Regulation Of Glycogen Synthesis Research Articles

Exploring the metabolic and antioxidant potential of solergy: Implications for enhanced animal production

Cell models are indispensable tools in biotechnology when investigating the functional properties of organic compounds. The emergence of various additives designed to enhance animal production has introduced the need for in-depth evaluations, which are often hindered by the complexities of in vivo testing. In this study, we harnessed cell-based models to scrutinize the impact of Solergy as a regulator of cellular metabolism with a particular focus on its modulation of glycogen and antioxidant effects. Our experiment was designed to include assessments of the influence of Solergy on the viability of both terrestrial and aquatic vertebrate cell models, which revealed the benign nature of Solergy and its lack of adverse effects. Furthermore, we examined the capacity of Solergy to modulate intracellular ATP concentrations and enhance glycogen accumulation. Notably, the antioxidant potential of Solergy and its ability to mitigate cellular aging were evaluated within the same cellular frameworks. The outcomes of our investigation suggest that Solergy is a potent metabolic regulator that elevates cellular activity while exerting an antioxidant effect. Importantly, our study demonstrates that Solergy does not induce changes in membrane oxidation. These findings indicate the potential of using Solergy to regulate glycogen synthesis, intracellular ATP concentrations, and oxidative stress in production animals. The multifaceted effects of this additive, which acts as both a metabolism enhancer and an antioxidant, open doors to the creation of custom diets tailored to meet specific production needs while maintaining stable production parameters.

Effects of ginseng peptides on the hypoglycemic activity and gut microbiota of a type 2 diabetes mellitus mice model

Ginseng peptide (GP) (100, 200, 400 mg/kg bw) lowered blood glucose levels, explored the relationship between GP and gut microbiota-based hypoglycemic effects. GP significantly reduced fasting blood glucose levels (25.38–13.37 mM), improved insulin resistance (IR) (9.78–5.02), considerably increased liver glycogen content (64.71–97.95 mg/g), glycolytic and gluconeogenesis enzyme activities in T2DM mice, significantly reduced free fatty acids (1.65–0.93 mM), triglycerides (1.55–0.66 mM), total cholesterol (14.75–5.43 mM), and low-density lipoprotein (4.12–2.36 mM) in the serum, significantly increased high-density lipoprotein levels (6.20–17.44 mM) to improve lipid metabolism disorders. According to colonic 16S rDNA sequencing results, GP-H regulated gut microbiota disorders and short chain fatty acid metabolism. Western blot analysis showed that GP could regulate glycogen synthesis, gluconeogenesis, and glucose transport by activating IRS-1/PI3K/Akt and AMPK signaling pathways and improve IR by inhibiting the mitochondrial apoptosis signaling pathway.

Identification and Characterization of GYS and GSK3β Provides Insights into the Regulation of Glycogen Synthesis in Jinjiang Oyster Crassostrea ariakensis

Glycogen, a stored form of glucose, is an important form of energy for aquatic shellfish, contributing to the flavor and quality of the oyster. The glycogen synthase (GYS) and glycogen synthase kinase 3β (GSK3β) are two major enzymes in the glycogenesis. However, the information of the two genes in the Jinjiang oyster Crassostrea ariakensis remains limited. In this study, we identified the genes of GYS and GSK3β and further explored their function in the glycogen synthesis of C. ariakensis. The GYS and GSK3β were distributed in all tested tissues, and high expression of GYS and glycogen content were detected in the gonad, labial palp, hepatopancreas, and mantle, while the high expression of GSK3β was observed in the gill and adductor muscle. The expression of GYS was positively correlated with the glycogen content, while GSK3β was negatively correlated. Additionally, knockdown of GSK3β using RNAi decreased the GYS expression, revealing the negative regulatory effect of GSK3β on GYS. These findings enrich the research data of GSK3β and GYS involved in glycogen synthesis, providing valuable information for further research on the function of GSK3β and GYS in the glycogen synthesis process of oyster.

Identification and Regulatory Roles of a New Csr Small RNA from Arctic Pseudoalteromonas fuliginea BSW20308 in Temperature Responses.

