Nipradilol can prevent left ventricular systolic and diastolic dysfunction after myocardial infarction in rats

Dipeptidyl peptidase-4 inhibitor improves cardiac function by attenuating adverse cardiac remodelling in rats with chronic myocardial infarction

NEW FINDINGS

What is the central question of this study? Although cardioprotective effects of dipeptidyl peptidase-4 (DPP-4) inhibitors have been demonstrated, their cardiac effects in chronic myocardial infarction (MI) are unclear. We determined the effects of a DPP-4 inhibitor on cardiac function and remodelling in rats with chronic MI. What is the main finding and its importance? We demonstrated, for the first time, that DPP-4 inhibitor, but not metformin, exerted similar efficacy in improving cardiac function and attenuating cardiac fibrosis compared with enalapril in rats with chronic MI. These findings reveal benefits additional to the glycaemic control by the DPP-4 inhibitor in chronic MI, and it might become the new drug of choice for MI in patients with diabetes mellitus. Adverse cardiac remodelling after myocardial infarction (MI) leads to progressive heart failure. Dipeptidyl peptidase-4 (DPP-4) inhibitors are new antidiabetic drugs that exert cardioprotection. However, their role in cardiac function and remodelling in chronic MI is unclear. We hypothesized that the DPP-4 inhibitor vildagliptin reduces adverse cardiac remodelling and improves cardiac function in rats with chronic MI. These effects were also compared with enalapril and metformin. Male Wistar rats (n = 36) with chronic MI induced by ligation of the left anterior descending coronary artery were divided into six groups to receive vehicle, vildagliptin (3 mg kg(-1)  day(-1) ), metformin (30 mg kg(-1)  day(-1) ), enalapril (10 mg kg(-1)  day(-1) ), combined metformin and enalapril or combined vildagliptin and enalapril for 8 weeks. At the end of the study, plasma malondialdehyde (MDA), heart rate variability (HRV), left ventricular (LV) function, pathological and biochemical studies of cardiac remodelling were investigated. Our study demonstrated that rats with chronic MI had increased oxidative stress levels, depressed HRV, adverse cardiac remodelling, indicated by cardiac fibrosis, and LV dysfunction. Treatment with vildagliptin or enalapril significantly decreased oxidative stress, attenuated cardiac fibrosis and improved HRV and LV function. We conclude that vildagliptin exerts similar cardioprotective effects to enalapril in attenuating oxidative stress and cardiac fibrosis and improving cardiac function in rats with chronic MI. Metformin does not provide these benefits in this model. Moreover, addition of either metformin or vildagliptin to enalapril does not provide additional benefit in attenuating cardiac remodelling or improving LV function compared with enalapril alone.

Long-Term Beneficial Effect of Infarct-Related Artery Patency in Acute Anterior Myocardial Infarction in Patients With Poor Myocardial Viability in the Region-at-Risk

BACKGROUND

Several studies have demonstrated the benefit of the patency of infarct-related artery (IRA) in acute myocardial infarction (AMI). However those studies have not been concerned with myocardial viability in the region-at-risk. In the present study the effect of the patency of IRA was investigated in the setting of anterior AMI with poor viable myocardium in the risk region.

METHODS AND RESULTS

From 1993 to 1996 patients with a first time anterior AMI and poor viable myocardium in the region-at-risk at 1 month after onset were identified and enrolled. Patients with a totally occluded IRA were included in the Non-Open group (n=44), and patients with a reperfused IRA were included in the Open group (n=49). At 5 years after onset, left ventricular function was better preserved in the Open group than in the Non-Open group (p<0.05). Kaplan-Meier survival curves for cardiac mortality and event-free survival curves revealed poor prognoses in the Non-Open group over a 5-year period (p<0.05, respectively). The advantages of a patent IRA were further seen in health-related quality-of-life outcomes (p<0.05).

CONCLUSIONS

Even in patients with poor myocardial viability after an anterior AMI, the patency of the IRA is strongly associated with improved long-term survival, independent of residual myocardium viability.

Effects of Cellular Cardiomyoplasty on Ventricular Remodeling Assessed by Doppler Echocardiography and Topographic Immunohistochemistry

BACKGROUND

Myocardial infarction (MI) promotes deleterious remodeling of the myocardium, resulting in ventricular dilation and pump dysfunction. Supplementing infarcted myocardium with neonatal myocyte would attenuate deleterious remodeling and so the present study used Doppler echocardiography and histology to analyze the cardiac function and histological regeneration of the damaged myocardium after cellular cardiomyoplasty.

METHODS AND RESULTS

Experimental MI was induced by 24-h coronary ligation followed by reperfusion in adult male Lewis rats and neonatal myocytes were injected directly into the infarct and peri-infarct regions. Three groups of animals were studied at 4 weeks after cellular cardiomyoplasty: noninfarcted control (control), MI plus sham injection (MI), and MI plus cell injection (MI + cell). Ventricular remodeling and cardiac performance were assessed by Doppler echocardiography or contrast echocardiography. At 4 weeks after cellular cardiomyoplasty, MI + cell hearts exhibited attenuation of global ventricular dilation and cardiac function compared with MI hearts not receiving cellular cardiomyoplasty. Immunohistochemically, connexin-43-positive small cells were observed in the vicinity of the infarction in MI + cell heart. By electron microscopy, these cells contained myofilaments with Z-bands and poorly developed intercalated disks, suggesting neonatal myocardial cells. Furthermore, the myocardial cells were often making close contact with interstitial cells.

CONCLUSIONS

Implanted neonatal myocytes form viable grafts after MI, resulting in attenuated ventricular dilation and enhanced contractile function. Echocardiography, electron microscopy, and immunohistochemistry are useful methods for assessing the functional and histological regeneration of the damaged myocardium.