Castration-induced testosterone deficiency increases fasting glucose associated with hepatic and extra-hepatic insulin resistance in adult male rats

Transgender Women with HIV Demonstrate Unique Non-Alcoholic Fatty Liver Disease Profiles

Purpose

Non-alcoholic fatty liver disease (NAFLD) prevalence and severity may be higher in people with human immunodeficiency virus (HIV) than the general population, and vary with sex and age. We explored NAFLD characteristics by gender.

Methods

Adult transgender women (TW), cisgender women (CW), and cisgender men (CM) with HIV on antiretroviral therapy and without other known causes of liver disease underwent screening for NAFLD (2017-2020). Circulating factors associated with NAFLD were measured. Hepatic steatosis and fibrosis were assessed using transient elastography by controlled attenuation parameter (CAP) and liver stiffness measurement (LSM), respectively. Analysis of variance/Wilcoxon testing compared normally/non-normally distributed variables, respectively. Logistic regression evaluated factors associated with CAP and LSM.

Results

Participants (n=194) had median age 48 years and body mass index 28.3 kg/m2; 42% were CM, 37% TW, and 21% CW; 95% were non-white; and 16% had diabetes, 40% dyslipidemia, and 49% hypertension. NAFLD prevalence was 59% using CAP ≥248 dB/m (≥S1 steatosis), 48% using CAP ≥260 dB/m (≥S2 steatosis), and 32% using CAP ≥285 dB/m (≥S3 steatosis). Compared to CM and CW, TW had the highest median CAP scores, were more likely to have ≥S2 steatosis, and had the highest insulin resistance, interleukin-6, and fetuin-A values. TW off versus on gender-affirming hormone therapy (GAHT) had slightly higher median CAP scores.

Conclusion

TW on GAHT had less hepatic steatosis than TW not on GAHT, although overall NAFLD severity was greater than expected for TW compared to CM and CW. The effects of estrogen supplementation and androgen deprivation on liver health in TW require further study.

Glucose Metabolism and Sex Hormones in Male Patients with Medication-naïve First-episode Schizophrenia: A Large-scale Cross-sectional Study

BACKGROUND

Schizophrenia (SCZ) usually begins in early adult life. The underlying molecular mechanisms of SCZ remain unclear. There is evidence for the involvement of abnormalities in metabolic and endocrine systems in SCZ, even in drug-naïve first-episode schizophrenia patients (DNFES). However, the association between impaired regulation of glucose metabolism and sex hormones was not studied in SCZ. This study aimed to evaluate the interrelationship between sex hormones and high fasting glucose levels in male DNFES patients.

METHODS

A total of 99 patients with SCZ were recruited, and fasting glucose, fasting insulin, the insulin resistance index (HOMA-IR), and sex hormones were measured.

RESULTS

We found that some male patients with SCZ had abnormal levels in glucose metabolism parameters and gonadal hormones that were not within the normal range. Linear regression analysis adjusted for age, waist circumference, and body mass index showed that testosterone levels were negatively associated with fasting insulin in male patients (β = -0.21, t = -2.2, p = 0.03).

CONCLUSION

Our findings confirm the abnormalities in glucose metabolism parameters and gonadal hormones at the onset of the illness in male DNFES patients with SCZ. In addition, there was an interaction effect between abnormal glucose metabolism and sex hormones in male patients.

The associations of total testosterone with probable nonalcoholic steatohepatitis and nonalcoholic fatty liver disease fibrotic progression in men with type 2 diabetes: a cross-sectional study

BACKGROUND

Testosterone has an impact on metabolic disorders and men with type 2 diabetes mellitus (T2DM) are predisposed to hypogonadism; meanwhile, patients with T2DM have higher risk of NAFLD. Therefore, we speculate that testosterone may affect the progression of NAFLD in T2DM patients and we aim to investigate whether total testosterone is associated with NAFLD progression in men with T2DM.

METHODS

A cross-sectional study. A total of 1782 male participants with T2DM were enrolled from seven communities in Shanghai. Probable nonalcoholic steatohepatitis (NASH) was defined by the concurrence of NAFLD and metabolic syndrome (MetS). NAFLD fibrosis score was used to identify patients with probable advanced fibrosis. Multinomial logistic regression and ordinal logistic regression was used to measure the association of total testosterone (independent variable) and the progression category of NAFLD (dependent variable).

RESULTS

In male, TT quartiles were negatively associated with probable NASH (Q1 vs. Q4 OR 2.07 95% CI 1.31-3.28, P for trend = 0.001) and inflammatory progression of NAFLD with OR of 1 SD increment of ln (TT) 0.81 (95% CI 0.72-0.92, P for trend < 0.001), but positively with fibrotic progression (Q1 vs. Q4 OR 0.45, 95% CI 0.29-0.72, P for trend = 0.001) with OR of 1 SD increment of ln (TT) 1.24 (95% CI 1.07-1.45). According to stratified analyses, for inflammatory progression, the interactions of age strata, duration of diabetes strata, and dyslipidemia status with 1 SD increment of ln (TT) were significant (P for interaction 0.007, 0.003, and 0.012, respectively); as for fibrotic progression, we found no interactions (all P for interaction ≥ 0.05).

CONCLUSIONS

Different associations between TT and inflammatory and fibrotic progression of NAFLD in male were observed, suggesting different roles of TT in inflammatory and fibrotic stages of NAFLD.

