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postgraduate thesis: Adaptor protein APPL1 counteracts streptozotocin-induced diabetes and ß cells loss in mice

TitleAdaptor protein APPL1 counteracts streptozotocin-induced diabetes and ß cells loss in mice
Authors
Issue Date2015
PublisherThe University of Hong Kong (Pokfulam, Hong Kong)
Citation
Chen, Z. [陈展睿]. (2015). Adaptor protein APPL1 counteracts streptozotocin-induced diabetes and ß cells loss in mice. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b5699951
AbstractLoss of pancreatic β cells mass and function are the major contributors to the pathogenesis of type 1 and type 2 diabetes mellitus. Inflammation is a key culprit in mediating β-cell dysfunction and subsequent apoptosis in diabetes. APPL1, an adaptor protein containing a NH2-terminal Bin1/Amphiphysin/Rvs167 domain, a central pleckstrin homology domain and C-terminal phosphotyrosine binding domain, regulates insulin and adiponectin signaling cascades, thereby maintaining glucose homeostasis. Human with loss-of-function mutations in APPL1 gene develop diabetes. We previously demonstrated that APPL1 promotes insulin sensitivity and insulin secretion by fine-tuning Akt activity. In type 2 diabetic mice, β cell APPL1 is decreased, leading to defective insulin secretion and subsequent glucose intolerance. In this study, we aimed to explore whether APPL1 involves in β-cell mass maintenance and β-cell inflammation in type 1 diabetes using in vivo and ex vivo approaches. Like in type 2 diabetes, APPL1 expression was dramatically decreased in pancreatic β cells of streptozotocin (STZ)-induced and genetically inherited type 1 diabetic mouse models. The reduction of APPL1 was associated with diminished insulin content and increased insulitis in type 1 diabetic mice. Interestingly, treatment with diabetogenic cytokine cocktail (tumor necrosis factor α [TNFα], interleukin 1 β [IL1 β] and interferon 1-γ [IFN γ]) reduced APPL1 mRNA expression in pancreatic islets. To directly examine whether APPL1 plays a role in type 1 diabetes, we injected APPL1 global knockout (KO) mice and their wild-type (WT) littermates with STZ to induce β cell apoptosis and diabetes. Genetic ablation of APPL1 exacerbated STZ-induced hyperglycemia, glucose intolerance, impaired glucose-stimulated insulin secretion. These changes were associated with reduced β-cell mass and insulin content and increased insulitis in APPL1 KO mice. The reduced β cell mass was due to elevated β cell apoptosis and reduced β cell proliferation in APPL1 KO mice. To test whether β-cell specific overexpression of APPL1 counteracts STZ-induced diabetes, we created two distinct mouse models that expressed human APPL1 under the control of rat insulin promoter and modified mouse insulin promoter using transgenic and adeno-associated viral (AAV) gene transfer approaches, respectively. Immunoblotting and immunohistochemical analysis revealed that exogenous APPL1 were detected in pancreatic β cells of the above APPL1 overexpression mouse models. AAV-mediated overexpression of APPL1 in β cells conferred resistance to diabetes induced by STZ. STZ-induced reduction in pancreatic β-cell mass and insulin content were partially reversed by APPL1 overexpression, and these changes were due to decreased β-cell apoptosis and increased β-cell proliferation. Likewise, transgenic expression of APPL1 in β cells prevented STZ-induced diabetes. Further analysis revealed that APPL1 regulated both β-cell apoptosis and inflammation in β cells using ex vivo and in vitro approaches. APPL1 deficiency potentiated STZ- and the cytokine cocktail-induced inflammatory response in β cells, as evidenced by increased expression of inducible nitric oxide synthase, NF-κB activity and inflammatory chemokines. These results collectively suggest that APPL1 is a key common signaling molecule protects β cell from apoptosis and inflammation, and it might represent a potential target for the future development of new strategies for treating and preventing type 1 diabetes.
DegreeMaster of Philosophy
SubjectDiabetes
Carrier proteins
Pancreatic beta cells
Dept/ProgramMedicine
Persistent Identifierhttp://hdl.handle.net/10722/223042

 

