Association between Traffic-Related Air Pollution, Subclinical Inflammation and Impaired Glucose Metabolism: Results from the SALIA Study

Abstract

BackgroundEnvironmental and lifestyle factors regulate the expression and release of immune mediators. It has been hypothesised that ambient air pollution may be such an external factor and that the association between air pollution and impaired glucose metabolism may be attributable to inflammatory processes. Therefore, we assessed the associations between air pollution, circulating immune mediators and impaired glucose metabolism. MethodsWe analysed concentrations of 14 pro- and anti-inflammatory immune mediators as well as fasting glucose and insulin levels in plasma of 363 women from the Study on the influence of Air pollution on Lung function, Inflammation and Aging (SALIA, Germany). Exposure data for a group of pollutants such as nitrogen oxides (NO2, NOx) and different fractions of particulate matter were available for the participants' residences. We calculated the association between the pollutants and impaired glucose metabolism by multiple regression models. ResultsThe study participants had a mean age of 74.1 (SD 2.6) years and 48% showed impaired glucose metabolism based on impaired fasting glucose or previously diagnosed type 2 diabetes. Only long-term exposure NO2 and NOx concentrations showed positive associations (NO2: OR 1.465, 95% CI 1.049-2.046, NOx: OR 1.409, 95% CI 1.010-1.967) per increased interquartile range of NO2 (14.65 µg/m3) or NOx (43.16 µg/m3), respectively, but statistical significance was lost after correction for multiple comparisons. Additional adjustment for circulating immune mediators or the use of anti-inflammatory medication had hardly any impact on the observed ORs. ConclusionsOur results suggest that exposure to nitrogen oxides may contribute to impaired glucose metabolism, but the associations did not reach statistical significance so that further studies with larger sample sizes are required to substantiate our findings. Our data do not preclude a role of inflammatory mechanisms in adipose or other tissues which may not be reflected by immune mediators in plasma.

Ambient Air Pollution and Type 2 Diabetes Mellitus: A Systematic Review of Epidemiologic Research

“…In a study of 8,018 residents (prevalence of T2DM=8%) from Westfriesland, Netherlands, NO 2 was not associated with the prevalence of T2DM [17]. A study conducted in the SALIA cohort, Germany (N=363, 100% women, prevalence of IGM=48%) found significant positive associations of IGM with NO 2 (OR=1.47 (95% CI, 1.05, 2.05) per IQR increase) and NO x (OR=1.41 (95% CI, 1.01, 1.97)) [28]. Finally, in an ecological study of the association between county-level PM 2.5 concentrations and diabetes prevalence in the US [25], a 10 μg/m 3 increase in PM 2.5 was associated with a 1.15% (95% CI, 1.02, 1.32%) increase in the diabetes prevalence in 2004 and a 0.92% (95% CI, 0.75, 1.13%) increase in 2005.…”

“…For the incidence and prevalence studies and observational diabetes mortality studies, either annual concentrations of particulate matters (mostly PM 2.5 or PM 10 and PM 10–2.5 (coarse particles)) or nitrogen oxides (NO x or NO 2 ) which were estimated using land-use regression [10, 11, 15, 17, 26–28, 30] or satellite-based approach [13] were used as exposure metrics, whereas ecological studies of DM mortality or hospital/emergency admissions (except the study by Kloog et al [22]) used daily concentrations of criteria pollutants (PM 2.5 , PM 10 , NO 2 , CO, SO 2 , and O 3 ) based on central monitoring or the nearest monitors. Given the differences in study design and disease etiology between long-term air pollution effects on the development of T2DM vs. short-term air pollution effects on daily diabetes mortality or morbidity, we discussed causal relationships based on epidemiologic findings by these two study designs separately.…”

Ambient Air Pollutants Have Adverse Effects on Insulin and Glucose Homeostasis in Mexican Americans

“…Recent studies also found positive associations between ambient and traffic-related air pollutants and impaired glucose metabolism (3,4), with most studies assessing the impact of acute exposures. A study in Taiwan documented that elevated 5-day average O 3 was associated with increased fasting glucose (4).…”

“…Only a few human studies have been performed and have suggested that short- and long-term exposure to air pollutants adversely affects key T2D-related pathways including glucose metabolism (3,4), insulin resistance (5–8), and dyslipidemia (4,9). While most previous studies have been conducted among Caucasians (3,7) and Asians (4,8), the effects in other populations with generally higher risk for T2D, such as Latinos (10) and African Americans (11), have not been adequately studied. Additionally, the informativeness of results from these studies is limited by the use of surrogate indices of insulin resistance, for example, HOMA of insulin resistance (HOMA-IR), which have well-documented limitations compared with detailed measures of insulin resistance such as intravenous glucose tolerance test and glucose clamps.…”

MECHANISMS IN ENDOCRINOLOGY: Effect of long-term exposure to air pollution on type 2 diabetes mellitus risk: a systemic review and meta-analysis of cohort studies

“…Inflammation is another potential mechanism explaining the associations reported in this meta-analysis. There is high possibility for the activation of the inflammatory pathway and oxidative stress pathway by particulate matter (38,39,40). Previous studies also suggest that PM2.5 can recruit inflammatory cells via CC chemokine receptor 2-dependent mechanism, which is a known inflammatory mechanism in the pathogenesis underlying the association between air pollution and type 2 diabetes (35,41).…”