The influence of type 1 diabetes mellitus on spermatogenic gene expression

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.

Type I Diabetes in Zebrafish Reduces Sperm Quality and Increases Insulin and Glucose Transporter Transcripts

Type I diabetes is a prominent human pathology with increasing incidence in the population; however, its cause is still unknown. This disease promotes detrimental effects on reproduction, such as lower sperm motility and DNA integrity. Hence, the investigation of the underlying mechanisms of this metabolic disturbance in reproduction and its transgenerational consequences is of the utmost importance. The zebrafish is a useful model for this research considering its high homology with human genes as well as its fast generation and regeneration abilities. Therefore, we aimed to investigate sperm quality and genes relevant to diabetes in the spermatozoa of Tg(ins:nfsb-mCherry) zebrafish, a model for type I diabetes. Diabetic Tg(ins:nfsb-mCherry) males showed significantly higher expression of transcripts for insulin a (insa) and glucose transporter (slc2a2) compared to controls. Sperm obtained from the same treatment group showed significantly lower sperm motility, plasma membrane viability, and DNA integrity compared to that from the control group. Upon sperm cryopreservation, sperm freezability was reduced, which could be a consequence of poor initial sperm quality. Altogether, the data showed similar detrimental effects related to type I diabetes in zebrafish spermatozoa at the cellular and molecular levels. Therefore, our study validates the zebrafish model for type I diabetes research in germ cells.

Elevated testicular apoptosis is associated with elevated sphingosine driven by gut microbiota in prediabetic sheep

BACKGROUND

Men with prediabetes often exhibit concomitant low-quality sperm production or even infertility, problems which urgently require improved therapeutic options. In this study, we have established a sheep model of diet-induced prediabetes that is associated with spermatogenic defects and have explored the possible underlying metabolic causes.

RESULTS

We compared male sheep fed a normal diet with those in which prediabetes was induced by a rich diet and with a third group in which the rich diet was supplemented by melatonin. Only the rich diet group had symptoms of prediabetes, and in these sheep, we found impaired spermatogenesis characterized by a block in the development of round spermatids and an increased quantity of testicular apoptotic cells. Comparing the gut microbiomes and intestinal digest metabolomes of the three groups revealed a distinctive difference in the taxonomic composition of the microbiota in prediabetic sheep, and an altered metabolome, whose most significant feature was altered sphingosine metabolism; elevated sphingosine was also found in blood and testes. Administration of melatonin alleviated the symptoms of prediabetes, including those of impaired spermatogenesis, while restoring a more normal microbiota and metabolic levels of sphingosine. Fecal microbiota transplantation from prediabetic sheep induced elevated sphingosine levels and impaired spermatogenesis in recipient mice, indicating a causal role of gut microbiota in these phenotypes.

CONCLUSIONS

Our results point to a key role of sphingosine in the disruption of spermatogenesis in prediabetic sheep and suggest it could be a useful disease marker; furthermore, melatonin represents a potential prebiotic agent for the treatment of male infertility caused by prediabetes.

The Potential Role of C-peptide in Sexual and Reproductive Functions in Type 1 Diabetes Mellitus: An Update

BACKGROUND

Although hyperglycaemia is known to be the leading cause of diabetic complications, the beneficial effect of optimal glucose control in preventing diabetic complications is still far from being proven. In fact, such complications may not be related to glycaemic control alone.

OBJECTIVE

This review summarizes several studies that suggest that a C-peptide deficiency could be new and common pathophysiology for complications in type 1 diabetes, including sexual and reproductive dysfunction.

METHODS

We reviewed in vitro, in vivo, and human studies on the association between C-peptide deficiency or C-peptide replacement therapy and complications in type 1 diabetes. It seems that Cpeptide replacement therapy may interrupt the connection between diabetes and sexual/reproductive dysfunction.

RESULTS

The Diabetes Control and Complications Trial suggested that maintaining C-peptide secretion is associated with a reduced incidence of retinopathy, nephropathy, and hypoglycaemia. Risk of vascular, hormonal, and neurologic damage in the structures supplying blood to the penis increases with increasing levels of HbA1. However, several human studies have suggested an association between C-peptide production and hypothalamic/pituitary functions. When exposed to C-peptide, cavernosal smooth muscle cells increase the production of nitric oxide. C-peptide in diabetic rats improves sperm count, sperm motility, testosterone levels, and nerve conduction compared to non-treated diabetic rats.

CONCLUSION

C-peptide deficiency may be involved, at least partially, in the development of several pathological features associated with type 1 diabetes, including sexual/reproductive dysfunction. Preliminary studies have reported that C-peptide administration protects against diabetic microand macrovascular damages as well as sexual/reproductive dysfunction. Therefore, further studies are needed to confirm these promising findings.

