Posts tagged circadian rhythms
Articles and news from the latest research reports.
Sleep Deprivation May Disrupt Your Genes
Far more than just leaving you yawning, a small amount of sleep deprivation disrupts the activity of genes, potentially affecting metabolism and other functions in the human body, a new study suggests.
It’s not clear how your health may be affected by the genetic disruption if you don’t get enough sleep. Still, the research raises the possibility that the effects of too little sleep could have long-lasting effects on your body.
"If people regularly restrict their sleep, it is possible that the disruption that we see … could have an impact over time that ultimately determines their health outcomes as they age in later life," said study co-author Simon Archer, who studies sleep at the University of Surrey, in England.
The study was published online Feb. 25 in the Proceedings of the National Academy of Sciences.
At issue is how a lack of enough sleep affects the human body. While it’s obvious that people get tired when they don’t sleep, scientists have only recently started to understand how sleep deprivation affects more than the brain, said Dr. Charles Czeisler, chief of the division of sleep medicine at Brigham and Women’s Hospital, in Boston. Research has suggested that sleep is important all the way down to the level of cells, said Czeisler, who was not involved in the new study.
For the study, researchers recruited 26 volunteers who spent a week getting a normal amount of sleep (8.5 hours) and a week getting less than normal (5.7 hours). The participants were still able to enter periods of deep sleep.
The researchers then studied the genes of the participants in blood samples and found that numerous genes, including some related to metabolism, became less active.
So what does that mean for the body? “We have no idea,” Archer said, “but these effects are not minor.” They appear to be similar to those that separate normal from abnormal types of tissue in the body, he said.
Archer said the next step will be to investigate how a lack of sleep affects the body in the long term and to figure out whether some kinds of people are more vulnerable to sleep deprivation’s negative effects on health.
For his part, Czeisler praised the study and said it raises the prospect of a blood test that will tell doctors if a patient’s body is being affected because he or she isn’t getting enough sleep. That’s important because substances such as caffeine can hide the effects of lack of sleep so patients don’t realize there’s a problem, he said.
What about the possibility of a pill that mimics the effects of sleep so people don’t have to bother getting some shut-eye in the first place? There’s no evidence to support the idea of such a pill, Czeisler said, although there’s ongoing research into how to improve the quality of sleep that people do manage to get.
(Image: iStock)
Circadian rhythms can be modified for potential treatment of disorders
UC Irvine-led studies have revealed the cellular mechanism by which circadian rhythms – also known as the body clock – modify energy metabolism and also have identified novel compounds that control this action. The findings point to potential treatments for disorders triggered by circadian rhythm dysfunction, ranging from insomnia and obesity to diabetes and cancer.
UC Irvine’s Paolo Sassone-Corsi, one of the world’s leading researchers on the genetics of circadian rhythms, led the studies and worked with international groups of scientists. Their results are detailed in two companion pieces appearing this week in the early online edition of the Proceedings of the National Academy of Science (1 , 2).
“Circadian rhythms of 24 hours govern fundamental physiological functions in almost all organisms,” said Sassone-Corsi, the Donald Bren Professor of Biological Chemistry. “The circadian clocks are intrinsic time-tracking systems in our bodies that anticipate environmental changes and adapt themselves to the appropriate time of day. Disruption of these rhythms can profoundly influence human health.”
He added that up to 15 percent of people’s genes are regulated by the day-night pattern of circadian rhythms.
In the first study of its kind, a team of researchers led by faculty at the Perelman School of Medicine at the University of Pennsylvania and the Baylor College of Medicine, has analyzed data on the impact of prolonged operational confinement on sleep, performance, and mood in astronauts from a groundbreaking international effort to simulate a 520-day space mission to Mars. The findings, published online-first in the Proceedings of the National Academy of Sciences, revealed alterations of life-sustaining sleep patterns and neurobehavioral consequences for crew members that must be addressed for successful adaption to prolonged space missions.
"The success of human interplanetary spaceflight, which is anticipated to be in this century, will depend on the ability of astronauts to remain confined and isolated from Earth much longer than previous missions or simulations," said David F. Dinges, PhD, professor and chief, Division of Sleep and Chronobiology in the Department of Psychiatry at the Perelman School of Medicine, and co-lead author of the new study. "This is the first investigation to pinpoint the crucial role that sleep-wake cycles will play in extended space missions."
