Requirement for distinct vesicle-associated membrane proteins in insulin- and AMP-activated protein kinase (AMPK)-induced translocation of GLUT4 and CD36 in cultured cardiomyocytes

Upon stimulation of insulin signalling or contraction-induced AMP-activated protein kinase (AMPK) activation, the glucose transporter GLUT4 and the long-chain fatty acid (LCFA) transporter CD36 similarly translocate from intracellular compartments to the plasma membrane of cardiomyocytes to increase uptake of glucose and LCFA, respectively. This similarity in regulation of GLUT4 traffic and CD36 traffic suggests that the same families of trafficking proteins, including vesicle-associated membrane proteins (VAMPs), are involved in both processes. While several VAMPs have been implicated in GLUT4 traffic, nothing is known about the putative function of VAMPs in CD36 traffic. Therefore, we compared the involvement of the myocardially produced VAMP isoforms in insulin- or contraction-induced GLUT4 and CD36 translocation. Five VAMP isoforms were silenced in HL-1 cardiomyocytes. The cells were treated with insulin or the contraction-like AMPK activator oligomycin or were electrically stimulated to contract. Subsequently, GLUT4 and CD36 translocation as well as substrate uptake were measured. Three VAMPs were demonstrated to be necessary for both GLUT4 and CD36 translocation, either specifically in insulin-treated cells (VAMP2, VAMP5) or in oligomycin/contraction-treated cells (VAMP3). In addition, there are VAMPs specifically involved in either GLUT4 traffic (VAMP7 mediates basal GLUT4 retention) or CD36 traffic (VAMP4 mediates insulin- and oligomycin/contraction-induced CD36 translocation). The involvement of distinct VAMP isoforms in both GLUT4 and CD36 translocation indicates that CD36 translocation, just like GLUT4 translocation, is a vesicle-mediated process dependent on soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex formation. The ability of other VAMPs to discriminate between GLUT4 and CD36 translocation allows the notion that myocardial substrate preference can be modulated by these VAMPs

Minimal information for studies of extracellular vesicles 2018 (MISEV2018): a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines

The last decade has seen a sharp increase in the number of scientific publications describing physiological and pathological functions of extracellular vesicles (EVs), a collective term covering various subtypes of cell-released, membranous structures, called exosomes, microvesicles, microparticles, ectosomes, oncosomes, apoptotic bodies, and many other names. However, specific issues arise when working with these entities, whose size and amount often make them difficult to obtain as relatively pure preparations, and to characterize properly. The International Society for Extracellular Vesicles (ISEV) proposed Minimal Information for Studies of Extracellular Vesicles (“MISEV”) guidelines for the field in 2014. We now update these “MISEV2014” guidelines based on evolution of the collective knowledge in the last four years. An important point to consider is that ascribing a specific function to EVs in general, or to subtypes of EVs, requires reporting of specific information beyond mere description of function in a crude, potentially contaminated, and heterogeneous preparation. For example, claims that exosomes are endowed with exquisite and specific activities remain difficult to support experimentally, given our still limited knowledge of their specific molecular machineries of biogenesis and release, as compared with other biophysically similar EVs. The MISEV2018 guidelines include tables and outlines of suggested protocols and steps to follow to document specific EV-associated functional activities. Finally, a checklist is provided with summaries of key points

Process for the preparation of hydrocarbons from a vegetable feedstock

The present invention relates to a hydrodeoxygenation process wherein activated carbon is used as support material for catalysts comprising sulfided Ni and sulfided Mo or W as hydrogenation component. The catalyst in this process shows stable activity over a prolonged period of time, while the process further shows selectivity for the direct hydrodeoxygenation pathway selectively producing C n paraffinic hydrocarbons over C n-1 paraffinic hydrocarbons

A real support effect on the hydrodeoxygenation of methyl oleate by sulfided NiMo catalysts

