Sage Journals: Discover world-class research

Abstract

High blood pressure, obesity, abnormal lipid profile, which often coexist with diabetes, tend to be associated with preclinical cardiovascular abnormalities and may contribute to the association of diabetes with cardiovascular events. Many studies have proved that streptozotocin (STZ) is responsible for type-2-diabetes-induced cardiovascular complications. Long-term perindopril therapy in patients with hypertension and diabetes has been observed to correct carotid remodeling by reducing hypertrophy. We studied the effect of perindopril (1 mg/kg/d orally [po]) on cardiovascular complications in neonatal model of rats, which was induced by administering STZ (90 mg/kg, intraperitoneally [ip]), in 5-d-old wistar rats and cardiac hypertrophy induced by isoprenaline (ISO; 5 mg/kg, ip) for 10 d. Various biochemical, cardiac, and hemodynamic parameters were measured at the end of 8 weeks of treatment in diabetes model and 10 d in hypertrophy model. STZ produced hyperglycemia, hyperinsulinemia, dyslipidemia, hypertension, bradycardia, increased creatinine kinase (CK-MB), lactate dehydrogenase enzymes (LDH) and C-reactive protein (CRP) levels, cardiac hypertrophy, and oxidative stress. Chronic treatment with perindopril significantly prevented STZ-induced hyperglycemia and hyperinsulinemia and controlled dyslipdemia in diabetic rats. Further, perindopril produced a significant reduction in elevated levels of CRP, LDH, and CK. STZ-induced hypertension and bradycardia were also prevented by perindopril treatment. Perindopril also produced beneficial effect by preventing cardiac hypertrophy as evident from cardiac hypertrophy index and left ventricular hypertrophic index. Perindopril also prevented STZ-induced oxidative stress. Similar results were obtained in ISO-induced cardiac hypertrophic model, which confirms the beneficial role of perindopril in cardiac hypertrophy. In conclusion, our data from both studies suggest that perindopril produced beneficial effect on cardiac complications.

Keywords

Perindopril type-2 diabetes mellitus ISO cardiac hypertrophy

Introduction

Hypertension is very frequently associated with diabetic subjects, that is about 50% of diabetes patients, irrespective of whether they are type-1 or type-2, are hypertensive, and they contribute appreciably to cardiovascular morbidity and mortality by the acceleration of diabetic microvascular and macrovascular complications.¹ High blood pressure (BP), obesity, and abnormal lipid profile, which often coexist with diabetes, tend to be associated with preclinical cardiovascular abnormalities and may contribute to the association of diabetes with cardiovascular events.² Among patients with type-2 diabetes, coronary heart disease, myocardial infarction (MI), stroke and peripheral vascular disease are few important causes of mortality and morbidity.³ Individuals with hypertension and diabetes have accelerated progression of these complications, and management of hypertension in these patients reduces the risks and progression of diabetes-associated complications.⁴

Many studies have proved that streptozotocin (STZ) is responsible for type-2-diabetes-induced cardiovascular complications. STZ enters the β cell via a glucose transporter (GLUT2) and causes alkylation of DNA. DNA damage induces activation of poly–adenosine diphosphate (ADP) ribosylation, a process that is more important for the diabetogenicity of STZ than DNA damage itself. Poly-ADP ribosylation leads to depletion of cellular nicotinamide adenine dinucleotide (NAD+) and adenosine triphosphate (ATP). Enhanced ATP dephosphorylation after STZ treatment supplies a substrate for xanthine oxidase, resulting in the formation of superoxide radicals. Consequently, hydrogen peroxide and hydroxyl radicals are also generated. Furthermore, STZ liberates toxic amounts of nitric oxide that inhibits aconitase activity and participates in DNA damage. As a result of the STZ action, β cells undergo the destruction by necrosis.⁵

In hypertensive patients, increased angiotensin II (Ang II) is known to impair insulin intracellular signaling⁶ and pancreatic islet structure.⁷ It has been suggested that Ang II may have a deleterious effect on glucose metabolism by increasing reactive oxygen species (ROS) and inducing inflammation, decreasing blood flow in many tissue beds, and stimulating the sympathetic nervous system.⁸ Hypertension and impaired glucose tolerance leads to decrease in arterial compliance and structural and functional cardiac changes such as left ventricular hypertrophy (LVH) and left ventricular diastolic dysfunction.^9,10

The antihypertensive efficacy of perindopril, a potent angiotensin-converting enzyme inhibitor (ACE) inhibitor, is well documented. Approximately 65% of patients attained a diastolic BP of <90 mmHg after 4 or 6 weeks of treatment; after 6 months, this had increased to more than 94% of patients in two of the studies.^11,12 Long-term perindopril therapy in patients with hypertension and diabetes has been observed to correct carotid remodeling by reducing carotid artery wall hypertrophy and increasing internal diameter.¹³ During the Diabetes Artery Perindopril Hypertension Normalization Excess Stiffness (DAPHNET) study, in which 57 patients with hypertension and type-2 diabetes were randomized to perindopril 4 mg/d or 8 mg/d, a dose-dependent reduction in carotid artery stiffness was observed that was independent of BP reduction.¹⁴ In a double-blind, 1-year, parallel trial comparing perindopril to atenolol in untreated hypertensive subjects, perindopril increased small artery diameter and reduced the ratio of media thickness to lumen diameter, whereas atenolol had no effect.¹⁵ In experimental animal studies, perindopril demonstrated protective effects against aortic endothelial cells¹⁶ and endothelium-dependent relaxation.¹⁷ Perindopril also enhanced myocardial angiogenesis in a model of metabolic syndrome in rats¹⁸ and demonstrated an antitrophic effect in mesenteric arteries in diabetic rats.¹⁹ In rats with STZ-induced diabetes, perindopril attenuated mesenteric vascular hypertrophy and it was suggested that this antitrophic effect resulted from the inhibition of transforming growth factor (TGF) expression.²⁰ In SHR diabetic rats, perindopril produced an improvement in insulin sensitivity, prevented dyslipidemia and cardiac dysfunction associated with STZ-induced diabetes in Wistar and SHR rats.²¹ Despite these, direct study of perindopril in type-2 diabetic complications is not reported. Hence, in the present investigation, we have evaluated the effect of perindopril on cardiovascular complications associated with type-2 diabetes. Simultaneously we have analyzed the direct effect of perindopril on cardiac hypertrophy.

