This just in from Boston Children’s Hospital: The immune system may play a key role in the asthma that can develop along with obesity — and that new understanding may point to possible ways to stop or treat obesity-related asthma.
A finding of broad potential impact in a country where one-third of the population is obese and more than 25 million people have asthma. From the Children’s press release on the study just out in the journal Nature Medicine:
A growing body of literature links asthma with obesity, but the reason for the link has been unknown. Both conditions have become more common over the last several decades. The new study, led by Dale Umetsu, MD, PhD, and Hye Young Kim, PhD, of the Division of Allergy and Immunology at Boston Children’s, explored obesity’s effects on the immune system.
The researchers studied mice that were fed a high-fat diet causing them to become obese. Unlike mice fed normal diets, the obese mice developed airway hyper-reactivity or constricted and twitchy airways, the predominant feature of asthma.
In the study, obesity appeared to alter the innate immune system—the body’s first responder to infection—in several ways to cause lung inflammation.
In addition, when IL-1β [a protein linked to inflammation] production was blocked with the drug anakinra (Kineret, Swedish Orphan Biovitrum), used to treat rheumatoid arthritis, the obese mice did not develop asthma.
Although the researchers were unable to study human patients directly, they did examine lung fluid from 10 patients with lung disease who underwent bronchoalveolar lavage, a diagnostic test. Those with severe asthma had increased numbers of ILC3 cells producing IL-17 as compared with those with mild asthma or no asthma—circumstantial evidence suggesting that the mouse model may mirror what occurs in obese people who develop asthma.
“Obese people have been noted to have elevated systemic levels of IL-17 and IL-1β, particularly those who have non-allergic asthma,” notes Umetsu.
(The release notes that Umetsu has since left Children’s and gone on to become principal medical director at Genentech.)