Glycogenolysis Pathways Research Articles

Impact of hypoxia on glucose metabolism and hypoxia signaling pathways in juvenile horseshoe crabs Tachypleus tridentatus

Marine hypoxia poses a significant challenge in the contemporary marine environment. The horseshoe crab, an ancient benthic marine organism, is confronted with the potential threat of species extinction due to hypoxia, making it an ideal candidate for studying hypoxia tolerance mechanisms. In this experiment, juvenile Tachypleus tridentatus were subjected to a 21-day trial at DO:2 mg/L (hypoxia) and DO:6 mg/L conditions. The experimental timeline included a 14-day exposure phase followed by a 7-day recovery period. Sampling occurred on days 0, 7, 14, and 21, where the period from day 14 to day 21 corresponds to seven days of recuperation. Several enzymatic activities of important proteins throughout this investigation were evaluated, such as succinate dehydrogenase (SDH), phosphofructokinase (PFK), hexokinase (HK), lactate dehydrogenase (LDH), and pyruvate kinase (PK). Concurrently, the relative expression of hexokinase-1 (HK), hypoxia-inducible factor 1-alpha inhibitor (FIH), and hypoxia-inducible factor 1-alpha (HIF-1α), pyruvate dehydrogenase phosphatase (PDH), succinate dehydrogenase assembly factor 4 (SDH), and Glucose-6-phosphatase (G6Pase) were also investigated. These analyses aimed to elucidate alterations in the hypoxia signaling pathway and respiratory energy metabolism. It is revealed that juvenile T. tridentatus initiated the HIF pathway under hypoxic conditions, resulting in an upregulation of HIF-1α and FIH-1 gene expression, which in turn, influenced a shift in metabolic patterns. Particularly, the activity of glycolysis-related enzymes was promoted significantly, including PK, HK, PKF, LDH, and the related HK gene. In contrast, enzymes linked to aerobic respiration, PDH, and SDH, as well as the related PDH and SDH genes, displayed down-regulation, signifying a transition from aerobic to anaerobic metabolism. Additionally, the activity of gluconeogenesis-related enzymes such as PK and G6Pase gene expression were significantly elevated, indicating the activation of gluconeogenesis and glycogenolysis pathways. Consequently, juvenile T. tridentatus demonstrated an adaptive response to hypoxic conditions, marked by changes in respiratory energy metabolism modes and the activation of hypoxia signaling pathways.

Dietary Betaine Improves Glucose Metabolism in Obese Mice

BackgroundObesity caused by the overconsumption of energy-dense foods high in fat and sugar has contributed to the growing prevalence of type 2 diabetes. Betaine, found in food or supplements, has been found to lower blood glucose concentrations, but its exact mechanism of action is not well understood. ObjectivesA comprehensive evaluation of the potential mechanisms by which betaine supplementation improves glucose metabolism. MethodsHyperglycemic mice were fed betaine to measure the indexes of glucose metabolism in the liver and muscle. To explore the mechanism behind the regulation of betaine on glucose metabolism, Ribonucleic Acid-Seq was used to analyze the livers of the mice. In vitro, HepG2 and C2C12 cells were treated with betaine to more comprehensively evaluate the effect of betaine on glucose metabolism. ResultsBetaine was added to the drinking water of high-fat diet-induced mice, and it was found to reduce blood glucose concentrations and liver triglyceride concentrations without affecting body weight, confirming its hypoglycemic effect. To investigate the specific mechanism underlying its hypoglycemic effect, protein-protein interaction enrichment analysis of the liver revealed key nodes associated with glucose metabolism, including cytochrome P450 family activity, insulin sensitivity, glucose homeostasis, and triglyceride concentrations. The Kyoto Encyclopedia of Genes and Genomes and gene ontogeny enrichment analyses showed significant enrichment of the Notch signaling pathway. These results provided bioinformatic evidence for specific pathways through which betaine regulates glucose metabolism. Key enzyme activities involved in glucose uptake, glycogen synthesis, and glycogenolysis pathways of the liver and muscle were measured, and improvements were observed in these pathways. ConclusionsThis study provides new insight into the mechanisms by which betaine improves glucose metabolism in the liver and muscle and supports its potential as a drug for the treatment of metabolic disorders related to glucose.