DC FieldValueLanguage
dc.contributor.authorChen, Zhanrui-
dc.contributor.author陈展睿-
dc.date.accessioned2016-02-17T23:14:38Z-
dc.date.available2016-02-17T23:14:38Z-
dc.date.issued2015-
dc.identifier.citationChen, Z. [陈展睿]. (2015). Adaptor protein APPL1 counteracts streptozotocin-induced diabetes and ß cells loss in mice. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b5699951-
dc.identifier.urihttp://hdl.handle.net/10722/223042-
dc.description.abstractLoss of pancreatic β cells mass and function are the major contributors to the pathogenesis of type 1 and type 2 diabetes mellitus. Inflammation is a key culprit in mediating β-cell dysfunction and subsequent apoptosis in diabetes. APPL1, an adaptor protein containing a NH2-terminal Bin1/Amphiphysin/Rvs167 domain, a central pleckstrin homology domain and C-terminal phosphotyrosine binding domain, regulates insulin and adiponectin signaling cascades, thereby maintaining glucose homeostasis. Human with loss-of-function mutations in APPL1 gene develop diabetes. We previously demonstrated that APPL1 promotes insulin sensitivity and insulin secretion by fine-tuning Akt activity. In type 2 diabetic mice, β cell APPL1 is decreased, leading to defective insulin secretion and subsequent glucose intolerance. In this study, we aimed to explore whether APPL1 involves in β-cell mass maintenance and β-cell inflammation in type 1 diabetes using in vivo and ex vivo approaches. Like in type 2 diabetes, APPL1 expression was dramatically decreased in pancreatic β cells of streptozotocin (STZ)-induced and genetically inherited type 1 diabetic mouse models. The reduction of APPL1 was associated with diminished insulin content and increased insulitis in type 1 diabetic mice. Interestingly, treatment with diabetogenic cytokine cocktail (tumor necrosis factor α [TNFα], interleukin 1 β [IL1 β] and interferon 1-γ [IFN γ]) reduced APPL1 mRNA expression in pancreatic islets. To directly examine whether APPL1 plays a role in type 1 diabetes, we injected APPL1 global knockout (KO) mice and their wild-type (WT) littermates with STZ to induce β cell apoptosis and diabetes. Genetic ablation of APPL1 exacerbated STZ-induced hyperglycemia, glucose intolerance, impaired glucose-stimulated insulin secretion. These changes were associated with reduced β-cell mass and insulin content and increased insulitis in APPL1 KO mice. The reduced β cell mass was due to elevated β cell apoptosis and reduced β cell proliferation in APPL1 KO mice. To test whether β-cell specific overexpression of APPL1 counteracts STZ-induced diabetes, we created two distinct mouse models that expressed human APPL1 under the control of rat insulin promoter and modified mouse insulin promoter using transgenic and adeno-associated viral (AAV) gene transfer approaches, respectively. Immunoblotting and immunohistochemical analysis revealed that exogenous APPL1 were detected in pancreatic β cells of the above APPL1 overexpression mouse models. AAV-mediated overexpression of APPL1 in β cells conferred resistance to diabetes induced by STZ. STZ-induced reduction in pancreatic β-cell mass and insulin content were partially reversed by APPL1 overexpression, and these changes were due to decreased β-cell apoptosis and increased β-cell proliferation. Likewise, transgenic expression of APPL1 in β cells prevented STZ-induced diabetes. Further analysis revealed that APPL1 regulated both β-cell apoptosis and inflammation in β cells using ex vivo and in vitro approaches. APPL1 deficiency potentiated STZ- and the cytokine cocktail-induced inflammatory response in β cells, as evidenced by increased expression of inducible nitric oxide synthase, NF-κB activity and inflammatory chemokines. These results collectively suggest that APPL1 is a key common signaling molecule protects β cell from apoptosis and inflammation, and it might represent a potential target for the future development of new strategies for treating and preventing type 1 diabetes.-
dc.languageeng-
dc.publisherThe University of Hong Kong (Pokfulam, Hong Kong)-
dc.relation.ispartofHKU Theses Online (HKUTO)-
dc.rightsThe author retains all proprietary rights, (such as patent rights) and the right to use in future works.-
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.subject.lcshDiabetes-
dc.subject.lcshCarrier proteins-
dc.subject.lcshPancreatic beta cells-
dc.titleAdaptor protein APPL1 counteracts streptozotocin-induced diabetes and ß cells loss in mice-
dc.typePG_Thesis-
dc.identifier.hkulb5699951-
dc.description.thesisnameMaster of Philosophy-
dc.description.thesislevelMaster-
dc.description.thesisdisciplineMedicine-
dc.description.naturepublished_or_final_version-

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