Androgen Deficiency Exacerbates High-Fat Diet-Induced Metabolic Alterations in Male Mice

Metabolic dysfunction-associated steatotic liver disease: A sexually dimorphic disease and breast and gynecological cancer

Metabolic dysfunction-associated steatotic liver disease (MASLD) has become a global public health and economic burden worldwide in the past few decades. Epidemiological studies have shown that MASLD is a multisystem disease that is associated not only with liver-related complications but also with an increased risk of developing extrahepatic cancers. MASLD is a sexually dimorphic disease with sex hormones playing an important role in the development and progression of MASLD, especially by the levels and ratios of circulating estrogens and androgens. MASLD is associated with hormone-sensitive cancers including breast and gynecological cancer. The risk of breast and gynecological cancer is elevated in individuals with MASLD driven by shared metabolic risk factors including obesity and insulin resistance. Multiple potential mechanisms underline these associations including metabolic dysfunction, gut dysbiosis, chronic inflammation and dysregulated release of hepatokines. However, the effect of hormone therapy including hormone replacement therapy and anti-estrogen treatment on MASLD and female-specific cancers remains debatable at this time. This synopsis will review the associations between MASLD and breast and gynecological cancer, their underlying mechanisms, implications of hormonal therapies, and their future directions.

Exercise improves glucose and lipid metabolism in high fat diet feeding male mice through androgen/androgen receptor-mediated metabolism regulatory factors

Exercise alleviates high fat diet (HFD)-induced glycolipid metabolism disorders, but the mechanisms are not discovered totally. Low androgen/androgen receptor (AR) levels are associated with glycolipid metabolism disorders in males, and androgen/AR modulate glycolipid metabolism-related regulators such as peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC1-α), Forkhead box O1 (FoxO1), phosphoenolpyruvate carboxy kinase (PEPCK) and stearyl-coenzyme A desaturase 1 (SCD1). In the present study, we blockaded androgen (by castration) and inhibited or activated AR activity (by AR antagonist flutamide and agonist S4, respectively) to clarify androgen/AR's roles in exercise-induced alleviation of glycolipid metabolism disorders in male high fat diet (HFD) feeding mice and the underlying mechanisms. We found that: (1) exercise reversed HFD-induced glycolipid metabolism disorders, including restoring fasting blood glucose (FBG), glucose tolerance, TC and TG, accompanied with the increases of serum testosterone and AR in muscle and liver. (2) castration exacerbated HFD-induced impairment of glucose tolerance and increases of TC and TG, and abolished the lowering effect of exercise on FBG and TC. Flutamide further impaired glucose tolerance, increased plasm LDL content, and attenuated exercise-induced improvements of FBG and TG content. (3) exercise reduced the levels of FoxO1 and SCD1, increased PGC-1α in muscle and liver of HFD mice; whereas castration and flutamide reversed exercise-induced improvements of these indicators. Furthermore, S4 rectified the levels of FoxO1, PGC-1α and SCD1 in HFD mice even in absence of androgen. In conclusion, androgen/AR, especially AR, play important roles in alleviating glycolipid metabolism disorders in HFD mice at sedentary and exercise states, which might fulfill through FOXO1, PGC-1α and SCD1.

The role of androgens and global and tissue-specific androgen receptor expression on body composition, exercise adaptation, and performance

Gonadal testosterone stimulates skeletal muscle anabolism and contributes to sexually differentiated adipose distribution through incompletely understood mechanisms. Observations in humans and animal models have indicated a major role for androgen receptor (AR) in mediating sex differences in body composition throughout the lifespan. Traditional surgical, genetic and pharmacological studies have tested systemic actions of circulating androgens, and more recent transgenic approaches have allowed for tests of AR gene function in specific androgen responsive niches contributing to body composition, including: skeletal muscle and surrounding interstitial cells, white and brown adipose, as well as trabecular and cortical bone. Less well understood is how these functions of gonadal androgens interact with exercise. Here, we summarize the understood mechanisms of action of AR and its interactions with exercise, specifically on outcomes of body composition and muscle function, and the global- and tissue-specific role of AR in regulating skeletal muscle, adipose, and bone morphology. Additionally, we describe the known effects of androgen and AR manipulation on female body composition, muscle morphology, and sport performance, while highlighting a need for greater inclusion of female subjects in human and animal muscle physiology and endocrinology research.

Histone Deacetylase 9 Deletion Inhibits Hepatic Steatosis and Adipose Tissue Inflammation in Male Diet-Induced Obese Mice

AIM

The goal of this study was to determine the role of histone deacetylase 9 (HDAC9) in the development of diet-induced metabolic dysfunction-associated steatohepatitis (MASH) and white adipose tissue (WAT) dysfunctions.

METHODS

We fed male and female mice with global Hdac9 knockout (KO) and their wild-type (WT) littermates an obesogenic high-fat/high-sucrose/high-cholesterol (35%/34%/2%, w/w) diet for 20 weeks.

RESULTS

Hdac9 deletion markedly inhibited body weight gain and liver steatosis with lower liver weight and triglyceride content than WT in male mice but not females. Consistently, hepatic expression of genes crucial for de novo lipogenesis was markedly suppressed only in male, but not female, Hdac9 KO mice. However, Hdac9 deletion had a minimal effect on hepatic inflammation and fibrosis. In WAT, Hdac9 KO showed less adipocyte hypertrophy, inflammation, and fibrosis in male mice compared with WT. In addition, indirect calorimetry demonstrated that male Hdac9 KO mice had significantly higher metabolic rates, respiratory exchange ratios, and energy expenditure without altering physical activities than WT, which was not observed in female mice.

CONCLUSIONS

Our findings indicate that global deletion of Hdac9 prevented the development of obesity, hepatic steatosis, and WAT inflammation and fibrosis in male mice with diet-induced obesity and MASH, suggesting that a sex-dependent role of HDAC9 may exist in the pathways mentioned above.

Effects of the Interaction Between Oxidative Balance Score and Polygenic Risk Scores on Incidence of Metabolic Syndrome in Middle-Aged Korean Adults

Oxidative stress is implicated in insulin resistance, obesity, and metabolic syndromes (MetSs). However, the interplay between oxidative stress and genetic predisposition during the development of MetS remains unclear. In this study, we aimed to investigate the effects of the interaction between oxidative balance score (OBS) and polygenic risk score (PRS) on the incidence of MetS in middle-aged Korean adults. We analyzed data from 25,879 participants aged ≥40 years from the Health Examinees Cohort of the Korean Genome and Epidemiology Study. The OBS was calculated using 11 antioxidant and five pro-oxidant factors. A genome-wide association study and clumping analysis identified 16 independent single-nucleotide polymorphisms associated with MetS that were used to calculate individual PRSs. Multivariable Cox proportional hazard models adjusted for confounding variables were used to assess the impact of OBS and PRS on the incidence of MetS. During a mean follow-up period of 4.3 years, we recorded 3153 cases of MetS. In both men and women, the group with the lowest OBS and a high PRS had a 1.50-fold (hazard ratio [HR] 1.50, 95% confidence interval [CI] 1.07-2.11) and 1.89-fold (HR 1.89, 95% CI 1.40-2.56) higher incidence, respectively, of MetS compared to those with the highest OBS and a low PRS. Among women with a high PRS, the HRs decreased significantly across OBS quintiles 1 through 5 (p for trend = 0.009). These findings suggest that managing the oxidative balance may be particularly crucial for individuals with a high genetic risk for MetS.

Endocannabinoid System and Metabolism: The Influences of Sex

The endocannabinoid system (ECS) is a lipid signaling system involved in numerous physiological processes, such as endocrine homeostasis, appetite control, energy balance, and metabolism. The ECS comprises endocannabinoids, their cognate receptors, and the enzymatic machinery that tightly regulates their levels within tissues. This system has been identified in various organs, including the brain and liver, in multiple mammalian and non-mammalian species. However, information regarding the sex-specific regulation of the ECS remains limited, even though increasing evidence suggests that interactions between sex steroid hormones and the ECS may ultimately modulate hepatic metabolism and energy homeostasis. Within this framework, we will review the sexual dimorphism of the ECS in various animal models, providing evidence of the crosstalk between endocannabinoids and sex hormones via different metabolic pathways. Additionally, we will underscore the importance of understanding how endocrine-disrupting chemicals and exogenous cannabinoids influence ECS-dependent metabolic pathways in a sex-specific manner.

The androgen receptor in mesenchymal progenitors regulates skeletal muscle mass via Igf1 expression in male mice

Androgens exert their effects primarily by binding to the androgen receptor (AR), a ligand-dependent nuclear receptor. While androgens have anabolic effects on skeletal muscle, previous studies reported that AR functions in myofibers to regulate skeletal muscle quality, rather than skeletal muscle mass. Therefore, the anabolic effects of androgens are exerted via nonmyofiber cells. In this context, the cellular and molecular mechanisms of AR in mesenchymal progenitors, which play a crucial role in maintaining skeletal muscle homeostasis, remain largely unknown. In this study, we demonstrated expression of AR in mesenchymal progenitors and found that targeted AR ablation in mesenchymal progenitors reduced limb muscle mass in mature adult, but not young or aged, male mice, although fatty infiltration of muscle was not affected. The absence of AR in mesenchymal progenitors led to remarkable perineal muscle hypotrophy, regardless of age, due to abnormal regulation of transcripts associated with cell death and extracellular matrix organization. Additionally, we revealed that AR in mesenchymal progenitors regulates the expression of insulin-like growth factor 1 (Igf1) and that IGF1 administration prevents perineal muscle atrophy in a paracrine manner. These findings indicate that the anabolic effects of androgens regulate skeletal muscle mass via, at least in part, AR signaling in mesenchymal progenitors.

