ScienceDaily (Apr. 6, 2010) — Performance of an hour or more of physical activity per day by adolescents is associated with control of body weight even among those who are genetically predisposed to obesity, according to a report in the April issue of Archives of Pediatrics & Adolescent Medicine, one of the JAMA/Archives journals.
"There is compelling evidence that human obesity is a multifactorial disorder where both genes and lifestyle factors, including diet and physical activity, are important contributors," the authors write as background information in the article. "Among the obesity-related genes, polymorphisms in the fat mass- and obesity-associated gene (FTO) are strongly associated with body fat estimates in populations of different ethnic background or ages." Each copy of a mutation in this gene may be associated with a weight increase of approximately 1.5 kilograms or 3.3 pounds.
The U.S. Department of Health and Human Services recently released updated guidelines recommending that children and adolescents participate in physical activity for 60 minutes per day or longer, with most exercise being of moderate to vigorous intensity. To see if this level of physical activity reduces the effects of mutations in the FTO gene on body fat, Jonatan R. Ruiz, Ph.D., of the Karolinska Institutet, Huddinge, Sweden, and colleagues studied 752 adolescents who were part of a cross-sectional study in 10 European countries between October 2006 and December 2007.
Of the participating teens, 275 (37 percent) had no copies of the obesity mutation, 354 (47 percent) had one copy and 123 (16 percent) had two copies. The mutation was associated with a higher body mass index (BMI), higher body fat percentage and a larger waist circumference.
However, among participants who met the daily physical activity recommendations, the effect of the gene mutation was much lower. For each copy of the mutated gene, those who exercised as recommended had a BMI an average of 0.17 higher than those with no mutations, compared with 0.65 higher per mutation among those who did not meet exercise requirements. Similarly, each mutated gene was associated with an increase of 0.4 percent in body fat and a 0.6-centimeter increase in waist circumference among those who met activity guidelines, compared with a 1.7 percent increase in body fat and a 1.15 centimeter increase in waist circumference among those who did not.
"These findings have important public health implications and indicate that meeting the physical activity recommendations may offset the genetic predisposition to obesity associated with the FTO polymorphism in adolescents," the authors write. "Indeed, adolescents meeting the daily physical activity recommendations may overcome the effect of this gene on obesity-related traits."
Source: http://newscri.be/link/1066000
Thursday, 8 April 2010
Depression Associated With Sustained Brain Signals: Genetic Mutation in Mice Elevates Their Risk of Stress-Induced Depression
ScienceDaily (Apr. 6, 2010) — Depression and schizophrenia can be triggered by environmental stimuli and often occur in response to stressful life events. However, some people have a higher predisposition to develop these diseases, which highlights a role for genetics in determining a person's disease risk.
A high number of people with depression have a genetic change that alters a protein that cells use to talk to each other in the brain. Imaging of people with depression also shows that they have greater activity in some areas of their brain. Unfortunately, the techniques that are currently available have not been able to determine why stress induces pathological changes for some people and how their genetics contribute to disease.
A new mouse model may provide some clues about what makes some people more likely to develop depression after experiencing stress. A collaborative group of European researchers created a mouse that carries a genetic change associated with depression in people. "This model has good validity for understanding depression in the human, in particularly in cases of stress-induced depression, which is a fairly widespread phenomenon" says Dr. Alessandro Bartolomucci, the first author of the research published in the journal, Disease Models and Mechanisms (DMM).
The scientists made genetic changes in the transporter that moves a signaling protein, serotonin, out of the communication space between neurons in the brain. The changes they made are reminiscent of the genetic changes found in people who have a high risk of developing depression.
"There is a clear relationship between a short form of the serotonin transporter and a very high vulnerability to develop clinical depression when people are exposed to increasing levels of stressful life events." says Dr. Bartolomucci, "This is one of the first studies performed in mice that only have about 50% of the normal activity of the transporter relative to normal mice, which is exactly the situation that is present in humans with high vulnerability to depression."
Mice with the genetic change were more likely to develop characteristics of depression and social anxiety, which researchers measure by their degree of activity and their response to meeting new mice. The work from this study now allows researchers to link the genetic changes that are present in humans with decreased serotonin turnover in the brain. It suggests that the genetic mutation impedes the removal of signaling protein from communication areas in the brain, which may result in an exaggerated response to stress.
Dr. Bartolomucci points out that many of the chemical changes they measured occurred in the areas of the brain that regulate memory formation, emotional responses to stimuli and social interactions, which might be expected. "What we were surprised by was the magnitude of vulnerability that we observed in mice with the genetic mutation and the selectivity of its effects."
