Genetic association and bidirectional Mendelian randomization for causality between gut microbiota and six lung diseases

Causal association between epigenetic age acceleration and two pulmonary vascular diseases: pulmonary arterial hypertension and pulmonary embolism-a bidirectional Mendelian study

BACKGROUND

Pulmonary arterial hypertension (PAH) is a relatively rare but severe disease with a poor prognosis. Pulmonary embolism (PE) is a serious condition that can cause sudden death. Epigenetic age acceleration (EAA) is a robust indicator derived from the DNA methylation-based epigenetic clock, which can predict the extent of aging. It has been proved that the epigenetic clock and EAA are associated with many cardiovascular diseases, while their associations with PAH and PE remain inconclusive. Our study aims to investigate the associations among these factors.

METHOD

By harnessing summary-level data from large-scale genome-wide association studies (GWAS), we designed a two-sample bidirectional Mendelian randomization (MR) analysis to assess the causal associations between measures of three epigenetic clocks, including GrimAge acceleration (n = 34,467), Hannum Age acceleration (n = 34,449) and PhenoAge acceleration (n = 34,463) and PAH (including 125 cases and 162,837 controls), as well as PE (including 3940 cases and 480,658 controls). The inverse variance-weighted (IVW) method was used as the primary method for MR analysis. Other methods, such as MR egger and weighted mode, served as complements to the IVW approach, were also applied in the analyses. Then, the MR pleiotropy test and MR-PRESSO test, which are effective tools for quality control of MR analysis, were subsequently used to ensure the accuracy of the study.

RESULTS

The forward MR analysis indicated that all three epigenetic clocks had no significant effects on PAH or PE. The reverse analysis indicated that the onset and progression of PAH and PE had insignificant effects on three epigenetic clocks. The results of the quality control assessment confirmed that our findings were reliable.

CONCLUSION

Our two-sample bidirectional MR analysis suggested that there is no significant association between epigenetic clocks and these two pulmonary vascular diseases.

Application of Microbiome-Based Therapies in Chronic Respiratory Diseases

The application of microbiome-based therapies in various areas of human disease has recently increased. In chronic respiratory disease, microbiome-based clinical applications are considered compelling options due to the limitations of current treatments. The lung microbiome is ecologically dynamic and affected by various conditions, and dysbiosis is associated with disease severity, exacerbation, and phenotype as well as with chronic respiratory disease endotype. However, it is not easy to directly modulate the lung microbiome. Additionally, studies have shown that chronic respiratory diseases can be improved by modulating gut microbiome and administrating metabolites. Although the composition, diversity, and abundance of the microbiome between the gut and lung are considerably different, modulation of the gut microbiome could improve lung dysbiosis. The gut microbiome influences that of the lung via bacterial-derived components and metabolic degradation products, including short-chain fatty acids. This phenomenon might be associated with the cross-talk between the gut microbiome and lung, called gut-lung axis. There are multiple alternatives to modulate the gut microbiome, such as prebiotics, probiotics, and postbiotics ingestion and fecal material transplantation. Several studies have shown that high-fiber diets, for example, present beneficial effects through the production of short-chain fatty acids. Additionally, genetically modified probiotics to secrete some beneficial molecules might also be utilized to treat chronic respiratory diseases. Further studies on microbial modulation to regulate immunity and potentiate conventional pharmacotherapy will improve microbiome modulation techniques, which will develop as a new therapeutic area in chronic respiratory diseases.