Effects of Calorie Restriction on Preserving Male Fertility Particularly in a State of Obesity

PURPOSE OF REVIEW

Highlight the importance of exploring nutritional interventions that could be applied as alternative or supplementary therapeutic strategies to enhance men's fertility.

RECENT FINDINGS

Lifestyle choices have prompted extensive discussions regarding its implications and applications as a complementary therapy. The growing concern over the decline in sperm quality underscores the urgency of investigating these alternative interventions. Calorie restriction (CR) has emerged as a promising strategy to improve male fertility. The efficacy of CR depends on factors like age, ethnicity and genetics. Clinical studies, such as CALERIE, have shown an improvement in serum testosterone level and sexual drive in men with or without obesity. Additionally, CR has been shown to positively impact sperm count and motility; however, its effects on sperm morphology and DNA fragmentation remain less clear, and the literature has shown discrepancies, mainly due to the nature of technically dependent assessment tools. The review advocates a personalized approach to CR, considering individual health profiles to maximize its benefits. It underscores the need for routine, accessible diagnostic techniques in male reproductive health. It suggests that future research should focus on personalized dietary interventions to improve male fertility and overall well-being in individuals with or without obesity and unravel CR's immediate and lasting effects on semen parameters in men without obesity.

Effect of Metformin on Sertoli Cell Fatty Acid Metabolism and Blood-Testis Barrier Formation

Sertoli cells (SCs) are essential to maintaining germ cell development. Metformin, the main pharmacologic treatment for pediatric type 2 diabetes, is administered to children during SC maturation. The present study aimed to analyze whether metformin affects SC energy metabolism and blood-testis barrier (BTB) integrity. Primary SC cultures were used for the in vitro studies. In vivo effects were studied in Sprague-Dawley rats treated with 200 mg/kg metformin from Pnd14 to Pnd30. Metformin decreased fatty acid oxidation and increased 3-hydroxybutyrate production in vitro. Moreover, it decreased the transepithelial electrical resistance across the monolayer and induced ZO-1 redistribution, suggesting an alteration of cell junctions. In vivo, a mild but significant increase in BTB permeability and ZO-1 expression was observed in the metformin group, without changes in testicular histology and meiosis progression. Additionally, adult rats that received metformin treatment during the juvenile period showed no alteration in BTB permeability or daily sperm production. In conclusion, metformin exposure may affect BTB permeability in juvenile rats, but this seems not to influence spermatogenesis progression. Considering the results obtained in adult animals, it is possible to speculate that metformin treatment during the juvenile period does not affect testicular function in adulthood.

Thyme extract could overcome diabetes-induced reproductive dysfunction by inhibiting oxidative damage and increasing the expression of insulin receptor substrate and pyruvate kinase in the rat sperm

OBJECTIVES

Oxidative stress and disruption of energy metabolism in the reproductive system, especially sperm, play a significant role in diabetes-related infertility. Zataria multiflora Boissis (ZMB), a medicinal plant containing various bioactive compounds, may have efficacy in treating metabolic diseases and reproductive disorders. Therefore, the aim of this study was to investigate the effects of different doses of ZMB extract on diabetes-induced reproductive dysfunction by assessing oxidative damage and the gene expression of insulin receptor substrate (IRS) and pyruvate kinase (PK) in male rats' sperm.

METHODS

Sixty adult male Wistar rats were randomly divided into six groups; control (C), diabetes (D), and diabetic animals treated with glibenclamide (G, 50 mg/kg) and thyme extract (T100, T200, and T400). Diabetes was induced by intraperitoneal injection of Streptozotocin (STZ) (50 mg/kg). Insulin, glucose, oxidative and pro-inflammatory markers in the serum, and gene expressions of IRS, and PK were measured in the stored sperms in the epididymis. Changes in the process of spermatogenesis were assessed through the histological evaluation of the testis. Gas chromatography-mass spectrometry (GC-MS) was used to analyze the quantity and quality of thyme extract.

KEY FINDINGS

The study results indicated that body weight, food intake, and sperm parameters significantly improved in a dose-dependent manner in the T200 group compared to the other groups. Additionally, in the same group, pro-inflammatory biomarkers, DNA fragmentation, and MDA levels decreased, while the levels of catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) enzymes in the stored epididymal sperm significantly improved compared to the other groups. The expression of IRS and PK, along with the mean counts of spermatogenesis cell lines (especially Sertoli cells), significantly increased in the T200 group.

