Background G protein-coupled receptors (GPCR) are well-characterized regulators of a plethora of physiological functions among them the modulation of adipogenesis and adipocyte function. The class of Adhesion GPCR (aGPCR) and their role in adipose tissue, however, is poorly studied. With respect to the demand for novel targets in obesity treatment, we present a comprehensive study on the expression and function of this enigmatic GPCR class during adipogenesis and in mature adipocytes. Methods The expression of all aGPCR representatives was determined by reanalyzing RNA-Seq data and by performing qPCR in different mouse and human adipose tissues under low-and high-fat conditions. The impact of aGPCR expression on adipocyte differentiation and lipid accumulation was studied by siRNA-mediated knockdown of all expressed members of this receptor class. The biological characteristics and function of mature adipocytes lacking selected aGPCR were analyzed by mass spectrometry and biochemical methods (lipolysis, glucose uptake, adiponectin secretion). Results More than ten aGPCR are significantly expressed in visceral and subcutaneous adipose tissues and several aGPCR are differentially regulated under high-caloric conditions in human and mouse. Receptor knockdown of six receptors resulted in an impaired adipogenesis indicating their expression is essential for proper adipogenesis. The altered lipid composition was studied in more detail for two representatives, ADGRG2/GPR64 and ADGRG6/GPR126. While GPR126 is mainly involved in adipocyte differentiation, GPR64 has an additional role in mature adipocytes by regulating metabolic processes. Conclusions Adhesion GPCR are significantly involved in qualitative and quantitative adipocyte lipid accumulation and can control lipolysis. Factors driving adipocyte formation and function are governed by signaling pathways induced by aGPCR yielding these receptors potential targets for treating obesity.
Background: Staphylococcus aureus remains a common cause of ventilatorassociated pneumonia, with little change in infection rates over the past 15 years. This phase 2 study evaluated suvratoxumab, an anti-alpha-toxin monoclonal antibody, in reducing incidence of S. aureus pneumonia in intensive care unit (ICU) subjects on mechanical ventilation (MV). Methods:We did a multicenter, single-dose, randomized, placebo-controlled, doubleblind, phase 2 pilot trial in 9 countries. Eligible subjects were patients in an ICU ≥18 years of age, currently intubated and on MV, positive for S. aureus lower respiratory tract (LRT) colonization as assessed by polymerase chain reaction (PCR) of endotracheal aspirate, and with no diagnosis of new-onset pneumonia. Subjects were excluded if they had confirmed or suspected acute ongoing staphylococcal disease; had received anti-S. aureus antibiotics for >48 hours; had a CPIS ≥6, APACHE-II score ≥25, a SOFA score ≥9; or had active pulmonary disease that would impair the ability to diagnose pneumonia. Subjects were screened for S. aureus lower respiratory tract (LRT) colonization using real-time polymerase chain reaction (PCR).Colonized subjects were randomly assigned 1:1:1 to a single intravenous infusion of suvratoxumab 2000 mg, 5000 mg or placebo. Randomization was stratified by country and by whether subjects received anti-S. aureus systemic antibiotic therapy. Based on pre-defined PK criteria, the 2000 mg arm was discontinued upon the recommendation of the data monitoring committee at an interim analysis. Primary efficacy endpoint was incidence of S. aureus pneumonia, adjudicated by a blinded independent panel, through 30 days post dose in the modified intent-to-treat study population. Primary safety endpoints were Francois et al. Suvratoxumab Ph2 (NCT02296320) D3 5 treatment-emergent AEs assessed through 30 and 90 days, treatment-emergent SAEs, adverse events of special interest, and new onset chronic disease, all assessed through 190 days. Findings: PCR screening of 737 ICU subjects identified 213 with S. aureus colonization; of these, 96 were randomized to receive suvratoxumab 5000 mg and 100 to placebo. At 30 days, 17/96 (17•7%) suvratoxumab and 26/100 (26•0%) placebo subjects had developed S. aureus pneumonia (relative risk reduction, 31.9%; 90% confidence interval [CI], −7•5 to 56•8; P = 0•166). At 30 days, incidences of treatmentemergent adverse events (AEs) and serious AEs were similar in suvratoxumab and placebo groups (90•6% [87/96] vs. 90•0% [90/100] and 37•5% [36/96] vs 32•0% [32/100], respectively). At 90 and 190 days, incidence of treatment-emergent AEs was still similar in suvratoxumab and placebo groups (92.
