Mechanistic insights into targeting APLN/APJ for ameliorating testosterone deficiency and reproductive disorders in diabetic mice

Type 2 diabetes mellitus (T2DM) is frequently associated with testosterone deficiency, which affects male reproductive function. Currently, exogenous testosterone replacement therapy poses inherent risks, underscoring the need to develop safer and more effective treatment strategies. This study aimed to elucidate the mechanism by which ML221, a potent apelin receptor (APJ) functional antagonist, promotes testosterone secretion, and alleviates reproductive dysfunction. Diabetic mouse models demonstrated reduced testosterone levels, impaired spermatogenesis, and low sperm quality. Elevated APLN expression impaired Leydig cell function and testosterone synthesis. Treatment with ML221 restored testosterone levels and spermatogenesis in diabetic mice. Mechanistically, ML221 regulated Leydig cell metabolism by elevating S-D-lactoylglutathione levels, reducing mitochondrial reactive oxygen species, preserving mitochondrial membrane potential, and enhancing adenosine triphosphate production. At the epigenetic level, ML221 enhanced the binding of nuclear receptor subfamily 2 group F member 2 to the promoters of testosterone-synthesizing genes, thereby facilitating testosterone biosynthesis. These findings advance the understanding of the male reproductive system in the context of diabetes and highlight ML221 as a potential therapeutic approach for T2DM-induced testosterone deficiency.