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1.
Health Technol Assess ; 23(60): 1-88, 2019 10.
Article in English | MEDLINE | ID: mdl-31661431

ABSTRACT

BACKGROUND: The randomised controlled trial is widely considered to be the gold standard study for comparing the effectiveness of health interventions. Central to its design is a calculation of the number of participants needed (the sample size) for the trial. The sample size is typically calculated by specifying the magnitude of the difference in the primary outcome between the intervention effects for the population of interest. This difference is called the 'target difference' and should be appropriate for the principal estimand of interest and determined by the primary aim of the study. The target difference between treatments should be considered realistic and/or important by one or more key stakeholder groups. OBJECTIVE: The objective of the report is to provide practical help on the choice of target difference used in the sample size calculation for a randomised controlled trial for researchers and funder representatives. METHODS: The Difference ELicitation in TriAls2 (DELTA2) recommendations and advice were developed through a five-stage process, which included two literature reviews of existing funder guidance and recent methodological literature; a Delphi process to engage with a wider group of stakeholders; a 2-day workshop; and finalising the core document. RESULTS: Advice is provided for definitive trials (Phase III/IV studies). Methods for choosing the target difference are reviewed. To aid those new to the topic, and to encourage better practice, 10 recommendations are made regarding choosing the target difference and undertaking a sample size calculation. Recommended reporting items for trial proposal, protocols and results papers under the conventional approach are also provided. Case studies reflecting different trial designs and covering different conditions are provided. Alternative trial designs and methods for choosing the sample size are also briefly considered. CONCLUSIONS: Choosing an appropriate sample size is crucial if a study is to inform clinical practice. The number of patients recruited into the trial needs to be sufficient to answer the objectives; however, the number should not be higher than necessary to avoid unnecessary burden on patients and wasting precious resources. The choice of the target difference is a key part of this process under the conventional approach to sample size calculations. This document provides advice and recommendations to improve practice and reporting regarding this aspect of trial design. Future work could extend the work to address other less common approaches to the sample size calculations, particularly in terms of appropriate reporting items. FUNDING: Funded by the Medical Research Council (MRC) UK and the National Institute for Health Research as part of the MRC-National Institute for Health Research Methodology Research programme.


This Difference ELicitation in TriAls2 (DELTA2) advice and recommendations document aims to help researchers choose the 'target difference' in a type of research study called a randomised controlled trial. The number of people needed to be involved in a study ­ the sample size ­ is usually based on a calculation aimed to ensure that the difference in benefit between treatments is likely to be detected. The calculation also accounts for the risk of a false-positive finding. No more patients than necessary should be involved. Choosing a 'target difference' is an important step in calculating the sample size. The target difference is defined as the amount of difference in the participants' response to the treatments that we wish to detect. It is probably the most important piece of information used in the sample size calculation. How we decide what the target difference should be depends on various factors. One key decision to make is how we should measure the benefits that treatments offer. For example, if we are evaluating a treatment for high blood pressure, the obvious thing to focus on would be blood pressure. We could then proceed to consider what an important difference in blood pressure between treatments would be, based on experts' views or evidence from previous research studies. This document seeks to provide assistance to researchers on how to choose the target difference when designing a trial. It also provides advice to help them clearly present what was done and why, when writing up the study proposal or reporting the study's findings. The document is also intended to be read by those who decide whether or not a proposed study should be funded. Clarifying a study's aim and getting a sensible sample size is important. It can affect not only those involved in the study, but also future patients who will receive treatment.


Subject(s)
Randomized Controlled Trials as Topic , Sample Size , Biomedical Research , Clinical Trials, Phase III as Topic , Clinical Trials, Phase IV as Topic , Delphi Technique , Education , Humans
3.
BMJ Open ; 9(6): e027795, 2019 06 28.
Article in English | MEDLINE | ID: mdl-31256030

ABSTRACT

INTRODUCTION: Diabetic macular oedema (DMO) and proliferative diabetic retinopathy (PDR) are the major causes of sight loss in people with diabetes. Due to the increased prevalence of diabetes, the workload related to these complications is increasing making it difficult for Hospital Eye Services (HSE) to meet demands. METHODS AND ANALYSIS: Effectiveness of Multimodal imaging for the Evaluation of Retinal oedema And new vesseLs in Diabetic retinopathy (EMERALD) is a prospective, case-referent, cross-sectional diagnostic study. It aims at determining the diagnostic performance, cost-effectiveness and acceptability of a new form of surveillance for people with stable DMO and/or PDR, which entails multimodal imaging and image review by an ophthalmic grader, using the current standard of care (evaluation of patients in clinic by an ophthalmologist) as the reference standard. If safe, cost-effective and acceptable, this pathway could help HES by freeing ophthalmologist time. The primary outcome of EMERALD is sensitivity of the new surveillance pathway in detecting active DMO/PDR. Secondary outcomes include specificity, agreement between new and the standard care pathway, positive and negative likelihood ratios, cost-effectiveness, acceptability, proportion of patients requiring subsequent full clinical assessment, unable to undergo imaging, with inadequate quality images or indeterminate findings. ETHICS AND DISSEMINATION: Ethical approval was obtained for this study from the Office for Research Ethics Committees Northern Ireland (reference 17/NI/0124). Study results will be published as a Health Technology Assessment monograph, in peer-reviewed national and international journals and presented at national/international conferences and to patient groups. TRIAL REGISTRATION NUMBER: NCT03490318 and ISRCTN:10856638.


