Cardiomyocyte volume-weighted nuclear volume and spironolactone therapy in spontaneously hypertensive rats

OBJECTIVE: To evaluate the blood pressure (BP) and cardiomyocyte nuclei hypertrophy of spontaneously hypertensive rats (SHR) treated with spironolactone and with spironolactone and an angiotensin-converting enzyme inhibitor and calcium channel blocker. STUDY DESIGN: Six groups with 5 SHR each were treated for 13 weeks: control group, spironolactone groups (5, 10 and 30 mg/kg/d, or low, moderate and high doses, respectively), and spironolactone and enlapril or/and verapamil. Blood pressure (BP) and cardiomyocyte volume-weighted nuclear volume (VWNV) were studied. RESULTS: The usual evolution of BP in young adult SHR was greatly altered by spironolactone treatment, with either attenuation or reversion of the BP tendency to increase. The treatments efficiently reduced the cardiomyocyte VWNV > 45%, confirming efficient action of both spironolactone monotherapy at moderate and high dose and spironolactone combined with enalapril or verapamil. However, the high dose of spironolactone, and spironolactone plus enalapril or verapamil showed no significant differences in cardiomyocyte VWNV. Correlation between VWNV and BP (13th week) suggested that BP degree influences cardiomyocyte VWNV. CONCLUSION: The effect of spironolactone monotherapy seems to be dose dependent, and the combination with enalapril or verapamil improves spironolactone efficiency in BP reduction but not in prevention/attenuation of cardiac myocyte nuclear hypertrophy.     

Enalapril improves albuminuria by preventing glomerular loss of heparan sulfate in diabetic rats

Angiotensin converting enzyme (ACE) inhibitors, particularly enalapril and captopril, have been shown to decrease proteinuria in diabetic animals and human subjects. Since heparan sulfate proteoglycan confers a negative charge on the glomerular basement membrane, and either decreased synthesis or loss of this charge causes albuminuria in diabetic animals, we examined the possibility that enalapril prevents albuminuria through glomerular preservation of heparan sulfate in long-term diabetic rats. A total of 22 male Wistar rats were used in the study. Diabetes was induced in 15 rats by a single intraperitoneal injection of streptozotocin (60 mg/kg). The remaining 7 rats received buffer. One week following induction of diabetes, 8 diabetic rats were allowed to drink tap water containing enalapril at a concentration of 50 mg/liter; the remaining 7 diabetic and 7 nondiabetic rats were given only tap water. The drug treatment was continued for 20 weeks. Systolic blood pressure and 24-hr urinary excretion of albumin were measured at 2, 8, 16, and 20 weeks. At the end of 20 weeks, all rats were killed, kidneys were removed, and glomeruli were isolated by differential sieving technique. Total glycosaminoglycan and heparan sulfate synthesis was determined by incubating glomeruli in the presence of [35S]sulfate. Characterization of heparan sulfate was performed by ion-exchange chromatography. Systolic blood pressures were significantly lower in enalapril-treated diabetic rats compared to untreated diabetic rats. Diabetic glomeruli synthesized less heparan sulfate than glomeruli from nondiabetic rats. Also, glomerular heparan sulfate content of diabetics was significantly lower than that of nondiabetics. Further characterization of heparan sulfate showed that the fraction eluted with 1 M NaCl was significantly lower and the fraction eluted with 1.25 M NaCl significantly higher in diabetic than in normal rats. Enalapril treatment normalized not only glomerular synthesis and content but also various fractions of heparan sulfate in diabetic rats. Diabetic rats excreted increased quantities of heparan sulfate and albumin than nondiabetic rats. Enalapril therapy prevented both these increases in diabetic rats. These data suggest that enalapril treatment improves albuminuria through preservation of glomerular heparan sulfate and prevention of its urinary loss in diabetic rats.     

Randomised,double blind,multicentre comparison of hydrochlorothiazide,atenolol, nitrendipine,and enalapril in antihypertensive treatment: results of the HANE study. HANE Trial Research Group.

