The operation of glucose 6-phosphatase (EC 3.1.3.9) (Glc6Pase) stems from the interaction of at least two highly hydrophobic proteins embedded in the ER membrane, a heavily glycosylated catalytic subunit of m 36 kDa (P36) and a 46-kDa putative glucose 6-phosphate (Glc6P) translocase (P46). Topology studies of P36 and P46 predict, ...

Previously, we have described significant effects of human insulin on glucose metabolism in the yeast Saccharomyces cerevisiae under conditions of growth limitation. These regulations apparently rely on a transmembrane receptor capable of binding human insulin and responding by tyrosine/serine phosphorylation of a specific set of polypeptides [Müller, G., Rouveyre, N., ...

The effects of alloxan diabetes and subsequent treatment with insulin on extra-mitochondrial oxygen metabolism in terms of D-amino acid oxidase (DAAO), xanthine oxidase and catalase were examined. The DAAO activity in the liver with D-alanine and D-serine decreased by 33-62% in the diabetic group while the decrease in the kidneys ...

Glycogen-targeting subunits of protein phosphatase-1, such as protein targeting to glycogen (PTG), direct the phosphatase to the glycogen particle, where it stimulates glycogenesis. We have investigated the metabolic impact of overexpressing PTG in liver of normal rats. After administration of PTG cDNA in a recombinant adenovirus, animals were fasted or ...

BACKGROUND: Obesity is often accompanied by a decreased ability of insulin to stimulate glucose uptake and glycogenesis in skeletal muscle. The aim of this study was to investigate the rate of glycogen formation and of muscular glucose content in relation to insulin sensitivity under euglycemic conditions. MATERIALS AND METHODS: We ...

Thiazolidinediones (TZD) have been shown to have anti-diabetic effects including the ability to decrease fasting hyperglycemia and hyperinsulinemia, increase insulin-mediated glucose disposal rate (M) and decrease hepatic glucose production, but the mechanisms of action are not well established. To determine whether a TZD (R-102380, Sankyo Company Ltd., Tokyo, Japan) could ...

Calorie restriction (CR) has previously been shown to unexpectedly induce a reversal of in vivo insulin action (phosphorylation instead of dephosphorylation) on skeletal muscle glycogen synthase (GS) in four out of six long-term calorie-restricted (CR) monkeys. The purpose of the present study was to determine whether this increase in Ka ...

Zucker diabetic fatty rats develop type 2 diabetes concomitantly with peripheral insulin resistance. Hepatocytes from these rats and their control lean counterparts have been cultured, and a number of key parameters of glucose metabolism have been determined. Glucokinase activity was 4.5-fold lower in hepatocytes from diabetic rats than in hepatocytes ...

BACKGROUND/AIMS: Insulin resistance in cancer patients may play an important role in post-operative outcomes. METHODOLOGY: In an effort to understand the mechanism responsible, we measured glucose uptake by euglycemic hyperinsulinemic glucose clamp, glycogen content in skeletal muscle, liver, and adipose tissue by an enzymatic method, and facilitative glucose transporter mRNA ...

The effects of fasting on the pathways of insulin-stimulated glucose disposal were explored in three groups of seven normal subjects. Group 1 was submitted to a euglycemic hyperinsulinemic clamp ( approximately 100 microU/ml) after both a 12-h and a 4-day fast. The combined use of [3-(3)H]- and [U-(14)C]glucose allowed us ...

It has been demonstrated in the conscious dog that portal glucose infusion creates a signal that increases net hepatic glucose uptake and hepatic glycogen deposition. Experiments leading to an understanding of the mechanism by which this change occurs will be facilitated if this finding can be reproduced in the rat. ...

Aminoguanidine (AMG) was prepared more than 100 years ago. During the last 10 years two important effects of AMG have been discovered which have made this molecule attract a lot of interest. Firstly, AMG inhibits, in vitro and in vivo, formation of highly reactive advanced glycosylation end products (AGEs) associated ...

The glycogen-associated regulatory subunit of protein phosphatase-1 (PP-1G) plays a major role in insulin-stimulated glycogen synthesis and thus the regulation of nonoxidative glucose disposal in skeletal muscle. In a general population of Caucasians a polymorphism at codon 905 of PP-1G from an aspartate to tyrosine has been reported to be ...

