Ethnicity, sex, FADS genetic variation, and hormonal contraceptive use influence delta-5- and delta-6-desaturase indices and plasma docosahexaenoic acid concentration in young Canadian adults: a cross-sectional study.

Salma A Abdelmagid,Ahmed El-Sohemy,Alaa Badawi,Shannon E Clarke,David M Mutch,David Wl Ma,Kaitlin Roke,Daiva E Nielsen

doi:10.1186/s12986-015-0010-9

Abstract

BackgroundThere is great interest in the relationship between polyunsaturated fatty acids and health. Yet, the combinatory effect of factors such as sex, ethnicity, genetic polymorphisms and hormonal contraceptives (HC) on the concentrations of these fatty acids is unknown. Therefore, we sought to determine the effects of FADS polymorphisms, and HC use in females, on aggregate desaturase indices (ADI), and plasma docosahexaenoic acid (DHA) concentrations in Caucasian and East Asian males and females.MethodsFasting plasma samples were collected from subjects (Caucasian males: 113 and females: 298; East Asian males: 98 and females: 277) from the Toronto Nutrigenomics and Health Study. Fatty acid concentrations were measured by gas chromatography. ADI were estimated by dividing concentrations of arachidonic acid by linoleic acid (n-6 ADI) and eicosapentaenoic acid (EPA) by α-linolenic acid (n-3 ADI). [DHA/EPA] desaturase index was used to determine effects of FADS2 polymorphisms and HC use on EPA conversion to DHA.ResultsIn Caucasians, associations between n-6 ADI and multiple SNP (FADS1 rs174547, FADS2 rs174576, and rs174611 in males; FADS1 rs174547, FADS2 rs174570, rs174576, rs174679, rs174611, rs174593, rs174626, rs2072114, rs2845573, and rs2851682 in females) withstood multiple testing. In East Asian females, 5 SNP-n-6 ADI associations (FADS2 rs174602, rs174626, rs2072114, rs2845573, and rs2851682) withstood multiple testing. One FADS2 SNP was associated with altered [DHA/EPA] desaturase index in Caucasian females only (rs174576, p < 0.0001). HC use had a significant effect on DHA concentrations in Caucasian females only (P < 0.0001).ConclusionsWe demonstrate ethnic- and sex-specific effects of FADS polymorphisms on desaturase indices, and ethnic-specific effect of HC use on plasma DHA concentrations.Electronic supplementary materialThe online version of this article (doi:10.1186/s12986-015-0010-9) contains supplementary material, which is available to authorized users.

Highlights

There is great interest in the relationship between polyunsaturated fatty acids and health
In East Asian males and females, there were no significant differences in values of HOMA-IR and energy intake from fats or levels of insulin, LDL-cholesterol, triglycerides and free fatty acids
P-values were determined using multiple linear regression models which were adjusted for BMI, age, dietary linoleic acid (LA), α-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), % total energy from dietary fat and physical activity

Summary

Introduction

There is great interest in the relationship between polyunsaturated fatty acids and health. Several factors have been implicated in the alteration of endogenous fatty acid levels These include diet, genetic variations and hormonal regulation [11,12]. FADS genetic variations have been shown to be associated with increased HOMA-IR and insulin resistance as well as hsCRP levels; FADS polymorphisms can play a role in modifying disease risk [16,17]. Another modifier is hormonal contraceptives (HC) which have been positively correlated with DHA levels in women [18,19]

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