Neonatal exposure to metformin: effects on rat Sertoli cell proliferation

Abstract

Sertoli cell (SC) proliferation, a factor defining SC population size, occurs during a restricted period of time. In rats, fetal and postnatal periods up to 15 days of age constitute the time period for SC mitosis. Metformin (MET), a first line anti-hyperglycemic agent, has started to be used in pediatric population at ages when SCs are still proliferating. In addition to its strong anti-diabetic properties, numerous studies have demonstrated that MET has anti-proliferative activity. Additionally, we have previously demonstrated in SC cultures obtained from 8-day old rats that MET decreases basal and FSH-stimulated SC proliferation. The aim of this study was to analyze the in vivo relevance of MET treatment on SC proliferation. At postnatal day 3 (Pnd3), rat pups were randomly assigned to the following groups: MET (receiving daily 200 mg/kg MET i.p., day 3-7) and control group (receiving daily sterile saline solution i.p.). At Pnd8, a set of animals were injected with BrdU (50 mg/kg i.p.) before sacrifice to evaluate cell proliferation. In another set of animals, testes were utilized to perform SC isolation for gene expression analysis. Our results showed that MET group exhibited a significant decrease in BrdU incorporation in SC compared to controls (n=6 p<0.05). In addition, MET group showed a reduction in Cyclin D1 and E2 and an increase in p21Cip mRNA levels in isolated SC (n=6 p<0.05). Considering that a single SC can support a limited number of germ cells, we studied the impact of neonatal treatment with MET on sperm parameters in adult animals. Epididymal sperm parameters were evaluated at Pnd90. No differences in sperm motility, morphology or number between groups were observed. Thus, our results showed that MET exerted a mild but significant suppressive effect on Sertoli cell proliferation with no further impact on spermatogenesis and epididymal maturation. (PICT2015-0228).