A low level of serum total testosterone is independently associated with nonalcoholic fatty liver disease

Transcriptomic analysis of hepatic responses to testosterone deficiency in miniature pigs fed a high-cholesterol diet

Background

Recent studies have indicated that low serum testosterone levels are associated with increased risk of developing hepatic steatosis; however, the mechanisms mediating this phenomenon have not been fully elucidated. To gain insight into the role of testosterone in modulating hepatic steatosis, we investigated the effects of testosterone on the development of hepatic steatosis in pigs fed a high-fat and high-cholesterol (HFC) diet and profiled hepatic gene expression by RNA-Seq in HFC-fed intact male pigs (IM), castrated male pigs (CM), and castrated male pigs with testosterone replacement (CMT).

Results

Serum testosterone levels were significantly decreased in CM pigs, and testosterone replacement attenuated castration-induced testosterone deficiency. CM pigs showed increased liver injury accompanied by increased hepatocellular steatosis, inflammation, and elevated serum alanine aminotransferase levels compared with IM pigs. Moreover, serum levels of total cholesterol, low-density lipoprotein cholesterol, and triglycerides were markedly increased in CM pigs. Testosterone replacement decreased serum and hepatic lipid levels and improved liver injury in CM pigs. Compared to IM and CMT pigs, CM pigs had lower serum levels of superoxide dismutase but higher levels of malondialdehyde. Gene expression analysis revealed that upregulated genes in the livers of CM pigs were mainly enriched for genes mediating immune and inflammatory responses, oxidative stress, and apoptosis. Surprisingly, the downregulated genes mainly included those that regulate metabolism-related processes, including fatty acid oxidation, steroid biosynthesis, cholesterol and bile acid metabolism, and glucose metabolism. KEGG analysis showed that metabolic pathways, fatty acid degradation, pyruvate metabolism, the tricarboxylic acid cycle, and the nuclear factor-kappaB signaling pathway were the major pathways altered in CM pigs.

Conclusions

This study demonstrated that testosterone deficiency aggravated hypercholesterolemia and hepatic steatosis in pigs fed an HFC diet and that these effects could be reversed by testosterone replacement therapy. Impaired metabolic processes, enhanced immune and inflammatory responses, oxidative stress, and apoptosis may contribute to the increased hepatic steatosis induced by testosterone deficiency and an HFC diet. These results deepened our understanding of the molecular mechanisms of testosterone deficiency-induced hepatic steatosis and provided a foundation for future investigations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1283-0) contains supplementary material, which is available to authorized users.

Testosterone suppresses the expression of regulatory enzymes of fatty acid synthesis and protects against hepatic steatosis in cholesterol-fed androgen deficient mice

AIMS

Non-alcoholic fatty liver disease and its precursor hepatic steatosis is common in obesity and type-2 diabetes and is associated with cardiovascular disease (CVD). Men with type-2 diabetes and/or CVD have a high prevalence of testosterone deficiency. Testosterone replacement improves key cardiovascular risk factors. The effects of testosterone on hepatic steatosis are not fully understood.

MAIN METHODS

Testicular feminised (Tfm) mice, which have a non-functional androgen receptor (AR) and very low serum testosterone levels, were used to investigate testosterone effects on high-cholesterol diet-induced hepatic steatosis.

KEY FINDINGS

Hepatic lipid deposition was increased in Tfm mice and orchidectomised wild-type littermates versus intact wild-type littermate controls with normal androgen physiology. Lipid deposition was reduced in Tfm mice receiving testosterone treatment compared to placebo. Oestrogen receptor blockade significantly, but only partially, reduced the beneficial effects of testosterone treatment on hepatic lipid accumulation. Expression of key regulatory enzymes of fatty acid synthesis, acetyl-CoA carboxylase alpha (ACACA) and fatty acid synthase (FASN) were elevated in placebo-treated Tfm mice versus placebo-treated littermates and Tfm mice receiving testosterone treatment. Tfm mice on normal diet had increased lipid accumulation compared to littermates but significantly less than cholesterol-fed Tfm mice and demonstrated increased gene expression of hormone sensitive lipase, stearyl-CoA desaturase-1 and peroxisome proliferator-activated receptor-gamma but FASN and ACACA were not altered.