Small RNAs (sRNAs) play a very important role in gene regulation at the posttranscriptional level. However, sRNAs from nonmodel microorganisms, extremophiles in particular, have been rarely explored. We discovered a putative sRNA, termed Pf1 sRNA, in Pseudoalteromonas fuliginea BSW20308 isolated from the polar regions in our previous work. In this study, we identified the sRNA and investigated its regulatory role in gene expression under different temperatures. Pf1 sRNA was confirmed to be a new member of the CsrB family but has little sequence similarity with Escherichia coli CsrB. However, Pf1 sRNA was able to bind to CsrA from E. coli and P. fuliginea BSW20308 to regulate glycogen synthesis. The Pf1 sRNA knockout strain (ΔPf1) affected motility, fitness, and global gene expression in transcriptomes and proteomes at 4°C and 32°C. Genes related to carbon metabolism, amino acid metabolism, salinity tolerance, antibiotic resistance, oxidative stress, motility, chemotaxis, biofilm, and secretion systems were differentially expressed in the wild-type strain and the ΔPf1 mutant. Our study suggested that Pf1 sRNA might play an important role in response to environmental changes by regulating global gene expression. Specific targets of the Pf1 sRNA-CsrA system were tentatively proposed, such as genes involved in the type VI secretion system, TonB-dependent receptors, and response regulators, but most of them have an unknown function. Since this is the first study of CsrB family sRNA in Pseudoalteromonas and microbes from the polar regions, it provides a novel insight at the posttranscriptional level into the responses and adaptation to temperature changes in bacteria from extreme environments. This study also sheds light on the evolution of sRNA in extreme environments and expands the bacterial sRNA database. IMPORTANCE Previous research on microbial temperature adaptation has focused primarily on functional genes, with little attention paid to posttranscriptional regulation. Small RNAs, the major posttranscriptional modulators of gene expression, are greatly underexplored, especially in nonpathogenic and nonmodel microorganisms. In this study, we verified the first Csr sRNA, named Pf1 sRNA, from Pseudoalteromonas, a model genus for studying cold adaptation. We revealed that Pf1 sRNA played an important role in global regulation and was indispensable in improving fitness. This study provided us a comprehensive view of sRNAs from Pseudoalteromonas and expanded our understanding of bacterial sRNAs from extreme environments.

Roles of second messengers in the regulation of cyanobacterial physiology: the carbon-concentrating mechanism and beyond.

Second messengers are a fundamental category of small molecules and ions that are involved in the regulation of many processes in all domains of life. Here we focus on cyanobacteria, prokaryotes playing important roles as primary producers in the geochemical cycles due to their capability of oxygenic photosynthesis and carbon and nitrogen fixation. Of particular interest is the inorganic carbon-concentrating mechanism (CCM), which allows cyanobacteria to concentrate CO2 near RubisCO. This mechanism needs to acclimate toward fluctuating conditions, such as inorganic carbon availability, intracellular energy levels, diurnal light cycle, light intensity, nitrogen availability, and redox state of the cell. During acclimation to such changing conditions, second messengers play a crucial role, particularly important is their interaction with the carbon control protein SbtB, a member of the PII regulator protein superfamily. SbtB is capable of binding several second messengers, uniquely adenyl nucleotides, to interact with different partners in a variety of responses. The main identified interaction partner is the bicarbonate transporter SbtA, which is regulated via SbtB depending on the energy state of the cell, the light conditions, and different CO2 availability, including cAMP signaling. The interaction with the glycogen branching enzyme, GlgB, showed a role for SbtB in the c-di-AMP-dependent regulation of glycogen synthesis during the diurnal life cycle of cyanobacteria. SbtB has also been shown to impact gene expression and metabolism during acclimation to changing CO2 conditions. This review summarizes the current knowledge about the complex second messenger regulatory network in cyanobacteria, with emphasis on carbon metabolism.

Macrophage GSK3β-deficiency inhibits the progression of hepatocellular carcinoma and enhances the sensitivity of anti-PD1 immunotherapy

BackgroundGlycogen synthase kinase 3β (GSK3β) was originally discovered to regulate glycogen synthesis and show a relationship to tumors. However, the biological functions of GSK3β in tumor-associated macrophages (TAMs) in cancers...

