Genetic factors account for most of the variation in serum tryptase--a twin study.
BACKGROUND
Mast cells are involved in a number of diseases, including inflammatory diseases such as asthma. Tryptase is a known marker of mast cell burden and activity. However, little is known about the genetic influence on serum tryptase variation. Also, only few and conflicting data exist on serum tryptase in asthma.


OBJECTIVE
To estimate the overall contribution of genetic and environmental factors to the variation in serum tryptase and to examine the correlation between serum tryptase and asthma, rhinitis, markers of allergy, airway inflammation, and airway hyperresponsiveness (AHR) in a sample of Danish twins.


METHODS
A total of 575 twins underwent a skin prick test and had lung function, AHR to methacholine, exhaled nitric oxide and serum tryptase measured. Multiple regression and variance components models (using the statistical package SOLAR) were computed.


RESULTS
Serum tryptase values were available in 569 subjects. Intraclass correlations of serum tryptase in monozygotic and dizygotic twin pairs were 0.84 and 0.42 (P < .001). Variance decomposition showed that genetic factors accounted for 82% (95% confidence interval 74-90, P < .001) of the variation in serum tryptase. Body mass index and sex, but not asthma, rhinitis, or AHR, were correlated to serum tryptase.


CONCLUSIONS
As much as 82% of the variation in serum tryptase is due to genetic factors. Body mass index and sex, but not asthma or AHR to methacholine, correlate to serum tryptase. A genetic overlap may exist between serum tryptase and body mass index.
Department of Respiratory Medicine, Copenhagen University Hospital, Bispebjerg, Denmark. Electronic address: asgersverrild@gmail.com.
Asger
A
Sverrild
Sophie
S
van der Sluis
Kirsten O
KO
Kyvik
Lene H
LH
Garvey
Celeste
C
Porsbjerg
Vibeke
V
Backer
Simon F
SF
Thomsen
D000328:Adult; D000485:Allergens / Q000276:immunology; D001249:Asthma / Q000097:blood* / Q000235:genetics / Q000503:physiopathology; D015992:Body Mass Index; D016535:Bronchial Hyperreactivity / Q000097:blood* / Q000235:genetics / Q000503:physiopathology; D017449:Dermatitis, Allergic Contact / Q000097:blood* / Q000235:genetics / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D016210:Methacholine Chloride; D008875:Middle Aged; D009569:Nitric Oxide / Q000378:metabolism; D012220:Rhinitis / Q000097:blood* / Q000235:genetics / Q000503:physiopathology; D012882:Skin Tests; D013147:Spirometry; D053802:Tryptases / Q000097:blood*; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D055815:Young Adult
D000485:Allergens; D016210:Methacholine Chloride; D009569:Nitric Oxide; D053802:Tryptases