SIGNIFICANCE

An action of testosterone on hepatic lipid deposition which is independent of the classic AR is implicated. Testosterone may act in part via an effect on the key regulatory lipogenic enzymes to protect against hepatic steatosis.

Low serum sex hormone-binding globulin is associated with nonalcoholic fatty liver disease in type 2 diabetic patients

INTRODUCTION

Studies have indicated that low serum sex hormone-binding globulin (SHBG) and testosterone levels are associated with nonalcoholic fatty liver disease (NAFLD). However, it remains unclear whether an association exists between SHBG and NAFLD independent of testosterone.

OBJECTIVE

This study was aimed to investigate the relationship between SHBG and both total and free testosterone levels with NAFLD.

SUBJECTS AND MEASURES

One hundred and twenty patients with NAFLD and 120 age-, sex- and BMI-matched patients with non-NAFLD were enrolled into a case-control study. Serums SHBG, total testosterone (TT), liver enzymes, lipids, insulin, C-peptide and plasma glucose were measured. Free testosterone (FT) and fatty liver index were calculated.

RESULTS

Serum SHBG levels were significantly lower in NAFLD group than in non-NAFLD group (24·5 ± 11·0 vs 37·6 ± 14·4 nm, P < 0·001). After adjustment for age, smoking status, alcohol use, duration of diabetes, BMI and fasting C-peptide, serum SHBG levels in men and women were inversely associated with NAFLD, with odds ratio (OR) and 95% confidence interval (CI) in the forth quartile as 0·05 (0·01-0·30) and 0·25 (0·08-0·77) compared with the first quartile (OR = 1·00). Additional adjustment for TT in men and FT in women did not materially alter the association. The relationship between serum TT (for men) and FT (for women) with NAFLD was attenuated and even diminished after multivariable adjustment for known risk factors and SHBG.

CONCLUSION

Low serum SHBG levels, but not TT or FT, are associated with NAFLD in type 2 diabetic patients.

Nonalcoholic fatty liver disease is a negative risk factor for prostate cancer recurrence

Nonalcoholic fatty liver disease (NAFLD) is closely related to the metabolic syndrome, which is associated with an increased risk of various malignancies. In this study, we investigated the association between NAFLD and prostate cancer biochemical recurrence (BCR) after radical prostatectomy. Consecutive prostate cancer patients who underwent radical prostatectomy were enrolled from two hospitals in Korea and randomly assigned to the training (n=147) or validation set (n=146). The presence of NAFLD, BMI, preoperative prostate-specific antigen, and histological findings including Gleason score (GSc) were analyzed in regard to their association with BCR. NAFLD was diagnosed based on ultrasonography or unenhanced computed tomography images. BCR-free survival rates were calculated using the Kaplan-Meier method. In the training set, 32 (21.8%) patients developed BCR during a median follow-up period of 51 (inter-quartile range, 35-65) months. In the multivariate analysis, the presence of NAFLD (hazard ratio (HR), 0.36; 95% CI, 0.14-0.97; P=0.04) was an independent negative predictive factor of BCR after adjustment for pathological GSc. Applied to the validation set, the presence of NAFLD maintained its prognostic value for longer time-to-BCR (HR, 0.17; 95% CI, 0.06-0.49; P=0.001). In the subgroup analysis of patients with NAFLD, NAFLD fibrosis score was a single independent negative predictor for BCR (HR, 0.54; 95% CI, 0.30-0.98; P=0.04). Our study demonstrated that NAFLD may play a protective role against BCR after radical prostatectomy for prostate cancer. Further study is warranted to elucidate the mechanism of protective effect in patients with NAFLD.

Prevalence of low testosterone levels in men with type 2 diabetes mellitus: a cross-sectional study

Background:

A high prevalence of low serum testosterone (LST) in men with type 2 diabetes have been reported worldwide. The aim of this study was to determine the prevalence and associated factors of LST in men with type 2 diabetes.

Materials and Methods:

This was a cross-sectional study, conducted among 1,089 men (aged 30-70 years) with type 2 diabetes who consecutively attended a major diabetes center in Amman, Jordan, between August 2008 and February 2009. The patients’ demographic characteristics were collected using a prestructured questionnaire. Duration of diabetes, smoking habits, presence of retinopathy, neuropathy, and nephropathy were collected from the medical records. All participants were asked to complete the Androgen Deficiency in Ageing Male (ADAM) questionnaire. Venous blood sample was collected to test for total testosterone (TT), free testosterone (FT), sex hormone binding globulin (SHBG), follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), serum lipids, and glycosylated hemoglobin (HbA1c). LST was defined as TT <3 ng/ml.

