title: Dietary fat alters membrane composition in rod outer segments in normal and diabetic rats: impact on content of very-long-chain (C > or = 24) polyenoic fatty acids.
abstract: The effect of high n - 3 (5.8%, w/w) vs. a low n - 3 (1.2%, w/w) fatty acids in a diet with a low ratio of polyunsaturated/saturated fatty acids (P/S = 0.27) content was investigated to determine the effect of diet on the level of long- and very-long-chain fatty acids (VLCFA C > or = 24) in phospholipids of rod outer segments (ROS) of normal and diabetic rats. After 6 weeks of feeding, diets high in n - 3 fatty acids increased the levels of 22:5(n - 3) and 22:6(n - 3), while decreasing the 22:5(n - 6) level in all major phospholipid classes. n - 6 and n - 3 VLCFA of C24 to C34 with 4, 5 and 6 double bonds were found only in phosphatidylcholine (PC) while other phospholipid classes contained only C24 fatty acids as minor components. The content of VLCFA in PC was approx. 6.7% (w/w) of total fatty acids in the ROS. Feeding a high n - 3 fatty acid diet significantly reduced n - 6 tetraenoic VLCFA in all phospholipids. In the diabetic state, the levels of n - 6 tetraenes and pentaenes in individual phospholipids were different from control animals. This study demonstrates that the VLCFA content of photoreceptor cells reflects the dietary level of n - 3 fatty acids fed. The unique polyenoic n - 6 and n - 3 VLCFA appear to be synthesized from shorter chain precursors which respond to altering the ratio of n - 6/n - 3 fatty acids fed.
authors.affiliation: Nutrition and Metabolism Research Group, University of Alberta, Edmonton, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Suh
authors.forename: A A
authors.initials: AA
authors.lastname: Wierzbicki
authors.forename: M T
authors.initials: MT
authors.lastname: Clandinin
mesh_terms: D000818:Animals; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D004041:Dietary Fats / Q000494:pharmacology*; D005227:Fatty Acids / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D008297:Male; D008563:Membrane Lipids / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism; D010714:Phosphatidylethanolamines / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism; D010718:Phosphatidylserines / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012374:Rod Cell Outer Segment / Q000378:metabolism*; D014886:Weaning
chemical_list: D004041:Dietary Fats; D005227:Fatty Acids; D008563:Membrane Lipids; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010716:Phosphatidylinositols; D010718:Phosphatidylserines