title: Desaturation of linoleic acid in the small bowel is increased by short-term fasting and by dietary content of linoleic acid.
abstract: The rate of desaturation of linoleic acid (18:2(n - 6)) and level of arachidonic acid (20: 4(n - 6)) in mucosal microsomes from small intestine of rats fasted for 24 h or fed diets of different fatty acid composition was examined. Fasting or feeding a diet high in linoleic acid increased delta 6-desaturase activity, a rate-limiting enzyme in the arachidonic acid biosynthetic pathway in the jejunum. After fasting, delta 6-desaturase activity was also enhanced in the ileum. Feeding a diet rich in n - 3 fatty acids had no significant effect on delta 6-desaturase activity in jejunal or ileal mucosal microsomes. Following fasting, arachidonic acid content of microsomal total phospholipids increased in the jejunum with a concomitant decrease in linoleic acid content. Arachidonic acid and 18:2(n - 6) concentration remained unchanged in ileal microsomes after short-term food withdrawal. Feeding a diet containing n - 3 fatty acids lowered the content of 20:4(n - 6) and increased 20:5(n - 3) and 22:6(n - 3) levels in both jejunal and ileal microsomes. These data indicate that the level of 20:4(n - 6) and the biosynthesis of 20:4(n - 6) by desaturation-chain elongation of 18:2(n - 6) in the rat enterocyte responds rapidly to change in physiological conditions such as fasting and dietary fat composition.
authors.affiliation: Department of Foods and Nutrition, Faculty of Home Economics, University of Alberta, Edmonton, Canada.
authors.forename: M L
authors.initials: ML
authors.lastname: Garg
authors.forename: M
authors.initials: M
authors.lastname: Keelan
authors.forename: A B
authors.initials: AB
authors.lastname: Thomson
authors.forename: M T
authors.initials: MT
authors.lastname: Clandinin
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism; D004041:Dietary Fats / Q000494:pharmacology*; D005215:Fasting; D044943:Fatty Acid Desaturases / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism; D007421:Intestine, Small / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000378:metabolism*; D050602:Linoleoyl-CoA Desaturase; D008297:Male; D008861:Microsomes / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D004041:Dietary Fats; D008041:Linoleic Acids; D010743:Phospholipids; D016718:Arachidonic Acid; D002784:Cholesterol; D019787:Linoleic Acid; D044943:Fatty Acid Desaturases; D050602:Linoleoyl-CoA Desaturase