RESUMEN
BACKGROUND: Lipids are regulators of insulitis and ß-cell death in type 1 diabetes development, but the underlying mechanisms are poorly understood. Here, we investigated how the islet lipid composition and downstream signaling regulate ß-cell death. METHODS: We performed lipidomics using three models of insulitis: human islets and EndoC-ßH1 ß cells treated with the pro-inflammatory cytokines interlukine-1ß and interferon-γ, and islets from pre-diabetic non-obese mice. We also performed mass spectrometry and fluorescence imaging to determine the localization of lipids and enzyme in islets. RNAi, apoptotic assay, and qPCR were performed to determine the role of a specific factor in lipid-mediated cytokine signaling. RESULTS: Across all three models, lipidomic analyses showed a consistent increase of lysophosphatidylcholine species and phosphatidylcholines with polyunsaturated fatty acids and a reduction of triacylglycerol species. Imaging assays showed that phosphatidylcholines with polyunsaturated fatty acids and their hydrolyzing enzyme phospholipase PLA2G6 are enriched in islets. In downstream signaling, omega-3 fatty acids reduce cytokine-induced ß-cell death by improving the expression of ADP-ribosylhydrolase ARH3. The mechanism involves omega-3 fatty acid-mediated reduction of the histone methylation polycomb complex PRC2 component Suz12, upregulating the expression of Arh3, which in turn decreases cell apoptosis. CONCLUSIONS: Our data provide insights into the change of lipidomics landscape in ß cells during insulitis and identify a protective mechanism by omega-3 fatty acids. Video Abstract.
Asunto(s)
Ácidos Grasos Omega-3 , Islotes Pancreáticos , N-Glicosil Hidrolasas , Ratones , Animales , Humanos , Islotes Pancreáticos/metabolismo , Muerte Celular , Citocinas/metabolismo , Ácidos Grasos Omega-3/metabolismo , Ácidos Grasos Insaturados , Fosfatidilcolinas/metabolismoRESUMEN
Protein tyrosine phosphatase N2 (PTPN2) is a type 1 diabetes (T1D) candidate gene identified from human genome-wide association studies. PTPN2 is highly expressed in human and murine islets and becomes elevated upon inflammation and models of T1D, suggesting that PTPN2 may be important for ß-cell survival in the context of T1D. To test whether PTPN2 contributed to ß-cell dysfunction in an inflammatory environment, we generated a ß-cell-specific deletion of Ptpn2 in mice (PTPN2-ß knockout [ßKO]). Whereas unstressed animals exhibited normal metabolic profiles, low- and high-dose streptozotocin-treated PTPN2-ßKO mice displayed hyperglycemia and accelerated death, respectively. Furthermore, cytokine-treated Ptpn2-KO islets resulted in impaired glucose-stimulated insulin secretion, mitochondrial defects, and reduced glucose-induced metabolic flux, suggesting ß-cells lacking Ptpn2 are more susceptible to inflammatory stress associated with T1D due to maladaptive metabolic fitness. Consistent with the phenotype, proteomic analysis identified an important metabolic enzyme, ATP-citrate lyase, as a novel PTPN2 substrate.
Asunto(s)
Diabetes Mellitus Tipo 1 , Ratones , Humanos , Animales , Diabetes Mellitus Tipo 1/genética , Proteína Tirosina Fosfatasa no Receptora Tipo 2/genética , Proteína Tirosina Fosfatasa no Receptora Tipo 2/metabolismo , Monoéster Fosfórico Hidrolasas , Estudio de Asociación del Genoma Completo , Proteómica , Glucosa , Ratones NoqueadosRESUMEN
Diabetes is an epidemic with increasing incidence across the world. Most individuals who are afflicted by this disease have type 2 diabetes, but there are many who suffer from type 1, an autoimmune disorder. Both types of diabetes have complex genetic underpinnings that are further complicated by epigenetic and environmental factors. A less prevalent and often under diagnosed subset of diabetes cases are characterized by single genetic mutations and include Maturity Onset Diabetes of the Young (MODY) and Neonatal Diabetes Mellitus (NDM). While the mode of action and courses of treatment for all forms of diabetes are distinct, the diseases all eventually result in the dysfunction and/or death of the pancreatic ß cell - the body's source of insulin. With loss of ß cell function, blood glucose homeostasis is disrupted, and life-threatening complications arise. In this review, we focus on how model systems provide substantial insights into understanding ß cell biology to inform our understanding of all forms of diabetes. The strengths and weaknesses of animal, hPSC derived ß-like cell, and organoid models are considered along with discussion of GATA6, a critical transcription factor frequently implicated in pancreatic dysfunction with developmental origins; experimental studies of GATA6 have highlighted the advantages and disadvantages of how each of these model systems can be used to inform our understanding of ß cell specification and function in health and disease.
