Abstract: The effect of a novel fish oil supplement enriched in very-long-chain (C≥24) polyunsaturated fatty acids (VLCPUFAs) on cardiometabolic risk factors and visual function will be assessed in this bench-to-bedside proposal. VLCPUFAs play important tissue specific roles that cannot be fulfilled by more abundant shorter-chain FAs. The ELOVL2 enzyme in the liver is responsible for converting docosapentaenoic acid (DPA: 22:5 n-3) to tetracosapentaenoic acid (TPA: 24:5 n-3), which is further extended in 2-carbon steps to chain lengths greater than 36 carbons by the ELOVL4 enzyme in the retina, brain and testis. Heterozygous ELOVL4 mutations lead to Stargardt-like macular dystrophy, a progressive form of macular degeneration that causes blindness in young adults. Some ELOVL4 mutations lead to spinocerebellar ataxia. VLCPUFAs are also important in spermatogenesis and have been proposed to be involved in male infertility. Fish oil-derived PUFAs (EPA: 20:5 n-3, DHA: 22:6 n-3) exert potent anti-inflammatory and cardiometabolic benefits, but in clinical trials like AREDS2 they have not consistently slowed the progression of age-related macular degeneration (AMD). Standard fish oils, however, contain less than 1% (w:w) VLCPUFAs. Retinal levels of VLCPUFAs decrease with age and are especially low in AMD patients. Because ELOVL2 expression markedly decreases with aging due to promoter methylation, we hypothesized that the age-related declined in VLCPUFAs could be ameliorated with a dietary supplement containing TPA. We recently showed in aged mice that dietary supplementation with a novel fish oil enriched in VLCPUFAs (C24-C28) not only improved retinal function, but also had beneficial effects on cardiometabolic risk factors (decreased plasma lipids and improved insulin-sensitivity). Some of these beneficial effects are possibly due to the ability of VLCPUFAs to act as PPAR-agonists. We found that TPA was a more potent PPAR (α and γ) agonist than EPA and DHA. Our results, therefore, suggest that VLCPUFA-rich fish oil could be more effective than EPA, a currently approved treatment for cardiovascular disease prevention and could also be a new nutritional therapy for AMD. For our basic science aims, we plan to examine in more detail the mechanism of action of VLCPUFAs. EPA/DHA are known to exert their anti-inflammatory and insulin-sensitizing effects by G-protein-coupled receptors (GPRs). Drs. Danner and Wang, NHLBI and CC associate investigators, will identify possible GPR targets for chemically synthesized VLCPUFA and elucidate their signaling pathways, using specific GPR knockdown and knockout cells expressing reporter genes. Dr. Bernstein, an extramural co-investigator, will compare chemically synthesized VLCPUFA versus EPA/DHA, as well as VLCPUFA-rich fish oil versus regular EPA/DHA-rich fish oil, for their ability to slow retinal degeneration in Elovl4 conditional knockout mice. Dr. Remaley’s lab at NHLBI will perform a similar study in ApoE-KO mi...