letrozole-treated mice exhibited dyslipidemia after 5 weeks of treatment but no evidence of hepatic disease. Our study demonstrated that the letrozole-induced PCOS mouse model exhibits multiple features of the metabolic dysregulation observed in obese, hyperandrogenic women with PCOS. This model will be useful for mechanistic studies investigating how hyperandrogenemia affects metabolism in females.

A Guide for the Design of Pre-clinical Studies on Sex Differences in Metabolism

In animal models, the physiological systems involved in metabolic homeostasis exhibit a sex difference. Investigators often use male rodents because they show metabolic disease better than females. Thus, females are not used precisely because of an acknowledged sex difference that represents an opportunity to understand novel factors reducing metabolic disease more in one sex than the other. The National Institutes of Health (NIH) mandate to consider sex as a biological variable in preclinical research places new demands on investigators and peer reviewers who often lack expertise in model systems and experimental paradigms used in the study of sex differences. This Perspective discusses experimental design and interpretation in studies addressing the mechanisms of sex differences in metabolic homeostasis and disease, using animal models and cells. We also highlight current limitations in research tools and attitudes that threaten to delay progress in studies of sex differences in basic animal research.

Brown adipose tissue activation by rutin ameliorates polycystic ovary syndrome in rat

Polycystic ovary syndrome (PCOS) is a complex endocrinopathy that is characterized by anovulation, hyperandrogenism and polycystic ovary. However, there is a lack of effective treatment for PCOS at present because the pathologic cause of PCOS has not been elucidated. Although it has been known that brown adipose tissue transplantation ameliorates PCOS by activating endogenous BAT, BAT transplantation is not applicable in clinic. Therefore, BAT activation with natural compound could be an effective treatment strategy for PCOS patients. Here, we found that 3 weeks of rutin (a novel compound for BAT activation) treatment increased BAT activation, thereby it improved thermogenesis and systemic insulin sensitivity in dehydroepiandrosterone (DHEA)-induced PCOS rat. In addition, the expression levels of ovarian steroidogenic enzymes such as P450C17, aromatase, 3β-HSD, 17β-HSD and STAR were up-regulated in rutin-treated PCOS rat. Furthermore, acyclicity and the serum level of luteinizing hormone were normalized, and a large number of mature ovulated follicle with a reduction of cystic formation were observed in PCOS rat after rutin treatment. Finally, rutin treatment surprisingly improved fertility and birth defect in PCOS rat. Collectively, our results indicate that rutin treatment significantly improves systemic insulin resistance and ovarian malfunction in PCOS, and our findings in this study provide a novel therapeutic option for the treatment of PCOS by activating BAT with rutin.

The role of stress in PCOS

Polycystic ovary syndrome (PCOS) is a complex endocrinopathy affecting a remarkable proportion of premenopausal women. Different studies have shown that stress is widely encountered in women with PCOS. Areas covered: As PCOS is a multifaceted disorder, 'stress' incorporates different translations. We performed a literature review, focusing on the most recent data, regarding the multipotent role of stress in the syndrome. Expert commentary: Stress is believed to be an important component of PCOS. It encompasses different definitions that are all equivalent, like metabolic, inflammatory, oxidative and emotional stress. However, the type of stress that distinguishes PCOS is metabolic stress. It becomes evident early in life and constitutes the pathophysiological heart of the syndrome. Metabolic stress along with the other types of stress are the progenitors of severe long-term health implications, which exacerbate further the reproductive, metabolic and psychological derangements of the syndrome, leading to an endless cycle of chronic illness.

Polycystic Ovary Syndrome Presents Higher Sympathetic Cardiac Autonomic Modulation that is not altered by Strength Training

Polycystic ovary syndrome (PCOS) may present important comorbidities, such as cardiovascular and metabolic diseases, which are often preceded by changes in cardiac autonomic modulation. Different types of physical exercises are frequently indicated for the prevention and treatment of PCOS. However, little is known about the effects of strength training on the metabolic, hormonal, and cardiac autonomic parameters. Therefore, our aim was to investigate the effects of strength training on the autonomic modulation of heart rate variability (HRV) and its relation to endocrine-metabolic parameters in women with PCOS. Fifty-three women were divided into two groups: CONTROL (n=26) and PCOS (n=27). The strength training lasted 4 months, which was divided into mesocycles of 4 weeks each. The training load started with 70% of one repetition maximum (1RM). Blood samples were collected before and after intervention for analysis of fasting insulin and glucose, HOMA-IR, testosterone, androstenedione and testosterone/androstenedione (T/A) ratio. Spectral analysis of HRV was performed to assess cardiac autonomic modulation indexes. The PCOS group presented higher insulin and testosterone levels, T/A ratio, along with increased sympathetic cardiac autonomic modulation before intervention. The training protocol used did not cause any change of endocrine-metabolic parameters in the CONTROL group. Interestingly, in the PCOS group, reduced testosterone levels and T/A ratio. Additionally, strength training did not have an effect on the spectral parameter values of HRV obtained in both groups. Strength training was not able to alter HRV autonomic modulation in women with PCOS, however may reduce testosterone levels and T/A ratio.

