Berberine-induced bioactive metabolites of the gut microbiota improve energy metabolism.

Objective: Berberine (BBR) clinically lowers blood lipid and glucose levels via multi-target mechanisms. One of the possible mechanisms is related to its effect on the short chain fatty acids (SCFAs) of the gut microbiota. The goal of this study is to investigate the therapeutic effect and mode of action of BBR working through SCFAs of the gut microbiota (especially, butyrate).

Methods: Gas chromatography (GC) was used to detect butyrate and other SCFAs chemically. The effect of BBR on butyrate production was investigated in vitro as well as in several animal systems. Microarrays were used to analyze the composition change in the intestinal bacteria community after treatment with BBR. BBR-induced change in the energy production and gene regulation of intestinal bacteria was examined in order to elucidate the underlying molecular mechanisms.

Results: We show that oral administration of BBR in animals promoted the gut microbiota to produce butyrate, which then enters the blood and reduces blood lipid and glucose levels. Incubating gut bacterial strains in vitro with BBR increased butyrate production. Orally treating animals directly with butyrate reduced blood lipid and glucose levels through a mechanism different from that of BBR. Intraperitoneal BBR administration did not increase butyrate but reduced blood lipid and glucose levels, suggesting that BBR has two modes of action: the direct effect of the circulated BBR and the indirect effect working through butyrate of the gut microbiota. Pre-treating animals orally with antibiotics abolished the effect of BBR on butyrate. A mechanism study showed that BBR (given orally) modified mice intestinal bacterial composition by increasing the abundance of butyrate-producing bacteria. Furthermore, BBR suppressed bacterial ATP production and NADH levels, resulting in increased butyryl-CoA and, eventually, butyrate production via upregulating phosphotransbutyrylase/butyrate kinase and butyryl-CoA:acetate-CoA transferase in bacteria.

Conclusion: Promotion of butyrate (etc) production in gut microbiota might be one of the important mechanisms of BBR in regulating energy metabolism.