A glucose-sensitive gel formulation containing concanavalin A and glycogen has been reported previously. Precipitation resulting from the addition of concanavalin A to glycogen has been documented, but the formation of glucose-sensitive gels based on lectin-glycogen interactions is novel and used here in our studies. An improved in-vitro self-regulating drug-delivery system, ...

In this study, the potentially beneficial effects of preoperative treatment with glucose, insulin and potassium in a randomized series of 30 consecutive patients undergoing mitral valve replacement, who were in the third and fourth functional groups of the New York Heart Association scale, were investigated. Fifteen patients received glucose, insulin ...

The role of increased glucose transport in the hormonal regulation of glycogen synthase by insulin was investigated in 3T3-L1 adipocytes. Insulin treatment stimulated glycogen synthase activity 4-5-fold in these cells. Cytosolic glycogen synthase levels decreased by 75% in response to insulin, whereas, conversely, the glycogenolytic agent isoproterenol increased cytosolic enzyme ...

Metabolic control analysis was used to calculate the distributed control of insulin-stimulated skeletal muscle glucose disposal in awake rats. Three separate hyperinsulinemic infusion protocols were performed: 1) protocol I was a euglycemic (approximately 6 mM)-hyperinsulinemic (10 mU. kg(-1). min(-1)) clamp, 2) protocol II was a hyperglycemic ( approximately 11 mM)-hyperinsulinemic ...

Using a specific 13C NMR localization method, 13C label incorporation into the glycogen C1 resonance was measured while infusing [1-(13)C]glucose in intact rats. The maximal concentration of [1-(13)C]glycogen was 5.1 +/- 0.6 micromol g(-1) (mean +/- SE, n = 8). During the first 60 min of acute hyperglycemia, the rate ...

Chronic exposure (48 h) to glucosamine resulted in a dose-dependent reduction of basal and insulin-stimulated glucose uptake activities in human skeletal muscle cell cultures from nondiabetic and type 2 diabetic subjects. Insulin responsiveness of uptake was also reduced. There was no change in total membrane expression of either GLUT1, GLUT3, ...

Intensively treating type I diabetics with continuous subcutaneous insulin infusions or multiple daily insulin injections to normalize mean blood glucose concentrations significantly reduces the onset of secondary diabetic complications when compared to conventionally treated diabetics. Our studies focused on characterizing hepatic enzyme expression in intensively and conventionally treated diabetic rats. ...

Glycogen synthase is an excellent in vitro substrate for protein phosphatase-1 (PP1), which is potently inhibited by the phosphorylated forms of DARPP-32 (dopamine- and cAMP-regulated phosphoprotein, M(r) = 32,000) and Inhibitor-1. To test the hypothesis that the activation of glycogen synthase by insulin is due to a decrease in the ...

BACKGROUND: Insulin resistance, a major factor in the pathogenesis of type 2 diabetes mellitus, is due mostly to decreased stimulation of glycogen synthesis in muscle by insulin. The primary rate-controlling step responsible for the decrease in muscle glycogen synthesis is not known, although hexokinase activity and glucose transport have been ...

Carbon nuclear magnetic resonance (13C NMR) spectroscopy and phosphorus (31p) NMR spectroscopy have been used to help define the contribution of insulin-stimulated muscle glycogen synthesis to whole-body insulin-stimulated glucose metabolism in normal individuals and the extent to which this process is defective in patients with type 2 (non-insulin-dependent) diabetes. Assessments ...

To test whether, in horses, the concentration of muscle glycogen can be influenced by increasing the uptake of glucose into the muscle cells or by providing a gluconeogenic precursor, 9 trained half-bred riding horses performed on a treadmill a 1.5 h competition exercise test (CET). Each horse performed CET 3 ...

The effects of L-glutamate and insulin on glycogen synthesis in astrocytes were examined. L-Glutamate and insulin both stimulated glycogen synthesis in primary cultures of rat astrocytes in a dose-dependent manner, as measured by the incorporation of 14C from [14C]glucose into glycogen. D-Aspartate also increased the incorporation of 14C into glycogen. ...

