title: Does insulin-like growth factor-1 mediate protein-induced kidney growth in infants? A secondary analysis from a randomized controlled trial.
abstract: BACKGROUND
  Animal models have shown that insulin-like growth factor I (IGF-I) may mediate protein-induced kidney growth. Our aim was to analyze the effect of IGF-I on protein-induced kidney growth in healthy infants.
  
  
  METHODS
  This is a secondary analysis of a randomized trial that compared growth of infants fed with a higher-protein (HP) (n = 169) vs. lower-protein (LP) (n = 182) formula (in the first year of life). Outcome measures were anthropometric parameters, kidney volume (cm(3)), and total and free IGF-I (ng/ml).
  
  
  RESULTS
  The highest levels of total and free IGF-I were found in the HP group. Both parameters correlated significantly with BMI z-score (r = 0.229, P < 0.001 and r = 0.223, P < 0.001, respectively), kidney volume (r = 0.115, P = 0.006 and r = 0.208, P < 0.001, respectively), and kidney volume/body length (r = 0.109, P = 0.010 and r = 0.194, P < 0.001, respectively) at 6 mo. Linear regression analyses showed a significant effect of free IGF-I on kidney volume in models, including significant effects of HP formula and anthropometry. The structural equation model revealed a significant direct effect of the HP formula on kidney volume and an indirect effect mediated by free IGF-I.
  
  
  CONCLUSIONS
  This study suggests that IGF-I partly mediates protein-induced kidney growth in healthy infants. IGF-I could be involved in a pathway for the programming of the renal system.
authors.affiliation: Pediatrics Research Unit, Universitat Rovira i Virgili, IISPV, Reus, Spain.
authors.forename: Veronica
authors.initials: V
authors.lastname: Luque
authors.forename: Joaquin
authors.initials: J
authors.lastname: Escribano
authors.forename: Veit
authors.initials: V
authors.lastname: Grote
authors.forename: Natalia
authors.initials: N
authors.lastname: Ferre
authors.forename: Berthold
authors.initials: B
authors.lastname: Koletzko
authors.forename: Dariusz
authors.initials: D
authors.lastname: Gruszfeld
authors.forename: Piotr
authors.initials: P
authors.lastname: Socha
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Langhendries
authors.forename: Philippe
authors.initials: P
authors.lastname: Goyens
authors.forename: Ricardo
authors.initials: R
authors.lastname: Closa-Monasterolo
mesh_terms: D000886:Anthropometry; D004044:Dietary Proteins / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D007223:Infant; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007668:Kidney / Q000000981:diagnostic imaging / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*; D018709:Statistics, Nonparametric; D014463:Ultrasonography
chemical_list: D004044:Dietary Proteins; D007334:Insulin-Like Growth Factor I