Background: Since LNA and ALA compete for the rate-limiting enzyme, Δ6-desaturase, it is hypothesized that the current high LNA consumption from the Western diet would impede the conversion of ALA to SDA by Δ6-desaturase, and eventually EPA, and DHA. Therefore, this study aims to understand the contribution of dietary LNA and Δ6-desaturase on n-3 PUFA synthesis. Methods: 168 BALB/c mice were randomized to a high (6 en%) or low (0.6 en%) LNA diet with n-3 PUFA from either flaxseed oil (FO; 0.6 en% ALA) or Ahiflower oil (AO; 0.4 en% ALA+0.2 en% SDA). They consumed 13C-ALA spiked diets for six weeks followed by a diet switch to the same diets without 13C-ALA spiking. Liver was collected at 0, 1, 3, 7, 14, 28, 56, 112, and 168 post diet switches. δ13C signatures were quantified by gas chromatography-combustion-isotope ratio mass spectrometry. Liver EPA and DHA synthesis/turnover rate (Jout) were calculated. Results: With high LNA intake, mice on AO diet have significantly higher rate of EPA Jout compared to FO diet suggesting that bypassing the competitive Δ6-desaturase step with dietary SDA can increase EPA synthesis; however, this does not carry forward to DHA synthesis. With low dietary LNA, the EPA Jout was not significantly different between FO and AO diets, but DHA Jout was significantly higher with FO diet than AO diet. Conclusions: Ahiflower oil may be a good plant-alternative to increase liver EPA synthesis when consuming the Western diet. Analysis of EPA and DHA Jout in the brain are in progress.
2025. ISSFAL Quebec City June 30, 2025, • Session 10: Lipid Metabolism II, Submission 85 • ISSFAL 2025