Angiotensin-converting enzyme inhibition reduces lipid deposits in myocardium and improves left ventricular function of obese zucker rats

Inflammatory atherosclerotic plaque identification by SPECT/CT imaging of LFA-1 using [111In] In-DANBIRT in a novel dyslipidemic rat model

INTRODUCTION

Atherosclerosis is prevalent globally, closely associated with dyslipidemia and other metabolic dysfunction. Early diagnosis of atherosclerosis is challenging due to limited diagnostic capabilities that need to be expanded with animal models with enhanced vascular biology like rats. Our previous research showed [111In] In-DANBIRT has potential as a diagnostic tool for detecting atherosclerosis in mice. The primary aim of the present study is to evaluate [111In] In-DANBIRT in a novel atherosclerotic rat with early- and late-stage atherosclerosis and metabolic disease.

METHODS

We characterized metabolic and body composition differences in these novel dyslipidemic rats under different diets using serum chemistry and dual-energy X-ray absorptiometry (DEXA) scan, respectively. We performed 1-h post-injection in vivo molecular imaging of ApoE knockout, lean Zucker (LZ) male rats at baseline and followed them into 10 weeks of either normal or high-fat/cholesterol diet implementation (22 weeks of age).

RESULTS

We identified significant differences in body composition and metabolic changes in ApoE knockout rats compared to ApoE wildtype rats. Our findings indicate an increased uptake of [111In] In-DANBIRT in ApoE knockout, lean Zucker (LZ) rats, particularly in the descending aorta, a location where early-stage atherosclerosis is commonly found. Our findings, however, also revealed that the ApoE knockout, Zucker diabetic fatty (ZDF) model has high mortality rate, which may be attributed to alterations of critical enzymes involved in regulating metabolism and liver function.

CONCLUSION

Our results are highly encouraging as they demonstrated the potential of [111In] In-DANBIRT to detect early-stage atherosclerosis in rats that might otherwise go unnoticed by other methods, showcasing the high sensitivity of [111In] In-DANBIRT. Our future studies will aim to establish a viable T2D atherosclerosis model in rats with more advanced stages of the disease to further demonstrate the reliability of [111In] In-DANBIRT as a diagnostic tool for patients in all stages of atherosclerosis.

Effects of aerobic exercise training on cardiac renin-angiotensin system in an obese Zucker rat strain

OBJECTIVE

Obesity and renin angiotensin system (RAS) hyperactivity are profoundly involved in cardiovascular diseases, however aerobic exercise training (EXT) can prevent obesity and cardiac RAS activation. The study hypothesis was to investigate whether obesity and its association with EXT alter the systemic and cardiac RAS components in an obese Zucker rat strain.

METHODS

THE RATS WERE DIVIDED INTO THE FOLLOWING GROUPS: Lean Zucker rats (LZR); lean Zucker rats plus EXT (LZR+EXT); obese Zucker rats (OZR) and obese Zucker rats plus EXT (OZR+EXT). EXT consisted of 10 weeks of 60-min swimming sessions, 5 days/week. At the end of the training protocol heart rate (HR), systolic blood pressure (SBP), cardiac hypertrophy (CH) and function, local and systemic components of RAS were evaluated. Also, systemic glucose, triglycerides, total cholesterol and its LDL and HDL fractions were measured.

RESULTS

The resting HR decreased (∼12%) for both LZR+EXT and OZR+EXT. However, only the LZR+EXT reached significance (p<0.05), while a tendency was found for OZR versus OZR+EXT (p = 0.07). In addition, exercise reduced (57%) triglycerides and (61%) LDL in the OZR+EXT. The systemic angiotensin I-converting enzyme (ACE) activity did not differ regardless of obesity and EXT, however, the OZR and OZR+EXT showed (66%) and (42%), respectively, less angiotensin II (Ang II) plasma concentration when compared with LZR. Furthermore, the results showed that EXT in the OZR prevented increase in CH, cardiac ACE activity, Ang II and AT2 receptor caused by obesity. In addition, exercise augmented cardiac ACE2 in both training groups.

CONCLUSION

Despite the unchanged ACE and lower systemic Ang II levels in obesity, the cardiac RAS was increased in OZR and EXT in obese Zucker rats reduced some of the cardiac RAS components and prevented obesity-related CH. These results show that EXT prevented the heart RAS hyperactivity and cardiac maladaptive morphological alterations in obese Zucker rats.

Improvement of left ventricular diastolic function induced by β-blockade: a comparison between nebivolol and metoprolol

OBJECTIVES

Enhanced adrenergic drive is involved in the development of left ventricular (LV) diastolic dysfunction observed in metabolic syndrome (MS). Thus, β-blockers might improve LV dysfunction observed in MS, but whether this occurs is unknown.

