0341: AMPK exerts an insulin-sensitizing effect on cardiac glucose uptake by multiple molecular mechanisms including cytoskeleton reorganization

BackgroundInsulin-resistant cardiomyocytes are characterized by a decreased ability of insulin to stimulate glucose uptake. We have previously shown that the activation of AMPK by metformin or phenformin restores insulin-sensitivity in insulin-resistant cardiomyocytes. The aim of our present work is to understand by which molecular mechanisms AMPK exerts its insulin sensitizing effect. In this study we focused on the mTOR/p70S6K pathway and on cytoskeleton reorganization. mTOR/p70S6K, which is known to be inhibited by AMPK, is able to reduce insulin signaling via a negative feedback loop involving serine phosphorylation of IRS-1. On the other hand, cytoskeleton reorganization, which is a known target of AMPK, is responsible for the translocation of the glucose transporter GLUT4 to the plasma membrane.MethodsAdult rat cardiomyocytes were primary cultured and treated with different agents including insulin, AMPK activator (phenformin), mTOR inhibitor rapamycin and/or actin cytoskeleton inhibitor latrunculin B. Glucose uptake was assessed by detritiation of 2-3H-glucose.ResultsFirst, we tested if rapamycin was able to mimic AMPK activators. Similarly to phenformin, rapamycin increased the insulin-dependent phosphorylation of Akt involved in the regulation of glucose uptake. Despite the ability of rapamycin to induce this Akt over-phosphorylation, rapamycin was not able to restore the insulin-dependent stimulation of glucose uptake like phenformin did. On the other hand, latrunculin B abolished the insulin-sensitizing action of phenformin on glucose uptake, in insulin-sensitive as well as in insulinresistant cells.Conclusionsactin cytoskeleton reorganization but not mTOR/p70S6K, is involved in the insulin-sensitizing effect of AMPK on cardiac glucose uptake. The role played by Small G proteins, known to be involved in the regulation of actin cytoskeleton is under investigation

3D histopathology of stenotic aortic valve cusps using ex vivo microfocus computed tomography

BackgroundCalcific aortic stenosis (AS) is the most prevalent heart valve disease in developed countries. The aortic valve cusps progressively thicken and the valve does not open fully due to the presence of calcifications. In vivo imaging, usually used for diagnosis, does not allow the visualization of the microstructural changes associated with AS.MethodsEx vivo high-resolution microfocus computed tomography (microCT) was used to quantitatively describe the microstructure of calcified aortic valve cusps in full 3D. As case study in our work, this quantitative analysis was applied to normal-flow low-gradient severe AS (NF-LG-SAS), for which the medical prognostic is still highly debated in the current literature, and high-gradient severe AS (HG-SAS).ResultsThe volume proportion of calcification, the size and number of calcified particles and their density composition was quantified. A new size-based classification considering small-sized particles that are not detected with in vivo imaging was defined for macro-, meso- and microscale calcifications. Volume and thickness of aortic valve cusps, including the complete thickness distribution, were also determined. Moreover, changes in the cusp soft tissues were also visualized with microCT and confirmed by scanning electron microscopy images of the same sample. NF-LG-SAS cusps contained lower relative amount of calcifications than HG-SAS. Moreover, the number and size of calcified objects and the volume and thickness of the cusps were also lower in NF-LG-SAS cusps than in HG-SAS.ConclusionsThe application of high-resolution ex vivo microCT to stenotic aortic valve cusps provided a quantitative description of the general structure of the cusps and of the calcifications present in the cusp soft tissues. This detailed description could help in the future to better understand the mechanisms of AS

Role of AMP-activated protein kinase in regulating hypoxic survival and proliferation of mesenchymal stem cells

