Diet-induced obesity in male C57BL/6 mice decreases fertility as a consequence of disrupted blood-testis barrier

Cholesterol dynamics in rabbit liver: High-fat diet, olive oil, and synergistic dietary effects

BACKGROUND & AIMS

Lipid metabolism disorders contribute to a range of human diseases, including liver-related pathologies. Rabbits, highly sensitive to dietary cholesterol, provide a model for understanding the development of liver disorders. Sterol regulatory element-binding protein isoform 2 (SREBP2) crucially regulates intracellular cholesterol pathways. Extra-virgin olive oil (EVOO) has shown reducing cholesterol levels and restoring liver parameters affected by HFD. The aim was to investigate the molecular impact of an HFD and supplemented with EVOO on rabbit liver cholesterol metabolism.

APPROACH & RESULTS

Male rabbits were assigned to dietary cohorts, including control, acute/chronic HFD, sequential HFD with EVOO, and EVOO. Parameters such as serum lipid profiles, hepatic enzymes, body weight, and molecular analyses. After 6 months of HFD, plasma and hepatic cholesterol increased with decreased SREBP2 and 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR) expression. Prolonged HFD increased cholesterol levels, upregulating SREBP2 mRNA and HMGCR protein. Combining this with EVOO lowered cholesterol, increased SREBP2 mRNA, and upregulated low-density lipoprotein receptor (LDLR) expression. HFD-induced metabolic dysfunction-associated fatty liver disease was mitigated by EVOO. In conclusion, the SREBP2 system responds to dietary changes.

CONCLUSIONS

In rabbits, the SREBP2 system responds to dietary changes. Acute HFD hinders cholesterol synthesis, while prolonged HFD disrupts regulation, causing SREBP2 upregulation. EVOO intake prompts LDLR upregulation, potentially enhancing cholesterol clearance and restoring hepatic alterations.

The non-canonical bivalent gene Wfdc15a controls spermatogenic protease and immune homeostasis

Male infertility can be caused by chromosomal abnormalities, mutations and epigenetic defects. Epigenetic modifiers pre-program hundreds of spermatogenic genes in spermatogonial stem cells (SSCs) for expression later in spermatids, but it remains mostly unclear whether and how those genes are involved in fertility. Here, we report that Wfdc15a, a WFDC family protease inhibitor pre-programmed by KMT2B, is essential for spermatogenesis. We found that Wfdc15a is a non-canonical bivalent gene carrying both H3K4me3 and facultative H3K9me3 in SSCs, but is later activated along with the loss of H3K9me3 and acquisition of H3K27ac during meiosis. We show that WFDC15A deficiency causes defective spermiogenesis at the beginning of spermatid elongation. Notably, depletion of WFDC15A causes substantial disturbance of the testicular protease-antiprotease network and leads to an orchitis-like inflammatory response associated with TNFα expression in round spermatids. Together, our results reveal a unique epigenetic program regulating innate immunity crucial for fertility.

Hirsutella sinensis intensifies testicular function and spermatogenesis in male mice with high-fat diet-induced obesity

BACKGROUND

Hirsutella sinensis (HS) is a mycelium isolated from the fruiting body of the medicinal mushroom Cordyceps sinensis . This study explored whether HS treatment affects reproductive dysfunction in a high-fat diet (HFD)-induced mouse model and regulates various mechanisms, focusing on oxidative stress, apoptosis, inflammation, and autophagy.

METHODS

Twenty-four C57BL/6J (B6) mice were randomly divided into a standard chow diet (NCD)- or HFD-fed group for 24 weeks. During the final 8 weeks, half of the HFD-fed mice were orally administered HS (HFD + HS). Biochemical markers, including glucose, insulin, triglycerides, and total cholesterol, were assessed, and hormones, including testosterone, follicle-stimulating hormone (FSH), and luteinizing hormone (LH), were analyzed. Liver and testicular histology, as well as sperm quality markers such as sperm motility, sperm count, and percentage of sperm with normal morphology, were observed. The activities of the testicular antioxidants superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPx) and the products of lipid peroxidation, such as malondialdehyde (MDA), were measured. The protein expression levels of apoptosis-, autophagy- and inflammation-related markers were measured.

RESULTS

The HFD-fed mice had abnormal sex hormone levels, poor sperm quality, and a destroyed testicular structure, with increased oxidative stress and apoptosis in the testis. HS supplementation in HFD-fed mice attenuated testicular apoptosis by suppressing the Bax/Bcl-xl ratio and cleaved caspase 3 protein expression. The HS-treated mice exhibited improved reproductive function, possibly due to reduced oxidative stress and apoptosis, suggesting that HS has a protective effect against HFD-induced testicular damage.

CONCLUSION

Male mice supplemented with HS exhibited attenuated poor semen quality and reduced testosterone levels brought about by HFD-induced obesity by reducing oxidative stress.

Signatures of metabolic diseases on spermatogenesis and testicular metabolism

Diets leading to caloric overload are linked to metabolic disorders and reproductive function impairment. Metabolic and hormonal abnormalities stand out as defining features of metabolic disorders, and substantially affect the functionality of the testis. Metabolic disorders induce testicular metabolic dysfunction, chronic inflammation and oxidative stress. The disruption of gastrointestinal, pancreatic, adipose tissue and testicular hormonal regulation induced by metabolic disorders can also contribute to a state of compromised fertility. In this Review, we will delve into the effects of high-fat diets and metabolic disorders on testicular metabolism and spermatogenesis, which are crucial elements for male reproductive function. Moreover, metabolic disorders have been shown to influence the epigenome of male gametes and might have a potential role in transmitting phenotype traits across generations. However, the existing evidence strongly underscores the unmet need to understand the mechanisms responsible for transgenerational paternal inheritance of male reproductive function impairment related to metabolic disorders. This knowledge could be useful for developing targeted interventions to prevent, counteract, and most of all break the perpetuation chain of male reproductive dysfunction associated with metabolic disorders across generations.

Molecular insights into Sertoli cell function: how do metabolic disorders in childhood and adolescence affect spermatogonial fate?

Male infertility is a major public health concern globally with unknown etiology in approximately half of cases. The decline in total sperm count over the past four decades and the parallel increase in childhood obesity may suggest an association between these two conditions. Here, we review the molecular mechanisms through which obesity during childhood and adolescence may impair future testicular function. Several mechanisms occurring in obesity can interfere with the delicate metabolic processes taking place at the testicular level during childhood and adolescence, providing the molecular substrate to hypothesize a causal relationship between childhood obesity and the risk of low sperm counts in adulthood.

The effects of fine particulate matter on the blood-testis barrier and its potential mechanisms

With the rapid expansion of industrial scale, an increasing number of fine particulate matter (PM2.5) has bringing health concerns. Although exposure to PM2.5 has been clearly associated with male reproductive toxicity, the exact mechanisms are still unclear. Recent studies demonstrated that exposure to PM2.5 can disturb spermatogenesis through destroying the blood-testis barrier (BTB), consisting of different junction types, containing tight junctions (TJs), gap junctions (GJs), ectoplasmic specialization (ES) and desmosomes. The BTB is one of the tightest blood-tissue barriers among mammals, which isolating germ cells from hazardous substances and immune cell infiltration during spermatogenesis. Therefore, once the BTB is destroyed, hazardous substances and immune cells will enter seminiferous tubule and cause adversely reproductive effects. In addition, PM2.5 also has shown to cause cells and tissues injury via inducing autophagy, inflammation, sex hormones disorder, and oxidative stress. However, the exact mechanisms of the disruption of the BTB, induced by PM2.5, are still unclear. It is suggested that more research is required to identify the potential mechanisms. In this review, we aim to understand the adverse effects on the BTB after exposure to PM2.5 and explore its potential mechanisms, which provides novel insight into accounting for PM2.5-induced BTB injury.

Taste receptor type 1 member 3 regulates Western diet-induced male infertility

Western diet (WD), characterized by a high intake of fats and sugary drinks, is a risk factor for male reproductive impairment. However, the molecular mechanisms underlying this remain unclear. Taste receptor type 1 member 3 (TAS1R3), activated by ligands of WD, is highly expressed in extra-oral tissues, particularly in the testes. Here, we investigated to determine the effects of WD intake on male reproduction and whether TAS1R3 mediates WD-induced impairment in male reproduction. Male C57BL/6 J wild-type (WT) and Tas1r3 knockout (KO) mice were fed either a normal diet and plain water (ND) or a 60 % high-fat-diet and 30 % (w/v) sucrose water (WD) for 18 weeks (n = 7-9/group). Long-term WD consumption significantly impaired sperm count, motility and testicular morphology in WT mice with marked Tas1r3 overexpression, whereas Tas1r3 KO mice were protected from WD-induced reproductive impairment. Testicular transcriptome analysis revealed downregulated AMP-activated protein kinase (AMPK) signaling and significantly elevated AMPK-targeted nuclear receptor 4A1 (Nr4a1) expression in WD-fed Tas1r3 KO mice. In vitro studies further validated that Tas1r3 knockdown in Leydig cells prevented the suppression of Nr4a1 and downstream steroidogenic genes (Star, Cyp11a1, Cyp17a1, and Hsd3b1) caused by high glucose, fructose, and palmitic acid levels, and maintained the levels of testosterone. Additionally, we analyzed the public human dataset to assess the clinical implications of our findings and confirmed a significant association between TAS1R3 and male-infertility-related diseases. Our findings suggest that TAS1R3 regulates WD-induced male reproductive impairment via the AMPK/NR4A1 signaling and can be a novel therapeutic target for male infertility.