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

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

Effects of testicular sperm aspiration upon first cycle ICSI-ET for type 2 diabetic male patients

Male diabetes mellitus (DM) can affect erectile function and sperm quality. In severe cases, DM can lead to retrograde or no ejaculation, so testicular sperm aspiration (TESA) is combined with intracytoplasmic sperm injection (ICSI) to treat subfertility and infertility for DM couples. However, the effect of TESA upon ICSI (TESA-ICSI) for DM patients remains unclear. This research investigated the effect of TESA-ICSI on first cycle ICSI-embryo transfer (ICSI-ET) for type 2 diabetic mellitus (T2DM) patients and the potential mechanisms. The subjects consisted of 1219 male patients with azoospermia or retrograde ejaculation who were treated with TESA-ICSI from 2015.01 to 2019.11. They were classified into two groups, the T2DM group (n = 54) and non-diabetic control group (n = 1165). Sperm selection for injection was performed using motile sperm organelle morphology examination criteria. The number of available embryos and the high-quality embryo rates following a single ET as well as cleavage, fertilization, implantation, clinical pregnancy and the abortion rates were noted. Compared with the non-diabetic group, the available embryo rate (75.20 ± 26.40% vs.78.36 ± 23.25%) and high-quality embryo rate (46.49 ± 30.37% vs. 47.55 ± 28.57%) in the T2DM group were lower and the abortion rate (20.83% vs. 8.88%) was higher, but these differences were not statistically significant. There were no significant differences in clinical pregnancy, implantation, normal fertilization, and cleavage rates between the two groups. The results show that TESA for male T2DM patients does not influence the effect of ICSI. For T2DM patients with severe oligozoospermia, asthenospermia, teratozoospermia, or retrograde ejaculation that do not meet ICSI criteria, TESA-ICSI may perhaps be considered for reproductive assistance.

ABBREVIATIONS

DM: diabetes mellitus; TESA: testicular sperm aspiration; ICSI: intracytoplasmic sperm injection; ICSI-ET; ICSI-embryo transfer; LH: luteinizing hormone; mL: milliliter; TES: testosterone; FSH: follicle-stimulating hormone; P: progesterone; HCG: human chorionic gonadotropin.

High fat diet causes distinct aberrations in the testicular proteome

Diet has important effects on normal physiology and the potential deleterious effects of high fat diets and obesity on male reproductive health are being increasingly described. We conducted a histological review of the effects of chronic high fat (HF) diet (using a mouse model fed a 45% fat diet for 21 weeks) with a discovery proteomic study to assess for changes in the abundance of proteins in the testis. Mice on a HF diet became obese and developed glucose intolerance. Using mass spectrometry, we identify 102 proteins affected in the testis of obese mice. These included structural proteins important for the blood testis barrier (filamin A, FLNA), proteins involved in oxidative stress responses (spermatogenesis associated 20, SPATA-20) and lipid homoeostasis (sterol regulatory element-binding protein 2, SREBP2 and apolipoprotein A1, APOA1). In addition, an important regulator protein paraspeckle component 1, PSPC-1, which interacts with the androgen receptor was significantly downregulated. Proteomic data was validated using both Western blotting and immunostaining which confirmed and localised protein expression in both mouse and human testis using biopsy specimens. This study focused mainly on the abnormalities that occurred at the protein level and as a result, we have identified several candidate proteins and conducted pathway analysis around the effects of HF diet on the testis providing novel insights not previously described. Some of the identified targets could be targeted therapeutically and future work is directed in this area.

Protective effects of Equisetum arvense methanolic extract on sperm characteristics and in vitro fertilization potential in experimental diabetic mice: An experimental study

Background

Diabetes mellitus is a metabolic disorder characterized by impaired insulin secretion or the inability of tissues to respond to insulin. This disease can damage the testis and reduce semen quality. Therefore, it can impair the potential for male fertility. Different herbal therapeutic treatments have been used to control diabetes and its complications.

Objective

This study aimed to evaluate the effects of streptozotocin-induced diabetes on sperm and in vitro fertilization (IVF) potential and investigate the protective effects of Equisetum arvense methanolic extract on diabetic mice.

Materials and Methods

Twenty-four adult male mice were divided into four groups: control-sham, diabetic, diabetic + Equisetum extract (250 mg/kg), and diabetic + Equisetum extract (500 mg/kg). After 45 days, sperm samples were collected from the cauda epididymis to evaluate the characteristics of sperm (including viability, count, motility, morphology and chromatin/DNA integrity of sperm) and the IVF potential.

Results

Sperm motility and viability were increased remarkably (p ≤ 0.001) in the treated groups compared with the non-treated diabetic group. The decrease in sperm count in the diabetic group compared with the treated groups was not significant. Moreover, the percentage of sperm with DNA damage, nuclear immaturity, and abnormal morphology was decreased significantly (p ≤ 0.001) in the treated groups compared with the diabetic group. The treated animals exhibited remarkably higher fertilization rates and a higher percentage of fertilized oocytes that developed toward the blastocyst stage compared with the non-treated diabetic group (p ≤ 0.001).

