Deleterious effects of obesity upon the hormonal and molecular mechanisms controlling spermatogenesis and male fertility

Do lifestyle practices impede male fertility?

Alongside an increasing prevalence of couple and male infertility, evidence suggests there is a global declining trend in male fertility parameters over the past few decades. This may, at least in part, be explained through detrimental lifestyle practices and exposures. These include alcohol and tobacco consumption, use of recreational drugs (e.g., cannabis, opioids and anabolic steroids), poor nutritional habits, obesity and metabolic syndrome, genital heat stress (e.g., radiation exposure through cell phones and laptops, prolonged periods of sitting, tight-fitting underwear and recurrent hot baths or saunas), exposure to endocrine-disrupting chemicals (e.g., pesticide residue, bisphenol A, phthalates and dioxins) and psychological stress. This review discusses these lifestyle practices and the current evidence associated with male infertility. Furthermore, known mechanisms of action are also discussed for each of these. Common mechanisms associated with a reduction in spermatogenesis and/or steroidogenesis due to unfavourable lifestyle practices include inflammation and oxidative stress locally or systemically. It is recommended that relevant lifestyle practices are investigated in clinical history of male infertility cases, particularly in unexplained or idiopathic male infertility. Appropriate modification of detrimental lifestyle practices is further suggested and recommended in the management of male infertility.

The Role of Diet and Weight Loss in Improving Secondary Hypogonadism in Men with Obesity with or without Type 2 Diabetes Mellitus

Despite growing recognition of the issue, obesity represents one of the most common public health problems, and its rates are still increasing globally. Among the number of comorbidities and complications associated with obesity, hypogonadism is listed, and this disorder, although frequently neglected, is characterized by a relevant impact on both quality of life and life expectancy. It is generally accepted that hypogonadism secondary to obesity is functional since it is reversible following weight loss. This review summarizes all current research examining the bidirectional relationship between excess body weight and low testosterone levels. Specifically, it evaluates the role that diet, with or without physical activity, plays in improving body weight and hypogonadism in adult and elderly men with obesity, with or without type 2 diabetes mellitus.

Transgenerational effect of parental obesity and chronic parental bisphenol A exposure on hormonal profile and reproductive organs of preadolescent Wistar rats of F1 generation: A one-generation study

There is a global concern about adverse health effects of endocrine-disrupting chemicals (EDCs). Bisphenol A (BPA), an estrogenic and obesogenic compound, used in the plastic and medical industry has a dominant position among EDCs as far as human health and regulatory scenario are concerned. Due to its omnipresence across the biosphere, population of all age groups and health status is unavoidably exposed to BPA. Transgenerational exposure to BPA and its effects have also been recognized. However, there is no report on the transgenerational effect of BPA on metabolically disordered parents, such as obese ones. We studied effect of BPA exposure in F0 generation and its impact on F1 generation and factored parental obesity in transgenerational effect of concurrent exposure to low dose BPA (10 ppm × 180 days) in Wistar rats in a one-generation study protocol. The exposed F0 generation animals were crossed and F1 generation was analyzed 35 days after birth for indications of reproductive toxicity. We observed changes in hormone levels and disturbance in glucose and lipid homeostasis. Animals showed increased serum cholesterol and triglycerides along with higher birth weight and rapid weight gain. Histopathological evidence confirmed the presence of regressive and inflammatory changes in the ovary and testis. The test group showed metabolic disturbances in comparison to control group. Our study showed the additive effect of parental obesity in transgenerational reproductive toxicity of BPA. Female animals of F1 generation of BPA-treated obese parents showed more insulin resistance than males with similar exposure scenario. Our study highlights the confounding role of metabolic disorders such as obesity in the transgenerational toxicity of BPA, which otherwise itself is implicated in the aetiology of such metabolic disorders, directly or indirectly.

