Pre- and post-conditioning hormesis in elderly mice, rats, and humans: its loss and restoration.

This paper assessed differences and similarities in the capacity for preconditioning (PC) and post-conditioning (PostC) to prevent ischemic reperfusion (IR) damage to the heart in the old/elderly as compared to young adult mice, rats, and humans. While PC reliably reduces myocardial ischemia-induced heart damage by about 30-60 % in young adult (2-3 months old) mice and rats, such protection begins to diminish in middle age (1 year old) and is fully lost in the old and elderly (≥18 months). Common rearing practices (i.e., no exercise; ad libitum feeding) are strongly associated with the loss of PC to prevent IR damage to the heart in old/elderly rodents. Substantial restoration of lost PC in old/elderly animal models is affected via various types of exercise and exercise protocols, several types of dietary interventions and pharmacological means. Evidence of PC-mediated cardioprotection in old/elderly humans via epidemiological investigations has been reported using multiple research protocols. These findings suggest the need for animal studies to better reflect human dietary, exercise and lifestyle patterns to enhance their extrapolative relevance.