Joint effects of fatty acid desaturase 1 polymorphisms and dietary polyunsaturated fatty acid intake on circulating fatty acid proportions

Abstract

Background Polyunsaturated fatty acids (PUFAs) are associated with a lower risk of multiple diseases. Fatty acid desaturase 1 gene (FADS1) polymorphisms and dietary PUFA intake are both established determinants of circulating PUFA proportions. Objective We explored the joint effects of FADS1 polymorphisms and dietary PUFA intake on circulating PUFA proportions. Design We studied 2288 participants from a nested case-control study of coronary artery disease among participants who provided blood samples in the Nurses' Health Study and the Health Professionals Follow-Up Study. Dietary PUFA intake was obtained from semiquantitative food-frequency questionnaires. FADS1 rs174546 was genotyped by using the Affymetrix 6.0 platform, and circulating PUFA proportions were measured with gas-liquid chromatography. Linear regression models were used to examine the associations between rs174546 and circulating proportions of each fatty acid. Gene-diet interactions were tested by including a cross-product term of dietary intake of each PUFA by rs174546 genotype in the linear regression models. Results After adjustment for sex and ancestry, each copy of the C allele of rs174546 was associated with higher circulating proportions of arachidonic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) and lower proportions of linoleic acid and α-linolenic acid. The magnitude of positive association between higher consumption of dietary EPA or DHA and circulating proportions of EPA increased with each copy of the rs174546-T allele (P-interaction = 0.01 and 0.007, respectively). Each 1-SD increment in EPA intake was associated with an average 3.7% increase in circulating EPA proportions among participants with the rs174546-CC genotype and an average 7.8% increase among participants with the TT genotype. Conclusions Carriers of the T allele at FADS1 rs174546 may need higher doses of dietary EPA and DHA to achieve the same circulating proportions of EPA as carriers of the C allele. The implications of these findings on disease risk and dietary guidelines require further study.