Blood has many roles in the metaphorical life of the human body. It’s the organ of kinship (“blood ties”), the seat of emotion (“blood lust”) and a vehicle for identity (“travel is in his blood”). But might it also be a window on the body’s fate?
Many scientists are trying to answer that question as a practical matter, not a metaphor. They are scouring the blood for biomarkers — easily measured substances that illuminate what’s going on in hard-to-reach places.
Biomarkers aren’t new to medicine. Many lab tests are, in fact, tests of biomarkers. Sugar or protein in a sample of urine can shed light on what’s happening in the kidneys or pancreas. The concentration of cholesterol in the blood may hint at disease in the arteries. What’s changed is medicine’s ability to measure more molecules, with greater precision and less cost, than was possible in the past.
The result is a storehouse of information on millions of people, most of it available at the prick of a hypodermic needle. When the health and longevity of those people are correlated with the readings of their biomarkers, it becomes possible to find biomarker profiles that predict risk of future disease or early death.
A recent attempt to do just that was described this year in the journal Aging Cellby Paola Sebastiani, a biostatistician at the Boston University School of Public Health. Her subjects were members of the Long Life Family Study — 5,000 people in 550 families with a predilection for longevity.
The volunteers in the study were subjected to many blood tests. Sebastiani and her colleagues focused on 19 that proved to be most informative. The tests included common ones (hemoglobin concentration, serum albumin) and exotic ones (C-reactive protein, insulinlike growth factor). Together, the tests shed light on six domains of physiology, including inflammation, kidney function and blood-sugar metabolism.
A computer algorithm analyzed the test results in the thousands of volunteers and determined that they fell into 26 patterns, or clusters. Each cluster contained people with similar test results. The biggest one had 2,200 people, all of whom had test readings close to the average for the whole study population. They became the reference group.
“The methodology that I used is to look at multiple markers simultaneously, which is challenging. You have to have a lot of data to be able to do this,” Sebastiani said. The researchers found the clusters differed from each other, and from the reference group, in their rates of cancer, heart disease, diabetes and premature death, and also in measures of aging, such as grip strength and walking speed. As expected, one cluster was considerably healthier than the average, with a low incidence of disease and early death. Its members seemed to have biological ages younger than their chronological ages.
In short, the 19 blood tests together formed a biomarker that told people whether they were aging prematurely, and predicted in general terms the chances of developing serious illness or dying early.
SOURCE: David Brown
The Washington Post