Electrophysiological properties of human beta-cell lines EndoC-βH1 and -βH2 conform with human beta-cells

© The Author(s) 2018Limited access to human islets has prompted the development of human beta cell models. The human beta cell lines EndoC-βH1 and EndoC-βH2 are increasingly used by the research community. However, little is known of their electrophysiological and secretory properties. Here, we monitored parameters that constitute the glucose-triggering pathway of insulin release. Both cell lines respond to glucose (6 and 20 mM) with 2- to 3-fold stimulation of insulin secretion which correlated with an elevation of [Ca2+]i, membrane depolarisation and increased action potential firing. Similar to human primary beta cells, KATP channel activity is low at 1 mM glucose and is further reduced upon increasing glucose concentration; an effect that was mimicked by the KATP channel blocker tolbutamide. The upstroke of the action potentials reflects the activation of Ca2+ channels with some small contribution of TTX-sensitive Na+ channels. The repolarisation involves activation of voltage-gated Kv2.2 channels and large-conductance Ca2+-activated K+ channels. Exocytosis presented a similar kinetics to human primary beta cells. The ultrastructure of these cells shows insulin vesicles composed of an electron-dense core surrounded by a thin clear halo. We conclude that the EndoC-βH1 and -βH2 cells share many features of primary human β-cells and thus represent a useful experimental model.Peer reviewedFinal Published versio

Reduced somatostatin signalling leads to hypersecretion of glucagon in mice fed a high-fat diet

Objectives:&nbsp;Elevated plasma glucagon is an early symptom of diabetes, occurring in subjects with impaired glucose regulation. Here, we explored alpha-cell function in female mice fed a high-fat diet (HFD)&mdash;a widely used mouse model of prediabetes. Methods:&nbsp;We fed female mice expressing the Ca2+&nbsp;indicator GCaMP3 specifically in alpha-cells an HFD or control (CTL) diet. We then conducted&nbsp;in&nbsp;vivo&nbsp;phenotyping of these mice, as well as experiments on isolated (ex&nbsp;vivo) islets and in the&nbsp;in situ&nbsp;perfused pancreas. Results:&nbsp;In&nbsp;vivo,&nbsp;HFD-fed mice exhibited increased fed plasma glucagon levels and a reduced response to elevations in plasma glucose. Glucagon secretion from isolated islets and in the perfused mouse pancreas was elevated under both hypo- and hyperglycaemic conditions. In mice fed a CTL diet, increasing glucose reduced intracellular Ca2+&nbsp;([Ca2+]i) (oscillation frequency and amplitude). This effect was also observed in HFD mice; however, both the frequency and amplitude of the [Ca2+]i&nbsp;oscillations were higher than those in CTL alpha-cells. Given that alpha-cells are under strong paracrine control from neighbouring somatostatin-secreting delta-cells, we hypothesised that this elevation of alpha-cell output was due to a lack of somatostatin (SST) secretion. Indeed, SST secretion in isolated islets from HFD mice was reduced but exogenous SST also failed to suppress glucagon secretion and [Ca2+]i&nbsp;activity from HFD alpha-cells, in contrast to observations in CTL mice. Conclusions:&nbsp;These findings suggest that reduced delta-cell function, combined with intrinsic changes in alpha-cell sensitivity to somatostatin, accounts for the hyperglucagonaemia in mice fed an HFD.</p

Corporate environmental responsibility and criminology

This article addresses corporate environmental responsibility (CER) and aims to present a criminological analysis of it. We studied the opinion of a number of principle actors involved in CER in Europe in order to determine how they perceive it in terms of its definition, aetiology and approaches. For each of these dimensions we relate back to a criminological framework to ascertain how it is positioned in the green criminological debate. We start out by providing information on what corporate environmental responsibility is and how it relates to corporate social responsibility and sustainable development. Then we outline the theoretical framework in accordance with the three central themes for the criminological analysis of CER: definition, aetiology and approaches. We also explain the method that was used (semi-structured interviews). Next, we present the results according to the same threefold structure. Finally we discuss these results in a last part, which is divided in two. First, we look at the challenges that the criminological perspective poses for CER in terms of definition, aetiology and approaches. The second part of the discussion turns the question around and wonders how CER could contribute to greening criminology

Identification of a Novel β-Cell Glucokinase (GCK) Promoter Mutation (−71G>C) That Modulates GCK Gene Expression Through Loss of Allele-Specific Sp1 Binding Causing Mild Fasting Hyperglycemia in Humans