Adipocyte deficiency of ACE2 increases systolic blood pressures of obese female C57BL/6 mice

BACKGROUND

Obesity increases the risk for hypertension in both sexes, but the prevalence of hypertension is lower in females than in males until menopause, despite a higher prevalence of obesity in females. We previously demonstrated that angiotensin-converting enzyme 2 (ACE2), which cleaves the vasoconstrictor, angiotensin II (AngII), to generate the vasodilator, angiotensin-(1-7) (Ang-(1-7)), contributes to sex differences in obesity-hypertension. ACE2 expression in adipose tissue was influenced by obesity in a sex-specific manner, with elevated ACE2 expression in obese female mice. Moreover, estrogen stimulated adipose ACE2 expression and reduced obesity-hypertension in females. In this study, we hypothesized that deficiency of adipocyte ACE2 contributes to obesity-hypertension of females.

METHODS

We generated a mouse model of adipocyte ACE2 deficiency. Male and female mice with adipocyte ACE2 deficiency or littermate controls were fed a low (LF) or a high fat (HF) diet for 16 weeks and blood pressure was quantified by radiotelemetry. HF-fed mice of each sex and genotype were challenged by an acute AngII injection, and blood pressure response was quantified. To translate these findings to humans, we performed a proof-of-principle study in obese transwomen in which systemic angiotensin peptides and blood pressure were quantified prior to and after 12 weeks of gender-affirming 17β-estradiol hormone therapy.

RESULTS

Adipocyte ACE2 deficiency had no effect on the development of obesity in either sex. HF feeding increased systolic blood pressures (SBP) of wild-type male and female mice compared to LF-fed controls. Adipocyte ACE2 deficiency augmented obesity-induced elevations in SBP in females, but not in males. Obese female, but not obese male mice with adipocyte ACE2 deficiency, had an augmented SBP response to acute AngII challenge. In humans, plasma 17β-estradiol concentrations increased in obese transwomen administered 17β-estradiol and correlated positively with plasma Ang-(1-7)/AngII balance, and negatively to SBP after 12 weeks of 17β-estradiol administration.

CONCLUSIONS

Adipocyte ACE2 protects female mice from obesity-hypertension, and reduces the blood pressure response to systemic AngII. In obese transwomen undergoing gender-affirming hormone therapy, 17β-estradiol administration may regulate blood pressure via the Ang-(1-7)/AngII balance.

Is low body mass index a risk factor for semen quality? A PRISMA-compliant meta-analysis

BACKGROUND

Male infertility has become a worldwide public health problem. However, the effect of low body mass index (BMI) is still controversial.

METHODS

Relevant articles in Pubmed, Embase, Web of science, and Wanfang database published until September 2017 were searched without language restriction. We performed a meta-analysis about low BMI and semen parameters containing total sperm count, concentration, semen volume, and sperm motility (overall and progressive), including 709 men with low BMI and 14,622 men with normal BMI.

RESULTS

Thirteen studies were included in this meta-analysis and a total of 15,331 individuals were accumulated. We pooled data from these articles and found standardized weighted mean differences in semen parameters (total sperm count and semen volume) showed significant difference between low BMI and normal BMI.

CONCLUSIONS

This systematic review with meta-analysis has confirmed that there was a relationship between low BMI and semen quality, which suggesting low BMI may be a harmful factor of male infertility. Yet lacking of the raw data may influence the accuracy of the results. Further researches are needed to identify the role of underweight in male sterility.

Adipocytokines may delay pubertal maturation of human Sertoli cells

Reproduction is an important target of obesity complications, including adverse effects on spermatogenesis and steroidogenesis. Adipocytokines are key mediators in various complications of obesity. Our aim was to study the potential of adipocytokines to affect Sertoli cell function, which is crucial for spermatogenesis, and possibly link these findings to the observed attenuation of spermatogenesis in obese males. Testicular biopsies were obtained from healthy donors. Highly purified adult human Sertoli cells (HSCs) were isolated by fluorescence-activated cell sorting. Cells were cultured and exposed to different concentrations of adipocytokines (10-1000ngmL-1 ) for 2-7 days. Expression of selected Sertoli cell genes was quantified by quantitative polymerase chain reaction. Long-term treatment (7 days) of HSCs with higher concentrations of chemerin, irisin, nicotinamide phosphoribosyltransferase (Nampt), resistin and progranulin significantly suppressed FSH receptor expression (by 79%, 83%, 64%, 71% and 26% respectively; P P invitro , may negatively affect Sertoli cell maturation and retain these cells in a more prepubertal stage. This could negatively affect testis function and add to fertility problems in obese adults.

