A new strain of human coronaviruses (hCoVs), Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), has been identified to be responsible for the current outbreak of the coronavirus disease 2019 (COVID-19). Though major symptoms are primarily generated from the respiratory system, neurological symptoms are being reported in some of the confirmed cases, raising concerns of its potential for intracranial invasion and neurological manifestations, both in the acute phase and in the long-term. At present, it remains unclear the extent to which SARS-CoV-2 is present in the brain, and if so, its pathogenic role in the central nervous system (CNS). Evidence for neuroinvasion and neurovirulence of hCoVs has been recognised in animal and human studies. Given that SARS-CoV-2 belongs to the same family and shares characteristics in terms of receptor binding properties, it is worthwhile exploring its potential CNS manifestations. This review summarises previous findings from hCoVs in relation to the CNS, and compares these with the new strain, aiming to provide a better understanding of the effects of SARS-CoV-2 on the CNS.

BACKGROUND AND PURPOSEThe neutral amino acid transporter B 0 AT1 (SLC6A19) has recently been identified as a possible target to treat type 2 diabetes and related disorders. B 0 AT1 mediates the Na + -dependent uptake of all neutral amino acids. For surface expression and catalytic activity, B 0 AT1 requires coexpression of collectrin (TMEM27). In this study, we established tools to identify and evaluate novel inhibitors of B 0 AT1. EXPERIMENTAL APPROACHA CHO-based cell line was generated, stably expressing collectrin and B 0 AT1. Using this cell line, a high-throughput screening assay was developed, which uses a fluorescent dye to detect depolarisation of the cell membrane during amino acid uptake via B 0 AT1. In parallel to these functional assays, we ran a computational compound screen using AutoDock4 and a homology model of B 0 AT1 based on the high-resolution structure of the highly homologous Drosophila dopamine transporter. KEY RESULTSWe characterized a series of novel inhibitors of the B 0 AT1 transporter. Benztropine was identified as a competitive inhibitor of the transporter showing an IC 50 of 44 ± 9 μM. The compound was selective with regard to related transporters and blocked neutral amino acid uptake in inverted sections of mouse intestine. CONCLUSION AND IMPLICATIONSThe tools established in this study can be widely used to identify new transport inhibitors. Using these tools, we were able to identify compounds that can be used to study epithelial transport, to induce protein restriction, or be developed further through medicinal chemistry. AbbreviationsCHO-BC, CHO cells stably transfected with B 0 AT1 and collectrin; FGF21, fibroblast growth factor 21; GIP, gastric inhibitory peptide; GLP-1, glucagon-like peptide 1; MW, molecular weight; NMDG, N-methyl-D-glucamine

Background: Collectrin is required for membrane expression of the broad neutral amino acid transporters (B 0 AT1 and -3). Results: Collectrin activates B

Research System-L transporters and the pancreatic β-cell AbstractThe branched-chain amino acids (BCAA) leucine, isoleucine and valine, are essential amino acids that play a critical role in cellular signalling and metabolism. They acutely stimulate insulin secretion and activate the regulatory serine/threonine kinase mammalian target of rapamycin complex 1 (mTORC1), a kinase that promotes increased β-cell mass and function. The effects of BCAA on cellular function are dependent on their active transport into the mammalian cells via amino acid transporters and thus the expression and activity of these transporters likely influence β-cell signalling and function. In this report, we show that the System-L transporters are required for BCAA uptake into clonal β-cell lines and pancreatic islets, and that these are essential for signalling to mTORC1. Further investigation revealed that the System-L amino acid transporter 1 (LAT1) is abundantly expressed in the islets, and that knockdown of LAT1 using siRNA inhibits mTORC1 signalling, leucine-stimulated insulin secretion and islet cell proliferation. In summary, we show that the LAT1 is required for regulating β-cell signalling and function in islets and thus may be a novel pharmacological/nutritional target for the treatment and prevention of type 2 diabetes.

