Processes in your body do amazing things for your wellbeing. Just one hormone, leptin, plays a vital role in fertility, energy metabolism and bone mass, but now researchers from Columbia University Medical Centre (CUMC) have found that this hormone also regulates airway diameter, which could explain why the wellness of people with obesity is at risk to asthma. The findings also indicate that this asthma could be relieved with medications that inhibit signalling through the leptin function-mediating parasympathetic nervous system.
According to Gerard Karsenty MD, PhD, professor and chair of genetics and development and professor of medicine at CUMC, and lead author of the study, ‘Our study started with the clinical observation that both obesity and anorexia can lead to asthma’, which led the team ‘to suspect that there must be a signal coming from fat cells that somehow affects the lungs – directly or indirectly’. Karsenty says that as leptin is a protein made by fat cells that circulates in the bloodstream and travels to the brain, this made the hormone the more likely candidate.
The researchers did studies in mice which showed that if your weight and fat mass is abnormally low or high, you are at risk of bronchoconstriction (airway narrowing) and diminished lung function. They then showed that leptin increases airway diameter independently of, and at a lower threshold than, its regulation of appetite, and regardless of local inflammation in the bronchi.
This led the team to give obese, asthmatic mice a substance that increased their lung inflammation, and then they infused leptin in their brains to see if it could be used as a treatment for asthma. ‘There was no effect on inflammation, but airway diameter and lung functions were normal,’ said Dr. Karsenty, which proves that ‘at least in the mouse, you can cure obesity-related asthma without affecting inflammation.’
He concluded that while clinical trials are still needed to make this or a more active and selective drug recommendable for the treatment of body weight-associated asthma, ‘The therapeutic implication is that it may be possible to correct asthma in obese people with drugs that inhibit parasympathetic signalling – and thereby increase leptin-related brain signalling’.
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