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

Comparative Study of the Restoring Effect of Metformin, Gonadotropin, and Allosteric Agonist of Luteinizing Hormone Receptor on Spermatogenesis in Male Rats with Streptozotocin-Induced Type 2 Diabetes Mellitus

We compared the effectiveness of human chorionic gonadotropin (hCG; 5 days, 20 IU/rat/day), allosteric luteinizing hormone receptor agonist TP04 (5 days, 20 mg/kg/day), and metformin (28 days, 120 mg/kg/day) in restoring spermatogenesis in male rats with type 2 diabetes mellitus. hCG and TP04 increased the levels of testosterone and expression of the steroidogenic protein StAR, the number of spermatogenic cells, thickness of the seminal epithelium, and the number and motility of mature sperm that were reduced in diabetic rats, though they did not reduce the number of defective spermatozoa. Metformin had a weak effect on steroidogenesis, but was not inferior to luteinizing hormone receptor agonist by its restorative effect on spermatogenesis and also reduced the number of defective forms of spermatozoa. Thus, the spermatogenesis-restoring effect of metformin and luteinizing hormone receptor agonist in type 2 diabetes mellitus are comparable, despite different mechanisms of action.

The impact of diabetes mellitus type 1 on male fertility: Systematic review and meta-analysis

BACKGROUND

Some evidence suggests that diabetes mellitus type 1 (DM1) could affect male fertility, gonadal axis, semen parameters, and spermatogenesis because of effects of hyperglycemia and insulin deficiency. Anyhow, the exact impact of DM1 on male fertility is unclear.

OBJECTIVES

To review the studies evaluating paternity rate, male gonadal axis, and semen parameters in men with DM1.

MATERIALS AND METHODS

A review of relevant literature from January 1980 to December 2020 was performed. Only studies published in English reporting data on fatherhood (rate of children by natural fertility), hormonal and seminal parameters were included. Out of 14 retrieved articles, the eight studies evaluating semen parameters were meta-analyzed.

RESULTS

The rate of children (four studies) was lower than controls among men affected by DM1, especially in men with a longer duration of disease. The data of gonadal hormonal profile in DM1 men (six studies) are very heterogeneous and a neutral effect of DM1 or a condition of subclinical hypogonadism could not be concluded. Meta-analysis showed that men with DM1 (n = 380), compared with controls (n = 434), have significantly lower normal sperm morphology [-0.36% (-0.66; -0.06), p < 0.05, six studies] and sperm progressive motility [33.62% (-39.13; -28.11), p < 0.001, two studies] and a trend toward a lower seminal volume [-0.51 (-1.03; 0.02), p = 0.06, eight studies], without difference in total sperm count and concentration. Data on scrotal ultrasound and sperm DNA fragmentation are too few. No study evaluated other factors of male infertility, such as transrectal ultrasound, semen infections, sperm auto-antibodies, and retrograde ejaculation.

DISCUSSION

DM1 might impair male fertility and testis functions (endocrine, spermatogenesis), but definition of its actual impact needs further studies.

CONCLUSION

Men with DM1 should be evaluated with a complete hormonal, seminal, and ultrasound workup to better define their fertility potential and need for follow up of testis functions.

MicroRNA regulation of the proliferation and apoptosis of Leydig cells in diabetes

BACKGROUND

The number of patients with diabetes is increasing worldwide. Diabetic testicular damage can cause spermiogenesis disorders and sexual dysfunction. We thus explored the role of miRNAs in diabetic testicular damage, and revealed that they could serve as effective prevention and treatment therapeutic targets.

METHODS

Streptozotocin (STZ) was used to generate a rat model of type 2 diabetes. Rat testicular tissues were used for miRNA and mRNA sequencing. Through bioinformatics analysis, we constructed an miRNA-mRNA diabetic testicular damage regulatory network and screened for key miRNAs. We also used Leydig cells to generate a diabetic cell model and detected the downstream target genes of miRNAs, secretion of testosterone, and proliferation and apoptotic levels to elucidate the role and mechanism of the selected miRNAs in diabetic testicular damage.