The Integration of Metabolomics with Other Omics: Insights into Understanding Prostate Cancer

Our understanding of prostate cancer (PCa) has shifted from solely caused by a few genetic aberrations to a combination of complex biochemical dysregulations with the prostate metabolome at its core. The role of metabolomics in analyzing the pathophysiology of PCa is indispensable. However, to fully elucidate real-time complex dysregulation in prostate cells, an integrated approach based on metabolomics and other omics is warranted. Individually, genomics, transcriptomics, and proteomics are robust, but they are not enough to achieve a holistic view of PCa tumorigenesis. This review is the first of its kind to focus solely on the integration of metabolomics with multi-omic platforms in PCa research, including a detailed emphasis on the metabolomic profile of PCa. The authors intend to provide researchers in the field with a comprehensive knowledge base in PCa metabolomics and offer perspectives on overcoming limitations of the tool to guide future point-of-care applications.

Testosterone Deficiency Promotes Hypercholesteremia and Attenuates Cholesterol Liver Uptake via AR/PCSK9/LDLR Pathways

BACKGROUND

Testosterone deficiency is reportedly correlated with an elevation of cholesterol in plasma, but the mechanism remains unclear. Our objective was to investigate the effects of testosterone deficiency on cholesterol metabolism and the corresponding molecular changes in vivo and in vitro.

METHODS

SD rats were randomized into three groups: sham-operated (SHAM), subtotal orchiectomized (SO), and orchiectomized (ORX) and fed for 8 weeks. HepG2 cells were cultured with medium containing testosterone with the final concentrations of 0, 10, 30, and 300 nM. Method of isotope tracing and fluorescence labelling was adopted to investigate cholesterol metabolism. Several key molecules of cholesterol metabolism were also analyzed.

RESULTS

SO and ORX rats displayed dysfunctional liver uptake of cholesterol. HepG2 cells incubated with testosterone of lower and excessive level exhibited reduced capacity of cholesterol uptake. Further investigation revealed that lack of testosterone induced increased proprotein convertase subtilisin/kexin type 9 (PCSK9) and decreased low-density lipoprotein receptor (LDLR) both in vivo and in vitro. Moreover, the androgen receptor (AR) antagonist flutamide mimicked the effects of testosterone deficiency on PCSK9 and LDLR indicating the role of AR as a mediator in triggering attenuating liver cholesterol uptake in which testosterone instead of dihydrotestosterone (DHT) is the major functional form of androgen.

CONCLUSION

Testosterone deficiency attenuated cholesterol liver uptake mediated by the PCSK9-LDLR pathway, in which AR and testosterone without transforming to DHT play important roles.

Associations among gonadal hormone, triglycerides and cognitive decline in female patients with major depressive disorders

BACKGROUND

Cognitive impairment has been identified as a core feature of depression. Serum triglycerides (TG), gonadal hormone and sex difference were shown to influence cognitive performance. The purpose of this study was to investigate the associations among serum TG, gonadal hormone, sex difference and cognitive performance in patients with major depressive disorders (MDD).

METHODS

The enrolled 183 patients (male/female = 80/103) meeting DSM-IV criteria for MDD were divided into high TG group (patients-HTG) and normal TG group (patients-NTG) according to TG level. Serum TG, estradiol (E2) and testosterone (T) levels were measured by the glycerokinase peroxidase-peroxidase and chemiluminescence methods. Cognition was assessed by the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). The study was conducted between August 2016 and January 2020.

RESULTS

In female, patients-HTG had lower immediate memory, language, attention, delayed memory and RBANS total scores than patients-NTG after adjusting for covariates. There were significant differences in serum E2 and T levels between patients-HTG and patients-NTG in female after controlling for covariates. In female patients-HTG, serum E2 level was positively associated with immediate memory, delayed memory and RBANS total scores, and serum T level was positively related to immediate memory, language and RBANS total scores. These findings were not seen in male patients.

CONCLUSIONS

Our data suggested that patients-HTG exhibited poorer cognitive function compared with patients-NTG in female. Moreover, the decline in serum gonadal hormone level might contribute to the high TG development of female MDD, and was further implicated in their cognitive decline.

Mice lacking the proton channel Hv1 exhibit sex-specific differences in glucose homeostasis

Sex as a physiologic factor has a strong association with the features of metabolic syndrome. Our previous study showed that loss of the voltage-gated proton channel Hv1 inhibits insulin secretion and leads to hyperglycemia and glucose intolerance in male mice. However, there are significant differences in blood glucose between male and female Hv1-knockout (KO) mice. Here, we investigated the differences in glucose metabolism and insulin sensitivity between male and female KO mice and how sex steroids contribute to these differences. We found that the fasting blood glucose in female KO mice was visibly lower than that in male KO mice, which was accompanied by hypotestosteronemia. KO mice in both sexes exhibited higher expression of gluconeogenesis-related genes in liver compared with WT mice. Also, the livers from KO males displayed a decrease in glycolysis-related gene expression and an increase in gluconeogenesis-related gene expression compared with KO females. Furthermore, exogenous testosterone supplementation decreased blood glucose levels in male KO mice, as well as enhancing insulin signaling. Taken together, our data demonstrate that knockout of Hv1 results in higher blood glucose levels in male than female mice, despite a decreased insulin secretion in both sexes. This sex-related difference in glucose homeostasis is associated with the glucose metabolism in liver tissue, likely due to the physiological levels of testosterone in KO male mice.

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.

Diabetes Mellitus Causes Male Reproductive Dysfunction: A Review of the Evidence and Mechanisms

The metabolic disorders caused by diabetes can lead to various complications, including dysfunction of the male reproductive system. In patients with diabetes, long-term hyperglycemia results in diabetic vascular neuropathy, oxidative stress injury, abnormal zinc metabolism, and insulin resistance syndrome. In addition, insulin deficiency and resistance in diabetes can damage the hypothalamus, pituitary gland, gonads, and perigonads. This can reduce the secretion of sex hormones including gonadotropin-releasing hormone, follicle stimulating hormone, luteinizing hormone, and testosterone, and can lead to testicular atrophy, stromal cell atrophy, seminiferous tubule damage, spermatogenic cell damage, and other structural injuries of the male reproductive organs. These actions can affect male fertility and reproductive health. Herein, we review studies that report a causative role of diabetes in male reproductive function. We also discuss the evidence-based mechanisms involved in the processes of diabetes-related male sexual and reproductive dysfunction as well as the progress in treatment.

