The Interplay of Prolactin and the Glucocorticoids in the Regulation of β-Cell Gene Expression, Fatty Acid Oxidation, and Glucose-Stimulated Insulin Secretion: Implications for Carbohydrate Metabolism in Pregnancy

Deteriorating islet β-cell function is key in the progression of an impaired glucose tolerance state to overt type 2 diabetes (T2D), a transition that can be delayed by exercise. We have previously shown that trained rats are protected from heart ischemia–reperfusion injury in correlation with an increase in cardiac tissue fatty-acid oxidation. This trained metabolic phenotype, if induced in the islet, could also prevent β-cell failure in the pathogenesis of T2D. To assess the effect of training on islet lipid metabolism and insulin secretion, female Sprague–Dawley rats were exercised on a treadmill for 90 min/d, 4 d/week, for 10 weeks. Islet fatty-acid oxidation, the expression of key lipid metabolism genes, and glucose-stimulated insulin secretion were determined in freshly isolated islets from trained and sedentary control rats after a 48 h rest period from the last exercise. Although this moderate training reduced plasma glycerol, free fatty acids, and triglyceride levels by about 40%, consistent with reduced lipolysis from adipose tissue, it did not alter islet fatty-acid oxidation, nor the islet expression of key transcription factors and enzymes of lipid metabolism. The training also had no effect on glucose-stimulated insulin secretion or its amplification by free fatty acids. In summary, chronic exercise training did not cause an intrinsic change in islet lipid metabolism. Training did, however, substantially reduce the exposure of islets to exogenous lipid, thereby providing a potential mechanism by which exercise can prevent islet β-cell failure leading to T2D.

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Cyanidin Stimulates Insulin Secretion and Pancreatic β-Cell Gene Expression through Activation of l-type Voltage-Dependent Ca2+ Channels

Nutrients ◽

10.3390/nu9080814 ◽

2017 ◽

Vol 9 (8) ◽

pp. 814 ◽

Cited By ~ 13

Author(s):

Tanyawan Suantawee ◽

Sara Elazab ◽

Walter Hsu ◽

Shaomian Yao ◽

Henrique Cheng ◽

...

Keyword(s):

Gene Expression ◽

Insulin Secretion ◽

Pancreatic Β Cell ◽

Β Cell ◽

Voltage Dependent ◽

Cell Gene Expression ◽

Cell Gene ◽

Ca2 Channels

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Pericytes contribute to the islet basement membranes to promote beta-cell gene expression

Scientific Reports ◽

10.1038/s41598-021-81774-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Lina Sakhneny ◽

Alona Epshtein ◽

Limor Landsman

Keyword(s):

Gene Expression ◽

Cell Function ◽

Basement Membranes ◽

Cell Physiology ◽

Β Cells ◽

Β Cell ◽

Cell Clustering ◽

Β Cell Function ◽

Cell Gene Expression ◽

Glucose Stimulated Insulin Secretion

Abstractβ-Cells depend on the islet basement membrane (BM). While some islet BM components are produced by endothelial cells (ECs), the source of others remains unknown. Pancreatic pericytes directly support β-cells through mostly unidentified secreted factors. Thus, we hypothesized that pericytes regulate β-cells through the production of BM components. Here, we show that pericytes produce multiple components of the mouse pancreatic and islet interstitial and BM matrices. Several of the pericyte-produced ECM components were previously implicated in β-cell physiology, including collagen IV, laminins, proteoglycans, fibronectin, nidogen, and hyaluronan. Compared to ECs, pancreatic pericytes produce significantly higher levels of α2 and α4 laminin chains, which constitute the peri-islet and vascular BM. We further found that the pericytic laminin isoforms differentially regulate mouse β-cells. Whereas α2 laminins promoted islet cell clustering, they did not affect gene expression. In contrast, culturing on Laminin-421 induced the expression of β-cell genes, including Ins1, MafA, and Glut2, and significantly improved glucose-stimulated insulin secretion. Thus, alongside ECs, pericytes are a significant source of the islet BM, which is essential for proper β-cell function.

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Differential gene expression between Zucker Fatty rats and Zucker Diabetic Fatty rats: a potential role for the immediate-early gene Egr-1 in regulation of beta cell proliferation

Journal of Molecular Endocrinology ◽

10.1677/jme.1.01792 ◽

2005 ◽

Vol 35 (1) ◽

pp. 13-25 ◽

Cited By ~ 34

Author(s):

Kay E Garnett ◽

Philip Chapman ◽

Julie A Chambers ◽

Ian D Waddell ◽

David S W Boam

Keyword(s):

