Calorie restriction and SIR2 genes--towards a mechanism.

Calorie restriction is the first and most compelling example of life extension in mammals. Much speculation about how CR works has focused on ideas of what causes aging. Since these causes themselves are much disputed, I have instead focused my thinking on lessons from simple model organisms, which have emerged from recent genetic studies. These findings can now be integrated with numerous, elegant studies on CR over the decades, which provide a treasure trove of information about physiological changes that are elicited by this regimen. In this paper, I present data showing that the SIR2 gene is a strong candidate to regulate CR in the simple model organisms, such as yeast and Drosophila. I then summarize what is known about the mammalian Sirt1 as it relates to physiological changes during CR, and discuss how this mechanism may impact on life span, as well as diseases of aging.