The effect of the support on the catalytic performance of sulfided NiMo in the hydrodeoxygenation of methyl oleate as a model compound for triglyceride upgrading to green diesel was investigated. NiMo sulfides were prepared by impregnation and sulfidation on activated carbon, silica, γ-alumina and amorphous silica-alumina (ASA). High sulfidation degrees were obtained in all cases. Despite the use of a chelating agent to minimize metal-support interactions, the support had a significant influence on the morphology of the active phase (MoS2 dispersion and stacking). All catalysts convert methyl oleate to C17 and C18 olefins and paraffins. Initially, NiMo/Al2O3 and NiMo/ASA displayed the highest overall HDO activity, but these catalysts deactivated slowly during the week on stream. Finally, they exhibited similar activity as NiMo/SiO2. NiMo/C and NiMo/SiO2 did not deactivate. The NiMo/C catalyst was appreciably more active than the others after prolonged reaction. The high initial and then deactivating performance of NiMo/Al2O3 and NiMo/ASA is due to the Lewis acidity of surface Al species active in methyl oleate hydrolysis. It has earlier been demonstrated that deposition of heavy products on the alumina surface deactivates these sites. SiO2 lacks such sites, resulting in lower catalytic performance. The NiMo/C support is more active in methyl oleate hydrolysis. This can be either due to intrinsically higher activity of the metal sulfide on carbon or to acidic surface groups. Besides, the reaction data show that the C18 hydrocarbons selectivity for NiMo/SiO2 and NiMo/C was substantially higher than for the other two catalysts. Clearly, the support has a significant influence on the performance of NiMo sulfide in methyl oleate HDO. The use of activated carbon as the support presents high and stable HDO activity of methyl oleate with good C18 hydrocarbons selectivity

A model compound (methyl oleate, oleic acid, triolein) study of triglycerides hydrodeoxygenation over alumina-supported NiMo sulfide

We studied hydrodeoxygenation of model compounds for vegetable oil into diesel-range hydrocarbons on a sulfided NiMo/γ-Al2O3 catalyst under trickle-flow conditions. Methyl oleate (methyl ester of oleic acid, a C18 fatty acid with one unsaturated bond in the chain) represented the C18 alkyl esters in natural fats, oils and greases. The effect of temperature and pressure on activity and product distribution (mainly C17 and C18 hydrocarbons) were studied. Hydrolysis of the methyl ester results in fatty acid intermediates, which are converted by direct hydrodeoxygenation to C18 hydrocarbons or decarbonated (by decarbonylation or decarboxylation) to C17 hydrocarbons. Reactant inhibition is more pronounced for the former route. The reaction is hardly inhibited by H2S, H2O, CO and tetralin solvent. H2S and to a lesser extent H2O increase the C17/C18 hydrocarbon ratio, because they inhibit direct hydrodeoxygenation more than decarbonation. The catalyst surface contains different sites for direct hydrodeoxygenation and decarbonation reactions. During methyl oleate HDO, the catalyst slowly deactivated, mainly due to blocking of Lewis acid sites of the alumina support that catalyze methyl oleate hydrolysis. The catalyst was much more active in the HDO of triolein (glyceryl trioleate, representative triglyceride model compound) than in methyl oleate HDO, to be attributed to very facile hydrolysis of triglycerides. Although the overall kinetics of methyl oleate and triolein HDO were similar, our results show that the catalyst and H2S play a much more important role in the hydrolysis of methyl oleate than in hydrolysis of triglycerides

Formation of acid sites in amorphous silica-alumina

A suite of amorphous silica-aluminas (ASAs) was prepared by homogeneous deposition–precipitation (HDP) of aluminium on a silica surface followed by calcination. The HDP process was investigated in detail by 27Al NMR spectroscopy of solid and liquid aliquots of the synthesis mixture. Deposition occurs predominantly via a hydrolytic adsorption of aluminium onto the hydroxyl groups of the silica surface. Precipitation becomes more significant at higher aluminium concentration. Depending on the aluminium loading, the surface contains four- and six-coordinated aluminium as well as patches of aluminium hydroxides. Calcination results in two competing process, that is the diffusion of aluminium into the silica network and sintering of aluminium into separate patches of a phase which mainly consists of octahedral Al. These ASAs exhibit Brønsted acidity similar to industrial amorphous silica-aluminas prepared by the grafting of aluminium on very reactive silica gels. Their acidity does not vary systematically with the aluminium concentration, except below 5 wt% Al2O3. The acidity increases with the calcination temperature. The active sites form due to the diffusion of aluminium into the silica network at high temperatures, leading to Al substitutions of Si atoms. This is expected as the acidity does not correlate with anything else, viz., the amount of four-coordinated aluminium nor the presence of segregated Al or five-coordinated aluminium at the interface of these domains and the mixed silica-alumina phase. The surface of an amorphous silica-alumina consists of isolated aluminium grafted onto the silica surface (pure silica-alumina phase) with a very small amount of aluminium in the silica network, which brings about the Brønsted acidity, and small patches of aluminium oxides.status: publishe

