scholarly journals The TRPC6-AMPK Pathway is Involved in Insulin-Dependent Cytoskeleton Reorganization and Glucose Uptake in Cultured Rat Podocytes

2018 ◽  
Vol 51 (1) ◽  
pp. 393-410 ◽  
Author(s):  
Patrycja Rachubik ◽  
Maria Szrejder ◽  
Dorota Rogacka ◽  
Irena Audzeyenka ◽  
Michał Rychłowski ◽  
...  
Keyword(s):  
Glucose Uptake ◽  
Glomerular Filtration ◽  
Glucose Transport ◽  
Signaling Proteins ◽  
Filtration Barrier ◽  
Cytoskeleton Reorganization ◽  
Insulin Dependent ◽  
Trpc6 Channel ◽  
Amp Activated Protein Kinase

Background/Aims: Podocytes are dynamic polarized cells on the surface of glomerular capillaries that are an essential part of the glomerular filtration barrier. AMP-activated protein kinase (AMPK), a key regulator of glucose and fatty acid metabolism, plays a major role in obesity and type 2 diabetes. Accumulating evidence suggests that TRPC6 channels are crucial mediators of calcium transport in podocytes and are involved in regulating glomerular filtration. Here we investigated whether the AMPK-TRPC6 pathway is involved in insulin-dependent cytoskeleton reorganization and glucose uptake in cultured rat podocytes. Methods: Western blot and immunofluorescence analysis confirmed AMPKα and TRPC6 expression, the phosphorylation of proteins associated with actin cytoskeleton reorganization (PAK, rac1, and cofilin), and the expression of insulin signaling proteins (Akt, Insulin receptor). Coimmunoprecipitation and immunofluorescence results demonstrated AMPKα/TRPC6 interaction. To ask whether TRPC6 is involved in the insulin regulation of glucose transport, we measured insulin-dependent (1, 2-3H)-deoxy-D-glucose uptake into podocytes after reducing TRPC6 activity pharmacologically and biochemically (TRPC6 siRNA). Results: The results suggested a key role for the TRPC6 channel in the mediation of insulin-dependent activation of AMPKα2 and glucose uptake. Moreover, AMPK and TRPC6 activation were required to stimulate the Rac1 signaling pathway. Conclusion: These results suggest a potentially important new mechanism that regulates glucose transport in podocytes and that could be injurious during diabetes.

scholarly journals The TRPC6-AMPK pathway is involved in cytoskeleton reorganization and glucose uptake in podocytes

2018 ◽  
Author(s):  
Patrycja Rachubik ◽  
Maria Szrejder ◽  
Dorota Rogacka ◽  
Irena Audzeyenka ◽  
Michał Rychłowski ◽  
...  
Keyword(s):  
Glucose Uptake ◽  
Glomerular Filtration ◽  
Glomerular Filtration Barrier ◽  
Filtration Barrier ◽  
Cytoskeleton Reorganization ◽  
Insulin Dependent ◽  
Trpc6 Channel ◽  
Amp Activated Protein Kinase ◽  
Glomerular Capillaries

AbstractPodocytes are dynamic polarized cells on the surface of glomerular capillaries that are an essential part of the glomerular filtration barrier. AMP-activated protein kinase (AMPK), a key regulator of glucose and fatty acid metabolism, plays a major role in obesity and type 2 diabetes. Accumulating evidence suggests that TRPC6 channels are crucial mediators of calcium transport in podocytes and are involved in regulating glomerular filtration barrier. Here we investigated whether the AMPK-TRPC6 pathway is involved in insulin-dependent cytoskeleton reorganization and glucose uptake in cultured rat podocytes. Insulin regulates the interaction of TRPC6 with AMPKα2 in cultured rat podocytes The results suggested a key role for the TRPC6 channel in the mediation of insulin-dependent activation of AMPKα2, actin cytoskeleton reorganization and glucose uptake in podocyte. Moreover, AMPK and TRPC6 activation were required to stimulate the Rac1 signaling pathway. These results suggest a potentially important new mechanism that regulates glucose transport in podocytes and that could be injurious during diabetes.