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.

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.

Associations between serum total, free and bioavailable testosterone and non-alcoholic fatty liver disease in community-dwelling middle-aged and elderly women

BACKGROUND AND AIMS

Non-alcoholic fatty liver disease (NAFLD) is considered both a cause and consequence of the metabolic syndrome (MetS). While emerging evidence has indicated that testosterone is associated with MetS, the relationship between testosterone and NAFLD in women remains unclear. Therefore, this study investigated the associations between serum testosterone levels and NAFLD prevalence risk in a community-based cross-sectional study.

METHODS

A total of 2117 adult women were included in the analysis. Serum total testosterone (TT) was measured by chemiluminescence immunoassay, and other testosterone-related indices, such as concentrations and percentages of calculated free testosterone (cFT) and bioavailable testosterone (BioT), and free androgen index (FAI), were also calculated. NAFLD was diagnosed by clinical criteria. Logistic regression was used to explore these associations.

RESULTS

There were significant differences in TT, FAI, cFT and BioT between women with and without NAFLD (all P<0.001). Multivariate logistic-regression analyses demonstrated that both absolute concentrations and percentages of cFT and BioT were positively associated with NAFLD risk prevalence in all models. Adjusted ORs (95% CI) for quartile 4 vs quartile 1 of % cFT and % BioT were 5.94 (4.29-8.22) and 5.21 (3.79-7.17) in model 2, and 4.35 (3.07-6.18) and 3.58 (2.55-5.03) in model 3 (all P<0.001 for trend). In addition, quartiles of TT, FAI, cFT and BioT were significantly correlated with degree of hepatic steatosis. ROC analysis also showed that % cFT and % BioT were more accurate for predicting NAFLD prevalence than was TT.

CONCLUSION

Serum cFT and BioT were positively associated with NAFLD risk, and elevated levels of cFT and BioT could be independent risk factors of NAFLD prevalence in middle-aged and elderly women.

Fatty acid-binding protein 1 increases steer fat deposition by facilitating the synthesis and secretion of triacylglycerol in liver

Castration is an important means of improving the beef quality via increasing fat deposition. However, little is known about the molecular mechanism underlying the fat deposition after castration. Here, the intramuscular fat (IMF) content of the steer group was shown to be much higher than the bull group. To understand transcriptional changes in the genes involved in fat deposition following castration, differential expression patterns of mRNAs in liver tissue were investigated in steers and bulls using RNA sequencing. In total, we obtained 58,282,367-54,918,002 uniquely mapped reads, which covered 90.13% of the currently annotated transcripts; 5,864 novel transcripts and optimized 9,088 known genes were determined. These results indicated that castration could change the expression patterns of mRNAs in liver tissue, and 282 differentially expressed genes (DEGs) were detected between steers and bulls. KEGG pathway analysis showed that the DEGs were mostly enriched in PPAR signaling pathway, steroid biosynthesis, steroid hormone biosynthesis, and biosynthesis of fatty acids. Furthermore, eight DEGs were corroborated via quantitative real-time PCR and we found that FABP1 gene knockdown in bovine hepatocytes prominently reduced intracellular triacylglycerol (TAG) synthesis and very low density lipoprotein (VLDL) secretion in culture medium. In summary, these results indicate that FABP1 may promote fat deposition by promoting the production and secretion of TAG and VLDL in steer liver.

Reproductive Endocrinology of Nonalcoholic Fatty Liver Disease

The liver and the reproductive system interact in a multifaceted bidirectional fashion. Sex steroid signaling influences hepatic endobiotic and xenobiotic metabolism and contributes to the pathogenesis of functional and structural disorders of the liver. In turn, liver function affects the reproductive axis via modulating sex steroid metabolism and transport to tissues via sex hormone-binding globulin (SHBG). The liver senses the body's metabolic status and adapts its energy homeostasis in a sex-dependent fashion, a dimorphism signaled by the sex steroid milieu and possibly related to the metabolic costs of reproduction. Sex steroids impact the pathogenesis of nonalcoholic fatty liver disease, including development of hepatic steatosis, fibrosis, and carcinogenesis. Preclinical studies in male rodents demonstrate that androgens protect against hepatic steatosis and insulin resistance both via androgen receptor signaling and, following aromatization to estradiol, estrogen receptor signaling, through regulating genes involved in hepatic lipogenesis and glucose metabolism. In female rodents in contrast to males, androgens promote hepatic steatosis and dysglycemia, whereas estradiol is similarly protective against liver disease. In men, hepatic steatosis is associated with modest reductions in circulating testosterone, in part consequent to a reduction in circulating SHBG. Testosterone treatment has not been demonstrated to improve hepatic steatosis in randomized controlled clinical trials. Consistent with sex-dimorphic preclinical findings, androgens promote hepatic steatosis and dysglycemia in women, whereas endogenous estradiol appears protective in both men and women. In both sexes, androgens promote hepatic fibrosis and the development of hepatocellular carcinoma, whereas estradiol is protective.

