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Fed State Protein Turnover in Healthy Older Persons under a Usual Protein-Rich Diet

Authors

  • Karina Pfrimer,

    1. Authors Pfrimer, Moriguti, and Ferriolli are with Div. of General Internal and Geriatric Medicine and author Marchini is with Div. of Clinical Nutrition, Dept. of Internal Medicine, School of Medicine of Ribeirão Preto, Univ. of São Paulo, Brazil. Direct inquiries to author Pfrimer (E-mail: karinapfrimer@uol.com.br).
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  • Julio Sergio Marchini,

    1. Authors Pfrimer, Moriguti, and Ferriolli are with Div. of General Internal and Geriatric Medicine and author Marchini is with Div. of Clinical Nutrition, Dept. of Internal Medicine, School of Medicine of Ribeirão Preto, Univ. of São Paulo, Brazil. Direct inquiries to author Pfrimer (E-mail: karinapfrimer@uol.com.br).
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  • Julio Cesar Moriguti,

    1. Authors Pfrimer, Moriguti, and Ferriolli are with Div. of General Internal and Geriatric Medicine and author Marchini is with Div. of Clinical Nutrition, Dept. of Internal Medicine, School of Medicine of Ribeirão Preto, Univ. of São Paulo, Brazil. Direct inquiries to author Pfrimer (E-mail: karinapfrimer@uol.com.br).
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  • Eduardo Ferriolli

    1. Authors Pfrimer, Moriguti, and Ferriolli are with Div. of General Internal and Geriatric Medicine and author Marchini is with Div. of Clinical Nutrition, Dept. of Internal Medicine, School of Medicine of Ribeirão Preto, Univ. of São Paulo, Brazil. Direct inquiries to author Pfrimer (E-mail: karinapfrimer@uol.com.br).
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Abstract

ABSTRACT:  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/m2 and a mean daily protein intake of 1.34 g of protein/kg were studied. A 9-h whole-body 15N-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 15N-glycine method. The results show that total nitrogen output was 3.2 ± 0.96 g/N and intake 7.7 ± 1 g/N, 15N 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.

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