Telmisartan, an
angiotensin II-receptor blocker (ARB), is a partial agonist of the
peroxisome proliferator-activated receptor-gamma (
PPAR-gamma). We investigated whether
telmisartan improved the pathophysiology of
myocardial infarction in diabetes partially through the
PPAR-gamma pathway by assessing a variety of indices, e.g., hemodynamic, biochemical, histoarchitectural changes, and apoptosis. Diabetes was induced by a single dose of
streptozotocin (70 mg/kg, IP). Diabetic rats received either
telmisartan (10 mg/kg/day, orally), the
PPAR-gamma antagonist
GW9662 (1 mg/kg/day, IP), or both for 14 days with concurrent administration of
isoproterenol (85 mg/kg, SC) on days 13 and 14. Compared with diabetic controls, diabetic rats with
myocardial infarction exhibited altered hemodynamic profiles and reduction in the activities of
creatine kinase-MB isoenzyme,
lactate dehydrogenase,
superoxide dismutase,
catalase, and
glutathione level along with increased level of
malondialdehyde in the heart. Further, diabetic animals with
myocardial infarction exhibited increased myonecrosis,
edema, and apoptotic cell death. Treatment with
telmisartan significantly improved the redox status of the myocardium with subsequent cardiac functional recovery. However, significant effects were lowered in animals treated with
telmisartan plus
GW9662.
Telmisartan markedly inhibited Bax expression, TUNEL-positive cells, myonecrosis, and
edema. On the other hand, administration of
telmisartan plus
GW9662 did not elicit the same effects, nor did they increase Bcl-2
protein expression in
isoproterenol-induced myocardially infarcted diabetic rats when administered concomitantly or individually. Moreover, down-regulated
PPAR-gamma expression in myocardially infarcted diabetic hearts was increased by
telmisartan treatment. In addition to class effects of ARBs,
telmisartan reduces oxidative stress and apoptosis and improves cardiac function via the
PPAR-gamma pathway.