Polyunsaturated fatty acids are involved in regulatory mechanism of fatty acid homeostasis via daf-2/insulin signaling in Caenorhabditis elegans.

Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8572, Japan.

Molecular and cellular endocrinology 2010 Jul 29

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The development of the dauer form of Caenorhabditis elegans daf-2(e1370) enhances the expression of genes such as fatty acid desaturase fat-6 and fat-7 and fatty acid elongase elo-2, and increases the level of triglyceride (TAG). RNA interference (RNAi) of the fat-6, fat-7, and elo-2 genes lowers fat accumulation in the nematode. We recently clarified the fact that RNAi of fat-related genes, especially fat-2, reduced fat accumulation and activated DAF-16. FAT-2 regulates the first step of polyunsaturated fatty acid (PUFA) synthesis. RNAi of fat-2 induced nuclear translocation of DAF-16 and increased the level of TAG that could be detected by Oil Red-O, but suppressed the accumulation of lipid dyed by Nile red. TAG levels are also increased in the adult daf-2(e1370), whereas Nile red staining showed fat reduction. Introduction of RNAi of fat-2, fat-6, fat-7, and elo-2 genes into the daf-16 deficient worm recovered Nile red-stained lipid storage. These results suggest that Nile red stained the lipids except TAG, and that the levels of these lipids are regulated by daf-16. In fat-2, fat-6, fat-7, and elo-2-RNAi worms, the Nile red-stained fat level was restored through addition of fatty acids, especially PUFA. This suggests that reduction of Nile red-dyed lipid reflects the disorder of fatty acid metabolism. Furthermore, treatment of the fat-2-RNAi worm with PUFA--using the fatty acids from linoleic acid through eicosapentaenoic acid--suppressed nuclear localization of DAF-16. These results suggest that PUFA acts as a mediator of daf-2/insulin signaling and that daf-16 might be involved in fatty acid homeostasis under the control of PUFA. 2010 Elsevier Ireland Ltd. All rights reserved.

Citation

Makoto Horikawa, Kazuichi Sakamoto. Polyunsaturated fatty acids are involved in regulatory mechanism of fatty acid homeostasis via daf-2/insulin signaling in Caenorhabditis elegans. Molecular and cellular endocrinology. 2010 Jul 29;323(2):183-92