Endothelial dysfunction: associations with exposure to ambient fine particles in diabetic individuals

Abstract

Background: Exposure to fine airborne particulate matter [< or =2.5 microm in aerodynamic diameter (PM(2.5))] has been associated with cardiovascular and hematologic effects, especially in older people with cardiovascular disease. Some epidemiologic studies suggest that adults with diabetes also may be a particularly susceptible population.

Objectives: The purpose of this study was to analyze the short-term effects of ambient PM(2.5) on markers of endothelial function in diabetic volunteers.

Methods: We conducted a prospective panel study in 22 people with type 2 diabetes mellitus in Chapel Hill, North Carolina (USA), from November 2004 to December 2005. We acquired daily measurements of PM(2.5) and meteorologic data at central monitoring sites. On 4 consecutive days, we measured endothelial function by brachial artery ultrasound in all participants and by pulsewave measurements in a subgroup. Data were analyzed using additive mixed models with a random participant effect and adjusted for season, day of the week, and meteorology.

Results: Flow-mediated dilatation decreased in association with PM(2.5) during the first 24 hr, whereas small-artery elasticity index decreased with a delay of 1 and 3 days. These PM(2.5)-associated decrements in endothelial function were greater among participants with a high body mass index, high glycosylated hemoglobin A1c, low adiponectin, or the null polymorphism of glutathione S-transferase M1. However, high levels of myeloperoxidase on the examination day led to strongest effects on endothelial dysfunction.

Conclusions: These data demonstrate that PM(2.5) exposure may cause immediate endothelial dysfunction. Clinical characteristics associated with insulin resistance were associated with enhanced effects of PM on endothelial function. In addition, participants with greater oxidative potential seem to be more susceptible.

Keywords: air pollution; diabetes; endothelial dysfunction; environmental epidemiology; particulate matter.

Figure 1

Patient visits, air temperature, and PM_2.5 between 19 November 2004 and 9 December 2005. (A) Data points represent the week each of the 22 participants visited the HSF. (B) Daily 24-hr temperature averages (midnight to midnight) calculated from continuous 2-min data collected from the HSF rooftop. (C) Imputed 24-hr average PM_2.5 concentrations (midnight to midnight) collected at the official network station.

Figure 2

Effect modification of FMD by markers representing diabetic disease control or medication use. The estimates are given as percent change of mean FMD level based on a 10-μg/m³ increment of PM_2.5; error bars indicate 95% CIs. p-Values indicate the significance of the interaction term.

Figure 3

Effect modification of FMD (A) and SAEI (B) by the GSTM1 genotype. The estimates are given as percent change of mean FMD level based on a 10-μg/m³ increment of PM_2.5; error bars indicate 95% CIs. p-Values indicate the significance of the interaction term.