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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12.06.07
Posted in Biology at the University of Virginia, Gaesser, Jacob Canon, The Oscar Show, UVa College of Arts & Sciences, University of Virginia, biology, kinesiology, metabolism, physiology, stress at 1:10 pm by Jacob Canon
In today’s show we will discuss the research of UVa professor of exercise physiology Glenn Gaesser and his findings on what has come to be termed “BAD CARBS.”
With the holiday season upon us, traditional meals are a big part of the celebration. Meat, vegetables and breads are a big part of these feasts. Breads and other sources of carbohydrates have become a big concern for individuals worried about their weight and health. The latest common wisdom on carbohydrates claims that eating so-called “bad carbs” will make you fat. But University of Virginia professor Glenn Gaesser, professor of exercise physiology and director of the kinesiology program in the Curry School of Education says, “that’s just nonsense. Eating sandwiches with white bread, or an occasional doughnut, isn’t going to kill you, or necessarily even lead to obesity.”
A popular speaker, Gaesser has lectured on the subject of fitness, body weight and health at numerous national and international meetings and has appeared on dozens of radio and TV shows in North America. In an article in the October issue of the Journal of the American Dietetic Association, Gaesser analyzed peer-reviewed, scientific research on carbohydrate consumption, glycemic index and body weight. In this article he gives the first detailed review of the literature on the correlation between them. His findings run counter to the current consensus on the effects of “good” and “bad” carbs.
Gaesser, author of “It’s the Calories, Not the Carbs” and other books, found that diets high in carbohydrates are almost universally associated with slimmer bodies. More importantly, Gaesser found that consuming lots of high-glycemic foods is not associated with higher body weights. In fact, several large studies in the United States revealed that high-glycemic diets were linked to better weight control. “There is no reason to be eating fewer carbs — they’re not the enemy,” says Gaesser.
The description of carbohydrates as “good” or “bad” is based on glycemic index, a measure of the quality of the carbohydrate in terms of how much it raises blood sugar. Foods having a high GI are generally thought to be “bad” because they raise blood sugar more than “good” carbs do. Proponents of the glycemic index claim that this leads to excessive insulin secretion, which can cause weight gain and health problems. Foods such as whole-grain breads are said to offer “good” carbs, because they have a lower GI than white bread, for example. Likewise, a glass of pineapple juice has a high GI compared to apple juice. Several popular low-carb diets use glycemic index as a key feature for optimum weight control, but it is not a reliable description of carbohydrate quality, Gaesser says. Digestion is a complicated process. It’s very difficult to determine the GI of a whole meal, for instance, so it doesn’t really make sense to use GI or “glycemic load” — the glycemic index multiplied by the quantity ingested — as a guide to eating.
After looking at hundreds of articles on large-scale studies using surveys or randomized, controlled trials, Gaesser says they show that “people who consume high-carb diets tend to be slimmer, and often healthier, than people who consume low-carb diets.” Even high-glycemic foods have a place in the diet, he said, attributing that to the overall higher quality of a high-carb diet, which includes more fiber-rich and other nutritional foods.
Gaesser also looked for a clear association between carbohydrate consumption and illnesses, such as type 2 diabetes, heart disease and cancer. He found no compelling evidence that avoiding carbohydrates with a high GI helps prevent these diseases and others.Gaesser said, “People with diabetes, as well as very sedentary women who are obese, may benefit from lowering their consumption of foods with a high GI. Reducing any part of the diet — carbs, proteins or fats — will result in modest weight loss in the short term, if calorie consumption is reduced, he points out. But for long-term weight maintenance, a high-carb, low-fat diet is still the best bet.”
You’ve been listening to the Oscar Show… I’m Jacob Canon. Join us next week when our topic will be the research of UVa biology professor DeForest Mellon and his work concerning how the brain detects, integrates and uses co-joined yet dissimilar sensory inputs.
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