TNFR1 membrane reorganization promotes distinct modes of TNFα signaling

Signaling by the ubiquitously expressed tumor necrosis factor receptor 1 (TNFR1) after ligand binding plays an essential role in determining whether cells exhibit survival or death. TNFR1 forms distinct signaling complexes that initiate gene expression programs downstream of the transcriptional regulators NFκB and AP-1 and promote different functional outcomes, such as inflammation, apoptosis, and necroptosis. Here, we investigated the ways in which TNFR1 was organized at the plasma membrane at the nanoscale level to elicit different signaling outcomes. We confirmed that TNFR1 forms preassembled clusters at the plasma membrane of adherent cells in the absence of ligand. After trimeric TNFα binding, TNFR1 clusters underwent a conformational change, which promoted lateral mobility, their association with the kinase MEKK1, and activation of the JNK/p38/NFκB pathway. These phenotypes required a minimum of two TNFR1-TNFα contact sites; fewer binding sites resulted in activation of NFκB but not JNK and p38. These data suggest that distinct modes of TNFR1 signaling depend on nanoscale changes in receptor organization.

Plasma glucose in screening for diabetes and pre-diabetes: how much is too much? Analysis of fasting plasma glucose and oral glucose tolerance test in Sri Lankans

BACKGROUND

Fasting plasma glucose (FPG) is the most commonly used screening tool for diabetes in Sri Lanka. Cut-off values from American Diabetes Association recommendations are adopted in the absence of local data. We aimed to establish FPG cut offs for Sri Lankans to screen for diabetes and pre-diabetes.

METHODS

Data on FPG and diabetes/pre-diabetes status were obtained from Sri Lanka Diabetes and Cardiovascular Study (SLDCS), a community based island wide observational study conducted in 2005-6. Sensitivity specificity and area under the ROC curve were calculated for different FPG values.

RESULTS

Study included 4014 community dwelling people after excluding people already on treatment for diabetes or pre-diabetes. Mean age was 45.3 (± 15) years and 60.4% were females. FPG cut off of 5.3 mmol/L showed better sensitivity and specificity than 5.6 mmol/L in detecting diabetes (87.8% and 84.4% Vs 80.8% and 92.1%) and pre-diabetes (54.7% and 87.0% Vs 43.8% and 94.2%).

CONCLUSIONS

A lower FPG cut off of 5.3 mmol/L has a better sensitivity and acceptable specificity in screening for diabetes and pre-diabetes in Sri Lankan adults.

Coronin 1B Reorganizes the Architecture of F-Actin Networks for Contractility at Steady-State and Apoptotic Adherens Junctions

In this study we sought to identify how contractility at adherens junctions influences apoptotic cell extrusion. We first found that the generation of effective contractility at steady-state junctions entails a process of architectural reorganization whereby filaments that are initially generated as poorly organized networks of short bundles are then converted into co-aligned perijunctional bundles. Reorganization requires coronin 1B, which is recruited to junctions by E-cadherin adhesion and is necessary to establish contractile tension at the zonula adherens. When cells undergo apoptosis within an epithelial monolayer, coronin 1B is also recruited to the junctional cortex at the apoptotic/neighbor cell interface in an E-cadherin-dependent fashion to support actin architectural reorganization, contractility, and extrusion. We propose that contractile stress transmitted from the apoptotic cell through E-cadherin adhesions elicits a mechanosensitive response in neighbor cells that is necessary for the morphogenetic event of apoptotic extrusion to occur.

Prediction of 10-year vascular risk in patients with diabetes: the AD-ON risk score

AIMS

To formulate a combined cardiovascular risk score in diabetes that could be useful both to physicians and healthcare funders.

METHODS

Data were derived from the Action in Diabetes and Vascular Disease: Preterax and Diamicron Modified Release Controlled Evaluation Observational (ADVANCE-ON) study, a randomized controlled trial (mean duration 5 years) with a post-randomization follow-up (mean 4.9 years), that included 11 140 high-risk patients with diabetes. The outcome analysed was the occurrence of either fatal or non-fatal macrovascular or renal disease. A Cox regression model was used to determine weightings in the risk score. The resultant score was recalibrated to each of three major global regions, as covered by the ADVANCE-ON study.

RESULTS

Over a median of 9.9 years, 1145 patients experienced at least one component of the combined outcome event. The resultant score, the AD-ON risk score, incorporated 13 demographic or clinical variables. Its discrimination was modest [c-statistic = 0.668 (95% confidence interval 0.651, 0.685)] but its calibration was excellent (predicted and observed risks coincided well, within disparate global regions). In terms of the integrated discrimination improvement index, its performance was marginally superior, over a 10-year risk horizon, to existing risk scores in clinical use, from a restricted version of the same data, for macrovascular and renal disease separately.

CONCLUSIONS

The AD-ON risk score has advantages over the existing vascular risk scores in diabetes that used data from the original ADVANCE trial, which treat macrovascular and renal diseases separately. These advantages include its simplicity of use and global application.

Botulinum neurotoxin type-A enters a non-recycling pool of synaptic vesicles

Neuronal communication relies on synaptic vesicles undergoing regulated exocytosis and recycling for multiple rounds of fusion. Whether all synaptic vesicles have identical protein content has been challenged, suggesting that their recycling ability may differ greatly. Botulinum neurotoxin type-A (BoNT/A) is a highly potent neurotoxin that is internalized in synaptic vesicles at motor nerve terminals and induces flaccid paralysis. Recently, BoNT/A was also shown to undergo retrograde transport, suggesting it might enter a specific pool of synaptic vesicles with a retrograde trafficking fate. Using high-resolution microscopy techniques including electron microscopy and single molecule imaging, we found that the BoNT/A binding domain is internalized within a subset of vesicles that only partially co-localize with cholera toxin B-subunit and have markedly reduced VAMP2 immunoreactivity. Synaptic vesicles loaded with pHrodo-BoNT/A-Hc exhibited a significantly reduced ability to fuse with the plasma membrane in mouse hippocampal nerve terminals when compared with pHrodo-dextran-containing synaptic vesicles and pHrodo-labeled anti-GFP nanobodies bound to VAMP2-pHluorin or vGlut-pHluorin. Similar results were also obtained at the amphibian neuromuscular junction. These results reveal that BoNT/A is internalized in a subpopulation of synaptic vesicles that are not destined to recycle, highlighting the existence of significant molecular and functional heterogeneity between synaptic vesicles.

Efficacy and safety of canagliflozin when used in conjunction with incretin-mimetic therapy in patients with type 2 diabetes

AIMS

To assess the efficacy and safety of canagliflozin, a sodium glucose co-transporter 2 (SGLT2) inhibitor, in patients with type 2 diabetes enrolled in the CANagliflozin cardioVascular Assessment Study (CANVAS) who were on an incretin mimetic [dipeptidyl peptidase-4 (DPP-4) inhibitor or glucagon-like peptide-1 (GLP-1) receptor agonist].

METHODS

CANVAS is a double-blind, placebo-controlled study that randomized participants to canagliflozin 100 or 300 mg or placebo added to routine therapy. The present post hoc analysis assessed the efficacy and safety of canagliflozin 100 and 300 mg compared with placebo in subsets of patients from CANVAS who were taking background DPP-4 inhibitors or GLP-1 receptor agonists with or without other antihyperglycaemic agents at week 18.

