Effects of Linoleic and Alpha-Linolenic Ratios and Concentrations on In Vitro Endothelial Cell Responses

Although many studies have found that two essential fatty acids, linoleic acid (LA; n-6 polyunsaturated fatty acid, PUFA) and -linolenic acid (ALA; n-3 PUFA), are closely related to the occurrence and development of cardiovascular disease (CVD), the effects of LA and ALA ratios and concentrations on CVD risk are not well known. The aim of this study is to investigate the effects of various LA/ALA ratios (1:1, 5:1, 10:1, and 20:1) and their concentrations on inflammation, oxidative stress, endothelial cell functions, and the mechanism in human umbilical vein endothelial cells (EA.hy926 cell line). The results indicate that low LA/ALA ratio might provide CVD benefits at low PUFA concentration while low LA/ALA ratio (1:1) increases CVD risk at high PUFA concentration. The results show that the effects of LA and ALA on inflammation, oxidative stress, endothelial cell functions, and the related gene expression are influenced by not only LA/ALA ratios but also their concentrations, and the mechanism may be mediated through PKC/NF-B inflammatory and NO/eNOS signaling pathways by regulation of the NOX4 pathway.Practical Applications: Lipid metabolism, inflammation, oxidative stress, and endothelial cell functions play an important role in the pathogenesis of CVD, which may be affected by an imbalance in the LA/ALA ratio. However, the effects of LA/ALA ratios on CVD risk are influenced by PUFA concentrations. The study provides a method to design diets beneficial for CVD prevention. The low LA/ALA ratio (1:1) could up-regulate increase the gene expression level of PKC and eNOS gene while NF-B and NOX4 gene expression levels are up-regulated to increase oxidative stress, which could cause the oxidation of BH4 and uncoupling of eNOS under high PUFA concentration. Uncoupling eNOS generated O2-, instead of NO, which could damage vascular endothelial cell function. This is different from the role of eNOS in the production of NO under normal physiological conditions, which shows the duality of eNOS on atherosclerosis. The results indicate both LA and ALA ratios and concentrations are important for CVD risk.