Study Uncovers Clues as to How Calorie Restriction Extends Lifes

Scientists have known for sometime that calorie restriction can extend the lifespan of a variety of organisms from yeast to mammals. Many scientists believe that cutting calories increases longevity by slowing the metabolism, and therefore reducing the number of cell-damaging free radicals circulating throughout the body. However, new research conducted at Massachusetts Institute of Technology suggests that calorie restriction may work in exactly the opposite way.

In previous studies, Dr Leonard Guarente and his colleagues found that they could extend the lifespan of yeast cells by giving them an extra copy of a gene known as Sir2. Deleting the gene had exactly the opposite effect and dramatically cut the organism's lifespan. Thus, suggesting that Sir2 plays a vital role in longevity. The researchers also found that the activity of Sir2 is linked to the metabolism. Now new research by the team suggests that calorie restriction does not slow the metabolism, but instead actually increases the oxygen consumption of cells. Further investigations revealed that it is also possible to extend the lifespan of yeast cells by overexpressing a gene thought to increase oxygen consumption, however like calorie restriction this method of increasing longevity is also dependent on the Sir2 gene.

Guarente's latest study suggests that the relationship between calorie restriction, the Sir2 gene, and increased lifespan is far more complex than previously thought. Furthermore, as increasing an organism's oxygen consumption, would, in theory, also raise free radical levels, the findings imply that cutting calories does not lengthen the life span by fighting oxidative stress.

SOURCE/REFERENCE: Nature 2002; 418:287-288, 344-348