Subject(s)
Diabetes Mellitus, Type 1/diagnostic imaging , Diabetes Mellitus, Type 2/diagnostic imaging , Diabetic Retinopathy/diagnostic imaging , Multimodal Imaging/standards , Papilledema/diagnostic imaging , Adolescent , Adult , Aged , Cost-Benefit Analysis , Cross-Sectional Studies , Diabetes Mellitus, Type 1/economics , Diabetes Mellitus, Type 2/economics , Diabetic Retinopathy/economics , Evaluation Studies as Topic , Fluorescein Angiography/economics , Fluorescein Angiography/standards , Humans , Middle Aged , Multicenter Studies as Topic , Multimodal Imaging/economics , Papilledema/economics , Prospective Studies , Tomography, Optical Coherence/economics , Tomography, Optical Coherence/standards , Young Adult
4.
Trials ; 20(1): 246, 2019 Apr 29.
Article in English | MEDLINE | ID: mdl-31036048

ABSTRACT

BACKGROUND: Chronic rhinosinusitis (CRS) is a common source of ill health; 11% of UK adults reported CRS symptoms in a worldwide population study. Guidelines are conflicting regarding whether antibiotics should be included in primary medical management, reflecting the lack of evidence in systematic reviews. Insufficient evidence to inform the role of surgery contributes to a fivefold variation in UK intervention rates. The objective of this trial is to establish the comparative effectiveness of endoscopic sinus surgery (ESS) or a prolonged course of antibiotics (clarithromycin) in adult patients with CRS in terms of symptomatic improvement and costs to the National Health Service compared with standard medical care (intranasal medication) at 6 months. METHODS/DESIGN: A three-arm parallel-group trial will be conducted with patients who remain symptomatic after receiving appropriate medical therapy (either in primary or secondary care). They will be randomised to receive: (1) intranasal medication plus ESS, (2) intranasal medication plus clarithromycin (250 mg) or (3) intranasal medication plus a placebo. Intranasal medication (current standard medical care) is defined as a spray or drops of intranasal corticosteroids and saline irrigations. The primary outcome measure is the SNOT-22 questionnaire, which assesses disease-specific health-related quality of life. The study sample size is 600. Principal analyses will be according to the randomised groups irrespective of compliance. The trial will be conducted in at least 16 secondary or tertiary care centres with an internal pilot at six sites for 6 months. DISCUSSION: The potential cardiovascular side effects of macrolide antibiotics have been recently highlighted. The effectiveness of antibiotics will be established through this trial, which may help to reduce unnecessary usage and potential morbidity. If ESS is shown to be clinically effective and cost-effective, the trial may encourage earlier intervention. In contrast, if it is shown to be ineffective, then there should be a significant reduction in surgery rates. The trial results will feed into the other components of the MACRO research programme to establish best practice for the management of adults with CRS and design the ideal patient pathway across primary and secondary care. TRIAL REGISTRATION: ISRCTN36962030 . Registered on 17 October 2018.


Subject(s)
Anti-Bacterial Agents/administration & dosage , Clarithromycin/administration & dosage , Endoscopy , Nasal Polyps/therapy , Nasal Surgical Procedures/methods , Rhinitis/therapy , Sinusitis/therapy , Administration, Oral , Anti-Bacterial Agents/adverse effects , Chronic Disease , Clarithromycin/adverse effects , Comparative Effectiveness Research , Drug Administration Schedule , Endoscopy/adverse effects , Female , Humans , Male , Multicenter Studies as Topic , Nasal Polyps/diagnosis , Nasal Surgical Procedures/adverse effects , Pilot Projects , Randomized Controlled Trials as Topic , Rhinitis/diagnosis , Sinusitis/diagnosis , Time Factors , Treatment Outcome , United Kingdom
5.
BMJ Open ; 9(3): e028474, 2019 03 23.
Article in English | MEDLINE | ID: mdl-30904879

ABSTRACT

INTRODUCTION: Optimal management of distal radius fractures in adults remains controversial. Previous evidence and current clinical guidelines tell us that, if a closed reduction of a dorsally displaced fracture is possible, Kirschner wires (K-wires) are the preferred form of surgical fixation. However, the question remains whether there is any need to perform surgical fixation following a successful closed reduction, or is a simple plaster cast as effective? This is the protocol for a randomised controlled trial of manipulation and surgical fixation with K-wires versus manipulation and casting in the treatment of dorsally displaced distal radius fractures. METHODS AND ANALYSIS: Adult patients with an acute dorsally displaced fracture of the distal radius are potentially eligible to take part. Prior to surgery, baseline demographic data, radiographs, data on pain/function using the Patient-Rated Wrist Evaluation Score (PRWE) and health-related quality of life (HRQoL) using the EuroQoL 5-dimension 5-level (EQ-5D-5L) will be collected. A randomisation sequence, stratified by centre, intra-articular extension of the fracture and age, will be administered via a secure web-based service. Each patient will be randomly allocated to either 'manipulation and surgical fixation with K-wires' or 'manipulation and plaster casting'. A clinical assessment, radiographs and records of early complications will be recorded at 6 weeks. PRWE and HRQoL outcome data will be collected at 3, 6 and 12 months post-randomisation. Further information will be requested with regard to healthcare resource use and any complications. ETHICS AND DISSEMINATION: The National Research Ethic Committee approved this study on 6 October 2016 (16/SC/0462).The National Institute for Health Research Health Technology Assessment monograph and a manuscript to a peer-reviewed journal will be submitted on completion of the trial. The results of this trial will substantially inform clinical practice on the clinical and cost-effectiveness of the treatment of this injury. TRIAL REGISTRATION NUMBER: ISRCTN11980540; Pre-results.