OBJECTIVE: To compare the effectiveness and tolerability of hydrochlorothiazide, atenolol, nitrendipine, and enalapril in patients with mild to moderate hypertension. DESIGN: Randomised multicentre trial over 48 weeks with double blind comparison of treatments. SETTING: 48 centres in four countries. PATIENTS: 868 patients with essential hypertension (diastolic blood pressure 95-120 mm Hg) INTERVENTIONS: Initial treatment (step 1) consisted of 12.5 mg hydrochlorothiazide (n = 215), 25 mg atenolol (n = 215), 10 mg nitrendipine (n = 218), or 5 mg enalapril (n = 220) once daily. If diastolic blood pressure was not reduced to < 90 mm Hg within four weeks, doses were increased to 25 mg, 50 mg, 20 mg, 10 mg, respectively, once daily (step 2) and after two more weeks to twice daily (step 3). The eight week titration phase was followed by an additional 40 weeks for patients who had reached the target diastolic pressure. MAIN OUTCOME MEASURES: Blood pressure by means of an automatic device with repeated measurements. RESULTS: After eight weeks the response rate for atenolol (63.7%) was significantly higher than for enalapril (50.0%), hydrochlorothiazide (44.7%), or nitrendipine (44.5%). After one year atenolol was still more effective (48.0%) than hydrochlorothiazide (35.4%) and nitrendipine (32.9%), but not significantly better than enalapril (42.7%). The treatment related dropout rate was higher (P < 0.001) in the nitrendipine group (n = 28). CONCLUSIONS: There is no evidence of superiority for antihypertensive effectiveness or tolerability of the "new" classes of antihypertensives (calcium channel blockers and angiotensin converting enzyme inhibitors). As these drugs are now widely used as treatment of first choice, our results further emphasise the need for studies confirming that they also reduce morbidity and mortality, as has been shown for diuretics and beta blockers.     

How well can blood pressure be controlled? Progress report on the Systolic Hypertension in Europe Follow-Up Study (Syst-Eur 2)

Background

The randomised, double-blind, placebo-controlled Systolic Hypertension in Europe trial (Syst-Eur 1) proved that blood pressure (BP) lowering therapy starting with nitrendipine reduces the risk of cardiovascular complications in elderly patients with isolated systolic hypertension. In an attempt to confirm the safety of long-term antihypertensive therapy based on a dihydropyridine, the Syst-Eur patients remained in open follow-up after the end of Syst-Eur 1. This paper presents the second progress report of this follow-up study (Syst-Eur 2). It describes BP control and adherence to study medications.

Methods

After the end of Syst-Eur 1 all patients, treated either actively or with placebo, were invited either to continue or to start antihypertensive treatment with the same drugs as previously used in the active treatment arm. In order to reach the target BP (sitting SBP <150 mmHg), the first line agent, nitrendipine, could be associated with enalapril and/or hydrochlorothiazide.

Results

Of the 3787 eligible patients, 3516 (93%) entered Syst-Eur 2. At the last available visit, 72% of the patients were taking nitrendipine. SBP/DBP at entry in Syst-Eur 2 averaged 160/83 mmHg in the former placebo group and 151/80 mmHg in the former active-treatment group. At the last follow-up visit SBP/DBP in the patients previously randomised to placebo or active treatment had decreased by 16/5 mmHg and 7/5 mmHg, respectively. The target BP was reached by 74% of the patients.

Conclusion

Substantial reductions in systolic BP may be achieved in older patients with isolated systolic hypertension with a treatment strategy starting with the dihydropyridine calcium-channel blocker, nitrendipine, with the possible addition of enalapril and/or hydrochlorothiazide.     

Converting enzyme inhibition and kidney function in normotensive diabetic patients with persistent microalbuminuria.

