This is the first in a series of notes on a hot paper published recently on the extension of the lifespan of yeast. Why is this important? We are zeroing in on why caloric restriction, the only known life extension agent, works in mice. It is apparently related to the SIR2 gene in mice which is also seen in yeast. An overview of this area of research can be found on Professor Guarente’s web site at MIT.
Brad Johnson, who works in Guarente’s lab, provides a succinct statement on the issues. “Others in the lab have shown that overexpression of the SIR2 gene in yeast and in C. elegans can extend the lifespan of these organisms. SIR2 is also required for the lifespan-extending effects of caloric restriction in yeast. Caloric restriction can extend lifespan in many different organisms, and this fact, coupled with the proven effects of SIR2 in two evolutionarily diverged organisms, argues that SIR2 genes may have a conserved role in regulating lifespan. Humans have seven different SIR2 homologues. How can we determine if SIR2 genes play a role in human aging? If naturally-occurring polymorphisms in SIR2 genes affect their activity, these activity changes might be tied to different rates of aging or age-associated disease. We are attempting to address the role of SIR2 genes in human longevity by testing for an association of single nucleotide polymorphisms in the human SIR2 genes with lifespan and several physiologic measures of aging in the Framingham Heart Study population. This work is being done in collaboration with Dr. Alan Herbert and his coworkers at Boston University.”