Islet amyloid polypeptide (IAPP) aggregates to form amyloid fibrils in patients with type 2 diabetes and acts as a potent stimulus for interleukin (IL)-1β secretion by bone marrow–derived macrophages. We sought to determine the contribution of resident islet macrophages to IAPP-induced inflammation and β-cell dysfunction. In cultured islets, macrophages (F4/80+CD11b+CD11c+ cells) were required for IAPP-induced mRNA expression of the proinflammatory cytokines IL-1β, tumor necrosis factor-α, and IL-6 and the anti-inflammatory cytokines IL-10 and IL-1 receptor antagonist. Moreover, IAPP-induced IL-1β synthesis and caspase-1 activation were detected in macrophages but not other islet cell types. Transgenic mice with β-cell human IAPP (hIAPP) expression had impaired glucose tolerance, elevated islet Il1b mRNA, and decreased Il10 and Il1rn expression following high-fat feeding. Islet macrophages were the major source of these transcripts and expressed increased cell surface Ly6C and CD11c in hIAPP transgenic mice. Clodronate liposome–mediated depletion of islet macrophages improved glucose tolerance and blocked proinflammatory gene expression in hIAPP-expressing mice, despite increasing the amount of islet amyloid. These data provide the first evidence that IAPP aggregates skew resident islet macrophages toward a proinflammatory phenotype and suggest a mechanism by which anti-inflammatory therapies may protect β-cells from IAPP-induced islet dysfunction.
This article contains Supplementary Data online at http://diabetes.diabetesjournals.org/lookup/suppl/doi:10.2337/db13-0863/-/DC1.
See accompanying article, p. 1448.
- Received May 31, 2013.
- Accepted November 8, 2013.
- © 2014 by the American Diabetes Association.
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