Friday, November 26, 2010
Amino-acid imbalance explains extension of lifespan by dietary restriction in Drosophila
This paper in Nature, December 31, 2009 disproves the theory of resource allocation in which "high survival, associated with dietary restrictino, and high reproductive rate, associated with full feeding, are mutally exclusive." The authors show that different combinations of amino acids are responsible for longevity and fecundity, and that both can occur when either methionine is the only amino acid in the diet or when methionine is excluded from an otherwise normal diet. Therefore, the standard tradeoff observed between allocating resources to repair or growth is based on a nutritional sensing and signalling pathway that must involve methionine.
The authors go on to show that this pathway is the insulin sugar-sensing pathway by knocking out insulin receptors in Drosophila. In the figure above flies expressing a dominant negative called lnRDN (diamonds) live much longer, regardless of diet, than do wildtype (triangles) and control with a deGAL4 promoter (squares). Whether these findings apply to humans could possibly be answered with population nutritional and health data, but these can be hard to access.
Very well written.