RESULTS

Of the 4330 patients in CANVAS, 316 were taking DPP-4 inhibitors and 95 were taking GLP-1 receptor agonists. At 18 weeks, canagliflozin 100 and 300 mg provided larger placebo-subtracted reductions in glycated haemoglobin (HbA1c) in patients taking DPP-4 inhibitors [-0.56% (95% confidence interval [CI]: -0.77, -0.35), and -0.75% (95% CI: -0.95, -0.54), respectively] and GLP-1 receptor agonists [-1.00% (95% CI: -1.35, -0.65), and -1.06% (95% CI: -1.43, -0.69), respectively]. Body weight and blood pressure (BP) reductions were seen with canagliflozin versus placebo in both subsets. Higher incidences of genital mycotic infections and osmotic diuresis-related adverse events (AEs) were seen with canagliflozin compared with placebo. The incidence of hypoglycaemia was numerically higher with canagliflozin versus placebo; nearly all events occurred in patients on background insulin or insulin secretagogues.

CONCLUSIONS

In patients on background incretin mimetics, canagliflozin improved HbA1c, body weight and BP, with an increased incidence of AEs related to SGLT2 inhibition.

Efficacy and safety of once-weekly glucagon-like peptide 1 receptor agonists for the management of type 2 diabetes: a systematic review and meta-analysis of randomized controlled trials

AIM

To assess the efficacy and safety of recently approved once-weekly glucagon-like peptide 1 receptor agonists (GLP-1 RAs) in patients with type 2 diabetes.

METHODS

We conducted a systematic review and meta-analysis of randomized controlled trials comparing any GLP-1 RA licensed for once-weekly dosing (albiglutide, dulaglutide or exenatide extended release) with placebo or other antidiabetic agents. We searched Medline, Embase, the Cochrane Library and grey literature for articles published up to December 2014 and extracted data in duplicate.

RESULTS

In our systematic review we included 33 trials with a total of 16 003 participants. Compared with placebo the change in glycated haemoglobin (HbA1c) concentration was -0.66% [six studies; 95% confidence interval (CI) -1.14 to -0.19; I(2)  = 88%] with albiglutide, and -1.18% (seven studies; 95% CI -1.34 to -1.02; I(2)  = 65%) with dulaglutide. Based on data from placebo-controlled trials, we did not detect statistically significant weight-sparing benefits for albiglutide or dulaglutide. Compared with other antidiabetic agents, once-weekly GLP-1 RAs outperformed sitagliptin, daily exenatide and insulin glargine in terms of HbA1c-lowering (mean differences -0.40%; 95% CI -0.66 to -0.14; I(2)  = 85%, -0.44%; 95% CI -0.58 to -0.29; I(2)  = 40% and -0.28; 95% CI -0.45 to -0.10; I(2)  = 81%, respectively). The main adverse effects of treatment included gastrointestinal and injection site reactions.

CONCLUSIONS

Given their dosing scheme and overall efficacy and safety profile, once-weekly GLP-1 RAs are a convenient therapeutic option for use as add-on to metformin.

Effect of phosphorylation on EGFR dimer stability probed by single-molecule dynamics and FRET/FLIM

Deregulation of epidermal growth factor receptor (EGFR) signaling has been correlated with the development of a variety of human carcinomas. EGF-induced receptor dimerization and consequent trans- auto-phosphorylation are among the earliest events in signal transduction. Binding of EGF is thought to induce a conformational change that consequently unfolds an ectodomain loop required for dimerization indirectly. It may also induce important allosteric changes in the cytoplasmic domain. Despite extensive knowledge on the physiological activation of EGFR, the effect of targeted therapies on receptor conformation is not known and this particular aspect of receptor function, which can potentially be influenced by drug treatment, may in part explain the heterogeneous clinical response among cancer patients. Here, we used Förster resonance energy transfer/fluorescence lifetime imaging microscopy (FRET/FLIM) combined with two-color single-molecule tracking to study the effect of ATP-competitive small molecule tyrosine kinase inhibitors (TKIs) and phosphatase-based manipulation of EGFR phosphorylation on live cells. The distribution of dimer on-times was fitted to a monoexponential to extract dimer off-rates (koff). Our data show that pretreatment with gefitinib (active conformation binder) stabilizes the EGFR ligand-bound homodimer. Overexpression of EGFR-specific DEP-1 phosphatase was also found to have a stabilizing effect on the homodimer. No significant difference in the koff of the dimer could be detected when an anti-EGFR antibody (425 Snap single-chain variable fragment) that allows for dimerization of ligand-bound receptors, but not phosphorylation, was used. These results suggest that both the conformation of the extracellular domain and phosphorylation status of the receptor are involved in modulating the stability of the dimer. The relative fractions of these two EGFR subpopulations (interacting versus free) were obtained by a fractional-intensity analysis of ensemble FRET/FLIM images. Our combined imaging approach showed that both the fraction and affinity (surrogate of conformation at a single-molecule level) increased after gefitinib pretreatment or DEP-1 phosphatase overexpression. Using an EGFR mutation (I706Q, V948R) that perturbs the ability of EGFR to dimerize intracellularly, we showed that a modest drug-induced increase in the fraction/stability of the EGFR homodimer may have a significant biological impact on the tumor cell's proliferation potential.

The influence of family history of diabetes on disease prevalence and associated metabolic risk factors among Sri Lankan adults

AIMS

To describe the influence of family history on diabetes prevalence and associated metabolic risk factors in a nationally representative sample from Sri Lanka.

METHODS

A cross sectional national survey was conducted among 5000 adults in Sri Lanka. Family history was evaluated at three levels: (1) parents, (2) grandparents (paternal and maternal) and (3) siblings. A binary-logistic regression analysis controlling for confounders (age, gender, BMI and physical activity) was performed in all patients with 'presence of diabetes' as the dichotomous dependent variable and using family history in father, mother, maternal grandmother/grandfather, paternal grandmother/grandfather, siblings and children as binary independent variables.

RESULTS

The sample size was 4485, mean age was 46.1 ± 15.1 years and 39.5% were males. In all adults, the prevalence of diabetes was significantly higher in patients with a family history (23.0%) than those without (8.2%) (P < 0.001). When family history was present in both parents, the prevalence of diabetes was 32.9%. Presence of a family history significantly increased the risk of diabetes [odds ratio (OR): 3.35, 95% confidence interval (CI): 2.78-4.03], obesity (OR: 2.45, 95% CI: 1.99-2.99), hypertension (OR: 1.25, 95% CI: 1.08-1.45) and metabolic syndrome (OR: 2.28, 95% CI: 1.97-2.63). In all adults, the presence of a family history of diabetes in a father (OR: 1.29, 95% CI: 1.02-1.63), mother (OR: 1.23, 95% CI: 1.11-1.36), paternal grandfather (OR: 1.27, 95% CI: 1.14-1.41), siblings (OR: 4.18, 95% CI: 3.34-5.22) and children (OR: 5.47, 95% CI: 2.93-10.19) was associated with a significantly increased risk of developing diabetes.

CONCLUSIONS

Family history and diabetes had a graded association in the Sri Lankan population, because the prevalence increased with the increasing number of generations affected. Family history of diabetes was also associated with the prevalence of obesity, metabolic syndrome and hypertension. Individuals with a family history of diabetes form an easily identifiable group who may benefit from targeted interventions.

