Irisin vs. Treadmill Exercise in Post Myocardial Infarction Cardiac Rehabilitation in Rats

Abstract

Irisin is an exercise-induced myokine that could play a role in post-myocardial infarction (MI) cardiac rehabilitation. We investigated the ability of dihydromyricetin to mimic the effects of exercise on raising serum irisin and on enhancing cardiac function and remodeling following MI in rats. MI was induced in albino rats by subcutaneous injection of isoproterenol (85mg/kg) for 2 consecutive days at an interval of 24h. One week post-MI, rats either underwent physical exercise by running on a motor-driven treadmill at 25m/min, 30min/d, 5d/week or received orally dihydromyricetin 100mg/kg/d, for 8weeks. Exercise and dihydromyricetin raised serum irisin 1.8 and 1.9 folds as compared to sedentary rats (p <0.001) with no difference between both regimens (p=0.992). There was an improvement of cardiac remodeling where β-myosin heavy chain level was not different in exercise and dihydromyricetin groups from normal group (p=0.695, p=0.470). The heart rate variability domains increased back to normal. However, exercise was superior to dihydromyricetin in improving cardiac contractility by increasing carotid blood flow, stroke volume and cardiac output to be insignificant from normal rats (p=0.899, p=0.850, p=0.912). Meanwhile, treatment with dihydromyricetin showed reduction by 29% of carotid blood flow, 24% of stroke volume and 25% of cardiac output compared to normal rats (p <0.001). DHM could mimic the effect of exercise in stimulating irisin secretion but it is not as effective as exercise in improving myocardial contractility.