Key interactions by conserved polar amino acids located at the transmembrane helical boundaries in Class B GPCRs modulate activation, effector specificity and biased signalling in the glucagon-like peptide-1 receptor

Class B GPCRs can activate multiple signalling effectors with the potential to exhibit biased agonism in response to ligand stimulation. Previously, we highlighted key TM domain polar amino acids that were crucial for the function of the GLP-1 receptor, a key therapeutic target for diabetes and obesity. Using a combination of mutagenesis, pharmacological characterisation, mathematical and computational molecular modelling, this study identifies additional highly conserved polar residues located towards the TM helical boundaries of Class B GPCRs that are important for GLP-1 receptor stability and/or controlling signalling specificity and biased agonism. This includes (i) three positively charged residues (R3.30227, K4.64288, R5.40310) located at the extracellular boundaries of TMs 3, 4 and 5 that are predicted in molecular models to stabilise extracellular loop 2, a crucial domain for ligand affinity and receptor activation; (ii) a predicted hydrogen bond network between residues located in TMs 2 (R2.46176), 6 (R6.37348) and 7 (N7.61406 and E7.63408) at the cytoplasmic face of the receptor that is important for stabilising the inactive receptor and directing signalling specificity, (iii) residues at the bottom of TM 5 (R5.56326) and TM6 (K6.35346 and K6.40351) that are crucial for receptor activation and downstream signalling; (iv) residues predicted to be involved in stabilisation of TM4 (N2.52182 and Y3.52250) that also influence cell signalling. Collectively, this work expands our understanding of peptide-mediated signalling by the GLP-1 receptor

Thiamine Prescribing Practices for Adult Patients Admitted to an Internal Medicine Service

ABSTRACTBackground: Thiamine (vitamin B1) is an essential cofactor responsible for the breakdown of glucose, and its deficiency is associated with Wernicke encephalopathy (WE). There is a lack of evidence from systematic studies on the optimal dosing of thiamine for WE.Objectives: The primary objective was to describe the prescribing patterns for IV thiamine in adult patients admitted to a large teaching hospital. The secondary objective was to evaluate the clinical resolution of WE symptoms (confusion, ataxia, and/or ocular motor abnormalities) inrelation to the dose of IV thiamine prescribed.Methods: A retrospective design was used to review data for adult patients admitted to an internal medicine service from June 1, 2014, to June 30, 2015. All patients included in the study received IV thiamine: low-dose therapy was defined as 100 mg IV daily and high-dose therapy was defined as dosage greater than 100 mg IV daily.Results: A total of 141 patients were included; low-dose thiamine was prescribed for 115 (81.6%) and high-dose thiamine for 26 (18.4%). Patients for whom high-dose thiamine was prescribed were more likely to be those in whom a diagnosis of WE was being considered (12/26[46.2%] versus 5/115 [4.3%], p < 0.001). Of the total 219 IV thiamine doses ordered, 180 (82.2%) were for 100 mg, and 143 (65.3%) were prescribed for once-daily administration. There was no statistically significant difference in the time to resolution of WE symptoms for patients receiving high-dose versus low-dose thiamine.Conclusions: A wide variety of thiamine prescribing patterns were noted. This study did not show a difference in time to resolution of WE symptoms in relation to the dose of IV thiamine. Additional large-scale studies are required to determine the optimal dosing of thiamine for WE.RÉSUMÉContexte : La thiamine (vitamine B1) est un cofacteur essentiel responsable du métabolisme du glucose. Une carence en thiamine est associée à l’encéphalopathie de Wernicke (EW). Or, on observe une absence de données probantes provenant d’analyses systématiques portant sur laposologie optimale de thiamine dans le traitement de l’EW.Objectifs : L’objectif principal était de décrire les habitudes de prescription de thiamine à administrer par voie intraveineuse chez les patients adultes admis dans un important hôpital universitaire. L’objectif secondaire était d’évaluer la disparition clinique des symptômes de l’EW (confusion, ataxie ou troubles moteurs oculaires) en fonction de la dose prescrite de thiamine à administrer par voie intraveineuse.Méthodes : Un plan d’étude rétrospectif a été utilisé pour étudier les données concernant les patients adultes admis à un service de médecine interne entre le 1er juin 2014 et le 30 juin 2015. Tous les patients à l’étude ont reçu de la thiamine par voie intraveineuse : le traitement à faible dose était de 100 mg par jour et le traitement à dose élevée excédait 100 mg par jour.Résultats : Au total, 141 patients ont été admis à l’étude; l’on a prescrit une faible dose de thiamine à 115 (81,6 %) d’entre eux et une dose élevée aux 26 (18,4 %) autres. Les patients qui se sont vus prescrire une dose élevée de thiamine étaient vraisemblablement ceux pour qui l’on envisageait un diagnostic d’EW (12/26 [46,2 %] contre 5/115 [4,3 %], p < 0,001). Pour l’ensemble des 219 doses prescrites de thiamine à administrer par voie intraveineuse, 180 (82,2 %) étaient de 100 mg et 143 (65,3 %) devaient être injectées à une fréquence uniquotidienne. On n’a relevé aucune différence statistiquement significative quant au temps de disparition des symptômes de l’EW entre les patients ayant reçu une dose élevée de thiamine et ceux en ayant reçu une faible dose.Conclusions : On a noté une grande variété d’habitudes de prescription de la thiamine. La présente étude n’a pas montré que la dose de thiamine administrée par voie intraveineuse changeait le temps nécessaire à la disparition des symptômes de l’EW. Il est nécessaire de mener de plus amples études à grande échelle afin de déterminer quelle est la posologie optimale de thiamine dans le traitement de l’EW

