| Description: |
Increased levels of protein-associated O-linked N-acetylglucosamine (O-GlcNAc) have been correlated with increased tolerance to stress. Therefore the goal of this study was to determine whether enhanced flux through the hexosamine biosynthesis pathway (HBP), which leads to elevated levels of O-GlcNAc, increased the tolerance of the heart to ischemia and reperfusion (I/R). Hearts from male rats were isolated and perfused with Krebs-Henseliet buffer containing 5mM glucose, and global, no-flow ischemia was in-duced for 20min followed by 60 min reperfusion. 20 min pre-treatment with 10 mM glu-cosamine, which enters the HBP directly, significantly improved functional recovery and decreased cardiac Troponin I release during reperfusion. This protection was associated with a marked increase in the level of O-GlcNAc. Pre-treatment with 5mM alloxan, an inhibitor of O-GlcNAc transferase (OGT), the enzyme that catalyzes O-GlcNAcylation, completely reversed the protection seen with glucosamine and prevented the increase in O-GlcNAc. Glutamine: fructose-6-phosphate amidotransferase (GFAT) regulates the en-try of glucose into the HBP, and glutamine is essential for GFAT activity. 30 min |