Reduced Expression of Chl1 gene Impairs Insulin Secretion by Down-Regulating the Expression of Key Molecules of β-cell Function

2019 ◽  
Author(s):  
Jalal Taneera ◽  
Sarah Dhaiban ◽  
Mahmood Hachim ◽  
Abdul Khader Mohammed ◽  
Debasmita Mukhopadhyay ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Cell Viability ◽  
Rna Sequencing ◽  
Cell Function ◽  
Enrichment Analysis ◽  
Gene Set Enrichment Analysis ◽  
Insulin Biosynthesis ◽  
Sequencing Data ◽  
Β Cell ◽  
Β Cell Function

AbstractSilencing of Chl1 gene expression has been previously reported to reduce insulin secretion. Nevertheless, the mechanism underlying this effect remains unclear. In this study, we performed a serial of studies to investigate how Chl1 affects insulin secretion in INS-1 cells. RNA-sequencing was used to investigate the expression of CHL1 in human adipose, liver, muscle, and human islets. Silencing of Chl1 in INS-1 cells was done to assess its impact on the insulin secretion, content, cell viability, and apoptosis. In addition, gene set enrichment analysis (GSEA) was performed to identify possible molecular signatures that associate with Chl1 expression silencing.RNA sequencing data revealed a high expression of CHL1 in pancreatic islets and adipose tissues compared to liver and muscles tissues. Diabetic islets exhibited a lower expression of CHL1 as compared to non-diabetic islets. CHL1 expression was found to correlate positively with insulin secretory index, GLP1R but inversely with HbA1c and BMI. Silencing of Chl1 in INS-1 cells markedly reduced insulin content and secretion. The expression of key molecules of β-cell function including Insulin, Pdx1, Gck, Glut2, and Insrβ was down-regulated in Chl1-silenced cells at transcriptional and translational levels. Cell viability, apoptosis, and proliferation rate were not affected. GSEA showed that the insulin-signaling pathway was influenced in Chl1-silenced cells. Silencing of Chl1 impairs β-cell function by disrupting the activity of key signaling pathways of importance for insulin biosynthesis and secretion.

Let7b-5p is Upregulated in the Serum of Emirati Patients with Type 2 Diabetes and Regulates Insulin Secretion in INS-1 Cells

2020 ◽  
Author(s):  
Hayat Aljaibeji ◽  
Noha Mousaad Elemam ◽  
Abdul Khader Mohammed ◽  
Hind Hasswan ◽  
Mahammad Al Thahyabat ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Insulin Secretion ◽  
Cell Viability ◽  
Cell Function ◽  
Serum Levels ◽  
Insulin Content ◽  
Β Cell ◽  
Control Subjects ◽  
Β Cell Function

Abstract Let7b-5p is a member of the Let-7 miRNA family and one of the top expressed miRNAs in human islets that implicated in glucose homeostasis. The levels of Let7b-5p in type 2 diabetes (T2DM) patients or its role in β-cell function is still unclear. In the current study, we measured the serum levels of let7b-5p in Emirati patients with T2DM (with/without complications) and control subjects. Overexpression or silencing of let7b-5p in INS-1 (832/13) cells was performed to investigate the impact on insulin secretion, content, cell viability, apoptosis, and key functional genes. We found that serum levels of let7b-5p are significantly (p<0.05) higher in T2DM-patients or T2DM with complications compared to control subjects. Overexpression of let7b-5p increased insulin content and decreased glucose-stimulated insulin secretion, whereas silencing of let7b-5p reduced insulin content and secretion. Modulation of the expression levels of let7b-5p did not influence cell viability nor apoptosis. Analysis of mRNA and protein expression of hallmark genes in let7b-5p transfected cells revealed a marked dysregulation of Insulin, Pancreatic And Duodenal Homeobox 1 (PDX1), glucokinase (GCK), glucose transporter 2 (GLUT2), and INSR. In conclusion, an appropriate level of let7b-5p is essential to maintain β-cell function and may be regarded as a biomarker for T2DM.

scholarly journals Protein restriction in early life is associated with changes in insulin sensitivity and pancreatic β-cell function during pregnancy

2012 ◽  
Vol 109 (2) ◽  
pp. 236-247 ◽  
Author(s):  
Letícia Martins Ignácio-Souza ◽  
Sílvia Regina Reis ◽  
Vanessa Cristina Arantes ◽  
Bárbara Laet Botosso ◽  
Roberto Vilela Veloso ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Protein Kinase ◽  
Early Life ◽  
Cell Function ◽  
Secretory Process ◽  
Insulin Biosynthesis ◽  
Β Cell ◽  
Pregnant Rats ◽  
Β Cell Function ◽  
Glucose Stimulated Insulin Secretion

