title: Role of selected amino acids on plasma IGF-I concentration in infants.
abstract: OBJECTIVE
  Insulin-like growth factor-I (IGF-I) is related to growth and its secretion is modified by protein intake in early infancy. We examined the relationship of dietary protein and circulating amino acids on plasma IGF-I levels and early growth.
  
  
  METHODS
  Healthy formula-fed infants (n = 213) were randomly assigned to receive either a protein-reduced infant formula with alpha-lactalbumin-enriched whey and free tryptophan and phenylalanine (IF) or an isocaloric standard formula without free amino acids (CF) for the first 120 days of life. A group of breastfed (BF) infants was studied as a non-randomized reference cohort. Biochemical variables were measured shortly after birth (subpopulation) and at an age of 120 days. A path analysis was used to explore the relationship between IGF-I, insulin and amino acids. Results are derived from secondary analyses of a randomized controlled trial.
  
  
  RESULTS
  Plasma concentrations of IGF-I at 120 days were significantly higher in IF than in CF infants [58.5 (15.0) vs. 53.7 (9.95) ng/mL; p = 0.020]. BF infants showed lower IGF-I concentrations of 41.6 (10.7) ng/mL. All amino acids but Thr and Cit had a more marked effect on insulin than on IGF-I level. Considering weight, sex and feeding group, Trp explained an equal percentage of variance of IGF-I and insulin (total R212.5 % of IGF-I and 12.3 % of insulin), while branched-chain AA explained an up to twofold higher variance of insulin than IGF-I. Compared to CF, IF explained 18.9 % of the IGF-I level (p = 0.03), while for insulin no direct effect was detectable.
  
  
  CONCLUSIONS
  Higher IGF-I concentrations and growth velocities in infants receiving protein-reduced IF indicate that the protein concentration of an infant formula alone does not control IGF-I levels and growth. Other components (e.g., selected amino acids) of infant formulae might control directly or indirectly via insulin influence IGF-I.
authors.affiliation: Dr. von Hauner Children's Hospital, Ludwig Maximilians University of Munich, Munich, Germany. Manja.Fleddermann@med.uni-muenchen.de.
authors.forename: Manja
authors.initials: M
authors.lastname: Fleddermann
authors.affiliation: Dr. von Hauner Children's Hospital, Ludwig Maximilians University of Munich, Munich, Germany.
authors.forename: Hans
authors.initials: H
authors.lastname: Demmelmair
authors.affiliation: Dr. von Hauner Children's Hospital, Ludwig Maximilians University of Munich, Munich, Germany.
authors.forename: Veit
authors.initials: V
authors.lastname: Grote
authors.affiliation: Endocrine Research Unit, Medizinische Klinik und Poliklinik IV, Ludwig Maximilians University of Munich, Munich, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Bidlingmaier
authors.affiliation: Endocrine Research Unit, Medizinische Klinik und Poliklinik IV, Ludwig Maximilians University of Munich, Munich, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Grimminger
authors.affiliation: Endocrine Research Unit, Medizinische Klinik und Poliklinik IV, Ludwig Maximilians University of Munich, Munich, Germany.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Bielohuby
authors.affiliation: Dr. von Hauner Children's Hospital, Ludwig Maximilians University of Munich, Munich, Germany.
authors.forename: Berthold
authors.initials: B
authors.lastname: Koletzko
mesh_terms: D000596:Amino Acids / Q000097:blood* / Q000502:physiology; D004032:Diet; D004044:Dietary Proteins; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007223:Infant; D041943:Infant Formula; D007227:Infant Nutritional Physiological Phenomena; D007231:Infant, Newborn; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D007768:Lactalbumin / Q000008:administration & dosage; D008297:Male; D008895:Milk, Human; D010649:Phenylalanine / Q000008:administration & dosage; D014364:Tryptophan / Q000008:administration & dosage; D015430:Weight Gain / Q000502:physiology
chemical_list: D000596:Amino Acids; D004044:Dietary Proteins; D007328:Insulin; D010649:Phenylalanine; D007334:Insulin-Like Growth Factor I; D014364:Tryptophan; D007768:Lactalbumin
keywords: Alpha-lactalbumin; Growth regulation; Human milk; Infant formula; Insulin-like growth factor-I