Ameliorative effects of Myrtus communis L. extract involving the inhibition of oxidative stress on high fat diet-induced testis damage in rats

The possible protective effects of Myrtus communis L. (MC) extract on a high fat diet (HFD)-induced testicular injury in a rat model were investigated using histological and biochemical methods. Wistar albino rats were divided into three groups: a standard diet control group; a HFD group; and an HFD+MC group. The HFD and HFD+MC groups were fed with a HFD for 16 weeks. MC extract (100 mg/kg) was given orally five days a week to the rats in the HFD+MC group during the last four weeks of the experiment. Leptin, triglyceride, high-density lipoproteins, cholesterol, estrogen, testosterone, LH and FSH were analyzed in blood serum. Sperm parameters were evaluated from the epididymis. Testicular morphology, proliferative, apoptotic and NADPH oxidase-2 (NOX2)-positive cells were evaluated histologically. Testicular oxidative stress parameters were analyzed biochemically. In the HFD group, lipid and hormone profiles were changed, abnormal spermatozoa, degenerated seminiferous tubules with apoptotic and NOX2-positive cells were increased in number, and sperm motility and germinal proliferative cells decreased compared to the control group. Moreover, testicular malondialdehyde, 8-hydroxy-2-deoxyguanosine and myeloperoxidase levels increased, whereas glutathione and superoxide dismutase levels decreased in the HFD group compared to the control group. All these histological and biochemical features were ameliorated by MC treatment of HFD-fed rats. In conclusion, HFD caused alterations in sperm parameters and testicular morphology by increasing oxidative damage and apoptosis. MC extract may have potential protective effects by inhibiting oxidative damage.

Dysbiosis of Gut Microbiome Aggravated Male Infertility in Captivity of Plateau Pika

Captivity is an important and efficient technique for rescuing endangered species. However, it induces infertility, and the underlying mechanism remains obscure. This study used the plateau pika (Ochotona curzoniae) as a model to integrate physiological, metagenomic, metabolomic, and transcriptome analyses and explore whether dysbiosis of the gut microbiota induced by artificial food exacerbates infertility in captive wild animals. Results revealed that captivity significantly decreased testosterone levels and the testicle weight/body weight ratio. RNA sequencing revealed abnormal gene expression profiles in the testicles of captive animals. The microbial α-diversity and Firmicutes/Bacteroidetes ratio were drastically decreased in the captivity group. Bacteroidetes and Muribaculaceae abundance notably increased in captive pikas. Metagenomic analysis revealed that the alteration of flora increased the capacity for carbohydrate degradation in captivity. The levels of microbe metabolites' short-chain fatty acids (SCFAs) were significantly high in the captive group. Increasing SCFAs influenced the immune response of captivity plateau pikas; pro-inflammatory cytokines were upregulated in captivity. The inflammation ultimately contributed to male infertility. In addition, a positive correlation was observed between Gastranaerophilales family abundance and testosterone concentration. Our results provide evidence for the interactions between artificial food, the gut microbiota, and male infertility in pikas and benefit the application of gut microbiota interference in threatened and endangered species.

Risk assessment and environmental consequences of the use of the Allium-derived compound propyl-propane thiosulfonate (PTSO) in agrifood applications

The organosulfur compound propyl-propane thiosulfonate (PTSO), mainly found in Allium cepa, has a promising use in the agrifood industry. To confirm its safety for livestock, consumers, and environment, toxicological assessment is needed. In this regard, endocrine-disrupting chemicals (EDCs) are in the spotlight of research. Therefore, as part of the risk assessment of PTSO, in the present work, an in vivo study was performed in mice exposed to PTSO to investigate its potential reproductive toxicity considering fertility, genetic and endocrine endpoints. Five-weeks-old CD1 mice (80 males, 80 females) were exposed for 11 or 16 weeks (males or females, respectively) to different doses of PTSO (0, 14, 28 and 55 mg PTSO/kg b.w./day; 20 animals per group and sex) through the food pellets. No clinical observations or mortality and no changes in absolute organ weights and relative organ weights/body weight or brain ratios occurred during the study. The estrous cycle did not undergo any significant toxicologically relevant change. Most of the sex hormones displayed normal values. Some alterations in the expression of some genes related to reproduction is only observed in females, but they do not appear to have consequences in the development of sex organs. Docking results showed the impossibility of stable binding to estrogen and androgen receptors. Considering all the results obtained, the safe profile of PTSO can be confirmed for different agrifood applications at the conditions assayed.

A short-term high-fat diet alters rat testicular activity and blood-testis barrier integrity through the SIRT1/NRF2/MAPKs signaling pathways

Background

Overweight/obesity are metabolic disorder resulting from behavioral, environmental, and heritable causes. WHO estimates that 50% of adults and 30% of children and adolescents are overweight or obese, and, in parallel, an ongoing decline in sperm quality and male fertility has been described. Numerous studies demonstrated the intimate association between overweight/obesity and reproductive dysfunction due to a highly intricate network of causes not yet completely understood. This study expands the knowledge on the impact of a short-term high-fat diet (st-HFD) on rat testicular activity, specifically on steroidogenesis and spermatogenesis, focusing on the involved molecular mechanisms related to mitochondrial dynamics, blood-testis barrier (BTB) integrity, and SIRT1/NRF2/MAPKs pathways.

Methods

Ten adult Male Wistar rats were divided into two groups of five and treated with a standard diet or an HFD for five weeks. At the end of the treatment, rats were anesthetized and sacrificed by decapitation. Blood was collected for serum sex hormone assay; one testis was stored at -80ÅãC for western blot analysis, and the other, was fixed for histological and immunofluorescence analysis.

Results

Five weeks of HFD results in reduced steroidogenesis, increased apoptosis of spermatogenic cells, and altered spermatogenesis, as highlighted by reduced protein levels ofmeiotic and post-meiotic markers. Further, we evidenced the compromission of the BTB integrity, as revealed by the downregulation of structural proteins (N-Cadherin, ZO-1, occludin, connexin 43, and VANGL2) other than the phosphorylation of regulative kinases (Src and FAK). At the molecular level, the impairment of mitochondrial dynamics (fission, fusion, andbiogenesis), and the dysregulation of the SIRT1/NRF2/MAPKs signaling pathways, were evidenced. Interestingly, no change was observed in the levels of pro-inflammatory markers (TNFα, NF-kB, and IL-6).

Conclusions

The combined data led us to confirm that overweight is a less severe state than obesity. Furthermore, understanding the molecular mechanisms behind the association between metabolic disorders and male fertility could improve the possibility of identifying novel targets to prevent and treat fertility disorders related to overweight/obesity.

Paternal Obesity Induced by High-Fat Diet Impairs the Metabolic and Reproductive Health of Progeny in Rats

Due to the increased incidence of obesity, it is of great importance to identify all the possible consequences in those who suffer from it and their descendants. This study aimed to investigate how paternal obesity, resulting from an 18-week high-fat diet (HFD), affects the metabolic and reproductive health of offspring. In the fathers (F0 generation), the HFD led to significant weight gain, primarily due to increased visceral fat. It also resulted in impaired glucose control and reduced insulin sensitivity. Furthermore, F0 males from the HFD group had reduced sperm concentration and lower sperm viability but were still able to sire litters. F1 offspring were monitored during 18 weeks; F1 offspring from obese fathers displayed increased body weight during the experimental window, especially in males, without significant metabolic disturbances. Additionally, F1 males showed reduced sperm viability, indicating potential reproductive implications. On the other hand, F1 females showed normal estrous cycle patterns but had a reduced number of primordial follicles, suggesting a decrease in their follicular reserve and reproductive potential. This study highlights that metabolic and reproductive issues may be passed down to future generations through the paternal line.