Materials and methods

The protocol of the experiment was approved by institutional animal ethics committee as per the guidance of committee for the purpose of control and supervision of experiments on animals (CPCSEA), Ministry of social justice and Empowerment, Government of India (Protocol No: IPS/PCOL/MPH10/003, Dated January 23, 2010). Animals used in the experiment were obtained from Zydus-Cadila Pharmaceuticals Ltd. All biochemical diagnostic kits were procured from Labcare Diagnostics Pvt. Ltd., India.

Isoprenaline-induced cardiac hypertrophy

Cardiac hypertrophy was induced by intraperitonial injection of isoprenaline (ISO; 5mg/kg/d) once daily for 10 d. Sprague Dawley rats of either sex were randomly divided into 4 groups: control (CON), control treated with perindopril (COP), disease control (DIC) and disease treated with perindopril (DIP). Perindopril was dissolved in distilled water and administered orally at a dose of 1 mg/kg/d with food and water ad libitum.

Neonatal type-2 diabetes

Five-day-old Wistar neonates of either sex were injected with 90 mg/kg intraperitoneal (ip) STZ (Sigma Ltd., USA) in 0.9% sodium chloride solution. CON neonates received equivalent amount of isotonic saline. The neonates were left with their own mothers and weaned at 4 weeks of age. Twelve weeks after the injection of STZ, the animals were checked for fasting glucose levels with the help of available diagnostic kit (Labcare Diagnostics Pvt. Ltd., India). The animals showing fasting glucose levels >170 mg/dl were considered as diabetic and divided into 4 groups: CON, COP, DIC and DIP. Perindopril was dissolved in distilled water and administered orally at a dose of 1 mg/kg/d with food and water ad libitum for 8 weeks.

Blood sample collection and serum analysis

At the end of 10th day and 8 weeks of treatment, blood was collected from the retro orbital plexuses under light ether anesthesia. Serum samples were analyzed for glucose (GLUCOSE-SLR enzymatic colorimetric test GOD-POD), cholesterol (CHOLESTEROL-SLR enzymatic colorimetric test), high-density lipoprotein–cholesterol (HDL-C; HDL CHOLESTEROL direct enzymatic colorimetric, Liquid), triglycerides (TRIGLYCERIDES enzymatic colorimetric test—GPO PAP), C-reactive protein (CRP; CRP-SRL enzymatic colorimetric test), lactate dehydrogenase (LDH; LDH-SLR kinetic test) and creatinine kinase (CK-MB; CK-MB-SLR measurement of CK-MB activity serum and plasma) spectrophotometrically (Shimadzu UV-1601, Japan). Serum insulin was estimated for diabetic model by radioimmunoassay technique using diagnostic kits obtained from Board of Radiation and Isotope Technologay, Mumbai, India, using gamma counter (Packard, USA).

Hemodynamic and cardiac parameters

Hemodynamic parameter viz. BP, heart rate, rate of pressure development and decay were recorded by invasive method of carotid artery cannulation (Iworx 118 System Inc., USA). After withdrawal of blood samples from retro-orbital plexus and recording hemodynamic parameters, animals were sacrificed, heart and femur were excised, and extraneous tissues were separated. Wet weight of the entire heart, left ventricle and length of femur was recorded to calculate the index of cardiac hypertrophy as wet heart weight to femur length ratio and the LVH index as left ventricular weight (LVW) to heart weight ratio. As described earlier, quantification of LV glutathione (GSH)²² and malondialdehyde (MDA) levels²³ was carried out.

Reduced GSH measurement

LV tissue was homogenized in 50 mmol/L Tris-HCI buffer (pH 7.4). The homogenate was centrifuged sequentially at 10,000g for 20 min, then at 100,000g for 60 min. To 0.5 ml of tissue supernatant, 1.5 ml of 0.2 mol/L Tris-HCI buffer (20 mmol/L EDTA, pH 8.2), 0.1 ml of 0.01 mol/L of 5,5’-dithiobis-(2-nitrobenzoic acid) and 7.9 ml of methanol were added. The mixture was incubated at 37°C with occasional shaking for 30 min. The mixture was then centrifuged at 3,000g for 15 min and the absorbance of the supernatant was determined at 412 nm.²²

MDA measurement

The supernatant, 0.5 mL, of homogenized LV tissue and 2.5 ml of 10% trichloracetic acid were added into the tubes and mixed. After incubating for 15 min at 90°C and cooling with cold water the mixture was centrifuged at 3000 rpm for 10 min. Two milliliters of supernatant were taken and 1 ml of 0.675% TBA was added. The tubes were sealed and incubated at 90°C for 15 min and then cooled to room temperature. The optical density was measured at 532 nm by a spectrophotometer.²³

Statistical analysis

Results are expressed as mean ± SEM. Statistical differences between the means of the various groups were evaluated using Student’s t test by SPSS 16 software. Data were considered statistically significant at p < 0.05.

Results

General features

Diabetic rats showed significant decrease in body weight at the end of eighth week as compared to the CON group. Chronic treatment with perindopril did not alter the body weight of CON rats. Diabetic rats also showed significant increase in food and water intake at the end of eighth week as compared to the CON group. Chronic treatment with perindopril produced a significant decrease in food and water intake (Table 1).