Background and purposeSouth Western Sydney comprises of a culturally and linguistically diverse (CALD) and lower socioeconomic status population group within the state of New South Wales. Geographic location and sociodemographic factors play important roles in access to healthcare and may be crucial in the success of time-critical acute stroke intervention. The aim of this study was to examine the trends in the delayed presentation to emergency department (ED) and identify factors associated with prehospital delay for an acute stroke/transient ischaemic attack (TIA) at a comprehensive stroke centre.MethodsPatient health-related data were extracted for stroke/TIA discharges for the period 2009–2017. Electronic medical record data were used to determine sociodemographic characteristics and prehospital factors, and their associations with delayed presentation≥4.5 hours from stroke onset were studied.ResultsDuring the 9-year period, population-adjusted stroke/TIA discharge rates increased from 540 to 676 per 100 000. A significant reduction in the proportion of patients presenting to ED<4.5 hours (56% in 2009 versus 46% in 2017, p<0.001) was observed. Younger patients aged 55–64 and 65–74 years, those belonging to Polynesia, South Asia and Mainland Southeast Asia, and those not using state ambulance as the mode of arrival to the hospital were at increased risk of prehospital delay.ConclusionsComprehensive reappraisal of educational programmes for early stroke recognition is required in our region due to delayed ED presentations of younger and specific CALD communities of stroke/TIA patients.

Recent studies have established that dietary protein restriction improves metabolic health and glucose homeostasis. SLC6A19 (B0AT1) is the major neutral amino acid transporter in the intestine and carries out the bulk of amino acid absorption from the diet. Mice lacking SLC6A19 show signs of protein restriction, have improved glucose tolerance, and are protected from diet-induced obesity. Pharmacological blockage of this transporter could be used to induce protein restriction and to treat metabolic diseases such as type 2 diabetes. A few novel inhibitors of SLC6A19 have recently been identified using in vitro compound screening, but it remains unclear whether these compounds block the transporter in vivo. To evaluate the efficacy of SLC6A19 inhibitors biomarkers are required that can reliably detect successful inhibition of the transporter in mice. A gas chromatography mass spectrometry (GC-MS)-based untargeted metabolomics approach was used to discriminate global metabolite profiles in plasma, urine and faecal samples from SLC6A19ko and wt mice. Due to inefficient absorption in the intestine and lack of reabsorption in the kidney, significantly elevated amino acids levels were observed in urine and faecal samples. By contrast, a few neutral amino acids were reduced in the plasma of male SLC6A19ko mice as compared to other biological samples. Metabolites of bacterial protein fermentation such as p-cresol glucuronide and 3-indole-propionic acid were more abundant in SLC6A19ko mice, indicating protein malabsorption of dietary amino acids. Consistently, plasma appearance rates of [14C]-labelled neutral amino acids were delayed in SLC6A19ko mice as compared to wt after intra-gastric administration of a mixture of amino acids. Receiver operating characteristic (ROC) curve analysis was used to validate the potential use of these metabolites as biomarkers. These findings provide putative metabolite biomarkers that can be used to detect protein malabsorption and the inhibition of this transporter in intestine and kidney.

Lack of B 0 AT1 (SLC6A19) partially protects mice against the onset of non-alcoholic steatohepatitis (NASH). To achieve a similar outcome through pharmacological treatment, we improved previously identified inhibitors of B 0 AT1 by medicinal chemistry and identified second generation inhibitors by high through-put screening. Modified diarylmethine compounds inhibited B 0 AT1 with IC 50 values ranging from 8-90 mM. A second generation of inhibitors was derived from high-throughput screening and showed higher affinity (IC 50 of 1-15 mM) and strong selectivity against amino acid transporters with similar substrate specificity, such as ASCT2 (SLC1A5) and LAT1 (SLC7A5). All compounds were unrelated to B 0 AT1 substrates, but were likely to bind in the vicinity of the substrate binding site.

Glucagon-like peptide 1 receptor (GLP1R) agonists, such as exendin-4, potentiate glucosestimulated insulin secretion and are currently used in the management of type 2 diabetes. Interestingly, GLP1R agonists also have the ability to augment b-cell mass. In this report, we provide evidence that in the presence of glucose, exendin-4 stimulates rodent islet cell DNA replication via the activation of ribosomal protein S6 kinase 1 (S6K1) and that this is mediated by the protein kinase B (PKB)-dependent activation of mTOR complex 1 (mTORC1). We show that activation of this pathway is caused by the autocrine or paracrine activation of the IGF1 receptor (IGF1R), as siRNA-mediated knockdown of the IGF1R effectively blocked exendin-4-stimulated PKB and mTORC1 activation. In contrast, pharmacological inactivation of the epidermal growth factor receptor has no discernible effect on exendin-4-stimulated PKB or mTORC1 activation. Therefore, we conclude that GLP1R agonists stimulate b-cell proliferation via the PKB-dependent stimulation of mTORC1/S6K1 whose activation is mediated through the autocrine/paracrine activation of the IGF1R. This work provides a better understanding of the molecular basis of GLP1 agonist-induced b-cell proliferation which could potentially be exploited in the identification of novel drug targets that increase b-cell mass.