Immune cells in the intestine help with tissue repair and provide protection against microbial infection. In a new study, researchers found that one of these cells called intestinal intraepithelial lymphocyte (IEL) also has a role in controlling the body's metabolism.

IELs Slow Down Metabolism

The presence of the immune cells limits the availability of the hormones called incretin GLP-1 that help speed up metabolism. By limiting these hormones, the natural IELs essentially slow down the metabolism of the body and conserve energy the body gets from food.

Study researcher Filip Swirski, from Massachusetts General Hospital Center for Systems Biology, and colleagues said these immune cells tend to slow down metabolism and send ingested food to be stored as fat instead of being converted into energy.

In experiments involving engineered mice, researchers found the animals that lack IELs could consume diets high in fat, salt, and sugar without developing metabolic conditions such as obesity, heart disease, hypertension, and diabetes. They also stayed trim.

Normal mice, on the other hand, developed high blood pressure and glucose intolerance. They also became obese.

Immune Cells May Explain Why Some People Tend To Get Fat

The research published in the journal Nature on Jan. 30 offers insights on why some people tend to get fat and some are resistant to becoming overweight.

"We often speak of people who have a 'high metabolism' and seem to be able to eat whatever they want without gaining weight, while others struggle with obesity," said Swirski. "These cells, which are known for their function in the immune system, also appear to play an important role in that metabolic choice."

Energy-Saving Mechanism

The efficient use of energy provided an essential advantage over the course of human evolution when food was scarce. Organisms can survive longer when they store instead of burn some of the ingested energy.

The researchers, however, said that with the present abundance of food, this energy-saving mechanism backfires and even lead to unhealthy outcomes.

"Although the function of IELs may prove advantageous when food is scarce, present-day overabundance of diets high in fat and sugar renders this metabolic checkpoint detrimental to health," Swirski and colleagues wrote in their study.

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