Glucosamine-induced endoplasmic reticulum stress affects GLUT4 expression via activating transcription factor 6 in rat and human skeletal muscle cells

AIMS/HYPOTHESIS: Glucosamine, generated during hyperglycaemia, causes insulin resistance in different cells. Here we sought to evaluate the possible role of endoplasmic reticulum (ER) stress in the induction of insulin resistance by glucosamine in skeletal muscle cells. METHODS: Real-time RT-PCR analysis, 2-deoxy-D: -glucose (2-DG) uptake and western blot analysis were carried out in rat and human muscle cell lines. RESULTS: In both rat and human myotubes, glucosamine treatment caused a significant increase in the expression of the ER stress markers immunoglobulin heavy chain-binding protein/glucose-regulated protein 78 kDa (BIP/GRP78 [also known as HSPA5]), X-box binding protein-1 (XBP1) and activating transcription factor 6 (ATF6). In addition, glucosamine impaired insulin-stimulated 2-DG uptake in both rat and human myotubes. Interestingly, pretreatment of both rat and human myotubes with the chemical chaperones 4-phenylbutyric acid (PBA) or tauroursodeoxycholic acid (TUDCA), completely prevented the effect of glucosamine on both ER stress induction and insulin-induced glucose uptake. In both rat and human myotubes, glucosamine treatment reduced mRNA and protein levels of the gene encoding GLUT4 and mRNA levels of the main regulators of the gene encoding GLUT4 (myocyte enhancer factor 2 a [MEF2A] and peroxisome proliferator-activated receptor-gamma coactivator 1alpha [PGC1alpha]). Again, PBA or TUDCA pretreatment prevented glucosamine-induced inhibition of GLUT4 (also known as SLC2A4), MEF2A and PGC1alpha (also known as PPARGC1A). Finally, we showed that overproduction of ATF6 is sufficient to inhibit the expression of genes GLUT4, MEF2A and PGC1alpha and that ATF6 silencing with a specific small interfering RNA is sufficient to completely prevent glucosamine-induced inhibition of GLUT4, MEF2A and PGC1alpha in skeletal muscle cells. CONCLUSIONS/INTERPRETATION: In this work we show that glucosamine-induced ER stress causes insulin resistance in both human and rat myotubes and impairs GLUT4 production and insulin-induced glucose uptake via an ATF6-dependent decrease of the GLUT4 regulators MEF2A and PGC1alpha

ENPP1 Affects Insulin Action and Secretion: Evidences from In Vitro Studies

The aim of this study was to deeper investigate the mechanisms through which ENPP1, a negative modulator of insulin receptor (IR) activation, plays a role on insulin signaling, insulin secretion and eventually glucose metabolism. ENPP1 cDNA (carrying either K121 or Q121 variant) was transfected in HepG2 liver-, L6 skeletal muscle- and INS1E beta-cells. Insulin-induced IR-autophosphorylation (HepG2, L6, INS1E), Akt-Ser473, ERK1/2-Thr202/Tyr204 and GSK3-beta Ser9 phosphorylation (HepG2, L6), PEPCK mRNA levels (HepG2) and 2-deoxy-D-glucose uptake (L6) was studied. GLUT 4 mRNA (L6), insulin secretion and caspase-3 activation (INS1E) were also investigated. Insulin-induced IR-autophosphorylation was decreased in HepG2-K, L6-K, INS1E-K (20%, 52% and 11% reduction vs. untransfected cells) and twice as much in HepG2-Q, L6-Q, INS1E-Q (44%, 92% and 30%). Similar data were obtained with Akt-Ser473, ERK1/2-Thr202/Tyr204 and GSK3-beta Ser9 in HepG2 and L6. Insulin-induced reduction of PEPCK mRNA was progressively lower in untransfected, HepG2-K and HepG2-Q cells (65%, 54%, 23%). Insulin-induced glucose uptake in untransfected L6 (60% increase over basal), was totally abolished in L6-K and L6-Q cells. GLUT 4 mRNA was slightly reduced in L6-K and twice as much in L6-Q (13% and 25% reduction vs. untransfected cells). Glucose-induced insulin secretion was 60% reduced in INS1E-K and almost abolished in INS1E-Q. Serum deficiency activated caspase-3 by two, three and four folds in untransfected INS1E, INS1E-K and INS1E-Q. Glyburide-induced insulin secretion was reduced by 50% in isolated human islets from homozygous QQ donors as compared to those from KK and KQ individuals. Our data clearly indicate that ENPP1, especially when the Q121 variant is operating, affects insulin signaling and glucose metabolism in skeletal muscle- and liver-cells and both function and survival of insulin secreting beta-cells, thus representing a strong pathogenic factor predisposing to insulin resistance, defective insulin secretion and glucose metabolism abnormalities

Il diritto alla vita del concepito e l’interruzione volontaria della gravidanza nella giurisprudenza costituzionale

