Long-Term Chronic Intermittent Hypobaric Hypoxia Induces Glucose Transporter (GLUT4) Translocation Through AMP-Activated Protein Kinase (AMPK) in the Soleus Muscle in Lean Rats

The objective of this study was to evaluate the antihyperlipidemic and antihyperglycemic effects and mechanism of the extract ofClitocybe nuda(CNE), in high-fat- (HF-) fed mice. C57BL/6J was randomly divided into two groups: the control (CON) group was fed with a low-fat diet, whereas the experimental group was fed with a HF diet for 8 weeks. Then, the HF group was subdivided into five groups and was given orally CNE (including C1: 0.2, C2: 0.5, and C3: 1.0 g/kg/day extracts) or rosiglitazone (Rosi) or vehicle for 4 weeks. CNE effectively prevented HF-diet-induced increases in the levels of blood glucose, triglyceride, insulin (P<0.001,P<0.01,P<0.05, resp.) and attenuated insulin resistance. By treatment with CNE, body weight gain, weights of white adipose tissue (WAT) and hepatic triacylglycerol content were reduced; moreover, adipocytes in the visceral depots showed a reduction in size. By treatment with CNE, the protein contents of glucose transporter 4 (GLUT4) were significantly increased in C3-treated group in the skeletal muscle. Furthermore, CNE reduces the hepatic expression of glucose-6-phosphatase (G6Pase) and glucose production. CNE significantly increases protein contents of phospho-AMP-activated protein kinase (AMPK) in the skeletal muscle and adipose and liver tissues. Therefore, it is possible that the activation of AMPK by CNE leads to diminished gluconeogenesis in the liver and enhanced glucose uptake in skeletal muscle. It is shown that CNE exhibits hypolipidemic effect in HF-fed mice by increasing ATGL expression, which is known to help triglyceride to hydrolyze. Moreover, antidiabetic properties of CNE occurred as a result of decreased hepatic glucose production via G6Pase downregulation and improved insulin sensitization. Thus, amelioration of diabetic and dyslipidemic states by CNE in HF-fed mice occurred by regulation of GLUT4, G6Pase, ATGL, and AMPK phosphorylation.

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α-amyrin induce GLUT4 translocation mediated by AMPK and PPARδ/γ in C2C12 myoblasts

Canadian Journal of Physiology and Pharmacology ◽

10.1139/cjpp-2021-0027 ◽

2021 ◽

Author(s):

Abraham Giacoman-Martínez ◽

Francisco Javier Alarcón-Aguilar ◽

Alejandro Zamilpa-Alvarez ◽

Fengyang Huang ◽

Rodrigo Romero ◽

...

Keyword(s):

Skeletal Muscle ◽

Protein Kinase ◽

Glucose Transporter ◽

Metabolic Diseases ◽

Muscle Cells ◽

Skeletal Muscle Cells ◽

Peroxisome Proliferator ◽

Glut4 Translocation ◽

Pentacyclic Triterpene ◽

C2c12 Myoblasts

α-amyrin, a natural pentacyclic triterpene, have anti-hyperglycemic effect in mice and dual PPARδ/γ action in 3T3-L1 adipocytes, and potential in the control of type 2 diabetes (T2D). About 80% of glucose uptake occurs in skeletal muscle cells, playing a significant role in IR and T2D. Peroxisome-proliferator activated receptors (PPARs), in particular PPARδ and PPARγ, are involved in the regulation of lipids and carbohydrates and, along adenosine-monophosphate (AMP)-activated protein kinase (AMPK) and protein kinase B (Akt/PKB), are implicated in translocation of glucose transporter 4 (GLUT4). However, it is still unknown whether α-amyrin can affect these pathways in skeletal muscle cells. The work's objective was to determine the action of α-amyrin in PPARδ, PPARγ, AMPK, and Akt/PKB in C2C12 myoblasts. The expression of PPARδ, PPARγ, FATP, and GLUT4 was quantified using RT-qPCR and Western blot. α-amyrin increased these markers along with p-AMPK but not p-Akt/PKB. Molecular docking showed that α-amyrin acts as an AMPK-allosteric activator, and may be related to GLUT4 translocation, evidenced by confocal microscopy. These data support that α-amyrin could have an insulin-mimetic action in C2C12 myoblasts and should be considered as a bioactive molecule for new multitarget drugs with utility in T2D and other metabolic diseases.

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Reduction of Insulin-Stimulated Glucose Uptake in L6 Myotubes by the Protein Kinase Inhibitor SB203580 Is Independent of p38MAPK Activity

Endocrinology ◽

10.1210/en.2005-0404 ◽

2005 ◽

Vol 146 (9) ◽

pp. 3773-3781 ◽

Cited By ~ 52

Author(s):

C. N. Antonescu ◽

C. Huang ◽

W. Niu ◽

Z. Liu ◽

P. A. Eyers ◽

...

