Maternal indole supplementation protects offspring from NAFLD through altered microbiota- and AHR-mediated ceramide metabolism
MaternalWestern-style diet (WD) disrupts early life gut microbiota in the offspring and is associated with pediatric nonalcoholic fatty liver disease (NAFLD). Here, we report that oral supplementation with gut-derived tryptophan metabolites indole (Ind) or indole-3-acetate (I3A) during pregnancy and lactation in WD-fed dams had persistent effects in offspring liver, acting on key upstream regulators in WD-challenged offspring that suppress pathways for steatosis, fibrosis, and oxidative stress. Maternal Ind or I3A activated aryl hydrocarbon receptor (AHR) signaling, leading to increases in long-chain and very long-chain (VLC) ceramides in offspring liver and small intestine. These effects were evident as early as postnatal day 14. The tryptophan metabolite 5-hydroxyindoleacetate (5-HIAA), an AHR ligand, was depleted in offspring by maternal WD and restored by maternal I3A treatment. Fecal transplantation studies demonstrated that VLC ceramides and liver fibrosis remodeling were mediated by maternal indoles altering the gut microbiota, with strong associations with Lactobacillaceae. Collectively, these findings define a novel and persistent protective effect of maternal Ind and I3A to prevent NAFLD, acting both directly on the liver and through the microbiota. These tryptophan metabolites may serve as therapeutic targets for future interventional studies aimed at prevention of pediatric NAFLD. Overall design: A mouse model of maternal WD was used to investigate the effect in offspring of indole (Ind) or indole-3-acetate (I3A)  exposure during gestation and lactation.  Offspring were weaned to a chow (CH) diet for 9 weeks, followed by a 4-week WD challenge until 16 weeks of age. Bulk RNA-seq was run on liver tissue from these four groups of offspring.