Acrosome reaction is impaired in spermatozoa of obese men: a preliminary study

A ripple effect? The impact of obesity on sperm quality and function

Infertility affects approximately 15% of couples trying to conceive. Male-related causes account for roughly 50% of cases, with obesity emerging as a possible significant factor. Obesity, defined as a body mass index of 30.0 or higher, has become a widespread epidemic associated with numerous health issues, including a decrease of fertility. This review discusses the relationship between obesity and male infertility, particularly focusing on sperm quality and function. An overview of the literature suggests that obesity may influence the male reproductive system via disruptions in hormonal profiles, oxidative stress, and inflammation, leading to changes in sperm parameters. Several studies have discussed if obesity causes a decrease in sperm concentration, motility, and normal morphology, so far without a consensus being reached. However, available evidence suggests an impairment of sperm function in obese men, due to an increase in DNA damage and oxidative stress, impaired mitochondrial function and acrosome reaction in response to progesterone. Finally, the relationship between obesity and assisted reproductive technologies outcomes remains debatable, with conflicting evidence regarding the influence on fertilisation, pregnancy, and live birth rates. Therefore, the actual impact of obesity on human spermatozoa still needs to be clarified, due to the multiple factors potentially in play.

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.

Mechanisms That Protect Mammalian Sperm from the Spontaneous Acrosome Reaction

To acquire the capacity to fertilize the oocyte, mammalian spermatozoa must undergo a series of biochemical reactions in the female reproductive tract, which are collectively called capacitation. The capacitated spermatozoa subsequently interact with the oocyte zona-pellucida and undergo the acrosome reaction, which enables the penetration of the oocyte and subsequent fertilization. However, the spontaneous acrosome reaction (sAR) can occur prematurely in the sperm before reaching the oocyte cumulus oophorus, thereby jeopardizing fertilization. One of the main processes in capacitation involves actin polymerization, and the resulting F-actin is subsequently dispersed prior to the acrosome reaction. Several biochemical reactions that occur during sperm capacitation, including actin polymerization, protect sperm from sAR. In the present review, we describe the protective mechanisms that regulate sperm capacitation and prevent sAR.

Diet-induced maternal obesity and overnutrition cause a decrease in the sperm quality of the offspring

The present work aimed to study the changes caused by maternal obesity and overnutrition in both the quality and function of spermatozoa of the offspring. To this end, female rats received either a standard (SD) or cafeteria (CD) diet from 22 days of age until the weaning of their offspring, and the male offspring (OSD and OCD respectively) were used. Different endpoints in the offspring, as body weight, weight gain and glycemia were recorded and the testes were removed at 60 days of age. Different spermatozoa parameters, such as mitochondrial function, functional integrity of the sperm plasma membrane, capacitation, and acrosome status, were evaluated. The OCD group was heavier than the OSD group and exhibited lower testis and epididymal indices. The OCD group also showed a decrease in the ability of the sperm tail to react in the presence of a hypoosmotic solution, deficiency in sperm mitochondrial function, a lower percentage of spermatozoa without acrosome when exposed to a capacitation medium, and a higher number of abnormal metaphases. In addition, compared with OSD, OCD rats had a higher number of TUNEL-positive cells in the histological sections of the testis, and greater presence of reactive oxygen species in the spermatozoa, evaluated by a fluorescent probe. However, the OCD group displayed lower protein levels of cytochrome c and caspase-3 in testis tissue than the control group. These results suggest that maternal obesity and overnutrition program the offspring to develop poor sperm quality and function, which may imply a condition of subfertility.

Restoring Impaired Fertility Through Diet: Observations of Switching From High-Fat Diet During Puberty to Normal Diet in Adulthood Among Obese Male Mice

BACKGROUND

Obesity is associated with a decrease in testicular function, yet the effects and mechanisms relative to different stages of sexual development remain unclear. The aim of this study is to determine whether high-fat diet-induced obesity impairs male fertility during puberty and in adulthood, and to ascertain its underlying mechanisms. This study aims to further reveal whether restoring to a normal diet can improve impaired fertility.

METHODS

Male mice were divided into 6 groups: the group N and H exposed to a normal diet or high-fat diet during puberty. The group NN or NH were further maintained a normal diet or exposed to high-fat diet in adulthood, the group HH or HN were further maintained high-fat diet or switched to normal diet in adulthood. Metabolic parameters, fertility parameters, testicular function parameters, TUNEL staining and testicular function-related proteins were evaluated, respectively.

RESULTS

The fertility of the mice in the high-fat diet group was impaired, which validated by declines in pregnancy rates and litter weight loss. Further analysis demonstrated the increased level of oxidative stress, the increased number of spermatogenic cell apoptosis and decreased number of sperm and decreased acrosome integrity. The expression of steroidogenic acute regulatory (StAR) and spermatogenesis related proteins (WT-1) decreased. Fertility among the HN group recovered, accompanied by the recovery of metabolism, fertility and testicular function parameters, StAR and WT-1 expression.

CONCLUSIONS

The findings suggest that high-fat diet-induced obesity impairs male fertility during puberty and in adulthood. The loss of acrosome integrity, the increase of oxidative stress, the increase of cells apoptosis and the down-regulation of StAR and WT-1 may be the underlying mechanisms. Switching from high-fat diets during puberty to normal diets in adulthood can improve male fertility.

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.

Association of diabetes and obesity with sperm parameters and testosterone levels: a meta-analysis

BACKGROUND

The present study performed two distinct meta-analyses with common outcomes (sperm parameters); one was performed in obese individuals (and non-obese controls) and the other in diabetic individuals (and non-diabetic controls).

