Science News - June 4, 2011

An antiaging dog food wouldn’t just allow people to keep their canine companions longer. Since dogs have shorter life spans than people, an antiaging effect would be evident sooner in dogs. “We think that a compound like mannoheptulose or a glycolytic inhibitor is going to be superior to any of the products that are out there, because of the fact that it does work somewhat similarly to true caloric restriction,” Ingram says.

But mannoheptulose isn’t the only natural substance that appears to mimic a state of calorie restriction. The most headline-grabbing compound of the bunch has been the sirtuin-targeting resveratrol.

Celebrity compounds under fire

In cells, sirtuins have a day job of stripping acetyl groups (small carbon-rich chemical bunches) from proteins. Most important, the enzymes are particularly busy during times of mild stress, such as when calorie intake drops. Somehow, for reasons that are still being worked out, cells awash in sirtuins are more protected from damage.

“ When we are obese, the body gets lazy and turns those protections off,” says David Sinclair, who studies aging at Harvard Medical School in Boston. A decade of research has suggested that sirtuins may help shield the body from a number of afflictions, including diabetes, stroke and even neurodegenerative diseases such as Alzheimer’s and Parkinson’s.

Sirtuins’ path to stardom began in
questioning whether the effect was a test-
ing artifact or resveratrol and three other
Sirtris compounds actually activated
SIRT1. “Our present data are significant
for the field as we provided strong evi-
dence that neither the Sirtris series nor
resveratrol are direct SIRT1 activators,”
the team wrote.

Targeting cell growth Less controversial, but toting its own baggage, is the drug rapamycin. It has the advantage of already being on the market and having an almost undisputed record of lengthening life span in animals. The drug has long been prescribed to transplant patients because it helps guard against rejection. It has also been investigated in cancer treatment because it has the capacity to starve tumors of nutrients — and indeed, transplant patients taking rapamycin appear to have a lower cancer risk.

Gaining more days In a classic caloric restriction study, mice fed a normal amount died younger than those receiving 30 percent fewer calories (left). Older male mice given the drug rapamycin starting at 600 days of age (middle) and mice genetically engineered without a functional S6K1 protein (right), a crucial player in nutrient sensing and cell growth, also tended to live longer.