How much does obesity affect the male reproductive function?

Obesity is considered a worldwide epidemic disease. Many pathological conditions have been associated to obesity but the evidence relating to impaired fertility in males with obesity are contrasting. The aim of this review was to evaluate the interplay between obesity and male fertility, analyzing evidence from in vitro and in vivo studies to clinical trials. Obesity seems to be responsible of secondary hypogonadism. Here, we propose a new classification including central, peripheral and testicular factors that may affect the hypothalamic-pituitary-gonadal axis. Moreover, some studies demonstrated a direct action of obesity on sperm count and sperm characteristics, mediated by impaired Sertoli cells function, increased scrotal temperature, oxidative stress and accumulation of toxic substances and liposoluble endocrine disruptors in fat tissue. Recent studies have explored obesity-related epigenetic effects in sperm cells which may cause diseases in offspring. Moreover, not only in females but also males, obesity has been linked to reduced outcomes of in vitro fertilization, with a reduction of pregnancy rate and an increase of pregnancy loss. Finally, we reviewed the effects of weight modifications through diet or bariatric surgery on obesity-related reproductive dysfunction. In this regard, several studies have demonstrated that weight loss has been associated with a restoration of gonadal hormones levels.

Assessment of Gender-Affirming Hormone Therapy Requirements

PURPOSE

There are currently no recommendations regarding the starting doses of hormone therapy for individuals with gender dysphoria. The purpose of this study was to assess the hormone dose needed to achieve target hormone levels in transgender men and transgender women, and whether body mass index (BMI) affects these doses.

METHODS

A retrospective chart review of subjects seeking gender-affirming hormone therapy was performed. Height, weight, hormone doses, and serum hormone levels were collected from charts. Data were analyzed for a correlation between BMI and effective hormone dosing (dose that achieved hormone levels in the target range).

RESULTS

Charts from 319 subjects were reviewed; however, only 84 transgender women and 71 transgender men had serum hormone levels available and only 40 transgender women and 54 transgender men had plasma hormone levels in the target range (normal range for affirmed gender). For transgender women, there was a significant negative correlation between BMI and effective estradiol dose (r = -0.337, p = 0.04). For transgender men, there was a positive correlation between BMI and effective testosterone dose (r = 0.409, p = 0.002).

CONCLUSION

Increased BMI was associated with lower estrogen dose requirements in transgender women. In transgender men, an increase in BMI was associated with increased testosterone dose requirements. These results suggest that BMI may influence effective gender-affirming hormone dosing; however, further studies are needed to examine its utility in determining the initial hormone dose.

Serum FSH level is lower in dysovulating than in ovulating non-PCOS obese women, independently of body mass index

OBJECTIVES

The prevalence of ovulation disorder (OD) is 3-fold higher in obese than normal-weight women. Most ODs are associated with concomitant polycystic ovary syndrome (PCOS), but obesity by itself can cause OD, through mechanisms that remain poorly documented. The literature on obese non-PCOS women with OD is sparse. The aim of the present study was to analyze a population of obese non-PCOS women with OD to shed further light on the mechanism of ovulation disorder.

MATERIAL AND METHODS

This retrospective observational study of infertile obese women without PCOS compared a control group without OD (n=45) to a study group with OD (n=30) (OD group). Clinical, hormonal, and ultrasound characteristics were collected between cycle days 2 and 5. Women older than 37 years and women with PCOM (polycystic ovarian morphology) or hormonal disorder were excluded.

RESULTS

Body mass index (BMI) was significantly higher in the OD group, as were waist circumference and insulin and leptin serum levels. Conversely, serum follicle stimulating hormone (FSH) levels were significantly lower. After adjustment for BMI, only serum FSH level remained significantly different between the 2 groups. Discriminant analysis suggested that FSH may have a much stronger effect on OD than BMI.

CONCLUSION

Low serum FSH level may contribute to OD in some obese women, independently of BMI. The pathophysiological mechanism of this finding and its impact on therapeutic strategies must be clarified.

