GLP-1 Receptor Agonist Exenatide Attenuates the Detrimental Effects of Obesity on Inflammatory Profile in Testis and Sperm Quality in Mice

DNA Aptamer Raised against Advanced Glycation End Products Improves Sperm Concentration, Motility, and Viability by Suppressing Receptors for Advanced Glycation End Product-Induced Oxidative Stress and Inflammation in the Testes of Diabetic Mice

Type 2 diabetes mellitus (T2DM) is a risk factor for male infertility, but the underlying molecular mechanisms remain unclear. Advanced glycation end products (AGEs) are pathogenic molecules for diabetic vascular complications. Here, we investigated the effects of the DNA aptamer raised against AGEs (AGE-Apt) on testicular and sperm abnormalities in a T2DM mouse model. KK-Ay (DM) and wild-type (non-DM) 4- and 7-week-old male mice were sacrificed to collect the testes and spermatozoa for immunofluorescence, RT-PCR, and histological analyses. DM and non-DM 7-week-old mice were subcutaneously infused with the AGE-Apt or control-aptamer for 6 weeks and were then sacrificed. Plasma glucose, testicular AGEs, and Rage gene expression in 4-week-old DM mice and plasma glucose, testicular AGEs, oxidative stress, and pro-inflammatory gene expressions in 7-week-old DM mice were higher than those in age-matched non-DM mice, the latter of which was associated with seminiferous tubular dilation. AGE-Apt did not affect glycemic parameters, but it inhibited seminiferous tubular dilation, reduced the number of testicular macrophages and apoptotic cells, and restored the decrease in sperm concentration, motility, and viability of 13-week-old DM mice. Our findings suggest that AGEs-Apt may improve sperm abnormality by suppressing AGE-RAGE-induced oxidative stress and inflammation in the testes of DM mice.

Effects of glucagon-like peptide-1 receptor agonists on spermatogenesis-related gene expression in mouse testis and testis-derived cell lines

Glucagon-like peptide-1 (GLP-1) is an incretin released into the gastrointestinal tract after food ingestion, and stimulates insulin secretion from the beta cells of the pancreatic islets. Incretins have recently been reported to have extrapancreatic actions, and they are anticipated to have potential efficacy for conditions such as male infertility as well as diabetes. However, the effects of incretins on male reproductive function remain unclear. In this study, GLP-1 receptor expression and the effects of GLP-1 on spermatogenesis-associated genes were investigated using mouse testes and testis-derived cultured cell lines. Glp1r mRNA and GLP-1 protein were expressed in mouse testes at levels comparable to or greater than those in positive control adipose tissue, and the liver and intestine, and also in a Sertoli cell line (TM4) and a Leydig cell line (MA-10) as well as the GC-1 spg and GC-2 spd (ts) germ cell lines. TM4 cells treated with the GLP-1 receptor agonist exenatide showed transiently and significantly upregulated Kitl, Pdgfa, and Glp1r mRNA expression. Furthermore, at 1 hr post-exenatide administration to male mice, Kitl and Glp1r mRNA expression levels were significantly increased, and Pdgfa mRNA expression level also showed a tendency toward increase. TM4 cells were treated with various cell-activating agents, and bucladesine elicited significantly increased Glp1r mRNA expression. We suggest that GLP-1 provides acute stimulation of Sertoli cells in the mouse testis and has a stimulatory effect on the expression of spermatogenesis-related genes.

Glucagon-like peptide-1 receptor agonist exendin 4 ameliorates diabetes-associated vascular calcification by regulating mitophagy through the AMPK signaling pathway

BACKGROUND

Vascular calcification (VC) is a complication in diabetes mellitus (DM) patients. Osteogenic phenotype switching of vascular smooth muscle cells (VSMCs) plays a critical role in diabetes-related VC. Mitophagy can inhibit phenotype switching in VSMCs. This study aimed to investigate the role of the glucagon-like peptide-1 receptor (GLP-1R) agonist exendin 4 (EX4) in mitophagy-induced phenotype switching.

MATERIALS AND METHODS

The status of VC in T2DM mice was monitored using Von Kossa and Alizarin Red S (ARS) staining in mouse aortic tissue. Human aortic smooth muscle cells were cultured in high glucose (HG) and β-glycerophosphate (β-GP) conditioned medium. Accumulation of LC3B and p62 was detected in the mitochondrial fraction. The effect of EX4 in vitro and in vivo was investigated by knocking down AMPKα1.

RESULTS

In diabetic VC mice, EX4 decreased the percentage of von Kossa/ARS positive area. EX4 inhibited osteogenic differentiation of HG/β-GP-induced VSMCs. In HG/β-GP-induced VSMCs, the number of mitophagosomes was increased, whereas the addition of EX4 restored mitochondrial function, increased the number of mitophagosome-lysosome fusions, and reduced p62 in mitochondrial frictions. EX4 increased the phosphorylation of AMPKα (Thr172) and ULK1 (Ser555) in HG/β-GP-induced VSMCs. After knockdown of AMPKα1, ULK1 could not be activated by EX4. The accumulation of LC3B and p62 could not be reduced after AMPKα1 knockdown. Knockdown of AMPKα1 negated the therapeutic effects of EX4 on VC of diabetic mice.

CONCLUSION

EX4 could promote mitophagy by activating the AMPK signaling pathway, attenuate insufficient mitophagy, and thus inhibit the osteogenic phenotype switching of VSMCs.

Decrease in Sperm Parameters in the 21st Century: Obesity, Lifestyle, or Environmental Factors? An Updated Narrative Review

Semen quality represents a compelling factor for fertility, and delineating the normal values has proven difficult. In the last four decades, several authors have reported a noticeable decline in sperm parameters. Also, studies investigating 'time to pregnancy' have shown that fecundity begins to be reduced when sperm numbers decrease below 30 million, even though according to the 6th edition of the WHO manual, the normal value is currently 16 million/mL or 39 million per ejaculate. There exists sufficient data to suggest a decline in sperm counts over time, even though the clear reason for this adverse trend is not well established, but some associations have been hypothesised, such as maternal smoking during pregnancy. Additional potential factors have yet to be fully illustrated but involve poor diet, increased obesity, and exposure to environmental toxins. Moreover, the change in environmental conditions and more common exposure to endocrine-disrupting chemicals (EDCs), such as pesticides and herbicides, as well as bisphenol A, phthalates, polychlorinated biphenyls, and heavy metals, starting from prenatal life and continuing into adulthood, may exhibit probable features explaining the reduction in sperm parameters. Therefore, the main goal of this narrative review is to furnish an overview of the possible effects of exposure to EDCs on testicular function and spermatogenesis and, also, to summarise the evidence regarding a decrease in sperm quality and examine its potential consequences.