Relationship among seminal antigenicity, antioxidant status and metabolically active sperm from Holstein-Friesian (Bos taurus) bulls

Sperm antigenicity has been implicated as a regulatory factor for acquiring fertilizing competence in the female reproductive tract. Overt immune response against the sperm proteins leads to idiopathic infertility. Hence, the aim of the study was to evaluate the influence of the auto-antigenic potential of sperm on the antioxidant status, metabolic activities and reactive oxygen species (ROS) in bovine. Semen from Holstein-Friesian bulls (n = 15) was collected and classified into higher (HA, n = 8) and lower (LA, n = 7) antigenic groups based on micro-titer agglutination assay. The neat semen was subjected to the evaluation of bacterial load, leukocyte count, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and lipid peroxidation (LPO) levels. Antioxidant activities in seminal plasma and intracellular ROS levels in the post-thawed sperm were estimated. The number of leukocytes was lower (p < .05) in the HA than the LA semen. The percentage of metabolically active sperm was higher (p < .05) in HA than the LA group. The activities of total non-enzymatic antioxidant, superoxide dismutase (SOD) and catalase (CAT) were higher (p < .05) while glutathione peroxidase activity was lower (p < .05) in the seminal plasma of LA group. The LPO levels of neat sperm and the percentage sperm positive for intracellular ROS in the cryopreserved sample were lower (p < .05) in the HA group. Auto-antigenic levels were positively correlated with the percentage of metabolically active sperm (r = 0.73, p < .01). However, the seminal auto-antigenicity was negatively (p < .05) correlated with the levels of SOD (r=-0.66), CAT (r=-0.72), LPO (r=-0.602) and intracellular ROS (r=-0.835). The findings were represented in graphical abstract. It is inferred that the higher auto-antigenic levels protect the quality of bovine semen by promoting sperm metabolism and lowering ROS and LPO levels.

Switching from high-fat diet to normal diet ameliorate BTB integrity and improve fertility potential in obese male mice

Obesity is a prominent risk factor for male infertility, and a high-fat diet is an important cause of obesity. Therefore, diet control can reduce body weight and regulate blood glucose and lipids, but it remains unclear whether it can improve male fertility and its mechanism. This study explores the effects of switching from a high-fat diet (HFD) to a normal diet (ND) on the fertility potential of obese male mice and its related mechanisms. In our study, male mice were separated into three groups: normal diet group (NN), continuous high-fat diet group (HH), and return to normal diet group (HN). The reproductive potential of mice was tested through cohabitation. Enzymatic methods and ELISA assays were used to measure metabolic indicators, follicle-stimulating hormone (FSH) levels and intratesticular testosterone levels. Transmission electron microscopy and immunofluorescence with biotin tracers assessed the integrity of the blood-testis barrier (BTB). Malondialdehyde (MDA), superoxide dismutase (SOD), and reactive oxygen species (ROS) were inspected for the assessment of oxidative stress. The expression and localization of BTB-related proteins were detected through the immunoblot and immunofluorescence. The mice in the high-fat diet group indicated increased body weight and epididymal fat weight, elevated serum TC, HDL, LDL, and glucose, decreased serum FSH, and dramatic lipid deposition in the testicular interstitium. Analysis of fertility potential revealed that the fertility rate of female mice and the number of pups per litter in the HH group were significantly reduced. After the fat intake was controlled by switching to a normal diet, body weight and epididymal fat weight were significantly reduced, serum glucose and lipid levels were lowered, serum FSH level was elevated and the deposition of interstitial lipids in the testicles was also decreased. Most significantly, the number of offspring of male mice returning to a normal diet was significantly increased. Following further mechanistic analysis, the mice in the sustained high-fat diet group had disrupted testicular BTB integrity, elevated levels of oxidative stress, and abnormal expression of BTB-related proteins, whereas the restoration of the normal diet significantly ameliorated the above indicators in the mice. Our study confirms diet control by switching from a high-fat diet to a normal diet can effectively reduce body weight, ameliorate testicular lipotoxicity and BTB integrity in male mice, and improve fertility potential, providing an effective treatment option for obese male infertility.

The impact of dietary fructose on gut permeability, microbiota, abdominal adiposity, insulin signaling and reproductive function

The excessive intake of fructose in the regular human diet could be related to global increases in metabolic disorders. Sugar-sweetened soft drinks, mostly consumed by children, adolescents, and young adults, are the main source of added fructose. Dietary high-fructose can increase intestinal permeability and circulatory endotoxin by changing the gut barrier function and microbial composition. Excess fructose transports to the liver and then triggers inflammation as well as de novo lipogenesis leading to hepatic steatosis. Fructose also induces fat deposition in adipose tissue by stimulating the expression of lipogenic genes, thus causing abdominal adiposity. Activation of the inflammatory pathway by fructose in target tissues is thought to contribute to the suppression of the insulin signaling pathway producing systemic insulin resistance. Moreover, there is some evidence that high intake of fructose negatively affects both male and female reproductive systems and may lead to infertility. This review addresses dietary high-fructose-induced deteriorations that are obvious, especially in gut permeability, microbiota, abdominal fat accumulation, insulin signaling, and reproductive function. The recognition of the detrimental effects of fructose and the development of relevant new public health policies are necessary in order to prevent diet-related metabolic disorders.

Capacitation induces changes in metabolic pathways supporting motility of epididymal and ejaculated sperm

Mammalian sperm require sufficient energy to support motility and capacitation for successful fertilization. Previous studies cataloging the changes to metabolism in sperm explored ejaculated human sperm or dormant mouse sperm surgically extracted from the cauda epididymis. Due to the differences in methods of collection, it remains unclear whether any observed differences between mouse and human sperm represent species differences or reflect the distinct maturation states of the sperm under study. Here we compare the metabolic changes during capacitation of epididymal versus ejaculated mouse sperm and relate these changes to ejaculated human sperm. Using extracellular flux analysis and targeted metabolic profiling, we show that capacitation-induced changes lead to increased flux through both glycolysis and oxidative phosphorylation in mouse and human sperm. Ejaculation leads to greater flexibility in the ability to use different carbon sources. While epididymal sperm are dependent upon glucose, ejaculated mouse and human sperm gain the ability to also leverage non-glycolytic energy sources such as pyruvate and citrate.

What do we know about blood-testis barrier? current understanding of its structure and physiology

Blood-testis barrier (BTB) creates a particular compartment in the seminiferous epithelium. Contacting Sertoli cell-Sertoli cell plasma membranes possess specialized junction proteins which present a complex dynamic of formation and dismantling. Thus, these specialized structures facilitate germ cell movement across the BTB. Junctions are constantly rearranged during spermatogenesis while the BTB preserves its barrier function. Imaging methods are essential to studying the dynamic of this sophisticated structure in order to understand its functional morphology. Isolated Sertoli cell cultures cannot represent the multiple interactions of the seminiferous epithelium and in situ studies became a fundamental approach to analyze BTB dynamics. In this review, we discuss the contributions of high-resolution microscopy studies to enlarge the body of morphofunctional data to understand the biology of the BTB as a dynamic structure. The first morphological evidence of the BTB was based on a fine structure of the junctions, which was resolved with Transmission Electron Microscopy. The use of conventional Fluorescent Light Microscopy to examine labelled molecules emerged as a fundamental technique for elucidating the precise protein localization at the BTB. Then laser-scanning confocal microscopy allowed the study of three-dimensional structures and complexes at the seminiferous epithelium. Several junction proteins, like the transmembrane, scaffold and signaling proteins, were identified in the testis using traditional animal models. BTB morphology was analyzed in different physiological conditions as the spermatocyte movement during meiosis, testis development, and seasonal spermatogenesis, but also structural elements, proteins, and BTB permeability were studied. Under pathological, pharmacological, or pollutant/toxic conditions, there are significant studies that provide high-resolution images which help to understand the dynamic of the BTB. Notwithstanding the advances, further research using new technologies is required to gain information on the BTB. Super-resolution light microscopy is needed to provide new research with high-quality images of targeted molecules at a nanometer-scale resolution. Finally, we highlight research areas that warrant future studies, pinpointing new microscopy approaches and helping to improve our ability to understand this barrier complexity.

Oral administration of Turnera diffusa willd. ex Schult. extract ameliorates steroidogenesis and spermatogenesis impairment in the testes of rats with type-2 diabetes mellitus

ETHNOPHARMACOLOGICAL RELEVANCE

Turnera diffusa Willd. ex Schult. (T. diffusa) has traditionally been used to treat male reproductive dysfunction and have aphrodisiac properties.

AIMS OF THE STUDY

This study aims to investigate the ability of T. diffusa to ameliorate the impairment in testicular steroidogenesis and spermatogenesis in DM that might help to improve testicular function, and subsequently restore male fertility.

MATERIALS AND METHODS

DM-induced adult male rats were given 100 mg/kg/day and 200 mg/kg/day T. diffusa leaf extract orally for 28 consecutive days. Rats were then sacrificed; sperm and testes were harvested and sperm parameter analysis were performed. Histo-morphological changes in the testes were observed. Biochemical assays were performed to measure testosterone and testicular oxidative stress levels. Immunohistochemistry and double immunofluorescence were used to monitor oxidative stress and inflammation levels in testes as well as Sertoli and steroidogenic marker proteins' expression.

RESULTS

Treatment with T. diffusa restores sperm count, motility, and viability near normal and reduces sperm morphological abnormalities and sperm DNA fragmentation in diabetic rats. T. diffusa treatment also reduces testicular NOX-2 and lipid peroxidation levels, increases testicular antioxidant enzymes (SOD, CAT, and GPx) activities, ameliorates testicular inflammation via downregulating NF-ΚB, p-Ikkβ and TNF-α and upregulating IκBα expression. In diabetic rats, T. diffusa treatment increases testicular steroidogenic proteins (StAR, CYP11A1, SHBG, and ARA54, 3 and 17β-HSD) and plasma testosterone levels. Furthermore, in diabetic rats treated with T. diffusa, Sertoli cell marker proteins including Connexin 43, N-cadherin, and occludin levels in the testes were elevated.

