Periexercise coingestion of branched-chain amino acids and carbohydrate in men does not preferentially augment resistance exercise–induced increases in phosphatidylinositol 3 kinase/protein kinase B–mammalian target of rapamycin pathway markers indicative of muscle protein synthesis

Mar 25, 2014Nutrition research (New York, N.Y.)

Taking branched-chain amino acids and carbs before exercise does not boost muscle-building signals after resistance training in men

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Abstract

Significant increases in insulin and glucose levels were observed after carbohydrate (CHO) and carbohydrate plus branched-chain amino acid (BCAA) supplementation.

Resistance exercise (RE) was performed by 27 males who were divided into three groups: CHO, CHO + BCAA, and placebo (PLC).
Serum insulin and glucose levels showed significant increases in both CHO and CHO + BCAA groups compared to the PLC group.
Phosphorylated levels of muscle signaling markers, including insulin receptor substrate 1 (IRS-1), protein kinase B, and mammalian target of rapamycin, significantly increased over time.
Carbohydrate and CHO + BCAA supplementation significantly raised IRS-1 levels compared to the PLC group.
No additional benefits in muscle signaling markers indicative of protein synthesis were found with the coingestion of CHO and BCAA compared to CHO alone.

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The effects of a single bout of resistance exercise (RE) in conjunction with periexercise branched-chain amino acid (BCAA) and carbohydrate (CHO) ingestion on skeletal muscle signaling markers indicative of muscle protein synthesis were determined. It was hypothesized that CHO + BCAA would elicit a more profound effect on these signaling markers compared with CHO. Twenty-seven males were randomly assigned to CHO, CHO + BCAA, or placebo (PLC) groups. Four sets of leg presses and leg extensions were performed at 80% 1 repetition maximum. Supplements were ingested 30 minutes and immediately before and after RE. Venous blood and muscle biopsy samples were obtained immediately before supplement ingestion and 0.5, 2, and 6 hours after RE. Serum insulin and glucose and phosphorylated levels of muscle insulin receptor substrate 1 (IRS-1), protein kinase B, mammalian target of rapamycin, phosphorylated 70S6 kinase, and 4E binding protein 1 were assessed. Data were analyzed by 2-way repeated-measures analysis of variance. Significant group × time interactions were observed for glucose and insulin (P < .05) showing that CHO and CHO + BCAA were significantly greater than PLC. Significant time main effects were observed for IRS-1 (P = .001), protein kinase B (P = .031), mammalian target of rapamycin (P = .003), and phosphorylated 70S6 kinase (P = .001). Carbohydrate and CHO + BCAA supplementation significantly increased IRS-1 compared with PLC (P = .002). However, periexercise coingestion of CHO and BCAA did not augment RE-induced increases in skeletal muscle signaling markers indicative of muscle protein synthesis when compared with CHO.

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Periexercise coingestion of branched-chain amino acids and carbohydrate in men does not preferentially augment resistance exercise–induced increases in phosphatidylinositol 3 kinase/protein kinase B–mammalian target of rapamycin pathway markers indicative of muscle protein synthesis

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