Gene Expression ◽

Type 2 Diabetes ◽

Cell Proliferation ◽

Transcription Factors ◽

Insulin Secretion ◽

Early Gene ◽

Β Cell ◽

Zucker Diabetic Fatty Rats ◽

Glucose Stimulated Insulin Secretion

The β-cell failure that characterises type 2 diabetes is likely to involve altered expression of many genes. We aimed to identify global changes in gene expression underlying β-cell dysfunction in pre-diabetic Zucker Diabetic Fatty rat islets, followed by functional studies to verify our findings. Gene expression profiles in islets from 6-week-old Zucker Diabetic Fatty rats and Zucker Fatty rat controls were analysed using Affymetrix microarrays. Totally 977 genes were found to be differentially regulated, comprising large groups of membrane and structural proteins, kinases, channels, receptors, transporters, growth factors and transcription factors. We are particularly interested in transcription factors, which can have profound effects on cellular function. Thus a subset of those with no role yet defined in the β-cell was selected for further study namely the immediate-early gene Egr-1, PAG608, rCGR19 and mSin3b. Tissue specificity of these factors varied but interestingly Egr-1 expression was highly enriched in the pancreatic islet. To determine a possible role of Egr-1 in the β-cell, Egr-1 expression in INS-1 cells was silenced using RNA interference (RNAi). Glucose-stimulated insulin secretion in these cells was then measured using ELISA and cell proliferation was measured by [3H]thymidine incorporation. Small interfering RNA (siRNA)-mediated silencing of the Egr-1 gene inhibited its induction by glucose but had no observable effect on glucose-stimulated insulin secretion. However, Egr-1 gene silencing did inhibit proliferation of INS-1 cells in a glucose-independent manner. Our studies have revealed a role for Egr-1 and suggest that reduced Egr-1 gene expression may contribute to decreased β-cell proliferation and the consequent β-cell failure observed in the later stages of type 2 diabetes.

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Adenovirus-mediated overexpression of liver carnitine palmitoyltransferase I in INS1E cells: effects on cell metabolism and insulin secretion

Biochemical Journal ◽

10.1042/bj3640219 ◽

2002 ◽

Vol 364 (1) ◽

pp. 219-226 ◽

Cited By ~ 47

Author(s):

Blanca RUBÍ ◽

Peter A. ANTINOZZI ◽

Laura HERRERO ◽

Hisamitsu ISHIHARA ◽

Guillermina ASINS ◽

...

Keyword(s):

Fatty Acids ◽

Insulin Secretion ◽

Fatty Acid ◽

Fatty Acid Oxidation ◽

Fold Increase ◽

Acid Oxidation ◽

Β Cells ◽

Β Cell ◽

Carnitine Palmitoyltransferase I ◽

Cpt I

Lipid metabolism in the β-cell is critical for the regulation of insulin secretion. Pancreatic β-cells chronically exposed to fatty acids show higher carnitine palmitoyltransferase I (CPT I) protein levels, higher palmitate oxidation rates and an altered insulin response to glucose. We examined the effect of increasing CPT I levels on insulin secretion in cultured β-cells. We prepared a recombinant adenovirus containing the cDNA for the rat liver isoform of CPT I. The overexpression of CPT I in INS1E cells caused a more than a 5-fold increase in the levels of CPT I protein (detected by Western blotting), a 6-fold increase in the CPT activity, and an increase in fatty acid oxidation at 2.5mM glucose (1.7-fold) and 15mM glucose (3.1-fold). Insulin secretion was stimulated in control cells by 15mM glucose or 30mM KCl. INS1E cells overexpressing CPT I showed lower insulin secretion on stimulation with 15mM glucose (−40%; P<0.05). This decrease depended on CPT I activity, since the presence of etomoxir, a specific inhibitor of CPT I, in the preincubation medium normalized the CPT I activity, the fatty-acid oxidation rate and the insulin secretion in response to glucose. Exogenous palmitate (0.25mM) rescued glucose-stimulated insulin secretion (GSIS) in CPT I-overexpressing cells, indicating that the mechanism of impaired GSIS was through the depletion of a critical lipid. Depolarizing the cells with KCl or intermediary glucose concentrations (7.5mM) elicited similar insulin secretion in control cells and cells overexpressing CPT I. Glucose-induced ATP increase, glucose metabolism and the triacylglycerol content remained unchanged. These results provide further evidence that CPT I activity regulates insulin secretion in the β-cell. They also indicate that up-regulation of CPT I contributes to the loss of response to high glucose in β-cells exposed to fatty acids.

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Sexually Dimorphic Effects of Maternal Sildenafil Citrate Treatment on Pancreatic β-Cell Gene Expression in Growth-Restricted Fetal Lambs

Journal of Paediatrics and Child Health ◽

10.1111/jpc.13882_162 ◽

2018 ◽

Vol 54 ◽

pp. 63-63

Keyword(s):

Gene Expression ◽

Sildenafil Citrate ◽

Sexually Dimorphic ◽

Pancreatic Β Cell ◽

Β Cell ◽

Cell Gene Expression ◽

Cell Gene

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Chromomycin A2 potently inhibits glucose-stimulated insulin secretion from pancreatic β cells

10.1101/337113 ◽

2018 ◽

Author(s):

Michael A Kalwat ◽

In Hyun Hwang ◽

Jocelyn Macho ◽

Magdalena G Grzemska ◽

Jonathan Z Yang ◽

...