SUMMARY

In conclusion, thymol appears to alleviate diabetes-induced reproductive dysfunction by inhibiting oxidative damage, improving the metabolic state, and upregulating the expression of IRS and PK genes in the sperm of male rats.

Diabetes-induced male infertility: potential mechanisms and treatment options

Male infertility is a physiological phenomenon in which a man is unable to impregnate a fertile woman during a 12-month period of continuous, unprotected sexual intercourse. A growing body of clinical and epidemiological evidence indicates that the increasing incidence of male reproductive problems, especially infertility, shows a very similar trend to the incidence of diabetes within the same age range. In addition, a large number of previous in vivo and in vitro experiments have also suggested that the complex pathophysiological changes caused by diabetes may induce male infertility in multiple aspects, including hypothalamic-pituitary-gonadal axis dysfunction, spermatogenesis and maturation disorders, testicular interstitial cell damage erectile dysfunction. Based on the above related mechanisms, a large number of studies have focused on the potential therapeutic association between diabetes progression and infertility in patients with diabetes and infertility, providing important clues for the treatment of this population. In this paper, we summarized the research results of the effects of diabetes on male reproductive function in recent 5 years, elaborated the potential pathophysiological mechanisms of male infertility induced by diabetes, and reviewed and prospected the therapeutic measures.

Erythritol attenuates testicular dysfunction in diabetic rat via suppression of oxidative stress, inflammation and apoptosis

Hyperglycemia -induced oxidative stress and inflammation have been closely associated with diabetes complications including testicular dysfunction. Conversely, reducing blood glucose and/or use of antioxidant have been associated with reduced diabetes complications. The present study investigated the effect of erythritol (which has both antioxidant and blood glucose lowering function) on diabetes -induced testicular dysfunction in rats. Thirty male Wistar rats (170-200g) were randomly divided into 5 groups: 1) control; 2) erythritol; 3) diabetic; 4) diabetic + erythritol 1000 mg/kg; and 5) diabetic + metformin 300 mg/kg. After 8 weeks of treatment period, blood sample, testes and epididymis were collected for reproductive hormones, biochemical and histological examinations, and sperm analysis respectively. There was a significant (p < 0.05) decrease in sperm count, sperm motility, sperm morphology and serum reproductive hormones (Follicle stimulating hormone (FSH), Leutinizing hormone (LH), testosterone and gonadotropin releasing hormone (GnRH)) of diabetes rat compared to control. Also, diabetes rat showed increase in sperm and testicular malonaldehyde (MDA) and decrease in sperm and testicular superoxide dismutase (SOD) activity and glutathione (GSH) level. Further, diabetes rat showed reduced testicular weight, decreased testicular 17β-HSD and 3β-HSD activity and testicular histo-architectural alteration which were accompanied by decrease testicular vascular endothelial growth factor (VEGF) and concomitant increase in testicular myeloperoxidase activity and level of caspase 3. The present results indicates that induction of diabetes in rat causes reduction in the level of reproductive hormones (Testosterone, LH and FSH) as well as sperm and testicular oxidative stress causing abnormal sperm parameters, and biochemical and histo-architectural alterations in the testes of rats. In addition, the present results suggest that erythritol administration reduced blood glucose and ameliorated hyperglycemia -induced oxidative stress -mediated alterations in both sperm and testes of diabetes rat. Further, the present study suggests that erythritol improved testicular oxidative stress, inflammation and apoptosis by up-regulating VEGF.

Dapagliflozin Mitigated Elevated Disomic and Diploid Sperm in a Mouse Model of Diabetes and Recover the Disrupted Ogg1, Parp1, and P53 Gene Expression

