Cardiac-derived CTRP9 mediates the protection of empagliflozin against diabetes-induced male subfertility in mice

Previous studies have shown beneficial effects of empagliflozin (Empa), a selective inhibitor of the sodium-glucose cotransporter 2 (SGLT2), on diabetes and cardiovascular outcomes in patients with diabetes. However, whether Empa could ameliorate diabetes mellitus (DM)-induced male spermatogenesis dysfunction remains unclear. Our study aimed to investigate the effect of Empa in the development of DM-induced male spermatogenesis dysfunction and to reveal the molecular mechanisms. DM mice were orally treated with Empa to investigate the effects of Empa on DM-induced male mice spermatogenesis dysfunction. We employed a cardiac-specific C1q/tumor necrosis factor-related protein 9 (CTRP9)-deficient mouse model and a cardiac-specific CTRP9 overexpression mouse model to investigate its role in the protection of Empa against diabetes-induced male subfertility. We found that Empa treatment could improve DM-induced male mice subfertility. Interestingly, we discovered that cardiac-derived CTRP9 was decreased in DM mice and this decrease was prevented by Empa treatment. A CTRP9 blocking antibody or cardiac-specific depletion of CTRP9 abolished the protection of Empa on DM-induced male subfertility. Cardiac-specific CTRP9 overexpression ameliorated DM-induced male subfertility. Mechanistically, we identified that cardiac-derived CTRP9 increased steroidogenesis in mice with diabetes in a PKA-dependent manner. We also provided direct evidence that activation of AMP activated protein kinase α (AMPKα)/nuclear factor (erythroid-derived 2)-like 2 (Nrf2) signalling pathway by CTRP9 was responsible for the attenuation of ferroptosis in Leydig cells. In conclusions, we supposed that Empa was a potential therapeutic agent against DM-induced male mice spermatogenesis dysfunction.