A study in mice suggests that a drug that can turn fat into brown could help fight obesity

Our body contains two types of fat: white fat and brown fat. If white fat stores calories, brown fat burns energy and could help us lose weight. Scientists at the University of Cambridge have found a way to make white fat "browner" and increase its effectiveness.

Although their study was conducted on mice, they hope that this discovery will result in humans and will provide a potential new drug to help fight obesity.

Obesity is a condition in which individuals accumulate more and more fat until their fat stops functioning. This can lead to diseases such as diabetes. However, not all fat tissue is bad: the fat that accumulates in obesity is called "white fat", but a second form of fat called "brown fat" could be used to treat the condition. 39; obesity.

Brown fat and white fat consist of fat cells called adipocytes, but in brown fat, these cells are rich in mitochondria – the "batteries" that feed our bodies – which give the tissue its brown color. The brown fat also contains more blood vessels to allow the body to provide it with oxygen and nutrients.

While white fat contains energy, brown fat burns it in a process called "thermogenesis". When it is fully activated, only 100 g of brown fat can burn 3,400 calories a day – which is significantly higher than most people 's daily food intake and enough to fight against. obesity.

We all have brown fat – or brown adipose tissue, as we call it – in our body, but it is found more abundantly in newborns and hibernating animals (where the heat produced by the brown fat allows them to survive even in cold weather.). As we age, the amount of brown fat in our body decreases.

It is not enough to have more brown fat, you must also activate the tissue. Currently, the only way to activate brown fat is to put people in the cold to mimic hibernation, which is both inconvenient and unpleasant, or to treat them with drugs called adrenergic agonists , which can cause heart attacks. It is also necessary to increase the number of blood vessels in the tissues to route the nutrients to the fat cells and the number of nerve cells to allow the brain to "turn on" the tissues.

In 2012, a team led by Professor Toni Vidal-Puig of the Wellcome Trust-MRC Metabolic Sciences Institute at the University of Cambridge identified a molecule called BMP8b that regulates fat activation. brown in the tissues of the brain and brain. They showed that suppressing the gene in mice producing this protein prevented brown fat from functioning.

Now in a study published today in the newspaper Nature CommunicationsProfessor Vidal-Puig led an international team of researchers that showed that increasing the amount of BMP8b mice that can produce increases the function of their brown fat. This implies that BMP8b, present in the blood, could potentially be used as a medicine to increase the amount of brown fat in humans, while making it more active. Further research will be needed to demonstrate if this is the case.

To carry out their research, the team used mice bred to produce higher levels of protein in adipose tissue. As expected, they found that increasing BMP8b levels turned some of the white fat into brown fat, a process known as beiging and thus increased the amount of energy burned by the tissues.

They showed that higher levels of BMP8b make the tissue more sensitive to adrenergic nerve signals – the same pathway as agonist adrenergic drugs. This may allow the use of lower doses of these drugs to activate brown fat in people, thus reducing their risk of heart attack.

Unexpectedly, but importantly, the team also discovered that the molecule increased the amount of blood vessels and nerves in the brown fat.

"Many studies have found molecules that promote the development of brown fat, but it is not enough to increase the amount of brown fat to treat diseases – it must be possible to get enough nutrients and be turned on," says Professor Vidal-Puig, lead author of the study.

Co-author Sam Virtue, also from the Institute of Metabolic Science, adds, "It's like taking a one-liter engine out of a car and keeping a two-liter engine at your disposal. square. In theory, the car can go faster, but if you only have a tiny fuel hose to the engine and you do not connect the accelerator pedal, it will not do much of well. The BMP8b increases the size of the engine, and installs a new fuel line and connects the throttle! "

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More information:
Vanessa Pellegrinelli et al. BMP8b secreted by adipocytes intervenes in the adrenergic-induced remodeling of the neurovascular network in adipose tissue, Nature Communications (2018). DOI: 10.1038 / s41467-018-07453-x