Source: http://newscri.be/
A high number of people with depression have a genetic change that alters a protein that cells use to talk to each other in the brain. Imaging of people with depression also shows that they have greater activity in some areas of their brain. Unfortunately, the techniques that are currently available have not been able to determine why stress induces pathological changes for some people and how their genetics contribute to disease.
A new mouse model may provide some clues about what makes some people more likely to develop depression after experiencing stress. A collaborative group of European researchers created a mouse that carries a genetic change associated with depression in people. "This model has good validity for understanding depression in the human, in particularly in cases of stress-induced depression, which is a fairly widespread phenomenon" says Dr. Alessandro Bartolomucci, the first author of the research published in the journal, Disease Models and Mechanisms (DMM).
The scientists made genetic changes in the transporter that moves a signaling protein, serotonin, out of the communication space between neurons in the brain. The changes they made are reminiscent of the genetic changes found in people who have a high risk of developing depression.
"There is a clear relationship between a short form of the serotonin transporter and a very high vulnerability to develop clinical depression when people are exposed to increasing levels of stressful life events." says Dr. Bartolomucci, "This is one of the first studies performed in mice that only have about 50% of the normal activity of the transporter relative to normal mice, which is exactly the situation that is present in humans with high vulnerability to depression."
Mice with the genetic change were more likely to develop characteristics of depression and social anxiety, which researchers measure by their degree of activity and their response to meeting new mice. The work from this study now allows researchers to link the genetic changes that are present in humans with decreased serotonin turnover in the brain. It suggests that the genetic mutation impedes the removal of signaling protein from communication areas in the brain, which may result in an exaggerated response to stress.
Dr. Bartolomucci points out that many of the chemical changes they measured occurred in the areas of the brain that regulate memory formation, emotional responses to stimuli and social interactions, which might be expected. "What we were surprised by was the magnitude of vulnerability that we observed in mice with the genetic mutation and the selectivity of its effects."
Source: http://newscri.be/
Wednesday, 7 April 2010
Pigeon Flocks Let the Best Bird Lead
Even the bird-brained can follow a leader. When pigeons fly in flocks, each bird falls behind another with better navigational skill, and the savviest among them leads the flock, scientists report in the April 8 Nature.
The research suggests hierarchies can serve peaceful purposes in the animal kingdom, where dominance by brute force is often the rule. “A pecking order tends to be just that — a pecking order,” says Iain Couzin of Princeton University, an expert in collective behavior who was not involved in the research.
The research also suggests that for pigeons, dominance isn’t set in stone. While one bird often emerged as the leader, other birds also stepped up. This flexibility in leadership had previously been seen only in some small groups of fish.
From schools to packs to swarms to flocks, collective behavior is widespread among animals. But in many cases, the important interactions are with nearest neighbors, and control of the group’s movement is distributed among members rather than hierarchical.
Biological physicist Tamás Vicsek of Eötvös Loránd University in Budapest and his colleagues studied flight dynamics in homing pigeons, which fly in flocks but conveniently return to their roosts. The researchers outfitted 13 pigeons with tiny backpacks carrying GPS devices that measured shifts in birds’ flight direction five times per second. Flocks of eight to 10 birds flew with the devices during homing flights (a roughly 14-kilometer trip back to the roost) and spontaneous “free” flights near home. Each bird also flew solo flights of about 15 kilometers each.
Analysis of GPS logs showed that for each excursion, the flock had one leader followed by at least three or four other birds. Each of these followers was in turn followed by other birds in the flock. Comparing the solo flight paths to the group flights showed that the birds with the best navigational skills led the flock.
While flocks have hierarchies, they’re not dictatorships, notes Vicsek. One bird led eight of the 13 flights, while other birds took the lead on the rest of the trips. Vicsek likens the dynamics to a group of peers deciding where to eat dinner. “Maybe someone knows the area restaurants best, or there is a person who’s a gourmand — or maybe they are the most outspoken,” he says. This one person might pick the place to eat for several nights, although another person might chime in now and then. And then there is the person with no say, whom everyone knows has terrible taste in food.
“These pigeons know each other. They know which is the smartest. The fastest bird will even follow the slower one who knows the way home the best,” say Vicsek. Videos of the birds’ positions during flight showed that if the best navigator moves a little to the left, it takes about a third of a second for other birds to do the same. But if the least savvy bird makes a move “the others don’t care,” Vicsek says.
Pigeons’ brains may be wired for follow-the-leader, comments behavioral neuroscientist Lucia Jacobs of the University of California, Berkeley. When the left eye sees something, for example, it sends all the visual information to the right brain hemisphere, and vice versa. This “extreme lateralization” may play a role in organizing flocks, the new work suggests. A pigeon following another was most likely to be flying on its partner’s right, seeing this leader with its left eye. “It’s very cool,” Jacobs says.
Images: Zsuzsa Ákos,
http://newscri.be/link/1065733
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