Epigenetics and asthma among children: A meta-analysis

Background: The field of epigenetics has been providing some conclusive and consistent evidences in explaining causal relationship between environmental triggers, epigenetic changes and asthma. Epigenetics is the study of heritable changes in gene expression that occur without directly altering the DNA sequence. Epigenetic mechanisms have the potential explain many mysterious in the pathogenesis of asthma like: 1) Susceptibility to pre-natal exposures, 2) Variable natural history of asthma, and 3) Reversible phenotypes. Some of the most common epigenetic mechanisms that are found to influence asthmatic phenotypes are: 1) DNA methylation, 2) Post-translational modification of histone proteins, and 3) non-coding RNAs. Method: A comprehensive literature search was conducted, with key words “Epigenetics”, “Asthma”, “Allergy”, and “Children” using PubMed, Medline, Highwire, CINAHL, and Google Scholar. The search resulted in 7 potential and full text articles including 6 epidemiological studies and 1 review article. Of all, 5 epidemiological studies and 1 review paper will be considered in the meta-analysis. Meta-analysis is being conducted and random effect models will be generated. Heterogeneity will be assessed. Results: Adjusting for exposure later in pregnancy and in infancy, the relative risk for children exposed to folic acid supplements in the first trimester for wheeze was 1.06 (95% CI 1.03 to 1.10), for lower respiratory tract infections was 1.09 (95% CI 1.02 to 1.15), for hospitalizations for lower respiratory tract infections was 1.24 (95% CI 1.09 to 1.41). The results suggest that methyl donors in the maternal diet during pregnancy may influence respiratory health in children consistent with epigenetic mechanisms. Conclusion: Maternal smoking cessation before pregnancy can greatly reduce the risk of childhood asthma. Epigenetics demands the application of new technologies to epidemiological studies to know more about the underlying mechanisms of asthma at molecular level and thus offers a great promise to understand a theoretically preventable disease.