Effect of insulin on functional parameters of human cryopreserved sperms

Leptin and prolactin reduce cryodamage in normozoospermic human semen samples during cryopreservation

OBJECTIVES

Cryopreservation has destructive effects on the function and structure of spermatozoa. It is known that leptin and prolactin play an active role in decreasing the rates of reactive oxygen species and DNA fragmentation, as well as enhancing sperm motility. Hence, this experiment aimed to investigate the effects of leptin and prolactin as pro-survival factors on the normozoospermic human semen samples during cryopreservation.

MATERIAL AND METHODS

Semen samples were collected from 15 healthy, fertile men ranging from 25 to 40 years. Cryopreservation of the samples was performed in liquid nitrogen over a period of two weeks, using five varying concentrations of leptin/prolactin, 0, 10, 100, 500, and 1000ng/ml respectively. Sperm motility, total caspase activity, and mitochondrial and cytosolic ROS were measured by flowcytometry, TUNEL, and other appropriate tests after thawing of the samples.

RESULTS

Both hormones were observed to have positive effects on the motility of the samples post-cryopreservation, the highest improvement being in the 100ng/ml concentration leptin and prolactin in comparison to the control group (P=0.01 and P=0.041, respectively). A significant reduction of mitochondrial ROS was also observed in 100 and 1000ng/ml of leptin (P=0.042), and there was a considerable decrease in the cytosolic ROS in the 100ng/ml of prolactin in comparison to the control group (P=0.048). Total caspase activity was also highly reduced in the 100, 500, and 1000ng/ml of leptin compared to the control group (P=0.039). Interestingly, both hormones also significantly decreased DNA fragmentation in 1000ng/ml compared to the control group (P=0.042).

CONCLUSION

It can be concluded that leptin and prolactin act as protective agents against cryodamage to spermatozoa during cryopreservation.

Effect of autologous platelet-rich plasma on human sperm quality during cryopreservation

As a source of growth factors, platelet-rich plasma (PRP) has been widely used in the repair of various injuries due to its cytoprotective properties in regenerative medicine. The objective of the present study was to investigate the effect of autologous PRP supplementation on the quality of frozen-thawed human sperm. Twelve normozoospermic semen samples were collected, and each sample was divided into 4 aliquots and added with different proportions of PRP (0%, 2%, 5%, and 10%) separately, followed by cryopreservation. Sperm motility, viability, membrane integrity, DNA fragmentation index (DFI), reactive oxygen species (ROS) levels and mitochondrial membrane potential were measured and analyzed. The results showed that the addition of 5% PRP improved sperm progressive motility (30.3 ± 2.7 VS. 28.1 ± 2.6), viability (65.5 ± 4.2 VS. 59.6 ± 3.9), and membrane integrity (52.4 ± 3.6 VS. 49.2 ± 3.4) after cryopreservation (P < 0.05). Slight attenuation of ROS generation, restoration of mitochondrial membrane potential and reduction of DNA fragments were also observed in post-thawed sperm supplemented with PRP, but there was no significant (P > 0.05). In conclusion, autologous PRP has a partial protective effect on cryopreservation of human spermatozoa, and the combined application with other high-efficiency cryoprotectant is worthy of further study.

A closer look at the role of insulin for the regulation of male reproductive function

While insulin demonstrates to have a considerable influence on the reproductive system, there are various unanswered questions regarding its precise sites, mechanisms of action, and roles for the developing and functioning of the adult male reproductive system. Apart from its effects on glucose level, insulin has an important role in the reproductive system directly by binding on insulin and IGF receptors in the brain and testis. To date, however, the effect of insulin or its alterations on blood-testis-barrier, as an important regulator of normal spermatogenesis and fertility, has not yet been studied. This review aimed to focus on the experimental and clinical studies to describe mechanisms by which insulin affects the hypothalamic-pituitary-gonadal (HPG) axis, testicular cells, spermatozoa, and sexual behavior. Moreover, we discussed the mechanism and impact of insulin changes in type 1 (insulin deficiency along with persisted or even increased sensitivity) and 2 (insulin resistance along with increased insulin level at the early stages of disease) diabetes and obesity on the male reproductive tract.

