STING signaling in islet macrophages impairs insulin secretion in obesity

The innate immune regulator stimulator of interferon genes(STING)mediates self-DNA sensing and leads to the induction of type I interferons and inflammatory cytokines,which promotes the progression of various inflammatory and autoimmune diseases.Innate immune system plays a critical role in regulating obesity-induced islet dysfunction,whereas the potential effect of STING signaling is not fully understood.Here,we demonstrate that STING is mainly expressed and activated in islet macrophages upon high-fat diet(HFD)feeding.Sting^(-/-)alleviates HFD-induced islet inflammation by inhibiting the expression of pro-inflammatory cytokines and the infiltration of macrophages.Mechanically,palmitic acid incubation promotes mitochondrial DNA leakage into the cytosol and subsequently activates STING pathway in macrophages.Additionally,STING activation in macrophages impairs glucose-stimulated insulin secretion by mediating the engulfment ofβcell insulin secretory granules.Pharmacologically inhibiting STING activation enhances insulin secretion to control hyperglycemia.Together,our results reveal a regulatory mechanism in controlling the islet inflammation and insulin secretion in dietinduced obesity and suggest that selective blocking of the STING activation may be a promising strategy for treating type 2 diabetes.