Letters to the Editor

Am. J. Hum. Genet. 50:236, 1992

Interaction of Apolipoprotein E Genotype and Dietary Cholesterol in Determining Plasma Cholesterol Levels To the Editor:

In discussing the possible interaction between apolipoprotein E (apo E) genotype and dietary cholesterol intake, Hallman et al. (1991) suggest that our findings in a Nigerian population (Sepehrnia et al. 1989) fail to support the hypothesis that the magnitude of apo E allelic effects is modulated by dietary levels of cholesterol. While we may have failed to make this point clear, we believe that the results from Nigeria are consistent with the dietary hypothesis of Utermann (1987). The Nigerians have the highest apo E*4 allele frequency reported in human populations, except in New Guinea (Kamboh and Ferrell 1990); yet their mean cholesterol level is low compared with those of European populations. This is due to a diet high in saturated fat, from palm oil used in food preparation, but low in cholesterol. In addition, the estimated average effect of the E*4 allele in this population is lower than that estimated in European populations, although the overall effect is to raise plasma cholesterol levels. Consistent with Utermann's hypothesis, the direction of the effect is the same as that seen in other populations, but the magnitude of the effect is reduced in this population consuming a low-cholesterol diet. Direct interpopulation comparison of allelic effects must be made with caution, since the estimation of allelic effects involves the mean cholesterol level and 236

the gene frequency, both of which may vary widely across populations. Direct confirmation of Utermann's hypothesis awaits genotype-specific metabolic studies. R. E. FERRELL AND M. ILYAS KAMBOH Department of Human Genetics University of Pittsburgh Pittsburgh References Kamboh MI, Ferrell RE (1990) Genetic studies of human apolipoproteins. XV. An overview of IEF immunoblotting methods to screen apolipoprotein polymorphisms. Hum Hered 40:193-207 Hallman DM, Boerwinkle E, Saha N, Sandholzer C, Menzel HJ, Csaizair A, Utermann G (1991) The apolipoprotein E polymorphism: a comparison of allele frequencies and effects in nine populations. Am J Hum Genet 49:338-349 Sepehrnia B, Kamboh MI, Adams-Campbell LL, Bunker CH, Nwankwo M, Majumder PP, Ferrell RE (1989) Genetic studies of human apolipoproteins. X. The effect of the apolipoprotein E polymorphism on quantitative levels of lipoproteins in Nigerian blacks. Am J Hum Genet 45: 586-591 Utermann G (1987) Apolipoprotein E polymorphism in health and disease. Am Heart J 113:433-440 © 1992 by The American Society of Human Genetics. All rights reserved.

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Interaction of apolipoprotein E genotype and dietary cholesterol in determining plasma cholesterol levels.

Letters to the Editor Am. J. Hum. Genet. 50:236, 1992 Interaction of Apolipoprotein E Genotype and Dietary Cholesterol in Determining Plasma Cholest...
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