Bangalore: Mankind may finally get to the bottom of several mysteries regarding sleep, including why, thanks to the fruit fly because scientists have identified a sleep-promoting molecule in the insect and claim this can help in understanding the genetic basis of sleep and, eventually, address sleep disorders.
(COMMON SLEEP DISORDERS) In Friday’s issue of the journal Science, researchers from Howard Hughes Medical Institute and Division of Sleep Medicine, University of Pennsylvania, report that they have found a gene, named “sleepless”, which is responsible for silencing of specific neurons in the brain that are critical for sleep. “Identification of similar molecules in mammals may lead to therapies for sleeplessness,” says Amita Sehgal, one of the lead researchers and a neurobiologist from University of Pennsylvania, in an email.
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Not much is understood about sleep at any level, says B. Gitanjali, who specializes in sleep medicine at the Jawaharlal Institute of Postgraduate Medical Education and Research in Puducherry, and set up the first sleep laboratory in south India in 1994.
“This is really an exciting study since for the first time there is evidence suggesting that reduced membrane excitability (or neuronal silencing) may be a central feature of sleep,” says Dr Gitanjali.
The sleepless gene encodes a specific protein, the levels of which correlate with the amount of sleep—its significant deficiency causes severe reduction in sleep.
“The discovery of genes like ‘sleepless’ could have major implications towards research on pharmaco-therapeutic agents for sleep disorders such as insomnia, which is prevalent worldwide,” says Suresh Kumar, consultant in neurology and sleep medicine at Vijaya Health Centre and Fortis Malar Hospital in Chennai.
Sleep is a physiological process that accounts for one-third of the typical human being’s lifespan. Sleep deprived humans feel miserable and fare poorly in mental tasks just as sleep-deprived rats deteriorate in health and fail in their laboratory fitness tests.
Still, it’s difficult to imagine that a slumbering fly can shed light on how sleep maintains the brain and metabolism. But simple animals such as worms, fruit flies and zebrafish are turning out to be the new genetic models in sleep laboratories across the world because their genomes and nervous systems are easy to study. The first published description of fruit fly sleep came in 2000.
Besides, fruit flies—with four pairs of chromosomes (human beings have 23), including one pair that determines sex just as it does in humans—have always been the preferred test-animals for genetic studies.
All animals seem to require sleep, as distinct from rest, and quite often this is linked to their day-night activity or circadian rhythm, says K. Vijay Raghavan, director of the National Centre of Biological Sciences in Bangalore, who studies neurobiology of movement in fruit flies. “If sleep can be studied in the fruit fly, it will be greatly valuable for understanding sleep in humans as many neuronal circuits and mechanisms are conserved between fly and human as also the genes involved,” he adds.
Sleep is regulated by two main processes—circadian and homeostatic. The circadian clock regulates the timing of sleep, whereas the homeostatic mechanism controls the need for sleep. It’s the latter that is thought to influence sleep under normal conditions as well as recovery sleep after deprivation. The present research unravels the molecular mechanisms underlying homeostatic regulation, which was so far unclear.
These are, of course, early days and the findings need to be carried further by other workers in the field, says Dr Gitanjali, who thinks both basic research and popular awareness about sleep-related disorders are poor in India.
Studies on the exact incidence and prevalence of insomnia, one of the commonest sleep disorders in India, are lacking. Clinicians such as Dr Kumar and Dr Gitanjali say they are increasingly finding insomnia as a “major problem” per se as well as in relation to medical disorders such as heart disease, stroke, diabetes and depression and claim it accounts for up to 50% of sleep-related complaints that require medical intervention.
Narcolepsy (excessive day-time sleepiness) remains poorly diagnosed in India as neither the doctor nor the patient understands the disorder. Besides creating more awareness in the public and among professionals, India needs to have more sleep centres so that more cases of narcolepsy can be picked up, suggests Dr Kumar. “Sleep medicine is not even a part of the medical curriculum in undergraduate and postgraduate studies,” he says.