Asthma affects millions of children already at a young age. We were born with an environment full of small organisms called a microbiota. Within the first few minutes and hours of our life, they begin to stimulate but also educate our immune system. The largest immune organ is our gut, where the maturation of the immune system and the maturation of colonizing bacteria, the gut microbiome, go hand in hand. After profound disturbances in the first year of life, the maturation process, the composition of the intestinal microbiome gradually stabilizes and accompanies us for our life. Children who grow up on a farm have a lower risk of developing asthma than children who do not live on a farm. The mechanisms behind this farm protective effect on childhood asthma are largely unknown. A group of researchers from Helmholtz Zentrum München and the von Hauner Children’s Hospital of the Ludwig Maximilians University of Munich have clarified how the intestinal microbiome of children is involved in the protection process. Previous research by the group showed a protective effect against asthma from a diverse environmental microbiome, particularly pronounced in farm-dwelling children.
The question now was whether this effect could be attributed to the maturation process of the early gut microbiome. Life on the farm appears to increase the maturation of the gut microbiome in children. Researchers analyzed fecal samples from more than 700 newborns partly raised on traditional farms between the ages of 2 and 12 months who took part in PASTURE, a European cohort, which has been running for nearly 20 years with funding from the European Commission. They found that a relatively large portion of the farm’s protective effect on childhood asthma was mediated by the maturation of the gut microbiome in the first year of life. This suggests that the children on the farm are in contact with possibly microbial environmental factors that interact with the gut microbiome and give this protective effect. Researchers anticipated the effects of nutrition on gut microbiome maturation, but were surprised to find strong effects of livestock-related exposures, such as livestock stays. This underlines the importance of the environment for the protective effect. Additionally, vaginal delivery and breastfeeding fostered a protective microbiome in the first two months of life.
Furthermore, the researchers found an inverse association of asthma with the measured level of fecal butyrate. Butyrate is a short-chain fatty acid that is known to have a protective effect against asthma in mice. The researchers concluded that gut bacteria such as Roseburia and Coprococcus with the potential to produce short-chain fatty acids may contribute to the protection of asthma in humans as well. Children with a mature gut microbiome showed more of these bacteria than other children. Researchers have shown that the protective effect of asthma does not depend on a single bacterium, but on the maturation of the entire gut microbiome. This finding questions the approach of using single bacteria as probiotics for asthma prevention. Rather, probiotics should be tested for their sustained effect on the compositional structure of the gut microbiome and its maturation early in life. The nutritional aspects analyzed in this study can be used for prevention strategies such as the consumption of cow’s milk. Raw unprocessed milk, however, cannot be recommended due to the risk of life-threatening infections such as from Escherichia coli.
Dr Markus Ege, professor of clinical-respiratory epidemiology at von Hauner Children’s Hospital, commented: “Our study provides further evidence that the gut may have an influence on lung health. A mature gut microbiome with a level high in short-chain fatty acids had a protective effect on children’s respiratory health in this study. This suggests the idea of a relevant gut-lung axis in humans. This also means, however, that an immature gut microbiome may contribute to the development of diseases. This underlines the need for prevention strategies in the first year of life, when the intestinal microbiome is highly plastic and susceptible to changes”. Scientists at von Hauner Children’s Hospital are currently conducting a clinical trial on the effects of minimally processed but microbiologically safe milk for the prevention of asthma and allergies (MARTHA study).
- Edited by Dr. Gianfrancesco Cormaci, PhD, specialist in Clinical Biochemistry.
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