Insomnia and Narcolepsy: Opposite Symptoms but the Same Root Cause?

Discovery of 'Sleep Regulation' Mechanism by Brain Neuro Peptides
"miR-137 indirectly controls Interleukin-13 affecting Hypocretin levels"

Insomnia and narcolepsy differ only in symptoms depending on the expression levels of the neuropeptide substance hypocretin, but their root cause is the same. Photo by Yonhap News

[Asia Economy Intern Reporter Kim Se-eun] Insomnia and narcolepsy, often considered opposite symptoms, actually share the same root cause.

The difference lies only in the expression level of a neuropeptide called hypocretin.

Insomnia patients have too much hypocretin in the hypothalamus of the brain, while narcolepsy patients have too little.

Sleep disorder researchers have focused their attention on hypocretin studies.

In Canada, since 2018, insomnia treatments that inhibit the action of hypocretin have been introduced. However, until now, little has been known about how to regulate the hypocretin levels in brain neurons.

Because of this lack of knowledge, the development of treatments targeting hypocretin has faced obstacles.

However, recently, a mechanism was discovered in which a specific type of RNA (miR) targets the human hypocretin gene to regulate both the quality and quantity of sleep.

This is the first time microRNA has been proven to be involved in sleep regulation. MicroRNAs are non-coding regulatory RNA molecules composed of 20 to 25 nucleopeptides.

Recently, scientists at the University of Copenhagen in Denmark published a research paper in the Proceedings of the National Academy of Sciences (PNAS) stating that hypocretin is involved in maintaining the order of sleep stages.

According to the paper, which was released on the American Association for the Advancement of Science (AAAS) website on the 30th, human sleep is divided into four distinct stages in a fixed order.

If this order is disrupted, sleep quality rapidly deteriorates. Narcolepsy patients find it difficult to maintain wakefulness during the day because their sleep stages are disturbed.

Three types of microRNAs?miR-137, miR-637, and miR-654-5p?were identified as regulators of human hypocretin gene expression.

During the analysis of data from the UK Biobank, a mutation in miR-137, which causes severe daytime sleepiness, was discovered. Suppressing this miR-137 increases hypocretin expression levels, thereby extending wakefulness.

Hypocretin is also closely related to the immune system.

When pathogens such as viruses invade and disrupt the immune system, sleep is affected. This means that the busy immune system also influences hypocretin levels.

This was also confirmed in the study, which found that interleukin 13 (IL-13) is involved in regulating hypocretin levels.

IL-13 acts as a signaling molecule that upregulates the action of miR-137, lowering hypocretin levels and making it difficult to maintain wakefulness.

However, the exact mechanism of IL-13’s action has not yet been clarified. The research team stated in the paper, "We are conducting experiments to find the answer."

This content was produced with the assistance of AI translation services.