Impact of apolipoprotein E polymorphism in determining interindividual variation in total cholesterol and low density lipoprotein cholesterol in Hispanics and non-Hispanic whites

Abstract

The extent of apolipoprotein E (apo E) polymorphism and its effect on eight quantitative risk factors for coronary heart disease (total cholesterol; low density lipoprotein (LDL) cholesterol; total high density lipoprotein and its subfractions, HDL2 and HDL3; triglycerides; fasting glucose and fasting insulin) has been determined in 238 randomly selected Hispanics (120 males and 118 females) and 201 non-Hispanic whites (NHWs) (105 males and 96 females) from the San Luis Valley, Colorado. The frequencies for the E * 2, E * 3 and E * 4 alleles were 0.048, 0.853 and 0.099, respectively, in Hispanics and 0.080, 0.783 and 0.137, respectively, in NHWs. Relatively low frequency of the E * 2 and E * 4 alleles in Hispanics compared with NHWs is consistent with the genetic and anthropologic data that Hispanics have substantial Amerindian admixture. The impact of apo E polymorphism on each quantitative trait was estimated after adjusting for concomitant variables including age, cigarette smoking and body mass index in both genders and pre- or post-menopause status in females. The distribution of eight quantitative traits was analyzed among three common apo E phenotypes, 3-2, 3-3 and 4-3. In Hispanics, significant variability among apo E phenotypes was observed for total cholesterol (P = 0.001) in females only and the apo E polymorphism accounts for 12.4% variation in total cholesterol and 15.2% variation in LDL-cholesterol. In NHWs, significant mean differences among apo E phenotypes were observed for total cholesterol in both males (P = 0.007) and females (P = 0.0004). In NHW males and females, the apo E polymorphism explained 9.2% and 12.4%, respectively, of the variation in total cholesterol, and 15.1% and 6.6%, respectively, of the variation in LDL-cholesterol. In NHWs, borderline significance levels were also noted for phenotype specific differences in HDL2-cholesterol in males (P = 0.04) and females (P = 0.05), for total HDL cholesterol in females (P = 0.02) and HDL3-cholesterol in females (P = 0.06). While the estimated effects of the apo E polymorphism on quantitative traits differ somewhat between Hispanics and non-Hispanic whites, this probably reflects the overall difference in frequencies of the less common alleles in the Hispanics rather than a biological difference in the effects of these alleles on lipid metabolism.