scholarly journals Low-Dose Acrolein, an Endogenous and Exogenous Toxic Molecule, Inhibits Glucose Transport via an Inhibition of Akt-Regulated GLUT4 Signaling in Skeletal Muscle Cells

2021 ◽  
Vol 22 (13) ◽  
pp. 7228
Author(s):  
Ching-Chia Wang ◽  
Huang-Jen Chen ◽  
Ding-Cheng Chan ◽  
Chen-Yuan Chiu ◽  
Shing-Hwa Liu ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Glucose Metabolism ◽  
Glucose Tolerance ◽  
Protein Expression ◽  
Glucose Uptake ◽  
Glucose Transport ◽  
Diabetic Patients ◽  
Type 2 Diabetic Patients ◽  
Type 2 Diabetic

Urinary acrolein adduct levels have been reported to be increased in both habitual smokers and type-2 diabetic patients. The impairment of glucose transport in skeletal muscles is a major factor responsible for glucose uptake reduction in type-2 diabetic patients. The effect of acrolein on glucose metabolism in skeletal muscle remains unclear. Here, we investigated whether acrolein affects muscular glucose metabolism in vitro and glucose tolerance in vivo. Exposure of mice to acrolein (2.5 and 5 mg/kg/day) for 4 weeks substantially increased fasting blood glucose and impaired glucose tolerance. The glucose transporter-4 (GLUT4) protein expression was significantly decreased in soleus muscles of acrolein-treated mice. The glucose uptake was significantly decreased in differentiated C2C12 myotubes treated with a non-cytotoxic dose of acrolein (1 μM) for 24 and 72 h. Acrolein (0.5–2 μM) also significantly decreased the GLUT4 expression in myotubes. Acrolein suppressed the phosphorylation of glucose metabolic signals IRS1, Akt, mTOR, p70S6K, and GSK3α/β. Over-expression of constitutive activation of Akt reversed the inhibitory effects of acrolein on GLUT4 protein expression and glucose uptake in myotubes. These results suggest that acrolein at doses relevant to human exposure dysregulates glucose metabolism in skeletal muscle cells and impairs glucose tolerance in mice.

Characterization of the role of the AMP-activated protein kinase in the stimulation of glucose transport in skeletal muscle cells

2002 ◽  
Vol 363 (1) ◽  
pp. 167-174 ◽  
Author(s):  
Lee G.D. FRYER ◽  
Fabienne FOUFELLE ◽  
Kay BARNES ◽  
Stephen A. BALDWIN ◽  
Angela WOODS ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Protein Kinase ◽  
Glucose Uptake ◽  
Glucose Transport ◽  
Phorbol Ester ◽  
Hyperosmotic Stress ◽  
Amp Activated Protein Kinase ◽  
Stimulation Of ◽  
Constitutively Active

Stimulation of AMP-activated protein kinase (AMPK) in skeletal muscle has been correlated with an increase in glucose transport. Here, we demonstrate that adenoviral-mediated expression of a constitutively active mutant of AMPKα leads to activation of glucose transport in a skeletal-muscle cell line, similar to that seen following treatment with 5-amino-imidazolecarboxamide (AICA) riboside, hyperosmotic stress or insulin. In contrast, expression of a dominant-negative form of AMPK blocked the stimulation of glucose transport by both AICA riboside and hyperosmotic stress, but was without effect on either insulin or phorbol-ester-stimulated transport. These results demonstrate that activation of AMPK is sufficient for stimulation of glucose uptake into muscle cells, and is a necessary component of the AICA riboside- and hyperosmotic-stress-induced pathway leading to increased glucose uptake. On the other hand, AMPK is not required in the insulin- or phorbol-ester-mediated pathways. Long-term (5 days) expression of the constitutively active AMPK mutant increased protein expression of GLUT1, GLUT4 and hexokinase II, consistent with previous reports on the chronic treatment of rats with AICA riboside. Expression of constitutively active AMPK had no detectable effect on p38 mitogen-activated protein kinase levels, although interestingly the level of protein kinase B was decreased. These results demonstrate that long-term activation of AMPK is sufficient to cause increased expression of specific proteins in muscle. Our results add further support to the hypothesis that long-term activation of AMPK is involved in the adaptive response of muscle to exercise training.

