Variability gene effect on cholesterol at the Kidd blood group locus

Abstract

The within-pair difference in lipid levels was examined in 142 monozygotic (MZ) twin pairs drawn from the population-based Norwegian Twin Panel. Mean within-pair difference in serum total cholesterol was lower in MZ pairs who were heterozygous for blood group Kidd genes or homozygous for the Jk^b gene than in pairs who were homozygous for the Jk^b gene. The difference between the two categories of homozygotes was significant at the 2% level. The analyses suggest that the main reason for the difference observed is a restrictive effect of the Jk^b gene on total cholesterol variability. No effect on triglycerides or HDL cholesterol variability was detected and there was no association between Kidd blood groups and sex and age-adjusted levels of cholesterol, triglycerides or HDL cholesterol. The present data confirm findings we reported when we introduced the study of within-pair variability in MZ twins as a method to analyse gene-environment interactions and validate the “variability gene” concept. A person's net risk for coronary heart disease may depend on his or her combination of “level genes” and “variability genes” as well as on environmental or life-style factors.