METHODS

PubMed, Embase, The Cochrane library, Web of Science, Scopus databases were searched to collect clinical studies related to the effects of obesity and diabetes on male sperm from inception to on 1st February 2021. Statistical meta-analyses were performed using the RevMan 5.4 software. Stata16 software was used to detect publication bias. The methodological quality of the included studies was assessed with the Ottawa-Newcastle scale using a star-based system.

RESULTS

A total of 44 studies were finally included in the present study, which enrolled 20,367 obese patients and 1386 patients with diabetes. The meta-analysis results showed that both obesity and diabetes were associated with reduced semen volume (obese versus non-obese controls: mean difference (MD) = - 0.25, 95% CI = (- 0.33, - 0.16), p < 0.001; diabetes versus non-diabetic controls: MD = - 0.45, 95% CI = (- 0.63, - 0.27), p < 0.001), reduced sperm count (obese versus non-obese controls: MD = - 23.84, 95% CI = (- 30.36, - 17.33), p < 0.001; diabetes versus non-diabetic controls: MD = - 13.12, 95% CI = (- 18.43, - 7.82), p < 0.001), reduced sperm concentration (obese versus non-obese controls: MD = - 7.26, 95% CI = (- 10.07, - 4.46), p < 0.001; diabetes versus non-diabetic controls: MD = - 11.73, 95% CI = (- 21.44, - 2.01), p = 0.02), reduced progressive motility (obese versus non-obese controls: MD = - 5.68, 95% CI = (- 8.79, - 2.56), p < 0.001; diabetes versus non-diabetic controls: MD = - 14.37, 95% CI = (- 21.79, - 6.96), p = 0.001), and decreased testosterone levels (obese versus non-obese controls: MD = - 1.11, 95% CI = (- 1.92, - 0.30), p = 0.007; diabetes versus non-diabetic controls: MD = - 0.37, 95% CI = (- 0.63, - 0.12), p = 0.004).

CONCLUSIONS

Current evidence suggests that obesity and diabetes negatively affect sperm parameters in men and are associated with low testosterone levels. Due to the limitation of the number and quality of included studies, the above conclusions need to be verified by more high-quality studies.

Effect of bariatric surgery on in vitro fertilization in infertile men with obesity

BACKGROUND

Obesity has previously been related to reduced female fertility, with prolonged waiting time to pregnancy among women with a body mass index (BMI) >35 kg/m² but there are few studies investigating the relationship between high BMI, bariatric surgery, and male fertility.

OBJECTIVES

The primary objective of this article was to investigate the effect of bariatric surgery on in vitro fertilization (IVF) outcomes in a cohort of men with morbid obesity who underwent sleeve gastrectomy (SG).

SETTING

University hospital, bariatric surgery unit.

METHODS

Pre- and postsurgery data on patient age, body mass index (BMI), and variables related to male fertility (semen volume, concentration, progressively motile sperm count, and sperm morphology) were collected; assisted reproductive technology outcomes before and after bariatric surgery were measured by the number of metaphase II oocytes; the number of top-quality oocytes and embryos; the number of fertilized oocytes; the number of transferred embryo; the implantation rate; the pregnancy rate; the live birth rate and the miscarriage rate.

RESULTS

Thirty-five men with obesity and idiopathic infertility were included in this study. We found a significant increase, after bariatric surgery, in semen volume, total sperm concentration, progressively motile sperm count, and sperm morphology. Considering IVF outcomes, mean number of top-quality oocytes, mean number of fertilized oocytes, mean number of embryos obtained, and top-quality embryos were significantly increased after bariatric procedure.

CONCLUSION

Bariatric surgery is confirmed to be safe and effective in increasing the outcomes of assisted reproductive technology treatment also in case of infertile men with obesity, both in terms of pregnancy and live birth rate.

Functions and Mechanisms of Lysine Glutarylation in Eukaryotes

Lysine glutarylation (Kglu) is a newly discovered post-translational modification (PTM), which is considered to be reversible, dynamic, and conserved in prokaryotes and eukaryotes. Recent developments in the identification of Kglu by mass spectrometry have shown that Kglu is mainly involved in the regulation of metabolism, oxidative damage, chromatin dynamics and is associated with various diseases. In this review, we firstly summarize the development history of glutarylation, the biochemical processes of glutarylation and deglutarylation. Then we focus on the pathophysiological functions such as glutaric acidemia 1, asthenospermia, etc. Finally, the current computational tools for predicting glutarylation sites are discussed. These emerging findings point to new functions for lysine glutarylation and related enzymes, and also highlight the mechanisms by which glutarylation regulates diverse cellular processes.

The Role of Resveratrol in Human Male Fertility

Resveratrol (RSV) (3,4′,5 trihydroxystilbene) is a natural non-flavonoid polyphenol widely present in the Mediterranean diet. In particular, RSV is found in grapes, peanuts, berries, and red wine. Many beneficial effects of this molecule on human health have been reported. In fact, it improves some clinical aspects of various diseases, such as obesity, tumors, hypertension, Alzheimer’s disease, stroke, cardiovascular diseases, and diabetes mellitus. However, little is known about the relationship between this compound and male fertility and the few available results are often controversial. Therefore, this review evaluated the effects of RSV on human male fertility and the mechanisms through which this polyphenol could act on human spermatozoa.