In questo lavoro, si è scelto di guardare alla disciplina dell’aborto attraverso la lente dei due giudizi di ammissibilità dei referendum che hanno avuto ad oggetto la l. 194/1978. L’acuita sensibilità che, ad ogni livello, si è sviluppata verso la vita del concepito tra un giudizio e l’altro, ha determinato la Corte, con la seconda pronuncia (la sent. n. 35/1997), a dichiarare l’inammissibilità del referendum e “blindare” la legge, in quanto a contenuto costituzionalmente vincolato. Ciò non nega, d’altro canto, un intervento del legislatore volto a migliorare le tutele ivi previste. Poiché lo spirito della legge sull’IVG è stato “tradito” dalle prassi applicative, ci s’interroga, pertanto, sull’opportunità di una modifica nel senso della “procedimentalizzazione” della formazione della volontà della donna

Study of Fiber Bragg Gratings Embedded in 3D-Printed Patches for Deformation Monitoring

Aim of this work is the analysis of the 3D printed patches embedding fiber Bragg gratings (FBGs) for deformation monitoring. In particular, the paper first describes the manufacturing process and the performances of FBGs embedded in PLA and ABS rectangular patches, showing that the sensitivity to temperature is strongly dependent on the material and on the dimension of the patches. Then, the deformation characteristics are, for the first time, explored showing that the thickness of the patch, influencing the neutral axis position, acts as gaining factor on the deformation sensitivity of the FBG sensor. Such results enable the application of FBG embedded in 3D-printed patches for deformation monitoring taking in proper consideration the dimension of the patches, in particular its thickness, that allows to enhance the wavelength shift of the applied FBG sensors

Curvature Sensor Based on FBGs Embedded in 3D Printed Patches

In this paper, a novel curvature sensor, is showed. The proposed sensor is based on two FBGs, properly embedded in a 3D printed patch: the FBGs measure the strain in two point at a different distance from the monitored structure and the curvature of the structure under test is estimated from the difference in their strain. The simple and compact sensor exhibits a curvature sensitivity of 1.39 nm/m-1 with a resolution equal to $7.2cdot 10^{-4},, ext{m}^{-1}$. The curvature test shows a very excellent agreement between the curvature recorded with the new sensing device and that of the reference sensor. Neutral axis position of the monitored structure can be also estimated with this sensor

Fiber Bragg gratings embedded in 3D-printed patches for sensitivity enhancement of deformation monitoring

In this work, we present and discuss on the sensing properties of a 3D printed patch embedding a fiber Bragg grating (FBG). In the paper, we first describe the fabrication process of the proposed sensing device and then we analyze its performance in terms of thermal sensitivity and deformation detection capability. In particular, FBGs were embedded in polylactic acid (PLA) rectangular patches that confer greater strength to the bare FBG and enhance their sensing capabilities. We show that the patch thickness, by increasing the distance between the optical sensor and the neutral axis of the structure where it is fixed, provides a gain factor in the device sensitivity to deformation. These results encourage the application of FBGs embedded in 3D-printed patches in the field of the structural monitoring where, by efficiently selecting patch dimensions, in particular the thickness, it is possible to improve the sensor robustness and, contemporary, the deformation sensitivity with respect to bare FBGs

FBGs in 3D printed objects monitoring

In this work, the embedding of fiber Bragg gratings (FBGs) in 3D printed patches is proposed with the multiple aims to demonstrate the capabilities of the FBGs to monitor the deformation state and the temperature of the sensorized devices and to show the possibility to use this approach in the realization of robust and efficient packages for fiber optical sensors. FBGs are embedded in the monitored structure, avoiding the complex wiring typical of strain gauges, and provide local strain measurements in real-time. The possible application of the patch as sensing device is investigated showing that the thickness of the substrate, influencing the neutral axis position, acts as gaining factor on the deformation sensitivity of the FBG, while the temperature sensitivity in more than ten time greater than the bare FGB one thanks to the high thermal expansion of the plastic material of which the patches are made. Such results enable the application the 3D-printed patches as packages for FBGs in the deformation and temperature monitoring

PROPENE POLYMERIZATION IN THE PRESENCE OF MGCL2-SUPPORTED ZIEGLER-NATTA CATALYSTS .4. EFFECTS OF LEWIS-BASES ON POLYMER STEREOCHEMISTRY

The stereochemistry of polypropenes obtained in the presence of several MgCl2-supported Ziegler-Natta catalyst systems comprising different Lewis bases has been investigated by C-13 NMR spectroscopy, with special attention paid to the ''less tactic'' (heptane-soluble) fractions. These have been found to consist of ''tendentially isotactic'' and ''tendentially syndiotactic'' stereosequences, in largely variable amounts (depending on the catalyst system). The microstructure of the former is in accordance with the enantiomorphic site model, whereas that of the latter suggests a stereocontrol arising from the asymmetry of the growing chain end. In both cases, propene insertion is primary (1-2). Polymerization conditions leading to the formation of ''syndiotacticrich'' polymers showing syndiotactic crystallinity have been identified

3D shape sensing with FBG-based patch: from the idea to the device

In this work, the advantages of 3D printing technology are combined with fiber Bragg grating (FBG) sensors to implement an innovative 3D shape sensor embedded in a 3D printed patch. The system allows to obtain a sensing patch able to provide a direct measure of curvature and neutral axis position in the 3D space in a simple manner and without requiring numerical simulations or mathematical models of the structure of interest. The experimental tests assess the proposed novel approach showing an optimal agreement between the measurements of the proposed patch with respect to the reference sensors. Furthermore, both the curvature sensitivity and resolution can be modulated by changing the distances among the FBGs inside the patch, tailoring the performances and the dimensions with the application requirements