Time-domain microfluidic fluorescence lifetime flow cytometry for high-throughput Förster resonance energy transfer screening

Sensing ion or ligand concentrations, physico-chemical conditions, and molecular dimerization or conformation change is possible by assays involving fluorescent lifetime imaging. The inherent low throughput of imaging impedes rigorous statistical data analysis on large cell numbers. We address this limitation by developing a fluorescence lifetime-measuring flow cytometer for fast fluorescence lifetime quantification in living or fixed cell populations. The instrument combines a time-correlated single photon counting epifluorescent microscope with microfluidics cell-handling system. The associated computer software performs burst integrated fluorescence lifetime analysis to assign fluorescence lifetime, intensity, and burst duration to each passing cell. The maximum safe throughput of the instrument reaches 3,000 particles per minute. Living cells expressing spectroscopic rulers of varying peptide lengths were distinguishable by Förster resonant energy transfer measured by donor fluorescence lifetime. An epidermal growth factor (EGF)-stimulation assay demonstrated the technique's capacity to selectively quantify EGF receptor phosphorylation in cells, which was impossible by measuring sensitized emission on a standard flow cytometer. Dual-color fluorescence lifetime detection and cell-specific chemical environment sensing were exemplified using di-4-ANEPPDHQ, a lipophilic environmentally sensitive dye that exhibits changes in its fluorescence lifetime as a function of membrane lipid order. To our knowledge, this instrument opens new applications in flow cytometry which were unavailable due to technological limitations of previously reported fluorescent lifetime flow cytometers. The presented technique is sensitive to lifetimes of most popular fluorophores in the 0.5-5 ns range including fluorescent proteins and is capable of detecting multi-exponential fluorescence lifetime decays. This instrument vastly enhances the throughput of experiments involving fluorescence lifetime measurements, thereby providing statistically significant quantitative data for analysis of large cell populations. © 2014 International Society for Advancement of Cytometry.

Steady-state acceptor fluorescence anisotropy imaging under evanescent excitation for visualisation of FRET at the plasma membrane

We present a novel imaging system combining total internal reflection fluorescence (TIRF) microscopy with measurement of steady-state acceptor fluorescence anisotropy in order to perform live cell Förster Resonance Energy Transfer (FRET) imaging at the plasma membrane. We compare directly the imaging performance of fluorescence anisotropy resolved TIRF with epifluorescence illumination. The use of high numerical aperture objective for TIRF required correction for induced depolarization factors. This arrangement enabled visualisation of conformational changes of a Raichu-Cdc42 FRET biosensor by measurement of intramolecular FRET between eGFP and mRFP1. Higher activity of the probe was found at the cell plasma membrane compared to intracellularly. Imaging fluorescence anisotropy in TIRF allowed clear differentiation of the Raichu-Cdc42 biosensor from negative control mutants. Finally, inhibition of Cdc42 was imaged dynamically in live cells, where we show temporal changes of the activity of the Raichu-Cdc42 biosensor.

Study to determine the durability of glycaemic control with early treatment with a vildagliptin-metformin combination regimen vs. standard-of-care metformin monotherapy-the VERIFY trial: a randomized double-blind trial

AIMS

Durability of good glycaemic control (HbA1c ) is of importance as it can be the foundation for delaying diabetic complications. It has been hypothesized that early initiation of treatment with the combination of oral anti-diabetes agents with complementary mechanisms of action can increase the durability of glycaemic control compared with metformin monotherapy followed by a stepwise addition of oral agents. Dipeptidyl peptidase-4 inhibitors are good candidates for early use as they are efficacious in combination with metformin, show weight neutrality and a low risk of hypoglycaemia. We aimed to test the hypothesis that early combined treatment of metformin and vildagliptin slows β-cell deterioration as measured by HbA1c .

METHODS

Approximately 2000 people with Type 2 diabetes mellitus who were drug-naive or who were treated with metformin for less than 1 month, and who have HbA1c of 48-58 mmol/mol (6.5-7.5%), will be randomized in a 1:1 ratio in VERIFY, a 5-year multinational, double-blind, parallel-group study designed to compare early initiation of a vildagliptin-metformin combination with standard-of-care initiation of metformin monotherapy, followed by the stepwise addition of vildagliptin when glycaemia deteriorates. Further deterioration will be treated with insulin. The primary analysis for treatment failure will be from a Cox proportional hazard regression model and the durability of glycaemic control will be evaluated by assessing treatment failure rate and the rate of loss in glycaemic control over time as co-primary endpoints.

SUMMARY

VERIFY is the first study to investigate the long-term clinical benefits of early combination treatment vs. the standard-of-care metformin monotherapy with a second agent added by threshold criteria.

The ErbB4 CYT2 variant protects EGFR from ligand-induced degradation to enhance cancer cell motility

The epidermal growth factor receptor (EGFR) is a member of the ErbB family that can promote the migration and proliferation of breast cancer cells. Therapies that target EGFR can promote the dimerization of EGFR with other ErbB receptors, which is associated with the development of drug resistance. Understanding how interactions among ErbB receptors alter EGFR biology could provide avenues for improving cancer therapy. We found that EGFR interacted directly with the CYT1 and CYT2 variants of ErbB4 and the membrane-anchored intracellular domain (mICD). The CYT2 variant, but not the CYT1 variant, protected EGFR from ligand-induced degradation by competing with EGFR for binding to a complex containing the E3 ubiquitin ligase c-Cbl and the adaptor Grb2. Cultured breast cancer cells overexpressing both EGFR and ErbB4 CYT2 mICD exhibited increased migration. With molecular modeling, we identified residues involved in stabilizing the EGFR dimer. Mutation of these residues in the dimer interface destabilized the complex in cells and abrogated growth factor-stimulated cell migration. An exon array analysis of 155 breast tumors revealed that the relative mRNA abundance of the ErbB4 CYT2 variant was increased in ER+ HER2- breast cancer patients, suggesting that our findings could be clinically relevant. We propose a mechanism whereby competition for binding to c-Cbl in an ErbB signaling heterodimer promotes migration in response to a growth factor gradient.

Long-term efficacy and safety comparison of liraglutide, glimepiride and placebo, all in combination with metformin in type 2 diabetes: 2-year results from the LEAD-2 study

AIMS

To investigate efficacy and safety of dual therapy with liraglutide and metformin in comparison to glimepiride and metformin, and metformin monotherapy over 2 years in patients with type 2 diabetes.

METHODS

In the 26-week the Liraglutide Effect and Action in Diabetes (LEAD)-2 core trial, patients (n = 1091) were randomized (2 : 2 : 2 : 1: 2) to liraglutide (0.6, 1.2 or 1.8 mg once-daily), placebo or glimepiride; all with metformin. Patients were enrolled if they were 18-80 years old with HbA1c 7.0-11.0% (previous monotherapy ≥3 months), or 7.0-10.0% (previous combination therapy ≥3 months), and body mass index ≤40 kg/m(2) . Patients completing the 26-week double-blinded phase could enter an 18-month open-label extension.

RESULTS

HbA1c decreased significantly with liraglutide (0.4% with 0.6 mg, 0.6% with 1.2 and 1.8 mg) versus 0.3% increase with metformin monotherapy (p < 0.0001). HbA1c decrease with liraglutide was non-inferior versus 0.5% decrease with glimepiride. Liraglutide groups experienced significant weight loss (2.1, 3.0 and 2.9 kg with 0.6, 1.2 and 1.8 mg, respectively) compared to weight gain (0.7 kg) with glimepiride (p < 0.0001). Weight loss with liraglutide 1.2 and 1.8 mg was significantly greater than with metformin monotherapy (1.8 kg; p = 0.0185 and p = 0.0378 for 1.2 and 1.8 mg, respectively). The occurrence of minor hypoglycaemia was <5.0% in all liraglutide groups, significantly less than with glimepiride (24.0%; p < 0.0001). Liraglutide was well tolerated overall: gastrointestinal events were more common than with glimepiride or metformin monotherapy, but occurrence decreased with time.

