Down with jet lag
The active agent metyrapone influences corticosterone synthesis and enables faster adaptation to altered circadian rhythms
Journeys across several time zones make our internal body clocks go haywire. We feel exhausted and tense, and our sleep pattern is out of synch. As scientists at the Max Planck Institute for Biophysical Chemistry have now succeeded in demonstrating for mice, the clocks associated with individual organs in the body adapt to the new time at different speeds. As a result, the body’s physiological processes are no longer coordinated. The adrenal gland plays a key role in this process. When the researchers switched off the adrenal clock or manipulated the synthesis of corticosterone by the adrenal gland with the help of metyrapone, the rodents adapted more quickly to the altered circadian rhythm. These insights could pave the way for a new approach to the hormonal treatment of the effects of jet lag and shift work. (Journal of Clinical Investigation, June 23, 2010).
Be they professional footballers on their way to the World Cup in South Africa or ordinary holidaymakers: people who cross several time zones by jet are prone to certain symptoms for a few days after the flight. During the day, they are crippled with exhaustion; at night they lie awake tossing and turning, unable to sleep, and many of the body’s functions are activated at the wrong time. What we have here is a clear case of jet lag. Our "internal body clock", which still beats to our old rhythm of day and night, must adapt to the new external time. The process works, however: after a few days, we feel in synch with the outside world again.
The problems that arise with jet lag are a clear example of how external influences can disrupt our internal body clock. An entire network of molecular clocks found in the different organs coordinate the body’s various physiological processes ranging from the heart beat, temperature, sleep requirement and hormone balance to behaviour. All of these clocks are controlled by the master pacemaker of the hypothalamic suprachiasmatic nuclei (SCN), which synchronises all of the body’s "peripheral" clocks with the outside world. At molecular level, all of the clocks are based on a handful of "clock" genes and proteins that regulate each other interactively and thus generate a molecular time signal in the form of a circadian rhythm - a term which originates from the Latin for approximately (circa) and day (dies).
Scientists at the Max Planck Institute for Biophysical Chemistry have for the first time systematically studied how individual "clock" genes and the internal clocks of the different organs synchronise with the new external time in the case of jet lag. The researchers were surprised by their findings. "The internal clocks and the ‘clock’ genes adapt to the altered external influences at varying speeds," says Gregor Eichele, Director of the Institute’s Genes and Behaviour Department. "When an organism suffers from jet lag, it would appear that the entire clock mechanism fails to tick at the right rhythm. As a result, numerous physiological processes are no longer coordinated."