Genistein mitigates diet-induced obesity and metabolic dysfunctions in gonadectomized mice with some sex-differential effects

Background

Obesity is associated with insulin resistance (IR) and metabolic dysfunction-associated steatotic liver disease (MASLD). Genistein, an isoflavone, is a promising natural compound for preventing and treating obesity and metabolic dysfunctions. We aimed to investigate the sex-specific protective effects of genistein on obesity, IR, and MASLD in a murine model of sex hormone deprivation with diet-induced obesity (DIO), mimicking postmenopausal women or aging men with metabolic syndrome.

Methods

Gonadectomized and sham-operated C57BL/6NJcl mice were fed a high-fat high-sucrose diet for 4 weeks to induce obesity (7 mice per group). In gonadectomized mice, genistein (16 mg/kg/day) or vehicle (7.5% dimethyl sulfoxide) was orally administered for 45 days. We assessed glucose homeostasis parameters, hepatic histopathology, and hepatic gene expression to investigate the effects of gonadectomy and genistein treatment.

Results

Gonadectomy exacerbated adiposity in both sexes. Ovariectomy diminished the protective effects of female gonadal hormones on the homeostatic model assessment for insulin resistance (HOMA-IR), serum alanine transaminase levels, hepatic steatosis score, and the expression of hepatic genes associated with MASLD progression and IR, such as Fasn, Srebf1, Saa1, Cd36, Col1a1, Pck1, and Ppargc1a. Genistein treatment in gonadectomized mice significantly reduced body weight gain and the hepatic steatosis score in both sexes. However, genistein treatment significantly attenuated HOMA-IR and the expression of the hepatic genes only in female mice.

Conclusion

Genistein treatment mitigates DIO-related MASLD in both male and female gonadectomized mice. Regarding hepatic gene expression associated with MASLD and IR, the beneficial effect of genistein was significantly evident only in female mice. This study suggests a potential alternative application of genistein in individuals with obesity and sex hormone deprivation, yet pending clinical trials.

Weighing in on the role of brown adipose tissue for treatment of obesity

Brown adipose tissue (BAT) activation is an emerging target for obesity treatments due to its thermogenic properties stemming from its ability to shuttle energy through uncoupling protein 1 (Ucp1). Recent rodent studies show how BAT and white adipose tissue (WAT) activity can be modulated to increase the expression of thermogenic proteins. Consequently, these alterations enable organisms to endure cold-temperatures and elevate energy expenditure, thereby promoting weight loss. In humans, BAT is less abundant in obese subjects and impacts of thermogenesis are less pronounced, bringing into question whether energy expending properties of BAT seen in rodents can be translated to human models. Our review will discuss pharmacological, hormonal, bioactive, sex-specific and environmental activators and inhibitors of BAT to determine the potential for BAT to act as a therapeutic strategy. We aim to address the feasibility of utilizing BAT modulators for weight reduction in obese individuals, as recent studies suggest that BAT's contributions to energy expenditure along with Ucp1-dependent and -independent pathways may or may not rectify energy imbalance characteristic of obesity.

Implications of innate immune sexual dimorphism for MASLD pathogenesis and treatment

Growing evidence suggests that metabolic dysfunction-associated steatotic liver disease (MASLD) is significantly higher in men versus women. Increased prevalence is observed in postmenopausal women, suggesting that age and sex (hormones) influence MASLD development and progression. Molecular data further reveal that sex regulates the innate immune responses with an essential role in MASLD progression. To date, there has been limited focus on the role of innate immune sexual dimorphism in MASLD, and differences between men and women are not considered in the current drug discovery landscape. In this review, we summarize the sex disparities and innate immune sexual dimorphism in MASLD pathogenesis. We further highlight the importance of harnessing sexual dimorphism in identifying therapeutic targets, developing pharmacological therapies, and designing (pre-) clinical studies for the personalized treatment for MASLD.

Serum Copper/Zinc Ratio in Overweight and Obese Children: a Cross-Sectional Study

To assess the association between serum copper/zinc ratio (CZR) and overweight/obesity in children. Sociodemographic and clinical data of children aged 8-18 years old were extracted from the National Health and Nutrition Examination Survey (NHANES) database in this cross-sectional study. These associations were explored using weighted univariate and multivariate logistic regression analyses with the odds ratios (ORs) and 95% confidence intervals (CIs). High serum CZR level was related to higher odds of overweight (OR = 1.74), obesity (OR = 5.26), and central obesity (OR = 2.99). Subgroup analyses showed that high serum CZR levels were associated with high odds of overweight in children aged ≥ 12 years old (OR = 2.19) and females (OR = 2.02), while the increased odds of obesity and central obesity were found in children aged ≥ 12 years old and both male and female. Elevated serum CZR level was linked to high odds of childhood overweight, obesity, and central obesity, and this relationship was also found in children with different age and gender.

Structural analysis of polysaccharide from Inonotus obliquus and investigate combined impact on the sex hormones, intestinal microbiota and metabolism in SPF male mice

The dysregulation of sex hormone levels is associated with metabolic disorders such as obesity. Inonotus obliquus polysaccharide (IOP) exhibits a promising therapeutic effect on conditions like obesity and diabetes, potentially linked to its influence on intestinal microbiota and metabolism. The exact cause and mechanisms that link sex hormones, gut microbiota and metabolism are still unknown. In this research, we examined the molecular weight, monosaccharide composition, and glycosidic bond type of IOP. We found that IOP mostly consists of alpha-structured 6‑carbon glucopyranose, with a predominant (1 → 4) linkage to monosaccharides and a uniform distribution. Following this, we administered two different concentrations of IOP to mice through gavage. The results of the enzyme-linked immunosorbent assay (ELISA) demonstrated a significant increase in testosterone (T) levels in the IOP group as compared to the control group. Additionally, the results of tissue immunofluorescence indicated that increased IOP led to a decrease in adiponectin content and an increase in SET protein expression. The study also revealed changes in the intestinal microbiota and metabolic changes in mice through 16S rRNA data and non-targeted LC-MS data, respectively. The study also found that IOP mainly affects pathways linked to glycerophospholipid metabolism. In addition, it has been observed that there is an increase in the number of beneficial bacteria, such as the Eubacterium coprostanoligenes group and g.Lachnospiraceae NK4A136 group, while the levels of metabolites that are linked to obesity or diabetes, such as 1,5-anhydrosorbitol, are reduced. Furthermore, biomarker screening has revealed that the main microorganism responsible for the differences between the three groups is g.Erysipelatoclostridiaceae. In summary, these findings suggest that IOP exerts its therapeutic effects through a synergistic interplay between sex hormones, gut microbiome composition, and metabolic processes.

Analysis of Sex Hormones, Insulin Dosage, and Risk Factors Associated With Male Diabetic Patients

The purpose of this study is to assess the influence of sex hormones and other indicators on risk factors for hypercoagulable states in male patients with type 2 diabetes mellitus. Ninety-two diabetic patients were divided into two groups based on testosterone levels: T1 group (testosterone <12 mmol/L) and T2 group (testosterone >12 mmol/L). Fifty-four non-diabetic patients were used as the control group. Sex hormone index, glucose, insulin, C-peptide, 24-h urinary free cortisol, thromboelastography, and insulin resistance index were measured by radioimmunoassay. Testosterone was lower in the diabetic men than in the control group (12.02 vs 14.77, p < .05), and was inversely related to blood coagulation status, blood glucose level, and cortisol level. Body mass index was positively correlated with estradiol and insulin resistance index. Testosterone was independently associated with the clotting process after controlling for age. Low testosterone is a risk factor for hypercoagulable state in diabetic men. Elevated estradiol and insulin resistance are influential factors for increased body mass index.

Analysis of the association between testosterone and cardiovascular disease potential risk factor apolipoprotein B in adult males without cancer: national health and nutrition examination survey 2011-2016

Background

Over the years, there has been extensive exploration of the association between testosterone and lipid profiles, yet the precise mechanisms underlying their interaction remain incompletely elucidated. Similarly, there is a dearth of research on the correlation between serum apolipoprotein B (apoB) and serum total testosterone (TT), particularly within specific populations.

