Avaliação computacional de compostos naturais como potenciais inibidores para PEPCK-M humana: uma alternativa para terapia contra o câncer de pulmão / Computational evaluation of natural compounds as potential inhibitors for human PEPCK-M: an alternative for lung cancer therapy

O câncer de pulmão é a principal causa de morte relacionada ao câncer no mundo. Entre os seus subtipos, o câncer de pulmão de células não-pequenas (CPCNP) é o mais frequente. Apesar dos tratamentos disponíveis, a taxa de sobrevida ainda é baixa para este subtipo, enfatizando a necessidade de novas alternativas terapêuticas. Recentemente, a isoforma mitocondrial da enzima fosfoenolpiruvato carboxiquinase (HsPEPCK-M) foi apontada como responsável pela adaptação metabólica no CPCNP capaz de permitir o crescimento tumoral mesmo em condições de deficiência de glicose. Esta adaptação é possível devido a função da HsPEPCK-M na gliconeogênese, convertendo o oxaloacetato em fosfoenolpiruvato na presença de GTP, o que representa um papel importante no suporte energético desses tumores. Neste contexto, foi demonstrado que a inibição ou knockdown desta enzima foi capaz de induzir a apoptose em CPCNP em condições de baixa glicose. Estes dados realçam a importância de identificar inibidores eficazes para HsPEPCK-M que possam, potencialmente, se tornar uma alternativa para o tratamento do CPCNP

Neste estudo, novos inibidores putativos foram propostos para a PEPCK-M humana (HsPEPCK-M) com base em uma abordagem guiada por computador, incluindo a modelagem de farmacóforo baseada em estrutura e triagem por atracamento molecular. As hipóteses de farmacóforo geradas foram utilizadas para a triagem virtual do conjunto de compostos naturais do banco ZINC, produzindo 7.124 compostos candidatos. Estes foram submetidos à estudos de atracamento molecular utilizando três conformações de HsPEPCK-M geradas por modelagem comparativa. O objetivo foi selecionar compostos com alta afinidade de ligação predita em relação a pelo menos uma das conformações de HsPEPCK-M. Após o atracamento molecular, 612 moléculas foram selecionadas como potenciais inibidores de HsPEPCK-M. Estes compostos foram então agrupados de acordo com sua similaridade estrutural. A análise do perfil químico e as análises do modo de ligação destes compostos permitiram a proposta de quatro compostos promissores: ZINC01656421, ZINC895296, ZINC00895535 e ZINC02571340. Estes compostos podem ser considerados potenciais candidatos a inibidores de HsPEPCK-M e também podem ser utilizados como compostos líderes para o desenvolvimento de novos inibidores de HsPEPCK-M. (AU)

The role of arecoline on hepatic insulin resistance in type 2 diabetes rats / 中国应用生理学杂志

<p><b>OBJECTIVE</b>To explore the effects of arecoline on hepatic insulin resistance in type 2 diabetes rats and to elucidate its possible mechanism.</p><p><b>METHODS</b>Forty five Wistar rats were fed with high fructose diet for 12 weeks to induce type 2 diabetic rat model. rats were randomly divided into 5 groups (n = 8): control group, model group and model group were treated with different dose (0, 0.5, 1, 5 mg/kg) of arecoline. After 4 weeks, the fasting blood glucose, blood lipid and insulin level measured , mRNA expression of liver constitutive androstane receptor (CAR), pregnane X receptor (PXR), glucose-6-phosphatase (G6Pase), phosphoenolpyruvate carboxykinase (PEPCK), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) were detected by reverse transcription polymerase chain reaction (RT-PCR), the protein expression of p-AKT and glucose transporter4 (GLUT4) were detected by Western blot.</p><p><b>RESULTS</b>1.5 mg/kg arecoline could significantly decrease the level of fasting blood glucose, blood lipid, blood insulin level and liver G6Pase, PEPCK, IL-6, TNF-alpha mRNA level in type 2 diabetes rats. 1.5 mg/kg arecoline also could significantly increase CAR, PXR mRNA level and p-AKT and GLUT4 protein expression.</p><p><b>CONCLUSION</b>Arecoline improved hepatic insulin resistance in type 2 diabetes rats by increasing the mRNA levels of CAR and PXR leading to the creased glucose metabolism and inflammation related genes expression.</p>

