Reduce Calories and Ward of Effects of Aging – Lesson from Rats

by Gopalan on Sep 22 2007 11:36 AM

Eat less to live well is the received wisdom.

Now researchers have found consumption of fewer calories could also help one fight off the effects of aging.

In their findings published in the Sept. 21 issue of the journal Cell, researchers from Harvard Medical School, Cornell Medical School and the National Institutes of Health say they 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 newly found genes, SIRT3 and SIRT4, do this by keeping the "heart" of the cell, its mitochondria, alive when it would typically wane and die.

It turns out then that mitochondria guard against cell death, and the two genes within the mitochondria actually carry out that task.

Mitochondria are compartments within a cell that are dedicated to energy production, and their loss is thought to be a major cause of aging.

The research thus identifies two potential drug targets that could be exploited to slow down the aging process, said lead researcher David Sinclair, director of the Paul F. Glenn Laboratories for Aging Research at Harvard Medical School.

Sinclair and his colleagues found that, when either rat or human cells were deprived of nutrients (as in a caloric-restriction diet), the overall cellular concentration of a compound known as NAD dropped precipitously -- but not within mitochondria. Indeed, following any kind of cellular stress, mitochondrial NAD concentration actually increased, 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.

"Said David Sinclair,. "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 on rats 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.

"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.