Posted 27 February 2006 - 04:45 AM
I don't have access to the full paper. Of note: "Its [carnosine] 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). "
Whether this competition is significant such that significant carnosine might not be absorbed in some situations, one can only speculate. However, this does tie in nicely with the "meat meal" reference cited above: the pharmacokinetic profile would be heavily influenced by the peptides attendant to the breakdown of the meat meal. So, taking it on an empty stomach will likely result in a shaper spike, and more rapid clearance, so even less concern it would seem, that levels might remain persistently high between, say, 250mg dosings at 6 hour intervals.
I suppose this still begs the question of whether one wants one type of pharmacokinetic profile, or the other, and hence *should* one take carnosine with a protein rich meal?
Biofactors. 2004;21(1-4):395-8. Related Articles, Links
Characterization of carnosine uptake and its physiological function in human intestinal epithelial Caco-2 cells.
Son DO, Satsu H, Kiso Y, Shimizu M.
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.
Carnosine (beta-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 H2O2-induced secretion of inflammatory cytokines in Caco-2 cells. The H2O2 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.
PMID: 15630234 [PubMed - indexed for MEDLINE]