Inhibition of Balloon Injury-Induced Neointimal Formation by Olmesartan and Pravastatin in Rats with Insulin Resistance

The combined effect of an angiotensin II type 1 receptor blocker and a 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor on vascular lesion formation in the insulin-resistant state has not been examined. We tested whether or not combined treatment is superior to single-drug treatment for inhibiting vascular lesion formation in insulin-resistant rats. The rats were maintained on a fructose-rich diet for 4 weeks and then treated with olmesartan (1 mg/kg/day) and/or pravastatin (10 mg/kg/day) for 3 weeks. After 1 week of drug treatment, balloon injury of the carotid arteries was performed. Two weeks later, the injured arteries were harvested for morphometry and immunostaining. Olmesartan and pravastatin each modestly attenuated neointimal formation without significant changes in blood pressure or serum lipid levels. The combination of olmesartan and pravastatin significantly suppressed the neointimal formation compared with either monotherapy. The number of terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL)-positive cells was increased by olmesartan but not by pravastatin. Olmesartan and pravastatin each decreased the number of Ki-67-positive cells, which indicates cell proliferation, to the same extent. The combined treatment increased the number of TUNEL-positive cells but did not affect the number of Ki-67-positive cells. The combined treatment decreased the insulin level and increased the number of circulating endothelial progenitor cells. These results suggest that the combination of olmesartan and pravastatin is beneficial for the treatment of vascular diseases in the insulin-resistant state independently of blood pressure or cholesterol levels.