Australian scientists have pioneered a way to grow in the laboratory “brown fat” - a wondrous tissue that burns energy to generate heat - a breakthrough which they claim could be the latest weapon in the battle against obesity.
They explain that people tend to be fatter when they have too much 'white fat' which is basically an organ of energy storage, whereas brown fat is like a heat generator. Around 50gm of white fat stores 300 kilocalories of energy. The same amount of brown fat burns 300 kilocalories a day. Everybody is born with brown fat, which is deposited around the neckline in newborns to ensure they stay warm. However by adulthood very limited amounts, if any, is left.
The team from Garvan Institute of Medical Research in Sydney has shown that brown fat can be grown in culture from stem cells biopsied from adults, giving hope that one day it would be possible to grow someone's brown fat outside the body and then transplant it.
The team led by Dr Paul Lee and Prof Ken Ho, successfully grew brown fat from the biopsied tissue of six patients, only two of whom had scanned positive for presence of brown fat.
Dr. Lee said, “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…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 PET-CT scans of close to 3,000 people, the team 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 blood.
“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,” Dr Lee said. Dr Lee said the rise in obesity in recent decades could be linked to the reduction in brown fat levels in humans. “In the past 20 or 30 years there's been something in the environment or our lifestyle that has wiped out brown fat and we have lost its protective mechanism…And it's probably because we're not keeping ourselves cold anymore. One argument is global warming, and I'm not talking about the greenhouse effect but we are keeping our indoor environments warmer so there's no reason for brown fat to grow.”
The findings have been published in the latest edition of the Endocrinology journal.