(FNA)- The carnival worker who tries to guess your age relies on aspects of your appearance, such as your posture and whether any wrinkles emanate from the corners of your eyes and lips. If the carny’s guess is more than a few years off, you win a stuffed koala.
But a team of Stanford University School of Medicine scientists doesn’t need to know how you look to guess your age. Instead, it watches a kind of physiological clock: the levels of 373 proteins circulating in your blood. If the clock is off, you don’t win a plush toy. But you may find out important things about your health.
“We’ve known for a long time that measuring certain proteins in the blood can give you information about a person’s health status — lipoproteins for cardiovascular health, for example,” said Tony Wyss-Coray, PhD, professor of neurology and neurological sciences, the D. H. Chen Professor II and co-director of the Stanford Alzheimer’s Disease Research Center. “But it hasn’t been appreciated that so many different proteins’ levels — roughly a third of all the ones we looked at — change markedly with advancing age.”
Changes in the levels of numerous proteins that migrate from the body’s tissues into circulating blood not only characterize, but quite possibly cause, the phenomenon of aging, Wyss-Coray said.
A paper describing the research will be published Dec. 5 in Nature Medicine. Wyss-Coray is the senior author. The lead author is neurology instructor Benoit Lehallier, PhD.
‘Proteins are the workhorses’
The researchers analyzed plasma — the cell-free, fluid fraction of blood — from 4,263 people ages 18-95. “Proteins are the workhorses of the body’s constituent cells, and when their relative levels undergo substantial changes, it means you’ve changed, too,” Wyss-Coray said. “Looking at thousands of them in plasma gives you a snapshot of what’s going on throughout the body.”
The study’s results suggest that physiological aging does not simply proceed at a perfectly even pace, but rather seems to chart a more herky-jerky trajectory, with three distinct inflection points in the human life cycle. Those three points, occurring on average at ages 34, 60 and 78, stand out as distinct times when the number of different blood-borne proteins that are exhibiting noticeable changes in abundance rises to a crest. This happens because instead of simply increasing or decreasing steadily or staying the same throughout life, the levels of many proteins remain constant for a while and then at one point or another undergo sudden upward or downward shifts. These shifts tend to bunch up at three separate points in a person’s life: young adulthood, late middle age and old age.