Scientists, including one of Indian-origin, have found that an implant made from stem cells that reside in white fat can help reduce weight gain and lower blood glucose levels in mice.
"What is truly exciting about this system is its potential to provide plentiful supplies of brown fat for therapeutic purposes," said study lead author Kevin Tharp, a PhD student in the Department of Nutritional Sciences and Toxicology at the University of California, Berkeley.
"The implant is made from the stem cells that reside in white fat, which could be made from tissue obtained through liposuction," he said.
"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," said the study's senior author, Andreas Stahl, an associate professor of nutritional sciences and toxicology.
There are three basic types of fat tissue in our bodies. There is the energy-storing white fat, and two kinds of energy-burning fat used to generate heat, namely brown fat, which arises during foetal development, and beige fat, which is brown-like fat formed within white fat tissue after exposure to cold and other situations.
The UC Berkeley experiment explored the idea of increasing brown-like beige fat without the temperature drop.
Stahl teamed up with Kevin Healy, UC Berkeley professor of bioengineering, and postdoctoral researcher Amit Jha to develop a system of physical cues to guide stem cell differentiation.
The researchers created a tightly knit 3D mesh in a hydrogel containing water, hyaluronic acid and short protein sequences associated with brown-fat growth and function.
Hyaluronic acid is a naturally occurring carbohydrate that helps make water thicker and gel-like.
They then took white-fat stem cells from mice genetically engineered to express an enzyme from fireflies. This made the cells luminescent, allowing the researchers to track them more easily.
The researchers then added the cells to the hydrogel and, before the mixture thickened, injected them under the skin of genetically identical mice.
They noticed an increase in the core body temperature of the mice at ambient temperatures of 21 degrees Celsius and after 24 hours at a chilly 4 degrees Celsius.
In both cases, the mice with the implanted cells were up to half a degree Celsius warmer than a control group of mice with no injection. The higher the concentration of cells, the larger the effect on temperature.
The researchers also put the experimental mice on a high-fat diet. By the end of three weeks, the mice with injected beige fat gained half as much weight and had lower levels of blood glucose and circulating fatty acids compared with control mice.
