Exposure to air pollutants and the gut microbiota: a potential link between exposure, obesity, and type 2 diabetes

Figures & data

Figure 1. Hypothesized mechanisms linking exposure to air pollutants with the gut microbiota and increased risk for obesity and type 2 diabetes.

Table 1. Summary of studies that examined air pollutants and the gut microbiota in murine models.

Study	Animal Model	Experimental Design	Key Findings
Kish et al.^Citation19	Wild-type 129/SvEv female fasted mice (n = 6-9)	Exposure to PM10 via gavage compared to vehicle control group daily for 7 or 14 d	Alterations in gut microbial composition ↑ Intestinal permeability and inflammatory cytokines ↑ Intestinal damage
Li et al.^Citation20	Low-density lipoprotein receptor null mice (n = 12 and 11)	Consumption of high-fat diet exposed to ultrafine particles compared to vehicle control for 3 d/week for 10 weeks	↑ Verrucomicrobia bacteria and TNF-alpha levels ↓ Actinobacteria, Cyanobacteria, Firmicutes, and beta-diversity ↑ Intestinal inflammation
Ribière et al.^Citation21	C57BL/6 mice (n = 8-11)	Consumption of BaP diet, sunflower seed oil, or saline solution via oral gavage for 28 d	Alterations in composition and abundance of gut microbiota in BaP group ↑ Ileum and colon mucosa inflammation
Mutlu et al.^Citation22	C57BL/6 male mice (n = 10 and 10)	Exposure to concentrated PM2.5 air compared to filtered air	↑ Alpha diversity in some parts of GI tract ↑ Beta-diversity throughout the GI tract ↑ TNF-alpha expression in the colon
Wang et al.^Citation23	C57Bl/6 J mice (n = 10 and 10)	Exposure to concentrated PM2.5 air compared to filtered air for 12 months	↓ Fecal bacterial community richness ↑ Insulin resistance

The table shows the five murine studies included in this review. The table describes the animals examined, experimental design, and key findings. These studies examined the associations between inhaled and/or ingested air pollutants and gut microbial diversity, the relative abundance of gut bacterial taxa, gut barrier integrity, intestinal inflammation, and/or insulin resistance.

Figure 2. Gut bacterial phyla associated with exposure to air pollutants in animal and human studies.

Table 2. Summary of studies that examined air pollutants and the gut microbiota in humans.

Author	Study Population/Model Colon	Study Design	Key Findings
Alderete et al.^Citation24	Adolescents and young adults from Southern California (n = 43)	Correlations between traffic-related air pollution exposure and gut microbial composition	↑ Traffic-related air pollution exposure was correlated with ↓ Bacteroidaceae, ↑ Coriobacteriaceae, and ↑ fasting glucose levels
Liu et al.^Citation25	Adults from 14 randomly selected districts in southern China (n = 5,828)	Associations between PM2.5 and PM1 exposure with gut dysbiosis and glucose metabolism	↑ PM2.5 and PM1 exposure was associated with ↑ impaired fasting glucose and ↓ alpha diversity Association between particulate matter exposure and impaired fasting glucose was partially mediated by gut microbial diversity
Taylor et al.^Citation91	Model of proximal colon developed from a human donor	Gut microbial characterization after zinc oxide (ZnO), titanium dioxide (TiO2), and cerium dioxide (CeO2) exposure	↑ Nanoparticles resulted in ↑ hydrophobicity and ↓ pH ↑ CeO2 resulted in ↓ butyric acid production

The table shows the three human studies included in this review. The table describes the study population or model colon along with the study design and key findings. These studies examined associations between exposure to air pollutants or nanoparticles with gut microbial diversity, the relative abundance of gut bacterial taxa, gut barrier integrity, and/or measures of glucose metabolism.

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