Obesity resistance and deregulation of lipogenesis in Δ6-fatty acid desaturase (FADS2) deficiency

Δ-6-fatty acid desaturase (FADS2) is the key enzyme in the biosynthesis of polyunsaturated fatty acids (PUFAs), the essential structural determinants of mammalian membrane lipid-bilayers. We developed the auxotrophic fads2(-/-) mouse mutant to assess the enigmatic role of ω3- and ω6-PUFAs in lipid homeostasis, membrane structure and function. Obesity resistance is another major phenotype of the fads2(-/-) mutant, the molecular basis of which is unknown. Phospholipidomic profiling of membrane systems of fads2(-/-)mice revealed diacylglycerol-structures, deprived of PUFAs but substituted with surrogate eicosa-5,11,14-trienoic acid. ω6-Arachidonic (AA) and ω3-docosahexaenoic acid (DHA) supplemented diets transformed fads2(-/-) into AA-fads2(-/-) and DHA-fads2(-/-) mutants. Severely altered phospholipid-bilayer structures of subcellular membranes of fads2(-/-) liver specifically interfered with maturation of transcription factor sterol-regulatory-element-binding protein, the key regulator of lipogenesis and lipid homeostasis. This study strengthens the concept that specific PUFA-substituted membrane phospholipid species are critical constituents of the structural platform operative in lipid homeostasis in normal and disease conditions.

Quantitative lipid analysis and life span of the fat-3 mutant of Caenorhabditis elegans

The long-chain polyunsaturated fatty acids (LC PUFAs) docosahexaenoic acid (DHA, 22:6n3) and eicosapentaenoic acid (EPA, 20:5n3) are important for health and development of organisms, but the precise biological function of these molecules is not known. It has been suggested that they may play a part in aging, as they are highly susceptible to oxidation. A genetic mutant of Caenorhabditis elegans (fat-3), which lacks a functional delta-6 desaturase, and thus LC PUFAs including EPA, allows dietary manipulation of long-chain n3 fatty acids in this nematode. The life span of C. elegans strains N2 (wild-type) and BX30 [fat-3(wa22)] with and without supplemental EPA and DHA was analyzed. In addition, quantitative analysis was performed on total lipids, phospholipids, and triglycerides, as it is important to understand where fatty acids are being partitioned among the various lipid classes. The results show a beneficial effect of these molecules on the life span of C. elegans and will aid in the elucidation of the underlying causes of PUFA deficiency in the simple animal C. elegans as well as in humans.