Rosiglitazone Improves Exercise Function in Type 2 Diabetes

Study suggests that in addition to improving insulin sensitivity, thiazolidinediones may increase exercise capacity in patients with established type 2 diabetes.

Dr. Judith G. Regensteiner from University of Colorado Health Sciences Center, Denver, Colorado stated that, “There are important defects in exercise capacity in people with type 2 diabetes that we need to understand since the abnormalities have implications in terms of cardiovascular health.”

Based on the fact that rosiglitazone improves insulin sensitivity and endothelial function, Dr. Regensteiner and colleagues investigated whether administration of rosiglitazone would improve exercise capacity in 20 adults with uncomplicated type 2 diabetes.

Measures of fasting glucose level and insulin resistance improved in the patients treated with rosiglitazone, the authors report. Placebo-treated patients also showed modest improvements in insulin resistance.

VO2max improved significantly after four months of treatment with rosiglitazone, the report indicates, whereas placebo-treated patients showed no improvement in VO2max.

Endothelial function, as measured by brachial artery diameter response to cuff-induced hyperemia, improved significantly after administration of rosiglitazone, the researchers note, but there was no change after administration of placebo. Similar results were seen in the hyperemic forearm blood flow response measured by plethysmography.

Among rosiglitazone-treated patients, changes in VO2max correlated with measures of insulin resistance but not with measures of glycemic control, the investigators observe.

“To our knowledge,” the researchers conclude, “this finding marks the first report demonstrating that a pharmacological intervention with a thiazolidinedione improves exercise capacity in persons with type 2 diabetes. The mechanism(s) leading to these improvements cannot be determined in the present study.”

“[This study] suggests that in addition to improving insulin sensitivity, thiazolidinediones may increase exercise capacity in patients with established type 2 diabetes,” write Dr. Nathan K. LeBrasseur and Dr. Neil B. Ruderman from Boston University School of Medicine, Boston, Massachusetts in a related commentary.

“Its effects on VO2max in the present study were modest, suggesting that their efficacy for this purpose in people with established type 2 diabetes may be limited or that a period of treatment in excess of four months is needed,” the editorial adds.

“We are planning a study submission to NIH to study the effects of thiazolidinediones (TZDs) and exercise training combined versus either treatment alone on improving cardiovascular exercise capacity in people with type 2 diabetes,” Dr. Regensteiner said. “We are interested in seeing whether a TZD can potentially enhance the effects of exercise training. We are interested both in the practical benefits and also the mechanisms by which these two treatments might work together.”

Diabetes Care 2005;28:2877-2883,2975-2977.

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