CONCLUSIONS

Liraglutide provided sustained glycaemic control over 2 years comparable to that provided by glimepiride. Liraglutide was well tolerated, and was associated with weight loss and a low rate of hypoglycaemia.

Waist to height ratio: a better anthropometric marker of diabetes and cardio-metabolic risks in South Asian adults

AIMS

Obesity associated metabolic diseases have reached epidemic levels in many South Asian countries. Conventional anthropometric indices have poor sensitivity and specificity for detecting people with increased metabolic risks. The aim of this study was to investigate and compare WHtR (Waist to Height Ratio) as a marker of diabetes and cardio-metabolic risks with existing classical anthropometric indices such as; Body Mass Index (BMI), Waist Circumference (WC) and Waist to Hip Ratio (WHR) in a large sub-population of ethnic South Asians.

METHODS

A total of 5000 subjects recruited from a nationally representative community-based sample using multi-stage random cluster-sampling method. Anthropometric, biochemical and clinical parameters were measured. Receiver-operating characteristic (ROC) curves were performed and area under the curve (AUC) was calculated for each anthropometric index.

RESULTS

Sample size was 4485. The mean WHtR in all adults was 0.496 (±0.077), males (0.477±0.065) had a significant lower WHtR than females (0.508±0.081) (p<0.001). WHtR had the highest correlation with metabolic parameters. In all adults, males and females the AUC of WHtR was significantly higher than that of BMI, WC and WHR in diabetes mellitus, pre-diabetes, hypertension, metabolic syndrome and hypercholesterolemia. Mean age, fasting blood glucose, 2-h post prandial blood Glucose, total cholesterol, LDL cholesterol, triglycerides, systolic blood pressure and diastolic blood pressure were all significantly higher among all adults, males and females with WHtR≥0.5.

CONCLUSIONS

WHtR is a simple and effective anthropometric index to identify obesity associated metabolic risks among Sri Lankan adults.

Time-domain fluorescence lifetime imaging techniques suitable for solid-state imaging sensor arrays

We have successfully demonstrated video-rate CMOS single-photon avalanche diode (SPAD)-based cameras for fluorescence lifetime imaging microscopy (FLIM) by applying innovative FLIM algorithms. We also review and compare several time-domain techniques and solid-state FLIM systems, and adapt the proposed algorithms for massive CMOS SPAD-based arrays and hardware implementations. The theoretical error equations are derived and their performances are demonstrated on the data obtained from 0.13 μm CMOS SPAD arrays and the multiple-decay data obtained from scanning PMT systems. In vivo two photon fluorescence lifetime imaging data of FITC-albumin labeled vasculature of a P22 rat carcinosarcoma (BD9 rat window chamber) are used to test how different algorithms perform on bi-decay data. The proposed techniques are capable of producing lifetime images with enough contrast.

A multi-functional imaging approach to high-content protein interaction screening

Functional imaging can provide a level of quantification that is not possible in what might be termed traditional high-content screening. This is due to the fact that the current state-of-the-art high-content screening systems take the approach of scaling-up single cell assays, and are therefore based on essentially pictorial measures as assay indicators. Such phenotypic analyses have become extremely sophisticated, advancing screening enormously, but this approach can still be somewhat subjective. We describe the development, and validation, of a prototype high-content screening platform that combines steady-state fluorescence anisotropy imaging with fluorescence lifetime imaging (FLIM). This functional approach allows objective, quantitative screening of small molecule libraries in protein-protein interaction assays. We discuss the development of the instrumentation, the process by which information on fluorescence resonance energy transfer (FRET) can be extracted from wide-field, acceptor fluorescence anisotropy imaging and cross-checking of this modality using lifetime imaging by time-correlated single-photon counting. Imaging of cells expressing protein constructs where eGFP and mRFP1 are linked with amino-acid chains of various lengths (7, 19 and 32 amino acids) shows the two methodologies to be highly correlated. We validate our approach using a small-scale inhibitor screen of a Cdc42 FRET biosensor probe expressed in epidermoid cancer cells (A431) in a 96 microwell-plate format. We also show that acceptor fluorescence anisotropy can be used to measure variations in hetero-FRET in protein-protein interactions. We demonstrate this using a screen of inhibitors of internalization of the transmembrane receptor, CXCR4. These assays enable us to demonstrate all the capabilities of the instrument, image processing and analytical techniques that have been developed. Direct correlation between acceptor anisotropy and donor FLIM is observed for FRET assays, providing an opportunity to rapidly screen proteins, interacting on the nano-meter scale, using wide-field imaging.

A targeted siRNA screen identifies regulators of Cdc42 activity at the natural killer cell immunological synapse

Natural killer (NK) cells kill tumor cells and virally infected cells, and an effective NK cell response requires processes, such as motility, recognition, and directional secretion, that rely on cytoskeletal rearrangement. The Rho guanosine triphosphatase (GTPase) Cdc42 coordinates cytoskeletal reorganization downstream of many receptors. The Rho-related GTPase from plants 1 (ROP1) exhibits oscillatory activation behavior at the apical plasma membrane of growing pollen tubes; however, a similar oscillation in Rho GTPase activity has so far not been demonstrated in mammalian cells. We hypothesized that oscillations in Cdc42 activity might occur within NK cells as they interact with target cells. Through fluorescence lifetime imaging of a Cdc42 biosensor, we observed that in live NK cells forming immunological synapses with target cells, Cdc42 activity oscillated after exhibiting an initial increase. We used protein-protein interaction networks and structural databases to identify candidate proteins that controlled Cdc42 activity, leading to the design of a targeted short interfering RNA screen. The guanine nucleotide exchange factors RhoGEF6 and RhoGEF7 were necessary for Cdc42 activation within the NK cell immunological synapse. In addition, the kinase Akt and the p85α subunit of phosphoinositide 3-kinase (PI3K) were required for Cdc42 activation, the periodicity of the oscillation in Cdc42 activity, and the subsequent polarization of cytotoxic vesicles toward target cells. Given that PI3Ks are targets of tumor therapies, our findings suggest the need to monitor innate immune function during the course of targeted therapy against these enzymes.

Banting Memorial Lecture 2010^. Type 2 diabetes as an 'infectious' disease: is this the Black Death of the 21st century?

We are currently facing a global pandemic of obesity and Type 2 diabetes. In some settings, the population prevalence of Type 2 diabetes is 50%, and half of those affected will die from diabetes-related complications. Eight centuries ago, an epidemic of bubonic plague swept across Europe, killing at least half of its victims. We here draw comparisons between these two pandemics, proposing close analogies between the 'Black Death' of the 14th century and the modern-day equivalent of Type 2 diabetes. Both diseases can be considered in terms of an aetiological agent, a reservoir, a vector and a predisposing toxic environment; populations can be considered as highly susceptible to the transmissable agents of Type 2 diabetes in the setting of calorie excess, inadequate food labelling, poorly regulated advertising and sedentary lifestyles. As for tackling a pandemic of a contagious microbial pathogen, we believe that breaking the cycle of transmission in the diabetes epidemic must be underpinned by political will and prompt, decisive legislation backed by the medical community. Far from fearing that such measures edge us towards a 'nanny state', we believe individuals should expect a responsible government to safeguard them from the toxic milieu that puts them at risk of obesity and its complications, and that communities and populations have the right to have their health protected.