Infertility Improvement after Medical Weight Loss in Women and Men: A Review of the Literature

Infertility is a modern health problem. Obesity is another expanding health issue associated with chronic diseases among which infertility is also included. This review will focus on the effects of weight loss by medical therapy on fertility regarding reproductive hormonal profile, ovulation rates, time to pregnancy, implantation rates, pregnancy rates, normal embryo development, and live birth rates. We comprised medicine already used for weight loss, such as orlistat and metformin, and emerging medical treatments, such as Glucagon-Like Peptide-1 receptor agonists (GLP-1 RA). Their use is not recommended during a planned pregnancy, and they should be discontinued in such cases. The main outcomes of this literature review are the following: modest weight loss after medication and the duration of the treatment are important factors for fertility improvement. The fecundity outcomes upon which medical-induced weight loss provides significant results are the female reproductive hormonal profile, menstrual cyclicity, ovulation and conception rates, and pregnancy rates. Regarding the male reproductive system, the fertility outcomes that feature significant alterations after medically induced weight loss are as follows: the male reproductive hormonal profile, sperm motility, movement and morphology, weight of reproductive organs, and sexual function. The newer promising GLP-1 RAs show expectations regarding fertility improvement, as they have evidenced encouraging effects on improving ovulation rates and regulating the menstrual cycle. However, more human studies are needed to confirm this. Future research should aim to provide answers about whether medical weight loss therapies affect fertility indirectly through weight loss or by a possible direct action on the reproductive system.

Liraglutide ameliorates diabetic-induced testicular dysfunction in male rats: role of GLP-1/Kiss1/GnRH and TGF-β/Smad signaling pathways

Introduction: Glucagon-like peptide -1 (GLP-1) is released by intestinal cells to stimulate glucose-dependent insulin release from the pancreas. GLP-1 has been linked to ameliorating obesity and/or diabetic complications as well as controlling reproductive function. Liraglutide is a GLP-1 receptor agonist (GLP-1RA) with 97% homology with GLP-1. The main objective of this study was to investigate the ameliorative role of liraglutide in diabetic-induced reproductive dysfunction in male rats. Methods: Rats were randomly allocated into 3 groups; a control group, a diabetic group, and a liraglutide-treated diabetic group. Results: In the diabetic group, a significant increase in BMI, FBG, HbA1c, HOMA-IR, TC, TAG, LDL, IL6, TNFα, and MDA, as well as decreased serum insulin, HDL, GSH, total testosterone, LH, and FSH, were shown compared to the control group. Furthermore, A significant downregulation in relative hypothalamic gene expression of GLP-1R, PPAR-α, PGC-1α, kiss, kiss1R, leptin, leptin R, GnRH GLP-1R, testicular PGC-1α, PPARα, kiss1, kiss1R, STAR, CYP17A1, HSD17B3, CYP19A, CYP11A1, and Smad7, as well as upregulation in hypothalamic GnIH and testicular TGF- β and Smad2 expression, were noticed compared to the control group. Liraglutide treatment significantly improved such functional and structural reproductive disturbance in diabetic rats. Conclusion: GLP-1RAs ameliorated the deleterious effects of diabetes on reproductive function by targeting GLP-1/leptin/kiss1/GnRH, steroidogenesis, and TGF- β/Smad pathways.

Glucagon-like Peptide-1 Acts as Signaling Mediator to Modulate Human Sperm Performance via Targeting Akt, JNK and IRS-1 Cell Signaling Cascades: Novel Insights into Sperm Physiopathology

Recent evidence suggests that the male gonad is a potential target of glucagon-like peptide-1 (GLP-1). We investigated the effects of glucagon-like peptide-1 (GLP-1) on sperm function and the molecular mechanisms through which it may act. Semen samples of healthy men were incubated in the presence or absence of a GLP-1 mimetic analog, exendin-4 (Exe). In a different analysis, sperm were exposed to tumor necrosis factor (TNF-α) alone and, in some tubes, TNF-α was added after previous exposure to exendin-4 (Exe). Sperm parameters and protein-kinase B (p-Akt), insulin receptor substrate-1 (p-IRS-1 Ser312), and c Jun N-terminal protein kinase (p-JNK Thr183/Tyr185) were considered and evaluated. Sperm parameters, when incubated for 4 h in a simple defined balanced salt solution lacking protein, declined progressively with incubation time. The maximum decline was associated with a significant decrease in phosphorylated protein kinase B (p-Akt), concomitantly to an increase in insulin receptor substrate-1 (p-IRS-1 Ser312) and c Jun N-terminal protein kinase (p-JNK Thr183/Tyr185). Preincubation with exendin-4 (Exe) prevented this decline and maintained sperm motility (progressive-PM and total-TM). TNF-α exposure resulted in decreased sperm motility (PM and TM) and viability (V) in a concentration-dependent manner. Exe addition attenuated this TNF-α negative effect on sperm parameters. Glucagon-like peptide-1 (GLP-1) also acts by reducing levels of the "negative" kinases p-IRS-1Ser312 and p-JNK. An imbalance involving these three kinases in sperm, as it occurs in somatic cells, is a novel scenario that may participate in sperm physiopathology.

Exenatide improves hypogonadism and attenuates inflammation in diabetic mice by modulating gut microbiota

With the rising incidence of diabetes and its onset at a younger age, the impact on the male reproductive system has gradually gained attention. Exenatide is a glucagon-like peptide-1 receptor agonist effective in the treatment of diabetes. However, its role in diabetes-induced reproductive complications has rarely been reported. The study aimed to investigate the mechanism by which exenatide improved diabetic hypogonadism by regulating gut microbiota (GM) mediated inflammation. C57BL/6J mice were equally divided into normal control (NC), diabetic model control (DM) and exenatide-treated (Exe) groups. Testicular, pancreatic, colonic, and fecal samples were collected to assess microbiota, morphologic damage, and inflammation. Exenatide significantly reduced the fasting blood glucose (FBG) level in diabetic mice, increased the testosterone level, ameliorated the pathological morphological damage of islet, colon, and testes, and reduced the expression of pro-inflammatory factors, tumor necrosis factor-alpha (TNF-α) and interleukin (IL)-6 in colon and testis. Furthermore, exenatide significantly reduced the abundance of some pathogenic bacteria, such as Streptococcaceae and Erysipelotrichaceae, and increased that of beneficial bacteria Akkermansia. Probiotics, such as Lactobacillus were negatively correlated with TNF-α, nuclear factor-kappa-B (NF-κB), IL-6, and FBG. Conditional pathogenic bacteria such as Escherichia/Shigella Streptococcus were positively correlated with TNF-α, NF-κB, IL-6, and FBG. The fecal bacteria transplantation experiment revealed that the abundance of pathogenic bacteria, Peptostreptococcaceae, significantly decreased from Exe group mice to pseudo-sterile diabetic mice, and the pathological damage to testes was also alleviated. These data suggested the protective effects of exenatide on male reproductive damage induced by diabetes by regulating GM.

Gut microbiota involved in spermatogenic function of Sancai Lianmei granules in obese mice

Obesity is a well-established cause of reduced fertility and semen quality in men. Current evidence suggests that Sancai Lianmei granules (SCLM) effectively improve sexual function and semen quality in diabetic patients, while the gut microbiota can influence disease metabolism through various mechanisms. However, the effect of SCLM on the obesity-induced decrease in semen quality and on the gut microbiota is unclear. This study aimed to investigate the effects of SCLM on spermatogenic function and gut microbiota in obese mice. Obese mice were induced by a high-fat diet, and lipid metabolism, spermatogenic function, inflammatory factors, oxidative stress, and autophagy were analyzed to determine the effects of SCLM and SCLM-fecal microbiota transplantation (FMT). In addition, changes in the gut microbiota of mice were analyzed. SCLM and SCLM + FMT could effectively reduce the levels of total cholesterol (TC), high-density lipoprotein (HDL), and low-density lipoprotein (LDL); decrease the expression of oxidative stress products malondialdehyde (MDA) and 8-hydroxyde-oxyguanosine (8-OHdG); and increase sperm density and sperm viability in obese mice while inhibiting the inflammatory responses and excessive cellular autophagy, indicating that SCLM and SCLM + FMT exerted a protective effect on spermatogenic functions. Furthermore, SCLM affected the gut microbiota composition in mice. This study determined that obesity can lead to reduced sperm motility and affect the composition of the gut microbiota, while SCLM can regulate blood lipids in mice directly or indirectly by regulating gut microbiota changes, and may improve sperm motility in obese mice by reducing oxidative stress and autophagy. In addition, FMT enhanced this effect, which may be related to the diversity of gut microbiota.