Abstract 5813: Glycogen synthesis as potential novel target in triple negative breast cancer: Glycogen synthase 1 expression in human breast cancers and the impact of downregulation on proliferation of preclinical models

Abstract Background: Triple-negative breast cancer (TNBC) has a poor clinical prognosis and is characterized by a lack of druggable targets and a hypoxic tumor microenvironment. Hypoxia-induced glycogen accumulation and utilization are involved in cancer proliferation and therapy resistance, making modulation of glycogen metabolism of therapeutic interest. Therefore, we studied expression of glycogen synthase 1 (GYS1, the key regulator of glycogen synthesis) and glycogen stores in publicly available expression data and human breast tumors including TNBC. Also, we studied downregulation of GYS1 in preclinical breast cancer models, focusing on TNBC. Methods: GYS1 mRNA expression and correlations with survival per clinical subtype were assessed in the METABRIC dataset. A tissue micro-array was constructed from primary tumors of 396 breast cancer patients with long-term follow-up, including normal breast control tissue. Triplicate tissue cores were stained immunohistochemically for GYS1, glycogen and the hypoxic marker carbonic anhydrase 9, and with periodic acid-Schiff staining for glycogen. In four TNBC cell lines and an MDA-MB-231 xenograft model, GYS1 protein expression, glycogen content and cell proliferation in normoxia and hypoxia were evaluated +/- GYS1 knockdown by siRNA or shRNA. Sensitivity of shGYS1 cell lines to drugs targeting mitochondria was tested. Results: In the METABRIC dataset (n = 1904), overexpression of GYS1 mRNA was associated with poor overall survival (HR 1.20 [95% CI 1.05 - 1.38]), which was mainly driven by the TNBC patients (n = 299, HR 1.52 [95% CI 1.09 - 2.14]). Immunohistochemically, most primary breast tumors had elevated GYS1 levels and glycogen content compared to normal breast tissue, with subtype specific analyses ongoing. In all breast cancer cell lines, hypoxia induced GYS1 protein expression and increased glycogen content. Acute siRNA-mediated GYS1 knockdown decreased proliferation of (TN)BC cell lines and MDA-MB-231 spheroids in both hypoxia and normoxia. shGYS1 MDA-MB-231 cells had decreased glycogen levels and shGYS1 MDA-MB-231 xenograft growth was impaired, especially in the first six weeks after inoculation. In control xenografts, immunohistochemical GYS1 expression was most pronounced adjacent to the necrotic tumor core, whereas shGYS1 xenografts lacked GYS1 expression. Finally, shGYS1 MDA-MB-231 cells were more sensitive to inhibitors of mitochondrial protein homeostasis, suggesting a potential synergistic approach to overcome eventual metabolic adaptation. Conclusions: GYS1 is overexpressed in primary breast tumors and high mRNA levels correlate with poor survival in TNBC. GYS1 downregulation impairs TNBC proliferation in vitro and in vivo, highlighting glycogen synthesis as potential novel therapeutic target in TNBC. Citation Format: Ellen C. De Heer, Christos E. Zois, Esther Bridges, Mieke C. Zwager, Tineke van der Sluis, Bert van der Vegt, Carolien P. Schröder, Steven de Jong, Adrian L. Harris, Mathilde Jalving. Glycogen synthesis as potential novel target in triple negative breast cancer: Glycogen synthase 1 expression in human breast cancers and the impact of downregulation on proliferation of preclinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5813.

Citrullination of glucokinase is linked to autoimmune diabetes

Inflammation, including reactive oxygen species and inflammatory cytokines in tissues amplify various post-translational modifications of self-proteins. A number of post-translational modifications have been identified as autoimmune biomarkers in the initiation and progression of Type 1 diabetes. Here we show the citrullination of pancreatic glucokinase as a result of inflammation, triggering autoimmunity and affecting glucokinase biological functions. Glucokinase is expressed in hepatocytes to regulate glycogen synthesis, and in pancreatic beta cells as a glucose sensor to initiate glycolysis and insulin signaling. We identify autoantibodies and autoreactive CD4+ T cells to glucokinase epitopes in the circulation of Type 1 diabetes patients and NOD mice. Finally, citrullination alters glucokinase biologic activity and suppresses glucose-stimulated insulin secretion. Our study define glucokinase as a Type 1 diabetes biomarker, providing new insights of how inflammation drives post-translational modifications to create both neoautoantigens and affect beta cell metabolism.

