Science strives to easily chart circadian clock

LITTLE ROCK — Are you a morning lark or a night owl? Scientists use that simplified categorization to explain that different people have different internal body clocks, commonly called circadian clocks. Sleep-wake cycles, digestive activities, and many other physiological processes are controlled by these clocks.

In recent years, researchers have found that internal body clocks can also affect how patients react to drugs. For example, timing a course of chemotherapy to the internal body time of cancer patients can improve treatment efficacy and reduce side effects.

But physicians have not been able to routinely exploit these findings because determining internal body time is, well, time consuming. It’s also cumbersome. The most established and reliable method requires taking blood samples from a patient hourly and tracking levels of the hormone melatonin, which previous research has tied closely to internal body time.

Now a Japanese group has come up with an alternative method of determining internal body time by constructing what it calls a molecular timetable based on levels in blood samples of more than 50 metabolites - hormones and amino acids - that result from biological activity.The researchers established a molecular timetable based on samples from three subjects and validated it using the conventional melatonin measurement. They then used that timetable to determine the internal body times of other subjects by checking the levels of the metabolites in just two blood samples from each subject per day.

Having such a timetable could allow doctors to synchronize drug delivery to internal body time, the team reports online in the Proceedings of the National Academy of Sciences.