Absorption and metabolism of lysine Maillard products in relation to utilization of L-lysine

An in vivo study was conducted to investigate to what extent the lysine Maillard products are absorbed and metabolized and how they affect the absorption and utilization of L-lysine in protein synthesis. The lysine Maillard products, mono- (MFL) and difructose-L-lysine (DFL), were synthesized from a mixture of glucose and [14C]lysine (6:1). A portal vein catheterization technique with duodenal infusion and a jugular vein administration was employed for the study of absorption and metabolism, respectively. MFL was absorbed in a significant amount probably by active transport and incorporated into the liver microsome, whereas DFL was absorbed in a negligible amount probably through diffusion. Compared to 22% of lysine, 72% of the absorbed MFL was excreted. MFL retarded competitively the absorption of lysine, while DFL reduced the absorption of lysine by blocking the absorption site.