CONCLUSION

T. diffusa treatment could help to ameliorate the detrimental effects of DM on the testes, thus this plant has potential to be used to restore male fertility.

Novel Insights into circRNA Saga Coming from Spermatozoa and Epididymis of HFD Mice

Obesity is a pathophysiological disorder associated with adiposity accumulation, oxidative stress, and chronic inflammation state that is progressively increasing in younger population worldwide, negatively affecting male reproductive skills. An emerging topic in the field of male reproduction is circRNAs, covalently closed RNA molecules produced by backsplicing, actively involved in a successful spermatogenesis and in establishing high-quality sperm parameters. However, a direct correlation between obesity and impaired circRNA cargo in spermatozoa (SPZ) remains unclear. In the current work, using C57BL6/J male mice fed with a high-fat diet (HFD, 60% fat) as experimental model of oxidative stress, we investigated the impact of HFD on sperm morphology and motility as well as on spermatic circRNAs. We performed a complete dataset of spermatic circRNA content by a microarray strategy, and differentially expressed (DE)-circRNAs were identified. Using a circRNA/miRNA/target network (ceRNET) analysis, we identified circRNAs potentially involved in oxidative stress and sperm motility pathways. Interestingly, we demonstrated an enhanced skill of HFD sperm in backsplicing activity together with an inefficient epididymal circRNA biogenesis. Fused protein in sarcoma (FUS) and its ability to recruit quaking (QKI) could be involved in orchestrating such mechanism.

Obesity-induced oxidative stress and mitochondrial dysfunction negatively affect sperm quality

Obesity is a systemic metabolic disease that can induce male infertility or subfertility through oxidative stress. The aim of this study was to determine how obesity impairs sperm mitochondrial structural integrity and function, and reduces sperm quality in both overweight/obese men and mice on a high-fat diet (HFD). Mice fed the HFD demonstrated higher body weight and increased abdominal fat content than those fed the control diet. Such effects accompanied the decline in antioxidant enzymes, such as glutathione peroxidase (GPX) and catalase and superoxide dismutase (SOD) in testicular and epidydimal tissues. Moreover, malondialdehyde (MDA) content significantly increased in sera. Mature sperm in HFD mice demonstrated higher oxidative stress, including increased mitochondrial reactive oxygen species (ROS) levels and decreased protein expression of GPX1, which may impair mitochondrial structural integrity and reduce mitochondrial membrane potential (MMP) and ATP production. Moreover, cyclic AMPK phosphorylation status increased, whereas sperm motility declined in the HFD mice. Clinical studies demonstrated that being overweight/obese reduced SOD enzyme activity in the seminal plasma and increased ROS in sperm, accompanied by lower MMP and low-quality sperm. Furthermore, ATP content in the sperm was negatively correlated with increases in the BMI of all clinical subjects. In conclusion, our results suggest that excessive fat intake had similar disruptive effects on sperm mitochondrial structure and function, as well as oxidative stress levels in humans and mice, which in turn induced lower sperm motility. This agreement strengthens the notion that fat-induced increases in ROS and impaired mitochondrial function contribute to male subfertility.

Exercise improves testicular morphology and oxidative stress parameters in rats with testicular damage induced by a high-fat diet

Obesity and male infertility are problems that affect population. Exercise is a nonpharmacological way to reduce the negative health effects of obesity. The purpose of this study was to examine the effects of exercise on hormone levels, blood-testis barrier, and inflammatory and oxidative biomarkers in rats that became obese due to a high-fat diet (HFD). Male rats received a standard diet (STD group) or a HFD (HFD group) for 18 weeks. During the final 6 weeks of the experiment, swimming exercises (1 h/5 days/week) were given to half of these animals (STD + EXC and HFD + EXC groups). Finally, blood and testicular tissues were analysed by biochemical and histological methods. Body weight, leptin, malondialdehyde, interleukin-6, TNF-alpha and myeloperoxidase levels, apoptotic cells and DNA fragmentation were increased, and testis weight, insulin, FSH, LH, testosterone, glutathione and superoxide dysmutase levels, proliferative cells, ZO-1, occludin, and gap junction protein Cx43 immunoreactivity were decreased in the HFD group. All these hormonal, morphological, oxidative and inflammatory biomarkers were enhanced in the HFD + EXC group. It is thought that exercise protected testicular cytotoxicity by regulating hormonal and oxidant/antioxidant balances and testicular function, inhibiting inflammation and apoptosis, as well as preserving blood-testis barrier.

Pharmacological Inhibition of Inositol Hexakisphosphate Kinase 1 Protects Mice against Obesity-Induced Bone Loss

Obesity and type II diabetes mellitus (T2DM) are prominent risk factors for secondary osteoporosis due to the negative impacts of hyperglycemia and excessive body fat on bone metabolism. While the armamentarium of anti-diabetic drugs is expanding, their negative or unknown impacts on bone metabolism limits effectiveness. The inactivation of inositol hexakisphosphate kinase 1 (IP6K1) protects mice from high-fat-diet (HFD)-induced obesity (DIO) and insulin resistance by enhancing thermogenic energy expenditure, but the role of this kinase and the consequences of its inhibition on bone metabolism are unknown. To determine if IP6K1 inhibition in obese mice affords protection against obesity-induced metabolic derangements and bone loss, we maintained 2-month-old mice on a normal chow control diet or HFD under thermal neutral conditions for 100 d. Beginning on day 40, HFD-fed mice were divided into two groups and administered daily injections of vehicle or the pan-IP6K inhibitor TNP [N2-(m-Trifluorobenzyl), N6-(p-nitrobenzyl) purine]. HFD-fed mice developed obesity, hyperglycemia, hyperlipidemia, and secondary osteoporosis, while TNP administration protected mice against HFD-induced metabolic and lipid derangements and preserved bone mass, mineral density, and trabecular microarchitecture, which correlated with reduced serum leptin levels, reduced marrow adiposity, and preservation of marrow resident skeletal stem/progenitor cells (SSPCs). TNP also exhibited hypotensive activity, an unrealized benefit of the drug, and its prolonged administration had no adverse impacts on spermatogenesis. Together, these data indicate that the inhibition of IP6K1 using selective inhibitors, such as TNP, may provide an effective strategy to manage obesity and T2DM due to its bone sparing effects.

Bibliometric and visual analysis of blood-testis barrier research

Background: Extensive research on the blood-testis barrier has been undertaken in recent years. However, no systematic bibliometric study has been conducted on this subject. Our research aimed to identify the hotspots and frontiers of blood-testis barrier research and to serve as a guide for future scientific research and decision-making in the field.

Methods: Studies on the blood-testis barrier were found in the Web of Science Core Collection. VOSviewer, CiteSpace, and Microsoft Excel were used to conduct the bibliometric and visual analyses.

Results: We found 942 blood-testis barrier studies published in English between 1992 and 2022. The number of annual publications and citations increased significantly between 2011 and 2022, notably in the United States. China and the United States, the US Population Council, Endocrinology, and Cheng C. Yan were the most productive countries, institution, journal, and author, respectively. The study keywords indicated that blood-testis barrier research involves a variety of compositional features (tight junctions, cytoskeleton, adherens junctions), cell types (Sertoli cells, germ cells, Leydig cells, stem cells), reproductive toxicity (cadmium, nanoparticles, bisphenol-a), and relevant mechanisms (spermatogenesis, apoptosis, oxidative stress, dynamics, inflammation, immune privilege).

Conclusion: The composition and molecular processes of the blood-testis barrier as well as the blood-testis barrier in male infertility patients are the primary research hotspots in this field. In addition, future research will likely focus on treatment and the development of novel medications that target signal pathways in oxidative stress and apoptosis to preserve the blood-testis barrier. Further studies must extend to clinical diagnosis and therapy.

Melatonin supplementation preserves testicular function by attenuating lactate production and oxidative stress in high fat diet-induced obese rat model

Metabolic syndrome, including obesity has been documented as a critical factor in male reproductive dysfunction with subsequent reduction in male fertility. The therapeutic potential of melatonin has been demonstrated against oxidative stress-induced pathologies. Therefore, the present study investigated the effects of melatonin on testicular dysfunction associated with high fat diet (FD)-induced obese rat model, and the possible involvement of peroxisome proliferator-activated receptor-γ (PPAR-γ). Adult male Wistar rats (n = 6/group) were used: control group received vehicle (normal saline), obese group received 40% FD, melatonin-treated group received melatonin (4 mg/kg), and obese plus melatonin group received melatonin and 40% FD and the treatment lasted for 12 weeks. High fat diet caused increased body weight and testicular triglyceride, total cholesterol, malondialdehyde, γ-glutamyl transferase, lactate production and lactate/pyruvate ratio as well as decreased glutathione/glutathione peroxidase, nitric oxide and PPAR-γ and circulating testosterone. Nevertheless, all these alterations were attenuated when supplemented with melatonin. Taken together, these results demonstrates that FD-induced obesity causes testicular dysfunction. In addition, the results suggest that melatonin supplementation protects against obesity-associated testicular dysfunction and this effect is accompanied by upregulation of PPAR-γ.

