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From Glendale, Arizona, USA:

Our 8 year old son was diagnosed with Type 1 diabetes 11 months ago. Our understanding is that insulin is the "key" that allows glucose into cells for metabolism. What mechanism allows glucose to enter cells when exercising? Exercise greatly lowers our son's blood readings with less insulin required and more carbs added to the food plan. Our endocrinologist has not give us an explanation of this other than that it happens. We know it happens, but how?


Insulin's major function is to regulate total body glucose metabolism in all tissues except the brain. It does this by increasing the rate of glucose transport through the membranes of muscle and adipose tissue cells. In the total absence of insulin, only trace amounts of glucose can be transported into cells. Insulin is essentially the mediator of "facilitated diffusion," whereby glucose in the presence of insulin combines with a glucose carrier for transport into the cells. Insulin actually controls the rate of cellular glucose metabolism. By increasing the cellular uptake of glucose, both glucose and fat oxidation are maintained. Any glucose not immediately catabolized [broken down] for energy is stored as glycogen for later use.

Exercise adds to the blood glucose lowering effects of injected insulin, so individuals who exercise regularly usually have lower insulin requirements than individuals who do not exercise. During exercise, a smaller amount of insulin is needed for muscle cells to use glucose than at rest, and its effects can last for 24 to 48 hours. Muscle and liver glycogen (stored carbohydrate) is used for fuel during exercise and must be replenished after exercise. As a result, blood glucose levels drop and less insulin is required. Therefore, exercise improves the use and storage of glucose and decreases the amount of insulin required.


Original posting 28 Nov 97


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Last Updated: Tuesday April 06, 2010 15:08:54
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