Role of ω3 long-chain polyunsaturated fatty acids in reducing cardio-metabolic risk factors.

Mahinda Y Abeywardena, Glen S Patten

Cardiovascular disease is the leading cause of mortality in many economically developed nations, and its incidence is increasing at a rapid rate in emerging economies. Diet and lifestyle issues are closely associated with a myriad of cardiovascular disease risk factors including abnormal plasma lipids, hypertension, insulin resistance, diabetes and obesity, suggesting that diet-based approaches may be of benefit. Omega-3 longchain-polyunsaturated fatty acids (ω3 LC-PUFA) are increasingly being used in the prevention and management of several cardiovascular risk factors. Both the ω3 and ω6 PUFA families are considered essential, as the human body is itself unable to synthesize them. The conversion of the two precursor fatty acids - linoleic acid (18:2ω6) and α-linoleic acid (α18:3ω3) - of these two pathways to longer (≥C(20)) PUFA is inefficient. Although there is an abundance of ω6 PUFA in the food supply; in many populations the relative intake of ω3 LC-PUFA is low with health authorities advocating increased consumption. Fish oil, rich in eicosapentaenoic (EPA, 20:5ω3) and docosahexaenoic (DHA, 22:6ω3) acids, has been found to cause a modest reduction in blood pressure at a dose level of >3g/d both in untreated and treated hypertensives. Whilst a multitude of mechanisms may contribute to the blood pressure lowering action of ω3 LC-PUFA, improved vascular endothelial cell function appears to play a central role. Recent studies which evaluated the potential benefits of fish oil in type-2 diabetes have helped to alleviate concerns raised in some previous studies which used relatively large dose (5-8 g/d) and reported a worsening of glycemic control. Several meta-analyses have confirmed that the most consistent action of ω3 LC-PUFA in insulin resistance and type-2 diabetes is the reduction in triglycerides. In some studies, fish oil has been found to cause a small rise in LDL-cholesterol, but a change in the LDL particle size, from the smaller more atherogenic form to the larger, less damaging particle size, have also been noted. ω3 LC-PUFA are effective modulators of the inflammation that accompanies several cardio-metabolic abnormalities. Taking into consideration the pleiotropic nature of their actions, it can be concluded that dietary supplementation with ω3 LC-PUFA will lead to improvements in cardio-metabolic health parameters. These fatty acids pose only minor side effects and more importantly, do not interact adversely with the common drug therapies used in the management and treatment of hypertension, dyslipidemia, type-2 diabetes, and obesity/metabolic syndrome, but in some instances work synergistically, thereby providing additional cardiovascular benefits.