Scientists have uncovered a mechanism in a group of
immune cells in the gut that can sway nutrient metabolism to favor fat storage
over energy use.
The finding may help
explain why some people remain slim despite having eating habits that cause
others to gain weight.
The mechanism works when
intraepithelial T cells, which are a type of immune cell that resides in the
lining of the small intestine, have an active gene for the protein integrin beta 7.
In a study paper on their work that now appears
in the journal Nature, researchers at Massachusetts General
Hospital and Harvard Medical School, both in Boston, MA, describe mice that do
not have these particular cells as "metabolically hyperactive."
When they put mice lacking the cells on a high-fat,
high-sugar diet, the animals did not develop obesity, high blood pressure, high
cholesterol, heart disease, or diabetes.
"After you eat,"
says senior study author Filip K. Swirski, Ph.D., an associate professor
of radiology who
also works in the Center for Systems Biology, "your body can convert
energy into heat and burn it quickly or it can convert the food into fat and
store it for later use."
"These cells, which
are known for their function in the immune system, also appear to play an
important role in that metabolic choice," he adds.
Metabolism, fat storage, and energy use
The biochemistry of how
the body handles nutrients derived from food digestion is complex and requires
precise regulation.
The authors refer to
"strategically positioned metabolic sensors" that direct nutrients
down particular molecular pathways.
Their study identifies a pathway that prioritizes
fat storage over energy use. Such a function can preserve health by ensuring
that energy reserves are available during times of food scarcity.
However, for the many
people who today live in societies with an abundance of high-fat, high-sugar
foods, such a function is more likely to undermine health than support it.
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