Eating fewer calories could mean living longer: study

Eating fewer calories might protect the body from the effects of aging, U.S. researchers have found in studies on rats.

Their findings are published in the Sept. 21 issue of the journal Cell.

Researchers from Harvard Medical School, Cornell Medical School and the National Institutes of Health have discovered two genes that determine the lifespan of cells. When cells are exposed to certain types of stress, such as a reduction in calories, the genes go into overdrive, and fend off diseases associated with aging, such as cancer, diabetes and dementia.

The newlyfoundgenes, SIRT3 and SIRT4, do this by keeping the "heart" of the cell, its mitochondria, alive when it would typically wane and die.

When cells undergo a restriction in calories, they send signals through the membranes and activate a gene called NAMPT. When that gene's levels increase, a small molecule called NAD begins to collect in the mitochondria, in turn stimulating the mitochondrial enzymes created by SIRT3 and SIRT4.

The end result are mitochondria that grow stronger and increase their energy output, decreasing cells' aging processes.

"Mitochondria are the guardians of cell survival," said David Sinclair, associate professor of pathology at Harvard Medical School and senior author of the paper."If we can keep boosting levels of NAD in the mitochondria, which in turn stimulates buckets more of SIRT3 and SIRT4, then for a period of time the cell really needs nothing else."

Researchers conducted tests onrats in which one group was fed a sucrose diet and the other group fasted for 48 hours. In the rats that had fasted, NAD levels increased in their livers, they found.

The scientists believe that SIRT3 and SIRT4 may now be potential drug targets for diseases associated with aging. "We hope that these insights into the importance of mitochondrial NAD will facilitate a new understanding of and the development of novel approaches to treating diseases such as cancer and neurodegeneration," reads the report.