Liver type glycogen synthase (GYS2) and phosphorylase (PYGL) in largemouth bass (Micropterus salmoides): Cloning, characterization, and their transcriptional response to dietary carbohydrate content and resveratrol inclusion

Glycogen synthase (GS) and glycogen phosphorylase (GP) are considered as key enzymes involved in the regulation of glycogen synthesis and breakdown, respectively. In the present study, the liver type GS (GYS2) and GP (PYGL) of largemouth bass (Micropterus salmoides) were cloned and characterized, and meanwhile, their transcriptional expression in response to dietary carbohydrate levels and resveratrol inclusion, a non-flavonoid polyphenol involved in the regulation of glucose metabolism, was also investigated. Results showed that the full-length cDNA sequences of GYS2 and PYGL were 2477 bp and 3201 bp, which encoded 705 and 853 deduced amino acids, respectively. Gene sequence analysis revealed the conserved in evolution of GYS2 and PYGL. The GYS2 and PYGL of largemouth bass were both highly expressed in liver, rather than other detected tissues. The regulation of gene expression revealed that high dietary carbohydrate did not significantly impact the expression of GYS2, but significantly decreased the expression of PYGL. In addition, the supplementation of resveratrol significantly decreased the expression of GYS2, but significantly promoted the expression of PYGL, which partly accounted for beneficial role of resveratrol on alleviating hepatic glycogen accumulation in largemouth bass.

ROLE OF GSK-3 IN Wnt/β-CATENIN SIGNALING PATHWAY IN OBESITY

The complexity of the adipogenesis mechanism results from the impact of multiple cues, among which an important place is held by the components of the Wnt signaling pathway. The search for potential markers of the development of diseases related to obesity aroused an interest in the study of GSK-3 (glycogen synthase kinase), β-catenin. GSK-3β is an intracellular serine / threonine kinase found in the cytoplasm, nucleus, mitochondria, synthesized in all body tissues and involved in regulating metabolic processes, cell proliferation, apoptosis etc. The first of the discovered functions of GSK-3β was the regulation of glycogen synthesis. Active GSK-3β phosphorylates and thereby inhibits glycogen synthase. As a result of the insulin binding to the cell receptor via inositol-3-phosphate, protein kinase B (Akt1) is activated, which, in turn, phosphorylates and inhibits GSK-3β. In addition, GSK-3β is involved in the regulating glucose metabolism. The most important function of GSK-3β is the inhibition of the β-catenin protein. In a resting cell, GSK-3β in complex with the APC and Axin proteins binds and phosphorylates the β-catenin transcription factor, which leads to its ubiquitination and degradation. When Wnt proteins act on the cell, the Dvl protein is activated, which, by binding to GSK-3β, releases β-catenin, preventing its degradation, however, the role of GSK3α/β in the adipocyte inflammatory response has not yet been fully investigated, therefore it seems promising to study the role of GSK-3 in the Wnt/β-catenin signaling pathway in obesityThe aim of the study was to assess the activity of the components of the Wnt signaling pathway in obese patients by measuring the serum level of GSK-3 and β-catenin. There were enrolled 32 patients with progressive forms of I-III degree obesity in the absence of diabetes mellitus. The concentration of serum GSK-3α, GSK-3β, and β-catenin was measured by enzyme-linked immunoassay. Data are presented as absolute and relative (%) number of patients; arithmetic mean; medians, 1 and 3 quartiles – Ме (Q0.25-Q0.75). Obese patients contained a 7.5-fold increased serum level of GSK-3α (785 (371-1317.5) pg/ml) compared to healthy individuals 105 (102.5-110) pg/ml, (p < 0.001), paralleled with increased amount of GSK-3β, which level in obese patients was 295 (190-695) pg/ml, which is by 18.3% higher than those in healthy individuals 241 (218.75-287.5) pg/ml, p = 0.111. Amount of GSK-3 depending on the degree of obesity tended to increase, most often coupled to decreased β-catenin level which is consistent with the literature data and can be considered as a prognostic criterion for the course of pathological processes in obesity.

