The proliferation of research pertaining to the human gut microbiome has produced numerous findings that point to its role in a range of illnesses, including gastrointestinal, metabolic, and psychiatric diseases.1,2 In addition, emerging evidence suggests that the gut microbiome may contribute to the pathogenesis of atopy and asthma.

“There are exciting data that implicate the composition of the gut microbiome in early life — the first 1000 days — to the development of asthma, although the evidence to date remains correlative,” Cathryn R Nagler, PhD, the Bunning Food Allergy Professor and professor of pathology, medicine, pediatrics, and the college at the University of Chicago, told Pulmonology Advisor.

Some study results suggest that maternal-fetal microbiota transfer may be initiated in utero, with further bacterial transfer occurring during vaginal delivery and breastfeeding.3 Birth cohort studies have found that dysbiosis of the gut microbiota in the first years of life is associated with the subsequent development of asthma and allergy, including a 2018 prospective study (n=690) linking the composition of the gut microbiome at age 1 year with an increased risk for asthma at age 5 years.4

Such findings are “supported by work in mouse models that show age-dependent regulation of immunoglobulin E production by the gut microbiota and a potential direct role for specific bacteria, such as Lachnospira, Veillonella, Faecalibacterium, and Rothia, in mitigating asthma development during the first 100 days of life,” according to a recent review published in the Annals of Allergy, Asthma & Immunology.5 These bacteria were found to be reduced in children at risk for asthma. Meanwhile, when researchers inoculated germ-free mice with these specific taxa, airway inflammation decreased.6

Among the potential mechanisms driving the relationship between gut microbiota and asthma pathogenesis are altered levels of short-chain fatty acids “produced by fermentation of fiber by specific gut bacteria.” This may lead to an increased risk for asthma, according to murine and human studies.5 Other potential mediators include histamine and tryptophan metabolites.5

These observations suggest that interventions targeting the gut microbiome may ultimately prove useful in asthma management. “Microbiome-modulating therapeutics could be administered as both preventive or therapeutic modalities,” said Dr Nagler. While these therapies are not currently available for clinical use, many research scientists and biotechnology start-up companies are working to develop such strategies. “Much more work needs to be done to examine how bacteria and other microbes impact the host at the cellular and molecular level in both health and disease,” Dr Nagler said.

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