24 October 2013
Scientists now know how sleep deprivation devastates immune system
It has been observed for some time that insufficient sleep increases the risk of cardiovascular diseases and type 2 diabetes, but the exact mechanisms behind the effect were unknown. Now, University of Helsinki researchers have now shown what kinds of biological mechanisms related to sleep loss affect the immune system and trigger an inflammatory response. Specifically, they identified the genes which are most susceptible to sleep deprivation and examined whether these genes are involved in the regulation of the immune system.
The findings were obtained from experiments conducted at the sleep laboratory of the Finnish Institute of Occupational Health. Here, the researchers restricted the amount of sleep of a group of healthy young men to four hours per night for five days, imitating the schedule of a normal working week. Blood samples were taken before and after the sleep deprivation test. The results were then compared with samples from healthy men of comparable age who had been sleeping eight hours per night for the week.
"We compared the gene expression before and after the sleep deprivation period, and focused on the genes whose behavior was most strongly altered," explained researcher Vilma Aho. "The expression of many genes and gene pathways related to the functions of the immune system was increased during the sleep deprivation. There was an increase in activity of B cells which are responsible for producing antigens that contribute to the body's defensive reactions, but also to allergic reactions and asthma. This may explain the previous observations of increased asthmatic symptoms in a state of sleep deprivation."
The amount of certain interleukins (signaling molecules which promote inflammation) increased, as did the amount of associated receptors such as Toll-like receptors (TLR). On the gene level, this was apparent in the higher-than-normal expression of the TLR4 gene after sleep loss. CRP level was also elevated, indicating inflammation.
The researchers also wanted to examine the impact that long-term sleep deprivation could have on the immune system. The researchers compared participants who believed they were sleeping sufficiently with those who felt that they were not sleeping enough. Some of the gene-level changes observed in the experimental working week sleep restriction study were repeated in the population sample. These results, say the researchers, may help explain the connection between shorter sleep and the development of inflammatory diseases, such as cardiovascular disease and diabetes.
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Source: University of Helsinki