Protein palmitoylation-mediated palmitic acid sensing causes blood-testis barrier damage via inducing ER stress

Blood-testis barrier (BTB) damage promotes spermatogenesis dysfunction, which is a critical cause of male infertility. Dyslipidemia has been correlated with male infertility, but the major hazardous lipid and the underlying mechanism remains unclear. In this study, we firstly discovered an elevation of palmitic acid (PA) and a decrease of inhibin B in patients with severe dyszoospermia, which leaded us to explore the effects of PA on Sertoli cells. We observed a damage of BTB by PA. PA penetration to endoplasmic reticulum (ER) and its damage to ER structures were exhibited by microimaging and dynamic observation, and consequent ER stress was proved to mediate PA-induced Sertoli cell barrier disruption. Remarkably, we demonstrated a critical role of aberrant protein palmitoylation in PA-induced Sertoli cell barrier dysfunction. An ER protein, Calnexin, was screened out and was demonstrated to participate in this process, and suppression of its palmitoylation showed an ameliorating effect. We also found that ω-3 poly-unsaturated fatty acids down-regulated Calnexin palmitoylation, and alleviated BTB dysfunction. Our results indicate that dysregulated palmitoylation induced by PA plays a pivotal role in BTB disruption and subsequent spermatogenesis dysfunction, suggesting that protein palmitoylation might be therapeutically targetable in male infertility.

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An elevation of circulating PA was identified in patients with severe dyszoospermia.

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PA-induced over-palmitoylation in Sertoli cells leads to ER stress and BTB damage.

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The palmitoylation of the ER protein Calnexin regulates Sertoli cell barrier function.

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ω-3 PUFAs ameliorate PA-induced damage and over-palmitoylation in Sertoli cells.

Expression pattern and the roles of phosphatidylinositol phosphatases in testis

Phosphoinositides (PIs) are relatively rare lipid components of the cellular membranes. Their homeostasis is tightly controlled by specific PI kinases and phosphatases. PIs play essential roles in cellular signaling, cytoskeletal organization, and secretory processes in various diseases and normal physiology. Gene targeting experiments strongly suggest that in mice with deficiency of several PI phosphatases such as Pten, Mtmrs, Inpp4b, and Inpp5b, spermatogenesis is affected, resulting in partial or complete infertility. Similarly, in men, loss of several of the PIP phosphatases is observed in infertility characterized by the lack of mature sperm. Using available gene expression databases, we compare expression of known PI phosphatases in various testicular cell types, infertility patients, and mouse age-dependent testicular gene expression, and discuss their potential roles in testis physiology and spermatogenesis.

Diet and Male Fertility: The Impact of Nutrients and Antioxidants on Sperm Energetic Metabolism

Diet might affect male reproductive potential, but the biochemical mechanisms involved in the modulation of sperm quality remain poorly understood. While a Western diet is considered a risk factor for male infertility, the Mediterranean diet seems to protect against male infertility; moreover, the role of a vegetarian habitus in the preservation of sperm quality is controversial. The aim of this review is to analyze the molecular effects of single nutrients on sperm quality, focusing on their involvement in biochemical mechanisms related to sperm bioenergetics. It appears that diets rich in saturated fatty acids (SFA) and low in polyunsaturated fatty acids (PUFA) negatively affect sperm quality, whereas unsaturated fatty acids supplementation ameliorates sperm quality. In fact, the administration of PUFA, especially omega-3 PUFA, determined an increase in mitochondrial energetic metabolism and a reduction in oxidative damage. Carbohydrates and proteins are also nutritional modulators of oxidative stress and testosterone levels, which are strictly linked to sperm mitochondrial function, a key element for sperm quality. Moreover, many dietary natural polyphenols differentially affect (positively or negatively) the mitochondrial function, depending on their concentration. We believe that an understanding of the biochemical mechanisms responsible for sperm quality will lead to more targeted and effective therapeutics for male infertility.

LncRNA Tug1 maintains blood-testis barrier integrity by modulating Ccl2 expression in high-fat diet mice

Sertoli cells are essential for spermatogenesis in the testicular seminiferous tubules by forming blood-testis barrier (BTB) and creating a unique microenvironment for spermatogenesis. Many lncRNAs have been reported to participate in spermatogenesis. However, the role of long noncoding RNAs (lncRNAs) in Sertoli cells has rarely been examined. Herein, we found that a high-fat diet (HFD) decreased sperm quality, impaired BTB integrity and resulted in accumulation of saturated fatty acids (SFAs), especially palmitic acid (PA), in mouse testes. PA decreased the expression of tight junction (TJ)-related proteins, increased permeability and decreased transepithelial electrical resistance (TER) in primary Sertoli cells and TM4 cells. Moreover, lncRNA Tug1 was found to be involved in PA-induced BTB disruption by RNA-seq. Tug1 depletion distinctly impaired the TJs of Sertoli cells and overexpression of Tug1 alleviated the disruption of BTB integrity induced by PA. Moreover, Ccl2 was found to be a downstream target of Tug1, and decreased TJ-related protein levels and TER and increased FITC-dextran permeability in vitro. Furthermore, the addition of Ccl2 damaged BTB integrity after overexpression of Tug1 in the presence of PA. Mechanistically, we found that Tug1 could directly bind to EZH2 and regulate H3K27me3 occupancy in the Ccl2 promoter region by RNA immunoprecipitation and chromatin immunoprecipitation assays. Our study revealed an important role of Tug1 in the BTB integrity of Sertoli cells and provided a new view of the role of lncRNAs in male infertility.

Epimedium protects against dyszoospermia in mice with Pex3 knockout by exerting antioxidant effects and regulating the expression level of P16

Oxidative stress (OS) is one of the primary factors leading to male infertility. Oral administration of antioxidants has thus far been found to significantly improve the quality of human sperm. Therefore, antioxidant treatment has become the consensus among international experts on male infertility. In this study, peroxisomal biogenesis factor 3 (Pex3)-knockout (KO, -/-) mice were used as a model to compare the efficacy of three types of traditional Chinese medicine (TCM) granules (Epimedium [YYH], Cuscuta [TSZ], and Rhodiola [HJT]) for male reproductive function rescue. YYH was revealed to be the best and exerted a rescue effect on Pex3-/- mice with spermatogenesis defects. In addition, YYH prominently reduced ROS levels in the testes, inhibited DNA oxidative damage in spermatogenic cells, promoted the proliferation of spermatogenic cells, and inhibited apoptosis in Pex3-/- male mice. Furthermore, the mechanism by which YYH ameliorated dyszoospermia was confirmed via the establishment of cyclin-dependent kinase inhibitor 2 A (P16Ink4a)-KO mice. Specifically, Pex3-/- mice produced elevated amounts of ROS, which damaged germ cell DNA and further activated the signaling pathway of the cell senescence regulatory protein P16-CDK6, resulting in cell cycle arrest and eventually contributing to spermatogenesis dysfunction. YYH supplementation partially corrected the associated phenotype in gene KO mice by affecting P16 expression levels, thus improving the reproductive outcome to a certain extent.

High fat diet-induced obesity prolongs critical stages of the spermatogenic cycle in a Ldlr-/-.Leiden mouse model

Obesity can disturb spermatogenesis and subsequently affect male fertility and reproduction. In our study, we aim to elucidate at which cellular level of adult spermatogenesis the detrimental effects of obesity manifest. We induced high fat diet (HFD) obesity in low-density lipoprotein receptor knock-out Leiden (Ldlr^−/−.Leiden) mice, and studied the morphological structure of the testes and histologically examined the proportion of Sertoli cells, spermatocytes and spermatids in the seminiferous tubules. We examined sperm DNA damage and chromatin condensation and measured plasma levels of leptin, testosterone, cholesterol and triglycerides. HFD-induced obesity caused high plasma leptin and abnormal testosterone levels and induced an aberrant intra-tubular organisation (ITO) which is associated with an altered spermatids/spermatocytes ratio (2:1 instead of 3:1). Mice fed a HFD had a higher level of tubules in stages VII + VIII in the spermatogenic cycle. The stages VII + VII indicate crucial processes in spermatogenic development like initiation of meiosis, initiation of spermatid elongation, and release of fully matured spermatids. In conclusion, HFD-induced obese Ldlr^−/−.Leiden mice develop an aberrant ITO and alterations in the spermatogenic cycle in crucial stages (stages VII and VII). Thereby, our findings stress the importance of lifestyle guidelines in infertility treatments.

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.

