Calorie Restriction, Mitochondria, and Hormesis
A recent paper points to mitochondrially induced hormesis as a root cause of increased longevity with reduced calorie intake - which meshes well with the role of autophagy in this process. It confirms the importance of mitochondria in longevity, and once again shows that a little ongoing damage is actually a good thing: "Calorie restriction (CR) is the only proven regimen which confers lifespan extension benefits across the various phyla right from unicellular organisms like yeast to primates. In a bid to elucidate the mechanism of calorie-restriction-mediated life span extension, the role of mitochondria in the process was investigated. In this study, we found that the mitochondrial content in CR cells remains unaltered as compared to cells grown on nonrestricted media. However, mitochondria isolated from CR cells showed increased respiration and elevated reactive oxygen species levels without augmenting adenosine triphosphate (ATP) generation. The antioxidant defense system was amplified in CR mitochondria, and in CR cells a cross protection to hydrogen-peroxide-induced stress was also observed. Moreover, we also documented that a functional electron transport chain was vital for the life span extension benefits of calorie restriction. Altogether, our results indicate that calorie restriction elicits mitohormetic effect, which ultimately leads to longevity benefit."