A PET (Positron Emission Tomography) scan, showing deposits of brown fat around the neck
Media Release: 03 September 2011
Australian scientists believe that ‘brown fat’, a wondrous tissue that burns energy to generate heat, could help us fight obesity.
We are obese when we have too much ‘white fat’, which is basically an organ of energy storage. In contrast, brown fat is like a heat generator. Around 50 g of white fat stores 300 kilocalories of energy. The same amount of brown fat burns 300 kilocalories a day.
A research science team from Sydney’s Garvan Institute of Medical Research shows that brown fat can be grown in culture from stem cells biopsied from adults – giving hope that one day we might either be able to grow someone’s brown fat outside the body and then transplant it, or else stimulate its growth using drugs.
We are all born with supplies of brown fat around our necks, nature’s way of helping to keep us warm as infants. Until recently, it was thought to vanish in early childhood, but we now know that brown fat is present in most, if not all, adults mainly just behind the collarbone. Adults with brown fat are slimmer than those without.
Endocrinologists Dr Paul Lee and Professor Ken Ho in collaboration with Drs Michael Swarbrick and Jing Ting Zhao successfully grew brown fat from the biopsied tissue of six patients, only two of whom had scanned positive for presence of brown fat.
These results, to be printed in the October issue of Endocrinology, are already online. A commentary has appeared in the September edition of Endocrine News, observing that “experts in the field are heralding these results”.
“Although this is early work, it is a proof of concept study showing that the growth of brown fat cells is possible, using precursor cells taken from adult humans, under appropriate stimulation,” said Dr Paul Lee.
“Regardless of whether or not someone has lots of or little brown fat, the precursor cells are universally present. Under the appropriate growth factor and hormonal stimulation, the cells all grow and differentiate into mature brown fat cells.”
Using the PET-CT scans of close to 3,000 people, Lee recently showed a striking negative correlation between brown fat and weight. Those people with brown fat had significantly lower body mass indexes as well as lower glucose levels in the blood. His results were published in the American Journal of Physiology Endocrinology and Metabolism last September. A subsequent study by the same team published in the Journal of Clinical Endocrinology and Metabolism last month suggested the universal presence of brown fat in adult humans, a striking contrast to what was traditionally believed.
Lee is optimistic about targeting brown fat as an obesity intervention, commenting “it’s a highly metabolically active form of fat, and very exciting that we may be able to stimulate its growth in people.”
“At the same time, our study tells us that in people who are overweight, there may be factors in the environment or in the body that inhibit the growth of brown fat.”