Dietary intake of probiotic fermented milk benefits the gut and reproductive health in mice fed with an obesogenic diet

Probiotics have been suggested as alternatives to pharmacological drugs in the treatment of a variety of medical problems, including obesity management, which is often linked to low sperm production. Also, probiotic fermented products are known to boost host immune response, immunosenescence, infection tolerance, and redox homeostasis, but their direct role in male fertility has been less investigated. This study assessed the effect of two probiotic strains, L. fermentum NCDC 400 and L. rhamnosus NCDC 610, and fructooligosaccharide (FOS) fermented milk supplementation. We identified the significantly reduced oxidative stress markers in the plasma and liver of HF diet-fed animals. We determined the role of key testicular enzymes of steroidogenic pathway genes StAR, P450scc, and 17βHSD in maintaining the testosterone concentration and restoring testicular structures. In conclusion, the present work illustrated the ability of both probiotics L. fermentum NCDC 400 and L. rhamnosus NCDC 610 as regulatory agents with beneficial effects on weight loss and endogenous testosterone with substantially improved sperm motility in male diet-induced obesity (DIO) models. Our findings indicate that fermented milk supplementation may be an alternative treatment for preventing obesity and other related metabolic syndromes.

Intergenerational effects of a paternal Western diet during adolescence on offspring gut microbiota, stress reactivity, and social behavior

The global consumption of highly processed, calorie-dense foods has contributed to an epidemic of overweight and obesity, along with negative consequences for metabolic dysfunction and disease susceptibility. As it becomes apparent that overweight and obesity have ripple effects through generations, understanding of the processes involved is required, in both maternal and paternal epigenetic inheritance. We focused on the patrilineal effects of a Western-style high-fat (21%) and high-sugar (34%) diet (WD) compared to control diet (CD) during adolescence and investigated F0 and F1 mice for physiological and behavioral changes. F0 males (fathers) showed increased body weight, impaired glycemic control, and decreased attractiveness to females. Paternal WD caused significant phenotypic changes in F1 offspring, including higher body weights of pups, increased Actinobacteria abundance in the gut microbiota (ascertained using 16S microbiome profiling), a food preference for WD pellets, increased male dominance and attractiveness to females, as well as decreased behavioral despair. These results collectively demonstrate the long-term intergenerational effects of a Western-style diet during paternal adolescence. The behavioral and physiological alterations in F1 offspring provide evidence of adaptive paternal programming via epigenetic inheritance. These findings have important implications for understanding paternally mediated intergenerational inheritance, and its relevance to offspring health and disease susceptibility.

Dietary high-fructose reduces barrier proteins and activates mitogenic signalling in the testis of a rat model: Regulatory effects of kefir supplementation

There are limited data on the influence of fructose rich diet on the male reproductive system. Kefir may have health beneficial effects, but its mechanism of action remains mostly unclear. Herein, we investigated the impact of dietary high fructose on tight junction proteins and mitogenic pathways in rat testis as well as their modulation by kefir supplementation. Twenty-two male Wistar rats (4 weeks old) were divided into the following three groups: Control; Fructose; Fructose + Kefir. Fructose was added to drinking water at concentration of 20% and administered to the rats for 15 weeks and kefir was supplemented by gavage once a day during final 6 weeks. Dietary fructose-induced testicular degeneration was associated with the downregulation of the blood-testis barrier proteins, claudin-11 and N-cadherin as well as SIRT1 expression in testicular tissue of rats. However, p38MAPK, p-p38MAPK and p-ERK1/2 levels were increased in testis of fructose-fed rats. Interestingly, JNK1 and p-JNK1 protein levels were decreased following this dietary intervention. Raf1, ERK1/2, and caspase 3 and TUNEL staining of the testis reveal the activation of apoptosis due to fructose intake. Kefir supplementation markedly promoted the expression of claudin-11, SIRT1, JNK1 and p-JNK1 but suppressed testicular mitogenic and apoptotic factors in fructose-fed rats.

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.

Assessing puberty in female cheetahs (Acinonyx jubatus) via faecal hormone metabolites and body weight

With fewer than 7500 cheetahs remaining in the wild, ex situ cheetah populations serve as an insurance policy against extinction and a resource to study species' biology. This study aimed to identify the age of pubertal onset in ex situ female cheetahs using non-invasive faecal steroid hormone monitoring and body weights. Faecal samples from nine female cheetahs were collected two to three times weekly from 2 to 36months of age and body weights were recorded every 3months. Faecal oestrogen metabolites (FOM) and faecal glucocorticoid metabolites (FGM) were analysed using enzyme immunoassays and samples were categorised into 6-month intervals to compare endocrine characteristics. Faecal hormone and body weight data were analysed using generalised linear mixed models. Age was a significant predictor of mean and baseline FOM concentrations, number of FOM peaks, mean and maximum FOM peak concentrations and the number of cycles. Female cheetahs aged 24-30months exhibited a marked rise in mean FOM concentration and the number of FOM peaks and cycles increased with age until 24-30months. Females attained adult body weight by 21months of age. Mean and baseline FGM concentrations were highest at the 0-6 and 12-18months of age groups and did not follow the same FOM patterns. Based on body weight data, the FOM concentrations and peak patterning, females were considered pubertal from 24 to 30months of age. Characterisation of cheetah puberty has direct and significant implications for the improvement of management and reproductive success of cheetahs under human care. This information is particularly informative for identifying important windows of development, littermate dispersal and breeding introductions.

Muscle-generated BDNF (brain derived neurotrophic factor) maintains mitochondrial quality control in female mice

Mitochondrial remodeling is dysregulated in metabolic diseases but the underlying mechanism is not fully understood. We report here that BDNF (brain derived neurotrophic factor) provokes mitochondrial fission and clearance in skeletal muscle via the PRKAA/AMPK-PINK1-PRKN/Parkin and PRKAA-DNM1L/DRP1-MFF pathways. Depleting Bdnf expression in myotubes reduced fatty acid-induced mitofission and mitophagy, which was associated with mitochondrial elongation and impaired lipid handling. Muscle-specific bdnf knockout (MBKO) mice displayed defective mitofission and mitophagy, and accumulation of dysfunctional mitochondria in the muscle when they were fed with a high-fat diet (HFD). These animals also have exacerbated body weight gain, increased intramyocellular lipid deposition, reduced energy expenditure, poor metabolic flexibility, and more insulin resistance. In contrast, consuming a BDNF mimetic (7,8-dihydroxyflavone) increased mitochondrial content, and enhanced mitofission and mitophagy in the skeletal muscles. Hence, BDNF is an essential myokine to maintain mitochondrial quality and function, and its repression in obesity might contribute to impaired metabolism.Abbreviation: 7,8-DHF: 7,8-dihydroxyflavone; ACACA/ACC: acetyl Coenzyme A carboxylase alpha; ACAD: acyl-Coenzyme A dehydrogenase family; ACADVL: acyl-Coenzyme A dehydrogenase, very long chain; ACOT: acyl-CoA thioesterase; CAMKK2: calcium/calmodulin-dependent protein kinase kinase 2, beta; BDNF: brain derived neurotrophic factor; BNIP3: BCL2/adenovirus E1B interacting protein 3; BNIP3L/NIX: BCL2/adenovirus E1B interacting protein 3-like; CCL2/MCP-1: chemokine (C-C motif) ligand 2; CCL5: chemokine (C-C motif) ligand 5; CNS: central nervous system; CPT1B: carnitine palmitoyltransferase 1b, muscle; Cpt2: carnitine palmitoyltransferase 2; CREB: cAMP responsive element binding protein; DNM1L/DRP1: dynamin 1-like; E2: estrogen; EHHADH: enoyl-CoenzymeA hydratase/3-hydroxyacyl CoenzymeA dehydrogenase; ESR1/ER-alpha: estrogen receptor 1 (alpha); FA: fatty acid; FAO: fatty acid oxidation; FCCP: carbonyl cyanide-4-(trifluoromethoxy)phenylhydrazone; FFA: free fatty acids; FGF21: fibroblast growth factor 21; FUNDC1: FUN14 domain containing 1; HADHA: hydroxyacyl-CoA dehydrogenase trifunctional multienzyme complex subunit alpha; HFD: high-fat diet; iWAT: inguinal white adipose tissues; MAP1LC3A/LC3A: microtubule-associated protein 1 light chain 3 alpha; MBKO; muscle-specific bdnf knockout; IL6/IL-6: interleukin 6; MCEE: methylmalonyl CoA epimerase; MFF: mitochondrial fission factor; NTRK2/TRKB: neurotrophic tyrosine kinase, receptor, type 2; OPTN: optineurin; PA: palmitic acid; PARL: presenilin associated, rhomboid-like; PDH: pyruvate dehydrogenase; PINK1: PTEN induced putative kinase 1; PPARGC1A/PGC-1α: peroxisome proliferative activated receptor, gamma, coactivator 1 alpha; PRKAA/AMPK: protein kinase, AMP-activated, alpha 2 catalytic subunit; ROS: reactive oxygen species; TBK1: TANK-binding kinase 1; TG: triacylglycerides; TNF/TNFα: tumor necrosis factor; TOMM20: translocase of outer mitochondrial membrane 20; ULK1: unc-51 like kinase 1.

