HUNGER GAMES , HOW THE BRAIN BROWNS FAT TO AID WEIGHT LOSS
Researchers at Yale
School of Medicine have uncovered a molecular process in the brain known to
control eating that transforms white fat into brown fat. This process impacts
how much energy we burn and how much weight we can lose. The results are
published in the Oct. 9 issue of the journal Cell.
Obesity is a rising global
epidemic. Excess fatty tissue is a major risk factor for type 2 diabetes,
cardiovascular disease, hypertension, neurological disorders, and cancer.
People become overweight and obese when energy intake exceeds energy expenditure,
and excess calories are stored in the adipose tissues, which are made up of
both white and brown fat. While white fat primarily stores energy as
triglycerides, brown fat dissipates chemical energy as heat. The more brown fat
you have, the more weight you can lose.
It has previously been shown that
energy-storing white fat has the capacity to transform into energy-burning
"brown-like" fat. In this new study, researchers from the Yale
Program in Integrative Cell Signaling and Neurobiology of Metabolism, demonstrate
that neurons controlling hunger and appetite in the brain control the
"browning" of white fat.
Lead author Xiaoyong Yang,
associate professor of comparative medicine and physiology at Yale School of
Medicine, conducted the study with Tamas Horvath, professor and chair of
comparative medicine, and professor of neurobiology and Obstetrics/gynecology
at Yale School of Medicine, and their co-authors.
The team stimulated this browning
process from the brain in mice and found that it protected the animals from
becoming obese on a high-fat diet. The team then studied the molecular changes
in hunger-promoting neurons in the hypothalamus and found that the attachment
of a unique sugar called "O-GlcNAc" to potassium ion channels acts as
a switch to control brain activity to burn fat.
"Our studies reveal white fat
"browning" as a highly dynamic physiological process that the brain
controls," said Yang. "This work indicates that behavioral
modifications promoted by the brain could influence how the amount of food we
eat and store in fat is burned."
Yang said hunger and cold exposure
are two life-history variables during the development and evolution of mammals.
"We observed that food deprivation dominates over cold exposure in neural
control of white fat browning. This regulatory system may be evolutionarily
important as it can reduce heat production to maintain energy balance when we
are hungry. Modulating this brain-to-fat connection represents a potential
novel strategy to combat obesity and associated illnesses."
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