Effect of Beta-Blockers on Insulin Resistance in Patients With Dilated Cardiomyopathy

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Abstract
The aim of this study was to evaluate the effect of β-blockers on insulin resistance in patients with dilated cardiomyopathy (DCM). A secondary aim was to determine the effect of this treatment on plasma concentrations of tumor necrosis factor-α (TNF-α) and to investigate the relationships between this adipocytokine and insulin resistance. Insulin resistance determined using the Homeostatic Model Assessment (HOMA), echocardiographic measurements and analysis of plasma TNF-α concentration were carried out in 47 patients with DCM without diabetes mellitus before and after 6 months of β-blocker therapy. A reduction in left ventricular dimensions and an associated increase in ejection fraction occurred with β-blocker. The treatment resulted in a significant decrease in insulin resistance (HOMA index: Baseline, 2.73±3.36 vs, Month 6, 1.58±1.33, p=0.0347). Beta-blockade was also associated with a decrease in plasma TNF-α concentration although no significant relationship between this change and the improvement in insulin resistance was observed. Beta-blocker therapy in patients with DCM improved not only cardiac function, but also insulin resistance. The mechanism of the change in insulin function remains unclear, but may be related to improvements in left ventricular function or an attenuation of the inhibitory effect of reduction in TNF-α on insulin signaling. (Circ J 2003; 67: 701 - 704)