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Franca F. Kirchberg, Ulrike Harder, Martina Weber, Veit Grote, Hans Demmelmair, Wolfgang Peissner, Peter Rzehak, Annick Xhonneux, Clotilde Carlier, Natalia Ferre, Joaquin Escribano, Elvira Verduci, Piotr Socha, Dariusz Gruszfeld, Berthold Koletzko, Christian Hellmuth, for The European Childhood Obesity Trial Study Group, Dietary Protein Intake Affects Amino Acid and Acylcarnitine Metabolism in Infants Aged 6 Months, The Journal of Clinical Endocrinology & Metabolism, Volume 100, Issue 1, 1 January 2015, Pages 149–158, https://doi.org/10.1210/jc.2014-3157
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Abstract
The protective effect of breast-feeding against later obesity may be explained by the lower protein content compared with formula milk. However, the metabolic mechanisms remain unknown.
We studied the metabolic response to a higher or lower protein supply in infancy.
The Childhood Obesity Project study is a double-blind, randomized, multicenter intervention trial. Infants were randomized to receive a higher (HP) or lower protein (LP) content infant formula or were breast-fed.
Plasma samples of 691 infants who received formula milk with different protein content (HP, 2.05 g per 100 mL; LP, 1.25 g per 100 mL) or were breast-fed were collected.
Changes in plasma amino acid and acylcarnitine concentrations of 6-month-old infants according to different dietary protein supply were determined by liquid chromatography coupled to tandem mass spectrometry.
Twenty-nine metabolites differed significantly between the formula groups. Branched-chain amino acids (BCAAs) were the most discriminant metabolites. Their degradation products, the short-chain acylcarnitines C3, C4, and C5, were also significantly elevated in the HP group. A breakpoint analysis confirmed that with increasing BCAAs, the ratio between acylcarnitines and BCAAs decreases. Long-chain acylcarnitines were decreased in HP infants.
BCAAs seem to play a pivotal role in the effect of a high-protein diet on β-oxidation and fat storage. We provide new evidence for a possible saturation of the BCAA degradation pathway that may represent the mechanism by which high-protein intake affects the metabolic regulation. Moreover, it appears to inhibit the initial step of the β-oxidation, thus leading to high early weight gain and body fat deposition.
