title: Level of polyunsaturated fatty acids and the n-6 to n-3 polyunsaturated fatty acid ratio in the rat diet alter serum lipid levels and lymphocyte functions.
abstract: In order to further examine the effects of dietary polyunsaturated fatty acids (PUFA) upon blood lipid levels and lymphocyte functions, weanling rats were fed for 6 weeks on high fat (178 g/kg) diets which differed in the ratio of n-6:n-3 PUFA (100, 20, 10, 5, 1) and in the absolute level of PUFA (17.5 or 35 g/100 g fatty acids). The n-6:n-3 PUFA ratio of the diets was decreased by replacing linoleic acid with alpha-linolenic acid while the PUFA content of the diets was decreased by replacing PUFA with palmitic acid. Serum cholesterol concentrations decreased as the n-6:n-3 PUFA ratio of the low PUFA diet decreased. The ex vivo proliferation of spleen lymphocytes from rats fed the low PUFA diets decreased as the n-6:n-3 PUFA ratio of the diet decreased; the proliferation of spleen lymphocytes from high PUFA-fed rats was less affected by the n-6:n-3 PUFA ratio of the diet. Natural killer cell activity was lower for spleen lymphocytes from rats fed high PUFA diets with n-6:n-3 PUFA ratios of 100 or 20 than for those from rats fed low PUFA diets with these ratios. The natural killer cell activity of spleen lymphocytes decreased as the n-6:n-3 PUFA ratio of the low PUFA diet decreased. These findings indicate that dietary alpha-linolenic acid has significant blood lipid-lowering and immunomodulatory effects in rats, but that the effect is dependent upon the total PUFA content of the diet. The ratios of linoleic and alpha-linolenic acids to other fatty acids (e.g. palmitic, oleic) are important in determining the precise effect of manipulations of the fatty acid composition of the diet.
authors.affiliation: Department of Biochemistry, University of Oxford, UK.
authors.forename: N M
authors.initials: NM
authors.lastname: Jeffery
authors.forename: E A
authors.initials: EA
authors.lastname: Newsholme
authors.forename: P C
authors.initials: PC
authors.lastname: Calder
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001681:Biological Assay; D002784:Cholesterol / Q000097:blood; D004032:Diet; D004042:Dietary Fats, Unsaturated / Q000008:administration & dosage; D005227:Fatty Acids / Q000032:analysis; D005230:Fatty Acids, Nonesterified / Q000097:blood; D015525:Fatty Acids, Omega-3 / Q000008:administration & dosage; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated / Q000008:administration & dosage* / Q000737:chemistry; D016014:Linear Models; D008055:Lipids / Q000097:blood*; D008214:Lymphocytes / Q000502:physiology*; D008297:Male; D051381:Rats; D011917:Rats, Inbred Lew; D013154:Spleen / Q000166:cytology; D014280:Triglycerides / Q000097:blood; D014810:Vitamin E / Q000097:blood
chemical_list: D004042:Dietary Fats, Unsaturated; D005227:Fatty Acids; D005230:Fatty Acids, Nonesterified; D015525:Fatty Acids, Omega-3; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated; D008055:Lipids; D014280:Triglycerides; D014810:Vitamin E; D002784:Cholesterol