AMPK Enhances Insulin-Stimulated GLUT4 Regulation via Lowering Membrane Cholesterol

AMP-activated protein kinase (AMPK) enhances glucose transporter GLUT4 regulation. AMPK also suppresses energy-consuming pathways such as cholesterol synthesis. Interestingly, recent in vitro and in vivo data suggest that excess membrane cholesterol impairs GLUT4 regulation. Therefore, this study tested whether a beneficial, GLUT4-regulatory aspect of AMPK stimulation involved cholesterol lowering. Using L6 myotubes stably expressing an exofacial myc-epitope-tagged-GLUT4, AMPK stimulation by 5-aminoimidazole-4-carboxamide-1-β-d-ribonucleoside (AICAR; 45 min, 1 mm) or 2,4-dinitrophenol (DNP; 30 min, 200 μm) increased cell surface GLUT4myc labeling by approximately ∼25% (P < 0.05). Insulin (20 min, 100 nm) also increased GLUT4myc labeling by about 50% (P < 0.05), which was further enhanced (∼25%, P < 0.05) by AICAR or DNP. Consistent with AMPK-mediated suppression of cholesterol synthesis, AICAR and DNP decreased membrane cholesterol by 20–25% (P < 0.05). Whereas AMPK knockdown prevented the enhanced basal and insulin-stimulated GLUT4myc labeling by AICAR and DNP, cholesterol replenishment only blocked the AMPK-associated enhancement in insulin action. Cells cultured in a hyperinsulinemic milieu, resembling conditions in vivo that promote the progression/worsening of insulin resistance, displayed an increase in membrane cholesterol. This occurred concomitantly with a loss of cortical filamentous actin (F-actin) and defects in GLUT4 regulation by insulin. These derangements were prevented by AMPK stimulation. Examination of skeletal muscle from insulin-resistant Zucker rats revealed a similar elevation in membrane cholesterol and loss of F-actin. Lowering cholesterol to control levels restored F-actin structure and insulin sensitivity. In conclusion, these data suggest a novel aspect of GLUT4 regulation by AMPK involves membrane cholesterol lowering. Moreover, this AMPK-mediated process protected against hyperinsulinemia-induced insulin resistance.

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Crosstalk between the AMP-activated kinase and insulin signaling pathways rescues murine blastocyst cells from insulin resistance

Reproduction ◽

10.1530/rep-08-0161 ◽

2008 ◽

Vol 136 (3) ◽

pp. 335-344 ◽

Cited By ~ 24

Author(s):

Erica Louden ◽

Maggie M Chi ◽

Kelle H Moley

Keyword(s):

Insulin Resistance ◽

Signaling Pathways ◽

Insulin Signaling ◽

Kinase Activity ◽

Pi3 Kinase ◽

Ampk Activation ◽

Embryonic Cells ◽

Insulin Resistant

Maternal insulin resistance results in poor pregnancy outcomes. In vivo and in vitro exposure of the murine blastocyst to high insulin or IGF1 results in the down-regulation of the IGF1 receptor (IGF1R). This in turn leads to decreased glucose uptake, increased apoptosis, as well as pregnancy resorption and growth restriction. Recent studies have shown that blastocyst activation of AMP-activated protein kinase (AMPK) reverses these detrimental effects; however, the mechanism was not clear. The objective of this study was to determine how AMPK activation rescues the insulin-resistant blastocyst. Using trophoblast stem (TS) cells derived from the blastocyst, insulin resistance was recreated by transfecting with siRNA to Igf1r and down-regulating expression of the protein. These cells were then exposed to AMPK activators 5-aminoimidazole-4-carboxamide riboside and phenformin, and evaluated for apoptosis, insulin-stimulated 2-deoxyglucose uptake, PI3-kinase activity, and levels of phospho-AKT, phospho-mTor, and phospho-70S6K. Surprisingly, disrupted insulin signaling led to decreased AMPK activity in TS cells. Activators reversed these effects by increasing the AMP/ATP ratio. Moreover, this treatment increased insulin-stimulated 2-deoxyglucose transport and cell survival, and led to an increase in PI3-kinase activity, as well as increased P-mTOR and p70S6K levels. This study is the first to demonstrate significant crosstalk between the AMPK and insulin signaling pathways in embryonic cells, specifically the enhanced response of PI3K/AKT/mTOR to AMPK activation. Decreased insulin signaling also resulted in decreased AMPK activation. These findings provide mechanistic targets in the AMPK signaling pathway that may be essential for improved pregnancy success in insulin-resistant states.

