Long-term in vitro exposure to high glucose increases proinsulin-like-molecules release by isolated human islets

Bertuzzi, Federico; Saccomanno, K.; Socci, C.; Davalli, A. M.; Taglietti, M; Berra, C; Dalcin, E; Monti, L.; Pozza, G.; Pontiroli, A. E.

doi:10.1677/joe.0.1580205

Cited by 17 publications

(14 citation statements)

References 37 publications

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“…Culture of human pancreatic islets for 48 h at 27 mM glucose thus markedly increased the ratio of immunoreactive proinsulin to insulin in islets and in secreted products both during and after culture [61]. Similar results were obtained in other studies [59,62,63]. We additionally find that the increased ratio both of stored and secreted products was normalized by blocking insulin secretion with diazoxide [61].…”

Section: Overstimulation By Hyperglycemiasupporting

confidence: 89%

Dysfunctional insulin secretion in type 2 diabetes: role of metabolic abnormalities

Grill¹,

Björklund

2000

CMLS, Cell. Mol. Life Sci.

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Insulin secretion is finely tuned to the requirements of tissues by tight coupling to prevailing blood glucose levels. The normal regulation of insulin secretion is coupled to glucose metabolism in the pancreatic B cell, a major but not exclusive signal for secretion being closure of K+ ATP (adenosine' triphosphate)-dependent channels in the cell membrane through an increase in cytosolic ATP/adenosine diphosphate. Insulin secretion in type 2 diabetes is abnormal in several respects due to genetic causes but also due to the metabolic environment of the pancreatic B cells. This environment may be particularly important for the deterioration of insulin secretion which occurs with increasing duration of diabetes. Factors in the environment with potential importance include overstimulation, a negative effect of hyperglycemia per se ('glucotoxicity') as well as adverse effects of elevated fatty acids ('lipotoxicity'). Elucidating the mechanisms behind these factors as well as their clinical importance will pave the way for treatment which could preserve B-cell function in type 2 diabetic patients.

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Section: Overstimulation By Hyperglycemiasupporting

confidence: 89%

Dysfunctional insulin secretion in type 2 diabetes: role of metabolic abnormalities

Grill¹,

Björklund

2000

CMLS, Cell. Mol. Life Sci.

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“…Then, the grids were incubated with goat anti-mouse IgG coated with 10-nm colloidal gold particles. Finally, the sections were rinsed with PBS and distilled water, fixed in 2.5% glutaraldehyde, and stained with uranyl acetate (35). All experiments were examined with a Philips electron microscope.…”

mentioning

confidence: 99%

High Glucose Causes Apoptosis in Cultured Human Pancreatic Islets of Langerhans

et al. 2001

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Type 2 diabetes is characterized by insulin resistance and inadequate insulin secretion. In the advanced stages of the disease, ␤-cell dysfunction worsens and insulin therapy may be necessary to achieve satisfactory metabolic control. Studies in autopsies found decreased ␤-cell mass in pancreas of people with type 2 diabetes. Apoptosis, a constitutive program of cell death modulated by the Bcl family genes, has been implicated in loss of ␤-cells in animal models of type 2 diabetes. In this study, we compared the effect of 5 days' culture in high glucose concentration (16.7 mmol/l) versus normal glucose levels (5.5 mmol/l) or hyperosmolar control (mannitol 11 mmol/l plus glucose 5 mmol/l) on the survival of human pancreatic islets. Apoptosis, analyzed by flow cytometry and electron and immunofluorescence microscopy, was increased in islets cultured in high glucose (HG5) as compared with normal glucose (NG5) or hyperosmolar control (NG5؉MAN5). We also analyzed by reverse transcriptase-polymerase chain reaction and Western blotting the expression of the Bcl family genes in human islets cultured in normal glucose or high glucose. The antiapoptotic gene Bcl-2 was unaffected by glucose change, whereas Bcl-xl was reduced upon treatment with HG5. On the other hand, proapoptotic genes Bad, Bid, and Bik were overexpressed in the islets maintained in HG5. To define the pancreatic localization of Bcl proteins, we performed confocal immunofluorescence analysis on human pancreas. Bad and Bid were specifically expressed in ␤-cells, and Bid was also expressed, although at low levels, in the exocrine pancreas. Bik and Bcl-xl were expressed in other endocrine islet cells as well as in the exocrine pancreas. These data suggest that in human islets, high glucose may modulate the balance of proapoptotic and antiapoptotic Bcl proteins toward apoptosis, thus favoring ␤-cell death.

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“…Glucose toxicity is thought to increase oxidative stress (29,30), decrease insulin content and insulin secretion (4,24,37), and release proinsulin-like molecules (5) and in general affects the transcriptional and metabolic profile of ␤-cells (4,5,6). Glucose toxicity is thought to increase oxidative stress (29,30), decrease insulin content and insulin secretion (4,24,37), and release proinsulin-like molecules (5) and in general affects the transcriptional and metabolic profile of ␤-cells (4,5,6).…”

Section: Discussionmentioning

confidence: 99%

ERp46 is reduced by high glucose and regulates insulin content in pancreatic β-cells

Alberti¹,

Karamessinis²,

Peroulis³

et al. 2009

American Journal of Physiology-Endocrinology and Metabolism

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Our studies focus on ERp46, an endoplasmic reticulum (ER) component, and analyze its involvement in glucose toxicity and in insulin production. Differences in pancreatic beta-TC-6 cell proteome under conditions of low vs. high glucose were examined by proteomic approaches, including two-dimensional gel electrophoresis, image analysis, and mass spectrometry. Among differentially expressed proteins, ERp46, a novel endoplasmic reticulum component, was examined further. The expression of ERp46 in pancreatic sections was analyzed by immunocytochemistry, and high glucose-induced alterations of expression were evaluated in cultured beta-cells, in isolated pancreatic islets, and in the pancreas of db/db diabetic animals. Inhibition of ERp46 expression by siRNA was performed to study its role in insulin production, in secretion, and in ER stress. Proteomic analysis led to identification of 46 differentially expressed spots corresponding to 23 proteins. Since ERp46 is a novel protein with a possible crucial role in secretory cells, we further analyzed its role in beta-cell function. ERp46 expression is reduced in high glucose concentration in beta-TC-6 cells and in isolated murine islets. Further analysis revealed high expression of ERp46 in pancreatic islets compared with exocrine tissue. Interestingly, a marked decrease in ERp46 expression was found in the pancreatic islets of db/db mice. Most importantly, siRNA-mediated knockdown of ERp46 in cultured beta-cells led to a significant decrease in the insulin content; however, no alterations in insulin mRNA levels were observed under these conditions. In addition, reduced expression of ERp46 by siRNA increased the expression of CHOP and peIF2a, indicating development of ER stress. We conclude that ERp46 may be an important component in the phenomenon of "glucose toxicity" involved in insulin production at the posttranslational level.

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Long-term in vitro exposure to high glucose increases proinsulin-like-molecules release by isolated human islets

Cited by 17 publications

References 37 publications

Dysfunctional insulin secretion in type 2 diabetes: role of metabolic abnormalities

Dysfunctional insulin secretion in type 2 diabetes: role of metabolic abnormalities

High Glucose Causes Apoptosis in Cultured Human Pancreatic Islets of Langerhans

ERp46 is reduced by high glucose and regulates insulin content in pancreatic β-cells

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