Influence of gastric bypass surgery on hepatic gluconeogenesis in type 2 diabetic Goto Kakizaki rats / 中华胃肠外科杂志

<p><b>OBJECTIVE</b>To investigate the influence and significance of gastric bypass surgery on hepatic gluconeogenesis in type 2 diabetic Goto Kakizaki(GK) rats.</p><p><b>METHODS</b>Forty GK rats were randomly divided into Roux-en-Y gastric bypass group(group A) and sham operation group(group B). Differences in glucose tolerance experiment(OGTT) at preoperative and postoperative 1, 2 and 4 weeks were compared and weight was recorded. Glycated hemoglobin levels were measured preoperatively and 4 weeks postoperatively. The animals were sacrificed 4 weeks after surgery and liver tissues were harvested to detect the relative expression of mRNA and protein of glucose 6 phosphatase(G-6-P) and phosphoenol pyruvate kinase(PEPCK) with RT-PCR and Western blot.</p><p><b>RESULTS</b>Fasting blood glucose levels were 6.5, 4.9, and 4.7 mmol/L in group A, and were 10.3, 10.4, and 12.5 mmol/L in group B, and the differences between two groups were statistically significant(P<0.05). The blood glucose level at 2 h after stomach lavage were 8.3, 6.4 and 5.5 mmol/L in group A, and were 21.4, 23.8 and 24.7 mmol/L in group B at postoperative 1, 2, 4 weeks, and the differences between two groups were statistically significant(P<0.05). The glycosylated hemoglobin at postoperative 4 weeks was(6.8±1.0)%, significantly lower than that in group B[(7.9±0.8)%, P<0.05]. Hepatic G-6-P and PEPCK mRNA relative expression at postoperative 4 weeks was reduced by 21.0% and 25.9% respectively as compared to group B, and the protein expression reduced as well. Immunohistochemistry showed that hepatic glycogen sedimentary in group A increased significantly.</p><p><b>CONCLUSION</b>The relative mRNA and protein level of key enzymes of hepatic gluconeogenesis are significantly decreased after Roux-en-Y gastric bypass surgery and hepatic gluconeogenesis is reduced, which may be a potential mechanism of the decrease of blood glucose.</p>

Effect of gastric bypass surgery on mRNA expression level of hepatic phosphoenolpyruvate carboxykinase in type 2 diabetic Goto-Kakizaki rats / 中华胃肠外科杂志

<p><b>OBJECTIVE</b>To investigate the effects of gastric bypass surgery(GBP) on hepatic phosphoenolpyruvate carboxykinase(PEPCK) mRNA expression in type 2 diabetic Goto-Kakizaki rats.</p><p><b>METHODS</b>Male GK rats were randomized into three groups: gastric bypass surgery(n=10), sham operation with diet restriction(n=10), and sham operation alone(n=10). Liver specimens of GK rats were collected during the intraoperative period for self-control study and 8 weeks after surgery. Fasting blood glucose, food intake, and body weight were recorded before surgery and 1, 2, 4, 8 weeks after surgery. The expression of PEPCK mRNA was measured by real-time PCR.</p><p><b>RESULTS</b>The fasting plasma glucose level decreased from(17.6±2.1) mmol/L before surgery to(7.5±0.9) mmol/L 8 weeks after surgery in GBP group. The level of PEPCK mRNA decreased from 1.08±0.38 before surgery to 0.41±0.10 8 weeks after surgery, significantly lower than that in sham operation alone group(1.04±0.12)(P<0.01). The level of PEPCK mRNA in diet restriction group increased from 1.15±0.16 before surgery to 2.54±0.82 8 weeks after surgery(P<0.01). The expression of PEPCK mRNA in diet restriction was significantly higher than that in CBP group(P<0.01).</p><p><b>CONCLUSIONS</b>GBP can significantly improve hyperglycemia in type 2 diabetic GK rat models, which may be associated with the decrease of hepatic PEPCK mRNA level.</p>

