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2؉ -sensitive nuclear translocation of a chimeric protein bearing the nuclear localization signal of a nuclear factor of activated T-cells transcription factor. The attenuation of CCE by hyperglycemia was prevented by azaserine, an inhibitor of hexosamine biosynthesis, and partially by inhibitors of oxidative stress. This complements previous work showing that increasing hexosamine metabolites in neonatal cardiomyocytes also inhibited CCE. The inhibition of CCE by hyperglycemia thus provides a likely explanation for the transition to diabetic cardiomyopathy as well as to the protection afforded to injury after ischemia/reperfusion in diabetic models. Diabetes

Stress-induced hyperglycemia is necessary for maximal rates of survival after severe hemorrhage; however, the responsible mechanisms are not clear. One consequence of hyperglycemia is an increase in hexosamine biosynthesis, which leads to increases in levels of O-linked attachment of N-acetyl-glucosamine (O-GlcNAc) on nuclear and cytoplasmic proteins. This modification has been shown to lead to improved survival of isolated cells after stress. In view of this, we hypothesized that glucosamine (GlcNH2), which more selectively increases the levels of O-GlcNAc administration after shock, will have salutary effects on organ function after trauma hemorrhage (TH). Fasted male rats that underwent midline laparotomy were bled to a mean arterial blood pressure of 40 mmHg for 90 min and then resuscitated with Ringer lactate (four times the shed blood volume). Administration of 2.5 mL of 150 mmol L GlcNH2 midway during resuscitation improved cardiac output 2-fold compared with controls that received 2.5 mL of 150 mmol L NaCl. GlcNH2 also improved perfusion of various organs systems, including kidney and brain, and attenuated the TH-induced increase in serum levels of IL-6 (902+/-224 vs. 585+/-103 pg mL) and TNF-alpha (540+/-81 vs. 345+/-110 pg mL) (values are mean+/-SD). GlcNH2 administration resulted in significant increase in protein-associated O-GlcNAc in the heart and brain after TH. Thus, GlcNH2 administered during resuscitation improves recovery from TH, as assessed by cardiac function, organ perfusion, and levels of circulating inflammatory cytokines. This protection correlates with enhanced levels of nucleocytoplasmic protein O-GlcNAcylation and suggests that increased O-GlcNAc could be the mechanism that links stress-induced hyperglycemia to improved outcomes.

Hyperglycemia diminishes positive inotropic responses to agonists that activate phospholipase C (PLC) and generate inositol trisphosphate (1,4,5). The mechanisms underlying both the inotropic responses and hyperglycemia's effects on them remain undetermined, but data from isolated cardiomyocytes suggest the involvement of capacitative Ca 2؉ entry (CCE), the influx of Ca 2؉ through plasma membrane channels activated in response to depletion of endoplasmic or sarcoplasmic reticulum Ca 2؉ stores. In neonatal rat cardiomyocytes, hyperglycemia decreased CCE induced by PLC-mediated agonists. The attenuation of CCE was also seen with glucosamine, and the inhibition by hyperglycemia was prevented by azaserine, thereby implicating hexosamine biosynthesis as the responsible metabolic pathway. In the current study, the importance of hexosamine metabolites to hyperglycemia's effects on inotropic responses was examined in isolated perfused rat hearts. The inhibition by hyperglycemia of phenylephrine-induced inotropy was reversed with azaserine and mimicked by glucosamine. An independent inhibitor of CCE, SKF96365, was also effective in blunting inotropy. These treatments did not inhibit inotropy induced by activation of adenylate cyclase through ␤-adrenergic receptors. These data thus implicate CCE in responses to PLC-mediated agonists in the intact heart and point to the hexosamine pathway's negative effect on CCE as being central to the inhibition seen with hyperglycemia.

The enzyme phosphoglucomutase functions at a key point in carbohydrate metabolism. In this paper, we show that the synthesis of the major isoform of yeast phosphoglucomutase, encoded by the GAL5 (PGM2) gene, is regulated in a manner that is distinct from that previously described for other enzymes involved in galactose metabolism in the yeast Saccharomyces cerevisiae. Accumulation of this isoform increased four-to sixfold when the culture experienced either glucose depletion or heat shock. However, heat shock induction did not occur unless the cells were under glucose repression. This nonadditive increase in expression suggests that the regulatory mechanisms controlling the heat shock induction and glucose repression of the GAL5 gene are functionally related. We previously demonstrated that phosphoglucomutase is modified by a posttranslational Glc-phosphorylation reaction. We now show that this posttranslational modification, like phosphoglucomutase expression itself, is also regulated by galactose induction and glucose repression. Finally, no evidence was found to indicate that the Glc-phosphorylation of phosphoglucomutase alters its enzymatic activity under the conditions examined.The interconversion of Glc-1-P and Glc-6-P, a key metabolic trafficking point in all cells, is carried out by the enzyme phosphoglucomutase (EC 2.7.5.1). In Saccharomyces cerevisiae cells grown on galactose as the primary carbon source, the Glc-1-P formed as a result of galactose metabolism is converted to Glc-6-P by phosphoglucomutase as a required step in providing cells with carbon-containing precursors. When yeast cells are grown on other carbon sources, phosphoglucomutase functions primarily to convert Glc-6-P to Glc-1-P. Glc-1-P is required for the synthesis of the sugar nucleotide UDP-Glc, which acts as a precursor for the synthesis of oligosaccharides and trehalose. Phosphoglucomutase consists of two isoforms in S. cerevisiae (31). The major isoform is encoded by the GAL5 (PGM2) gene (8), while the gene encoding the minor isoform is called PGM1 (3).The synthesis of most enzymes involved in the galactose utilization (Leloir) pathway is subject to tight control by overlapping mechanisms of glucose repression and galactose induction, leading to as much as a 1,000-fold induction of enzyme levels when a yeast culture is shifted from glucose to galactose medium. In contrast, phosphoglucomutase was regarded as a constitutively expressed enzyme for many years (3, 12). Since phosphoglucomutase function is also required for growth on media containing glucose as the carbon source, this conclusion was consistent with its metabolic function. However, phosphoglucomutase synthesis is also regulated by glucose repression and galactose induction, although the magnitude of this regulation is considerably weaker than that of other genes involved in galactose metabolism (23). The galactose regulation of the GAL5 gene, like other genes encoding proteins in the Leloir pathway, is mediated by the Gal4p-Gal80p regulatory system. Gal4p acts as a posi...