Cardiovascular effects of sulphonylurea derivatives. Implications for the treatment of NIDDM?

Sulphonylurea derivatives are widely used in the treatment of non-insulin-dependent diabetes mellitus. The mechanism of action of the insulino-tropic effect of these agents is based on the closure of adenosine-5'-triphosphate (ATP)-sensitive potassium channels (KATP-channels) in the beta cells of the pancreas. In the last decade, these KATP-channels have been demonstrated in myocardial cells as well as in vascular smooth muscle cells. During myocardial ischaemia, the KATP-channels are thought to open by a fall in the cytosolic ATP concentration. The increase in the extracellular adenosine concentration, and the release of endothelium-derived hyperpolarizing factor (EDHF) during ischaemia may further contribute to the opening of cardiovascular KATP-channels. Independently from the mechanism of opening, sulphonylurea derivatives have been reported to block the opening of cardiovascular KATP-channels. Related to the role of KATP-channel-opening in the (patho)physiology of ischaemia, the use of sulphonylurea derivatives significantly modifies the outcome of experimental myocardial infarction. Sulphonylurea derivatives impair the recovery of the contractile function and increase the ultimate infarct size in animal models. In contrast, sulphonylurea derivatives have a beneficial effect on the incidence of ventricular fibrillation as occurs after ischaemic incidents of the myocardium. Based on these experimental observations, human studies are indicated to investigate whether the use of these drugs modifies the clinical outcome of cardiovascular events in patients with non-insulin dependent diabetes mellitus.