Dr. David Killilea: Children’s Scientist Contributes to Research Linking High Zinc Levels and Kidney Stones

David Killilea, PhD, a staff scientist at Children’s Hospital Oakland Research Institute (CHORI), co-authored a study into the causes of kidney stones. The study was conducted by the University of California, San Francisco (UCSF), in collaboration with the Buck Institute for Research on Aging in Marin County and CHORI. Published May 13 in the prestigious scientific journal PLOS ONE, the study revealed that high levels of zinc in the body may contribute to kidney stone formation. Kidney stones are hard, often jagged masses of crystalized minerals that form in the kidney. Some kidney stones are very small and pass through the body without even being noticed. Larger stones may get stuck in the urinary tract, however, causing severe pain and blood in the urine. According to the National Institutes of Health (NIH), kidney stones are one of the most common disorders of the urinary tract, affecting nearly 10 percent of the U.S. population. Each year in the U.S., people suffering with kidney stones make over a million visits to health care providers, including over 300,000 visits to emergency rooms due to the pain. While kidney stones are more common in adults, they also are becoming increasingly common in infants, children, and teenagers from all races and ethnicities. “Nearly 90 percent of kidney stones are calcium-based, but we really don’t know what causes those stones to form,” says Dr. Killilea. “In the past, urologists recommended limiting the amount of calcium in the diet to help prevent the formation of kidney stones, but that did not turn out to be very useful. So we wanted to learn what other factors might contribute to the formation of kidney stones.”

The lead author of the study, Thomas Chi, MD, an assistant professor of medicine in the UCSF Department of Urology, approached Buck Institute researchers to participate in the study because of their experience in using fruit flies to model various diseases. Dr. Chi also approached Dr. Killilea to participate in the study because of his expertise in minerals. The first step was to recognize what others had taken for granted. “Years ago, researchers noticed that fruit flies produced little crystal ‘granules’ in their primitive kidney-like structures, but that finding had been mostly ignored,” Dr. Killilea explains. “Only recently have we found that these granules are similar in some ways to kidney stones in people. Fruit flies are easily managed in the laboratory, and we can manipulate their genetics and diet. We started screening the genes that might play a role in calcification, and we came across a gene that plays a role in metabolizing zinc. At the same time, I was analyzing the fl y granules to see what was in them, and I found relatively high levels of zinc. The way these results came together was a nice surprise!”

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