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Abstract 630: Novel Chimeric Anti-proteoglycan Antibody Inhibits Arterial Retention of Proatherogenic Lipoproteins in a Rat Model of Insulin Resistance

Arteriosclerosis Thrombosis and Vascular Biology ◽

10.1161/atvb.36.suppl_1.630 ◽

2016 ◽

Vol 36 (suppl_1) ◽

Author(s):

Yosdel Soto ◽

Rabban Mangat ◽

Ana M Vázquez ◽

Spencer D Proctor

Keyword(s):

Insulin Resistance ◽

Monoclonal Antibody ◽

Ex Vivo ◽

Dependent Manner ◽

Insulin Resistant ◽

Remnant Lipoproteins ◽

Preferential Binding ◽

Carotid Vessels

Background: The response-to-retention hypothesis for atherosclerosis describes subendothelial retention of apolipoprotein B-containing lipoproteins mediated by proteoglycans (PG). Further we know that diabetes is also associated with both increased circulating chylomicron remnants and remodeling of proatherogenic PGs. We have recently reported antiatherogenic properties of a novel chimeric monoclonal antibody (chP3R99) that recognizes PG sulfated molecules. Hypothesis: chP3R99 monoclonal antibody may interfere with the interaction of atherogenic lipoproteins with arterial sulfated PGs during insulin resistance. Methods and Results: chP3R99 antibody recognized sulfated glycosaminoglycans by ELISA showing a preferential binding to chondroitin sulfate. Also, chP3R99 blocked the interaction of proatherogenic lipoproteins with this glycosaminoglycan in vitro in a dose-dependent manner and its intravenous injection into healthy Sprague-Dawly rats (n=6, 1 mg/animal) inhibited LDL (4 mg/kg; intraperitoneally) aortic retention. To further assess this property in an insulin resistant condition, carotid arteries from control and JCR:LA-cp rats (n=4) were perfused ex vivo with apoB48 containing remnant lipoproteins (prepared via rabbit hepatectomy procedure), with or without Cy3-LDL (150 μg/mL) for 20 minutes. Confocal microscopy analysis revealed an increased arterial retention of both remnants (3.6 fold) and LDL (2.8 fold) in carotid vessels from insulin resistant rats relative to control. However, chP3R99 pre-perfusion resulted in decreased retention of remnants (-30%) and LDL (-60%) associated arterial cholesterol. Data suggests that the chP399 antibody may interfere with the arterial attachment of both remnants and LDL in vivo, but with differential efficacy. Conclusions: Relative to LDL, remnant lipoproteins had preferential accumulation in arterial vessels from insulin resistant rats ex vivo , which could then be inhibited by acute pre-exposure to the chP3R99 antibody. These in vivo data support the concept for an innovative approach to target the retention of proatherogenic lipoproteins in a pre-clinical setting.

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Insulin Regulates Glucagon-Like Peptide-1 Secretion from the Enteroendocrine L Cell

Endocrinology ◽

10.1210/en.2008-0726 ◽

2009 ◽

Vol 150 (2) ◽

pp. 580-591 ◽

Cited By ~ 104

Author(s):

Gareth E. Lim ◽

Guan J. Huang ◽

Nina Flora ◽

Derek LeRoith ◽

Christopher J. Rhodes ◽

...

Keyword(s):

