DOI: 10.2337/db07-0830
Non-obese diabetic (NOD) mice congenic for a targeted deletion of 12/15- lipoxygenase are protected from autoimmune diabetes.1University of Virginia Objective: 12/15-lipoxygenase (12/15-LO), one of a family of fatty acid oxidoreductase enzymes, reacts with polyenoic fatty acids to produce pro-inflammatory lipids. 12/15-LO is expressed in macrophages and pancreatic ß-cells. It enhances interleukin 12 production by macrophages, and several of its products induce apoptosis of ß cells at nanomolar concentrations in vitro. We had previously demonstrated a role for 12/15-LO in ß-cell damage in the streptozotocin model of diabetes. Since the gene encoding 12/15-LO (gene designation: Alox15) lies within the Idd4 diabetes susceptibility interval in NOD mice, we hypothesized that 12/15-LO is also a key regulator of diabetes susceptibility in the NOD mouse. Research Design and Methods: We developed NOD mice carrying an inactivated 12/15-LO locus (NOD-Alox15null) using a speed congenic protocol and the mice were monitored for development of insulitis and diabetes. Results: NOD mice deficient in 12/15-LO develop diabetes at a markedly reduced rate compared to NOD mice (2.5% vs. >60% in females by 30 weeks). Non-diabetic female NOD-Alox15null mice demonstrate improved glucose tolerance, as well as significantly reduced severity of insulitis and improved ß-cell mass, when compared to age-matched non-diabetic NOD females. Disease resistance is associated with decreased numbers of islet-infiltrating activated macrophages at 4 weeks of age in NOD-Alox15null mice, preceding the development of insulitis. Subsequently, islet-associated infiltrates are characterized by decreased numbers of CD4+ T cells and increased Foxp3+ cells. Conclusions: These results suggest an important role for 12/15-LO in conferring susceptibility to autoimmune diabetes in NOD mice through its effects on macrophage recruitment or activation.
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