No abstract

Blood and tissue contents of polyunsaturated fatty acid (PUFA) and long-chain PUFA (LC-PUFA) are related to numerous health outcomes including cardiovascular health, allergies, mental health and cognitive development. Evidence has accumulated to show that in addition to diet, common polymorphisms in the fatty acid desaturase (FADS) gene cluster have very marked effects on human PUFA and LC-PUFA status. Recent results suggest that in addition to fatty acid desaturase 1 and fatty acid desaturase 2, the gene product of fatty acid desaturase 3 is associated with desaturating activity. New data have become available to show that FADS single nucleotide polymorphisms (SNPs) also modulate docosahexaenoic acid status in pregnancy as well as LC-PUFA levels in children and in human milk. There are indications that FADS SNPs modulate the risk for allergic disorders and eczema, and the effect of breastfeeding on later cognitive development. Mechanisms by which FADS SNPs modulate PUFA levels in blood, breast milk and tissues should be explored further. More studies are required to explore the effects of FADS gene variants in populations with different ethnic backgrounds, lifestyles and dietary habits, and to investigate in greater depth the interaction of gene variants, diet and clinical end points, including immune response and developmental outcomes. Analyses of FADS gene variants should be included into all sizeable cohort and intervention studies addressing biological effects of PUFA and LC-PUFA in order to consider these important confounders, and to enhance study sensitivity and precision.

This article is available online at http://www.jlr.org ing the relationship between FA status and cardiovascular disease ( 3 ). Furthermore, the availability of n-3 long-chain polyunsaturated fatty acids (LC-PUFAs) has been related to mental development in infants ( 4 ) as well as to the attenuation of the decline of mental performance in the elderly ( 5 ). The n-6 LC-PUFA dihomo-␥ -linolenic acid and arachidonic acid and the n-3 LC-PUFA eicosapentaenoic acid are precursors of eicosanoids with different biological effects ( 6 ). The determination of FA status has a pivotal role in clinical trials and cross-sectional studies ( 7-9 ) and is a valuable biomarker for the quality of consumed dietary fat ( 10 ).Conventional methods for analyzing the FA composition in biological samples consist of several analytical steps and are, therefore, cumbersome and time consuming. Typically, a skilled chemist requires 2 days for analyzing 10-20 samples ( 11 ). In the last years, different approaches are employed to overcome this disadvantage. Fast gas chromatographic techniques were introduced and optimized for fatty acid methyl ester (FAME) analyses and quantifi cation ( 11, 12 ), but sample preparation has been the timeand cost-expensive factor. Therefore, new approaches focus on simplifying and reducing sample preparation steps like lipid extraction, lipid separation, and FAME synthesis. Masood and Salem ( 11 ) developed a robotic transesterification method for the analysis of FAs from total plasma lipids. Akoto et al. ( 13 ) The FA composition of cellular and plasma lipids is of major importance for many biological functions. Although limited by different turnover rates and widely differing contribution of individual lipid classes to total pools, there is generally a reasonable correlation between FA composition of cellular and of plasma lipids ( 1 ). In clinical studies and epidemiological observations, only blood is easily accessible for analysis and can be assessed in large numbers of subjects ( 2 ). Many studies have aimed at investigat-

BackgroundAssociation of genetic-variants in the FADS1-FADS2-gene-cluster with fatty-acid-composition in blood of adult-populations is well established. We analyze this genetic-association in two children-cohort-studies. In addition, the association between variants in the FADS-gene-cluster and blood-fatty-acid-composition with eczema was studied.Methods and Principal FindingsData of two population-based-birth-cohorts in the Netherlands and Germany (KOALA, LISA) were pooled (n = 879) and analyzed by (logistic) regression regarding the mutual influence of single-nucleotide-polymorphisms (SNPs) in the FADS-gene-cluster (rs174545, rs174546, rs174556, rs174561, rs3834458), on polyunsaturated fatty acids (PUFA) in blood and parent-reported eczema until the age of 2 years. All SNPs were highly significantly associated with all PUFAs except for alpha-linolenic-acid and eicosapentaenoic-acid, also after correction for multiple-testing. All tested SNPs showed associations with eczema in the LISA-study, but not in the KOALA-study. None of the PUFAs was significantly associated with eczema neither in the pooled nor in the analyses stratified by study-cohort.Conclusions and SignificancePUFA-composition in young children's blood is under strong control of the FADS-gene-cluster. Inconsistent results were found for a link between these genetic-variants with eczema. PUFA in blood was not associated with eczema. Thus the hypothesis of an inflammatory-link between PUFA and eczema by the metabolic-pathway of LC-PUFAs as precursors for inflammatory prostaglandins and leukotrienes could not be confirmed by these data.

BackgroundPlasma fatty acid (FA) composition reflects dietary intake and endogenous turnover and is associated with health outcomes on a short and long term basis. The total plasma FA pool represents the composition of all FA containing lipid fractions. We developed a simplified and affordable high-throughput method for the analysis of total plasma FA composition, suitable for large studies.Methodology/Principal FindingsThe total lipid FA from 100 µl plasma is transferred in situ into methyl esters, avoiding initial extraction and drying steps. The fatty acid methyl esters are extracted once and analyzed by gas chromatography. For the new direct in situ transesterification method optimal, reaction parameters were determined. Intra-assay analysis (n = 8) revealed coefficients of variation below 4% for FA contributing more than 1% to total FA.Conclusions/SignificanceThe results show good agreement with FA concentrations obtained by a reference method. The new direct in situ transesterification method is robust and simple. Sample preparation time and analysis costs are reduced to a minimum. This method is an economically and ecologically superior alternative to conventional methods for assessing plasma FA status in large studies.