title: The negative association between plasma ghrelin and IGF-I is modified by obesity, insulin resistance and type 2 diabetes.
abstract: OBJECTIVE
  Ghrelin is a natural growth hormone-releasing peptide thought to be involved in the regulation of energy metabolism. The recent studies concerning the association between ghrelin and insulin-like growth factor-I (IGF-I) concentrations have shown either negative correlation or no correlation at all. The aims of this study were to clarify the association between ghrelin and IGF-I concentrations in a large cohort and to characterize whether obesity, insulin resistance and type 2 diabetes affect this association.
  
  
  METHODS
  We analysed fasting plasma ghrelin and IGF-I concentrations of 1,004 middle-aged subjects of the population-based OPERA study. Insulin resistance was estimated using QUICKI.
  
  
  RESULTS
  IGF-I concentrations were negatively associated with ghrelin concentrations in the analysis of all subjects before (beta=-0.32, p<0.001) and after adjustments for BMI, insulin levels, sex and age (beta=-0.40, p<0.001). The association was particularly strong in males and in the higher BMI tertiles. The degree of association varied in relation to the glycaemic status: no insulin resistance: r(2)=6.5% (p<0.001), insulin resistance without type 2 diabetes: r(2)=21.0% (p<0.001), type 2 diabetes: r(2)=25.4 (p<0.001). IGF-I levels explained larger proportion (r(2)=9.8%) of the variation in ghrelin concentrations compared to fasting insulin concentration (r(2)=3.0%) and BMI (r(2)=1.5%).
  
  
  CONCLUSIONS
  There is a negative and independent association between ghrelin and IGF-I concentrations in middle-aged subjects. The interaction between IGF-I and ghrelin is modified by obesity, IR and type 2 diabetes. Further studies are warranted to elucidate the role of ghrelin in the development of these states.
authors.affiliation: Department of Internal Medicine, University of Oulu, P.O. Box 5000, 90014 Oulu, Finland. seppo.poykko@ppshp.fi
authors.forename: S M
authors.initials: SM
authors.lastname: Pöykkö
authors.forename: O
authors.initials: O
authors.lastname: Ukkola
authors.forename: H
authors.initials: H
authors.lastname: Kauma
authors.forename: E
authors.initials: E
authors.lastname: Kellokoski
authors.forename: S
authors.initials: S
authors.lastname: Hörkkö
authors.forename: Y A
authors.initials: YA
authors.lastname: Kesäniemi
mesh_terms: D000328:Adult; D001161:Arteriosclerosis / Q000453:epidemiology; D015331:Cohort Studies; D003924:Diabetes Mellitus, Type 2 / Q000097:blood*; D005260:Female; D005387:Finland / Q000453:epidemiology; D054439:Ghrelin; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood*; D036361:Peptide Hormones / Q000097:blood*; D012044:Regression Analysis; D015203:Reproducibility of Results; D012307:Risk Factors; D012727:Sex Characteristics
chemical_list: D054439:Ghrelin; D036361:Peptide Hormones; D007334:Insulin-Like Growth Factor I