London: It’s a familiar feeling you get when you’re sick – you don’t want to eat or move, all you want to do is sleep. We think it’s because our body is expending all its energy fighting the infection. But a new study claims it in fact all boils down to a chemical affecting activity in the nervous system cells.
Scientists at the University of Pennsylvania studied the simple nervous system of a roundworm to show how one cell can change your whole body’s response to sickness. The study, conducted at the university’s Perelman School of Medicine, looked at the nervous system of a roundworm – parasites that generally live in the human gut.
During sickness, cells are under stress and organisms experience sleepiness to promote sleep and recover from that stress. Scientists found in the worm a single nerve cell called Alpha-Lipoic Acid (ALA), which released a group of chemicals that send signals between brain neurons.
ALA has been known to assist the body’s energy production and acts as a powerful antioxidant. It can help treat nerve damage, protect the liver, and possibly help slow the progression of Alzheimer’s disease. The main chemical released, FLP-13, causes sleep by turning down activity in the nervous system cells that help keep organisms awake.
Researchers examined genetic mutations to determine which genes caused the worms to fall asleep when that chemical was released. The worms with mutations that cause them to lack a receptor protein on cell surfaces, called DMSR-1, did not become sleepy in response to FLP-13. This indicates that DMSR-1 is essential for sleep to be triggered.
Researchers next want to study whether illness-induced sleepiness in humans and other mammals is triggered via a similar mechanism. If so, this research may be a critical step toward developing drugs to treat human fatigue associated with sickness and other conditions.
Senior author Dr. David Raizen, an associate professor of neurology and a member of the Center for Sleep and Circadian Neurobiology, said: ‘Sleep is vitally important in helping both people and animals to recover during sickness.
‘Similar signaling may operate in humans and other animals to regulate sleep during sickness. These findings create a launching pad towards future research into the mechanisms for illness-induced sleepiness in humans and other organisms.’
Previous studies, also conducted by the Perelman School of Medicine, showed the importance of sleep in fighting infection by studying fruit flies. Researchers purposely infected fruit flies that were either sleep-deprived or non-sleep-deprived with Serratia marcescens or Pseudomonas aeruginosa bacteria.
They found that the sleep-deprived flies had greater survival after the infection compared with the non-sleep-deprived flies. Sleep deprivation seemed to make the fruit flies sleep more after being infected with the bacteria. The researchers also genetically engineered the flies to sleep more before they were infected with bacteria.
These flies were able to survive long after being infected and were better able to clear the bacteria from their bodies, therefore suggesting sleep has a positive effect on the immune response.