Caloric restriction restores the cardioprotective effect of preconditioning in the rat heart.

Preconditioning (PC) describes the observation that brief periods of ischemia paradoxically protect the heart and limit necrosis caused by a subsequent more prolonged period of ischemia. However, the PC response is attenuated in hearts from 9- to 12-month-old Sprague-Dawley rats, as compared to young adults. This study determined whether long-term caloric restriction (CR) could preserve the PC response, since CR increases ischemic tolerance in these hearts. Following 6 months of CR, isolated hearts underwent PC followed by ischemia and reperfusion. In contrast to control hearts in which PC response was attenuated, PC in CR hearts was clearly of benefit. In these hearts, aortic flow was increased resulting in a dramatic improvement of cardiac output. Our study suggests that CR is effective in preserving the PC response.