Thermograph of
brown-like fat implanted in anesthetized animal at room temperature.
The implant, shown
in area A, is significantly warmer (30.86 degrees Celsius maximum)
compared with the
control region in area B (29.43 degrees Celsius maximum).
(Photo by Kevin
Tharp and Andreas Stahl)
(August 20, 2015) Scientists
at UC Berkeley have developed a novel way to engineer the growth and expansion
of energy-burning “good” fat, and then found that this fat helped reduce weight
gain and lower blood glucose levels in mice.
The authors of the study, published Aug. 20 in the journal
Diabetes, said their technique could eventually lead to new approaches to
combat obesity, diabetes and other metabolic disorders.
The researchers used a specifically tailored hydrogel to
“scaffold” and control an implant containing stem cells to form a functional
brown-fat-like tissue. While white fat — the kind associated with obesity —
stores excess energy, brown fat serves as a heat generator, burning calories as
it does its job.
Appearance of
implant, less than a centimeter long, removed after two weeks.
Notably, the fat
shows the development of blood vessels and a marked brown hue.
(Photo by Kevin
Tharp and Andreas Stahl)
“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 Ph.D. student in the Department of Nutritional
Sciences and Toxicology. “The implant is made from the stem cells that reside
in white fat, which could be made from tissue obtained through liposuction.”
Human babies, which cannot yet produce heat by shivering,
have greater stores of brown fat, so-called because it contains high levels of
darker-hued mitochondria. It was once believed that brown fat disappears with
age, but in recent years, this tissue has been discovered in the neck,
shoulders, and spinal cord among adults.
Implants respond
to a stimulated cold challenge with increased fat uptake.
Images on top are
anesthetized animals with implants that emit light
proportionally to
the uptake rate of fatty acids. The bar graphs show the
higher rate of
activity under stimulated conditions.
(Image by Kevin
Tharp and Andreas Stahl)
“This is figuratively and literally a hot area of research
right now,” said the study’s senior author, Andreas Stahl, an associate
professor of nutritional sciences and toxicology. “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.”
Studies have shown that cold temperatures can bump up
activity in brown fat. Stahl noted, however, that the exposure to cold often
led to increases in food intake, as well, potentially negating any
calorie-burning benefits from brown-fat activity.