scholarly journals Amylin impairment of insulin effects on glycogen synthesis and phosphoenolpyruvate carboxykinase gene expression in rat primary cultured hepatocytes

1994 ◽  
Vol 304 (2) ◽  
pp. 449-453 ◽  
Author(s):  
S Baqué ◽  
J J Guinovart ◽  
A M Gómez-Foix
Keyword(s):  
Gene Expression ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Mrna Level ◽  
Rat Hepatocytes ◽  
Synthesis Rate ◽  
Cultured Hepatocytes ◽  
Glycogen Accumulation ◽  
Primary Cultured Hepatocytes

The ability of amylin to impair hepatic insulin action is controversial. We have found that the effect of amylin in primary cultured hepatocytes is strongly dependent on the culture conditions. Only in hepatocytes preincubated in the presence of fetal serum did amylin, at concentrations ranging from 1 to 100 nM, reduce insulin-stimulated glycogen synthesis rate and glycogen accumulation without showing direct effects. Neither basal glycogen synthase nor glycogen phosphorylase activity was modified by amylin treatment. Nevertheless, amylin (100 nM) blocked the activation of glycogen synthase by insulin. Amylin also proved capable of opposing the reduction in the expression of the phosphoenolpyruvate carboxykinase (PEPCK) gene induced by insulin, whereas the basal mRNA level of PEPCK was unaffected by amylin treatment. Thus, these results show that, in cultured rat hepatocytes, amylin is indeed able to interfere with insulin regulation of glycogenesis and PEPCK gene expression, favouring the hypothesis that amylin may modulate liver sensitivity to insulin.

scholarly journals Nitric oxide inhibits glycogen synthesis in isolated rat hepatocytes

1998 ◽  
Vol 330 (2) ◽  
pp. 1045-1049 ◽  
Author(s):  
Fleur SPRANGERS ◽  
P. Hans SAUERWEIN ◽  
A. Johannes ROMIJN ◽  
M. George van WOERKOM ◽  
J. Alfred MEIJER
Keyword(s):  
Nitric Oxide ◽  
Glucose Metabolism ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Rat Hepatocytes ◽  
Inhibitory Effect ◽  
No Donor ◽  
Isolated Rat Hepatocytes ◽  
Intracellular Glucose

There is increasing evidence for the existence of intrahepatic regulation of glucose metabolism by Kupffer cell products. Nitric oxide (NO) is known to inhibit gluconeogenic flux through pyruvate carboxylase and phosphoenolpyruvate carboxykinase. However, NO may also influence glucose metabolism at other levels. Using hepatocytes from fasted rats incubated with the NO-donor S-nitroso-N-acetylpenicillamine, we have now found that the synthesis of glycogen from glucose is even more sensitive to inhibition by NO than gluconeogenesis. Inhibition of glycogen production by NO was accompanied by a rise in intracellular glucose 6-phosphate and UDPglucose. Activity of glycogen synthase, as measured in extracts of hepatocytes after the cells had been exposed to NO, was decreased. Experiments with gel-filtered liver extracts revealed that inhibition of glycogen synthase was caused by an inhibitory effect of NO on the conversion of glycogen synthase b into glycogen synthase a.

scholarly journals Cyclin Partners Determine Pho85 Protein Kinase Substrate Specificity In Vitro and In Vivo: Control of Glycogen Biosynthesis by Pcl8 and Pcl10

1998 ◽  
Vol 18 (6) ◽  
pp. 3289-3299 ◽  
Author(s):  
Dongqing Huang ◽  
Jason Moffat ◽  
Wayne A. Wilson ◽  
Lynda Moore ◽  
Christine Cheng ◽  
...  
Keyword(s):  
Gene Expression ◽  
Acid Phosphatase ◽  
Protein Kinase ◽  
Substrate Specificity ◽  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Glycogen Accumulation ◽  
Acid Phosphatase Gene