Conclusion

The methanolic extract of the Equisetum arvense inhibited diabetes-induced detrimental effects on sperm quality and fertilization rate, which may have been associated with hypoglycemic and antioxidative activities in this plant.

The effects of the Lactobacillus acidophilus ATCC 4356 on the oxidative stress of reproductive system in diabetic male rats

BACKGROUND

Background: Oxidative stress plays an important role in the development of diabetic complications.

OBJECTIVE

This study evaluated the impact of pre- and post-treatment with Lactobacillus acidophilus ATCC 4356 on the oxidant and anti-oxidant factors of testis and epididymis in streptozotocin-induced diabetic rats.

MATERIALS AND METHODS

Thirty male Wistar rats (10 wk old) weighing 220-230 g. were divided into five groups (n = 6/ each): 1- normal group, 2- normal lactobacillus group, 3- diabetic group, 4- diabetic + lactobacillus before (DLB) group, and 5- diabetic + lactobacillus after (DLA) group. The normal and diabetic groups received daily 1 mL normal saline for 6 wk. Normal lactobacillus group received daily L. acidophilus for 6 wk. Group DLB received daily L. acidophilus for 2 wk before diabetes and for 4 wk after diabetes. Group DLA received daily 1 mL normal saline for 2 wk before diabetes and L. acidophilus for 4 wk after diabetes. The dose of L. acidophilus was 1 × 109 CFU/mL.

RESULTS

The administration of L. acidophilus worsened blood glucose level and reduced the levels of Malondialdehyde (p ≤ 0.0001) and Hydrogen peroxide (p ≤ 0.0001) and, Catalase and Glutathione peroxidase activity increased in the testis. In epididymis, Glutathione peroxidase and Catalase (p = 0.013) activity increased and Hydrogen peroxide concentration reduced, while Malondialdehyde concentration did not show any changes compared to the diabetic rats. Also, there was no significant difference between DLB and DLA groups, in these markers.

CONCLUSION

Data obtained suggests that L. acidophilus has anti-oxidant effects on the testis and sometime in the epididymis in diabetic rats.

Tempol improves oxidant/antioxidant parameters in testicular tissues of diabetic rats

AIMS

Oxidative stress induced by diabetes mellitus (DM) is considered as one of the main causes of infertility in diabetic patients. The aim of the present study was to assess the effect of Tempol - as a synthetic antioxidant- on the testis oxidative stress and sperm parameters in type 2 diabetic (T2D) rats.

MAIN METHODS

Twenty male Wistar rats were divided into 4 groups. Control groups (C) and diabetic groups (D); the control and diabetic groups received Tempol (100 mg/kg) for one month. Sperm parameters and oxidative stress biomarkers were evaluated in testicular tissue.

KEY FINDINGS

The results demonstrated that administration of Tempol in diabetic rats improved sperm motility and viability and decreased the count of abnormal sperms. Also Tempol decreased the fasting blood sugar (FBS) and lipid peroxidation (LPO). In addition, Tempol significantly increased total antioxidant capacity (TAC) levels in testis tissue of T2D rats. Histopathological changes were also improved in the diabetic treated group.

SIGNIFICANCE

Taken together, the results indicated that Tempol improved fertility parameters in a diabetic rat through reducing oxidative stress.

Ocimum gratissimum leaf extract may precipitate infertility in male diabetic Wistar rats

Objective:

This study was designed to investigate the Ocimum gratissimum (OG) effects on sperm quality and testicular cytoarchitecture in alloxan-induced diabetic rats.

Method:

Twenty male Wistar rats (150-200 g) were assigned into 4 groups (n=5) as A (control), B (OG), C (Dia) and D (Dia+OG). Groups A and B were normal animals receiving distilled water or OG (400 mg/kg), respectively while diabetes was induced by alloxan monohydrate (100 mg/kg) in groups C and D, followed by the administration of distilled water or OG, respectively for 28 days. Blood samples were obtained for fasting blood glucose (FBG) and fructosamine determination while, epididymis and testes were obtained for sperm quality assessment using computer-assisted sperm analyzer and testicular histomorphometry, respectively. Seminiferous tubule diameter and interstitial space distance were quantified in hematoxylin and eosin stained slides. Statistical analysis was done using ANOVA and student t-test at α0.05.

Results:

Fructosamine and FBG were reduced in Dia+OG (80.11±3.80µmol/L and 132.0±8.41mg/dl, respectively) compared with Dia (139.66±4.29µmol/L and 285.6±26.69mg/dl, respectively). Sperm count was unchanged in Dia, but decreased in OG and Dia+OG; abnormal sperm cells increased in OG, Dia and Dia+OG. Mild vacuolation in the seminiferous tubule, disorganized germinal cells layer, arrested sperm maturation with empty spermatozoa in lumen, decreased seminiferous tubule diameter and increased interstitial space were found in the testes of OG, Dia and Dia+OG compared with control.

