title: Mechanisms of pancreatic beta-cell death in type 1 and type 2 diabetes: many differences, few similarities.
abstract: Type 1 and type 2 diabetes are characterized by progressive beta-cell failure. Apoptosis is probably the main form of beta-cell death in both forms of the disease. It has been suggested that the mechanisms leading to nutrient- and cytokine-induced beta-cell death in type 2 and type 1 diabetes, respectively, share the activation of a final common pathway involving interleukin (IL)-1beta, nuclear factor (NF)-kappaB, and Fas. We review herein the similarities and differences between the mechanisms of beta-cell death in type 1 and type 2 diabetes. In the insulitis lesion in type 1 diabetes, invading immune cells produce cytokines, such as IL-1beta, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma. IL-1beta and/or TNF-alpha plus IFN-gamma induce beta-cell apoptosis via the activation of beta-cell gene networks under the control of the transcription factors NF-kappaB and STAT-1. NF-kappaB activation leads to production of nitric oxide (NO) and chemokines and depletion of endoplasmic reticulum (ER) calcium. The execution of beta-cell death occurs through activation of mitogen-activated protein kinases, via triggering of ER stress and by the release of mitochondrial death signals. Chronic exposure to elevated levels of glucose and free fatty acids (FFAs) causes beta-cell dysfunction and may induce beta-cell apoptosis in type 2 diabetes. Exposure to high glucose has dual effects, triggering initially "glucose hypersensitization" and later apoptosis, via different mechanisms. High glucose, however, does not induce or activate IL-1beta, NF-kappaB, or inducible nitric oxide synthase in rat or human beta-cells in vitro or in vivo in Psammomys obesus. FFAs may cause beta-cell apoptosis via ER stress, which is NF-kappaB and NO independent. Thus, cytokines and nutrients trigger beta-cell death by fundamentally different mechanisms, namely an NF-kappaB-dependent mechanism that culminates in caspase-3 activation for cytokines and an NF-kappaB-independent mechanism for nutrients. This argues against a unifying hypothesis for the mechanisms of beta-cell death in type 1 and type 2 diabetes and suggests that different approaches will be required to prevent beta-cell death in type 1 and type 2 diabetes.
authors.affiliation: Laboratory of Experimental Medicine, Faculty of Medicine, Erasmus Hospital, Université Libre de Bruxelles (ULB), Route de Lennik 808, CP-618, 1070 Brussels, Belgium. mcnop@ulb.ac.be
authors.forename: Miriam
authors.initials: M
authors.lastname: Cnop
authors.forename: Nils
authors.initials: N
authors.lastname: Welsh
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Jonas
authors.forename: Anne
authors.initials: A
authors.lastname: Jörns
authors.forename: Sigurd
authors.initials: S
authors.lastname: Lenzen
authors.forename: Decio L
authors.initials: DL
authors.lastname: Eizirik
mesh_terms: D016923:Cell Death; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology / Q000473:pathology*; D003924:Diabetes Mellitus, Type 2 / Q000276:immunology / Q000473:pathology*; D006801:Humans; D050417:Insulin-Secreting Cells / Q000473:pathology*; D007371:Interferon-gamma / Q000502:physiology; D007375:Interleukin-1 / Q000502:physiology; D008954:Models, Biological
chemical_list: D007375:Interleukin-1; D007371:Interferon-gamma