Prevalence of overweight and obesity in Sri Lankan adults

The aim of the study was to determine the prevalence of overweight, obesity and abdominal obesity, and the underlying socio-demographic correlates among Sri Lankan adults. Data were from 4532 adults aged ≥18 years randomly selected for a national level study on diabetes and cardiovascular disease. Weight, height and waist circumference (WC) were measured and body mass index (BMI) calculated. The mean (95% confidence interval) BMI and WC were 21.1 kg m(-2) (20.9-21.3), 22.3 kg m(-2) (22.1-22.4) and 78.0 cm (77.5-78.6) and 77.5 cm (77.0-78.0) for males and females, respectively. According to the proposed World Health Organization cut-off values for Asians, the percentage of Sri Lankan adults in the overweight, obese and centrally obese categories were 25.2%, 9.2% and 26.2%, respectively. Based on the cut-offs for Caucasians, these were 16.8%, 3.7% and 10.8%. Our findings were compatible with prevalence of obesity in regional countries. In addition, female sex, urban living, higher education, higher income and being in the middle age were shown to be associated with overweight and obesity in Sri Lankans. In conclusion, we have documented a relatively high prevalence of overweight and obesity, particularly, abdominal obesity among adults in Sri Lanka which is a middle-income country. Urgent public health interventions are needed to control the problem at an early stage.

Vildagliptin add-on to metformin produces similar efficacy and reduced hypoglycaemic risk compared with glimepiride, with no weight gain: results from a 2-year study

AIM

To show that vildagliptin added to metformin is non-inferior to glimepiride in reducing HbA1c levels from baseline over 2 years.

METHODS

A randomized, double-blind, active-comparator study of patients with type 2 diabetes mellitus inadequately controlled (HbA1c 6.5-8.5%) by metformin monotherapy. Patients received vildagliptin (50 mg twice daily) or glimepiride (up to 6 mg/day) added to metformin.

RESULTS

In all, 3118 patients were randomized (vildagliptin, n = 1562; glimepiride, n = 1556). From similar baseline values (7.3%), after 2 years adjusted mean (s.e.) change in HbA1c was comparable between vildagliptin and glimepiride treatment: -0.1% (0.0%) and -0.1% (0.0%), respectively. The primary objective of non-inferiority was met. A similar proportion of patients reached HbA1c <7% (36.9 and 38.3%, respectively), but with vildagliptin more patients reached this target without hypoglycaemia (36.0% vs. 28.8%; p = 0.004). The initial response (IR) was sustained for a mean (s.d.) of 309 (244) days with vildagliptin versus 270 (223) days for glimepiride (p < 0.001) (IR = nadir HbA1c where change from baseline > or =0.5% or HbA1c < or =6.5% within the first six months of treatment. After IR was detected, sustained response = time between nadir and an increase of >0.3% above IR). Independent of disease duration, age was a predictor of effect sustainability. Fewer patients experienced hypoglycaemia with vildagliptin (2.3% vs. 18.2% with glimepiride) with a 14-fold difference in the number of hypoglycaemic events (59 vs. 838). Vildagliptin had a beneficial effect on body weight [mean (s.e.) change from baseline -0.3 (0.1) kg; between-group difference -1.5 kg; p < 0.001]. Overall, both treatments were well tolerated and displayed similar safety profiles.

CONCLUSIONS

Vildagliptin add-on has similar efficacy to glimepiride after 2 years' treatment, with markedly reduced hypoglycaemia risk and no weight gain.

An assessment of lifestyle video education for people newly diagnosed with type 2 diabetes

BACKGROUND

Education plays a key role in the development of self-management skills for people with type 2 diabetes, although there is limited evidence for the use of video education.

AIMS

To develop a video-based lifestyle education programme for people newly diagnosed with type 2 diabetes and to evaluate changes in knowledge, biomedical indices and quality of life.

METHODS

Forty-two newly diagnosed type 2 diabetic subjects were recruited and randomly allocated to either a video education or control group. Data were collected at baseline and 6 months after the intervention. Subjects (43% male) had a mean (SD) age of 60.8 (9.6) years, weight 89.5 (15.5) kg, BMI 31.3 (5.1) kg m(2), glycated haemoglobin (A1c) 7.4 (1.7)%, total cholesterol 4.7 (1.2) mmol L(-1), high-density lipoprotein cholesterol 1.15 (0.34) mmol L(-1), triglycerides 1.8 (1.0) mmol L(-1), low-density lipoprotein cholesterol 2.8 (1.0) mmol L(-1), pedometer reading 5721 (3446) steps per day. There were 63.7% correct answers given to the ADKnowl questionnaire and the WHO-5 Well-Being score was 65.8%.

RESULTS

At 6 months, the intervention group showed increased knowledge compared to controls (74.3% versus 56.4% correct answers, P < or = 0.0001). Although there were no significant differences in changes over 6 months between the two groups, the intervention group showed improvements in A1c (-0.7%, P = 0.024), total cholesterol (-0.5 mmol L(-1), P = 0.017), low-density lipoprotein cholesterol (-0.5, P = 0.018) and increased physical activity measured by pedometer (1266 steps per day, P = 0.043) from baseline, with no significant changes in the control group.

CONCLUSIONS

A brief video intervention increased diabetes knowledge amongst those newly diagnosed with type 2 diabetes and may comprise an effective way of directing education to such individuals.

Time-lapse FRET microscopy using fluorescence anisotropy

We present recent data on dynamic imaging of Rac1 activity in live T-cells. Förster resonance energy transfer between enhanced green and monomeric red fluorescent protein pairs which form part of a biosensor molecule provides a metric of this activity. Microscopy is performed using a multi-functional high-content screening instrument using fluorescence anisotropy to provide a means of monitoring protein-protein activity with high temporal resolution. Specifically, the response of T-cells upon interaction of a cell surface receptor with an antibody coated multi-well chamber was measured. We observed dynamic changes in the activity of the biosensor molecules with a time resolution that is difficult to achieve with traditional methodologies for observing Förster resonance energy transfer (fluorescence lifetime imaging using single photon counting or frequency domain techniques) and without spectral corrections that are normally required for intensity based methodologies.

The diabetes epidemic in Sri Lanka – a growing problem

Diabetes mellitus, which was once considered a disease of the developed world, has become a worldwide pandemic, with two thirds of the global diabetic population living in the developing countries. Local studies show a definite upward trend in the prevalence of diabetes mellitus. The earliest available study on a rural community in 1990 reported a prevalence of 2.5%. The largest-ever study on the diabetes prevalence in Sri Lanka was published in 2005. It showed a prevalence of 14.2% among males and 13.5% among females. The World Health Organisation and the International Diabetic Federation estimates and forecasts are much lower than the available local prevalence rates, and what may be predicted from the prevalence rates in South India. Further research is necessary to investigate the exact underlying mechanisms for the South Asian epidemic. Wider preventive programmes need to be urgently implemented to stem the tide.

Weight loss with liraglutide, a once-daily human glucagon-like peptide-1 analogue for type 2 diabetes treatment as monotherapy or added to metformin, is primarily as a result of a reduction in fat tissue

AIM

The effect on body composition of liraglutide, a once-daily human glucagon-like peptide-1 analogue, as monotherapy or added to metformin was examined in patients with type 2 diabetes (T2D).

METHODS

These were randomized, double-blind, parallel-group trials of 26 [Liraglutide Effect and Action in Diabetes-2 (LEAD-2)] and 52 weeks (LEAD-3). Patients with T2D, aged 18-80 years, body mass index (BMI) < or =40 kg/m(2) (LEAD-2), < or =45 kg/m(2) (LEAD-3) and HbA1c 7.0-11.0% were included. Patients were randomized to liraglutide 1.8, 1.2 or 0.6 mg/day, placebo or glimepiride 4 mg/day, all combined with metformin 1.5-2 g/day in LEAD-2 and to liraglutide 1.8, 1.2 or glimepiride 8 mg/day in LEAD-3. LEAD-2/3: total lean body tissue, fat tissue and fat percentage were measured. LEAD-2: adipose tissue area and hepatic steatosis were assessed.

