Posts tagged circadian rhythms
NIH study of rats shows DNA regions thought inactive highly involved in body’s clock
Long stretches of DNA once considered inert dark matter appear to be uniquely active in a part of the brain known to control the body’s 24-hour cycle, according to researchers at the National Institutes of Health.
Working with material from rat brains, the researchers found some expanses of DNA contained the information that generate biologically active molecules. The levels of these molecules rose and fell, in synchrony with 24-hour cycles of light and darkness. Activity of some of the molecules peaked at night and diminished during the day, while the remainder peaked during the day and diminished during the night.
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Filed under brain pineal gland melatonin lncRNA genomics neuroscience circadian rhythms science
New research from the Hebrew University of Jerusalem shows that a carefully scheduled high-fat diet can lead to a reduction in body weight and a unique metabolism in which ingested fats are not stored, but rather used for energy at times when no food is available.
The results were published in FASEB Journal under the title ‘Timed high-fat diet resets circadian metabolism and prevents obesity.’
Previous research has established that disrupting mammals’ daily rhythms, or feeding them a high-fat diet, disrupts metabolism and leads to obesity. The researchers wanted to determine the effect of combining a high-fat diet with long-term feeding on a fixed schedule. They hypothesized that careful scheduling of meals would regulate the biological clock and reduce the effects of a high-fat diet that, under normal circumstances, would lead to obesity.
Filed under circadian rhythms obesity weight loss nutrition neuroscience psychology brain science
Daily or “circadian” rhythms including the sleep wake cycle, and rhythms in hormone release are controlled by a molecular clock that is present in every cell of the human body. This human clock has its own inbuilt, default rhythm of almost exactly 24 hours that allows it to stay finely tuned to the daily cycle generated by the rotation of Earth. This beautiful symmetry between the human clock and the daily cycle of Earth’s rotation is disrupted by exposure to artificial light cycles, and by irregular meal, work and sleep times. This mismatch between the natural circadian rhythms of our bodies and the environment is called “circadian desynchrony.”
“Electric light allowed humans to override an ancient synchronization between the rhythm of the human clock and the environment, and over the last century, daily rhythms in meal, sleep and working times have gradually disappeared from our lives … The human clock struggles to remain tuned to our highly irregular lifestyles, and I believe that this causes metabolic and other health problems, and makes us more likely to become obese." - Dr. Cathy Wyse (Chronobiology research group, University of Aberdeen)
Filed under circadian desynchrony circadian rhythms science neuroscience brain psychology obesity
Zebrafish Study Explains Why the Circadian Rhythm Affects Your Health
The circadian rhythm is regulated by a “clock” that reacts to both incoming light and genetic factors.
In an article now being published in the scientific journal Cell Reports, it is demonstrated for the first time that disruption of the circadian rhythm immediately inhibit blood vessel growth in zebra fish embryos.
During experiments with hours-old zebra fish embryos, the researchers manipulated their circadian rhythm through exposing them to lighting conditions varying from constant darkness to constant light. The growth of blood vessels in the various groups was then studied. The results showed that exposure to constant light (1800 lux) markedly impaired blood vessel growth; additionally, it affected the expression of genes that regulate the circadian clock.
"The results can definitely be translated into clinical circumstances. Individuals with disrupted circadian rhythms — for example, shift workers who work under artificial lights at night, people with sleeping disorders or a genetic predisposition — should be on guard against illnesses associated with disrupted blood vessel growth," says Lasse Dahl Jensen, researcher in Cardiovascular Physiology at Linköping University (LiU), and lead writer of the article.
Such diseases include heart attack, stroke, chronic inflammation, and cancer. Disruptions in blood vessel growth can also affect fetal development, women’s reproductive cycles, and the healing of wounds.
Filed under blood vessels brain circadian rhythms health neuroscience psychology science diseases
A new study reveals that the brain clock itself is driven, in part, by metabolism, the production and flow of chemical energy in cells. The researchers focused primarily on a phenomenon known as “redox” in tissues of the SCN from the brains of rats and mice.
Redox represents the energy changes of cellular metabolism (usually through the transfer of electrons). When a molecule gains one or more electrons, scientists call it a reduction; when it loses electrons, they say it is oxidized. These redox reactions, the researchers found, oscillate on a 24-hour cycle in the brain clock, and literally open and close channels of communication in brain cells.
“The language of the brain is electrical; it determines what kind of signals one part of the brain sends to the other cells in its tissue, as well as the other parts of the brain nearby,” said University of Illinois cell and developmental biology professor Martha Gillette, who led the study.
“The fundamental discovery here is that there is an intrinsic oscillation in metabolism in the clock region of the brain that takes place without external intervention. And this change in metabolism determines the excitable state of that part of the brain.”
The new findings alter basic assumptions about how the brain works, Gillette said.
“Basically, the idea has always been that metabolism is serving brain function. What we’re showing is metabolism is part of brain function,” she said. “Our study implies that changes in cellular metabolic state could be a cause, rather than a result, of neuronal activity.”
Filed under brain circadian rhythms metabolism neuroscience psychology science
ScienceDaily (Aug. 1, 2012) — Scientists have known for some time that throwing off the body’s circadian rhythm can negatively affect body chemistry. In fact, workers whose sleep-wake cycles are disrupted by night shifts are more susceptible to chronic inflammatory diseases such as diabetes, obesity and cancer.
Researchers at the Salk Institute for Biological Studies have now found a possible molecular link between circadian rhythm disturbances and an increased inflammatory response. In a study published July 9 in Proceedings of the National Academy of Sciences, the Salk team found that the absence of a key circadian clock component called cryptochrome (CRY) leads to the activation of a signaling system that elevates levels of inflammatory molecules in the body.
