Aging Delayed in Older Mice Given Blood Enzyme from Young Mice

A study from Washington University School of Medicine in St. Louis has found a whole new way to fight off the years. The research has revealed that a protein that is abundant in the blood of young mice plays a key role in keeping mice healthy mad youthful.

Extending lifespan by 16%

The protein is an enzyme called eNAMPT and the researchers found that supplementing older mice with it extends their life spans by about 16%. The protein is responsible for producing a fuel called NAD.

"We have found a totally new pathway toward healthy aging," said senior author Shin-ichiro Imai, MD, PhD, a professor of developmental biology.

"That we can take eNAMPT from the blood of young mice and give it to older mice and see that the older mice show marked improvements in health -- including increased physical activity and better sleep -- is remarkable."

Imai's work differs from other studies focused on transfusing whole blood from young mice to old mice. Instead, Imai's group increased levels of solely the eNAMPT.

The results were nothing short of impressive. "We were surprised by the dramatic differences between the old mice that received the eNAMPT of young mice and old mice that received saline as a control," Imai said.

"These are old mice with no special genetic modifications, and when supplemented with eNAMPT, their wheel-running behaviors, sleep patterns and physical appearance -- thicker, shinier fur, for example -- resemble that of young mice."

Imai's group has also experimented with other ways to boost NAD by giving oral doses of a molecule called NMN, the chemical eNAMPT produces. 

Maintaining NAD levels

"We think the body has so many redundant systems to maintain proper NAD levels because it is so important," Imai said.

"Our work and others' suggest it governs how long we live and how healthy we remain as we age. Since we know that NAD inevitably declines with age, whether in worms, fruit flies, mice or people, many researchers are interested in finding anti-aging interventions that might maintain NAD levels as we get older."

Furthermore, the research indicated that levels of eNAMPT in the blood were highly correlated with the number of days the mice lived. All mice that received saline solution as a control had died before day 881, about 2.4 years, while of the mice that received eNAMPT, one is still alive surpassing 1,029 days, or about 2.8 years.

"We could predict, with surprising accuracy, how long mice would live based on their levels of circulating eNAMPT," Imai said.

"We don't know yet if this association is present in people, but it does suggest that eNAMPT levels should be studied further to see if it could be used as a potential biomarker of aging."

The study also revealed that females had higher levels of the enzyme. The findings are published in the journal Cell Metabolism.