Etifoxine reverses weight gain and alters the colonic bacterial community in a mouse model of obesity

Obesity is intimately associated with diet and dysbiosis of gut microorganisms but anxiolytics, widely used in treatment of psychiatric conditions, frequently result in weight gain and associated metabolic disorders. We are interested in effects of the anxiolytic etifoxine, which has not been studied with respect to weight gain or effects on gut microorganisms. Here we induced obesity in mice by feeding a high-fat diet but found that intraperitoneal administration of etifoxine resulted in weight loss and decreased serum cholesterol and triglycerides. Obese mice had increased hepatic transcripts associated with lipid metabolism (cyp7 alpha 1, cyp27 alpha 1, abcg1 and LXR alpha) and inflammatory factors (TNF alpha and IL18) but these effects were reversed after etifoxine treatment other than cyp7 alpha 1. Taxonomic profiles of the organisms from the caecum were generated by 16S rRNA gene sequencing and Obese and etifoxine mice show differences by diversity metrics, Differential Abundance and functional metagenomics. Organisms in genus Oscillospira and genera from Lachnospiraceae family and Clostridiales order are higher in Control than Obese and at intermediate levels with etifoxine treatment. With respect to community metabolic potential, etifoxine mice have characteristics similar to Control and particularly with respect to metabolism of butanoate, sphingolipid, lipid biosynthesis and xenobiotic metabolism. We suggest mechanisms where-by etifoxine influences processes of host, such as on bile acid synthesis, and microbiota, such as signalling from production of butanoate and sphingosine, resulting in decreased cholesterol, lipids and inflammatory factors. We speculate that the indirect effect of etifoxine on microbial composition is mediated by microbial beta-glucuronidases that metabolise excreted etifoxine glucuronides.