Effect of a high-fat-sucrose diet on in vivo insulin receptor kinase activation.

Insulin-stimulated glucose uptake into muscle is depressed by high-fat-sucrose (HFS) feeding of rats. To investigate the mechanism of this insulin resistance, the in vivo activation of the insulin receptor kinase in liver and muscle of control and HFS-fed rats was determined. Rats were injected with glucose and insulin and killed 0, 5, 15, and 30 min after injection. Insulin binding was not changed in partially purified receptors from muscle of HFS rats. In control rats insulin receptor kinase activity was maximally stimulated threefold in liver at 5 min and fourfold in muscle at 15 min after insulin-glucose injection. The insulin-stimulated tyrosine kinase activity of receptors isolated from the liver of rats fed the HFS diet was decreased by 30% in comparison with the controls. In contrast, receptors isolated from muscle did not show any difference in basal or insulin-stimulated kinase activity between HFS-fed and control rats. Decreased in vivo activation of the insulin receptor kinase may be at least partially responsible for insulin resistance in liver. Because insulin binding and insulin stimulation of receptor kinase were normal in muscle of HFS-fed animals, it is concluded that the insulin resistance of glucose uptake into muscle is caused by a defect distal to the insulin receptor.