The contribution of dietary amino acids and endogenous hyperinsulinemia to prandial protein anabolism still has not been established. To this end, leucine estimates ([1-14C]leucine infusion, plasma α-ketoisocaproic acid [KIC] specific activity [SA] as precursor pool SA) of whole-body protein kinetics and fractional secretory rates (FSRs) of albumin, fibrinogen, antithrombin III, and immunoglobulin G (IgG) were measured in three groups of healthy volunteers during intragastric infusion of water (controls, n = 5), liquid glucose-lipid-amino acid (AA) meal (meal+AA, n = 7), or isocaloric glucose-lipid meal (meal-AA, n = 7) that induced the same insulin response as the meal+AA. The results of this study demonstrate that 1) by increasing (P < 0.01) whole-body protein synthesis and decreasing (P < 0.01) proteolysis, dietary amino acids account for the largest part (~90%) of postprandial protein anabolism; 2) the ingestion of an isocaloric meal deprived of amino acids exerts a modest protein anabolic effect (10% of postprandial protein anabolism) by decreasing amino acid oxidation and increasing (P < 0.01) albumin synthesis; 3) albumin FSR is increased (~20%) by postprandial hyperinsulinemia (meal-AA) and additionally increased (~50%) by amino acid intake (meal+AA); 4) IgG FSR is stimulated (~40%) by amino acids, not by insulin; and 5) fibrinogen and antithrombin III FSR are not regulated by amino acids or insulin.
ASJC Scopus subject areas
- Internal Medicine
- Endocrinology, Diabetes and Metabolism