RESULTS

Using second-generation sequencing, we identified 19 differentially expressed miRNAs and 555 mRNAs in the testes of diabetic rats. Based on computational prediction of targets and negative regulation relationships, we constructed a miRNA-mRNA regulatory network, including 12 miRNAs and 215 mRNAs. KEGG enrichment analysis revealed that genes were more concentrated on the survival signalling pathway. Based on this, we screened 2 key miRNAs, miR-504 and miR-935. In vitro, glucose could induce an increase in miR-504 and miR-935, whereas a decrease in MEK5 and MEF2C in a dose-dependent manner. Overexpression of miR-504 and miR-935 led to the decreased expression of MEK5 and MEF2C, decreased proliferation rate of Leydig cells, increased apoptotic rate, and decreased secretion of testosterone. Whereas, knockdown of miR-504 and miR-935 displayed opposite tendencies.

CONCLUSIONS

miRNAs play important roles in diabetic testicular damage. miR-504 and miR-935 might regulate testicular damage through the classic survival pathway of MEK5-ERK5-MEF2C. Targeted inhibition of miR-504 and miR-935 could reverse the high-glucose-induced testicular complications, thus posing as a potential therapeutic approach in diabetic testicular injury.

RNA N6-methyladenosine modification, spermatogenesis, and human male infertility

RNA N6-methyladenosine (m6A) modification is one of the main forms of posttranscriptional modification, and its dysregulation is involved in a series of pathological processes. RNA m6A regulators, which mediate dynamic RNA m6A modification, are expressed in almost all types of testicular cells, including spermatogenetic cells and somatic cells. Cumulative studies have found that knockout of RNA m6A regulators in the testis leads to abnormal metabolism of the target mRNAs, which eventually causes spermatogenetic disorders and infertility. To date, a role for dysregulated RNA m6A modification in human male infertility remains elusive; however, dysregulated expression of RNA m6A regulators in abnormal human semen samples, including oligospermia, asthenozoospermia and azoospermia, has been found. Therefore, we speculate that abnormal RNA m6A methylation may be an important mechanism of male infertility. In this review, we summarize the recent findings regarding the spatiotemporal expression of RNA m6A regulators in the testes, mechanisms of RNA m6A modification in spermatogenesis and the relation between dysregulated RNA m6A regulators and human male infertility. In addition, we also discuss future directions in studying the molecular mechanism of male infertility and exploring their clinical applications from the viewpoint of RNA m6A modification.

Dietary Antioxidants in the Treatment of Male Infertility: Counteracting Oxidative Stress

Infertility affects about 15% of the population and male factors only are responsible for ~25-30% of cases of infertility. Currently, the etiology of suboptimal semen quality is poorly understood, and many environmental and genetic factors, including oxidative stress, have been implicated. Oxidative stress is an imbalance between the production of free radicals, or reactive oxygen species (ROS), and the capacity of the body to counteract their harmful effects through neutralization by antioxidants. The purpose of this review, by employing the joint expertise of international researchers specialized in nutrition and male fertility areas, is to update the knowledge about the reproductive consequences of excessive ROS concentrations and oxidative stress on the semen quality and Assisted Reproduction Techniques (ART) clinical outcomes, to discuss the role of antioxidants in fertility outcomes, and finally to discuss why foods and dietary patterns are more innocuous long term solution for ameliorating oxidative stress and therefore semen quality results and ART fertility outcomes. Since this is a narrative review and not a systematic/meta-analysis, the summarized information in the present study should be considered cautiously.

Impact of diabetic hyperglycaemia and insulin therapy on autophagy and impairment in rat epididymis

Blood glucose dysregulation and hyperglycaemia caused by diabetes mellitus are intimately associated with male infertility. Two-month-old Sprague-Dawley rats were given a single dose of streptozotocin (55 mg/kg) by intraperitoneal injection to induce type I diabetes mellitus (DM group). The treatment group was given 1 unit/day of insulin for 16 weeks (INS group). The normal control group (NC group) was given food ad libitum. In the DM group, the histological analysis of caput and cauda epididymal ducts showed broken stereocilia and more lipid vacuolisations in the principal cells. The interstitial hyperplasia and inflammatory cell infiltration were observed in epididymal tissues. Transmission electron microscopy observation showed that the principal cells in the DM group contained more vacuoles, partly lost stereocilia, and swollen mitochondria. The autophagosomes were observed as well. Western blotting results of LC3II/I and P62 protein expression indicated that autophagy was downregulated in the DM group. The total antioxidant activity and GPx5 expression of epididymal tissues were also decreased. In the INS group, significant improvements were observed in epididymal tissues. Our study suggests that diabetic hyperglycaemia causes autophagy dysregulation in epididymal tissues, which may play a role in diabetes-induced rat epididymal injury. Insulin treatment is beneficial for diabetic-associated epididymal dysfunction.

