Alaskan Eskimos inhabit the polar and subpolar regions of Alaska, and here they consume a diet composed largely of locally sourced foods, mainly from the sea. This food includes large amounts of fish and other marine life that is a rich sources of omega-3 fatty acids. Observational studies suggest that Alaskan Eskimos have low prevalences of insulin resistance, metabolic syndrome and type 2 diabetes, and this has been suggested to be due to their high consumption of eicosapentaenoic acid (EPA, C20:5 (n-3) and docosahexaenoic acid (DHA, C22:6 (n-3)) which belong to the omega-3 family of fatty acids. Omega-3 fatty acids are able to block the conversion of omega-6 fatty acids to pro-inflammatory eicosanoids, and therefore have a particular anti-inflammatory effect. As inflammation is a cause of oxidative stress, and oxidative stress is in turn a cause of insulin resistance, omega-3 fatty acids may improve insulin sensitivity and in turn decrease the risk of blood sugar disorders associated with insulin resistance.
Researchers1 have investigated the associations between long chain omega-3 marine oils and risk factors for cardiovascular disease in nearly 500 Alaskan Eskimos between the ages of 25 and 74 years. Dietary intakes of long chain omega-3 fish oils were also estimated from 24 hour dietary recall sheets. The results of the study showed that plasma concentrations of omega-3 fatty acid were significantly and highly correlated with the dietary intake of omega-3 fatty acids. Plasma omega-3 fatty acids were also associated with high density lipoprotein (HDL) concentrations in plasma. Inverse associations between plasma levels of omega-3 fatty acids and fasting insulin levels, postprandial insulin levels, postprandial glucose levels, insulin resistance, fasting triglyceride levels and diastolic blood pressure were also observed. The authors concluded that the high intake of omega-3 fatty acids in the Eskimo diet was protective of the development of insulin resistance and the associated metabolic syndrome.
The omega-3 fatty acids investigated in this study included EPA and DHA, along with docosapentaenoic acid. Docosapentaenoic is a generic term for any C22:5 fatty acid that can include both omega-3 and omega-6 fatty acids. The form of importance in this study was clupanodonic acid (DPA, C22:5 (n-3)) an intermediate between EPA and DHA in the essential fatty acid pathway of man. The omega-3 fatty acids EPA, DHA and DPA can be interconverted using cellular elongase and desaturase enzymes and this forms a pool of omega-3 fatty acids in cell membranes. The EPA in the cellular membrane is converted to a group of heterogeneous 20 carbon eicosanoids which have diverse functions in cellular metabolism. It is the conversion of EPA to these eicosanoids that requires the same enzyme system as the conversion of arachidonic acid (AA, C20:4 (n-6)) to its specific eicosanoids, these having pro-inflammatory effects. Inhibition of this enzyme system by EPA therefore has a strong anti-inflammatory effect.
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