Important nutrient sources and carbohydrate metabolism patterns in the growth and development of spargana

BackgroundSparganosis is a worldwide food-borne parasitic disease caused by spargana infection, which infects the muscle of frogs and snakes as well as many tissues and organs in humans. There are currently no viable treatments for sparganosis. Understanding spargana’s nutrition source and carbohydrate metabolism may be crucial for identifying its energy supply and establishing methods of treatment for sparganosis.MethodsUsing an amino acid analyzer and nutrient concentration detection kits, we assessed nutrient concentrations in the muscles of Fejervarya limnocharis and Pelophylax plancyi infected or not infected with spargana. Quantitative polymerase chain reaction (PCR) was used to quantify the major enzymes involved in five glucose metabolism pathways of spargana developing in vivo. We also used quantitative PCR to assess key enzymes and transcriptome sequencing to explore the regulation of carbohydrate metabolic pathways in vitro in response to different 24-h food treatments.ResultsInfected muscle tissues had considerably higher concentrations of glucogenic and/or ketogenic amino acids, glucose, and glycogen than non-infected muscle tissues. We discovered that the number of differentially expressed genes in Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis was larger in low-glucose than in other dietary groups. We examined differences in the expression of genes producing amino acid transporters, glucose transporters, and cathepsins in spargana grown in various nutritional environments. In the normal saline group, only the major enzymes in the tricarboxylic acid cycle (TCA), glycogenesis, and glycogenolysis pathways were expressed. The l-glutamine group had the greatest transcriptional levels of critical rate-limiting enzymes of gluconeogenesis and glycogenesis. Furthermore, the low-glucose group had the highest transcriptional levels of critical rate-limiting enzymes involved in the TCA, glycolytic, and glycogenolysis pathways. Surprisingly, when compared to the in vitro culturing groups, spargana developing in vivo exhibited higher expression of these critical rate-limiting enzymes in these pathways, with the exception of the pentose phosphate pathway.ConclusionsSpargana have a variety of nutritional sources, and there is a close relationship between nutrients and the carbohydrate metabolism pathways. It takes a multi-site approach to block nutrient absorption and carbohydrate metabolism pathways to provide energy to kill them.Graphical

Befunolol as a potential inhibitor of glycogen phosphorylase: an in silico approach

Glycogen phosphorylase (GP) is a rate-limiting allosteric enzyme in the glycogenolysis pathway that contributes to hyperglycemia in type 2 diabetes (T2D). Hence, researchers consider GP a validated target to treat T2D. Commercial antidiabetic drugs are effective but have undesirable effects. Our search for a safer drug led us to investigate a potential GP inhibitor that could modulate blood glucose levels with minimal or no side effects. Herein, we report seven structural analogs of the reference compound N-acetyl-beta-D-glucopyranosyl amine (NBG) (analog of D-glucose) targeting the active site of human liver GPa (PDB ID: 1FC0). In silico molecular docking studies were conducted to predict GPa-ligand interactions. We analyzed drug-likeness and absorption, distribution, metabolism, excretion, and toxicity (ADMET) parameters using AutoDock 4.2, Discovery Studio, SwissADME, ProTox-II, and ADMETlab web tools. Among all compounds, befunolol (−8.83 kcal/mol) exhibited the highest affinity than NBG (−6.20 kcal/mol) for the binding pocket of GPa and inferred a good pharmacokinetic profile. Toxicological endpoint prediction analysis showed befunolol as a non-hERG blocker and non-carcinogenic with a drug score (0.95) higher than NBG (0.30) and an LD50 value of 922 mg/kg. A molecular dynamics simulation of befunolol and NBG for 100 ns using Schrödinger software revealed the stability of protein-ligand complexes. Overall, our findings suggest that befunolol could represent a potential therapeutic drug candidate worth exploring in cell-based and pre-clinical studies.