UDP-glucose pyrophosphorylase 2, a regulator of glycogen synthesis and glycosylation, is critical for pancreatic cancer growth

UDP-glucose pyrophosphorylase 2 (UGP2), the enzyme that synthesizes uridine diphosphate (UDP)-glucose, rests at the convergence of multiple metabolic pathways, however, the role of UGP2 in tumor maintenance and cancer metabolism remains unclear. Here, we identify an important role for UGP2 in the maintenance of pancreatic ductal adenocarcinoma (PDAC) growth in both in vitro and in vivo tumor models. We found that transcription of UGP2 is directly regulated by the Yes-associated protein 1 (YAP)-TEA domain transcription factor (TEAD) complex, identifying UGP2 as a bona fide YAP target gene. Loss of UGP2 leads to decreased intracellular glycogen levels and defects in N-glycosylation targets that are important for the survival of PDACs, including the epidermal growth factor receptor (EGFR). These critical roles of UGP2 in cancer maintenance, metabolism, and protein glycosylation may offer insights into therapeutic options for otherwise intractable PDACs.

The Role of GSK-3 in Cancer Immunotherapy: GSK-3 Inhibitors as a New Frontier in Cancer Treatment.

The serine/threonine kinase glycogen synthase kinase-3 (GSK-3) was initially identified because of its key role in the regulation of glycogen synthesis. However, it is now well-established that GSK-3 performs critical functions in many cellular processes, such as apoptosis, tumor growth, cell invasion, and metastasis. Aberrant GSK-3 activity has been associated with many human diseases, including cancer, highlighting its potential therapeutic relevance as a target for anticancer therapy. Recently, newly emerging data have demonstrated the pivotal role of GSK-3 in the anticancer immune response. In the last few years, many GSK-3 inhibitors have been developed, and some are currently being tested in clinical trials. This review will discuss preclinical and initial clinical results with GSK-3β inhibitors, highlighting the potential importance of this target in cancer immunotherapy. As described in this review, GSK-3 inhibitors have been shown to have antitumor activity in a wide range of human cancer cells, and they may also contribute to promoting a more efficacious immune response against tumor target cells, thus showing a double therapeutic advantage.

Pharmacological inhibition of GSK3 promotes TNFα-induced GM-CSF via up-regulation of ERK signaling in nasopharyngeal carcinoma (NPC)

Granulocyte-macrophage colony stimulating factor (GM-CSF) functions to drive nasopharyngeal cancer (NPC) metastasis via recruitment and activation of macrophages. However, the source and the regulation of GM-CSF in tumor microenvironment of NPC are not fully understood. In this study, we found that TNFα induced GM-CSF production in NPC CNE1, CNE2, and 5-8F cells in time- and dose-dependent manners. GM-CSF production was tolerant, because the pre-treatment of NPC cells with TNFα down-regulated the GM-CSF production induced by TNFα re-treatment. TNFα activated glycogen synthase kinase-3 (GSK-3), which is an enzyme to regulate glycogen synthesis, and also is a critical downstream element of the PI3K/Akt to regulate cell survival. GSK3 inhibitors up-regulated TNFα-induced GM-CSF, and reversed GM-CSF tolerance induced by TNFα pre-treatment, suggesting that GSK3 activation down-regulated GM-CSF production. GM-CSF down-regulation was not related to ubiquitin-editing enzyme A20. The over-expression of A20 did not regulate GM-CSF production induced by TNFα. However, GSK3 inhibitors up-regulated ERK activation, which contributed to the production of GM-CSF induced by TNFα, suggesting that GSK3 negatively regulated TNFα-induced GM-CSF via down-regulation of ERK signaling. Taking together, these results suggested that GSK3 pathway may be a target for the regulation of TNFα-induced GM-CSF in the tumor microenvironment.

Scaffolding Protein IQ Motif Containing GTPase Activating Protein 2 Regulates Liver Metabolic Homeostasis