Expression of RXFP2 receptor on human spermatozoa and the anti-apoptotic and antioxidant effects of insulin-like factor 3

Insulin-like factor 3 (INSL3) has an important role in the human reproductive system; however, its detailed function is still mysterious. We aimed to investigate the possibility of expression of RXFP2 receptor on human spermatozoa and to determine the anti-apoptotic and antioxidant mechanism derived the binding of INSL3 and RXFP2. In this experimental study, the expression/location of the RXFP2 receptor was determined on the spermatozoa of fertile and infertile men. Twenty samples from 20 fertile men were collected and divided into 6 parts (control group, and five groups treated with INSL3 10, 100, 250, 500, 1,000 ng/ml). DNA damage, active caspase, reactive oxygen species (ROS) and sperm parameters were evaluated by TUNEL, flow cytometry, optical microscope and computer-assisted sperm analysis. The expression of RXFP2 was confirmed by Western blot. Immunocytochemistry illustrated that this receptor is expressed in the posterior half of the spermatozoa's head. The INSL3 at concentrations of 500 and 1,000 ng/ml reduced the active caspase and mitochondrial ROS, and also reduced DNA fragmentation at 1,000 ng/ml. Besides, INSL3 500 and 1,000 ng/ml significantly increased the sperm motility. This study confirmed the presence of RXFP2 receptor in fertile and infertile men's spermatozoa, indicating the highly dose-dependent efficacy of the INSL3, which may have promising impacts on the in-vitro fertilisation outcomes.

Plasma estradiol-17β, cortisol, and insulin concentrations and serum biochemical parameters surrounding puberty in Japanese Black beef bulls with normal and abnormal semen

The associations of semen abnormalities with circulating hormones (estrogens, glucocorticoid, insulin) and common biochemical parameters are unclear in beef bulls. We compared plasma concentrations of estradiol-17β, cortisol, and insulin and serum biochemical parameters surrounding puberty in Japanese Black beef bulls (n = 96) with normal post-thaw or abnormal semen (fresh and frozen). Blood samples were collected monthly from 4 to 24 months of age (n = 50) for the assays of plasma estradiol, cortisol, and insulin and every 3 months from 6 to 21 months of age (n = 92) for the serum biochemical analyses. Semen was collected weekly from 12 months until at least 18 months of age. Fresh semen was evaluated for semen volume, sperm progressive motility, concentrations, and morphological defects. The normal fresh semen was frozen by a standard method and examined for post-thaw sperm motility and fertility, which were evaluated for rates of transferable embryos. Bulls were classified as having either normal fresh semen or abnormal fresh semen (when at least one of the above test items was abnormal for 6 months). The normal fresh semen was categorized as having either normal post-thaw semen or low fertility post-thaw semen. The abnormal fresh semen was categorized as having sperm morphological defects, low motility, or morphological defects plus low motility. Plasma cortisol concentrations in the abnormal fresh semen group were higher than those of the normal fresh semen group (p < 0.0001). Plasma estradiol-17β and insulin concentrations in the low-fertility post-thaw semen group were lower than those of the normal post-thaw semen group (p < 0.0001). Serum aspartate aminotransferase and magnesium concentrations were greater for the abnormal fresh semen group vs. the normal fresh semen group (p < 0.005). These results suggest that fresh semen abnormality in pubertal beef bulls might be associated with increased circulating aspartate aminotransferase, magnesium and cortisol. Low-fertility post-thaw semen could have been involved with the lower peripheral estradiol and insulin levels in beef bulls.

Inclusion of ovine enriched serum with vitamin E and polyunsaturated fatty acids in the freezing medium: a new strategy to improve human frozen-thawed sperm parameters

The objective was to evaluate the effect of inclusion of 2.5% and 5% ovine serum, enriched with vitamin E (Vit E) and fish oil (FO), in human sperm freezing medium. Serum samples were prepared from sixteen rams (n = 4) feeding on a without supplemented diet, and diets supplemented with Vit E, FO and Vit E + FO. Semen samples, from 60 normozoospermic men, were frozen in: (I) a commercial freezing medium (SpermFreeze™; control medium), (II) the commercial freezing medium containing foetal bovine serum, (III) the commercial freezing medium + nonenriched serum (serum group), (IV) the commercial freezing medium + Vit E enriched serum (Vit E group), (V) the commercial freezing medium + FO enriched serum (FO group) and (VI) the commercial freezing medium + Vit E + FO enriched serum (Vit E + FO group). Sperm total and progressive motility, morphology, viability and plasma membrane integrity were significantly higher (p ≤ .05) in Vit E and Vit E + FO groups compared with the control group. Mitochondrial membrane potential did not differ between treatments (p > .05). It was concluded that ovine serum enriched with vitamin E and vitamin E + FO improved the quality of human spermatozoa but enriched serum containing FO could not improve the sperm cryo-injuries.