The effects of a long term reduction in blood pressure on the kidney function of normotensive diabetic patients who had persistent microalbuminuria (30-300 mg albumin/24 hours) were studied in two groups of 10 such patients before and during six months of treatment with either 20 mg enalapril or placebo daily. Treatments were assigned randomly in a double blind fashion. Before treatment both groups had similar clinical characteristics, weight, diet, total glycosylated haemoglobin, median albumin excretion rate (enalapril group 124 mg/24 h, placebo group 81 mg/24 h), and mean arterial pressure (enalapril group 100 (SD 8) mm Hg, placebo group 99 (6) mm Hg). During treatment weight, urinary urea excretion, and total glycosylated haemoglobin remained unchanged. The mean arterial pressure decreased in the enalapril group but not in the placebo group (enalapril group 90 (10) mm Hg, placebo group 98 (8) mm Hg). The median albumin excretion rate also fell in the enalapril group but not in the placebo group (enalapril group 37 mg/24 h, placebo group 183 mg/24 h.) The glomerular filtration rate rose in the enalapril group from 130 (23) ml/min/1.73 m2 to 141 (24) ml/min/1.73 m2, and total renal resistances and fractional albumin clearance decreased while fractional albumin clearance increased in the placebo group. These results show that in patients who have diabetes but not hypertension a reduction in blood pressure by inhibition of converting enzyme for six months can reduce persistent microalbuminuria, perhaps by decreasing the intraglomerular pressure.     

Effective control of glycemic status and toxicity in Zucker diabetic fatty rats with an orally administered vanadate compound

A novel black tea decoction containing vanadate has successfully replaced insulin in a rat model of insulin-dependent diabetes but is untested in non-insulin-dependent diabetic animals. A tea-vanadate decoction (TV) containing 30 or 40 mg sodium orthovanadate was administered by oral gavage to two groups of Zucker diabetic fatty rats and a conventional water vehicle containing 30 or 40 mg of sodium orthovanadate to two others. In the latter group receiving the 30-mg dose, vanadate induced diarrhea in 50% of the rats and death in 10%. In contrast, TV-treated rats had no incidence of diarrhea and no deaths. Symptoms were more severe in both groups with higher vanadate doses, so these were discontinued. After approximately 16 weeks, the level of vanadium in plasma and tissue extracts was negligible in a further group of untreated rats but highly elevated after vanadate treatment. Vanadium levels were not significantly different between the TV-treated diabetic rats and the diabetic rats given vanadate in a water vehicle. Over the 115 days of the study, blood glucose levels increased from approximately 17 to 25 mmol/L in untreated diabetic rats. This was effectively lowered (to <10 mmol/L) by TV treatment. Fasting blood glucose levels were 5, 7, and 20 mmol/L in control (nondiabetic, untreated), TV-treated and untreated diabetic rats, respectively. Rats required treatment with TV for only approximately 50% of the days in the study. Increase in body mass during the study was significantly lower in untreated diabetic rats (despite higher food intake) than the other groups. Body mass gain and food intake were normal in TV-treated rats. Water intake was 28 mL/rat daily in control rats, 130 mL/rat daily in untreated diabetic rats, and 52 mL/rat daily in TV-treated diabetic rats. Plasma creatinine and aspartate aminotransferase levels were significantly depressed in untreated diabetic rats, and TV treatment normalized this. Our results demonstrate that a novel oral therapy containing black tea and vanadate possesses a striking capacity to regulate glucose and attenuates complications in a rat model of type II diabetes.     

Ganglioside Treatment of Streptozotocin-Diabetic Rats Prevents Defective Axonal Transport of 6-Phosphofructokinase Activity

This study measured axonal transport of 6-phosphofructokinase (PFK) and aldolase activities in the sciatic nerves of rats with short-term streptozotocin-induced diabetes. The diabetic rats showed deficits in anterograde (69% of controls; p less than 0.001) and retrograde (33% of controls; p less than 0.01) accumulations of PFK activity as well as its content per unit length of unconstricted sciatic nerve (86% of controls; p less than 0.05). There were no accumulation deficits in aldolase activity in the nerves of the diabetic rats, although the activity per unit length of unconstricted nerve was deficient (81% of controls; p less than 0.05). Treatment of diabetic rats with mixed bovine brain gangliosides (10 mg/kg of body weight/day, i.p.) did not affect the deficit in PFK activity in unconstricted nerve (84% of ganglioside-treated controls; p less than 0.01), but all the other defects in enzyme activities were prevented completely. The diabetic rats also showed a reduction of 7% (p less than 0.01) in sciatic nerve dry weight per unit length, which was prevented by ganglioside treatment. In contrast, the reduced motor nerve conduction velocity, accumulation of polyol pathway metabolites, and depletion of myo-inositol, characteristic of untreated short-term diabetes, were unaffected by ganglioside treatment.     

