CHICAGO, June 13 (Xinhua) -- Supplementing older mice with a protein obtained from younger mice appears to slow the decline in health and extend the life spans of older mice by about 16 percent, a study from Washington University School of Medicine in St. Louis found.
The circulating protein is an enzyme called eNAMPT, which is known to orchestrate a key step in the process cells use to make energy, according to the study published Thursday in the journal Cell Metabolism.
In an intriguing finding, the researchers showed that levels of eNAMPT in the blood were highly correlated with the number of days the mice lived. More eNAMPT meant a longer life span, and less meant a shorter one.
The researchers also showed increased life span with delivering eNAMPT to normal old mice. All mice that received saline solution as a control had died before day 881, about 2.4 years. 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," said senior author Shin-ichiro Imai, a professor of developmental biology. "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 found sex differences in levels of eNAMPT, with female mice consistently showing higher levels of the enzyme.
"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, say thicker and shinier fur, resemble that of young mice."
The researchers noted that eNAMPT is also carried in extracellular vesicles in humans. In the next step, they will investigate whether low levels are associated with disease in aging people and whether supplementing eNAMPT in extracellular vesicles could serve as an anti-aging intervention in older people.