Effect of diesel exhaust inhalation on antioxidant and oxidative stress responses in adults with metabolic syndrome

Abstract

Background: Traffic-related air pollution is associated with cardiovascular morbidity and mortality. Although the biological mechanisms are not well understood, oxidative stress may be a primary pathway. Subpopulations, such as individuals with metabolic syndrome (MeS), may be at increased risk of adverse effects associated with air pollution. Our aim was to assess the relationship between exposure to diesel exhaust (DE) and indicators of systemic antioxidant and oxidative responses in adults with MeS. We hypothesized that DE exposure would result in greater oxidative stress and antioxidant responses compared with filtered air (FA).

Methods: Ten adult subjects with MeS were exposed on separate days for two hours to FA or DE (at 200μg/m3), in a double blind, crossover experiment. Urinary 8-isoPGF2α (F2-isoprostanes), and 8-hydroxy-2’-deoxyguanosine (8-OHdG) were assessed as markers of oxidative stress at 3 hrs and 22 hrs, respectively, after exposure initiation. To assess the short-term antioxidant response we analyzed plasma ascorbic acid (AA) 90 minutes after exposure initiation. All outcomes were compared to pre-exposure levels, and mean changes were compared between FA and DE exposures.

Results: Mean changes in urinary F2-isoprostanes (ng/mg creatinine), (−0.05 [95% CI = −0.29, 0.15]), and 8-OHdG (μg/g creatinine) (−0.09 [−0.13, 0.31]), were not statistically significant. Mean changes in plasma AA (mg/dl) were also not significant (−0.02 [−0.78, 0.04]).

Conclusions: In this carefully controlled experiment, we did not detect significant changes in oxidative stress or systemic antioxidant responses in subjects with MeS exposed to 200μg/m3 DE.

Keywords::

• Air pollution
• diesel exhaust
• oxidative stress
• antioxidants
• metabolic syndrome
• controlled exposure experiment
• crossover studies
• vehicle emissions/toxicity
• adult
• biological markers
• human
• male
• female

Acknowledgements

We thank the staff of the GCRC, the CNRU, our engineering staff, Tim Larson, Tim Gould, and Jim Stewart, and our sample handling and processing technicians Pat Janssen and Jasmine Wilkerson, as well as our project coordinator Mary Aulet, and all of the volunteers who agreed to participate in this study.

Declaration of interest: Support for this study was provided by grants R830954 and R827355 from the Environmental Protection Agency, K24ES013195 and P30ES07033 from the National Institute of Environmental Health Sciences, F32AT003366-01 from the National Center for Complementary and Alternative Medicine, M01RR00037 from the National Center for Research Resources, and P30DK035816 from the National Institute of Diabetes and Digestive and Kidney Diseases. The authors declare that they have no competing interests.