Results:

Overall, 36.5% of patients with diabetes had TT level <3 ng/ml and 29% had symptoms of androgen deficiency. Of those with serum testosterone level <3 ng/ml, 80.2% had symptoms of androgen deficiency, 16.9% had primary hypogonadism (HG), and 83.1% had secondary HG. Univariate analysis showed a significant relationship between age, income, education, body mass index (BMI), smoking, duration of diabetes, diabetic nephropathy, diabetic neuropathy, and HbA1c. Multivariate logistic regression analysis indicated age, income, BMI, and diabetic neuropathy as the independent risk factors of LST.

Conclusions:

The prevalence of LST among men with type 2 diabetes is high. Age, income, BMI, and diabetic neuropathy were found to be the independent risk factors for LST.

Nonalcoholic steatohepatitis as a novel player in metabolic syndrome-induced erectile dysfunction: an experimental study in the rabbit

A pathogenic link between erectile dysfunction (ED) and metabolic syndrome (MetS) is now well established. Nonalcoholic steatohepatitis (NASH), the hepatic hallmark of MetS, is regarded as an active player in the pathogenesis of MetS-associated cardiovascular disease (CVD). This study was aimed at evaluating the relationship between MetS-induced NASH and penile dysfunction. We used a non-genomic, high fat diet (HFD)-induced, rabbit model of MetS, and treated HFD rabbits with testosterone (T), with the selective farnesoid X receptor (FXR) agonist obeticholic acid (OCA), or with the anti-TNFα mAb infliximab. Rabbits fed a regular diet were used as controls. Liver histomorphological and gene expression analysis demonstrated NASH in HFD rabbits. Several genes related to inflammation (including TNFα), activation of stellate cells, fibrosis, and lipid metabolism parameters were negatively associated to maximal acetylcholine (Ach)-induced relaxation in penis. When all these putative liver determinants of penile Ach responsiveness were tested as covariates in a multivariate model, only the association between hepatic TNFα expression and Ach response was confirmed. Accordingly, circulating levels of TNFα were increased 15-fold in HFD rabbits. T and OCA dosing in HFD rabbits both reduced TNFα liver expression and plasma levels, with a parallel increase of penile eNOS expression and responsiveness to Ach. Also neutralization of TNFα with infliximab treatment fully normalized HFD-induced hypo-responsiveness to Ach, as well as responsiveness to vardenafil, a phosphodiesterase type 5 inhibitor. Thus, MetS-induced NASH in HFD rabbits plays an active role in the pathogenesis of ED, likely through TNFα, as indicated by treatments reducing liver and circulating TNFα levels (T or OCA), or neutralizing TNFα action (infliximab), which significantly improve penile responsiveness to Ach in HFD rabbits.

Testosterone replacement ameliorates nonalcoholic fatty liver disease in castrated male rats

Nonalcoholic fatty liver disease is common in developed countries and is associated with obesity, metabolic syndrome, and type 2 diabetes. T deficiency is a risk factor for developing these metabolic deficiencies, but its role in hepatic steatosis has not been well studied. We investigated the effects of T on the pathogenesis of hepatic steatosis in rats fed a high-fat diet (HFD). Adult male rats were randomly placed into four groups and treated for 15 weeks: intact rats on regular chow diet (RCD), intact rats on liquid HFD (I+HFD), castrated rats on HFD (C+HFD), and castrated rats with T replacement on HFD (C+HFD+T). Fat contributed 71% energy to the HFD but only 16% of energy to the RCD. Serum T level was undetectable in castrated rats, and T replacement led to 2-fold higher mean serum T levels than in intact rats. C+HFD rats gained less weight but had higher percentage body fat than C+HFD+T. Severe micro- and macrovesicular fat accumulated in hepatocytes with multiple inflammatory foci in the livers of C+HFD. I+HFD and C+HFD+T hepatocytes demonstrated only mild to moderate microvesicular steatosis. T replacement attenuated HFD-induced hepatocyte apoptosis in castrated rats. Serum glucose and insulin levels were not increased with HFD in any group. Immunoblots showed that insulin-regulated proteins were not changed in any group. This study demonstrates that T deficiency may contribute to the severity of hepatic steatosis and T may play a protective role in hepatic steatosis and nonalcoholic fatty liver disease development without insulin resistance.

