November 14, 2018
Do you take medicine at a certain time of day? If so, those pharmacy instructions may be about to change: The first simple blood test to identify your body’s precise internal time clock as compared to the external time has been developed by scientists at Northwestern University’s Feinberg School of Medicine in Chicago.
The test, called TimeSignature— which requires only two blood draws— can tell physicians and researchers the time in your body, no matter what global time zone you live in or might be visiting. For instance, even if it’s 8 a.m. in the external world, it might be 6 a.m. in your body.
“This is a much more precise and sophisticated measurement than identifying whether you are a morning lark or a night owl,” said the study’s lead author, Rosemary Braun, assistant professor of Preventive Medicine (Biostatistics) at Northwestern’s Feinberg School of Medicine. “We can assess a person’s biological clock to within 1.5 hours.
Previously, measurements this precise could only be achieved through a costly and laborious process of taking samples every hour over a span of multiple hours. “Various groups have tried to get at internal circadian time from a blood test, but nothing has been as accurate or as easy to use as TimeSignature,” Braun said.
Processes in nearly every tissue and organ system in the body are orchestrated by an internal biological clock, which directs circadian rhythm, such as the sleep-wake cycle. Some people’s internal clocks are in sync with external time— but others are out of sync and considered “misaligned.”
The new test for the first time will offer researchers the opportunity to easily examine the impact of misaligned circadian clocks in a range of diseases from heart disease to diabetes and Alzheimer’s disease. When the blood test eventually becomes clinically available, it also will provide doctors with a measurement of an individual’s internal biological clock to guide medication dosing at the most effective time for his or her body.
The software and algorithm are available for free to other researchers so they can assess physiological time in a person’s body. Northwestern has filed for a patent on the blood test.
“This is really an integral part of personalized medicine,” said coauthor Dr. Phyllis Zee, chief of Sleep Medicine in Neurology at Feinberg and a Northwestern Medicine neurologist. “So many drugs have optimal times for dosing. Knowing what time it is in your body is critical to getting the most effective benefits. The best time for you to take the blood pressure drug or the chemotherapy or radiation may be different from somebody else.”
The test measures 40 different gene expression markers in the blood and can be taken any time of day, regardless of whether the patient had a good night’s sleep or was up all night with a baby.
A link between circadian misalignment and diabetes, obesity, depression, heart disease, and asthma has been identified in preclinical research by scientist Joe Bass, chief of Endocrinology, Metabolism and Molecular Medicine at Feinberg.
The study was published on September 10 in the Proceedings of the National Academy of Sciences.
Research contact: rbraun@northwestern.edu
