Gene Expression Profiles Of Islets Research Articles

Beta cell adaptation to pregnancy requires prolactin action on both beta and non-beta cells

Pancreatic islets adapt to insulin resistance of pregnancy by up regulating β-cell mass and increasing insulin secretion. Previously, using a transgenic mouse with global, heterozygous deletion of prolactin receptor (Prlr+/−), we found Prlr signaling is important for this adaptation. However, since Prlr is expressed in tissues outside of islets as well as within islets and prolactin signaling affects β-cell development, to understand β-cell-specific effect of prolactin signaling in pregnancy, we generated a transgenic mouse with an inducible conditional deletion of Prlr from β-cells. Here, we found that β-cell-specific Prlr reduction in adult mice led to elevated blood glucose, lowed β-cell mass and blunted in vivo glucose-stimulated insulin secretion during pregnancy. When we compared gene expression profile of islets from transgenic mice with global (Prlr+/−) versus β-cell-specific Prlr reduction (βPrlR+/−), we found 95 differentially expressed gene, most of them down regulated in the Prlr+/− mice in comparison to the βPrlR+/− mice, and many of these genes regulate apoptosis, synaptic vesicle function and neuronal development. Importantly, we found that islets from pregnant Prlr+/− mice are more vulnerable to glucolipotoxicity-induced apoptosis than islets from pregnant βPrlR+/− mice. These observations suggest that down regulation of prolactin action during pregnancy in non-β-cells secondarily and negatively affect β-cell gene expression, and increased β-cell susceptibility to external insults.

Hypoxia-inducible factor-1α mediates the expression of mature β cell-disallowed genes in hypoxia-induced β cell dedifferentiation

Hypoxia affects the function of pancreatic β cells, and the molecular mechanism underlying hypoxia-related β cell dysfunction in human type 2 diabetes mellitus (T2DM) remains to be elucidated. In this study, by comparing the gene expression profiles of islets from nondiabetic and T2D subjects using gene chip array, we aimed to elucidate that hypoxia signaling pathways are activated in human T2DM islets. CoCl2 treatment, which was employed to mimic hypoxic stimulation in human islets, decreased insulin secretion, insulin content, and the functional gene expression of human islets. In parallel, the expression of mature β cell-disallowed genes was upregulated by CoCl2, including progenitor cell marker NGN3, β cell differentiation marker ALDH1A3, and genes that are typically inhibited in mature β cells, namely, GLUT1 and LDHA, indicating that CoCl2-mimicked hypoxia induced β cell dedifferentiation of human islets. This finding in human islets was confirmed in mouse β cell line NIT-1. By using Dimethyloxalylglycine (DMOG) to activate hypoxia-inducible factor-1α (HIF-1α) or siRNAs to knockdown HIF-1α, we found that HIF-1α was a key regulator of hypoxia-induced dedifferentiation of β cells by upregulating mature β cell-disallowed genes. Our findings suggested that HIF-1α activation might be an important contributor to β cell dedifferentiation in human T2DM islets, and HIF-1α-targeted therapies may have the potential to reverse β cell dedifferentiation of human T2DM islets.

Protective effects of the SGLT2 inhibitor luseogliflozin on pancreatic β-cells in db/db mice: The earlier and longer, the better.

We compared the protective effects of sodium glucose co-transporter (SGLT) 2 inhibitor luseogliflozin on pancreatic β-cells between early and advanced stages of diabetes and between short- and long-term use. Diabetic db/db mice were treated with luseogliflozin for 2 weeks in an early stage of diabetes (7-9 weeks of age) and an advanced stage of diabetes (16-18 weeks) for a longer period of time (7-18 weeks). We performed various morphological analyses of pancreatic islets and examined gene expression profiles in islets after such treatment. In diabetic db/db mice, insulin biosynthesis and secretion were markedly increased by luseogliflozin in an early stage of diabetes but not in an advanced stage. In addition, β-cell mass was preserved by luseogliflozin only in an early stage. Furthermore, when db/db mice were treated with luseogliflozin for a longer period of time, starting from an early stage, β-cell function and mass were markedly preserved even after a longer period of time compared to untreated db/db mice. Luseogliflozin exerts more protective effects in an early stage of diabetes compared to an advanced stage, and longer-term use of luseogliflozin exerts more beneficial effects on pancreatic β-cells compared to short-term use.

