Mendelian-randomization study reveals causal relationships between nitrogen dioxide and gut microbiota

Area of Science:

• Environmental Health
• Microbiome Research
• Genetic Epidemiology

Background:

• Growing evidence links environmental exposures to human health outcomes.
• The gut microbiome plays a crucial role in host physiology and disease.
• Understanding the impact of air pollutants like nitrogen dioxide on the gut microbiome is essential for public health.

Approach:

• A two-sample Mendelian randomization study was conducted using large-scale genetic data for nitrogen dioxide exposure (N=456,380) and gut microbiota composition (N=13,266).
• Multiple statistical methods, including inverse variance weighted, MR-Egger, and weighted median, were employed to assess causal relationships.
• Cochran's Q statistic and colocalization analysis were used to evaluate heterogeneity and shared causal variants, respectively.

Key Points:

• Nitrogen dioxide exposure was causally associated with alterations in several gut bacteria, including significant inverse relationships with Akkermansia, Bacteroides, Barnesiella, Holdemania, and Sellimonas.
• Positive associations were observed between nitrogen dioxide exposure and Coprococcus 3, Eubacterium hallii group, and Olsenella.
• No significant heterogeneity or horizontal pleiotropy was detected, and colocalization analysis supported the links between nitrogen dioxide and Akkermansia and E. hallii.

Conclusions:

• This study provides genetic evidence that increased exposure to nitrogen dioxide can causally influence the composition of the human gut microbiota.
• These findings highlight a potential mechanism through which air pollution may affect host health via gut dysbiosis.
• Further research is warranted to explore the clinical implications of these nitrogen dioxide-gut microbiota interactions.