The muscle protein synthetic response to the combined ingestion of protein and carbohydrate is not impaired in healthy older men.

Aging is associated with a progressive decline in skeletal muscle mass. been hypothesized that an attenuated muscle protein synthetic response main anabolic stimuli may contribute to the age-related loss of muscle The aim of the present study was to compare the muscle protein synthetic following ingestion of a meal-like amount of dietary protein plus between healthy young and older men. Twelve young (21 +/- 1 years) and (75 +/- 1 years) men consumed 20 g of intrinsically L-[1-13C]phenylalanine-labeled protein with 40 g of carbohydrate. specifically produced intrinsically L-[1-13C]phenylalanine-labeled allowed us to assess the subsequent incorporation of casein-derived into muscle protein. Blood samples were collected at regular intervals, muscle biopsies obtained prior to and 2 and 6 h after protein plus ingestion. The acute post-prandial rise in plasma glucose and insulin concentrations was significantly greater in the older compared with the males. Plasma amino acid concentrations increased rapidly following ingestion in both groups. However, plasma leucine concentrations were significantly lower at t = 90 min in the older when compared with the (P < 0.05). Muscle protein-bound L-[1-13C]phenylalanine enrichments 0.0071 +/- 0.0016 and 0.0072 +/- 0.0013 mole percent excess (MPE) at 2 h 0.0229 +/- 0.0016 and 0.0213 +/- 0.0024 MPE at 6 h following ingestion intrinsically labeled protein in the young and older males, differences between groups (P > 0.05). We conclude that the use of protein-derived amino acids for muscle protein synthesis is not impaired healthy older men following intake of protein plus carbohydrate.