Elongation and desaturation of fatty acids are critical in growth, lipid metabolism, and ontogeny of Caenorhabditis elegans

Recently, it was reported that a deficit in the mouse stearoyl-CoA desaturase 1 gene decreases biosynthesis and accumulation of fatty acid and revitalizes the b-oxidation of fatty acid. To examine the physiological role of fatty acid desaturase (FAT) and elongase (ELO)-gene transduction in ontogeny, fatty acid accumulation and individual lifespan, we performed bacteria-mediated RNA interference (RNAi) in the nematode Caenorhabditis elegans. Suppression of the expression of FAT-2 gene mRNA caused a drastic decrease in the amount of body fat and defects in egg-hatching. The amount of body fat was markedly decreased, and body size reduced, by down regulation of FAT-6 and FAT-7, whereas lifespan was drastically reduced. RNAi of the FAT-2 gene caused a remarkable increase of the b-oxidation-related gene expression and the DAF-16 transcriptional activity, whereas, ELO-2 RNAi caused a remarkable decrease in fatty acid biosynthesis-related gene expression. Additionally, RNAi of FAT-6 decreased the mRNA levels of the genes involved in fatty acid syn-thesis, and FAT-7 RNAi increased the mRNA levels of b-oxidation system genes. These results indicated that the elongation and desaturation of fatty acids are integra