Aims Mesenchymal stem cells (MSCs) are widely used for cell therapy, particularly for the treatment of ischaemic heart disease. Mechanisms underlying control of their metabolism and proliferation capacity, critical elements for their survival and differentiation, have not been fully characterized. AMP-activated protein kinase (AMPK) is a key regulator known to metabolically protect cardiomyocytes against ischaemic injuries and, more generally, to inhibit cell proliferation. We hypothesized that AMPK plays a role in control of MSC metabolism and proliferation. Methods and results MSCs isolated from murine bone marrow exclusively expressed the AMPKα1 catalytic subunit. In contrast to cardiomyocytes, a chronic exposure of MSCs to hypoxia failed to induce cell death despite the absence of AMPK activation. This hypoxic tolerance was the consequence of a preference of MSC towards glycolytic metabolism independently of oxygen availability and AMPK signalling. On the other hand, A-769662, a well-characterized AMPK activator, was able to induce a robust and sustained AMPK activation. We showed that A-769662-induced AMPK activation inhibited MSC proliferation. Proliferation was not arrested in MSCs derived from AMPKα1-knockout mice, providing genetic evidence that AMPK is essential for this process. Among AMPK downstream targets proposed to regulate cell proliferation, we showed that neither the p70 ribosomal S6 protein kinase/eukaryotic elongation factor 2-dependent protein synthesis pathway nor p21 was involved, whereas p27 expression was increased by A-769662. Silencing p27 expression partially prevented the A-769662-dependent inhibition of MSC proliferation. Conclusion MSCs resist hypoxia independently of AMPK whereas chronic AMPK activation inhibits MSC proliferation, p27 being involved in this regulatio

Towards standardization of echocardiography for the evaluation of left ventricular function in adult rodents : a position paper of the ESC Working Group on Myocardial Function

This work was supported by AIRC IG grant 2016 19032 to S.Z.; FEDER through Compete 2020 –Programa Operacional Competitividade E Internacionalização(POCI), the project DOCNET (norte-01-0145-feder-000003), supported by Norte Portugal regional operational programme (norte 2020), under the Portugal 2020 partnership agreement, through the European Regional Development Fund (ERDF), the project NETDIAMOND (POCI-01-0145-FEDER-016385), supported by European Structural And Investment Funds, Lisbon’s regional operational program 2020 to I.P.F.; grants from FSR-FNRS, FRC (Cliniques Universitaires Saint-Luc) and from Action de Recherche Concertée (UCLouvain) to C.B., E.P.D. and L.B; the ERA-Net-CVD project MacroERA,01KL1706, FP7-Homage N° 305507, and IMI2-CARDIATEAM (N° 821508)to S.H.,the DZHK (German Centre for Cardiovascular Research) and the German Ministry of Research and Education (BMBF)to F.W., T.E. and L.C., the Netherlands Cardiovascular Research Initiative, an initiative with support of the Dutch Heart Foundation, CVON2016-Early HFPEF, 2015-10, CVON She-PREDICTS, grant 2017-21, CVON Arena-PRIME, 2017-18, Flemish Research FoundationFWO G091018N and FWO G0B5930N to S.H.; Federico II University/Ricerca di Ateneo grant to C.G..T.; the European Research Area Networks on Cardiovascular Diseases (ERA-CVD) [LYMIT-DIS 2016, MacroERA], Fonds Wetenschappelijk Onderzoek [1160718N] to I.C; the Deutsche Forschungsgemeinschaft (DFG TH903/20-1, KFO311), the Transregio-SFB INST 95/15641 and the EU Horizon 2020 project Cardioregenix (GA 825670)to T.TPeer reviewedPostprin

21e journée de cardiologie octobre 2013 : le syndrome coronarien aigu du patient diabétique

Le diabète assombrit le pronostic des patients souffrant d’un syndrome coronarien aigu. La présence du diabète est souvent ignorée par le patient et doit être systématiquement recherchée lors d’un événement coronarien aigu que ce soit à l’hôpital ou après le séjour hospitalier. Le diabète influence la prise en charge des patients pour la rapidité de réalisation d’une angiographie chez les patients avec un syndrome coronarien sans sus-décalage persistant du segment ST, pour la stratégie de revascularisation pour ces mêmes patients et pour le choix des antiagrégants plaquettaires. Le traitement de prévention secondaire chez le patient diabétique associe un traitement antihypertenseur, une statine à haute dose et une double antiagrégation plaquettaire. L’intensité du contrôle glycémique doit être nuancé en fonction du type de patien