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Pioglitazone prevents cardiac remodeling in high-fat, high-calorie-induced Type 2 diabetes mellitus

Department of Physiology and Biophysics, University of Louisville School of Medicine, Louisville, Kentucky

Submitted 19 December 2005 ; accepted in final form 17 February 2006

The agonists of peroxisome proliferator-activated receptor- (PPAR) ameliorate cardiovascular complications associated with diabetes mellitus. We tested the hypothesis that recovery from ailing to failing myocardium in diabetes by PPAR agonist is in part due to decreased matrix metalloproteinase-9 (MMP-9) activation and left ventricular (LV) tissue levels of homocysteine (Hcy). C57BL/6J mice were made diabetic (D) by feeding them a high-fat calorie diet. PPAR was activated by adding pioglitazone (Pi) to the diet. After 6 wk, mice were grouped into: normal calorie diet (N), D, N + Pi and D + Pi (n = 6 in each group). LV variables were measured by echocardiography, endothelial-myocyte (E-M) coupling was measured in cardiac rings, and MMP-9 activation was measured by zymography. Blood glucose levels were twofold higher in D mice compared with N mice. Pi decreased the levels of glucose in D mice to the levels in N mice. LV Hcy levels were 3.5 ± 0.5 µM in N groups compared with 12.4 ± 0.6 µM in D groups. Treatment with Pi normalized the LV levels of Hcy but had no effect on plasma levels of Hcy. In the D group, LV contraction was reduced compared with that of the N group and was ameliorated by treatment with Pi. LV wall thickness was reduced to 0.25 ± 0.02 mm in the D group compared with 0.42 ± 0.01 mm in the N group. LV diastolic diameter was 3.05 ± 0.01 mm in the D group compared with 2.20 ± 0.02 mm in the N group. LV systolic diameter was 1.19 ± 0.02 mm in the D group and 0.59 ± 0.01 mm in the N group. Pi normalized the LV variables in D mice. The responses to ACh and nitroprusside were attenuated in diabetic hearts, suggesting that there was E-M uncoupling in the D group compared with the N group, which was ameliorated by Pi. Plasma and LV levels of MMP-2 and -9 activities were higher in the D group than in the N group but normalized after Pi treatment. These results suggest that E-M uncoupling in the myocardium, in part, is due to increased MMP activities secondary to suppressing PPAR activity in high-fat, calorie-induced Type 2 diabetes mellitus.

endothelial myocyte coupling; nitric oxide; matrix metalloproteinase; homocysteine; heart failure; acetylcholine; nitroprusside; cardiac rings; peroxisome proliferator

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