Abstract 102: Cardiac-specific Overactivation of the Mechanistic Target of Rapamycin Complex 1 Induces Metabolic, Structural and Functional Remodeling

2015 ◽  
Vol 117 (suppl_1) ◽  
Author(s):  
Giovanni Davogustto ◽  
Rebecca Salazar ◽  
Hernan Vasquez ◽  
Heinrich Taegtmeyer
Keyword(s):  
Glucose Uptake ◽  
Glucose Transporter ◽  
Target Of Rapamycin ◽  
Glycolytic Intermediate ◽  
Glucose Transporter 1 ◽  
Structural Remodeling ◽  
Mechanistic Target Of Rapamycin ◽  
Metabolic Remodeling ◽  
Functional Remodeling ◽  
Mtorc1 Activation

The heart remodels metabolically and structurally before it fails. Metabolically, the heart increases its reliance on carbohydrates for energy provision. Structurally, the heart hypertrophies to sustain increased hemodynamic stress. There is evidence suggesting that the activation of the mechanistic Target Of Rapamycin Complex 1 (mTORC1) pathway is closely tied to glucose uptake by the heart to drive the metabolic and structural remodeling. We have previously shown that with insulin stimulation or increases in workload, the glycolytic intermediate glucose 6-phosphate (G6P) is required to activate mTORC1. Sustained mTORC1 activation leads, in turn, to ER stress and contractile dysfunction. Studies by others in the kidney have shown that mTORC1 activation upregulates glucose transporter 1 (Glut1) expression and glucose uptake. We therefore test the hypothesis that chronic mTORC1 overactivation results in G6P accumulation, and precedes structural and functional remodeling in the heart. We developed mice with inducible, cardiac-specific deficiency of the protein tuberin (TSC2), a member of the tuberous sclerosis complex, the principal inhibitor of mTORC1. Intracellular G6P concentrations were measured enzymatically. Immunoblotting was performed on protein markers to confirm activation of mTORC1 downstream targets and of the unfolded protein response. Histologic analysis were performed to assess structural changes. Serial echocardiograms were performed to evaluate cardiac function. The results indicate that chronic mTORC1 activation through inducible, cardiac-specific deletion of TSC2 is accompanied by G6P accumulation and metabolic remodeling. Metabolic remodeling precedes structural and functional remodeling. We suggest that in the heart, sustained mTORC1 activation is a key driver of metabolic and structural remodeling.

Differential glycolytic and glycogenogenic transduction pathways in male and female bovine embryos produced in vitro

2012 ◽  
Vol 24 (2) ◽  
pp. 344 ◽  
Author(s):  
M. Garcia-Herreros ◽  
I. M. Aparicio ◽  
D. Rath ◽  
T. Fair ◽  
P. Lonergan
Keyword(s):  
Glucose Metabolism ◽  
Protein Expression ◽  
Glucose Uptake ◽  
Glucose Transporter ◽  
Glycogen Synthase ◽  
Bovine Embryos ◽  
High Concentration ◽  
Glucose Transporter 1 ◽  
Male And Female ◽  
Glut 1

Previous studies have shown that developmental kinetic rates following IVF are lower in female than in male blastocysts and that this may be related to differences in glucose metabolism. In addition, an inhibition of phosphatidylinositol 3-kinase (PI3-K) inhibits glucose uptake in murine blastocysts. Therefore, the aim of this study was to identify and compare the expression of proteins involved in glucose metabolism (hexokinase-I, HK-I; phosphofructokinase-1, PFK-1; pyruvate kinase1/2, PK1/2; glyceraldehyde-3-phosphate dehydrogenase, GAPDH; glucose transporter-1, GLUT-1; and glycogen synthase kinase-3, GSK-3) in male and female bovine blastocysts to determine whether PI3-K has a role in the regulation of the expression of these proteins. Hexokinase-I, PFK-1, PK1/2, GAPDH and GLUT-1 were present in bovine embryos. Protein expression of these proteins and GSK-3 was significantly higher in male compared with female blastocysts. Inhibition of PI3-K with LY294002 significantly decreased the expression of HK-I, PFK-1, GAPDH, GSK-3 A/B and GLUT-1. Results showed that the expression of glycolytic proteins HK-I, PFK-1, GAPDH and PK1/2, and the transporters GLUT-1 and GSK-3 is regulated by PI3-K in bovine blastocysts. Moreover, the differential protein expression observed between male and female blastocysts might explain the faster developmental kinetics seen in males, as the expression of main proteins involved in glycolysis and glycogenogenesis was significantly higher in male than female bovine embryos and also could explain the sensitivity of male embryos to a high concentration of glucose, as a positive correlation between GLUT-1 expression and glucose uptake in embryos has been demonstrated.