Androgens in polycystic ovary syndrome: lessons from experimental models

PURPOSE OF REVIEW

There is substantial evidence to support a role for androgens acting via the androgen receptor in the development of the pathological disorder, polycystic ovary syndrome (PCOS). PCOS is the most common endocrine condition in women, but its etiology remains unknown. This review focuses on how animal experimental models of PCOS are providing strong evidence to support hyperandrogenism as an important mediator in the development of PCOS characteristics.

RECENT FINDINGS

A variety of animal models for PCOS have now been established by increasing androgen exposure, supporting a role for androgens in the pathogenesis of PCOS. However, some androgens can be aromatized into estrogens leading to confusion on which PCOS traits are primary mediated via androgenic (mediated via the androgen receptor) or estrogenic (mediated via the estrogen receptor) mechanisms. Recent findings from studies comparing the induction of PCOS by aromatizable and nonaromatizable androgens, as well as androgen receptor knockout mouse models have enhanced our understanding of the mechanisms underlying PCOS, and verify that androgen receptor-mediated actions play a key role in the development of PCOS.

SUMMARY

Animal models have provided strong evidence to support that androgen receptor-mediated actions are key mediators in the development of PCOS traits.

Age and sex dependent effects of early overnutrition on metabolic parameters and the role of neonatal androgens

Background

Males and females respond differently to diverse metabolic situations. Being raised in a small litter is reported to cause overnutrition that increases weight gain and predisposes an individual to metabolic disturbances in adulthood; however, existing data are inconsistent. Indeed, significant weight gain and/or metabolic disturbances, such as hyperinsulinemia and hyperleptinemia, are sometimes not encountered. We hypothesized that these inconsistencies could be due to the animal’s sex and/or age at which metabolic parameters are measured.

Methods

To analyze the effects of neonatal overnutrition, male and female Wistar rats were raised in litters of 4 or 12 pups/dam and killed at postnatal days (PND) 10, 21, 30, 50, 85, or 150. In a second study to determine if neonatal sex steroid levels influence sex differences in metabolic parameters, female rats were treated with testosterone on PND1. Effects on weight, length, fat pads, adipokine production, and serum levels of glucose, metabolic hormones, and cytokines were analyzed in both studies.

Results

By PND10, both males and females raised in small litters had increased body weight, body length, adiposity, and serum glucose, insulin, leptin, and adiponectin levels. Females had a greater increase in inguinal fat, and males had higher expression of leptin messenger RNA (mRNA) and serum insulin, as well as increased testosterone levels. Most of the litter size effects diminished or disappeared after weaning and reappeared during adulthood in males, with sex differences in body size and adiposity being apparent postpubertally. Treatment of females with testosterone on PND1 tended to masculinize some metabolic parameters in adulthood such as increased body weight and serum leptin levels.

Conclusions

Our results indicate that (1) both sex and age determine the response to neonatal overnutrition; (2) differences in neonatal sex steroid levels may participate in the development of sex differences in metabolic parameters in adulthood and possibly in the response to neonatal overnutrition; and (3) the comparison of circulating hormone and cytokine levels, even in normal control animals, should take into consideration the early neonatal nutritional environment.

Brown adipose tissue transplantation ameliorates polycystic ovary syndrome

Polycystic ovary syndrome (PCOS), which is characterized by anovulation, hyperandrogenism, and polycystic ovaries, is a complex endocrinopathy. Because the cause of PCOS at the molecular level is largely unknown, there is no cure or specific treatment for PCOS. Here, we show that transplantation of brown adipose tissue (BAT) reversed anovulation, hyperandrogenism, and polycystic ovaries in a dehydroepiandrosterone (DHEA)-induced PCOS rat. BAT transplantation into a PCOS rat significantly stabilized menstrual irregularity and improved systemic insulin sensitivity up to a normal level, which was not shown in a sham-operated or muscle-transplanted PCOS rat. Moreover, BAT transplantation, not sham operation or muscle transplantation, surprisingly improved fertility in PCOS rats. Interestingly, BAT transplantation activated endogenous BAT and thereby increased the circulating level of adiponectin, which plays a prominent role in whole-body energy metabolism and ovarian physiology. Consistent with BAT transplantation, administration of adiponectin protein dramatically rescued DHEA-induced PCOS phenotypes. These results highlight that endogenous BAT activity is closely related to the development of PCOS phenotypes and that BAT activation might be a promising therapeutic option for the treatment of PCOS.

