The effects of dietary trilinoelaidin on fatty acid and acyl desaturases in rat liver.

The effects of incremental amounts of dietary t,t-18:2 on liver microsomal delta 5 and delta 6 acyl desaturase activities were studied. The hepatic concentration of t,t-18:2 increased linearly from 0 to 1.6 mg/g liver as dietary t,t-18:2 was increased from 0--50% of dietary fat. This apparently inhibited the conversion of linoleic to arachidonic acid in liver tissue because linoleic acid increased from 1.2 to 3.1 mg/g liver, while arachidonic acid concurrently decreased from 3.9 to 1.9 mg/g liver tissue. This reflected the inhibition of delta 6 desaturase by t,t-18:2. The delta 6 desaturase activity in liver microsomes of rats fed 10, 20, and 50% of t,t-18:2 in their dietary lipids was 97, 75, and 51% of the activity of rats fed no t,t-18:2. In vitro tests showed that t,t-18:2 specifically inhibited liver delta 6 desaturase. The delta 5 desaturase activities did not increase significantly as dietary t,t-18:2 levels increased. This study showed that dietary t,t-18:2 by depressing delta 6 desaturase activity may affect essential fatty acid metabolism.