A decrease of docosahexaenoic acid in testes of mice fed a high-fat diet is associated with impaired sperm acrosome reaction and fertility

Obesity is a major worldwide health problem that is related to most chronic diseases, including male infertility. Owing to its wide impact on health, mechanisms underlying obesity-related infertility remain unknown. In this study, we report that mice fed a high-fat diet (HFD) for over 2 months showed reduced fertility rates and increased germ cell apoptosis, seminiferous tubule degeneration, and decreased intratesticular estradiol (E2) and E2-to-testosterone ratio. Interestingly, we also detected a decrease in testicular fatty acid levels, behenic acid (C22:0), and docosahexaenoic acid (DHA, 22:6n-3), which may be related to the production of dysfunctional spermatozoa. Overall, we did not detect any changes in the frequency of seminiferous tubule stages, sperm count, or rate of in vitro capacitation. However, there was an increase in spontaneous and progesterone-induced acrosomal exocytosis (acrosome reaction) in spermatozoa from HFD-fed mice. These data suggest that a decrease in E2 and fatty acid levels influences spermatogenesis and some steps of acrosome biogenesis that will have consequences for fertilization. Thus, our results add new evidence about the adverse effect of obesity in male reproduction and suggest that the acrosomal reaction can also be affected under this condition.

Circulating Zinc and Copper Levels are Associated with Sperm Quality in Obese Men after Metabolic Surgery: A Pilot Study

(1) Background: Inadequate levels of several trace elements and vitamins may impair spermatogenesis in men. Although weight loss after metabolic surgery normalizes male reproductive hormones, sperm quality seems to not improve. We hypothesized that circulating concentrations of zinc, copper and other trace elements and vitamins might be involved. (2) Methods: We studied 20 men submitted to metabolic surgery at baseline and after two years. Hormone profiles, serum trace elements and vitamins were studied together with sperm analysis. (3) Results: At follow-up, serum testosterone, follicle-stimulating hormone and inhibin B concentrations increased showing a beneficial hormonal response for spermatogenesis. Conversely, serum copper, zinc and ferritin showed a decline after surgery. In total, 33% of men showed zinc deficiency, 27% copper deficiency and 20% iron deficiency, among others. Sperm analysis showed that all revaluated patients had at least one abnormal parameter. Serum zinc concentrations showed a positive correlation with progressive motility (r = 0.577, p = 0.031), and serum ferritin a positive correlation with sperm volume (ρ = 0.535, p = 0.049). Serum copper showed a weak and near significant correlation with motility (r = 0.115, p = 0.051). (4) Conclusions: The lack of improvement in sperm quality in obese men after metabolic surgery may be related to nutrient malabsorption, especially zinc, copper and iron.

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.

Bariatric Surgery Impact on Reproductive Hormones, Semen Analysis, and Sperm DNA Fragmentation in Men with Severe Obesity: Prospective Study

PURPOSE

Growing evidence in the literature suggests that obesity is capable of altering reproductive hormone levels and male fertility. Effects on classic semen parameters and sperm DNA fragmentation (SDF), however, have not been properly established. Additionally, the impact of bariatric surgery (BS) on those parameters is still controversial.

MATERIALS AND METHODS

In Phase 1, 42 patients with obesity and 32 fertile controls were submitted to reproductive hormone evaluation, semen analysis, and SDF testing. In Phase 2, patients with obesity were submitted to BS or clinical follow-up and were invited to 6-month revaluation.

RESULTS

Phase 1: Men with obesity have higher levels of estradiol, LH, and FSH and lower levels of total testosterone (TT) when compared with eutrophic fertile men. Additionally, they present worse semen parameters, with reduction in ejaculated volume and sperm concentration, worse sperm motility and morphology, and higher SDF. Phase 2: 32 patients returned to revaluation. Eighteen were submitted to BS (group S) and 14 were not submitted to any specific therapeutic regimen (group NS). In group S, TT more than doubled after surgery (294.5 to 604 ng/dL, p < 0.0001). Worsening of sperm concentration and total ejaculated sperm count were also noticed, and 2 patients became azoospermic after BS. SDF, however, improved after the procedure. No changes in the variables studied were observed in non-operated patients.

CONCLUSION

In this prospective study, we have found that BS results in improvements in reproductive hormone levels and SDF after 6-month follow-up. Sperm concentration, however, reduced after the procedure.

The Mechanism of Zinc Sulfate in Improving Fertility in Obese Rats Analyzed by Sperm Proteomic Analysis

This study investigates the mechanism underlying the improving effect of zinc on fertility in obese rats using proteomics. The effects of three different doses of ZnSO₄ on spermatogenesis and hormone levels were studied. Testicular spermatogenesis was observed by HE staining. Serum estrogen and testosterone levels were measured by chemiluminescent microparticle immunoassay. Sperm proteomic analysis was performed by liquid chromatography-mass spectrometry. The DAVID database was used to perform the GO enrichment analysis and KEGG pathway analysis of the differentially expressed genes, and the STRING online database was used to construct a PPI network. The sperm count, sperm motility, and testosterone hormones of the ZnSO₄-treated rats group were increased. ZnSO₄ improved testicular structure and spermatogenesis abnormalities caused by obesity. Proteomic analysis showed that there were 401 differentially expressed proteins in a total of 6 sperm samples from the ZnSO₄-treated group and the obesity groups. Differential proteins were input into the DAVID website. The 341 identified proteins were then classified according to their biological functions. The KEGG analysis showed that the enriched signal pathways included glycolysis/gluconeogenesis, carbon metabolism, citrate cycle, fatty acid metabolism, and pyruvate metabolism. Some proteins were shown to be associated with valine, leucine, and isoleucine degradation pathways. STRING analysis obtained 36 node proteins. Cytoscape analysis showed that these proteins mainly participated in nine networks including metabolic process, oxidation-reduction, aerobic respiration, RNA splicing, and glutathione conjugation. ZnSO₄ may improve the fertility of obese male rats by regulating protein expression related to metabolism, inflammation, and sperm maturation.

