Abstract
Type 1 diabetes (T1D) is a consequence of autoimmune-mediated destruction of pancreatic β-cells and the leading causes for this process are incompletely understood. Our previous work suggests the involvement of lipid signaling from immune cells on T1D development. Relevant lipids were shown to be generated by the Ca2+-independent phospholipase A2β (iPLA2β), which is ubiquitously expressed and hydrolyzes membrane phospholipids at the sn-2 position to release bioactive lysophospholipids and free fatty acids such as arachidonic acid. Arachidonic acid can be metabolized to generate eicosanoids, many of which are pro-inflammatory. We found that iPLA2β activation promotes pro-inflammatory M1 macrophage phenotype and that selective inhibition of iPLA2β preserves β-cell mass and reduces T1D incidence and insulitis in the NOD mice. Herein, we report that NOD macrophages generate significantly higher pro-inflammatory lipids and reduced anti-inflammatory lipids than C57 macrophages during the prediabetic phase. Such changes in the lipidome are mitigated with reduced expression of iPLA2β. Specifically, lipidomics analyses revealed that NOD.iPLA2β+/- macrophage production of multiple pro-inflammatory lipids (PGE2, leukotrienes, 12-HETE, DHETs) is decreased, and of anti-inflammatory lipids increased, relative to NOD-derived macrophages. The mitigated inflammatory lipid signature during the prediabetic phase the NOD.iPLA2β+/- contributed to a reduced T1D incidence. These findings suggest a role for macrophage iPLA2β-derived lipids (iDLs) in T1D development. In support, adoptive transfer of NOD.iPLA2β+/- macrophages reduced T1D incidence and improved glucose tolerance; and conditional knockout of iPLA2β in macrophages reduced T1D incidence in the NOD mice. We hypothesize that iDLs produced by macrophages contribute to T1D development and that these could be targeted to prevent onset/progression of T1D.
Disclosure
A. Almutairi: None. Y. Gai: None. X.Y. Lei: None. M.A. Park: None. C. Chalfant: None. S. Ramanadham: None. D. Stephenson: None.
Funding
National Institute of Diabetes and Digestive and Kidney Diseases (R01DK110292); National Institute of Allergy and Infectious Diseases (R21AI146743)