title: Dietary cholesterol and/or n-3 fatty acid modulate delta 9-desaturase activity in rat liver microsomes.
abstract: 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-desaturase 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), and 18:1(n-9) in microsomal membranes. These results suggest that delta 9-desaturase activity is dependent on the cholesterol contents as well as the n-3 fatty acid content of microsomal membranes on which it is localized.
mesh_terms: D000818:Animals; D002791:Cholesterol, Dietary / Q000494:pharmacology*; D004041:Dietary Fats / Q000494:pharmacology; D004042:Dietary Fats, Unsaturated / Q000494:pharmacology; D004281:Docosahexaenoic Acids / Q000494:pharmacology; D015118:Eicosapentaenoic Acid / Q000494:pharmacology; D044943:Fatty Acid Desaturases / Q000037:antagonists & inhibitors*; D005227:Fatty Acids / Q000378:metabolism / Q000494:pharmacology*; D005395:Fish Oils / Q000494:pharmacology; D008042:Linolenic Acids / Q000494:pharmacology; D008043:Linseed Oil / Q000494:pharmacology; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D010743:Phospholipids / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013230:Stearoyl-CoA Desaturase; D017962:alpha-Linolenic Acid
chemical_list: D002791:Cholesterol, Dietary; D004041:Dietary Fats; D004042:Dietary Fats, Unsaturated; D005227:Fatty Acids; D005395:Fish Oils; D008042:Linolenic Acids; D010743:Phospholipids; D017962:alpha-Linolenic Acid; D004281:Docosahexaenoic Acids; D008043:Linseed Oil; D015118:Eicosapentaenoic Acid; D044943:Fatty Acid Desaturases; D013230:Stearoyl-CoA Desaturase; C029627:delta-9 fatty acid desaturase