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  • Title: Fatty acid inhibition of hormonal induction of acetyl-coenzyme A carboxylase in hepatocyte monolayers.
    Author: Salati LM, Clarke SD.
    Journal: Arch Biochem Biophys; 1986 Apr; 246(1):82-9. PubMed ID: 2870683.
    Abstract:
    Primary cultures of adult rat hepatocytes were utilized to ascertain the impact of free fatty acids on the insulin plus dexamethasone induction of acetyl-CoA carboxylase. Lipogenesis was induced threefold by the combination of insulin and dexamethasone. The rise in fatty acid synthesis was accompanied by a comparable increase in the rate-determining enzyme acetyl-CoA carboxylase. Dexamethasone was required for the insulin induction of acetyl-CoA carboxylase. Under the permissive action of glucocorticoid, 10(-7) M insulin maximally increased enzyme activity. Half-maximum stimulation occurred with 5 X 10(-9) M insulin. Media containing 0.2 mM palmitate, oleate, linoleate, arachidonate, or docosahexaenoate significantly suppressed the hormonal induction of acetyl-CoA carboxylase. The extent of suppression was only 30-35% and did not vary with chain length or degree of unsaturation. Carboxylase activity was not suppressed further by raising the concentration of linoleate to 0.5 mM; however, 0.5 mM palmitate depleted the cells of ATP and abolished acetyl-CoA carboxylase activity. Therefore, based upon the inhibitory characteristics of the various fatty acids and the lack of a concentration dependency of the fatty acid inhibition, it would appear that fatty acid inhibition of the induction of acetyl-CoA carboxylase activity may not be a direct, physiological regulatory mechanism.
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