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Am J Clin Nutr. 2006 Sep;84(3):623-32. Links
Co-ingestion of protein and leucine stimulates muscle protein synthesis rates to the same extent in young and elderly lean men.
* Koopman R,
* Verdijk L,
* Manders RJ,
* Gijsen AP,
* Gorselink M,
* Pijpers E,
* Wagenmakers AJ,
* van Loon LJ.
Departments of Human Biology and Movement Sciences, Maastricht University, Maastricht, Netherlands; Numico Research BV, Wageningen, Netherlands.
BACKGROUND: The progressive loss of skeletal muscle mass with aging is attributed to a disruption in the regulation of skeletal muscle protein turnover.
OBJECTIVE: We investigated the effects on whole-body protein balance and mixed-muscle protein synthesis rates of the ingestion of carbohydrate with or without protein and free leucine after simulated activities of daily living.
DESIGN: Eight elderly (75 +/- 1 y) and 8 young (20 +/- 1 y) lean men were randomly assigned to 2 crossover experiments in which they consumed either carbohydrate (CHO) or carbohydrate plus protein and free leucine (CHO+Pro+Leu) after performing 30 min of standardized activities of daily living. Primed, continuous infusions with l-[ring-(13)C(6)]phenylalanine and l-[ring-(2)H(2)]tyrosine were applied, and blood and muscle samples were collected to assess whole-body protein turnover and the protein fractional synthetic rate in the vastus lateralis muscle over a 6-h period. RESULTS: Whole-body phenylalanine and tyrosine flux were significantly higher in the young than in the elderly men (P < 0.01). Protein balance was negative in the CHO experiment but positive in the CHO+Pro+Leu experiment in both groups. Mixed-muscle protein synthesis rates were significantly greater in the CHO+Pro+Leu than in the CHO experiment in both the young (0.082 +/- 0.005%/h and 0.060 +/- 0.005%/h, respectively; P < 0.01) and the elderly (0.072 +/- 0.006%/h and 0.043 +/- 0.003%/h, respectively; P < 0.01) subjects, with no significant differences between groups.
CONCLUSIONS: Co-ingestion of protein and leucine with carbohydrate after activities of daily living improves whole-body protein balance, and the increase in muscle protein synthesis rates is not significantly different between lean young and elderly men.
http://www.ajcn.org/cgi/reprint/84/3/623.pdf
Co-ingestion of protein and leucine stimulates muscle protein synthesis rates to the same extent in young and elderly lean men.
* Koopman R,
* Verdijk L,
* Manders RJ,
* Gijsen AP,
* Gorselink M,
* Pijpers E,
* Wagenmakers AJ,
* van Loon LJ.
Departments of Human Biology and Movement Sciences, Maastricht University, Maastricht, Netherlands; Numico Research BV, Wageningen, Netherlands.
BACKGROUND: The progressive loss of skeletal muscle mass with aging is attributed to a disruption in the regulation of skeletal muscle protein turnover.
OBJECTIVE: We investigated the effects on whole-body protein balance and mixed-muscle protein synthesis rates of the ingestion of carbohydrate with or without protein and free leucine after simulated activities of daily living.
DESIGN: Eight elderly (75 +/- 1 y) and 8 young (20 +/- 1 y) lean men were randomly assigned to 2 crossover experiments in which they consumed either carbohydrate (CHO) or carbohydrate plus protein and free leucine (CHO+Pro+Leu) after performing 30 min of standardized activities of daily living. Primed, continuous infusions with l-[ring-(13)C(6)]phenylalanine and l-[ring-(2)H(2)]tyrosine were applied, and blood and muscle samples were collected to assess whole-body protein turnover and the protein fractional synthetic rate in the vastus lateralis muscle over a 6-h period. RESULTS: Whole-body phenylalanine and tyrosine flux were significantly higher in the young than in the elderly men (P < 0.01). Protein balance was negative in the CHO experiment but positive in the CHO+Pro+Leu experiment in both groups. Mixed-muscle protein synthesis rates were significantly greater in the CHO+Pro+Leu than in the CHO experiment in both the young (0.082 +/- 0.005%/h and 0.060 +/- 0.005%/h, respectively; P < 0.01) and the elderly (0.072 +/- 0.006%/h and 0.043 +/- 0.003%/h, respectively; P < 0.01) subjects, with no significant differences between groups.
CONCLUSIONS: Co-ingestion of protein and leucine with carbohydrate after activities of daily living improves whole-body protein balance, and the increase in muscle protein synthesis rates is not significantly different between lean young and elderly men.
http://www.ajcn.org/cgi/reprint/84/3/623.pdf