Relationship between mouse liver delta 9 desaturase activity and plasma lipids.

This study was undertaken to investigate the total plasma fatty acid composition and the relationship between plasma triacylglycerol (TG) levels and liver delta 9 desaturase activity in mice fed n-3 and/or n-6 fatty acid or hydrogenated coconut oil (HCO) (maximum 25 mg/g) supplemented diets. Generally, plasma TG levels and delta 9 desaturase activity were inversely correlated with the ratio of the sum of long chain n-6 fatty acids to 18:2n-6 and to the ratio of the sum of long chain n-3 fatty acids to 18:n-3, but they were positively correlated with the ratio of products and substrates (18:1/18:0) of the enzyme in plasma total lipids. The n-3 fatty acid (mainly 20:5n-3) enriched diet, when compared to the HCO diet at 21 d, caused a significant reduction in plasma TG levels but not in delta 9 desaturase activity. However, a marked reduction in plasma TG content (50-60%) and delta 9 desaturase activity (55-70%) was observed when both 20:5n-3 and 18:3n-6 were supplemented in the diet. The plasma TG levels and delta 9 desaturase activity rose again when the animals were fed the HCO diet or chow. The results suggest that low dose supplementation of a mixture of n-3 (mainly 20:5n-3) and n-6 (18:3n-6) fatty acids modified both plasma TG content and liver delta 9 desaturase activity, in parallel.