Study: Urban air pollution and insulin resistance, type 2 diabetes and obesity

Relation

Alderete TL, Habre R, Toledo-Corral CM, et al. Longitudinal associations between air pollution and insulin sensitivity, β-cell function, and obesity among Latino children in Los Angeles [published online ahead of print January 30, 2017].diabetes.

Objective

Confirmation of epidemiological evidence that air pollutants are associated with a higher risk of type 2 diabetes mellitus (T2DM).

Draft

Longitudinal experiment

Participant

314 Latino youth ages 8 to 15 in the Los Angeles area who participated in the Childhood Obesity Research Center Air Study; All participants were either overweight or obese. These children were recruited between 2001 and 2012 and followed for an average of 3.4 years. None of the people included in the study were diabetic (assessed by an oral glucose tolerance test) or were taking medications that would affect insulin or glucose tolerance.

Study parameters assessed

Levels of pollutants in ambient air, including nitrogen monoxide, nitrogen dioxide (NO₂) and particulate matter less than 2.5 microns (PM2.5) were estimated using data collected from monitoring stations in the Los Angeles area. Monthly average exposure values ​​were calculated from daily values ​​and based on the distance from the monitoring stations (using a distance squared weighting algorithm).

Doctors need to start paying attention to the myriad adverse health effects of simply breathing air in all metropolitan areas.

Insulin sensitivity was assessed using an insulin-modified commonly administered 13-sample intravenous glucose tolerance test. Data from this test provided an assessment for whole body insulin sensitivity (Si), acute insulin response to glucose (AIRg), and assessment of beta cell function (disposition index [DI]). Body mass index (BMI) was also measured throughout the study.

Primary outcome measures

Primary outcome measures included:

• Ganzkörper-Insulinsensitivität
• Akute Insulinreaktion auf Glukose
• Beta-Zell-Funktion
• Adipositas

Key insights

Both PM2.5 and NO₂were independently associated with a statistically significant reduction in insulin sensitivity; NO₂was associated with a statistically significant decrease in beta cell function. Both PM2.5 and NO₂were associated with a statistically significant increase in BMI.

Practice implications

Lifestyle approaches to preventing and treating insulin resistance, metabolic syndrome, and T2DM typically focus on diet and exercise to reduce the number of calories consumed and increase the number of calories burned. Nevertheless, a number of environmental pollutants have been clearly associated with an increased risk of T2DM, including persistent organic pollutants and arsenic.

In the last decade, articles have begun to link vehicle exhaust—the ambient air pollution that is generally elevated in urban areas around the world—to metabolic abnormalities. Over the past 7 years, several studies have shown that adults and adolescents are exposed to higher levels of nitric oxide, NO₂, and PM2.5 had higher rates of T2DM. Three studies have shown that children and adults with increased exposure to vehicle exhaust had higher calculated insulin resistance (using Homeostatic Model Assessment of Insulin Resistance [HOMA-IR]).^1-3Because HOMA-IR results are not always confirmed by glucose tolerance testing, this longitudinal study was conducted.

This new study adds to the accumulating evidence that urban air pollution is linked to insulin resistance, beta cell function and obesity. Doctors need to start paying attention to the myriad adverse health effects of simply breathing air in all metropolitan areas. Home air purification devices, which force air through a series of filters to remove particles as small as 1 micron, should be on the list of “must-haves” for all patients, right alongside water filters, organic versions of the “dirty dozen” (most toxic fruits and vegetables), and exercise.