The liver plays a central role in maintaining metabolic flexibility by regulating signaling pathways. Disruption in this process can lead to metabolic disease, such as obesity and cardiovascular risk. Scaffold proteins are well known to coordinate many signaling cascades. Since IQ Motif Containing GTPase Activating Protein 2 (IQGAP2) is a highly expressed scaffold protein in the liver, we examined its role in regulating metabolic programs. Adult wild type and Iqgap2−/− mice were fed ad libitum or fasted for 24 hours (9.00 am, or ZT4) and both male and female mice were used in this study to determine for sex differences in metabolism. We examined their gross morphology, performed serum biochemical assays and quantified expression of key enzymes regulating metabolic pathways including fat and carbohydrates. We found deficiency of IQGAP2 did not alter gross morphological features, liver‐to‐body weight ratio or white adipose tissue (WAT) weight. Iqgap2−/− male mice did not show pronounced differences in metabolic gene expression or fuel accumulation. In contrast, Iqgap2−/− female mice showed decreased expression of gluconeogenic, ketogenic and fatty acid oxidation genes. This basal decrease was compensated upon fasting with higher induction of ketogenic and gluconeogenic programs in Iqgap2−/− female mice. Our preliminary data suggest female Iqgap2−/− mice have defective nutrient storage. The two main hepatic fuel stores are glycogen and triglycerides. While hepatic triglycerides were not altered in female Iqgap2−/− mice, glycogen accumulation was significantly reduced. Histological analysis of hepatic glycogen accumulation showed distinct pericentral zonation which was apparent in the fed state. Consistent with this result, female Iqgap2−/− livers displayed reduced expression of genes regulating glycogen synthesis and degradation. Taken together, these data suggest a novel role for IQGAP2 in regulating hepatic fuel storage, especially glycogen levels.Support or Funding InformationIllinois Campus Research Board and American Cancer Society

Arrestin domain-containing 3 (Arrdc3) modulates insulin action and glucose metabolism in liver

Insulin action in the liver is critical for glucose homeostasis through regulation of glycogen synthesis and glucose output. Arrestin domain-containing 3 (Arrdc3) is a member of the α-arrestin family previously linked to human obesity. Here, we show that Arrdc3 is differentially regulated by insulin in vivo in mice undergoing euglycemic-hyperinsulinemic clamps, being highly up-regulated in liver and down-regulated in muscle and fat. Mice with liver-specific knockout (KO) of the insulin receptor (IR) have a 50% reduction in Arrdc3 messenger RNA, while, conversely, mice with liver-specific KO of Arrdc3 (L-Arrdc3 KO) have increased IR protein in plasma membrane. This leads to increased hepatic insulin sensitivity with increased phosphorylation of FOXO1, reduced expression of PEPCK, and increased glucokinase expression resulting in reduced hepatic glucose production and increased hepatic glycogen accumulation. These effects are due to interaction of ARRDC3 with IR resulting in phosphorylation of ARRDC3 on a conserved tyrosine (Y382) in the carboxyl-terminal domain. Thus, Arrdc3 is an insulin target gene, and ARRDC3 protein directly interacts with IR to serve as a feedback regulator of insulin action in control of liver metabolism.

Glycogen synthase kinase-3 as a key regulator of cognitive function.

Glycogen synthase kinase-3 (GSK-3) is a highly conserved and multifunctional serine/threonine protein kinase widely distributed in eukaryotic cells. GSK-3 is originally thought to be an enzyme that regulates glycogen synthesis. It was subsequently found that GSK-3 influences many critical cellular functions, such as cell structure, neural plasticity, gene expression, and neuronal survival. Recently, GSK-3 has been found to be associated with cognition, and its dysregulation leads to cognitive impairments in many diseases, including Alzheimer's disease, diabetes, depression, Parkinson's disease, and others. In this review, we summarized the current knowledge about the structure of GSK-3, the regulation of GSK-3 activity, and its role in cognitive function and cognitive-related disease.

Effects of a fructose-rich diet and chronic stress on insulin signaling and regulation of glycogen synthase kinase-3 beta and the sodium-potassium pump in the hearts of male rats.

Both a diet rich in fructose and chronic stress exposure induce metabolic and cardiovascular disturbances. The aim of this study was to examine the effects of the fructose-rich diet and chronic stress, separately and in combination, on insulin signaling and molecules regulating glycogen synthesis and ion transport in the heart, and to reveal whether these effects coincide with changes in glucocorticoid receptor (GR) activation. Male Wistar rats were subjected to 10% fructose in drinking water and/or to chronic unpredictable stress for 9 weeks. Protein expression and/or phosphorylation of the insulin receptor (IR), protein tyrosine phosphatase 1B, insulin receptor substrate 1 (IRS1), protein kinase B (Akt), extracellular signal-regulated kinase 1/2 (ERK1/2), glycogen synthase kinase-3β (GSK-3β) and Na+/K+-ATPase α-subunits in cardiac tissue were analyzed by western blot. GR distribution between cytosolic and nuclear fractions was also analyzed. The fructose-rich diet decreased the level of pERK1/2 (Thr202/Tyr204) and pGSK-3β (Ser9) independently of stress, while chronic stress increased the IRS1 content and prevented the fructose diet-induced decrease of the pAkt (Ser473) level. The fructose-rich diet in combination with chronic stress reduced the protein content of cardiac IR and attenuated IRS1 upregulation. Separate treatments increased the protein content of Na+/K+-ATPase α1- and α2-subunits, while after combined treatment the α2 content was at the control level and the α1 content was lower than the control level. The effect of combined treatment on cardiac IR and α2-subunit expression could be mediated by increased GR nuclear accumulation. Our study provides new insights into the effects of chronic stress and a combination of the fructose diet and chronic stress on the studied molecules in the heart.

