Honokiol attenuates diabetes by enriching Akkermansia muciniphila andregulating tryptophan metabolism in mice

Diabetes mellitus (DM) is a chronic disease influenced by gut microbiome disturbances. Honokiol (HON), a low oral bioavailability compound from Magnolia officinalis bark, has demonstrated potential as a treatment for DM. This research investigates the effects of HON on gut microbiota and host metabolism to elucidate its mechanism of action in DM. After 8 weeks of intervention through fecal microbiota transplantation (FMT) or antibiotic treatment, HON improved glucose tolerance and lipid metabolism in a gut microbiota-dependent manner. Specifically, HON administration significantly increased Akkermansia muciniphila (AKK) abundance and modulated tryptophan (TRP) metabolism, as evidenced by 16S ribosomal ribonucleic acid (rRNA) gene sequencing and untargeted/targeted metabolomics analysis. Notably, research revealed that AKK metabolized TRP into tryptamine (TA) and other metabolites in vitro . Both AKK and TA activated the aryl hydrocarbon receptor (AHR) pathway, increasing circulating glucagon-like peptide-1 (GLP-1) levels and ameliorating diabetes-related symptoms in DM mice. These findings indicate that HON’s hypoglycemic effect primarily stems from AHR-GLP-1 pathway activation through targeted modulation of AKK and microbial TRP metabolite TA, potentially enhancing HON’s clinical applications.