Berberine impairs spermatogenesis in mice by modulating ornithine metabolism via gut microbiota regulation

Berberine (BBR) is used to treat diarrhea clinically, its reproductive toxicity, however, is poorly documented. This study aims to investigate the impact of BBR on the male reproductive system. Gradient doses of BBR were administered orally to experimental mice for consecutive 14 days. The gut microbiota, sperm concentration of cauda epididymis, and serum testosterone levels were measured after the last dose for assessing the effects of BBR. Moreover, the metabolome and transcriptome of the mice and microbiota were also investigated. Intragastric BBR administration resulted in a significant decrease in serum testosterone levels and epididymal sperm concentration in mice, which was attributed to a dramatic decrease of Muribaculaceae abundance in the gut microbiota of mice. Both fecal microbiota transplantation (FMT) and polyethylene glycol (PEG) treatment experiments also demonstrated that Muribaculaceae is necessary for spermatogenesis. Metabolomic analysis revealed that BBR affected the arginine and proline metabolism pathways, of which ornithine levels were downregulated after BBR administration. Intragastric administration of M.intestinale and its metabolite ornithine to BBR-treated mice achieved a recovery of sperm concentration and testosterone levels. RNA sequencing of testes showed the genes related to the LDLR-mediated cholesterol-synthesis testosterone pathway were downregulated after BBR administration. The levels of testosterone increased and Ldlr gene became more transcriptionally active in TM3 cells cultured in media supplemented with ornithine. This study for the first time revealed an association between BBR-induced gut Muribaculaceae dysbiosis and defects in spermatogenesis via ornithine metabolism, which provided a candidate and strategy for the treatment of infertility caused by a decreased serum testosterone level-induced by gut microbiota dysbiosis.