Your immune system is important for protecting you against viruses and bacteria and even cancer, but does it play a role in controlling weight too? A recent study shows that a certain type of immune cell called invariant natural killer t-cells or iNKT cells may help to control body fat and reduce the risk of obesity. At the same time, not having enough of these cells may lead to weight gain.
Natural Killer Cells, Immunity and Obesity
Your immune system is made up of a variety of cell types, some of which produce antibodies that protect you against foreign invaders like viruses and bacteria. One type of immune cell called natural killer cells helps your body eliminate health-threatening viruses and tumor cells. Natural killer cells are a type of white blood cell that contains toxic granules they release when they recognize a cancerous cell or a cell infected by a virus. This kills the cell and keeps you healthy. Scientists recently discovered that a special type of natural killer cell called iNKT is present in human and mice fat cells. At least in mice, these cells seem to guard against weight gain, metabolic syndrome, obesity, and type 2 diabetes.
Researchers at Beth Israel Deaconess Medical Center found that mice that were genetically deficient in iNKT cells gained weight and developed type 2 diabetes when they ate a high-fat diet, but when they took iNKT cells from normal mice and placed them into mice that were deficient, the mice lost weight even though they continued to eat a high-fat diet. Even more significantly from a health standpoint, their blood sugars returned to normal levels.
iNKT cells are cells you want more of in your adipose tissue if you’re trying to control your weight. Research shows that iNKT cells are plentiful in the fat tissue of people and animals of normal weight but are reduced in number in people who are obese. On the other hand, when obese people lose weight through bariatric surgery or natural weight loss, the number of iNKT cells increases to a normal level.
Turn on Natural Killer Cells to Lose Weight?
Researchers have even found a way to turn on iNKT cells by injecting mice with a lipid called aGC, also known as alpha-galactosylceramide. Even small doses of this iNKT cell activator caused weight loss and improvements in metabolic function in mice. Plus, it appears to be safe and is currently in clinical trials as a treatment for some types of cancer. It’s possible that aGC might one day be used to activate natural killer cells in fat tissue to promote weight loss.
The Bottom Line?
Immunity, inflammation, and obesity seem to be closely related. Research suggests that obesity affects immunity in a variety of ways and that fat tissue itself produces chemicals called cytokines that cause inflammation and contribute to some of the health risks of obesity like metabolic syndrome and type 2 diabetes. Experts believe that fatty tissue is just as active as some endocrine organs. Now it appears that the immune system influences fat cells as well through the activity of iNKT cells. It goes to show that there are lots of “players” controlling how much adipose tissue you carry around and that weight gain may be more complicated than “calories in, calories out.”
Nutr Rev. 1994 Feb;52(2 Pt 1):37-50.
Science Daily. “Natural Killer Cell”
Harvard Science. “Fat Fighters Found in Fat Tissue”