Protective effects of thymoquinone on streptozotocin-induced diabetic nephropathy

The aim of this study was designed to investigate the possible beneficial effects of the thymoquinone (TQ) in streptozotocine (STZ)-induced diabetes in rats. The rats were randomly allotted into one of three experimental groups: A (control), B (diabetic untreated), and C (diabetic treated with TQ); each group contain ten animals. B and C groups received STZ. Diabetes was induced in two groups by a single intra-peritoneal (i.p) injection of STZ (50 mg/kg, freshly dissolved in 5 mmol/l citrate buffer, pH 4.5). Two days after STZ treatment, development of diabetes in two experimental groups was confirmed by measuring blood glucose levels in a tail vein blood samples. Rats with blood glucose levels of 250 mg/dl or higher were considered to be diabetic. The rats in TQ treated groups were given TQ (50 mg/kg body weight) once a day orally by using intra gastric intubation for 12 weeks starting 2 days after STZ injection. Treatment of TQ reduced the glomerular size, thickening of capsular, glomerular and tubular basement membranes, increased amounts of mesangial matrix and tubular dilatation and renal function as compared with diabetics untreated. We conclude that TQ therapy causes renal morphologic and functional improvement after STZ-induced diabetes in rats. We believe that further preclinical research into the utility of TQ treatment may indicate its usefulness as a potential treatment in diabetic nephropathy.     

Low-Dose Dextromethorphan,a NADPH Oxidase Inhibitor,Reduces Blood Pressure and Enhances Vascular Protection in Experimental Hypertension

Background

Vascular oxidative stress may be increased with age and aggravate endothelial dysfunction and vascular injury in hypertension. This study aimed to investigate the effects of dextromethorphan (DM), a NADPH oxidase inhibitor, either alone or in combination treatment, on blood pressure (BP) and vascular protection in aged spontaneous hypertensive rats (SHRs).

Methodology/Principal Findings

Eighteen-week-old WKY rats and SHRs were housed for 2 weeks. SHRs were randomly assigned to one of the 12 groups: untreated; DM monotherapy with 1, 5 or 25 mg/kg/day; amlodipine (AM, a calcium channel blocker) monotherapy with 1 or 5 mg/kg/day; and combination therapy of DM 1, 5 or 25 mg/kg/day with AM 1 or 5 mg/kg/day individually for 4 weeks. The in vitro effects of DM were also examined. In SHRs, AM monotherapy dose-dependently reduced arterial systolic BP. DM in various doses significantly and similarly reduced arterial systolic BP. Combination of DM with AM gave additive effects on BP reduction. DM, either alone or in combination with AM, improved aortic endothelial function indicated by ex vivo acetylcholine-induced relaxation. The combination of low-dose DM with AM gave most significant inhibition on aortic wall thickness in SHRs. Plasma total antioxidant status was significantly increased by all the therapies except for the combination of high-dose DM with high-dose AM. Serum nitrite and nitrate level was significantly reduced by AM but not by DM or the combination of DM with AM. Furthermore, in vitro treatment with DM reduced angiotensin II-induced reactive oxygen species and NADPH oxidase activation in human aortic endothelial cells.

Conclusions/Significance

Treatment of DM reduced BP and enhanced vascular protection probably by inhibiting vascular NADPH oxidase in aged hypertensive animals with or without AM treatment. It provides the potential rationale to a novel combination treatment with low-dose DM and AM in clinical hypertension.     

Possible role of VEGF in the progression of kidney disease in streptozotocin (STZ)-induced diabetic rats: effects of an ACE inhibitor and an angiotensin II receptor antagonist.

