Quantification of GLUT4 Gene Expression in Human Atrial Myocardium of Hypertensive Patients and the Effect of Experimental Ischaemia Thereupon

Journal of Clinical and Basic Cardiology

Tscheliessnigg KH¹  Lewinski D¹  Mangge H¹  Scherr E¹  Gasser R¹  Trantina-Yates A¹  Mächler H¹  Ablasser K¹  Gasser S¹  Roessl U¹  Dellacher A¹ 

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关键词: GLUT4;    Hypertonie;    Ischämie;    Kardiologie;    Myokard;    cardiology;    heart;    hypertension;    ischaemia;   

DOI  :  

学科分类：心脏病和心血管学

来源: Krause & Pachernegg GmbH

【 摘 要 】

Introduction: Transmembrane glucose transport and thus cellular high-energy metabolism of the cardiovascular system depend largely on theinsulin-responsive GLUT4 isoform of the trans-membrane glucose transport molecule. GLUT4 plays a key role in the development of myocardialand vascular stiffness, in the context of osmolarity, compartmental water distribution and homeostasis. In hypertensive rats, expression ofGLUT4 mRNA as well as the amount of protein in the membrane was found to be decreased. In the context of hypertension and ischaemia, noreports can be found on GLUT4 in human myocardium. Myocardial ischaemia increases glucose uptake through translocation of GLUT1 andGLUT4 from an intracellular compartment to sarcolemma. This appears to be a beneficial effect during ischaemia and possibly recovery. Insulinand ischaemia have additive effects in the increase of in vivo glucose utilisation and augment glucose transporter translocation. Delivery of glucoseto the glycolytic pathway appears to be a major controlling site of glycolysis in low-flow ischaemia. While many experimental studies suggest thatan increase in glucose uptake and metabolism by the ischaemic myocardium help protect myocardial cells from irreversible injury, little or nothingis known in this context about human cardiac trans-membrane glucose transport, SLC2A4-expression and its regulation.Methods: We investigatedtissue samples (60–150 mg) from the right atrial auricle from patients with arterial hypertension subjected to cardiac surgery, which weresnap-frozen in liquid nitrogen and stored at –70 °C until homogenisation. RNA-Isolation and cDNA transcription: Total RNA was extractedby the TRIZOL® method (Invitrogen Corp., Carlsbad, CA, USA) and further purified using RNeasy Mini Kit (QIAGEN Inc., Hilden,GER). RNA was transcribed into DIG-labelled cDNA. For reverse transcription of isolated RNA we used the High Capacity cDNA ArchiveKit (Applied Biosystems) and the Thermocycler MyCyclerTM from Biorad. Real-time PCR was performed using the LightCycler® 2.0 System(Roche). Furthermore, in human cardiac tissue (right auricle), using microarray technique, we first looked at general changes in expression profilesduring simulated myocardial ischaemia and then at the behaviour of SLC2A4 (GLUT4, solute carrier family 2 [facilitated glucose transporter],member 4) as well as its regulator gene SLC2A4RG. Then, using real-time PCR (Light Cycler), we quantified GLUT4 mRNA expressionchanges under ischaemic and control conditions in normotensive and hypertensive patients. Results: We showed in 28 patients that GLUT4mRNA was significantly less expressed in patients with arterial hypertension compared to controls. Using the microarray technique, we found thatboth the expression of GLUT4 gene (SLC2A4) and its regulator gene remain practically unchanged in experimental ischaemia. In real-timePCR (Light Cycler), the mean ratio for GLUT4 gene expression compared to the housekeeping gene G6PDH was under well oxygenatedconditions –0.0052 ± 0.0203 and under N2-simulated ischaemia 0.0179 ± 0.0196 (n = 8; ± SEM). No statistically significant differencecould be found between the two groups, however, results show a trend towards a slight increase in expression. Summary: Our experiments showthat GLUT4 mRNA expression is in fact decreased in arterial hypertension compared to normal controls. From these data, one can deduce thatarterial hypertension is genuinely associated with decreased GLUT4 expression. However, no significant changes are seen in the expression of the GLUT4 gene as well as in its regulatory gene after 30 minutes of N2-mediated experimental ischaemia. Similarly, biological processes involvedin glucose metabolism are not significantly de-regulated, as are others. This, as well as a slight trend towards up-regulation, can be interpreted asan attempt of the myocyte to maintain the energy metabolism stable under hypoxic conditions.

【 授权许可】

Unknown