By altering two genes, scientists from the National Institutes of Health were able to extend the lifespan of mice by about 20%. In humans, that's equal to gaining about 16 years.

Researchers, who reported their findings in the journal Cell Reports on Aug. 29., genetically engineered mice to make them produce only 25% of the normal amount of two very similar proteins called mTOR1 and mTOR2. Decreased activity of these genes has been linked to longer lifespan in past studies of yeast, worms, and flies.

In the study, the average lifespan for engineered mice was 28 months for males and 31.5 months for females, compared to 22.9 for males and 26.5 for females in normal mice.

The engineered mice, although smaller than the normal mice, also had better memory and coordination, and had stronger muscles. On the downside, the longer-lived mice had lower bone density and were more susceptible to infection with age, which could because they need the proteins for their immune system to function properly.

"The conclusion we'd like to draw is that aging is not regulated in all tissues by the same mechanism," study researcher Toren Finkel told The Scientist. "Tissues and organs can age independently of each other and independently of the overall organism, too."

There are actually two different mTOR proteins that are part of an incredibly complex protein system in mammalian cells. Defects in this system has been linked to cancer, osteoporosis, Alzheimer's, diabetes, and other age-related diseases.

In humans, mTOR protein levels can be lowered using an immunosuppressant drug called rapamycin, but researchers cannot be certain that these drugs would have the same life-enhancing effects as altering the mTOR genes.

"What we need right now is for scientists and the public to wake up to the concept that you can slow aging," the Buck Institute for Aging Research's president Brian Kennedy, who wasn't involved in the new study, told the Wall Street Journal. "If you do, you prevent many of the diseases that we're so scared of and that are associated with aging."