To characterize the contribution of glycogen synthase kinase 3beta (GSK3beta) inactivation to insulin-stimulated glucose metabolism, wild-type (WT-GSK), catalytically inactive (KM-GSK), and uninhibitable (S9A-GSK) forms of GSK3beta were expressed in insulin-responsive 3T3-L1 adipocytes using adenovirus technology. WT-GSK, but not KM-GSK, reduced basal and insulin-stimulated glycogen synthase activity without affecting the -fold ...

Neutrophils from patients suffering from glycogen storage disease type Ib (GSD-Ib) show several defects. one of which is a decreased rate of glucose utilization. In this study, we established experimental conditions to show the stimulation of the neutrophil respiratory burst by extracellular glucose. With phorbol-myristate-acetate as stimulus of the burst, ...

The effect of bolus intravenous injection of sub-LD50 (35 micrograms Kg-1) of the neurotoxic fraction (F3) of the Egyptian cobra Naja haje on the plasma level of ACTH and serum levels of cortisol, insulin, glucose, total lipids, triacylglycerols, free fatty acids, total cholesterol, HDL and LDL-cholesterol, and glycogen content of ...

The development of late onset non-insulin dependent diabetes mellitus (NIDDM) is due to a complicated interplay between genes and environment on one side, and the interaction between metabolic defects in various tissues including the pancreatic beta cell (decreased insulin secretion), skeletal muscle (insulin resistance), liver (increased gluconeogenesis), adipose tissue (increased ...

In glycogen-containing muscle, glycogenesis appears to be controlled by glucose 6-phosphate (6-P) provision, but after glycogen depletion, an autoinhibitory control of glycogen could be a determinant. We analyzed in cultured human muscle the contribution of glycogen depletion versus glucose 6-P in the control of glycogen recovery. Acute deglycogenation was achieved ...

A major function of insulin in target tissues is the activation of glycogen synthase. Phosphatidylinositol 3-kinase (PI3K) has been implicated in the insulin-induced activation of glycogen synthase, although the true function of this enzyme remains unclear. Data presented here demonstrate that the PI3K inhibitors wortmannin and LY-294002 block the insulin-stimulated ...

The activation of c-Jun N-terminal kinase (JNK) by insulin and anisomycin has been reported to result in increases in glycogen synthase (GS) activity in rat skeletal muscle (Moxham et al., J Biol Chem, 1996, 271:30765-30773). In addition, the protein kinase C (PKC) inhibitor, RO 31-8220, has been reported to activate ...

Glucosamine infusion induces insulin resistance in vivo, but the effect of glucosamine on intracellular metabolites of the hexosamine pathway, especially glucosamine-6-phosphate (GlcN6P) is unknown. Because of the structural similarity of glucose-6-phosphate (G-6-P) and GlcN6P, we hypothesized that accumulation of this metabolite might alter the activities of enzymes such as glycogen ...

Because glucose is an important metabolic fuel during perinatal development, the effect of restriction of maternal dietary glucose on the developmental profile of neonatal glucoregulatory pathways was investigated. Pregnant rats were fed isoenergetic diets (0, 12, 24 or 60% glucose) and offspring were killed at seven postpartum time periods: 0-2, ...

Adult (20-day-old) Hymenolepis diminuta were cut into 12 pieces of equal length, and the individual pieces of the tapeworm's strobila were analyzed. There was a continuous gradient of decreasing concentrations of glucose (mM) and decreasing levels of glycogen (microgram/mg wt) in the strobila. The ethanol extracts of the individual pieces ...

Previous investigations have reported that soluble fiber reduces the plasma glucose and insulin changes after an oral glucose load. To improve the palatability of a soluble-fiber feeding, this study addressed how a combined, soluble fiber (delivered in capsule form) and a preexercise CHO feeding would affect metabolic responses during exercise. ...

The activating effect of vanadate on glycogenesis and on glycogen synthase (uridine diphosphate-glucose-glycogen glucosyl transferase) activity was studied in rat adipocytes and compared with that of insulin. Using several approaches and specific blockers, we found that vanadate and insulin resemble each other, in the activation of glycogen synthase, in several ...

In healthy individuals, glycogen recovery after a strong depletion is known to be rapid and insulin independent during the initial phase, and subsequently, slow and insulin dependent. Free fatty acids (FFAs) as a putative source of insulin resistance (IR) could thus impair glycogen recovery during the second period. Using in ...

