Effect of orchiectomy on renal function in control and diabetic rats with chronic inhibition of nitric oxide.

1. Male gender is associated with higher blood pressure (BP) and more rapid loss of renal function in a spectrum of clinical and experimental renal diseases, including diabetic nephropathy. Consequently, modulation of testosterone levels could exert beneficial effects in the diabetic kidney. 2. The aim of the present study was to determine whether testosterone deficiency (orchiectomy) could influence BP and renal function in streptozotocin-diabetic rats, with or without accelerated endothelial dysfunction achieved by chronic inhibition of nitric oxide (NO) synthesis using N(G)-nitro-L-arginine methyl ester (l-NAME; 40-100 mg/L in the drinking water for 2 weeks), as well as in age-matched non-diabetic rats subjected to the same interventions. 3. Orchiectomy did not affect L-NAME-induced increases in BP in non-diabetic or diabetic rats. In non-diabetic rats, orchiectomy prevented L-NAME-induced increases in proteinuria. These effects on proteinuria were not observed in diabetic rats. In non-diabetic rats, orchiectomy had no effect on renal haemodynamics in animals receiving vehicle and did not affect L-NAME-induced changes in renal haemodynamics, characterized by reductions in renal plasma flow (RPF) and higher filtration fractions (FF). In intact diabetic rats, L-NAME treatment resulted in lower RPF. This difference was not observed in diabetic rats subjected to orchiectomy, although L-NAME-treated diabetic orchiectomized rats had lower RPF and higher FF compared with vehicle-treated intact diabetic rats. 4. In conclusion, we report modest beneficial effects of orchiectomy on proteinuria in normal, but not in diabetic, rats with inhibition of NO production. This suggests that testosterone reduction does not attenuate the deleterious impact of the diabetic metabolic milieu in the kidney.

Isozyme-nonselective N-substituted bipiperidylcarboxamide acetyl-CoA carboxylase inhibitors reduce tissue malonyl-CoA concentrations, inhibit fatty acid synthesis, and increase fatty acid oxidation in cultured cells and in experimental animals.

Inhibition of acetyl-CoA carboxylase (ACC), with its resultant inhibition of fatty acid synthesis and stimulation of fatty acid oxidation, has the potential to favorably affect the multitude of cardiovascular risk factors associated with the metabolic syndrome. To achieve maximal effectiveness, an ACC inhibitor should inhibit both the lipogenic tissue isozyme (ACC1) and the oxidative tissue isozyme (ACC2). Herein, we describe the biochemical and acute physiological properties of CP-610431, an isozyme-nonselective ACC inhibitor identified through high throughput inhibition screening, and CP-640186, an analog with improved metabolic stability. CP-610431 inhibited ACC1 and ACC2 with IC50s of approximately 50 nm. Inhibition was reversible, uncompetitive with respect to ATP, and non-competitive with respect to bicarbonate, acetyl-CoA, and citrate, indicating interaction with the enzymatic carboxyl transfer reaction. CP-610431 also inhibited fatty acid synthesis, triglyceride (TG) synthesis, TG secretion, and apolipoprotein B secretion in HepG2 cells (ACC1) with EC50s of 1.6, 1.8, 3.0, and 5.7 microm, without affecting either cholesterol synthesis or apolipoprotein CIII secretion. CP-640186, also inhibited both isozymes with IC50sof approximately 55 nm but was 2-3 times more potent than CP-610431 in inhibiting HepG2 cell fatty acid and TG synthesis. CP-640186 also stimulated fatty acid oxidation in C2C12 cells (ACC2) and in rat epitrochlearis muscle strips with EC50s of 57 nm and 1.3 microm. In rats, CP-640186 lowered hepatic, soleus muscle, quadriceps muscle, and cardiac muscle malonyl-CoA with ED50s of 55, 6, 15, and 8 mg/kg. Consequently, CP-640186 inhibited fatty acid synthesis in rats, CD1 mice, and ob/ob mice with ED50s of 13, 11, and 4 mg/kg, and stimulated rat whole body fatty acid oxidation with an ED50 of approximately 30 mg/kg. Taken together, These observations indicate that isozyme-nonselective ACC inhibition has the potential to favorably affect risk factors associated with the metabolic syndrome.

Differing cardioprotective efficacy of the Na+/Ca2+ exchanger inhibitors SEA0400 and KB-R7943.

KB-R7943 and SEA0400 are Na(+)/Ca(2+) exchanger (NCX) inhibitors with differing potency and selectivity. The cardioprotective efficacy of these NCX inhibitors was examined in isolated rabbit hearts (Langendorff perfused) subjected to regional ischemia (coronary artery ligation) and reperfusion. KB-R7943 and SEA0400 elicited concentration-dependent reductions in infarct size (SEA0400 EC(50): 5.7 nM). SEA0400 was more efficacious than KB-R7943 (reduction in infarct size at 1 microM: SEA0400, 75%; KB-R7943, 40%). Treatment with either inhibitor yielded similar reductions in infarct size whether administered before or after regional ischemia. SEA0400 (1 microM) improved postischemic recovery of function (+/-dP/dt), whereas KB-R7943 impaired cardiac function at >/=1 microM. At 5-20 microM, KBR-7943 elicited rapid and profound depressions of heart rate, left ventricular developed pressure, and +/-dP/dt. Thus the ability of KB-R7943 to provide cardioprotection is modest and limited by negative effects on cardiac function, whereas the more selective NCX inhibitor SEA0400 elicits marked reductions in myocardial ischemic injury and improved +/-dP/dt. NCX inhibition represents an attractive approach for achieving clinical cardioprotection.

A novel nonpeptidic caspase-3/7 inhibitor, (S)-(+)-5-[1-(2-methoxymethylpyrrolidinyl)sulfonyl]isatin reduces myocardial ischemic injury.

The efficacy of a novel, nonpeptidic, caspase 3/7-selective inhibitor, (S)-(+)-5-[1-(2-methoxymethylpyrrolidinyl)sulfonyl]isatin (MMPSI) for reducing ischemic injury in isolated rabbit hearts or cardiomyocytes was evaluated. MMPSI (0.1-10 microM) evoked a concentration-dependent reduction in infarct size (up to 56% vs. control; IC(50)=0.2 microM). Furthermore, apoptosis (DNA laddering, soluble nucleosomes) was reduced in the ischemic area-at-risk. MMPSI inhibited recombinant human caspase-3 with an IC(50)=1.7 microM. Apoptosis in H9c2 cells after 16-h simulated ischemia and 2-h simulated reperfusion was significantly reduced by MMPSI in a concentration-dependent manner (IC(50)=0.5 microM); similar effects were observed in isolated adult rabbit cardiomyocytes (IC(50)=1.5 microM). These data support an important role for caspase-3/7 in mediating myocardial ischemic injury. Furthermore, these data indicate that cardioprotection via caspase-3/7 inhibition is attainable via a small molecule (nonpeptidic) inhibitor, a necessary step in making this approach therapeutically viable.