Protective effects of Liuweidihuangwan on hepatic insulin resistance in OLETF rats / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the mechanism through which Liuweidihuangwan improves hepatic insulin resistance in type 2 diabetic rats.</p><p><b>METHODS</b>With LETO rats as the normal control group, OLETF rats were treated daily with or without Liuweidihuangwan. At 8, 32, and 40 weeks of the treatment, 3 rats were randomly selected from each group for histological examination of the liver tissues and for detection of phosphoenolpyruvate carboxylase kinase (PEPCK) mRNA expression using RT-PCR and insulin receptor substrate-1 (IRS-1) and IRS-2 protein expressions using Western blotting.</p><p><b>RESULTS</b>Compared with LETO rats, OLETF rats showed progressive destruction of the lobular structures and hepatic steatosis in the liver over time. OLETF rats with Liuweidihuangwan treatment had basically normal lobular structure with only mild fatty degeneration in the liver. RT-PCR detection demonstrated a significantly higher PEPCK mRNA expression in untreated OLETF rats than in LETO rats (P<0.01), but a significantly lowered PEPCK expression in OLETF rats after Liuweidihuangwan dosing (P<0.01). Western blotting showed that significantly lower p-IRS-1 and p-IRS-2 protein expressions in untreated OLETF rats than those in LETO rats and treated OLTEF rats (P<0.05).</p><p><b>CONCLUSION</b>Liuweidihuangwan improves hepatic insulin resistance in OLETF rats by inhibiting the activity of gluconeogenic key enzyme (PEPCK) in the liver and enhancing IRS-1 and IRS-2 expressions in the insulin signaling pathway.</p>

Hypoglycemic effect of Octomeles sumatrana aqueous extract in streptozotocin-induced diabetic rats and its molecular mechanisms

OBJECTIVE@#To investigate the hypoglycemic effect of the aqueous extract of Octomeles sumatrana (O. sumatrana) (OS) in streptozotocin-induced diabetic rats (STZ) and its molecular mechanisms.@*METHODS@#Diabetes was induced by intraperitoneal (i.p.) injection of streptozotocin (55 mg/kg) in to male Sprague-Dawley rats. Rats were divided into six different groups; normal control rats were not induced with STZ and served as reference, STZ diabetic control rats were given normal saline. Three groups were treated with OS aqueous extract at 0.2, 0.3 and 0.5 g/kg, orally twice daily continuously for 21 d. The fifth group was treated with glibenclamide (6 mg/kg) in aqueous solution orally continuously for 21 d. After completion of the treatment period, biochemical parameters and expression levels of glucose transporter 2 (Slc2a2), glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PCK1) were determined in liver by quantitative real time PCR.@*RESULTS@#Administration of OS at different doses to STZ induced diabetic rats, resulted in significant decrease (P<0.05) in blood glucose level in a dose dependent manner by 36%, 48%, and 64% at doses of 0.2, 0.3 and 0.5 g/kg, respectively, in comparison to the STZ control values. Treatment with OS elicited an increase in the expression level of Slc2a2 gene but reduced the expression of G6Pase and PCK1 genes. Morefore, OS treated rats, showed significantly lower levels of serum alanine transaminase (ALT), aspartate aminotransferase (AST) and urea levels compared to STZ untreated rats. The extract at different doses elicited signs of recovery in body weight gain when compared to STZ diabetic controls although food and water consumption were significantly lower in treated groups compared to STZ diabetic control group.@*CONCLUSIONS@#O. sumatrana aqueous extract is beneficial for improvement of hyperglycemia by increasing gene expression of liver Slc2a2 and reducing expression of G6Pase and PCK1 genes in streptozotocin-induced diabetic rats.

