Birgitte Kornum, a brain scientist, was recently relegated to Rome for a few of the world''s largest sleep conferences. There were pharmaceutical companies everywhere, with booths, information materials, and campaigns.
All of them wanted to treat daytime insomnia or to turn off the brain during the day. Many of them also focused on hypocretin, which is a protein found in brain cells and which has recently sparked a lot of attention in sleep research.
Hypocretin is believed to play a role in both insomnia, which is a reduced ability to fall asleep at night, and in narcolepsy, which is a reduced ability to stay awake during the day. It is possible that people suffering from insomnia may have too much hypocretin in the brain, while people suffering from narcolepsy have too little. Additionally, researchers believe hypocretin may play a role in depression, ADHD, and other mental hysteria.
The hypocretin system in the brain is already known; there is even a new medication for insomnia to help alleviate the effects of hypocretin, which was recently introduced in Canada in 2018. However, there is no knowledge about how hypocretin is regulated inside the cells.
In a new study, Associate Professor Birgitte Kornum and her colleagues discussed the topic in an reputed journal PNAS. The study involves testing of mice, zebrafish, and human cells, and the researchers collaborated with their neighbours at the Department of Cellular and Molecular Medicine of Copenhagen.
MicroRNA associated with sleep regulation
The team of researchers has spent several years exploring one of the cellular mechanisms that affect hypocretin levels. Here they have focused on a small molecule called microRNA-137 (miR-137).
We discovered that miR-137 helps regulate hypocretin. For normal sleep, you need to have the right amount of hypocretin in the brain at the correct time, and miR-137 also assists in this process. Birgitte Kornum, an associate professor at Aalborg University, has reviewed the findings.
MicroRNA regulates several cell interactions, including hypocretin levels. In this manner, there is a lot of research interest in microRNAs, which might be targeted in order to regulate these processes.
Previously, the scientists knew quite little about miR-137 in the brain, but now, the Birgitte Kornums research team has demonstrated that it is associated with hypocretin regulation and thus with sleep.
This is the first time a microRNA is linked to sleep regulation. We calculated the amount of genetic mutations in miR-137 that result in increased risk of sleepiness in the morning. According to Birgitte Kornum, the research demonstrates how complex sleep is.
Hypocretin affects sleep stages
Hypocretin, which has captured the attention of pharmaceutical companies, has also had a negative impact on the sleep patterns.
Our sleep is usually divided into four stages. Each stage follows a specific order, and this order is crucial to our sleep''s quality.
Patients with mild hypocretin experience muddled sleep periods. Our findings from mice testing demonstrate that hypocretin has in store for these stages, according to Anja Holm, the first author of the study, who conducted the tests together with Birgitte Kornum.
Existing research suggests that we need to acquire more knowledge of hypocretin regulation in order to resolve the issue. This way, Danish researchers point to another important component of the puzzle, namely the immune system.
When you have a fever and the immune system is working hard, you often feel ill. So we know that something happens to the hypocretin level when the body is attempting to combat a viral infection, for example, and we are looking at this process. According to Birgitte Kornum,
We show that one of the immune systems transmitter substances, IL-13, has a special effect on hypocretin. As we add IL-13, we can confirm that it has an effect on miR-137, but also on the level of hypocretin in the body. Although, we are currently conducting testing that might be able to provide us with a clue.