Inheritance of high density lipoprotein and lipoprotein lipase and hepatic lipase activity

The role of genetic and environmental factors in the regulation of plasma high density lipoprotein (HDL) was estimated in 17 monozygotic (MZ) and 18 dizygotic (DZ) male twins randomly selected from the Finnish Twin Cohort Study. In addition to HDL cholesterol, we determined the HDL subfractions, HDL2 and HDL3, and the major HDL apoproteins (apo) A-I and A-II. The activities of lipoprotein lipase (LPL) and hepatic lipase (HL) were also assayed from postheparin plasma to get information on their possible contribution to the heritability of HDL. Evidence for the genetic component in the regulation of plasma HDL received support from the heritability estimate of 0.34. The different heritability estimates of HDL2 and HDL3 (h2 of 0.56 and less than 0, respectively) support the idea that the HDL subfraction distribution might be important in the genetic regulation of plasma HDL level. This also received support from the heritability of apo A-I (h2 = 0.66), mainly varying in HDL2, and the lack of it in apo A-II, found mainly in HDL3. These conclusions were strengthened by standardizing the data with relative ponderosity. Postheparin plasma HL activity had a high pairwise correlation coefficient in the MZ twins (r = 0.80, p less than 0.001), whereas LPL displayed no within-pair correlation. Neither of the lipolytic enzymes, LPL or HL, showed any correlation in the DZ twins. Therefore, it is suggested that part of the genetic regulation of the HDL and its subfraction distribution might be mediated through the activity of HL.