Loss of 5α-reductase type 1 accelerates the development of hepatic steatosis but protects against hepatocellular carcinoma in male mice

Nonalcoholic fatty liver disease (NAFLD) has been associated with glucocorticoid excess and androgen deficiency, yet in the majority of patients with steatohepatitis, circulating cortisol and androgen levels are normal. The enzyme 5α-reductase (5αR) has a critical role in androgen and glucocorticoid action. We hypothesize that 5αR has an important role in the pathogenesis of steatohepatitis through regulation of intracrine/paracrine hormone availability. Human liver samples from patients with NAFLD and normal donor tissue were used for gene expression and immunohistochemical analysis. NAFLD samples were scored using the Kleiner classification. In addition, 5αR1(-/-), 5αR2(-/-), and wild-type (WT) mice were fed normal chow or American lifestyle-induced obesity syndrome (ALIOS) diet for 6 or 12 months. Liver histology was graded and staged. Hepatic and circulating free fatty acid and triglyceride levels were quantified, and gene and protein expression was measured by real-time PCR and immunohistochemistry. 5αR1 and -2 were highly expressed in human liver, and 5αR1 protein expression increased with severity of NAFLD. 5αR1(-/-) (but not 5αR2(-/-)) mice fed an ALIOS diet developed greater hepatic steatosis than WT mice, and hepatic mRNA expression of genes involved in insulin signaling was decreased. Furthermore, 60% of WT mice developed focal hepatocellular lesions consistent with hepatocellular carcinoma after 12 months of the ALIOS diet, compared with 20% of 5αR2(-/-) and 0% of 5αR1(-/-) mice (P < .05). 5αR1 deletion accelerates the development of hepatic steatosis but may protect against the development of NAFLD-related hepatocellular neoplasia and therefore has potential as a therapeutic target.

Non-alcoholic fatty liver disease in common endocrine disorders

Non-alcoholic fatty liver disease (NAFLD) is a spectrum of disease spanning from simple benign steatosis to steatohepatitis with fibrosis and scarring that can eventually lead to cirrhosis. Its prevalence is rising rapidly and is developing into the leading indication for liver transplantation worldwide. Abnormalities in endocrine axes have been associated with NALFD, including hypogonadism, hypothyroidism, GH deficiency and hypercortisolaemia. In some instances, correction of the endocrine defects has been shown to have a beneficial impact. While in patients with type 2 diabetes the association with NAFLD is well established and recognised, there is a more limited appreciation of the condition among common endocrine diseases presenting with hormonal excess or deficiency. In this review, we examine the published data that have suggested a mechanistic link between endocrine abnormalities and NAFLD and summarise the clinical data endorsing these observations.

Sex steroids and sex hormone-binding globulin in postmenopausal women with nonalcoholic fatty liver disease

OBJECTIVE

The evaluation of serum sex steroids and sex hormone-binding globulin (SHBG) levels in postmenopausal women with nonalcoholic fatty liver disease (NAFLD) and their association to the disease severity.

DESIGN

Twenty-two postmenopausal women with biopsy-proven NAFLD and 18 matched controls were recruited. Blood samples for serum SHBG, total testosterone, estradiol levels and standard biochemical tests were obtained after overnight fasting. Free androgen index (FAI), calculated free (cFT) and bioavailable testosterone were estimated by standard formulas.

RESULTS

The NAFLD group had lower serum SHBG levels and higher values of cFT, bioavailable testosterone and FAI, despite exhibiting similar to controls levels of serum total testosterone and estradiol. Serum SHBG levels (adjusted odds ratio [aOR]=0.912; 95% CI 0.854-0.973), bioavailable testosterone (aOR=1.254; 95% CI 1.010-1.556) and FAI (aOR=2.567; 95% CI 1.153-5.716), but not cFT, were associated with NAFLD independently of age, body mass index (BMI) and waist circumference. Serum estradiol levels were associated with the presence of nonalcoholic steatohepatitis (NASH) independently of age, BMI and waist circumference (aOR=0.727; 95% CI 0.537-0.985).

