2012 Progress Report: Long Term Metabolic Consequences of Exposures to Multipollutant Atmospheres in the Great Lakes Region

EPA Grant Number: R834797C003
Subproject: this is subproject number 003 , established and managed by the Center Director under grant R834797
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: Great Lakes Air Center for Integrative Environmental Research
Center Director: Harkema, Jack
Title: Long Term Metabolic Consequences of Exposures to Multipollutant Atmospheres in the Great Lakes Region
Investigators: Rajagopalan, Sanjay , Sun, Qinghua
Institution: The Ohio State University - Main Campus , University of Michigan - Ann Arbor
Current Institution: The Ohio State University - Main Campus
EPA Project Officer: Ilacqua, Vito
Project Period: December 1, 2010 through November 30, 2015 (Extended to December 31, 2016)
Project Period Covered by this Report: December 1, 2011 through November 30,2012
RFA: Clean Air Research Centers (2009) RFA Text |  Recipients Lists
Research Category: Health Effects , Air

Objective:

We have recently demonstrated that short-term exposure to inhaled concentrated airborne particulate (CAP) matter <2.5μm (PM2.5) results in components of cardiometabolic syndrome (CMS) including development of hypertension and insulin resistance. In this project, we hypothesize that chronic inhalation of CAP in conjunction with gaseous components such as ozone from distinct multipollutant atmospheres synergistically interacts with diet and genetic susceptibility to influence development of CMS. Project 3 is an integral component of the overarching theme of this center that primary air pollutants, fine PM (PM2.5) and ozone (O3), cause cardiometabolic health effects that are dependent on the local atmospheric multipollutant milieu, predisposing factors, and the interactive toxicity of multipollutant coexposure. The experiments proposed are natural extensions of human research outlined in Project 1 and acute experiments in Project 2 and will focus on conducting chronic inhalation toxicology studies in diet fed and genetic models of obesity/diabetes. In Aim 1, simultaneous chronic exposure to multipollutant CAP from two locations in Columbus, OH representing near-roadside/traffic or remotely transported/aged emissions will be examined in combination with high fat chow (HFC). The impact of CAP on glucose/ insulin homeostasis, adipokines, insulin signaling, adipose and pulmonary inflammation and an analysis of dose dependence and CAP components most likely associated with these effects will be evaluated in diet sensitive (C57BL/6) and genetic models of Type II diabetes susceptibility (KKA/y). In Aim 2, we will investigate the effect of co-exposure of multipollutant CAP with ozone on the temporal development of insulin resistance and adipose/lung inflammation using the KKA/y model. We will assess dose response relationship of multipollutant-O3 mixture on insulin resistance measures (HOMA-IR and IPGTT) and novel mediators of innate immune, pivotal in the development of metabolic derangement. Based on data from Aims 1 and 2, we will design experiments in Aim 3, which will help us assess chronic effects of multipollutant CAP in potentiating inflammatory monocyte activation and infiltration into tissue niches as a central mechanism for mediating adverse metabolic effects of CAP. Using state of the art multiple exposure systems available at OSU (OASIS-1 and OASIS-2) and MI in conjunction the resources available at the ECC including the use of several novel and novel high-time resolution exposure characterization methods, GLACIER offers an unprecedented opportunity to elucidate relevant mechanisms responsible for the effects of multipollutant CAP on the pathogenesis of insulin resistance and inflammation. The insights gleaned from the acute studies planned in Projects 1 and 2 in conjunction with chronic studies in Project 3, have significant public health ramifications and may eventually lead to policy changes to avert environmental exposure to PM2.5.

Progress Summary:

Exposure Facilities:

As part of year 1, we have commissioned a new exposure facility that will allow simultaneous near roadway exposure concomitant with our existing facility that will mimic regional exposure. We have done preliminary testing and this location is already exposing animals. Figure 1 details exposure concentrations in this facility.
 
