The No-Go and Nonsense-Mediated RNA Decay Pathways Are Regulated by Inflammatory Cytokines in Insulin-Producing Cells and Human Islets and Determine β-Cell Insulin Biosynthesis and Survival

Ghiasi, Seyed Mojtaba; Krogh, Nicolai; Tyrberg, Björn; Mandrup‐Poulsen, Thomas

doi:10.2337/db18-0073

Cited by 19 publications

(46 citation statements)

References 48 publications

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“…Gene expression levels were normalised to the housekeeping mRNA Hprt1 (encoding hypoxanthineguanine phosphoribosyltransferase-1) through the −ΔC t method. Methods are described in detail elsewhere [12]. As positive control, kidney tissue from rats and human donors were subjected to the same procedure.…”

Section: Gene Expression Proceduresmentioning

confidence: 99%

No direct effect of SGLT2 activity on glucagon secretion

et al. 2019

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Aims/hypothesis Sodium-glucose cotransporter (SGLT) 2 inhibitors constitute a new class of glucose-lowering drugs, but they increase glucagon secretion, which may counteract their glucose-lowering effect. Previous studies using static incubation of isolated human islets or the glucagon-secreting cell line α-TC1 suggested that this results from direct inhibition of alpha cell SGLT1/2-activity. The aim of this study was to test whether the effects of SGLT2 on glucagon secretion demonstrated in vitro could be reproduced in a more physiological setting. Methods We explored the effect of SGLT2 activity on glucagon secretion using isolated perfused rat pancreas, a physiological model for glucagon secretion. Furthermore, we investigated Slc5a2 (the gene encoding SGLT2) expression in rat islets as well as in mouse and human islets and in mouse and human alpha, beta and delta cells to test for potential inter-species variations. SGLT2 protein content was also investigated in mouse, rat and human islets. Results Glucagon output decreased three-to fivefold within minutes of shifting from low (3.5 mmol/l) to high (10 mmol/l) glucose (4.0 ± 0.5 pmol/15 min vs 1.3 ± 0.3 pmol/15 min, p < 0.05). The output was unaffected by inhibition of SGLT1/2 with dapagliflozin or phloridzin or by addition of the SGLT1/2 substrate α-methylglucopyranoside, whether at low or high glucose concentrations (p = 0.29-0.99). Insulin and somatostatin secretion (potential paracrine regulators) was also unaffected. Slc5a2 expression and SGLT2 protein were marginal or below detection limit in rat, mouse and human islets and in mouse and human alpha, beta and delta cells. Conclusions/interpretation Our combined data show that increased plasma glucagon during SGLT2 inhibitor treatment is unlikely to result from direct inhibition of SGLT2 in alpha cells, but instead may occur downstream of their blood glucoselowering effects.

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Section: Gene Expression Proceduresmentioning

confidence: 99%

No direct effect of SGLT2 activity on glucagon secretion

et al. 2019

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“…Real-time qPCR was performed on 12 ng cDNA in triplicate with SybrGreen PCR mastermix (Life Technologies, Naerum, Denmark) and specific primers ( Table 2 ) and run in a Real-Time PCR machine (Applied Biosystems, Naerum, Denmark). The gene expression level was normalized to HPRT1 through −∆Ct analysis [ 44 ].…”

Section: Methodsmentioning

confidence: 99%

The Connexin 43 Regulator Rotigaptide Reduces Cytokine-Induced Cell Death in Human Islets

Ghiasi

Hansen

Christensen

et al. 2020

IJMS

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Background: Intercellular communication mediated by cationic fluxes through the Connexin family of gap junctions regulates glucose-stimulated insulin secretion and beta cell defense against inflammatory stress. Rotigaptide (RG, ZP123) is a peptide analog that increases intercellular conductance in cardiac muscle cells by the prevention of dephosphorylation and thereby uncoupling of Connexin-43 (Cx43), possibly via action on unidentified protein phosphatases. For this reason, it is being studied in human arrhythmias. It is unknown if RG protects islet cell function and viability against inflammatory or metabolic stress, a question of considerable translational interest for the treatment of diabetes. Methods: Apoptosis was measured in human islets shown to express Cx43, treated with RG or the control peptide ZP119 and exposed to glucolipotoxicity or IL-1β + IFNɣ. INS-1 cells shown to lack Cx43 were used to examine if RG protected human islet cells via Cx43 coupling. To study the mechanisms of action of Cx43-independent effects of RG, NO, IkBα degradation, mitochondrial activity, ROS, and insulin mRNA levels were determined. Results: RG reduced cytokine-induced apoptosis ~40% in human islets. In Cx43-deficient INS-1 cells, this protective effect was markedly blunted as expected, but unexpectedly, RG still modestly reduced apoptosis, and improved mitochondrial function, insulin-2 gene levels, and accumulated insulin release. RG reduced NO production in Cx43-deficient INS-1 cells associated with reduced iNOS expression, suggesting that RG blunts cytokine-induced NF-κB signaling in insulin-producing cells in a Cx43-independent manner. Conclusion: RG reduces cytokine-induced cell death in human islets. The protective action in Cx43-deficient INS-1 cells suggests a novel inhibitory mechanism of action of RG on NF-κB signaling.

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“…Since the levels of preproinsulin mRNA in the islets of individuals with normoglycaemia or type 2 diabetes do not significantly differ, its stability is unlikely to be affected in type 2 diabetes [32,33]. On the other hand, in mouse islets and insulinoma (MIN6) cells exposed to proinflammatory cytokines, no-go and nonsense-mediated RNA decay pathways are upregulated, lowering the levels of preproinsulin mRNA [34]. It is, therefore, possible that inflammation in pancreatic islets in type 1 diabetes alters preproinsulin mRNA stability, while its alternative splicing seems unaffected [35].…”

Section: Regulation Of Preproinsulin Mrna Stability In Health and Diamentioning

confidence: 99%

The making of insulin in health and disease

et al. 2020

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The discovery of insulin in 1921 has been one of greatest scientific achievements of the 20th century. Since then, the availability of insulin has shifted the focus of diabetes treatment from trying to keep patients alive to saving and improving the life of millions. Throughout this time, basic and clinical research has advanced our understanding of insulin synthesis and action, both in healthy and pathological conditions. Yet, multiple aspects of insulin production remain unknown. In this review, we focus on the most recent findings on insulin synthesis, highlighting their relevance in diabetes.

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The No-Go and Nonsense-Mediated RNA Decay Pathways Are Regulated by Inflammatory Cytokines in Insulin-Producing Cells and Human Islets and Determine β-Cell Insulin Biosynthesis and Survival

Cited by 19 publications

References 48 publications

No direct effect of SGLT2 activity on glucagon secretion

No direct effect of SGLT2 activity on glucagon secretion

The Connexin 43 Regulator Rotigaptide Reduces Cytokine-Induced Cell Death in Human Islets

The making of insulin in health and disease

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