Chronic administration of atorvastatin could partially ameliorate erectile function in streptozotocin-induced diabetic rats

The efficacy of statins is related to the ‘common soil’ hypothesis, which proposes oxidative stress and inflammation as main pathophysiologic processes in the disease group of diabetes and endothelial dysfunction. This study evaluated the recovery of erectile function after administration of chronic statin alone in streptozotocin (STZ)-induced diabetes mellitus (DM) rats, focusing on the anti-oxidative effects and consequentially recuperated endothelial function. A total of 45 male Sprague-Dawley rats (8 weeks old) were divided into three groups (n = 15 each): an age-matched normal control group (Control group), an uncontrolled DM group (DM group), and a statin-treated group (Statin group). The rats in the DM and Statin group received an injection of STZ (60 mg/kg). Beginning 10 weeks after the establishment of DM, the Statin group received daily treatment with atorvastatin (10 mg/kg) via oral gavage for four weeks. After 14 weeks, the results of the experiment were evaluated. The ratios of intracavernosal pressure (ICP) to mean arterial pressure (MAP) were recorded with cavernosometry (20 Hz, 3 V, 0.2 msec for 30 seconds) before and after the intravenous administration of udenafil (1 mg/kg). Expression of alpha-smooth muscle actin (α-SMA) was evaluated using cavernosal tissue. In addition, changes in RhoA translocation ratio and myosin phosphatase target subunit 1 (MYPT1) phosphorylation were evaluated with western blot. Superoxide dismutase (SOD) and malondialdehyde (MDA) levels were also analyzed as measurements of oxidative stress levels. The ICP/MAP and area under the curve (AUC)/MAP ratios of the Statin group were obviously superior to the DM group, but were not comparable to the Control group (P<0.001). The level of oxidative stress, namely SOD activity, was also significantly lower in the Statin group than in the DM group (P = 0.015), and was comparable to the Control group. In contrast, MDA levels were not considerably different among the groups (P = 0.217). The RhoA translocation ratio was not significantly different among the groups (P = 0.668), whereas MYPT1 phosphorylation in the Statin group was significantly lower than in the DM group (P = 0.030), and similar to the Control group. Expression of α-SMA in the Statin group was higher than in the DM group (P<0.001), and comparable to the Control group. Chronic statin treatment alone showed anti-oxidative effects and helped to restore the erectile mechanism, but did not lead to the full recovery of erectile function in STZ-induced DM rats. Therefore, combination therapy rather than a single agent should be the preferred treatment strategy for DM-associated erectile dysfunction, especially in the setting of severe diabetes.