Activation of AMPK is essential for AICAR-induced glucose uptake by skeletal muscle but not adipocytes

2002 ◽  
Vol 282 (6) ◽  
pp. E1239-E1244 ◽  
Author(s):  
Hideyuki Sakoda ◽  
Takehide Ogihara ◽  
Motonobu Anai ◽  
Midori Fujishiro ◽  
Hiraku Ono ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Glucose Uptake ◽  
Glucose Transport ◽  
Muscle Cells ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Ampk Activation ◽  
Wild Type ◽  
Rat Soleus Muscle ◽  
Amp Activated Protein Kinase

5-Aminoimidazole-4-carboxamide ribonucleoside (AICAR) reportedly activates AMP-activated protein kinase (AMPK) and stimulates glucose uptake by skeletal muscle cells. In this study, we investigated the role of AMPK in AICAR-induced glucose uptake by 3T3-L1 adipocytes and rat soleus muscle cells by overexpressing wild-type and dominant negative forms of the AMPKα2 subunit by use of adenovirus-mediated gene transfer. Overexpression of the dominant negative mutant had no effect on AICAR-induced glucose transport in adipocytes, although AMPK activation was almost completely abolished. This suggests that AICAR-induced glucose uptake by 3T3-L1 adipocytes is independent of AMPK activation. By contrast, overexpression of the dominant negative AMPKα2 mutant in muscle markedly suppressed both AICAR-induced glucose uptake and AMPK activation, although insulin-induced uptake was unaffected. Overexpression of the wild-type AMPKα2 subunit significantly increased AMPK activity in muscle but did not enhance glucose uptake. Thus, although AMPK activation may not, by itself, be sufficient to increase glucose transport, it appears essential for AICAR-induced glucose uptake in muscle.

scholarly journals РARTICULAR QUALITIES OF THE RENAL OSMOREGULATORY FUNCTION IN PATIENTS WITH TYPE 2 DIABETES

2015 ◽  
pp. 21-26 ◽  
Author(s):  
E.S. Kuznetsova ◽  
A.S. Kuznetsova ◽  
V.V. Shuhtin ◽  
A.I. Gozhenko
Keyword(s):  
Type 2 Diabetes ◽  
Renal Function ◽  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Freezing Point ◽  
Insulin Dependent ◽  
Insulin Dependent Diabetic ◽  
Osmoregulatory Function

The aim of the study was to examine the osmoregulatory state of renal function in patients with type 2 diabetes in a water - salt load with 0,5% NaCl in the amount of 0.5% of body weight. Materials and methods. The study involved 56patients with insulin - dependent diabetic nephropathy,24 men (42.9%) and 32 women (57.1%), aged from 38 to 81 years. The osmolality was measured by freezing point depression on osmomat 030 - D (USA). Glomerular filtration rate (GFR) was calculated by the formula GFR - EPI with subsequent determination of renal functional reserve. Results. It demonstrated that renal osmoregulatory function provides effective regulation of osmotic homeostasis even in a reduced amount of nephrons, but as the glomerular filtration rate decreses to 30 ml/min, the excretion of osmotically active substances gradually decrease too. Conclusion. Osmoregulatory disturbances in the renal function in patients with 2 types diabetes depend both on the reduction in GFR, - and on changes in the functional capacity of nephron's tubules.

scholarly journals During Adipocyte Remodeling, Lipid Droplet Configurations Regulate Insulin Sensitivity through F-Actin and G-Actin Reorganization

