MIT researchers have gained insight into why sever calorie-restriction in a wide variety of organisms leads to life-extension.
"These findings provide a simple model for activation of Sir2 and extension of life span by calorie restriction," the authors write. "Our findings suggest that the NAD/NADH ratio can serve a critical regulatory function, determining the life span of yeast mother cells. A reduction in this nucleotide activates Sir2 to extend the life span in calorie restriction."
In previous research, Guarente found that rather than a slower metabolism leading to a slower rate of respiration, it turns out that respiration in yeast cells under calorie restriction goes up, not down. "A high respiration rate is intimately connected with calorie restriction in yeast," he said. "A high respiration rate activates SIR2. When respiration goes up, NADH goes down and SIR2 goes up. When SIR2 goes up, longevity happens."
