title: Muscle and liver protein synthesis adapt efficiently to food deprivation and refeeding in 12-month-old rats.
abstract: Our aim was to analyze mechanisms involved in the adaptation of protein metabolism to food deprivation and refeeding in adult rats. Twelve-month-old rats, which had been food-deprived for 113 h and refed for 6 h, were injected subcutaneously with a flooding dose of valine (with 50% [1-13C]-L-valine) to measure in vivo protein synthesis in tibialis anterior, soleus and liver. Protein and RNA contents were also measured. In both muscles, protein mass was maintained during food deprivation. Due to a drop in protein synthetic capacity (Cs), total and myofibrillar protein synthesis rates were reduced in food-deprived rats and were not stimulated by a 6-h refeeding. In contrast, protein levels were maintained lower than RNA levels in liver during food deprivation, and Cs was higher than in fed rats. Protein synthesis rates and ribosomal efficiency were reduced in food-deprived rats. Due to maintenance of protein synthetic capacity, there was a rapid stimulation of liver protein synthesis with refeeding, which induced a significant rise in protein mass (also related to an inhibition of protein degradation). In conclusion, coordinated responses of liver and muscles allowed a sparing of muscle proteins during food deprivation and a rapid recovery of liver proteins during refeeding. Control of ribosome quantity could play a critical role in these adaptations in tissue protein synthesis in adult rats.
authors.affiliation: Laboratoire d'Etude du Métabolisme Azoté, INRA Clermont-Ferrand Theix, Champanelle, France.
authors.forename: L
authors.initials: L
authors.lastname: Mosoni
authors.forename: T
authors.initials: T
authors.lastname: Malmezat
authors.forename: M C
authors.initials: MC
authors.lastname: Valluy
authors.forename: M L
authors.initials: ML
authors.lastname: Houlier
authors.forename: P P
authors.initials: PP
authors.lastname: Mirand
mesh_terms: D000375:Aging / Q000378:metabolism; D000818:Animals; D001835:Body Weight / Q000502:physiology; D004435:Eating / Q000502:physiology*; D005508:Food Deprivation / Q000502:physiology*; D008099:Liver / Q000737:chemistry / Q000378:metabolism*; D008297:Male; D009124:Muscle Proteins / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics; D018482:Muscle, Skeletal / Q000737:chemistry / Q000378:metabolism*; D009929:Organ Size / Q000502:physiology; D014176:Protein Biosynthesis; D011506:Proteins / Q000032:analysis / Q000235:genetics; D012313:RNA / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014633:Valine / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology
chemical_list: D009124:Muscle Proteins; D011506:Proteins; D012313:RNA; D014633:Valine