ABSTRACT In Saccharomyces cerevisiae, PHO85 encodes a cyclin-dependent protein kinase (Cdk) with multiple roles in cell cycle and metabolic controls. In association with the cyclin Pho80, Pho85 controls acid phosphatase gene expression through phosphorylation of the transcription factor Pho4. Pho85 has also been implicated as a kinase that phosphorylates and negatively regulates glycogen synthase (Gsy2), and deletion of PHO85 causes glycogen overaccumulation. We report that the Pcl8/Pcl10 subgroup of cyclins directs Pho85 to phosphorylate glycogen synthase both in vivo and in vitro. Disruption of PCL8 and PCL10 caused hyperaccumulation of glycogen, activation of glycogen synthase, and a reduction in glycogen synthase kinase activity in vivo. However, unlikepho85 mutants, pcl8 pcl10 cells had normal morphologies, grew on glycerol, and showed proper regulation of acid phosphatase gene expression. In vitro, Pho80-Pho85 complexes effectively phosphorylated Pho4 but had much lower activity toward Gsy2. In contrast, Pcl10-Pho85 complexes phosphorylated Gsy2 at Ser-654 and Thr-667, two physiologically relevant sites, but only poorly phosphorylated Pho4. Thus, both the in vitro and in vivo substrate specificity of Pho85 is determined by the cyclin partner. Mutation ofPHO85 suppressed the glycogen storage deficiency ofsnf1 or glc7-1 mutants in which glycogen synthase is locked in an inactive state. Deletion of PCL8and PCL10 corrected the deficit in glycogen synthase activity in both the snf1 and glc7-1 mutants, but glycogen synthesis was restored only in the glc7-1mutant strain. This genetic result suggests an additional role for Pho85 in the negative regulation of glycogen accumulation that is independent of Pcl8 and Pcl10.

scholarly journals Assessment of the Phenolic Profiles, Hypoglycemic Activity, and Molecular Mechanism of Different Highland Barley (Hordeum vulgare L.) Varieties

2020 ◽  
Vol 21 (4) ◽  
pp. 1175 ◽  
Author(s):  
Na Deng ◽  
Bisheng Zheng ◽  
Tong Li ◽  
Rui Hai Liu
Keyword(s):  
Molecular Mechanism ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Glucose Transporter ◽  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Hypoglycemic Activity ◽  
Hordeum Vulgare L ◽  
Glycogen Accumulation ◽  
Phenolic Profiles ◽  
Highland Barley

The phenolic profiles, hypoglycemic activity, and molecular mechanism of the effect on type 2 diabetes mellitus (T2DM) of four highland barley varieties were investigated in the present study. The fundamental phenolics in highland barley were ferulic acid, naringin, and catechin, which mainly existed in bound form. These varieties showed favorable hypoglycemic activity via inhibition of α-glucosidase and α-amylase activities, enhancement of glucose consumption, glycogen accumulation and glycogen synthase 2 (GYS2) activity, and down-regulation of glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK) activities. Specifically, ZQ320 variety exhibited the strongest hypoglycemic activity compared to the other varieties. Highland barley phenolics could inhibit gluconeogenesis and motivate glycogen synthesis via down-regulating the gene expression of G6Pase, PEPCK, and glycogen synthase kinase 3β (GSK3β), while activating the expression of insulin receptor substrate-1 (IRS-1), phosphatidylinositol 3 kinase (PI3K), serine/threonine kinase (Akt), GYS2, and glucose transporter type 4 (GLUT4). Therefore, phenolics from highland barley could be served as suitable candidates for therapeutic agent in T2DM to improve human health.

scholarly journals Catestatin reduces hyperglycemia in insulin-resistant mice by redirecting glucose-6-phosphate from the gluconeogenic to the glycogenic pathway

2020 ◽  
Author(s):  
Gautam Bandyopadhyay ◽  
Kechun Tang ◽  
Nicholas J.G. Webster ◽  
Geert van den Bogaart ◽  
Sushil K. Mahata
Keyword(s):  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Glucose Production ◽  
Liver Glycogen ◽  
Hepatic Glycogen ◽  
Cultured Hepatocytes ◽  
Glycogen Accumulation ◽  
Insulin Resistant ◽  
Glucose Levels ◽  
Gsk 3Β

AbstractObjectiveDefects in hepatic glycogen synthesis contribute to postprandial hyperglycemia in type 2 diabetic (T2D) patients. Chromogranin A (CgA) peptide Catestatin (CST: hCgA352-372) inhibits dephosphorylation of glucose 6-phosphate (G6P) and improves glucose tolerance in insulin-resistant mice. Here, we seek to determine whether CST also reduces hyperglycemia by increasing hepatic glycogen synthesis.MethodsWe determined liver glycogen, G6P, and UDP glucose (UDPG); plasma insulin, glucagon, norepinephrine (NE), and epinephrine (EPI) levels, and glycogen synthase (GYS) activities in fed and fasted liver of lean and obese wild-type and genetically obese CST knockout (KO) mice after treatments with saline, CST or insulin. We determined glycogen synthesis and glycogenolysis in cultured hepatocytes. We analyzed phosphorylation signals of GYS2 and GSK-3β by immunoblotting.ResultsCST stimulated glycogen accumulation in fed and fasted liver and in cultured hepatocytes. CST reduced plasma NE and EPI levels, suggesting that CST promotes glycogenesis by inhibiting catecholamine-induced glycogenolysis. CST also directly stimulated glycogenesis and inhibited NE and EPI-induced glycogenolysis in hepatocytes. CST elevated the levels of G6P and UDPG and increased GYS activity, thus redirecting G6P to the glycogenic pathway. CST-KO mice had decreased liver glycogen that was restored by treatment with CST, reinforcing the crucial role that CST plays in hepatic glycogenesis.ConclusionsWe conclude that CST directly promotes the glycogenic pathway and reduces plasma glucose levels in insulin-resistant mice by (i) reducing glucose production from G6P, (ii) increasing glycogen synthesis from G6P via formation of UDPG, and (iii) reducing glycogenolysis.

scholarly journals Pho85p, a cyclin-dependent protein kinase, and the Snf1p protein kinase act antagonistically to control glycogen accumulation in Saccharomyces cerevisiae.

