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The present study was designed to assess the effects of dietary leucine supplementation on muscle protein synthesis and whole body protein kinetics in elderly individuals. Twenty healthy male subjects (70 +/- 1 years) were studied before and after continuous ingestion of a complete balanced diet supplemented or not with leucine. A primed (3.6 micromol(More)
Aging is characterized by a decrease of muscle mass associated with a decrease in postprandial anabolism. This study was performed to gain a better understanding of the intracellular mechanisms involved in the stimulation of muscle protein synthesis by amino acids and their role in the decrease of muscle sensitivity to food intake during aging. The effects(More)
We studied glucocorticoid-induced muscle wasting and subsequent recovery in adult (7-mo-old) and old (22-mo-old) rats, since the increased incidence of various disease states may result in glucocorticoids hypersecretion in aging. Adult and old rats received dexamethasone in their drinking water and were then allowed to recover. Muscle wasting occurred more(More)
Aging is characterized by a progressive loss of muscle mass. A decrease of muscle protein synthesis stimulation has been detected in the postprandial state and correlated to a decrease of muscle protein synthesis sensitivity to leucine in vitro. This study was undertaken to examine the effect of a leucine-supplemented meal on postprandial (PP) muscle(More)
A study was designed to compare the effects, in vitro, of insulin-like growth factor-1 (IGF-1) and insulin on rat epitrochlearis muscle metabolism during aging (1, 6-8, or 18-20 months). Our results showed that in young epitrochlearis, IGF-1 was equipotent to insulin in stimulating 2-deoxy-glucose and aminoisobutyric acid transport but more potent in(More)
Aging induces a dysregulation of immune and inflammation functions that may affect protein synthesis rates in lymphoid tissue and plasma proteins. We quantified in vivo synthesis rates of thymus, spleen and plasma proteins, including albumin and acute phase proteins, in adult (8 mo old) and old (22 mo old) rats using the flooding dose method [L-(1-(13)C)(More)
This study was designed to evaluate the role of phosphatidylinositol (PI3) kinase, p70 S6 kinase (p70S6K), and mitogen-activated protein (MAP) kinase in the regulation of muscle protein metabolism by insulin and insulin-like growth factor I (IGF-I). Wortmannin and LY294002 (inhibitors of P13 kinase) both abolished the stimulation of protein synthesis by(More)
Acute leucine supplementation of the diet has been shown to blunt defects in postprandial muscle protein metabolism in old rats. This study was undertaken to determine whether the effect of leucine persists in a 10-d experiment. For this purpose, adult (9 mo) and old (21 mo) rats were fed a semiliquid 18.2 g/100 g protein standard diet during the 8-h dark(More)
OBJECTIVE We previously found that aging was characterized by a decreased sensitivity of muscle protein synthesis to leucine and that a free leucine-supplemented diet corrected this defect in old rats and elderly humans. The present experiment was undertaken to evaluate the efficiency of selected leucine-rich proteins to stimulate postprandial muscle(More)
This study was performed to assess the effect of glucocorticoids (dexamethasone) on insulin- and IGF-I-regulated muscle protein metabolism in adult and old rats. Muscle atrophy occurred more rapidly in old rats, and recovery of muscle mass was impaired when compared with adults. Muscle wasting resulted mainly from increased protein breakdown in adult rat(More)