When it comes to sleep disorders, researchers have spent years analyzing the human brain in the search for possible treatment targets. A new study, however, suggests that one such target may actually lie in skeletal muscles.
Researchers found that high levels of a protein called BMAL1 in the muscles of mice helped them to recover from the effects of sleep deprivation, while low levels of the protein interfered with sleep.
In the rodents' brains, however, BMAL1 levels appeared to have little influence on sleep or the effects of disrupted sleep.
Study co-author Dr. Joseph S. Takahashi, who is chairman of science at the University of Texas Southwestern Medical Center in Dallas, and team recently reported their findings in the journal eLife.
According to the Centers for Disease Control and Prevention (CDC), adults should aim to get at least 7 hours of sleep every night to help maintain health and well-being. However, statistics show that more than a third of adults in the United States fail to meet these recommendations.
Since sleep is triggered by chemical signaling in the brain, it makes sense that this complex organ has been the primary focus of research into sleep disorders. But the new study from Dr. Takahashi and colleagues suggests that muscles may also play a role.
Lack of muscular BMAL1 disrupted sleep
The researchers came to their findings by assessing how the BMAL1 protein affects sleep in mice.
BMAL1 is a known regulator of the circadian rhythm, which is defined as "physical, mental, and behavioral changes that follow a roughly 24-hour cycle, responding primarily to light and darkness in an organism's environment."
The team notes that previous animal studies have shown that deletion of BMAL1 can impact a number of sleep-related behaviors. However, researchers have been unable to pinpoint the underlying mechanisms for this association.
For their study, Dr. Takahashi and team investigated how the presence and absence of BMAL1 in the brains and muscles of mice influenced various aspects of sleep, including sleep quality and recovery from sleep deprivation.
The researchers found that eliminating BMAL1 from the brains of mice had no influence on sleep-related behaviors, and this did not change when the protein was restored.
Interestingly, however, the team found that deleting BMAL1 from the muscles of the mice not only led to severe sleep disruption, but it also increased the rodents' need for sleep and hampered their ability to recover from sleep deprivation.
When the researchers reintroduced BMAL1 to the muscles of the mice, their ability to recover from disrupted sleep was restored.
Findings 'may provide new drug targets'
According to Dr. Takahashi, these results indicate that the sleep process is not solely controlled by the brain. "This finding is completely unexpected and changes the ways we think sleep is controlled," he says.
"These studies show that factors in muscles can signal to the brain to influence sleep. If similar pathways exist in people, this would provide new drug targets for the treatment of sleep disorders."
Dr. Joseph S. Takahashi
Additionally, the researchers say that their results may lead to therapies to combat sleepiness among individuals who need to stay awake for long periods, such as airline pilots.