Table 1.

Effects of perindopril on glucose, insulin and cardiac parameters^a

Parameters	CON	COP	DIC	DIP
Glucose (mg/dl)	95.63 ± 2.4	91.56 ± 1.8	240.48 ± 8.4^b	151.24 ± 5.6^c
Insulin (μU/ml)	42.21 ± 2.7	42.0 ± 1.5	62.27 ± 4.27^b	52.04 ± 0.94^c
CK-MB (U/l)	19.40 ± 0.27	19.44 ± 0.67	53.25 ± 0.28^b	23.25 ± 0.07^c
LDH (U/l)	1238.6 ± 19.8	1197.7 ± 24	2290.06 ± 30.3^b	1543.7 ± 22.8^c
CRP (mg/l)	1.24 ± 0.02	1.57 ± 0.05	12.41 ± 0.2^b	5.338 ± 0.27^c

Each group contains 6 numbers of animals.

^a Values are expressed as Mean ± SEM.

^b Significantly different from control (P < 0.05).

^c Significantly different from diabetic control group (P < 0.05).

CON, control; COP, control treated with perindopril; DIC, diseased control; DIP, diseased treated with perindopril; CRP, C-reactive protein; LDH, lactate dehydrogenase; CK-MB, creatinine kinase.

Biochemical parameters

STZ-induced diabetic rats were found to exhibit significant hyperglycemia and hyperinsulinamia as compared to the CON rats. Chronic treatment with perindopril produced significant decrease in elevated serum glucose and insulin levels.

There was a significant increase in total cholesterol, very-low-density lipoprotein (VLDL), atherogenic index and triglycerides levels, and significant decrease in HDL-cholesterol levels in STZ diabetic rats as well as hypertrophic rats compared to the CON rats. Chronic treatment with perindopril showed a significant reduction in the levels of total cholesterol, VLDL, atherogenic index and TG, with a significant increase in HDL-C levels in both the models (Table 2).

Table 2.

Effect of perindopril on lipid profile^a

Parameters	DISEASE	CON	COP	DIC	DIP
Serum cholesterol (mg/dl)	Hypertrophic	41.35 ± 5.43	45.1 ± 5.12	86.23 ± 5^b	47.29 ± 3.0^c
Serum cholesterol (mg/dl)	Diabetic	51.29 ± 1.5	51.56 ± 1.7	77.83 ± 1.9^b	59.12 ± 1.2^c
HDL-cholesterol (mg/dl)	Hypertrophic	38.36 ± 1.11	36.60 ± 1.21	26.34 ± 0.81^b	34.98 ± 1.8^c
HDL-cholesterol (mg/dl)	Diabetic	39.66 ± 1.2	38.55 ± 1.2	16.92 ± 0.65^b	33.02 ± 1.4^c
Serum triglyceride (mg/dl)	Hypertrophic	129.19 ± 13.86	121.29 ± 13.9	276.96 ± 12.21^b	161.37 ± 9.1^c
Serum triglyceride (mg/dl)	Diabetic	135.6 ± 3.2	129.05 ± 3.3	280.8 ± 2.9^b	172.9 ± 3.5^c
VLDL levels (mg/dl)	Hypertrophic	25.83 ± 2.1	24.25 ± 1.8	55.39 ± 1.37^b	32.27 ± 1.93^c
VLDL levels (mg/dl)	Diabetic	27.12 ± 1.22	25.8 ± 2.2	56.16 ± 1.43^b	34.58 ± 2.34^c
Atherosclerosis index (Units)	Hypertrophic	0.53 ± .02	0.526 ± .03	1.02 ± .021^b	0.672 ± .032^c
Atherosclerosis index (Units)	Diabetic	0.539 ± .011	0.525 ± .032	1.21 ± .018^b	0.716 ± .037^c

Each group contains 6 numbers of animals.

^a Values are expressed as Mean ± SEM.

^b Significantly different from control (p < 0.05).

^c Significantly different from diabetic control group (p < 0.05).

CON, control; COP, control treated with perindopril; DIC, diseased control; DIP, diseased treated with perindopril; HDL, high-density lipoprotein; VLDL, very-low-density lipoprotein.

Cardiovascular parameters

Serum cardiac biomarkers

STZ-induced diabetes produced a significant increase in the levels of serum LDH, CK and CRP as compared to CON rats. Chronic treatment with perindopril significantly reduced the elevated levels of serum LDH, CK and CRP in diabetic rats (Table 1).

Cardiac parameters

The cardiac hypertrophy and left ventricular weight (LVW) to heart weight ratio which is a measure of LVH index was significantly high in hypertrophic and diabetic animals as compared to DIC animals (Figure 1A and B). Chronic treatment with perindopril significantly reduced cardiac hypertrophy index and LVH index of diabetic and hypertrophic rats. LVW to total body weight (LVW/TBW) and LVW to right ventricle weight (LWV/RVW) ratios were also found to be significantly higher in both hypertrophic and diabetic rats than that of the the CON rats. Chronic treatment with perindopril significantly reduced the LVW/TBW and LWV/RVW ratios of diabetic and hypertrophic rats (Table 3).

Figure 1.,B,

A, Effect of perindopril on the change in cardiac hypertrophy index. Each bar represents mean ± SEM of six experiments. *Significantly different from control. ^#Significantly different from DIC. B, Effect of perindopril on the change in left ventricular hypertrophy index. Each bar represents mean ± SEM of six experiments. *Significantly different from control. ^#Significantly different from DIC. CON, control animals; COP, control animals treated with perindopril (1 mg/kg/d); DIB, diseased animals; DIP, diseased animals treated with perindopril (1 mg/kg/d).

Table 3.