Association between parental anthropometric measures and the outcomes of intracytoplasmic sperm injection cycles

PURPOSE

To study the association between body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), and waist-to-height ratio (WHtR), and response to controlled ovarian stimulation, semen quality, and intracytoplasmic sperm injection (ICSI) outcomes.

METHODS

This prospective observational study included data from 402 couples undergoing ICSI between January/2010-September/2016. Participants had their weight, height, waist, and hip measured before ICSI treatment.

RESULTS

Gonadotropin dose was positively associated with maternal WHR. Maternal WC and WHR negatively influenced the estradiol level, number of follicles, oocytes, and mature oocytes. Maternal BMI negatively influenced oocyte yield. Semen volume was negatively influenced by male BMI. Sperm concentration was negatively associated with WHR and WHtR. Progressive sperm motility was negatively influenced by all anthropometric measures (AMs). The TMSC was negatively affected by all AM but WC. Significant differences were observed in all ICSI outcomes except pregnancy and miscarriage rates, favoring women with AM below the cut off values compared to women above the cut off. It was observed that men with AM below the cut off values showed significantly higher rates of fertilization, embryo and blastocyst development, implantation, and pregnancy than men above the cut off. When combined maternal and paternal AM were analyzed, significant differences were observed in fertilization, embryo and blastocyst development and implantation rates, favoring couples with normal BMI, WC, and WHR.

CONCLUSIONS

Lower AMs have a protective effect on fertility. Awareness and counseling on how to minimize its impact in both partners could improve ICSI outcomes.

Hypothalamic Gliosis by MRI and Visceral Fat Mass Negatively Correlate with Plasma Testosterone Concentrations in Healthy Men

OBJECTIVE

This study aimed to determine whether a relationship was evident between gliosis in the mediobasal hypothalamus (MBH) and plasma testosterone concentrations in men.

METHODS

A total of 41 adult men (aged 18-50 years) from 23 twin pairs underwent fasting morning blood draw and brain magnetic resonance imaging. T2 relaxation time was used to quantify gliosis in the MBH and control areas in the putamen and amygdala. Plasma concentrations of testosterone and 17β-estradiol were measured by liquid chromatography-tandem mass spectrometry. Body composition including visceral adiposity was measured by dual x-ray absorptiometry.

RESULTS

A negative association was found between MBH T2 relaxation time and plasma concentrations of both free and total testosterone (r = -0.29, P < 0.05 and r = -0.37, P < 0.01, respectively). Visceral adiposity exhibited a negative correlation with plasma total testosterone concentration (r = -0.45, P = 0.001) but a positive correlation with MBH T2 relaxation time (r = 0.24, P = 0.03). The negative correlation between plasma total testosterone and MBH T2 relaxation time remained significant after adjustment for visceral adiposity, age, BMI, and insulin resistance.

CONCLUSIONS

In healthy men across a range of BMIs, MBH gliosis was associated with higher visceral adiposity but lower endogenous testosterone. These findings suggest that MBH gliosis could provide novel mechanistic insights into gonadal dysfunction in men with obesity.

Maternal obesity in the rat impairs male offspring aging of the testicular antioxidant defence system

A high-fat diet during intrauterine development predisposes offspring (F₁) to phenotypic alterations, such as lipid synthesis imbalance and increased oxidative stress, causing changes in male fertility. The objective of this study was to evaluate the effects of maternal obesity during pregnancy and lactation on antioxidant enzymes in the F₁ testes. Female Wistar rats (F₀) were fed either a control (C, 5% fat) or an obesogenic (MO, maternal obesity, 25% fat) diet from weaning and throughout subsequent pregnancy and lactation. F₁ offspring were weaned to the control diet. Testes were retrieved at 110, 450 and 650 postnatal days (PND) for real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) and immunohistochemical (IHC) antioxidant enzyme analyses. Catalase was similar between groups by RT-qPCR, whereas by IHC it was higher in the MO group at all ages than in the C group. Superoxide dismutase 1 (SOD1) had lower expression at PND 110 in MO than in C by both techniques; at PND 450 and 650 by immunoanalysis SOD1 was higher in MO than in C. Glutathione peroxidase 1 (GPX1), GPX2 and GPX4 by RT-qPCR were similar between groups and ages; by IHC GPX1/2 was higher in MO than in C, whereas GPX4 showed the opposite result at PND 110 and 450. In conclusion, antioxidant enzymes in the rat testes are modified with age. Maternal obesity negatively affects the F₁ testicular antioxidant defence system, which, in turn, can explain the decrease in reproductive capacity.