Obesity significantly alters the human sperm proteome, with potential implications for fertility

PURPOSE

In men, obesity may lead to poor semen parameters and reduced fertility. However, the causative links between obesity and male infertility are not totally clear, particularly on a molecular level. As such, we investigated how obesity modifies the human sperm proteome, to elucidate any important implications for fertility.

METHODS

Sperm protein lysates from 5 men per treatment, classified as a healthy weight (body mass index (BMI) ≤ 25 kg/m2) or obese (BMI ≥ 30 kg/m2), were FASP digested, submitted to liquid chromatography tandem mass spectrometry, and compared by label-free quantification. Findings were confirmed for several proteins by qualitative immunofluorescence and a quantitative protein immunoassay.

RESULTS

A total of 2034 proteins were confidently identified, with 24 proteins being significantly (p < 0.05) less abundant (fold change < 0.05) in the spermatozoa of obese men and 3 being more abundant (fold change > 1.5) compared with healthy weight controls. Proteins with altered abundance were involved in a variety of biological processes, including oxidative stress (GSS, NDUFS2, JAGN1, USP14, ADH5), inflammation (SUGT1, LTA4H), translation (EIF3F, EIF4A2, CSNK1G1), DNA damage repair (UBEA4), and sperm function (NAPA, RNPEP, BANF2).

CONCLUSION

These results suggest that oxidative stress and inflammation are closely tied to reproductive dysfunction in obese men. These processes likely impact protein translation and folding during spermatogenesis, leading to poor sperm function and subfertility. The observation of these changes in obese men with no overt andrological diagnosis further suggests that traditional clinical semen assessments fail to detect important biochemical changes in spermatozoa which may compromise fertility.

Effect of Different Exercise Loads on Testicular Oxidative Stress and Reproductive Function in Obese Male Mice

This study is aimed at investigating the effect of different exercise loads on the reproductive function of obese male mice and the underlying mechanisms. Male mice with high-fat diet-induced obesity were divided into obesity control (OC), obesity moderate-load exercise (OME), and obesity high-load exercise (OHE) groups. The OME and OHE groups were subjected to swimming exercise 5 days per week over a duration of 8 weeks, with the exercise load progressively increased to 2 h per day in the OME group and 2 h twice per day in the OHE group. In the OC group mice without exercise regimen, we observed a decrease in mRNA expression of antioxidant enzymes, increase in free radical products, upregulation of mRNA and protein expression of nuclear factor-κB and proinflammatory cytokines, inhibition of mRNA and protein expression of testosterone synthases, decrease in the serum testosterone level and sperm quality, and increase in sperm apoptosis. Although both moderate-load exercise and high-load exercise reduced body fat, only moderate-load exercise effectively alleviated obesity-induced oxidative stress, downregulated the expression of nuclear factor-κB and proinflammatory cytokines, and reversed the decrease in mRNA and protein expression of testosterone synthases, serum testosterone level, and sperm quality. These changes were not observed in the OHE group mice. Obesity-induced testicular oxidative stress and inflammatory response decreased testosterone synthesis and sperm quality. Moderate-load exercise alleviated the negative effect of obesity on male reproductive function by decreasing testicular oxidative stress and inflammatory responses. Although high-load exercise effectively reduced body fat, its effects on alleviating oxidative stress and improving male reproductive function were limited.

Metformin Improves Fertility in Obese Males by Alleviating Oxidative Stress-Induced Blood-Testis Barrier Damage

Background/Aims

Obesity, which is related to increased oxidative stress in various tissues, is a risk factor for male infertility. Metformin is reported to have an antioxidant effect; however, the precise role of metformin in obesity-induced male infertility remains unknown. The current study is aimed at exploring the effects of metformin and characterizing its underlying mechanism in the fertility of obese males.

Methods

An obese male mouse model was generated by feeding mice with a high-fat diet; then, the mice were administered metformin in water for 8 weeks. Reproductive ability, metabolic parameters, and follicle-stimulating hormone (FSH) were assessed by cohabitation, enzymatic methods, and ELISA, respectively. Damage to the integrity of the blood-testis barrier (BTB), which ensures spermatogenesis, was assessed by transmission electron microscopy and immunofluorescence with a biotin tracer. Malondialdehyde (MDA), superoxide dismutase (SOD), and reactive oxygen species (ROS) were employed for the assessments of oxidative stress. BTB-related proteins were measured by immunoblotting. Nuclear factor κB (NF-κB) was assessed by immunofluorescence.

Results

High-fat-diet-fed mice presented evident lipid metabolic disturbances, disrupted BTB integrity, and decreased reproductive function. Metformin alleviated the decrease in male fertility, decreased ectopic lipid deposition in the testis, and increased serum FSH levels. A further mechanistic analysis revealed that metformin ameliorated the high-fat-diet-induced injury to the BTB structure and permeability and restored the disordered BTB-related proteins, which might be associated with an improvement in oxidative stress and a recovery of NF-κB activity in Sertoli cells (SCs).

Conclusion

Metformin improves obese male fertility by alleviating oxidative stress-induced BTB damage. These findings provide new insights into the effect of metformin on various diseases and suggest future possibilities in the treatment of male infertility.

