It is known that insulin resistance is present long before the onset of type 2 diabetes and results not only from genetics and lifestyle factors but likely also from environmental conditions.  Now, a study from researchers at Helmholtz Zentrum München shows that exposure to air pollution in the home increases the risk of developing insulin resistance as a pre-diabetic state of type 2 diabetes.  The team state that their findings suggest the disease can become manifest due to lifestyle, genetic factors, and traffic-related air pollution.  The study is published in the journal Diabetes.

Previous studies show an association between air pollution and type 2 diabetes risk.  Type 2 diabetes susceptibility loci have been increasingly identified through genome-wide analyses. So far, over sixty type 2 diabetes genetic risk variants have been identified. It is hoped by selecting diabetes gene risk variants identified in genome-wide association studies for interaction with air pollution, a novel mechanistic understanding may evolve.  Effects of inhaled pollutants that are also supported by evidence include the contribution to systemic inflammation, autonomic imbalance, weight gain, and to insulin resistance, thought to be in part the result of inhalants stimulating an innate immune response.  However, the underlying mechanisms and susceptibilities are still subject to active research.  The current study investigates the association between modelled long-term exposure to air pollution in the home and biomarkers related to insulin resistance, subclinical inflammation and adipokines.

The current study analyzes the data of nearly 3,000 participants, for which various markers for insulin resistance and inflammation were identified. Non-diabetic individuals underwent an oral glucose tolerance test to detect whether their glucose metabolism was impaired.  The group compared these data with the concentrations of air pollutants at the homes of the participants, which they estimated using predictive models based on repeated measurements at 20 sites for particle measurements and at 40 sites for nitrogen dioxide measurements in the city and in the rural counties.

Results show that people who already have an impaired glucose metabolism, pre-diabetic individuals, are particularly vulnerable to the effects of air pollution.  Data findings show that in these individuals, the association between increases in their blood marker levels and increases in air pollutant concentrations is particularly significant. The researchers conclude that over the long-term, especially for people with impaired glucose metabolism, air pollution is a risk factor for type 2 diabetes.

The lab stress that they are also concerned that the concentrations of air pollutants, though below EU threshold values, are still above the proposed guidelines of the WHO, and as a consequence, they demand changes in government policy to lower the threshold for acceptable air pollution levels.  They go on to add that the association between increased exposure to air pollution and respiratory and cardiovascular diseases has also been clearly established.

The team surmise that their findings suggest an association between long-term exposure to air pollution and insulin resistance in the general population, mainly attributable to pre-diabetic individuals.  For the future, the researchers state that they now plan to investigate the influence of ultra fine particles on diabetes risk.

Source: Helmholtz Zentrum München