Do body mass index, hormone profile and testicular volume effect sperm retrieval rates of microsurgical sperm extraction in the patients with nonobstructive azoospermia?

OBJECTIVE

We aimed to evaluate the effect of body mass index (BMI), follicle stimulating hormone (FSH), and luteinizing hormone (LH) levels and the mean testicular volume on sperm retrieval rates in microsurgical sperm extraction (microTESE) in the patients with nonobstructive azoospermia (NOA).

MATERIAL AND METHODS

The data of 282 infertile patients with NOA were analysed retrospectively. The patients with normal karyotype and no Y microdeletions were included in the study. The patients were classified according to their BMI scores and the medical history, physical examination and hormonal parameters were evaluated. The overall data were processed statistically with chi-square and logistic regression analysis and the relation between preoperative findings and sperm retrieval rates was investigated.

RESULTS

The sperm retrieval rate of 282 patients after microTESE was found as 41.1%. There was no statistically significant difference in sperm retrieval rates among the subgroups classified according to BMI. FSH and LH levels and the mean testicular volume and pathologic findings were significantly correlated with sperm retrieval rates.

CONCLUSION

Finally significant correlation was determined between sperm retrieval rates and FSH, and LH levels and testicular volumes but no statistically significant difference was found in sperm retrieval rates among BMI groups.

Obesity, a serious etiologic factor for male subfertility in modern society

Obesity, defined as excessive accumulation of fat in adipose tissue, is a metabolic disorder resulting from behavioral, environmental and heritable causes. Obesity increases the risks of hypertension, diabetes, cardiovascular disease, sleep apnea, respiratory problems, osteoarthritis and cancer. Meanwhile, the negative impact of obesity on male reproduction is gradually recognized. According to the clinical investigations and animal experiments, obesity is correlated with reductions in sperm concentration and motility, increase in sperm DNA damage and changes in reproductive hormones. Several mechanisms can elucidate the effects of obesity on sperm functions and male subfertility, i.e., the excessive conversion of androgens into estrogens in redundant adipose tissue causes sexual hormone imbalance, subsequently resulting in hypogonadism. Secondly, adipokines produced by adipose tissue induce severe inflammation and oxidative stress in male reproductive tract, directly impairing testicular and epididymal tissues. Moreover, increased scrotal adiposity leads to increase gonadal heat, continuously hurting spermatogenesis. Therefore, obesity alters the systematic and regional environment crucial for spermatogenesis in testis and sperm maturation in epididymis, and finally results in poor sperm quality including decreased sperm motility, abnormal sperm morphology and acrosome reaction, changed membrane lipids and increased DNA damage. Furthermore, recent studies indicate that epigenetic changes may be a consequence of increased adiposity. A major effort to identify epigenetic determinants of obesity revealed that sperm DNA methylation and non-coding RNA modification are associated with BMI changes and proposed to inherit metabolic comorbidities across generations. This review will explain how obesity-related changes in males to influence sperm function and male fertility as well.

A high-fat, high-protein diet attenuates the negative impact of casein-induced chronic inflammation on testicular steroidogenesis and sperm parameters in adult mice