Keyword(s):

Protein Kinase ◽

Glucose Uptake ◽

Glucose Transporter ◽

Kinase Inhibitor ◽

Dominant Negative ◽

Small Interfering Rnas ◽

Insulin Stimulation ◽

L6 Myotubes ◽

Low Levels ◽

Glucose Transporter Glut4

Abstract Insulin increases glucose uptake through translocation of the glucose transporter GLUT4 to the plasma membrane. We previously showed that insulin activates p38MAPK, and inhibitors of p38MAPKα and p38MAPKβ (e.g. SB203580) reduce insulin-stimulated glucose uptake without affecting GLUT4 translocation. This observation suggested that insulin may increase GLUT4 activity via p38α and/or p38β. Here we further explore the possible participation of p38MAPK through a combination of molecular strategies. SB203580 reduced insulin stimulation of glucose uptake in L6 myotubes overexpressing an SB203580-resistant p38α (drug-resistant p38α) but barely affected phosphorylation of the p38 substrate MAPK-activated protein kinase-2. Expression of dominant-negative p38α or p38β reduced p38MAPK phosphorylation by 70% but had no effect on insulin-stimulated glucose uptake. Gene silencing via isoform-specific small interfering RNAs reduced expression of p38α or p38β by 60–70% without diminishing insulin-stimulated glucose uptake. SB203580 reduced photoaffinity labeling of GLUT4 by bio-LC-ATB-BMPA only in the insulin-stimulated state. Unless low levels of p38MAPK suffice to regulate glucose uptake, these results suggest that the inhibition of insulin-stimulated glucose transport by SB203580 is likely not mediated by p38MAPK. Instead, changes experienced by insulin-stimulated GLUT4 make it susceptible to inhibition by SB203580.

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AS160, the Akt substrate regulating GLUT4 translocation, has a functional Rab GTPase-activating protein domain

Biochemical Journal ◽

10.1042/bj20050887 ◽

2005 ◽

Vol 391 (1) ◽

pp. 87-93 ◽

Cited By ~ 273

Author(s):

Cristinel P. Mîinea ◽

Hiroyuki Sano ◽

Susan Kane ◽

Eiko Sano ◽

Mitsunori Fukuda ◽

...

Keyword(s):

Glucose Transporter ◽

Protein Domain ◽

Rab Gtpase ◽

Significant Activity ◽

Glut4 Translocation ◽

Gtpase Activating Protein ◽

Akt Phosphorylation ◽

Intracellular Vesicles ◽

Glucose Transporter Glut4 ◽

Protein Kinase Akt

Recently, we described a 160 kDa protein (designated AS160, for Akt substrate of 160 kDa) with a predicted Rab GAP (GTPase-activating protein) domain that is phosphorylated on multiple sites by the protein kinase Akt. Phosphorylation of AS160 in adipocytes is required for insulin-stimulated translocation of the glucose transporter GLUT4 to the plasma membrane. The aim of the present study was to determine whether AS160 is in fact a GAP for Rabs, and, if so, what its specificity is. We first identified a group of 16 Rabs in a preparation of intracellular vesicles containing GLUT4 by MS. We then prepared the recombinant GAP domain of AS160 and examined its activity against many of these Rabs, as well as several others. The GAP domain was active against Rabs 2A, 8A, 10 and 14. There was no significant activity against 14 other Rabs. GAP activity was further validated by the finding that the recombinant GAP domain with the predicted catalytic arginine residue replaced by lysine was inactive. Finally, it was found by immunoblotting that Rabs 2A, 8A and 14 are present in GLUT4 vesicles. These results indicate that AS160 is a Rab GAP, and suggest novel Rabs that may participate in GLUT4 translocation.

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Octaphlorethol A, a marine algae product, exhibits antidiabetic effects in type 2 diabetic mice by activating AMP-activated protein kinase and upregulating the expression of glucose transporter 4

Food and Chemical Toxicology ◽

10.1016/j.fct.2016.02.022 ◽

2016 ◽

Vol 91 ◽

pp. 58-64 ◽

Cited By ~ 21

Author(s):

Seung-Hong Lee ◽

Seok-Chun Ko ◽

Min-Cheol Kang ◽

Dae Ho Lee ◽

You-Jin Jeon

Keyword(s):

Protein Kinase ◽

Marine Algae ◽

Glucose Transporter ◽

Diabetic Mice ◽

Glucose Transporter 4 ◽

Amp Activated Protein Kinase ◽

Type 2 Diabetic ◽

Antidiabetic Effects

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Regulation of multisite phosphorylation and 14-3-3 binding of AS160 in response to IGF-1, EGF, PMA and AICAR

Biochemical Journal ◽

10.1042/bj20070649 ◽

2007 ◽

Vol 407 (2) ◽

pp. 231-241 ◽

Cited By ~ 122

Author(s):

Kathryn M. Geraghty ◽

Shuai Chen ◽

Jean E. Harthill ◽

Adel F. Ibrahim ◽

Rachel Toth ◽

...