1996 ◽  
Vol 16 (8) ◽  
pp. 4357-4365 ◽  
Author(s):  
D Huang ◽  
I Farkas ◽  
P J Roach
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Kinase ◽  
Kinase Activity ◽  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Mutant Gene ◽  
Glycogen Synthase Kinase ◽  
Partial Purification ◽  
Glycogen Accumulation ◽  
Dependent Protein

In Saccharomyces cerevisiae, nutrient levels control multiple cellular processes. Cells lacking the SNF1 gene cannot express glucose-repressible genes and do not accumulate the storage polysaccharide glycogen. The impaired glycogen synthesis is due to maintenance of glycogen synthase in a hyperphosphorylated, inactive state. In a screen for second site suppressors of the glycogen storage defect of snf1 cells, we identified a mutant gene that restored glycogen accumulation and which was allelic with PHO85, which encodes a member of the cyclin-dependent kinase family. In cells with disrupted PHO85 genes, we observed hyperaccumulation of glycogen, activation of glycogen synthase, and impaired glycogen synthase kinase activity. In snf1 cells, glycogen synthase kinase activity was elevated. Partial purification of glycogen synthase kinase activity from yeast extracts resulted in the separation of two fractions by phenyl-Sepharose chromatography, both of which phosphorylated and inactivated glycogen synthase. The activity of one of these, GPK2, was inhibited by olomoucine, which potently inhibits cyclin-dependent protein kinases, and contained an approximately 36-kDa species that reacted with antibodies to Pho85p. Analysis of Ser-to-Ala mutations at the three potential Gsy2p phosphorylation sites in pho85 cells implicated Ser-654 and/or Thr-667 in PHO85 control of glycogen synthase. We propose that Pho85p is a physiological glycogen synthase kinase, possibly acting downstream of Snf1p.

Hormonal Regulation of Aldolase B Gene Expression in Rat Primary Cultured Hepatocytes

1998 ◽  
Vol 350 (2) ◽  
pp. 291-297 ◽  
Author(s):  
Jun-itsu Ito ◽  
Takejiro Kuzumaki ◽  
Kaoru Otsu ◽  
Yoshihito Iuchi ◽  
Kiichi Ishikawa
Keyword(s):  
Gene Expression ◽  
Hormonal Regulation ◽  
Cultured Hepatocytes ◽  
Primary Cultured Hepatocytes ◽  
Aldolase B

Liver glyconeogenesis: a pathway to cope with postprandial amino acid excess in high-protein fed rats?

2007 ◽  
Vol 292 (4) ◽  
pp. R1400-R1407 ◽  
Author(s):  
Dalila Azzout-Marniche ◽  
Claire Gaudichon ◽  
Clémence Blouet ◽  
Cécile Bos ◽  
Véronique Mathé ◽  
...  
Keyword(s):  
Gene Expression ◽  
Small Intestine ◽  
Amino Acid ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Glycogen Synthesis ◽  
High Protein ◽  
Hepatic Glycogen ◽  
Molecular Evidence ◽  
Experimental Conditions ◽  
Fed State

This paper provides molecular evidence for a liver glyconeogenic pathway, that is, a concomitant activation of hepatic gluconeogenesis and glycogenesis, which could participate in the mechanisms that cope with amino acid excess in high-protein (HP) fed rats. This evidence is based on the concomitant upregulation of phosphoenolpyruvate carboxykinase (PEPCK) gene expression, downregulation of glucose 6-phosphatase catalytic subunit (G6PC1) gene expression, an absence of glucose release from isolated hepatocytes and restored hepatic glycogen stores in the fed state in HP fed rats. These effects are mainly due to the ability of high physiological concentrations of portal blood amino acids to counteract glucagon-induced liver G6PC1 but not PEPCK gene expression. These results agree with the idea that the metabolic pathway involved in glycogen synthesis is dependent upon the pattern of nutrient availability. This nonoxidative glyconeogenic disposal pathway of gluconeogenic substrates copes with amino excess and participates in adjusting both amino acid and glucose homeostasis. In addition, the pattern of PEPCK and G6PC1 gene expression provides evidence that neither the kidney nor the small intestine participated in gluconeogenic glucose production under our experimental conditions. Moreover, the main glucose-6-phosphatase (G6Pase) isoform expressed in the small intestine is the ubiquitous isoform of G6Pase (G6PC3) rather than the G6PC1 isoform expressed in gluconeogenic organs.

