Experimental drug no Methuselah formula

Compound lets mice live healthier, but not longer, lives

An experimental compound helps mice stay healthy longer, but it doesn’t extend their lives.

The substance, known as SRT1720, is intended to mimic the effects of caloric restriction. Scientists have found that calorie restriction can greatly stretch the life span of a wide variety of organisms, including dogs, mice, rats, fruit flies, worms and yeast. Proteins known as sirtuins are necessary for calorie restriction’s life-span extension, with a protein called sirtuin 1, or SIRT1, getting the most attention.

Strict calorie diets aren’t for everybody, and scientists have been searching for ways to mimic calorie restriction’s effect in pill or supplement form. Researchers have used a chemical found in red wine and other foods to turn on SIRT1’s antiaging activity. But that chemical, resveratrol, probably does lots of other things in the body too.

So scientists turned to SRT1720 because it activates SIRT1 without appearing to affect other proteins.

In a new study, published in the March 13 Cell Reports, researchers found that the substance reduced inflammation, slowed down cataracts and improved cholesterol numbers and other measures of a healthy metabolism in mice. What it didn’t do was lengthen the rodents’ maximum possible life spans. The mice tended to live no longer than 160 weeks — about three years — regardless of whether or not they ate the compound as part of a standard diet, report experimental gerontologist Rafael de Cabo of the National Institute on Aging in Baltimore and colleagues.

The researchers also tested whether the supplement could reverse the effects of an unhealthy diet. Mice were fed a high-fat diet starting at about 6 months old. Some of those mice also got SRT1720.  

Mice eating a high fat diet died on average at about 80 weeks old. None lived longer than 140 weeks, months less than their counterparts on a standard diet. The fat-fed mice that got the supplement were healthier, weighed less and had a longer average lifespan — about 110 weeks — than those that didn’t eat the compound. But even with SRT1720’s help, the longest-lived fat-fed mice could not make it past 140 weeks. “The compound delays the effect of the high fat diet tremendously,” de Cabo says, but eventually the animals pay for the unhealthy diet with a shortened maximum life span.

Healthy diets and exercise are still the best prescription for a long life, he says, but compounds such as SRT1720 may eventually help people stay well longer.

To Tomas Prolla, a geneticist who studies aging at the University of Wisconsin–Madison, the results mean that “the root causes of aging have not been affected” by the drug. But, he adds, “Some health parameters associated with aging have been improved.” Compounds such as resveratrol (SN: 8/2/08, p. 14), SRT1720 and the diabetes drug metformin (SN: 11/30/13, p. 18) may improve the quality of life, but researchers still haven’t figured out how to lengthen it without restricting calories. 

Editor’s Note: This story was updated on April 1, 2014, to correct the age of the mice when they started the high-fat diet.

Tina Hesman Saey is the senior staff writer and reports on molecular biology. She has a Ph.D. in molecular genetics from Washington University in St. Louis and a master’s degree in science journalism from Boston University.

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