Subject(s)
Bone Wires , Casts, Surgical , Fracture Fixation, Internal , Orthopedic Procedures/methods , Radius Fractures/surgery , Radius/injuries , Adolescent , Adult , Aged , Aged, 80 and over , Female , Fracture Fixation/methods , Humans , Male , Manipulation, Orthopedic , Middle Aged , Randomized Controlled Trials as Topic , Research Design , Young Adult
7.
Trials ; 19(1): 606, 2018 Nov 05.
Article in English | MEDLINE | ID: mdl-30400926

ABSTRACT

BACKGROUND: A key step in the design of a RCT is the estimation of the number of participants needed in the study. The most common approach is to specify a target difference between the treatments for the primary outcome and then calculate the required sample size. The sample size is chosen to ensure that the trial will have a high probability (adequate statistical power) of detecting a target difference between the treatments should one exist. The sample size has many implications for the conduct and interpretation of the study. Despite the critical role that the target difference has in the design of a RCT, the way in which it is determined has received little attention. In this article, we summarise the key considerations and messages from new guidance for researchers and funders on specifying the target difference, and undertaking and reporting a RCT sample size calculation. This article on choosing the target difference for a randomised controlled trial (RCT) and undertaking and reporting the sample size calculation has been dual published in the BMJ and BMC Trials journals METHODS: The DELTA2 (Difference ELicitation in TriAls) project comprised five major components: systematic literature reviews of recent methodological developments (stage 1) and existing funder guidance (stage 2); a Delphi study (stage 3); a two-day consensus meeting bringing together researchers, funders and patient representatives (stage 4); and the preparation and dissemination of a guidance document (stage 5). RESULTS AND DISCUSSION: The key messages from the DELTA2 guidance on determining the target difference and sample size calculation for a randomised caontrolled trial are presented. Recommendations for the subsequent reporting of the sample size calculation are also provided.


Subject(s)
Randomized Controlled Trials as Topic , Sample Size , Delphi Technique , Guidelines as Topic , Humans , Numbers Needed To Treat , Research Report
8.
Trials ; 19(1): 542, 2018 Oct 10.
Article in English | MEDLINE | ID: mdl-30305155

ABSTRACT

BACKGROUND: A key step in the design of a randomised controlled trial is the estimation of the number of participants needed. The most common approach is to specify a target difference in the primary outcome between the randomised groups and then estimate the corresponding sample size. The sample size is chosen to provide reassurance that the trial will have high statistical power to detect the target difference at the planned statistical significance level. Alternative approaches are also available, though most still require specification of a target difference. The sample size has many implications for the conduct of the study, as well as incurring scientific and ethical aspects. Despite the critical role of the target difference for the primary outcome in the design of a randomised controlled trial (RCT), the manner in which it is determined has received little attention. This article reports the development of the DELTA2 guidance on the specification and reporting of the target difference for the primary outcome in a sample size calculation for a RCT. METHODS: The DELTA2 (Difference ELicitation in TriAls) project has five components comprising systematic literature reviews of recent methodological developments (stage 1) and existing funder guidance (stage 2), a Delphi study (stage 3), a 2-day consensus meeting bringing together researchers, funders and patient representatives (stage 4), and the preparation and dissemination of a guidance document (stage 5). RESULTS: The project started in April 2016. The literature search identified 28 articles of methodological developments relevant to a method for specifying a target difference. A Delphi study involving 69 participants, along with a 2-day consensus meeting were conducted. In addition, further engagement sessions were held at two international conferences. The main guidance text was finalised on April 18, 2018, after revision informed by feedback gathered from stages 2 and 3 and from funder representatives. DISCUSSION: The DELTA2 Delphi study identified a number of areas (such as practical recommendations and examples, greater coverage of different trial designs and statistical approaches) of particular interest amongst stakeholders which new guidance was desired to meet. New relevant references were identified by the review. Such findings influenced the scope, drafting and revision of the guidance. While not all suggestions could be accommodated, it is hoped that the process has led to a more useful and practical document.


Subject(s)
Clinical Trial Protocols as Topic , Numbers Needed To Treat , Randomized Controlled Trials as Topic/methods , Consensus , Data Interpretation, Statistical , Delphi Technique , Humans , Numbers Needed To Treat/standards , Randomized Controlled Trials as Topic/standards , Randomized Controlled Trials as Topic/statistics & numerical data , Treatment Outcome
9.
EBioMedicine ; 33: 282-288, 2018 Jul.
Article in English | MEDLINE | ID: mdl-29983350

