Scientists have brought some good news for the obese, that brown adipose tissue is capable of burning fat.
The researchers found that unlike white fat pads, brown tissue contains loads of mitochondria, miniature power stations, which among other things can burn up fat.
In doing this, they normally generate a voltage similar to that of a battery, which then provides energy for cellular processes.
However, the mitochondria of brown fat cells have a short circuit. They go full steam ahead all the time. The energy released when the fat is broken down is released as heat.
"This is actually what is intended. Brown fat acts like a natural heating system," said Professor Alexander Pfeifer from the Bonn PharmaCentre.
For example, babies would get cold very quickly without this mechanism.
Until now, it was thought that brown fat only occurred in newborn babies and was lost with age.
However, now researchers could show that even adults have a deposit of brown fat in the neck area.
But with very overweight people this deposit is only moderately active or is completely absent.
The scientists from Bonn, Heidelberg, Cologne, Martinsried and the Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM, now revealed that a signalling pathway which is controlled by the PKG enzyme takes on a key role in this process.
This signalling pathway results in the stem cells of the fatty tissue becoming brown fat cells.
For this, it switches on the mass production of mitochondria and ensures that UCP is formed, the substance that creates the short circuit.
"Furthermore, we were able to show that PKG makes brown fat cells susceptible to insulin. Therefore PKG also controls how much fat is burnt in general," explained Alexander Pfeifer.
The researchers suspect that a disorder of the brown fatty tissue can lead to obesity in adults.
If it were possible to turn on the 'natural heating system' on again, the problem of unwanted fat would be quickly solved.
It has been estimated that 50 grams of active brown fatty tissue is sufficient for increasing the basal metabolic rate by 20 per cent.
"With the same nutrition and activity the fat reserves would melt at a rate of five kilos per year. This makes our results interesting from a therapeutic perspective. By blocking the PKG signalling path in the brown fat we basically want to fight fat with fat," explained Pfeifer.