Comparative effects of sex hormone deprivation on the brain of insulin-resistant rats

Obese-insulin resistance following chronic high-fat diet consumption led to cognitive decline through several mechanisms. Moreover, sex hormone deprivation, including estrogen and testosterone, could be a causative factor in inducing cognitive decline. However, comparative studies on the effects of hormone-deprivation on the brain are still lacking. Adult Wistar rats from both genders were conducted sham operations or orchiectomies/ovariectomies and given a normal diet or high-fat diet for 4, 8, and 12 weeks. Blood was collected to determine the metabolic parameters. At the end of the experiments, rats were decapitated and their brains were collected to determine brain mitochondrial function, brain oxidative stress, hippocampal plasticity, insulin-induced long-term depression, dendritic spine density, and cognition. We found that male and female rats fed a high-fat diet developed obese-insulin resistance by week 8 and brain defects via elevated brain oxidative stress, brain mitochondrial dysfunction, impaired insulin-induced long-term depression, hippocampal dysplasticity, reduced dendritic spine density, and cognitive decline by week 12. In normal diet-fed rats, estrogen-deprivation, not testosterone-deprivation, induced obese-insulin resistance, oxidative stress, brain mitochondrial dysfunction, impaired insulin-induced long-term depression, hippocampal dysplasticity, and reduced dendritic spine density. In high-fat-diet-fed rats, estrogen deprivation, not testosterone-deprivation, accelerated and aggravated obese-insulin resistance and brain defects at week 8. In conclusion, estrogen deprivation aggravates brain dysfunction more than testosterone deprivation through increased oxidative stress, brain mitochondrial dysfunction, impaired insulin-induced long-term depression, and dendritic spine reduction. These findings may explain clinical reports which show more severe cognitive decline in aging females than males with obese-insulin resistance.

Sex hormones, obesity and type 2 diabetes: is there a link?

An imbalance in sex hormones has an important impact on type 2 diabetes (T2DM) mainly through the involvement of visceral adipose tissue. Androgens have an interesting sex-dimorphic association with T2DM, since hyperandrogenism in females and hypogonadism in males are risk factors for T2DM. Thus, treatments aimed at correcting hyperandrogenism in females and hypogonadism in males may prevent the development of T2DM or help in its treatment.

Metabolic Effects of Testosterone Hormone Therapy in Normal and Orchiectomized Male Rats: From Indirect Calorimetry to Lipolytic Enzymes

BACKGROUND AND AIM

Changes in total energy expenditure (TEE) and substrate metabolism may help explain the metabolic actions of testosterone (T). This study measured respiratory quotient (RQ), TEE, ghrelin, insulin, and key lipolysis enzyme concentrations in relation to body weight (wt) and food intake (FI) in both normal and bilaterally orchiectomized rats with/without T treatment.

METHODS

In total, thirty-two male Wistar rats (300-400 g) were divided into four groups (n = 8/group), including (a) sham-operated and vehicle-injected group (Sham), (b) T-treated sham group (T-Sham) for which sham-operated rats were injected with IM testosterone undecanoate (100 mg/kg, for one week), (c) orchiectomy and vehicle-injected group (Orch), and (d) T-replaced orchiectomy group (T-Orch). After one week, FI and wt were automatically recorded, indirect calorimetry parameters were measured, and blood samples were collected to measure T, ghrelin, insulin, growth hormone (GH), glucose, hormone-sensitive lipase (HSL), adipocyte triglyceride lipase (ATGL), free fatty acids (FFA), and lipid profiles.

RESULTS

Orchiectomy decreased ghrelin, GH, and insulin levels, increased TEE and RQ, and lowered FI and wt. The T-Orch group exhibited increased levels of ghrelin (3-fold), insulin, GH, blood levels of lipolysis products, TEE, and FI in addition to reduced glucose levels (P < 0.05). This group demonstrated no significant changes in wt. In the T-Sham group, T increased ghrelin and insulin levels (P < 0.05) with strong positive correlations (r = 0.663 and 0.644, respectively, P < 0.05), increased ATGL levels, RQ toward carbohydrate utilization ranges, and TEE, and reduced HSL levels (P < 0.05) with insignificant changes in FI or wt.

CONCLUSIONS

T administration in orchiectomized rats significantly increased orexigenic mediators such as ghrelin and insulin without inducing any significant changes in wt. The mechanism for this finding might be the increased TEE and the stimulation of lipolysis through the ATGL enzyme. The associated rise of GH might help in interference with accumulation of lipid in adipose tissue. Apart from the effect on GH, T-Sham showed similar effects of T supplementation.

Gender and Sex Differences in Adipose Tissue

PURPOSE OF REVIEW

As the ongoing epidemic of adult and childhood obesity grows, it puts a greater burden on individuals and the healthcare system due to increased prevalence of obesity-associated diseases. An important area that has gained much attention recently is the sex and gender difference related to obesity and associated complications. Basic science and clinical studies have now improved our understanding of obesity and have discovered adipose tissue biology to be key in metabolism.

RECENT FINDINGS

There is evidence related to the sex dichotomy in obesity in a variety of areas including adipocyte function, sex hormone effects, genetics, and metabolic inflammation leading to critical differences in adipose tissue biology. The sex and gender difference in adipose tissue is a factor that should be considered when studying an individuals' risk for obesity and metabolic dysfunction. This understanding is important for strategizing treatment and prevention measures.

Possible mechanisms underlying fatty liver in a rat model of male hypogonadism: A protective role for testosterone

AIMS

To investigate the effects of testosterone (Test) deficiency and testosterone replacement therapy (TRT) on the development of non-alcoholic fatty liver disease (NAFLD) and associated peripheral insulin resistance (IR) in male rats and to illustrate the underlying mechanisms of action.

