PACAP ameliorates the fertility of obese mice through PAC1/PKA/ERK/Nrf2 signal axis

Obesity is strongly linked to male infertility. Apoptotic inflammatory response caused by oxidative stress in testicular spermatogenic cells is one of the important causes of obesity-related male infertility. As bioactive peptide is secreted by the pituitary gland, pituitary adenylate cyclase activating polypeptide (PACAP) has a powerful triple role of anti-oxidation, anti-apoptosis, and anti-inflammation, and it is involved in the male reproduction regulation, but the specific mechanism remains unknown. The purpose of this study is to explore the role of PACAP in obesity-related male infertility. In cellular level experiments, mouse spermatocytes (GC-2) were treated with palmitate (PA) to establish an high-fat injury cell model in vitro and then treated with PACAP. In animal-level experiments, C57BL/6 male mice were fed with a high-fat diet (HFD) to induce obesity and subsequently treated with PACAP. The cell mechanism studies show that PACAP selectively binded to the PAC1 receptor to attenuate palmitic acid-induced mouse spermatogenic cell (GC-2) oxidative damage and apoptotic inflammatory response via the PKA/ERK/Nrf2 signaling axis. However, this mechanism was inhibited in GC-2 cells inhibiting the activity of Nrf2. The animal experiment studies show that PACAP treatment ameliorated obesity characteristics, including body weight, epididymal adipose weight, testes/body weight, serum lipids levels, and reproductive hormone levels in vivo. Additionally, PACAP was shown to improve the reproductive function of the obese mice, which was characterized by improved testis morphology and sperm parameters via Keap1/Nrf2/ARE pathway. These beneficial effects of PACAP were abolished in obese mice with testes-specific knockdown of Nrf2. Our data suggested that PACAP could ameliorate fertility in obese male mice and may be a promising candidate drug for obesity-induced male infertility.