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Heritabilities of Lipids in Young European American and African American Twins

Published online by Cambridge University Press:  21 February 2012

Anastasia Iliadou
Affiliation:
Clinical Epidemiology Unit, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
Harold Snieder
Affiliation:
Georgia Prevention Institute, Department of Pediatrics, Medical College of Georgia, Augusta Georgia, United States of America; Twin Research and Genetic Epidemiology Unit, St.Thomas' Hospital, London, United Kingdom.
Xiaoling Wang
Affiliation:
Georgia Prevention Institute, Department of Pediatrics, Medical College of Georgia, Augusta Georgia, United States of America.
Frank A. Treiber
Affiliation:
Georgia Prevention Institute, Department of Pediatrics, Medical College of Georgia, Augusta Georgia, United States of America.
Catherine L. Davis*
Affiliation:
Georgia Prevention Institute, Department of Pediatrics, Medical College of Georgia, Augusta Georgia, United States of America. [email protected]
*
*Address for correspondence: Catherine L. Davis, PhD, Georgia Prevention Institute, Dept. of Pediatrics, Medical College of Georgia, 1499 Walton Way (HS-1640), Augusta, Georgia 30912, USA.

Abstract

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Twin studies of lipids have almost exclusively involved Caucasians. People of African descent are known to show a healthier lipid profile, but relatively little is known about ethnic differences in genetic and environmental influences on lipids. One hundred and six African American (AA) and 106 European American (EA) twins (30 singletons and 91 complete pairs: 49 monozygotic, 21 dizygotic and 21 opposite-sex) from the south-eastern United States were studied (mean age 17.9 ± 3.2 years; 79% fasting). Lipids were assayed with the Cholestech LDX system. Analyses were adjusted for fasting status. Generalized estimating equations were used to test for the effects of sex and ethnicity on means, controlling for the dependence within twin pairs. Structural equation modeling was used to estimate genetic and environmental effects on each lipid variable. Females showed higher high-density lipoprotein (HDL) values than males (p < .001) and AAs showed higher HDL values than EAs (p < .001). EA males had higher triglyceride values than other groups (p = .02). All parameter estimates could be set equal across sex. Parameter estimates for total cholesterol, triglycerides and HDL could be set equal across ethnicity. The best fitting model for low- density lipoprotein (LDL) showed higher heritability in AAs (.92) than EAs (.69). Heritabilities ranged from 69% to 92%, with remaining variation explained by nonshared environmental effects. Adjustment for body mass index had virtually no effect on the heritability estimates. In this first twin study on lipids to include AAs, no ethnic differences in heritability were found except for LDL, where AAs exhibited higher estimates.

Type
Articles
Copyright
Copyright © Cambridge University Press 2005