Methods

We conducted a cross-sectional study to assess the relationship between serum TT concentration and serum apoB concentration. Using the National Health and Nutrition Examination Survey (NHANES) from 2011 to 2016, we employed weighted generalized linear models, weighted univariate, weighted multivariate analysis, and smooth curve fitting to assist in exploring the relationship between serum TT and apoB. Serum apoB concentration served as the independent variable, and serum TT concentration as the dependent variable. ApoB was divided into four quartiles-Q1 (<0.7g/L, N=691), Q2 (≥0.7g/L to <0.9g/L, N=710), Q3 (≥0.9g/L to <1.1g/L, N=696), and Q4 (≥1.1g/L, N=708)-thereby further solidifying the stable association between the two. Additionally, the application of smooth curve fitting will contribute to a more detailed elucidation of the specific relationship between serum TT concentration and serum apoB concentration under different factors (Drinking, Smoke, Diabetes, Hypertension, and High cholesterol level.).

Results

The results indicate a negative correlation between serum TT concentration and apoB concentration (β=-113.4; 95% CI: -146.6, -80.2; P<0.001). After adjusting for confounding variables, the negative correlation between apoB concentration and TT concentration remains significant (β=-61.0; 95% CI: -116.7, -5.2; P=0.040). When apoB concentration was converted from a continuous variable to a categorical variable (quartiles: Q1<0.7g/L; Q2:≥0.7g/L to<0.9g/L; Q3:≥0.9g/L to <1.1g/L; Q4: ≥1.1g/L), TT level of participants in the highest quartile (≥1.1g/L) was -47.2 pg/mL (95% CI: -91.2, -3.3; P=0.045) lower than that in the lowest quartile (<0.7g/L). The smooth curve fitting diagram revealed differences in the relationship between TT concentration and apoB among individuals with different cardiovascular disease (CVD) risk factors.

Conclusions

This study elucidates a robust inverse correlation between serum TT concentration and apoB concentration, maintaining statistical significance even upon adjustment for confounding factors. These findings present a promising avenue for addressing the prevention and treatment of low testosterone and CVD.

Lifespan Effects of Muscle-Specific Androgen Receptor Overexpression on Body Composition of Male and Female Rats

Androgenic actions of gonadal testosterone are thought to be a major mechanism promoting sex differences in body composition across the lifespan. However, this inference is based on studies of androgen receptor (AR) function in late adolescent or emerging adult rodents. Here we assess body composition and AR expression in skeletal muscle of rats at defined ages, comparing wild-type (WT) to transgenic human skeletal actin-driven AR overexpression (HSAAR) rats which overexpress AR in skeletal muscle. Male and female HSAAR and WT Sprague Dawley rats (N = 288) underwent dual-energy x-ray absorptiometry (DXA) scanning and tissue collection at postnatal day (PND) 1, 10, 21, 42, 70, 183, 243, and 365. Expected sex differences in body composition and muscle mass largely onset with puberty (PND-21), with no associated changes to skeletal muscle AR protein. In adulthood, HSAAR increased tibialis anterior (TA) and extensor digitorum longus mass in males, and reduced the expected gain in gonadal fat mass in both sexes. In WT rats, AR protein was reduced in soleus, but not TA, throughout life. Nonetheless, soleus AR protein expression was greater in male rats than female rats at all ages of sexual development, yet only at PND-70 in TA. Overall, despite muscle AR overexpression effects, results are inconsistent with major sex differences in body composition during sexual development being driven by changes in muscle AR, rather suggesting that changes in ligand promote sexual differentiation of body composition during pubertal timing. Nonetheless, increased skeletal muscle AR in adulthood can be sufficient to increase muscle mass in males, and reduce adipose in both sexes.

Endocrine aspects of metabolic dysfunction-associated steatotic liver disease (MASLD): Beyond insulin resistance

While the association of metabolic dysfunction-associated steatotic liver disease (MASLD) with obesity and insulin resistance is widely appreciated, there are a host of complex interactions between the liver and other endocrine axes. While it can be difficult to definitively distinguish direct causal relationships and those attributable to increased adipocyte mass, there is substantial evidence of the direct and indirect effects of endocrine dysregulation on the severity of MASLD, with strong evidence that low levels of growth hormone, sex hormones, and thyroid hormone promote the development and progression of disease. The impact of steroid hormones, e.g. cortisol and dehydroepiandrosterone, and adipokines is much more divergent. Thoughtful assessment, based on individual risk factors and findings, and management of non-insulin endocrine axes is essential in the evaluation and management of MASLD. Multiple therapeutic options have emerged that leverage various endocrine axes to reduce the fibroinflammatory cascade in MASH.

Sex and gonadectomy modify behavioral seizure susceptibility and mortality in a repeated low-dose kainic acid systemic injection paradigm in mice

OBJECTIVE

Sex differences in epilepsy appear driven in part due to effects of gonadal steroids, with varying results in experimental models based on species, strain, and method of seizure induction. Furthermore, removing the main source of these steroids via gonadectomy may impact seizure characteristics differently in males and females. Repeated low-dose kainic acid (RLDKA) systemic injection paradigms were recently shown to reliably induce status epilepticus (SE) and hippocampal histopathology in C57BL/6J mice. Here, we investigated whether seizure susceptibility in a RLDKA injection protocol exhibits a sex difference and whether gonadectomy differentially influences response to this seizure induction paradigm in males and females.

METHODS

Adult C57BL/6J mice were left gonad-intact as controls or gonadectomized (females: ovariectomized, OVX; males: orchidectomized, ORX). At least 2 weeks later, KA was injected ip, every 30 minutes at 7.5 mg/kg or less until the animal reached SE, defined by at least 5 generalized seizures (GS, Racine stage 3 or higher). Parameters of susceptibility to GS induction, SE development, and mortality rates were quantified.

RESULTS

No differences in seizure susceptibility or mortality were observed between control males and control females. Gonadectomized mice exhibited increased susceptibility and reduced latency to both GS and SE in comparison to corresponding controls of the same sex, but the effects were stronger in males. In addition, ORX males, but not OVX females, exhibited strongly increased seizure-induced mortality.

SIGNIFICANCE

The RLDKA protocol is notable for its efficacy in inducing SE and seizure-induced histopathology in C57BL/6J mice, the background for many transgenic strains in current use in epilepsy research. The present results indicate that this protocol may be beneficial for investigating the effects of gonadal hormone replacement on seizure susceptibility, mortality, and seizure-induced histopathology, and that gonadectomy unmasks sex differences in susceptibility to seizures and mortality not observed in gonad-intact controls.

An overview on androgen-mediated actions in skeletal muscle and adipose tissue

Androgens are a class of steroid hormones primarily associated with male sexual development and physiology, but exert pleiotropic effects in either sex. They have a crucial role in various physiological processes, including the regulation of skeletal muscle and adipose tissue homeostasis. The effects of androgens are mainly mediated through the androgen receptor (AR), a ligand-activated nuclear receptor expressed in both tissues. In skeletal muscle, androgens via AR exert a multitude of effects, ranging from increased muscle mass and strength, to the regulation of muscle fiber type composition, contraction and metabolic functions. In adipose tissue, androgens influence several processes including proliferation, fat distribution, and metabolism but they display depot-specific and organism-specific effects which differ in certain context. This review further explores the potential mechanisms underlying androgen-AR signaling in skeletal muscle and adipose tissue. Understanding the roles of androgens and their receptor in skeletal muscle and adipose tissue is essential for elucidating their contributions to physiological processes, disease conditions, and potential therapeutic interventions.

Testosterone Restores Body Composition, Bone Mass, and Bone Strength Following Early Puberty Suppression in a Mouse Model Mimicking the Clinical Strategy in Trans Boys

Transgender youth increasingly present at pediatric gender services. Some of them receive long-term puberty suppression with gonadotropin-releasing hormone analogues (GnRHa) before starting gender-affirming hormones (GAH). The impact of GnRHa use started in early puberty on bone composition and bone mass accrual is unexplored. It is furthermore unclear whether subsequent GAH fully restore GnRHa effects and whether the timing of GAH introduction matters. To answer these questions, we developed a mouse model mimicking the clinical strategy applied in trans boys. Prepubertal 4-week-old female mice were treated with GnRHa alone or with GnRHa supplemented with testosterone (T) from 6 weeks (early puberty) or 8 weeks (late puberty) onward. Outcomes were analyzed at 16 weeks and compared with untreated mice of both sexes. GnRHa markedly increased total body fat mass, decreased lean body mass, and had a modest negative impact on grip strength. Both early and late T administration shaped body composition to adult male levels, whereas grip strength was restored to female values. GnRHa-treated animals showed lower trabecular bone volume and reduced cortical bone mass and strength. These changes were reversed by T to female levels (cortical bone mass and strength) irrespective of the time of administration or even fully up to adult male control values (trabecular parameters) in case of earlier T start. The lower bone mass in GnRHa-treated mice was associated with increased bone marrow adiposity, also reversed by T. In conclusion, prolonged GnRHa use started in prepubertal female mice modifies body composition toward more fat and less lean mass and impairs bone mass acquisition and strength. Subsequent T administration counteracts GnRHa impact on these parameters, shaping body composition and trabecular parameters to male values while restoring cortical bone architecture and strength up to female but not male control levels. These findings could help guide clinical strategies in transgender care. © 2023 American Society for Bone and Mineral Research (ASBMR).

