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Scientists know that if they transfuse blood from a young mouse to an old one, that can stave off or even reverse some signs of aging. What they don't know is what in the blood is responsible for this. Researchers now report that they have identified hundreds of proteins in human blood that wax and wane in surprising ways as we age. NPR's science correspondent Richard Harris reports that could provide important clues to maintaining health.
RICHARD HARRIS, BYLINE: It's no secret that hormones that circulate in our blood change over the years. They're far from alone. Scientists have discovered hundreds of blood proteins that change as we age. Tony Wyss-Coray at Stanford University and his colleagues used a technique that allowed them to look at nearly 3,000 proteins at a time and followed their progress as a function of age.
TONY WYSS-CORAY: When we went into this, we assumed you age gradually so we would see these changes taking place relatively steadily as individuals get older.
HARRIS: Instead, Wyss-Coray and his colleagues report in Nature Medicine that these proteins change in three distinct waves, the first of which happens during our 30s.
WYSS-CORAY: So we found this first wave very early very surprisingly, and then we found a second wave around 60 and the third one, the most prominent one, really, at around 80 years of age.
HARRIS: These observations raise a host of questions about the biology of aging. Like, what's going on in our 30s? Nobody's ever seen that before, he says.
WYSS-CORAY: And that's where we want to hone in and try to understand that moving forward.
HARRIS: And what do the changes actually mean?
WYSS-CORAY: Most of the proteins in the blood are actually from other tissue sources. So we can start to ask, where do these proteins come from? And if they change with age and they come, for example, from the liver, that would tell us that the liver is aging.
HARRIS: Eventually, Wyss-Coray says, he would like to compare a patient's blood protein pattern with a pattern that's normally seen in people of that age to produce a personalized aging clock.
WYSS-CORAY: Where I can tell you, based on the composition of your blood, your kidney seems to be aging faster than it should.
HARRIS: Thinking back to those age-reversing experiments in mice, it might also be possible to isolate proteins in the blood that contribute to that effect. Research groups are already studying proteins one by one to find those that can influence healthy aging. And Wyss-Coray founded a company that's actually running an Alzheimer's study based on this general idea. With this flood of new data, it's a daunting task to figure out whether each of these proteins causes age-related changes, slows them down or is merely a result of aging.
WYSS-CORAY: But we're getting closer by using this method, I think.
TOSHIKO TANAKA: This is really the first step in categorizing and cataloging the age-related biomarkers.
HARRIS: Toshiko Tanaka at the National Institute on Aging has also been studying proteins in the blood. Her group published a study last year. She says the field is suddenly making rapid progress.
TANAKA: One of the great things about these advancements in technology is that it's becoming a lot cheaper (laughter) to measure a lot of these molecules, so bigger studies and more studies can assess the same proteins.
HARRIS: That's an important step to validate discoveries. But it's also the case that there is a vast sea of blood proteins and other constituents to explore, any of which may be involved in health and disease. So Tanaka isn't expecting quick answers.
TANAKA: I hope by the time my kids are old, this is something that we can improve their health trajectory.
HARRIS: Richard Harris, NPR News.
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