title: Heritability of plasma adiponectin levels and body mass index in twins.
abstract: BACKGROUND
  Adiponectin is suspected to exert antiatherogenic, antiinflammatory, and insulin-sensitizing effects. However, the relative importance of the genetic and environmental factors in influencing plasma adiponectin levels (ADPN) remains unclear.
  
  
  OBJECTIVE
  The aim of the study was to investigate whether ADPN and body mass index (BMI) are genetically determined.
  
  
  METHODS
  In a series of 60 pairs of healthy twins, we estimated genetic variance and heritability of ADPN and BMI using both ANOVA and path analysis methods. Twins were genotyped at two biallelic single nucleotide polymorphisms (SNPs) at the gene encoding adiponectin: the +45 T/G (on exon 2) and the -11377 G/C (on the promoter).
  
  
  RESULTS
  A total of 30 pairs of twins were Monozygotic (MZ), and 30 were dizygotic (DZ). The mean ADPN (+/-SD) was 10.6 +/- 5.7 in MZ and 11.1 +/- 4.5 in DZ twins (nonsignificant). Three tests of heritability (within pair = 1.13, P < 0.0001; among components = 1.62, P = 0.005; and intraclass correlation 1.34, P < 0.0001) consistently showed ADPN heritability. The preferred model of a likelihood-based analysis included an additive genetic influence and an individually unique environmental influence for ADPN, accounting for 88% and 12% of ADPN variance, respectively. We found a significantly higher within-pair difference of ADPN in DZ than in MZ pairs, and in +45 T/G SNP discordant compared with concordant DZ twins, indicating a significant effect of this adiponectin gene SNP on ADPN.
  
  
  CONCLUSIONS
  ADPN shows significant genetic variance and heritability, which is independent of BMI and partly accounted for by the +45 T/G, but not the -11377 G/C adiponectin gene SNP.
authors.affiliation: Department of Clinical and Experimental Medicine, Clinica Medica 4 University Hospital, University of Padova, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Cesari
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Narkiewicz
authors.forename: Renzo
authors.initials: R
authors.lastname: De Toni
authors.forename: Enrico
authors.initials: E
authors.lastname: Aldighieri
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Williams
authors.forename: Gian Paolo
authors.initials: GP
authors.lastname: Rossi
mesh_terms: D052242:Adiponectin / Q000097:blood* / Q000235:genetics*; D000293:Adolescent; D000328:Adult; D000465:Algorithms; D000483:Alleles; D000704:Analysis of Variance; D015992:Body Mass Index; D004777:Environment; D005091:Exons / Q000235:genetics; D005260:Female; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide; D011401:Promoter Regions, Genetic / Q000235:genetics; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic
chemical_list: D052242:Adiponectin