290-OR: Altered In-Situ Expression of Proinsulin-Insulin in Pancreatic Islets Reflects Metabolic and Molecular Defects in Type 2 Diabetic and Glucose-Intolerant Living Donors

Abstract

Proinsulin (PI) processing is altered in beta-cells during T2D progression. However, the molecular mechanisms driving such alterations are not fully characterized neither their occurrence were correlated with patients’ metabolic profile. To fill this gap, we investigated the correlation between pancreatic proinsulin (PI) expression and phenotypic/functional changes of beta-cells during metabolic stress in extensively clinical characterized impaired glucose tolerant (IGT, n=7) and T2D (n=4) individuals, compared to normal glucose tolerant (NGT, n=4). We analyzed microdissected pancreatic islets collected from surgical pancreas biopsies. The expression of genes associated to ER stress and β cell phenotype were evaluated. Given the high heterogeneity among pancreatic islets, we also performed a single islets analysis in n=88 islets from n=3 NGT, n=3 IGT and n=3 T2D patients. PDIA1, GRP78 and XBP1 genes, involved in unfolded protein response (UPR), were significantly upregulated in pancreatic islets of IGT and T2D patients vs. NGT (p<0.05) and were positively correlated with in-situ PI/INS ratio (r=0.6; p=0.01) and colocalization (r=0.5, p<0.05), with in-vivo measurements of glucose intolerance (r=0.6-0.8; p<0.001) and β cell functional reduction (r=-0.6; p=0.04).Single islets phenotyping approach revealed a progressively increased heterogeneity from NGT to IGT and T2D patients. Of note, in-situ PI/INS ratio and colocalization were positively correlated with the expression of UPR genes (r=0.3; p<0.01) and negatively with those associated to β cell identity (r=-0.2; p<0.01). Our data demonstrated that altered PI processing in β-cell reflected metabolic and molecular defects in IGT and T2D patients. Further, single islet phenotyping analysis revealed a high heterogeneity among pancreatic islets in terms of ER stress and β-cell differentiation profile during metabolic alterations. Disclosure N. Brusco: None. C. Cefalo: None. U. Capece: None. F. Impronta: None. A. Mari: Research Support; Self; Eli Lilly and Company. F. Dotta: None. A. Giaccari: None. T. Mezza: None. G. Sebastiani: None. G. Licata: None. G. E. Grieco: None. G. Di giuseppe: None. L. Nigi: None. D. Fignani: None. S. Moffa: None. F. Cinti: None. Funding Università Cattolica del Sacro Cuore (FondiAteneo Linea D.1, anno 2020); Italian Ministry of Education, University and Research (GR-2018-12365577); European Foundation for the Study of Diabetes; AstraZeneca