RESULTS

LEAD-2: fat percentage with liraglutide 1.2 and 1.8 mg/metformin was significantly reduced vs. glimepiride/metformin (p < 0.05) but not vs. placebo. Visceral and subcutaneous adipose tissue areas were reduced from baseline in all liraglutide/metformin arms. Except with liraglutide 0.6 mg/metformin, reductions were significantly different vs. changes seen with glimepiride (p < 0.05) but not with placebo. Liver-to-spleen attenuation ratio increased with liraglutide 1.8 mg/metformin possibly indicating reduced hepatic steatosis. LEAD-3: reductions in fat mass and fat percentage with liraglutide monotherapy were significantly different vs. increases with glimepiride (p < 0.01).

CONCLUSION

Liraglutide (monotherapy or added to metformin) significantly reduced fat mass and fat percentage vs. glimepiride in patients with T2D.

Apolipoproteins in diabetes dyslipidaemia in South Asians with young adult-onset diabetes: distribution, associations and patterns

Background

Apolipoproteins B (apoB) and AI (apoAI) are strong predictors of cardiovascular disease (CVD). We describe apolipoprotein distributions and their associations with lipids and diabetes subtype in diabetic young adult South Asians.

Methods

In 995 subjects with diabetes, we measured fasting total cholesterol (TC), high-density lipoprotein cholesterol (HDLC), triglycerides (TG), apoB and apoAI, glycosylated haemoglobin (HbA1c) and glutamic acid decarboxylase antibodies (GADA). Low-density lipoprotein cholesterol (LDLC) and non-HDLC (NHDLC) were calculated. We compared values in subjects aged 15–50 y from the United States National Health and Nutrition Examination Survey (NHANES).

Results

Median age and duration of diabetes were 38 (range 14–45) and 4 (0–24) y. Men had significantly higher TC, TG, NHDLC, TC/HDLC, apoB/AI and NHDLC/apoB, and lower apoAI than women. Compared with the reference group, patients with type 1 diabetes had lower TG, apoB:apoAI and HDLC:apoAI, and higher HDLC and apoAI. Patients with type 2 diabetes had higher TG, TC, LDLC, NHDLC, TC:HDL, apoB, apoAI and apoB:apoAI, and lower HDLC, LDLC:apoB and HDLC:apoAI. Among patients with type 2 diabetes, 54% had high apoB (>1.2 g/L) and 33% also had high TG (>1.5 mmol/L). Measures of obesity (body mass index and waist circumference) were weakly correlated with lipid and apoprotein parameters, suggesting a modest contribution to dyslipidaemia.

Conclusions

A large proportion of young adult Sri Lankan patients with type 2 diabetes has a low LDLC:apoB and high apoB and/or TG, suggesting that these patients are at increased risk of CVD.

Glycaemic risk assessment in children and young people with Type 1 diabetes mellitus

AIM

To ascertain if those with diabetes (and their carers) ascribe a similar level of risk to blood glucose control as healthcare professionals.

METHODS

We used a structured questionnaire to ask fifty healthcare professionals how 'dangerous' a given blood glucose value was. Their answers were modelled to produce an algorithm of assessed risk. To examine if patients (and their carers) would apportion a similar level of risk to that of healthcare professionals, the same questionnaire was issued to fifty children and adolescents with Type 1 diabetes. For patients under 8 years old the carers completed the questionnaires (n = 23). Both patient and carers together completed the questionnaire for those aged 8-11 years (n = 15) and patients over the age of 11 years completed the questionnaire themselves (n = 12). The median results and interquartile range of the assessed level of risk, as determined by the two groups, were compared using a generalized linear model.

RESULTS

A significant difference (P < 0.0001) was identified between the median risk assessments of the two groups. The zero level of assessed risk was upward shifted in the patient group by 0.8 mmol/l and indicated the patients' view of risk increased.

CONCLUSIONS

Patients with Type 1 diabetes (and their carers) evaluate the risk from blood glucose values differently from healthcare professionals. The euglycaemic state (zero ascribed risk) that patients chose was 0.8 mmol/l greater than that of healthcare professionals, indicating, perhaps, hypoglycaemia avoidance, a more pragmatic approach or less exposure to current trends in glycaemic control.

Fluorescence lifetime spectroscopy and imaging of nano-engineered glucose sensor microcapsules based on glucose/galactose-binding protein

We aimed to develop microsensors for eventual glucose monitoring in diabetes, based on fluorescence lifetime changes in glucose/galactose-binding protein (GBP) labelled with the environmentally sensitive fluorophore dye, badan. A mutant of GBP was labelled with badan near the binding site, the protein adsorbed to microparticles of CaCO(3) as templates and encapsulated in alternating nano-layers of poly-L-lysine and heparin. We used fluorescence lifetime imaging (FLIM) with two-photon excitation and time-correlated single-photon counting to visualize the lifetime changes in the capsules. Addition of glucose increased the mean lifetime of GBP-badan by a maximum of approximately 2 ns. Analysis of fluorescence decay curves was consistent with two GBP states, a short-lifetime component (approximately 0.8 ns), likely representing the open form of the protein with no bound glucose, and a long-lifetime component (approximately 3.1 ns) representing the closed form with bound glucose and where the lobes of GBP have closed round the dye creating a more hydrophobic environment. FLIM demonstrated that increasing glucose increased the fractional proportion of the long-lifetime component. We conclude that fluorescence lifetime-based glucose sensing using GBP encapsulated with nano-engineered layer-by-layer films is a glucose monitoring technology suitable for development in diabetes management.

Stroboscopic fluorescence lifetime imaging

We report a fluorescence lifetime imaging technique that uses the time integrated response to a periodic optical excitation, eliminating the need for time resolution in detection. A Dirac pulse train of variable period is used to probe the frequency response of the total fluorescence per pulse leading to a frequency roll-off that is dependent on the relaxation rate of the fluorophores. The technique is validated by demonstrating wide-field, realtime, lifetime imaging of the endocytosis of inorganic quantum dots by a cancer cell line. Surface charging of the dots in the intra-cellular environment produces a switch in the fluorescence lifetime from approximately 40 ns to < 10 ns. A temporal resolution of half the excitation period is possible which in this instance is 15 ns. This stroboscopic technique offers lifetime based imaging at video rates with standard CCD cameras and has application in probing millisecond cell dynamics and in high throughput imaging assays.

Essential role of hIST1 in cytokinesis

The last steps of multivesicular body (MVB) formation, human immunodeficiency virus (HIV)-1 budding and cytokinesis require a functional endosomal sorting complex required for transport (ESCRT) machinery to facilitate topologically equivalent membrane fission events. Increased sodium tolerance (IST) 1, a new positive modulator of the ESCRT pathway, has been described recently, but an essential function of this highly conserved protein has not been identified. Here, we describe the previously uncharacterized KIAA0174 as the human homologue of IST1 (hIST1), and we report its conserved interaction with VPS4, CHMP1A/B, and LIP5. We also identify a microtubule interacting and transport (MIT) domain interacting motif (MIM) in hIST1 that is necessary for its interaction with VPS4, LIP5 and other MIT domain-containing proteins, namely, MITD1, AMSH, UBPY, and Spastin. Importantly, hIST1 is essential for cytokinesis in mammalian cells but not for HIV-1 budding, thus providing a novel mechanism of functional diversification of the ESCRT machinery. Last, we show that the hIST1 MIM activity is essential for cytokinesis, suggesting possible mechanisms to explain the role of hIST1 in the last step of mammalian cell division.

