title: Heritability of arterial function, fitness, and physical activity in youth: a study of monozygotic and dizygotic twins.
abstract: OBJECTIVE
  To examine the role of heredity in determining flow-mediated dilation in young people by comparing conduit artery endothelial function in monozygotic and dizygotic twins. We also determined relationships between physical activity and fitness in each twin subset.
  
  
  METHODS
  Flow-mediated dilation was assessed with high-resolution ultrasonography of the brachial artery in 22 twin pairs (11 monozygotic pairs 13.3 ± 1.6 years, 11 dizygotic pairs 13.6 ± 1.6 years). Fitness was assessed as peak oxygen uptake during an incremental treadmill test. Physical activity was measured with accelerometry. Twin versus twin intraclass correlations were performed for both groups.
  
  
  RESULTS
  Flow-mediated dilation was significantly correlated in monozygotic twins only (r = 0.60, P = .02). Heritability of flow-mediated dilation was estimated at 0.44. Total PA time (monozygotic r = 0.77, dizygotic r = 0.60, P < .05) and light physical activity time (monozygotic r = 0.67, dizygotic r = 0.63, P < .05) correlated significantly in both groups. The peak oxygen uptake (r = 0.84, P < .01) was correlated only in monozygotic twins.
  
  
  CONCLUSIONS
  Genetic factors appear to be responsible for a modest portion of the flow-mediated dilation response, suggesting that flow-mediated dilation can be influenced by environmental factors.
authors.affiliation: Research Institute for Sport and Exercise Science, Liverpool John Moore's University, Liverpool, UK.
authors.forename: Nicola
authors.initials: N
authors.lastname: Hopkins
authors.forename: Gareth
authors.initials: G
authors.lastname: Stratton
authors.forename: Jose
authors.initials: J
authors.lastname: Maia
authors.forename: Toni M
authors.initials: TM
authors.lastname: Tinken
authors.forename: Lee E
authors.initials: LE
authors.lastname: Graves
authors.forename: Tim N
authors.initials: TN
authors.lastname: Cable
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Green
mesh_terms: D000293:Adolescent; D001158:Arteries / Q000502:physiology*; D003430:Cross-Sectional Studies; D004730:Endothelium, Vascular / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000235:genetics*; D010809:Physical Fitness; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic