Danish sleep researchers stress 'right amount of hypocretin in brain at right time'

Danish researchers from the University of Copenhagen and Aalborg University have presented a new study that shows a tiny molecule present in brain cells can affect the levels of hypocretin, which is responsible for regulating our waking and sleeping patterns, keeping us alert during the day and causing drowsiness at night.

According to a news release, the study found that people with a genetic variation of this molecule are more prone to experiencing daytime sleepiness.

In the study, the researchers focused on a small molecule called microRNA-137 (miR-137), which is associated with sleep regulation. They discovered that miR-137 helps regulate hypocretin levels, which is crucial for normal sleep.

"We discovered that miR-137 helps regulate hypocretin," said associate professor Birgitte Kornum. "To experience normal sleep, you need to have the right amount of hypocretin in the brain at the right time, and miR-137 helps with that. Though MiR-137 is also found in other parts of the body, it is especially pronounced in the brain."

Kornum and her colleagues from the Department of Neuroscience and Aalborg University published this study in the journal PNAS that sheds light on the regulation of hypocretin in brain cells. 

Hypocretin, a protein found in brain cells, is suspected to play a role in sleep disorders like insomnia and narcolepsy, as well as mental disorders like depression and ADHD.

The team found genetic mutations in miR-137 that cause daytime sleepiness in both mice and zebrafish, and they were able to connect it to the level of hypocretin in the brain.

The researchers also found that the immune system's transmitter substance, IL-13, affects the level of hypocretin in the body. They showed that when they add IL-13, it affects miR-137 and the level of hypocretin, but they still don't know why. 

Kornum says the study highlights how complex the machinery of sleep is, and they are currently conducting tests to understand the process further. Hypocretin also affects the order of sleep stages, and narcolepsy patients with low levels of hypocretin experience muddled sleep stages. 

The researchers point to the importance of gaining more knowledge about the regulation of hypocretin to solve sleep disorders.