Astragaloside IV Increases Phosphorylation of GSK‐3β And S6K1 via The AKT Pathway in C2C12 Muscle Cells

Astragaloside IV (AsIV) is the primary active component of the Astragalus membranaceus herb, used in traditional Chinese medicine to treat metabolic disorders. Through in vitro and in vivo experimentation, this saponin phytochemical has been shown to regulate glycogen synthesis through protein kinase B (AKT)‐mediated phosphorylation of glycogen synthase kinase 3 beta (GSK‐3β). Phosphorylation of GSK‐3β at Ser9 downregulates the enzyme's activity and promotes glucose uptake and responsiveness. Along with control of glucose homeostasis, AKT activation is an important regulator of protein synthesis via the downstream phosphorylation of mammalian target of rapamycin (mTOR) and ribosomal protein S6 kinase beta‐1 (S6K1). While AsIV has been shown to exhibit metabolic benefits, there is little data investigating the possible effect of this compound on protein synthesis. In order to determine the effect of AsIV on protein synthetic pathways, C2C12 murine muscle cells were treated with AsIV and the phosphorylation levels of key enzyme were assessed.We found that AsIV induced phosphorylation of key protein synthetic targets in a time and dose‐dependent manner. By two hours of AsIV treatment, C2C12 cells had the greatest increase in AKT phosphorylation. These cells also had a 1.6‐fold increase in GSK‐3β phosphorylation and a 4‐fold increase in S6K1 activation, compared to controls. These results suggest that AsIV can phosphorylate AKT in a time‐dependent manner, with subsequent activation of S6K1 and inactivation of GSK‐3β. This suggests that AsIV may be capable of increasing the rate of protein synthesis in muscle cells. These findings help to further understand the molecular changes that occur in muscle cells and serve as a potential therapeutic mechanism to combat muscle loss.Support or Funding InformationThis work was supported by the Wehner Student Research Program at Montclair State UniversityThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Fructose-1,6-bisphosphatase: From a glucose metabolism enzyme to multifaceted regulator of a cell fate.

Fructose-1,6-bisphosphatase (FBPase) is one of the ancient, evolutionarily conserved enzymes of carbohydrate metabolism. It has been described for a first time in 1943, however, for the next half a century mostly kinetic and structural parameters of animal FBPases have been studied. Discovery of ubiquitous expression of the muscle isozyme of FBPase, thus far considered to merely regulate glycogen synthesis from carbohydrate precursors, and its nuclear localisation in several cell types has risen new interest in the protein, resulting in numerous publications revealing complex functions/properties of FBPase. This review summarises the current knowledge of FBPase in animal cells providing evidence that the enzyme merits the name of moonlighting protein.

Lafora Disease: A Ubiquitination-Related Pathology.

Lafora disease (LD, OMIM254780) is a rare and fatal form of progressive myoclonus epilepsy (PME). Among PMEs, LD is unique because of the rapid neurological deterioration of the patients and the appearance in brain and peripheral tissues of insoluble glycogen-like (polyglucosan) inclusions, named Lafora bodies (LBs). LD is caused by mutations in the EPM2A gene, encoding the dual phosphatase laforin, or the EPM2B gene, encoding the E3-ubiquitin ligase malin. Laforin and malin form a functional complex that is involved in the regulation of glycogen synthesis. Thus, in the absence of a functional complex glycogen accumulates in LBs. In addition, it has been suggested that the laforin-malin complex participates in alternative physiological pathways, such as intracellular protein degradation, oxidative stress, and the endoplasmic reticulum unfolded protein response. In this work we review the possible cellular functions of laforin and malin with a special focus on their role in the ubiquitination of specific substrates. We also discuss here the pathological consequences of defects in laforin or malin functions, as well as the therapeutic strategies that are being explored for LD.