scholarly journals Heterogeneous Expression of Proinsulin Processing Enzymes in Beta Cells of Non-diabetic and Type 2 Diabetic Humans

2019 ◽  
Vol 67 (6) ◽  
pp. 385-400 ◽  
Author(s):  
Gladys Teitelman
Keyword(s):  
Type 2 Diabetes ◽  
Beta Cells ◽  
Human Pancreas ◽  
Proprotein Convertase ◽  
Expression Levels ◽  
Processing Enzymes ◽  
Proinsulin Processing ◽  
Heterogeneous Expression ◽  
Human Beta Cells

Although there is evidence indicating transcriptional and functional heterogeneity in human beta cells, it is unclear whether this heterogeneity extends to the expression level of the enzymes that process proinsulin to insulin in beta cells. To address this question, the expression levels of prohormone convertases (PC) 1/3, proprotein convertase 2 (PC2), and carboxypeptidase E (CPE) were determined in immune-stained sections of human pancreas. In non-diabetic donors, the level of proprotein convertase 1/3 (PC1/3) expression varied among beta cells of each islet but the average per islet was similar for all islets of each donor. Although the average PC1/3 expression of all islets examined per sample was unique for each pancreas, donors had similar levels of proinsulin/insulin expression. PC2 expression in beta cells showed less pronounced inter- and intraislet variation while CPE levels were fairly constant. The relationship between PC1/3 and PC2 expression levels was variable among different donors. Type 2 diabetes had an uneven effect on the expression levels of all three enzymes as they decrease only in some islets in a section. These findings suggest the presence of intraislet, but not interislet, variation in the expression of the proinsulin processing enzymes in non-diabetic subjects and a heterogeneous effect of type 2 diabetes on enzyme expression in islets.

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

Diabetologia ◽  
2019 ◽  
Vol 63 (2) ◽  
pp. 395-409 ◽  
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.

Hyperglycemia causes oxidative stress in pancreatic beta-cells of GK rats, a model of type 2 diabetes

Diabetes ◽  
1999 ◽  
Vol 48 (4) ◽  
pp. 927-932 ◽  
Author(s):  
Y. Ihara ◽  
S. Toyokuni ◽  
K. Uchida ◽  
H. Odaka ◽  
T. Tanaka ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Type 2 Diabetes ◽  
Beta Cells ◽  
Pancreatic Beta Cells ◽  
Gk Rats

scholarly journals A Pilot Study towards the Impact of Type 2 Diabetes on the Expression and Activities of Drug Metabolizing Enzymes and Transporters in Human Duodenum

2019 ◽  
Vol 20 (13) ◽  
pp. 3257 ◽  
Author(s):  
Sophie Gravel ◽  
Benoit Panzini ◽  
Francois Belanger ◽  
Jacques Turgeon ◽  
Veronique Michaud
Keyword(s):  
Type 2 Diabetes ◽  
Mrna Expression ◽  
Drug Metabolizing Enzymes ◽  
Mrna Levels ◽  
Metabolizing Enzymes ◽  
Expression Levels ◽  
The Impact ◽  
Duodenal Biopsies ◽  
Mrna Expression Levels

To characterize effects of type 2 diabetes (T2D) on mRNA expression levels for 10 Cytochromes P450 (CYP450s), two carboxylesterases, and three drug transporters (ABCB1, ABCG2, SLCO2B1) in human duodenal biopsies. To compare drug metabolizing enzyme activities of four CYP450 isoenzymes in duodenal biopsies from patients with or without T2D. mRNA levels were quantified (RT-qPCR) in human duodenal biopsies obtained from patients with (n = 20) or without (n = 16) T2D undergoing a scheduled gastro-intestinal endoscopy. CYP450 activities were determined following incubation of biopsy homogenates with probe substrates for CYP2B6 (bupropion), CYP2C9 (tolbutamide), CYP2J2 (ebastine), and CYP3A4/5 (midazolam). Covariables related to inflammation, T2D, demographic, and genetics were investigated. T2D had no major effects on mRNA levels of all enzymes and transporters assessed. Formation rates of metabolites (pmoles mg protein−1 min−1) determined by LC-MS/MS for CYP2C9 (0.48 ± 0.26 vs. 0.41 ± 0.12), CYP2J2 (2.16 ± 1.70 vs. 1.69 ± 0.93), and CYP3A (5.25 ± 3.72 vs. 5.02 ± 4.76) were not different between biopsies obtained from individuals with or without T2D (p > 0.05). No CYP2B6 specific activity was measured. TNF-α levels were higher in T2D patients but did not correlate with any changes in mRNA expression levels for drug metabolizing enzymes or transporters in the duodenum. T2D did not modulate expression or activity of tested drug metabolizing enzymes and transporters in the human duodenum. Previously reported changes in drug oral clearances in patients with T2D could be due to a tissue-specific disease modulation occurring in the liver and/or in other parts of the intestines.