The interaction between obesity and chronic inflammation has been studied. Diet-induced obesity or chronic inflammation could reduce the testicular functions of males. However, the mechanism underlying the reproductive effects of fattening foods in males with or without chronic inflammation still needs further discussion. This study was aimed to investigate the effects of high-fat, high-protein diet on testicular steroidogenesis and sperm parameters in adult mice under physiological and chronic inflammatory conditions. Because casein can trigger a non-infectious systemic inflammatory response, we used casein injection to induce chronic inflammation in male adult Kunming mice. Twenty-four mice were randomly and equally divided into four groups: (i) normal diet+saline (Control); (ii) normal diet+casein (ND+CS); (iii) high-fat, high-protein diet+saline (HFPD+SI); (iv) high-fat, high-protein diet+casein (HFPD+CS). After 8weeks, there was a significant increase in body weight for groups HFPD+SI and HFPD+CS and a decrease in group ND+CS compared with the control. The serum levels of tumor necrosis factor alpha (TNF-α), interleukin-10 (IL-10) and lipid profiles were increased markedly in groups ND+CS, HFPD+SI and HFPD+CS compared with the control. A remarkable reduction of serum adiponectin level occurred in group HFPD+CS compared with group ND+CS. Sperm parameters (sperm count, viability and abnormality) were also adversely affected in groups ND+CS and HFPD+SI. Groups ND+CS and HFPD+SI showed severe pathological changes in testicular tissues. Semiquantitative RT-PCR, Western blot and immunohistochemical staining also showed significant reductions in both testicular mRNA and protein levels of steroidogenic acute regulatory (StAR) and cytochrome P450scc (CYP11A1) in groups HFPD+SI and HFPD+CS compared with the control, whereas testicular mRNA and protein levels of 3β-hydroxysteroid dehydrogenase (3β-HSD) in groups HFPD+SI and HFPD+CS significantly increased. The mRNA and protein levels of the StAR and 3β-HSD in group HFPD+CS were both higher than those of in group ND+CS. These results indicated that Kunming male mice with high-fat, high-protein diet and casein injection for 8weeks can be used to establish a diet-induced obesity and chronic systemic inflammation. The sperm parameters in groups ND+CS and HFPD+SI decreased accompanied by pathological changes of testicular tissue. This resultant effect of reduced serum testosterone levels was associated with the overproduction of TNF-α and IL-10 and down-regulation of StAR and CYP11A1. Under the same casein-induced chronic inflammation condition, the mice with high-fat, high-protein diet had better testicular steroidogenesis activity and sperm parameters compared with the mice in normal diet, indicating that the mice with casein-induced inflammatory injury consuming a high-fat, high-protein diet gained weight normally, reduced serum adiponectin level and increased testosterone production by an upregulation of 3β-HSD expression. High-fat, high-protein diet attenuated the negative impact of casein-induced chronic inflammation on testicular steroidogenesis and sperm parameters.

Aerobic exercise blocks interleukin-6 levels and germ cell apoptosis in obese rats

To investigate the effect of a high-fat diet and aerobic exercise intervention and its related mechanism on rat germ cell apoptosis. Forty male Sprague-Dawley rats were randomly divided into control group, high-fat diet group, control exercise group and high-fat exercise group. Rats were fed with high-fat diet or were given weight-free swimming. The levels of TG, TC, HDL, LDL and IL-6 in serum of rats were measured. The body weight, body length and inguinal fat weight were measured to calculate the Lee's index and lipid/body weight ratio. The expression of IL-6 mRNA in inguinal fat and IL-6R,Bcl-2 and Bax mRNA in testis was detected by RT-PCR. The morphological structure of testis was observed, and the Johnsen's ten-point score was calculated by HE staining, and the germ cell apoptosis was detected by TUNEL method. We got from the experimental results: a high-fat diet induces obesity and lipid metabolism disorder, alters testis morphological structure and increases germ cell apoptosis in rats. Aerobic exercise improves the lipid metabolism disorder and interferes with germ cell apoptosis by reducing interleukin-6 and interleukin-6 receptor expression.

Management of weight loss in obesity-associated male infertility: a spotlight on bariatric surgery

In recent years, there has been a paralleled increase between male obesity and infertility rates. Obesity is associated with impaired hypothalamic-pituitary-gonadal axis, aberrant semen parameters, and subfertility or infertility. Weight loss is strongly recommended for the management of obesity-associated infertility. Lifestyle modifications that include caloric restriction and increased physical activity have a short-lived impact. Bariatric surgery is a better and more durable weight loss alternative. Comprehensive information about the benefits of weight loss on obesity-associated male infertility following bariatric surgery is still emerging. In this review, we discuss the hormonal, physical and environmental mechanism contributing to obesity-associated infertility. We then assess weight loss approaches, which include lifestyle modification, medical and surgical approaches, that can improve fertility in obese men. This review focuses also on bariatric surgery for the management of obese men seeking fertility treatment. Anecdotal evidence suggesting that bariatric surgery can impair fertility is also discussed.

