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In rats fed a high protein diet, almost half of the carbon skeletons derived from dietary amino acid deamination are not oxidized during the postprandial phase
Author(s) -
Gaudichon Claire,
AzzoutMarniche Dalila,
Luengo Catherine,
Dare Sophie,
Even Patrick,
Tomé Daniel
Publication year - 2007
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.21.5.a162-a
Subject(s) - postprandial , amino acid , deamination , chemistry , glycogen , oxidative deamination , medicine , urine , metabolism , gluconeogenesis , biochemistry , endocrinology , urea , biology , enzyme , insulin
We showed in rats fed a high protein diet an increase of PEPCK but not G6Pase gene expression in the liver, suggesting that newly synthesized glucose could be stored into glycogen. Thus a part of deaminated dietary amino acids may not be oxidized. To quantify this, we performed a double tracer study. Fifteen rats were fed for 2 weeks a normal (NP, n=7) or a high (HP, n=8) protein diet. The day before the test, they were placed into a calorimetric chamber and infused with a NaCl solution. After fasting overnight, rats ingested a 4 g NP or HP meal, containing 5 mg of 20 U‐ 13 C and U‐ 15 N amino acids. CO 2 and O 2 exchanges were continuously recorded, urines were collected and blood and expired air were sampled for 4 h. Rats were sacrificed to collect total blood, bladder urine and digestive contents. Isotope enrichments were determined by IRMS. The % of deamination was calculated from 15 N recovery in the urines and body urea, and the % of oxidation from 13 C recovery in expired CO 2 . Postprandial fate of dietary amino acidsIn NP rats, 91 % of deaminated amino acids were oxidized in the 4h postprandial phase, versus 47 % in HP rats. We thus confirmed that a significant part of neosynthesized glucose from dietary amino acids in rats fed a HP diet was stored into liver glycogen. This phenomenon must be considered to correct calorimetry equations used to calculate the substrate oxidation.