Increases in numerical chromosomal syndromes were observed in children of diabetic mothers. However, the effects of diabetes on male reproduction, specifically numerical chromosomal aberrations (aneuploidy), have not been studied. Furthermore, despite the increasing use of dapagliflozin for diabetes treatment, no data exists on its ability to affect aneuploidy levels in germ cells. Thus, our investigation aimed to evaluate the effects of diabetes on spontaneous sperm aneuploidy and whether treatment with dapagliflozin influences the frequency of aneuploidy in the sperm of an experimental diabetic animal model. Our findings show that dapagliflozin has no aneugenic effects on the meiotic stages of spermatogenesis. In contrast, diabetes raised the frequency of aneuploidy, and dapagliflozin administration decreased the elevated levels of disomic and diploid sperm. The level of oxidative stress was markedly increased in diabetic mice, but were reduced by dapagliflozin treatment. Furthermore, the expression of some of DNA repair genes was disrupted in diabetic animals, whereas dapagliflozin therapy restored these disruptions and significantly enhanced DNA repair. Thus, dapagliflozin may effectively ameliorate diabetes-induced aneugenic effects on male meiosis and treating diabetic patients with dapagliflozin may effectively mitigate the transmission of diabetes-induced chromosomal defects to offspring.

Impacts of the DPP-4 Inhibitor Saxagliptin and SGLT-2 Inhibitor Dapagliflozin on the Gonads of Diabetic Mice

Diabetes mellitus is a metabolic disease that can cause systemic problems, including testicular dysfunction. Several diabetes medications have demonstrated potential adverse effects on the male reproductive system; however, the effects of saxagliptin and dapagliflozin have not been sufficiently examined. This investigation studied the impacts of saxagliptin and dapagliflozin treatments on the gonads in a male mouse model of diabetes. Testicular disturbances were assessed by sperm DNA damage, diakinesis-metaphase I chromosome examination, and spermiogram analysis. Our results showed more sperm DNA damage, more spermatocyte chromosome aberrations, lower sperm motility/count, and more sperm morphological anomalies in diabetic mice than in the control mice. Dapagliflozin significantly restored all examined measures to the control values in diabetic mice, unlike saxagliptin, which exacerbated the reduction in sperm count and motility. Both drugs significantly restored the gonadal redox imbalances in diabetic mice by decreasing reactive oxygen species accumulation and increasing glutathione levels. In conclusion, our study presents preliminary evidence for the safety and efficacy of dapagliflozin in alleviating testicular abnormalities induced by diabetes, making it a promising candidate drug for patients with diabetes in their reproductive age. As saxagliptin may have negative effects on fertility, its prescription should be avoided in young male diabetic patients.

Tropisetron improved testicular inflammation in the streptozotocin-induced diabetic rats: The role of toll-like receptor 4 (TLR4) and mir146a

As a serotonin antagonist, tropisetron positively affects blood glucose lowering, insulin synthesis, pancreas inflammation, and apoptosis in diabetes. Reproductive disorders are one of the diabetes-induced chronic complications. The present study aimed to evaluate the effect of tropisetron on diabetes-induced testicular inflammation, its signaling pathway, and mir146a. To this end, animals were assigned to the control, tropisetron, diabetes (DM), DM-tropisetron, and DM-glibenclamide groups. Streptozotocin (50 mg/kg) was intraperitoneally injected to provide diabetes. Tropisetron and glibenclamide were then administrated intraperitoneally for 2 weeks after diabetes induction. Testes histology, real-time polymerase chain reaction, western blot analysis, ELISA, and immunohistochemistry assays were also performed. The finding revealed that tropisetron significantly improved diabetes-induced testis damages, lowered TLR4, TRAF6, IRAK1, NF-κB, and caspase3 protein expressions, and decreased TNF-α and IL-1 levels. Moreover, the mir146a expression declined following the tropisetron treatment. This study demonstrated that the significant role of tropisetron in lowering testicular inflammation and apoptosis might have been due to the inhibition of the TLR4/IRAK1/TRAF6 signaling pathway and thereby the attenuation of NF-κB and caspase3 expression and inflammatory cytokines. Furthermore, the downregulation of mir146a, as an inflammatory microRNA interacting with TLR4, showed another pathway, through which tropisetron improved diabetes-induced testicular injuries.

Effects of diabetes mellitus on sperm quality and fertility outcomes: Clinical evidence

BACKGROUND

Diabetes mellitus is a global epidemic characterized by high morbidity and mortality. Diabetes mellitus can lead to acute and chronic systemic complications. Among them, a negative effect of diabetes mellitus on sperm quality and male/couple fertility has been suggested. However, available studies in diabetes mellitus men evaluated relatively small cohorts with discordant results.

OBJECTIVES

To evaluate the clinical evidences of the effects of diabetes mellitus on sperm quality and fertility outcomes.

