title: Dietary protein intake affects amino acid and acylcarnitine metabolism in infants aged 6 months.
abstract: BACKGROUND
  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.
  
  
  OBJECTIVE
  We studied the metabolic response to a higher or lower protein supply in infancy.
  
  
  METHODS
  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.
  
  
  METHODS
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Division of Metabolic and Nutritional Medicine (F.F.K., U.H., M.W., V.G., H.D., W.P., P.R., B.K., C.H.), Dr von Hauner Children's Hospital, 80337 Munich, Germany; Centre Hospitalier Chrétien St Vincent (A.X.), 4000 Liège-Rocourt, Belgium; Department of Paediatrics (C.C.), University Children's Hospital Queen Fabiola, Université Libre de Bruxelles, 1020 Brussels, Belgium; Paediatrics Research Unit (N.F., J.E.), Universitat Rovira i Virgili, 43201 Reus, Spain; Department of Paediatrics (E.V.), San Paolo Hospital, University of Milan, 20142 Milano, Italy; and Neonatal Intensive Care Unit (P.S., D.G.), Children's Memorial Health Institute, 04-736 Warsaw, Poland.
authors.forename: Franca F
authors.initials: FF
authors.lastname: Kirchberg
authors.forename: Ulrike
authors.initials: U
authors.lastname: Harder
authors.forename: Martina
authors.initials: M
authors.lastname: Weber
authors.forename: Veit
authors.initials: V
authors.lastname: Grote
authors.forename: Hans
authors.initials: H
authors.lastname: Demmelmair
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Peissner
authors.forename: Peter
authors.initials: P
authors.lastname: Rzehak
authors.forename: Annick
authors.initials: A
authors.lastname: Xhonneux
authors.forename: Clotilde
authors.initials: C
authors.lastname: Carlier
authors.forename: Natalia
authors.initials: N
authors.lastname: Ferre
authors.forename: Joaquin
authors.initials: J
authors.lastname: Escribano
authors.forename: Elvira
authors.initials: E
authors.lastname: Verduci
authors.forename: Piotr
authors.initials: P
authors.lastname: Socha
authors.forename: Dariusz
authors.initials: D
authors.lastname: Gruszfeld
authors.forename: Berthold
authors.initials: B
authors.lastname: Koletzko
authors.forename: Christian
authors.initials: C
authors.lastname: Hellmuth
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D001835:Body Weight / Q000502:physiology*; D001942:Breast Feeding; D002331:Carnitine / Q000031:analogs & derivatives* / Q000378:metabolism; D004044:Dietary Proteins / Q000008:administration & dosage*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007223:Infant; D007225:Infant Food; D008297:Male; D009765:Obesity / Q000209:etiology / Q000378:metabolism
chemical_list: D000596:Amino Acids; D004044:Dietary Proteins; C116917:acylcarnitine; D002331:Carnitine