Aquaporin 9 regulates Leydig cell steroidogenesis in diabetes

Diabetes mellitus induced hyperglycemia increases oxidative stress, which contributes to impairment of male reproductive function. Aquaporins (AQPs) belong to a transmembrane protein superfamily containing 13 isoforms (AQP0-12), differentially expressed in various organs, and play a pivotal role in male reproductive function. In the current study, we investigated the relationship between AQPs and testicular steroidogenesis under hyperglycemia in vivo and in vitro. The effect of high glucose on the role of AQPs in Leydig cell steroidogenesis was analyzed in diabetic rats (in-vivo) and LC540 rat Leydig cells (in vitro) via enzyme assays, quantitative RT-PCR, siRNA knock down and western blotting. AQP 9 was significantly up-regulated in STZ-induced diabetic rat testis and high glucose treated LC540 cells. Further, oxidative stress marker nuclear factor erythroid 2-related factor 2 (Nrf2) expression was decreased with impaired testicular steroidogenesis under hyperglycemia. Knock-down of AQP 9 resulted in increased Nrf2 expression and thus increased testicular steroidogenesis in hyperglycemia. Diabetes-associated hyperglycemia induced oxidative stress is a widely proven cause for diabetes-related male infertility. Our results collectively suggest that AQP 9 impairs testicular steroidogenesis via the regulation of oxidative stress in diabetes.