Overeating triggers a metabolic response in
the hypothalamus region of the brain which prompts people to eat even more,
contributing to increased levels of caloric consumption, new research shows.
The new study, published in the journal Cell,
examines the pathways that contribute to obesity. The researchers at the University of Wisconsin-Madison
and the University of California, San
Diego, investigated “metabolic inflammation,” a
chronic, low-level condition often seen in obesity related diseases.
The research focused on the “master switch”
of inflammation, called IKKbeta/NF kappa B that is usually turned off. When
they fed mice a high-fat diet, it became active. When it was switched on in the
hypothalamus of mice on a high-fat diet,
the body ignored signals from leptin, a hormone that normally helps regulate
appetite, and insulin, which helps convert food into energy.
Then the scientists used genetic
engineering to flip that master switch off in the hypothalamus of other mice. In
mice genetically altered to block the pathway, even with a high fat diet
available, they were able to maintain a healthy weight. They were “significantly
protected” from becoming obese, the researchers wrote.
Stimulating the protein complex, called IKKbeta/NK-kappaB,
made the mice eat more, while suppressing it made them eat less.
“Persistent stimuli from excessive amount
of calories can trigger this response before the overt onset of obesity, and
this response when induced can promote overeating, contributing to increased
levels of caloric overconsumption,” said Dr. Dongsheng Cai, senior author of
the study. He said this process can be like a vicious cycle.
The “pathway” is normally associated with
the immune system, and inflammation, one of the body’s defence systems. While
in the past scientists believed the protein connected to inflammatory reactions
used to help the body fight infection, it now appears to promote obesity. Suppressing
that pathway might be a new strategy in the battle with obesity and related
diseases. Dr Dongsheng Cai said that that the pathway could possibly be used in
anti-obesity drugs. However, researchers warned that the pathway identified as
a crucial player in this process could interfere with the body’s immune system
because inflammation is one of the body’s weapons for fighting infection.
The findings add another element on the
list of factors that predispose children and adults to obesity. A recent study
showed that a brain chemical, known as BDNF (brain derived neurotrophic
factor), plays a crucial role in regulating the quantity of food that people eat
and their chances of becoming obese. The brain chemical is believed to work in
a combination with other substances, including the hormone leptin, that
regulate appetite and body weight. It appears that leptine indirectly triggers
the release of BDNF in the hypothalamus, the part of the brain which helps to
control body temperature and plays a role in controlling eating.
Obesity is one of the main health problems of the world, with 400 million obese people classified by the World Health
Organisation around the world. Obesity is also a significant risk factor for a
number of chronic diseases such as heart disease and type 2 dyabetes, but
efforts are done in order to better understand the factors that contribute to
this health condition.
