Fed state protein turnover in healthy older persons under a usual protein-rich diet.
The objective of this study was to verify the protein turnover rates of healthy older persons under a usual protein-rich diet and to compare values to those described in the literature. This cross-sectional study was conducted at Metabolism Unit, Univ. Hospital of the School of Medicine of Ribeirao Preto, Univ. of Sao Paulo, Brazil. In this study, 7 healthy older persons aged 65.4 +/- 2.8 y, with BMI 22.7 +/- 2.4 kg/m(2) and a mean daily protein intake of 1.34 g of protein/kg were studied. A 9-h whole-body (15)N-glycine single-dose study was performed after an overnight fast. During the study, each subject received 6 isoenergetic, isonitrogenous meals at 2-h intervals based on their average intake. Ammonium, urea, and total nitrogen were quantified and analyzed by mass spectrometry, with the determination of total protein turnover rates by the (15)N-glycine method. The results show that total nitrogen output was 3.2 +/- 0.96 g/N and intake 7.7 +/- 1 g/N, (15)N nitrogen flux was 30.6 +/- 6.3 g/9 h. Endogenous nitrogen balance was positive (4.5 g +/- 1 g/N in 9 h). In conclusion, the protein turnover of healthy older persons under a usual protein-rich diet is positive during the fed state and has synthesis and degradation rates similar to those previously described in studies involving diet adaptation periods.
Pfrimer
Karina
K
Div. of General Internal and Geriatric Medicine, Univ. of São Paulo, Brazil. karinapfrimer@uol.com.br
Marchini
Julio Sergio
JS
Moriguti
Julio Cesar
JC
Ferriolli
Eduardo
E
D000368:Aged; D000375:Aging / Q000378:metabolism*; D000641:Ammonia / Q000652:urine; D000886:Anthropometry; D004044:Dietary Proteins / Q000008:administration & dosage*; D005260:Female; D005998:Glycine; D006801:Humans; D008297:Male; D008875:Middle Aged; D009584:Nitrogen / Q000652:urine; D009587:Nitrogen Isotopes; D011506:Proteins / Q000378:metabolism*; D014508:Urea / Q000097:blood / Q000652:urine
D004044:Dietary Proteins; D009587:Nitrogen Isotopes; D011506:Proteins; D000641:Ammonia; D014508:Urea; D009584:Nitrogen; D005998:Glycine