Synergy in lignin upgrading by a combination of Cu-based mixed oxide and Ni-phosphide catalysts in supercritical ethanol

The depolymerization of lignin to bioaromatics usually requires a hydrodeoxygenation (HDO) step to lower the oxygen content. A mixed Cu–Mg–Al oxide (CuMgAlOx) is an effective catalyst for the depolymerization of lignin in supercritical ethanol. We explored the use of Ni-based cocatalysts, i.e. Ni/SiO2, Ni2P/SiO2, and Ni/ASA (ASA = amorphous silica alumina), with the aim of combining lignin depolymerization and HDO in a single reaction step. While the silica-supported catalysts were themselves hardly active in lignin upgrading, Ni/ASA displayed comparable lignin monomer yield as CuMgAlOx. A drawback of using an acidic support is extensive dehydration of the ethanol solvent. Instead, combining CuMgAlOx with Ni/SiO2 and especially Ni2P/SiO2 proved to be effective in increasing the lignin monomer yield, while at the same time reducing the oxygen content of the products. With Ni2P/SiO2, the lignin monomer yield was 53 wt %, leading to nearly complete deoxygenation of the aromatic products

The nature of the sulfur tolerance of amorphous silica-alumina supported NiMo(W) sulfide and Pt hydrogenation catalysts

Amorphous silica-alumina (ASA) based NiMo and NiW sulfide and Pt hydrogenation catalysts were prepared and compared in toluene hydrogenation in the presence of H2S to alumina- and silica-supported reference catalysts with the aim to elucidate the influence of (strong) Brønsted acidity of the support on the sulfur tolerance. Despite precautions to prepare NiMo sulfide catalysts with equal morphology, the stacking degree of the MoS2 phase was found to decrease with alumina content of the ASA. Similar but more pronounced differences of the stacking degree were observed among the NiW sulfide catalysts. This variation in the stacking degree had a substantial effect on the catalytic activity of dibenzothiophene hydrodesulfurization. ASA-based catalysts show higher activity and improved sulfur tolerance in toluene hydrogenation compared to their alumina- and silica based counterparts. However, the sulfur tolerance does not correlate with the number of strong Brønsted acid sites, nor, indeed, with total Brønsted acidity. Instead, it decreases with increasing Al content of the ASA support. The sulfur tolerance of the active metal sulfide phase is related to the electronegativity of the support. That silica itself does not follow this trend is surmised to be due to its lack of Lewis acid sites, necessary for introducing the active phase-support effect

Particle size distribution of exosomes and microvesicles determined by transmission electron microscopy, flow cytometry, nanoparticle tracking analysis, and resistive pulse sensing.

BACKGROUND: Enumeration of extracellular vesicles has clinical potential as a biomarker for disease. In biological samples, the smallest and largest vesicles typically differ 25-fold in size, 300,000-fold in concentration, 20,000-fold in volume, and 10,000,000-fold in scattered light. Because of this heterogeneity, the currently employed techniques detect concentrations ranging from 10(4) to 10(12) vesicles mL(-1) . OBJECTIVES: To investigate whether the large variation in the detected concentration of vesicles is caused by the minimum detectable vesicle size of five widely used techniques. METHODS: The size and concentration of vesicles and reference beads were measured with transmission electron microscopy (TEM), a conventional flow cytometer, a flow cytometer dedicated to detecting submicrometer particles, nanoparticle tracking analysis (NTA), and resistive pulse sensing (RPS). RESULTS: Each technique gave a different size distribution and a different concentration for the same vesicle sample. CONCLUSION: Differences between the detected vesicle concentrations are primarily caused by differences between the minimum detectable vesicle sizes. The minimum detectable vesicle sizes were 70-90 nm for NTA, 70-100 nm for RPS, 150-190 nm for dedicated flow cytometry, and 270-600 nm for conventional flow cytometry. TEM could detect the smallest vesicles present, albeit after adhesion on a surface. Dedicated flow cytometry was most accurate in determining the size of reference beads, but is expected to be less accurate on vesicles, owing to heterogeneity of the refractive index of vesicles. Nevertheless, dedicated flow cytometry is relatively fast and allows multiplex fluorescence detection, making it most applicable to clinical research