Multidisciplinary docking, kinetics and X-ray crystallography studies of baicalein acting as a glycogen phosphorylase inhibitor and determination of its’ potential against glioblastoma in cellular models

Glycogen phosphorylase (GP) is the rate-determining enzyme in the glycogenolysis pathway. Glioblastoma (GBM) is amongst the most aggressive cancers of the central nervous system. The role of GP and glycogen metabolism in the context of cancer cell metabolic reprogramming is recognised, so that GP inhibitors may have potential treatment benefits. Here, baicalein (5,6,7-trihydroxyflavone) is studied as a GP inhibitor, and for its effects on glycogenolysis and GBM at the cellular level. The compound is revealed as a potent GP inhibitor against human brain GPa (Ki = 32.54 μM), human liver GPa (Ki = 8.77 μM) and rabbit muscle GPb (Ki = 5.66 μM) isoforms. It is also an effective inhibitor of glycogenolysis (IC50 = 119.6 μM), measured in HepG2 cells. Most significantly, baicalein demonstrated anti-cancer potential through concentration- and time-dependent decrease in cell viability for three GBM cell-lines (U-251 MG, U-87 MG, T98-G) with IC50 values of ∼20–55 μM (48- and 72-h). Its effectiveness against T98-G suggests potential against GBM with resistance to temozolomide (the first-line therapy) due to a positive O6-methylguanine-DNA methyltransferase (MGMT) status. The solved X-ray structure of rabbit muscle GP–baicalein complex will facilitate structure-based design of GP inhibitors. Further exploration of baicalein and other GP inhibitors with different isoform specificities against GBM is suggested.

LBODP039 Glycogenic Hepatopathy- An Underrecognized Complication Of Diabetes

Abstract Introduction Glycogenic hepatopathy (GH) is an infrequently described complication of predominantly type 1 diabetes characterized by liver dysfunction and hepatomegaly. This condition is different from the more common nonalcoholic fatty liver disease (NAFLD) which is clinically indistinguishable. Liver biopsy is currently the only way to differentiate the two conditions. We present a 19 year old female with persistent transaminasemia secondary to glycogenic hepatopathy associated with poorly controlled type 1 diabetes. Case Description A 19 year old female was admitted with DKA secondary to facial cellulitis. She had a past history of poorly controlled type 1 DM since age 9, proteinuria, and transaminasemia since age 14. Initial labs showed elevated plasma glucose 365 mg/dL, bicarbonate 15 mEq/L, anion gap 22, positive betahydroxybutyrate, AST 208 mmol/L, ALT 136 mmol/L, and HbA1c 12. 0%. She was successfully resuscitated from DKA. Repeat liver function tests showed further elevation of AST 819 mmol/L and ALT 346 mmol/L. Ultrasound of liver showed increased echotexture reported as steatosis. Further history revealed significant financial difficulty due to which patient was using different kinds of basal and bolus insulins interchangeably. She would sometimes use bolus insulin to cover for lack of basal insulin. Prior gastroenterology workup showed ANA positivity in a speckled pattern but was otherwise unrevealing for infective, autoimmune, or alcoholic hepatitis. Liver biopsy was therefore recommended by inpatient gastroenterology. Liver biopsy revealed spotty mild lobular hepatitis and focal portal fibrosis consistent with glycogenic hepatopathy. Features of autoimmune hepatitis were not seen in liver biopsy. Discussion Glycogen hepatopathy seems to represent an acquired form of glycogen storage disorder. Pathophysiology is suspected to be a combination of hyperglycemia and hyperinsulinemia leading to increased glycogen accumulation in hepatocytes while glycogenolysis is suppressed. This mechanism seems to correlate with our patient who reported use of large doses of short acting insulin followed by glucose administration to counteract hypoglycemia. Abnormal glucagon activity or enzymes deficiencies in glycogenolysis pathway (as reported with congenital glycogenstorage disorders) have not been elucidated. Recent data has also questioned reversibility and long term safety as liver biopsies of patients with glycogenic hepatopathy have demonstrated varying degrees of fibrosis. Newer MRI protocols seem to be able to distinguish GH from NAFLD, and this is important as these are pathophysiologically distinct and will have different management strategies. This case highlights glycogenic hepatopathy as an underrecognized complication of diabetes that will require improved recognition and further investigation to evaluate long term consequences. Presentation: No date and time listed