ABSTRACT

BACKGROUND: Dupuytren's disease is a common fibrotic condition of the hand that causes irreversible flexion contractures of the fingers, with no approved therapy for early stage disease. Our previous analysis of surgically-excised tissue defined tumour necrosis factor (TNF) as a potential therapeutic target. Here we assessed the efficacy of injecting nodules of Dupuytren's disease with a TNF inhibitor. METHODS: Patients were randomised to receive adalimumab on one occasion in dose cohorts of 15 mg in 0.3 ml, 35 mg in 0.7 ml, or 40 mg in 0.4 ml, or an equivalent volume of placebo in a 3:1 ratio. Two weeks later the injected tissue was surgically excised and analysed. The primary outcome measure was levels of mRNA expression for α-smooth muscle actin (ACTA2). Secondary outcomes included levels of α-SMA and collagen proteins. The trial was registered with ClinicalTrial.gov (NCT03180957) and the EudraCT (2015-001780-40). FINDINGS: We recruited 28 patients, 8 assigned to the 15 mg, 12 to the 35 mg and 8 to the 40 mg adalimumab cohorts. There was no change in mRNA levels for ACTA2, COL1A1, COL3A1 and CDH11. Levels of α-SMA protein expression in patients treated with 40 mg adalimumab (1.09 ±â€¯0.09 ng per µg of total protein) were significantly lower (p = 0.006) compared to placebo treated patients (1.51 ±â€¯0.09 ng/µg). The levels of procollagen type I protein expression were also significantly lower (p < 0.019) in the sub group treated with 40 mg adalimumab (474 ±â€¯84 pg/µg total protein) compared with placebo (817 ±â€¯78 pg/µg). There were two serious adverse events, both considered unrelated to the study drug. INTERPRETATION: In this dose-ranging study, injection of 40 mg of adalimumab in 0.4 ml resulted in down regulation of the myofibroblast phenotype as evidenced by reduction in expression of α-SMA and type I procollagen proteins at 2 weeks. These data form the basis of an ongoing phase 2b clinical trial assessing the efficacy of intranodular injection of 40 mg adalimumab in 0.4 ml compared to an equivalent volume of placebo in patients with early stage Dupuytren's disease. FUNDING: Health Innovation Challenge Fund (Wellcome Trust and Department of Health) and 180 Therapeutics LP.


Subject(s)
Actins/metabolism , Adalimumab/administration & dosage , Anti-Inflammatory Agents/administration & dosage , Collagen Type I/metabolism , Dupuytren Contracture/drug therapy , Actins/genetics , Adalimumab/pharmacology , Anti-Inflammatory Agents/pharmacology , Collagen Type I/genetics , Double-Blind Method , Down-Regulation , Drug Administration Schedule , Dupuytren Contracture/genetics , Dupuytren Contracture/metabolism , Female , Gene Expression Regulation/drug effects , Humans , Injections , Male , Treatment Outcome
10.
BMJ Open ; 8(1): e019944, 2018 01 26.
Article in English | MEDLINE | ID: mdl-29374679

ABSTRACT

INTRODUCTION: Sliding hip screw fixation is well established in the treatment of trochanteric fractures of the hip. The X-Bolt Dynamic Hip Plating System builds on the successful design features of the sliding hip screw but differs in the nature of the fixation in the femoral head. A randomised pilot study suggested that the X-bolt Dynamic Hip Plating System might provide similar health-related quality of life while reducing the risk of revision surgery when compared with the sliding hip screw. This is the protocol for a multicentre randomised trial of sliding hip screw versus X-Bolt Dynamic Hip Plating System for patients 60 years and over treated for a trochanteric fracture of the hip. METHODS AND ANALYSIS: Multicentre, multisurgeon, parallel, two-arm, randomised controlled trial. Patients aged 60 years and older with a trochanteric hip fracture are potentially eligible. Participants will be randomly allocated on a 1:1 basis to either sliding hip screw or X-Bolt Dynamic Hip Plating System. Otherwise, all care will be in accordance with National Institute for Health and Care Excellence guidance. A minimum of 1128 patients will be recruited to obtain 90% power to detect a 0.075-point difference in EuroQol-5D health-related quality of life at 4 months postrandomisation. Secondary outcomes include mortality, residential status, revision surgery and radiographic measures. The treatment effect will be estimated using a two-sided t-test adjusted for age, gender and cognitive impairment based on an intention-to-treat analysis. ETHICS AND DISSEMINATION: National Research Ethics Committee approved this study on 5 February 2016 (16/WM/0001). The study is sponsored by the University of Oxford and funded through an investigator initiated grant by X-Bolt Orthopaedics. A manuscript for a high-impact peer-reviewed journal will be prepared, and the results will be disseminated to patients through local mechanisms at participating centres. TRIAL REGISTRATION NUMBER: ISRCTN92825709.


Subject(s)
Bone Plates , Bone Screws , Fracture Fixation, Intramedullary/methods , Hip Fractures/surgery , Aged , Aged, 80 and over , Female , Fracture Fixation, Intramedullary/adverse effects , Hip Fractures/mortality , Humans , Linear Models , Male , Middle Aged , Pilot Projects , Quality of Life , Reoperation/statistics & numerical data , Research Design , Treatment Outcome , United Kingdom
11.
Trials ; 18(1): 271, 2017 06 12.
Article in English | MEDLINE | ID: mdl-28606102

