Loss of tetraspanin-7 expression reduces pancreatic ß-cell exocytosis Ca2+ sensitivity but has limited effect on systemic metabolism.

BACKGROUND: Tetraspanin-7 (Tspan7) is an islet autoantigen involved in autoimmune type 1 diabetes and known to regulate ß-cell L-type Ca2+ channel activity. However, the role of Tspan7 in pancreatic ß-cell function is not yet fully understood. METHODS: Histological analyses were conducted using immunostaining. Whole-body metabolism was tested using glucose tolerance test. Islet hormone secretion was quantified using static batch incubation or dynamic perifusion. ß-cell transmembrane currents, electrical activity and exocytosis were measured using whole-cell patch-clamping and capacitance measurements. Gene expression was studied using mRNA-sequencing and quantitative PCR. RESULTS: Tspan7 is expressed in insulin-containing granules of pancreatic ß-cells and glucagon-producing α-cells. Tspan7 knockout mice (Tspan7y/- mouse) exhibit reduced body weight and ad libitum plasma glucose but normal glucose tolerance. Tspan7y/- islets have normal insulin content and glucose- or tolbutamide-stimulated insulin secretion. Depolarisation-triggered Ca2+ current was enhanced in Tspan7y/- ß-cells, but ß-cell electrical activity and depolarisation-evoked exocytosis were unchanged suggesting that exocytosis was less sensitive to Ca2+ . TSPAN7 knockdown (KD) in human pseudo-islets led to a significant reduction in insulin secretion stimulated by 20 mM K+ . Transcriptomic analyses show that TSPAN7 KD in human pseudo-islets correlated with changes in genes involved in hormone secretion, apoptosis and ER stress. Consistent with rodent ß-cells, exocytotic Ca2+ sensitivity was reduced in a human ß-cell line (EndoC-ßH1) following Tspan7 KD. CONCLUSION: Tspan7 is involved in the regulation of Ca2+ -dependent exocytosis in ß-cells. Its function is more significant in human ß-cells than their rodent counterparts.

A Safety Evaluation of the Resumption of Elective Orthopaedic Services in Higher Risk Patients During the COVID-19 Pandemic.

Introduction The COVID-19 pandemic has caused mass disruption to all aspects of society, with elective orthopaedics not spared. The pandemic has the potential to cause a tsunami of health burden in the community if elective services are not resumed to pre-pandemic levels of activity. Studies have shown that elective orthopaedics can be safely carried out in a COVID-19 free hospital. This study reviewed the transition in operating at an independent COVID-19 free hospital to an NHS hospital concurrently treating patients with COVID-19. Methods A strategy of phased relaxation of clinical comorbidity criteria was followed. Patients from the orthopaedic waiting list were selected according to these criteria and observed recommended preoperative isolation protocols. Operations were undertaken in the independent sector under the COVID-19 contract and the NHS site. Patients were assessed from all phases in the resumption of services. In-hospital and post-operative complications with specific enquiries regarding the development of COVID-19 symptoms or the need and outcome for COVID-19 testing at 14 days and six weeks was recorded. Results This study included 263 patients, of which 155 were female. The mean age of patients was 52.45. The mean BMI of all patients was 29.1 kg/m2. Additionally, 124 patients were American Society of Anesthesiologists (ASA) grade 1, 117 ASA grade 2 and 22 ASA grade 3 and 167 patients underwent a major operation, with total hip replacement being the most common operation. There were no in-hospital complications. No patients had a positive test result or symptoms of COVID-19 in the six-week post-operative period. Conclusion In summary, we demonstrated that elective orthopaedic surgery can be safely undertaken via a green pathway in a higher risk patient cohort when COVID-19 is prevalent in the community.