Irisin Improves High-Fat Diet-Induced Sexual Dysfunction in Obese Male Rats

Exercise-induced muscle hormone "irisin" controls luteinizing hormone and follicle-stimulating hormone secretion by bovine gonadotrophs

Irisin is a hormone secreted by muscle in response to exercise. The irisin receptor (IrisinR) is a heterodimer of integrin alpha V (ITGAV) and integrin beta 5 (ITGB5) subunits. Since irisin may mediate some beneficial effects of exercise on animal reproduction, we tested the hypothesis that bovine gonadotrophs express IrisinR and irisin stimulates luteinizing hormone (LH) and follicle stimulating hormone (FSH) secretion by gonadotrophs. Reverse transcription polymerase chain reaction was used to detect the mRNA expression of both ITGAV and ITGB5 in the anterior pituitary glands (APs) of post pubertal heifers and mouse gonadotroph cell line "LβT2." Western blotting was used to detect protein expression in bovine APs. Immunofluorescence microscopy, utilizing the same antibody, visualized IrisinR on the plasma membrane of majority of gonadotrophs. We prepared AP cells from healthy postpubertal heifers, cultured them for 3.5 d, and treated them with increasing concentrations (0, 0.01, 0.1, 1, or 10 nM) of irisin for 5 min before either no treatment or gonadotropin-releasing hormone (GnRH) stimulation. After 2 h, media were harvested for LH and FSH assays. Irisin (0.1-10 nM) stimulated basal LH and FSH secretion, and these stimulatory effects were inhibited by the extracellular signal-regulated kinase or SMAD pathway inhibitors. In the presence of GnRH, irisin at 0.01-1 nM stimulated LH and FSH secretion. A higher dose of irisin (10 nM), however, suppressed the GnRH-induced LH and FSH levels. In conclusion, bovine gonadotrophs expressed IrisinR, and irisin controlled LH and FSH secretion from bovine gonadotrophs.

Irisin as an emerging target in the regulation of reproductive functions in health and disease

Germ cells are highly conserved in the gonads, nurtured to either develop into a gamete or self-renew into a stem cell reserve. Preserving the germ cell pool and protecting the reproductive organs is essential for maintaining an individual's fertility. Several factors, including a sedentary lifestyle, pollutants, hormonal disruption, drugs, and a disease condition, have been shown to impair normal reproductive function. Irisin has recently been identified as an adipomyokine involved in modulating physiological functions based on the body's metabolic status. It is being studied for its role in various functions, including fertility. Findings show the localization of irisin in various parts of the reproductive axis, with the highest levels observed during puberty and pregnancy. This raises questions about its role and function in reproduction. Studies support irisin's role in protecting against disease-induced reproductive abnormalities and infertility. Therefore, the current review focuses on how irisin influences spermatogenesis and ovarian follicular development and plays a significant role in indirectly preserving the germ cell pool by protecting the gonads against oxidative stress and inflammation.

Obesity and male fertility disorders

Often associated with obesity, male infertility represents a widespread condition that challenges the wellbeing of the couple. In this article, we provide a comprehensive and critical analysis of studies exploring the association between obesity and male reproductive function, to evaluate the frequency of this association, and establish the effects of increased body weight on conventional and biofunctional sperm parameters and infertility. In an attempt to find possible molecular markers of infertility in obese male patients, the numerous mechanisms responsible for infertility in overweight/obese patients are reviewed in depth. These include obesity-related functional hypogonadism, insulin resistance, hyperinsulinemia, chronic inflammation, adipokines, irisin, gut hormones, gut microbiome, and sperm transcriptome. According to meta-analytic evidence, excessive body weight negatively influences male reproductive health. This can occurr through a broad array of molecular mechanisms. Some of these are not yet fully understood and need to be further elucidated in the future. A better understanding of the effects of metabolic disorders on spermatogenesis and sperm fertilizing capacity is very useful for identifying new diagnostic markers and designing therapeutic strategies for better clinical management of male infertility.

Insulin-like growth factor-1 promotes the testicular sperm production by improving germ cell survival and proliferation in high-fat diet-treated male mice

BACKGROUND

A decrease in semen volume among men is comparable to the rising prevalence of obesity worldwide. The anabolic hormone insulin-like growth factor-1 (IGF-1) can promote proliferation and differentiation in cultured mouse spermatogonial stem cells and alleviate abnormal in vitro spermatogenesis. Additionally, serum IGF-1 level is negatively correlated with body mass index. Whereas the role of IGF-1 in the sperm production in obese men remains unclear.