scholarly journals Antagonistic Controls of Autophagy and Glycogen Accumulation by Snf1p, the Yeast Homolog of AMP-Activated Protein Kinase, and the Cyclin-Dependent Kinase Pho85p

2001 ◽  
Vol 21 (17) ◽  
pp. 5742-5752 ◽  
Author(s):  
Zhong Wang ◽  
Wayne A. Wilson ◽  
Marie A. Fujino ◽  
Peter J. Roach
Keyword(s):  
Protein Kinase ◽  
Stationary Phase ◽  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Glycogen Storage ◽  
Wild Type ◽  
Gene Encoding ◽  
Glycogen Accumulation ◽  
Yeast Homolog ◽  
Glycogen Stores

ABSTRACT In the yeast Saccharomyces cerevisiae, glycogen is accumulated as a carbohydrate reserve when cells are deprived of nutrients. Yeast mutated in SNF1, a gene encoding a protein kinase required for glucose derepression, has diminished glycogen accumulation and concomitant inactivation of glycogen synthase. Restoration of synthesis in an snf1 strain results only in transient glycogen accumulation, implying the existence of otherSNF1-dependent controls of glycogen storage. A genetic screen revealed that two genes involved in autophagy, APG1and APG13, may be regulated by SNF1. Increased autophagic activity was observed in wild-type cells entering the stationary phase, but this induction was impaired in ansnf1 strain. Mutants defective for autophagy were able to synthesize glycogen upon approaching the stationary phase, but were unable to maintain their glycogen stores, because subsequent synthesis was impaired and degradation by phosphorylase, Gph1p, was enhanced. Thus, deletion of GPH1 partially reversed the loss of glycogen accumulation in autophagy mutants. Loss of the vacuolar glucosidase, SGA1, also protected glycogen stores, but only very late in the stationary phase. Gph1p and Sga1p may therefore degrade physically distinct pools of glycogen. Pho85p is a cyclin-dependent protein kinase that antagonizes SNF1control of glycogen synthesis. Induction of autophagy inpho85 mutants entering the stationary phase was exaggerated compared to the level in wild-type cells, but was blocked in apg1 pho85 mutants. We propose that Snf1p and Pho85p are, respectively, positive and negative regulators of autophagy, probably via Apg1 and/or Apg13. Defective glycogen storage in snf1cells can be attributed to both defective synthesis upon entry into stationary phase and impaired maintenance of glycogen levels caused by the lack of autophagy.

Control of glycogen synthesis is shared between glucose transport and glycogen synthase in skeletal muscle fibers

2000 ◽  
Vol 278 (2) ◽  
pp. E234-E243 ◽  
Author(s):  
Iñaki Azpiazu ◽  
Jill Manchester ◽  
Alexander V. Skurat ◽  
Peter J. Roach ◽  
John C. Lawrence
Keyword(s):  
Skeletal Muscle ◽  
Glucose Transport ◽  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Muscle Fibers ◽  
Fiber Types ◽  
Oxidative Potential ◽  
Glycogen Accumulation ◽  
Tibialis Muscle ◽  
Fast Twitch

The effects of transgenic overexpression of glycogen synthase in different types of fast-twitch muscle fibers were investigated in individual fibers from the anterior tibialis muscle. Glycogen synthase was severalfold higher in all transgenic fibers, although the extent of overexpression was twofold greater in type IIB fibers. Effects of the transgene on increasing glycogen and phosphorylase and on decreasing UDP-glucose were also more pronounced in type IIB fibers. However, in any grouping of fibers having equivalent malate dehydrogenase activity (an index of oxidative potential), glycogen was higher in the transgenic fibers. Thus increasing synthase is sufficient to enhance glycogen accumulation in all types of fast-twitch fibers. Effects on glucose transport and glycogen synthesis were investigated in experiments in which diaphragm, extensor digitorum longus (EDL), and soleus muscles were incubated in vitro. Transport was not increased by the transgene in any of the muscles. The transgene increased basal [14C]glucose into glycogen by 2.5-fold in the EDL, which is composed primarily of IIB fibers. The transgene also enhanced insulin-stimulated glycogen synthesis in the diaphragm and soleus muscles, which are composed of oxidative fiber types. We conclude that increasing glycogen synthase activity increases the rate of glycogen synthesis in both oxidative and glycolytic fibers, implying that the control of glycogen accumulation by insulin in skeletal muscle is distributed between the glucose transport and glycogen synthase steps.

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