Keyword(s):

Growth Factor ◽

Protein Kinase ◽

Glucose Transporter ◽

Kinase Inhibitors ◽

Hek 293 ◽

293 Cells ◽

Ribosomal S6 Kinase ◽

Phosphoinositide 3 Kinase ◽

Amp Activated Protein Kinase

AS160 (Akt substrate of 160 kDa) mediates insulin-stimulated GLUT4 (glucose transporter 4) translocation, but is widely expressed in insulin-insensitive tissues lacking GLUT4. Having isolated AS160 by 14-3-3-affinity chromatography, we found that binding of AS160 to 14-3-3 isoforms in HEK (human embryonic kidney)-293 cells was induced by IGF-1 (insulin-like growth factor-1), EGF (epidermal growth factor), PMA and, to a lesser extent, AICAR (5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside). AS160-14-3-3 interactions were stabilized by chemical cross-linking and abolished by dephosphorylation. Eight residues on AS160 (Ser318, Ser341, Thr568, Ser570, Ser588, Thr642, Ser666 and Ser751) were differentially phosphorylated in response to IGF-1, EGF, PMA and AICAR. The binding of 14-3-3 proteins to HA–AS160 (where HA is haemagglutinin) was markedly decreased by mutation of Thr642 and abolished in a Thr642Ala/Ser341Ala double mutant. The AGC (protein kinase A/protein kinase G/protein kinase C-family) kinases RSK1 (p90 ribosomal S6 kinase 1), SGK1 (serum- and glucocorticoid-induced protein kinase 1) and PKB (protein kinase B) displayed distinct signatures of AS160 phosphorylation in vitro: all three kinases phosphorylated Ser318, Ser588 and Thr642; RSK1 also phosphorylated Ser341, Ser751 and to a lesser extent Thr568; and SGK1 phosphorylated Thr568 and Ser751. AMPK (AMP-activated protein kinase) preferentially phosphorylated Ser588, with less phosphorylation of other sites. In cells, the IGF-1-stimulated phosphorylations, and certain EGF-stimulated phosphorylations, were inhibited by PI3K (phosphoinositide 3-kinase) inhibitors, whereas the RSK inhibitor BI-D1870 inhibited the PMA-induced phosphorylations. The expression of LKB1 in HeLa cells and the use of AICAR in HEK-293 cells promoted phosphorylation of Ser588, but only weak Ser341 and Thr642 phosphorylations and binding to 14-3-3s. Paradoxically however, phenformin activated AMPK without promoting AS160 phosphorylation. The IGF-1-induced phosphorylation of the novel phosphorylated Ser666-Pro site was suppressed by AICAR, and by combined mutation of a TOS (mTOR signalling)-like sequence (FEMDI) and rapamycin. Thus, although AS160 is a common target of insulin, IGF-1, EGF, PMA and AICAR, these stimuli induce distinctive patterns of phosphorylation and 14-3-3 binding, mediated by at least four protein kinases.

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Specialized sorting of GLUT4 and its recruitment to the cell surface are independently regulated by distinct Rabs

Molecular Biology of the Cell ◽

10.1091/mbc.e13-02-0103 ◽

2013 ◽

Vol 24 (16) ◽

pp. 2544-2557 ◽

Cited By ~ 51

Author(s):

L. Amanda Sadacca ◽

Joanne Bruno ◽

Jennifer Wen ◽

Wenyong Xiong ◽

Timothy E. McGraw

Keyword(s):

Plasma Membrane ◽

Glucose Uptake ◽

Glucose Transporter ◽

Receptor Activation ◽

Glut4 Translocation ◽

Insulin Stimulation ◽

Transport Vesicles ◽

Glucose Transporter Glut4

Adipocyte glucose uptake in response to insulin is essential for physiological glucose homeostasis: stimulation of adipocytes with insulin results in insertion of the glucose transporter GLUT4 into the plasma membrane and subsequent glucose uptake. Here we establish that RAB10 and RAB14 are key regulators of GLUT4 trafficking that function at independent, sequential steps of GLUT4 translocation. RAB14 functions upstream of RAB10 in the sorting of GLUT4 to the specialized transport vesicles that ferry GLUT4 to the plasma membrane. RAB10 and its GTPase-activating protein (GAP) AS160 comprise the principal signaling module downstream of insulin receptor activation that regulates the accumulation of GLUT4 transport vesicles at the plasma membrane. Although both RAB10 and RAB14 are regulated by the GAP activity of AS160 in vitro, only RAB10 is under the control of AS160 in vivo. Insulin regulation of the pool of RAB10 required for GLUT4 translocation occurs through regulation of AS160, since activation of RAB10 by DENND4C, its GTP exchange factor, does not require insulin stimulation.

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