scholarly journals Transient Silencing of a Type IV P-Type ATPase,Atp10c, Results in Decreased Glucose Uptake in C2C12 Myotubes

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
S. E. Hurst ◽  
S. C. Minkin ◽  
J. Biggerstaff ◽  
M. S. Dhar
Keyword(s):  
Type 2 Diabetes ◽  
Glucose Uptake ◽  
Glucose Transporter ◽  
Mapk Pathway ◽  
Specific Inhibitor ◽  
C2c12 Myotubes ◽  
Glucose Transporter 1 ◽  
Transfected Cells

Atp10cis a strong candidate gene for diet-induced obesity and type 2 diabetes. To identify molecular and cellular targets of ATP10C,Atp10cexpression was alteredin vitroin C2C12 skeletal muscle myotubes by transient transfection with anAtp10c-specific siRNA. Glucose uptake assays revealed that insulin stimulation caused a significant 2.54-fold decrease in 2-deoxyglucose uptake in transfected cells coupled with a significant upregulation of native mitogen-activated protein kinases (MAPKs), p38, and p44/42. Additionally, glucose transporter-1 (GLUT1) was significantly upregulated; no changes in glucose transporter-4 (GLUT4) expression were observed. The involvement of MAPKs was confirmed using the specific inhibitor SB203580, which downregulated the expression of native and phosphorylated MAPK proteins in transfected cells without any changes in insulin-stimulated glucose uptake. Results indicate thatAtp10cregulates glucose metabolism, at least in part via the MAPK pathway, and, thus, plays a significant role in the development of insulin resistance and type 2 diabetes.

High-intensity muscle contraction-mediated increases in Akt1 and Akt2 phosphorylation do not contribute to mTORC1 activation and muscle protein synthesis

2020 ◽  
Vol 128 (4) ◽  
pp. 830-837 ◽  
Author(s):  
Yuki Maruyama ◽  
Chisaki Ikeda ◽  
Koki Wakabayashi ◽  
Satoru Ato ◽  
Riki Ogasawara
Keyword(s):  
Protein Synthesis ◽  
Resistance Exercise ◽  
Muscle Contraction ◽  
High Intensity ◽  
Gastrocnemius Muscle ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Target Of Rapamycin ◽  
Mechanistic Target Of Rapamycin ◽  
Mtorc1 Activation

High-intensity muscle contraction (HiMC) is known to induce muscle protein synthesis, a process in which mechanistic target of rapamycin (mTOR) is reported to play a critical role. However, the mechanistic details have not been completely elucidated. Here, we investigated whether Akt plays a role in regulating HiMC-induced mTORC1 activation and muscle protein synthesis using a rodent model of resistance exercise and MK2206 (an Akt kinase inhibitor). The right gastrocnemius muscle of male C57BL/6J mice aged 10 wk was isometrically contracted via percutaneous electrical stimulation (100 Hz, 5 sets of 10 3-s contractions, 7-s rest between contractions, and 3-min rest between sets), while the left gastrocnemius muscle served as a control. Vehicle or MK2206 was injected intraperitoneally 6 h before contraction. MK2206 inhibited both resting and HiMC-induced phosphorylation of Akt1 Ser-473 and Akt2 Ser-474. MK2206 also inhibited the resting phosphorylation of p70S6K and 4E-BP1, which are downstream targets of mTORC1; however, it did not inhibit the HiMC-induced increase in phosphorylation of these targets. Similarly, MK2206 inhibited the resting muscle protein synthesis, but not the resistance exercise-induced muscle protein synthesis. On the basis of these observations, we conclude that although Akt2 regulates resting mTORC1 activity and muscle protein synthesis, HiMC-induced increases in mTORC1 activity and muscle protein synthesis are Akt-independent processes. NEW & NOTEWORTHY Akt is well known to be an upstream regulator of mechanistic target of rapamycin (mTOR) and has three isoforms in mammals, namely, Akt1, Akt2, and Akt3. We found that high-intensity muscle contraction (HiMC) increases Akt1 and Akt2 phosphorylation; however, HiMC-induced increases in mTORC1 activity and muscle protein synthesis are Akt-independent processes.

