Gut microbiota metabolism of dietary fiber influences allergic airway disease and hematopoiesis.
Level 5 - mechanism / opinion, no new human data
Preclinical animal model study
PubMed 24390308 · doi:10.1038/nm.3444
What was done
Mice were fed either a high-fermentable fiber or low-fiber diet to measure changes in gut and lung microbiota composition (specifically the Firmicutes to Bacteroidetes ratio), circulating short-chain fatty acids (SCFAs), and susceptibility to allergic airway inflammation. The researchers also treated mice with the SCFA propionate to analyze its effects on bone marrow hematopoiesis, macrophage and dendritic cell (DC) precursor generation, lung DC phagocytic and Th2-promoting capacity, and the functional requirement for SCFA receptors GPR41 (FFAR3) and GPR43 (FFAR2).
What was found
The abstract reports directional findings without quantitative data. A high-fiber diet increased circulating SCFAs and protected mice against allergic lung inflammation, whereas a low-fiber diet decreased SCFAs and exacerbated allergic airway disease. Propionate treatment enhanced the bone marrow generation of macrophage and DC precursors, populating the lungs with DCs that had high phagocytic capacity but an impaired ability to activate TH2 cell effector responses. The anti-inflammatory effects of propionate required GPR41, but not GPR43.
Why it matters
This study outlines a gut-lung immune axis where gut microbial fermentation of dietary fiber produces circulating SCFAs that systemically alter bone marrow hematopoiesis to attenuate allergic airway disease.
Limits
The study was conducted exclusively in mice; relevance to human asthma, diet, and immune function cannot be assumed without clinical validation. The abstract reports no numerical values, sample sizes, exact fiber dosages, or statistical confidence intervals.
Cited by
- supports Fermentation of dietary fiber by gut microbiota generates short-chain fatty acids that regulate regulatory T cell (Treg) differentiation and hematopoiesis.
- partial Fermentation of dietary fiber by gut bacteria produces short-chain fatty acids that signal the immune system to increase regulatory T cells, increase natural killer T cells, stimulate hematopoiesis, and decrease inflammatory T cells.