Reduced metabolic insulin sensitivity following sub-acute exposures to low levels of ambient fine particulate matter air pollution

摘要

Epidemiological studies suggest that fine particulate matter (PM_(2.5)) may increase the risk for developing diabetes mellitus (DM). To evaluate possible mechanisms explaining these associations, we investigated if sub-acute ambient-level exposures can impair insulin sensitivity. Twenty-five healthy adults living in rural Michigan were transported to an urban location for 5 consecutive days (exposure-block) of daily 4- to 5-hour-long ambient air pollution exposures. Health outcomes, including the homeostasis model assessment of insulin resistance (HOMA-IR) the primary outcome of insulin sensitivity, were measured at 3 time points in relation to exposure-blocks: 7 days prior to start; on the last exposure-day; and 7 days after completion. PM_(2.5) was monitored at the urban exposure site and at community monitors near subjects' residences. We calculated 3 "sub-acute" exposure periods (approximately 5-days-long) starting retrospective from the time of health outcome measurements (PM2.5 ranges: 9.7 ± 3.9 to 11.2 ± 3.9 µg-m~(-3)). A 10 ug·m~(-3) increase in sub-acute PM_(2.5) exposures was associated with increased HOMA-IR (+0.7,95% confidence interval (CI) 0.1 to 1.3; p = 0.023) and reduced heart rate variability (standard deviation of normal-to-normal intervals [-13.1 ms, 95%CI -25.3 to -0.9; p = 0.035]). No alterations in other outcomes (inflammatory markers, vascular function) occurred in relation to PM_(2.5) exposures. Our findings suggest that ambient PM_(2.5), even at low levels, may reduce metabolic insulin sensitivity supporting the plausibility that air pollution could potentiate the development of DM.