1H NMR-Based Identification of Intestinally Absorbed Metabolites by Ussing Chamber Analysis of the Rat Cecum

The large intestine (cecum and colon) is a complex biochemical factory of vital importance to human health. It plays a major role in digestion and absorption by salvaging nutrients from polysaccharides via fermentation initiated by the bacteria that comprise the gut microbiome. We hypothesize that the intestinal epithelium absorbs a limited number of luminal metabolites with bioactive potential while actively excluding those with toxic effects. To explore this concept, we combined 1H NMR detection with Ussing chamber measurements of absorptive transport by rat cecum. Numerous metabolites transported across the epithelium can be measured simultaneously by 1H NMR, a universal detector of organic compounds, alleviating the need for fluorescent or radiolabeled compounds. Our results demonstrate the utility of this approach to delineate the repertoire of fecal solutes that are selectively absorbed by the cecum and to determine their transport rates.