Two endothelium-derived factors, endothelin (ET), a vasoconstrictor, and vascular endothelial growth factor (VEGF), an angiogenic factor are thought to be involved in the pathogenesis of diabetic vascular complications. The aim of this study was to determine the effects of an angiotensin II type I (AT-1) receptor antagonist and an ACE inhibitor on the pathogenesis of VEGF and ET-1-mediated kidney disease in STZ-induced diabetic rats. Two days after STZ administration, diabetic rats were treated for 8 weeks with enalapril maleate, an ACE inhibitor, candesartan cilexetil, an AT-1 receptor antagonist, or saline. Urinary albumin and N-acetyl beta-D glucosaminidase (NAG) excretion as well as the VEGF protein content in the kidney were all found to be elevated in diabetic rats. Administration of enalapril maleate or candesartan cilexetil decreased the level of microalbuminuria and NAG excretion in diabetic rats. Administration of enalapril maleate also suppressed the elevated renal VEGF protein content in these animals while candesartan cilexetil treatment had no effect. Serum ET-1 and VEGF levels were unchanged by these treatments. These data support a role for AT-1 receptor antagonists and ACE inhibitors in the prevention of diabetic nephropathy, and suggest that the former may work by reducing renal VEGF levels.     

Enalapril treatment corrects the reduced response to bradykinin in diabetes increasing the B2 protein expression

Considering the growing importance of the interaction between components of kallikrein-kinin and renin-angiotensin systems in physiological and pathological processes, particularly in diabetes mellitus, the aim of the present study was to investigate the effect of enalapril on the reduced response of bradykinin and on the interaction between angiotensin-(1-7) (Ang-(1-7)) and bradykinin (BK), important components of these systems, in an insulin-resistance model of diabetes. For the above purpose, the response of mesenteric arterioles of anesthetized neonatal streptozotocin-induced (n-STZ) diabetic and control rats was evaluated using intravital microscopy. In n-STZ diabetic rats, enalapril treatment restored the reduced response to BK but not the potentiation of BK by Ang-(1-7) present in non-diabetic rats. The restorative effect of enalapril was observed at a dose that did not correct the altered parameters induced by diabetes such as hyperglycemia, glicosuria, insulin resistance but did reduce the high blood pressure levels of n-SZT diabetic rats. There was no difference in mRNA and protein expressions of B1 and B2 kinin receptor subtypes between n-STZ diabetic and control rats. Enalapril treatment increased the B2 kinin receptor expression. From our data, we conclude that in diabetes enalapril corrects the impaired BK response probably by increasing the expression of B2 receptors. The lack of potentiation of BK by Ang-(1-7) is not corrected by this agent.     

Contrasting effects of enalapril and metoprolol on proteinuria in diabetic nephropathy.

OBJECTIVE--To assess whether angiotensin converting enzyme inhibition reduces proteinuria in diabetic nephropathy more than blood pressure reduction with other antihypertensive treatment. DESIGN--Prospective, open randomised study lasting eight weeks in patients with diabetic nephropathy. SETTING--Outpatient nephrology clinics. PATIENTS--40 Patients with type I diabetes and diabetic nephropathy with reduced renal function. INTERVENTION--Antihypertensive treatment with enalapril or metoprolol, usually combined with frusemide. MAIN OUTCOME MEASURES--Arterial blood pressure and urinary excretion of albumin and protein. RESULTS--Arterial blood pressure after eight weeks was 135/82 (SD 13/7) mm Hg in the group given enalapril and 136/86 (16/12) mm Hg in the group given metoprolol. Proteinuria and albuminuria were similar in both groups before randomisation. After eight weeks'' treatment, the geometric mean albumin excretion was 0.7 (95% confidence interval 0.5 to 1.2) g/24 h in the patients given enalapril and 1.6 (1.1 to 2.5) g/24 h in the patients given metoprolol (p less than 0.02). The proteinuria was 1.1 (0.7 to 1.7) and 2.4 (1.6 to 3.6) g/24 h respectively (p less than 0.02). CONCLUSIONS--Antihypertensive treatment with enalapril reduced proteinuria in patients with diabetic nephropathy more than an equally effective antihypertensive treatment with metoprolol. This points to a specific antiproteinuric effect of the angiotensin converting enzyme inhibitor independent of the effect on systemic blood pressure.     

