Effects of cilnidipine on muscle fiber composition, capillary density and muscle blood flow in fructose-fed rats

The aim of this study was to examine the roles of muscle fiber composition, capillary density and muscle blood flow in insulin resistance (IR) and the effect of cilnidipine, a calcium channel blocker in fructose-fed rats (FFR ). Six-week-old male Sprague-Dawley rats were fed either normal rat chow or fructose-rich chow for 6 weeks. For the last 2 weeks, the rats were treate d by gavage with a vehicle (Control and FFR groups) or with cilnidipine (FF R + Cil group). Blood pressure (BP) and insulin sensitivity were assessed i n the sixth week. Muscle fiber composition, capillary density and blood flo w in the soleus muscle were evaluated. BP of FFR was significantly higher t han that of the controls. Cilnidipine significantly lowered BP in FFR. Insu lin sensitivity was significantly lower in FFR than in the controls. Cilnid ipine significantly improved IR in FFR. The composite ratio of type I fiber s in the soleus muscle was significantly lower in FFR than in the controls, but that of type II fibers was significantly higher in FFR. Treatment with cilnidipine resulted in recovery of this ratio to that of the controls. In sulin sensitivity was found to be significantly correlated with the composi te ratio of either type I fibers or type II fibers. There were no intergrou p differences in capillary density. Muscle blood flow in the FFR + Cil grou p was higher than that in the Control or FFR groups. These results suggest that muscle fiber composition is linked to IR and that cilnidipine may impr ove IR in FFR either by modulating muscle fiber composition or by increasin g muscle blood flow.