Central IKKβ inhibition prevents air pollution mediated peripheral inflammation and exaggeration of type II diabetes

BACKGROUND: Prior experimental and epidemiologic data support a link between exposure to fine ambient particulate matter (<2.5 μm in aerodynamic diameter, PM(2.5)) and development of insulin resistance/Type II diabetes mellitus (Type II DM). We investigated the role of hypothalamic inflammation in PM(2.5)-mediated diabetes development. METHODS: KKay mice, a genetically susceptible model of Type II DM, were assigned to either concentrated PM(2.5) or filtered air (FA) for 4–8 weeks via a versatile aerosol concentrator and exposure system, or administered intra-cerebroventricular with either IKKβ inhibitor (IMD-0354) or TNFα antibody (infliximab) for 4–5 weeks simultaneously with PM(2.5) exposure. Glucose tolerance, insulin sensitivity, oxygen consumption and heat production were evaluated. At euthanasia, blood, spleen, visceral adipose tissue and hypothalamus were collected to measure inflammatory cells using flow cytometry. Standard immunohistochemical methods and quantitative PCR were used to assess targets of interest. RESULTS: PM(2.5) exposure led to hyperglycemia and insulin resistance, which was accompanied by increased hypothalamic IL-6, TNFα, and IKKβ mRNA expression and microglial/astrocyte reactivity. Targeting the NFκB pathway with intra-cerebroventricular administration of an IKKβ inhibitor [IMD-0354, n = 8 for each group)], but not TNFα blockade with infliximab [(n = 6 for each group], improved glucose tolerance, insulin sensitivity, rectified energy homeostasis (O(2) consumption, CO(2) production, respiratory exchange ratio and heat generation) and reduced peripheral inflammation in response to PM(2.5). CONCLUSIONS: Central inhibition of IKKβ prevents PM(2.5) mediated peripheral inflammation and exaggeration of type II diabetes. These results provide novel insights into how air pollution may mediate susceptibility to insulin resistance and Type II DM.