G-Protein Coupled Receptors in Human Sperm: An In Silico Approach to Identify Potential Modulatory Targets

G protein-coupled receptors (GPCRs) are involved in several physiological processes, and they represent the largest family of drug targets to date. However, the presence and function of these receptors are poorly described in human spermatozoa. Here, we aimed to identify and characterize the GPCRs present in human spermatozoa and perform an in silico analysis to understand their potential role in sperm functions. The human sperm proteome, including proteomic studies in which the criteria used for protein identification was set as <5% FDR and a minimum of 2 peptides match per protein, was crossed with the list of GPCRs retrieved from GLASS and GPCRdb databases. A total of 71 GPCRs were identified in human spermatozoa, of which 7 had selective expression in male tissues (epididymis, seminal vesicles, and testis), and 9 were associated with male infertility defects in mice. Additionally, ADRA2A, AGTR1, AGTR2, FZD3, and GLP1R were already associated with sperm-specific functions such as sperm capacitation, acrosome reaction, and motility, representing potential targets to modulate and improve sperm function. Finally, the protein-protein interaction network for the human sperm GPCRs revealed that 24 GPCRs interact with 49 proteins involved in crucial processes for sperm formation, maturation, and fertilization. This approach allowed the identification of 8 relevant GPCRs (ADGRE5, ADGRL2, GLP1R, AGTR2, CELSR2, FZD3, CELSR3, and GABBR1) present in human spermatozoa that can be the subject of further investigation to be used even as potential modulatory targets to treat male infertility or to develop new non-hormonal male contraceptives.

Investigating the therapeutic options for diabetes-associated male infertility as illustrated in animal experimental models

Diabetes is a rising global health concern and an increasingly common cause of male infertility. Although the definitive pathophysiological mechanisms underpinning the association between diabetes and infertility is unclear, there are several animal studies showing diabetes to be a detrimental factor on reproductive health through apoptosis, oxidative stress and impairment of steroidogenesis. Furthermore, as reflected in animal models, antidiabetic strategies and relevant treatments are beneficial in the management of infertile men with diabetes as the recovery of euglycemic status affects positively the spermatogenesis. However, the available data are still evolving and specific conclusion in human populations are not possible yet. In this review, we are discussing the current literature concerning the association of diabetes and male infertility, focusing on the therapeutic approach as illustrated in animals' models.

Diet-induced obesity impairs spermatogenesis: the critical role of NLRP3 in Sertoli cells

Background

Accumulating evidence indicates a key role of Sertoli cell (SC) malfunction in spermatogenesis impairment induced by obesity. Nucleotide-binding oligomerization domain-like receptor with a pyrin domain 3 (NLRP3) is expressed in SCs, but the role of NLRP3 in the pathological process of obesity-induced male infertility remains unclear.

Methods

NLRP3-deficient mice were fed a high-fat diet for 24 weeks to establish obesity-related spermatogenesis impairment. In another set of experiments, a lentiviral vector containing a microRNA (miR)-451 inhibitor was injected into AMP-activated protein kinase α (AMPKα)-deficient mouse seminiferous tubules. Human testis samples were obtained by testicular puncture from men with obstructive azoospermia whose samples exhibited histologically normal spermatogenesis. Isolated human SCs were treated with palmitic acid (PA) to mimic obesity model in vitro.

Results

Increased NLRP3 expression was observed in the testes of obese rodents. NLRP3 was also upregulated in PA-treated human SCs. NLRP3 deficiency attenuated obesity-related male infertility. SC-derived NLRP3 promoted interleukin-1β (IL-1β) secretion to impair testosterone synthesis and sperm performance and increased matrix metalloproteinase-8 (MMP-8) expression to degrade occludin via activation of nuclear factor-kappa B (NF-κB). Increased miR-451 caused by obesity, decreased AMPKα expression and sequentially increased NADPH oxidase activity were responsible for the activation of NLRP3. miR-451 inhibition protected against obesity-related male infertility, and these protective effects were abolished by AMPKα deficiency in mice.

Conclusions

NLRP3 promoted obesity-related spermatogenesis impairment. Increased miR-451 expression, impaired AMPKα pathway and the subsequent ROS production were responsible for NLRP3 activation. Our study provides new insight into the mechanisms underlying obesity-associated male infertility.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41232-022-00203-z.

Adipose Tissue Dysfunction and Obesity-Related Male Hypogonadism

Obesity is a chronic illness associated with several metabolic derangements and comorbidities (i.e., insulin resistance, leptin resistance, diabetes, etc.) and often leads to impaired testicular function and male subfertility. Several mechanisms may indeed negatively affect the hypothalamic–pituitary–gonadal health, such as higher testosterone conversion to estradiol by aromatase activity in the adipose tissue, increased ROS production, and the release of several endocrine molecules affecting the hypothalamus–pituitary–testis axis by both direct and indirect mechanisms. In addition, androgen deficiency could further accelerate adipose tissue expansion and therefore exacerbate obesity, which in turn enhances hypogonadism, thus inducing a vicious cycle. Based on these considerations, we propose an overview on the relationship of adipose tissue dysfunction and male hypogonadism, highlighting the main biological pathways involved and the current therapeutic options to counteract this condition.

Protective effect of indole-3-carbinol on testis of a high fat diet induced obesity

We investigated the effects of obesity caused by a high fat diet (HFD) on rat testes and evaluated the possible protective effects of indole-3-carbinol (IND). We used 24 8-10-week-old 200 g male rats randomly assigned to 4 groups: non-obese control (NC), obese control (OC), non-obese IND group (NI), obese + IND group (OI). Testis samples were examined using stereological, immunohistochemical, biochemical and histological methods. The number of spermatogenic cells, Leydig cells, mean volume of testes and seminiferous tubules was significantly decreased in the OC group compared to the NC group, but these values were increased significantly in the OI group compared to the OC group. We found a significant increase in catalase and myeloperoxidase activities in the OC group compared to the NC group. In the OI group, catalase and myeloperoxidase levels were decreased compared to the OC group. TUNEL-positive cells also were increased in the OC group compared to the NC group (p < 0.05), but these were fewer in the OI group than the OC group. We found marked morphological changes in testicular tissues between the NC and OC groups, as well as between the OI and OC groups. We found that HFD induced obesity was detrimental to rat testes and that administration of IND ameliorated testicular changes caused by obesity.

