Long misunderstood, the lesser-known brown fat in our bodies is beginning to be recognised as a vital tissue, playing an important role in metabolism.
For the first time, researchers from Sydney’s Garvan Institute of Medical Research have shown that brown fat may help control blood sugar fluctuations. The study is published today in Cell Metabolism.
The findings could lead to new therapeutic targets for diabetes, which is reaching epidemic levels worldwide.
Unlike white fat, which stores energy, brown fat burns energy to produce heat – “a bit like a very powerful heat generator,” says lead author Dr Paul Lee.
In adults, brown fat is mostly found above the collarbone and in the neck, but importantly, everyone has a different amount.
“People with brown fat are leaner, and have lower glucose,” explains Lee. Those with less or no brown fat “tend to be more overweight,” he says.
By measuring brown fat activity and blood glucose levels in 15 healthy adults continuously and in real time, the researchers found they shared a close relationship.
“It looks like the more brown fat one has, the more influence it has on blood glucose,” says Lee.
Morning fat activity
Participants with larger brown fat deposits showed less fluctuation in blood glucose, and their blood glucose levels dropped after a surge in brown fat activity.
Those with less brown fat had larger fluctuations in blood sugar, and individuals with no detectable brown fat had the widest variations.
By tracking brown fat activity during the day – using a small thermometer over the collarbone to detect brown fat heating up as it activates – the team also showed the tissue has a “thermogenic circadian rhythm,” and was most active in the morning.
“This early morning temperature boost may have an evolutionary origin, generating heat and preparing our ancestors for hunting and gathering in the cold as the day begins,” Lee speculates.
“Once we identify the activators of this rhythm, then those activators could potentially be therapeutic targets.”
Stabilising to curb diabetes
Blood glucose variations are a precursor to type 2 diabetes, which is characterised by high levels of blood sugar.
“Brown fat may be acting like a buffer or stabiliser of glucose levels, thereby protecting us from diabetes,” says Lee.
Dr Dana Hutchinson from the Monash Institute of Pharmaceutical Sciences says that new therapies for type 2 diabetes are needed, as current treatments such as Metformin and insulin stop working as the disease progresses.
“This is probably the first paper showing human brown fat potential for regulating glucose, which is quite important,” Hutchinson says. “If you don’t know how the mechanism works, you can’t design any therapies with it.”
While the research brings brown fat into the frame for new diabetes treatments, Lee says it is not the solution to a cure.
“I can’t emphasise enough: a healthy diet and regular exercise are still the cornerstones of maintaining a healthy metabolism,” he says.