Probiotic VSL#3 alleviates intrahepatic cholestasis of pregnancy by upregulating farnesoid X receptor-fibroblast growth factor 15 through regulation of the gut microbiota

Intrahepatic cholestasis of pregnancy (ICP) poses significant risks to both maternal and fetal health, and treatment options remain limited. This study investigated the efficacy and underlying mechanisms of VSL#3 in alleviating ICP. Clinical fecal and blood samples were collected from 26 patients with ICP and 21 healthy pregnant women. The gut microbiota composition was analyzed using 16S rRNA sequencing. To further explore causality, we established a fecal microbiota transplantation-ICP mouse model using fecal samples from ICP patients, as well as an estrogen-induced ICP mouse model. Compared with healthy pregnant women, ICP patients exhibited a distinct gut microbiota profile, characterized by an increased abundance of Bacteroides and Alistipes. Serum FGF19 levels were significantly lower in ICP patients, showing a negative correlation with liver function markers, such as serum total bile acid (TBA), and a positive correlation with beneficial genera including Bifidobacterium, Ruminococcus, Blautia, Dorea, Eubacterium (hallii group) and Ruminococcus (torques group). VSL#3 treatment in mice alleviated ICP manifestations by improving liver histopathology, reducing TBA and alanine aminotransferase levels, increasing FGF15 concentrations, and enhancing fetal outcomes. These beneficial effects were abolished by co-administration of the FXR antagonist Z-guggulsterone, confirming the role of FXR signaling. In conclusion, VSL#3 alleviated ICP by modulating the gut microbiota to activate the FXR-FGF15 axis, thereby reducing bile acid synthesis and improving maternal and fetal outcomes.