P.114: Altered Glucose Response in Human Beta Cells Following Modulation of Muscarinic Receptor

Nor1, the third member of the Nr4a subfamily of nuclear receptor, is garnering increased interest in view of its role in the regulation of glucose homeostasis. Our previous study highlighted a proapoptotic role of Nor1 in pancreatic beta cells and showed that Nor1 expression was increased in islets isolated from type 2 diabetic individuals, suggesting that Nor1 could mediate the deterioration of islet function in type 2 diabetes. However, the mechanism remains incompletely understood. We herein investigated the subcellular localization of Nor1 in INS832/13 cells and dispersed human beta cells. We also examined the consequences of Nor1 overexpression on mitochondrial function and morphology. Our results show that, surprisingly, Nor1 is mostly cytoplasmic in beta cells and undergoes mitochondrial translocation upon activation by proinflammatory cytokines. Mitochondrial localization of Nor1 reduced glucose oxidation, lowered ATP production rates, and inhibited glucose-stimulated insulin secretion. Western blot and microscopy images revealed that Nor1 could provoke mitochondrial fragmentation via mitophagy. Our study unveils a new mode of action for Nor1, which affects beta-cell viability and function by disrupting mitochondrial networks.

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Stearoyl CoA desaturase is a gatekeeper that protects human beta cells against lipotoxicity and maintains their identity

Diabetologia ◽

10.1007/s00125-019-05046-x ◽

2019 ◽

Vol 63 (2) ◽

pp. 395-409 ◽

Cited By ~ 4

Author(s):

Masaya Oshima ◽

Séverine Pechberty ◽

Lara Bellini ◽

Sven O. Göpel ◽

Mélanie Campana ◽

...

Keyword(s):

Type 2 Diabetes ◽

Endoplasmic Reticulum ◽

Endoplasmic Reticulum Stress ◽

Beta Cell ◽

Beta Cells ◽

Cell Identity ◽

Human Beta Cells ◽

Human Beta Cell ◽

Stearoyl Coa Desaturase

Abstract Aims/hypothesis During the onset of type 2 diabetes, excessive dietary intake of saturated NEFA and fructose lead to impaired insulin production and secretion by insulin-producing pancreatic beta cells. The majority of data on the deleterious effects of lipids on functional beta cell mass were obtained either in vivo in rodent models or in vitro using rodent islets and beta cell lines. Translating data from rodent to human beta cells remains challenging. Here, we used the human beta cell line EndoC-βH1 and analysed its sensitivity to a lipotoxic and glucolipotoxic (high palmitate with or without high glucose) insult, as a way to model human beta cells in a type 2 diabetes environment. Methods EndoC-βH1 cells were exposed to palmitate after knockdown of genes related to saturated NEFA metabolism. We analysed whether and how palmitate induces apoptosis, stress and inflammation and modulates beta cell identity. Results EndoC-βH1 cells were insensitive to the deleterious effects of saturated NEFA (palmitate and stearate) unless stearoyl CoA desaturase (SCD) was silenced. SCD was abundantly expressed in EndoC-βH1 cells, as well as in human islets and human induced pluripotent stem cell-derived beta cells. SCD silencing induced markers of inflammation and endoplasmic reticulum stress and also IAPP mRNA. Treatment with the SCD products oleate or palmitoleate reversed inflammation and endoplasmic reticulum stress. Upon SCD knockdown, palmitate induced expression of dedifferentiation markers such as SOX9, MYC and HES1. Interestingly, SCD knockdown by itself disrupted beta cell identity with a decrease in mature beta cell markers INS, MAFA and SLC30A8 and decreased insulin content and glucose-stimulated insulin secretion. Conclusions/interpretation The present study delineates an important role for SCD in the protection against lipotoxicity and in the maintenance of human beta cell identity. Data availability Microarray data and all experimental details that support the findings of this study have been deposited in in the GEO database with the GSE130208 accession code.

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83 - INS rs3842753 SNP Genotype Associated With Type 1 Diabetes Risk Modulates Insulin mRNA Expression Distribution in Single Nondiabetic Human Beta Cells

Canadian Journal of Diabetes ◽

10.1016/j.jcjd.2020.08.089 ◽

2020 ◽

Vol 44 (7) ◽

pp. S32-S33

Author(s):

Su Wang ◽

Stephane Flibotte ◽

Joan Camunas-Soler ◽

Patrick E. Macdonald ◽

James Johnson

Keyword(s):

Type 1 Diabetes ◽

Mrna Expression ◽

Beta Cells ◽

Diabetes Risk ◽

Human Beta Cells ◽

Insulin Mrna

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Pax4 Expression does not Transduce Pancreatic Alpha Cells to Beta Cells

Cellular Physiology and Biochemistry ◽

10.1159/000430146 ◽

2015 ◽

Vol 36 (5) ◽

pp. 1735-1742 ◽

Cited By ~ 4

Author(s):

Ling Chen ◽

Jing Zhang ◽

Zhuo Zhang ◽

Yaping Chu ◽

Bing Song ◽

...

Keyword(s):

Blood Glucose ◽

Beta Cell ◽

Beta Cells ◽

Cell Number ◽

Diabetic Patients ◽

Alpha Cells ◽

Diabetic Mice ◽

Glucose Response ◽

Pancreatic Alpha Cells

Background/Aims: The lack of available beta cells greatly limits the use of beta cell transplantation as a therapy for diabetes. Thus, generation of beta cells from other sources is substantially required. Pax4 has been shown to induce reprograming of alpha cells into beta cells during embryogenesis. Nevertheless, whether expression of Pax4 in adult alpha cells could trigger this alpha-to-beta cell reprogramming is unknown. Methods: Here we generated an adeno-associated virus carrying Pax4 and GFP under a CMV promoter (AAV-Pax4). We used AAV-Pax4 to transduce a mouse alpha cell line in vitro, and to transduce primary alpha cells in diabetic mice. Reprogramming was examined by double immunostaining and by changes in beta cell number. The effects on blood glucose were evaluated by fasting blood glucose and glucose response. Results: In vitro, Pax4 overexpression neither induced insulin expression, nor suppressed glucagon expression in alpha cells. In vivo, Pax4 overexpression failed to increase beta cell number, and did not alter hyperglycemia and glucose response in diabetic mice. Conclusion: Pax4 expression is not sufficient to transduce pancreatic alpha cells into beta cells. Overexpression of Pax4 in alpha cells may not increase functional beta cell number in diabetic patients.

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