Incorporating mechanical cues into cellular responses allows us to experience our direct environment. Specialized cells can perceive and discriminate between different physical properties such as level of vibration, temperature, or pressure. Mechanical forces are abundant signals that also shape general cellular responses such as cytoskeletal rearrangement, differentiation, or migration and contribute to tissue development and function. The molecular structures that perceive and transduce mechanical forces are specialized cytoskeletal proteins, cell junction molecules, and membrane proteins such as ion channels and metabotropic receptors. G protein-coupled receptors (GPCRs) have attracted attention as metabotropic force receptors as they are among the most important drug targets. This review summarizes the function of mechano-sensitive GPCRs, specifically, the angiotensin II type 1 receptor and adrenergic, apelin, histamine, parathyroid hormone 1, and orphan receptors, focusing particularly on the advanced knowledge gained from adhesion-type GPCRs. We distinguish between shear stress and cell swelling/stretch as the two major types of mechano-activation of these receptors and contemplate the potential contribution of the force-from-lipid and force-from-tether models that have previously been suggested for ion channels.
G protein-coupled receptors (GPCRs) modulate a variety of physiological functions and have been proven to be outstanding drug targets. However, approximately one-third of all non-olfactory GPCRs are still orphans in respect to their signal transduction and physiological functions. Receptors of the class of Adhesion GPCRs (aGPCRs) are among these orphan receptors. They are characterized by unique features in their structure and tissue-specific expression, which yields them interesting candidates for deorphanization and testing as potential therapeutic targets. Capable of G-protein coupling and non-G protein-mediated function, aGPCRs may extend our repertoire of influencing physiological function. Besides their described significance in the immune and central nervous systems, growing evidence indicates a high importance of these receptors in metabolic tissue. RNAseq analyses revealed high expression of several aGPCRs in pancreatic islets, adipose tissue, liver, and intestine but also in neurons governing food intake. In this review, we focus on aGPCRs and their function in regulating metabolic pathways. Based on current knowledge, this receptor class represents high potential for future pharmacological approaches addressing obesity and other metabolic diseases.
Diamond-like carbon (DLC) is a biocompatible material that has many potential biomedical applications, including in orthopaedics. DLC layers doped with Cr at atomic percent (at.%) of 0, 0.9, 1.8, 7.3, and 7.7 at.% were evaluated with reference to their osteoinductivity with human bone marrow mesenchymal stromal cells (hMSCs), immune activation potential with RAW 264.7 macrophage-like cells, and their effect on apoptosis in Saos-2 human osteoblast-like cells and neonatal human dermal fibroblasts (NHDFs). At mRNA level, hMSCs on DLC doped with 0.9 and 7.7 at.% of Cr reached higher maximum values of both RUNX2 and alkaline phosphatase. An earlier onset of mRNA production of type I collagen and osteocalcin was also observed on these samples; they also supported the production of both type I collagen and osteocalcin. RAW 264.7 macrophages were screened using a RayBio™ Human Cytokine Array for cytokine production. 10 cytokines were at a concentration more than 2 × as high as the concentration of a positive control, but the values for the DLC samples were only moderately higher than the values on glass. NHDF cells, but not Saos-2 cells, had a higher expression of pro-apoptotic markers Bax and Bim and a lower expression of anti-apoptotic factor BCL-XL in proportion to the Cr content. Increased apoptosis was also proven by annexin V staining. These results show that a Cr-doped DLC layer with a lower Cr content can act as an osteoinductive material with relatively low immunogenicity, but that a higher Cr content can induce cell apoptosis.
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