Insulin Resistance ◽

Oral Glucose ◽

Phosphatidylinositol 3 Kinase ◽

Insulin Resistant ◽

L Cell ◽

Glucagon Like Peptide ◽

Glucagon Like Peptide 1 ◽

Phosphatidylinositol 3

Insulin resistance and type 2 diabetes mellitus are associated with impaired postprandial secretion of glucagon-like peptide-1 (GLP-1), a potent insulinotropic hormone. The direct effects of insulin and insulin resistance on the L cell are unknown. We therefore hypothesized that the L cell is responsive to insulin and that insulin resistance impairs GLP-1 secretion. The effects of insulin and insulin resistance were examined in well-characterized L cell models: murine GLUTag, human NCI-H716, and fetal rat intestinal cells. MKR mice, a model of chronic hyperinsulinemia, were used to assess the function of the L cell in vivo. In all cells, insulin activated the phosphatidylinositol 3 kinase-Akt and MAPK kinase (MEK)-ERK1/2 pathways and stimulated GLP-1 secretion by up to 275 ± 58%. Insulin resistance was induced by 24 h pretreatment with 10−7m insulin, causing a marked reduction in activation of Akt and ERK1/2. Furthermore, both insulin-induced GLP-1 release and secretion in response to glucose-dependent insulinotropic peptide and phorbol-12-myristate-13-acetate were significantly attenuated. Whereas inhibition of phosphatidylinositol 3 kinase with LY294002 potentiated insulin-induced GLP-1 release, secretion was abrogated by inhibiting the MEK-ERK1/2 pathway with PD98059 or by overexpression of a kinase-dead MEK1-ERK2 fusion protein. Compared with controls, MKR mice were insulin resistant and displayed significantly higher fasting plasma insulin levels. Furthermore, they had significantly higher basal GLP-1 levels but displayed impaired GLP-1 secretion after an oral glucose challenge. These findings indicate that the intestinal L cell is responsive to insulin and that insulin resistance in vitro and in vivo is associated with impaired GLP-1 secretion. Insulin is a novel secretagogue of the incretin hormone, glucagon-like peptide-1 (GLP-1), and L cell insulin resistance impairs heterologous secretagogue-induced GLP-1 secretion in vitro and in vivo.

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PEG-BHD1028 Peptide Regulates Insulin Resistance and Fatty Acid β-Oxidation, and Mitochondrial Biogenesis by Binding to Two Heterogeneous Binding Sites of Adiponectin Receptors, AdipoR1 and AdipoR2

International Journal of Molecular Sciences ◽

10.3390/ijms22020884 ◽

2021 ◽

Vol 22 (2) ◽

pp. 884

Author(s):

In Kyung Lee ◽

Gyuyoup Kim ◽

Do-Hwi Kim ◽

Brian B. Kim

Keyword(s):

Insulin Resistance ◽

Fatty Acid ◽

Mitochondrial Biogenesis ◽

Binding Sites ◽

Action Spectrum ◽

C2c12 Cells ◽

In Vivo Models ◽

Insulin Resistant

Adiponectin plays multiple critical roles in modulating various physiological processes by binding to its receptors. The functions of PEG-BHD1028, a potent novel peptide agonist to AdipoRs, was evaluated using in vitro and in vivo models based on the reported action spectrum of adiponectin. To confirm the design concept of PEG-BHD1028, the binding sites and their affinities were analyzed using the SPR (Surface Plasmon Resonance) assay. The results revealed that PEG-BHD1028 was bound to two heterogeneous binding sites of AdipoR1 and AdipoR2 with a relatively high affinity. In C2C12 cells, PEG-BHD1028 significantly activated AMPK and subsequent pathways and enhanced fatty acid β-oxidation and mitochondrial biogenesis. Furthermore, it also facilitated glucose uptake by lowering insulin resistance in insulin-resistant C2C12 cells. PEG-BHD1028 significantly reduced the fasting plasma glucose level in db/db mice following a single s.c. injection of 50, 100, and 200 μg/Kg and glucose tolerance at a dose of 50 μg/Kg with significantly decreased insulin production. The animals received 5, 25, and 50 μg/Kg of PEG-BHD1028 for 21 days significantly lost their weight after 18 days in a range of 5–7%. These results imply the development of PEG-BHD1028 as a potential adiponectin replacement therapeutic agent.

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Amylin-insulin relationships in insulin resistance with and without diabetic hyperglycemia

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1993.265.3.e446 ◽

1993 ◽

Vol 265 (3) ◽

pp. E446-E453 ◽

Cited By ~ 6

Author(s):

T. R. Pieber ◽

D. T. Stein ◽

A. Ogawa ◽

T. Alam ◽

M. Ohneda ◽

...

