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Feto-placental and coronary endothelial genes implicated in miscarriage, congenital heart disease and stillbirth, a systematic review and meta-analysis.
The first trimester placenta is very rarely investigated for placental vascular formation in developmental or diseased contexts. Defects in placental formation can cause heart defects in the fetus, and vice versa. Determining the causality is therefore difficult as both organs develop concurrently and express many of the same genes. Here, we performed a systematic review to determine feto-placental and coronary endothelial genes implicated in miscarriages, stillbirth and congenital heart defects (CHD) from human genome wide screening studies. 4 single cell RNAseq datasets from human first/early second trimester cardiac and placental samples were queried to generate a list of 1187 endothelial genes. This broad list was cross-referenced with genes implicated in the pregnancy disorders above. 39 papers reported feto-placental and cardiac coronary endothelial genes, totalling 612 variants. Vascular gene variants were attributed to the incidence of miscarriage (8 %), CHD (4 %) and stillbirth (3 %). The most common genes for CHD (NOTCH, DST, FBN1, JAG1, CHD4), miscarriage (COL1A1, HERC1), and stillbirth (AKAP9, MYLK), were involved in blood vessel and cardiac valve formation, with roles in endothelial differentiation, angiogenesis, extracellular matrix signaling, growth factor binding and cell adhesion. NOTCH1, AKAP12, CHD4, LAMC1 and SOS1 showed greater relative risk ratios with CHD. Many of the vascular genes identified were expressed highly in both placental and heart EC populations. Both feto-placental and cardiac vascular genes are likely to result in poor endothelial cell development and function during human pregnancy that leads to higher risk of miscarriage, congenital heart disease and stillbirth.
Evaluation of Cerebrospinal Fluid α-Synuclein Seed Amplification Assay in Progressive Supranuclear Palsy and Corticobasal Syndrome.
BACKGROUND: Seed amplification assay (SAA) testing has been developed as a biomarker for the diagnosis of α-synuclein-related neurodegenerative disorders. OBJECTIVE: The objective of this study was to assess the rate of α-synuclein SAA positivity in progressive supranuclear palsy (PSP) and corticobasal syndrome (CBS) and to analyze clinical and pathological features of SAA-positive and -negative cases. METHODS: A total of 96 cerebrospinal fluid samples from clinically diagnosed PSP (n = 59) and CBS (n = 37) cases were analyzed using α-synuclein SAA. RESULTS: Six of 59 (10.2%) PSP cases were α-synuclein SAA positive, including one case who was MSA-type positive. An exploratory analysis showed that PSP cases who were Parkinson's disease-type positive were older and had a shorter disease duration compared with SAA-negative cases. In contrast, 11 of 37 (29.7%) CBS cases were α-synuclein SAA positive, including two cases who were MSA-type positive. CONCLUSIONS: Our results suggest that α-synuclein seeds can be detected in PSP and CBS using a cerebrospinal fluid α-synuclein SAA, and in PSP this may impact on clinical course. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.
Loss of electrical β-cell to δ-cell coupling underlies impaired hypoglycaemia-induced glucagon secretion in type-1 diabetes.
Diabetes mellitus involves both insufficient insulin secretion and dysregulation of glucagon secretion1. In healthy people, a fall in plasma glucose stimulates glucagon release and thereby increases counter-regulatory hepatic glucose production. This response is absent in many patients with type-1 diabetes (T1D)2, which predisposes to severe hypoglycaemia that may be fatal and accounts for up to 10% of the mortality in patients with T1D3. In rats with chemically induced or autoimmune diabetes, counter-regulatory glucagon secretion can be restored by SSTR antagonists4-7 but both the underlying cellular mechanism and whether it can be extended to humans remain unestablished. Here, we show that glucagon secretion is not stimulated by low glucose in isolated human islets from donors with T1D, a defect recapitulated in non-obese diabetic mice with T1D. This occurs because of hypersecretion of somatostatin, leading to aberrant paracrine inhibition of glucagon secretion. Normally, KATP channel-dependent hyperpolarization of β-cells at low glucose extends into the δ-cells through gap junctions, culminating in suppression of action potential firing and inhibition of somatostatin secretion. This 'electric brake' is lost following autoimmune destruction of the β-cells, resulting in impaired counter-regulation. This scenario accounts for the clinical observation that residual β-cell function correlates with reduced hypoglycaemia risk8.
The age-dependent development of abnormal cardiac metabolism in the peroxisome proliferator-activated receptor α-knockout mouse.