GLP-1 responds to postprandial hyperglycemia by reducing transcription level in grass carp (Ctenopharyngodon idella)

Glucagon-like peptide-1 (GLP-1), a member of the proglucagon derived peptide family, is a highly effective incretin to reduce plasma glucose and inhibit food intake in mammals. The physiological function of GLP-1 has been elucidated in some ‘glucose intolerant’ carnivorous fishes. To lay a better understanding in fish glucose intolerance, we synthesized homologous GLP-1 peptide and explored its roles in appetite and glucose regulation under intraperitoneal (IP) injection in herbivorous grass carp which has higher glucose intolerance. The results showed that GLP-1 increased plasma glucose in grass carp. The hyperglycemic effect of the fish GLP-1 was mainly through promoting gluconeogenesis, accompanied by inhibition of glycogen synthesis and stimulation of glycogenolysis pathway. In addition, GLP-1 upregulated the expression of anorexigenic gene (cart) and decreased the orexigenic genes (npy and agrp) expression in grass carp hypothalamus as a conservative way to inhibit the appetite under GLP-1 injection after 2 h. Taken together, the hyperglycemic effect and anorectic role of GLP-1 were performed in a basically consistent manner across fishes with different food habits. What’s more, the gene expressions of proglucagon yielded GLP-1 in foregut and hindgut of grass carp were significantly decreased after a meal within 24 h, indicating that fish might suppress the accumulation of plasma glucose by decreasing GLP-1 expression in a unique way to herbivorous fish. Therefore, this study provided a new perspective for illustrating the difference in glucose utilization among fishes with different food habits based on GLP-1.

An In Silico and an In Vitro Inhibition Analysis of Glycogen Phosphorylase by Flavonoids, Styrylchromones, and Pyrazoles.

Glycogen phosphorylase (GP) is a key enzyme in the glycogenolysis pathway. GP inhibitors are currently under investigation as a new liver-targeted approach to managing type 2 diabetes mellitus (DM). The aim of the present study was to evaluate the inhibitory activity of a panel of 52 structurally related chromone derivatives; namely, flavonoids, 2-styrylchromones, 2-styrylchromone-related derivatives [2-(4-arylbuta-1,3-dien-1-yl)chromones], and 4- and 5-styrylpyrazoles against GP, using in silico and in vitro microanalysis screening systems. Several of the tested compounds showed a potent inhibitory effect. The structure–activity relationship study indicated that for 2-styrylchromones and 2-styrylchromone-related derivatives, the hydroxylations at the A and B rings, and in the flavonoid family, as well as the hydroxylation of the A ring, were determinants for the inhibitory activity. To support the in vitro experimental findings, molecular docking studies were performed, revealing clear hydrogen bonding patterns that favored the inhibitory effects of flavonoids, 2-styrylchromones, and 2-styrylchromone-related derivatives. Interestingly, the potency of the most active compounds increased almost four-fold when the concentration of glucose increased, presenting an IC50 < 10 µM. This effect may reduce the risk of hypoglycemia, a commonly reported side effect of antidiabetic agents. This work contributes with important considerations and provides a better understanding of potential scaffolds for the study of novel GP inhibitors.

Biophysical and functional properties of purified glucose-6-phosphatase catalytic subunit 1