Real-life experience with IV fosfomycin in Canada: Results from the Canadian LEadership on Antimicrobial Real-life usage (CLEAR) registry

ABSTRACT: Objectives: Data on the use of intravenous (IV) fosfomycin in Canada are limited. Using data captured by the Canadian LEadership on Antimicrobial Real-life usage (CLEAR) registry, we report the use of IV fosfomycin in Canadian patients. Methods: The CLEAR registry uses the web-based data management program, REDCapTM (https://rcsurvey.radyfhs.umanitoba.ca/surveys/?s=F7JXNDFXEF) to facilitate clinicians’ entering of details associated with their clinical experiences using IV fosfomycin. Results: Data were available for 59 patients treated with IV fosfomycin. The most common infections treated were: bacteraemia or sepsis (25.4% of patients), complicated urinary tract infection (20.3%), ventilator-associated bacterial pneumonia (18.6%), and hospital-acquired pneumonia (13.6%). IV fosfomycin was used to treat Gram-negative (88.1%) and Gram-positive (10.2%) infections. The most common pathogens treated were carbapenem-resistant Enterobacterales (44.1%), multidrug-resistant Pseudomonas aeruginosa (18.6%), vancomycin-resistant Enterococcus faecium (5.1%), and methicillin-resistant Staphylococcus aureus (3.4%). IV fosfomycin was primarily used due to resistance to initially prescribed therapies (69.5%), frequently in combination with other agents (86.4%). Microbiological success (eradication/presumed eradication) occurred in 77.4% of patients, and clinical success (clinical cure/improvement) occurred in 62.5%. Overall, 15.3% of patients died because of their infection. Adverse effects were not documented in 73.1% of patients, and no patient discontinued therapy because of an adverse effect. Conclusions: In Canada, IV fosfomycin is used primarily as directed therapy to treat a variety of severe infections caused by Gram-negative and Gram-positive bacteria. It is primarily used in patients infected with bacteria resistant to other agents and as part of combination therapy. Its use is associated with relatively high microbiological and clinical cure rates, and it has an excellent safety profile