The 520-day simulation, which was developed by the Institute for Biomedical Problems (IBMP) of the Russian Academy of Sciences, and sponsored in part by the European Space Agency (ESA), was initiated on June 3, 2010 when the hatches were closed on a 550-cubic-meter IBMP spacecraft-like confinement facility in Russia. The simulated mission, involving an international, six-man team of volunteers, involved more than 90 experiments and realistic scenarios to gather valuable psychological and medical data on the effects of a long-term deep space flight. The 520-day mission was broken into three phases: 250 days for the trip to Mars, 30 days on the surface, and 240 days for the return to Earth.
“As the only U.S. research team involved with the Mars 520-day simulation, the study required international coordination and strong collaborations to ensure that the experiments were conducted in a thorough and rigorous manner,” said Jeffrey P. Sutton, MD, PhD, professor and director, Center for Space Medicine at Baylor College of Medicine, and senior study author. The investigators monitored the crew’s rest-activity patterns, performance and psychological responses to determine the extent to which sleep loss, fatigue, stress, mood changes and conflicts occurred during the mission.
Measurements included continuous recordings of body movements using wrist actigraphy (a noninvasive means of estimating sleep and movement intensity), and light exposure and weekly computer-based neurobehavioral assessments to identify changes in the crew’s activity levels, sleep quantity and quality, sleep–wake intervals, alertness performance, and workload throughout the 17 months of mission confinement.
Data from the actigraph devices revealed that crew sedentariness increased across the mission, as illustrated by decreased waking movement and increased sleep and rest times. The majority of crewmembers also experienced one or more disturbances of sleep quality, alertness deficits, or altered sleep–wake intervals and timing, suggesting inadequate circadian synchronization.
"Taken together, these measurements point to the need to identify markers of differential vulnerability to abnormal decrease in muscular movement and sleep– wake changes in crew members during the prolonged isolation of exploration spaceflight and the need to ensure maintenance of the Earth’s natural circadian rhythm, sleep quantity and quality, and optimal activity levels during exploration missions," said Mathias Basner, MD, PhD, MSc, assistant professor of Sleep and Chronobiology in Psychiatry at Penn, and co-lead author.
The research team concludes that successful adaptation to such missions will require crews to transit in spacecraft and live in surface habitats that artificially mimic aspects of Earth’s sleep-wake activity cycles, such as appropriately timed light exposure, food intake, and exercise. This dynamic will be necessary to maintain neurocognition and human behavior throughout the flight.
Rhythmic Changes in Gene Activation Power the Circadian Clock
Rhythms underlie the daily functions of mammals, from sleep-wake cycles to metabolic processes in the liver. The circadian clock has evolved in response to daily changes in temperature and light in the environment. At the root of circadian rhythms are daily fluctuations in gene expression, which occur in part through the process of transcription—the creation of RNA from sequences of DNA. Although past studies have uncovered how changes in transcription states relate to irreversible processes, for example when cells become more specialized, much less is known about how transcription fluctuates in synch with recurring cycles.
Today saw the launch of Re-Timer, a wearable green light device invented by Flinders University sleep researchers to reset the body’s internal clock.
The portable device, which is worn like a pair of sunglasses and emits a soft green light onto the eyes, will help to counter jet lag, keep shift workers more alert and get teenagers out of bed by advancing or delaying sleeping patterns.
Psychologist Professor Leon Lack, the device’s chief inventor, said that the light from Re-Timer stimulates the part of the brain responsible for regulating the 24-hour body clock.
The device has been designed with the benefit of 25 years of sleep research at Flinders University.
“Body clocks or circadian rhythms influence the timing of all our sleeping and waking patterns, alertness, performance levels and metabolism,” Professor Lack said.
“Photoreceptors in our eyes detect sunlight, signal our brain to be awake and alert, and set our rhythms accordingly. These rhythms vary regularly over a 24-hour cycle. However, this process is often impaired by staying indoors, traveling to other times zones, working irregular hours, or a lack of sunlight during winter months.
“Our extensive research studies have shown that green light is one of the most effective wavelengths for advancing or delaying the body clock, and to date is the only wearable device using green light.”
Professor Lack recommended wearing the glasses for three days for 50 minutes each day either after awakening in the morning to advance the body clock, or before bed for those wanting to delay the body clock to wake up later.
He said that Re-Timer’s light therapy offers a safer and, in many cases, more effective treatment for mistimed sleep than drug alternatives.
The device is being produced by local manufacturing firm SMR Components.