"There is compelling evidence that low-grade, constant inflammation could be the underlying cause of chronic diseases such as diabetes, obesity and cancer," says senior author Inder Verma, a professor in Salk’s Laboratory of Genetics and the Irwin and Joan Jacobs Chair in Exemplary Life Science. "Our results strongly indicate that an arrhythmic clock system, induced by the absence of CRY proteins, alone is sufficient to increase the stress level of cells, leading to the constant expression of inflammatory proteins and causing low-grade, chronic inflammation."
Cryptochrome serves as a break to slow the circadian clock’s activity, signaling our biological systems to wind down each evening. In the morning, CRY stops inhibiting the clock’s activity, helping our physiology ramp up for the coming day.
To gain insight into the role of circadian clock components on immune function, the Salk scientists measured the expression of inflammatory mediators in the hypothalamus (the area of the brain responsible for sleep-wake cycle regulation) of mice with deleted CRY genes. Through a variety of tests, these knockout mice showed a significant increase in the expression of certain inflammatory proteins known as cytokines, including interleukin-6 and tumor necrosis factor-α, compared to mice with CRY genes.
"Our findings demonstrate that a lack of cryptochrome activates these proinflammatory molecules, indicating a potential role for cryptochrome in the regulation of inflammatory cytokine expression," says Satchidananda Panda, an associate professor in Salk’s Regulatory Biology Laboratory and one of the senior authors of the study.
In addition, the researchers found that a lack of CRY activated the NF-kB pathway, a molecular signaling conduit that controls many genes involved in inflammation. NF-kB is a protein complex in a cell’s cytoplasm, “just happily doing nothing,” says Verma. In response to stimuli, it is transferred to the cell’s nucleus, where it binds to inflammation genes and turns them on. The regulation of these genes is tightly controlled, but NF-kB does not completely shut off their expression. This lingering expression causes inflammation.
"Every time this pathway is turned on, there is a residual amount of inflammation left in the body," says Rajesh Narasimamurthy, a research associate in Verma’s laboratory and the paper’s first author. "That adds up over time, contributing to inflammation-related diseases like obesity and diabetes."
Previous research has shown that suppressing the activity of the NF-kB pathway might be a suitable therapy for some diseases. For example, NF-kB is activated automatically in cancer cells of multiple myeloma, which affects infection-fighting plasma cells in the bone marrow and allows the cells to proliferate. Drugs that inhibit this activity might be able to degrade NF-kB to the point that it may kill off the disease.
The researchers say the goal now is to find out how to suppress NF-kB activation in the short term to treat diseases like diabetes. They caution that any long-term suppression of the pathway could lead to chronic infection. “We would like to find molecules that modify this activity and focus on those small-molecule inhibitors to treat disease,” Verma adds.
Source: Science Daily
Filed under CRY NF-kB circadian rhythms cryptochrome diabetes disease inflammatory diseases neuroscience obesity science protein
Neuroscientist keeps astronauts awake with ISS lighting tweaks
A neuroscientist is working with Nasa to develop special lamps that could help restore the circadian rhythm of exhausted astronauts working aboard the International Space Station (ISS).
Thomas Jefferson University neuroscientist George C Brainard, who has headed up the university’s Light Research Program since 1984, received approval for the lights in early 2012 and 100 of the LED models are due to be sent to Nasa by mid-2015. The lights have three different colour temperatures to help ease the astronauts into morning, nighttime and normal working mode.
"An astronaut here on Earth experiences a 24-hour day/night cycle just like you and I," explained Brainard. "Now when they’re on the space station, they’re circling the planet every 90 minutes. So they’ve gone from a 24-hour day to a 90-minute day."
Filed under LED bulbs NASA circadian rhythms mood neuroscience performance science sleep space astronauts
July 12, 2012
Biologists at UC San Diego have discovered a chemical that offers a completely new and promising direction for the development of drugs to treat metabolic disorders such as type 2 diabetes—a major public health concern in the United States due to the current obesity epidemic.
Their discovery, detailed in a paper published July 13 in an advance online issue of the journal Science, initially came as a surprise because the chemical they isolated does not directly control glucose production in the liver, but instead affects the activity of a key protein that regulates the internal mechanisms of our daily night and day activities, which scientists call our circadian rhythm or biological clock.
Scientists had long suspected that diabetes and obesity could be linked to problems in the biological clock. Laboratory mice with altered biological clocks, for example, often become obese and develop diabetes. Two years ago, a team headed by Steve Kay, dean of the Division of Biological Sciences at UC San Diego, discovered the first biochemical link between the biological clock and diabetes. It found that a key protein, cryptochrome, that regulates the biological clocks of plants, insects and mammals also regulates glucose production in the liver and that altering the levels of this protein could improve the health of diabetic mice.
Now Kay and his team have discovered a small molecule—one that can be easily developed into a drug—that controls the intricate molecular cogs or timekeeping mechanisms of cryptochrome in such a manner that it can repress the production of glucose by the liver. Like mice and other animals, humans have evolved biochemical mechanisms to keep a steady supply of glucose flowing to the brain at night, when we’re not eating or otherwise active.
"At the end of the night, our hormones signal that we’re in a fasting state," said Kay. "And during the day, when we’re active, our biological clock shuts down those fasting signals that tell our liver to make more glucose because that’s when we’re eating."
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Filed under science neuroscience brain psychology circadian rhythms diabetes cryptochrome