Effect of perindopril on hemodynamic and cardiac parameters^a

Parameters	DISEASE	CON	COP	DIC	DIP
Heart rate (bpm)	Hypertrophic	342 ± 7	345 ± 4	314 ± 3^b	334 ± 6^c
Heart rate (bpm)	Diabetic	333 ± 12	343 ± 3	245 ± 6^b	305 ± 4^c
Blood pressure (mmHg)	Hypertrophic	122 ± 1	116 ± 1	161 ± 4^b	132 ± 1^c
Blood pressure (mmHg)	Diabetic	122 ± 5	118 ± 4	165 ± 3^b	132 ± 4^c
LVW/RVW	Hypertrophic	3.4 ± 0.06	3.65 ± 0.05	7.9 ± 0.05^b	5.12 ± 0.04^c
LVW/RVW	Diabetic	3.8 + 0.02	3.72 + 0.03	8.1 ± 0.07	5.23 + 0.06
LVW/BW ratio	Hypertrophic	2.13 ± 0.015	2.14 ± 0.023	2.93 ± 0.09^b	2.82 ± 0.063^c
LVW/BW ratio	Diabetic	2.514 + 0.03	2.575 + 0.1	3.72 + 0.1^b	3.13 + 0.1^c

Each group contains 6 numbers of animals.

^a Values are expressed as mean ± SEM.

^b Significantly different from control (p < 0.05).

^c Significantly different from diabetic control group (p < 0.05).

CON, control; COP, control treated with perindopril; DIC, diseased control; DIP, diseased treated with perindopril; LVW, left ventricular weight; RVW, right ventricular weight; BW, body weight.

Oxidative stress

STZ-induced diabetes and ISO produced a significant increase in serum MDA levels as compared to CON rats (Figure 2A). Chronic treatment with perindopril significantly reduced the elevated serum MDA in diseased rats. STZ-induced diabetes and ISO also produced a significant decrease in serum GSH levels as compared to CON rats. Chronic treatment with perindopril significantly increased the reduced serum GSH in diseased rats (Figure 2B).

Figure 2.

A, Effect of perindopril on serum glutathione levels. Each bar represents mean ± SEM of six experiments. *Significantly different from control. ^#Significantly different from DIC. Figure .2. B, Effect of perindopril on lipid peroxidation. Each bar represents mean ± SEM of six experiments. *Significantly different from Control. ^#Significantly different from DIC. CON, control animals; COP, control animals treated with perindopril (1 mg/kg/d); DIB, diseased animals; DIP, diseased animals treated with perindopril (1 mg/kg/d).

Hemodynamic parameters

STZ-induced diabetic rats exhibited significantly increase in BP and significantly decrease in heart rate. Chronic treatment with perindopril in diabetic rats exhibited significant decrease in BP and significant increase in heart rate (Table 3). Rate of pressure development and decay was significantly decreased in diabetic control rats. Treatment with perindopril significantly increased the rate of pressure development and decay (Figure 3). Similar results were also found in ISO-induced cardiac hypertrophy model.

Figure 3.

Effect of perindopril on the rate of pressure development and decay. Each bar represents mean ± SEM of six experiments. *Significantly different from Control. ^#Significantly different from disease control. CON, control animals; COP, control animals treated with Perindopril (1 mg/kg/d); DIB, diseased animals; DIP, diseased animals treated with perindopril (1 mg/kg/d).

Discussion

Hypertensive diabetics have been reported to have more cardiovascular disease with 6–7 time higher mortality rate compared to normotensive diabetics ^24–26 In the present investigation, we found that STZ produced cardinal signs and characteristics of diabetes, viz. loss of body weight, polyphagia, polyuria and polydipsia. Chronic treatment with perindopril significantly decreased polydipsia and polyphagia.

Insulin resistance and hyperinsulinemia have been postulated to play a significant role in the etiology of hypertension.²⁷ Insulin resistance and hyperinsulinemia appear to increase the risks of diabetes, dyslipidemia and hypertension,²⁸ and are implicated in atherogenesis, either via the increase in proinflammatory cytokines implicated in insulin resistance or via the direct proliferative effects of insulin itself on arterial smooth muscle cells.²⁹ In the present investigation, STZ-induced diabetic rats exhibited significantly increased glucose and insulin levels, and chronic treatment with perindopril in diabetic rats significantly decreased the insulin and glucose levels. Ang II is responsible for blocking the differentiation of adipocytes, leading to accumulation of lipids in muscle, liver and pancreas and, in turn, reducing insulin sensitivity.³⁰ Thus, perindopril, being an ACE inhibitor, might prevent ANG-II-induced phosphorylation of insulin, thereby controlling glucose and insulin levels. In a genetically obese animal model of type-2 diabetes, blockade of the renin angiotensin aldosterone system (RAAS) with perindopril attenuated changes in islet cell structure and insulin secretion.³¹ Fogari et al.³² found that perindopril, but not the angiotensin receptor blocker losartan, improved insulin sensitivity and reduced fibrinogen levels in overweight patients with hypertension. Thus, our reports are in consistence with several clinical reports suggesting beneficial role of perindopril in glycemic control.

Hypertriglyceridemia and low HDL-cholesterol levels are common in patients with type-2 diabetes or insulin resistance.³³ In insulin-resistant state, endothelial cell lipoprotein lipase activity is decreased, as is the conversion of cholesterol ester–enriched VLDL to LDL, which is injurious to endothelial cells after receptor-mediated uptake³⁴ and contribute to endothelial dysfunction.³⁵ In the present investigation, we have also found that serum cholesterol and triglyceride levels were significantly increased in hypertrophic and STZ-induced diabetic rats and treatment with perindopril significantly reduced the elevated cholesterol and triglyceride levels. Various studies suggest that renin–angiotensin system is responsible for hyperlipidemia and atherosclerotic disease.^36,37 Endothelial dysfunction occurs when there is an upset in the balance of Ang II and growth factors. Ang II facilitates oxidation of LDL and its uptake by scavenger receptor on monocytes/macrophages and upregulates lipooxygenase as a basis of enhanced endothelial uptake of oxidized LDL.³⁸ Thus, perindropril, being an ACE inhibitor, might inhibit the Ang II-mediated oxidation of LDL. Fennessy et al.³⁹ have reported that administration of perindopril during the 6 weeks of cholesterol feeding reduced lipid accumulation in developing atheromatous plaques of the carotid artery and in fatty streaks of the aorta in rabbit model of cholesterol-induced atherosclerosis. Thus, our reports are in consistence with the other studies that perindopril prevents dyslipidemia, which in turn suggests its beneficial role in endothelial dysfunction and atherosclerotic diseases.

