The role of FLVCR1 and FLVCR2 in choline transport in the Caco-2 intestinal epithelial cell model and rat small intestine

Choline is a vital cationic nutrient for maintaining organismal homeostasis, partially synthesized in the liver but primarily obtained from dietary sources. While previous studies have explored mechanisms of choline absorption in intestinal cells, the precise roles of specific transporters remain to be fully elucidated. This study aimed to investigate the roles of the choline transporters feline leukemia virus subgroup C receptor 1 (FLVCR1) and FLVCR2. Using MDCKII cells expressing human FLVCR1 or FLVCR2, the study revealed that FLVCR1 facilitates choline efflux from the basolateral membrane, while FLVCR2 enables choline uptake through the apical membrane. Functional analyses of FLVCR1 and FLVCR2 variants identified mutations that significantly reduce choline uptake activity. Knockdown experiments in Caco-2 cells resulted in significantly reduced cellular uptake of choline. Functional analysis of choline transport in the everted tissue sacs of the rat small intestine suggested that Flvcr2 aids intestinal choline uptake. Conclusively, the findings of this study indicate that FLVCR1 and FLVCR2 work cumulatively to regulate intestinal choline absorption. These findings provide novel insights into the roles of FLVCR1 and FLVCR2 and offer bases for further research into choline transport mechanisms in the small intestine.