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Glycogen turnover in heart-derived H9c2 cells Cheung, Kevin K.Y.

Abstract

5'-AMP activated protein kinase (AMPK) plays a central role in modulating the energy metabolism in the heart when the heart is under metabolic stress. In theory, AMPK activation should decrease glycogen synthesis and enhance its degradation. Thus, we determined the effect of AMPK activation on glycogen metabolism in H9c2 cells, a heart-derived cell line. 5-amino-4-imidazolecarboxamide riboside (AICAR, 1 mM and 2 mM), recognized activator of AMPK, causes an increase in glycogen turnover by simultaneously stimulating degradation and synthesis of glycogen, and significantly increased the rate of glycolysis and glucose uptake. Glycogen turnover also occurs in H9c2 cells under a variety of conditions, even in the setting of very high rates of glycogen degradation. However, data on the phosphorylation state of AMPK and ACC suggested that AMPK was not activated by AICAR. In addition, the results on the activity level of glycogen synthase (GS) and glycogen phosphorylase (GP) did not show significant changes with AICAR stimulation. The detected activity levels of GS and GP did not account for the observed increase in glycogen synthesis. I speculate that AICAR's effect on glycogen turnover could be mediated by allosteric activation. Overall, H9c2 succeeded in providing a readily accessible and established isolated cell system with cardiac myocyte properties as a tool to investigate the role of AMPK in cardiac energy metabolism. The results and methods obtained from H9c2 could be readily adapted to be used on isolated adult cardiomyocytes for better representation of heart tissue.

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