The anti-oxidant roles of Taurine and Hypotaurine on acrosome integrity, HBA and HSPA2 of the human sperm during vitrification and post warming in two different temperature

Despite advances in vitrification techniques for sperm cryopreservation, cryo-damages of sperm caused by generation of reactive oxygen species (ROS) continue to impede implementation of this technique. This study analyses the effects of taurine and hypotaurine as anti-oxidants during vitrification of human sperms. The study was performed in two steps. In the first step, 20 normospermic semen samples were vitrified in the presence of varying concentrations of taurine and hypotaurine, and their effects as anti-oxidant agents on classical sperm parameters, hyaluronan-binding assay (HBA), lipid peroxidation (LPO) and acrosome reaction (AR) were studied. Statistical analyses showed that the sperm parameters in all vitrified groups decreased significantly (P < 0.05) compared to the fresh group. However, HBA and acrosome integrity in vitrified groups containing taurine and 50 mM of hypotaurine were better than in the control group (P < 0.05). The morphology of the vitrified group was good only in the group that contained 50 mM of hypotaurine (P < 0.05). Based on the results from the first step, 50 mM of hypotaurine was considered the ideal anti-oxidant formulation and further tests were carried out on 10 normospermic semen samples with this protecting agent. In addition to the mentioned parameters, the expression of heat shock proteinA2 (HSPA2) was studied in the vitrified group with 50 mM hypotaurine, warmed under two different warming temperatures 37 and 42 °C. 50 mM Hypotaurine was found to equally improve motility, morphology, HBA, and AR after warming at 37 °C and 42 °C (P < 0.05). However, at both warming temperatures, the expression of HSPA2 was reduced in all vitrified groups comparing to the fresh group (P < 0.05). In conclusion, taurine and hypotaurine antioxidants, especially 50 mM hypotaurine, are able to reduce deleterious cryo-injuries on morphology, acrosome and HBA and improve sperm recovery at both warming temperatures (37 and 42 °C). However, they do not have any protective action on expression of HSPA2.

Seminal but not Serum Levels of Holotranscobalamin are Altered in Morbid Obesity and Correlate with Semen Quality: A Pilot Single Centre Study

Vitamin B12 (cobalamin) is an essential cofactor in the one-carbon metabolism. One-carbon metabolism is a set of complex biochemical reactions, through which methyl groups are utilised or generated, and thus plays a vital role to many cellular functions in humans. Low levels of cobalamin have been associated to metabolic/reproductive pathologies. However, cobalamin status has never been investigated in morbid obesity in relation with the reduced semen quality. We analysed the cross-sectional data of 47-morbidly-obese and 21 lean men at Careggi University Hospital and evaluated total cobalamin (CBL) and holotranscobalamin (the active form of B12; holoTC) levels in serum and semen. Both seminal and serum concentrations of holoTC and CBL were lower in morbidly obese compared to lean men, although the difference did not reach any statistical significance for serum holoTC. Seminal CBL and holoTC were significantly higher than serum levels in both groups. Significant positive correlations were observed between seminal holoTC and total sperm motility (r = 0.394, p = 0.012), sperm concentration (r = 0.401, p = 0.009), total sperm number (r = 0.343, p = 0.028), and negative correlation with semen pH (r = -0.535, p = 0.0001). ROC analysis supported seminal holoTC as the best predictor of sperm number (AUC = 0.769 ± 0.08, p = 0.006). Our findings suggest that seminal rather than serum levels of holoTC may represent a good marker of semen quality in morbidly obese subjects.

Acrosome reaction and chromatin integrity as additional parameters of semen analysis to predict fertilization and blastocyst rates

BACKGROUND

Traditional semen parameters have shown little to none predictive value for fertilization and blastocyst viability for a successful pregnancy. Therefore, the purpose of this study was to explore the usefulness of incorporating the acrosome reaction (AR) and chromatin integrity to conventional semen analysis to individually predict the fertile potential of sperm samples.

METHODS

A cross-sectional study was conducted in 69 participants undergoing IVF using oocyte donation. Semen samples were collected and evaluated for: AR [spontaneous (sAR) and induced (iAR)] by flow cytometry using anti-CD46-FITC, Acrosome Response to an Ionophore Challenge (ARIC), chromatin integrity by Sperm Chromatin Structure Assay (DNA Fragmentation Index-%DFI and High DNA Stainability-%HDS), WHO semen analysis, fertilization and blastocyst rates.

RESULTS

The participant age was 40.0 ± 6.1 years (66% were normozoospermic). Sperm morphology, sAR, iAR, and ARIC were associated with the fertilization (β = 3.56, R² = 0.054; β = - 5.92, R² = 0.276; β = 1.83, R² = 0.150; and β = 2.10, R² = 0.270, respectively, p < 0.05). A logit model was developed to calculate the probability of fertilization (≥ 60%) for each participant, using the sperm morphology and ARIC as independent variables, followed by ROC analysis to determine a cutoff probability of 0.65 (specificity = 80.6%, sensitivity = 63.2%). %DFI was inversely associated with the viable blastocyst rate (β = - 1.77, R² = 0.057, p = 0.003), by the logit model and ROC analysis, a cutoff probability of 0.70 (specificity = 80.6%, sensitivity = 72.3%) was obtained to predict blastocyst viability (≥ 40%). There was no difference in the results with normozoospermic samples (n = 46).

CONCLUSIONS

The incorporation of ARIC and %DFI allowed to obtain predictive models for high fertilization and blastocyst rates in an individualized way, being promising tools to improve the diagnosis of male fertility potential for research or assisted reproduction, even in men with unknown infertility.

The complex association between metabolic syndrome and male hypogonadism

BACKGROUND

The complex association between metabolic syndrome (MetS) and male hypogonadism is well established. A number of observational studies show that low testosterone is associated with insulin resistance and an increased risk for diabetes mellitus and MetS in men.

