Indolepropionic acid reduces obesity-induced metabolic dysfunction through colonic barrier restoration mediated via tuft cell-derived IL-25.

Abstract

Previous studies have indicated that indolepropionic acid (IPA), derived from dietary tryptophan via gut microbiota conversion, is negatively correlated with type 2 diabetes mellitus and systemic low-grade inflammation. However, the effects of IPA administration on obesity, as well as the underlying mechanisms, remain unclear. In the present study, we observed that obesity leads to a dramatic reduction in IPA levels in both the serum and colonic mucosa, and IPA supplementation exerted beneficial effects on weight, as well as on glucose and lipid metabolism disorders. In adipose tissue, IPA treatment had no direct effect on adipocyte differentiation, but it significantly ameliorated adipose inflammation, thus preventing adipocyte enlargement. Moreover, IPA administration promoted gut integrity, increased the expression of tight junction proteins, and downregulated colonic inflammation; these effects were demonstrated to have a poor relationship with gut microbiota composition. Mechanistically, IPA significantly promoted the expansion of the tuft cell lineage in the gut and increased the secretion of interleukin-25 both in vivo and ex vivo, which contributes to the integrity of the gut barrier. This may partly depend on the free fatty acid receptor 3 pathway in tuft cells. Overall, our results demonstrate that IPA supplementation prevents the development of high-fat diet-induced obesity and metabolic disorders by restoring tuft cell-interleukin-25-mediated colonic barrier integrity; hence, IPA could be a potential agent for treatment of obesity.