ABSTRACT

BACKGROUND: A key step in the design of a randomised controlled trial (RCT) is the estimation of the number of participants needed. By far the most common approach is to specify a target difference and then estimate the corresponding sample size; this sample size is chosen to provide reassurance that the trial will have high statistical power to detect such a difference between the randomised groups (at the planned statistical significance level). The sample size has many implications for the conduct of the study, as well as carrying scientific and ethical aspects to its choice. Despite the critical role of the target difference for the primary outcome in the design of an RCT, the manner in which it is determined has received little attention. This article reports the protocol of the Difference ELicitation in TriAls (DELTA2) project, which will produce guidance on the specification and reporting of the target difference for the primary outcome in a sample size calculation for RCTs. METHODS/DESIGN: The DELTA2 project has five components: systematic literature reviews of recent methodological developments (stage 1) and existing funder guidance (stage 2); a Delphi study (stage 3); a 2-day consensus meeting bringing together researchers, funders and patient representatives, as well as one-off engagement sessions at relevant stakeholder meetings (stage 4); and the preparation and dissemination of a guidance document (stage 5). DISCUSSION: Specification of the target difference for the primary outcome is a key component of the design of an RCT. There is a need for better guidance for researchers and funders regarding specification and reporting of this aspect of trial design. The aim of this project is to produce consensus based guidance for researchers and funders.


Subject(s)
Delphi Technique , Endpoint Determination/standards , Randomized Controlled Trials as Topic/standards , Research Design/standards , Sample Size , Consensus , Humans
12.
Nat Commun ; 8: 14733, 2017 03 31.
Article in English | MEDLINE | ID: mdl-28361903

ABSTRACT

Steviol glycosides (SGs), such as stevioside and rebaudioside A, are natural, non-caloric sweet-tasting organic molecules, present in extracts of the scrub plant Stevia rebaudiana, which are widely used as sweeteners in consumer foods and beverages. TRPM5 is a Ca2+-activated cation channel expressed in type II taste receptor cells and pancreatic ß-cells. Here we show that stevioside, rebaudioside A and their aglycon steviol potentiate the activity of TRPM5. We find that SGs potentiate perception of bitter, sweet and umami taste, and enhance glucose-induced insulin secretion in a Trpm5-dependent manner. Daily consumption of stevioside prevents development of high-fat-diet-induced diabetic hyperglycaemia in wild-type mice, but not in Trpm5-/- mice. These results elucidate a molecular mechanism of action of SGs and identify TRPM5 as a potential target to prevent and treat type 2 diabetes.


Subject(s)
Diterpenes, Kaurane/pharmacology , Glucosides/pharmacology , Insulin-Secreting Cells/drug effects , Sweetening Agents/pharmacology , TRPM Cation Channels/drug effects , Taste/drug effects , Animals , Blood Glucose/drug effects , Blood Glucose/metabolism , Diabetes Mellitus, Type 2/metabolism , Diet, High-Fat , Female , HEK293 Cells , Humans , Insulin/metabolism , Insulin Secretion , Insulin-Secreting Cells/metabolism , Male , Mice , Mice, Knockout , Patch-Clamp Techniques , TRPM Cation Channels/metabolism
13.
J Clin Invest ; 125(12): 4714-28, 2015 Dec.
Article in English | MEDLINE | ID: mdl-26571400

ABSTRACT

Strategies aimed at mimicking or enhancing the action of the incretin hormone glucagon-like peptide 1 (GLP-1) therapeutically improve glucose-stimulated insulin secretion (GSIS); however, it is not clear whether GLP-1 directly drives insulin secretion in pancreatic islets. Here, we examined the mechanisms by which GLP-1 stimulates insulin secretion in mouse and human islets. We found that GLP-1 enhances GSIS at a half-maximal effective concentration of 0.4 pM. Moreover, we determined that GLP-1 activates PLC, which increases submembrane diacylglycerol and thereby activates PKC, resulting in membrane depolarization and increased action potential firing and subsequent stimulation of insulin secretion. The depolarizing effect of GLP-1 on electrical activity was mimicked by the PKC activator PMA, occurred without activation of PKA, and persisted in the presence of PKA inhibitors, the KATP channel blocker tolbutamide, and the L-type Ca(2+) channel blocker isradipine; however, depolarization was abolished by lowering extracellular Na(+). The PKC-dependent effect of GLP-1 on membrane potential and electrical activity was mediated by activation of Na(+)-permeable TRPM4 and TRPM5 channels by mobilization of intracellular Ca(2+) from thapsigargin-sensitive Ca(2+) stores. Concordantly, GLP-1 effects were negligible in Trpm4 or Trpm5 KO islets. These data provide important insight into the therapeutic action of GLP-1 and suggest that circulating levels of this hormone directly stimulate insulin secretion by ß cells.


Subject(s)
Glucagon-Like Peptide 1/pharmacology , Insulin-Secreting Cells/metabolism , Insulin/metabolism , Protein Kinase C/metabolism , TRPM Cation Channels/metabolism , Animals , Humans , Insulin/genetics , Insulin Secretion , Insulin-Secreting Cells/cytology , Ion Transport/drug effects , Ion Transport/genetics , Membrane Potentials/drug effects , Membrane Potentials/genetics , Mice , Mice, Knockout , Protein Kinase C/genetics , TRPM Cation Channels/genetics , Tetradecanoylphorbol Acetate/pharmacology
14.
J Biol Chem ; 290(35): 21376-92, 2015 Aug 28.
Article in English | MEDLINE | ID: mdl-26152717