Identification of conserved regulatory elements in mammalian promoter regions: a case study using the PCK1 promoter / 基因组蛋白质组与生物信息学报·英文版

A systematic phylogenetic footprinting approach was performed to identify conserved transcription factor binding sites (TFBSs) in mammalian promoter regions using human, mouse and rat sequence alignments. We found that the score distributions of most binding site models did not follow the Gaussian distribution required by many statistical methods. Therefore, we performed an empirical test to establish the optimal threshold for each model. We gauged our computational predictions by comparing with previously known TFBSs in the PCK1 gene promoter of the cytosolic isoform of phosphoenolpyruvate carboxykinase, and achieved a sensitivity of 75% and a specificity of approximately 32%. Almost all known sites overlapped with predicted sites, and several new putative TFBSs were also identified. We validated a predicted SP1 binding site in the control of PCK1 transcription using gel shift and reporter assays. Finally, we applied our computational approach to the prediction of putative TFBSs within the promoter regions of all available RefSeq genes. Our full set of TFBS predictions is freely available at http://bfgl.anri.barc.usda.gov/tfbsConsSites.

Increased expression of gluconeogenic enzymes in the liver of IUGR rats and subsequent insulin resistance / 中国当代儿科杂志

<p><b>OBJECTIVE</b>Intrauterine growth retardation (IUGR) is associated with insulin resistance in later life but the mechanism remains unclear. To explore the molecular mechanism of insulin resistance, we determined the expression of gluconeogenic enzymes as well as the expression of transcription factor which promotes gluconeogenesis in the liver of IUGR rats.</p><p><b>METHODS</b>Rat model of IUGR was established by maternal proteindouble ended arrowmalnutrition. Hepatic mRNA levels of the key enzymes for gluconeogenesis, PEPCK and G6Pase, and of peroxisome proliferator-activated receptor-gammacoactivator (PGC) -1alpha were measured by RT- PCR in male IUGR pup rats at 3 and 8 weeks of their lives. Hepatic PGC-1alpha protein levels were determined by Western blot.</p><p><b>RESULTS</b>The average birth weights of the IUGR group (4.97+/-0.83 g) were significantly lower than normal controls (6.54+/-0.52 g) (P<0.01). Until to 4 weeks of age, the weights of the IUGR rats increased to the control level and were higher than normal controls at 8 weeks of age (P<0.05). There were no significant differences in blood glucose and insulin concentrations between the IUGR rats and normal controls at 3 weeks of age. By 8 weeks of age, the IUGR rats showed high insulin concentrations (P<0.01) and high insulin resistance index (P<0.05) compared with the controls. Hepatic PGC-1alpha mRNA and protein levels as well as hepatic mRNA levels of PEPCK and G6Pase in IUGR rats significantly increased at 3 and 8 weeks compared with controls.</p><p><b>CONCLUSIONS</b>An increased PGC-1alpha expression may contribute to increased mRNA levels of PEPCK and G6Pase, and thus induce the development of insulin resistance in later life in IUGR rats.</p>

The effect of endotoxemia on gluconeogenesis in livers and kidneys during acute hepatic failure / 中华肝脏病杂志

