Effects Of Creatine On The Translocation Of Glucose Transport Protein4 In Hypoxic H9C2 Cardiomyocytes

To investigate the influence of creatine on translocation of glucose transport proteins GLUT4 in hypoxic H9C2 cardiom yocytes.Methods: sodium azide(NaN3), a specific inhibitor of cytochrome C oxidase, was used as a modle to mimic chemical hypoxia in H9C2 cardiomyocytes . H9C2 cardiomyocytes were randomized to control group, chemical hypoxia group indused by NaN3 , creatine group and hypoxia plus creatine group . Then we used differential centrifugation and discontinous sucrose gradient to separate plasma membranes and intracellular membranes from all groups , and then determined the expression of GLUT4 in these separated membrane fractions with Western blot. Discussion: During metabolic stress, such as ischemia or hypoxia, glucose becomes the principal energy source for the heart. It has been shown that increased cardiac glucose uptake during metabolic stress has a protective effect on cell survival and heart function. We used sodium azide(NaN3), a specific inhibitor of cytochrome C oxidase (COX) , to mimic chemical hypoxia to investigate the influence of creatine alone or plus chemical hypoxia on the translocation of GLUT4 in H9C2 cardiomyocytes. The physiological roles of creatine in the human body have been extensively investigated. Its main biochemical effect in skeletal muscle, usually described as the'energy shuttle', is to transfer chemical energy from mitochondria, where ATP is produced, to the myofibrils. More than 60% is in the form of phosphocreatine (PCr) and the remainder is stored in the non-phosphorylated form. A number of studies regarding beneficial effects of creatine supplementation on muscle glucose metabolism have been reported. For example, creatine supplementation improves impaired glucose tolerance and increases glycogen content. Creatine supplementation increases glucose oxidation and translocation of GLUT4 in L6 rat skeletal muscle cells. Our data suggested that both NaN3-induced chemical hypoxia and hypoxia plus creatine caused different degree translocation of GLUT4 molecules to the plasma membrane from intracellular membranes in H9C2 cardiomyocytes. Creatine increased translocation of GLUT4 in hypoxic H9C2 cardiomyocytes. The difference between the degree of translocation induced by hypoxia on the one hand and hypoxia plus creatine on the other hand seemed most likely to be a result of the stimulation of different intracellular signaling pathways, or creatine enhanced intracellular signaling pathways that hypoxia induced translocation of GLUT4. It has significant clinical implications that creatine increased translocation of GLUT4 in hypoxic H9C2 cardiomyocytes. It caused greater recruitment of GLUT4 to the sarcolemma, thereby increasing the ability of hypoxic cardiomyocytes to utilize extracellular glucose, thus enhancing the protective increase in glucose metabolism. Results :Both chemical hypoxia and creatine alone or hypoxia plus creatine significantly increased the expression of GLUT4 in the plasma membranes compared to controls with a concomitant decrease of GLUT4 in intracellular membranes (p<0.05), indicating that translocation of GLUT4 from an intracellular compartment to the plasma membrane in H9C2 cardiomyocytes. Conclusion:Both NaN3-induced chemical hypoxia and hypoxia plus creatine caused different degree translocation of GLUT4 molecules to the plasma membrane from intracellular membranes in H9C2 cardiomyocytes. Creatine increased translocation of glucose transport protein4 in hypoxic H9C2 cardiomyocytes.