Affiliations: Department of Applied Biological Chemistry, Graduate
School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi,
Bunkyo-ku, Tokyo 113-8657, Japan | Suntory Institute for Health Care Science, 1-1-1
Wakayamadai, Shimamoto-cho, Mishima-gun, Osaka 618-8503, Japan
Abstract: Carnosine (β-Ala-L-His) is known to have the
physiological functions of an antioxidant. Although dietary carnosine is
thought to be absorbed across intestinal epithelial cells, the mechanism for
this absorption is not yet well understood and its function in the intestinal
tract is also obscure. The intestinal transport of carnosine was characterized
in the present study by using human intestinal Caco-2 cells, and its
physiological function in these cells was further examined. The carnosine
uptake was proton-dependent, being activated by lowering the apical pH value.
Its uptake was significantly inhibited by other dipeptides, whereas it was not
inhibited by other amino acids. These characteristics of the carnosine uptake
strongly suggest its transport into the cells via peptide transporter 1
(PepT1). Since carnosine has antioxidative activity, we studied its effect on
the H_2O_2-induced secretion of
inflammatory cytokines in Caco-2 cells. The
H_2O_2-induced increase in IL-8 secretion
was inhibited by a pretreatment with carnosine for 3 h, this inhibition being
presented in a dose-dependent manner. These results suggest that carnosine had
a protective effect against oxidative stress in intestinal epithelial
cells.
