Endocrine Abstracts

Introduction: Mitochondrial uncoupling proteins (UCPs) are channel proteins present in the mitochondrial inner membrane which are responsible for the transport of protons between the mitochondrial intermembrane space and the matrix. Currently, six UCP homologues had been identified (UCP1-6). UCPs are major regulators of reactive oxygen species (ROS) production, general cellular redox state and metabolism. UCPs also exhibit specific functions, such as UCP1 and thermogenesis or UCP2 and regulation of insulin secretion in beta-pancreatic cells. Altered expression and function of UCPs have been linked with the onset of metabolic diseases, including obesity and diabetes mellitus and increased oxidative stress. Male infertility is an overlooked comorbidity related to metabolic diseases since the testis is susceptible to metabolic alterations and increased oxidative stress. However, the expression and function of UCPs in the human testis remain unknown.

Aim of the study: The main objective of this study was to identify the expression of the different UCPs homologues in human Sertoli cells (hSCs). In addition, the function of UCPs on the mitochondrial activity and metabolism of hSCs was analysed through its inhibition by genipin, a specific UCP inhibitor.

Matherials and methods: Primary cultures of human Sertoli cells from healthy men with conserved spermatogenesis were established (n=6). Total RNA was extracted and all UCP homologues (UCP1-6) mRNA expression was analysed by RT-PCR. UCP1-3 were detected by immunofluorescence. Then, UCPs were inhibited in hSCs by genipin, a specific UCP inhibitor, (0.5, 5, 50, and 100 µM). Cellular viability, proliferation, and ROS production were accessed after 24 h treatment. Mitochondria function was accessed by Seahorse XF Cell Mito Stress assay. Culture media were collected and analysed by ¹H-NMR.

Results: We were able to identify all UCPs homologues (UCP1-6) in hSCs. The inhibition of UCPs by high concentrations of genipin decreased hSCs proliferation but no cytotoxicity was observed. In addition, UCP inhibition by genipin decreased mitochondrial activity in a dose-dependent manner. Interestingly, no increased ROS production was observed.

Conclusion: We were able to identify, to the best of our knowledge, for the first time the expression of UCPs (UCP1-6) in hSCs. UCPs can regulate the mitochondrial activity and metabolism of hSCs. Our results suggest that UCPs dysfunction could play a central role in the crosstalk between metabolic disorders, high oxidative stress and male infertility.