Microbiota-derived tryptophan indoles increase after gastric bypass surgery and reduce intestinal permeability in vitro and in vivo.

The novel findings are that obese subjects have lower levels of IPA, a solely bacterially derived tryptophan derivative, and IPA improved intestinal barrier function in vitro and DIO mice. Reduced plasma IPA levels and reversal by surgery may be a consequence of intestinal indole-producing microbiota but underlying mechanisms warrant further investigation.