on February 10, 2009
Published online before print February 10, 2009, doi: 10.1161/CIRCHEARTFAILURE.108.765750
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Original Article |
Inhibition of PKC-β by Ruboxistaurin Preserves Cardiac Function and Reduces Extra-Cellular Matrix Production in Diabetic Cardiomyopathy
1 St. Michael's Hospital and University of Toronto; St. Vincent's Hospital, Victoria;
2 St. Vincent's Hospital, Victoria;
3 St. Vincent's Hospital, Melbourne;
4 St. Michael's Hospital and University of Toronto;
5 Monash University
6 E-mail: richard.gilbert{at}utoronto.ca
Background—Heart failure is a common cause of morbidity and mortality in diabetic patients that frequently manifests in the absence of impaired left ventricular systolic function. In contrast to the strong evidence base for the treatment of systolic heart failure, the treatment of heart failure with preserved left ventricular function is uncertain and therapeutic targets beyond blockade of the renin-angiotensin-aldosterone and β-adrenergic systems are being sought. One such target is the β isoform of protein kinase C (PKC), implicated in both the complications of diabetes and in cardiac dysfunction in the non-diabetic setting.
Methods and Results—Using a hemodynamically-validated rodent model of diabetic diastolic heart failure (DHF), the (mRen-2)27 transgenic rat (Ren-2), we sought to determine whether selective inhibition of PKC-β would preserve cardiac function and reduce structural injury. Diabetic rats were randomized to receive either vehicle or the PKC-β inhibitor, ruboxistaurin (RBX, 20mg/kg/d) and followed for 6 weeks. Compared with untreated animals, RBX-treated diabetic rats demonstrated preserved systolic and diastolic function, as measured by the slope of preload recruitable stroke work relationship (p<0.05), and the slope of the end-diastolic pressure volume relationship (p<0.01). Collagen I deposition and cardiomyocyte hypertrophy were both reduced in diabetic animals treated with RBX (p<0.01), as was phosphorylated-Smad2, an index of transforming growth factor-β (TGF-β) activity (p<0.01 for all, versus untreated diabetic rats).
Conclusions—Protein kinase C-β inhibition attenuated diastolic dysfunction, myocyte hypertrophy and collagen deposition, and also preserved cardiac contractility. PKC-β inhibition may represent a novel therapeutic strategy for the prevention of diabetes-associated cardiac dysfunction.
Key Words: heart failure • PKC-beta • diabetic diastolic heart failure • fibrosis • cardiomyocyte hypertrophy
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