Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.3.9 (glucose-6-phosphatase)
3,081 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cultured astroglial cells are able to utilize the monosaccharides glucose, mannose, or fructose as well as the sugar alcohol sorbitol as energy fuel. Astroglial uptake of the aldoses is carrier-mediated, whereas a non-saturable transport mechanism is operating for fructose and sorbitol. The first metabolic step for all sugars, including fructose being generated by enzymatic oxidation of sorbitol, is phosphorylation by hexokinase. Besides glucose only mannose may serve as substrate for build-up of astroglial glycogen. Whereas glycogen synthase appears to be present in astrocytes as well as neurons, the exclusive localization of glycogen phosphorylase in astrocytes and ependymal cells of central nervous tissue correlates well with the occurrence of glycogen in these cells. The identification of lactic acid rather than glucose as degradation product of astroglial glycogen appears to render the presence of glucose-6-phosphatase in cultured astrocytes an enigma. The colocalization of pyruvate carboxylase, phosphenolpyruvate carboxykinase and fructose-1,6-bisphosphatase points to astrocytes as being the gluconeogenic cell type of the CNS.
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PMID:Metabolic pathways for glucose in astrocytes. 929 44

The mRNA abundance of several hepatic glycolytic and gluconeogenic enzymes and blood hormone concentrations were determined in hemorrhagic hypotension-induced rats before and after resuscitation with lactated Ringer's. Northern blot analysis of total liver RNA after 30 min of hemorrhage showed control values for phospho-enolpyruvate carboxykinase and fructose-1,6-bisphosphatase mRNA, but significantly lower values for 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (6PF2K/FBPase) as well as 2.5-fold increases in glucose-6-phosphatase (Glu-6-Pase) mRNA. The latter finding is in agreement with the greatly reduced intracellular levels of fructose-6-phosphate and glucose-6-phosphate, and the results are consistent with a rapid activation of hepatic gluconeogenesis by the concomitant decrease in 6PF2K/FBPase and increase in Glu-6-Pase. Blood insulin levels were decreased during hemorrhage and with resuscitation, whereas glucocorticoids were increased 1.5-fold in both cases. Glucagon was unchanged during hemorrhage, but was reduced with resuscitation. Lactated Ringer's resuscitation seemed to affect 6PF2K/FBPase only, which was restored to, and even exceeded, control values. In contrast, Glu-6-Pase mRNA was increased to fourfold control values. The increase in Glu-6-Pase and the decrease in 6PF2K/FBPase mRNA is probably at the level of altered transcriptional rates, because insulin, which plays a dominant role in the regulation of these genes, was decreased during hemorrhage. It remains to be determined what factors are causing further induction of Glu-6-Pase gene after lactated Ringer's resuscitation when hepatic glucose metabolism seems to have reverted to the glycolytic mode.
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PMID:Alterations in hepatic 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase and glucose-6-phosphatase gene expression after hemorrhagic hypotension and resuscitation. 936 51

The effect of dehydroepiandrosterone (DHEA) on the hepatic and muscle glucose metabolizing enzymes and on blood glucose were investigated in insulin-resistant diabetic C57BL/KsJ-db/db mice and their heterozygote littermates (db/+m). The results were compared with those after troglitazone administration under the same conditions. Despite hyperinsulinemia, hepatic glucose-6-phosphatase (G6Pase) and fructose-1,6-bisphosphatase (FBPase) activities are higher in db/db than in db/+m mice. Dietary administration of DHEA and that of troglitazone for 15 days to respective groups of five mice each significantly decreased blood glucose in db/db mice and hepatic G6Pase and FBPase activities in both db/db and db/+m mice. Hepatic G6Pase and FBPase activities showed a linear relationship with blood glucose in all groups of mice, suggesting that the activities of G6Pase and FBPase are closely related to blood glucose levels. Because androstenedione, a DHEA metabolite, barely affected either of these enzyme activities or blood glucose in db/db mice, the actions of DHEA, which are similar to those of troglitazone, are presumed to be caused by DHEA itself. DHEA is considered to be a modulating agent for the activities of hepatic gluconeogenic enzymes in db/db mice.
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PMID:Dehydroepiandrosterone suppresses the elevated hepatic glucose-6-phosphatase and fructose-1,6-bisphosphatase activities in C57BL/Ksj-db/db mice: comparison with troglitazone. 1042 76

The effects of insulin, sodium orthovanadate and a hypoglycemic plant material, Trigonella foenum graecum (fenugreek) seed powder were studied on the activities of glucose-6-phosphatase and fructose-1,6-bisphosphatase in diabetic liver and kidney. The significantly increased activities of the two enzymes during diabetes in liver and kidney were found to be lowered to almost control values by the use of the antidiabetic compounds. Diabetic liver exhibited a much greater increase in the activities of the two enzymes than diabetic kidney. The highest percentage of reversal to normal values was seen using the combination of vanadate and Trigonella seed powder. The lowered rate of growth of the animals as well as the increased blood sugar were reversed almost to the control levels by the Trigonella seed powder and vanadate treatment. The inclusion of the Trigonella seed powder overcame the toxicity of vanadium encountered when it was given alone as insulin mimetic agent. Much lower levels of vanadate were needed when it was given in combination with Trigonella seed powder. Their combined effects were better at restoring the above parameters than those induced by insulin administration.
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PMID:Modulation of some gluconeogenic enzyme activities in diabetic rat liver and kidney: effect of antidiabetic compounds. 1064 Nov 46

