Metabolic pathways implicated in the kinectic impairment of muscle glutamine homeostatis in adult and old glucocorticoid-treated rats

An impairment of muscle glutamine metabolism in response to dexamethasone (DEX) occurs with aging. To better characterize this alteration, we have investigated muscle glutamine release with regard to muscle glutamine production (net protein breakdown, de novo glutamine synthesis) in adult and old gl...

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Bibliographic Details
Published in:American journal of physiology: endocrinology and metabolism 2004-10, Vol.50 (4), p.E671
Main Authors: Minet-Quinard, R, Moinard, C, Villie, F, Vasson, M P, Cynober, L
Format: Article
Language:English
Subjects:
Age
Amino acids
Kinetics
Metabolism
Muscular system
Proteins
Rodents
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Summary:An impairment of muscle glutamine metabolism in response to dexamethasone (DEX) occurs with aging. To better characterize this alteration, we have investigated muscle glutamine release with regard to muscle glutamine production (net protein breakdown, de novo glutamine synthesis) in adult and old glucocorticoid-treated rats. Male Sprague-Dawley rats (3 or 24 mo old) were divided into seven groups: three groups received 1.5 mg/kg of DEX once a day by intraperitoneal injection for 3, 5, or 7 days; three groups were pair fed to the three treated groups, respectively; and one control group of healthy rats was fed ad libitum. Muscle glutamine synthetase activity increased earlier in old rats (day 3) than in adult rats (day 7), whereas an increase in muscle glutamine release occurred later in old rats (day 5) than in adult DEX-treated rats (day 3). Consequently, muscle glutamine concentration decreased later in old rats (day 5) than in adults (day 3). Finally, net muscle protein breakdown increased only in old DEX-treated rats (day 7). In conclusion, the impairment of muscle glutamine metabolism is due to a combination of an increase in glutamine production and a delayed increase in glutamine release. [PUBLICATION ABSTRACT]
ISSN:0193-1849
1522-1555