Exenatide and Dapagliflozin Combination Enhances Sertoli Cell Secretion of Key Metabolites for Spermatogenesis

The incidence of metabolic diseases such as type 2 diabetes mellitus (DM) and obesity has been increasing dramatically. Both diseases are closely linked and new approaches for type 2 DM treatment aim to enable weight loss. A combined therapy of dapagliflozin and exenatide has been used against type 2 DM, influencing allbody glucose dynamics. Spermatogenesis is highly dependent on the metabolic cooperation established between Sertoli cells (SCs) and developing germ cells. To study the effects of dapagliflozin and exenatide on SC metabolism, mouse SCs were treated in the presence of sub-pharmacologic, pharmacologic, and supra-pharmacologic concentrations of dapagliflozin (50, 500, 5000 nM, respectively) and/or exenatide (2.5, 25, 250 pM, respectively). Cytotoxicity of these compounds was evaluated and the glycolytic profile, glycogen content assay, and lipid accumulation of SCs were determined. Dapagliflozin treatment decreased fat cellular deposits, demonstrating its anti-obesity properties at the cellular level. Polytherapy of exenatide plus dapagliflozin increased lactate production by SCs, which has been reported to improve sperm production and quality. Thus, the results herein suggest that the use of these two pharmacological agents can protect male fertility, while improving their glucose homeostasis and inducing weight loss.

Effects of empagliflozin on the expression of kisspeptin gene and reproductive system function in streptozotocin-induced diabetic male rats

One of the main health concerns of diabetes is testicular dysfunction and impairment of reproductive function and sperm quality which can cause male infertility. kisspeptin is a hypothalamic neuropeptide hormone that is involved in the regulation of energy metabolism, gonadotrophin-releasing hormone (GnRH), and reproductive function. In the present study, the therapeutic effects of empagliflozin (sodium-glucose co-transporter 2 inhibitors) on kisspeptin expression along with reproductive function were investigated in diabetic male Wistar rats. Diabetes was induced by a single dose injection of 60 mg/kg streptozotocin. Empagliflozin in doses of 10 and 25 mg/kg body weight was used for 8 weeks. Serum samples, testis, epididymis, and pancreas tissues were collected at the end of the experiments. Lipid profiles, oxidative stress markers, blood hormones, expression of kisspeptin along with pathological alterations of the testis were assayed using real-time PCR, biochemical, and histological technics. Data have shown that empagliflozin improved hyperglycemia, reproductive impairment, oxidative stress condition, and histopathological alterations of pancreatic and testis tissues in diabetic animals. It improved the serum levels of sex hormones, insulin, leptin, and the expression of kisspeptin in the testes tissues. Spermatogenesis is also improved in treated animals. Data indicated that the administration of empagliflozin can ameliorate symptoms of diabetes. It probably has promising antidiabetic potential and may improve the male infertility of diabetic subjects. To our knowledge, this is the first experimental evidence for the potential impact of empagliflozin on kisspeptin expression in diabetic male rats.

The Effects of the New Therapeutic Treatments for Diabetes Mellitus on the Male Reproductive Axis

One of the complications of chronic hyperglycemia and insulin resistance due to type 2 diabetes mellitus (T2DM) on the hypothalamic-pituitary-gonadal axis in men, is the high prevalence of hypogonadotropic hypogonadism, which has been recently defined as functional hypogonadism, characterized by low testosterone associated with inappropriately normal gonadotropin levels. Although the pathophysiology of this hormonal imbalance may be related to several factors, including glycemic control, concomitant sleep apnea, insulin resistance, the main role is determined by the degree of central or visceral obesity and the consequent inflammatory state. Several drugs have been developed to treat T2DM such as glucagon-like peptide-1 receptor agonists, dipeptidyl peptidase 4 inhibitors, and sodium-glucose co-transporter 2 inhibitors. All appear to be effective in ameliorating blood glucose control, by lowering inflammation and body weight, and most seem to reduce the risk of micro- and macrovascular damage as a consequence of uncontrolled diabetes. A few studies have evaluated the impact of these drugs on gonadal function in T2DM patients with hypogonadism, with promising results. This review summarizes the main current knowledge of the effects of these new antidiabetic drugs on the hypothalamus-pituitary-gonadal axis, showing their potential future application in addition to glucose control in dysmetabolic male patients.

Metabolic syndrome and male fertility disorders: Is there a causal link?

Infertility is a global health problem affecting 10-15% of couples in reproductive age. Recent studies have provided growing evidence supporting that lifestyle factors can affect male fertility through alterations in endocrine profiles, spermatogenesis and/or sperm function. One of these critical factors could be the change in the food intake behavior in modern societies that produces metabolic alterations. Regarding this, metabolic syndrome (MetS) prevalence has increased in epidemic in the last 40-50 years. Although MetS is associated with advanced age, changes in lifestyles have accelerated the appearance of symptoms in the reproductive age. We review herein the current understanding of the relationship between MetS and the male reproductive status. For this purpose, in this narrative review a comprehensive literature search was made in both animal models and men, allowing us to evaluate such relationship. This analysis showed a high variability in the reproductive phenotypes observed in patients and mice suffering MetS, including sperm parameters, fertility and offspring health. In view of this, we proposed that the reproductive effects, which are diverse and not robust, observed among MetS-affected males, might depend on additional factors not associated with the metabolic condition and contributed not only by the affected male but also by his partner. With this perspective, this review provides a more accurate insight of this syndrome critical for the identification of specific diagnostic indicators and treatment of MetS-induced fertility disorders.

The evolving story of incretins (GIP and GLP-1) in metabolic and cardiovascular disease: A pathophysiological update

The incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) have their main physiological role in augmenting insulin secretion after their nutrient-induced secretion from the gut. A functioning entero-insular (gut-endocrine pancreas) axis is essential for the maintenance of a normal glucose tolerance. This is exemplified by the incretin effect (greater insulin secretory response to oral as compared to "isoglycaemic" intravenous glucose administration due to the secretion and action of incretin hormones). GIP and GLP-1 have additive effects on insulin secretion. Local production of GIP and/or GLP-1 in islet α-cells (instead of enteroendocrine K and L cells) has been observed, and its significance is still unclear. GLP-1 suppresses, and GIP increases glucagon secretion, both in a glucose-dependent manner. GIP plays a greater physiological role as an incretin. In type 2-diabetic patients, the incretin effect is reduced despite more or less normal secretion of GIP and GLP-1. While insulinotropic effects of GLP-1 are only slightly impaired in type 2 diabetes, GIP has lost much of its acute insulinotropic activity in type 2 diabetes, for largely unknown reasons. Besides their role in glucose homoeostasis, the incretin hormones GIP and GLP-1 have additional biological functions: GLP-1 at pharmacological concentrations reduces appetite, food intake, and-in the long run-body weight, and a similar role is evolving for GIP, at least in animal studies. Human studies, however, do not confirm these findings. GIP, but not GLP-1 increases triglyceride storage in white adipose tissue not only through stimulating insulin secretion, but also by interacting with regional blood vessels and GIP receptors. GIP, and to a lesser degree GLP-1, play a role in bone remodelling. GLP-1, but not GIP slows gastric emptying, which reduces post-meal glycaemic increments. For both GIP and GLP-1, beneficial effects on cardiovascular complications and neurodegenerative central nervous system (CNS) disorders have been observed, pointing to therapeutic potential over and above improving diabetes complications. The recent finding that GIP/GLP-1 receptor co-agonists like tirzepatide have superior efficacy compared to selective GLP-1 receptor agonists with respect to glycaemic control as well as body weight has renewed interest in GIP, which previously was thought to be without any therapeutic potential. One focus of this research is into the long-term interaction of GIP and GLP-1 receptor signalling. A GLP-1 receptor antagonist (exendin [9-39]) and, more recently, a GIP receptor agonist (GIP [3-30] NH₂ ) and, hopefully, longer-acting GIP receptor agonists for human use will be helpful tools to shed light on the open questions. A detailed knowledge of incretin physiology and pathophysiology will be a prerequisite for designing more effective incretin-based diabetes drugs.