Glucose-6-phosphatase catalytic subunit 1 (G6PC1) plays a critical role in hepatic glucose production during fasting by mediating the terminal step of the gluconeogenesis and glycogenolysis pathways. In concert with accessory transport proteins, this membrane-integrated enzyme catalyzes glucose production from glucose-6-phosphate (G6P) to support blood glucose homeostasis. Consistent with its metabolic function, dysregulation of G6PC1 gene expression contributes to diabetes, and mutations that impair phosphohydrolase activity form the clinical basis of glycogen storage disease type 1a. Despite its relevance to health and disease, a comprehensive view of G6PC1 structure and mechanism has been limited by the absence of expression and purification strategies that isolate the enzyme in a functional form. In this report, we apply a suite of biophysical and biochemical tools to fingerprint the in vitro attributes of catalytically active G6PC1 solubilized in lauryl maltose neopentyl glycol (LMNG) detergent micelles. When purified from Sf9 insect cell membranes, the glycosylated mouse ortholog (mG6PC1) recapitulated functional properties observed previously in intact hepatic microsomes and displayed the highest specific activity reported to date. Additionally, our results establish a direct correlation between the catalytic and structural stability of mG6PC1, which is underscored by the enhanced thermostability conferred by phosphatidylcholine and the cholesterol analog cholesteryl hemisuccinate. In contrast, the N96A variant, which blocks N-linked glycosylation, reduced thermostability. The methodologies described here overcome long-standing obstacles in the field and lay the necessary groundwork for a detailed analysis of the mechanistic structural biology of G6PC1 and its role in complex metabolic disorders.

Diallyl-n-Sulfide of Garlic Inhibits Glycogenolysis in Heat-Stressed Laying Sentul Chicken

Heat stress causes a decrease in metabolic function and immunity, which results in a decrease in production. The provision of natural extracts such as the active compound dyally n-suldifa (Dn-S) is one strategy to overcome the adverse effects of heat stress. One hundred and twenty-five female laying native chickens, with an average body weight of 1213.83±15.52 g, 40 weeks old, were used in this experiment, to study the impact of Dn-S administration from garlic on the metabolite profile of the glycogenolysis pathway. laying. Laying hens were distributed into five treatment groups, each with 25 samples. Dn-S isolation from garlic isolated by distillation technique. The study was carried out with five types of experimental treatments, as follows the group with a comfort zone temperature (24°C) and without the administration of Diallyl n-Sulfide (Dn-S), heat stress (38°C) and without Dn-S, heat stress (38°C) and 100 µL Dn-S, heat stress (38°C) and 125 µL Dn-S, heat stress (38°C) and 150 µL Dn-S/head. Based on the results of the study, it was shown that heat stress causes an increase in the rate of glycogenolysis and intermediate metabolites and their catalyzing enzymes. It appears that the administration of 150 µL Dn-S, effectively reduces the rate of glycogenolysis. It was concluded that heat stress on laying hens could be avoid by administering garlic Dn-S.

Optimization and Validation of an In Vitro Standardized Glycogen Phosphorylase Activity Assay.

Glycogen phosphorylase (GP) is a key enzyme in the glycogenolysis pathway and a potential therapeutic target in the management of type 2 diabetes. It catalyzes a reversible reaction: the release of the terminal glucosyl residue from glycogen as glucose 1-phosphate; or the transfer of glucose from glucose 1-phosphate to glycogen. A colorimetric method to follow in vitro the activity of GP with usefulness in structure-activity relationship studies and high-throughput screening capability is herein described. The obtained results allowed the choice of the optimal concentration of enzyme of 0.38 U/mL, 0.25 mM glucose 1-phosphate, 0.25 mg/mL glycogen, and temperature of 37 °C. Three known GP inhibitors, CP-91149, a synthetic inhibitor, caffeine, an alkaloid, and ellagic acid, a polyphenol, were used to validate the method, CP-91149 being the most active inhibitor. The effect of glucose on the IC50 value of CP-91149 was also investigated, which decreased when the concentration of glucose increased. The assay parameters for a high-throughput screening method for discovery of new potential GP inhibitors were optimized and standardized, which is desirable for the reproducibility and comparison of results in the literature. The optimized method can be applied to the study of a panel of synthetic and/or natural compounds, such as polyphenols.

