A study conducted by Columbia University Medical Center (CUMC) researchers found the reason why obese people are more prone to asthma problems is due to a dysfunction of a hormone called leptin that's responsible for fertility, energy metabolism, bone mass and the regulation of airway diameter.
Researcher found that leptin, which is produced by fat cells, are found in abundance in overweight people and signals the brain to narrow the airway, causing breathing problems.
"Our study started with the clinical observation that both obesity and anorexia can lead to asthma," said Gerard Karsenty MD, PhD, professor and chair of genetics and development and professor of medicine at CUMC, and lead author of the study. "This led us to suspect that there must be a signal coming from fat cells that somehow affects the lungs -- directly or indirectly."
The most likely candidate was leptin, a protein made by fat cells that circulates in the bloodstream and travels to the brain.
Obesity is one of the reasons for narrowing of the airway, scientifically known as bronchoconstriction. People with asthma are more affected by obesity as it worsens breathing problems. It can also disrupt treatment of this illness through mechanisms that are yet to be researched upon.
The study that was conducted on mice found that extremely high or abnormally low body fat affects the function of the lungs causing bronchoconstriction.
The study was carried across two separate experiments to make sure the findings affected and worsened asthma problems. In the first experiment, obese mice were taken and a substance that increases lung inflammation was monitored. When leptin was inserted into the brain of the mice for four days it was found that "there was no effect on inflammation, but airway diameter and lung functions were normal," said Dr. Karsenty. "This showed that, at least in the mouse, you can cure obesity-related asthma without affecting inflammation."
In the second experiment, obese mice with asthma were treated with a drug that decreases parasympathetic tone. It was found that the illness could be treated.
The findings were published in the online edition of the journal Cell Metabolism.