Erectile function in men with type 2 diabetes treated with dulaglutide: an exploratory analysis of the REWIND placebo-controlled randomised trial

BACKGROUND

Diabetes is a major risk factor for erectile dysfunction, however, the effect of GLP-1 receptor agonists on erectile dysfunction is unknown. We aimed to assess the incidence, prevalence, and progression of erectile dysfunction in men treated with dulaglutide compared with placebo, and to determine whether dulaglutide's effect on erectile dysfunction was consistent with its effect on other diabetes-related outcomes.

METHODS

The Researching Cardiovascular Events with a Weekly Incretin in Diabetes (REWIND) trial was a double-blind, placebo-controlled randomised trial of the effect of dulaglutide on cardiovascular outcomes. REWIND was done at 371 sites in 24 countries. Men and women aged older than 50 years with type 2 diabetes, who had either a previous cardiovascular event or cardiovascular risk factors, were randomly assigned (1:1) to receive either dulaglutide or placebo. Participating men were offered the opportunity to complete the standardised International Index of Erectile Function (IIEF) questionnaire at baseline, 2 years, 5 years, and study end. We did an exploratory analysis, in which we included participants who completed a baseline and at least 1 follow-up IIEF questionnaire. The primary outcome for these analyses was the first occurrence of moderate or severe erectile dysfunction following randomisation, assessed by the erectile function subscores on IIEF. This analysis was part of the REWIND trial, which is registered with ClinicalTrials.gov, NCT01394952.

FINDINGS

Between Aug 18, 2011, and Aug 14, 2013, 3725 (70·1%) of 5312 male participants with a mean age of 65·5 years (SD 6·4 years) were analysed, of whom 1487 (39·9%) had a history of cardiovascular disease, and 2104 (56·5%) had moderate or severe erectile dysfunction at baseline. The incidence of erectile dysfunction following randomisation was 21·3 per 100 person-years in the dulaglutide group and 22·0 per 100 person-years in the placebo group (HR 0·92, 95% CI 0·85-0·99, p=0·021). Men in the dulaglutide group also had a lesser fall in erectile function subscore compared with the placebo group, with a least square mean difference of 0·61 (95% CI 0·18-1·05, p=0·006).

INTERPRETATION

Long-term use of dulaglutide might reduce the incidence of moderate or severe erectile dysfunction in men with type 2 diabetes.

FUNDING

Eli Lilly and Company.

Role of Glucose-Lowering Medications in Erectile Dysfunction

Erectile dysfunction (ED) is a long-term complication of type 2 diabetes (T2D) widely known to affect the quality of life. Several aspects of altered metabolism in individuals with T2D may help to compromise the penile vasculature structure and functions, thus exacerbating the imbalance between smooth muscle contractility and relaxation. Among these, advanced glycation end-products and reactive oxygen species derived from a hyperglycaemic state are known to accelerate endothelial dysfunction by lowering nitric oxide bioavailability, the essential stimulus of relaxation. Although several studies have explained the pathogenetic mechanisms involved in the generation of erectile failure, few studies to date have described the efficacy of glucose-lowering medications in the restoration of normal sexual activity. Herein, we will present current knowledge about the main starters of the pathophysiology of diabetic ED and explore the role of different anti-diabetes therapies in the potential remission of ED, highlighting specific pathways whose activation or inhibition could be fundamental for sexual care in a diabetes setting.

Liraglutide treatment counteracts alterations in adipose tissue metabolism induced by orchiectomy in rats

AIMS

The reduction in androgens serum concentration is a physiological condition that accompanies age advancement but can also occur because of prostate cancer and gender affirming treatment or pathological conditions such as functional hypogonadism. However, androgen deficiency is related to a higher risk of developing metabolic disorders such as obesity and type 2 diabetes mellitus (T2DM). Considering that glucagon-like peptide 1 (GLP1) analogs are increasingly used in the treatment of T2DM, we investigated if liraglutide could also attenuate the metabolic changes caused by orchiectomy in rats.

MAIN METHODS

Wistar rats were orchiectomized (ORC), and subdivided in four groups: sham saline, sham liraglutide, ORC saline, and ORC liraglutide. After sixty days, metabolic parameters were evaluated in blood, muscle, liver, brown (BAT) and white adipose tissue (WAT) visceral depots. Glucose utilization, oxidation, and conversion to lipids by de novo lipogenesis, and basal and adrenaline-stimulated lipolysis were evaluated in BAT and WAT depots.

KEY FINDINGS

Orchiectomy increased triglyceridemia, BAT and rtWAT weight, and lipolysis and reduced glucose utilization. Liraglutide treatment reversed these effects.

SIGNIFICANCE

These results indicate that liraglutide improves triglyceridemia and glucose metabolism in WAT depots, which suggests that it may be a promising therapeutic strategy to handle disruptions in energy metabolism caused by androgen deficiency.

Metabolic responses and benefits of glucagon-like peptide-1 (GLP-1) receptor ligands

Glucagon-like peptide-1 (GLP-1) is an incretin hormone that has undergone a revolutionary turnaround from discovery to clinically approved therapeutic. Rapid progress in drug design and formulation has led from initial development of short- and long-acting drugs suitable for daily or weekly parenteral administration, respectively, through to the most recent approval of an orally active GLP-1 agent. The current review outlines the biological action profile of GLP-1 including the various beneficial metabolic responses in pancreatic and extra-pancreatic tissues, including the gastrointestinal tract, liver, bone and kidney as well as the reproductive cardiovascular and CNS. We then briefly consider clinically approved GLP-1 receptor ligands and recent advances in this field. Given the sustained evolution in the area of GLP-1 drug development and excellent safety profile, as well as the plethora of metabolic benefits, clinical approval for use in diseases beyond diabetes and obesity is very much conceivable.

Is there a role for glucagon-like peptide-1 receptor agonists in the treatment of male infertility?

Glucagon‐like peptide‐1 receptor agonists (GLP1‐RAs) are novel anti‐hyperglycemic drugs efficacious on glucose control, weight loss, and cardiovascular prevention. These drugs may also be effective in modulating testicular function. In fact, they increase serum testosterone levels in diabetic and/or obese patients with functional hypogonadism on a dysmetabolic basis. Although part of this effect can be ascribed to weight loss, some evidence suggests that there is a direct effect at the testicular level. Indeed, human Leydig, Sertoli, and germ cells express GLP1 receptors. GLP1‐RAs improve sperm metabolism, motility, and insulin secretion in vitro. Likewise, GLP1‐RAs exert positive effects on the metabolism of human Sertoli cells in vitro. Finally, GLP1 is secreted by mouse Leydig cells and this suggests the presence of a paracrine mechanism by which these cells could support the metabolism of Sertoli cells. Therefore, the widespread use of GLP1‐RAs in clinical practice may reveal an important role in the management of male infertility in obese and/or diabetic patients given the negative impact of these diseases on testicular steroidogenesis and spermatogenesis. This should suggest the design of randomized controlled studies aimed at evaluating the effects of these drugs on testicular function.

