Diminished Postprandial Muscle Protein Synthetic Response To Protein Ingestion In Obese Adults

Abstract

Excess body fat blunts muscle protein synthesis rates under hyperinsulinemic, hyperaminoacidemic clamp conditions. However, the efficacy of the ingestion of single meal containing ample amounts of protein to augment postprandial muscle protein synthesis rates has not been studied in obese and overweight adults. PURPOSE: We aimed to compare myofibrillar protein synthesis after protein ingestion in healthy weight, overweight, and obese adults. METHODS: 10 healthy-weight (24±1 y, BMI 22.7±0.4 kg/m2, HOMA-IR 1.4±0.2), 10 overweight (26±2 y, BMI 27.1±0.5 kg/m2, HOMA-IR 1.25±0.11), and 10 obese (27±3 y, BMI 35.9±1.3 kg/m2, HOMA-IR 5.8±0.8) men and women underwent a primed continuous L-[ring-13C6]phenylalanine infusion. Blood and muscle biopsy samples were collected at rest and after ingestion of 36 g of protein to assess plasma amino acid and insulin concentrations and myofibrillar protein synthesis rates. RESULTS: Protein ingestion increased plasma essential amino acid concentrations similarly in all participants (time effect: P<0.05) with concentrations peaked at 2 h and returning to baseline values at 5 h. The obese participants had a greater peak postprandial plasma insulin response to protein ingestion than the overweight and healthy-weight participants (obese 56.7±8.0 compared to overweight 11.9±1.6 and healthy-weight 14.3±1.7 μIU/L, P<0.001). Protein ingestion increased myofibrillar protein synthesis in both the healthy-weight (rest: 0.057±0.006 %/h, fed: 0.084±0.014 %/h) and overweight groups (rest: 0.061±0.007, fed: 0.087±0.019 %/h) (P<0.05) with no increase in the obese group (rest: 0.055±0.005 %/h, fed: 0.067±0.005 %/h, P=0.45). CONCLUSIONS: Increased adiposity led to an impaired postprandial muscle protein synthetic response to protein ingestion in obese adults when compared to healthy-weight and overweight individuals. These data suggest that poor skeletal muscle remodeling may underlie early metabolic impairments in apparently “healthy” obese adults. Funding provided by the National Pork Board