Important polyunsaturated fatty acid found in fish oils. It serves as the precursor for the prostaglandin-3 and thromboxane-3 families. A diet rich in eicosapentaenoic acid lowers serum lipid concentration, reduces incidence of cardiovascular disorders, prevents platelet aggregation, and inhibits arachidonic acid conversion into the thromboxane-2 and prostaglandin-2 families. [PubChem]
EPA can be used for lowering elevated triglycerides in those who are hyperglyceridemic. In addition, EPA may play a therapeutic role in patients with cystic fibrosis by reducing disease severity and may play a similar role in type 2 diabetics in slowing the progression of diabetic nephropathy.
Eicosanoids are chemical messengers derived from 20-carbon polyunsaturated fatty acids that play critical roles in immune and inflammatory responses. Both 20-carbon omega-6 fatty acids (arachidonic acid) and 20-carbon omega-3 fatty acids (EPA) can be found in cell membranes. During an inflammatory response, arachidonic acid and EPA are metabolized by enzymes known as cyclooxygenases and lipoxygenases to form eicosanoids. Increasing omega-3 fatty acid intake increases the EPA content of cell membranes and decreases the arachidonic acid content, resulting in higher proportions of eicosanoids derived from EPA. Physiologic responses to arachidonic acid-derived eicosanoids differ from responses to EPA-derived eicosanoids. In general, eicosanoids derived from EPA are less potent inducers of inflammation, blood vessel constriction, and clotting than eicosanoids derived from arachidonic acid.
Mechanism of action
The anti-inflammatory, antithrombotic and immunomodulatory actions of EPA is probably due to its role in eicosanoid physiology and biochemistry. Most eicosanoids are produced by the metabolism of omega-3 fatty acids, specifically, arachidonic acid. These eicosanoids, leukotriene B4 (LTB4) and thromboxane A2 (TXA2) stimulate leukocyte chemotaxis, platelet aggregation and vasoconstriction. They are thrombogenic and artherogenic. On the other hand, EPA is metabolized to leukotriene B5 (LTB5) and thromboxane A3 (TXA3), which are eicosanoids that promote vasodilation, inhibit platelet aggregation and leukocyte chemotaxis and are anti-artherogenic and anti-thrombotic. The triglyceride-lowering effect of EPA results from inhibition of lipogenesis and stimulation of fatty acid oxidation. Fatty acid oxidation of EPA occurs mainly in the mitochondria. EPA is a substrate for Prostaglandin-endoperoxide synthase 1 and 2. It also appears to affect the function and bind to the Carbohydrate responsive element binding protein (ChREBP) and to a fatty acid receptor (G-coupled receptor) known as GP40.
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