Abstract
Background: The endocannabinoid system (ECS) overactivation, associated with increased inflammatory process, may act as a risk factor for coronary artery disease (CAD). Dietary fat may influence the ECS tone. The aim of the present study was to investigate the effect of flaxseed oil on the erythrocyte membrane fatty acid profile and ECS activity by the measurement of serum N-arachydonoil ethanolamine (AEA) and cannabinoid receptor type-1 (CB1), cannabinoid receptor type-2 (CB2), and fatty acid amide hydrolase (FAAH) mRNA expression. Methods: This clinical trial was performed on 44 patients with CAD. The intervention group received 1.5% fat milk supplemented with flaxseed oil (containing 2.5 g α-linolenic acid or ALA), while the placebo group received 1.5% fat milk for 10 weeks. The fatty acid profile of erythrocyte membrane phospholipids was measured by gas chromatography. The AEA level was determined using an ELISA kit, and real-time PCR was performed to measure CB1, CB2, and FAAH mRNA expression pre- and post-intervention. Results: Flaxseed oil supplementation resulted in a significant increase in the ALA content and a significant reduction in linoleic acid (LA) content of membrane phospholipids, compared to the placebo group (MD = − 0.35 and 2.89, respectively; P < 0.05). The within group analysis showed that flaxseed oil supplementation caused a significant reduction in both LA and arachidonic acid (MD = − 4.84 and − 4.03, respectively; P < 0.05) and an elevation in the ALA (MD = 0.37, P < 0.001) content of membrane phospholipids compared with the baseline. In the intervention group, a marked reduction was observed in the serum AEA level after 10 weeks of intervention, compared with the placebo group (MD = 0.64, P = 0.016). Changes in CB2 mRNA expression in the flaxseed oil group were significant (fold change = 1.30, P = 0.003), compared with the placebo group.
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Key Points
CB1/CB2 receptors play different roles in atherosclerosis development. CB1 activation results in a proinflammatory response through production of reactive oxygen species in macrophages derived from human atheroma, whereas activation of CB2 receptors modulates immune challenges on immune cells and decreases tumor necrosis factor-alpha (TNF-α) production which may suppress the atherosclerosis process. The beneficial effects of omega-3-rich oils can be partly attributed to CB2-mediated effects in ECS. Omega-3 fatty acids may act as precursors of bioactive endocannabinoid epoxides, such as eicosapentaenoyl ethanolamide (EPEA) and docosahexaenoyl ethanolamide (DHEA) products, which bind to CB1 and CB2. ECS may act as a missing link in promoting the beneficial effects of omega-3- rich oils in suppression of inflammation, atherosclerosis, and CAD. This research aimed to determine the effects of 10 weeks of intervention with 200 mL of milk, containing 5 g of flaxseed oil, on erythrocyte membrane lipids, and ECS activity by the measurement of serum AEA, CB1, CB2, and fatty acid amide hydrolase (FAAH) mRNA expression. ECS functions within cardiovascular tissues and ECS dysregulation has been reported in both obese and CAD individuals, with specific clinical effects on systemic lipid metabolism, restenosis, and inflammation. Th objective here was to determine if the favorable effects of flaxseed oil can be attributed to its role in the modulation of endocannabinoids in CAD patients, possibly by limiting the availability of biosynthetic precursors for endocannabinoids (i.e., LA and AA) and increasing omega-3 fatty acid content of membrane phospholipids. In the present study, 5 g of flaxseed oil supplementation per day, rich in ALA, led to the significant reduction of LA and significant elevation of ALA in erythrocyte phospholipids. In the present trial, flaxseed oil exerted the greatest effects on CB2 receptor expression; this effect might be related to the high content of ALA. A marginally significant reduction was observed in the mRNA expression of CB1. The findings related to FAAH indicated a marginally significant upregulation suggestive of the regulation of endocannabinoid degradation pathway in favor of reduction in AEA. The results showed that flaxseed oil in milk emulsion (containing 2.5 g of ALA) could decrease AEA levels and increase CB2 mRNA expression. Flaxseed oil may exert cardioprotective properties by reducing ECS overactivity.