OBJECTIVE

To investigate the therapeutic effect and potential mechanism of IGF-1 on spermatogenesis of high-fat diet (HFD)-induced obesity mice.

METHODS

An HFD-induced obesity mouse model was established. Alterations in testicular morphology, sperm count, proliferation, and apoptosis were observed by H&E staining,immunohistochemistry, immunofluorescence, and Western blotting. Exogenous recombinant IGF-1 was administered to obese mice to investigate the correlations between altered testicular IGF-1 levels and sperm production.

RESULTS

The sperm count was reduced, the testicular structure was disordered, and sex hormone levels were abnormal in HFD-fed mice compared with normal diet-fed mice. The expression of proliferation-related antigens such as proliferating cell nuclear antigen (PCNA) and Ki-67 was decreased, while that of proapoptotic proteins such as c-caspase3 was increased in testes from HFD-fed mice. Most importantly, the phosphorylation of insulin-like growth factor-1 receptor (IGF-1R) in testes was decreased due to reductions in IGF-1 from hepatocytes and Sertoli cells. Recombinant IGF-1 alleviated these functional impairments by promoting IGF-1R, Akt, and Erk1/2 phosphorylation in the testes.

CONCLUSIONS

Insufficient IGF-1/IGF-1R signaling is intimately linked to damaged sperm production in obese male mice. Exogenous IGF-1 can improve survival and proliferation as well as sperm production. This study provides a novel theoretical basis and a target for the treatment of obese men with oligozoospermia.

Bezafibrate alleviates diabetes-induced spermatogenesis dysfunction by inhibiting inflammation and oxidative stress

The metabolic disorders caused by diabetes can lead to various complications, including male spermatogenesis dysfunction. Exploring effective therapeutics that attenuate diabetes mellitus (DM)-induced male subfertility is of great importance. Pharmaceuticals targeting PPARα activation such as bezafibrate have been regarded as an important strategy for patients with diabetes. In this study, we use streptozocin (STZ) injection to establish a type 1 DM mice model and use bezafibrate to treat DM mice and evaluate the effects of bezafibrate on the spermatogenic function of the DM male mice. Bezafibrate treatment exhibited protective effects on DM-induced spermatogenesis deficiency, as reflected by increased testis weight, improved histological morphology of testis, elevated sperm parameters, increased serum testosterone concentration as well as increased mRNA levels of steroidogenesis enzymes. Meanwhile, testicular cell apoptosis, inflammation accumulation and oxidative stress status were also shown to be alleviated by bezafibrate compared with the DM group. In vivo and in vitro studies, PPARα specific inhibitor and PPARα knockout mice were further used to investigate the role of PPARα in the protective effects of bezafibrate on DM-induced spermatogenesis dysfunction. Our results indicated that the protection of bezafibrate on DM-induced spermatogenesis deficiency was abrogated by PPARα inhibition or deletion. Our study suggested that bezafibrate administration could ameliorate DM-induced spermatogenesis dysfunction and may represent a novel practical strategy for male infertility.

Sarcopenia and Diabetes: A Detrimental Liaison of Advancing Age

Sarcopenia is an age-related clinical complaint characterized by the progressive deterioration of skeletal muscle mass and strength over time. Type 2 diabetes (T2D) is associated with faster and more relevant skeletal muscle impairment. Both conditions influence each other, leading to negative consequences on glycemic control, cardiovascular risk, general health status, risk of falls, frailty, overall quality of life, and mortality. PubMed/Medline, Scopus, Web of Science, and Google Scholar were searched for research articles, scientific reports, observational studies, clinical trials, narrative and systematic reviews, and meta-analyses to review the evidence on the pathophysiology of di-abetes-induced sarcopenia, its relevance in terms of glucose control and diabetes-related outcomes, and diagnostic and therapeutic challenges. The review comprehensively addresses key elements for the clinical definition and diagnostic criteria of sarcopenia, the pathophysiological correlation be-tween T2D, sarcopenia, and related outcomes, a critical review of the role of antihyperglycemic treatment on skeletal muscle health, and perspectives on the role of specific treatment targeting myokine signaling pathways involved in glucose control and the regulation of skeletal muscle metabolism and trophism. Prompt diagnosis and adequate management, including lifestyle inter-vention, health diet programs, micronutrient supplementation, physical exercise, and pharmaco-logical treatment, are needed to prevent or delay skeletal muscle deterioration in T2D.

