AUTOIMMUNE
April 25, 2013

A Big, Fat Autoimmune Problem

What being overweight does to your immune system is not good and explains some of the health problems associated with obesity.

Obesity is intimately linked to a laundry list of health problems — heart disease, stroke, and diabetes, to name a few. But what exactly is it about being overweight that causes these problems?

We know that obesity pushes the body into a state of chronic inflammation. But what many don’t realize is that obesity is also associated with autoimmune problems, in which one’s immune system is actually attacking the body’s own tissue.

Researchers have been getting closer to understanding just why this connection exists. If it were fully understood, it would theoretically be possible to design a treatment to block obesity-related diseases from occurring in obese people. A new study provides some clues about the relationship.

Obesity is also associated with autoimmunity, in which one’s immune system is actually attacking the body’s own tissue.

Blood levels of a protein called AIM increase in people who are obese, and this protein plays a role in the lifespan of certain immune cells known as macrophages, as well as helping reduce the storage of fat in the body. Previous research has shown that blocking the protein in mice reduces obesity-related inflammation.

The study found that when mice are fed high-fat diets, there is an increase in an antibody that is very involved in any autoimmune defense. This antibody, produced in the blood, is known as immunoglobulin M or IgM. IgM binds to AIM, and the duo hangs out in the bloodstream, rather than being excreted in the urine. Its presence in the blood seems to lead to the formation of auto-antibodies and thereby autoimmunity.

"Our report for the first time explains how obesity causes an initial autoimmune response, namely production of multiple antibodies against self-antigens, and also defines a key molecule in this autoimmune process," said study author Toru Miyazaki in a statement.

The team also found that blocking AIM in mice protected them from developing autoimmunity, a finding that might be of use in the therapeutic arena. “AIM inhibition potentially could be used as a therapy to prevent not only insulin resistance and metabolic disorders but also autoimmunity under obese conditions," the authors write. Testing in humans is the next step.

Will the findings from this study lead to a drug treatment to prevent obesity-related autoimmune problems? That's unclear right now, but certainly the possibility is enticing to researchers. What researchers still don't know is if blocking this pathway would remove all of the health risks associated with obesity, or if there are other factors that also play important roles. Regardless, even with a new "blocking" drug, presumably people would still be encouraged to lose weight.

In the meantime, the tried-and-true methods for preventing obesity-related health problems – and, of course, obesity itself – from occurring are always the best bet, and have lots of research to back them up. Eating well, exercising, and taking care of your mental health are hard methods to argue against.

The study was carried out by a team at the University of Tokyo, and published in Cell Reports.

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