OBJECTIVE: Inactivating mutations in glucokinase (GCK) cause mild fasting hyperglycemia. Identification of a GCK mutation has implications for treatment and prognosis; therefore, it is important to identify these individuals. A significant number of patients have a phenotype suggesting a defect in glucokinase but no abnormality of GCK. We hypothesized that the GCK beta-cell promoter region, which currently is not routinely screened, could contain pathogenic mutations; therefore, we sequenced this region in 60 such probands. RESEARCH DESIGN AND METHODS: The beta-cell GCK promoter was sequenced in patient DNA. The effect of the identified novel mutation on GCK promoter activity was assessed using a luciferase reporter gene expression system. Electrophoretic mobility shift assays (EMSAs) were used to determine the impact of the mutation on Sp1 binding. RESULTS: A novel -71G>C mutation was identified in a nonconserved region of the human promoter sequence in six apparently unrelated probands. Family testing established cosegregation with fasting hyperglycemia (> or = 5.5 mmol/l) in 39 affected individuals. Haplotype analysis in the U.K. family and four of the Slovakian families demonstrated that the mutation had arisen independently. The mutation maps to a potential transcriptional activator binding site for Sp1. Reporter assays demonstrated that the mutation reduces promoter activity by up to fourfold. EMSAs demonstrated a dramatic reduction in Sp1 binding to the promoter sequence corresponding to the mutant allele. CONCLUSIONS: A novel beta-cell GCK promoter mutation was identified that significantly reduces gene expression in vitro through loss of regulation by Sp1. To ensure correct diagnosis of potential GCK-MODY (maturity-onset diabetes of the young) cases, analysis of the beta-cell GCK promoter should be included

Cellular characterisation of the GCKR P446L variant associated with type 2 diabetes risk

Aims/hypothesis Translation of genetic association signals into molecular mechanisms for diabetes has been slow. The glucokinase regulatory protein (GKRP; gene symbol GCKR) P446L variant, associated with inverse modulation of glucose- and lipid-related traits, has been shown to alter the kinetics of glucokinase (GCK) inhibition. As GCK inhibition is associated with nuclear sequestration, we aimed to determine whether this variant also alters the direct interaction between GKRP and GCK and their intracellular localisation. Methods Fluorescently tagged rat and human wild-type (WT)- or P446L-GCKR and GCK were transiently transfected into HeLa cells and mouse primary hepatocytes. Whole-cell and nuclear fluorescence was quantified in individual cells exposed to low- or high-glucose conditions (5.5 or 25 mmol/l glucose, respectively). Interaction between GCK and GKRP was measured by sensitised emission-based fluorescence resonance energy transfer (FRET) efficiency

Local history – local history collection basis

Cilj je rada skrenuti pozornost na nekoliko elemenata bitnih za zavičajne zbirke i ukazati na njihov značaj. Prvenstveno i osnovno – lokalna je povijest temelj zavičajne zbirke. Njezino istraživanje, zasnovano na brojnim znanstveno-istraživačkim metodama, polazišna je točka za izgradnju zbirke, prezentaciju i komunikaciju sadržaja, a temeljeno na multidisciplinarnosti. Uz tradicionalne oblike prezentacije i komunikacije, knjižničarima na raspolaganju stoje i elektronički, posebice mrežna stranica. Takav pristup podrazumijeva dodatne kompetencije i afinitete zavičajnoga knjižničara. Istaknuta su dva, često zanemarena izvora za istraživanje povijesti – usmena povijest kao temelj socijalne povijesti te efemerna građa, kao „blago, a ne smeće“.The aim is to direct attention to several elements essential for the local history collections and indicate their importance. Firstly and foremost – a local history is the basis of local history collection. Research, based on a number of scientific research methods, is the starting point for building a collection, content presentation and communication, and justified on the multidisciplinary. In addition to traditional forms of presentation and communication, library materials are also available electronically, in particular web page. Such an approach entails additional competence and affinity local history librarians. Two often overlooked source for research history are featured – oral history as the foundation of social history and the ephemera, as “a treasure, not trash.

Genetic variant effects on gene expression in human pancreatic islets and their implications for T2D

Most signals detected by genome-wide association studies map to non-coding sequence and their tissue-specific effects influence transcriptional regulation. However, key tissues and cell-types required for functional inference are absent from large-scale resources. Here we explore the relationship between genetic variants influencing predisposition to type 2 diabetes (T2D) and related glycemic traits, and human pancreatic islet transcription using data from 420 donors. We find: (a) 7741 cis-eQTLs in islets with a replication rate across 44 GTEx tissues between 40% and 73%; (b) marked overlap between islet cis-eQTL signals and active regulatory sequences in islets, with reduced eQTL effect size observed in the stretch enhancers most strongly implicated in GWAS signal location; (c) enrichment of islet cis-eQTL signals with T2D risk variants identified in genome-wide association studies; and (d) colocalization between 47 islet cis-eQTLs and variants influencing T2D or glycemic traits, including DGKB and TCF7L2. Our findings illustrate the advantages of performing functional and regulatory studies in disease relevant tissues.Peer reviewe