AIMS

To elucidate the association between MetS and male hypogonadism, present epidemiological data on the co-existence of the two comorbidities, enlighten the underlying pathophysiology and appraise the effects of testosterone supplementation therapy (TTh) and lifestyle modifications on MetS and body composition in men.

MATERIALS AND METHODS

Systematic search to PubMed and Medline databases for publications reporting data on association between MetS and male hypogonadism.

RESULTS

Both MetS and male hypogonadism have a high prevalence in the general population and are frequently co-existing e.g. in males with diabetes. Accumulating evidence from animal and human studies suggests that MetS is involved in the pathogenesis of hypogonadism in males as well as the other way around. On the other hand, there is evidence for a favorable effect of testosterone supplementation in testosterone deficient men with MetS and/or diabetes mellitus.

CONCLUSIONS

Studies with superior methodological characteristics are needed in order to establish a role for testosterone supplementation in men with MetS and/or diabetes mellitus.

iTRAQ-based analysis of sperm proteome from normozoospermic men achieving the rescue-ICSI pregnancy after the IVF failure

Background

In the assisted reproduction, the infertile molecules of spermatozoa from normozoospermic men who underwent the unexplained failure of in vitro fertilization (IVF) due to the lack of sperm binding to the normal zona pellucida, and then achieved pregnancy with the rescue intracytoplasmic sperm injection (R-ICSI) remain unclear. More works are still necessary to explore this male infertile mechanism.

Methods

Normozoospermicmen with the IVF pregnancy and normozoospermic men with the R-ICSI pregnancy after the conventional IVF failure were collected. iTRAQ-based proteomic approach were performed to reveal the new infertile causes between the IVF pregnancy men and the R-ICSI pregnancy men. To validate the confidence of proteome data, the individual samples were analyzed by western blot and immunofluorescence. Further, the spontaneous acrosome reactions were measured to evaluate the sperm quality.

Results

Compared with IVF pregnancy group, 56 sperm proteins were differentially expressed in the R-ICSI pregnancy group. Bioinformatic analyses (PANTHER, DAVID, PubMed and STRING) indicated these altered sperm proteins were involved in various molecular functions: reproduction, chromosome organization, and sperm-oocyte interaction. Moreover, the confidence of proteome data was confirmed by western blot and immunofluorescence using the individual samples, which were consistent with our proteomic data. Additionally, an increased rate of the spontaneous acrosome reaction rate was found in the R-ICSI pregnancy group.

Conclusions

The sealtered sperm proteins and the increased spontaneous acrosome reaction rate might account for this unexplained male infertility in the R-ICSI pregnancy patients. The present proteomic results will throw light on the better understanding of the unexplained infertile mechanisms underlying these normozoospermic man who achieved R-ICSI pregnancy after IVF failure.

Electronic supplementary material

The online version of this article (10.1186/s12014-018-9203-3) contains supplementary material, which is available to authorized users.

Sugar-sweetened beverage intake and serum testosterone levels in adult males 20-39 years old in the United States

BACKGROUND

This population-based study was designed to investigate whether consumption of sugar-sweetened beverages (SSB) is associated with lower serum total testosterone concentration in men 20-39 years old.

METHODS

All data for this study were retrieved from the National Health and Nutrition Examination Survey (NHANES) 2011-2012. The primary outcome was serum testosterone concentration, and main independent variable was SSB intake. Other variables included age, race/ethnicity, poverty/income ratio, body mass index (BMI), serum cotinine, heavy drinking, and physical activity.

RESULTS

Among all subjects (N = 545), 486 (90.4%) had normal testosterone levels (defined as ≥231 ng/dL) and 59 (9.6%) had low testosterone levels (defined as < 231 ng/dL). Multivariate logistic regression revealed the odds of low testosterone was significantly greater with increasing SSB consumption (Q4 [≥442 kcal/day] vs. Q1 [≤137 kcal/day]), adjusted odds ratio [aOR] = 2.29, p = 0.041]. After adjusting for possible confounding variables, BMI was an independent risk factor for low testosterone level; subjects with BMI ≥ 25 kg/m² had a higher risk of having a low testosterone level than those with BMI < 25 kg/m² (aOR = 3.68, p = 0.044).

CONCLUSION

SSB consumption is significantly associated with low serum testosterone in men 20-39 years old in the United States.

Massive Weight Loss Obtained by Bariatric Surgery Affects Semen Quality in Morbid Male Obesity: a Preliminary Prospective Double-Armed Study

OBJECTIVES

The aim of this study is to evaluate the effect of massive weight loss on the seminal parameters at 6 months from bariatric surgery.

DESIGN

Two-armed prospective study performed in 31 morbidly obese men, undergoing laparoscopic roux-en-Y-gastric bypass (n = 23) or non-operated (n = 8), assessing sex hormones, conventional (sperm motility, morphology, number, semen volume), and non-conventional (DNA fragmentation and seminal interleukin-8), semen parameters, at baseline and after 6 months from surgery or patients' recruitment.

RESULTS

In operated patients only, a statistically significant improvement in the sex hormones was confirmed. Similarly, a positive trend in the progressive/total sperm motility and number was observed, though only the increase in semen volume and viability was statistically significant (Δ = 0.6 ml and 10%, P < 0.05, respectively). A decrease in the seminal interleukin-8 levels and in the sperm DNA fragmentation was also present after bariatric surgery, whereas these parameters even increased in non-operated subjects. Age-adjusted multivariate analysis showed that the BMI variations significantly correlated with the changes in the sperm morphology (β = -0.675, P = 0.025), sperm number (β = 0.891, P = 0.000), and semen volume (r = 0.618, P = 0.015).

