scholarly journals Cytokeratin 8 Inhibits Hepatic Glycogen Synthesis in Type 2 Diabetes Mellitus by Modulating Insulin-dependent IRS1/PI3K/Akt-GSK3β Pathway

2021 ◽  
Author(s):  
Mingzhu Sun ◽  
Jin Sun ◽  
Zhidong Wang ◽  
Xiaojuan Quan ◽  
Lin Zhang ◽  
...  
Keyword(s):  
Mouse Model ◽  
Western Blotting ◽  
Glycogen Synthesis ◽  
Hepatic Glycogen ◽  
Expression Levels ◽  
Empty Vector ◽  
High Glucose Medium ◽  
Insulin Dependent ◽  
Underlying Mechanisms

Abstract Purpose: Cytokeratin 8(CK8) is a cytoskeletal protein mainly expressed in the liver. Recent studies have found that CK8 was closely related to glycogen synthesis. However, the role and the underlying mechanisms of CK8 in hepatic glycogen synthesis in type 2 diabetes mellitus (T2DM) have remained to be fully elucidated. Therefore, this study aimed to investigate the effects and the underlying mechanisms of CK8 on hepatic glycogen synthesis in T2DM.Methods The T2D mouse model was constructed by high energy feed of 8-10 weeks old C57BL/6J male mice. The model was validated by OGTT test and ITT test. The liver samples of T2DM patients were collected and the expression levels of CK8, IRS1, PI3K, Akt, GSK3β, p-PI3K p-Akt and p-GSK3β were determined by Western blotting. Then, at the cellular level the murine NCTC 1469 cells were used, and to up-regulate and down-regulate the CK8 gene the overexpression plasmid was constructed and transfected and RNA interference technology was applied, and CK8, IRS1, PI3K, Akt, GSK3β, p-IRS1, p-PI3K p-Akt and p-GSK3β were detected by Western blotting. Immunohistochemistry was used to detect the level of glycogen synthase (GS) and glycogen staining experiments was performed by PAS. At the animal level, the T2D mouse model was used to up-regulate and down-regulate the CK8 gene using an adenovirus vector. The levels of CK8, PI3K, Akt, GSK3β, p-PI3K, p-Akt and p-GSK3β in rat liver were detected by Western blotting, immunohistochemistry was used to detect the level of GS and glycogen staining experiments was performed by PAS.Results The expression levels of IRS1, p-PI3K, p-Akt and p-GSK3β were significantly higher, while the expression levels of CK8 was significantly lower in control group than in the liver of T2D mice or T2DM patients. Upregulation of CK8 in murine NCTC 1469 cells treated with high-glucose medium, we found IRS1, p-IRS1, p-PI3K, p-Akt and p-GSK3β were significantly decreased, the level of GS was significantly decreased, and glycogen synthesis was inhibited compared with NCTC1469 cells transfected with empty vector. Downregulation of CK8 in murine NCTC 1469 cells murine treated with high-glucose medium, we found IRS1, p-IRS1, p-PI3K, p-Akt and p-GSK3β were significantly higher, the level of GS was significantly increased, and glycogen synthesis was promoted compared with NCTC1469 cells transfected with sh-NC. Upregulation of CK8 in the T2D mouse model, we found p-PI3K, p-Akt and p-GSK3β were significantly lower compared with T2D mouse model transfected with empty vector. The level of GS was significantly decreased, and glycogen synthesis was inhibited. Downregulation of CK8 in the T2D mouse model, we found p-PI3K, p-Akt and p-GSK3β were significantly increased, and the level of GS was significantly increased, and glycogen synthesis was promoted compared with T2D mouse model transfected with sh-NC.Conclusions Overall, this experiment provides a new molecular target for the treatment of T2DM by revealing the role of CK8 inhibiting hepatic glycogen synthesis in T2DM via regulating insulin-dependent IRS1/PI3K-Akt-GSK3β pathway. CK8 may play an important role in the pathogenesis of glycogen synthesis in T2DM.