ABSTRACT

Pancreatic ß cells are electrically excitable and respond to elevated glucose concentrations with bursts of Ca(2+) action potentials due to the activation of voltage-dependent Ca(2+) channels (VDCCs), which leads to the exocytosis of insulin granules. We have examined the possible role of nicotinic acid adenine dinucleotide phosphate (NAADP)-mediated Ca(2+) release from intracellular stores during stimulus-secretion coupling in primary mouse pancreatic ß cells. NAADP-regulated Ca(2+) release channels, likely two-pore channels (TPCs), have recently been shown to be a major mechanism for mobilizing Ca(2+) from the endolysosomal system, resulting in localized Ca(2+) signals. We show here that NAADP-mediated Ca(2+) release from endolysosomal Ca(2+) stores activates inward membrane currents and depolarizes the ß cell to the threshold for VDCC activation and thereby contributes to glucose-evoked depolarization of the membrane potential during stimulus-response coupling. Selective pharmacological inhibition of NAADP-evoked Ca(2+) release or genetic ablation of endolysosomal TPC1 or TPC2 channels attenuates glucose- and sulfonylurea-induced membrane currents, depolarization, cytoplasmic Ca(2+) signals, and insulin secretion. Our findings implicate NAADP-evoked Ca(2+) release from acidic Ca(2+) storage organelles in stimulus-secretion coupling in ß cells.


Subject(s)
Calcium Channels/metabolism , Endosomes/metabolism , Insulin-Secreting Cells/metabolism , NADP/analogs & derivatives , Animals , Calcium/metabolism , Calcium Channels/genetics , Cells, Cultured , Glucose/metabolism , Insulin/metabolism , Insulin-Secreting Cells/cytology , Male , Membrane Potentials , Mice , Mice, Knockout , NADP/metabolism
15.
Hypertension ; 64(3): 523-9, 2014 Sep.
Article in English | MEDLINE | ID: mdl-24914196

ABSTRACT

ATP-sensitive potassium channels (KATP) regulate a range of biological activities by coupling membrane excitability to the cellular metabolic state. In particular, it has been proposed that KATP channels and specifically, the channel subunits Kir6.1 and SUR2B, play an important role in the regulation of vascular tone. However, recent experiments have suggested that KATP channels outside the vascular smooth muscle compartment are the key determinant of the observed behavior. Thus, we address the importance of the vascular smooth muscle KATP channel, using a novel murine model in which it is possible to conditionally delete the Kir6.1 subunit. Using a combination of molecular, electrophysiological, in vitro, and in vivo techniques, we confirmed the absence of Kir6.1 and KATP currents and responses specifically in smooth muscle. Mice with conditional deletion of Kir6.1 showed no obvious arrhythmic phenotype even after provocation with ergonovine. However, these mice were hypertensive and vascular smooth muscle cells failed to respond to vasodilators in a normal fashion. Thus, Kir6.1 underlies the vascular smooth muscle KATP channel and has a key role in vascular reactivity and blood pressure control.


Subject(s)
Blood Pressure/physiology , KATP Channels/physiology , Muscle, Smooth, Vascular/physiology , Animals , Calcitonin Gene-Related Peptide/pharmacology , Disease Models, Animal , Hypertension/physiopathology , In Vitro Techniques , KATP Channels/deficiency , KATP Channels/genetics , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , Muscle, Smooth, Vascular/cytology , Muscle, Smooth, Vascular/drug effects , Patch-Clamp Techniques , Pinacidil/pharmacology , Vasodilator Agents/pharmacology
16.
Cell Biol Toxicol ; 27(1): 13-40, 2011 Feb.
Article in English | MEDLINE | ID: mdl-20589437

ABSTRACT

Many anticancer drugs are myelotoxic and cause bone marrow depression; however, generally, the marrow/blood returns to normal after treatment. Nevertheless, after the administration of some anti-neoplastic agents (e.g. busulphan, BU) under conditions as yet undefined, the marrow may begin a return towards normal, but normality may not be achieved, and late-stage/residual marrow injury may be evident. The present studies were conducted to develop a short-term mouse model (a 'screen') to identify late-stage/residual marrow injury using a brief regimen of drug administration. Female BALB/c mice were treated with BU, doxorubicin (DOX), cisplatin (CISPLAT) or cyclophosphamide (CYCLOPHOS) on days 1, 3 and 5. In 'preliminary studies', a maximum tolerated dose (MTD) for each drug was determined for use in 'main studies'. In main studies, mice were treated with vehicle (control), low and high (the MTD) dose levels of each agent. Necropsies were performed, and blood parameters and femoral/humeral nucleated marrow cell counts (FNCC/HNCC) were assessed on six occasions (from days 1 to 60/61 post-dosing). Late-stage/residual changes were apparent in BU-treated mice at day 61 post-dosing: RBC, Hb and haematocrit were reduced, mean cell volume/mean cell haemoglobin were increased and platelet and FNCC counts were decreased. Mice given DOX, CISPLAT and CYCLOPHOS, in general, showed no clear late-stage/residual effects (day 60/61). It was concluded that a brief regimen of drug administration, at an MTD, with assessment at day 60/61 post-dosing was a suitable short-term method/screen in the mouse for detecting late-stage/residual marrow injury for BU, a drug shown to exhibit these effects in man.


