AUGUSTA, Ga. — “Pear-shaped” people, whose weight is generally distributed more evenly rather than above the waist in “apple-shaped” individuals, are better protected against dementia. Beige fat cells, typically found in higher amounts in the bodies of those with pear-shaped bodies, reduce inflammation linked to dementia, new research shows.
Pear-shaped individuals are already at lower risk of heart disease and diabetes, as well as cognitive decline. However, now, following new research, scientists say beige fat cells, or adipocytes, are “indispensable” to the neuroprotective and anti-inflammatory effects of subcutaneous fat, which is a mixture of white and beige cells.
Interestingly, the researchers write that beige fat is more common in younger people, and exercise and cold exposure seem to enable the “beigeing””of white fat cells. The team behind the finding says they hope their discovery could lead to preventative treatments for dementia. These could include drugs that mimic the effects of the fat, or even go so far as to freeze beige fat at an early age and transplant it in patients when they are older.
“If we can figure out what it is about beige fat that limits inflammation and maybe what it is about beige fat that improves brain plasticity, then maybe we can mimic that somehow with a drug or with cold-stimulated beiging or even taking out some of your subcutaneous fat when you are young, freezing it and giving it back to you when you are older,” explains Dr. Alexis Stranahan, a neuroscientist at the Medical College of Georgia at Augusta University, in a statement.
The scientists made their discovery by testing male mice with a specific missing gene. This missing gene would prevent adipocytes in the subcutaneous fat from “beigeing” or browning, resulting in subcutaneous fat that is more like visceral fat, the kind of fat found around organs and in the belly. On a high-fat diet, it’s already been shown that these mice develop diabetes faster than those with normal amounts of beige fat. Previous studies have shown that transplanting subcutaneous fat into obese mice improved their metabolism in just a few weeks.
Transplanting beige fat results ‘in improvements at center of learning and memory’
In the tests, while both the normal mice and mice missing this gene gained about the same amount of weight over four weeks, mice without functional beige fat showed more cognitive problems on testing. Their brains and bodies also showed a strong inflammation in response to the high-fat diet. This inflammation affected microglial cells – immune cells in the brain – which can contribute to dementia and other brain problems.
Before they ever developed diabetes, the microglia of the mice, whose ages were comparable to a 20-something-year-old human, were already showing inflammation. In experiments, normal mice displayed inflammation as well, but alongside an anti-inflammatory response which helped minimize problems.
The researchers also transplanted subcutaneous fat from young, lean healthy mice into otherwise normal, but now-obese, mice who had developed dementia-like behavior after remaining on a high-fat diet for 10 to 12 weeks. Transplanting resulted in improvements at the center of learning and memory deep in the brain. Results also that beige fat interacts with immune cells, inducing the anti-inflammatory protein IL-4 in the subcutaneous fat. IL-4 is one of the proteins required for cold to stimulate the “beigeing” of fat.
The fat also induced IL-4 in microglia and T cells in the immune response of the meninges, a sort of multilayer cap that fits over the brain to help protect it. Likewise, T cells in the choroid plexus, where cerebrospinal fluid is produced, were induced by IL-4.
Researchers say it was the recipient’s own T cells in the meninges that were called to protective action by the transplanted beige fat cells, not immune cells from the transplanted fat itself. These findings suggest IL-4 is directly involved in communication between beige fat cells and neurons in the brain, in a process Dr. Stranahan compares to the game “Whisper Down The Lane.”
“It’s exciting because we have a way for peripheral immune cells to interact with the brain in a way that promotes cognition,” says Dr. Stranahan.
The team now hopes to carry out further research into whether the location of the transplanted fat matters and whether transplanting visceral fat to a subcutaneous area reduces its damaging effect. they also want to explore these issues in female mice since the current studies were limited to males and to find out how subcutaneous fat sends an anti-inflammatory message.
The findings are published in the journal Nature Communications.
South West News Service writer William Janes contributed to this report.