Rapamycin, an immunosuppressant drug, could treat Hutchinson-Gilford progeria syndrome (progeria), according to a recent study published in Science Translational Medicine.

Progeria is a rare genetic disease that prematurely ages affected individuals, who then die before adulthood in most cases from age-related diseases.

Progeria is caused by the expression of a toxic protein that accumulates in cells, which breaks down the cells and makes them sick. 

Scientists have now shown that rapamycin treatment on cultured progeria cells reverses the damages from the toxin, removes the waste, and reduces the symptoms of aging. 

It also reduces the symptoms of aging in healthy cells.

Scientists believed that senescence, or biological aging, is caused by a combination of genetic programming and environmental damages. Examples of environmental damages may include the accumulation of toxins (e.g. progeria's symptoms), damages to cells, damages to DNA, and the cross-linking of sugar to proteins.

The reversal of these environmental induced-aging effects (like progeria's symptoms), therefore, should slow (if not reverse) the effects of natural aging.

Studies have already demonstrated that mice treated with rapamycin live 13 percent longer for females and 9 percent longer for males. Rapamycin treatment has also extended the lifespan of worms, fruit flies and yeast. 

Scientists believe rapamycin works by inhibiting the pathway of mTOR, a life-span and protein synthesis regulating protein, which when suppressed slows the process of aging.

Professor Randy Strong of the University of Texas described rapamycin's effect the following way (via Time):

We're actually tricking the cells into thinking that they're depleted of nutrients. Rather than the animals losing weight -- we haven't noticed any weight loss -- they may be just using their proteins more efficiently, and then repairing proteins more efficiently.

Scientists further theorize that certain diets, like calorie restriction, are associated with longevity because they inhibit mTOR.

Rapamycin, however, could come with serious side effects if it were administered as an anti-aging drug to humans.   

An immunosuppressant, it suppresses the immune system's ability to fight disease and causes hyperlipidemia (elevated levels of cholesterol and triglycerides in the blood).

For now, a healthy diet remains perhaps the best anti-aging medicine we have.