Subject(s)
Antineoplastic Agents/toxicity , Busulfan/toxicity , Cisplatin/toxicity , Cyclophosphamide/toxicity , Doxorubicin/toxicity , Animals , Blood Cells/cytology , Blood Cells/drug effects , Bone Marrow Cells/cytology , Bone Marrow Cells/drug effects , Cell Count , Female , Hematocrit , Hemoglobins/analysis , Mice , Mice, Inbred BALB C
17.
Am J Physiol Cell Physiol ; 299(5): C948-59, 2010 Nov.
Article in English | MEDLINE | ID: mdl-20686072

ABSTRACT

Recently, overexpression of the genes TMEM16A and TMEM16B has been shown to produce currents qualitatively similar to native Ca(2+)-activated Cl(-) currents (I(ClCa)) in vascular smooth muscle. However, there is no information about this new gene family in vascular smooth muscle, where Cl(-) channels are a major depolarizing mechanism. Qualitatively similar Cl(-) currents were evoked by a pipette solution containing 500 nM Ca(2+) in smooth muscle cells isolated from BALB/c mouse portal vein, thoracic aorta, and carotid artery. Quantitative PCR using SYBR Green chemistry and primers specific for transmembrane protein (TMEM) 16A or the closely related TMEM16B showed TMEM16A expression as follows: portal vein > thoracic aorta > carotid artery > brain. In addition, several alternatively spliced variant transcripts of TMEM16A were detected. In contrast, TMEM16B expression was very low in smooth muscle. Western blot analysis with different antibodies directed against TMEM16A revealed a number of products with a consistent band at ∼120 kDa, except portal vein, where an 80-kDa band predominated. TMEM16A protein was identified in the smooth muscle layers of 4-µm-thick slices of portal vein, thoracic aorta, and carotid artery. In isolated myocytes, fluorescence specific to a TMEM16A antibody was detected diffusely throughout the cytoplasm, as well as near the membrane. The same antibody used in Western blot analysis of lysates from vascular tissues also recognized an ∼147-kDa mouse TMEM16A-green fluorescent protein (GFP) fusion protein expressed in HEK 293 cells, which correlated to a similar band detected by a GFP antibody. Patch-clamp experiments revealed that I(ClCa) generated by transfection of TMEM16A-GFP in HEK 293 cells displayed remarkable similarities to I(ClCa) recorded in vascular myocytes, including slow kinetics, steep outward rectification, and a response similar to the pharmacological agent niflumic acid. This study shows that TMEM16A expression is robust in murine vascular smooth muscle cells, consolidating the view that this gene is a viable candidate for the native Ca(2+)-activated Cl(-) channel in this cell type.


Subject(s)
Chloride Channels/metabolism , Myocytes, Smooth Muscle/physiology , Protein Biosynthesis , Protein Isoforms/metabolism , Alternative Splicing , Animals , Anoctamin-1 , Cell Line , Chloride Channels/genetics , Gene Expression Profiling , Humans , Mice , Mice, Inbred BALB C , Molecular Sequence Data , Myocytes, Smooth Muscle/cytology , Patch-Clamp Techniques , Protein Isoforms/genetics , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , Tissue Distribution
18.
Cardiovasc Res ; 87(3): 476-84, 2010 Aug 01.
Article in English | MEDLINE | ID: mdl-20172862

ABSTRACT

AIMS: Calcium-activated chloride channels (CACCs) share common pharmacological properties with Kcnma1-encoded large conductance K(+) channels (BK(Ca) or K(Ca)1.1) and it has been suggested that they may co-exist in a macromolecular complex. As K(Ca)1.1 channels are known to localize to cholesterol and caveolin-rich lipid rafts (caveolae), the present study investigated whether Ca(2+)-sensitive Cl(-) currents in vascular myocytes were affected by the cholesterol depleting agent methyl-beta-cyclodextrin (M-betaCD). METHODS AND RESULTS: Calcium-activated chloride and potassium currents were recorded from single murine portal vein myocytes in whole cell voltage clamp. Western blot was undertaken following sucrose gradient ultracentrifugation using protein lysates from whole portal veins. Ca(2+)-activated Cl(-) currents were augmented by 3 mg mL(-1) M-betaCD with a rapid time course (t(0.5) = 1.8 min). M-betaCD had no effect on the bi-modal response to niflumic acid or anthracene-9-carboxylate but completely removed the inhibitory effects of the K(Ca)1.1 blockers, paxilline and tamoxifen, as well as the stimulatory effect of the K(Ca)1.1 activator NS1619. Discontinuous sucrose density gradients followed by western blot analysis revealed that the position of lipid raft markers caveolin and flotillin-2 was altered by 15 min application of 3 mg mL(-1) M-betaCD. The position of K(Ca)1.1 and the newly identified candidate for CACCs, TMEM16A, was also affected by M-betaCD. CONCLUSION: These data reveal that CACC properties are influenced by lipid raft integrity.


Subject(s)
Chloride Channels/metabolism , Cholesterol/deficiency , Membrane Microdomains/metabolism , Muscle, Smooth, Vascular/metabolism , Myocytes, Smooth Muscle/metabolism , Animals , Anoctamin-1 , Blotting, Western , Caveolins/metabolism , Centrifugation, Density Gradient , Chloride Channels/drug effects , Large-Conductance Calcium-Activated Potassium Channel alpha Subunits/metabolism , Membrane Microdomains/drug effects , Membrane Potentials , Membrane Proteins/metabolism , Membrane Transport Modulators/pharmacology , Mice , Mice, Inbred BALB C , Muscle, Smooth, Vascular/drug effects , Myocytes, Smooth Muscle/drug effects , Neoplasm Proteins/metabolism , Patch-Clamp Techniques , Portal Vein/metabolism , Time Factors , beta-Cyclodextrins/pharmacology
19.
J Biol Chem ; 284(47): 32507-21, 2009 Nov 20.
Article in English | MEDLINE | ID: mdl-19767392

