Interrelationship between the dietary regulation of fatty acid synthesis and the fatty acyl-CoA desaturases.

In this paper we present further evidence for the close control of fatty acid synthetase and stearoyl-CoA desaturase. Furthermore, we have established that whereas dietary palmitic acid may influence the activity of this desaturase but not of fatty acid synthetase, dietary linoleic acid appears to control both these enzymes. Finally, we have studied the influence of dietary fat and carbohydrate on the activities of the delta6 and delta5 desaturases. The former is only slightly affected by these dietary components. The delta5 desaturase activity is stimulated as the dietary fat content rises but is unaffected by dietary carbohydrate. The control of these enzymes is therefore independent of the control of fatty acid synthetase and stearoyl-CoA desaturase. From the data presented, the magnitude of the controlling effect of polyunsaturated fatty acids on fatty acid synthetase and stearoyl-CoA desaturase activity is determined and its relevance to lipogenesis in man based on daily intake of carbohydrate and linoleic acid is discussed.