Why do colds make you tired?

Why colds make you tired

A protein called TNF-alpha is responsible for the exhaustion and tiredness during a cold, for example: It is produced by immune cells to trigger an inflammatory reaction in the body as a measure against infection. This central immune messenger has long been suspected of being able to trigger states of exhaustion. Rheumatism patients, for example, in whom the amount of TNF-alpha in the blood is constantly increased, complain more often of tiredness, and in animal experiments, too, mice with artificially increased TNF-alpha concentrations became more sluggish and less active than their conspecifics.

But only now have a research team led by Gionata Cavadini been able to show how this effect comes about: It is due to an interaction between TNF-alpha and the clock of the internal clock. The messenger substance dampens the activity of some genes in the brain that control the daily sleep and wake cycle. These genes are still switched on and off in their usual rhythm, but when they are active they only run at half power, so to speak. The researchers were able to observe the consequences directly in some mice? the animals used their exercise bikes less than their conspecifics and were generally less on the move in their cages.

Although there has not yet been a corresponding study in humans, the researchers believe that they can transfer the results. This assumption is also supported by the observation that cancer patients often complain of severe exhaustion during treatment with TNF-alpha. However, simply omitting or intercepting the messenger substance in such cases or in people with chronic inflammatory diseases is not a solution: This severely weakens the immune system, and there is also evidence that a TNF-alpha deficiency favors the development of autoimmune diseases. A more precise understanding of the relationship between TNF-alpha and the internal clock could therefore help to find alternative treatment approaches, the researchers hope.

Gionata Cavadini (University Hospital Zurich) et al .: PNAS, online advance publication, DOI: 10.1073 / pnas.0701466104 ddp / Wissenschaft.de? Ilka Lehnen-Beyel
July 18, 2007

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