2019 ◽  
Vol 39 (20) ◽  
Author(s):  
Jong In Kim ◽  
Jeu Park ◽  
Yul Ji ◽  
Kyuri Jo ◽  
Sang Mun Han ◽  
...  
Keyword(s):  
Insulin Sensitivity ◽  
Glucose Uptake ◽  
Lipid Droplet ◽  
Actin Polymerization ◽  
Actin Dynamics ◽  
Filamentous Actin ◽  
Cytoskeleton Reorganization ◽  
Beige Adipocytes ◽  
Actin Structure ◽  
Insulin Dependent

ABSTRACT Adipocytes have unique morphological traits in insulin sensitivity control. However, how the appearance of adipocytes can determine insulin sensitivity has not been understood. Here, we demonstrate that actin cytoskeleton reorganization upon lipid droplet (LD) configurations in adipocytes plays important roles in insulin-dependent glucose uptake by regulating GLUT4 trafficking. Compared to white adipocytes, brown/beige adipocytes with multilocular LDs exhibited well-developed filamentous actin (F-actin) structure and potentiated GLUT4 translocation to the plasma membrane in the presence of insulin. In contrast, LD enlargement and unilocularization in adipocytes downregulated cortical F-actin formation, eventually leading to decreased F-actin-to-globular actin (G-actin) ratio and suppression of insulin-dependent GLUT4 trafficking. Pharmacological inhibition of actin polymerization accompanied with impaired F/G-actin dynamics reduced glucose uptake in adipose tissue and conferred systemic insulin resistance in mice. Thus, our study reveals that adipocyte remodeling with different LD configurations could be an important factor to determine insulin sensitivity by modulating F/G-actin dynamics.

scholarly journals Contraction-Mediated Glucose Transport in Skeletal Muscle is Regulated by a Framework of AMPK, TBC1D1/4 and Rac1

2021 ◽  
Author(s):  
Christian de Wendt ◽  
Lena Espelage ◽  
Samaneh Eickelschulte ◽  
Christian Springer ◽  
Laura Toska ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Glucose Uptake ◽  
Glucose Transport ◽  
Glucose Transporter ◽  
Metabolic Response ◽  
Signaling Axis ◽  
Glucose Transporter Glut4 ◽  
Amp Activated Protein Kinase ◽  
Response To Exercise ◽  
Specific Contribution

The two closely related RabGTPase-activating proteins (RabGAPs) TBC1D1 and TBC1D4, both substrates for the AMP-activated protein kinase AMPK, play important roles in exercise metabolism and contraction-dependent translocation of the glucose transporter GLUT4 in skeletal muscle. However, the specific contribution of each RabGAP in contraction signaling is mostly unknown. In this study, we investigated the cooperative AMPK/RabGAP signaling axis in the metabolic response to exercise/contraction using a novel mouse model deficient in active skeletal muscle AMPK, combined with knockout of either <i>Tbc1d1</i>, <i>Tbc1d4</i> or both RabGAPs. AMPK-deficiency in muscle reduced treadmill exercise performance. Additional deletion of <i>Tbc1d1</i> but not <i>Tbc1d4 </i>resulted in further decrease in exercise capacity. In oxidative <i>Soleus</i> muscle, AMPK deficiency reduced contraction-mediated glucose uptake and deletion of each or both RabGAPs had no further effect. In contrast, in glycolytic <i>EDL</i> muscle, AMPK deficiency reduced contraction-stimulated glucose uptake and deletion of <i>Tbc1d1 </i>but not <i>Tbc1d4 </i>led to a further decrease. Importantly, skeletal muscle deficient in AMPK and both RabGAPs still exhibited residual contraction-mediated glucose uptake, which was completely abolished by inhibition of the GTPase <i>Rac1</i>. Our results demonstrate a novel mechanistic link between glucose transport and <a></a><a>the GTPase signaling framework in skeletal muscle in response to contraction.</a>

