Sialic acid exacerbates polycystic ovary syndrome in mice by modulating gut microbiota-mediated bile acid metabolism and FXR activation

Polycystic ovary syndrome (PCOS) is a prevalent endocrine disorder in women. Accumulating evidence indicates that gut dysbiosis and metabolic disturbances are associated with the pathogenesis of PCOS. However, the mechanisms by which metabolic alterations influence gut homeostasis and contribute to PCOS progression remain poorly understood. Here, we show that N-acetylneuraminic acid (Neu5Ac) exacerbates dehydroepiandrosterone (DHEA)-induced PCOS phenotypes in female mice in a gut microbiota-dependent manner. Specifically, Neu5Ac promotes the expansion of the gut Ligilactobacillus salivarius (L. sa) with bile salt hydrolase (BSH) activity. Administration of L. sa to DHEA-treated mice worsens PCOS symptoms by reducing levels of the conjugated bile acid tauroursodeoxycholic acid (TUDCA) via BSH activity. Reduced TUDCA enhances intestinal farnesoid X receptor (FXR) activation, leading to suppression of IL-22 production. Mechanistically, IL-22 attenuates DHEA-induced ovarian ferroptosis by activating the STAT3 signaling pathway. These findings reveal that sialic acid-mediated bile acid-FXR-IL-22 signaling contributes to PCOS pathogenesis, highlighting a potential therapeutic strategy for PCOS intervention.