METHODS

An extensive Medline search was performed identifying studies in the English language.

RESULTS

The prevalence of diabetes mellitus in infertile men ranges from 0.7% to 1.4%, while the prevalence of infertility in diabetes mellitus men, evaluated in a few studies, ranges from 35% to 51%. Male diabetes mellitus seems to play a negative effect on couple fecundity, while being childless or subfertile men might increase the risk of diabetes mellitus. Available cross-sectional studies investigating semen parameters and male sexual hormones in men with diabetes mellitus are heterogeneous, assessed relatively small cohorts, show often discordant results and frequently are not directly comparable to derive robust conclusions. Two meta-analyses support a negative effect of diabetes mellitus on sperm normal morphology and no effect on sperm total count, with contradictory results regarding other semen parameters. Considering only studies on type 1 diabetes mellitus men, meta-analyses support a negative effect of diabetes mellitus on sperm motility and no effect on sperm total count, with contradictory results regarding other semen parameters. The rate of children observed among type 1 diabetes mellitus men was lower than controls, especially in subjects with a longer diabetes mellitus duration. Couples with a diabetes mellitus male partner undergoing assisted reproduction techniques showed lower pregnancy rates than controls. No study evaluated the impact of diabetes mellitus treatment on semen quality and male fertility.

CONCLUSIONS

Overall, available data show that diabetes mellitus might impair male reproductive health and couple fertility. However, further larger and full of details studies are needed.

A systematic review on the role of melatonin and its mechanisms on diabetes-related reproductive impairment in non-clinical studies

BACKGROUND

Diabetes-induced reproductive complications can lead to subfertility and infertility, raising the need to protect reproductive organs. There are limited medications used to improve reproductive health in diabetic patients. Melatonin, mainly produced by the pineal gland, may improve diabetes-associated reproductive complications through various mechanisms and may be a preferred candidate to protect the reproductive system. The present review aims to elucidate the underlying mechanisms of melatonin's effect on the reproductive system adversely affected by diabetes mellitus (DM).

METHODS

A comprehensive systematic literature electronic search was done using the PRISMA guidelines. Web of Science, PubMed, Embase, and Scopus were searched for publications up to June 2022. Search terms were selected based on the study purpose and were explored in titles and abstracts. After screening, out of a total of 169 articles, 14 pertinent articles were included based on our inclusion and exclusion criteria.

RESULTS

The results of studies using rats and mice suggest that DM adversely affects reproductive tissues, including testes and epididymis, prostate, corpus cavernosum, and ovary leading to alterations in histological and biochemical parameters compared to the normal groups. Treatment with melatonin improves oxidative stress, blocks apoptosis induced by endoplasmic reticulum stress and caspase activation, reduces pro-inflammation cytokines, and enhances steroidogenesis.

CONCLUSION

Melatonin exerted a protective action on the impaired reproductive system in in-vivo and in-vitro models of DM. The topic has to be followed up in human pregnancy cases that will need more time to be collected and approved.

Impacts of Immunometabolism on Male Reproduction

The physiological process of male reproduction relies on the orchestration of neuroendocrine, immune, and energy metabolism. Spermatogenesis is controlled by the hypothalamic-pituitary-testicular (HPT) axis, which modulates the production of gonadal steroid hormones in the testes. The immune cells and cytokines in testes provide a protective microenvironment for the development and maturation of germ cells. The metabolic cellular responses and processes in testes provide energy production and biosynthetic precursors to regulate germ cell development and control testicular immunity and inflammation. The metabolism of immune cells is crucial for both inflammatory and anti-inflammatory responses, which supposes to affect the spermatogenesis in testes. In this review, the role of immunometabolism in male reproduction will be highlighted. Obesity, metabolic dysfunction, such as type 2 diabetes mellitus, are well documented to impact male fertility; thus, their impacts on the immune cells distributed in testes will also be discussed. Finally, the potential significance of the medicine targeting the specific metabolic intermediates or immune metabolism checkpoints to improve male reproduction will also be reassessed.