The Mechanisms Involved in Obesity-Induced Male Infertility

BACKGROUND

Obesity resulted by imbalance between the intake of energy and energy consumption can lead to growth and metabolic disease development in people. Both in obese men and animal models, several studies indicate that obesity leads to male infertility.

OBJECTIVE

This review has discussed some mechanisms involved in obesity-induced male infertility.

METHODS

Online documents were searched through Science Direct, Pubmed, Scopus, and Google Scholar websites dating from 1959 to recognize studies on obesity, kisspeptin, leptin, and infertility.

RESULTS

Obesity induced elevated inflammatory cytokines and oxidative stress can affect male reproductive functions, including spermatogenesis disorders, reduced male fertility power and hormones involved in the hypothalamus-pituitary-gonadal axis.

CONCLUSION

There is significant evidence that obesity resulted in male infertility. Obesity has a negative effect on male reproductive function via several mechanisms such as inflammation and oxidative stress.

Diet-induced obesity is associated with altered expression of sperm motility-related genes and testicular post-translational modifications in a mouse model

Obesity is a metabolic disease and its relation with male subfertility has aroused a growing concern. However, it is unclear whether gene expression and post-translational modifications (PTMs), two vital molecular mechanisms regulating cellular functions, are associated with obesity-induced male reproductive dysfunction. In this study, male obesity with compromised sperm motility was induced by a high-fat diet (HFD) using a mouse model. The expression of motility related-genes, the level of histone modifications, and the global profiles of post-translational modifications (PTMs), were examined in testes of HFD and control mice by quantitative real-time PCR and western blot, respectively. Outer dense fiber protein 2, a major component of outer dense fibers in the sperm tail, is the most obviously down-regulated gene out of 11 evaluated genes, showing a reduction of about 50% RNA level in testes of obese male mice compared with that in control mice. Semi-quantitative analysis of the western blot demonstrated that ∼56% enrichment of di-methylated histone (H)3 lysine (K)36, ∼59% enrichment of 2-hydroxyisobutyrylated H4K8, ∼32% decrease of propionylated H3K23, ∼33% decrease of crotonylated H4K8, and ∼45% decrease of acetylated H3K122 and H4K8 were detected in testes of male HFD mice compared with that in control mice. In addition, male obesity up-regulated the testicular levels of ubiquitination by ∼18%, tyrosine nitration by ∼20%, lysine succinylation by ∼25%, lysine benzoylation by ∼28%, lysine malonylation by ∼32%, lysine glutarylation by ∼36%, lysine propionylation by ∼42%, lysine 2-hydroxyisobutyrylation by ∼45%, and SUMO1 modification by ∼59%, and down-regulated the testicular levels of O-GlcNAcylation by ∼12%, lysine crotonylation by ∼22%, and lysine acetylation by 35%. These findings indicate that altered gene expression and PTMs are associated with the obesity-induced male reproductive dysfunction.

Transcriptome Analysis of Testis from HFD-Induced Obese Rats (Rattus norvigicus) Indicated Predisposition for Male Infertility

Obesity is a worldwide life-threatening metabolic disorder, associated with various chronic diseases, including male infertility. Obesity was induced by high fat diet (HFD), and testis RNA was used for the transcriptome analysis using RNAseq via Illumina NovaSeq 6000 System and NovaSeq 6000 Kit. Gene expression level was estimated as FPKM (Fragments Per Kilobase of transcript per Million mapped reads). Differential expressed genes (DEGs) were annotated against gene ontology (GO) and KEGG databases. More than 63.66 million reads per sample were performed with 100 bp cutoff and 6 Gb sequencing depth. Results of this study revealed that 267 GO terms (245 biological processes (BP), 14 cellular components (CC), eight molecular functions (MF)), and 89 KEGG pathways were significantly enriched. Moreover, total numbers of 136 genes were differentially expressed (107 upregulated, 29 downregulated) with |FC| ≥ 2 and bh adjusted <0.05. Interesting DEGs were detected, including obesity and lipid metabolism-related genes, immune response-related genes, cytochrome P450 genes, including aromatase were upregulated, whereas genes related to male fertility and fertilization, cell adhesion, and olfactory receptors were downregulated. The combined expression pattern of the DEGs in obese animals indicated an increase in cholesterol metabolism. Furthermore, high aromatase activity enhances the testosterone turnover into estradiol and lowers the testosterone/estradiol (T/E) ratio, which ultimately reduces fertility. In addition, downregulation of cadherens junction components genes leads to the pre-mature release of sperm from Sertoli cells resulting in the reduction of fertility. Moreover, the downregulation of olfactory receptor genes reduces the chemotaxis capacity of sperms in tracking the oocyte for fertilization, which reduces male fertility. Furthermore, various obesity molecular markers were detected in our transcriptome. The results of this study will enhance our understanding of the molecular network of obesity development, development of obesity novel molecular diagnosis markers, molecular bases of obesity-induced infertility, and the development of anti-obesity drugs.

Glucagon-like peptide-1 receptor is expressed in human and rodent testis

BACKGROUND

The incretin hormone glucagon-like peptide-l (GLP-1) is an important regulator of post-prandial insulin secretion, acting through a G protein-coupled cell surface receptor (GLP-1R). In addition to its expression in pancreatic β-cells, several studies suggested that GLP-1R is located in extra-pancreatic tissues.

OBJECTIVES

In this study, we examined for the first time the testicular distribution of the GLP-1R, both in normal human and neoplastic testicular tissues as well as in rodent testis and rodent testicular cell lines.

METHODS AND METHODS

The GLP-1R distribution in testicular section has been evaluated by immunohistochemistry, the specificity of IHC was validated by demonstrating a positive staining for GLP-1RmRNA by RISH technology. While GLP-1R expression in terms of protein was detected by western blot analysis, Moreover, mRNA levels were determined in human testis, in rodent Leydig, and Sertoli cell lines.

RESULTS

Using immunohistochemistrya specific staining for GLP-1R was detected in Leydig cells. The specificity of IHC was validated by demonstrating a positive staining for GLP-1RmRNA only in these cell types. Species differences in the GLP-1R expression between humans and rodents were observed. Interestingly, a decreased expression of the receptor in rodent tumor Leydig cell line and an absence in human Leydig tumor samples was detected.

DISCUSSION

It may be hypothesized that GLP-1R acts like an oncosuppressor in Leydig tumors. A role in regulation of hormone secretion by GLP-1 has been shown in other endocrine cells, therefore we hypothesized that GLP-1R is able to modulate somehow the Leydig cell function.

CONCLUSION

In our findings, a careful evaluation of human testicular tissues and rodent testis revealed Leydig cells as a potential target for GLP-1. Collectively, an effect of GLP-1R in Leydig cell function may be presumed although future studies are needed to ascertain the GLP-1R's role both in normal and tumor Leydig cells.

