As levels of vehicle exhaust nitrogen oxide increased, there was a corresonding reduction in the gut bacteria Bacteroidaceae. An increase in the gut bacteria Coriobacteriaceae was also noted, which increased fasting glucose. Home addresses were used to estimate vehicle traffic air pollution in the homes of 43 adolescents. Scientists stated higher air pollution over time may contribute to obesity and insulin resistance through known inflammatory pathways related to changes in the gut microbiome (Boulangé et al., 2016; Cani et al., 2009). Read more for authors' concluding paragraph.
Below is the concluding paragraph as stated by the 7 scientists involved in this University of California study,
To our knowledge, this is the first study to show that increased TRAP (Traffic Related Air Pollution) exposure is associated with the gut microbiota. This study supports the hypothesis that environmental exposures, such as TRAP, have the potential to alter the relative abundance of gut bacteria. Results from this study also suggest that increased TRAP may negatively impact metabolic health through alterations in the composition and/or function of the gut microbiome, but larger studies are needed to confirm these initial findings. ..............................................
ABSTRACT
Background
Traffic-related air pollution (TRAP) exposure has been linked to type 2 diabetes and metabolic dysfunction in humans. Animal studies suggest that air pollutants may alter the composition of the gut microbiota, which may negatively impact metabolic health through changes in the composition and/or function of the gut microbiome.
Objectives
The primary aim of this study was to determine whether elevated TRAP exposure was correlated with gut bacterial taxa in overweight and obese adolescents from the Meta-AIR (Metabolic and Asthma Incidence Research) study. The secondary aim was to examine whether gut microbial taxa correlated with TRAP was also correlated with risk factors for type 2 diabetes (e.g., fasting glucose levels). We additionally explored whether correlations between TRAP and these metabolic risk factors could be explained by the relative abundance of these taxa.
Methods
Participants (17–19 years; n=43) were enrolled between 2014–2016 from Southern California. The CALINE4 line dispersion model was used to model prior year residential concentrations of nitrogen oxides (NOx) as a marker of traffic emissions. The relative abundance of fecal microbiota was characterized by 16S rRNA sequencing and spearman partial correlations were examined after adjusting for body fat percent.
Results
Freeway TRAP was correlated with decreased Bacteroidaceae (r=−0.48; p=0.001) and increased Coriobacteriaceae (r=0.48; p<0.001). These same taxa were correlated with fasting glucose levels, including Bacteroidaceae (r=−0.34; p=0.04) and Coriobacteriaceae (r=0.41; p<0.01). Further, freeway TRAP was positively correlated fasting glucose (r=0.45; p=0.004) and Bacteroidaceae and Coriobacteriaceae explained 24% and 29% of the correlation between TRAP and fasting glucose levels.
Conclusions
Increased TRAP exposure was correlated with gut microbial taxa and fasting glucose levels. Gut microbial taxa that were correlated with TRAP partially explained the correlation between TRAP and fasting glucose levels. These results suggest that exposure to air pollutants may negatively impact metabolic health via alterations in the gut microbiota.