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.

Glycolysis as key regulatory step in FSH-induced rat Sertoli cell proliferation: Role of the mTORC1 pathway.

The definitive number of Sertoli cells (SCs), achieved during the proliferative periods, defines the spermatogenic capacity in adulthood. It is recognized that FSH is the main mitogen targeting SC and that it exerts its action, at least partly, through the activation of the PI3K/Akt/mTORC1 pathway. mTORC1 controls a large number of cellular functions, including glycolysis and cell proliferation. Interestingly, recent evidence revealed that the glycolytic flux might modulate mTORC1 activity and, consequently, cell cycle progression. Although mature SC metabolism has been thoroughly studied, several aspects of metabolism regulation in proliferating SC are still to be elucidated. The objective of this study was to explore whether aerobic glycolysis is regulated by FSH through mTORC1 pathway in proliferating SC, and to assess the involvement of glycolysis in the regulation of SC proliferation. The present study was carried out utilizing 8-day-old rat SC cultures. The results obtained show that FSH enhances glycolytic flux through the induction of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3) and lactate dehydrogenase A (LDHA) in an mTORC1 dependent manner. In addition, PFKFB3 and LDH inhibitors prevent FSH from activating mTORC1 and stimulating SC proliferation and glycolysis, presumably through mTORC1 pathway inhibition. In summary, FSH simultaneously regulates SC proliferation and glycolysis in an mTORC1 dependent manner, and glycolysis seems to cooperate with FSH in the stimulation of both cellular functions through the modulation of the same signalling pathway. Therefore, a positive feedback between the mTORC1 pathway and glycolysis triggered by FSH is hypothesized.

Low Doses of Glyphosate/Roundup Alter Blood-Testis Barrier Integrity in Juvenile Rats.

It has been postulated that glyphosate (G) or its commercial formulation Roundup (R) might lead to male fertility impairment. In this study, we investigated the possible effects of G or R treatment of juvenile male rats on blood-testis barrier function and on adult male sperm production. Pups were randomly assigned to the following groups: control group (C), receiving water; G2 and G50 groups, receiving 2 and 50 mg/kg/day G respectively; and R2 and R50 groups receiving 2 and 50 mg/kg/day R respectively. Treatments were performed orally from postnatal day (PND) 14 to 30, period of life that is essential to complete a functional blood-testis barrier. Evaluation was done on PND 31. No differences in body and testis weight were observed between groups. Testis histological analysis showed disorganized seminiferous epithelium, with apparent low cellular adhesion in treated animals. Blood-testis barrier permeability to a biotin tracer was examined. A significant increase in permeable tubules was observed in treated groups. To evaluate possible mechanisms that could explain the effects on blood-testis barrier permeability, intratesticular testosterone levels, androgen receptor expression, thiobarbituric acid reactive substances (TBARS) and the expression of intercellular junction proteins (claudin11, occludin, ZO-1, connexin43, 46, and 50 which are components of the blood-testis barrier) were examined. No modifications in the above-mentioned parameters were detected. To evaluate whether juvenile exposure to G and R could have consequences during adulthood, a set of animals of the R50 group was allowed to grow up until PND 90. Histological analysis showed that control and R50 groups had normal cellular associations and complete spermatogenesis. Also, blood-testis barrier function was recovered and testicular weight, daily sperm production, and epididymal sperm motility and morphology did not seem to be modified by juvenile treatment. In conclusion, the results presented herein show that continuous exposure to low doses of G or R alters blood-testis barrier permeability in juvenile rats. However, considering that adult animals treated during the juvenile stage showed no differences in daily sperm production compared with control animals, it is feasible to think that blood-testis barrier impairment is a reversible phenomenon. More studies are needed to determine possible damage in the reproductive function of human juvenile populations exposed to low doses of G or R.

In vitro effects of glyphosate and Roundup on Sertoli cell physiology.

Roundup (R), a formulation that contains glyphosate (G) as the active ingredient, is a commonly used nonselective herbicide that has been proposed to affect male fertility. It is well known that an adequate Sertoli cell function is essential to maintain germ cell development. The aim of the present study was to analyze whether G and R are able to affect Sertoli cell functions, such as energy metabolism and blood-testis barrier (BTB) integrity. Sertoli cell cultures from 20-day-old rats were exposed to 10 and 100 ppm of G or R, doses which do not decrease cell viability. Neither G nor R caused impairment in lactate production or fatty acid oxidation. G and R decreased Transepithelial Electrical Resistance, which indicates the establishment of a Sertoli cell junction barrier. However, neither G nor R modified the expression of claudin11, ZO1 and occludin, proteins that constitute the BTB. Analysis of cellular distribution of claudin11 by immunofluorescence showed that G and R induced a delocalization of the signal from membrane to the cytoplasm. The results suggest that G and R could alter an important function of Sertoli cell such as BTB integrity and thus they could compromise the normal development of spermatogenesis.