The level of the glycogen targetting regulatory subunit R5 of protein phosphatase 1 is decreased in the livers of insulin-dependent diabetic rats and starved rats

2001 ◽  
Vol 360 (2) ◽  
pp. 449-459 ◽  
Author(s):  
Gareth J. BROWNE ◽  
Mirela DELIBEGOVIC ◽  
Stefaan KEPPENS ◽  
Willy STALMANS ◽  
Patricia T. W. COHEN
Keyword(s):  
Phosphatase Activity ◽  
Protein Phosphatase ◽  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Diabetic Rats ◽  
Protein Phosphatase 1 ◽  
Regulatory Subunit ◽  
Hepatic Glycogen ◽  
Insulin Dependent ◽  
Insulin Dependent Diabetic

Hepatic glycogen synthesis is impaired in insulin-dependent diabetic rats owing to defective activation of glycogen synthase by glycogen-bound protein phosphatase 1 (PP1). The identification of three glycogen-targetting subunits in liver, GL, R5/PTG and R6, which form complexes with the catalytic subunit of PP1 (PP1c), raises the question of whether some or all of these PP1c complexes are subject to regulation by insulin. In liver lysates of control rats, R5 and R6 complexes with PP1c were found to contribute significantly (16 and 21% respectively) to the phosphorylase phosphatase activity associated with the glycogen-targetting subunits, GL–PP1c accounting for the remainder (63%). In liver lysates of insulin-dependent diabetic and of starved rats, the phosphorylase phosphatase activities of the R5 and GL complexes with PP1c were shown by specific immunoadsorption assays to be substantially decreased, and the levels of R5 and GL were shown by immunoblotting to be much lower than those in control extracts. The phosphorylase phosphatase activity of R6–PP1c and the concentration of R6 protein were unaffected by these treatments. Insulin administration to diabetic rats restored the levels of R5 and GL and their associated activities. The regulation of R5 protein levels by insulin was shown to correspond to changes in the level of the mRNA, as has been found for GL. The in vitro glycogen synthase phosphatase/phosphorylase phosphatase activity ratio of R5-PP1c was lower than that of GL–PP1c, suggesting that R5–PP1c may function as a hepatic phosphorylase phosphatase, whereas GL–PP1c may be the major hepatic glycogen synthase phosphatase. In hepatic lysates, more than half the R6 was present in the glycogen-free supernatant, suggesting that R6 may have lower affinity for glycogen than R5 and GL

scholarly journals Loss of the hepatic glycogen-binding subunit (GL) of protein phosphatase 1 underlies deficient glycogen synthesis in insulin-dependent diabetic rats and in adrenalectomized starved rats

1998 ◽  
Vol 333 (2) ◽  
pp. 253-257 ◽  
Author(s):  
Martin J. DOHERTY ◽  
Joan CADEFAU ◽  
Willy STALMANS ◽  
Mathieu BOLLEN ◽  
Patricia T. W. COHEN
Keyword(s):  
Protein Phosphatase ◽  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Diabetic Rats ◽  
Catalytic Subunit ◽  
Protein Phosphatase 1 ◽  
Hepatic Glycogen ◽  
Insulin Dependent ◽  
Insulin Dependent Diabetic ◽  
Binding Subunit

Hepatic glycogen synthesis is impaired in insulin-dependent diabetic rats and in adrenalectomized starved rats, and although this is known to be due to defective activation of glycogen synthase by glycogen synthase phosphatase, the underlying molecular mechanism has not been delineated. Glycogen synthase phosphatase comprises the catalytic subunit of protein phosphatase 1 (PP1) complexed with the hepatic glycogen-binding subunit, termed GL. In liver extracts of insulin-dependent diabetic and adrenalectomized starved rats, the level of GL was shown by immunoblotting to be substantially reduced compared with that in control extracts, whereas the level of PP1 catalytic subunit was not affected by these treatments. Insulin administration to diabetic rats restored the level of GL and prolonged administration raised it above the control levels, whereas re-feeding partially restored the GL level in adrenalectomized starved rats. The regulation of GL protein levels by insulin and starvation/feeding was shown to correlate with changes in the level of the GL mRNA, indicating that the long-term regulation of the hepatic glycogen-associated form of PP1 by insulin, and hence the activity of hepatic glycogen synthase, is predominantly mediated through changes in the level of the GL mRNA.