Contraction signaling to glucose transport in skeletal muscle

2005 ◽  
Vol 99 (1) ◽  
pp. 330-337 ◽  
Author(s):  
Niels Jessen ◽  
Laurie J. Goodyear
Keyword(s):  
Type 2 Diabetes ◽  
Skeletal Muscle ◽  
Protein Kinase ◽  
Glucose Transport ◽  
Glut4 Translocation ◽  
Signaling Mechanism ◽  
Energy Sensing ◽  
Knockout Animals ◽  
Amp Activated Protein Kinase

Contracting skeletal muscles acutely increases glucose transport in both healthy individuals and in people with Type 2 diabetes, and regular physical exercise is a cornerstone in the treatment of the disease. Glucose transport in skeletal muscle is dependent on the translocation of GLUT4 glucose transporters to the cell surface. It has long been believed that there are two major signaling mechanisms leading to GLUT4 translocation. One mechanism is insulin-activated signaling through insulin receptor substrate-1 and phosphatidylinositol 3-kinase. The other is an insulin-independent signaling mechanism that is activated by contractions, but the mediators of this signal are still unknown. Accumulating evidence suggests that the energy-sensing enzyme AMP-activated protein kinase plays an important role in contraction-stimulated glucose transport. However, more recent studies in transgenic and knockout animals show that AMP-activated protein kinase is not the sole mediator of the signal to GLUT4 translocation and suggest that there may be redundant signaling pathways leading to contraction-stimulated glucose transport. The search for other possible signal intermediates is ongoing, and calcium, nitric oxide, bradykinin, and the Akt substrate AS160 have been suggested as possible candidates. Further research is needed because full elucidation of an insulin-independent signal leading to glucose transport would be a promising pharmacological target for the treatment of Type 2 diabetes.

Regulation of glucose transporters by insulin and extracellular glucose in C2C12 myotubes

2006 ◽  
Vol 291 (4) ◽  
pp. E817-E828 ◽  
Author(s):  
Taku Nedachi ◽  
Makoto Kanzaki
Keyword(s):  
Skeletal Muscle ◽  
Glucose Uptake ◽  
Glucose Transport ◽  
Glucose Transporter ◽  
C2c12 Myotubes ◽  
Glut4 Translocation ◽  
Insulin Stimulation ◽  
Extracellular Glucose ◽  
Insulin Dependent ◽  
Stimulation Of

It is well established that insulin stimulation of glucose uptake in skeletal muscle cells is mediated through translocation of GLUT4 from intracellular storage sites to the cell surface. However, the established skeletal muscle cell lines, with the exception of L6 myocytes, reportedly show minimal insulin-dependent glucose uptake and GLUT4 translocation. Using C2C12 myocytes expressing exofacial-Myc-GLUT4-enhanced cyan fluorescent protein, we herein show that differentiated C2C12 myotubes are equipped with basic GLUT4 translocation machinery that can be activated by insulin stimulation (∼3-fold increase as assessed by anti-Myc antibody uptake and immunostaining assay). However, this insulin stimulation of GLUT4 translocation was difficult to demonstrate with a conventional 2-deoxyglucose uptake assay because of markedly elevated basal glucose uptake via other glucose transporter(s). Intriguingly, the basal glucose transport activity in C2C12 myotubes appeared to be acutely suppressed within 5 min by preincubation with a pathophysiologically high level of extracellular glucose (25 mM). In contrast, this activity was augmented by acute glucose deprivation via an unidentified mechanism that is independent of GLUT4 translocation but is dependent on phosphatidylinositol 3-kinase activity. Taken together, these findings indicate that regulation of the facilitative glucose transport system in differentiated C2C12 myotubes can be achieved through surprisingly acute glucose-dependent modulation of the activity of glucose transporter(s), which apparently contributes to obscuring the insulin augmentation of glucose uptake elicited by GLUT4 translocation. We herein also describe several methods of monitoring insulin-dependent glucose uptake in C2C12 myotubes and propose this cell line to be a useful model for analyzing GLUT4 translocation in skeletal muscle.

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