scholarly journals Ecklonia cavaInhibits Glucose Absorption and Stimulates Insulin Secretion in Streptozotocin-Induced Diabetic Mice

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Hye Kyung Kim
Keyword(s):  
Insulin Secretion ◽  
Protein Expression ◽  
Glucose Uptake ◽  
Glucose Transporter ◽  
Islet Cells ◽  
Glucose Absorption ◽  
Oral Glucose ◽  
Diabetic Mice ◽  
Glucose Transporter 1

Aims of study. Present study investigated the effect ofEcklonia cava(EC) on intestinal glucose uptake and insulin secretion.Materials and methods. Intestinal Na+-dependent glucose uptake (SGU) and Na+-dependent glucose transporter 1 (SGLT1) protein expression was determined using brush border membrane vesicles (BBMVs). Glucose-induced insulin secretion was examined in pancreatic β-islet cells. The antihyperglycemic effects of EC, SGU, and SGLT1 expression were determined in streptozotocin (STZ)-induced diabetic mice.Results. Methanol extract of EC markedly inhibited intestinal SGU of BBMV with the IC50value of 345 μg/mL. SGLT1 protein expression was dose dependently down regulated with EC treatment. Furthermore, insulinotrophic effect of EC extract was observed at high glucose media in isolated pancreatic β-islet cellsin vitro. We next conducted the antihyperglycemic effect of EC in STZ-diabetic mice. EC supplementation markedly suppressed SGU and SGLT1 abundance in BBMV from STZ mice. Furthermore, plasma insulin level was increased by EC treatment in diabetic mice. As a result, EC supplementation improved postprandial glucose regulation, assessed by oral glucose tolerance test, in diabetic mice.Conclusion. These results suggest that EC play a role in controlling dietary glucose absorption at the intestine and insulinotrophic action at the pancreas contributing blood glucose homeostasis in diabetic condition.

scholarly journals Glucocorticoids Enhance Intestinal Glucose Uptake Via the Dimerized Glucocorticoid Receptor in Enterocytes

Endocrinology ◽  
2012 ◽  
Vol 153 (4) ◽  
pp. 1783-1794 ◽  
Author(s):  
Sybille D. Reichardt ◽  
Michael Föller ◽  
Rexhep Rexhepaj ◽  
Ganesh Pathare ◽  
Kerstin Minnich ◽  
...  
Keyword(s):  
Small Intestine ◽  
Glucose Uptake ◽  
Molecular Mechanism ◽  
Glucose Transport ◽  
Transcriptional Control ◽  
Glucose Transporter ◽  
Gene Activation ◽  
Mouse Strains ◽  
Glucose Transporter 1

Glucocorticoid (GC) treatment of inflammatory disorders, such as inflammatory bowel disease, causes deranged metabolism, in part by enhanced intestinal resorption of glucose. However, the underlying molecular mechanism is poorly understood. Hence, we investigated transcriptional control of genes reported to be involved in glucose uptake in the small intestine after GC treatment and determined effects of GC on electrogenic glucose transport from transepithelial currents. GRvillinCre mice lacking the GC receptor (GR) in enterocytes served to identify the target cell of GC treatment and the requirement of the GR itself; GRdim mice impaired in dimerization and DNA binding of the GR were used to determine the underlying molecular mechanism. Our findings revealed that oral administration of dexamethasone to wild-type mice for 3 d increased mRNA expression of serum- and GC-inducible kinase 1, sodium-coupled glucose transporter 1, and Na+/H+ exchanger 3, as well as electrogenic glucose transport in the small intestine. In contrast, GRvillinCre mice did not respond to GC treatment, neither with regard to gene activation nor to glucose transport. GRdim mice were also refractory to GC, because dexamethasone treatment failed to increase both, gene expression and electrogenic glucose transport. In addition, the rise in blood glucose levels normally observed after GC administration was attenuated in both mutant mouse strains. We conclude that enhanced glucose transport in vivo primarily depends on gene regulation by the dimerized GR in enterocytes, and that this mechanism contributes to GC-induced hyperglycemia.

scholarly journals Comparative study of expression and activity of glucose transporters between stem cell-derived brain microvascular endothelial cells and hCMEC/D3 cells