Restoration of direct pathway glycogen synthesis flux in the STZ-diabetes rat model by insulin administration

2012 ◽  
Vol 303 (7) ◽  
pp. E875-E885 ◽  
Author(s):  
Ana F. Soares ◽  
Rui A. Carvalho ◽  
Francisco J. Veiga ◽  
Marco G. Alves ◽  
Fátima O. Martins ◽  
...  
Keyword(s):  
De Novo ◽  
Glycogen Synthesis ◽  
Insulin Dependent Diabetes ◽  
De Novo Lipogenesis ◽  
Hepatic Glycogen ◽  
Insulin Administration ◽  
Indirect Pathway ◽  
Direct Pathway ◽  
Nocturnal Feeding ◽  
Insulin Dependent

Type 1 diabetes subjects are characterized by impaired direct pathway synthesis of hepatic glycogen that is unresponsive to insulin therapy. Since it is not known whether this is an irreversible defect of insulin-dependent diabetes, direct and indirect pathway glycogen fluxes were quantified in streptozotocin (STZ)-induced diabetic rats and compared with STZ rats that received subcutaneous or intraperitoneal insulin (I-SC or I-IP). Three groups of STZ rats were studied at 18 days post-STZ treatment. One group was administered I-SC and another I-IP as two daily injections of short-acting insulin at the start of each light and dark period for days 9–18. A third group did not receive any insulin, and a fourth group of nondiabetic rats was used as control. Glycogen synthesis via direct and indirect pathways, de novo lipogenesis, and gluconeogenesis were determined over the nocturnal feeding period using deuterated water. Direct pathway was residual in STZ rats, and glucokinase activity was also reduced significantly from control levels. Insulin administration restored both net glycogen synthesis via the direct pathway and glucokinase activity to nondiabetic control levels and improved the lipogenic pathway despite an inefficient normalization of the gluconeogenic pathway. We conclude that the reduced direct pathway flux is not an irreversible defect of insulin-dependent diabetes.

Molecular regulation of insulin granule biogenesis and exocytosis

2016 ◽  
Vol 473 (18) ◽  
pp. 2737-2756 ◽  
Author(s):  
Pia V. Röder ◽  
Xiuming Wong ◽  
Wanjin Hong ◽  
Weiping Han
Keyword(s):  
Peptide Hormone ◽  
Signaling Cascades ◽  
Β Cells ◽  
Glucose Levels ◽  
Exogenous Glucose ◽  
Blood Glucose Levels ◽  
Insulin Dependent ◽  
Underlying Mechanisms ◽  
Disease Stages

Type 2 diabetes mellitus (T2DM) is a metabolic disorder characterized by hyperglycemia, insulin resistance and hyperinsulinemia in early disease stages but a relative insulin insufficiency in later stages. Insulin, a peptide hormone, is produced in and secreted from pancreatic β-cells following elevated blood glucose levels. Upon its release, insulin induces the removal of excessive exogenous glucose from the bloodstream primarily by stimulating glucose uptake into insulin-dependent tissues as well as promoting hepatic glycogenesis. Given the increasing prevalence of T2DM worldwide, elucidating the underlying mechanisms and identifying the various players involved in the synthesis and exocytosis of insulin from β-cells is of utmost importance. This review summarizes our current understanding of the route insulin takes through the cell after its synthesis in the endoplasmic reticulum as well as our knowledge of the highly elaborate network that controls insulin release from the β-cell. This network harbors potential targets for anti-diabetic drugs and is regulated by signaling cascades from several endocrine systems.

scholarly journals Polycytosine RNA-Binding Protein 1 Regulates Osteoblast Function via a Ferroptosis Pathway in Type 2 Diabetic Osteoporosis