 
These results suggest that we are able to successfully concentrate roadway PM and nearly a five-fold increase in BC levels compared to ambient concentrations. During the year 1 for Project 3, we first investigated how PM2.5 exposure enhanced inflammation. For this set of experiments, we exposed mice to regional PM2.5 in our other exposure facility as these required long-term exposures that predated the commission of the near roadway facility. Figure 1 details the results of this exposure.
 
 
In year 1 since our exposure facilities were being built, we focused on continuation of prior experiments involving understanding the mechanism of heightened innate immune inflammation in response to air pollution. We initially investigated the effects of CCR2 in mediating inflammation, CCR2-/- mice were exposed to concentrated ambient PM2.5 or filtered air (FA) for 6 hours per day, 5 days per week for a total of 14 weeks in a versatile aerosol concentrator exposure system. Mice were fed HFD (60% from fat-adjusted calorie diet) and metabolic indices such as Glucose tolerance and insulin resistance was evaluated. At the end of the experiment, blood, spleen and visceral adipose tissue were collected to measure inflammatory monocytes or activated macrophages with flow cytometry. Western blot were used to test protein levels. Immunohistochemistry was used d to test macrophage infiltration (F4/80) in visceral adipose tissue and aortic sections. Real time PCR was used to examine gene expression. Vascular function of aorta was assessed with myography.
 
 
Main Results of Exposure in CCR2-/- and wild type mice (C57Bl/6 background):
 
After 14 weeks CAP exposure in conjunction with HFD, mice were sacrificed and glucose homeostasis
was evaluated by IPGTT and ITT. Figure 2 reveals that CAP exposure exaggerated insulin resistance
demonstrated by abnormality of ITT and calculated HOMA-IR, which were normalized by CCR2 deficiency.

Our prior experiments have suggested an effect of PM2.5 in increasing peripheral inflammation. We then investigate the effects of CAP exposure on inflammatory monocytes in blood and spleen in mice exposed to FA or PM2.5 for 14 weeks. Results demonstrated that the increase in inflammatory monocytes in response to PM2.5 were reversed in blood by CCR2 deficiency and the this monocyte subset was lower in CCR2 -/- mice than wild type mice (Figure 3). We next tested the effect of exposure on insulin signaling pathways and MAPK activation in the liver. A selective increase in p38 MAPK signaling in the liver was noted, an effect mediated likely by PM2.5 and attenuated by CCR2 deficiency. These results are portrayed in Figure 4. We also investigated endothelium function and vascular response to insulin in aorta, another target organ of insulin resistance. It demonstrated that CAP exposure impairs endothelium function and insulin-induced vasorelaxation, which were not modified by CCR2 deficiency (Figure 5).

To assess the effect of CAP exposure on insulin resistance, we further visceral adipose tissue, a major source of inflammatory cytokines and free fatty acids in insulin resistance. In contrast to the lack of alteration of insulin signaling in liver, phosphorylation of Akt at ser473 was decreased significantly in adipose tissue with deficiency. CCR2 deficiency markedly alleviated these changes. To investigate the mechanism of insulin resistance in visceral adipose tissue, we firstly measured macrophage infiltration (F4/80+ staining) and quantified VAT infiltration by inflammatory macrophages using flow cytometry. Our results indicated that CCR2 mediated infiltration of visceral adipose tissue by inflammatory macrophages defined as CD11b+F4/80+ and CD11c+F4/80+ cells plays a pivotal role in PM2.5- exaggarated insulin resistance (Figure 6). 

Conclusions:
 
Chronic PM2.5 exposure exaggerated HFD-induced insulin resistance, which was improved in CCR2-/- mice. Improvement in IR was accompanied by reduced inflammatory monocytes in blood and spleen. Insulin signaling was reduced in VAT with PM2.5 exposure along with pronounced VAT infiltration. There was evidence of activation of MAPK pathways in the liver both of which were improved in the CCR-/- mice. Our results suggest a critical role for CCR2 in PM2.5 mediated effects. 
 