Nuclear receptors as potential therapeutic targets in peripheral arterial disease and related myopathy

Peripheral arterial disease (PAD) is a prevalent cardiovascular complication of limb vascular insufficiency, causing ischemic injury, mitochondrial metabolic damage and functional impairment in the skeletal muscle, and ultimately leading to immobility and mortality. While potential therapies have been mostly focussed on revascularization, none of the currently available pharmacological treatments are fully effective in PAD, often leading to amputations, particularly in chronic metabolic diseases. One major limitation of focussed angiogenesis and revascularization as a therapeutic strategy is a limited effect on metabolic restoration and muscle regeneration in the affected limb. Therefore, additional preclinical investigations are needed to discover novel treatment options for PAD preferably targeting multiple aspects of muscle recovery. In this review, we propose nuclear receptors expressed in the skeletal muscle as potential candidates for ischemic muscle repair in PAD. We review classic steroid and orphan receptors that have been reported to be involved in the regulation of paracrine muscle angiogenesis, oxidative metabolism, mitochondrial biogenesis and muscle regeneration, and discuss how these receptors could be critical for recovery from ischemic muscle damage. Furthermore, we identify existing gaps in our understanding of nuclear receptor signalling in the skeletal muscle and propose future areas of research that could be instrumental in exploring nuclear receptors as therapeutic candidates for treating PAD.

Androgen action on myogenesis throughout the lifespan; comparison with neurogenesis

Androgens' pleiotropic actions in promoting sex differences present not only a challenge to providing a comprehensive account of their function, but also an opportunity to gain insights by comparing androgenic actions across organ systems. Although often overlooked by neuroscientists, skeletal muscle is another androgen-responsive organ system which shares with the nervous system properties of electrochemical excitability, behavioral relevance, and remarkable capacity for adaptive plasticity. Here we review androgenic regulation of mitogenic plasticity in skeletal muscle with the goal of identifying areas of interest to those researching androgenic mechanisms mediating sexual differentiation of neurogenesis. We use an organizational-activational framework to relate broad areas of similarity and difference between androgen effects on mitogenesis in muscle and brain throughout the lifespan, from early organogenesis, through pubertal organization, adult activation, and aging. The focus of the review is androgenic regulation of muscle-specific stem cells (satellite cells), which share with neural stem cells essential functions in development, plasticity, and repair, albeit with distinct, muscle-specific features. Also considered are areas of paracrine and endocrine interaction between androgen action on muscle and nervous system, including mediation of neural plasticity of innervating and distal neural populations by muscle-produced trophic factors.

STE20 kinase TAOK3 regulates type 2 immunity and metabolism in obesity

Healthy adipose tissue (AT) contains ST2+ Tregs, ILC2s, and alternatively activated macrophages that are lost in mice or humans on high caloric diet. Understanding how this form of type 2 immunity is regulated could improve treatment of obesity. The STE20 kinase Thousand And One amino acid Kinase-3 (TAOK3) has been linked to obesity in mice and humans, but its precise function is unknown. We found that ST2+ Tregs are upregulated in visceral epididymal white AT (eWAT) of Taok3-/- mice, dependent on IL-33 and the kinase activity of TAOK3. Upon high fat diet feeding, metabolic dysfunction was attenuated in Taok3-/- mice. ST2+ Tregs disappeared from eWAT in obese wild-type mice, but this was not the case in Taok3-/- mice. Mechanistically, AT Taok3-/- Tregs were intrinsically more responsive to IL-33, through higher expression of ST2, and expressed more PPARγ and type 2 cytokines. Thus, TAOK3 inhibits adipose tissue Tregs and regulates immunometabolism under excessive caloric intake.

A proposal from the liver forum for the management of comorbidities in non-alcoholic steatohepatitis therapeutic trials

The current document has been developed by the Liver Forum who mandated the NAFLD-Associated Comorbidities Working Group - a multistakeholder group comprised of experts from academic medicine, industry and patient associations - to identify aspects of diverse comorbidities frequently associated with non-alcoholic steatohepatitis (NASH) that can interfere with the conduct of therapeutic trials and, in particular, impact efficacy and safety results. The objective of this paper is to propose guidance for the management of relevant comorbidities in both candidates and actual participants in NASH therapeutic trials. We relied on specific guidelines from scientific societies, when available, but adapted them to the particulars of NASH trials with the aim of addressing multiple interacting requirements such as maintaining patient safety, reaching holistic therapeutic objectives, minimising confounding effects on efficacy and safety of investigational agents and allowing for trial completion. We divided the field of action into: first, analysis and stabilisation of the patient's condition before inclusion in the trial and, second, management of comorbidities during trial conduct. For the former, we discussed the concept of acceptable vs. optimal control of comorbidities, defined metabolic and ponderal stability prior to randomisation and weighed the pros and cons of a run-in period. For the latter, we analysed non-hepatological comorbid conditions for changes or acute events possibly occurring during the trial, including changes in alcohol consumption, in order to detail when specific interventions are necessary and how best to manage concomitant drug intake in line with methodological constraints. These recommendations are intended to act as a guide for clinical trialists and are open to further refinement when additional data become available.

Sarcopenia, osteoporosis and frailty

Muscles and bones are intricately connected tissues displaying marked co-variation during development, growth, aging, and in many diseases. While the diagnosis and treatment of osteoporosis are well established in clinical practice, sarcopenia has only been classified internationally as a disease in 2016. Both conditions are associated with an increased risk of adverse health outcomes such as fractures, dysmobility and mortality. Rather than focusing on one dimension of bone or muscle mass or weakness, the concept of musculoskeletal frailty captures the overall loss of physiological reserves in the locomotor system with age. The term osteosarcopenia in particular refers to the double jeopardy of osteoporosis and sarcopenia. Muscle-bone interactions at the biomechanical, cellular, paracrine, endocrine, neuronal or nutritional level may contribute to the pathophysiology of osteosarcopenia. The paradigm wherein muscle force controls bone strength is increasingly facing competition from a model centering on the exchange of myokines, osteokines and adipokines. The most promising results have been obtained in preclinical models where common drug targets have been identified to treat these conditions simultaneously. In this narrative review, we critically summarize the current understanding of the definitions, epidemiology, pathophysiology, and treatment of osteosarcopenia as part of an integrative approach to musculoskeletal frailty.

Central androgen action reverses hypothalamic astrogliosis and atherogenic risk factors induced by orchiectomy and high-fat diet feeding in male mice

Hypogonadism in males confers elevated cardiovascular disease (CVD) risk by unknown mechanisms. Recent radiological evidence suggests that low testosterone (T) is associated with mediobasal hypothalamic (MBH) gliosis, a central nervous system (CNS) cellular response linked to metabolic dysfunction. To address mechanisms linking CNS androgen action to CVD risk, we generated a hypogonadal, hyperlipidemic mouse model with orchiectomy (ORX) combined with hepatic PCSK9 overexpression. After 4 wk of high-fat, high-sucrose diet (HFHS) consumption, despite equal body weights and glucose tolerance, androgen-deficient ORX mice had a more atherogenic lipid profile and increased liver and leukocyte inflammatory signaling compared with sham-operated control mice. Along with these early CVD risk indicators, ORX markedly amplified HFHS-induced astrogliosis in the MBH. Transcriptomic analysis further revealed that ORX and high-fat diet feeding induced upregulation of inflammatory pathways and downregulation of metabolic pathways in hypothalamic astrocytes. To interrogate the role of sex steroid signaling in the CNS in cardiometabolic risk and MBH inflammation, central infusion of T and dihydrotestosterone (DHT) was performed on ORX mice. Central DHT prevented MBH astrogliosis and reduced the liver inflammatory signaling and monocytosis induced by HFHS and ORX; T had a partial protective effect. Finally, a cross-sectional study in 41 adult men demonstrated a positive correlation between radiological evidence of MBH gliosis and plasma lipids. These findings demonstrate that T deficiency in combination with a Western-style diet promotes hypothalamic gliosis concomitant with increased atherogenic risk factors and provide supportive evidence for regulation of lipid metabolism and cardiometabolic risk determinants by the CNS action of sex steroids.NEW & NOTEWORTHY This study provides evidence that hypothalamic gliosis is a key early event through which androgen deficiency in combination with a Western-style diet might lead to cardiometabolic dysregulation in males. Furthermore, this work provides the first evidence in humans of a positive association between hypothalamic gliosis and LDL-cholesterol, advancing our knowledge of CNS influences on CVD risk progression.

