The Effect of Leucine-Enriched Beta-Lactoglobulin Versus an Isonitrogenous Whey Protein Isolate on Skeletal Muscle Protein Anabolism in Young Healthy Males

Background: Beta-lactoglobulin (BLG) is a protein found within whey protein (WP) that is rich in essential amino acids, most notably, leucine (LEU). LEU is considered the most potent EAA in the postprandial stimulation of muscle protein synthesis (MPS), such that sub-optimal protein/essential amino acid (EAA) doses containing higher LEU content elicit muscle anabolism comparable to larger protein doses. Here we explored the effects of naturally LEU-rich BLG (~10 g protein) versus isonitrogenous whey protein isolate (WPI, ~10g) on MPS. Methods: Ten healthy young men (26 ± 2 y; 179 ± 2 cm; 81 ± 3 kg) received BLG (1.57g LEU) or WPI (1.02g LEU) in a randomised double-blind cross-over fashion. A primed constant intravenous infusion of [1,2 13C2] LEU was used to determine MPS (isotope ratio mass spectrometry) at baseline and in response to feeding (FED) and feeding-plus-exercise (FED-EX; 6X8 unilateral leg extensions; 75% 1-RM). Plasma insulin and EAA’s were quantified. Results: Plasma EAA, branched chain amino acid (BCAA) and LEU concentrations increased rapidly following both protein supplements but exhibited a significantly greater EAA/BCAA/leucinemia, following BLG (P< 0.05 for all). MPS increased significantly in both FED and FED-EX (n = 8) states, with no significant differences evident between supplements. Conclusions: Both BLG and WPI effectively stimulated MPS doses in young healthy males, with BLG offering an advantage in EAA/BCAA/leucine bioavailability. It follows that future research should explore the potential of BLG in populations exhibiting anabolic resistance and exercise anabolism-deficiency, such as older adults, also in frail and clinical populations, to assess its utility in preserving muscle mass under conditions of sub-optimal protein intake.