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

Abstract

Although many studies have found that two essential fatty acids, linoleic acid (LA; n‐6 polyunsaturated fatty acid, PUFA) and α‐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 PKCα/NF‐κB 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 PKCα and eNOS gene while NF‐κB 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 normalO2−, 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.

Lowering the linoleic acid to alpha-linoleic acid ratio decreases the production of inflammatory mediators by cultured human endothelial cells

“…In contrast, limited knowledge exists on the underlying biological effects on inflammatory processes when cells are exposed to a combination of PUFAs. However, a recent study by Yang et al examined various LA:ALA ratios (1:1, 5:1,10:1 and 20:1) on markers of inflammation, oxidative stress and cell function in endothelial cells and found no appreciable differences in IL-6 and TNF-α concentrations across ratios of LA:ALA in unstimulated cells [25]. In contrast, a previous animal study found that rats fed a high-fat diet based on plant oils with resulting in a low n-6:n-3 PUFA ratio (1:1 and 5:1) had lower serum levels of IL-6, TNF-α and C-reactive protein (CRP) compared with rats fed with a high n-6:n-3 PUFA ratio (20:1) diet [26].…”

Beneficial effect of walnuts on vascular tone is associated with Akt signalling, voltage-dependent calcium channel LTCC and ATP-sensitive potassium channel Kv1.2

“…Namely, walnuts contain considerable amounts of L-arginine, which is the precursor amino acid for NO biosynthesis (Xiao et al 2018) and improves serum NO level (Joukar et al 2017). The effects of LA and ALA, highly represented in walnut kernel, on endothelial cell functions and the related gene expression are influenced by LA/ALA ratios and their concentrations, and the mechanism may be partially mediated through NO/eNOS signalling pathways (Yang et al 2018). On the other hand, eNOS-derived NO blocks Ca 2+ influx through the sarcolemmal LTCC in cardiac myocytes (Farah et al 2018).…”

Atherosclerosis Development and Aortic Contractility in Hypercholesterolemic Rabbits Supplemented with Two Different Flaxseed Varieties

“…An in vitro study on endothelial cells confirmed the beneficial effect of a low LA/ALA ratio (1:1) on cardiovascular risk but only at a low PUFA concentration, whereas the same low LA/ALA ratio might raise the risk of cardiovascular diseases at a high PUFA concentration [ 46 ]. The effects of LA/ALA ratios on endothelial function might depend on proinflammatory factors, since a low LA/ALA ratio upregulated the nuclear factor κB (a key factor in inflammatory response in atherosclerosis) gene at a high PUFA concentration [ 46 ]. Therefore, the high PUFA concentration provided to rabbits with flaxseed-rich diets in our study might change the effect of the low LA/ALA ratio in W86 flaxseed to promote atherosclerosis via enhancing the inflammatory response.…”

“…The mentioned in vitro study involving endothelial cells indicated different effects of the LA/ALA ratios on the NO level, depending on PUFA concentration, with no effect on the endothelin-1 (ET-1) level [ 46 ]. Although a low LA/ALA ratio raised the eNOS gene expression, the same low LA/ALA ratio caused a decrease in the NO/ET-1 and NO levels compared to a higher LA/ALA ratio at a high PUFA concentration.…”