Molecular insights into quality and authentication of sheep meat from proteomics and metabolomics

Sheep meat (encompassing lamb, hogget and mutton) is an important source of animal protein in many countries, with a unique flavour and sensory profile compared to other red meats. Flavour, colour and texture are the key quality attributes contributing to consumer liking of sheep meat. Over the last decades, various factors from 'farm to fork', including production system (e.g., age, breed, feeding regimes, sex, pre-slaughter stress, and carcass suspension), post-mortem manipulation and processing (e.g., electrical stimulation, ageing, packaging types, and chilled and frozen storage) have been identified as influencing different aspects of sheep meat quality. However conventional meat-quality assessment tools are not able to elucidate the underlying mechanisms and pathways for quality variations. Advances in broad-based analytical techniques have offered opportunities to obtain deeper insights into the molecular changes of sheep meat which may become biomarkers for specific variations in quality traits and meat authenticity. This review provides an overview on how omics techniques, especially proteomics (including peptidomics) and metabolomics (including lipidomics and volatilomics) are applied to elucidate the variations in sheep meat quality, mainly in loin muscles, focusing on colour, texture and flavour, and as tools for authentication. SIGNIFICANCE: From this review, we observed that attempts have been made to utilise proteomics and metabolomics techniques on sheep meat products for elucidating pathways of quality variations due to various factors. For instance, the improvement of colour stability and tenderness could be associated with the changes to glycolysis, energy metabolism and endogenous antioxidant capacity. Several studies identify proteolysis as being important, but potentially conflicting for quality as the enhanced proteolysis improves tenderness and flavour, while reducing colour stability. The use of multiple analytical methods e.g., lipidomics, metabolomics, and volatilomics, detects a wider range of flavour precursors (including both water and lipid soluble compounds) that underlie the possible pathways for sheep meat flavour evolution. The technological advancement in omics (e.g., direct analysis-mass spectrometry) could make analysis of the proteins, lipids and metabolites in sheep meat routine, as well as enhance the confidence in quality determination and molecular-based assurance of meat authenticity.

Sex and timing of gonadectomy relative to puberty interact to influence weight, body composition, and feeding behaviors in mice

Gonadal sex steroids are important regulators of energy balance in adult rodents, and gonadectomy (GDX) has opposing effects on weight gain in sexually mature males and females. Puberty is associated with the emergence of sex differences in weight, body composition, and feeding behaviors, yet the role of gonadal hormones at puberty remains unclear. To address this, we performed GDX or sham surgery in male and female C57Bl/6 mice at postnatal day (P)25 (prepubertal) or P60 (postpubertal) timepoints and measured weight and body composition for 35 days, after which ad libitum and operant food intake was measured using Feeding Experimentation Device 3 (FED3s) in the home cage. Consistent with previous studies, postpubertal GDX caused weight gain in females and weight loss in males and increased adiposity in both sexes. However, prepubertal GDX decreased weight gain and altered body composition across the adolescent transition (P25 to P60) in males but had no effect in females. Despite the varied effects on weight, GDX decreased food intake and motivation for food as assessed in operant tasks regardless of sex or timing of surgery relative to puberty. Our findings indicate that GDX interacts with both sex and age at surgery to influence weight, body composition, and feeding behavior.

Multi-Omics Analysis of Transcriptomic and Metabolomics Profiles Reveal the Molecular Regulatory Network of Marbling in Early Castrated Holstein Steers

The intramuscular fat (IMF), or so-called marbling, is known as potential determinant of the high quality beef in China, Korea, and Japan. Of the methods that affect IMF content in cattle, castration is markedly regarded as an effective and economical way to improve the deposition of IMF but with little attention to its multi-omics in early-castrated cattle. The aim of this study was to investigate the liver transcriptome and metabolome of early-castrated Holstein cattle and conduct a comprehensive analysis of two omics associated with the IMF deposition using transcriptomics and untargeted metabolomics under different treatments: non−castrated and slaughtered at 16 months of age (GL16), castrated at birth and slaughtered at 16 months of age (YL16), and castrated at birth and slaughtered at 26 months of age (YL26). The untargeted metabolome was analyzed using ultrahigh-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. The transcriptome of the hepatic genes was analyzed to identify marbling-related genes. Using untargeted metabolomics, the main altered metabolic pathways in the liver of cattle, including those for lipid and amino acid metabolism, were detected in the YL16 group relative to the GL16 and YL26 groups. Significant increases in the presence of betaine, alanine, and glycerol 3-phosphate were observed in the YL16 group (p < 0.05), which might have contributed to the improved beef-marbling production. Compared to the GL16 and YL26 groups, significant increases in the presence of glutathione, acetylcarnitine, and riboflavin but decreases in diethanolamine and 2-hydroxyglutarate were identified in YL16 group (p < 0.05), which might have been beneficial to the beef’s enhanced functional quality. The gene expressions of GLI1 and NUF2 were downregulated and that of CYP3A4 was upregulated in the YL16 group; these results were strongly correlated with the alanine, betaine, and leucine, respectively, in the liver of the cattle. In conclusion, implementation of early castration modified the hepatic metabolites and the related biological pathways by regulating the relevant gene expressions, which could represent a better rearing method for production of high marbled and healthier beef products.

Myocytic androgen receptor overexpression does not affect sex differences in adaptation to chronic endurance exercise

Muscle-specific androgen receptor (AR) overexpression (HSAAR transgene) in sedentary male rats results in reduced adiposity, increased mitochondrial enzyme activity, and selective increase in Type 2b myofiber size. Here, we tested chronic endurance exercise interactions with this phenotype in both sexes. Across 9 weeks, rats ran 5×/week on motorized running wheels at increasing speeds and durations. Exercise reduced fat mass in all groups, but sex affected endurance exercise outcomes such that absolute lean mass increased only in females and total body mass decreased only in males. Expected sex differences were observed with males exhibiting greater total body and lean mass; absolute and relative fat mass; bone mineral density; extensor digitorum longus (EDL) myofiber size and glycolytic proportion; but lesser Type 2a and Type 1 myosin expression in tibialis anterior. Observed HSAAR outcomes were not altered by sex, with transgenic rats having greater lean mass, Type 2a myosin expression in soleus, and glycolytic myofiber size in EDL. Tibialis AR content was independently affected by sex, HSAAR, and exercise. No sex differences were observed in tibialis AR expression in wild-type rats, although HSAAR males had greater AR content than HSAAR females. We identified a moderate correlation between AR expression and glycolytic myofiber size, but not whole-body composition. Overall, results suggest myocytic AR overexpression and chronic exercise, despite sharing a similar phenotype to adaptation, are mediated by distinct mechanisms. Further, this study illustrates sex differences in adaptation to chronic endurance exercise, and suggests sex-similarity in the relationship between muscle AR and exercise response.

Adaptations in bone, lean, and total mass after forced endurance exercise are sex-dependent in rats.

Sex differences in muscle fiber-type size and proportion, lean body mass, and bone density are independent of exercise in rats.

Myocytic AR overexpression promotes lean body mass and glycolytic myofiber size in both sexes.

Skeletal muscle AR protein is elevated by chronic endurance exercise in rats, and these changes in AR content are correlated with improved glycolytic myofiber size.

Androgen receptor functions in pericentral hepatocytes to decrease gluconeogenesis and avoid hyperglycemia and obesity in male mice

BACKGROUND

Although the impact of hepatic androgen receptor (AR) pathway on liver pathogenesis was documented, its physiological function in normal liver is remained unclear. This study aims to investigate if hepatic AR acts on metabolism, the major liver function, using a hepatic-specific AR-transgenic (H-ARTG) mouse model.

METHODS

We established the albumin promoter driven H-ARTG mice and included wild type (WT) and H-ARKO mice for study. The body weight, specific metabolic parameters and results from various tolerance tests were compared in different groups of mice fed a chow diet, from 2 to 18 months of age. Glucose feeding and insulin treatment were used to study the expression and zonal distribution pattern of AR and related genes in liver at different prandial stages.

RESULTS

The body weight of H-ARTG mice fed a chow diet was 15 % lower than that of wild-type mice, preceded by lower blood glucose and liver triglyceride levels caused by AR reduced hepatic gluconeogenesis. The opposite phenotypes identified in H-ARKO and castrated H-ARTG mice support the critical role of activated AR in decreasing gluconeogenesis and triglyceride levels in liver. Hepatic AR acting by enhancing the expression of cytosolic glycerol-3-phosphate dehydrogenase (cGPDH), a key of glycerophosphate shuttle, was identified as one mechanism to decrease gluconeogenesis from glycerol. We further found AR normally expressed in zone 3 of hepatic lobules. Its level fluctuates dependent on the demand of glucose, decreased by fasting but increased by glucose uptake or insulin stimulation.

CONCLUSION

AR is a newly identified zone 3 hepatic gene with function in reducing blood glucose and body weight in mice. It suggests that stabilization of hepatic AR is a new direction to prevent hyperglycemia, obesity and nonalcoholic fatty liver disease (NAFLD) in males.

Effects of endurance training on metabolic enzyme activity and transporter protein levels in the skeletal muscles of orchiectomized mice

This study investigated whether endurance training attenuates orchiectomy (ORX)-induced metabolic alterations. At 7 days of recovery after sham operation or ORX surgery, the mice were randomized to remain sedentary or undergo 5 weeks of treadmill running training (15-20 m/min, 60 min, 5 days/week). ORX decreased glycogen concentration in the gastrocnemius muscle, enhanced phosphofructokinase activity in the plantaris muscle, and decreased lactate dehydrogenase activity in the plantaris and soleus muscles. Mitochondrial enzyme activities and protein content in the plantaris and soleus muscles were also decreased after ORX, but preserved, in part, by endurance training. In the treadmill running test (15 m/min, 60 min) after 4 weeks of training, orchiectomized sedentary mice showed impaired exercise performance, which was restored by endurance training. Thus, endurance training could be a potential therapeutic strategy to prevent the hypoandrogenism-induced decline in muscle mitochondrial content and physical performance.