METHODS

We assessed in Zucker fa/fa rats the effects of short- (5 days) and long-term (90 days) metoprolol ('pure' β-blockade; 80 mg/kg/day) or nebivolol (β-blocker with vasodilating properties; 5mg/kg/day) treatment on LV hemodynamics and remodeling, as well as the long-term effects on coronary and peripheral endothelial dysfunction.

RESULTS

At identical degree of β(1)-receptor blockade, metoprolol and nebivolol decreased heart rate to the same extent and preserved cardiac output via increased stroke volume. None of the β-blockers, either after long- or short-term administration, modified LV end-systolic pressure-volume relation. Both β-blockers reduced, after long-term administration, LV end-diastolic pressure, Tau and end-diastolic pressure-volume relation, and this was associated with reduced LV collagen density, but not heart weight. Similar hemodynamic effects were also observed after short-term nebivolol, but not short-term metoprolol. These short-term effects of nebivolol were abolished by NO synthase inhibition. At the vascular level, nebivolol, and to a lesser extend metoprolol, improved NO dependent coronary vasorelaxation, which was abolished by NO synthase inhibition.

CONCLUSIONS

In a model of MS, the β-blockers metoprolol and nebivolol improve to the same extent LV hemodynamics, remodeling and diastolic function, but nebivolol prevent more markedly endothelium dependent vasorelaxation involving a more marked enhancement of NO bio-availability.

Antifibrotic effects of pioglitazone on the kidney in a rat model of type 2 diabetes mellitus

BACKGROUND

Recent evidence suggests that treatment of type 2 diabetes with thiazolidinediones [peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonists], ameliorates glomerulosclerosis and tubulointerstitial fibrosis in the rat kidney. In the current work, we have investigated whether these drugs, and specifically pioglitazone (PGT), act by preventing fibrosis and kidney dysfunction mainly through antioxidant and anti-inflammatory effects, independently of glycaemic control.

METHODS

Male 2- to 3-month-old obese Zucker fa/fa (OZR) and ZDF fa/fa rats (ZDFR), and their control the lean Zucker rat (LZR), were used. Diabetic rats were given either a low dose (0.6 mg/kg/day) or a high dose (12 mg/ kg/day) of PGT in the chow for 2 or 4-5 months. Glycaemia, blood pressure, creatinine clearance and proteinuria were determined, and the underlying histopathology was defined with markers of fibrosis, glomerular damage, oxidative stress and inflammation by immunohistochemistry/ quantitative image analysis in tissue sections, and western blots and ad hoc assays in fresh tissue.

RESULTS

PGT at low doses given for 4-5 months considerably reduced blood pressure, proteinuria and creatinine clearance. This was associated with amelioration of renal tissue damage and fibrosis, evidenced by the glomerulosclerosis, tubulointerstitial fibrosis, tubular atrophy and podocyte injury indexes, and of oxidative stress and inflammation, as shown by the decrease in the respective markers, although glycaemia remained high and obesity was not affected.

CONCLUSIONS

These results indicate that low doses of PGT ameliorate renal fibrosis and preserve renal function in this animal model of metabolic syndrome, independently of glycaemic control or effects on body weight.

ACE inhibition and AT1 receptor blockade prevent fatty liver and fibrosis in obese Zucker rats

OBJECTIVE

Non-alcoholic steatohepatitis (NASH), which is a common liver disease in industrialized countries, is associated with obesity, hypertension, and type-2 diabetes (metabolic syndrome). Since angiotensin II (ANG II) has been suggested to play an important role in liver inflammation and fibrosis, the purpose of this study was to investigate whether therapy against renin-angiotensin system (RAS) may provide some beneficial effect in liver of an animal model of metabolic syndrome.

METHODS AND PROCEDURES

For 6 months, obese Zucker rats (OZRs) were treated as follows: OZR-group, OZR + Perindopril (P) group, OZR + Irbesartan (IRB) group, OZR + Amlodipine (AML) group, and lean Zucker rats (LZRs) group as a control. Livers were evaluated by immunohistochemistry techniques using corresponding antibodies.

RESULTS

All treated groups showed a similar reduction in blood pressure compared to untreated OZR. Therapy either with IRB or P improves insulin sensitivity and reduces hepatic enzyme level with respect to untreated OZR. Conversely, AML failed to modify both parameters. Untreated OZR displayed higher hepatic ANG II levels and steatosis together with a marked increase in tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and transforming growth factor-beta1 (TGF-beta1) level compared to LZR. Following RAS inhibition either by P or IRB, a significant reduction (P < 0.01) in the immunostaining of TNF-alpha, IL-6 and TGF-beta1 compared to untreated OZR was observed.

DISCUSSION

These results indicate that ANG II expression is increased in the liver of these animals with steatohepatitis. Furthermore, RAS control by either angiotensin-converting enzyme inhibition or AT1 receptor blockade seems to provide a beneficial modulation concerning the inflammatory response to liver injury in this model. Consequently, blockade of RAS could be a new approach to prevent or to treat patients with NASH.