title: Cross-sectional and longitudinal associations between insulin-like growth factor I and metabolic syndrome: a general population study in German adults.
abstract: BACKGROUND
  A previous study showed an inverse association between the insulin-like growth factor I (IGF-I) and the risk of impaired glucose tolerance or diabetes mellitus. Moreover, myocardial infarction patients with high baseline IGF-I levels had a lower risk of diabetes mellitus. These data suggested a protective effect of IGF-I against the development of metabolic syndrome. However, there are no longitudinal data regarding IGF-I and metabolic syndrome. The aim of the present study was to investigate the longitudinal association between IGF-I and metabolic syndrome.
  
  
  METHODS
  Data from the population-based Study of Health in Pomerania, Germany, were used for cross-sectional (n = 3903) and longitudinal (n = 2143) analyses (5-year follow-up). Metabolic syndrome was defined by three or more of the following five components: abdominal obesity, elevated triglycerides, reduced high-density lipoprotein cholesterol, elevated blood pressure and elevated nonfasting glucose. Serum IGF-I and IGF binding protein 3 (IGFBP-3) were determined by chemiluminescence immunoassays. Logistic and Poisson regression analyses were performed to determine associations.
  
  
  RESULTS
  In cross-sectional analyses high IGFBP-3 as well as high and low IGF-I/IGFBP-3 ratio levels were associated with prevalent metabolic syndrome. In longitudinal analyses, the direction of the relation changed: men but not women with high IGF-I or IGF-I/IGFBP-3 ratio levels had an increased, whereas men with low levels had a decreased risk of incident metabolic syndrome.
  
  
  CONCLUSIONS
  In concordance with previous studies, our cross-sectional analyses showed a relation between low IGF-I/IGFBP-3 ratio and the prevalence of metabolic syndrome. In contrast, the longitudinal analyses indicated that a high IGF-I level was a risk marker for incident metabolic syndrome.
authors.affiliation: Institute of Clinical Chemistry and Laboratory Medicine, University Medicine Greifswald, Ferdinand-Sauerbruch-Straße NK, D-17475, Greifswald, Germany.
authors.forename: Nele
authors.initials: N
authors.lastname: Friedrich
authors.forename: Matthias
authors.initials: M
authors.lastname: Nauck
authors.forename: Sabine
authors.initials: S
authors.lastname: Schipf
authors.forename: Henry
authors.initials: H
authors.lastname: Völzke
authors.forename: Georg
authors.initials: G
authors.lastname: Brabant
authors.forename: Henri
authors.initials: H
authors.lastname: Wallaschofski
mesh_terms: D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D005858:Germany / Q000453:epidemiology; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008137:Longitudinal Studies; D008297:Male; D024821:Metabolic Syndrome / Q000097:blood / Q000453:epidemiology*; D008875:Middle Aged; D012307:Risk Factors; D055815:Young Adult
chemical_list: D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I
keywords: IGF-I; IGFBP-3; Study of Health in Pomerania (SHIP); metabolic syndrome; type 2 diabetes mellitus