CONCLUSION

The massive weight loss obtained with bariatric surgery was associated with an improvement in some semen parameters. The correlations found between weight loss and semen parameter variations after surgery suggest that these might occur early downstream of the testis and more slowly than the changes in the sex hormones.

Serum Retinol, Folic Acid, and Copper Are Associated With Sperm Abnormalities in Men With Obesity

BACKGROUND AND OBJECTIVES

Micronutrients may influence the development and differentiation of sperm cells. The aim of this study was to assess the possible association of deficiencies in several vitamins and trace elements with sperm abnormalities in men with obesity.

PARTICIPANTS AND METHODS

Thirty male patients with moderate to severe obesity and ten lean controls who gave written informed consent were included. Anthropometric parameters were recorded. Hormonal and lipid profiles were analyzed, as well as serum concentrations of zinc, copper, retinol, α-tocopherol, 25-hydroxyvitamin D, cobalamin, and folic acid. For sperm analysis, we used the reference values proposed by the World Health Organization.

RESULTS

Fourteen of the thirty men (47%) presented abnormal sperm results. The most common abnormality was low motility in 33% of them, followed by low sperm concentration in 27% of the patients. Patients with abnormal sperm results showed lower serum folic acid (p = 0.005) and higher serum estradiol (p = 0.015) and copper (p = 0.033) than lean controls. The ejaculate volume inversely correlated with body mass index (BMI; r = -0.378, p = 0.016) and serum estradiol (r = -0.328, p = 0.041). Total number of sperm correlated inversely with BMI (r = -0.428, p = 0.006) and serum estradiol (r = -0.507, p = 0.001) and positively with serum folic acid (r = 0.356, p = 0.026) and retinol (r = 0.421, p = 0.009). Total motility of sperm inversely correlated with BMI (r = -0.433, p = 0.005), serum estradiol (r = -0.475, p = 0.002), and copper (r = -0.416, p = 0.012) and positively correlated with serum folic acid (r = 0.522, p = 0.001) and retinol (r = 0.350, p = 0.034).

CONCLUSIONS

Sperm abnormalities in men with obesity are associated with excess body weight and micronutrient concentrations.

Cholesterol: A Gatekeeper of Male Fertility?

Cholesterol is essential for mammalian cell functions and integrity. It is an important structural component maintaining the permeability and fluidity of the cell membrane. The balance between synthesis and catabolism of cholesterol should be tightly regulated to ensure normal cellular processes. Male reproductive function has been demonstrated to be dependent on cholesterol homeostasis. Here we review data highlighting the impacts of cholesterol homeostasis on male fertility and the molecular mechanisms implicated through the signaling pathways of some nuclear receptors.

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.

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.

Body mass index and human sperm quality: neither one extreme nor the other

The aim of the present study was to investigate the still contentious association between body mass index (BMI) and seminal quality. To this end, 4860 male patients (aged 18–65 years; non-smokers and non-drinkers), were classified according to BMI as either underweight (UW; BMI <20 kg m–2; n = 45), normal weight (NW; BMI 20–24.9 kg m–2; n = 1330), overweight (OW; BMI 25–29.9 kg m–2; n = 2493), obese (OB; BMI 30–39.9 kg m–2; n = 926) or morbidly obese (MOB; BMI ≥40 kg m–2; n = 57). Conventional semen parameters and seminal concentrations of fructose, citric acid and neutral α-glucosidase (NAG) were evaluated. The four parameters that reflect epididymal maturation were significantly lower in the UW and MOB groups compared with NW, OW and OB groups: sperm concentration, total sperm count (103.3 ± 11.4 and 121.5 ± 20.6 and vs 157.9 ± 3.6, 152.4 ± 2.7 or 142.1 ± 4.3 spermatozoa ejaculate–1 respectively, P < 0.05), motility (41.8 ± 2.5 and 42.6 ± 2.6 vs 47.8 ± 0.5, 48.0 ± 0.4 or 46.3 ± 0.6 % of motile spermatozoa respectively, P < 0.05) and NAG (45.2 ± 6.6 and 60.1 ± 7.9 vs 71.5 ± 1.9, 64.7 ± 1.3 or 63.1 ± 2.1 mU ejaculate-1 respectively, P < 0.05). Moreover, the percentage of morphologically normal spermatozoa was decreased in the MOB group compared with the UW, NW, OW and OB groups (4.8 ± 0.6% vs 6.0 ± 0.8%, 6.9 ± 0.1%, 6.8 ± 0.1 and 6.4 ± 0.2%, respectively; P < 0.05). In addition, men in the MOB group had an increased risk (2.3- to 4.9-fold greater) of suffering oligospermia and teratospermia (P < 0.05). Both morbid obesity and being underweight have a negative effect on sperm quality, particularly epididymal maturation. These results show the importance of an adequate or normal bodyweight as the natural best option for fertility, with both extremes of the BMI scale as negative prognostic factors.

