Partially hydrolyzed soy protein shows enhanced transport of amino acids compared to nonhydrolyzed protein across an intestinal epithelial cell monolayer

Abstract

Consumption of protein hydrolysates has been proposed to stimulate muscle protein anabolism to a higher degree than intact (nonhydrolyzed) proteins due to their ability to more effectively provide amino acids for muscle protein synthesis (MPS). Our objective was to evaluate whether amino acid uptake & transport to the basolateral surface of intestinal Caco‐2 cells was enhanced for soy protein hydrolysates compared to nonhydrolyzed soy protein. Intact & partially hydrolyzed soy proteins were subject to simulated gut digestion using pepsin & pancreatin. The resultant soluble peptide fractions (7 mg/mL) were applied to the apical surface of Caco‐2 monolayers (n = 4 to 6 per treatment) & incubated for 3 hours. Volume from each basolateral chamber was harvested, lyophilized & quantitatively analyzed for free amino acids using ion‐exchange chromatography & comparison to an included reference standard. Concentrations of all amino acids in the basolateral media were higher by a mean of 44% (p = 0.019) for hydrolyzed soy protein compared to that from the nonhydrolyzed protein with Asx, Glx & Lys showing the greatest differences. These data support the hypothesis that intestinal absorption of hydrolyzed soy protein may result in a more rapid absorption & increased availability of dietary amino acids. This would be important in conditions where rapid & increased levels of amino acids are needed such as in the stimulation of MPS.