Effects of Caponization on Growth Performance and Carcass Composition of Yangzhou Ganders

Simple Summary

Goose meat is recognized as one of the healthiest foods. Goose capons are specially bred and consumed in several parts of China for their high-quality meat. However, the effects of caponization on goose growth and carcass traits have remained uninvestigated, and its molecular mechanisms remain unclear. In this research, caponization lowered testosterone and increased the total cholesterol and triglyceride concentrations in serum. Caponization increased live weights by promoting food intake and abdominal fat deposition, and improved meat quality by increasing intermuscular fat. Changes in the expression of these genes indicate that caponization increases the live weight mainly by increasing fat deposition rather than muscle growth. These results expand our understanding of the mechanisms of caponization on growth performance and fat deposition in ganders.

Abstract

In this study, we determined the effects of caponization on the growth performance and carcass traits of Yangzhou ganders. Fifty sham operated geese (the control group) and 80 caponized geese (the caponized group) were selected at 150 days of age and reared until 240 days of age. At 210 days of age, 30 geese from the caponized group were selected and fed with testosterone propionate (testosterone group). The results showed that caponization lowered testosterone and increased the total cholesterol and triglyceride concentrations in serum, live weights, average 15 day gains, and feed intake. Abdominal fat and intramuscular fat were significantly higher in the caponized geese than in the control at 240 days. Gene expression analysis showed that caponization promoted abdominal fat deposition and intermuscular fat content by upregulating the expression of adipogenic genes in the liver, adipose tissue, and muscle tissue. The high expression of SOCS3 in the hypothalamus, liver, and muscle of caponized geese suggests that caponization may lead to negative feedback regulation and leptin resistance. Changes in the expression of these genes, along with the downregulation of PAX3 in the breast muscle and MYOG in the leg muscles, indicate that caponization increases the live weight mainly by increasing fat deposition rather than muscle growth. These results expand our understanding of the mechanisms of caponization on growth performance and fat deposition in ganders.

Sex hormones regulate metainflammation in diet-induced obesity in mice

Men have a statistically higher risk of metabolic and cardiovascular disease than premenopausal women, but the mechanisms mediating these differences are elusive. Chronic inflammation during obesity contributes to disease risk and is significantly more robust in males. Prior work demonstrated that compared with obese males, obese females have reduced proinflammatory adipose tissue macrophages (ATMs). Given the paucity of data on how sex hormones contribute to macrophage responses in obesity, we sought to understand the role of sex hormones in promoting obesity-induced myeloid inflammation. We used gonadectomy, estrogen receptor-deficient alpha chimeras, and androgen-insensitive mice to model sex hormone deficiency. These models were evaluated in diet-induced obesity conditions (high-fat diet [HFD]) and in vitro myeloid assays. We found that ovariectomy increased weight gain and adiposity. Ovariectomized females had increased ATMs and bone marrow myeloid colonies compared with sham-gonadectomized females. In addition, castrated males exposed to HFD had improved glucose tolerance, insulin sensitivity, and adiposity with fewer Ly6chi monocytes and bone marrow myeloid colonies compared with sham-gonadectomized males, although local adipose inflammation was enhanced. Similar findings were observed in androgen-insensitive mice; however, these mice had fewer CD11c+ ATMs, implying a developmental role for androgens in myelopoiesis and adipose inflammation. We concluded that gonadectomy results in convergence of metabolic and inflammatory responses to HFD between the sexes, and that myeloid estrogen receptor alpha contributes minimally to diet-induced inflammatory responses, whereas loss of androgen-receptor signaling improves metabolic and inflammatory outcomes. These studies demonstrate that sex hormones play a critical role in sex differences in obesity, metabolic dysfunction, and myeloid inflammation.

Beyond the X Factor: Relevance of Sex Hormones in NAFLD Pathophysiology

Non-alcoholic fatty liver disease (NAFLD) is a major health issue worldwide, being frequently associated with obesity, unbalanced dietary regimens, and reduced physical activity. Despite their greater adiposity and reduced physical activity, women show a lower risk of developing NAFLD in comparison to men, likely a consequence of a sex-specific regulation of liver metabolism. In the liver, sex differences in the uptake, synthesis, oxidation, deposition, and mobilization of lipids, as well as in the regulation of inflammation, are associated with differences in NAFLD prevalence and progression between men and women. Given the major role of sex hormones in driving hepatic sexual dimorphism, this review will focus on the role of sex hormones and their signaling in the regulation of hepatic metabolism and in the molecular mechanisms triggering NAFLD development and progression.

Fat biology and metabolic balance: On the significance of sex

Obesity and its related metabolic disorders have become prevalent and fatal, which are faced by the entire human beings since decades. An energy equilibrium is urgently important for human metabolic health, which requires the participation of multiple organs, such as adipose tissues, liver and skeletal muscles. It seems that both sex and age play a role in the above processes. In this review, we focus on the sexual dimorphism in energy metabolism mediated by adipose tissues, including white and thermogenic (brown/beige) adipose tissues. Remarkably, past investigations have focused on targeting brown/beige adipose tissues to combat obesity because of their contributions to non-shivering thermogenesis. However, sex differences in the regulation of adipose tissue metabolism are likely overlooked. Particularly, increasing data show that males display more visceral fat than females, and females show increased visceral fat after menopause. Visceral adiposity is more deleterious and closely related to metabolic disorders, such as cardiovascular diseases. In this review, we discuss current findings on sexual dimorphism in WAT and BAT biology for a better metabolic balance in humans.

Evaluation of the subcapsular technique for primary closure castration in donkeys (Equus asinus)

This study described the subcapsular technique for primary closure castration in donkeys with special regard to its efficiency and welfare impacts. The study was conducted on twelve adult male donkeys, allocated randomly into two groups; subcapsular castration (SC) and open castration (OC) groups, whether the donkeys were subjected to surgical castration either by subcapsular or open castration techniques, respectively. Testosterone, cortisol, lactate, glucose, total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), triglyceride (TG), and nitric oxide (NO) were measured before and after castration. Pain-associated behavioral activities were recorded post-castration. The SC was successfully performed in donkeys through a single paramedian scrotal incision. The SC was efficient as OC in reducing testosterone levels. The pain score decreased in the SC compared to the OC over time. The SC was an efficient and reliable technique for primary closure castration in donkeys with minimal postoperative complications and care and good cosmetic, physiological, and behavioral outcomes. It can be an alternative to other castration techniques in equines.

Testosterone Reduces Body Fat in Male Mice by Stimulation of Physical Activity Via Extrahypothalamic ERα Signaling

Testosterone (T) reduces male fat mass, but the underlying mechanisms remain elusive, limiting its clinical relevance in hypogonadism-associated obesity. Here, we subjected chemically castrated high-fat diet-induced adult obese male mice to supplementation with T or the nonaromatizable androgen dihydrotestosterone (DHT) for 20 weeks. Both hormones increased lean mass, thereby indirectly increasing oxygen consumption and energy expenditure. In addition, T but not DHT decreased fat mass and increased ambulatory activity, indicating a role for aromatization into estrogens. Investigation of the pattern of aromatase expression in various murine tissues revealed the absence of Cyp19a1 expression in adipose tissue while high levels were observed in brain and gonads. In obese hypogonadal male mice with extrahypothalamic neuronal estrogen receptor alpha deletion (N-ERαKO), T still increased lean mass but was unable to decrease fat mass. The stimulatory effect of T on ambulatory activity was also abolished in N-ERαKO males. In conclusion, our work demonstrates that the fat-burning action of T is dependent on aromatization into estrogens and is at least partially mediated by the stimulation of physical activity via extrahypothalamic ERα signaling. In contrast, the increase in lean mass upon T supplementation is mediated through the androgen receptor and indirectly leads to an increase in energy expenditure, which might also contribute to the fat-burning effects of T.

Maintenance of muscle mass in adult male mice is independent of testosterone

Testosterone is considered a potent anabolic agent in skeletal muscle with a well-established role in adolescent growth and development in males. However, the role of testosterone in the regulation of skeletal muscle mass and function throughout the lifespan has yet to be fully established. While some studies suggest that testosterone is important for the maintenance of skeletal muscle mass, an understanding of the role this hormone plays in young, adult, and old males with normal and low serum testosterone levels is lacking. We investigated the role testosterone plays in the maintenance of muscle mass by examining the effect of orchiectomy-induced testosterone depletion in C57Bl6 male mice at ages ranging from early postnatal through old age (1.5-, 5-, 12-, and 24-month old mice). Following 28 days of testosterone depletion, we assessed mass and fiber cross-sectional-area (CSA) of the tibialis anterior, gastrocnemius, and quadriceps muscles. In addition, we measured global rates of protein synthesis and degradation using the SuNSET method, western blots, and enzyme activity assays. Twenty-eight days of testosterone depletion resulted in reduced muscle mass in the two youngest cohorts, but had no effect in the two oldest cohorts. Mean CSA decreased only in the youngest cohort and only in the tibialis anterior muscle. Testosterone depletion resulted in a general increase in proteasome activity at all ages. No change in protein synthesis was detected at the terminal time point. These data suggest that within physiological serum concentrations, testosterone may not be critical for the maintenance of muscle mass in mature male mice; however, in young mice testosterone is crucial for normal growth.