MATERIALS AND METHODS

male Sprague Dawley rats were divided into 3 groups as follows: 1) sham-operated group (n = 11), 2) ORCD-induced group (n = 9) exposed to orchidectomy (ORCD), achieved by complete surgical removal of testicles, and 3) ORCD + Test treated group (n = 10) (11 ng/mL Test propionate, 3x/week, S.C.).

RESULTS

Data revealed significant increases in final body, liver, visceral and subcutaneous fats weights with significant increases in fasting plasma glucose and insulin levels and HOMA-IR. Additionally, ORCD rats had higher UAC for measured glucose levels and insulin levels during OGTT and higher AUC for measured glucose levels during ITT. Interesting, higher serum and hepatic levels of TGs and CHOL and higher serum levels of LDL were seen in ORCD-induced rats. Mechanistically, significant increases in mRNA levels of SREBP-1, SREBP-2, ACC-1, FAS, HMGCOAR and HMGCOAS with significant increases in protein levels of both precursor and mature SREBP-1 and SREBP-2, PPAR-α, p-PPAR-α, CPT-1 and UCP-2 and significant lower protein levels p-AMPK and p-ACC-1 were detected in livers of ORCD rats. Test administration to ORCD-induced rats significantly ameliorated all of the above mentioned biochemical endpoints and reversed the effect of ORCD on mRNA and protein levels of these targets. In conclusion, Test deficiency could be an independent risk factor for the development of NAFLD by upregulation of lipid synthesis and disturb fatty acids oxidation whereas Test therapy is a protective strategy.

Role of androgens in energy metabolism affecting on body composition, metabolic syndrome, type 2 diabetes, cardiovascular disease, and longevity: lessons from a meta-analysis and rodent studies

Testosterone is a sex hormone produced by testicular Leydig cells in males. Blood testosterone concentrations increase at three time-periods in male life-fetal, neonatal (which can be separated into newborn and infant periods), and pubertal stages. After peaking in the early 20s, the blood bioactive testosterone level declines by 1-2% each year. It is increasingly apparent that a low testosterone level impairs general physical and mental health in men. Here, this review summarizes recent systematic reviews and meta-analyses of epidemiological studies in males (including cross-sectional, longitudinal, and androgen deprivation studies, and randomized controlled testosterone replacement trials) in relation to testosterone and obesity,  body composition, metabolic syndrome, type 2 diabetes, cardiovascular disease, and longevity. Furthermore, underlying mechanisms are discussed using data from rodent studies involving castration or androgen receptor knockout. This review provides an update understanding of the role of testosterone in energy metabolism. Abbreviations AR: androgen receptor; CV: cardiovascular; FDA: US Food and Drug Administration; HFD: high-fat diet; KO: knockout; MetS: metabolic syndrome; RCT: randomized controlled trial; SHBG: sex hormone binding globulin; SRMA: systematic review and meta-analysis; TRT: testosterone replacement therapy; T2DM:type 2 diabetes mellitus.

Hepatic actions of androgens in the regulation of metabolism

PURPOSE OF REVIEW

The purpose of this review is to summarize recent findings on hepatic actions of androgens in the regulation of protein, lipid and glucose metabolism. The rationale for liver-targeted testosterone use will be provided.

RECENT FINDINGS

Liver-targeted testosterone administration, via the oral route, induces protein anabolic effect by reducing the rate of protein oxidation to a similar extent to that of systemic testosterone administration. Recent evidence indicates that testosterone exerts whole-body anabolic effect through inhibition of nitrogen loss via the hepatic urea cycle. Several hepatic effects of androgens, particularly on glucose metabolism, are direct and take place before any changes in body composition occur. This includes an increase in insulin secretion and sensitivity, and reduction in hepatic glucose output by testosterone. Furthermore, lack of testosterone in the liver exacerbates diet-induced impairment in glucose metabolism. In the liver, androgens induce the full spectrum of metabolic changes through interaction with growth hormone or aromatization to estradiol.

SUMMARY

Liver-targeted testosterone therapy may open up a new approach to achieve whole-body anabolism without systemic side-effects. Aromatizable androgens may be superior to nonaromatizable androgens in inducing a complex spectrum of direct, estrogen-mediated and other hormone-mediated effects of androgens.

Contribution of Hepatic Retinaldehyde Dehydrogenase Induction to Impairment of Glucose Metabolism by High-Fat-Diet Feeding in C57BL/6J Mice

Obesity and insulin resistance are associated with overexpression of retinaldehyde dehydrogenase 1 (RALDH1). We aimed to investigate the roles of hepatic RALDH1 induction in glucose metabolism impairment using mice fed with high-fat-diet (HFD). Mice were fed with HFD for 8 weeks and treated with RALDH inhibitor citral for another 4 weeks. Oral glucose tolerance test (OGTT), pyruvate tolerance test (PTT) and insulin tolerance test were performed. Expressions of phosphoenolpyruvate carboxykinase 1 (PCK1), glucokinase (GCK) and RALDH1 were measured. Therapeutic effects of citral were also documented in diabetic rats. Effects of retinaldehyde on PCK1 and GCK expressions were examined in rat primary hepatocytes and HepG2 cells. The results showed that HFD mice were characterized by hyperlipidaemia and insulin resistance, accompanied by significantly increased RALDH1 activity and expression. Citral (10 and 50 mg/kg) ameliorated HFD-induced hyperlipidaemia and insulin resistance, as demonstrated by the improved fasting glucose, insulin levels and lipid profiles. OGTT and PTT demonstrated that citral reversed HFD-induced glucose disposal impairment and glucose production enhancement. Citral also reversed the increased PCK1 expression and decreased GCK expression by HFD. Citral therapeutic effects were reconfirmed in diabetic rats. In vitro data indicated that retinaldehyde had the strongest PCK1 induction in primary hepatocytes of diabetic rats compared with HFD rats and control rats, in line with the increased RALDH1 expression. Citral reversed the retinaldehyde-induced PCK1 expression in primary rat hepatocytes and HepG2 cells. In conclusion, RALDH1 induction impaired glucose metabolism partly via modulating PCK1 and GCK expressions. Citral improved glucose metabolism through inhibiting RALDH activity.

