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A new method for the multi‐tissue estimation of protein turnover by compartmental analysis of the nitrogen isotope dynamics in rats fed a 15 N‐enriched diet
Author(s) -
Poupin Nathalie,
Huneau JeanFrançois,
Mariotti François,
Bos Cécile,
Tomé Daniel,
Fouillet Hélène
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.983.14
Subject(s) - protein turnover , metabolism , kidney , isotope , amino acid , compartment (ship) , chemistry , dynamics (music) , nitrogen , biochemistry , skeletal muscle , stable isotope ratio , biology , medicine , protein biosynthesis , endocrinology , physics , oceanography , organic chemistry , quantum mechanics , geology , acoustics
The rate at which a tissue incorporates the diet isotopic composition is known to relate to its metabolic activity. We propose a new approach to determine the fractional synthesis rate (FSR) of various body proteins simultaneously, based on the detailed analysis of the dynamic of δ 15 N ( 15 N: 14 N ratio relative to a standard) changes in the protein (P) and amino acid (AA) fractions of tissues following a shift in the diet δ 15 N. We measured the δ 15 N of the P and AA fractions of liver, kidney and muscle in male Wistar rats on days 0, 3, 8 and 17 after their initial diet was switched to a similar but 15 N‐enriched diet. We observed that the rate of incorporation of the new diet δ 15 N signature varied among tissues and reflected their protein turnover rates. We then developed a two‐compartment model representative of each tissue protein metabolism, which described the relationships between protein turnover and δ 15 N dynamics in P and AA. Using this model for the analysis of the observed δ 15 N dynamics, we estimated tissue FSR values of 22%/d, 18%/d and 4%/d for liver, kidney and muscle, respectively. Those values are in good correlation with findings from classic tracer studies, but with a systematic difference. Compared to usual approaches, such analysis of tissue δ 15 N dynamics seems a promising tool for estimating FSR in a more integrated manner (i.e. for a wider range of organs and tissues and considering all AA in the precursor pool).