A Blind Circadian Clock in Cavefish Reveals that Opsins Mediate Peripheral Clock Photoreception
The circadian clock is synchronized with the day-night cycle primarily by light. Fish represent fascinating models for deciphering the light input pathway to the vertebrate clock since fish cell clocks are regulated by direct light exposure. Here we have performed a comparative, functional analysis of the circadian clock involving the zebrafish that is normally exposed to the day-night cycle and a cavefish species that has evolved in perpetual darkness. Our results reveal that the cavefish retains a food-entrainable clock that oscillates with an infradian period. Importantly, however, this clock is not regulated by light. This comparative study pinpoints the two extra-retinal photoreceptors Melanopsin (Opn4m2) and TMT-opsin as essential upstream elements of the peripheral clock light input pathway.
"Blue" Light Could Help Teenagers Combat Stress
Adolescents can be chronically sleep deprived because of their inability to fall asleep early in combination with fixed wakeup times on school days. According to the CDC, almost 70 percent of school children get insufficient sleep—less than 8 hours on school nights. This type of restricted sleep schedule has been linked with depression, behavior problems, poor performance at school, drug use, and automobile accidents. A new study from the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute shows that exposure to morning short-wavelength “blue” light has the potential to help sleep-deprived adolescents prepare for the challenges of the day and deal with stress, more so than dim light.
The study was a collaboration between Associate Professor and Director of the LRC Light and Health Program Mariana Figueiro and LRC Director and Professor Mark S. Rea. Results of the study titled “Short-Wavelength Light Enhances Cortisol Awakening Response in Sleep-Restricted Adolescents,” were recently published in the open access International Journal of Endocrinology. The full text is available at http://www.hindawi.com/journals/ije/2012/301935/.
What Drives Your Daily Biological Clock?
Researchers working with fruit flies say they have discovered one way that the body’s biological clock controls brain-cell activity that influences daily rhythms.
They believe their findings might improve understanding about sleep-wake cycles and lead to new treatments for sleep disorders and jet lag.
"The findings answer a significant question: how biological clocks drive the activity of clock neurons, which, in turn, regulate behavioral rhythms," study senior author Justin Blau, associate professor in New York University’s department of biology, said in a university news release.
Previous research with fruit flies’ “clock genes” led to the discovery of similar genes in humans, according to the news release.
It was known that biological clocks control neuronal activity, but it wasn’t known how information from biological clocks drives rhythms in the electrical activity of pacemaker neurons that control daily rhythms.
The NYU team looked at pacemaker neurons in the central brain of fruit flies that set the timing of the daily transitions between sleep and wake. They isolated these neurons and identified sets of genes with different levels of activity at dawn and dusk.
Follow-up experiments found that the activity of a gene called Ir was much higher at dusk than at dawn and that it was more active in the pacemaker neurons than in the rest of the brain. The researchers also found that increasing or decreasing levels of Ir affected behavioral rhythms and changed the timing and strength of variations in the core clock.
"We were looking for an output of the biological clock that would link the core clock to neuronal activity," Blau said. "Ir seems to do this, but it also, remarkably, feeds back to regulate the core clock itself. Feedback loops seem to be deeply engrained into the biological clock and presumably help these clocks work so well."
The study was published in the October issue of the Journal of Biological Rhythms. Researchers have noted that results from animal studies do not necessarily translate to humans.
NYU researchers find electricity in biological clock
Biologists from New York University have uncovered new ways our biological clock’s neurons use electrical activity to help keep behavioral rhythms in order. The findings, which appear in the journal Current Biology, also point to fresh directions for exploring sleep disorders and related afflictions.
“This process helps explain how our biological clocks keep such amazingly good time,” said Justin Blau, an associate professor of biology at NYU and one of the study’s authors.
Blau added that the findings may offer new pathways for exploring treatments to sleep disorders because the research highlights the parts of our biological clock that “may be particularly responsive to treatment or changes at different times of the day.”
NYU Biologists Uncover Dynamic Between Biological Clock and Neuronal Activity
Biologists at New York University have uncovered one way that biological clocks control neuronal activity—a discovery that sheds new light on sleep-wake cycles and offers potential new directions for research into therapies to address sleep disorders and jetlag.
“The findings answer a significant question—how biological clocks drive the activity of clock neurons, which, in turn, regulate behavioral rhythms,” explained Justin Blau, an associate professor in NYU’s Department of Biology and the study’s senior author.
Their findings appear in the Journal of Biological Rhythms