Angiotensin‐Converting Enzyme Inhibition and Angiotensin AT1 Receptor Blockade Downregulate Angiotensin‐Converting Enzyme Expression and Attenuate Renal Injury in Streptozotocin‐Induced Diabetic Rats

Angiotensin‐converting enzyme (ACE) is upregulated in the diabetic kidney and contributes to renal injury. This study investigates the possible beneficial effects of the ACE inhibitor (ACEI), enalapril and the AT1 receptor blocker (ARB), valsartan, on renal ACE expression, renal structure, and function in streptozotocin (STZ)‐induced diabetic rats. Male Wistar rats were allocated into four groups: control, STZ‐diabetic rats, and STZ‐diabetic rats treated with either enalapril (10 mg/kg/day) or valsartan (50 mg/kg/day) for 8 weeks. Enalapril and valsartan reduced renal ACE mRNA and protein expression, Na⁺/K⁺‐ATPase activity, oxidative stress, and serum transforming growth factor‐β1 levels compared to the diabetic group. Both treatments normalized renal nitrate/nitrite levels and ameliorated the observed histopathological changes. In conclusion, ACE downregulation by ACEI and ARB indicates that angiotensin II upregulates ACE through AT1 receptor. Prevention of diabetes‐induced changes in ACE expression and Na⁺/K⁺‐ATPase activity could be a new explanation of the renoprotective effects of ACEIs and ARBs. © 2013 Wiley Periodicals, Inc. J BiochemMol Toxicol 27:378‐387, 2013; View this article online at wileyonlinelibrary.com . DOI 10.1002/jbt.21500     

Effects of chelator treatment on aorta and corpus cavernosum from diabetic rats.

Transition-metal catalyzed reactions contribute to oxidative stress, which has been implicated in the pathogenesis of diabetic complications. The aim was to evaluate the effects of treatment with the transition metal chelator trientine on endothelium-dependent relaxation of aorta and corpus cavernosum from streptozotocin-induced diabetes of 8 weeks duration in rats. Effects on cavernosum autonomic innervation were also examined. Diabetes caused a 30.1 +/- 3.8% reduction in maximum aorta endothelium-dependent relaxation to acetylcholine (ACh), which was markedly attenuated (72.7 +/- 10.6%) by trientine treatment. Reversal treatment (4 weeks untreated diabetes, 4 weeks trientine) did not effect endothelium-dependent relaxation compared with aortas from rats with 4 weeks of diabetes, however, there was a 22.5 +/- 6.2% improvement compared with 8 weeks of diabetes. Eight weeks of diabetes caused a 41.5 +/- 6.6% reduction in corpus cavernosum endothelium-dependent maximum relaxation to ACh that was 70.1 +/- 16.9% prevented by trientine. Cavernosum nonadrenergic, noncholinergic (NANC) nerve stimulation caused frequency-dependent relaxation to a maximum of 40.9 +/- 2.4%, which was reduced by diabetes to 24.2 +/- 2.1%. Trientine partially prevented this deficit, maximum relaxation being 31.9 +/- 2.3%. Thus, metal chelator treatment has beneficial effects on aorta and cavernosum endothelium-dependent relaxation and on cavernosum NANC innervation.     

Protective effect of caffeic acid phenethyl ester (CAPE) on lipid peroxidation and antioxidant enzymes in diabetic rat liver

The aim of this study was to examine the effect of caffeic acid phenethyl ester (CAPE) on lipid peroxidation (LPO) and the activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) in the liver of streptozotocin (STZ)-induced diabetic rats. Twenty-seven rats were randomly divided into three groups: group I, control non-diabetic rats (n = 9); group II, STZ-induced, untreated diabetic rats (n = 8); group III, STZ-induced, CAPE-treated diabetic rats (n = 10), which were intraperitoneally injected with CAPE (10 microM kg(-1) day(-1)) after 3 days followed by STZ treatment. The liver was excised after 8 weeks of CAPE treatment, the levels of malondialdehyde (MDA) and the activities of SOD, CAT, and GSH-Px in the hepatic tissues of all groups were analyzed. In the untreated diabetic rats, MDA markedly increased in the hepatic tissue compared with the control rats (p < 0.0001). However, MDA levels were reduced to the control level by CAPE. The activities of SOD, CAT, and GSH-Px in the untreated diabetic group were higher than that in the control group (p < 0.0001). The activities of SOD and GSH-Px in the CAPE-treated diabetic group were higher than that in the control group (respectively, p < 0.0001, p < 0.035). There were no significant differences in the activity of CAT between the rats of CAPE-treated diabetic and control groups. Rats in the CAPE-treated diabetic group had reduced activities of SOD and CAT in comparison with the rats of untreated diabetic group (p < 0.0001). There were no significant differences in the activity of GSH-Px between the rats of untreated diabetic and CAPE-treated groups. It is likely that STZ-induced diabetes caused liver damage. In addition, LPO may be one of the molecular mechanisms involved in STZ-induced diabetic damage. CAPE can reduce LPO caused by STZ-induced diabetes.     

