title: Does glutamine supplementation decrease the response of muscle glutamine synthesis to fasting in muscle in adult and very old rats?
abstract: BACKGROUND
  Glutamine synthetase (GS), a key enzyme in the production of glutamine, is preserved in rat skeletal muscle during aging but is increased with advanced age in vivo. The aim of this study was to determine whether glutamine supplementation affects up-regulation of GS by fasting in vivo in adult and very old female rats.
  
  
  METHODS
  Muscle GS activities were assessed in 5-day-fasted female Wistar adult (6 months) and very old (27 months) rats refed and supplemented with glutamine or other amino acids (alanine or glycine). Fed rats were used to investigate the possible effect of glutamine supplementation in the fed state.
  
  
  RESULTS
  After 5 days' fasting, the up-regulated GS activity was decreased whatever the type of amino acid supplementation (glutamine, alanine, and glycine) in adults, whereas it was only decreased by glutamine supplementation in very old rats). In the fed state, no effect of glutamine supplementation was observed even if GS activity remained up-regulated whatever the age and the period of supplementation.
  
  
  CONCLUSIONS
  These results confirm that glutamine has a specific role in very old rats. The up-regulated GS activity was decreased by an exogenous supply of glutamine only if intramuscular glutamine was depleted; this was confirmed by studies in the fed state. The up-regulated GS activity in both fed and fasted rats may be associated with increased glutamine requirements in the whole body.
authors.affiliation: Human Nutrition Unit, St Genes-Champanelle, France.
authors.forename: Michelle
authors.initials: M
authors.lastname: Mignon
authors.forename: Loïc
authors.initials: L
authors.lastname: Lêvêque
authors.forename: Emilie
authors.initials: E
authors.lastname: Bonnel
authors.forename: Dominique
authors.initials: D
authors.lastname: Meynial-Denis
mesh_terms: D000375:Aging / Q000378:metabolism / Q000502:physiology; D000818:Animals; D019587:Dietary Supplements; D004195:Disease Models, Animal; D005215:Fasting / Q000378:metabolism; D005260:Female; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism*; D005973:Glutamine / Q000096:biosynthesis* / Q000494:pharmacology*; D018482:Muscle, Skeletal / Q000201:enzymology / Q000378:metabolism*; D009751:Nutritional Requirements; D051381:Rats; D017208:Rats, Wistar
chemical_list: D005973:Glutamine; D005974:Glutamate-Ammonia Ligase