(n-3) Long chain polyunsaturated fatty acids dose-dependently increase oxygen utilization efficiency and inhibit arrhythmias after saturated fat feeding in rats
Fish oil (FO) modifies cardiac membrane phospholipid fatty acid composition to confer increased efficiency of oxygen utilization and anti-arrhythmic effects. We tested the capacity of low dose increments of FO, rich in (n-3) polyunsaturated fatty acids ((n-3) PUFA), to reverse the detrimental pro-arrhythmic and inefficient oxygen usage effects of dietary saturated fat (including high ratio of (n-6) PUFA to (n-3) PUFA) during ischemia and reperfusion. Wistar rats were fed a saturated fat enriched (SAT) diet (15.3% fat, including 12% saturated fat, added by weight) for 6 wk and were then divided into four groups (n=10/group) fed that diet or a 12% fat diet containing 3,6,or 12% FO in place of SAT for 6 wk. Paced (300/min), erythrocyte-perfused isolated working hearts were subjected to low coronary flow ischemia (15 min) and were then reperfused. At normoxic baseline, external work capacity increased marginally at 6 and 12% FO; however, marked dose-related reductions in oxygen consumption were evident due to FO dependent reduction in oxygen-energy utilization efficiency, and associated reductions in coronary flow and oxygen extraction. Post-ischemic recovery resulted in lower oxygen consumption, greater oxygen-energy utilization efficiency, reduced coronary release of creatine kinase and reduced incidence of arrhythmias in all FO groups compared to the SAT group. Fish oil at a dose as low as 3% of total fat dietary supplement effectively reversed the high oxygen requirements and pro-arrhythmic effects of a saturated fat-rich diet, even with continued consumption of saturated fat (9%) in this ex vivo animal model.