Conclusion:

Diabetes induces sperm impairments and distortions in testicular cytoarchitecture, which were aggravated by OG leaf extract in male Wistar rats.

In vivo administration of quercetin ameliorates sperm oxidative stress, inflammation, preserves sperm morphology and functions in streptozotocin-nicotinamide induced adult male diabetic rats

INTRODUCTION

Diabetes mellitus (DM) has been associated with sperm damage. In view of the fact that quercetin possesses antioxidant and anti-inflammatory activities, this compound may help to protect sperm against damage in DM. In this study, in-vivo effects of quercetin on sperm parameters in DM were investigated.

MATERIAL AND METHODS

Quercetin (10, 25 and 50 mg/kg/b.w.) was given orally to streptozotocin-nicotinamide induced adult male diabetic rats for 28 days. Following treatment completion, rats were sacrificed and sperm were harvested from the cauda epididymis. Sperm count, motility, viability, hyperosmotic swelling (HOS) tail-coiled sperm and morphology were assessed. Levels of lipid peroxidation (LPO) and anti-oxidative enzymes (SOD, CAT and GPx) in sperm with and without H₂O₂ incubation were determined by biochemical assays. Expression levels of SOD, CAT and GPx mRNAs in sperm were evaluated by qPCR. Sperm DNA integrity was estimated by flow cytometry while expression levels of the inflammatory markers NF-κβ and TNF-α in sperm were determined by Western blotting.

RESULTS

In diabetic rats receiving quercetin, sperm count and motility, viability and HOS tail-coiled sperm increased (p < 0.05) while sperm with abnormal morphology decreased. Moreover, sperm SOD, CAT, GPx activities and their mRNA expression levels increased while sperm LPO, NF-κβ and TNF-α levels decreased. In normal and diabetic rat sperm incubated with H₂O₂, a further increase in MDA and further decreases in SOD, CAT and GPx were observed, and these were ameliorated by quercetin treatment.

CONCLUSIONS

In-vivo administration of quercetin to diabetic rats helps to ameliorate sperm damage and improves sperm morphology and functions in DM.

Diabetes Mellitus and Infertility: Different Pathophysiological Effects in Type 1 and Type 2 on Sperm Function

Although the prevalence of sub-infertility in diabetic patients in childbearing age is known, the mechanisms by which diabetes mellitus (DM) causes male infertility are not completely explained. This detrimental effect is achieved with a variety of mechanisms that include pre-testicular, testicular, and post-testicular pathogenetic moments and can be different in type 1 diabetes mellitus (DM1) and type 2 diabetes mellitus (DM2) patients because of type of diabetes, duration of disease, and glycemic metabolic compensation. Aim of this study was to evaluate whether diabetic disease can be considered a risk factor for infertility considering the etiopathogenetic differences between DM1 and DM2 on sperm function. We enrolled 38 DM1 patients and 55 DM2 patients with idiopathic infertility history >12 months, and 100 healthy fertile subjects. The following outcomes were evaluated in optical microscopy and flow cytometry: sperm function (by conventional and biofunctional sperm parameters) and signs of urogenital infection/inflammation (by sperm leukocyte concentrations and indices of oxidative stress). Moreover, an andrological evaluation (by didymo-epididymal ultrasound evaluation, serum total testosterone, LH, and FSH measurements) was performed in DM1 and DM2 patients compared to controls. Diabetic patients showed a higher risk of becoming infertile and the pathophysiological mechanisms of damage were different in DM1 and DM2. Conventional sperm parameters of diabetic patients are worse than controls (p < 0.05). The DM2 caused an inflammatory condition with increased oxidative stress resulting in decreased sperm vitality and increased sperm DNA fragmentation. DM1 altered epididymal voiding causing low ejaculate volume and mitochondrial damage resulting in decreased sperm motility. These findings and evidences support the contention that DM could be regarded as cause of male infertility suggesting that the prevention of diabetic disease in DM2 and the follow-up of seminal parameters in DM1 could prevent fertility decline in these categories of patients.

Quail (Coturnix japonica) egg yolk bioactive components attenuate streptozotocin-induced testicular damage and oxidative stress in diabetic rats

INTRODUCTION

The testicular milieu is the machinery for the metabolism of testosterone in the male reproductive system.

PURPOSE

The dysfunction of this highly regenerating system is inevitable in the condition of glucose imbalance as a result of insulin machinery impairment. Therefore, it is imperative to recommend dietary intervention for attenuating the testicular dysfunction and oxidative stress resulting from STZ-induction of diabetes.

METHODS

STZ-induced diabetes (65 mg/kg, ip) was treated with QEYEM (50, 100 and 200 mg/kg/day) and quercetin (50 mg/kg/day) for 7weeks. In serum, glucose, testosterone, IL-6 and TNF-α levels were estimated, and in testis, tissues TBARS, sulfhydryl groups, nucleic acids and total protein (TP) levels were estimated. SOD, CAT and GST activities were also determined in testicular cells. Histopathological changes were evaluated in a cross-section of testis.

