Dietary cholesterol and/or n-3 fatty acid modulate delta(9)-desaturase activity in rat liver microsomes
1988
Garg, M.L. | Wierzbicki, A.A. | Thomson, A.B.R. | Clandinin, M.T.
delta(9)-Desaturase activity and fatty acid composition of liver microsomal phospholipids in rats fed diets enriched with either saturated (hydrogenated beef tallow) or alpha-linolenic (linseed oil) or eicosapentaenoic and docosahexaenoic (fish oil) acids with or without 2% cholesterol supplementation were investigated. Both the linseed oil and the fish oil diets inhibited delta(9)-desatrase activity in the rat liver microsomes. The inhibition was greater when feeding fish oil (90%) compared with the linseed oil (60%) diet. Dietary cholesterol feeding accelerated conversion of palmitic (16:0) to palmitoleic (16:1) acid, irrespective of the fatty acid supplement. Feeding the linseed oil diet decreased, while feeding the fish oil diet increased synthesis of the monounsaturated fatty acids of n-7 series (palmitoleic and vaccenic acid) and decreased 18:1(n-9) in microsomal membrane lipids when compared with animals fed beef tallow. Addition of 2% cholesterol to the otherwise low cholesterol diets led to accumulation of 16:1(n-7), 18:1(n-7) and 18:1(n-9) in microsomal membranes. These results suggest that delta(9)-desaturase activity is dependent on the cholesterol content as well as the n-3 fatty acid content of microsomal membranes on which it is localized.
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