‘Good’ fat implants could reduce weight gain

Energy-burning ‘good’ brown fat can be created in the laboratory and implanted in the body to help reduce weight gain and lower glucose levels, scientists have discovered.

So far, the man-made brown fat has only been implanted in mice, although the result was encouraging to the researchers from the University of California, Berkeley in the US.

“This is figuratively and literally a hot area of research right now,” said senior author Andreas Stahl of UC Berkeley. “We are the first to implant in mice an artificial brown-fat depot and show that it has the expected effects on body temperature and beneficial effects on metabolism.”

In the study, the research team worked with stem cells that they obtained from the energy storing or ‘bad’ white fat.

Next, they engineered a gel to support stem cells and encourage them to collectively turn into brown fat.

Several studies have demonstrated that brown and white fat can change into each other, and that cold temperatures can turn white adipose cells beige.

While traditional brown fat is formed during gestation, beige fat is energy-burning fat that started out white.

Aiming to produce beige fat without the chill, the research team found that placing the white fat stem cells over a scaffold-like structure — in this case a tightly knit 3D mesh in hydrogel — that was not too stiff did the job.

Hyaluronic acid, a naturally occurring carbohydrate that thickens water, and short protein sequences known to encourage brown fat growth and promote its functioning were also part of the mesh.

“It’s already known that for a number of organs, including the heart, the extracellular matrix in which a cell resides provides signals to guide growth and development,” says Kevin Healy, a professor of bioengineering at U Berkeley. “We applied this concept to stem cells isolated from white-fat tissue.”

White fat stem cells were obtained from mice that had been genetically engineered to express an enzyme from fireflies, making their fat cells luminescent and enabling the research team to visualize them.

Once the cells had been added to the scaffold, the research team injected them under the skin of genetically identical mice, where the gel polymerized, turning the fat cells beige.

Surveying the shining cells after implantation, the researchers observed an increase of half a degree Celsius in core body temperature of their beige-fat-injected mice, regardless of the ambient temperature.

A control group did not demonstrate this and when both groups were placed on a high-fat diet the beige-fat-injected mice gained half as much weight and demonstrated lower levels of blood glucose.

“This is a feasibility study, but the results were very encouraging,” says Stahl. “It is the first time an optimized 3D environment has been created to stimulate the growth of brown-like fat.”

The study was published in the journal Diabetes.

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