Sex differences in metabolic homeostasis, diabetes, and obesity

There are fundamental aspects of the control of metabolic homeostasis that are regulated differently in males and females. This sex asymmetry represents an evolutionary paradigm for females to resist the loss of energy stores. This perspective discusses the most fundamental sex differences in metabolic homeostasis, diabetes, and obesity. Together, the role of genetic sex, the programming effect of testosterone in the prenatal period in males, and the activational role of sex hormones at puberty produce two different biological systems in males and females that need to be studied separately. These sex-specific differences in energy homeostasis and metabolic dysfunction represent an untested source of factors that can be harnessed to develop relevant sex-based therapeutic avenues for diabetes, metabolic syndrome, and obesity.

Perinatal androgen exposure and adipose tissue programming: is there an impact on body weight fate?

Obesity is a major concern in public health because it is one of the main risk factors for the development of non-transmissible chronic diseases. The fact that there is a clear sex dimorphism in normal body fat distribution points out the role of sex steroids as key factors in the regulation and function of the adipose cell. Androgens affect adipogenesis and fat metabolism in the adipose tissue of males and females. Hormonal disorders during pregnancy may affect the fetal tissues, with long-term implications leading to the development of pathologies during adult life. Obesity and metabolic disease are among these. In this regard, animal models have demonstrated an abnormal fat distribution and modifications in the size and function of adipose cells in the female and male offspring of mothers exposed to androgen excess during pregnancy.

Paracrine and intracrine contributions of androgens and estrogens to adipose tissue biology: physiopathological aspects

In mammals, the male and female hormones androgen and estrogen act as endocrine regulators of energy metabolism. However, adipose tissue is also a site of androgen and estrogen synthesis; androgens convert to estrogens in these tissues, and adipose tissue is also a reservoir of steroids that act locally in a paracrine and intracrine manner. Thus, in adipose tissue, the local output of sex hormones is more complex than would be suggested by routine measurement of serum hormone concentrations. This review integrates studies on the effects of androgens and estrogens in the developmental programming of adipose tissue function in early life and addresses the contributions of local androgen and estrogen metabolism on adipose tissue function in adults.

Neonatal testosterone exposure induces early development of follicular cysts followed by sympathetic ovarian hyperinnervation

This study analysed the temporal association between ovarian cyst development induced by neonatal androgenisation and sympathetic innervation. Neonatal rats (postnatal Days 1 to 5) were treated with testosterone or dihydrotestosterone and the effects were evaluated at postnatal Days 20, 40, 90 or 180. Ovulation rate, number of cystic follicles and density of sympathetic fibres were analysed. The effects of surgical denervation or gonadotrophin stimulation were also assessed. Rats exposed to testosterone showed no oestrous cycle activity and did not ovulate, maintaining a polycystic ovarian morphology at all ages studied. Also, a significant increase in ovarian density of noradrenergic fibres was detected at postnatal Days 90 and 180. Sympathectomy was unable to re-establish ovarian activity; however, human chorionic gonadotrophin stimulation was enough to induce ovulation. The impact of dihydrotestosterone on ovarian function was less noticeable, showing the coexistence of corpora lutea and cystic structures without changes in sympathetic innervation. Our findings suggest that a remodelling of ovarian sympathetic innervation occurs as a response to modifications in the pattern of follicular growth induced by testosterone. A role of sympathetic innervation in the maintenance of the polycystic condition is suggested.

Effects of genistein in combination with conjugated estrogens on endometrial hyperplasia and metabolic dysfunction in ovariectomized mice

Tissue-selective estrogen complex (TSEC), which combines a selective estrogen receptor modulator (SERM) with one or more estrogens, is a novel approach to menopausal therapy. It has been demonstrated that the phytoestrogen genistein (GEN) exhibits mixed estrogen receptor agonist and antagonist activity, suggesting that GEN may have potential for use as a natural SERM. We evaluated, for the first time, the effects of GEN, conjugated estrogens (CE), and their pairing effects as a TSEC treatment on estrogen-induced endometrial hyperplasia and metabolic dysfunction in ovariectomized (OVX) mice fed a high-fat diet. CE replacement prevented fat accumulation in the adipose tissue and liver, improved glucose homeostasis, and induced endometrial hyperplasia in OVX mice. GEN at 100 mg/kg showed CE mimetic effects in preventing ovariectomy-induced metabolic dysfunctions without endometrial stimulation. Combination treatments with CE and GEN prevented metabolic dysfunctions more strongly than CE alone, but at both low and high doses, GEN did not reverse CE-induced endometrial hyperplasia. In addition, we found that in a TSEC regimen, a typical SERM raloxifene maintains the metabolic benefits of CE while simultaneously protecting the endometrium in OVX mice. These findings indicate that GEN acts as an estrogen agonist in metabolic regulation, but has no SERM function in the uteri of OVX mice.