The effects of caveolin1 on β cell proliferation.

Our study aims to access the influence of caveolin1 (CAV1) on β cell expression profiles. We knocked down the expression of CAV1 in both NIT-1 cells and islets isolated from C57BL/6J mice using an RNA interference technique, which was realized by the transfer of an shRNA vector targeting CAV1 mRNA into NIT-1 cells or islets through latent virus infection. First, we identified the change in gene expression profiles in islets, in which the CAV1 expression level was down-regulated, as ascertained by mouse gene expression microarray, and the results showed that pathways related to β cell proliferation and pancreatic secretion functions were significantly influenced. The results of MTT demonstrated that the knockdown of CAV1 expression in NIT-1 cells promoted proliferation. The protein array results showed that pro-apoptotic cytokines were down-regulated in the NIT-1 cell line with CAV1 knockdown. These findings suggest that CAV1 might be involved in apoptosis and proliferation regulation in β cells, and therefore could be a potential target for the development of novel therapies for diabetes mellitus.

Mechanism of Roux-en-Y Gastric Bypass Treatment for Type 2 Diabetes in Rats

ObjectivesRoux-en-Y gastric bypass (RYGB) is a novel therapy for diabetes. We aimed to explore the therapeutic mechanism of RYGB. MethodsAfter RYGB, animal models were established, and gene expression profile of islets was assessed. Additionally, gastrointestinal hormones were measured using enzyme-linked immunosorbent assays. Ca2+ was studied using confocal microscopy and patch-clamp technique. The morphology of islets and beta cells was observed using optical microscopy and electron microscopy. ResultsRYGB was an effective treatment in diabetic rats. Expression profiling data showed that RYGB produced a new metabolic environment and that gene expression changed to adapt to the new environment. The differential expression of genes associated with hormones, Ca2+ and cellular proliferation was closely related to RYGB and diabetes metabolism. Furthermore, the data verified that RYGB led to changes in hormone level and enhanced Ca2+ concentration changes and Ca2+ channel activity. Morphological data showed that RYGB induced the proliferation of islets and improved the function of beta cells. ConclusionsRYGB promoted a new metabolic environment while triggering changes to adapt to the new environment. These changes promoted the cellular proliferation of islets and improved the function of beta cells. The quantity of beta cells increased, and their quality improved, ultimately leading to insulin secretion enhancement.

Analysis of gene expression in pancreatic islets from diet-induced obese mice

In insulin-resistant status such as obesity, failure of pancreatic islets to increase insulin secretion leads to diabetes. We sought to screen for the islet genes that facilitate islet adaptation to obesity by comparing gene expression profiles between two strains of obesity-prone inbred mice with different propensities for hyperglycemia. C57BL/6J and AKR/J were fed regular rodent chow or high-fat diet, after which islet morphology, secretory function, and gene expression were assessed. AKR/J had lower blood glucose and higher insulin levels compared with C57BL/6J mice on regular rodent chow or high-fat diet. Insulin secretion was 3.2-fold higher in AKR/J than C57BL/6J mice following intraperitoneal glucose injection. Likewise, glucose-stimulated insulin secretion from isolated islets was higher in AKR/J. Additionally, islet mass was 1.4-fold greater in AKR/J compared with C57BL/6J. To elucidate the factors associated with the differences in islet function, we analyzed the gene expression profiles in islets in AKR/J and C57BL/6J mice. Of 14,000 genes examined, 202 were upregulated and 270 were downregulated in islets from diet-induced obese AKR/J mice compared with C57BL/6J mice. Key genes involved in islet signaling and metabolism, e.g., glucagon-like peptide-1 receptor, sterol Co-A desaturase 1 and 2, and fatty acid desaturase 2 were upregulated in obese AKR/J mice. The expression of multiple extracellular matrix proteins was also increased in AKR/J mice, suggesting a role in modulation of islet mass. Functional analyses of differentially regulated genes hold promise for elucidating factors linking obesity to alterations in islet function.

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

The beta-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 beta-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 beta-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 beta-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 [(3)H]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 beta-cell proliferation and the consequent beta-cell failure observed in the later stages of type 2 diabetes.