CRP, an acute phase reactant, produced mainly by liver and selectively binds to LDL, is found within atheromatous plaques and enhances complement activation.⁴⁰ CRP levels are elevated in type-2 diabetes.⁴¹ In a similar study, Goyal and coworkers found that STZ-administered group possessed high level of CRP, a important cardiac biomarker.⁴² In present study, we found a significant rise in CRP level in STZ-induced diabetic rats as compared to normal rats. Treatment with perindopril significantly decreased CRP levels in diabetic rats. Ang II has significant proinflammatory actions in the vascular wall, inducing the production of ROS, inflammatory cytokines, and adhesion molecules, elevating the CRP levels. Enhanced production of angiotensinogen, in turn, supplies more substrate to the activated vascular ras angiotensin system (RAS), wherein the locally produced Ang II synergizes with oxidized lipid to perpetuate atherosclerotic vascular inflammation and increases CRP levels.⁴³ Perindopril, being an ACE-inhibitor, inhibits Ang II-induced proinflammation and thereby decreases the CRP levels. This suggests that perindopril may serve as an important inhibitor of inflammatory cytokines in the myocardium.

The CK-MB is part of total CK and more specific for cardiac muscle than other striated muscle. CK-MB and LDH levels are reported to be increased in animal model of diabetes induced by STZ.⁴⁴ In our study, we found significant increase in LDH and CK levels in STZ-induced diabetic rats as compared to normal rats. Treatment with perindopril significantly reduced LDH and CK levels and further substantiates its beneficial effect by reducing the cardiovascular risk in diabetes mellitus. The activities of LDH and CK as well as lactate concentrations in the coronary venous effluent were reduced by 39.3%, 50%, and 60.6%, respectively, after chronic treatment with perindopril in stroke-prone SHR hypertensive rats, indicating the beneficial effect in cardiac damage.⁴⁵

Diabetes is associated with the activation of the RAAS and systemic nervous system (SNS), leading to compensatory changes in the size and shape of the cardiac chambers through cellular hypertrophy or remodeling. It has been reported that STZ induced cardiac hypertrophy, aggravating the cardiovascular complications.⁴⁶ A total of 72% of the diabetic patients are found to have LVH, whereas only 32% of the nondiabetic patients have LVH. LVH does not usually occur in diabetes unless hypertension coexists. Consequently, left ventricular mass index was greater in patients with hypertension and diabetes mellitus than in those without diabetes mellitus.⁴⁷ Also the ISO injection causes hypertrophic effect on heart via TGF-β⁴⁸ and stimulation of protein synthesis.⁴⁹ In the present study, cardiac hypertrophy index was found to be increased in both hypertrophic and STZ-induced diabetic hearts. Heart weight to body weight ratio and LVW/RVW ratio were also found to be higher in diseased hearts than control hearts in both models. Treatment with perindopril significantly decreased cardiac hypertrophy index, LVH index, heart weight to body weight ratio and LVW/RVW ratio in diseased rats. Ang II is reported to cause hypertrophy of cardiac myocytes and hyperplasia of cardiac nonmyocytes.⁵⁰ In STZ-induced diabetic rats with type-1 diabetes, perindopril attenuated mesenteric vascular hypertrophy, and it was suggested that this antitrophic effect resulted from inhibition of TGF-β expression.⁵¹ Thus, perindopril might inhibit the expression of hypertrophic genes and thus provide beneficial role in cardiac dysfunction.

STZ causes increased production of ROS due to the autooxidation of monosaccharides, leading to the production of superoxide and hydroxyl radicals.⁵² Reduced antioxidant capacity has been reported in cardiac tissue from diabetic animals.⁵³ In present study, we found a significant increase in pro-oxidant (MDA) levels and decrease in antioxidant (GSH) levels in STZ-induced diabetic and hypertrophic rats. Chronic treatment with perindopril showed a significant increase in antioxidant (GSH) and significant decrease in MDA levels in STZ-induced diabetic rats. Both experimental and clinical studies have provided functional evidence for stimulation of the renin–angiotensin system and simultaneously for activation of an NAD(P)H oxidase in the vascular wall. Activation of NAD(P)H oxidase and increased superoxide within the vascular wall have important implications for both the progression of atherosclerosis and the development of clinical event.^47,54 The ACE inhibitors reduce Ang II levels and increase bradykinin levels, suggesting that perindopril have important implications for vascular oxidative stress.^48,55 It has been established that perindopril reduced oxidative stress and increases the plasma antioxidant capacity in a prospective, randomized, parallel group study assessed in hypertensive patients.⁵⁵ Thus, perindopril may be beneficial in oxidative stress and lipid peroxidation during MI.