Novel model to study the physiological effects of temporary or prolonged sex steroid deficiency in male mice

Sex steroids are critical for skeletal development and maturation during puberty as well as for skeletal maintenance during adult life. However, the exact time during puberty when sex steroids have the highest impact as well as the ability of bone to recover from transient sex steroid deficiency is unclear. Surgical castration is a common technique to study sex steroid effects in rodents, but it is irreversible, invasive, and associated with metabolic and behavioral alterations. Here, we used a low dose (LD) or a high dose (HD) of gonadotropin-releasing hormone antagonist to either temporarily or persistently suppress sex steroid action in male mice, respectively. The LD group, a model for delayed puberty, did not show changes in linear growth or body composition, but displayed reduced trabecular bone volume during puberty, which fully caught up at adult age. In contrast, the HD group, representing complete pubertal suppression, showed a phenotype reminiscent of that observed in surgically castrated rodents. Indeed, HD animals exhibited severely impaired cortical and trabecular bone acquisition, decreased body weight and lean mass, and increased fat mass. In conclusion, we developed a rodent model of chemical castration that can be used as an alternative to surgical castration. Moreover, the transient nature of the intervention enables to study the effects of delayed puberty and reversibility of sex steroid deficiency.NEW & NOTEWORTHY We developed a rodent model of chemical castration, which can be used as an alternative to surgical castration. Moreover, the transient nature of the intervention enables to study the effects of delayed puberty and reversibility of sex steroid deficiency.

Testosterone metabolites differentially regulate obesogenesis and fat distribution

OBJECTIVE

Low testosterone in men (hypogonadism) is associated with obesity and type II diabetes. Testosterone replacement therapy has been shown to reverse these effects. However, the mechanisms by which testosterone regulates total fat mass, fat distribution, and metabolic health are unclear. In this study, we clarify the impact of hypogonadism on these parameters, as well as parse the role of testosterone from its downstream metabolites, dihydrotestosterone (DHT), and estradiol, in the regulation of depot-specific adipose tissue mass.

METHODS

To achieve this objective, we utilized mouse models of male hypogonadism coupled with hormone replacement therapy, magnetic resonance imaging (MRI), glucose tolerance tests, flow cytometry, and immunohistochemical techniques.

RESULTS

We observed that castrated mice develop increased fat mass, reduced muscle mass, and impaired glucose metabolism compared with gonadally intact males. Interestingly, obesity is further accelerated in castrated mice fed a high-fat diet, suggesting hypogonadism increases susceptibility to obesogenesis when dietary consumption of fat is elevated. By performing hormone replacement therapy in castrated mice, we show that testosterone impedes visceral and subcutaneous fat mass expansion. Testosterone-derived estradiol selectively blocks visceral fat growth, and DHT selectively blocks the growth of subcutaneous fat. These effects are mediated by depot-specific alterations in adipocyte size. We also show that high-fat diet-induced adipogenesis is elevated in castrated mice and that this can be rescued by androgen treatment. Obesogenic adipogenesis is also elevated in mice where androgen receptor activity is inhibited.

CONCLUSIONS

These data indicate that hypogonadism impairs glucose metabolism and increases obesogenic fat mass expansion through adipocyte hypertrophy and adipogenesis. In addition, our findings highlight distinct roles for testosterone, DHT, and estradiol in the regulation of total fat mass and fat distribution and reveal that androgen signaling blocks obesogenic adipogenesis in vivo.

Association between metabolic syndrome, hepatic steatosis, and testosterone deficiency: evidences from studies with men and rodents

Testosterone is the predominant androgen in men and the lack of it can be a trigger to the development of the metabolic syndrome. Here we review the relationship between testosterone deficiency, metabolic syndrome, and hepatic steatosis reported by studies with men and rodents. The prevalence of metabolic syndrome and testosterone deficiency is higher among older subjects. Low total and free testosterone levels were positively associated with disturbs on energy metabolism, changes in body fat distribution, and body composition. Studies reported visceral fat accumulation in men with hypogonadism and castrated rats. Despite some contradictions, the association between higher adiposity, low testosterone, and metabolic syndrome was a common point among the studies. Few studies evaluated the hepatic steatosis and found an association with hypogonadism. Most of the studies with rodents combined the castration with a high-fat diet to study metabolic disturbs. The importance of proper levels of testosterone for energy metabolism homeostasis in men was also underlined by studies that investigated the metabolic effects of testosterone replacement therapy and androgen deprivation therapy.

Moderate walnut consumption improved lipid profile, steroid hormones and inflammation in trained elderly men: a pilot study with a randomized controlled trial

The present study aimed to investigate the effect of walnut consumption on lipid profile, steroid hormones and inflammation in trained elderly men performing concurrent (resistance and endurance) training. Twenty healthy elderly males were divided into two matched groups, in a randomized controlled trial, that trained three sessions per week: concurrent training + dietary walnut consumption (15 g/day for six weeks, CTW: n = 10); concurrent training + control diet (CT: n = 10). Fasting blood samples were taken 48 hours before and after intervention for biochemical assessments. levels of high-density lipoprotein (HDL) increased only in CTW compared to baseline (19.8%, p < 0.01). Total cholesterol (TC), low-density lipoprotein (LDL) and triglyceride (TG) levels significantly decreased only for CTW (i.e., 13%, 18%, and 18.5% at p < 0.01 for all). Testosterone (T) increased after the training compared to pre-training for CTW and CT (10.3%, p < 0.01, 4.27% p < 0.05, respectively), but the increase was significantly higher in CTW (p < 0.05). Serum cortisol (C) was lower for CTW compared to CT (p < 0.01). C-reactive protein (CRP) decreased in CTW in comparison with CT. The present study revealed that 6-week moderate walnut supplementation (15 g/day) improved lipid profile, steroid hormones and systematic inflammation in aged men performing concurrent training. These findings could be attributable to the potential effect of polyunsaturated fatty acids (PUFA) contained in walnut (linoleic acid, n-6; linolenic acid, n-3).

Testosterone deficiency caused by castration increases adiposity in male rats in a tissue-specific and diet-dependent manner

Background

Testosterone deficiency in men is clinically associated with the development of metabolic syndrome, which manifests as obesity, hepatic steatosis, and type-2 diabetes. We investigated the effects of castration-induced testosterone deficiency on body adiposity and the expression of genes related to lipid metabolism and glucose uptake and androgen signaling in male rats fed a normal diet (ND) or a high-fat diet (HFD).

Methods

Changes in lipid and glucose metabolism and androgen signaling were investigated at physiological and molecular levels in the muscle, liver, and adipose tissues of non-castrated and castrated rats under ND or HFD feeding.

Results

Castration-induced testosterone deficiency predisposed animals on ND to early development of fatty liver by activating fatty acid (FA) synthesis, whereas HFD activated hepatic FA uptake CD36 expression, leading to the development of hepatic steatosis. In rats fed ND, castration induced muscle fat accumulation by activating CD36 expression. In the subcutaneous fat of ND-fed rats, castration increased adiposity and the expression of FA synthesis-related genes, but it decreased glucose transporter gene expression. In the abdominal fat of rats fed ND, castration increased adiposity by upregulating FA synthesis-related genes, and HFD promoted adiposity by inducing FA uptake, glucose transporter, and FA synthesis-related gene expression. In rats fed ND, castration decreased body growth and muscle weight and downregulated the expression of genes androgen signaling in the longissimus dorsi muscle.

Conclusions

Testosterone deficiency increases adiposity in a tissue-specific and diet-dependent manner. Testosterone deficiency decreases body and muscle weights and downregulates androgen signaling.

Lack of AR in LepRb Cells Disrupts Ambulatory Activity and Neuroendocrine Axes in a Sex-Specific Manner in Mice

Disorders of androgen imbalance, such as hyperandrogenism in females or hypoandrogenism in males, increase risk of visceral adiposity, type 2 diabetes, and infertility. Androgens act upon androgen receptors (AR) which are expressed in many tissues. In the brain, AR are abundant in hypothalamic nuclei involved in regulation of reproduction and energy homeostasis, yet the role of androgens acting via AR in specific neuronal populations has not been fully elucidated. Leptin receptor (LepRb)-expressing neurons coexpress AR predominantly in hypothalamic arcuate and ventral premammillary nuclei (ARH and PMv, respectively), with low colocalization in other LepRb neuronal populations, and very low colocalization in the pituitary gland and gonads. Deletion of AR from LepRb-expressing cells (LepRbΔAR) has no effect on body weight, energy expenditure, and glucose homeostasis in male and female mice. However, LepRbΔAR female mice show increased body length later in life, whereas male LepRbΔAR mice show an increase in spontaneous ambulatory activity. LepRbΔAR mice display typical pubertal timing, estrous cycles, and fertility, but increased testosterone levels in males. Removal of sex steroid negative feedback action induced an exaggerated rise in luteinizing hormone in LepRbΔAR males and follicle-stimulating hormone in LepRbΔAR females. Our findings show that AR can directly affect a subset of ARH and PMv neurons in a sex-specific manner and demonstrate specific androgenic actions in the neuroendocrine hypothalamus.

