Relationship between rat liver microsomal Δ6 and Δ5 desaturase activities and fatty acid composition: comparative effects of coconut and salmon oils during protein restriction

Abstract : The aim of this work was to compare the effects of coconut and salmon oils on rat liver microsomal Δ6 and Δ5 desaturations, during protein restriction. A higher Δ6 desaturase activity was noted in rats fed the low-protein coconut oil diet, in comparison with that occurring in rats fed either a low-protein or normal-protein salmon oil diet. No variation was observed in Δ5 desaturase activity or in 20:4n-6/ 18:2n-6 ratio. The fatty acid composition of liver microsomal phospholipids provided evidence of higher levels of 20:5n-3 and 22:6n-3 in the normal-protein salmon oil group, when compared with the low-protein salmon oil group. No influence of experimental diets on the total n-3 and total n-6 fatty acids could be demonstrated. Aside from investigating the effects of protein restriction on the liver microsomal desaturases, this work shows that there is no correlation between microsomal desaturation rates and microsomal phospholipid profiles even when diets are rich in polyunsaturated fatty acids (salmon oil).