Metabolic endotoxaemia related inflammation is associated with hypogonadism in overweight men

BACKGROUND

Obesity is associated with both impaired testosterone production and a chronic state of low grade inflammation. Previously it was believed that this inflammation was mediated by a decline in the immunosuppressive action of testosterone. However, more recently an alternative hypothesis (GELDING theory) has suggested that inflammation originating from the passage of intestinal bacteria into the circulation (metabolic endotoxaemia) may actually be the cause of impaired testicular function in obese men. The aim of this study is to investigate if metabolic endotoxaemia, as quantified by serum Lipopolysaccharide Binding Protein (LBP), is associated with impaired testicular endocrine function.

METHODS

A total of 50 men aged between 21 and 50 years (mean 35.1 ± 6.8 years) were assessed for adiposity (BMI, waist circumference and % body fat using bio-impedance), inflammatory status (serum CRP, IL-1β, IL-6, TNFα and LBP) and testicular endocrine function (serum testosterone, estradiol, AMH, LH and FSH). Statistical analysis was performed using Pearson correlation analysis, with log transformation of data where appropriate, and multi-variate regression.

RESULTS

Overall increasing adiposity (% body fat) was positively associated with metabolic endotoxaemia (LBP, r = 0.366, p = 0.009) and inflammation (CRP r = 0.531, p < 0.001; IL-6 r = 0.463, p = 0.001), while also being negatively correlated with serum testosterone (r = -0.403, p = 0.004). Serum testosterone levels were significantly negatively correlated with inflammation (CRP r = -0.471, p = 0.001; IL-6 r = -0.516, p < 0.001) and endotoxaemia (LBP) after adjusting for serum LH levels (p = -0.317, p = 0.03). Furthermore, serum IL-6 was negatively associated with AMH levels (r = -0.324, p = 0.023), with a negative trend between LBP and AMH also approaching significance (r = -0.267, p = 0.064).

CONCLUSIONS

Obesity and its associated metabolic endotoxaemia helps initiate a pro-inflammatory state characterised by raised serum IL-6 levels, which in turn is correlated with impairment of both Leydig (testosterone) and Sertoli cell function (AMH). These results open up the potential for new treatments of obesity related male hypogonadism that focus on preventing the endotoxaemia associated chronic inflammatory state.

Effects of obesity and exercise on testicular leptin signal transduction and testosterone biosynthesis in male mice

To explore the role of the testicular leptin and JAK-STAT[leptin (LEP)-JAK-STAT] pathway in testosterone biosynthesis during juvenile stages and exercise for weight loss, male C57BL/6J mice were randomly divided into normal-diet and high-fat diet groups. After 10 wk, mice in the high-fat diet-fed group were further divided randomly into obese control, obese moderate-volume exercise, and obese high-volume exercise groups. Mice in the obese moderate-volume exercise group were provided with 2 h/day, 6 days/wk swimming exercise for 8 wk, and mice in the obese high-volume exercise group underwent twice the amount of daily exercise intervention as the obese moderate-volume exercise group. The results showed that a high-fat diet causes obesity, leptin resistance, inhibition of the testicular LEP-JAK-STAT pathway, decreased mRNA and protein expression of steroidogenic factor-1, steroidogenic acute regulatory protein, and the P-450 side-chain cleavage enzyme, a decrease in the serum testosterone-to-estradiol ratio, and declines in sperm quality parameters. Both moderate and high-volume exercise were able to reduce body fat and increase the mRNA and protein expression of LEP-JAK-STAT, but only moderate exercise significantly increased the mRNA and protein expression of steroidogenic factor-1, steroidogenic acute regulatory protein, and P-450 side-chain cleavage enzyme and significantly reversed the serum testosterone-to-estradiol ratio and sperm quality parameters. These findings suggest that by impairing the testicular LEP-JAK-STAT pathway, early-stage obesity inhibits the biosynthesis of testosterone and sexual development and reduces male reproductive potential. Long-term moderate and high-volume exercise can effectively reduce body fat and improve obesity-induced abnormalities in testicular leptin signal transduction, whereas only moderate-volume exercise can reverse the negative impacts of obesity on male reproductive function.

