EFFECT OF LONG-CHAIN MONOUNSATURATED AND N-3 POLYUNSATURATED FATTY-ACIDS ON POSTPRANDIAL BLOOD AND LIVER LIPIDS IN RATS

The effects on blood and liver lipids after feeding rats with concentr ated fractions from fish oil consisting of mono-unsaturated fatty acid s (80% C20:1 and 22:1) or n-3 polyunsaturated fatty acids (85% C20:5 a nd 22:6 n-3) were examined. Mono-unsaturated fat had no effects on pla sma triacylglycerol, total cholesterol, phospholipids or unesterified fatty acid as compared to controls (lard). However, n-3 polyunsaturate d fatty acid-fed animals showed a significant decrease in plasma triac ylglycerol (74%), phospholipids (40%) and unesterified fatty acids (52 %). The concentrated fractions had no effects on liver lipids. While t he n-3 diet increased peroxisomal beta-oxidation 2.5-fold, there was o nly a slight increase with the mono-unsaturated diet. The fatty acid c omposition in plasma and liver phospholipids was changed with the vari ous diets; 20:4 n-6 was significantly reduced in plasma and liver with the mono-unsaturated diet, and with the n-3 diet in liver. The mono-u nsaturated diet, and especially the n-3 diet, increased the 20:5 n-3 l evel in both plasma and liver. Our results indicate that long-chain mo nounsaturated fatty acids in fish oil do not change the levels of plas ma lipids. The beneficial role of fish oil on the level of blood lipid s, may therefore be mostly attributed to the effects of long-chain n-3 fatty acids. However, the low 20:4 n-6 and high 20:5 n-3 levels in pl asma and liver phospholipids with the concentrated mono-unsaturated fa tty acid diet may be of importance for a favourable haemostatic balanc e with regard to cardiovascular diseases.