Autophagy-related 7 proteindependent autophagy mediates resveratrol-caused upregulation of mitochondrial biogenesis and steroidogenesis in aged Leydig cell

Abstract

Background: Mitochondrial dysfunction may contribute to decreased testosterone synthesis in aged Leydig cells. Resveratrol (RSV) as an antioxidant has been shown to exhibit multiple positive effects on mitochondrion, where steroidogenesis takes place. Whether RSV can improve steroidogenesis in aged testis is still unknown. This study investigates the effect of RSV on testosterone production during aging and corresponding changes in mitochondrial biogenesis and autophagy activity, which are closely associated with steroidogenesis. Whether ATG7, an important autophagy-related protein, functions in RSV-treated aged Leydig cells will also be explored.

Methods and results: Two-month-old male C57BL/6 mice were fed for 16 months by customized regular diet with or without RSV as diet supplement. Leydig cell line TM3 cells were treated with D-galactose to induce senescence, followed with or without RSV treatment. Results found that RSV supplement increased testosterone production in both aged mice and D-galactose-induced senescent Leydig cells. Western blot results revealed that RSV treatment elevated levels of steroidogenic rate-limiting enzymes StAR and 3β-HSD, as well as autophagy-related proteins LC3II, Beclin1, ATG5 and ATG7 and mitochondrial function-related proteins mtTFA and COXIV. However, after Atg7 was knocked down in senescent Leydig cells, even though RSV was added, levels of these proteins declined significantly, accompanied by decreased levels of mitochondrial transcript factors PGC-1α, mtTFA and NRF-1 and more fragmented mitochondria, demonstrating that Atg7 knockdown wrecked the protective effects of RSV on steroidogenesis in senescent Leydig cells.

Conclusion: ATG7-dependent autophagy plays a key role in RSV-brought testosterone production increase through regulating mitochondrial biogenesis in senescent Leydig cells.

Keywords: Aging; Autophagy; Mitochondrial biogenesis; Resveratrol; Steroidogenesis.