10.15.08
Posted in Biology at the University of Virginia, Body Clock, Jacob Canon, Nocturnin, Sleep, The Oscar Show, UVa College of Arts & Sciences, University of Virginia, biology, circadian rhythms, metabolism, nervous system, neurophysiology, physical health, physiology, sensory inputs, stress, visual processing at 11:04 am by Jacob Canon
In today’s show, adapted from an article written by Fariss Samarrai, Senior News Officer for the Office of Public Affairs, we will look at a team of UVa researchers who have discovered a switching mechanism in the eye that plays a key role in regulating the sleep/wake cycles in mammals.
Biologists at the University of Virginia have discovered a switching mechanism in the eye that plays a key role in regulating the sleep/wake cycles in mammals. The new finding demonstrates that light receptor cells in the eye are central to setting the rhythms of the brain’s primary timekeeper, the suprachiasmatic nuclei, which regulates activity and rest cycles. The finding appears in the current issue of the Proceedings of the National Academy of Sciences.
Susan Doyle, a research scientist at U.Va. and the study’s lead investigator said, “The finding is significant because it changes our understanding of how light input from the eye can affect activity and sleep patterns.”
Eyeing the Biological Clock [4:46m]:
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Funded by the National Institute of Mental Health, Doyle conducted her research with colleagues Tomoko Yoshikawa, a visiting scholar from Japan, and UVa undergraduate student Holly Hillson, in the laboratory of Michael Menaker, a leading researcher in the study of circadian rhythms.
Biological clocks are the body’s complex network of internal oscillators that regulate daily activity/rest cycles and other important aspects of physiology, including body temperature, heart rate and food intake.
The investigators did this by both reducing the intensity of light given to normal mice and also creating a mutated line of mice with reduced light sensitivity in their eyes, which rendered them fully active in the day but inactive at night, a complete reversal of the normal activity/rest cycles of mice.
The researchers discovered that they could reverse the “temporal niche” of mice—meaning that the animals’ activity phase could be switched from their normal nocturnality, or night activity, to being diurnal, or day active.
Doyle said, “This suggests that we have discovered an additional mechanism for regulating nocturnity and diurnity that is located in the light input pathways of the eye. The significance of this research for humans is that it could ultimately lead to new treatments for sleep disorders, perhaps even eye drops that would target neural pathways to the brain’s central timekeeper.”
An estimated one in six people in the United States suffer from sleep disorders, including insomnia and excessive sleepiness. And as the U.S. population ages, a growing number of people are developing visual impairments that can result in sleep disorders.
Besides sleep disorders, research in this field may eventually help treat the negative effects of shift work, aging and jet lag. Doyle said, “Currently, one in 28 Americans age 40 and over suffer from blindness or low vision, and this number is estimated to double in the next 15 years. Our discovery of the switching mechanism in the eye has direct relevance with respect to the eventual development of therapies to treat circadian and sleep disorders in the visually impaired.”
You’ve been listening to the Oscar Show, I’m Jacob Canon. Join us next week when we look at the University of Virginia’s Kath Weston and the journey that led to her new book, Traveling Light: On the Road with America’s Poor.
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01.09.08
Posted in Biology at the University of Virginia, Body Clock, Nocturnin, The Oscar Show, UVa College of Arts & Sciences, University of Virginia, biology, circadian rhythms, evolution, hypothalamus, metabolism, physical health at 12:15 pm by Jacob Canon
In today’s show, adapted from an article published on the Oscar web site written by Fariss Samarrai, we discuss the research of Carla Green, associate professor of biology at the University of Virginia, and a study she headed which says that the gene Nocturnin, working within the network of the body’s circadian clock, appears to be particularly important in the control of metabolism.
The body’s biological clock has been shown to regulate life’s activity/rest cycles by controlling energy levels, alertness, growth, moods and the effects of aging. Further study has revealed that these internal clocks are controlled by circadian rhythms. Rhythms that were established early in the history of life on the planet and evolved associated with the astronomical cycles that effect Earth’s environment such as the rise and setting of the sun and the passing of seasons. What is now being discovered is that certain elements, already known to be part of the body’s circadian network, may have a broader influence on the life of an individual.
In a study published in the journal, Proceedings of the National Academy of Sciences, Associate Professor of Biology at the University of Virginia Carla Green and her colleagues discovered that the gene Nocturnin, which participates in the regulation of the body’s biological rhythms, may also be a major control in regulating metabolism. The study showed that mice lacking the gene were resistant to weight gain when put on a high fat diet and also were resistant to the accumulation of fat in the liver.
Professor Green, said, “It’s been known for some time that there are many links between the circadian clock and various aspects of physiology and metabolism. This study suggests that Nocturnin is part of the network that the circadian clock uses to control important aspects of metabolism.”
In the study, Green and her colleagues, Nicholas Douris, a U.Va. graduate student who designed the study, U.Va. post-doctoral fellow Shihoko Kojima and Joseph Besharse of the Medical College of Wisconsin, used regular mice and genetically altered mice in which the Nocturnin gene was not present. The Nocturnin-deficient mice were divided into two groups; one group fed a normal diet, the other a very high fat diet. A group of normal mice were also fed a high fat diet.
The researchers found that both groups of genetically altered mice maintained normal weight and activity levels, and, of particular interest, the ones fed the high fat diet exhibited only slight weight gains, even over long periods of time. However, the normal mice on the high fat diet ballooned, gaining more than twice the weight of the Nocturnin-deficient mice. And, when the mice were dissected, the researchers found that the normal mice had, as expected, large concentrations of fat in their livers, whereas the altered mice had normal levels of fat.
Green said, “We were quite amazed at what we found. We thought that over time, as we continued to feed the mutant mice the high fat diet that they would eventually gain weight at some expected rate, but it never happened. These mice continued to stay slim while the normal mice nearly doubled in weight and developed fatty livers.”
Clock genes in the body’s organs operate in conjunction with a central time keeper in the brain, the hypothalamic suprachiasmatic nucleus, but also work somewhat independently, resulting in a complex system of oscillators regulating various functions of the body. Scientists are working to better understand how the genes and proteins of the circadian clock in mammals affect not only activity cycles but also rates of metabolism, which are tied to feeding cycles. Green said it is possible that, “A better understanding of Nocturnin’s function could eventually lead to medical treatments that could counteract the problems of obesity, which has become a major issue in modern society.”
We look forward to the continued study of this important new finding in the hope that its potentially far reaching health benefits will be realized in our lifetime.
You’ve been listening to the Oscar Show… I’m Jacob Canon. Join us next week when our topic will be UVa professor and chair of biomedical engineering Thomas Skalak and his efforts to develop real scientific evidence about the effectiveness of magnetic therapy.
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