When researchers at Columbia University Medical Center (CUMC) conducted a study with obese mice, they made a surprising find. These latest findings may explain why obese people are prone to asthma.
Gerard Karsenty, PhD is professor and chair of genetics and development and professor of medicine at CUMC. As lead author of the study, he explains:
“Our study started with the clinical observation that both obesity and anorexia can lead to asthma. This led us to suspect that there must be a signal coming from fat cells that somehow affects the lungs —directly or indirectly.”1
The researchers conclude the “signal” was likely due to the protein hormone leptin.
Derived from the fat cells, leptin plays a critical role in regulating energy intake and energy expenditure, including appetite and metabolism.2 It’s also crucial for fertility and bone health. And that’s not all. Leptin is necessary for regulating airway diameter.
The researchers noted abnormal body weight and fat mass results in constriction of airways in the lung as well as diminished lung function.
Next, they showed leptin increases airway diameter independently of, and at a lower threshold than, its regulation of appetite.
Leptin affects the airways by decreasing the activity of the parasympathetic nervous system. 3 It is often called the “rest and digest system.”
They found regulation of airway diameter occurs regardless of local inflammation.
A number of studies have shown an association between obesity and asthma.4 We now know obesity can cause narrowing of the airways. These latest findings suggest leptin is necessary for increasing airway diameter. And it does so independently of body weight and inflammation. Therapies that boost leptin-signaling may help open these airways to relieve asthma in obese people.
“Impaired lung function caused by decreased airway diameter (bronchoconstriction) is frequently observed whether body weight is abnormally high or low.” 3
Armed with this knowledge, we’ve now been given yet another reason to maintain a healthy body weight.
The title of the paper is “Inhibition of leptin regulation parasympathetic signaling as a cause of extreme body weight associated asthma.” And it’s published in the current online edition of Cell Metabolism (8 January 2013). 3
References
2 http://www.news-medical.net/health/What-is-Leptin.aspx
3 http://www.cell.com/cell-metabolism/retrieve/pii/S1550413112004950
4. http://onlinelibrary.wiley.com/doi/10.1111/j.1398-9995.2010.02402.x/full
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