Mosborne01 [creativecommons license] via Wikimedia Commons
For many organisms, including humans, the activity of certain biological processes and the expression of certain genes and proteins fluctuate predictably over a period of roughly 24 hours. These oscillations are maintained by an internal time-keeping mechanism called the circadian clock. ‘Body time’ refers to the setting of each individual’s circadian clock, which can vary by as much as 12 hours among individuals. Body time can also be influenced by working late-night shifts, suffering from jet lag or lacking regular routines (e.g., sleep, meal times). These individual variations are important because body time affects not only personal comfort and stress levels, but also potency and toxicity of some medications as well as the likelihood of developing diet-induced obesity. Hence, reliable determination of an individual’s body time is necessary to facilitate chronotherapy (or matching of drug delivery to body time) and time-restricted diet strategies. The conventional method for body time determination involves repeated blood sampling for the measurement of cortisol or melatonin over 24 hours or more under controlled environmental conditions. This approach has the advantage of measuring body time directly, but it is time- and labor-intensive and somewhat invasive. As an alternative, a group of Japanese scientists led by Takeya Kasukawa (RIKEN Center for Developmental Biology, Hyogo) and Masahiro Sugimoto (Keio University, Yamagata, and Kyoto University) developed a molecular timetable method for estimating body time.
Lab Anim. (NY) 41, 269 (2012).
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