Effects of chronic irisin treatment on brain monoamine levels in the hypothalamic and subcortical nuclei of adult male and female rats: An HPLC-ECD study

Monoaminergic systems are known to be involved in the pathophysiology of neuropsychiatric disorders and vegetative functions due to their established influence on hypothalamic and subcortical areas. These systems can be modulated by lifestyle factors, especially exercise, which is known to produce several beneficial effects on reproduction, brain health, and mental disorders. The fact that exercise is sensed by the brain shows that muscle-stimulated secretion of myokines allows direct crosstalk between the muscles and the brain. One of such exercise-induced beneficial effects on the brain is exhibited by irisin-a recently discovered PGC-1α-dependent adipo-myokine mainly secreted from skeletal muscle during exercise. Thus, we hypothesized that irisin may affect central monoamine levels and thus play an important role in the muscle-brain endocrine loop. To test this assertion, for 10 weeks, vehicle (deionized water) or 100 ng/kg irisin was injected intraperitoneally once a day to 12 male and 12 female rats after which the levels of monoamines and their metabolites were determined by HPLC-ECD. In the hypothalamic nuclei, irisin significantly decreased dopamine (DA) metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) (p<0.05), DOPAC/DA ratio (p<0.01) and noradrenaline (NA, p<0.05) levels in the anteroventral periventricular nucleus (AVPV), and DOPAC and NA levels in the medial preoptic area (mPOA) (p<0.05), having a crucial role in reproduction and sexual motivation, respectively. On the other hand, irisin significantly increased DOPAC levels in the lateral hypothalamic area (LHA) (p<0.05), which acts as a hunger center, while it significantly decreased the levels of DA, NA, and its metabolite 3,4-dihydroxyphenylglycol (DHPG) in the ventromedial hypothalamic nucleus (VMH) as a known satiety center (p<0.05). In nucleus accumbens (NaC), irisin significantly reduced 5-hydroxyindoleacetic acid (5-HIAA) levels (p<0.05), which are implicated in autism spectrum disorder (ASD) physiopathology. It also significantly increased DA levels in this area, thus exhibiting positive effects on depression and sexual dysfunction in men. On the other hand, it significantly decreased serotonin (5-HT) (p<0.01) and its metabolite 5-HIAA levels in the medial amygdala (MeA) (p<0.05), indicating that it may play a role in social behaviors. Moreover, it significantly attenuated NA levels in the same hypothalamic area, which is directly involved in stress-induced activation of the central noradrenergic system. These findings demonstrate for the first time that irisin induces significant changes in monoamine levels in many hypothalamic nuclei involved in feeding behavior and vegetative functions, as well as in subcortical nuclei related to neuropsychiatric disorders.

Association of BMI with erectile dysfunction: A cross-sectional study of men from an andrology clinic

Abnormal body mass index (BMI) is associated with an increased risk of erectile dysfunction (ED). However, the relationship between different BMI categories and the levels of ED severity remains unclear. In the current study, 878 men from the andrology clinic in Central China were recruited. Erectile function was assessed by the International Index of Erectile Function (IIEF) scores. Questionnaires included questions about demographic characteristics (age, height, weight, educational status), lifestyle habits (drinking, smoking, sleep time), and medical history. Logistic regression was used to examine the association between ED risk and BMI. The incidence of ED was 53.1%. BMI was significantly higher in men from the ED group than in those from the non-ED group (P = 0.01). Compared with the normal weight group, obese men had a higher risk of ED (OR = 1.97, 95% CI = 1.25-3.14, P = 0.004), even after adjustment for potential confounders (OR = 1.78, 95% CI = 1.10-2.90, P = 0.02). Moreover, the positive correlation between obesity and moderate/severe ED severity was confirmed by logistic regression analysis (moderate/severe ED, OR = 2.71, 95% CI = 1.44-5.04, P = 0.002), even after adjusting for potential confounders (OR = 2.51 95% CI = 1.24-5.09, P = 0.01). Collectively, our findings indicate a positive correlation between obesity and the risk of moderate/severe ED. Clinicians could pay more attention to moderate/severe ED patients to maintain a healthy body weight to improve erectile function.