Berberine alters the gut microbiota metabolism and impairs spermatogenesis

• Berberine (BBR) disrupts male reproductive function by reducing serum testosterone, sperm concentration, mating rate, and fecundity in mice. • The gut microbiota, specifically Muribaculaceae, is essential for spermatogenesis; BBR-induced reduction in Muribaculaceae abundance is a primary cause of impaired spermatogenesis. • Muribaculaceae regulates ornithine metabolism, which in turn modulates LDLR-mediated testosterone synthesis in Leydig cells. • Fecal microbiota transplantation or Muribaculaceae supplementation may offer a therapeutic strategy for infertility associated with gut microbiota dysbiosis.