Effect of vitamin E and allylamine on the proliferation of cultured aortic smooth muscle cells from streptozotocin-induced diabetic rats.

To investigate the effect of vitamin E on the proliferation activity of vascular smooth muscle cells (SMCs) in diabetes mellitus, [3H]-thymidine incorporation was measured in cultured SMCs isolated from normal and streptozotocin-induced diabetic rats treated with or without vitamin E and/or allylamine. Untreated diabetic rats demonstrated significantly elevated concentrations of serum total cholesterol, triglycerides and malondialdehyde (MDA). Allylamine caused a further increase in serum MDA. Treatment with vitamin E decreased the serum concentrations of triglycerides and MDA in both allylamine-treated and -untreated diabetic rats. [3H]-Thymidine incorporation in cultured SMCs from diabetic rats was significantly increased compared with that from normal rats. SMCs from allylamine-treated diabetic rats showed an enhanced increase in thymidine incorporation compared with that from untreated diabetic rats. The increase in thymidine incorporation in SMCs from untreated and allylamine-treated diabetic rats was significantly reduced by the treatment with vitamin E. These observations suggest that vitamin E has a preventive effect on the proliferation of vascular SMCs in diabetes, and that this effect may be mediated through an enhancement of free radical scavenging.     

Myocardial changes after spironolactone in spontaneous hypertensive rats. A laser scanning confocal microscopy study

The present study aims to objectivate by laser scanning confocal microscopy, the cardiac structure of the spontaneously hypertensive rats (SHR) treated with different doses of spironolactone, either alone or in combination with an angiotensin converting enzyme inhibitor or with a calcium channel blocker. Thirty SHRs were divided into six groups and treated during 13 weeks as follows: control, spironolactone (5, 10 and 30 mg/kg/day), spironolactone + enalapril and spironolactone + verapamil. Spironolactone action on the SHR blood pressure (BP) was dose-dependent. The cardiac hypertrophy was affected by the treatment with spironolactone (high dose) or a combination of spironolactone and Enalapril. The myocardial structure was less affected by the spironolactone monotherapy (at all doses) showing hypertrophied cardiac myocytes, focal areas of the reactive fibrosis, inflammatory infiltrate. The treatment with spironolactone in combination with enalapril or verapamil prevented these alterations. In conclusion, the monotherapy with spironolactone had only a limited effect in the preservation of the myocardial structure and in the attenuation of the interstitial fibrosis in SHRs, even after high dose. This action on the myocardium is more efficient when the spironolactone (even in medium dose) was associated with enalapril or verapamil.     

A nonspecific phosphotyrosine phosphatase inhibitor, bis(maltolato)oxovanadium(IV), improves glucose tolerance and prevents diabetes in Zucker diabetic fatty rats