Asunto(s)
Diabetes Mellitus Tipo 2 , Células Secretoras de Insulina , Humanos , Ratones , Animales , Diabetes Mellitus Tipo 2/complicaciones , Organoides , Páncreas , Células MadreRESUMEN
Pathogens such as the Epstein Barr virus (EBV) have long been implicated in the etiology of systemic lupus erythematosus (SLE). The Epstein Barr virus nuclear antigen I (EBNA-1) has been shown to play a role in the development of anti-nuclear antibodies characteristic of SLE. One mechanism by which EBV may play a role in SLE is molecular mimicry. We previously generated two monoclonal antibodies (mAbs) to EBNA-1 and demonstrated that they cross-react with double-stranded DNA (dsDNA). In the present study, we demonstrate that these mAbs have pathogenic potential. We show that they can bind to isolated rat glomeruli and that binding can be greatly diminished by pretreatment of glomeruli with DNase I, suggesting that these mAbs bind dsDNA in the kidney. We also demonstrate that these antibodies can deposit in the kidney when injected into mice and can induce proteinuria and elicit histopathological alterations consistent with glomerulonephritis. Finally, we show that these antibodies can cross-react with laminin and collagen IV in the extracellular matrix suggesting that direct binding to the glomerular basement membrane or mesangial matrix may also contribute to the antibody deposition in the kidney. In summary, our results indicate that EBNA-1 can elicit antibodies that cross-react with dsDNA, that can deposit in the kidney, and induce kidney damage. These results are significant because they support the role of a viral protein in SLE and lupus nephritis.
Asunto(s)
Anticuerpos Antinucleares/toxicidad , Anticuerpos Monoclonales/toxicidad , Anticuerpos Antivirales/inmunología , ADN/inmunología , Infecciones por Virus de Epstein-Barr/inmunología , Antígenos Nucleares del Virus de Epstein-Barr/inmunología , Glomérulos Renales/inmunología , Animales , Anticuerpos Antinucleares/inmunología , Anticuerpos Monoclonales/genética , Anticuerpos Monoclonales/inmunología , Anticuerpos Monoclonales/aislamiento & purificación , Colágeno/inmunología , Reacciones Cruzadas/inmunología , Desoxirribonucleasa I , Infecciones por Virus de Epstein-Barr/metabolismo , Matriz Extracelular/genética , Matriz Extracelular/inmunología , Femenino , Membrana Basal Glomerular/inmunología , Membrana Basal Glomerular/metabolismo , Glomerulonefritis/inmunología , Glomerulonefritis/patología , Glomerulonefritis/virología , Células HEK293 , Humanos , Inmunoglobulina G/inmunología , Glomérulos Renales/patología , Laminina/inmunología , Ratones , Ratones Endogámicos BALB C , Imitación Molecular , Proteinuria/inmunología , Ratas , Ratas Sprague-DawleyRESUMEN
Retinoic acid (RA) signaling is essential for multiple developmental processes, including appropriate pancreas formation from the foregut endoderm. RA is also required to generate pancreatic progenitors from human pluripotent stem cells. However, the role of RA signaling during endocrine specification has not been fully explored. In this study, we demonstrate that the disruption of RA signaling within the NEUROG3-expressing endocrine progenitor population impairs mouse ß cell differentiation and induces ectopic expression of crucial δ cell genes, including somatostatin. In addition, the inhibition of the RA pathway in hESC-derived pancreatic progenitors downstream of NEUROG3 induction impairs insulin expression. We further determine that RA-mediated regulation of endocrine cell differentiation occurs through Wnt pathway components. Together, these data demonstrate the importance of RA signaling in endocrine specification and identify conserved mechanisms by which RA signaling directs pancreatic endocrine cell fate.