Quercetin and vitamin E attenuate diabetes-induced testicular anomaly in Wistar rats via the mitochondrial-mediated apoptotic pathway

The role of quercetin and vitamin E treatment against streptozotocin (STZ)-induced testicular abnormalities in diabetic rats and the possible mechanism of action they use for protection were investigated. Diabetes was induced by STZ (45 mg/kg i.p. once) and blood glucose was determined. Plasmatic insulin, testosterone, luteinising hormone and follicle-stimulating hormone (FSH) were determined by ELISA. Levels of cytochrome c, caspase 3 and caspase 9 were evaluated by immunohistochemistry, while lesions were viewed by histology. Insulin played a role in testicular protection against male infertility through modulation of luteinising hormone (LH). This consequently increased Leydig and Sertoli cells and maturation of germ cells with the attached epididymis having abundant spermatozoa. The study showed a positive correlation in the levels of LH, FSH and testosterone; it was further established that all treatments normalised diabetes-induced alterations. Treatment with quercetin and vitamin E resulted in 34% decrease of apoptogenic cytochrome c release. This protected the testes against excessive apoptosis by decreasing caspase 3 and caspase 9 activation by up to 30 and 28% respectively (p < .05). Histology also showed that treatment prevented testicular cell death. The findings show that quercetin/vitamin E possess free radical scavenging properties that protected against testicular damage in diabetes. This suggests the possibility of pharmaco-therapeutic intervention.

Metformin inhibits human spermatozoa motility and signalling pathways mediated by protein kinase A and tyrosine phosphorylation without affecting mitochondrial function

Metformin is a leading antidiabetic drug that is used worldwide in the treatment of diabetes mellitus. This biguanide exerts metabolic and pleiotropic effects in somatic cells, although its invitro actions on human spermatozoa remain unknown. The present study investigated the effects of metformin on human sperm function. Human spermatozoa were incubated in the presence or absence of 10mM metformin for 8 or 20h, and motility was measured by computer-aided sperm analysis (CASA); other parameters were evaluated by flow cytometry. Metformin significantly reduced the percentage of motile, progressive and rapid spermatozoa and significantly decreased sperm velocity. Metformin did not affect viability, mitochondrial membrane potential (MMP) or mitochondrial superoxide anion generation of human spermatozoa at any time studied. However, metformin clearly inhibited the protein kinase (PK) A pathway and protein tyrosine phosphorylation at 8 and 20h, key regulatory pathways for correct sperm function. In summary, metformin treatment of human spermatozoa had a detrimental effect on motility and inhibited essential sperm signalling pathways, namely PKA and protein tyrosine phosphorylation, without affecting physiological parameters (viability, MMP, mitochondrial superoxide anion generation). Given the growing clinical use of metformin in different pathologies in addition to diabetes, this study highlights an adverse effect of metformin on spermatozoa and its relevance in terms of human fertility in patients who potentially could be treated with metformin in the future.

Protective effects of Salidroside on spermatogenesis in streptozotocin induced type-1 diabetic male mice by inhibiting oxidative stress mediated blood-testis barrier damage

Spermatogenic dysfunction is one of the major secondary complications of male diabetes. Salidroside (SAL) is the important active ingredients isolated from Herba Cistanche, which exhibits numerous pharmacological activities such as antioxidant, anti-diabetic, and anti-inflammatory effects. The present study was designed to determine whether SAL contributes to the recovery from spermatogenic dysfunction in streptozotocin (STZ) induced type-1 diabetic mice. SAL (25, 50, or 100 mg/kg) and Clomiphene citrate (CC, 5 mg/kg) were orally administered to male type-1 diabetic mice for 10 weeks. Testis tissues were collected for histopathological and biochemical analysis. Moreover, reproductive organ weight, sperm parameters, and testicular cell DNA damage were estimated. The results revealed that SAL significantly improved the weight of the reproductive organs, sperm parameters and testicular morphology to different degrees in type-1 diabetic mice. Furthermore, reactive oxygen species (ROS) and malondialdehyde (MDA) levels were significantly reduced, and the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH), markedly increased in the testicular tissue after SAL treatment. In addition, our data also showed a marked downregulation the fluorescence expressions of p38 MAPK phosphorylation and upregulation the protein expressions of ZO-1, Occludin, Claudin-11 and N-cadherin after SAL administration (100 mg/kg) compared with the type-1 diabetic group. In conclusion, these results demonstrated that SAL exerts protective effects on type-1 diabetes-induced male spermatogenic dysfunction, which is likely mediated by inhibiting oxidative stress-mediated blood testis barrier damage.

