Aerobic Exercise Enhances The Muscle Protein Anabolic Effect Of A Mixed Meal In Older Adults

Abstract

Muscle protein metabolism is resistant to the anabolic effects of mixed feeding and insulin in older adults. Aerobic exercise improves insulin sensitivity of muscle proteins in elders. We tested if an acute bout of aerobic exercise can also overcome the anabolic resistance to a mixed meal in healthy, sedentary older subjects (age: 70±3 yr).Using a randomized cross‐over design, we measured blood flow and muscle protein kinetics (13C6‐phenylalanine) at baseline and during mixed meal ingestion (20g of essential amino acids + 35g of glucose) on 2 occasions: after rest (CTRL) or after a bout of aerobic exercise (EX). We report preliminary data from 4 subjects. Blood flow (CTRL, basal: 2.09±0.49, meal: 2.52±0.88; EX, basal: 2.47±0.46, meal: 4.06±1.06 ml/min/100 ml leg) and mixed muscle protein synthesis (CTRL, basal: 0.054±0.008, meal: 0.053±0.006; EX, basal: 0.057±0.005, meal: 0.079±0.007 %/h) increased (P<0.05) from baseline during mixed meal ingestion only in EX but not in CTRL. Phenylalanine delivery to the leg increased significantly (P<0.05) in both conditions (CTRL, basal: 137±29, meal: 422±137; EX, basal: 142±17, meal: 714±123, nmol/min/100 ml leg), but the change was larger (P<0.05) in EX.In conclusion, these preliminary data suggest that a prior bout of aerobic exercise restores the anabolic effects of a mixed meal in older adults. This effect may be partially due to increased blood flow and amino acid delivery.Supported by NIA R01 AG018311 and P30 AG024832