RESULTS

Testosterone concentration was decreased while pro-inflammatory markers were increased in STZ-assaulted rats. Treatment using QEYEM of diabetic rats corrected assaults and reverse significantly the diabetic conditions. QEYEM-treated groups showed significant inhibition of TBARS levels and elevation of testicular GSH, NP-SH, total protein (TP) and nucleic acids-DNA and RNA levels. The QEYEM administration reversed the inhibited activities of SOD, CAT and GST in testicular cells in diabetic rats. The characterization of the extract carried out through HPLC analytical techniques revealed vitamins A, D and E concentrations of 0.645, 0.012 and 6.3 mg/100 g, respectively.

CONCLUSION

QEYEM supplementation to STZ-induced diabetic rats for seven (7) consecutive weeks is a potential intervention against testicular damage in adult diabetic rats, probably by decreasing oxidative stress.

The effects of diabetes on male fertility and epigenetic regulation during spermatogenesis

The effects of diabetes mellitus include long-term damages, dysfunctions, and failures of various organs. An important complication of diabetes is the disturbance in the male reproductive system. Glucose metabolism is an important event in spermatogenesis. Moreover, glucose metabolism is also important for maintaining basic cell activity, as well as specific functions, such as motility and fertilization ability in mature sperm. Diabetic disease and experimentally induced diabetes both demonstrated that either type 1 diabetes or type 2 diabetes could have detrimental effects on male fertility, especially on sperm quality, such as sperm motility, sperm DNA integrity, and ingredients of seminal plasma. Epigenetic modifications are essential during spermatogenesis. The epigenetic regulation represents chromatin modifications including DNA methylation, histone modifications, remodeling of nucleosomes and the higher-order chromatin reorganization and noncoding RNAs. If spermatogenesis is affected during the critical developmental window, embryonic gonadal development, and germline differentiation, environmentally-induced epigenetic modifications may become permanent in the germ line epigenome and have a potential impact on subsequent generations through epigenetic transgenerational inheritance. Diabetes may influence the epigenetic modification during sperm spermatogenesis and that these epigenetic dysregulation may be inherited through the male germ line and passed onto more than one generation, which in turn may increase the risk of diabetes in offspring.

Diabetes mellitus and functional sperm characteristics: A meta-analysis of observational studies

OBJECTIVE

Insulin resistance and diabetes mellitus (DM) are well defined causes of female infertility. Animal studies present evidence for decreased sperm quality, but conflicting results have been presented in clinically-orientated studies. We sought to evaluate whether DM affects functional sperm characteristics.

STUDY DESIGN

We searched the Medline, Scopus, ClinicalTrials.gov, and Cochrane Central Register of Controlled Trials databases.

RESULTS

DM seems to decrease the seminal volume (MD -0.66ml, 95% CI -1.10, -0.22) and the percentage of motile cells (MD -14.29%, 95% CI -22.76, -5.82) and increase the FSH values (MD 0.47mIU/ml, 95% CI 0.01, 0.93) of men who were screened for infertility. It does not, however, influence the total sperm count (MD 13.16 106 cells, 95% CI -22.75, 49.07), the percentage of normal sperm morphology (-3.06%, 95% CI -6.25, 0.14), or LH (MD 0.65mIU/ml, 95% CI -0.84, 2.13 Supp. Fig. 2) and testosterone values (MD -0.18ng/ml, 95% CI -0.60, 0.24).

CONCLUSION

Current evidence suggests that the presence of DM seems to influence functional sperm characteristics. Firm results are, however, precluded due to the significant heterogeneity of the included studies. Future prospective studies will clarify whether the DM affects semen quality and IVF outcome.

Spermatogenesis in humans and its affecting factors

Spermatogenesis is an extraordinary complex process. The differentiation of spermatogonia into spermatozoa requires the participation of several cell types, hormones, paracrine factors, genes and epigenetic regulators. Recent researches in animals and humans have furthered our understanding of the male gamete differentiation, and led to clinical tools for the better management of male infertility. There is still much to be learned about this intricate process. In this review, the critical steps of human spermatogenesis are discussed together with its main affecting factors.

Male obesity and subfertility, is it really about increased adiposity?

The prevalence of overweight and obesity in reproductive-aged men is increasing worldwide, with >70% of men >18 years classified as overweight or obese in some western nations. Male obesity is associated with male subfertility, impairing sex hormones, reducing sperm counts, increasing oxidative sperm DNA damage and changing the epigenetic status of sperm. These changes to sperm function as a result of obesity, are further associated with impaired embryo development, reduced live birth rates and increased miscarriage rates in humans. Animal models have suggested that these adverse reproductive effects can be transmitted to the offspring; suggesting that men's health at conception may affect the health of their children. In addition to higher adiposity, male obesity is associated with comorbidities, including metabolic syndrome, hypercholesterolemia, hyperleptinemia and a pro-inflammatory state, all which have independently been linked with male subfertility. Taken together, these findings suggest that the effects of male obesity on fertility are likely multifactorial, with associated comorbidities also influencing sperm, pregnancy and subsequent child health.