Organic Diallyl-n-Sulfide (Dn-S) inhibited the glycogenolysis pathway and heart failure of heat-stressed laying hens

Heat stress causes a decrease in metabolic and immune function, thus resulting in decreased production. Natural extracts such as the active compound diallyl-n-sulfide (Dn-S) are one strategy to overcome the adverse effects of heat stress. One hundred and fifty female laying hens, with a mean bodyweight of 1191.38±25.54 g, aged 11 weeks, were used in this experiment to study Dn-S’s impact from garlic on the metabolite profile of the glycogenolysis pathway and heart failure in laying hens. The sample of laying hens was divided into five treatment groups, each with 25 samples and the Dn-S from garlic isolated by distillation technique. The study was carried out with three types of experimental treatment, groups with a zone temperature of heat stress (38°C) and without Dn-S, heat stress (38°C) and 100 μL Dn-S/sample, heat stress (38°C) and 1125 μL Dn-S/sample, respectively. Based on the results of the study, it shows that heat stress causes an increase in the rate of glycogenolysis. It appears that the administration of 200 μL Dn-S effectively reduces the rate of glycogenolysis and can maintain a normal heart condition. It was concluded that heat stress in laying hens could be avoided by administering diallyl n-sulfide (Dn-S) from garlic. Dn-S has an essential role in preventing changes in the osmotic pressure of body fluids. Overall, it can cope with the metabolic and physiological changes associated with heat stress.

Characterising the dynamics of placental glycogen stores in the mouse

IntroductionThe placenta performs a range of functions to support fetal growth. In addition to facilitating nutrient transport, the placenta also stores glucose as glycogen, which is thought to maintain fetal glucose supply during late gestation. However, evidence to support such a role is currently lacking. Similarly, our understanding of the dynamics of placental glycogen metabolism in normal mouse pregnancy is limited. MethodsWe quantified the placental glycogen content of wild type C57BL/6JOlaHsd mouse placentas from mid (E12.5) to late (E18.5) gestation, alongside characterising the temporal expression pattern of genes encoding glycogenesis and glycogenolysis pathway enzymes. To assess the potential of the placenta to produce glucose, we investigated the spatiotemporal expression of glucose 6-phosphatase by qPCR and in situ hybridisation. Separate analyses were undertaken for placentas of male and female conceptuses to account for potential sexual dimorphism. ResultsPlacental glycogen stores peak at E15.5, having increased over 5-fold from E12.5, before declining by a similar extent by E18.5. Glycogen stores were 17% higher in male placentas than in females at E15.5. Expression of glycogen branching enzyme (Gbe1) was reduced ~40% towards term. Expression of the glucose 6-phosphatase isoform G6pc3 was enriched in glycogen trophoblast cells and increased towards term. DiscussionReduced expression of Gbe1 suggests a decline in glycogen branching towards term. Expression of G6pc3 by glycogen trophoblasts is consistent with an ability to produce and release glucose from glycogen stores. However, the ultimate destination of the glucose generated from placental glycogen remains to be elucidated.

Effect of Rubus anatolicus Leaf Extract on Glucose Metabolism in HepG2, CRI-D2 and C2C12 Cell Lines.

IntroductionThe aim of this study was to assess the effects of Rubus anatolicus on glucose metabolism in HepG2, CRI-D2 and C2C12 cell lines.Materials and MethodsR. anatolicus was collected in Golestan province, Iran. Three different cell lines HepG2 (human liver cell), CRI-D2 (mice pancreatic cell) and C2C12 (rat myoblast) were used for cell culture experiments. Cell viability was measured using MTT assay. Cells were treated with various concentrations of the extract (6.25–400 μg/mL) and then the extracellular glucose level and intracellular glycogen content were measured using colorimetric methods. The insulin level of the culture medium was measured using the ELISA method.ResultsOur findings showed that R. anatolicus extract enhances glucose uptake and consumption by all three cell lines. The R. anatolicus extract exposure also elevated cellular glycogen content in HepG2 and C2C12 cells (for 200 and 100 μg/mL) significantly. We found a significant increase in glucose uptake and consequently higher stimulation of insulin secretion in CRI-D2 cell pancreatic cells treated with R. anatolicus extract.ConclusionThe R. anatolicus appears to activate glucose uptake and cellular glycogen synthesis probably by activating the glycogenesis or inhibition of glycogenolysis pathways. The extract enhances insulin secretion in the pancreatic cells by increased glucose uptake.

Immunochemical Study of the Effect of F2Glc on Glycogen Synthase Translocation and Glycogen Synthesis in Isolated Rat Hepatocytes.