Effects of intravenous and oral di(2-ethylhexyl) phthalate (DEHP) and 20% Intralipid vehicle on neonatal rat testis, lung, liver, and kidney

The highest human exposures to the plasticizer di(2-ethylhexyl) phthalate (DEHP) occur through intravenous (iv) exposure from medical procedures. Rodent toxicity studies, mainly using oral exposures, have identified male reproductive toxicity after developmental exposure to DEHP as the primary concern. Other organs are also affected by DEHP and route may influence the degree of target organ involvement. Cammack et al. (2003) reported a critical study focused on testicular toxicity using oral and iv exposures of neonatal Sprague-Dawley rats to 60, 300, or 600 mg/kg body weight/day DEHP in Intralipid vehicle. The present study followed the same dosing paradigm and included assessment of additional organs to evaluate the potential utility of this design for DEHP alternatives. Reduction of testis weight was observed in all DEHP treatment groups and germ cell and Sertoli cell toxicity was observed at the two highest doses with both routes. Lung granulomas occurred in all iv DEHP groups, possibly related to increased fat particle size in DEHP lipid emulsions. Lung alveolar development was inhibited after both oral and iv high dose DEHP. Toxicity of oral Intralipid vehicle was observed in germ and Sertoli cells. The lack of such effects after iv vehicle exposure suggested that this may be a gut-mediated effect.

The role of glucagon-like peptide-1 in reproduction: from physiology to therapeutic perspective

BACKGROUND

Glucagon-like peptide-1 (GLP-1) receptor agonists (GLP-1 RAs) have become firmly established in the treatment of type 2 diabetes and obesity, disorders frequently associated with diminished reproductive health. Understanding of the role of GLP-1 and GLP-1 RAs in reproduction is currently limited and largely unaddressed in clinical studies.

OBJECTIVE AND RATIONALE

The purpose of this narrative review is to provide a comprehensive overview of the role of GLP-1 in reproduction and to address a therapeutic perspective that can be derived from these findings.

SEARCH METHODS

We performed a series of PubMed database systemic searches, last updated on 1 February 2019, supplemented by the authors' knowledge and research experience in the field. A search algorithm was developed incorporating the terms glucagon-like peptide-1, GLP-1, glucagon-like peptide-1 receptor, GLP-1R, or incretins, and this was combined with terms related to reproductive health. The PICO (Population, Intervention, Comparison, Outcome) framework was used to identify interventional studies including GLP-1 RAs and dipeptidyl peptidase-4 (DPP-4) inhibitors, which prevent the degradation of endogenously released GLP-1. We identified 983 potentially relevant references. At the end of the screening process, we included 6 observational (3 preclinical and 3 human) studies, 24 interventional (9 preclinical and 15 human) studies, 4 case reports, and 1 systematic and 2 narrative reviews.

OUTCOMES

The anatomical distribution of GLP-1 receptor throughout the reproductive system and observed effects of GLP-1 in preclinical models and in a few clinical studies indicate that GLP-1 might be one of the important modulating signals connecting the reproductive and metabolic system. The outcomes show that there is mostly stimulating role of GLP-1 and its mimetics in mammalian reproduction that goes beyond mere weight reduction. In addition, GLP-1 seems to have anti-inflammatory and anti-fibrotic effects in the gonads and the endometrium affected by obesity, diabetes, and polycystic ovary syndrome (PCOS). It also seems that GLP-1 RAs and DPP-4 inhibitors can reverse polycystic ovary morphology in preclinical models and decrease serum concentrations of androgens and their bioavailability in women with PCOS. Preliminary data from interventional clinical studies suggest improved menstrual regularity as well as increased fertility rates in overweight and/or obese women with PCOS treated with GLP-1 RAs in the preconception period.

WIDER IMPLICATIONS

GLP-1 RAs and DPP-4 inhibitors show promise in the treatment of diabetes and obesity-related subfertility. Larger interventional studies are needed to establish the role of preconception intervention with GLP-1 based therapies, assessing fertility outcomes in obesity, PCOS, and diabetes-related fertility problems. The potential impact of the dose- and exposure time-response of different GLP-1 RAs need further exploration. Future research should also investigate sex-specific variability of GLP-1 on reproductive outcomes, in particular on the gonads where the observations in males are most conflicting.

Human Sperm Express the Receptor for Glucagon-like Peptide-1 (GLP-1), Which Affects Sperm Function and Metabolism

AIM

Glucagon-like peptide-1 (GLP-1) produces pleiotropic effects binding to the GLP-1 receptor (GLP1-R), potentiating insulin secretion in the pancreas. GLP1-R is expressed in peripheral tissues and evidence for its role in reproduction has come from knockout mice, although the relationship between GLP-1 and male fertility needs to be clarified. Given that human sperm is an insulin-sensitive and insulin-secreting cell, we hypothesized that the GLP-1/GLP1-R axis may be expressed and functional in these cells.

RESULTS AND DISCUSSION

We revealed the presence of GLP1-R by Western blotting and immunofluorescence analyses. Because Exendin-4 (Ex-4) displays similar functional properties to native GLP-1, we used this agonist to perform a dose-response study on progressive motility and cholesterol efflux, showing that 300 pM Ex-4 was the most effective treatment. These actions are mediated by GLP1-R and independent from sperm-secreted insulin. The exposure to Ex-4 fueled phosphatidylinositol-3-kinase (PI3K)/AKT signaling and was reversed by H89, indicating a protein kinase A (PKA)-dependence of GLP-1/GLP1-R signaling. It emerged that in sperm, insulin secretion regulated by Ex-4 did not occur in a strictly glucose-dependent manner. A stimulatory action of Ex-4/GLP1-R on lactate dehydrogenase and glucose-6-phosphate dehydrogenase (G6PDH) activities was observed. Ex-4/GLP1-R decreased triglycerides content concomitantly to enhanced lipase and acyl-coenzyme A (acyl-CoA) dehydrogenase activities, addressing a lipolytic effect.

CONCLUSION

Collectively, we discovered that human sperm is a new GLP1 incretin target, broadening our knowledge about the effects of the GLP1-R agonist in the male reproductive field. Further findings in humans should be conducted in the future to confirm it and to improve the translational aspect of this study.

Caloric restriction alters the hormonal profile and testicular metabolome, resulting in alterations of sperm head morphology

Energy homeostasis is crucial for all physiological processes. Thus, when there is low energy intake, negative health effects may arise, including in reproductive function. We propose to study whether caloric restriction (CR) changes testicular metabolic profile and ultimately sperm quality. Male Wistar rats (n = 12) were randomized into a CR group fed with 30% fewer calories than weight-matched, ad libitum-fed animals (control group). Circulating hormonal profile, testicular glucagon-like peptide-1 (GLP-1), ghrelin and leptin receptors expression, and sperm parameters were analyzed. Testicular metabolite abundance and glycolysis-related enzymes were studied by NMR and Western blot, respectively. Oxidative stress markers were analyzed in testicular tissue and spermatozoa. Expressions of mitochondrial complexes and mitochondrial biogenesis in testes were determined. CR induced changes in body weight along with altered GLP-1, ghrelin, and leptin circulating levels. In testes, CR led to changes in receptor expression that followed those of the hormone levels; modified testicular metabolome, particularly amino acid content; and decreased oxidative stress-induced damage in testis and spermatozoa, although sperm head defects increased. In sum, CR induced changes in body weight, altering circulating hormonal profile and testicular metabolome and increasing sperm head defects. Ultimately, our data highlight that conditions of CR may compromise male fertility.

Can Antidiabetic Drugs Improve Male Reproductive (Dys)Function Associated with Diabetes?