Sperm glucose transport and metabolism in diabetic individuals

Individuals with diabetes mellitus (DM) present marked reduction in sperm quality and higher DNA damage in spermatozoa, evidencing that this metabolic disorder impairs male fertility. These effects are related to defective testicular metabolic pathways and signaling, resulting in altered sperm metabolism. Spermatozoa metabolize several substrates to ensure energy supplies and any alteration in this feature compromise sperm quality. For ATP production, spermatozoa require substrate availability and the involvement of specific hexose membrane carriers. DM is known to modulate the spermatozoa substrate consumption and/or production due to altered glycolytic behavior. In fact, glucose uptake and metabolism is highly deregulated in diabetic individuals. Herein, we present an overview of the implications of DM in sperm glucose uptake and metabolism. The understanding of these processes is essential to identify key mechanisms associated with DM-related male (in)fertility. Moreover, it may contribute to the development of therapeutics to counteract the dysfunction induced by DM in sperm metabolism.

Leptin monotherapy rescues spermatogenesis in male Akita type 1 diabetic mice

Type 1 diabetes is associated with subfertility in humans. The current treatment for type 1 diabetes, insulin monotherapy, is suboptimal to fully stabilize glycemia, potentially leading to this subfertility. Recent work has demonstrated that treatment with the energy-regulating hormone leptin, alone or in combination with insulin, can more effectively control glycemia in mouse models of type 1 diabetes. Here, we sought to determine whether the fertility defects in a type 1 diabetic mouse model, the Akita mouse, can be rescued with leptin monotherapy in the absence of any exogenous insulin. Akita homozygous mice treated with leptin alone had a larger total body size, testes, and seminal vesicles than their untreated siblings. Leptin treatment prevented testicular degeneration and rescued sperm motility to wild-type levels. Furthermore, sperm obtained from leptin-treated mice could successfully fertilize ooctyes in vitro. Despite completely rescuing spermatogenesis, the critical reproductive hormones LH and testosterone were only modestly higher than in untreated mice, indicating that a minimum threshold of these hormones must be met to maintain spermatogenesis. Cumulatively, these findings implicate the importance of leptin in maintaining fertility and support the use of leptin therapy in the treatment of type 1 diabetes.

Diabetes-induced oxidative DNA damage alters p53-p21CIP1/Waf1 signaling in the rat testis

Diabetes is increasingly becoming a major cause of large-scale morbidity and mortality. Diabetes-induced oxidative stress alters numerous intracellular signaling pathways. Although testicular dysfunction is a major concern in diabetic men, the mechanistic alterations in the testes that lead to hypogonadism are not yet clear. Oxidative mitochondrial DNA damage, as indicated by 7,8-dihydro-8-oxo-2'-deoxyguanosine, and phosphorylation of p53 at ser315 residue (p-p53ser315) increased in a stage- and cell-specific manner in the testes of rats that were diabetic for 1 month (DM1). Prolongation of diabetes for 3 months (DM3) led to an increase in nuclear oxidative DNA damage in conjunction with a decrease in the expression of p-p53ser315. The nuclei of pachytene and preleptotene spermatocytes, steps 1, 11, and 12 spermatids, secondary spermatocytes and the Sertoli cells, and the meiotic figures showed an increase in the expression of p-p53ser315. An increase in the expression of a downstream target of p53 and protein 21(cyclin-dependent kinase interacting protein 1/wild-type p53-activated factor 1) (p21(CIP1/Waf1)) in both diabetic groups did not show any time-dependent effects but occurred concurrent with an upregulation of p-p53ser315 in DM1 and a downregulation of the protein in DM3. In diabetic groups, the expression of p21(CIP1/Waf1) was mainly cytoplasmic but also perinuclear in pachytene spermatocytes and round spermatids. The cytoplasmic localization of p21(CIP1/Waf1) may be suggestive of an antiapoptotic role for the protein. The perinuclear localization is probably related to the cell cycle arrest meant for DNA damage repair. Diabetes upregulates p21(CIP1/Waf1) signaling in testicular germ cells in association with alteration in p-p53ser315 expression, probably to counteract DNA damage-induced cell death.