Prepubertal onset of obesity negatively impacts on testicular steroidogenesis in rats

Obesity is a global health problem and impacts negatively on levels of testosterone and quality of sperm production. At present little is known about mechanisms that attenuate testicular function in obese males. Our study characterized testicular steroidogenesis and explored levels of relevant paracrine and hormonal factors in rats with short- and long-term obesity. We have found that obesity state increased serum levels of estradiol and leptin in both groups of obese rats and inhibited the expression of StAR and Cyp11a1 associated with low levels of intratesticular testosterone in rats with long-term obesity. Further, long-term obesity reduced the number of Leydig cells, increased the testicular levels of the proinflammatory adipocytokine TNFα and the number of testicular macrophages. All together, our data indicate that long-term obesity may cause chronic inflammation in the testis and negatively impacts on Leydig cell steroidogenesis.

A high-fat diet fed during different periods of life impairs steroidogenesis of rat Leydig cells

This study evaluated the impact of a high-fat diet (HFD) during different stages of rat life, associated or not with maternal obesity, on the content of sex steroid hormones and morphophysiology of Leydig cells. The following periods of development were examined: gestation (O1), gestation and lactation (O2), from weaning to adulthood (O3), from lactation to adulthood (O4), gestation to adulthood (O5), and after sexual maturation (O6). The HFD contained 20% unsaturated fat, whereas the control diet had 4% fat. Maternal obesity was induced by feeding HFD 15 weeks before mating. All HFD groups presented increased body weight, hyperinsulinemia and reduced insulin sensitivity. Except for O1, all HFD groups exhibited a higher adiposity index, hyperleptinemia, reduced testosterone and estradiol testicular levels, and decreased testicular 17β-HSD enzyme . Morphometrical analyses indicated atrophy of Leydig cells in the O2 group. Myelin vesicles were observed in the mitochondrial matrix of Leydig cells in O3, O4, O5 and O6, and autophagosomes containing mitochondria were found in O5 and O6. In conclusion, HFD feeding, before or after sexual maturation, reduces the functional capacity of rat Leydig cells. Maternal obesity associated with HFD during pregnancy/lactation prejudices Leydig cell steroidogenesis and induces its atrophy in adulthood, even if it is replaced by a conventional diet at later stages of life. Regardless of the life period of exposure to HFD, deregulation of leptin is the main factor related to steroidogenic impairment of Leydig cells, and, in groups exposed for longer periods (O3, O4, O5 and O6), this is worsened by structural damage and mitochondrial degeneration of these cells.

Linking obesogenic dysregulation to prostate cancer progression

The global epidemic of obesity is closely linked to the development of serious co-morbidities, including many forms of cancer. Epidemiological evidence consistently shows that obesity is associated with a similar or mildly increased incidence of prostate cancer but, more prominently, an increased risk for aggressive prostate cancer and prostate cancer-specific mortality. Studies in mice demonstrate that obesity induced by high-fat feeding increases prostate cancer progression; however, the mechanisms underpinning this relationship remain incompletely understood. Adipose tissue expansion in obesity leads to local tissue dysfunction and is associated with low-grade inflammation, alterations in endocrine function and changes in lipolysis that result in increased delivery of fatty acids to tissues of the body. The human prostate gland is covered anteriorly by the prominent peri-prostatic adipose tissue and laterally by smaller adipose tissue depots that lie directly adjacent to the prostatic surface. We discuss how the close association between dysfunctional adipose tissue and prostate epithelial cells might result in bi-directional communication to cause increased prostate cancer aggressiveness and progression. However, the literature indicates that several 'mainstream' hypotheses regarding obesity-related drivers of prostate cancer progression are not yet supported by a solid evidence base and, in particular, are not supported by experiments using human tissue. Understanding the links between obesity and prostate cancer will have major implications for the health policy for men with prostate cancer and the development of new therapeutic or preventative strategies.