Aluminum phosphide (AlP), a poison extensively used as a grain fumigant and rodenticide, can cause an increase or decrease in blood glucose levels Both hypo- and hyper-glycemic effects of AlP can be attributed to the wide variety of changes in magnesium, calcium, phosphate, citrate and cortisol levels. These biochemical changes ...

Glycogen is a storage compound that provides both carbon and energy, but the mechanism for the regulation of its metabolism has not been fully clarified. Recently, we found a new glycogenolytic pathway in rat liver in which glycogen is first metabolized to 1, 5-anhydrofructose (AnFru) and then to 1,5-anhydroglucitol (AnGlc-ol). ...

Growth hormone (GH) deficiency in adults is characterized by central obesity, dyslipidemia, coagulopathy and glucose intolerance, all features of the "metabolic syndrome", explaining the increased cardiovascular morbidity and mortality associated with GH deficiency in adults. Employing the 2-step euglycemic-hyperinsulinemic clamp, we have demonstrated severe insulin resistance in GH-deficient adults, with ...

To examine the effects of safflower oil versus fish oil feeding on in vivo intramuscular glucose metabolism and relative pyruvate dehydrogenase (PDH) versus tricarboxylic acid (TCA) cycle flux, rats were pair-fed on diets consisting of 1) 59% safflower oil, 2) 59% menhaden fish oil, or 3) 59% carbohydrate (control) in ...

Eucalyptus globulus (eucalyptus) is used as a traditional treatment for diabetes. In this study, incorporation of eucalyptus in the diet (62.5 g/kg) and drinking water (2.5 g/L) reduced the hyperglycemia and associated weight loss of streptozotocin-treated mice. An aqueous extract of eucalyptus (AEE) (0.5 g/L) enhanced 2-deoxy-glucose transport by 50%, ...

Liver glycogen synthase activity is increased, and glycogen phosphorylase activity and glucose 6-phosphate content reduced by in vivo insulin during a euglycemic hyperinsulinemic clamp in lean young adult rhesus monkeys. To examine the mechanism of dephosphorylation of liver glycogen synthase and glycogen phosphorylase, the enzyme activities of protein phosphatase-1, protein ...

The differentiation of the L6 myogenic cell line was enhanced by the addition of dexamethasone, retinoic acid, insulin-like growth factor I (IGF-I), and creatine. Spontaneous contractions appeared from day 10 or 11 and persisted to day 14 or 15. Glucose transport was increased by insulin (100 nM) and IGF-I (5 ...

BACKGROUND & AIMS: Accelerated starvation and early recruitment of alternate fuels in cirrhosis have been attributed to reduced availability of hepatic glycogen. The aim of this study was to measure gluconeogenesis (as a marker of protein oxidation) in relation to total glucose production and glucagon-stimulated glycogenolysis. METHODS: Glucose and urea ...

Although the general pathways of glycogen synthesis and glycogenolysis are identical in all tissues, the enzymes involved are uniquely adapted to the specific role of glycogen in different cell types. In liver, where glycogen is stored as a reserve of glucose for extrahepatic tissues, the glycogen-metabolizing enzymes have properties that ...

We determined the contribution of all major energy substrates (glucose, glycogen, lactate, oleate, and triglycerides) during an acute increase in heart work (1 microM epinephrine, afterload increased by 40%) and the involvement of key regulatory enzymes, using isolated working rat hearts exhibiting physiologic values for contractile performance and oxygen consumption. ...

Primary cultures of rat hepatocytes were used to study the combined effects of insulin and dexamethasone on cyclic AMP phosphodiesterase 3 (PDE 3) and glycogen metabolism. PDE activity was measured in extracts obtained by hypotonic shock treatment of the particulate fraction from cultured hepatocytes. PDE 3 was identified by inhibition ...

The wood frog Rana sylvatica utilises glucose, derived from hepatic glycogen, as a cryoprotectant in order to survive freezing during winter hibernation, and glycogenolysis is initiated by hormonal and/or neural stimuli. The primary structure of insulin was determined from R. sylvatica and from two species of freeze-intolerant Ranid frogs R. ...