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Effects of Insulin Replacements, Inhibitors of Angiotensin, and PKCß's Actions to Normalize Cardiac Gene Expression and Fuel Metabolism in Diabetic Rats

¹ Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts
² Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
³ Indiana University School of Medicine, Indianapolis, Indiana
⁴ Warwick Medical School, Coventry, U.K

Address correspondence and reprint requests to George L. King, Research Director, Joslin Diabetes Center, One Joslin Place, Boston, MA 02215. E-mail: george.king{at}joslin.harvard.edu

Abbreviations: DMEM, Dulbecco's modified Eagle's medium; EDP, end diastolic pressure; FFA, free fatty acid; ICT, islet cell transplantation; NMR, nuclear magnetic resonance; NRCM, neonatal rat cardiomyocytes; OA, oleic acid; PDK, pyruvate dehydrogenase kinase; PKC, protein kinase C; STZ, streptozotocin; TCA, tricarboxylic acid; UCP, uncoupling protein

High-density oligonucleotide arrays were used to compare gene expression of rat hearts from control, untreated diabetic, and diabetic groups treated with islet cell transplantation (ICT), protein kinase C (PKC)ß inhibitor ruboxistaurin, or ACE inhibitor captopril. Among the 376 genes that were differentially expressed between untreated diabetic and control hearts included key metabolic enzymes that account for the decreased glucose and increased free fatty acid utilization in the diabetic heart. ICT or insulin replacements reversed these gene changes with normalization of hyperglycemia, dyslipidemia, and cardiac PKC activation in diabetic rats. Surprisingly, both ruboxistaurin and ACE inhibitors improved the metabolic gene profile (confirmed by real-time RT-PCR and protein analysis) and ameliorated PKC activity in diabetic hearts without altering circulating metabolites. Functional assessments using Langendorff preparations and ¹³C nuclear magnetic resonance spectroscopy showed a 36% decrease in glucose utilization and an impairment in diastolic function in diabetic rat hearts, which were normalized by all three treatments. In cardiomyocytes, PKC inhibition attenuated fatty acid–induced increases in the metabolic genes PDK4 and UCP3 and also prevented fatty acid–mediated inhibition of basal and insulin-stimulated glucose oxidation. Thus, PKCß or ACE inhibitors may ameliorate cardiac metabolism and function in diabetes partly by normalization of fuel metabolic gene expression directly in the myocardium.

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