Marginal protein intake results in reduced plasma IGF-I levels and skeletal muscle fiber atrophy in elderly women.
We investigated the effects of dietary protein on plasma IGF-I levels and muscle fiber cross-sectional area (CSA). Twelve healthy elderly women were randomly assigned to a weight-maintaining diet containing either 1.47 (marginal) or 2.94 (adequate) g protein/kg body cell mass (BCM)/d, (0.45 and 0.92 g/kg body weight/d, respectively) for 10wks. Plasma IGF-I levels and muscle fiber areas and distributions were evaluated at baseline and 10wks. After 10wks, both IGF-I and type I fiber CSA had declined significantly in subjects fed the marginal diet (30.1+/-2.1% and 32.7+/-7.9%, respectively) while they increased in those fed the adequate diet (19.5+/-7.0% and 22.3+/-7.5%, for IGF-I and type I CSA, respectively). The change in IGF-I was the only significantly associated with the change in type I fiber CSA (r2=0.70; p<0.03). These findings show that marginal dietary protein intakes will result in losses of muscle mass in the elderly and suggest a role for plasma IGF-I as a biochemical marker for the histological changes in skeletal muscle.
Castaneda
C
C
Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, 711 Washington St., Boston MA 02111. ccastaneda@hnrc. tufts.edu
Gordon
P L
PL
Fielding
R A
RA
Evans
W J
WJ
Crim
M C
MC
D000368:Aged; D000375:Aging / Q000502:physiology*; D015415:Biomarkers / Q000097:blood; D001823:Body Composition; D018753:Diet, Protein-Restricted / Q000009:adverse effects*; D004044:Dietary Proteins / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008137:Longitudinal Studies; D018485:Muscle Fibers, Skeletal / Q000473:pathology; D018482:Muscle, Skeletal / Q000473:pathology*; D009133:Muscular Atrophy / Q000175:diagnosis / Q000209:etiology*; D009584:Nitrogen / Q000378:metabolism
D015415:Biomarkers; D004044:Dietary Proteins; D007334:Insulin-Like Growth Factor I; D009584:Nitrogen