How our inner clock copes up with jet lag

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Washington, June 26 (ANI): In a rodent study, researchers have shown how individual "clock" genes and the internal clocks of the different organs synchronise with the new external time in the case of jet lag.

Travelling across different time zones makes our internal body clocks go haywire.

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.

Thus, the body's physiological processes are no longer coordinated.

They found that 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.

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.

Researchers have shown how individual "clock" genes and the internal clocks of the different organs cope up with jet lag.

"The internal clocks and the 'clock' genes adapt to the altered external influences at varying speeds. 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," said Gregor Eichele, Director of the Institute's Genes and Behaviour Department.

As the researchers discovered, the adrenal clock plays a key role in the body's adaptation to a new circadian rhythm.

When the scientists switched off the adrenal clock in mice, the rodents adapted their behaviour more quickly to the new time and made a more rapid return to their laps on the wheel in synch with the new external time.

Therefore, a functioning adrenal clock keeps the organism in a temporally stable state and halts the excessively rapid adaptation of the central clock in the SCN.

It is not necessary, however, to switch off the entire adrenal clock to enable the mice to better recover from jet lag.

When the scientists administered the active agent metyrapone to the mice, their corticosterone rhythm changed as did their sleeping/waking rhythm.

"If the mice were given metyrapone at the right time, they adapted faster to the disturbed circadian rhythm. While the 'sleep hormone' melatonin, which is commonly used to treat jet lag, mainly acts by generating tiredness and is therefore more suitable for use when flying east than west, with metyrapone, the mice's internal clock can be turned both forwards and back," explained junior scientist Silke Kiebling.

The insights could produce an entirely new approach to the treatment of jet lag in the future.

The study is published in the Journal of Clinical Investigation. (ANI)

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