2021 ◽  
Author(s):  
Hongdong Ma ◽  
yueming Jiang ◽  
Haitian Li ◽  
Maowei Yang
Keyword(s):  
Flow Cytometry ◽  
Western Blotting ◽  
High Glucose ◽  
Rna Binding ◽  
Binding Protein ◽  
Rna Binding Protein ◽  
Expression Levels ◽  
Diabetic Osteoporosis ◽  
Type 2 Diabetic

Abstract In recent years, type 2 diabetic osteoporosis has become a research hotspot for the complications of diabetes, but the specific mechanism of its occurrence and development remain unknown. Ferroptosis caused by iron overload is considered to be one of the important cause of type 2 diabetic osteoporosis. Polycytosine RNA-binding protein 1 (PCBP1), an iron ion chaperone, was considered as a protector of ferroptosis. The present study aimed to investigate the existence of ferroptosis and specific role of PCBP1 in the development of type 2 diabetes. Firstly, a Cell Counting Kit-8 assay was used to detect the changes of osteoblast viability under the influence of high glucose (HG) and/or ferroptosis inhibitor given at different concentrations and at different times. In addition, the morphological changes of mitochondria in osteoblasts under high glucose were examined via transmission electron microscopy, and the expression levels of PCBP1, ferritin and the ferroptosis-related protein glutathione peroxidase 4 (GPX4) under the action of high glucose were detected via western blotting. Furthermore, a lentivirus was used to silence and overexpress PCBP1. Western blotting was used to detect the expression of levels of the osteoblast functional proteins osteoprotegerin (OPG) and osteocalcin (OCN), while flow cytometry was used to detect the changes of reactive oxygen species (ROS) levels in each group. Under the action of high glucose, the viability of osteoblasts was significantly decreased and the number of mitochondria undergoing atrophy was significantly increased, PCBP1 and ferritin expression levels were increased and GPX4 expression was decreased. Western blotting results demonstrated that infection of the lentivirus overexpressing PCBP1, increased the expression levels of ferritin, GPX4, OPG and OCN, compared with the high glucose group. The flow cytometry results identified a reduction in ROS, and an opposite result was obtained after silencing PCBP1. In conclusion, it was suggested that PCBP1 may protect osteoblasts and reduce the harm caused by ferroptosis by promoting ferritin expression under a high glucose environment. Moreover, it was indicated that PCBP1 may be a potential therapeutic target for treating type 2 diabetic osteoporosis.

Irisin inhibits hepatic gluconeogenesis and increases glycogen synthesis via the PI3K/Akt pathway in type 2 diabetic mice and hepatocytes

2015 ◽  
Vol 129 (10) ◽  
pp. 839-850 ◽  
Author(s):  
Tong-Yan Liu ◽  
Chang-Xiang Shi ◽  
Run Gao ◽  
Hai-Jian Sun ◽  
Xiao-Qing Xiong ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Therapeutic Strategy ◽  
Hepatic Glucose Production ◽  
Glycogen Synthesis ◽  
Glucose Production ◽  
Hepatic Glycogen ◽  
Hepatic Glucose ◽  
Effective Therapeutic Strategy ◽  
Type 2 Diabetic

This study provide evidence that irisin reduces hepatic glucose production and the blood glucose level, increases hepatic glycogen synthesis and improves insulin resistance in type 2 diabetes. Irisin may be regarded as an effective therapeutic strategy for type 2 diabetes.

scholarly journals Pyrrolidine dithiocarbamate enhances hepatic glycogen synthesis and reduces FoxO1-mediated gene transcription in type 2 diabetic rats

2012 ◽  
Vol 302 (4) ◽  
pp. E409-E416 ◽  
Author(s):  
Tienian Zhu ◽  
Ruijing Zhao ◽  
Lizhong Zhang ◽  
Michel Bernier ◽  
Jiankun Liu
Keyword(s):  
Blood Glucose ◽  
Glycogen Synthesis ◽  
Fasting Blood Glucose ◽  
Diabetic Rats ◽  
Hepatic Glycogen ◽  
Pyrrolidine Dithiocarbamate ◽  
Glycogen Deposition ◽  
Gsk 3Β ◽  
Type 2 Diabetic

