Clinical

Aerobic exercise boosts peripheral insulin sensitivity in type 2 diabetics

The improvement in whole-body insulin sensitivity seen in type 2 diabetics who engage in aerobic exercise is due to gains in peripheral, not hepatic, insulin sensitivity, study findings indicate.

Dr. Jason J. Winnick from the department of molecular physiology at Vanderbilt University Medical Center, Nashville, and colleagues at Ohio State University, Columbus, determined the effect of 7 days of aerobic exercise training on peripheral and hepatic insulin sensitivity in 18 obese, mildly diabetic adults.

As reported in the Journal of Clinical Endocrinology and Metabolism for March, all study subjects discontinued their diabetes medications and then maintained an isocaloric diet consisting of 50% carbohydrate, 30% fat, and 20% protein for 15 days.

During the second week, 9 randomly selected subjects also walked on a treadmill for 50 minutes daily at 70% of maximum oxygen consumption. Each subject underwent an initial isoglycemic/hyperinsulinemic clamp after the first dietary control week and a second clamp after completing the second week.

Dr. Winnick told Reuters Health, "In response to our 1-week exercise training protocol that involved moderate intensity walking, there was a fairly large increase in insulin's ability to stimulate glucose uptake by the whole body (i.e., whole-body insulin sensitivity) and muscle (i.e., muscle insulin sensitivity). However, within the same time frame, the exercise training did not improve insulin's ability to stimulate decreases in liver glucose production."

It is likely, the researcher added, that in the absence of caloric restriction, it takes more than a week to improve hepatic insulin sensitivity in people with diabetes.

It is also worth noting, Dr. Winnick said, that, despite discontinuation of diabetes medications, the fasting blood glucose values did not change over the intervention period -- so glucose metabolism can improve within one week of starting an exercise program.

"In particular, blood glucose after a meal may be improved due to improved muscle glucose uptake, despite not showing a change in the fasting blood glucose level," Dr. Winnick explained.

J Clin Endocrinol Metab 2008;93:771-778.

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