The alarming increase in the number of diabetic patients worldwide raises concerns regarding the impact of the disease on global health, not to mention on social and economic aspects. Furthermore, the association of this complex metabolic disorder with male reproductive impairment is worrying, mainly due to the increasing chances that young individuals, at the apex of their reproductive window, could be affected by the disease, further contributing to the disturbing decline in male fertility worldwide. The cornerstone of diabetes management is glycemic control, proven to be effective in avoiding, minimizing or preventing the appearance or development of disease-related complications. Nonetheless, the possible impact of these therapeutic interventions on male reproductive function is essentially unexplored. To address this issue, we have made a critical assessment of the literature on the effects of several antidiabetic drugs on male reproductive function. While the crucial role of insulin is clear, as shown by the recovery of reproductive impairments in insulin-deficient individuals after treatment, the same clearly does not apply to other antidiabetic strategies. In fact, there is an abundance of controversial reports, possibly related to the various study designs, experimental models and compounds used, which include biguanides, sulfonylureas, meglitinides, thiazolidinediones/glitazones, bile acid sequestrants, amylin mimetics, as well as sodiumglucose co-transporter 2 (SGLT2) inhibitors, glucagon-like peptide 1 (GLP1), α-glucosidase inhibitors and dipeptidyl peptidase 4 (DPP4) inhibitors. These aspects constitute the focus of the current review.

High-fat diets reduce male reproductive success in animal models: A systematic review and meta-analysis

Sperm counts have shown a progressive decline across the world since the mid-1900s. Global rates of obesity have been climbing at a similarly alarming rate, suggesting that these two factors may be linked. However, studies examining the relationship between body mass index (BMI) and male fertility have produced conflicting results. These discrepancies among studies are commonly attributed to limitations that are inherent in human studies such as correlational data and confounding factors-limitations that are absent from animal studies. Hence, we conducted a systematic review and meta-analysis of animal studies that experimentally induced obesity with a high-fat diet and measured impacts on sperm traits and/or male fertility. Overall, we found strong, consistent evidence in animal studies that high-fat diets are detrimental for male fertility. Compared with controls, males fed a high-fat diet had smaller testes and sex accessory glands relative to body size, reduced semen quality, reduced mating success, and reduced fertilization success. This is the first time that experimental data of high-fat diet effects on male reproduction have been synthesized in a meta-analysis, and thus, our results provide novel insight to the complex question of how dietary-induced obesity affects male fertility. The strong negative effects detected in animal models suggest that the inconsistent results plaguing human studies are an artefact of limitations inherent in correlational studies rather than a true effect.

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.

Exenatide reduces oxidative stress and cell death in testis in iron overload rat model

Glucagon-like peptide-1 (GLP-1) has been demonstrated to affect the oxidative stress status in several in vitro, in vivo and clinical studies. The aim of the present study was to evaluate the effect of a GLP-1 analogue, exenatide, on oxidative stress parameters and apoptotic markers in testicular cells in an iron overload rat model. To obtain this model, the animals were randomly divided into three groups (n=6/group). Rats in the control group received intraperitoneal injections of saline. Intraperitoneal iron dextran (60 mg/kg/day) was given to Group FE for 5 days a week for 4 weeks. The third group (Group Fe +E) was given subcutaneous injections of 10 µg/kg exenatide in two divided doses for 4 weeks in addition to iron dextran. Testes of all rats were immediately removed for immunohistochemical staining and to measure the malondialdehyde level and superoxide dismutase enzyme activity. A significant reduction was observed in caspase-8 and -3 enzyme staining in testicular stromal and endothelial cells in exenatide injected iron overloaded rats when compared with controls. Oxidative stress markers malondialdehyde levels and superoxide dismutase enzyme activities were also significantly lower in exenatide-injected rats when compared with controls. These findings indicate that exenatide may be protective against the harmful effects of iron accumulation in testis. Further studies are required to evaluate how exenatide reduces oxidative stress and cell death in iron overloaded testis tissue.

Antidiabetic therapies and male reproductive function: where do we stand?

Diabetes mellitus has been increasing at alarming rates in recent years, thus jeopardizing human health worldwide. Several antidiabetic drugs have been introduced in the market to manage glycemic levels, and proven effective in avoiding, minimizing or preventing the appearance or development of diabetes mellitus-related complications. However, and despite the established association between such pathology and male reproductive dysfunction, the influence of these therapeutic interventions on such topics have been scarcely explored. Importantly, this pathology may contribute toward the global decline in male fertility, giving the increasing preponderance of diabetes mellitus in young men at their reproductive age. Therefore, it is mandatory that the reproductive health of diabetic individuals is maintained during the antidiabetic treatment. With this in mind, we have gathered the available information and made a critical analysis regarding the effects of several antidiabetic drugs on male reproductive function. Unlike insulin, which has a clear and fundamental role on male reproductive function, the other antidiabetic therapies' effects at this level seem incoherent. In fact, studies are highly controversial possibly due to the different experimental study approaches, which, in our opinion, suggests caution when it comes to prescribing such drugs to young diabetic patients. Overall, much is still to be determined and further studies are needed to clarify the safety of these antidiabetic strategies on male reproductive system. Aspects such as the effects of insulin levels variations, consequent of insulin therapy, as well as what will be the impact of the side effect hypoglycemia, common to several therapeutic strategies discussed, on the male reproductive system are still to be addressed.

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.

Glucagon and glucagon-like peptide-1 as novel anti-inflammatory and immunomodulatory compounds

Glucagon and glucagon-like peptide-1 (GLP-1) are polypeptide hormones that are produced by pancreatic α-cells and the intestine, respectively, whose main function is to control glucose homeostasis. The glucagon and GLP-1 levels are imbalanced in diabetes. Furthermore, type 1 diabetic patients and animals present with a diminished inflammatory response, which is related to some morbidities of diabetes, such as a higher incidence of infectious diseases, including sepsis. The focus of this review is to briefly summarize the state of the art concerning the effects of glucagon and GLP-1 on the inflammatory response. Here, we propose that glucagon and GLP-1 have anti-inflammatory properties, making them possible prototypes for the design and synthesis of new compounds to treat inflammatory diseases. In addition, glucagon, GLP-1 or their analogues or new derivatives may not only be important for managing inflammatory diseases but may also have the therapeutic potential to prevent, cure or ameliorate diabetes in patients by counteracting the deleterious effects of pro-inflammatory cytokines on the function and viability of pancreatic β-cells. In addition, GLP-1, its analogues or drugs that inhibit GLP-1 metabolism may have a doubly beneficial effect in diabetic patients by inhibiting the inflammatory response and reducing glycaemia.

Anti-Inflammatory Effects of GLP-1-Based Therapies beyond Glucose Control

Glucagon-like peptide-1 (GLP-1) is an incretin hormone mainly secreted from intestinal L cells in response to nutrient ingestion. GLP-1 has beneficial effects for glucose homeostasis by stimulating insulin secretion from pancreatic beta-cells, delaying gastric emptying, decreasing plasma glucagon, reducing food intake, and stimulating glucose disposal. Therefore, GLP-1-based therapies such as GLP-1 receptor agonists and inhibitors of dipeptidyl peptidase-4, which is a GLP-1 inactivating enzyme, have been developed for treatment of type 2 diabetes. In addition to glucose-lowering effects, emerging data suggests that GLP-1-based therapies also show anti-inflammatory effects in chronic inflammatory diseases including type 1 and 2 diabetes, atherosclerosis, neurodegenerative disorders, nonalcoholic steatohepatitis, diabetic nephropathy, asthma, and psoriasis. This review outlines the anti-inflammatory actions of GLP-1-based therapies on diseases associated with chronic inflammation in vivo and in vitro, and their molecular mechanisms of anti-inflammatory action.