Prevalence and projections of diabetes and pre-diabetes in adults in Sri Lanka--Sri Lanka Diabetes, Cardiovascular Study (SLDCS)

AIMS

To determine the prevalence of diabetes mellitus and pre-diabetes (impaired fasting glucose and impaired glucose tolerance) in adults in Sri Lanka. Projections for the year 2030 and factors associated with diabetes and pre-diabetes are also presented.

METHODS

This cross-sectional study was conducted between 2005 and 2006. A nationally representative sample of 5000 adults aged >or= 18 years was selected by a multi-stage random cluster sampling technique. Fasting plasma glucose was tested in all participants and a 75-g oral glucose tolerance test was performed in non-diabetic subjects. Prevalence was estimated for those > 20 years of age.

RESULTS

Response rate was 91% (n = 4532), males 40%, age 46.1 +/- 15.1 years (mean +/- standard deviation). The age-sex standardized prevalence (95% confidence interval) of diabetes for Sri Lankans aged >or= 20 years was 10.3% (9.4-11.2%) [males 9.8% (8.4-11.2%), females 10.9% (9.7-12.1%), P = 0.129). Thirty-six per cent (31.9-40.1%) of all diabetic subjects were previously undiagnosed. Diabetes prevalence was higher in the urban population compared with rural [16.4% (13.8-19.0%) vs. 8.7% (7.8-9.6%); P < 0.001]. The prevalence of overall, urban and rural pre-diabetes was 11.5% (10.5-12.5%), 13.6% (11.2-16.0%) and 11.0% (10.0-12.0%), respectively. Overall, 21.8% (20.5-23.1%) had some form of dysglycaemia. The projected diabetes prevalence for the year 2030 is 13.9%. Those with diabetes and pre-diabetes compared with normal glucose tolerance were older, physically inactive, frequently lived in urban areas and had a family history of diabetes. They had higher body mass index, waist circumference, waist-hip ratio, systolic/diastolic blood pressure, low-density lipoprotein cholesterol and triglycerides. Insulin was prescribed to 4.4% (2.7-6.1%) of all diabetic subjects.

CONCLUSIONS

One in five adults in Sri Lanka has either diabetes or pre-diabetes and one-third of those with diabetes are undiagnosed.

Diabetes mellitus among young adults in Sri Lanka--role of GAD antibodies in classification and treatment: the Sri Lanka Young Diabetes study

AIMS/HYPOTHESIS

Diabetes mellitus is increasing among young adult South Asians. The aim of this study was to determine the prevalence and phenotypic characteristics of diabetes subtypes based on GAD65 autoantibody (GADA) status in those with young adult-onset diabetes in Sri Lanka.

METHODS

Clinical, metabolic and GADA data were available for 992 consecutively recruited individuals with diabetes aged < or =45 years (age at diagnosis 16-40 years). Participants were classified according to the following definitions: type 1 diabetes, insulin-dependent <6 months from diagnosis; latent autoimmune diabetes in adults (LADA), GADA-positive, age > or =30 years and insulin-independent > or =6 months from diagnosis; type 2 diabetes, GADA-negative and insulin-independent > or =6 months from diagnosis.

RESULTS

The median (interquartile range) age at diagnosis and diabetes duration were 33.0 (29.0-36.1) and 4.0 (1.1-7.1) years, respectively; 42.1% were male. GADA positivity was seen in 5.4% of participants (n = 54) and GADA levels negatively correlated with age at diagnosis (p < 0.0001), BMI (p < 0.0001) and time to insulin requirement (p = 0.006). Type 1 diabetes, type 2 diabetes and LADA were present in 7.0%, 89.7% and 2.6%, respectively. The remaining 0.7% of the participants were GADA-positive, insulin independent > or =6 months from diagnosis and were diagnosed at age <30 years. The metabolic syndrome and homeostasis model assessment of beta cell function (HOMA %B) were lowest in GADA-positive type 1 diabetes and increased progressively in latent autoimmune diabetes, GADA-negative type 1 diabetes and type 2 diabetes. Among those requiring insulin, 69.2% had fasting C-peptide levels in the lowest quartile, whereas only 19.5% were GADA-positive (p < 0.0001).

CONCLUSIONS/INTERPRETATION

The prevalence of GADA-positive autoimmune diabetes is low among individuals with young adult-onset diabetes in Sri Lanka. Young-onset diabetic phenotypes appear as a continuum from autoimmune type 1 diabetes to type 2 diabetes.

N of 1 trials in diabetes: making individual therapeutic decisions

N of 1 trials are single-subject, randomised, crossover studies, in which the patient serves as their own control to compare the efficacy of a treatment. They offer an alternative to large, randomised clinical trials, which have limited applicability, and empirical testing, which is arbitrary in nature. N of 1 trials are regarded as providing the highest strength of evidence for individual subject decisions. They rely upon the patient expressing preferences and making shared decisions for determining the future therapy, and may therefore lead to the successful implementation of lifestyle interventions. N of 1 trials are an optimal approach for making therapeutic decisions in chronic diseases like diabetes mellitus, where decision-making is often reliant upon arbitrary criteria and clinical judgement.

Prevalence and clinical characteristics of maternally inherited diabetes and deafness caused by the mt3243A > G mutation in young adult diabetic subjects in Sri Lanka

AIMS

The maternally inherited mt3243A > G mutation is associated with a variable clinical phenotype including diabetes and deafness (MIDD). We aimed to determine the prevalence and clinical characteristics of MIDD in a large South Asian cohort of young adult-onset diabetic patients from Sri Lanka.

METHODS

DNA was available from 994 subjects (age of diagnosis 16-40 years, age at recruitment < or = 45 years). Mutation screening was performed using a QRT-PCR method on an ABI 7900HT system using sequence-specific probes. Samples with heteroplasm > or = 5.0% were considered positive.

RESULTS

Nine (four males) mutation-positive subjects were identified (prevalence 0.9%). They were diagnosed at a younger age (25.9 +/- 4.8 years vs. 31.9 +/- 5.6 years, P = 0.002) and were lean (body mass index [BMI] 18.7 +/- 2.7 kg/m(2) vs. 24.7 +/- 4.0 kg/m(2), P < 0.001) compared to NMCs. One mutation-positive subject (11.1%) had metabolic syndrome, compared to 633 (64.3%) of NMCs. Insulin therapy within 6 months of diagnosis was used in four (44.0%) carriers compared to 6.9% of NMCs (P = 0.002). Combined screening criteria of any two of maternal history of diabetes, personal history of hearing impairment and family history of hearing impairment only identified five (55%) of the carriers, with a positive predictive value of 7.4%.

CONCLUSIONS

The prevalence of mt3243A > G mutation among young adult-onset diabetic subjects from Sri Lanka was 0.9%. Our study demonstrates that a maternal family history of diabetes and either a personal and/or family history of deafness only distinguish half of patients with MIDD from Sri Lankan subjects with young-onset diabetes.