ABSTRACT

The present study was undertaken to determine whether the two ubiquitously expressed Ca(2+)-independent phosphatases PP1 and PP2A regulate Ca(2+)-activated Cl(-) currents (I(Cl(Ca))) elicited by 500 nM [Ca(2+)](i) in rabbit pulmonary artery (PA) myocytes dialyzed with or without 3 mM ATP. Reverse transcription-PCR experiments revealed the expression of PP1alpha, PP1beta/delta, PP1gamma, PP2Aalpha, PP2Abeta, PP2Balpha (calcineurin (CaN) Aalpha), and PP2Bbeta (CaN Abeta) but not PP2Bgamma (CaN Agamma) in rabbit PA. Western blot and immunofluorescence experiments confirmed the presence of all three PP1 isoforms and PP2A. Intracellular dialysis with a peptide inhibitor of calcineurin (CaN-AIP); the non-selective PP1/PP2A inhibitors okadaic acid (0.5, 10, or 30 nM), calyculin A (10 nM), or cantharidin (100 nM); and the selective PP1 inhibitor NIPP-1 (100 pM) potently antagonized the recovery of I(Cl(Ca)) in cells dialyzed with no ATP, whereas the PP2A-selective antagonist fostriecin (30 or 150 nM) was ineffective. The combined application of okadaic acid (10 nM) and CaN-autoinhibitory peptide (50 microM) did not potentiate the response of I(Cl(Ca)) in 0 ATP produced by maximally inhibiting CaN or PP1/PP2A alone. Consistent with the non-additive effects of either classes of phosphatases, the PP1 inhibitor NIPP-1 (100 pM) antagonized the recovery of I(Cl(Ca)) induced by exogenous CaN Aalpha (0.5 microM). These results demonstrate that I(Cl(Ca)) in PA myocytes is regulated by CaN and PP1 and/or PP2A. Our data also suggest the existence of a functional link between these two classes of phosphatases.


Subject(s)
Calcium/chemistry , Chlorine/chemistry , Gene Expression Regulation, Enzymologic , Lung/metabolism , Myocytes, Smooth Muscle/cytology , Phosphoric Monoester Hydrolases/chemistry , Pulmonary Artery/cytology , Animals , Cantharidin/pharmacology , Enzyme Inhibitors/pharmacology , Intracellular Signaling Peptides and Proteins/pharmacology , Marine Toxins , Okadaic Acid/pharmacology , Oxazoles/pharmacology , Patch-Clamp Techniques , Rabbits
20.
J Pharmacol Exp Ther ; 321(3): 1075-84, 2007 Jun.
Article in English | MEDLINE | ID: mdl-17347326

ABSTRACT

Because chloride (Cl(-)) channel blockers such as niflumic acid enhance large-conductance Ca(2+)-activated potassium channels (BK(Ca)), the aim of this study was to determine whether there is a reciprocal modification of Ca(2+)-activated chloride Cl(-) currents (I(ClCa)) by two selective activators of BK(Ca). Single smooth muscle cells were isolated by enzymatic digestion from murine portal vein and rabbit pulmonary artery. The BK(Ca) activators NS1619 [1,3-dihydro-1-[2-hydroxy-5-(trifluoromethyl-)phenyl]-5-(trifluoromethyl)-2H-benzimidazol-2-one] and isopimaric acid (IpA) augmented macroscopic I(ClCa) elicited by pipette solutions containing [Ca(2+)](i) > 100 nM without any alteration in current kinetics. Enhanced currents recorded in the presence of NS1619 or IpA reversed at the theoretical Cl(-) equilibrium potential, which was shifted by approximately -40 mV upon replacement of the external anion with the more permeable thiocyanate anion. NS1619 increased the sensitivity of calcium-activated chloride channel (Cl(Ca)) to Ca(2+) (approximately 100 nM at +60 mV) and induced a leftward shift in their voltage dependence (approximately 80 mV with 1 micro Ca(2+)). Single-channel experiments revealed that NS1619 increased the number of open channels times the open probability of small-conductance (1.8-3.1 pS) Cl(Ca) without any alteration in their unitary amplitude or number of observable unitary levels of activity. These data, in addition to the established stimulatory effects of niflumic acid on BK(Ca), show that there is similarity in the pharmacology of calcium-activated chloride and potassium channels. Although nonspecific interactions are possible, one alternative hypothesis is that the channel underlying vascular I(ClCa) shares some structural similarity to the BK(Ca) or that the latter K(+) channel physically interacts with Cl(Ca).


Subject(s)
Benzimidazoles/pharmacology , Carboxylic Acids/pharmacology , Chloride Channels/physiology , Myocytes, Smooth Muscle/drug effects , Phenanthrenes/pharmacology , Potassium Channels, Calcium-Activated/agonists , Animals , Calcium/pharmacology , Chloride Channel Agonists , Dose-Response Relationship, Drug , Electrophysiology , Mice , Mice, Inbred BALB C , Myocytes, Smooth Muscle/cytology , Myocytes, Smooth Muscle/physiology , Niflumic Acid/pharmacology , Portal Vein/cytology , Pulmonary Artery/cytology , Rabbits
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