<p><b>OBJECTIVES</b>To explore the effects of endotoxemia on gluconeogenesis in livers and kidneys during acute hepatic failure.</p><p><b>METHOD</b>Twenty-four healthy male SD rats were randomly divided into four groups (6 rats in each group) and all of them were injected intraperitoneally with solutions: group I with normal saline, group II with 400 mg/kg of D-galactosamine (D-GaLN), group III with 400 mg/kg of D-GaLN plus 50 microg/kg lipopolysaccharide(LPS), and group IV with 400 mg/kg of D-GaLN plus 500 microg/kg LPS. At 6 hours after the administration of different solutions intraperitoneally, blood samples were collected to examine blood urea nitrogen (BUN) and serum creatinine. Realtime PCR was used to study the expression of phosphoenolpyruvate carboxykinase (PEPCK) in the livers and kidneys.</p><p><b>RESULTS</b>No endotoxemia developed in group I or group II but it was evident in group III and group IV. The level of endotoxemia in group IV was higher than in group III (8.05+/-0.43, 3.50+/-2.25, P<0.05). After 6 hours of administration of LPS in group IV, hypoglycemia appeared, and blood glucose was normal in the other three groups. BUN and serum creatinine were all normal in the four groups, except that blood urea nitrogen was elevated in group IV. The mRNA of PEPCK in livers decreased gradually in all the four groups (2.54+/-1.32 vs 1.87+/-0.15 vs 0.91+/-0.13 vs 0.44+/-0.42, P<0.05). In the kidneys there was no change in the expression of PEPCK in group I and group II (0.75+/-0.03 and 0.77+/-0.04, P>0.05), but it increased in group III (0.75+/-0.03 vs 1.63+/-0.86, P<0.05), and decreased in group IV (0.75+/-0.03 vs 0.13+/-0.07, P<0.05).</p><p><b>CONCLUSION</b>During acute hepatic failure severe endotoxemia would damage the function of gluconeogenesis in livers and kidneys by inhibiting transcription of PEPCK and this can induce hypoglycemia.</p>

Cell volume changes affect gluconeogenesis in the perfused liver of the catfish Clarias batrachus.

In addition to lactate and pyruvate, some amino acids were found to serve as potential gluconeogenic substrates in the perfused liver of Clarias batrachus. Glutamate was found to be the most effective substrate, followed by lactate, pyruvate, serine, ornithine, proline, glutamine, glycine, and aspartate. Four gluconeogenic enzymes, namely phosphoenolpyruvate carboxykinase (PEPCK), pyruvate carboxylase (PC), fructose 1,6-bisphosphatase (FBPase) and glucose 6-phosphatase (G6Pase) could be detected mainly in liver and kidney, suggesting that the latter are the two major organs responsible for gluconeogenic activity in this fish. Hypo-osmotically induced cell swelling caused a significant decrease of gluconeogenic efflux accompanied with significant decrease of activities of PEPCK, FBPase and G6Pase enzymes in the perfused liver. Opposing effects were seen in response to hyperosmotically induced cell shrinkage. These changes were partly blocked in the presence of cycloheximide, suggesting that the aniso-osmotic regulations of gluconeogenesis possibly occurs through an inverse regulation of enzyme proteins and/or a regulatory protein synthesis in this catfish. In conclusion, gluconeogenesis appears to play a vital role in C. batrachus in maintaining glucose homeostasis, which is influenced by cell volume changes possibly for proper energy supply under osmotic stress.

Construction and identification of recombinant firefly luciferase reporter plasmid pGL2-PEPCK-Luc / 中国医学科学院学报

<p><b>OBJECTIVE</b>To evaluate in vitro regulation of phosphoenolpyruvate carboxykinase (PEPCK) gene promoter on gene transcription, and construct luciferase reporter plasmid pGL2-PEPCK-Luc.</p><p><b>METHODS</b>A 550 bp fragment of PEPCK promoter cut from plasmid pPEPCK-int was inserted into transitional vector PBS-SK to construct a transition plasmid PBS-PEPCK. Then the recombinant luciferase reporter plasmid pGL2-PEPCK-Luc was cloned.</p><p><b>RESULTS</b>Restriction enzymes and nucleotide sequence conformed that the coupling site of recombinant plasmid was correct without base mutation and deletion, and the sequence inserted was the same as data of GeneBank. The luciferase could be expressed in hepatoma cell transfected by pGL2-PEPCK-Luc.</p><p><b>CONCLUSION</b>Established a new means to study transcriptional regulation of PEPCK promoter.</p>

Effect of insulin, cAMP, and dexamethasone on phosphoenolpyruvate carboxykinase gene promoter in vitro / 中国医学科学院学报

