Release date: 2014-12-25
In an early study, researchers from the United States confirmed that certain immune system cells may play an important role in weight control. The study was published in the December 22 issue of Nature and was selected as the headline on the Nature website.
Although scientists have long known that some immune cells in mice may help prevent obesity, the new findings are the first to show that this is also the case in humans.
The researchers found that compared to lean people, an obese adult's abdominal fat is less common in immune cells called ILC2s. And in some mouse experiments, they found that ILC2s seem to promote the formation of "beige" fat cells, which are known to increase calorie burning in the body.
David Artis, a senior researcher at the project and a professor of immunology at Weill Cornell Medical College, said it seems that these ILC2 cells are not working properly in obese people.
Artis said that the exact cause or mechanism for this is not known, but these are key issues for future research. He hopes to eventually develop some new ways to solve the problem of obesity.
According to Artis, researchers have only begun to understand the mechanisms by which the immune system affects metabolism and weight control in the past few years. This may sound surprising, because the most well-known function of the immune system is to help the body fight off infection. But from an evolutionary point of view, this makes sense.
Although the immediate task of the immune system is to fight infection, it is conceivable that some of these components have evolved to have the ability to "communicate" with adipose tissue in adversity, thereby altering the body's metabolism.
"You can imagine that it actually tells fat tissue, 'We will be malnourished for a while, let us adapt to it,'" Artis said.
An obese researcher who did not participate in the study said the new study adds evidence to confirm that the immune system plays a role in weight management.
Dr. Charles Billington, an endocrinologist at the University of Minnesota and a spokesperson for the American Obesity Association, said: "This is really interesting. The link between immune function and metabolism is not a new concept. When people are injured or have an allergic reaction, the body often Will enter the "metabolism" state, accelerate the burning of calories.
But this study and other recent studies have revealed the immune system's effects on metabolism and the mechanisms that may affect long-term weight control, Billington said.
But he also stressed that there are still many unknowns. "There is some overlap between the immune system and metabolism, and we haven't really understood it yet."
ILC2s are seen as a group of immune cells that help fight infections and work in allergies. Artis and colleagues want to know if these cells are taking on other jobs.
The researchers began a study of abdominal fat samples from obese and normal-weight adults, and the results confirmed that fat from obese people had fewer ILC2s—like obese mice in the lab.
Subsequently, the researchers tested the effect of injection of interleukin-33 (IL-33) on laboratory mice. IL-33 is an immune system protein that acts as a "chemical messenger" between cells.
The study found that this treatment increased ILC2s in animal white fat and in turn increased calorie burning.
Billington explains that white fat is a type of fat that can store excess calories, often expressed as beer belly or waist fat. Another type of fat called brown fat, which occupies only a small space in the body, can burn calories.
Artis says scientists have long been looking for a way to upregulate brown fat. But in addition to white fat and brown fat, the body has a third type of fat - the so-called beige fat.
Like brown fat, beige fat burns calories and generates heat. More importantly, Artis says, it has the potential to play an important role in preventing obesity.
In some of its research groups, ILC2 cells appear to increase calorie burning by promoting the storage of beige fat in animals.
What does this mean for humans?
Artis said: "Obviously, we are still in the early stages of this research, there is still a lot of work to be done. And our goal is to develop some by better understanding the communication between the immune system and body fat. New ways to treat obesity."
But Billington believes that this will be a long road. He pointed out a big problem: Since some immune system cells have taken on a lot of work, how can you let them only increase the beige fat, and not do things that you don't want to happen - such as stimulating allergic reactions?
In a larger picture, obesity research has identified one thing: metabolism and weight control are complex. "It's unlikely that there will be any 'magic bullets' to fight obesity," Billington said.
Source: Biopass
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