BACKGROUND AND AIMS: Peroxisome proliferator-activated receptor α (PPARα) is crucial for regulating cardiac β-oxidation in the heart, liver, and kidney. Ageing can induce cardiac metabolic alterations, but the role of PPARα has not been extensively characterised. The aim of this research was to investigate the role of PPARα in the aged heart. METHODS: Hyperpolarized [1-13C]pyruvate was used to evaluate in vivo cardiac carbohydrate metabolism in fed and fasted young (3 months) and old (20-22 months) PPARα knockout (KO) mice versus controls. Cine MRI assessed cardiac structural and functional changes. Cardiac tissue analysis included qRT-PCR and Western blotting for Pparα, medium chain acyl-CoA dehydrenase (MCAD), uncoupling protein (UCP) 3, glucose transporter (GLUT) 4 and PDH kinase (PDK) 1,2, and 4 expression. RESULTS: PPARα-KO hearts from both young and old mice showed significantly reduced Pparα mRNA and a 58-59 % decrease in MCAD protein levels compared to controls. Cardiac PDH flux was similar in young control and PPARα-KO mice but 96 % higher in old PPARα-KO mice. Differences between genotypes were consistent in fed and fasted states, with reduced PDH flux when fasted. Increased PDH flux was accompanied by a 179 % rise in myocardial GLUT4 protein. No differences in PDK 1, 2, or 4 protein levels were observed between fed groups, indicating the increased PDH flux in aged PPARα-KO mice was not due to changes in PDH phosphorylation. CONCLUSIONS: Aged PPARα-KO mice demonstrated higher cardiac PDH flux compared to controls, facilitated by increased myocardial GLUT4 protein levels, leading to enhanced glucose uptake and glycolysis.
Optogenetic Determination of Dynamic and Cell-Type-Specific Inhibitory Reversal Potentials.
The reversal potential refers to the membrane potential at which the net current flow through a channel reverses direction. The reversal potential is determined by transmembrane ion gradients and, in turn, determines how the channel's activity will affect the membrane potential. Traditional investigation into the reversal potential of inhibitory ligand-gated ion channels (EInh) has relied upon the activation of endogenous receptors, such as the GABA-A receptor (GABAAR). There are, however, challenges associated with activating endogenous receptors, including agonist delivery, isolating channel responses, and the effects of receptor saturation and desensitization. Here, we demonstrate the utility of using a light-gated anion channel, stGtACR2, to probe EInh in the rodent brain. Using mice of both sexes, we demonstrate that the properties of this optically activated channel make it a suitable proxy for studying GABAAR receptor-mediated inhibition. We validate this agonist-independent optogenetic strategy in vitro and in vivo and further show how it can accurately capture differences in EInh dynamics following manipulations of endogenous ion fluxes. This allows us to explore distinct resting EInh differences across genetically defined neuronal subpopulations. Using this approach to challenge ion homeostasis mechanisms in neurons, we uncover cell-specific EInh dynamics that are supported by the differential expression of endogenous ion handling mechanisms. Our findings therefore establish an effective optical strategy for revealing novel aspects of inhibitory reversal potentials and thereby expand the repertoire of optogenetics.
A Facile Method to Quantify Synthetic Peptide Concentrations on Biomaterials.
While it is well understood that peptides can greatly improve cell-material interactions, it is often challenging to determine the concentration of the peptide which decorates a material. Herein, we describe a straightforward method using readily, synthetically accessible Fmoc peptides and commercially available reagents to measure the concentration of peptides on nanoparticles, surfaces, and hydrogels. To achieve this, the Fmoc protecting group from immobilized peptides is removed under optimized basic conditions. The dibenzofulvene released can be quantified by HPLC or UV-vis spectroscopy, enabling a direct experimental measurement of the concentration of the peptide. We show that we can measure the concentration of a BMP-2 peptide mimic on a hydrogel to determine the concentration required to stimulate osteogenesis of human mesenchymal stem cells. We envision that this methodology will enable a more thorough understanding of the concentration of synthetic peptides decorated on many biomaterials (e.g., nanoparticles, surfaces, hydrogels) to improve deconvolution of the interactions at the cell-material interface.
The release of GLP-1 from gut L cells is inhibited by low extracellular pH.
OBJECTIVE: The intestinal luminal pH profile varies from stomach to rectum and becomes disrupted in diseases. However, little is known about the pH dependence of incretin hormone secretion, with most in vitro studies having failed to consider this modulatory factor or having used nonphysiological buffer systems. Here, we report the extracellular pH (pHe) dependence of glucagon-like peptide-1 (GLP-1) exocytosis from L cells. METHODS: The pHe dependence of GLP-1 release from GLUTag cells and murine ex vivo primary gut cultures was detected by ELISA. GLP-1 release was measured over a range of pHe under a physiological (CO2/HCO3 -) buffering regime and in its absence (HEPES buffer). The relationship between intracellular pH (pHi) and pHe was mapped given that at least some component of pH sensitivity is likely to be intracellular. RESULTS: GLP-1 secretion from L cells was pHe-dependent and stimulated under alkaline conditions. In the absence of glucose or extracellular calcium, secretion remained at a pHe-insensitive baseline. pHi followed changes in pHe, but the relationship was offset to more alkaline levels in the absence of CO2/HCO3 - buffer and became shallower if [Cl-] changes that normally accompany [HCO3 -] changes were compensated iso-osmotically with gluconate. CONCLUSIONS: GLP-1 secretion is sensitive to pHe and the buffer present. Exploiting this mechanism therapeutically may benefit patients with obesity.