Effects of differential blockade of the renin-angiotensin system in postinfarcted rats.

The present study compared short-term effects of the AT(1)-receptor antagonist, irbesartan with the angiotensin-converting enzyme (ACE) inhibitor, enalapril on systemic haemodynamics and cardiac remodelling in post-myocardia-infarcted (MI) rats. MI Sprague-Dawley rats were orally treated for 4 weeks with irbesartan (50 mg/kg/day) or enalapril (10 mg/kg/day). Then, cardiac and systemic haemodynamics were measured. Compared with the sham-operated group, left ventricular end-diastolic pressure (LVEDP), diastolic pressure (LVDP), heart weight to body weight ratio were all significantly increased in the MI group while the LV contractility (dP/dt) and pulsatile arterial pressure were significantly reduced. Both drugs reduced the elevated LVEDP and LVDP and prevented cardiac hypertrophy. Furthermore, irbesartan attenuated the right shift of the pressure-volume curves, prevented postinfarction-induced increase in urinary cyclic guanosine monophosphate and reduced urinary aldosterone excretion. Although both drugs were able to prevent further cardiac hypertrophy and improved cardiac filling pressure, only irbesartan limited LV dilatation. These data indicate that blockade of the renin-angiotensin system at the level of AT1 receptors may have a better cardioprotective benefit than reducing angiotensin II levels by ACE inhibition.

Rimonabant reduces obesity-associated hepatic steatosis and features of metabolic syndrome in obese Zucker fa/fa rats.

This study investigated the effects of rimonabant (SR141716), an antagonist of the cannabinoid receptor type 1 (CB1), on obesity-associated hepatic steatosis and related features of metabolic syndrome: inflammation (elevated plasma levels of tumor necrosis factor alpha [TNFalpha]), dyslipidemia, and reduced plasma levels of adiponectin. We report that oral treatment of obese (fa/fa) rats with rimonabant (30 mg/kg) daily for 8 weeks abolished hepatic steatosis. This treatment reduced hepatomegaly, reduced elevation of plasma levels of enzyme markers of hepatic damage (alanine aminotransferase, gamma glutamyltransferase, and alkaline phosphatase) and decreased the high level of local hepatic TNFalpha currently associated with steatohepatitis. In parallel, treatment of obese (fa/fa) rats with rimonabant reduced the high plasma level of the proinflammatory cytokine TNFalpha and increased the reduced plasma level of the anti-inflammatory hormone adiponectin. Finally, rimonabant treatment also improved dyslipidemia by both decreasing plasma levels of triglycerides, free fatty acids, and total cholesterol and increasing the HDLc/LDLc ratio. All the effects of rimonabant found in this study were not or only slightly observed in pair-fed obese animals, highlighting the additional beneficial effects of treatment with rimonabant compared to diet. These results demonstrate that rimonabant plays a hepatoprotective role and suggest that this CB1 receptor antagonist potentially has clinical applications in the treatment of obesity-associated liver diseases and related features of metabolic syndrome.