Brewed Fresh Daily

Shedding light on why drastically restricting calorie intake prolongs life span in some organisms, MIT researchers have found that lowering the level of the common NADH coenzyme activates an anti-aging gene in yeast. MIT Biology Professor Leonard P. Guarente discovered in 2000 that calorie restriction activates the silenced information regulator (SIR2) gene, which makes a protein called Sir2 that is normally activated by the coenzyme molecule NAD. Guarente has shown that SIR2 is tied to extending life span in yeast and in the roundworm. Humans carry a similar gene. This latest study probes how Sir2 is activated by calorie restriction. The authors report that a coenzyme related to NAD, called NADH (nicotinamide adenine dinucleotide) inhibits Sir2 by blocking the action of NAD. During calorie restriction, levels of NADH decline in cells. This decrease in NADH allows NAD to better activate Sir2 and thereby extend life span. It remains to be seen whether these findings about yeast and NADH will relate to the extension of life span in mammals by calorie restriction.