0296 : Regulating O-GlcNAcylation by AMP-activated protein kinase, a new way to prevent hypertrophy development

Background We have previously shown that the AMPK specific activator, A769662, is able to block phenylephrine (PE)-induced hypertrophy without affecting the previously identified AMPK-related key regulators of cardiac hypertrophy, namely protein synthesis, NFAT and MAP kinase signaling. Hence, this study was undertaken to identify a novel mechanism by which AMPK can regulate cardiac hypertrophy. Methods Hypertrophy was induced in neonatal rat cardiomyocytes (NRVMs) using PE for 24h and AMPK was chronically activated with A769662. Hypertrophy was evaluated by immunostaining and cell surface area measurement. In vivo cardiac hypertrophy was induced by Angiotensin II (AngII) infusion by osmotic mini-pumps and AMPK was activated by metformin in drinking water. Protein expression, AMPK phosphorylation and OGlcNAc levels were evaluated by QPCR and western blot. Results First, we showed that PE-dependent cardiomyocyte hypertrophy was accompanied by an increase in O-GlcNAc levels. This hypertrophy was prevented by A769662 and this was associated with a decrease in O-GlcNAc levels. Then, using hexosamine biosynthesis pathway activators, i. e PUGNAc or glucosamine, we showed that increase in O-GlcNAc levels was able to reverse the anti-hypertrophic effect of AMPK activation in NRVMs. Similar results were obtained in adult rat cardiomyocytes. On the other hand, inhibition of hexosamine biosynthesis pathway by Azaserine or DON inhibited PE-induced cardiomyocyte hypertrophy and this effect was reversed by PUGNAc or glucosamine. In vivo experiments confirmed these in vitro data. Indeed, metformin was able to reduce cardiac hypertrophy and this correlated with a decrease in O-GlcNAc levels in WT mice but not in AMPKα2 knockout mice. Conclusion Collectively, our results suggest that AMPK regulates cardiac hypertrophy mainly by inhibiting O-GlcNAcylation signaling. AMPK and OGlcNAcylation signaling could be putative new therapeutic targets for treatment of cardiac hypertrophy.