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Programmed electrical stimulation in anesthetized marmoset monkeys was used to examine relative antiarrhythmic efficacies of dietary n -- 3 and n -- 6 polyunsaturated fatty acids (PUFAs) from fish and plant oils. Diets contained 31% of energy (en%) as fat, comprising 15 en% saturated fat and 7 en% PUFAs, obtained by blending sheep fat with sunflower seed (SF/ SSO) or fish oil (SF/FO) and a base diet. After 16-wk feeding, ventricular fibrillation (VF) was inducible in 6 of 10 animals on each diet under control conditions. The VF threshold (VFT) was significantly elevated in the SF/FO group (33.3 [+ or -] 3.1 mA; n = 6) compared with the SF/SSO group (14.3 [+ or -] 4.9 mA; n = 6). VFT, reduced during acute myocardial ischemia with 10 of 10 animals inducible per diet, remained significantly higher with SF/ FO feeding. The SF/FO diet contained 3.8 en% as n--3 PUFAs, which was incorporated as 31% of myocardial membrane fatty acids. Dietary n--3 PUFA reduced vulnerability of normal or ischemic myocardium to arrhythmias in a nonhuman primate.

This study compared monounsaturated oleic acid with n-6 and n-3 polyunsaturated fatty acids (PUFAs) for their ability to modify the vulnerability to cardiac arrhythmias during ischemia or reperfusion in rats. Replacement of saturated animal fat in the diet with oleic acid-rich olive oil did not significantly alter the incidence of ventricular fibrillation or other cardiac arrhythmias. Replacement with either n-6-rich sunflower seed oil or n-3-rich fish oil reduced the incidence and severity of arrhythmias occurring in ischemia. The fish oil significantly reduced reperfusion arrhythmias independently of antecedent ischemic arrhythmias. Fatal ventricular fibrillation was significantly reduced by n-6 (8%; n = 25) and n-3 (0%; n = 24) PUFA but not by monounsaturates (36%; n = 25) compared with saturated fat (42%; n = 24). The results suggest that dietary replacement of saturated fats by n-6 and especially n-3 PUFA but not monounsaturated fatty acids can reduce the likelihood of an ischemic event leading to sudden cardiac death. Am J Clin Nutr 1993;57:207-12.

Sudden cardiac death may result from arrhythmias such as ventricular fibrillation (VF); during arrhythmia the heart beat becomes uncoordinated and irregular. In animals, the dietary fat consumed over the long term can influence susceptibility to arrhythmias. Rats were studied to assess whether the adverse effect of saturated fats on the heart muscle could be arrested or even reversed in mature animals switched to polyunsaturated fats. The vast majority of rats that had been fed the high-saturated fat diet for nine or 18 months developed VF during and after experimental blockage of a coronary artery. There were no deaths attributable to VF among rats fed the saturated fat diet for nine months, but two thirds of those fed the diet for 18 months died of VF. Rats that were switched to polyunsaturated fats after nine months on saturated fats had a dramatically lower incidence of VF and mortality continued to be zero. Two types of polyunsaturated fats were used, n-3 fatty acids from tuna fish oil and n-6 fatty acids from sunflower seed oil. The n-3 fats were more effective at reversing susceptibility to VF than the n-6 type, which appears consistent with much research that has been done on the benefits of certain fish oils in reducing the risk of death from heart disease. The results show that improvements in dietary fat can be effective even in mature animals that have been fed a diet high in saturated fat over the long term. If these results can be extrapolated to humans, which is not certain, they suggest that even older persons could benefit from positive changes in their diets, and that while all polyunsaturated fats may lower risk of sudden cardiac death, fish consumption appears particularly useful. (Consumer Summary produced by Reliance Medical Information, Inc.)

The influence of diets containing [Gamma]-linolenic acid (GLA; 18:3n-6) on sciatic nerve conduction velocity (NCV) was determined in diabetic rats. NCV was lower in diabetic rats fed diets supplemented with olive oil or sunflower seed oil than in nondiabetic rats; rats supplemented with GLA during a 5-wk diabetic period, however, did not exhibit significantly lower NCV. The mean proportion of the phospholipid fatty acid linoleic acid (18:2n-6) was higher in the sciatic nerves of diabetic rats than in the nondiabetic groups irrespective of dietary lipid treatment. Additionally, the proportion of linoleic acid was higher in the diabetic rats fed sunflower oil than in all other groups. Dietary GLA supplementation did not significantly influence the fatty acid composition of nerve membrane phospholipids and there was no obvious correlation between the fatty acid composition of nerve membrane phospholipids and NCV. The content of fructose and glucose in sciatic nerves was higher, whereas that of myo-inositol was lower, in diabetic rats than in nondiabetic rats; however, this was not significantly influenced by dietary GLA. GLA administration did not significantly influence [Na.sup.+]-[K.sup.+]-exchanging ATPase or ouabain binding activity in sciatic nerve preparations, both of which remained nonsignificantly different in the diabetic and nondiabetic groups. The results suggest that dietary GLA can prevent the deficit in NCV induced by diabetes and that this effect is independent of the nerve phospholipid fatty acid profile, sugar and polyol content, [Na.sup.+]-[K.sup.+]-exchanging ATPase activity, and ouabain binding. GLA may prevent the deficit in NCV indirectly, possibly by its role as a precursor of vasodilatory prostaglandins. These results confirm that GLA is the active component of evening primrose oil. Am J Clin Nutr 2000;71 (suppl):386S-92S. KEY WORDS Diabetic neuropathy, streptozotocin, [Gamma]-linolenic acid, nerve conduction velocity, sciatic nerve polyols, [Na.sup.+]-[K.sup.+]-exchanging ATPase, ouabain binding, fatty acids, evening primrose oil, rats