CONCLUSIONS

Low SHBG levels and high metabolically active testosterone fractions were independently associated with NAFLD. Among NAFLD patients, serum estradiol levels were independently associated with NASH. However, these results need further validation from large-scale studies.

Testosterone deficiency induces markedly decreased serum triglycerides, increased small dense LDL, and hepatic steatosis mediated by dysregulation of lipid assembly and secretion in mice fed a high-fat diet

OBJECTIVE

Although low serum testosterone (T) is associated with metabolic disorders, the mechanism of this association is unclear. The objective of the present study was to investigate the combined effects of T deficiency and a high-fat diet (HFD) on hepatic lipid homeostasis in mice.

MATERIALS/METHODS

Orchiectomized (ORX) mice and sham-operated (SHAM) mice were randomly divided into five groups: SHAM mice fed a standard diet (SD), SHAM mice fed HFD, ORX mice fed SD, ORX mice fed HFD, and ORX mice fed HFD with T supplementation. After 4weeks of treatment, we investigated the synthesis and secretion of lipids in the liver and detailed serum lipoprotein profiles in each group.

RESULTS

ORX mice fed HFD showed increased hepatic steatosis, markedly decreased serum triglyceride (TG) and TG-VLDL content, and increased serum very small-LDL content. Gene expression analysis revealed that ORX mice fed HFD showed significantly decreased expression of microsomal triglyceride transfer protein, lipin-1, peroxisome proliferator-activated receptor (PPAR)-α and PPAR-γ coactivator 1-α, and significantly increased sterol regulatory element-binding protein-1, diacylglycerol acyltransferase-2 and fatty acid synthase. Reduction of hepatic AMPK phosphorylation was observed in ORX mice fed HFD. These perturbations in ORX mice fed HFD were normalized to the levels of SHAM mice fed HFD by T supplementation.

CONCLUSION

T deficiency is associated with failure of lipid homeostasis mediated by altered expression of genes involved in hepatic assembly and secretion of lipids.

Body compositional and cardiometabolic effects of testosterone therapy in obese men with severe obstructive sleep apnoea: a randomised placebo-controlled trial

BACKGROUND

The combination of male gender, obstructive sleep apnoea (OSA) and obesity magnifies cardiometabolic risk. There has been no systematic study evaluating whether testosterone therapy can improve cardiometabolic health in obese men with OSA by improving body composition, visceral abdominal fat and insulin sensitivity.

OBJECTIVE

To assess body compositional and cardiometabolic effects of testosterone treatment in obese men with severe OSA.

DESIGN

An 18-week randomised, double-blind, placebo-controlled and parallel group trial in 67 men.

METHODS

Participants (age=49 ± 12 years, apnoea hypopnoea index=39.9 ± 17.7 events/h, BMI=31.3 ± 5.2 kg/m(2)) were placed on a hypocaloric diet and received i.m. injections of either 1000 mg testosterone undecanoate (n=33) or placebo (n=34) for 18 weeks. Outcomes were the changes in body composition (total muscle mass, total and abdominal fat, total body dual-energy X-ray absorptiometry and computerised tomography (CT)), weight, insulin sensitivity (homeostasis model assessment), abdominal liver fat (CT), arterial stiffness (pulse wave analysis), resting metabolic rate and respiratory quotient (indirect calorimetry) and blood lipids and metabolic syndrome from baseline to week 18.

RESULTS

After 18 weeks, testosterone treatment increased insulin sensitivity (-1.14 units, 95% confidence interval (95% CI) -2.27 to -0.01, P<0.05), reduced liver fat (0.09 Hounsfield attenuation ratio, 95% CI 0.009 to 0.17, P=0.03) and increased muscle mass (1.6 kg, 95% CI 0.69 to 2.5, P=0.0009) to a greater extent than placebo. Other measures of body composition and regional adiposity as well as the number of participants with metabolic syndrome did not change. Testosterone also decreased arterial stiffness (augmentation index) by 3.2% (95% CI -6.01 to -0.46%, P=0.02) and decreased the respiratory quotient (95% CI -0.04, -0.08 to -0.001, P=0.04) after 18 weeks compared with placebo.

CONCLUSION

Eighteen weeks of testosterone therapy in obese men with OSA improved several important cardiometabolic parameters but did not differentially reduce overall weight or the metabolic syndrome. Longer term studies are required.