Increase in BP after treatment with STZ and ISO has been reported by several studies.⁵⁶ Hypertension is very frequently associated with diabetic subjects,² that is about 50% of patients with diabetes, irrespective of whether they are type-1 or type-2, are hypertensive. Several reasons are postulated for the development of hypertension in diabetes. One of the reasons for hypertension is loss of the autoregulatory (RAAS and SNS) response, which can amplify the damaging effects of systemic BP on small blood vessels.⁵⁷ Further, potentiation of bradykinin, a powerful vasodilator that enhances insulin signaling⁵⁸ and translocation of the glucose transporter in skeletal muscle, may be responsible for some of the hemodynamic and nonhemodynamic effects of ACE inhibition.^59,60 Of the ACE inhibitors, perindopril has the capacity to increase the ratio of bradykinin and Ang II.⁶¹ In the present study of chronic treatment with ACE inhibitors, perindopril significantly decreased the BP in treated rats compared to diseased rats in both models. Oral administration of perindopril has been demonstrated to be an effective BP-lowering agent in adult patients with mild-to-moderate hypertension in numerous randomized clinical trials.⁶² Bradycardia has been frequently observed in STZ diabetic rats⁶³ as well as in ISO-induced rats.⁶⁴ The development of STZ-induced bradycardia has been attributed to a downregulation of myocardial beta adrenoceptors, hypothyroidism,⁶⁵ depression of myocardial calcium metabolism,⁶⁶ reduced uptake of calcium by the sarcoplasmic reticulum and concomitantly depression of SR-calcium ATPase activity.⁶⁷ It is well established that Ang II exerts an inhibitory influence on baroreceptor reflex control of heart rate after either intravenous administration in several species.⁶⁸ Perindopril is an ACE inhibitor and it is possible that it may attenuate the Ang II-mediated inhibition of baroreceptor reflex. This may be the possible mechanism involved in the increased heart rate by perindopril treatment in hypertrophic rats in both the models.

In the present investigation, STZ and ISO injection decreased the rate of pressure development and decay, which is the direct indicator of myocardial contractility dysfunctioning and cardiac fibrosis. In present study, chronic treatment with perindopril significantly increased the rate of pressure development and decay. The data presented in a very interesting study clearly demonstrate that overexpression of the fast-twitch skeletal muscle SR Ca-ATPase and increase in the rate of pressure development and decay (+dp/dt and −dp/dt) in the mammalian heart results in significantly elevated Ca transport function and cardiac contractile performance. This study suggests that the SERCA pump level is a critical determinant of myocardial contractility.⁶⁹ STZ-induced diabetes in animal models causes changes in myocardial cellular calcium transport and contractile proteins, which result in subclinical myocardial contractility dysfunction.^70,71 Thus, perindopril appears to be beneficial in cardiac dysfunctioning.

From the above investigation we can concluded that perindopril prevents not only the STZ-induced metabolic abnormalities but also cardiovascular complications. Perindopril is also found to be beneficial in hypertrophy, which can make it an optimistic treatment in type-2 diabetes as well as in cardiac hypertrophy-induced cardiovascular complications.

Footnotes

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

References

Anderson

Hoffman

Balon

Mark

. Hyperinsulinemia produces both sympathetic neural activation and vasodilation in normal humans. J Clin Invest 1991; 87: 2246–2252.

The Hypertension in Diabetes Stydy Group. Hypertension in Diabetes Study (HDS): 1. Prevalence of hypertension in newly presenting type 2 diabetic patients and the association with risk factors for cardiovascular and diabetic complications. J Hypertens 1993; 11: 309–317.

Markku Laakso. Hyperglycemia and cardiovascular disease in type 2 diabetes. Diabetes 1999; 48: 197–184.

Helmy

. ADVANCE in management of vascular complications of diabetes. Lancet 2007; 370: 829–840.

Portha

Levacher

Picon

Rosselin

. Diabetogenic effect of STZ in the rat during the perinatal period. Diabetes 1974; 23: 889–895.

Hsueh

Law

. Cardiovascular risk continuum: implications of insulin resistance and diabetes. Am J Med 1998; 105: 4–14.

Tikellis

Wookey

Candido

Andrikopoulos

Thomas

Cooper

. Improved islet morphology after blockade of the renin-angiotensin system in the ZDF rat. Diabetes 2004; 53: 989–997.

Ingelfinger

Solomon

. Angiotensin- converting-enzyme inhibitors for impaired glucose tolerance – is there still hope? N Engl J Med 2006; 355: 1608–1610.

Salmasi

Dancy

. Glucose intolerance: the hidden danger in hypertensives! Int Angiol 2005; 24: 207–214.

10.

Burnier

Zanchi

. Blockade of the renin-angiotensin-aldosterone system: a key therapeutic strategy to reduce renal and cardiovascular events in patients with diabetes. J Hypertens 2006; 24: 11–25.

11.

Fressinaud

Berrut

Gallois

. Antihypertensive activity and acceptability based upon clinical and laboratory parameters of perindopril: chief results in 23,460 mild to moderate hypertension patients treated for 6 months in general practice (French). Ann Cardiol Angéiol 1993; 42: 51–59.

12.

Suraniti

Berrut

Marre

Fressinaud

. Antihypertensive efficacy and acceptability of perindopril in elderly hypertensive patients. Am J Cardiol 1993; 71: 28E–31E.

13.

Girerd

Giannattasio

Moulin

. Regression of radial artery wall hypertrophy and improvement of carotid artery compliance after long term antihypertensive treatment: the PERICLES study. J Am Coll Cardiol 1998; 31: 1064–1073.

14.

Tropeano

Boutouyrie

Pannier

. Brachial pressure-independent reduction in carotid stiffness after long term angiotensin converting enzyme inhibition in diabetic hypertensives. Hypertension 2006; 48: 1–7.

15.

Thybo

Stephens

Cooper

Aalkjaer

. Efficacy of antihypertensive treatment on small arteries of patients with previously untreated essential hypertension. Hypertension 1995; 25: 474–481.

16.

Zhou

Zhong

. Changes of ultrastructure and function of the aortic endothelium in streptozocin-diabetic rats and effect of perindopril. Bull Hunan Med Univ 2001; 26: 41–44.

