Desaturation of linoleic acid in the small bowel is increased by short-term fasting and by dietary content of linoleic acid
1992
Garg, M.L. | Keelan, M. | Thomson, A.B.R. | Clandinin, M.T.
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.
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