Leucine supplementation chronically improves muscle protein synthesis in older adults consuming the RDA for protein - PubMed (original) (raw)

Leucine supplementation chronically improves muscle protein synthesis in older adults consuming the RDA for protein

Shanon L Casperson et al. Clin Nutr. 2012 Aug.

Abstract

Background & aim: Protein-energy supplementation is routinely employed to combat muscle loss. However, success is often compromised by increased satiety, poor palatability, high costs and low compliance.

Methods: For 2-weeks we supplemented meals of older individuals with leucine (4 g/meal; 3 meals/day; days 2-14). Metabolic studies were performed prior to (Day 1) and following (Day 15) supplementation. Leucine was not provided on metabolic study days. Venous blood and vastus lateralis muscle biopsies were obtained during a primed constant infusion of L-[ring-(13)C(6)] phenylalanine. Mixed muscle fractional synthesis rate (FSR), body composition and markers of nutrient signaling (mTOR, 4E-BP1 and p70S6K1 phosphorylation) were measured before and after a low protein/carbohydrate simulated meal.

Results: The meal modestly increased FSR on Day 1 (postabsorptive: 0.063 ± 0.004 vs. postprandial: 0.075 ± 0.006%/h; p = 0.03), however, two weeks of leucine supplementation increased postabsorptive FSR (p = 0.004) and the response to the meal (p = 0.01) (postabsorptive: 0.074 ± 0.007 vs. postprandial: 0.10 ± 0.007%/h). Changes in FSR were mirrored by increased phosphorylation of mTOR, 4E-BP1 and p70S6K1 (p ≤ 0.1). No change in fat free mass was observed (p > 0.05).

Conclusions: In older adults, leucine supplementation may improve muscle protein synthesis in response to lower protein meals.

Copyright © 2012 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.

PubMed Disclaimer

Figures

Fig. 1

Fig. 1. Stable isotope infusion protocol

Stable isotope infusion studies were performed prior to (Day 1) and following (Day 15) leucine supplementation. Arterialized blood samples were obtained at 20-min intervals during an infusion of L-[ring-13C6] phenylalanine. Basal muscle biopsies from the vastus lateralis were obtained at 120 and 240 min. Postprandial muscle biopsies were obtained 30 and 180 min after consuming a simulated meal containing 7 g EAA and 10 g sugar.

Fig. 2

Fig. 2. Plasma phenylalanine enrichments

Plasma L-[ring-13C6] phenylalanine enrichments before and after the simulated meal on Day 1 and Day 15. Values are expressed as means ± SEM. * Significant difference from postabsorptive values.

Fig. 3

Fig. 3. Mixed muscle fractional synthesis rate (FSR)

Comparison of the mixed muscle FSR measured before (black bars) and after (white bars) ingestion of the simulated meal on Day 1and again on Day 15. Values are expressed as means ± SEM.

Fig. 4

Fig. 4. Intercellular and plasma mixed muscle fractional synthesis rate (FSR)

Comparison of the mixed-muscle postabsorptive (A) and postprandial (B) FSR measured on Day 1 and again on Day 15 utilizing muscle free phenylalanine as the precursor pool. Comparison of the mixed-muscle postabsorptive (C) and postprandial (D) FSR measured on Day 1 and again on Day 15 utilizing plasma phenylalanine as the precursor pool. Individual values are presented. Group values are expressed as means ± SEM.

Fig. 5

Fig. 5. Effects of chronic leucine supplementation on markers of nutrient signaling

Comparisons of the phosphorylation state of mTOR (A), p70S6K (B), and 4E-BP1 (C) obtained on Day 1 (□) and Day 15 (•). Protein phosphorylation and total protein were determined before and again at 30 and 180 min after ingestion of the simulated meal. A representative blot of the phosphorylation on Day 1 and Day 15 is shown above each graph. Values are expressed as means ± SEM. * significantly different from basal and # significantly different from Day 1; P < 0.05.

Fig. 6

Fig. 6. Insulin and glucose concentrations

Plasma insulin (A) and glucose (B) concentrations obtained at Day 0 (□) and Day 14 (•) of leucine supplementation. Measurements were made before and every 20 min after ingestion of the simulated meal. Values are expressed as means ± SEM. * significantly different from basal and # significantly different from Day 1; P < 0.05.

Similar articles

Cited by

References

    1. Volpi E, Mittendorfer B, Rasmussen BB, Wolfe RR. The response of muscle protein anabolism to combined hyperaminoacidemia and glucose-induced hyperinsulinemia is impaired in the elderly. J Clin Endocrinol Metab. 2000;85(12):4481–90. - PMC - PubMed
    1. Katsanos CS, Kobayashi H, Sheffield-Moore M, Aarsland A, Wolfe RR. Aging is associated with diminished accretion of muscle proteins after the ingestion of a small bolus of essential amino acids. Am J Clin Nutr. 2005;82(5):1065–73. - PubMed
    1. Cuthbertson D, Smith K, Babraj J, Leese G, Waddell T, Atherton P, et al. Anabolic signaling deficits underlie amino acid resistance of wasting, aging muscle. Faseb J. 2005;19(3):422–4. - PubMed
    1. Paddon-Jones D, Sheffield-Moore M, Aarsland A, Wolfe RR, Ferrando AA. Exogenous amino acids stimulate human muscle anabolism without interfering with the response to mixed meal ingestion. Am J Physiol Endocrinol Metab. 2005;288(4):E761–7. - PubMed
    1. Paddon-Jones D, Short KR, Campbell WW, Volpi E, Wolfe RR. Role of dietary protein in the sarcopenia of aging. Am J Clin Nutr. 2008;87(5):1562S–6S. - PubMed

Publication types

MeSH terms

Substances

Grants and funding

LinkOut - more resources