תזונה ותוספים Muscle Protein Breakdown has a Minor Role in the Protein Anabolic Response to Essenti

[Mike Bikov]

Am J Physiol Regul Integr Comp Physiol. 2010 Jun 2. [Epub ahead of print]
Muscle Protein Breakdown has a Minor Role in the Protein Anabolic Response to Essential Amino Acid and Carbohydrate Intake Following Resistance Exercise.

Glynn EL, Fry CS, Drummond MJ, Dreyer HC, Dhanani S, Volpi E, Rasmussen BB.

1University of Texas Medical Branch.
Abstract

Muscle protein breakdown (MPB) is increased following resistance exercise (RE), but ingestion of carbohydrate (CHO) during post-exercise recovery can decrease MPB with no affect on muscle protein synthesis (MPS). We sought to determine if a combination of essential amino acids (EAA) with low CHO (LCHO), or high CHO (HCHO) could effectively reduce MPB following RE and improve muscle protein net balance (NB). We hypothesized higher levels of CHO and resulting increases in circulating insulin would inhibit MPB and associated signaling, resulting in augmented NB. Thirteen male subjects were assigned to one of two groups receiving equivalent amounts of EAA (~20g) but differing CHO (LCHO=30, HCHO=90g). Groups ingested nutrients 1 hour after an acute bout of leg RE. Leg phenylalanine kinetics (e.g., MPB, MPS, NB), signaling proteins and mRNA expression were assessed on successive muscle biopsies using stable isotopic techniques, immunoblotting, and real-time qPCR respectively. MPB tended to decrease (P<0.1) and MPS increased (P<0.05) similarly in both groups following nutrient ingestion. No group differences were observed, but MuRF1 (muscle RING finger 1) protein content and MURF1 mRNA expression increased following RE and remained elevated following nutrient ingestion, while autophagy marker, light chain 3B (LC3B-II), decreased after nutrient ingestion (P<0.05). FOXO3a phosphorylation, total muscle atrophy F-box (MAFbx) protein, MAFbx and caspase-3 (CASP3) mRNA expression were unchanged. We conclude the enhanced muscle protein anabolic response detected when EAA+CHO are ingested post-RE is primarily due to an increase in MPS with minor changes in MPB, irrespective of CHO dose or circulating insulin level.​

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