The compound 2-deoxy-2-fluoro-α-D-glucopyranosyl fluoride (F2Glc), which is a nonmetabolized superior glucose analogue, is a potent inhibitor of glycogen phosphorylase and pharmacological properties are reported. Glycogen phosphorylase (GP) and glycogen synthase (GS) are responsible of the degradation and synthesis, respectively, of glycogen which is a polymer of glucose units that provides a readily available source of energy in mammals. GP and GS are two key enzymes that modulate cellular glucose and glycogen levels; therefore, these proteins are suggested as potential targets for the treatment of diseases related to glycogen metabolism disorders. We studied by Western Blot technique that F2Glc decreased GP activity, and we also showed that F2Glc did not affect GS activity and its translocation from a uniform cytosolic distribution to the hepatocyte periphery, which is crucial for glycogen synthesis, using immunoblotting and immunofluorescence labeling techniques. F2Glc specifically inhibits glycogenolysis pathway and permits a greater deposition of glycogen. These observations open up the possibility of further develop drugs that act specifically on GP. The ability to selectively inhibit GP, which is a key enzyme for the release of glucose from the hepatic glycogen reserve, may represent a new approach for the treatment of hyperglycemia in type 2 diabetes.

Effect of styrene exposure on plasma parameters, molecular mechanisms and gene expression in rat model islet cells

Styrene is an aromatic hydrocarbon compound present in the environment and have primary exposure through plastic industry. The current study was designed to evaluate styrene-induced toxicity parameters in rat plasma fasting blood glucose (FBG) level, oral glucose tolerance, insulin secretion, oxidative stress, and inflammatory cytokines in cellular and molecular levels. Styrene was dissolved in corn oil and administered at different doses (250, 500, 1000, 1500, 2000mg/kg/day and control) to each rat, for 42days. In treated groups, styrene significantly increased fasting blood glucose, plasma insulin (p<0.001) and glucose tolerance. Glucose tolerance, insulin resistance and hyperglycemia were found to be the main consequences correlating gene expression of islet cells. Styrene caused a significant enhancement of oxidative stress markers (p<0.001) and inflammatory cytokines in a dose and concentration-dependent manner in plasma (p<0.001). Moreover, the activities of caspase-3 and −9 of the islet cells were significantly up-regulated by this compound at 1500 and 2000mg/kg/day styrene administrated groups (p<0.001). The relative fold change of GLUD1 was downregulated (p<0.05) and upregulated at 1500 and 2000mg/kg, respectively (p<0.01). The relative fold changes of GLUT2 were down regulated at 250 and 1000mg/kg and up regulated in 500, 1500 and 2000mg/kg doses of styrene (p<0.01). The expression level of GCK indicated a significant upregulation at 250mg/kg and downregulation of relative fold changes in the remaining doses of styrene, except for no change at 2000mg/kg of styrene for GCK. Targeting genes (GLUD1, GLUT2 and GCK) of the pancreatic islet cells in styrene exposed groups, disrupted gluconeogenesis, glycogenolysis pathways and insulin secretory functions. The present study illustrated that fasting blood glucose, insulin pathway, oxidative balance, inflammatory cytokines, cell viability and responsible genes of glucose metabolism are susceptible to styrene, which consequently lead to other abnormalities in various organs.

Endogenous Protein Interactome of Human UDP-Glucuronosyltransferases Exposed by Untargeted Proteomics.