The effects of sericin in recovering spermatogenesis and sexual hormone levels in diabetic rats

Sericin-S (a hydrolysate from the silk protein sericin) is a natural antioxidant, which may improve spermatogenesis while having high biological safety, thus potentially useful for the treatment of male infertility. Our objective was to determine the effects of sericin-S on the sperm parameters and sexual hormone levels in a diabetic rat model. Thirty-six adult male rats were randomly divided in two groups, inducing diabetes in one of them by intraperitoneal administration of streptozotocin (STZ; 65 mg/kg). Both groups were randomly assigned to three subgroups, receiving oral gavage of saline, 1% or 2% sericin extract for 60 days. Therefore, the experimental design was a 2 × 3 factorial design of STZ and sericin treatments. One day after the last treatment, the rats were euthanized, weighed, the testes were processed (weigh, volume, and histology), and serum samples were processed for measuring sex hormone levels [testosterone, follicle-stimulating hormone, and luteinizing hormone (LH)]. STZ treatment decreased LH concentration and counts of spermatogonia, spermatocytes, and spermatids. Body and testis weights were significantly (p < 0.05) lower in the control group (non-diabetic saline) compared to the treated groups. In non-diabetic rats, sericin treatments increased (p < 0.05) the number of testicular cells (spermatogonia, spermatocytes, spermatids, Sertoli, and Leydig cells) and sex hormone concentrations. In diabetic rats, administration of sericin significantly (p < 0.05) improved sperm cell number and sex hormones levels. In nutshell, sericin can clearly modify sperm parameters and overall sex hormone function, and could improve spermatogenesis in normal and diabetic rats.

Protective effects of Astragalin on spermatogenesis in streptozotocin-induced diabetes in male mice by improving antioxidant activity and inhibiting inflammation

Spermatogenic dysfunction is a common complication in men with diabetes and is the most important manifestation of diabetes-related male reproduction damage. Astragalin (AG) is one of the main flavonoids from Cuscuta chinensis, which has rich pharmacological activities. This study aimed to establish whether AG may contribute to the recovery from spermatogenic dysfunction. AG (3.3, 10 and 30 mg/kg) and Clomiphene (5 mg/kg) were orally administered to streptozotocin-induced diabetic male mice for 8 weeks. After the experiments performed, reproductive organs, sperm parameters and histomorphological changes were analysed. Antioxidant and anti-inflammatory capacity were estimated in testicular tissues. The results revealed that AG significantly improved the reproductive organs, sperm parameters and testicular morphology to different degrees in diabetic mice. Nitric oxide (NO) and malondialdehyde (MDA) levels were significantly reduced, and the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT), markedly increased in the testicular tissue after AG was administered. Interestingly, AG also downregulated the protein expressions of tumour necrosis factor-α (TNF-α) and inducible nitric oxide synthase (iNOS) in testes. In conclusion, AG is a potential beneficial agent to protect diabetic-induced spermatogenic dysfunction in male mice by increasing antioxidant enzymes activities and inhibiting inflammation.

Effect of pharmacological doses of niacin on testicular structure and function in normal and diabetic rats

Male diabetic patients may experience adverse changes in testicular functions or structure. Niacin has antidyslipidemic properties in diabetic patients. We aimed to clarify the effect of pharmacological doses of niacin on testicular structure and function of normal and diabetic rats. Sixty adult male rats were treated as follows. Healthy control (HC); diabetic control (DC); NL and NH groups: normal rats that received niacin at 800 and 4,000 mg/kg of diet; DL and DH groups: diabetic rats that received niacin at 800 and 4,000 mg/kg diet for 50 days. In normal rats, obvious increase in serum testosterone especially in NL group associated with improved antioxidant status of testicular tissue was observed. In diabetic rats, niacin resulted in higher testicular weight/body weight and improved some histological parameters without affecting blood glucose, testosterone and sperm count. Testicular MDA content decreased. In conclusion, niacin especially at 800 mg/kg diet improves serum testosterone levels and antioxidant status of testes in normal rats. In diabetic rats, despite positive changes in histological features and antioxidant status of testes reproductive outcome including sperm count or testosterone levels were not improved. This study set the scene for further investigations on the effect of niacin on male reproductive system.