Pubertal down-regulation of Tetraspanin 8 in testicular Sertoli cells is crucial for male fertility

The alarming decline in sperm count has become a global concern in the recent decades. The division and differentiation of male germ cells (Gc) into sperm are governed by Sertoli cells (Sc) upon their functional maturation during puberty. However, the roles of genes regulating pubertal maturation of Sc have not been fully determined. We have observed that Tetraspanin 8 (Tspan8) is down-regulated in Sc during puberty in rats. However, there has been no in vivo evidence for a causal link between the down-regulation of Tspan8 expression and the onset of spermatogenesis as yet. To investigate this, we generated a novel transgenic (Tg) rat, in which the natural down-regulation of Tspan8 was prevented specifically in Sc from puberty up to adulthood. Adult Tg male rats showed around 98% reduction in sperm count despite having a similar level of serum testosterone (T) as the controls. Functional maturation of Sc was impaired as indicated by elevated levels of Amh and low levels of Kitlg and Claudin11 transcripts. The integrity of the blood testis barrier was compromised due to poor expression of Gja1 and Gc apoptosis was discernible. This effect was due to a significant rise in both Mmp7 and phospho P38 MAPK in Tg rat testis. Taken together, we demonstrated that the natural down-regulation of Tspan8 in Sc during puberty is a prerequisite for establishing male fertility. This study divulges one of the aetiologies of certain forms of idiopathic male infertility where somatic cell defect, but not hormonal deficiency, is responsible for impaired spermatogenesis.

Chlorella vulgaris or Spirulina platensis mitigate lead acetate-induced testicular oxidative stress and apoptosis with regard to androgen receptor expression in rats

The current research was constructed to throw the light on the protective possibility of Chlorella vulgaris (C. vulgaris) and Spirulina platensis (S. platensis) against lead acetate-promoted testicular dysfunction in male rats. Forty rats were classified into four groups: (i) control, (ii) rats received lead acetate (30 mg/kg bw), (iii) rats concomitantly received lead acetate and C. vulgaris (300 mg/kg bw), (vi) rats were simultaneously treated with lead acetate and S. platensis (300 mg/kg bw) via oral gavage for 8 weeks. Lead acetate promoted testicular injury as expressed with fall in reproductive organ weights and gonadosomatic index (GSI). Lead acetate disrupted spermatogenesis as indicated by sperm cell count reduction and increased sperm malformation percentage. Lead acetate-deteriorated steroidogenesis is evoked by minimized serum testosterone along with maximized follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels. Testicular oxidative, inflammatory, and apoptotic cascades are revealed by elevated acid phosphatase (ACP) and sorbitol dehydrogenase (SDH) serum leakage, declined testicular total antioxidative capacity (TAC) with elevated total oxidative capacity (TOC), tumor necrosis factor alpha (TNF-α), caspase-3 levels, lessened androgen receptor (AR) expression, and histopathological lesions against control. Our research highlights that C. vulgaris or S. platensis therapy can modulate lead acetate-promoted testicular dysfunction via their antioxidant activity as expressed by elevated TAC and reduced TOC, immunomodulatory effect as indicated by lessened TNF-α level, and anti-apoptotic potential that was revealed by minimized caspase-3 levels. As well as restoration of testicular histoarchitecture, androgen receptor, steroidogenesis, and spermatogenesis were detected with better impacts to S. platensis comparing with C. vulgaris. Therefore, further clinical trials are needed to test S. platensis and C. vulgaris as a promising candidate in treating male infertility.

Effect of Wuzi Yanzong Pills on Sertoli cells and blood-testis barrier in heat-stressed rats based on Akt signalling pathway

The blood-testis barrier (BTB) of Sertoli cells (SCs) is an important biological barrier that maintains spermatogenesis and provides a favourable microenvironment for spermatogenesis. However, heat stress can directly damage the BTB structural proteins of testicular SCs, leading to dyszoospermia. Wuzi Yanzong Pills (WYP) is a traditional Chinese medicine formula used to treat male reproductive diseases. However, whether WYP could ameliorate heat stress injury in primary SCs extracted from rat testes and BTB proteins remains unknown. Here, treatment with WYP (low, medium and high dose) increased the SC viability and the proliferation of cell antigen Ki67 significantly. Additionally, it promoted SC maturation, which presented in the form of increased androgen receptors (ARs) and decreased cytokeratin 18 (CK-18) in three WYP dose groups. WYP upregulated BTB proteins such as zonula occludens 1 (ZO-1) and occludin across all WYP groups and decreased phosphorylated Akt (p-Akt) in the middle and high-dose groups; however, ZO-1 and occludin recovery were reduced with the presence of Akt inhibitor in WYP groups. WYP improved SC viability and proliferation, and ameliorated dedifferentiation and BTB-proteins damaged by heat stress via Akt signalling. The findings present theoretical support for the effects of WYP in the management of dyszoospermia and male infertility.

Comparative protective effects of N-acetylcysteine and melatonin against obesity-induced testicular dysfunction in rats

N-acetylcysteine (NAC) and melatonin were reported to exert protective effects on testicular tissues. Thus, this study aimed to determine which of these is more efficient against obesity-induced testicular dysfunction in albino rats. A total of 32 adult male rats (195 ± 10 g) were divided into four groups: control, obese rats fed a high-fat diet (HFD), HFD+NAC (150 mg/kg per day, i.p.) and HFD+melatonin (10 mg/kg per day, i.p.), for 5 weeks. Testes and epididymis were weighed. Lipid profile, pituitary-testicular hormones, tumor necrosis factor α (TNFα), epididymal sperm parameters, testicular oxidant-antioxidant system, testicular and the epididymal histopathology and immunohistochemical localization for androgen receptors (AR) and Bax reaction were analyzed. Administration of NAC or melatonin significantly improved the lipid parameters, gonadal hormones, TNFα level, sperm count and abnormal morphology, oxidant-antioxidant system and the absolute testicular and epididymal mass with an enhancement of testicular architecture, AR expression and apoptosis as compared with that in the obese group. Additionally, as compared with the NAC group, the melatonin group had significantly reduced body mass index, total cholesterol, triglyceride, and TNFα and increased testosterone, sperm count, motility, superoxide dismutase activity, mitigated histomorphometrical changes, Bax expression, and increased testicular AR expression. Therefore, melatonin was more efficient than NAC in affording fortification against HFD-induced testicular dysfunction.

Obesity Causes Abrupt Changes in the Testicular Microbiota and Sperm Motility of Zebrafish

Background

Obesity is a recognized risk factor for low fertility and is becoming increasingly prevalent in many countries around the world. Obesity changes intestinal microbiota composition, causes inflammation of various organs, and also reduces sperm quality. Several microorganisms are present in the testis. However, whether obesity affects the changes of testicular microbiota and whether these changes are related to reduced fertility in obese men remain to be elucidated.

Methods

In the present study, a zebrafish obesity model was established by feeding with egg yolk powder. Sperm motility was measured by the Computer Assisted Sperm Analysis system, testicular microbial communities was assessed via 16s RNA sequencing, the immune response in zebrafish testis was quantified by quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay, and the testicular tissue structure was detected by electron microscopy and hematoxylin–eosin staining.

Results

Compared with the control group, zebrafish sperm motility was dramatically reduced, the expression of testicular proinflammatory cytokines in the testes was upregulated, and the blood–testis barrier structure was disrupted in the obese group. In addition, testicular microbiome composition was clearly altered in the obese group.

Conclusion

Obesity alters testicular microbiota composition, and the reason behind the decreased sperm motility in obese zebrafish may be related to changes in the testicular microbial communities.

Low protein diet and methyl-donor supplements modify testicular physiology in mice

The link between male diet and sperm quality has received significant investigation. However, the impact diet and dietary supplements have on the testicular environment has been examined to a lesser extent. Here, we establish the impact of a sub-optimal low protein diet (LPD) on testicular morphology, apoptosis and serum fatty acid profiles. Furthermore, we define whether supplementing a LPD with specific methyl donors abrogates any detrimental effects of the LPD. Male C57BL6 mice were fed either a control normal protein diet (NPD; 18% protein; n = 8), an isocaloric LPD (LPD; 9% protein; n = 8) or an LPD supplemented with methyl donors (MD-LPD; choline chloride, betaine, methionine, folic acid, vitamin B12; n = 8) for a minimum of 7 weeks. Analysis of male serum fatty acid profiles by gas chromatography revealed elevated levels of saturated fatty acids and lower levels of mono- and polyunsaturated fatty acids in MD-LPD males when compared to NPD and/or LPD males. Testes of LPD males displayed larger seminiferous tubule cross section area when compared to NPD and MD-LPD males, while MD-LPD tubules displayed a larger luminal area. Furthermore, TUNNEL staining revealed LPD males possessed a reduced number of tubules positive for apoptosis, while gene expression analysis showed MD-LPD testes displayed decreased expression of the pro-apoptotic genes Bax, Csap1 and Fas when compared to NPD males. Finally, testes from MD-LPD males displayed a reduced telomere length but increased telomerase activity. These data reveal the significance of sub-optimal nutrition for paternal metabolic and reproductive physiology.