Malnutrition in early life impairs glucose-stimulated insulin secretion in adulthood. Conversely, pregnancy is associated with a significant increase in glucose-stimulated insulin secretion under conditions of normoglycaemia. A failure in β-cell adaptive changes may contribute to the onset of diabetes. Thus, glucose homeostasis and β-cell function were evaluated in control-fed pregnant (CP) and non-pregnant (CNP) or protein-restricted pregnant (LPP) and non-pregnant (LPNP) rats, from fetal to adult life, and in protein-restricted rats that were recovered after weaning (RP and RNP). The typical insulin resistance of pregnancy was not observed in the RP rats, nor did pregnancy increase the insulin content/islet in the LPP group. The glucose dose–response curves from pregnant rats were shifted to the left in relation to the non-pregnant rats, except in the recovered group. Glucose utilisation but not oxidation in islets from the RP and LPP groups was reduced at a concentration of 8·3 mm-glucose compared with islets from the CP group. Cyclic AMP content and the potentiation of glucose-stimulated insulin secretion by isobutylmethylxanthine at a concentration of 2·8 mm-glucose indicated increased adenylyl cyclase 3 activity but reduced protein kinase A-α activity in islets from the RP and LPP rats. Protein kinase C (PKC)-α but not phospholipase C (PLC)-β1 expression was reduced in islets from the RP group. Phorbol-12-myristate 13-acetate produced a less potent stimulation of glucose-stimulated insulin secretion in the RP group. Thus, the alterations exhibited by islets from the LPP group appeared to be due to reduced islet mass and/or insulin biosynthesis. In the RP group the loss of the adaptive capacity apparently resulted from uncoupling between glucose metabolism and the amplifying signals of the secretory process, as well as a severe attenuation of the PLC/PKC pathway.

scholarly journals Pax6 Is Crucial for β-Cell Function, Insulin Biosynthesis, and Glucose-Induced Insulin Secretion

2012 ◽  
Vol 26 (4) ◽  
pp. 696-709 ◽  
Author(s):  
Yvan Gosmain ◽  
Liora S. Katz ◽  
Mounia Heddad Masson ◽  
Claire Cheyssac ◽  
Caroline Poisson ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Target Genes ◽  
Cell Function ◽  
Insulin Biosynthesis ◽  
Candidate Gene Approach ◽  
Mrna Levels ◽  
Β Cells ◽  
Β Cell ◽  
Cell Content ◽  
Β Cell Function

Abstract The Pax6 transcription factor is crucial for endocrine cell differentiation and function. Indeed, mutations of Pax6 are associated with a diabetic phenotype and a drastic decrease of insulin-positive cell number. Our aim was to better define the β-cell Pax6 transcriptional network and thus provide further information concerning the role of Pax6 in β-cell function. We developed a Pax6-deficient model in rat primary β-cells with specific small interfering RNA leading to a 75% knockdown of Pax6 expression. Through candidate gene approach, we confirmed that Pax6 controls the mRNA levels of the insulin 1 and 2, Pdx1, MafA, GLUT2, and PC1/3 genes in β-cells. Importantly, we identified new Pax6 target genes coding for GK, Nkx6.1, cMaf, PC2, GLP-1R and GIPR which are all involved in β-cell function. Furthermore, we demonstrated that Pax6 directly binds and activates specific elements on the promoter region of these genes. We also demonstrated that Pax6 knockdown led to decreases in insulin cell content, in insulin processing, and a specific defect of glucose-induced insulin secretion as well as a significant reduction of GLP-1 action in primary β-cells. Our results strongly suggest that Pax6 is crucial for β-cells through transcriptional control of key genes coding for proteins that are involved in insulin biosynthesis and secretion as well as glucose and incretin actions on β-cells. We provide further evidence that Pax6 represents a key element of mature β-cell function.

scholarly journals Mechanism of Prostacyclin-Induced Potentiation of Glucose-Induced Insulin Secretion

Endocrinology ◽  
2012 ◽  
Vol 153 (6) ◽  
pp. 2612-2622 ◽  
Author(s):  
Ewa Gurgul-Convey ◽  
Katarzyna Hanzelka ◽  
Sigurd Lenzen
Keyword(s):  
Insulin Secretion ◽  
Cell Function ◽  
Islet Cells ◽  
Receptor Activation ◽  
Insulin Biosynthesis ◽  
Β Cell ◽  
Atp Production ◽  
Mediators Of Inflammation ◽  
Β Cell Function

