Autophagy is a dynamic recycling mechanism that maintains beta cell homeostasis, whereas the related process of crinophagy also plays a specific role in insulin granule regulation. Impairment of autophagy and crinophagy have been implicated in beta cell death and dysfunction in the context of type 2 diabetes; however, there is currently no literature describing beta cell autophagy in type 1 diabetes pathogenesis. Therefore, we set out to determine if beta cell autophagy and crinophagy are impaired in the context of type 1 diabetes. We utilized immunofluorescent staining of LC3 (autophagosome marker), Lamp1 (lysosome marker), and proinsulin to analyze pancreatic islet autophagy and crinophagy in the NOD (non-obese diabetic) mouse model of type 1 diabetes as well as in human pancreas tissue obtained from the network for Pancreatic Organ donors with Diabetes (nPOD). We observed evidence of reduced macroautophagy in the residual proinsulin-positive islet cells of human donors with type 1 diabetescompared to controls, as measured by significantly reduced autophagosome:lysosome colocalization (p=0.034). Similarly, there was a trend towards reduced autophagosome:lysosome colocalization in islets of diabetic NOD mice compared to nondiabetic NOR mice (p=0.08). We also observed significantly reduced colocalization of proinsulin with lysosomes in the proinsulin positive cells from human donors with type 1 diabetes in comparison to both controls without diabetes (p=0.0014) and autoantibody positive donors (p= 0.0278), as well as in diabetic NOD vs. nondiabetic NOR mice (p=0.0121), suggesting that crinophagy is also reduced as a function of type 1 diabetes. Collectively, we provide evidence that macroautophagy and crinophagy are reduced in the context of type 1 diabetes. Considering these data in the context of what is known regarding the cell-protective effects of islet autophagy, we suggest targeting beta cell autophagy pathways as an approach to reduce apoptosis in individuals at risk for type 1 diabetes development.


C. Muralidharan: None. M. Marasco: Employee; Spouse/Partner; Eli Lilly and Company. J. Crowder: Employee; Spouse/Partner; Eli Lilly and Company. A.M. Conteh: None. A.K. Linnemann: None.

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