2017 ◽  
Vol 313 (4) ◽  
pp. C421-C429 ◽  
Author(s):  
Abraham J. Al-Ahmad
Keyword(s):  
Stem Cells ◽  
Endothelial Cells ◽  
Glucose Uptake ◽  
Glucose Transporter ◽  
Glucose Transporters ◽  
Microvascular Endothelial Cells ◽  
Brain Microvascular Endothelial Cells ◽  
Glucose Transporter 1 ◽  
Microvascular Endothelial

Glucose constitutes a major source of energy of mammalian brains. Glucose uptake at the blood-brain barrier (BBB) occurs through a facilitated glucose transport, through glucose transporter 1 (GLUT1), although other isoforms have been described at the BBB. Mutations in GLUT1 are associated with the GLUT1 deficiency syndrome, yet none of the current in vitro models of the human BBB maybe suited for modeling such a disorder. In this study, we investigated the expression of glucose transporters and glucose diffusion across brain microvascular endothelial cells (BMECs) derived from healthy patient-derived induced pluripotent stem cells (iPSCs). We investigated the expression of different glucose transporters at the BBB using immunocytochemistry and flow cytometry and measured glucose uptake and diffusion across BMEC monolayers obtained from two iPSC lines and from hCMEC/D3 cells. BMEC monolayers showed expression of several glucose transporters, in particular GLUT1, GLUT3, and GLUT4. Diffusion of glucose across the monolayers was mediated via a saturable transcellular mechanism and partially inhibited by pharmacological inhibitors. Taken together, our study suggests the presence of several glucose transporters isoforms at the human BBB and demonstrates the feasibility of modeling glucose across the BBB using patient-derived stem cells.

scholarly journals PPARγ-Independent Increase in Glucose Uptake and Adiponectin Abundance in Fat Cells

Endocrinology ◽  
2011 ◽  
Vol 152 (10) ◽  
pp. 3648-3660 ◽  
Author(s):  
Olga Dubuisson ◽  
Emily J. Dhurandhar ◽  
Rashmi Krishnapuram ◽  
Heather Kirk-Ballard ◽  
Alok K. Gupta ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Glycemic Control ◽  
Glucose Uptake ◽  
Glucose Transporter ◽  
Human Adipose Tissue ◽  
Peroxisome Proliferator ◽  
Mouse Embryonic Fibroblasts ◽  
Embryonic Fibroblasts ◽  
Glucose Transporter 1

Although thiazolidinediones (TZD) effectively improve hyperglycemia and increase adiponectin, a proinsulin-sensitizing adipokine, they also increase adipogenesis via peroxisome proliferator-activated receptor (PPAR)γ induction, which may be undesirable. Recent safety concerns about some TZD have prompted the search for next generation agents that can enhance glycemic control and adiponectin independent of PPARγ or adipogenesis. Reminiscent of TZD action, a human adenovirus, adenovirus 36 (Ad36), up-regulates PPARγ, induces adipogenesis, and improves systemic glycemic control in vivo. We determined whether this effect of Ad36 requires PPARγ and/or adipogenesis. Glucose uptake and relevant cell signaling were determined in mock-infected or human adenoviruses Ad36 or Ad2-infected cell types under the following conditions: 1) undifferentiated human-adipose-tissue-derived stem cells (hASC), 2) hASC differentiated as adipocytes, 3) hASC in presence or absence of a PPARγ inhibitor, 4) NIH/3T3 that have impaired PPARγ expression, and 5) PPARγ-knockout mouse embryonic fibroblasts. Mouse embryonic fibroblasts with intact PPARγ served as a positive control. Additionally, to determine natural Ad36 infection, human sera were screened for Ad36 antibodies. In undifferentiated or differentiated hASC, or despite the inhibition, down-regulation, or the absence of PPARγ, Ad36 significantly enhanced glucose uptake and PPARγ, adiponectin, glucose transporter 4, and glucose transporter 1 protein abundance, compared with mock or Ad2-infected cells. This indicated that Ad36 up-regulates glucose uptake and adiponectin secretion independent of adipogenesis or without recruiting PPARγ. In humans, natural Ad36 infection predicted greater adiponectin levels, suggesting a human relevance of these effects. In conclusion, Ad36 provides a novel template to metabolically remodel human adipose tissue to enhance glycemic control without the concomitant increase in adiposity or PPARγ induction associated with TZD actions.

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