The aim of the present study was to examine the effects of pyrrolidine dithiocarbamate (PDTC) on hepatic glycogen synthesis and FoxO1 transcriptional activity in type 2 diabetic rats and the mechanism underlying these effects. Fasting blood glucose and glycogen deposition, together with expressions of two key genes related to gluconeogenesis, were studied in the liver of rats fed a normal diet (NC), high-fat diet (HFD)-induced insulin-resistant rats made type 2 diabetic by a single intraperitoneal injection of streptozotocin (DM), and a DM with intervention of PDTC (DM + PDTC) for 1 wk. The phosphorylation of Akt, GSK-3β, and FoxO1 was assessed in liver extracts of fasted rats by Western blot, whereas indirect immunofluorescence staining was performed to determine the cellular distribution of FoxO1. The DM rats exhibited obvious increases in fasting blood glucose as well as decreased hepatic glycogen content compared with the NC group. Activation of the Akt/GSK-3β pathway and inactivating phosphorylation of FoxO1 were reduced greatly in DM rat livers ( P < 0.01). By contrast, PDTC treatment protected DM rats against high fasting blood glucose and hepatic glycogen deposition loss. PDTC also elicited an increase in Akt/GSK-3β signaling and subsequent inactivation and nuclear export of FoxO1 in DM rat livers, which translated into a significant reduction in the expression of two FoxO1 target genes, phospho enolpyruvate carboxykinase and glucose-6-phosphatase. This study suggests that PDTC enhances hepatic glycogen synthesis, whereas it reduces FoxO1 transcriptional activity in DM rats.

Resveratrol, a red wine antioxidant, possesses an insulin-like effect in streptozotocin-induced diabetic rats

2006 ◽  
Vol 290 (6) ◽  
pp. E1339-E1346 ◽  
Author(s):  
Hui-Chen Su ◽  
Li-Man Hung ◽  
Jan-Kan Chen
Keyword(s):  
Insulin Secretion ◽  
Glucose Uptake ◽  
Plasma Glucose ◽  
Glucose Concentration ◽  
Glycogen Synthesis ◽  
Body Weight Loss ◽  
Plasma Glucose Concentration ◽  
Hepatic Glycogen ◽  
Triglyceride Concentration

Aberrant energy metabolism is one characteristic of diabetes mellitus (DM). Two types of DM have been identified, type 1 and type 2. Most of type 2 DM patients eventually become insulin dependent because insulin secretion by the islets of Langerhans becomes exhausted. In the present study, we show that resveratrol (3,5,4′-trihydroxylstilbene) possesses hypoglycemic and hypolipidemic effects in streptozotocin-induced DM (STZ-DM) rats. In resveratrol-treated STZ-DM rats, the plasma glucose concentration on day 14 was reduced by 25.3 ± 4.2%, and the triglyceride concentration was reduced by 50.2 ± 3.2% compared with the vehicle-treated rats. In STZ-nicotinamide DM rats, the plasma glucose concentration on day 14 was reduced by 20.3 ± 4.2%, and the triglyceride concentration was reduced by 33.3 ± 2.2% compared with the vehicle-treated rats. Resveratrol administration ameliorates common DM symptoms, such as body weight loss, polyphagia, and polydipsia. In STZ-nicotinamide DM rats, resveratrol administration significantly decreased insulin secretion and delayed the onset of insulin resistance. Further studies showed that glucose uptake by hepatocytes, adipocytes, and skeletal muscle and hepatic glycogen synthesis were all stimulated by resveratrol treatment. Because the stimulation of glucose uptake was not attenuated in the presence of an optimal amount of insulin in insulin-responsive cells, the antihyperglycemic effect of resveratrol appeared to act through a mechanism(s) different from that of insulin.

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