Dehydroepiandrosterone (DHEA) is known to improve hyperglycemia of diabetic C57BL/KsJ-db/db mice that are obese and insulin resistant. In a previous study, we reported that DHEA as well as troglitazone suppresses the elevated hepatic gluconeogenic enzymes, glucose-6-phosphatase (G6Pase) and fructose-1,6-bisphosphatase (FBPase) activities in C57BL/KsJ-db/db mice. In the present study, we evaluated the changes in mRNA of G6Pase and FBPase in db/db mice. Despite hyperinsulinemia, the G6Pase mRNA level of db/db mice was elevated as compared to their heterozygote littermate db/+m mice. In contrast, the FBPase mRNA level was not elevated in db/db mice. Administration of DHEA for two weeks significantly decreased the blood glucose level and the elevated G6Pase mRNA level in db/db mice. No significant changes were seen in the FBPase mRNA level after the administration of DHEA. Administration of troglitazone also decreased the blood glucose and G6Pase mRNA level in db/db mice although no changes were seen in the FBPase mRNA level. These results suggest that the elevation of G6Pase mRNA is important in elucidating the cause of insulin resistance, and that the G6Pase gene is at least one target for the hypoglycemic effects of DHEA as an insulin sensitizing agent in db/db mice.
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PMID:Dehydroepiandrosterone suppresses elevated hepatic glucose-6-phosphatase mRNA level in C57BL/KsJ-db/db mice: comparison with troglitazone. 1122 57

The inappropriate overproduction of glucose by the liver is one of the key contributors to the hyperglycaemia of the diabetic state, and thus is a logical site of intervention for novel anti-diabetic approaches. Metformin is the only currently marketed anti-hyperglycaemic drug whose action is attributed largely to its having inhibitory effects on hepatic glucose production, but its molecular site and mechanism(s) of action remain unknown, whereas the liver acting PPAR alpha agonists have their effects primarily on lipid metabolism. This review therefore rather focuses on candidate molecular targets within the liver for anti-hyperglycaemic therapy, and describes potential rate-controlling receptors and enzymes within the glucose producing pathways (glycogenolysis and gluconeogenesis). Most focus is directed towards inhibitors of the enzymes glucose-6-phosphatase, fructose-1,6-bisphosphatase and glycogen phosphorylase, and towards glucagon receptor antagonists, as these appear to be the most advanced in preclinical and clinical development, although progress with other potential targets is also described. Evidence of the anti-diabetic potential of such agents from animal studies is presented, and the relative merits of each approach are reviewed and compared. It is likely that such agents will become important additions to the therapeutic approaches to combat diabetes.
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PMID:Pharmacological approaches to inhibit endogenous glucose production as a means of anti-diabetic therapy. 1152 55

In models of type 2 diabetes the expression of beta-cell genes is altered, but these changes have not fully explained the impairment in beta-cell function. We hypothesized that changes in beta-cell phenotype and global alterations in both carbohydrate and lipid pathways are likely to contribute to secretory abnormalities. Therefore, expression of genes involved in carbohydrate and lipid metabolism were analyzed in islets 4 weeks after 85-95% partial pancreatectomy (Px) when beta-cells have impaired glucose-induced insulin secretion and ATP synthesis. Px rats after 1 week developed mild to severe hyperglycemia that was stable for the next 3 weeks, whereas neither plasma triglyceride, non-esterified fatty acid, or islet triglyceride levels were altered. Expression of peroxisome proliferator-activated receptors (PPARs), with several target genes, were reciprocally regulated; PPARalpha was markedly reduced even at low level hyperglycemia, whereas PPARgamma was progressively increased with increasing hyperglycemia. Uncoupling protein 2 (UCP-2) was increased as were other genes barely expressed in sham islets including lactate dehydrogenase-A (LDH-A), lactate (monocarboxylate) transporters, glucose-6-phosphatase, fructose-1,6-bisphosphatase, 12-lipoxygenase, and cyclooxygenase 2. On the other hand, the expression of beta-cell-associated genes, insulin, and GLUT2 were decreased. Treating Px rats with phlorizin normalized hyperglycemia without effecting plasma fatty acids and reversed the changes in gene expression implicating the importance of hyperglycemia per se in the loss of beta-cell phenotype. In addition, parallel changes were observed in beta-cell-enriched tissue dissected by laser capture microdissection from the central core of islets. In conclusion, chronic hyperglycemia leads to a critical loss of beta-cell differentiation with altered expression of genes involved in multiple metabolic pathways diversionary to normal beta-cell glucose metabolism. This global maladaptation in gene expression at the time of increased secretory demand may contribute to the beta-cell dysfunction found in diabetes.
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PMID:Genetic regulation of metabolic pathways in beta-cells disrupted by hyperglycemia. 1178 87

