The mediated role of complement C3 in PM2.5 exposure and type 2 diabetes mellitus: an elderly panel study in Beijing, China

Environmental PM2.5-triggered stress responses in digestive diseases

Airborne particulate matter in fine and ultrafine ranges (aerodynamic diameter less than 2.5 μm, PM2.5) is a primary air pollutant that poses a serious threat to public health. Accumulating evidence has pointed to a close association between inhalation exposure to PM2.5 and increased morbidity and mortality associated with modern human complex diseases. The adverse health effect of inhalation exposure to PM2.5 pollutants is systemic, involving multiple organs, different cell types and various molecular mediators. Organelle damages and oxidative stress appear to play a major role in the cytotoxic effects of PM2.5 by mediating stress response pathways related to inflammation, metabolic alteration and cell death programmes. The organs or tissues in the digestive tract, such as the liver, pancreas and small intestines, are susceptible to PM2.5 exposure. This review underscores PM2.5-induced inflammatory stress responses and their involvement in digestive diseases caused by PM2.5 exposure.

Role of Liver Enzymes in the Relationship Between Particulate Matter Exposure and Diabetes Risk: A Longitudinal Cohort Study

CONTEXT

Particulate matter (PM) is an important risk factor for diabetes. However, its underlying mechanisms remain poorly understood. Although liver-derived biological intermediates may play irreplaceable roles in the pathophysiology of diabetes, few studies have explored this in the association between PM and diabetes.

OBJECTIVE

We investigated the role of liver enzymes in mediating the relationship between PM exposure and diabetes.

METHODS

We included a total of 7963 participants from the China Multi-Ethnic Cohort. Residential exposure to PM was assessed using a validated spatial-temporal assessment method. Diabetes was diagnosed according to the criteria from American Diabetes Association. Associations between PM, liver enzyme [including alanine aminotransferase (ALT), aspartate aminotransferase, alkaline phosphatase, and γ-glutamyl transpeptidase (GGT)], and diabetes were estimated using multivariable regression models. The function of liver enzymes in the relationship between PM and diabetes was assessed using mediation analysis.

RESULTS

PM exposure was positively associated with the odds of diabetes, with odds ratios of 1.32 (95% CI 0.83, 2.09), 1.33 (95% CI 1.07, 1.65), and 1.18 (95% CI 1.02, 1.36) for every 10-μg/m3 increment in ≤1 μm (PM1), ≤2.5 μm (PM2.5), and ≤10 μm (PM10) PM, respectively. ALT (4.47%) and GGT (4.78%) exhibited statistically significant mediation effects on the association between PM2.5 and diabetes, and the ALT (4.30%) also had a mediating role on PM10. However, none of the liver enzymes had a significant mediating effect on PM1.

CONCLUSION

The relationship between PM and diabetes is partially mediated by liver enzymes, suggesting that lipid accumulation, oxidative stress, and chronic inflammation in the liver may be involved in its pathogenesis.

Peat smoke inhalation alters blood pressure, baroreflex sensitivity, and cardiac arrhythmia risk in rats

Wildland fires (WF) are linked to adverse health impacts related to poor air quality. The cardiovascular impacts of emissions from specific biomass sources are however unknown. The purpose of this study was to assess the cardiovascular impacts of a single exposure to peat smoke, a key regional WF air pollution source, and relate these to baroreceptor sensitivity and inflammation. Three-month-old male Wistar-Kyoto rats, implanted with radiotelemeters for continuous monitoring of heart rate (HR), blood pressure (BP), and spontaneous baroreflex sensitivity (BRS), were exposed once, for 1-hr, to filtered air or low (0.38 mg/m³ PM) or high (4.04 mg/m³) concentrations of peat smoke. Systemic markers of inflammation and sensitivity to aconitine-induced cardiac arrhythmias, a measure of latent myocardial vulnerability, were assessed in separate cohorts of rats 24 hr after exposure. PM size (low peat = 0.4-0.5 microns vs. high peat = 0.8-1.2 microns) and proportion of organic carbon (low peat = 77% vs. high peat = 65%) varied with exposure level. Exposure to high peat and to a lesser extent low peat increased systolic and diastolic BP relative to filtered air. In contrast, only exposure to low peat elevated BRS and aconitine-induced arrhythmogenesis relative to filtered air and increased circulating levels of low-density lipoprotein cholesterol, complement components C3 and C4, angiotensin-converting enzyme (ACE), and white blood cells. Taken together, exposure to peat smoke produced overt and latent cardiovascular consequences that were likely influenced by physicochemical characteristics of the smoke and associated adaptive homeostatic mechanisms.