Posts Tagged "Genetics"

obesity1Investigators working to unravel the impact of genetics versus environment on traits such as obesity may also need to consider a new factor: when individuals were born.

In the current issue of PNAS Early Edition a multi-institutional research team reports finding that the impact of a variant in the FTO gene that previous research has linked to obesity risk largely depends on birth year, with no correlation between gene variant and obesity in study participants born in earlier years and a far stronger correlation than previously reported for those born in later years.

“Looking at participants in the Framingham Heart Study, we found that the correlation between the best known obesity-obesity 2associated gene variant and body mass index increased significantly as the year of birth of participants increased,” says Harvard Medical School instructor James Niels Rosenquist of the Massachusetts General Hospital (MGH) Department of Psychiatry, lead author of the report. “These results — to our knowledge the first of their kind — suggest that this and perhaps other correlations between gene variants and physical traits may vary significantly depending on when individuals were born, even for those born into the same families.”

obesity 3The authors note that most studies of interactions between genes and the environment have looked at differences within specific birth cohorts —groups born during a particular span of years — which would not account for changes in the larger environment that take place over time. To investigate whether different conditions experienced by different age groups might alter the impact of a gene variant, they analyzed data from participants in the Framingham Offspring Study (which follows the children of participants in the original study) gathered between 1971, when participants ranged in age from 27 to 63, and 2008.

Source: Harvard Gazette

*The Presidential Healthcare Center can design a personalized exercise prescription for you.

Coffee 1A new, large-scale study has identified six new genetic variants associated with habitual coffee drinking. The genome-wide meta-analysis, led by Harvard School of Public Health and Brigham and Women’s Hospital researchers, helps explain why a given amount of coffee or caffeine has different effects on different people and provides a genetic basis for future research exploring the links between coffee and health.

“Coffee and caffeine have been linked to beneficial and adverse health effects. Our findings may allow us to identify subgroups of people most likely to benefit from increasing or decreasing coffee consumption for optimal health,” said Marilyn Cornelis, research associate in the Department of Nutrition at Harvard School of Public Health and lead author of the study.

Genetics have long been suspected of contributing to individual differences in response to coffee and caffeine. However, pinpointing the specific genetic variants has been challenging.Coffee 3

The researchers, part of the Coffee and Caffeine Genetics Consortium, conducted a genome-wide meta-analysis of more than 120,000 regular coffee drinkers of European and African American ancestry. They identified two variants that mapped to genes involved in caffeine metabolism, POR and ABCG2 (two others, AHR and CYP1A2 had been identified previously). Two variants were identified near genes BDNF and SLC6A4 that potentially influence the rewarding effects of caffeine. Two others—near GCKR and MLXIPL, genes involved in glucose and lipid metabolism—had not previously been linked to the metabolism or neurological effects of coffee.

The findings suggest that people naturally modulate their coffee intake to experience the optimal effects exerted by caffeine and that the strongest genetic factors linked to increased coffee intake likely work by directly increasing caffeine metabolism.

coffee 2“The new candidate genes are not the ones we have focused on in the past, so this is an important step forward in coffee research,” said Cornelis.

“Like previous genetic analyses of smoking and alcohol consumption, this research serves as an example of how genetics can influence some types of habitual behavior,” said Daniel Chasman, associate professor at Brigham and Women’s Hospital and the study’s senior author.

Source: (Harvard School of Public Health)

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It’s possible that some of us are born not to run. According to an eye-opening new genetics study of lab rats, published in The Journal of Physiology, the motivation to exercise — or not — may be at least partly inherited.

For years, scientists have been bedeviled by the question of why so few people regularly exercise when we know that we should. There are obvious reasons, including poor health and jammed schedules. But researchers have begun to speculate that genetics might also play a role, as some recent experiments suggest. In one, published last year, sets of fraternal and identical adult twins wore activity monitors to track their movements. The results indicated that the twins were more alike in their exercise habits than a shared upbringing alone would explain. Their willingness to work out or sit all day depended to a large extent on genetics, the researchers concluded.

But which genes might be involved and how any differences in the activity of those genes might play out inside the body were mysteries. So scientists at the University of Missouri recently decided to delve into those issues by creating their own avid- or anti-exercising animals.

They accomplished this task by inter-breeding normal rats that had voluntarily run on wheels in the lab. The male rats that had run the most were bred with the female rats that also had run the most; those that had run the least were likewise mated. This scheme continued through many generations, until the scientists had two distinct groups of rats, some of which would willingly spend hours on running wheels, while the others would skitter on them only briefly, if at all.

In their first experiments with these rats, the researchers found some intriguing differences in the activity of certain genes in their brains. In normal circumstances, these genes create proteins that tell young cells to grow up and join the working world. But if the genes don’t function normally, the cells don’t receive the necessary chemical messages and remain in a prolonged, feckless cellular adolescence. Such immature cells cannot join the neural network and don’t contribute to healthy brain function.

In general, these genes worked normally in the brains of the rats bred to run. But their expression was quite different in the non-runners’ brains, particularly in a portion of the brain called the nucleus accumbens, which is involved in reward processing. In humans and many animals, the nucleus accumbens lights up when we engage in activities that we enjoy and seek out.

Presumably as a result, when the scientists closely examined the brains of the two types of rats, they found that by young adulthood the animals bred to run had more mature neurons in the nucleus accumbus than did the non-runners, even if neither group had actually done much running. In practical terms, that finding would seem to indicate that the brains of pups born to the running line are innately primed to find running rewarding; all those mature neurons in the reward center of the brain could be expected to fire robustly in response to exercise.

Conversely, the rats from the reluctant-running line, with their skimpier complement of mature neurons, would presumably have a weaker innate motivation to move.

Those results would be disheartening, except that in the final portion of the experiment the scientists had reluctant runners exercise by setting them on running wheels, while also providing some born-to-run animals with wheels. After six days, the unwilling runners had accumulated far less mileage, about 3.5 kilometers (two miles) per rat, compared to almost 34 kilometers each by the enthusiasts.

But the halfhearted runners’ brains were changing. Compared to others in their family line that had remained sedentary, they now showed more mature neurons in their nucleus accumbens. That part of their brain remained less well developed than among the naturally avid rat runners, but they were responding to exercise in ways that would seem likely to make it more rewarding.

What, if anything, these findings mean for people is “impossible to know at this point,” said Frank Booth, a professor of biomedical sciences at the University of Missouri who oversaw the study. Rat brains are not human brains, and rat motivations are at best opaque.

Even so, Dr. Booth said, his group’s data would seem to suggest “that humans may have genes for motivation to exercise and other genes for motivation to sit on the couch,” and over generations, one set of these genes could begin to predominate within a family. But predispositions are never dictatorial.

“People can decide to exercise,” whatever their inheritance, Dr. Booth said, and, as his study’s final experiment suggests, they could rewire their brains so that moving becomes a pleasure.

Source: New York Times

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