Combination of L-alanine and erythritol synergistically enhances water transport in an in vitro system using human-induced pluripotent stem cell-derived small intestinal epithelial cells

Glucose-containing beverages enhance water absorption from the lumen of the small intestine into capillaries via Na+-dependent glucose transporters. However, considering the harmful effects of excessive sugar, water absorption-promoting substances that do not worsen calorie intake and glucose metabolism are desirable. Alternative tools that avoid animal studies and clinical trials are required to quantitatively evaluate such substances. Here, we employed an in vitro system using human induced pluripotent stem (iPS) cell-derived small intestinal epithelial cells (hiPSC-SIECs) to evaluate the effects of glucose, amino acids, erythritol, and allose on water transport. Among the 15 amino acids, L-alanine had the greatest effect. Significant increases in water transport were also observed with erythritol and allose, which are promising sugar substitutes. Furthermore, L-alanine and erythritol showed synergistic effects. Overall, we demonstrate the efficacy of hiPSC-SIECs as an alternative tool for quantitation of water absorption and propose that L-alanine and erythritol can synergistically promote water absorption.