Arachidonic acid metabolites are crucial mediators of inflammation in diabetes. Although eicosanoids are established modulators of pancreatic β-cell function, the role of prostacyclin (prostaglandin I2) is unknown. Therefore, this study aimed to analyze the role of prostacyclin in β-cell function. Prostacyclin synthase (PGIS) was weakly expressed in rat islet cells but nevertheless significantly increased by incubation with 30 mM glucose, especially in non-β-cells. PGIS was overexpressed in INS1E cells, and the regulation of insulin secretion was analyzed. PGIS overexpression strongly potentiated glucose-induced insulin secretion along with increased insulin content and ATP production. Importantly, overexpression of PGIS potentiated only nutrient-induced insulin secretion. The effect of PGIS overexpression was mediated by prostacyclin released from insulin-secreting cells and dependent on prostacyclin receptor (IP receptor) activation, with concomitant cAMP production. The cAMP-mediated potentiation of glucose-induced insulin secretion by prostacyclin was independent of the protein kinase A pathway but strongly attenuated by the knockdown of the exchange protein directly activated by cAMP 2 (Epac2), pointing to a crucial role for Epac2 in this process. Thus, prostacyclin is a powerful potentiator of glucose-induced insulin secretion. It improves the secretory capacity by inducing insulin biosynthesis and probably by stimulating exocytosis. Our findings open a new therapeutical perspective for an improved treatment of type 2 diabetes.

scholarly journals mTORC1 and mTORC2 regulate insulin secretion through Akt in INS-1 cells

2012 ◽  
Vol 216 (1) ◽  
pp. 21-29 ◽  
Author(s):  
Olivier Le Bacquer ◽  
Gurvan Queniat ◽  
Valery Gmyr ◽  
Julie Kerr-Conte ◽  
Bruno Lefebvre ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Cell Function ◽  
Antagonistic Effect ◽  
Dominant Negative ◽  
Insulin Content ◽  
Insulin Biosynthesis ◽  
Direct Role ◽  
Β Cell Function ◽  
Glucose Stimulated Insulin Secretion

Regulated associated protein of mTOR (Raptor) and rapamycin-insensitive companion of mTOR (rictor) are two proteins that delineate two different mTOR complexes, mTORC1 and mTORC2 respectively. Recent studies demonstrated the role of rictor in the development and function of β-cells. mTORC1 has long been known to impact β-cell function and development. However, most of the studies evaluating its role used either drug treatment (i.e. rapamycin) or modification of expression of proteins known to modulate its activity, and the direct role of raptor in insulin secretion is unclear. In this study, using siRNA, we investigated the role of raptor and rictor in insulin secretion and production in INS-1 cells and the possible cross talk between their respective complexes, mTORC1 and mTORC2. Reduced expression of raptor is associated with increased glucose-stimulated insulin secretion and intracellular insulin content. Downregulation of rictor expression leads to impaired insulin secretion without affecting insulin content and is able to correct the increased insulin secretion mediated by raptor siRNA. Using dominant-negative or constitutively active forms of Akt, we demonstrate that the effect of both raptor and rictor is mediated through alteration of Akt signaling. Our finding shed new light on the mechanism of control of insulin secretion and production by the mTOR, and they provide evidence for antagonistic effect of raptor and rictor on insulin secretion in response to glucose by modulating the activity of Akt, whereas only raptor is able to control insulin biosynthesis.

Differential Loss of β-cell Function in Youth vs. Adults Following Treatment Withdrawal in the Restoring Insulin Secretion (RISE) Study

2021 ◽  
pp. 108948
Author(s):  
Kristina M. Utzschneider ◽  
Mark T. Tripputi ◽  
Alexandra Kozedub ◽  
Elena Barengolts ◽  
Sonia Caprio ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Cell Function ◽  
Treatment Withdrawal ◽  
Β Cell ◽  
Β Cell Function

scholarly journals Functional Role of Serotonin in Insulin Secretion in a Diet-Induced Insulin-Resistant State

