David Burke
Professor
Genetic tools for understanding an aging population
Age discrimination isn't just a workplace issue; some diseases preferentially pick on elders as well. Arthritis, high blood pressure, diabetes, bone loss, hearing loss, cancer and a host of other health problems become more likely as people grow older and eventually affect almost everyone who reaches advanced age.
As people are living longer and striving to maintain good health into their 80s, 90s and beyond, understanding age-dependent diseases becomes ever more important. But studying ailments associated with aging is a tricky matter. Any research project that aimed to track a cohort of people from birth into old age would outlast even the longest of scientific careers. And although these health conditions follow the predictable pattern of becoming more common, on average, with advancing age, individuals vary widely in how they're affected, says David Burke, who is developing tools for studying age-dependent diseases.
"Measure the blood pressure of a bunch of 18 year olds, and you'll find two things: that they all have normal, healthy values and that there's little inter-individual variation," says Burke, who is also an associate research scientist for the Institute of Gerontology. "But take that same group of people 70 years later and you'll see that not only is their blood pressure higher on average, but the range of values is much wider. It's the same group of people, with the same DNA, but there's been an increase in inter-individual variability."
Such variation makes scientific studies messier and more challenging, and for that reason, as well as the problem of following slowly-developing diseases over a lifetime, scientists tend to steer clear of this area of research. Consequently, "there are very few people working on this important problem, and the tools for studying age-dependent diseases are very poorly developed," Burke says.
But the knottiness doesn't faze Burke, who delights in tackling the difficult.
"The worst thing you can do is use your scientific career on something that's trivial or easy," he says. For the past 20 years, in collaboration with Dr. Andrzej Galecki and Dr. Richard Miller (U-M Institute of Gerontology and Department of Pathology), Burke has been developing a mouse model to explore individual variation in late-life health problems.
Mice are suitable stand-ins for people, he says. "They have almost the same DNA that we have; they have the same number of organs, the same number of cell types and the same level of complexity that we have; and they also show many of the same age-dependent changes that we see in humans: loss of muscle mass, loss of bone density, loss of neurological performance and dramatically increased rates of cancer incidence as they grow older." And instead of taking decades to attain old age, mice get old in just a few years, considerably shortening the time needed to study the course of the changes Burke is interested in.
One area of interest is cancer incidence.
"Cancer is an informational disease," says Burke. "In cancer, individual cells go from being well-behaved to growing uncontrollably, either because they've lost the instructions for correct growth control or because they're misinterpreting the instructions. What we can now do with our mouse model is monitor age-dependent changes in the information in cells."
Similarly, the model -- and the tissues that the researchers collect and freeze for future use from mice that are autopsied after death -- can shed light on age-dependent patterns in osteoporosis, hearing loss, muscle loss and other problems that afflict the aging. And because Burke is designing research tools and experimental strategies that can be applied to a whole classes of problem, he hopes they'll help solve tomorrow's scientific puzzles as well as today's.
"I take a very long-term view," he says. "What I'm doing now I hope will lay the groundwork for what we'll need 20 or 30 years from now, for studies that aren't even thought of yet."
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