Insulinoma presenting with long-standing depression, primary hypogonadism, and sertoli cell only syndrome

The aim was to report an unusual case of insulinoma presenting with long-standing depression and primary testicular failure. We describe a 34-year-old male with clinical, laboratory, and radiologic data consistent with islet cell tumor and seminiferous tubule failure primary hypogonadism. The literature is reviewed relative to the component of this syndrome, and a possible association is discussed. The subject was investigated for a long-standing history of depression requiring medical attention because of mental confusion and slurred speech and was found to have an insulinoma. He was diagnosed with primary gonadal failure and physical examination showed no evidence of dysmorphic features. Chromosomal analysis revealed normal 46 XY and testicular biopsy showed Sertoli cell only syndrome (SCOS). Biochemistry revealed endogenous hyperinsulinism and histology confirmed an islet cell tumor. He remained euglycemic postoperatively and on followup. From this report, we emphasize drawing clinicians' attention to the possibility of an association between insulinoma and primary testicular failure and suggest consideration of this diagnosis in patients with hypergonadotropic hypogonadism who may present with infertility.

Semen analysis: update on clinical value, current needs and future perspectives

At present, evaluation of male reproductive function consists primarily of routine semen analysis, a collection of conventional microscopic assessments ideally performed following the guidelines set by the World Health Organization. While providing some insight into testicular function, these long-performed tests are limited in the information that they impart; more specifically, they are unable to predict true fertility potential. As a consequence, there is a need for the appraisal and consideration of newer semen parameters that may be more indicative of reproductive success. Although various novel assays have been introduced that broaden the scope of information available to both researcher and clinician, the utility of these tests remains limited due to the lack of standardisation of protocols and the absence of clinically established, dependable reference ranges. As such, it is not surprising that most of these parameters and their associated methods remain recommended for ‘research purposes only’. With the burgeoning ‘omics’ revolution, nanotechnology and the development of new analytical instruments, there is now an opportunity for the identification and measurement of previously unknown features that may prove to be more indicative of each sperm's true functional status and capability. Once optimised, simplified, clinically validated and made more readily accessible, these new approaches hold the promise of forming the fulcrum upon which andrological investigations can enter a new era.

Effects of sesame oil on the reproductive parameters of diabetes mellitus-induced male rats

PURPOSE

The purpose of the present study was to investigate the effect of sesame oil on the reproductive parameters of diabetic male Wistar rats.

MATERIALS AND METHODS

The adult male rats in a split plot design were divided into normal (n=10), normal 5% (n=5; 5% sesame oil enriched diet), diabetic (Streptozocin induced diabetes; n=9), diabetic 5% (n=9; 5% sesame oil enriched diet), and diabetic 10% (n=9; 10% sesame oil enriched diet) groups. Diet supplementation continued for 56 days.

RESULTS

Sesame oil supplementation did not reduce the plasma glucose concentration of rats in the diabetic groups (p>0.05). The total spermatogonia, spermatocytes, Leydig cells/tubule, and the germ cell to Sertoli cell ratio were lower in the diabetic rats than the normal ones (p<0.05), and with the exception of spermatogonia counts, these values improved by the addition of sesame oil to the diet (p<0.05). The sperm progressive motility and viability were lower in the diabetic rats (p<0.05) and sesame oil supplementation did not improve them. Incorporation of sesame oil into the diet improved the plasma testosterone concentration of the diabetic rats in a dose-dependent manner (p<0.05).

CONCLUSIONS

In summary, sesame oil supplementation improved the reproductive parameters of diabetic rats at the levels of the testicular microstructure and function, but was not effective in protecting the epididymal sperm.

Dracaena arborea alleviates ultra-structural spermatogenic alterations in streptozotocin-induced diabetic rats

Background

Infertility is a common complication in diabetic men and experimental animals, mainly due to loss of germ cells by apoptotic cell death. The aim of this study was to evaluate the effects of aqueous and ethanol extracts of Dracaena arborea in streptozotocin-induced ultra-structural spermatogenic alterations in Wistar rats.

Methods

Diabetic animals were orally treated with Millipore water (10 ml/kg), sildenafil citrate (1.44 mg/kg) or Dracaena arborea aqueous (500 mg/kg) and ethanol (100 mg/kg) extracts for three weeks. A group of non diabetic rats received Millipore water (10 ml/kg) and served as healthy control group. Blood glucose was monitored at the beginning and the end of the study. One day after the last treatment, animals were sacrificed and the testes immediately removed were morphologically observed and prepared for electron microscopy analysis of spermatogenesis.

Results

Our results showed that Dracaena arborea was devoid of any anti-hyperglycemic activity. In the untreated diabetic rats, hyperglycemia severely damaged the testes morphology as well as the spermatogenic process as evidenced by the: thickness of basement membrane of the seminiferous tubule; mitochondria alteration; abnormal spermatocyte cells displaying polymorphous nuclei, cytoplasmic vacuolization and necrosis; and disorganization and degeneration of sperm germ cells. Administration of sildenafil citrate and Dracaena arborea extracts to the diabetic rats improved testes morphology and reversed, although not completely, the impairment of spermatogenesis; this alleviating effect was more pronounced in animals treated with the aqueous extract (500 mg/kg) of Dracaena arborea.

