Friday, August 22, 2008
The role of BMP-7 in Obesity
This from the Telegraph:
The promise of turning a beer gut into a six-pack has been raised from two studies into the link between fat and muscle.
But they say only the body's 'good' fat which we are born with can be transformed, and not the 'bad' fat created by over-eating and not exercising enough.
In two related studies published today in the journal Nature, scientists identify the factors that regulate fat formation and, most important, control the type of fat.
Although we all wish we had a little less of it, fat is essential for managing our energy balance and helping to regulate body temperature.
But there are two distinct types of fat tissue: white 'bad' fat acts as an energy store whereas brown 'good' fat, which largely disappears by adulthood, also helps in burning calories to generate body heat, which is crucial to keep babies warm.
Now one team has shown how to promote the manufacture of "good" brown fat, so we can burn more calories, while a second team, also working nearby on the US east coast in Boston, has shown how brown fat and muscle are linked, suggesting ways to interconvert the two. Both offer a new strategy to fight flab.
In the first study, Dr Yu-Hua Tseng and her colleagues at the Joslin Diabetes Centre, Harvard Medical School, identified one factor - bone morphogenetic protein 7 (BMP7) - that promotes brown fat development, after using gene therapy to introduce the protein into mice.
"Obesity is occurring at epidemic rates," comments Dr Yu-Hua Tseng. "We hope this study can be translated into applications to help treat or prevent obesity," though she stresses that "diet and exercise are still the best approaches for weight reduction in the general population."
he new work opens up the way for drugs to mimic the effects of BMP-7 and "may provide hope to these individuals in losing weight and preventing the metabolic disorders associated with obesity," she said, referring to the well known link between type two diabetes and obesity.
In the second Nature study, Prof Bruce Spiegelman and colleagues at the Dana-Farber Cancer Institute, Boston, show that the two types of fat develop from distinct cell types in the early embryo. They found a factor, called PRDM16, that regulates the switch between muscle and fat.
Knocking out PRDM16 in brown fat cells can convert them into muscle cells and they say that finding drugs to do this "could be powerful" when it comes to fighting obesity.
The confirmation will spur ongoing research with Dr Patrick Seale in his laboratory, he said, to see if drugs that rev up PRDM16 in mice -- and potentially, in people -- could convert white fat into brown fat and thereby treat obesity.
Another strategy, he said, might be to transplant brown fat cells into an overweight person to turn on the calorie-burning process. "I think we now have very convincing evidence that PRDM16 can turn cells into brown fat cells, with the possibility of combating obesity,"
Intriguingly, the link between brown fat and muscle has been known for centuries.
In 1551, when the Swiss naturalist Konrad Gessner first described brown adipose tissue, he stated that on examination it struck him it was "neither fat, nor flesh [nec pinguitudo, nec caro] - but something in between".
The new work shows that brown fat is more flesh-like than previously suspected.
These cells are brown because they are rich in energy burning structures called mitochondria. The new work makes sense of earlier research findings, such as the discovery that many proteins found in brown fat cells are more similar to those found in muscle than in white fat.
Health Survey for England data revealed that in 2006, 38 per cent of adults in England were overweight and 24 per cent were classified as obese.
Another report, Foresight: Tackling Obesities: Future Choices published last year, predicts that if no action is taken, by 2050, 60 per cent of men and 50 per cent of women and 25 per cent of children will be obese.