Keyword(s):

Insulin Secretion ◽

Natural Product ◽

Pancreatic Islet ◽

Islet Function ◽

Gene Promoters ◽

Β Cells ◽

Β Cell ◽

Regulatory Pathways ◽

Glucose Stimulated Insulin Secretion ◽

Cell Gene

ABSTRACTEnhancers or inhibitors of insulin secretion could become therapeutics as well as lead to the identification of requisite β-cell regulatory pathways and increase our understanding of pancreatic islet function. Toward this goal, we previously used an insulin-linked luciferase that is co-secreted with insulin in MIN6 β-cells to perform a high-throughput natural product screen for chronic effects on glucose-stimulated insulin secretion. Using multiple phenotypic analyses, we identified that one of the top natural product hits, chromomycin A2 (CMA2), potently inhibited insulin secretion through at least three mechanisms: disruption of Wnt signaling, interfering with β-cell gene expression, and suppression of triggering calcium (Ca2+) influx. Chronic treatment with CMA2 largely ablated glucose-stimulated insulin secretion even post-washout, but did not inhibit glucose-stimulated generation of ATP or Ca2+ influx. However, by using the KATP channel-opener diazoxide, we uncovered defects in depolarization-induced Ca2+ influx which may contribute to the suppressed secretory response. Glucose-responsive ERK1/2 and S6 phosphorylation were also disrupted by chronic CMA2 treatment. The FUSION bioinformatic database indicated that the phenotypic effects of CMA2 clustered with a number of Wnt/GSK3 pathway-related genes. Consistently, CMA2 decreased GSK3 phosphorylation and suppressed activation of a β-catenin activity reporter. CMA2 and a related compound mithramycin are described to have DNA-interaction properties, possibly abrogating transcription factor binding to critical β-cell gene promoters. We observed that CMA2, but not mithramycin, suppressed expression of PDX1 and UCN3. However, neither expression of INSI/II nor insulin content was affected by chronic CMA2. The mechanisms of CMA2-induced insulin secretion defects may involve components both proximal and distal to Ca2+ influx. Therefore, CMA2 is an example of a chemical that can simultaneously disrupt β-cell function through both non-cytotoxic and cytotoxic mechanisms. Future applications of CMA2 and similar aureolic acid analogs for disease therapies should consider the potential impacts on pancreatic islet function.

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The LIM homeodomain protein ISL1 mediates the function of TCF7L2 in pancreatic beta cells

Journal of Molecular Endocrinology ◽

10.1530/jme-17-0181 ◽

2018 ◽

Vol 61 (1) ◽

pp. 1-12 ◽

Cited By ~ 4

Author(s):

Weijuan Shao ◽

Vivian Szeto ◽

Zhuolun Song ◽

Lili Tian ◽

Zhong-Ping Feng ◽

...

Keyword(s):

Insulin Secretion ◽

Wnt Pathway ◽

Homeodomain Protein ◽

Adenovirus Infection ◽

Β Cell ◽

Downstream Target ◽

Cell Gene Expression ◽

Mouse Islets ◽

Cell Gene

Pancreatic β-cell Tcf7l2 deletion or its functional knockdown suggested the essential role of this Wnt pathway effector in controlling insulin secretion, glucose homeostasis and β-cell gene expression. As the LIM homeodomain protein ISL1 is a suggested Wnt pathway downstream target, we hypothesize that it mediates metabolic functions of TCF7L2. We aimed to determine the role of ISL1 in mediating the function of TCF7L2 and the incretin hormone GLP-1 in pancreatic β-cells. The effect of dominant negative TCF7L2 (TCF7L2DN) mediated Wnt pathway functional knockdown on Isl1 expression was determined in βTCFDN mouse islets and in the rat insulinoma cell line INS-1 832/13. Luciferase reporter assay and chromatin immunoprecipitation were utilized to determine whether Isl1 is a direct downstream target of Tcf7l2. TCF7L2DN adenovirus infection and siRNA-mediated Isl1 knockdown on β-cell gene expression were compared. Furthermore, Isl1 knockdown on GLP-1 stimulated β-catenin S675 phosphorylation and insulin secretion was determined. We found that TCF7L2DN repressed ISL1 levels in βTCFDN islets and the INS-1 832/13 cell line. Wnt stimulators enhanced Isl1 promoter activity and binding of TCF7L2 on Isl1 promoter. TCF7L2DN adenovirus infection and Isl1 knockdown generated similar repression on expression of β-cell genes, including the ones that encode GLUT2 and GLP-1 receptor. Either TCF7L2DN adenovirus infection or Isl1 knockdown attenuated GLP-1-stimulated β-catenin S675 phosphorylation in INS-1 832/13 cells or mouse islets and GLP-1 stimulated insulin secretion in INS-1 832/13 or MIN6 cells. Our observations support the existence of TCF7L2–ISL1 transcriptional network, and we suggest that this network also mediates β-cell function of GLP-1.

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