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Postprandial oxidative losses of free and protein‐bound amino acids in the diet: interactions and adaptation
Author(s) -
Nolles J. A.,
Verreijen A. M.,
Koopmanschap R. E.,
Verstegen M. W. A.,
Schreurs V. V. A. M.
Publication year - 2009
Publication title -
journal of animal physiology and animal nutrition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.651
H-Index - 56
eISSN - 1439-0396
pISSN - 0931-2439
DOI - 10.1111/j.1439-0396.2008.00820.x
Subject(s) - leucine , postprandial , amino acid , biochemistry , food science , biology , egg white , oxidative phosphorylation , complete protein , chemistry , medicine , endocrinology , insulin
Summary Postprandial oxidation of dietary free amino acids or egg white protein was studied using the [ 13 CO 2 ] breath test in rats, as well as in humans. Thirty‐eight male rats were assigned to four dietary test groups. Two diets only differed in their protein fraction. Diet I contained 21% egg white protein. For the breath test egg white protein, intrinsically labelled with [1‐ 13 C]‐leucine, was used as a substrate. Diet II contained the same amino acids as diet I, though not as egg white protein but in free form. Free [1‐ 13 C]‐leucine was used to label this diet. In addition, two 1:1 mixtures of both diets were used. During the breath test either the free amino acid or the protein fraction was labelled as in diets I or II. The animals were breath‐tested following short‐term (day 5) and long‐term adaptation (day 20) to their experimental diet. For all diets, including the mixed diets, postprandial oxidative losses on day 5 were significantly higher for the free leucine compared with the protein‐derived leucine. Differences between free and protein‐derived leucine oxidation had, however, largely disappeared on day 20. The human subjects were breath‐tested without any adaptation period to the diets. The oxidative losses of free leucine were also higher than those of protein‐derived leucine. None of the studies showed any indication for an interaction between the oxidation of protein‐derived amino acids and free amino acids. It is concluded that free and protein‐derived amino acids in the diet are mainly metabolized independently.