<p><b>OBJECTIVE</b>To study the effect of insulin, cyclic adenosine monophosphate (cAMP), and dexamethasone (DEX) on 550 bp (-600 -/+ 69) fragment of phosphoenolpyruvate carboxykinase (PEPCK) gene promoter by reporter gene.</p><p><b>METHODS</b>The recombinant pGL2-PEPCK-Luc and the control plasmid pSV-beta-Galactosidase were co-transfected to rat hepatoma cell line (CBRH7919) by lipofectin. By measuring luciferase activity, we evaluated in vitro regulation of PEPCK gene promoter on reporter gene transcription.</p><p><b>RESULTS</b>cAMP and DEX stimulated PEPCK promoter obviously; meanwhile, they also had accumulative effects. At different physiological concentrations, insulin had a suppressive effect on PEPCK promoter, which was dose-independent.</p><p><b>CONCLUSION</b>There is a perfect feedback mechanism for PEPCK promoter in hepatoma cell. 550 bp (-600 -/+ 69) fragment of PEPCK may be a candidate gene in the gene therapy of diabetes.</p>

Inhibition of phosphoenolpyruvate carboxykinase gene expression by metformin in cultured hepatocytes / 中华医学杂志(英文版)

<p><b>OBJECTIVE</b>To investigate the effect and mechanism of the antihyperglycemic agent metformin on the expression of phosphoenolpyruvate carboxykinase (PEPCK) gene in hepatocytes and to determine whether the effects of metformin in hepatocytes are transmitted throughout the known insulin signaling pathways.</p><p><b>METHODS</b>Confluent H4IIE rat heptoma cells were cultured for 16 h with 0.1 mmol/L metformin either in absence or presence of 0.1 nmol/L insulin, and then stimulated with various agents. The expression of PEPCK gene was examined by Northern blot analysis.</p><p><b>RESULTS</b>Therapeutic concentrations of metformin significantly inhibited basal PEPCK mRNA expression and also decreased cAMP and dexamethasone induced PEPCK gene expression through interaction with insulin. In the presence of insulin signaling pathway inhibitors wortmannin and UO126, metformin reduced PEPCK mRNA levels, but wortmannin blocked inhibitory regulation of insulin on PEPCK gene expression.</p><p><b>CONCLUSION</b>Metformin inhibits PEPCK gene expression via either an insulin-independent or an interacting-with-insulin manner. The results suggest that a possible mechanism by which metformin reduces gluconeogenesis could be associated with the inhibition of PEPCK gene expression.</p>

The limitations of paradigms: studies on the intermediary metabolism of Trypanosoma cruzi

We review the development of our knowledge and interpretations of the intermediary metabolism of Trypanosoma (Schizotrypanum) cruzi. Already in the 1950's it was clearly established that when this organism was exposed to large external concentrations of carbohydrates it was unable to catabolize them completely, even in the presence of oxygen, producing a mixture of CO2, dicarboxylic acids (succinic, malic) and alanine as end products. However, subsequent work tended to emphasize such paradigmatic features as a full complement of glycolytic enzymes in all stages of the life cycle of the parasite, a functional Kreb's cycle, a cytochrome-dependent electron transport chain and phosphorylative oxidation which suggested that T. cruzi had the basic metabolic properties of classical glucose-utilizing cells, in contrast with the degenerate glycolytic metabolism of bloodstream African trypanosomes. Only in the 1980's interest revived on the how and why of the incomplete carbohydrate catabolism by this parasite. The primary reason for this anomaly was found to be the presence of a constitutive phospho-enol-pyruvate carboxykinase (PEPCK, ATP-dependent, E.C.4.1.1.49), present in all stages of the parasite's life cycle, and the lack of regulation of the glycolytic route at its classical control points, hexokinase and phosphofructokinase. On the other hand, the presence of two distinct glutamate dehydrogenases (NAD+ and NADP(+)-dependent), the former being strictly regulated by the energy charge of the cell and the Krebs' cycle activity, indicated that amino acids can be a primary source of energy for this organism.(ABSTRACT TRUNCATED AT 250 WORDS)