The effect of severe dietary restriction on intramuscular glutamine concentrations and protein synthetic rate.
An investigation was carried out to examine the relationship between fractional muscle protein synthetic rate (FSR) and intramuscular glutamine concentration ({GLN}(i)) in rats that had a dietary intake which was deficient in both protein and energy. Young male rats (38 days old) were fed for 48 h on either 1) 25% of the ad lib intake of a 20% protein diet, or 2) glucose alone, sufficient to provide the same energy intake as in 1). In a separate study, 33 day old rats were starved completely for 48 h. Appropriate controls were included in both studies. Muscle FSR, which was reduced by 40% in both groups of energy restricted rats (P<0.001), was associated with a small increase in {GLN}(i) (P<0.05). Starvation produced a 60% reduction in FSR (P<0.01) and a 45% (P<0.05) reduction in {GLN}(i). It is concluded that reductions in muscle protein synthesis can occur by mechanisms independent of intramuscular glutamine concentration.
Khan
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MRC Dunn Nutrition Unit, Downham's Lane, Milton Road, Cambridge CB4 1XJ, UK.
Wusteman
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Wood
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Elia
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