Simvastatin, atorvastatin, and pravastatin equally improve the hemodynamic status of diabetic rats

Abstract

Aim: To investigate if the effect of statins improving cardiovascular (CV) status of diabetics is drug-specific or class-dependent, and the underlying mechanisms involved.

Methods: We compared the results of daily administration over a four-week period of a low dose (10 mg/kg per day) of atorvastatin (AV), simvastatin (SV), and pravastatin (PV) on cardiac performance in diabetic rats. Echocardiographic variables were tested, as well as systolic blood pressure (SBP), acetylcholine (ACh)-induced relaxation, plasma cholesterol levels, and perivascular fibrosis. Malondialdehyde (MDA) and 4-hydroxyalkenal (4-HAE), and endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) protein levels were also measured in cardiac and aortic homogenates.

Results: In untreated diabetic rats, cholesterol levels were higher than in control rats (CT; n = 8, P < 0.05), and the low dose of statins used did not modify these levels. In diabetic rats, SBP was higher than in CT, and was significantly reduced by all three statins (n = 10, P < 0.05). Echocardiographic parameters (EF, SV, and COI) were all lower in untreated diabetic rats than in CT (n = 10, P < 0.05). These CV parameters were equally improved by all three statins. The maximal relaxation (EMax) induced by ACh in aortic ring from diabetic rats was also improved. Moreover, this relaxation was abolished by 1 mmol/L NG-nitro-L-arginine methyl ester, suggesting the involvement of a NO-dependent mechanism.

Conclusion: AV, SV, and PV are equally effective in improving CV performance in diabetic rats. All tree statins decreased media thickness, perivascular fibrosis, and both MDA and 4-HAE in the aortas of diabetic rats, without affecting eNOS and iNOS protein levels. The observed hemodynamic benefits are cholesterol-independent. These benefits appear to be secondary to the improved endothelial function, and to the reduced vascular tone and remodeling that result from decreased oxidative stress.

Keywords: Cardiac function; Diabetes; Oxidative stress; Perivascular fibrosis; Statins.

Figure 1

Effects of four weeks treatment with atorvastatin, simvastatin, and pravastain (10 mg/kg per day) on diabetic rats and control. A: Stroke volume (mL); B: Ejection fraction (%); C: Cardiac output index (mL/min x 100 g BW). The results represent the mean ± SEM of 8 animals per group. All the statins significantly improved these CV parameters in diabetic rats. ^aP < 0.05 for diabetic rats vs CT; ^cP < 0.05 for untreated diabetic rats vs treated diabetic rats. STZ: Streptozotocin; AV: Atorvastatin; SV: Simvastatin; PV: Pravastatin; CT: Control.

Figure 2

Effects of four weeks treatment with atorvastatin, simvastatin, and pravastain (10 mg/kg per day) on systolic blood pressure (mmHg) in diabetic rats and control. The values shown are the means ± SEM of 10 animals per group. All statins significantly decreased blood pressure in diabetic rats. ^aP < 0.05 for diabetic rats vs CT; ^cP < 0.05 for untreated diabetic rats vs treated diabetic rats. AV: Atorvastatin; SV: Simvastatin; PV: Pravastatin; CT: Control.

Figure 3

Cumulative concentration response curves for acetylcholine-induced relaxation of aortic rings from diabetic rats after four weeks treatment with atorvastatin, simvastatin, and pravastatin (10 mg/kg per day). Aortic rings were precontracted with 0.1 μmol/L norepinephrine (NE) before the addition of cumulative concentrations of ACh. Note that the addition of 1 mmol/L L-NAME to the incubation bath inhibited ACh-induced relaxation. The values shown are the means ± SEM of 10 animals per group. ^aP < 0.05 for E_MAX between untreated diabetic rats and treated diabetic rats. AV: Atorvastatin; SV: Simvastatin; PV: Pravastatin; ACh: Acetylcholine.

Figure 4

Effect of four weeks treatment with atorvastatin, simvastatin, and pravastatin (10 mg/kg per day) on malondialdehyde + 4-hydroxyalkenal levels in aortic homogenates (A) and in cardiac homogenates (B) from diabetic rats and control. For diabetic rats, all statins equally reduced lipid peroxidation levels in aortic homogenates, but had no effect on these levels in cardiac homogenates. For CT, no effect of statins was observed in either aortic or cardiac homogenates. The values shown are the means ± SEM of 8 animals per group. ^aP < 0.05 for diabetic rats vs CT; ^cP < 0.05 for untreated diabetic rats vs treated diabetic rats. AV: Atorvastatin; SV: Simvastatin; PV: Pravastatin; CT: Control.

Figure 5

Representative histological sections of aortic segments from untreated and statin-treated diabetic rats, and untreated control. A: Quantified thickness of perivascular fibrosis in comparable aortic segments from treated diabetic rats and untreated diabetic rats. Perivascular fibrosis was higher in untreated diabetic rats than in CT. All statins decreased perivascular fibrosis in diabetic rats. The values shown are the means ± SEM of 5 animals per group, with the mean value for each animal based on five measurements of its aortic segment. ^aP < 0.05 for untreated diabetic rats vs untreated CT; ^cP < 0.05 for untreated diabetic rats vs treated diabetic rats; B: Representative histological sections (× 40, Azan-Mallory stain) of aortic segments from untreated diabetic rats and treated diabetic rats, demonstrating the typical reduction in perivascular fibrosis after treatment with each individual statin. AV: Atorvastatin; SV: Simvastatin; PV: Pravastatin; CT: Control.

Figure 6

Effect of four weeks treatment with atorvastatin, simvastatin, and pravastatin (10 mg/kg per day) on endothelial nitric oxide synthase (A) and inducible nitric oxide synthase (B) protein levels in aortic homogenates from treated and untreated diabetic rats, and untreated control. Data represent values normalized against β-actin and expressed as percent change relative to untreated CT. The values shown are the means ± SEM of five animals per group; ^aP < 0.05 for untreated diabetic rats vs untreated CT. Bottom: Representative Western blot for eNOS and iNOS of homogenized aortic tissue; AV: Atorvastatin; SV: Simvastatin; PV: Pravastatin; CT: Control; eNOS: Endothelial nitric oxide synthase; iNOS: Inducible nitric oxide synthase.

Figure 7

Effect of four weeks treatment with atorvastatin, simvastatin, and pravastatin (10 mg/kg per day) on endothelial nitric oxide synthase (A) and inducible nitric oxide synthase (B) protein levels in cardiac homogenates from treated and untreated diabetic rats, and untreated control. Data represent values normalized against β-actin and expressed as percent change relative to untreated CT. The values shown are the means ± SEM of five animals per group. No statistically significant differences were found. Bottom: Representative Western blot for eNOS and iNOS of homogenized cardiac tissue; AV: Atorvastatin; SV: Simvastatin; PV: Pravastatin; CT: Control; eNOS: Endothelial nitric oxide synthase; iNOS: Inducible nitric oxide synthase.