The effect of metformin treatment on the basal and gonadotropin-stimulated steroidogenesis in male rats with type 2 diabetes mellitus

Type 2 diabetes mellitus impairs reproductive functions in men, and important tasks are deciphering the mechanisms of testicular dysfunctions in diabetes and the search of effective approaches to their correction. The purpose was to study the effect of four-week metformin treatment (120 mg kg^-1  day^-1 ) of male Wistar rats with high-fat diet/low-dose streptozotocin-induced type 2 diabetes on basal and gonadotropin-stimulated steroidogenesis, intratesticular content of leptin and the leptin and luteinising hormone receptors and on spermatogenesis. Diabetic rats had hyperleptinaemia, androgen deficiency and reduced sperm count and quality, and in the testes, they had the increased leptin level and the decreased content of the leptin and luteinising hormone receptors and 17-hydroxyprogesterone. The stimulating effects of chorionic gonadotropin on testosterone production and expression of steroidogenic genes (Star, Cyp11a1) were decreased. Metformin restored basal and gonadotropin-stimulated blood testosterone levels. In the testes, it restored gonadotropin-stimulated 17-hydroxyprogesterone, androstenedione and testosterone levels, Star expression and the content of leptin and the leptin and luteinising hormone receptors. Metformin also improved epididymal sperm count and morphology. We concluded that metformin treatment normalises the testicular steroidogenesis in diabetic rats, which is due to restoration of the gonadotropin and leptin systems in the testes and is associated with an improvement in spermatogenesis.

Sperm parameters, DNA integrity, and protamine expression in patients with type II diabetes mellitus

Diabetes Mellitus (DM) is the most common endocrine disorder affecting many human physiological systems and tissues, including the reproductive organs in men. The age of individuals suffering from this disease has been falling rapidly in recent years. This study compared the effect of DM on sperm parameters, chromatin quality, and apoptosis, as well as the expression profile of protamine genes in men with and without DM using molecular and cytochemical assays. Sixty semen samples from the control group (N = 30) and case group (N = 30) were collected. There was a significant decrease in the percentages of sperm parameters in cases versus the controls (p˂0.05). Despite significantly higher percentages detected in spermatozoa with AB⁺, CMA3⁺, and TUNEL⁺, no change was demonstrated regarding protamines mRNA levels, as well as the P1/P2 ratios in cases in comparison with controls. In contrast, significant positive correlations were found between the quantity of P1 and P2 transcripts (r = 0.944, p < .001). The data indicated that DM not only caused a decrease in the quality of sperm parameters but also affected the sperm maturation process by increasing the substantial implications in the sperm DNA/chromatin levels of DM patients.IMPACT STATEMENTWhat is already known on this subject? Diabetes Mellitus (DM) is a chronic metabolic disorder affecting many human physiological systems and tissues, including the reproductive organs in men. The age of individuals suffering from this disease has been falling rapidly in recent years.What do the results of this study add? We found that DM not only caused a decrease in the quality of the sperm parameters, including motility and concentration, and an increase in morphological abnormalities but also affected the sperm maturation process by increasing the substantial implications in sperm DNA/chromatin levels of DM patients. Despite there being no significant difference in the mRNA levels of protamines between the two groups, our findings showed a positive correlation between the mRNA levels of P1 and progressive sperm motility.What are the implications of these findings for clinical practice and/or further research? Based on the results of this study, chromatin and DNA assessments can have important implications for increasing fertility, as complementary tests, in combination with routine laboratory tests. Since sperm standard parameters are not capable of examining the condition of the sperm nucleus, men with abnormal sperm DNA can also have normal spermatogram, and diabetes is prevalent in reproductive age.