Future Activities:

All aspects of the study protocol are approved by our IACUC. KKAY mice as specified in Aim 1 have undergone exposure at Polaris Exposure Facility (OASIS-2) in Columbus, OH, and the results are being summarized. We will thereafter begin specific aim 2.


Journal Articles on this Report : 3 Displayed | Download in RIS Format

Other subproject views: All 46 publications 35 publications in selected types All 35 journal articles
Other center views: All 147 publications 71 publications in selected types All 71 journal articles
Type Citation Sub Project Document Sources
Journal Article Brook RD, Rajagopalan S. Can what you breathe trigger a stroke within hours? Comment on "ambient air pollution and the risk of acute ischemic stroke". Archives of Internal Medicine 2012;172(3):235-236. R834797 (2014)
R834797 (2015)
R834797 (2016)
R834797 (Final)
R834797C003 (2012)
R834797C003 (Final)
  • Abstract from PubMed
  • Abstract: Archives of Internal Medicine-Abstract & Preview
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  • Journal Article Wold LE, Ying Z, Hutchinson KR, Velten M, Gorr MW, Velten C, Youtz DJ, Wang A, Lucchesi PA, Sun Q, Rajagopalan S. Cardiovascular remodeling in response to long-term exposure to fine particulate matter air pollution. Circulation:Heart Failure 2012;5(4):452-461. R834797 (2014)
    R834797 (2015)
    R834797 (2016)
    R834797 (Final)
    R834797C003 (2012)
    R834797C003 (Final)
  • Full-text from PubMed
  • Abstract from PubMed
  • Associated PubMed link
  • Full-text: American Heart Association-Full Text HTML
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  • Abstract: American Heart Association-Abstract
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  • Other: American Heart Association-Full Text PDF
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  • Journal Article Xu X, Liu C, Xu Z, Tzan K, Wang A, Rajagopalan S, Sun Q. Altered adipocyte progenitor population and adipose-related gene profile in adipose tissue by long-term high-fat diet in mice. Life Sciences 2012;90(25-26):1001-1009. R834797 (2014)
    R834797 (2015)
    R834797 (2016)
    R834797 (Final)
    R834797C003 (2012)
    R834797C003 (Final)
  • Full-text from PubMed
  • Abstract from PubMed
  • Associated PubMed link
  • Full-text: ScienceDirect-Full Text HTML
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  • Abstract: ScienceDirect-Abstract
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  • Other: ScienceDirect-Full Text PDF
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  • Supplemental Keywords:

    Ozone (O3) PM2.5, Type II Diabetes Mellitus (DM), Insulin Resistance (IR), Scientific Discipline, Air, ENVIRONMENTAL MANAGEMENT, air toxics, Health Risk Assessment, Biochemistry, Biology, Risk Assessment, ambient air quality, particulate matter, aerosol particles, susceptible populations, acute cardiovascualr effects, human exposure, physiology, cardiopulmonary, cardiotoxicity

    Relevant Websites:

    http://greatlakesairresearchcenter.org/ Exit

    Progress and Final Reports:

    Original Abstract
  • 2011 Progress Report
  • 2013 Progress Report
  • 2014 Progress Report
  • 2015 Progress Report
  • 2016 Progress Report
  • Final Report

  • Main Center Abstract and Reports:

    R834797    Great Lakes Air Center for Integrative Environmental Research

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R834797C001 Cardiometabolic Effects of Exposure to Differing Mixtures and Concentrations of PM2.5 in Obese and Lean Adults
    R834797C002 Cardiometabolic, Autonomic, and Airway Toxicity of Acute Exposures to PM2.5 from Multipollutant Atmospheres in the Great Lakes Region
    R834797C003 Long Term Metabolic Consequences of Exposures to Multipollutant Atmospheres in the Great Lakes Region