Abstract 1465: Cardiomyocyte Hypertrophy Induces O-linked-β-N-acetylglucosamine Modification of PGC-1α and Augments its Transcriptional Activity

Abstract

Background and Hypothesis: PGC-1α (peroxisome proliferator activated receptor-gamma coactivator-1α) coordinately regulates fatty acid metabolism. The O-linked β-N-acetylglucosamine post-translational modification (O-GlcNAc) of proteins is a glucose-derived metabolic signal. We hypothesized that metabolic changes during cardiomyocyte hypertrophy might involve interaction between glycolysis and fatty acid metabolism, specifically via O-GlcNAc modification of PGC-1α. Methods and Results: Mechanical stretch (24 h at 4%; Flexercell FX-4000) in neonatal rat cardiomyocytes (n > 4/group) induced a significant (p<0.05) increase (113 ± 35% over No Stretch) in ANP mRNA, confirming induction of hypertrophy. Mechanical stretch significantly augmented (p<0.001; n = 5) global O-GlcNAcylation of several proteins, which was completely reversed by adenoviral overexpression of the deglycosylating enzyme (O-GlcNAcase). Mechanical stretch also augmented mRNA levels of O-GlcNAc transferase (OGT: adds O-GlcNAc to proteins) and glutamine:fructose aminotransferase (GFAT: rate-limiting step for the O-GlcNAc sugar donor), further indicating recruitment of O-GlcNAc signaling. Immunoprecipitation identified PGC-1α as an O-GlcNAc target in this cardiomyocyte hypertrophy model. Real-time (q)-PCR revealed that O-GlcNAc modification of PGC-1α correlated with elevated mRNA levels (n=4/group) of MCAD and COXIV-5b, implying transcriptional activation of PGC-1α. Conclusions: Cardiomyocyte hypertrophy induces O-GlcNAcylation of PGC-1α and represents a surprising and novel potential regulatory interaction between glycolytic and fatty acid metabolism. This research has received full or partial funding support from the American Heart Association, AHA National Center.