Issue 201 Item 14 Metformin May Improve Sympathovagal Balance in Overweight Diab

The reduction in plasma free fatty acids (FFA) and insulin resistance that occurs with metformin therapy appears to improve sympathovagal balance in overweight patients with type 2 diabetes. Numerous reports, they say, have shown that elevated FFA levels and insulin resistance increase cardiovascular mortality in diabetics by promoting sympathetic hyperactivity. However, it is unclear if metformin therapy could reduce this elevated sympathetic tone.

To investigate, Dr. Giuseppe Paolisso, from the Second University of Naples, and colleagues assessed sympathovagal balance in 60 overweight diabetics treated with metformin for 4 months and 60 similar patients who received placebo. Insulin resistance was measured with the Homeostasis Model Assessment (HOMA) index and sympathovagal balance was assessed with heart rate variability.

Metformin therapy was associated with a significant drop in fasting plasma glucose, insulin, triglyceride, and FFA levels and with an improved HOMA index, the researchers point out.

Cardiac sympathovagal balance also improved significantly in metformin users, although mean arterial blood pressure did not change. On multivariate analysis, the change in FFA levels and the HOMA index were identified as independent predictors of sympathovagal balance.

The effect of metformin on cardiac autonomic nervous activities "seems related to a decrease in plasma FFA concentrations and insulin resistance," the investigators observe. The results, they add, "suggest that the drug might be useful in improving the sympathovagal balance" in such patients."
Am J Hypertens 2004;17:223-227.