Gut Bacteria Transform Berberine Into a Compound That Shields the Liver From Cholestasis

Cholestatic liver disease (CLD) is a serious condition in which bile cannot flow normally from the liver, leading to toxic bile accumulation, elevated liver enzymes, jaundice, and—in severe cases—cirrhosis or liver failure. Current FDA-approved treatments like ursodeoxycholic acid have limited efficacy, making new therapeutic strategies urgently needed.

This study investigated whether berberine (BBR), an isoquinoline alkaloid from Coptis chinensis with known antimicrobial and metabolic benefits, could treat CLD—and crucially, how. BBR has extremely low oral bioavailability and minimal systemic absorption, prompting investigators to hypothesize an indirect, gut-microbiota-mediated mechanism of action.

Using three complementary mouse models of CLD (bile duct ligation, ANIT-induced intrahepatic cholestasis, and mdr2-knockout mice), the team demonstrated that oral BBR robustly reduced hepatocyte necrosis and normalized serum markers including ALP, GGT, ALT, AST, total bilirubin, and total bile acids. Critically, intraperitoneal (direct systemic) BBR administration had no protective effect, implicating gut-mediated processes. When gut microbiota was depleted with an antibiotic cocktail, oral BBR lost its benefit, directly demonstrating microbiota dependence.

Fecal microbiota transplant (FMT) experiments refined the mechanism further: mice receiving stool from BBR-treated donors were protected even when their own gut bacteria were suppressed, pointing to transferable metabolites rather than microbial community restructuring as the active principle. Filtered fecal bacterial supernatants alone recapitulated the protective effect in antibiotic-pretreated mice.

Using 16S rRNA sequencing and LC-MS/MS metabolomics, the study identified dihydroberberine (dhBBR) as the key metabolite. Gut bacteria—particularly Bacteroides and Bifidobacterium expressing the enzyme nitroreductase—reduce BBR to dhBBR, which was confirmed in both mouse and human feces after oral BBR. Direct oral administration of dhBBR mimicked BBR's hepatoprotective effects, while also suppressing serum 5-HT levels. dhBBR was shown to inhibit TPH1 enzymatic activity and downregulate Tph1 gene transcription in intestinal enterochromaffin cells, reducing gut-derived serotonin production. Lower circulating 5-HT then diminishes activation of hepatic 5-HT receptors (5-HTRs), interrupting a pro-injury signaling axis in the liver.

A randomized, controlled clinical trial in patients with CLD validated these findings in humans: BBR treatment improved serum ALP, GGT, ALT, and AST and significantly decreased serum 5-HT levels. Together, these results establish a novel gut microbiota–BBR–dhBBR–5-HT–liver axis as a therapeutically actionable pathway in cholestatic liver disease.