Spatial, temporal, and inter-subject variation of the metabolome along the human upper intestinal tract

Abstract Most utilization of human diets occurs in the small intestine, which remains largely unstudied. Here, we used a novel non-invasive, ingestible sampling device to probe the spatiotemporal variation of upper intestinal luminal contents during routine daily digestion in 15 healthy subjects. We analyzed 274 intestinal samples and 60 corresponding stool homogenates by combining five metabolomics assays and 16S rRNA sequencing. We identified 1,909 metabolites, including sulfonolipids and novel bile acids. Stool and intestinal metabolomes differed dramatically. Food metabolites displayed known differences and trends in dietary biomarkers, unexpected increases in dicarboxylic acids along the intestinal tract, and a positive association between luminal keto acids and fruit intake. Diet-derived and microbially linked metabolites accounted for the largest inter-subject differences. Interestingly, subjects exhibited large variation in levels of bioactive fatty acid esters of hydroxy fatty acids (FAHFAs) and sulfonolipids. Two subjects who had taken antibiotics within 6 months prior to sampling showed markedly different patterns in these and other microbially related metabolites; from this variation, we identified Blautia species as most likely to be involved in FAHFA metabolism. Thus, in vivo sampling of the human small intestine under physiologic conditions can reveal links between diet, host and microbial metabolism.