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University of Cambridge scientists in brown fat breakthrough


By Paul Brackley


Our bodies contain white and brown fat but it's the white fat that is responsible for obesity (5725269)
Our bodies contain white and brown fat but it's the white fat that is responsible for obesity (5725269)

Not all fat is equal.

In fact, the brown fat in our bodies can actually help us lose weight as it contains cells rich mitochondria - the ‘batteries’ that power our body by burning through energy.

It is the white fat that we need to worry about, as it is that which stores calories and leads to obesity.

Now scientists at the University of Cambridge have uncovered a method of making the white fat browner, and of increasing the efficiency of brown fat.

While we all have some of this brown adipose tissue, as it is also known, it is found most abundantly in newborns and the amount in our bodies declines as we age.

Brown fat, which contains more blood vessels to allow the body to provide it with oxygen and nutrients, is also vital for hibernating animals, which use the warmth produced by it to survive in freezing temperatures.

It works using a process called thermogenesis, which uses a unique protein that allows protons to be uncoupled during the synthesis of a chemical called ATP (adenosine triphosphate) and energy to be dissipated as heat.

Fully activated, just 100g of brown fat can burn 3,400 calories a day. This is significantly higher than most people’s daily intake of food intake.

Brown adipocytes - brown fat cells - stained with hematoxylin and eosin. They contain many small lipid droplets distributed throughout the cytoplasm, thus acquiring a spongy appearance. (5725276)
Brown adipocytes - brown fat cells - stained with hematoxylin and eosin. They contain many small lipid droplets distributed throughout the cytoplasm, thus acquiring a spongy appearance. (5725276)

But the only ways for us to activate brown fat are to put people in the cold to mimic hibernation or treat them with adrenergic agonists drugs that can cause heart attacks.

It would also be necessary to increase the number of blood vessels in the tissue to carry nutrients to the fat cells and the number of nerve cells to allow the brain to switch on the tissue.

But in 2012, a team led by Professor Toni Vidal-Puig from the Wellcome Trust-MRC Institute of Metabolic Science, University of Cambridge, identified a molecule - BMP8b - that regulates the activation of brown fat in the brain and the body’s tissues. In mice, deleting a gene that produces this protein stopped brown fat from functioning.

Now, Prof Vidal-Puig has led an international research team that has shown that increasing how much BMP8b mice can produce increases the function of their brown fat.

Higher BMP8b levels changed some of the mice’s white fat into brown fat in a process called beiging and increased the amount of energy burnt by the tissue.

Although further research is needed, BMP8b is found in blood and could potentially be used as a drug both to increase the amount of brown fat in our bodies and make it more active.

Prof Vidal-Puig, lead author of the study published in Nature Communications, said: “There have been a lot of studies that have found molecules that promote brown fat development, but simply increasing the amount of brown fat will not work to treat disease – it has to be able to get enough nutrients and be turned on.”

With higher levels of BMP8b, the tissue is more sensitive to adrenergic signals from nerves. This is the same pathway targeted by adrenergic agonist drugs, which may allow lower doses of them to be used to activate brown fat in people, reducing the risk of heart attack.

The team were also surprised to see the molecule increased the amount of blood vessels and nerves in brown fat.

Co-author Dr Sam Virtue, also from the Institute of Metabolic Science, adds: “It’s like taking a one litre engine out of a car and sticking in a two litre engine in its place. In theory the car can go quicker, but if you only have a tiny fuel pipe to the engine and don’t connect the accelerator pedal it won’t do much good. BMP8b increases the engine size, and fits a new fuel line and connects up the accelerator!”

The research was funded by the British Heart Foundation, Medical Research Council, European Research Council, WHRI-Academy and Wellcome.

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