17.

Liu

Chen

You

Zhou

. Protective effect of perindopril on dysfunction of endothelium- dependent relaxation in diabetic rats. Bull Hunan Med Univ 2000; 25: 122–124.

18.

Toblli

Cao

DeRosa

Di Gennaro

. Angiotensin-converting enzyme inhibition and angiogenesis in myocardium of obese Zucker rats. Am J Hypertens 2004; 17: 172–180.

19.

Rumble

Komers

Cooper

. Kinins or nitric oxide, or both, are involved in the antitrophic effects of angiotensin converting enzyme inhibitors on diabetes-associated mesenteric vascular hypertrophy in the rat. J Hypertens 1996; 14: 601–607.

20.

Cooper

Cao

Rumble

Jandeleit

. Attenuation of diabetes-associated mesenteric vascular hypertrophy with perindopril: morphological and molecular biological studies. Metabolism 1998; 47: 24–27.

21.

Goyal

Lakkad

Bangaru

Rao

. Effects of chronic treatment with enalapril on STZ-induced diabetic rats. Pharmacol Res Commun 1997; 9: 133–139.

22.

Moron

Depierre

Mannervik

. Levels of glutathione, glutathione reductase and glutathione S-transferase activities in rat lung and liver. Biochim Biophys Acta 1979; 528: 67–78.

23.

Slater

Sawyer

. The stimulatory effects of carbon tetrachloride and other halogenoalkanes on peroxidative reactions in rat liver fractions in vitro. General features of the systems used. Biochem J 1971; 123: 8.

24.

Siragy

. ADVANCE in management of vascular complications of diabetes. Lancet 2007; 370: 829–840.

25.

UK Prospective Diabetes Study (UKPDS) Group. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). Lancet 1999; 354: 602.

26.

Cowie

Harris

. Diabetes and decline in heart disease mortality in U.S. adults. J Am Med Assoc 1999; 281: 1291–1297.

27.

Reaven

Chang

. Relationship between BP, plasma insulin and triglyceride concentration, and insulin action in spontaneously hypertensive rats and Wistar Kyoto rats. Am J Hypertension 1991; 4: 34–38.

28.

Fogari

Zoppi

Lazzari

Preti

. ACE inhibition but not Ang II antagonism reduces plasma fibrinogen and insulin resistance in overweight hypertensive patients. J Cardiovas Pharmacol 1998; 32: 616–620.

29.

Sjöholm

Nyström

. Endothelial inflammation in insulin resistance. Lancet 2005; 365: 610–612.

30.

Sharma

Janke

Gorzelniak

Engeli

. Angiotensin blockade prevents type 2 diabetes by formation of fat cells. Hypertension 2002; 40: 609–611.

31.

ALLHAT Collaborative Research Group. Major outcomes in high-risk hypertensive patients randomized to angiotensin-converting enzyme inhibitor or calcium channel blocker vs diuretic. JAMA 2002; 288: 2981–2997.

32.

Taskinen

. Quantitative and qualitative lipoprotein abnormalities in diabetes mellitus. Diabetes 1992; 41: 12–17.

33.

Tesfamariam

Brown

Cohen

. Elevated glucose impairs endothelium-dependent relaxation by activating protein kinase C. J Clin Invest 1991; 87: 1643–1648.

34.

Hsueh

Anderson

. Hypertension, the endothelial cell, and the vascular complications of diabetes mellitus. Hypertension 1992; 20: 253–263.

35.

Laragh

. Review course. Laragh's lessons in pathophysiology and clinical pearls for treating hypertension. Am J Hypertens 2001; 41: 84–89.

36.

Dzau

. Tissue angiotensin and pathobiology of vascular disease: a unifying hypothesis. Hypertension 2001; 37: 1047–1052.

37.

Zhang

Philips

Sawamura

Mehta

. Upregulation of endothelial receptor for oxidized low-density lipoprotein (LOX-1) in cultured human coronary artery endothelial cells by Ang II type 1 receptor activation. Circ Res 1999; 84: 1043–1049.

38.

Fennessy

Campbell

Mendelsohn

Campbell

. Angiotensin-converting enzyme inhibitors and atherosclerosis: relevance of animal models to human disease. Clin Exp Pharmacol Physiol 2007; 23: 30–32.

39.

Bhakdi

Toprzewski

Klouche

Hemmes

. Complement and atherogenesis. Binding of CRP to degraded, nonoxidised LDL enhance complement activation. Arterioscler Thromb Vasc Biol 1999; 19: 2348–2354.

40.

Pradhan

Manson

Rifai

Buring

Ridker

. Creactive protein, interleukin-6, and risk of developing type 2 diabetes mellitus. JAMA 2001; 286: 327–334.

41.

Goyal

Parmar

Goyal

Mehta

. Beneficial role of telmisartan on cardiovascular complications associated with STZ-induced type-2 diabetic rats. Pharmacol Rep 2011; 63(4): 956–966.

42.

Brasier

Recinos

Eledrisi

. Vascular inflammation and the renin angiotensin system. Arterioscler Thromb Vasc Biol 2002; 22: 1257–1266.

43.

Goyal

Mesariya

Goyal

Mehta

. Effect of telmisartan on cardiovascular complications associated with STZ- induced diabetic rats. Mol Cell Bioch 2008; 314(1-2): 123–131.

44.

Gohlke

Kuwer

Bartenbach

Schnell

Unger

. Effect of low-dose treatment with perindopril on cardiac function in stroke-prone spontaneously hypertensive rats: role of bradykinin. J Cardiovasc Pharmacol 1994; 24: 462–469.

45.

Goyal

Patel

Bhadada

. Comparative evaluation of spironolactone, atenolol, metoprolol, ramipril and perindopril on diabetes induced cardiovascular complications in type 1 diabetes in rats. Int J Diabetes Metab 2011; 19(1): 11–18.