Androgen signaling expands β-cell mass in male rats and β-cell androgen receptor is degraded under high-glucose conditions

A deficient pancreatic β-cell mass increases the risk of type 2 diabetes mellitus. Here, we investigated the effects of testosterone on the development of pancreatic β-cell mass in male rats. The β-cell mass of male rats castrated at 6 wk of age was reduced to ~30% of that of control rats at 16 wk of age, and castration caused glucose intolerance. Loss of β-cell mass occurred because of decreases in islet density per pancreas and β-cell cluster size. Castration was negatively associated with the number of Ki-67-positive β-cells and positively associated with the number of TUNEL-positive β-cells. These β-cell changes could be prevented by testosterone treatment. In contrast, castration did not affect β-cell mass in male mice. Androgen receptor (AR) localized differently in mouse and rat β-cells. Testosterone enhanced the viability of INS-1 and INS-1 #6, which expresses high levels of AR, in rat β-cell lines. siRNA-mediated AR knockdown or AR antagonism with hydroxyflutamide attenuated this enhancement. Moreover, testosterone did not stimulate INS-1 β-cell viability under high d-glucose conditions. In INS-1 β-cells, d-glucose dose dependently (5.5-22.2 mM) downregulated AR protein levels both in the presence and absence of testosterone. The intracellular calcium chelator (BAPTA-AM) could prevent this decrease in AR expression. AR levels were also reduced by a calcium ionophore (A23187), but not by insulin, in the absence of the proteasome inhibitor MG132. Our results indicate that testosterone regulates β-cell mass, at least in part, by AR activation in the β-cells of male rats and that the β-cell AR is degraded under hyperglycemic conditions.

Hepatic transcriptional changes in critical genes for gluconeogenesis following castration of bulls

Objective

This study was performed to understand transcriptional changes in the genes involved in gluconeogenesis and glycolysis pathways following castration of bulls.

Methods

Twenty Korean bulls were weaned at average 3 months of age, and castrated at 6 months. Liver tissues were collected from bulls (n = 10) and steers (n = 10) of Korean cattle, and hepatic gene expression levels were measured using quantitative real-time polymerase chain reaction. We examined hepatic transcription levels of genes encoding enzymes for irreversible reactions in both gluconeogenesis and glycolysis as well as genes encoding enzymes for the utilization of several glucogenic substrates. Correlations between hepatic gene expression and carcass characteristics were performed to understand their associations.

Results

Castration increased the mRNA (3.6 fold; p<0.01) and protein levels (1.4 fold; p< 0.05) of pyruvate carboxylase and mitochondrial phosphoenolpyruvate carboxykinase genes (1.7 fold; p<0.05). Hepatic mRNA levels of genes encoding the glycolysis enzymes were not changed by castration. Castration increased mRNA levels of both lactate dehydrogenase A (1.5 fold; p<0.05) and lactate dehydrogenase B (2.2 fold; p<0.01) genes for lactate utilization. Castration increased mRNA levels of glycerol kinase (2.7 fold; p<0.05) and glycerol-3-phosphate dehydrogenase 1 (1.5 fold; p<0.05) genes for glycerol utilization. Castration also increased mRNA levels of propionyl-CoA carboxylase beta (mitochondrial) (3.5 fold; p<0.01) and acyl-CoA synthetase short chain family member 3 (1.3 fold; p = 0.06) genes for propionate incorporation.

Conclusion

Castration increases transcription levels of critical genes coding for enzymes involved in irreversible gluconeogenesis reactions from pyruvate to glucose and enzymes responsible for incorporation of glucogenic substrates including lactate, glycerol, and propionate. Hepatic gluconeogenic gene expression levels were associated with intramuscular fat deposition.

Testosterone level and risk of type 2 diabetes in men: a systematic review and meta-analysis

BACKGROUND

Type 2 diabetes is a risk factor for testosterone deficiency and impaired sex steroid status. Some studies also investigated the association of testosterone level with diabetes risk in men, but reported controversial findings. To clarify this issue, we conducted a systematic review and meta-analysis.

METHODS

PubMed, EMBASE and Web of Science were searched for eligible cohort or nested case-control studies published up to August 15, 2017. Meta-analysis was used to calculate the pooled relative risk (RR) of type 2 diabetes associated with higher testosterone level.

RESULTS

Thirteen cohort or nested case-control studies with 16,709 participants were included. Meta-analysis showed that higher total testosterone level could significantly decrease the risk of type 2 diabetes in men (RR = 0.65; 95% CI 0.50-0.84; P = 0.001), and higher free testosterone level could also decrease the risk of type 2 diabetes in men (RR = 0.94; 95% CI 0.90-0.99; P = 0.014). After excluding two studies that did not calculate RRs by quartiles of testosterone levels, both higher total testosterone and free testosterone levels could decrease the risk of type 2 diabetes in men, and the pooled RRs were 0.62 (95% CI 0.51-0.76; P < 0.001) and 0.77 (95% CI 0.61-0.98; P = 0.03), respectively.

CONCLUSION

This meta-analysis suggests that higher testosterone level can significantly decrease the risk of type 2 diabetes in men. Therefore, combined with previous researches, the findings above suggest a reverse-causality scenario in the relation between testosterone deficiency and risk of type 2 diabetes in men.

Does long-term androgen deficiency lead to metabolic syndrome in middle-aged rats?