The androgen receptor regulates a druggable translational regulon in advanced prostate cancer

The androgen receptor (AR) is a driver of cellular differentiation and prostate cancer development. An extensive body of work has linked these normal and aberrant cellular processes to mRNA transcription; however, the extent to which AR regulates posttranscriptional gene regulation remains unknown. Here, we demonstrate that AR uses the translation machinery to shape the cellular proteome. We show that AR is a negative regulator of protein synthesis and identify an unexpected relationship between AR and the process of translation initiation in vivo. This is mediated through direct transcriptional control of the translation inhibitor 4EBP1. We demonstrate that lowering AR abundance increases the assembly of the eIF4F translation initiation complex, which drives enhanced tumor cell proliferation. Furthermore, we uncover a network of pro-proliferation mRNAs characterized by a guanine-rich cis-regulatory element that is particularly sensitive to eIF4F hyperactivity. Using both genetic and pharmacologic methods, we demonstrate that dissociation of the eIF4F complex reverses the proliferation program, resulting in decreased tumor growth and improved survival in preclinical models. Our findings reveal a druggable nexus that functionally links the processes of mRNA transcription and translation initiation in an emerging class of lethal AR-deficient prostate cancer.

The curious fate of bone following bariatric surgery: bone effects of sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB) in mice

BACKGROUND

Bone loss and increased fracture risk following bariatric surgery has been reported. We investigated whether the two most commonly performed surgeries, sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB), lead to bone loss. In addition, we examined whether fortification of the diet with calcium citrate prevents bone loss.

METHODS

We used mouse models for SG and RYGB and compared bone loss with a group of sham mice with similar weight loss. All groups were switched at the time of surgery to a low-fat diet (LFD). We also examined whether fortification of the diet with calcium citrate and vitamin D was able to prevent bone loss.

RESULTS

At 2 weeks we observed no major bone effects. However, at 8 weeks, both trabecular and cortical bone were lost to the same extent after SG and RYGB, despite increased calcium absorption and adequate serum levels of calcium, vitamin D, and parathyroid hormone (PTH). Diet fortification with calcium citrate and vitamin D was able to partially prevent bone loss.

CONCLUSIONS

Both SG and RYGB lead to excess bone loss, despite intestinal adaptations to increase calcium absorption. Fortifying the diet with calcium citrate and vitamin D partly prevented the observed bone loss. This finding emphasizes the importance of nutritional support strategies after bariatric surgery, but also affirms that the exact mechanisms leading to bone loss after bariatric surgery remain elusive and thus warrant further research.

The Effects of Androgens on Cardiometabolic Syndrome: Current Therapeutic Concepts

INTRODUCTION

Cardiometabolic syndrome (CMS), as a bunch of metabolic disorders mainly characterized by type 2 diabetes mellitus (T2DM), hypertension, atherosclerosis, central adiposity, and abdominal obesity triggering androgen deficiency, is one of the most critical threats to men. Although many significant preclinical and clinical findings explain CMS, new approaches toward common pathophysiological mechanisms and reasonable therapeutic targets are lacking.

AIM

To gain a further understanding of the role of androgen levels in various facets of CMS such as the constellation of cardiometabolic risk factors including central adiposity, dyslipidemia, insulin resistance, diabetes, and arterial hypertension and to define future directions for development of effective therapeutic modalities.

METHODS

Clinical and experimental data were searched through scientific literature databases (PubMed) from 2009 to October 2019.

MAIN OUTCOME MEASURE

Evidence from basic and clinical research was gathered with regard to the causal impact and therapeutic roles of androgens on CMS.

RESULTS

There are important mechanisms implicated in androgen levels and the risk of CMS. Low testosterone levels have many signs and symptoms on cardiometabolic and glycometabolic risks as well as abdominal obesity in men.

CLINICAL IMPLICATIONS

The implications of the findings can shed light on future improvements in androgen levels and add potentially predictive risk for CMS, as well as T2DM, abdominal obesity to guide clinical management in the early stage.

STRENGTHS & LIMITATIONS

This comprehensive review refers to the association between androgens and cardiovascular health. A limitation of this study is the lack of large, prospective population-based studies that analyze the effects of testosterone treatment on CMS or mortality.

CONCLUSION

Low testosterone levels have several common features with metabolic syndrome. Thus, testosterone may have preventive role in the progress of metabolic syndrome and subsequent T2DM, abdominal obesity, and cardiovascular disease and likely affect aging men's health mainly through endocrine and vascular mechanisms. Further studies are necessary to evaluate the therapeutic interventions directed at preventing CMS in men. Kirlangic OF, Yilmaz-Oral D, Kaya-Sezginer E, et al. The Effects of Androgens on Cardiometabolic Syndrome: Current Therapeutic Concepts. Sex Med 2020;8:132-155.

Role of gut microbiota in sex- and diet-dependent metabolic disorders that lead to early mortality of androgen receptor-deficient male mice

The gut microbiota is involved in metabolic disorders induced by androgen deficiency after sexual maturation in males (late-onset hypogonadism). However, its role in the energy metabolism of congenital androgen deficiency (e.g., androgen-insensitive syndrome) remains elusive. Here, we examined the link between the gut microbiota and metabolic disease symptoms in androgen receptor knockout (ARKO) mouse by administering high-fat diet (HFD) and/or antibiotics. HFD-fed male, but not standard diet-fed male or HFD-fed female, ARKO mice exhibited increased feed efficiency, obesity with increased visceral adipocyte mass and hypertrophy, hepatic steatosis, glucose intolerance, insulin resistance, and loss of thigh muscle. In contrast, subcutaneous fat mass accumulated in ARKO mice irrespective of the diet and sex. Notably, all HFD-dependent metabolic disorders observed in ARKO males were abolished after antibiotics administration. The ratios of fecal weight-to-food weight and cecum weight-to-body weight were specifically reduced by ARKO in HFD-fed males. 16S rRNA sequencing of fecal microbiota from HFD-fed male mice revealed differences in microbiota composition between control and ARKO mice. Several genera or species (e.g., Turicibacter and Lactobacillus reuteri, respectively) were enriched in ARKO mice, and antibiotics treatment spoiled the changes. Furthermore, the life span of HFD-fed ARKO males was shorter than that of control mice, indicating that androgen deficiency causes metabolic dysfunctions leading to early death. These findings also suggest that AR signaling plays a role in the prevention of metabolic dysfunctions, presumably by influencing the gut microbiome, and improve our understanding of health consequences in subjects with hypogonadism and androgen insensitivity.

Crucial role of androgen receptor in resistance and endurance trainings-induced muscle hypertrophy through IGF-1/IGF-1R- PI3K/Akt- mTOR pathway

Background

Androgen receptor (AR) has been reported to play vital roles in exercise-induced increase of muscle mass in rats, but needs to be further verified and the mechanism behind remains unclear. As AR target genes, insulin growth factor-1 (IGF-1) and IGF-1 receptor (IGF-1R) promote muscle hypertrophy through activating PI3K/Akt- mammalian target of rapamycin (mTOR) pathway, a classic pathway of muscle hypertrophy. So the main purpose of this study was using AR antagonist flutamide to demonstrate AR’s effect on training-induced muscle hypertrophy and its possible mechanism: IGF-1/IGF-1R- PI3K/Akt- mTOR pathway?

Methods

Forty-eight Sprague Dawley male rats aged 7 weeks were randomly divided into six groups: control (C), flutamide (F), resistance training (R), resistance training plus flutamide (R + F), endurance training (E), and endurance training plus flutamide (E + F) groups. Flutamide was used to block AR in rats. Rats in R and R + F groups fulfilled 3 weeks of ladder climbing with progressively increased load, while E and E + F rats completed 3-week moderate intensity aerobic exercise on a treadmill. The relative muscle mass (muscle mass/body weight) of rats was detected. Serum levels of testosterone and IGF-1 of rats were determined by ELISA, and mRNA levels of IGF-1R and mTOR in muscles by real-time PCR. Protein levels of AR, IGF-1, IGF-1R, mTOR, PI3K, Akt, p-PI3K and p-Akt in muscles were detected by Western blot.

Results

(1) The training-induced rise in the relative muscle mass and the expression levels of AR were only found in the gastrocnemius of R rats and in the soleus of E rats (selective muscle hypertrophy), which were blocked by flutamide. (2) Serum testosterone in the R and E rat were increased, and flutamide exerted no effect. (3) The levels of IGF-1, IGF-1R and mTOR as well as the activities of PI3K and Akt were enhanced selectively (in the gastrocnemius of R rats and in the soleus of E rats), which were reduced by flutamide. Conclusions: AR exerted an essential role in both resistance training and endurance training-induced muscle hypertrophy, which was mediated at least partly through IGF-1/IGF-1R- PI3K/Akt- mTOR pathway.