Obese people are ten times more likely to develop diabetes than thin people; But why? In trying to solve this puzzle, the researchers realized that the answer lies in the same system that controls the body’s fight or flight response. Findings in mice test long-held assumptions about how eating too much can make you sick.
A new study showed that following a high-fat diet causes a sudden activation of neurotransmitters throughout the body, and this event leads to the rapid breakdown of fatty tissue in the liver; That is, the same process that is usually controlled by insulin secretion. The release of high levels of fatty acids has been linked to many health problems, from diabetes to liver failure.
High levels of neurotransmitters lead to insulin resistance
Researchers previously thought that the main problem in obesity-related diabetes was defective insulin action; This means that the body cannot stop the dangerous release of fatty acids. However Martina Schweigera biochemist at the University of Graz in Austria, says that instead of these brakes (defective insulin) not working, there is a separate lever (neurotransmitters in the liver and other tissues) that accelerates. According to Schweiger, this finding will greatly change the way we understand obesity-related diabetes.
More than 890 million people worldwide are obese, which is one of the main risk factors for developing diabetes and other metabolic disorders. Researchers have long known that diabetes develops when insulin stops lowering blood glucose levels. Christoph Boettner and Kenichi Sakamotoboth physiologists at Rutgers University in New Brunswick, wanted to better understand the nature of insulin resistance in diabetes by conducting a study.
Buttner has been studying the role of insulin in the brain in regulating metabolism for a long time; So he and his team turned their attention to the sympathetic nervous system, which delivers neurotransmitters like norepinephrine to tissues throughout the body. The researchers used previously bred mouse models in which they deleted a gene that expresses a key enzyme needed to produce the neurotransmitter norepinephrine. The gene was only removed from some of the mouse’s organs, not the brain, to ensure that the animal could survive.
The researchers fed the modified mice a diet rich in fats such as pork, coconut oil, and soybean oil. Over two months of observation, modified and unmodified mice ate the same amount, gained similar weight, and maintained similar insulin signaling activity; That is, the series of events that occur after insulin binds to its target receptor in the cell.
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The modified mice did not increase the breakdown of adipose tissue and insulin resistance, and finally did not show signs of increased fatty liver and tissue inflammation. On the other hand, the unmodified mice developed insulin resistance, which can lead to diabetes. Mice also showed increased signs of inflammation and liver disease; This means that the elimination of norepinephrine in some organs in modified mice prevented insulin resistance.
Brain signals
Buttner says the study’s findings suggest that neurotransmitters are responsible for insulin resistance and related problems. He and his colleagues are now investigating the role of the neurotransmitters responsible in other conditions, such as insulin resistance caused by menopause.
“This study is very reliable, but there are still some pieces of the puzzle missing,” says Schweiger. “For example, the question now is how a high-fat diet increases neurotransmitters.”
Schweiger says more work is needed to better understand the implications of the findings for the public. So far, drugs that block the activity of neurotransmitters involved in the sympathetic nervous system have not shown any benefit in obese people.
Buettner suggests that if researchers focus on developing drugs that work specifically in certain tissues of the body while avoiding effects on the brain (such as eliminating norepinephrine in engineered mice), these drugs may be useful for treating diseases such as drug resistance. Insulin and obesity-related diabetes are more effective.