The pregnancy-induced increase in baseline circulating growth hormone in rats is not induced by ghrelin

The elevation in baseline circulating growth hormone (GH) that occurs in pregnant rats is thought to arise from increased pituitary GH secretion, but the underlying mechanism remains unclear. Distribution, Fourier and algorithmic analyses confirmed that the pregnancy-induced increase in circulating GH in 3-week pregnant rats was due to a 13-fold increase in baseline circulating GH (P < 0.01), without any significant alteration in the parameters of episodic secretion. Electron microscopy revealed that pregnancy resulted in a reduction in the proportion of mammosomatotrophs (P < 0.01) and an increase in type II lactotrophs (P < 0.05), without any significant change in the somatotroph population. However, the density of the secretory granules in somatotrophs from 3-week pregnant rats was reduced (P < 0.05), and their distribution markedly polarised; the granules being grouped nearest the vasculature. Pituitary GH content was not increased, but steady-state GH mRNA levels declined progressively during pregnancy (P < 0.05). In situ hybridisation revealed that pregnancy was accompanied by a suppression of GH-releasing hormone mRNA expression in the arcuate nuclei (P < 0.05) and enhanced somatostatin mRNA expression in the periventricular nuclei (P < 0.05), an expression pattern normally associated with increased GH feedback. Although gastric ghrelin mRNA expression was elevated by 50% in 3-week pregnant rats (P < 0.01), circulating ghrelin, GH-secretagogue receptor mRNA expression and the GH response to a bolus i.v. injection of exogenous ghrelin were all largely unaffected during pregnancy. Although trace amounts of 'pituitary' GH could be detected in the placenta with radioimmunoassay, significant GH-immunoreactivity could not be observed by immunohistochemistry, indicating that rat placenta itself does not produce 'pituitary' GH. Although not excluding the possibility that the pregnancy-associated elevation in baseline circulating GH could arise from alternative extra-pituitary sources (e.g. the ovary), our data indicate that this phenomenon is most likely to result from a direct alteration of somatotroph function.

A low-carbohydrate diet is more effective in reducing body weight than healthy eating in both diabetic and non-diabetic subjects

BACKGROUND

Low-carbohydrate diets are effective for weight reduction in people without diabetes, but there is limited evidence for people with Type 2 diabetes. Aims To assess the impact of a low-carbohydrate diet on body weight, glycated haemoglobin (HbA(1c)), ketone and lipid levels in diabetic and non-diabetic subjects.

METHODS

Thirteen Type 2 diabetic subjects (on diet or metformin) and 13 non-diabetic subjects were randomly allocated to either a low-carbohydrate diet (< or = 40 g carbohydrate/day) or a healthy-eating diet following Diabetes UK nutritional recommendations and were seen monthly for 3 months. Subjects (25% male) were (mean +/- sd) age 52 +/- 9 years, weight 96.3 +/- 16.6 kg, body mass index 35.1 kg/m(2), HbA(1c) 6.6 +/- 1.1%, total cholesterol 5.1 +/- 1.1 mmol/l, high-density lipoprotein cholesterol 1.3 +/- 0.4 mmol/l, low-density lipoprotein cholesterol 3.1 +/- 0.9 mmol/l, triglycerides (geometric mean) 1.55 (1.10, 2.35) mmol/l and ketones range 0.0-0.2 mmol/l.

RESULTS

Analysis was by intention to treat with last observation carried forward. Twenty-two of the participants (85%) completed the study. Weight loss was greater (6.9 vs. 2.1 kg, P = 0.003) in the low-carbohydrate group, with no difference in changes in HbA(1c), ketone or lipid levels.

CONCLUSIONS

The diet was equally effective in those with and without diabetes.

A method for assessing quality of control from glucose profiles

AIM

As the practice of multiple assessments of glucose concentration throughout the day increases for people with diabetes, there is a need for an assessment of glycaemic control weighted for the clinical risks of both hypoglycaemia and hyperglycaemia.

METHODS

We have developed a methodology to report the degree of risk which a glycaemic profile represents. Fifty diabetes professionals assigned risk values to a range of 40 blood glucose concentrations. Their responses were summarised and a generic function of glycaemic risk was derived. This function was applied to patient glucose profiles to generate an integrated risk score termed the Glycaemic Risk Assessment Diabetes Equation (GRADE). The GRADE score was then reported by use of the mean value and the relative percent contribution to the weighted risk score from the hypoglycaemic, euglycaemic, hyperglycaemic range, respectively, e.g. GRADE (hypoglycaemia%, euglycaemia%, hyperglycaemia%).

RESULTS

The GRADE scores of indicative glucose profiles were as follows: continuous glucose monitoring profile non-diabetic subjects GRADE = 1.1, Type 1 diabetes continuous glucose monitoring GRADE = 8.09 (20%, 8%, 72%), Type 2 diabetes home blood glucose monitoring GRADE = 9.97 (2%, 7%, 91%).

CONCLUSIONS

The GRADE score of a glucose profile summarises the degree of risk associated with a glucose profile. Values < 5 correspond to euglycaemia. The GRADE score is simple to generate from any blood glucose profile and can be used as an adjunct to HbA1c to report the degree of risk associated with glycaemic variability.

A method for assessing quality of control from glucose profiles

AIM

As the practice of multiple assessments of glucose concentration throughout the day increases for people with diabetes, there is a need for an assessment of glycaemic control weighted for the clinical risks of both hypoglycaemia and hyperglycaemia.

METHODS

We have developed a methodology to report the degree of risk which a glycaemic profile represents. Fifty diabetes professionals assigned risk values to a range of 40 blood glucose concentrations. Their responses were summarised and a generic function of glycaemic risk was derived. This function was applied to patient glucose profiles to generate an integrated risk score termed the Glycaemic Risk Assessment Diabetes Equation (GRADE). The GRADE score was then reported by use of the mean value and the relative percent contribution to the weighted risk score from the hypoglycaemic, euglycaemic, hyperglycaemic range, respectively, e.g. GRADE (hypoglycaemia%, euglycaemia%, hyperglycaemia%).

RESULTS

The GRADE scores of indicative glucose profiles were as follows: continuous glucose monitoring profile non-diabetic subjects GRADE = 1.1, Type 1 diabetes continuous glucose monitoring GRADE = 8.09 (20%, 8%, 72%), Type 2 diabetes home blood glucose monitoring GRADE = 9.97 (2%, 7%, 91%).

CONCLUSIONS

The GRADE score of a glucose profile summarises the degree of risk associated with a glucose profile. Values < 5 correspond to euglycaemia. The GRADE score is simple to generate from any blood glucose profile and can be used as an adjunct to HbA1c to report the degree of risk associated with glycaemic variability.

Optical antenna arrays in the visible range

We report on experimental observations of highly collimated beams of radiation generated when a periodic sub-wavelength grating interacts with surface bound plasmon-polariton modes of a thin gold film. We find that the radiation process can be fully described in terms of interference of emission from a dipole antenna array and modeling the structure in this way enables the far-field radiation pattern to be predicted. The directionality, multiplicity and divergence of the beams can be completely described within this framework. Essential to the process are the surface plasmon excitations: these are the driving mechanism behind the beam formation, phase-coupling radiation from the periodic surface structure and thus imposing a spatial coherence. Detailed fitting of the experimental and modeled data indicates the presence of scattering events involving the interaction of two surface plasmon polariton modes.

The UK Diabetes Research Network--an opportunity and a challenge

The Department of Health has funded a national diabetes network to support clinical research. The network will facilitate recruitment into clinical trials and has been widely welcomed by clinicians. However, if the network is to reach its full potential, all those involved will need to advocate a change in attitude towards clinical trials and research, encouraging participation and contribution of data. Clinicians need to be willing to take a proactive view about research studies, and to encourage patients to adopt a positive and altruistic attitude towards trial participation. The future of trials and other important clinical research in the UK may depend on it.