scholarly journals Disruption of Beta-Cell Mitochondrial Networks by the Orphan Nuclear Receptor Nor1/Nr4a3

Cells ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 168 ◽  
Author(s):  
Anne-Françoise Close ◽  
Nidheesh Dadheech ◽  
Hélène Lemieux ◽  
Qian Wang ◽  
Jean Buteau
Keyword(s):  
Beta Cell ◽  
Beta Cells ◽  
Nuclear Receptor ◽  
Pancreatic Beta Cells ◽  
Orphan Nuclear Receptor ◽  
Atp Production ◽  
Human Beta Cells ◽  
Glucose Stimulated Insulin Secretion ◽  
Mitochondrial Networks

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.

scholarly journals The Expression Level of mRNA, Protein, and DNA Methylation Status of FOSL2 of Uyghur in XinJiang in Type 2 Diabetes

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Jun Li ◽  
Siyuan Li ◽  
Ying Hu ◽  
Guolei Cao ◽  
Siyao Wang ◽  
...  
Keyword(s):  
Gene Expression ◽  
Type 2 Diabetes ◽  
Dna Methylation ◽  
Methylation Status ◽  
Methylation Data ◽  
Biochemical Indicators ◽  
Expression Levels ◽  
Protein Levels ◽  
Cpg Sites

Objective. We investigated the expression levels of both FOSL2 mRNA and protein as well as evaluating DNA methylation in the blood of type 2 diabetes mellitus (T2DM) Uyghur patients from Xinjiang. This study also evaluated whether FOSL2 gene expression had demonstrated any associations with clinical and biochemical indicators of T2DM. Methods. One hundred Uyghur subjects where divided into two groups, T2DM and nonimpaired glucose tolerance (NGT) groups. DNA methylation of FOSL2 was also analyzed by MassARRAY Spectrometry and methylation data of individual units were generated by the EpiTyper v1.0.5 software. The expression levels of FOS-like antigen 2 (FOSL2) and the protein expression levels were analyzed. Results. Significant differences were observed in mRNA and protein levels when compared with the NGT group, while methylation rates of eight CpG units within the FOSL2 gene were higher in the T2DM group. Methylation of CpG sites was found to inversely correlate with expression of other markers. Conclusions. Results show that a correlation between mRNA, protein, and DNA methylation of FOSL2 gene exists among T2DM patients from Uyghur. FOSL2 protein and mRNA were downregulated and the DNA became hypermethylated, all of which may be involved in T2DM pathogenesis in this population.

scholarly journals Metabolic and functional specialisations of the pancreatic beta cell: gene disallowance, mitochondrial metabolism and intercellular connectivity

Diabetologia ◽  
2020 ◽  
Vol 63 (10) ◽  
pp. 1990-1998 ◽  
Author(s):  
Guy A. Rutter ◽  
Eleni Georgiadou ◽  
Aida Martinez-Sanchez ◽  
Timothy J. Pullen
Keyword(s):  
Type 2 Diabetes ◽  
Insulin Secretion ◽  
Glucose Metabolism ◽  
Beta Cell ◽  
Beta Cells ◽  
Mitochondrial Metabolism ◽  
Monocarboxylate Transporter ◽  
Genome Wide Association Studies ◽  
Monocarboxylate Transporter 1

Abstract All forms of diabetes mellitus involve the loss or dysfunction of pancreatic beta cells, with the former predominating in type 1 diabetes and the latter in type 2 diabetes. Deeper understanding of the coupling mechanisms that link glucose metabolism in these cells to the control of insulin secretion is therefore likely to be essential to develop new therapies. Beta cells display a remarkable metabolic specialisation, expressing high levels of metabolic sensing enzymes, including the glucose transporter GLUT2 (encoded by SLC2A2) and glucokinase (encoded by GCK). Genetic evidence flowing from both monogenic forms of diabetes and genome-wide association studies for the more common type 2 diabetes, supports the importance for normal glucose-stimulated insulin secretion of metabolic signalling via altered ATP generation, while also highlighting unsuspected roles for Zn2+ storage, intracellular lipid transfer and other processes. Intriguingly, genes involved in non-oxidative metabolic fates of the sugar, such as those for lactate dehydrogenase (LDHA) and monocarboxylate transporter-1 ([MCT-1] SLC16A1), as well as the acyl-CoA thioesterase (ACOT7) and others, are selectively repressed (‘disallowed’) in beta cells. Furthermore, mutations in genes critical for mitochondrial oxidative metabolism, such as TRL-CAG1–7 encoding tRNALeu, are linked to maternally inherited forms of diabetes. Correspondingly, impaired Ca2+ uptake into mitochondria, or collapse of a normally interconnected mitochondrial network, are associated with defective insulin secretion. Here, we suggest that altered mitochondrial metabolism may also impair beta cell–beta cell communication. Thus, we argue that defective oxidative glucose metabolism is central to beta cell failure in diabetes, acting both at the level of single beta cells and potentially across the whole islet to impair insulin secretion.

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