NMR-based metabolomic studies reveal changes in biochemical profile of urine and plasma from rats fed with sweet potato fiber or sweet potato residue

Dietary fiber has attracted more interest in recent years because many studies have uncovered its disease preventive and health-promoting features: containing blood cholesterol and/or glucose attenuation and reducing obesity risk. However, the health effects of sweet potato fiber (SF) and sweet potato residue (SR) and the knowledge of their exact mechanisms of action are still not fully understood. This study investigates the effect of SF and SR administration on rat metabolism. Rats were randomly assigned to one of three dietary groups of 11 rats each and given a basal diet containing 15% SF, 15% SR, or no supplemental fiber (control). The groups were observed for 30 days, and urine and plasma samples were analyzed by proton nuclear magnetic resonance. Compared with the rats in the control group, those administered the diet containing SF exhibited significantly increased plasma levels of lipid, lactate, and myo-inositol, as well as urine levels of acetate, citrulline, N-acetylglutamate, and p-hydroxyphenylacetate. SF significantly decreased the plasma levels of glutamine, glutamine/glutamate, lysine, phosphorylcholine/glycerolphosphocholine, tyrosine, and glucose, as well as the urine level of allantoin. Moreover, SR significantly increased the plasma levels of acetone, lipid, and lactate, as well as the urine levels of acetamide, alanine, citrulline, ethanol, lactate, methylamine, methylmalonate, N-acetylglutamate, and alpha-hydroxybutyrate, compared with the control group. SR significantly decreased the plasma levels of citrate, glutamate, glutamine, isoleucine, lysine, methionine, and glucose, as well as the urine level of isobutyrate. These results suggest that SF and SR supplementation have certain systemic metabolic processes in common, including lipid metabolism, glycogenolysis and glycolysis metabolism, energy metabolism, protein biosynthesis, and gut microbiota metabolism. This study demonstrates the potential for the routine use of metabolomics in nutritional studies to characterize metabolic effects and understand the influence of diet on animal metabotypes.