Monocarboxylate transporter expression is associated with the absorption of benzoic acid in human intestinal epithelial cells

A diet rich in fruit and vegetables is associated with a decreased risk of developing a number of chronic diseases including colon cancer. The active components of the diet which exert these protective effects are unknown but may include small aromatic and phenolic acids. To elicit a physiological response, these acids must first be absorbed by the intestinal epithelium and the present study has focussed on one potential absorptive pathway - the monocarboxylate transporter MCT1. Using Caco-2 cells (a human intestinal cell line) we have established that benzoic acid uptake is pH-dependent (resulting in intracellular acidification) and is enhanced in cells expressing higher levels of MCT1 protein. A number of monohydroxybenzoic acids (including salicylic acid) also induced a decrease in intracellular pH which was of a similar magnitude to that elicited by benzoic acid itself, suggesting that they may all be substrates for the same transport pathway. The role of these small organic acids in maintaining normal cell physiology remains to be fully explored.