Effect of vanadyl acetylacetonate (VAc) and metformin on gluconeogenesis has been studied in isolated hepatocytes and kidney-cortex tubules of rabbit. Glucose formation from alanine+glycerol+octanoate, pyruvate or dihydroxyacetone was inhibited by 50-80% by 100 microM VAc or 500 microM metformin in renal tubules of control and alloxan-diabetic animals, while the inhibitory action of these compounds in hepatocytes was less pronounced (by about 20-30%). In contrast to VAc, metformin increased the rate of lactate formation by about 2-fold in renal tubules incubated with alanine+glycerol+octanoate. In view of VAc-induced changes in intracellular gluconeogenic intermediates and gluconeogenic enzyme activities, it is likely that this compound may decrease fluxes through pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose-1,6-bisphosphatase and glucose-6-phosphatase. In contrast to VAc, metformin-induced decrease in renal gluconeogenesis may result from a decline of cytosolic oxaloacetate level and consequently PEPCK activity. Following 6 days of VAc administration (1.275 mg Vkg(-1) body weight daily) the blood glucose level in alloxan-diabetic rabbits was normalised while blood glucose changes in control animals were not observed. On the contrary, in diabetic animals treated for 6 days with metformin (200 mg kg(-1) body weight day(-1)) a high blood glucose level was maintained. Unfortunately, VAc-treated control and diabetic rabbits exhibited elevated serum urea and creatinine levels. In VAc-treated animals vanadium was accumulated in kidney-cortex up to 7.6+/-0.6 microg Vg(-1) dry weight. In view of a potential vanadium nephrotoxicity a therapeutic application of vanadium compounds needs a critical re-evaluation.
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PMID:Inhibition of gluconeogenesis by vanadium and metformin in kidney-cortex tubules isolated from control and diabetic rabbits. 1196 Jun 14

Uteroplacental insufficiency and subsequent intrauterine growth retardation (IUGR) increase the risk of type 2 diabetes in humans and rats. Unsuppressed endogenous hepatic glucose production is a common component of the insulin resistance associated with type 2 diabetes. Peroxisome proliferator-activated receptor-gamma coactivator-1 (PGC-1) mediates hepatic glucose production by controlling mRNA levels of glucose-6-phosphatase (G-6-Pase), phosphoenolpyruvate carboxykinase (PEPCK), and fructose-1,6-bisphosphatase (FBPase). We therefore hypothesized that gene expression of PGC-1 would be increased in juvenile IUGR rat livers, and this increase would directly correlate with hepatic mRNA levels of PEPCK, G-6-Pase, and FBPase, but not glucokinase. We found that IUGR hepatic PGC-1 protein levels were increased to 230 +/- 32% and 310 +/- 47% of control values at d 0 and d 21 of life, respectively. Similarly, IUGR hepatic PGC-1 mRNA levels were significantly elevated at both ages. Concurrent with the increased PGC-1 gene expression, IUGR hepatic mRNA levels of G-6-Pase, PEPCK, and FBPase were also significantly increased, whereas glucokinase mRNA levels were significantly decreased. These data suggest that increased PGC-1 expression and subsequent hepatic glucose production contribute to the insulin resistance observed in the IUGR juvenile rat.
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PMID:Increased hepatic peroxisome proliferator-activated receptor-gamma coactivator-1 gene expression in a rat model of intrauterine growth retardation and subsequent insulin resistance. 1207 78

It has been shown recently that glutamine is taken up by the mouse kidney in vivo. However, knowledge about the fate of this amino acid and the regulation of its metabolism in the mouse kidney remains poor. Given the physiological and pathophysiological importance of renal glutamine metabolism and the increasing use of genetically modified mice in biological research, we have conducted a study to characterize glutamine metabolism in the mouse kidney. Proximal tubules isolated from fed and 48 h-starved mice and then incubated with a physiological concentration of glutamine, removed this amino acid and produced ammonium ions at similar rates. In agreement with this observation, activities of the ammoniagenic enzymes, glutaminase and glutamate dehydrogenase, were not different in the renal cortex of fed and starved mice, but the glutamate dehydrogenase mRNA level was elevated 4.5-fold in the renal cortex from starved mice. In contrast, glucose production from glutamine was greatly stimulated whereas the glutamine carbon removed, that was presumably completely oxidized in tubules from fed mice, was virtually suppressed in tubules from starved animals. In accordance with the starvation-induced stimulation of glutamine gluconeogenesis, the activities and mRNA levels of glucose-6-phosphatase, and especially of phosphoenolpyruvate carboxykinase, but not of fructose-1,6-bisphosphatase, were increased in the renal cortex of starved mice. On the basis of our in vitro results, the elevated urinary excretion of ammonium ions observed in starved mice probably reflected an increased transport of these ions into the urine at the expense of those released into the renal veins rather than a stimulation of renal ammoniagenesis.
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PMID:Effect of starvation on glutamine ammoniagenesis and gluconeogenesis in isolated mouse kidney tubules. 1216 89


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