The molecular basis of insulin resistance, a major risk factor for development of Type II diabetes, involves defective insulin signaling. Insulin-mediated signal transduction is negatively regulated by the phosphotyrosine phosphatase, PTP1B, and numerous studies have demonstrated that organo-vanadium compounds, which are nonselective phosphotyrosine phosphatase inhibitors, have insulin-mimetic properties. However, whether or not vanadium compounds can prevent the transition from insulin resistance to overt diabetes is unknown. We compared the ability of bis(maltolato)oxovanadium(IV) (BMOV), an orally bioavailable organo-vanadium compound, and rosiglitazone maleate (RSG), a known insulin sensitizer, to prevent development of diabetes in Zucker diabetic fatty (ZDF) rats. Treatment began at 6 weeks of age when animals are insulin resistant and hyperinsulinemic, but not yet hyperglycemic, and ended at 12 weeks of age, which is 4 weeks after ZDF rats typically develop overt diabetes. BMOV-treated ZDF rats did not develop hyperglycemia, showed significant improvement in insulin sensitivity, and retained normal pancreatic islet morphology and endocrine cell distribution, similar to RSG-treated animals. BMOV and RSG treatment also prevented the hyper-phagia and polydipsia present in untreated ZDF rats; however, BMOV-treated ZDF rats gained much less weight than did RSG-treated animals. Circulating levels of adiponectin decreased in untreated ZDF rats compared to lean controls, but these levels remained normal in BMOV-treated ZDF rats. In contrast, in RSG-treated ZDF rats, plasma adiponectin levels were nearly 4-fold higher than in lean control rats, primarily as a result of a large increase in the amount of low-molecular weight forms of adiponectin in circulation. These data demonstrate that phosphatase inhibition offers a new approach to diabetes prevention, one that may have advantages over current approaches.     

Chronic Cobalt Treatment Decreases Hyperglycemia in Streptozotocin-Diabetic Rats

Diabetes is a metabolic disorder characterized by elevated blood glucose levels. Although conventional treatments such as insulin and other drugs reduce blood glucose, there is still a therapeutic need for effective orally administered drugs. Trace elements like vanadium and tungstate have been successfully demonstrated to reduce blood glucose in experimental diabetes with minimal chronic complications. We investigated the anti-hyperglycemic effects of cobalt in streptozotocin-diabetic rats. Normal and diabetic rats were provided with drinking water containing 3.5 mM cobalt chloride for three weeks followed by 4 mM for four weeks. Body weights and fluid consumption were monitored on a daily basis, while food intake was recorded twice every week. Prior to termination, an oral glucose tolerance test was performed on the animals. Diabetic rats lost significant body weight (357 ± 2 gm) compared to controls (482 ± 3 gm). Body weight was further reduced by cobalt treatment (290 ± 2 gm). Although it was difficult to establish a dosing regimen without weight loss, food and fluid consumption in cobalt-treated diabetic rats improved significantly compared to untreated diabetics. Plasma glucose levels were significantly reduced with reference to diabetic controls (29.3 ± 0.9 mM) by the fourth week to a lower but still hyperglycemic level (13.6 ± 3.4 mM). Cobalt-treated diabetic rats demonstrated an enhanced ability to clear a glucose load compared to untreated diabetics. Cobalt treatment neither affected the feeding and drinking patterns nor plasma glucose in normoglycemic animals although body weights decreased compared to untreated controls. We conclude that chronic cobalt treatment decreases plasma glucose levels in STZ-diabetic rats and improves tolerance to glucose.     

Sodium Tungstate on Some Biochemical Parameters of the Parotid Salivary Gland of Streptozotocin-Induced Diabetic Rats: A Short-Term Study

Several studies have shown the antidiabetic properties of sodium tungstate. In this study, we evaluated some biochemical parameters of the parotid salivary gland of streptozotocin-induced diabetic rats treated with sodium tungstate solution (2 mg/ml). The studied groups were: untreated control (UC), treated control (TC), untreated diabetic (UD), and treated diabetic (TD). After 2 and 6 weeks of treatment, parotid gland was removed and total protein and sialic acid (free and total) concentration and amylase and peroxidase activities were determined. Data were compared by variance analysis and Tukey test (p < 0.05). The sodium tungstate treatment modestly decreased the glycemia of streptozotocin-induced diabetic rats. At week 2 of the study, parotid gland of diabetic rats presented a reduction of total protein concentration (55%) and an increase of amylase (120%) and peroxidase (160%) activities, free (150%) and total (170%) sialic acid concentration. No alteration in the evaluated parameters at week 6 of the study was observed. Sodium tungstate presented no significant effect in parotid gland. Our results suggest that diabetes causes initial modification in biochemical composition of parotid. However, this gland showed a recovery capacity after 6 week of the experimental time. Sodium tungstate has no effect in peripheral tissues, such as salivary glands.