Food and Behaviour Research

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Common genetic variants of the FADS1 FADS2 gene cluster and their reconstructed haplotypes are associated with fatty acid composition in phospholipids.

Schaeffer L, Gohlke H, Muller M, Heid IM, Palmer LJ, Kompauer I, Demmelmair H, Illig T, Koletzko B, Heinrich J (2006) Hum Mol Genet.  15(11) 1745-56.  

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Abstract:

Fatty acid composition in membranes plays an important role in cellular processes and has shown to be associated with the aetiology of several complex diseases in humans.

We report strong associations between variants in the human delta-5 and delta-6 desaturase genes FADS1 FADS2 and fatty acid composition in serum phospholipids. Eighteen polymorphisms located in this gene cluster were genotyped in 727 adults from Erfurt, a German centre of the European Community Respiratory Health Survey. The cluster is located at chromosome 11q12-11q13.1, a region repeatedly found to be linked with atopy and other complex diseases.

Polymorphisms and statistically reconstructed haplotypes of FADS1 and the upstream region of FADS2 showed strongest associations with the level of the direct precursor of inflammatory eicosanoids, the n-6 fatty acid arachidonic acid (C20:4n-6), also strong associations with levels of the n-6 fatty acids C18:2n-6, C18:3n-6, C20:2n-6, C20:3n-6, C22:4n-6 and of the n-3 fatty acids C18:3n-3, C20:5n-3 and C22:5n-3 (P-values < 1.0 x 10(-13)).

Carriers of the rare alleles of several SNPs and their respective haplotypes had a lower prevalence of allergic rhinitis and atopic eczema. No association was found for total and specific IgE levels.

FAB RESEARCH COMMENT:

This is the first study of humans to show clear links between blood concentrations of omega-3 and omega-6 long-chain polyunsaturated fatty acids (LC-PUFA) and genetic markers for the key enzymes needed to synthesise these LC-PUFA from the shorter chain omega-3 and omega-6. 

The so-called 'FADS' (Fatty Acid DesaturaSe) genes - FADS1 and FADS2 - code for the delta 5 and delta-6 desaturase enzymes respectively. These enzymes help to insert additional double-bonds into the carbon chain that forms the backbone of any PUFA, thus making them more 'unsaturated'.

FADS genotypes accounted for a remarkable 28% of the variance in blood concentrations of the key omega-6 LC-PUFA Arachidonic Acid, which gives rise to various substances that promote inflammation. Associations were also found between FADS gene markers and some allergic conditions including atopic eczema and chronic rhinitis.