title: Genetic factors explain half of all variance in serum eosinophil cationic protein.
abstract: BACKGROUND
  Eosinophil cationic protein (ECP) is one of four basic proteins of the secretory granules of eosinophils. It has a variety of functions associated with inflammatory responses. Little is known about the causes for variation in serum ECP levels.
  
  
  OBJECTIVE
  To identify factors associated with variation in serum ECP and to determine the relative proportion of the variation in ECP due to genetic and non-genetic factors, in an adult twin sample.
  
  
  METHODS
  A sample of 575 twins, selected through a proband with self-reported asthma, had serum ECP, lung function, airway responsiveness to methacholine, exhaled nitric oxide, and skin test reactivity, measured. Linear regression analysis and variance component models were used to study factors associated with variation in ECP and the relative genetic influence on ECP levels.
  
  
  RESULTS
  Sex (regression coefficient = -0.107, P < 0.001), body mass index (BMI) (0.007, P = 0.028), and airway responsiveness to methacholine (0.074, P = 0.001) were significantly associated with ECP. Adjusted for these factors, ECP correlated 0.53 (P < 0.001) and 0.27 (P = 0.001) in monozygotic and dizygotic twins, respectively (P-value for difference = 0.05). According to the most parsimonious variance component model, genetic factors accounted for 57% (CI: 42-72%, P < 0.001) of the variance in ECP levels, whereas the remainder (43%) was ascribable to non-shared environmental factors. The genetic correlation between ECP and airway responsiveness to methacholine was statistically non-significant (r = -0.11, P = 0.50).
  
  
  CONCLUSIONS
  Around half of all variance in serum ECP is explained by genetic factors. Serum ECP is influenced by sex, BMI, and airway responsiveness. Serum ECP and airway responsiveness seem not to share genetic variance.
authors.affiliation: Department of Dermato-allergology, Gentofte Hospital, Hellerup, Denmark.
authors.forename: C
authors.initials: C
authors.lastname: Elmose
authors.forename: A
authors.initials: A
authors.lastname: Sverrild
authors.forename: S
authors.initials: S
authors.lastname: van der Sluis
authors.forename: K O
authors.initials: KO
authors.lastname: Kyvik
authors.forename: V
authors.initials: V
authors.lastname: Backer
authors.forename: S F
authors.initials: SF
authors.lastname: Thomsen
mesh_terms: D000328:Adult; D003718:Denmark; D047150:Eosinophil Cationic Protein / Q000097:blood* / Q000235:genetics*; D004804:Eosinophils / Q000378:metabolism; D045853:Exhalation; D005260:Female; D014644:Genetic Variation; D006801:Humans; D006967:Hypersensitivity / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics; D007073:Immunoglobulin E / Q000097:blood / Q000276:immunology; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000378:metabolism; D012042:Registries; D012307:Risk Factors; D012882:Skin Tests; D011795:Surveys and Questionnaires; D014427:Twins; D055815:Young Adult
chemical_list: D009569:Nitric Oxide; D007073:Immunoglobulin E; D047150:Eosinophil Cationic Protein
keywords: asthma; eosinophil cationic protein; twin study