Protective effect of resveratrol on spermatozoa function in male infertility induced by excess weight and obesity

Male infertility is a complex, multifactorial and polygenic disease that contributes to ~50% cases of infertility. Previous studies have demonstrated that excess weight and obesity factors serve an important role in the development of male infertility. An increasing number of studies have reported that resveratrol may regulate the response of cells to specific stimuli that induce cell injury, as well as decrease germ cell apoptosis in mice or rats. In the present study, the semen quality and serum sex hormone levels were evaluated in 324 men, which included 73 underweight, 82 normal weight, 95 overweight and 74 obese men. All patients were referred to The Reproductive Medicine Center of Shanxi Women and Infants Hospital (Taiyuan, China) between January 2013 and January 2015. The aim of the present study was to investigate the effects of resveratrol treatment on the motility, plasma zinc concentration and acrosin activity of sperm from obese males. The sperm concentration, normal sperm morphology, semen volumes, DNA fragmentation rates and testosterone levels in men from the overweight and obese groups were markedly decreased when compared with men in the normal weight group. In addition, the progressive motility, seminal plasma zinc concentration and spermatozoa acrosin activity were notably decreased in the obese group compared with the normal weight group. However, estradiol levels were significantly increased in the overweight, obese and underweight groups compared with the normal weight group. Notably, semen samples from obese males with astenospermia treated with 0–100 µmol/l resveratrol for 30 min demonstrated varying degrees of improvement in sperm motility. When these semen samples were treated with 30 µmol/l resveratrol, sperm motility improved when compared to other doses of resveratrol. Therefore, 30 µmol/l resveratrol was selected for further experiments. Upon treatment of semen samples with resveratrol (30 µmol/l) for 30 min, the seminal plasma zinc concentration and spermatozoa acrosin activity increased significantly in the experimental group compared with the control group. These data suggest that male obesity negatively impacts on male reproductive potential, not only through altering hormone levels, but also by directly altering sperm function. In addition, resveratrol may have a therapeutic and protective effect against obesity-induced abnormalities in semen.

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

PROBLEM

Male obesity has been linked to subfecundity. This study is to investigate the effects of GLP-1 receptor (GLP-1R) agonist exenatide on sperm quality in high-fat diet (HFD)-induced obese mice.

METHOD OF STUDY

After 12 weeks of chow diet (CD) or HFD challenge, mice on HFD were allocated to either saline or exenatide (24 nmol/kg/day) interventions for 8 weeks. Sperm quality and the inflammatory profile of testis were compared among three groups.

RESULTS

Obesity reduced the quality of sperm and changed the inflammatory profile characterized by increased mRNA expression levels of TNF-α, MCP-1, and F4/80 in testis. Exenatide intervention reduced the expression of pro-inflammatory cytokines and improved the quality of sperm.

CONCLUSION

HFD-induced obesity leads to the impairment of sperm quality and increased inflammation of testis in mice, and the abnormal physiology can be attenuated by exenatide treatment. Exenatide treatment may bring additional profits to obese and diabetes men by improving sperm function.

Male obesity is associated with changed spermatozoa Cox4i1 mRNA level and altered seminal vesicle fluid composition in a mouse model

The rate of obesity among men of reproductive age has tripled in the last three decades. Previously, we demonstrated that paternal obesity resulted in impaired preimplantation developmental kinetics, compromised post-compaction metabolism and decreased blastocyst cell number when embryos were generated in vivo. Subsequently, using in vitro fertilization we found embryos of obese males to have altered metabolism before compaction, reduced inner cell mass cell number and retarded fetal development--the difference between these two studies being the method of embryo generation and the presence or absence of seminal plasma, respectively. Here, we hypothesize that both sperm and seminal plasma are affected by obesity, compromising embryogenesis and pregnancy health in a cumulative manner. Epididymal sperm and seminal vesicle fluid were collected from normal and obese C57BL/6 mice. RNA and DNA were extracted from spermatozoa for qPCR and global methylation analysis, respectively. Proteomic (Luminex) and metabolomic (GC-MS) techniques were employed to analyse the composition of seminal vesicle fluid. Nuclear encoded cytochrome c oxidase subunit IV isoform 1 (Cox4i1) of the terminal enzyme in the mitochondrial respiratory chain demonstrated significantly increased RNA levels in the sperm of obese males (P< 0.05). Quantitative seminal plasma analysis identified significant changes in levels of the hormones insulin, leptin and estradiol between normal and obese males (P < 0.05). Further, the metabolite composition of seminal vesicle fluid was significantly affected by obesity. Consequently, this study has determined that obesity affects both sperm and seminal plasma composition. The interaction between sperm and seminal plasma warrants further analysis.

Metabolic syndrome-associated sperm alterations in an experimental rabbit model: relation with metabolic profile, testis and epididymis gene expression and effect of tamoxifen treatment

The influence of metabolic syndrome (MetS) on sperm quality and function is debated. Using a well-established high fat diet (HFD) rabbit model resembling human MetS, including development of hypogonadism, we demonstrate that HFD decreased sperm motility, morphology and acrosome reaction in response to progesterone and increased sperm cholesterol content. All the above parameters were associated with most MetS features, its severity and plasma testosterone (T) at univariate analysis. After T adjustment, sperm morphology and motility retained a significant association, respectively, with mean arterial pressure and circulating cholesterol levels. MetS modified the expression of inflammatory and tissue remodelling genes in the testis and of aquaporins in the epididymis. In a multivariate analysis, sperm morphology resulted associated with testis expression of fibronectin and collagen type 1 genes, whereas motility with epididymis aquaporin 1 gene. Administration of tamoxifen, used in the treatment of idiopathic male infertility, to HFD rabbits partially restored motility, but further decreased morphology and increased spontaneous acrosome reaction, without restoring responsiveness to progesterone. Overall our results indicate that development of MetS produces detrimental effects on sperm quality and functionality by inducing metabolic disorders leading to alterations in testis and epididymis functions and evidence a role of hypertension as a new determinant of abnormal sperm morphology, in line with a previous human study from our group.