Lycium barbarum Polysaccharide Ameliorates Heat-Stress-Induced Impairment of Primary Sertoli Cells and the Blood-Testis Barrier in Rat via Androgen Receptor and Akt Phosphorylation

Male infertility induced by heat stress has been attracting more and more attention. Heat stress not only causes apoptosis of spermatocytes but also has adverse effects on Sertoli cells, further damaging spermatogenesis. Lycium barbarum polysaccharide (LBP) is the main bioactive component of Lycium barbarum, which has a protective effect on male reproduction, but its mechanism is still unclear. In this study, our results proved that LBP blocked the inhibitory effect on the proliferation activity of Sertoli cells after heat stress, reversed the dedifferentiation of Sertoli cells induced by heat stress, and ameliorated the structural integrity of the blood-testis barrier. In addition, it increased the expression of the androgen receptor and activated Akt signaling pathway to resist heat-stress-induced injury of Sertoli cells.

Advancing Semen Evaluation Using Lipidomics

Developing a deeper understanding of biological components of sperm is essential to improving cryopreservation techniques and reproductive technologies. To fully ascertain the functional determinants of fertility, lipidomic methods have come to the forefront. Lipidomics is the study of the lipid profile (lipidome) within a cell, tissue, or organism and provides a quantitative analysis of the lipid content in that sample. Sperm cells are composed of various lipids, each with their unique contribution to the overall function of the cell. Lipidomics has already been used to find new and exciting information regarding the fatty acid content of sperm cells from different species. While the applications of lipidomics are rapidly evolving, gaps in the knowledge base remain unresolved. Current limitations of lipidomics studies include the number of available samples to analyze and the total amount of cells within those samples needed to detect changes in the lipid profiles across different subjects. The information obtained through lipidomics research is essential to systems and cellular biology. This review provides a concise analysis of the most recent developments in lipidomic research. This scientific resource is important because these developments can be used to not only combat the reproductive challenges faced when using cryopreserved semen and artificial reproductive technologies in livestock such as cattle, but also other mammals, such as humans or endangered species.

Transfer- or 'transmission'-RNA fragments? The roles of tsRNAs in the reproductive system

Transfer-RNAs (tRNAs) help ribosomes decode mRNAs and synthesize proteins; however, tRNA fragments produced under certain conditions, known as tRNA-derived small RNAs (tsRNAs), have been found to play important roles in pathophysiological processes. In the reproductive system, tsRNAs are abundant in gametes and embryos and at the maternal-fetal interface, as well as in microvesicles like epididymosomes, seminal plasma exosomes, and syncytiotrophoblast-derived extracellular vesicles. tsRNAs can affect gamete cell maturation, zygote activation, and early embryonic development. tsRNAs can transmit epigenetic information to later generations. In particular, exposure to environmental factors such as nutrition, isoproterenol, and poly(I:C) may allow tsRNAs to transfer information to the gametes or placenta to alter offspring phenotype. The underlying mechanisms of tsRNAs action include transposon silencing, translation regulation, and target mRNA degradation. Herein, we review the currently reported tsRNAs in the reproductive system, their validated functions, and potential roles. A better understanding of this field may help to provide useful recommendations or develop strategies to increase fertility and conception of healthy babies.

Obesity and Male Reproduction; Placing the Western Diet in Context

There is mounting evidence that obesity has negative repercussions for reproductive physiology in males. Much of this evidence has accumulated from rodent studies employing diets high in fat and sugar ("high fat" or "western" diets). While excessive fats and carbohydrates have long been considered major determinants of diet induced obesity, a growing body of research suggests that the relationships between diet composition and obesity are more complex than originally thought, involving interactions between dietary macronutrients. However, rodent dietary models have yet to evolve to capture this, instead relying heavily on elevated levels of a single macronutrient. While this approach has highlighted important effects of obesity on male reproduction, it does not allow for interpretation of the complex, interacting effects of dietary protein, carbohydrate and fat. Further, the single nutrient approach limits the ability to draw conclusions about which diets best support reproductive function. Nutritional Geometry offers an alternative approach, assessing outcomes of interest over an extended range of dietary macronutrient compositions. This review explores the practical application of Nutritional Geometry to study the effects of dietary macronutrient balance on male reproduction, including experimental considerations specific to studies of diet and reproductive physiology. Finally, this review discusses the promising use of Nutritional Geometry in the development of evidence-based pre-conception nutritional guidance for men.

Rescue effect of sodium acetate in diabetes mellitus-associated testicular dysfunction is accompanied by PCSK9 modulation

Diabetes mellitus (DM) is a global health burden, affecting about 463 million of the adult population worldwide. Approximately 94% of diabetic male individuals develop varying degrees of testicular disorders (TDs), which usually result in hypogonadism, hypotestosteronemia and defective spermatogenesis and steroidogenesis. Short chain fatty acids (SCFAs) have shown potential benefits in metabolic health. However, its effect on TD associated with DM is not clear. Howbeit, the present study investigated the hypothesis that SCFAs, acetate would ameliorate TD accompanying DM, possibly by suppressing proprotein convertase subtilisin/kexin type 9 (PCSK9). Male Wistar rats (210-240 g) were allotted into groups (n = 6/group): control (vehicle; po), DM with/without 200 mg/kg (po) of sodium acetate (SAc). Diabetes was induced by streptozotocin 65 mg/kg (iv) after a dose of nicotinamide (110 mg/kg). Semen/biochemical and histological analyses were performed with appropriate methods. In addition to hyperglycemia, hyperinsulinemia and reduced insulin sensitivity, DM led to increased serum and testicular triglyceride or total cholesterol/high-density lipoprotein cholesterol ratio, low-density lipoprotein cholesterol, malondialdehyde, TNF-α, IL-6 and PCSK9 as well as reduced high-density lipoprotein cholesterol and glutathione. Moreover, DM caused TD which is characterized by altered sperm parameters, disrupted tissue architecture, atrophied seminiferous tubules, deleterious spermatogonia, disappearance of lumen and cellular degeneration as well as decreased luteinizing hormone and testosterone. However, the administration of SAc attenuated these alterations. The study demonstrates that DM-induced TD is accompanied by elevated PCSK9. The results however suggest that SAc rescues testicular disorder/dysfunction associated with DM by suppression of PCSK9 and improvement of insulin sensitivity.

Role of insulin in the neuroendocrine control of reproduction

Infertility associated with insulin resistance is characterised by abnormal hormone secretion by the hypothalamus, pituitary gland and gonads. These endocrine tissues can maintain insulin sensitivity even when tissues such as the muscle and liver become insulin-resistant, resulting in excessive insulin stimulation as hyperinsulinaemia develops. Experiments conducted to determine the role of neuronal insulin signalling in fertility were unable to recapitulate early findings of hypogonadotrophic hypogonadism in mice lacking insulin receptors throughout the brain. Rather, it was eventually shown that astrocytes critically mediate the effects of insulin on puberty timing and adult reproductive function. However, specific roles for neurones and gonadotrophs have been revealed under conditions of hyperinsulinaemia and by ablation of insulin and leptin receptors. The collective picture is one of multiple insulin-responsive inputs to gonadotrophin releasing hormone neurones, with astrocytes being the most important player.

Paternal Methyl Donor Supplementation in Rats Improves Fertility, Physiological Outcomes, Gut Microbial Signatures and Epigenetic Markers Altered by High Fat/High Sucrose Diet

Increased consumption of high fat/sucrose (HF/S) diets has contributed to rising rates of obesity and its co-morbidities globally, while also negatively impacting male reproductive health. Our objective was to examine whether adding a methyl donor cocktail to paternal HF/S diet (HF/S+M) improves health status in fathers and offspring. From 3–12 weeks of age, male Sprague Dawley rats consumed a HF/S or HF/S+M diet. Offspring were followed until 16 weeks of age. Body composition, metabolic markers, gut microbiota, DNA methyltransferase (DNMT) and microRNA expression were measured in fathers and offspring. Compared to HF/S, paternal HF/S+M diet reduced fat mass in offspring (p < 0.005). HF/S+M fathers consumed 16% fewer kcal/day, which persisted in HF/S+M female offspring and was explained in part by changes in serum glucagon-like peptide-1 (GLP-1) and peptide tyrosine tyrosine (PYY) levels. Compared to HF/S, HF/S+M fathers had a 33% improvement in days until conception and 300% fewer stillbirths. In fathers, adipose tissue DNMT3a and hepatic miR-34a expression were reduced with HF/S+M. Adult male offspring showed upregulated miR-24, -33, -122a and -143 expression while females exhibited downregulated miR-33 expression. Fathers and offspring presented differences in gut microbial signatures. Supplementing a paternal HF/S diet with methyl-donors improved fertility, physiological outcomes, epigenetic and gut microbial signatures intergenerationally.