Conclusion

Dracaena arborea improves testes morphology and restores spermatogenesis in type 1 diabetic rats, without having major anti-hyperglycemic properties. These effects could be attributed to saponins, flavonoids, phenols and sterols revealed in this plant, which could be a useful component in the treatment of diabetes-induced testicular dysfunction.

[The influence of diabetes mellitus on male reproductive function: a poorly investigated aspect of male infertility]

Whilst diabetes mellitus is known to have many systemic complications, male infertility, beyond impotence, retrograde ejaculation and hypogonadism, has not been widely recognised to be one of them. Due to the paucity of studies and inconsistencies regarding the condition's impact on semen quality, few fertility specialists consider the condition noteworthy. As a consequence little information exists as to its prevalence amongst infertile men. Recently the prevailing view has been challenged by findings showing that diabetes induces subtle molecular changes that are important for sperm quality and function. Diabetic men have been found to have a significantly higher percentage of sperm with nuclear DNA damage, a factor known to be associated with compromised fertility and increased miscarriage rates. The mechanism by which this diabetes-related sperm nDNA damage occurs remains unknown. The identification of high levels of advanced glycation end products (AGEs) and their receptor (RAGE) throughout the male reproductive tract coupled to changes in testicular metabolite levels and spermatogenic gene expression suggest that glycation may play an integral role in oxidative stress which in turn causes sperm nDNA damage. As glycation is a normal consequence of life and has been implicated in DNA fragmentation in a variety of seemingly unconnected conditions, it may constitute a common mechanism for the damage seen in sperm DNA.

In situ visualization of damaged DNA in human sperm by Raman microspectroscopy

BACKGROUND

Beyond determining the percentage of damaged sperm, current methods of DNA assessment are of limited clinical utility as they render the sample unusable. We evaluated Raman microspectroscopy, a laser-based non-invasive technique that provides detailed chemical 'fingerprints' of cells and which potentially could be used for nuclear DNA-based sperm selection.

METHODS

Eight healthy donors provided ejaculates. After system optimization, a minimum of 200 air-dried sperm/sample/donor, prior to/and after UVB irradiation, were assessed by two observers. Spectra were analysed by Principal Component, Spectral Angle and Wavelet Analyses.

RESULTS

Spectra provided a chemical map delineating each sperm head region. Principal Component Analysis showed clear separation between spectra from UV-irradiated and untreated samples whilst averaged data identified two regions of interest (1040 and 1400 cm(-1)). Local spectral analysis around the DNA PO(4) backbone peak (1042 cm(-1)), showed that changes in this region were indicative of DNA damage. Wavelet decomposition confirmed both the 1042 cm(-1) shift and a second UVB susceptible region (1400-1600 cm(-1)) corresponding to protein-DNA interactions. No difference was found between observer measurements.

CONCLUSIONS

Raman microspectroscopy can provide accurate and reproducible assessment of sperm DNA structure and the sites and location of damage.

Identification of increased amounts of eppin protein complex components in sperm cells of diabetic and obese individuals by difference gel electrophoresis

Metabolic disorders like diabetes mellitus and obesity may compromise the fertility of men and women. To unveil disease-associated proteomic changes potentially affecting male fertility, the proteomes of sperm cells from type-1 diabetic, type-2 diabetic, non-diabetic obese and clinically healthy individuals were comparatively analyzed by difference gel electrophoresis. The adaptation of a general protein extraction procedure to the solubilization of proteins from sperm cells allowed for the resolution of 3187 fluorescent spots in the difference gel electrophoresis image of the master gel, which contained the entirety of solubilized sperm proteins. Comparison of the pathological and reference proteomes by applying an average abundance ratio setting of 1.6 and a p ≤ 0.05 criterion resulted in the identification of 79 fluorescent spots containing proteins that were present at significantly changed levels in the sperm cells. Biometric evaluation of the fluorescence data followed by mass spectrometric protein identification revealed altered levels of 12, 71, and 13 protein species in the proteomes of the type-1 diabetic, type-2 diabetic, and non-diabetic obese patients, respectively, with considerably enhanced amounts of the same set of one molecular form of semenogelin-1, one form of clusterin, and two forms of lactotransferrin in each group of pathologic samples. Remarkably, β-galactosidase-1-like protein was the only protein that was detected at decreased levels in all three pathologic situations. The former three proteins are part of the eppin (epididymal proteinase inhibitor) protein complex, which is thought to fulfill fertilization-related functions, such as ejaculate sperm protection, motility regulation and gain of competence for acrosome reaction, whereas the putative role of the latter protein to function as a glycosyl hydrolase during sperm maturation remains to be explored at the protein/enzyme level. The strikingly similar differences detected in the three groups of pathological sperm proteomes reflect a disease-associated enhanced formation of predominantly proteolytically modified forms of three eppin protein complex components, possibly as a response to enduring hyperglycemia and enhanced oxidative stress.