Sustained Postprandial Muscle Protein Synthesis Rates after Protein Ingestion in Healthy Young Males

Abstract

We determined the effect of ingesting a single meal‐like amount of protein on protein digestion and absorption kinetics and the subsequent time‐dependent regulation of postprandial muscle protein synthesis rates in vivo in humans. Seven healthy young males (age: 22±1 y, BMI: 24.8±1.2 kg/m2) received a primed continuous L‐[ring‐2H5]phenylalanine infusions and ingested 38 g intrinsically L‐[1‐13C]phenylalanine‐labeled milk protein concentrate. Biopsies were collected from the vastus lateralis in the basal‐state and 1, 2, 3, and 5 h after protein ingestion. Exogenous phenylalanine appearance in the circulation rapidly increased after protein ingestion (P<0.001). Dietary protein‐derived phenylalanine released in the circulation was 11±2% of the total intake within the first 1 h, followed by 14±1%, 12±1%, and 20±1% within the subsequent 1–2 h, 2–3 h, and 3–5 h of the postprandial period, respectively (total 56±4% over the 5 h period). Myofibrillar protein synthesis rates tended (P=0.10) to increase (absolute change from basal: 0.010±0.008 %/h) immediately following protein ingestion at 0–1 h. Myofibrillar protein synthesis rates were significantly increased at 1–2 h (0.035±0.012 %/h) and myofibrillar protein synthesis remained elevated between 2–3 h (0.019±0.005 %/h) and 3–5 h (0.016±0.004 %/h) after protein ingestion when compared to basal rates (all, P<0.05). Our results show that postprandial muscle protein synthesis rates rapidly increase after protein ingestion and remain elevated above baseline values for at least 5 hours after protein ingestion in healthy young males.Support or Funding InformationIllinois Campus Research Board