46.

Grossman

Shemesh

Shamiss

Thaler

Carroll

Rosenthal

. Left ventricular mass in diabetes-hypertension. Arch Intern Med 1992; 152: 1001–1004.

47.

Guzik

West

Black

Vascular superoxide production by NAD(P)H oxidase: association with endothelial dysfunction and clinical risk factors. Circ Res 2000; 86: E85–E90.

48.

Laursen

Rajagopalan

Galis

. Role of superoxide in Ang II–induced but not catecholamine- induced hypertension. Circulation 1997; 95: 588–593.

49.

Hefti

Harder

Eppenberger

Schaub

. Signaling pathways in cardiac myocyte hypertrophy. J Mol Cell Cardiol 1997; 9: 2873–2892.

50.

Cooper

Cao

Rumble

Jandeleit

Allen

Gilbert

. Attenuation of diabetes-associated mesenteric vascular hypertrophy with perindopril: morphological and molecular biological studies. Metabolism 1998; 47: 24–27.

51.

Wolff

Dean

. Glucose autoxidation and protein modification. Biochem J 1987; 245:243–250.

52.

Low

Nickander

. Oxygen free radical effects in sciatic nerve in experimental diabetes. Diabetes 1991; 40: 873–877.

53.

Hermenegildo

Raya

Roma

Romero

. Decreased glutathione peroxidase activity m sciatic nerve of alloxan-induced diabetic and its correlation with blood glucose levels. Neurochem Res 1993; 18: 893–896.

54.

Warnholtz

Nickenig

Schulz

. Increased NADH oxidase–mediated superoxide production in the early stages of atherosclerosis: evidence for involvement of the renin-angiotensin system. Circulation 1999; 99: 2027–2033.

55.

Ghiadoni

Magagna

Versari

Different effect of antihypertensive drugs on conduit artery endothelial function. Hypertension 2003; 41: 1281–1286.

56.

Funakawa

Okahara

Imanishi

Komori

Yamamoto

Tochino

. Renin angiotensin system and prostacyclin biosynthesis in STZ diabetic rats. Eur J Pharmacol 1983; 94: 27–33.

57.

Tooke

Goh

. Endothelinopathy precedes type 2 diabetes. Diabetes Care 1998; 12: 2047–2049.

58.

Miyata

Taguchi

Uehara

Bradykinin potentiates insulinstimulated glucose uptake and enhances insulin signal through the bradykinin B2 receptor in dog skeletal muscle and rat L6 myoblasts. Eur J Endocrinol 1998; 138: 344–352.

59.

Dietze

Wcklmayr

Rett

Jacob

Henriksen

. Potential role of bradykinin in forearm muscle metabolism in humans. Diabetes 1996; 45(suppl 1): S110–S114.

60.

Rett

Wicklmayr

Dietze

Häring

. Insulin-induced glucose transporter (GLUT1 and GLUT4) translocation in cardiac muscle tissue is mimicked by bradykinin. Diabetes 1996; 45: S66–S69.

61.

Campbell

Kladis

Duncan

. Effects of converting enzyme inhibitors on angiotensin and bradykinin peptides. Hypertension 1994; 23: 439–449.

62.

PROGRESS Collaborative Group. Effects of a perindopril-based BP lowering regimen on cardiac outcomes among patients with cerebrovascular disease. Eur Heart J 2003; 24: 475–484.

63.

Goyal

Rodrigues

McNeill

. Effects of tri-iodo-lthyronine on cardiac responses to adrenergic agonists in STZ-induced diabetic rats. Gen Pharmacol 1987; 18: 357–362.

64.

Bhargava

Kasabdji

Thompson

. Subsensitivity to noradrenaline and ISO in rabbits acutely pre-treated with morphine. Gen Pharmacol 1977; 8: 257–261.

65.

Baba

Ishikawa

. Recent advances in pharmacological management of hypertension in diabetic patients with nephropathy. Effects of antihypertensive drugs on kidney function and insulin sensitivity. Drugs 1992; 43: 464–489.

66.

Nordin

Gilat

. Delayed after depolarisation and activity in ventricular muscle from rats in STZ induced diabetes. Circ Res 1990; 57: 28–34.

67.

Denton

Randle

. Concentration of triglycerides and phospholipids in rat heart and gastronemics muscle effect of alloxan diabetes and perfusion. Bio Chem J 1967; 104: 416–422.

68.

Oliveira

Santos

Khosla

Campagnole-Santos

. Changes in the baroreflex control of heart rate produced by central infusion of selective angiotensin antagonists in hypertensive rats. Hypertension 1996; 27: 1284–1290.

69.

Loukianov

Grupp

Enhanced myocardial contractility and increased Ca21 transport function in transgenic hearts expressing the fast-twitch skeletal muscle sarcoplasmic reticulum Ca21-ATPase. Circ Res 1998; 83; 889–897.

70.

Ganguly

Pierce

Dhalla

. Defective sarcoplasmic reticular calcium transport in diabetic cardiomyopathy. Am J Physiol 1983; 244: E528–E535.

71.

Giacomelli

Wiener

. Primary myocardial disease in the diabetic mouse: an ultrastructural study. Lab Invest 1979; 40: 460–473.

Perindopril protects against streptozotocin-induced hyperglycemic myocardial damage/alterations

Abstract

Keywords

Introduction

Materials and methods

Isoprenaline-induced cardiac hypertrophy

Neonatal type-2 diabetes

Blood sample collection and serum analysis

Hemodynamic and cardiac parameters

Reduced GSH measurement

MDA measurement

Statistical analysis

Results

General features

Biochemical parameters

Cardiovascular parameters

Serum cardiac biomarkers

Cardiac parameters

Oxidative stress

Hemodynamic parameters

Discussion

Footnotes

Funding

References