title: Heritability assessment of cartilage metabolism. A twin study on circulating procollagen IIA N-terminal propeptide (PIIANP).
abstract: OBJECTIVE
  The aim of this investigation was to estimate the heritability of circulating collagen IIA N-terminal propeptide (PIIANP) by studying mono- and dizygotic healthy twin pairs at different age and both genders.
  
  
  METHODS
  598 monozygotic (MZ) and dizygotic (DZ) twin individuals aged 18-59 years were recruited from the Danish Twin Registry. PIIANP was measured by competitive ELISA. The similarity of circulating PIIANP among MZ and DZ twins was assessed by intraclass correlations according to traits. The heritability was estimated by variance component analysis accounting for additive and dominant genetic factors as well as shared and non-shared environment but ignoring epistasis (genetic inter-locus interaction) and gene-environment interaction.
  
  
  RESULTS
  The intraclass correlation of PIIANP in MZ and DZ twins was 0.69 (0.60-0.76) and 0.46 (0.34-0.58) respectively indicating a significant genetic impact on PIIANP in serum. Additive genetic effects explained 45% (21-70%), shared environment 24% (7-53%) and non-shared environment 31% (24-39%) of the total variance. The heritability estimate did not differ across ages and between genders.
  
  
  CONCLUSIONS
  The study shows that approximately 45% of the collagen IIA synthesis as assessed by the collagen IIA N-terminal propeptide in serum is attributable to genetic effectors while individual and shared environment account for 24% and 31% respectively. The heritability does not differ between genders or according to age.
authors.affiliation: Department of Rheumatology C, Odense University Hospital, Denmark; University of Southern Denmark, Denmark. Electronic address: heidi.munk@rsyd.dk.
authors.forename: H L
authors.initials: HL
authors.lastname: Munk
authors.affiliation: The Danish Twin Registry, Epidemiology, Institute of Public Health, Denmark; University of Southern Denmark, Denmark. Electronic address: asvendsen@health.sdu.dk.
authors.forename: A J
authors.initials: AJ
authors.lastname: Svendsen
authors.affiliation: Epidemiology and Statistics, Institute of Public Health, Denmark; University of Southern Denmark, Denmark. Electronic address: jhjelmborg@health.sdu.dk.
authors.forename: J v B
authors.initials: Jv
authors.lastname: Hjelmborg
authors.affiliation: Institute for molecular Medicine, Denmark; University of Southern Denmark, Denmark. Electronic address: glsorensen@health.sdu.dk.
authors.forename: G L
authors.initials: GL
authors.lastname: Sorensen
authors.affiliation: Institute of Regional Health Services Research, Denmark; University of Southern Denmark, Denmark. Electronic address: KKyvik@health.sdu.dk.
authors.forename: K O
authors.initials: KO
authors.lastname: Kyvik
authors.affiliation: Department of Rheumatology C, Odense University Hospital, Denmark; University of Southern Denmark, Denmark. Electronic address: peter.junker@rsyd.dk.
authors.forename: P
authors.initials: P
authors.lastname: Junker
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D002356:Cartilage / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010446:Peptide Fragments / Q000097:blood* / Q000235:genetics; D011347:Procollagen / Q000097:blood* / Q000235:genetics; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D055815:Young Adult
chemical_list: D010446:Peptide Fragments; D011347:Procollagen; C109195:procollagen type IIA amino-terminal peptide
keywords: Cartilage; Heritability; PIIANP; Procollagen IIA N-terminal propeptide; Twin study; Type II collagen