The Effects of Dietary Carbohydrate Content on Insulin Binding and Glucose Metabolism by Isolated Rat Adipocytes*

The effects of changes in the amount of dietary carbohydrate (CHO) on cellular insulin and glucose metabolism have been assessed in rat adipocytes. Feeding animals a 67% CHO (fat-free) diet resulted in decreased insulin binding but enhanced activity of both the glucose transport system and intracellular pathways of glucose metabolism. Feeding rats a 67% fat (CHO-free) diet resulted in decreased insulin receptors as well as decreased activity of the glucose transport system and intracellular glucose metabolism. Therefore, the in vivo insulin resistance caused by a high fat, low CHO diet seems to be adequately explained, since all aspects of insulin's cellular action were depressed. On the other hand, at first approximation, the increased in vivo insulin response caused by a high CHO diet appears contradictory to the observed decrease in insulin binding. However, a probable explanation for this apparent paradox is provided by the enhanced activity of the cellular insulin effector systems distal to the insulin receptor. Therefore, the increased in vivo insulin responsiveness after high CHO feedings is most likely due to post receptor increases in various aspects of glucose metabolism.