Endocrinology ◽  
2014 ◽  
Vol 156 (2) ◽  
pp. 444-452 ◽  
Author(s):  
Kyuho Kim ◽  
Chang-Myung Oh ◽  
Mica Ohara-Imaizumi ◽  
Sangkyu Park ◽  
Jun Namkung ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Pancreatic Islets ◽  
Cell Function ◽  
Β Cell ◽  
Pancreas Perfusion ◽  
Insulin Resistant ◽  
Β Cell Function ◽  
Resistant State ◽  
Insulin Resistant State

The physiological role of serotonin, or 5-hydroxytryptamine (5-HT), in pancreatic β-cell function was previously elucidated using a pregnant mouse model. During pregnancy, 5-HT increases β-cell proliferation and glucose-stimulated insulin secretion (GSIS) through the Gαq-coupled 5-HT2b receptor (Htr2b) and the 5-HT3 receptor (Htr3), a ligand-gated cation channel, respectively. However, the role of 5-HT in β-cell function in an insulin-resistant state has yet to be elucidated. Here, we characterized the metabolic phenotypes of β-cell-specific Htr2b−/− (Htr2b βKO), Htr3a−/− (Htr3a knock-out [KO]), and β-cell-specific tryptophan hydroxylase 1 (Tph1)−/− (Tph1 βKO) mice on a high-fat diet (HFD). Htr2b βKO, Htr3a KO, and Tph1 βKO mice exhibited normal glucose tolerance on a standard chow diet. After 6 weeks on an HFD, beginning at 4 weeks of age, both Htr3a KO and Tph1 βKO mice developed glucose intolerance, but Htr2b βKO mice remained normoglycemic. Pancreas perfusion assays revealed defective first-phase insulin secretion in Htr3a KO mice. GSIS was impaired in islets isolated from HFD-fed Htr3a KO and Tph1 βKO mice, and 5-HT treatment improved insulin secretion from Tph1 βKO islets but not from Htr3a KO islets. Tph1 and Htr3a gene expression in pancreatic islets was not affected by an HFD, and immunostaining could not detect 5-HT in pancreatic islets from mice fed an HFD. Taken together, these results demonstrate that basal 5-HT levels in β-cells play a role in GSIS through Htr3, which becomes more evident in a diet-induced insulin-resistant state.

Impact of lack of suppression of glucagon on glucose tolerance in humans

1999 ◽  
Vol 277 (2) ◽  
pp. E283-E290 ◽  
Author(s):  
Pankaj Shah ◽  
Ananda Basu ◽  
Rita Basu ◽  
Robert Rizza
Keyword(s):  
Insulin Secretion ◽  
Glucose Concentration ◽  
Cell Function ◽  
Hormone Secretion ◽  
Glucose Production ◽  
Glucagon Secretion ◽  
Β Cell ◽  
Β Cell Function ◽  
Glucagon Suppression

People with type 2 diabetes have defects in both α- and β-cell function. To determine whether lack of suppression of glucagon causes hyperglycemia when insulin secretion is impaired but not when insulin secretion is intact, twenty nondiabetic subjects were studied on two occasions. On both occasions, a “prandial” glucose infusion was given over 5 h while endogenous hormone secretion was inhibited. Insulin was infused so as to mimic either a nondiabetic ( n = 10) or diabetic ( n = 10) postprandial profile. Glucagon was infused at a rate of 1.25 ng ⋅ kg−1 ⋅ min−1, beginning either at time zero to prevent a fall in glucagon (nonsuppressed study day) or at 2 h to create a transient fall in glucagon (suppressed study day). During the “diabetic” insulin profile, lack of glucagon suppression resulted in a marked increase ( P < 0.002) in both the peak glucose concentration (11.9 ± 0.4 vs. 8.9 ± 0.4 mmol/l) and the area above basal of glucose (927 ± 77 vs. 546 ± 112 mmol ⋅ l−1 ⋅ 6 h) because of impaired ( P < 0.001) suppression of glucose production. In contrast, during the “nondiabetic” insulin profile, lack of suppression of glucagon resulted in only a slight increase ( P< 0.02) in the peak glucose concentration (9.1 ± 0.4 vs. 8.4 ± 0.3 mmol/l) and the area above basal of glucose (654 ± 146 vs. 488 ± 118 mmol ⋅ l−1 ⋅ 6 h). Of interest, when glucagon was suppressed, glucose concentrations differed only minimally during the nondiabetic and diabetic insulin profiles. These data indicate that lack of suppression of glucagon can cause substantial hyperglycemia when insulin availability is limited, therefore implying that inhibitors of glucagon secretion and/or glucagon action are likely to be useful therapeutic agents in such individuals.

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