Evidence from clinical observational studies and animal experiments suggests that hypogonadism is associated with the metabolic syndrome. In most of the experiments, androgen deficiency is induced by gonadectomy in the adulthood and relatively short-term effects of hypogonadism on metabolic parameters are usually observed. The purpose of this study was to evaluate the metabolic effects of long-term androgen deficiency starting before puberty in middle-aged male rats. The components of the metabolic syndrome were examined in male, female and gonadectomized male rats at the age of 18months. Sex differences were observed in plasma testosterone, cholesterol, high-density lipoproteins and also in body weight and in glycemia dynamics during oral glucose tolerance test. Gonadectomy and long-term hypogonadism did not affect most of the analyzed metabolic parameters such as blood pressure, glycemia, plasma insulin and uric acid. The only exception was the significantly higher liver enzymes in plasma and triacylglycerol in liver found in gonadectomized males. Except low-density lipoprotein, neither treatment of middle-aged males and females with letrozole, nor supplementation of estradiol as the metabolite of testosterone in gonadectomized male rats changed any of the observed metabolic parameters. Our results suggest that long-term hypogonadism started before puberty does not induce metabolic syndrome in middle-aged male rats, but may affect the liver. Sex differences in metabolic parameters in middle-aged rats are not mediated by testosterone. Whether hypogonadism predispose to metabolic syndrome in combination with other risk factors needs further clarification.

Airborne PM2.5-Induced Hepatic Insulin Resistance by Nrf2/JNK-Mediated Signaling Pathway

Animal and epidemiological studies have suggested that exposure to airborne particulate matter (PM) with an aerodynamic diameter less than 2.5 μm (PM_2.5) is associated with the risk of developing type 2 diabetes. However, the mechanism underlying this risk is poorly understood. In the present study, we investigated the effects of PM_2.5 exposure on glucose homeostasis and related signaling pathways in mice. Wild-type and nuclear factor erythroid 2-related factor 2 (Nrf2) knockout (Nrf2^−/−) C57BL/6 male mice were exposed to either ambient concentrated PM_2.5 or filtered air (FA) for 12 weeks through a whole-body PM exposure system. At the end of the exposure, we assessed liver damage, and performed metabolic studies, gene expressions, as well as molecular signal transductions to determine the signaling pathways involving oxidative responses, insulin signaling, and glucose metabolism. Our results indicated that PM_2.5 exposure for 12 weeks caused significant liver damage as evidenced by elevated levels of aminotransferase (AST) and alanine aminotransferase (ALT). Furthermore, PM_2.5 exposure induced impaired glucose tolerance and inhibited glycogen synthesis, leading to hepatic insulin resistance indicated by higher glucose levels, higher area under the curve (AUC), and homeostasis model assessment of insulin resistance (HOMA-IR) values. We further found that PM_2.5 exposure significantly increased the expressions of Nrf2 and Nrf2-regulated antioxidant genes. Moreover, PM_2.5 exposure activated the c-Jun N-terminal kinase (JNK) signaling pathway and increased insulin receptor substrate-1 (IRS-1) phosphorylation at Ser³⁰⁷, but reduced protein kinase B phosphorylation at Ser⁴⁷³. Taken together, our study demonstrated PM_2.5 exposure triggered Nrf2-mediated oxidative responses and activated the JNK-mediated inhibitory signaling pathway, resulting in hepatic insulin resistance.

Investigation on hypoglycemic effects of ethanol extract of Alpinia nigra (Gaertn.) in animal model

Background:

Our study aims at exploring the hypoglycemic effect, efficacy, and possible mode of action of ethanol extract of Alpinia nigra (EEAN) as an antidiabetic agent in an animal model.

Methods:

Oral glucose tolerance test (OGTT) was used to identify primary hypoglycemic effect in mice. Three tests (glucose absorption, sucrose absorption, and disaccharidase activity) were carried out by gut perfusion and six segments studies to assess carbohydrate absorption and glucose utilization.

Results:

In OGTT, at 400 mg/kg and 800 mg/kg dose of EEAN extract significantly improved oral glucose tolerance among normal mice at 60 min and 90 min with compared to control. Both doses of extract significantly (P < 0.01) reduced blood glucose level and showed the hypoglycemic effect by retarding 11.43% and 20.82% of blood glucose level after 2 h of administration in glucose-induced mice, respectively. In situ perfused rat intestinal model demonstrated reduced glucose absorption at a 500 mg/kg dose. Inhibition of intestinal disaccharidase was also found by the extract. This was confirmed, yet again, via the six segment study. Throughout the length of the gastrointestinal tract, sucrose digestion was found to be inhibited which is also evident in the six segment study.

Conclusions:

This study suggests that the EEAN has hypoglycemic effects in a dose-dependent manner by inhibiting intestinal glucose absorption, and these may be effective in the treatment of diabetes. Further study is required to explicate the effect this extract or the active compounds have on the individual glucose transporters and the precise mechanism.

