Abstract
Long chain n-3 PUFA docosahexaenoic acid (DHA) is important for heart and brain function. Investigations of biologically plausible mechanisms using animal models associate cardioprotection with DHA incorporation into myocardial membranes that are largely derived from supra-physiological fish oil (FO) intake. We measured the incorporation of DHA into myocardial membranes of rats from low dietary FO intake within human dietary range and quantitatively assessed the influence of dietary n-6 PUFA. With rats fed diets containing 0.16%-5% FO, equal to 0.12%-8.7% energy (%en) as eicosapentaenoic acid (EPA) and DHA (EPA+DHA), and either 1.5%en or 7.5%en n-6 PUFA (linoleic acid) for four weeks, dietary n-6:n-3 PUFA ratios ranged from 74 to 0.3. Myocardial DHA concentration increased in a log-linear fashion with a dietary threshold of 0.019%en as EPA+DHA and half maximal dietary [EPA+DHA] equal to 0.29%en (95% CI, 0.23-0.35). Dietary linoleic acid intake did not influence myocardial DHA. Myocardial membranes are sensitive to absolute dietary intake of long chain n-3 PUFA at low %en in the rat, equivalent to a human intake of one meal of fatty fish per week or less. The dietary ratio of n-6:n-3 PUFA has no influence on long chain n-3 PUFA cellular incorporation from dietary fish oil.
Highlights
Long chain n-3 polyunsaturated fatty acids (PUFA) docosahexaenoic acid (DHA) is important for heart and brain function
This study found that very small intakes of fish oil can markedly increase the myocardial membrane long chain n-3 PUFA concentration
We identified a dietary threshold for the myocardial membrane incorporation of long chain n-3 PUFA, predicting that increased incorporation can be achieved when fish-oil intake exceeds 0.019% of dietary metabolizable energy as eicosapentaenoic acid (EPA)+DHA (0.027% of the diet by weight as fish oil (FO))
Summary
Long chain n-3 PUFA docosahexaenoic acid (DHA) is important for heart and brain function. We measured the incorporation of DHA into myocardial membranes of rats from low dietary FO intake within human dietary range and quantitatively assessed the influence of dietary n-6 PUFA. Myocardial membranes are sensitive to absolute dietary intake of long chain n-3 PUFA at low %en in the rat, equivalent to a human intake of one meal of fatty fish per week or less. Regular consumption of long chain n-3 polyunsaturated fatty acids (PUFA) from fish is associated with a low incidence of premature mortality from cardiovascular disease. The present study addressed two challenges to linking human disease risk to the biological mechanisms of n-3 PUFA action derived from animal studies It aimed to extend the concentration-effect relationship for membrane incorporation of n-3 PUFA to dietary concentrations within the range of human intake [22] and to estimate a
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