The conjugative metabolism mediated by UDP-glucuronosyltransferase enzymes (UGTs) significantly influences the bioavailability and biological responses of endogenous molecule substrates and xenobiotics including drugs. UGTs participate in the regulation of cellular homeostasis by limiting stress induced by toxic molecules, and by controlling hormonal signaling networks. Glucuronidation is highly regulated at genomic, transcriptional, post-transcriptional and post-translational levels. However, the UGT protein interaction network, which is likely to influence glucuronidation, has received little attention. We investigated the endogenous protein interactome of human UGT1A enzymes in main drug metabolizing non-malignant tissues where UGT expression is most prevalent, using an unbiased proteomics approach. Mass spectrometry analysis of affinity-purified UGT1A enzymes and associated protein complexes in liver, kidney and intestine tissues revealed an intricate interactome linking UGT1A enzymes to multiple metabolic pathways. Several proteins of pharmacological importance such as transferases (including UGT2 enzymes), transporters and dehydrogenases were identified, upholding a potential coordinated cellular response to small lipophilic molecules and drugs. Furthermore, a significant cluster of functionally related enzymes involved in fatty acid β-oxidation, as well as in the glycolysis and glycogenolysis pathways were enriched in UGT1A enzymes complexes. Several partnerships were confirmed by co-immunoprecipitations and co-localization by confocal microscopy. An enhanced accumulation of lipid droplets in a kidney cell model overexpressing the UGT1A9 enzyme supported the presence of a functional interplay. Our work provides unprecedented evidence for a functional interaction between glucuronidation and bioenergetic metabolism.

A Closed-Loop Control Scheme for Steering Steady States of Glycolysis and Glycogenolysis Pathway

Biochemical networks normally operate in the neighborhood of one of its multiple steady states. It may reach from one steady state to other within a finite time span. In this paper, a closed-loop control scheme is proposed to steer states of the glycolysis and glycogenolysis (GG) pathway from one of its steady states to other. The GG pathway is modeled in the synergism and saturation system formalism, known as S-system. This S-system model is linearized into the controllable Brunovsky canonical form using a feedback linearization technique. For closed-loop control, the linear-quadratic regulator (LQR) and the linear-quadratic gaussian (LQG) regulator are invoked to design a controller for tracking prespecified steady states. In the feedback linearization technique, a global diffeomorphism function is proposed that facilitates in achieving the regulation requirement. The robustness of the regulated GG pathway is studied considering input perturbation and with measurement noise.

Modulatory effect of Mengkudu fruit on the activities of key enzymes of glucose synthesis and utilization pathways of diabetic induced rats

ObjectiveThe present study was aimed to screen the secondary metabolites and evaluate the ameliorative potential of ethanolic extract of Morinda citrifolia (Mengkudu) Fruit Extract (MFE) on the glucose synthesis and utilization reactions. MethodsThe phytochemicals present in the Mengkudu fruit extract were qualitatively investigated. The blood glucose, glycogen content, and plasma insulin profiles and the activities of the key enzymes of glucose oxidation, and gluconeogenic pathways and glycogen metabolism in liver and kidney tissues in streptozotocin (STZ) induced experimental diabetic albino rats were assessed. ResultsThe diabetic rats orally treated with MFE (300 mg/kg b.w./day) for 30 days resulted in significant plunge in blood glucose, glycosylated hemoglobin levels and upswing in glycogen content and a significant progress in plasma insulin and C-peptide level. The distorted activities of key enzymes of glycolysis, TCA cycle, HMP shunt, gluconeogenesis, and glycogen metabolism such as glycogenesis and glycogenolysis pathways observed in liver and kidney tissues of diabetic rats were significantly reverted to near normalcy by the oral administration of MFE. Further, the results were compared with gliclazide, an oral standard drug. ConclusionThe results of the current study indicate that this fruit plays an indispensable character in regulating key enzymes of glucose synthesis and utilization reactions to sustain normoglycemia. Moreover consumption of Mengkudu fruit is nontoxic to the system and is hepatoprotective. Presence of biologically active ingredients such as alkaloids, flavonoids, triterpenoids, minerals, and vitamins presumed to account for the antihyperglycemic properties of M. citrifolia fruits.

An Optimization-Based Design Framework for Steering Steady States and Improving Robustness of Glycolysis–Glycogenolysis Pathway

A robust synthesis technique is devised for synergism and saturation systems, commonly known as S-systems, for controlling the steady states of the glycolysis-glycogenolysis pathway. The development of the robust biochemical network is essential owing to the fragile response to the perturbation of intrinsic and extrinsic parameters of the nominal S-system. The synthesis problem is formulated in a computationally attractive convex optimization framework. The linear matrix inequalities are framed to aim at the minimization of steady-state error, improvement of robustness, and utilization of minimum control input to the biochemical network.