Obesity does not aggravate osteoporosis or osteoblastic insulin resistance in orchiectomized rats

The present study aimed to test the hypothesis that testosterone deprivation impairs osteoblastic insulin signaling, decreases osteoblast survival, reduces bone density, and that obesity aggravates those deleterious effects in testosterone-deprived rats. Twenty four male Wistar rats underwent either a bilateral orchiectomy (O, n=12) or a sham operation (S, n=12). Then the rats in each group were further divided into two subgroups fed with either a normal diet (ND) or a high-fat diet (HF) for 12 weeks. At the end of the protocol, blood samples were collected to determine metabolic parameters and osteocalcin ratios. The tibiae were collected to determine bone mass using microcomputed tomography and for osteoblast isolation. The results showed that rats fed with HF (sham-operated HF-fed rats (HFS) and ORX HF-fed rats (HFO)) developed peripheral insulin resistance and had decreased trabecular bone density. In ND-fed rats, only the ORX ND-fed rats (NDO) group had decreased trabecular bone density. In addition, osteoblastic insulin resistance, as indicated by a decrease in tyrosine phosphorylation of the insulin receptor and Akt, were observed in all groups except the sham-operated ND-fed rats (NDS) rats. Those groups, again with the exception of the NDS rats, also had decreased osteoblastic survival. No differences in the levels of osteoblastic insulin resistance and osteoblastic survival were found among the NDO, HFS, and HFO groups. These findings suggest that either testosterone deprivation or obesity alone can impair osteoblastic insulin signaling and decrease osteoblastic survival leading to the development of osteoporosis. However, obesity does not aggravate those deleterious effects in the bone of testosterone-deprived rats.

Androgen receptor silences thioredoxin-interacting protein and competitively inhibits glucocorticoid receptor-mediated apoptosis in pancreatic β-Cells

Androgen receptor (AR) is known to bind to the same cis-element that glucocorticoid receptor (GR) binds to. However, the effects of androgen signaling on glucocorticoid signaling have not yet been elucidated. Here, we investigated the effects of testosterone on dexamethasone (DEX, a synthetic glucocorticoid)-induced apoptosis of pancreatic β-cells, which might be involved in the pathogenesis of type 2 diabetes mellitus in males. We used INS-1 #6 cells, which were isolated from the INS-1 pancreatic β-cell line and which express high levels of AR. Testosterone and dihydrotestosterone inhibited apoptosis induced by DEX in INS-1 #6 cells. AR knockdown and the AR antagonist hydroxyflutamide each diminished the anti-apoptotic effects of testosterone. AR was localized in the nucleus of both INS-1 #6 cells and pancreatic β-cells of male rats. Induction of thioredoxin-interacting protein (TXNIP) is known to cause pro-apoptotic effects in β-cells. Testosterone suppressed the DEX-induced increase of TXNIP at the transcriptional level. A Chromatin immunoprecipitation assays showed that both AR and GR competitively bound to the TXNIP promoter in ligand-dependent manners. Recombinant DNA-binding domain of AR bound to the same cis-element of the TXNIP promoter that GR binds to. Our results show that AR and GR competitively bind to the same cis-element of TXNIP promoter as a silencer and enhancer, respectively. These results indicate that androgen signaling functionally competes with glucocorticoid signaling in pancreatic β-cell apoptosis.

Modulation of Microbiota-Gut-Brain Axis by Berberine Resulting in Improved Metabolic Status in High-Fat Diet-Fed Rats

OBJECTIVE

To investigate whether or not berberine could improve metabolic status of high-fat-fed rats through modulation of microbiota-gut-brain axis.

METHODS

Berberine was administered on high-fat-fed Sprague-Dawley rats. Brain-gut hormones were detected, and changes of gut microbiota were analyzed by 16S rRNA gene sequencing.

RESULTS

Berberine could reduce weight gain and lipolysis in the high-fat diet-fed group. Moreover, trends of ameliorated insulin resistance and decreased endogenous glucose production were observed. In addition, the microbiota-gut-brain axis was found to be modulated, including structural and diversity changes of microbiota, elevated serum glucagon-like peptide-1 and neuropeptide Y level, decreased orexin A level, up-regulated glucagon-like peptide-1 receptor mRNA level as well as ultra-structural improvement of the hypothalamus.

CONCLUSION

Taken together, our findings suggest that berberine improved metabolic disorders induced by high-fat diet through modulation of the microbiota-gut-brain axis.

Dipeptidyl peptidase 4 inhibitor improves brain insulin sensitivity, but fails to prevent cognitive impairment in orchiectomy obese rats

It is unclear whether the dipeptidyl peptidase 4 (DPP4) inhibitor can counteract brain insulin resistance, brain mitochondrial dysfunction, impairment of hippocampal synaptic plasticity and cognitive decline in testosterone-deprived obese rats. We hypothesized that DPP4 inhibitor vildagliptin improves cognitive function in testosterone-deprived obese rats by restoring brain insulin sensitivity, brain mitochondrial function and hippocampal synaptic plasticity. Thirty male Wistar rats received either a sham-operated (S, n=6) or bilateral orchiectomy (ORX, n=24). ORX rats were divided into two groups and fed with either a normal diet (ND (NDO)) or a high-fat diet (HFO) for 12 weeks. Then, ORX rats in each dietary group were divided into two subgroups (n=6/subgroup) to receive either a vehicle or vildagliptin (3 mg/kg per day, p.o.) for 4 weeks. After treatment, cognitive function, metabolic parameters, brain insulin sensitivity, hippocampal synaptic plasticity and brain mitochondrial function were determined in each rat. We found that HFO rats exhibited peripheral and brain insulin resistance, brain mitochondrial dysfunction, impaired hippocampal synaptic plasticity and cognitive decline. NDO rats did not develop peripheral and brain insulin resistance. However, impaired hippocampal synaptic plasticity and cognitive decline occurred. Vildagliptin significantly improved peripheral insulin sensitivity, restored brain insulin sensitivity and decreased brain mitochondrial reactive oxygen species production in HFO rats. However, vildagliptin did not restore hippocampal synaptic plasticity and cognitive function in both NDO and HFO rats. These findings suggest that vildagliptin could not counteract the impairment of hippocampal synaptic plasticity and cognitive decline in testosterone-deprived subjects, despite its effects on improved peripheral and brain insulin sensitivity as well as brain mitochondrial function.