Keyword(s):

Insulin Resistance ◽

Insulin Dependent Diabetes Mellitus ◽

Male Rats ◽

In Vivo Studies ◽

Dependent Diabetes Mellitus ◽

Ru 486 ◽

Insulin Resistant ◽

Insulin Dependent

To determine if increased secretion of amylin can be implicated in the pathogenesis of non-insulin-dependent diabetes mellitus (NIDDM) in vitro and in vivo, we studied its relationships to insulin in insulin-resistant rats with and without NIDDM. In obesity-associated and dexamethasone-induced insulin resistance without diabetes, basal and stimulated secretion of amylin and insulin by isolated pancreata were proportionately elevated, leaving the amylin-to-insulin ratio (A/I) unchanged. By contrast, whenever diabetes occurred in dexamethasone-treated rats or in spontaneously diabetic obese insulin-resistant ZDF-drt male rats, a doubling of A/I was invariably observed due to an increase in amylin without a proportional increase in insulin secretion. Correction of dexamethasone-induced hyperglycemia with the glucocorticord receptor antagonist RU-486 was accompanied by a decline in A/I. Longitudinal in vivo studies demonstrated in both spontaneous and dexamethasone-induced models of NIDDM an increase in plasma A/I at the onset of hyperglycemia. In dexamethasone-induced diabetes, the increased A/I was associated with a high proamylin mRNA relative to proinsulin mRNA. We conclude that amylin and insulin expression and secretion rise in concert in compensated insulin-resistant states, but when hyperglycemia is present the increase in amylin exceeds that of insulin. Although a role of an increased A/I in the pathogenesis of NIDDM has not been established directly, these studies indicate that such a role could be possible.

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Amelioration of High-Insulin-Induced Skeletal Muscle Cell Insulin Resistance by Resveratrol Is Linked to Activation of AMPK and Restoration of GLUT4 Translocation

Nutrients ◽

10.3390/nu12040914 ◽

2020 ◽

Vol 12 (4) ◽

pp. 914 ◽

Cited By ~ 3

Author(s):

Filip Vlavcheski ◽

Danja J. Den Hartogh ◽

Adria Giacca ◽

Evangelia Tsiani

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

Glucose Transporter ◽

Muscle Cells ◽

Skeletal Muscle Cells ◽

Muscle Insulin Resistance ◽

Skeletal Muscle Insulin Resistance ◽

High Insulin

Insulin resistance, the hallmark of type 2 diabetes mellitus (T2DM), is linked to hyperinsulinemia, which develops to counterbalance initial peripheral hormone resistance. Studies indicate that chronically elevated levels of insulin lead to skeletal muscle insulin resistance by deregulating steps within the insulin signaling cascade. The polyphenol resveratrol (RSV) has been shown to have antidiabetic properties in vitro and in vivo. In the present study, we examined the effect of RSV on high insulin (HI)-induced insulin resistance in skeletal muscle cells in vitro and investigated the mechanisms involved. Parental and GLUT4myc-overexpressing L6 rat skeletal muscle cells were used. [3H]2-deoxyglucose (2DG) uptake was measured, and total and phosphorylated levels of specific proteins were examined by immunoblotting. Exposure of L6 cells to HI levels (100 nM) for 24 h decreased the acute-insulin-stimulated 2DG uptake, indicating insulin resistance. HI increased ser307 and ser636/639 phosphorylation of IRS-1 (to 184% ± 12% and 225% ± 28.9% of control, with p < 0.001 and p < 0.01, respectively) and increased the phosphorylation levels of mTOR (174% ± 6.7% of control, p < 0.01) and p70 S6K (228% ± 33.5% of control, p < 0.01). Treatment with RSV abolished these HI-induced responses. Furthermore, RSV increased the activation of AMPK and restored the insulin-mediated increase in plasma membrane GLUT4 glucose transporter levels. These data suggest that RSV has a potential to counteract the HI-induced muscle insulin resistance.

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Endothelial dysfunction in insulin-resistant rats is associated with oxidative stress and COX pathway dysregulation

Physiological Research ◽

10.33549/physiolres.931583 ◽

2009 ◽

pp. 499-509

Author(s):

A Oudot ◽

D Behr-Roussel ◽

S Compagnie ◽

S Caisey ◽

O Le Coz ◽

...

Keyword(s):

Oxidative Stress ◽

Insulin Resistance ◽

Vascular Dysfunction ◽

Pressor Response ◽

In Vitro Study ◽

Cardiovascular Complications ◽

Insulin Resistant ◽

Pathway Dysregulation

Because insulin resistance is inevitably associated with cardiovascular complications, there is a need to further investigate the potential involvement of oxidative stress and the cyclo-oxygenase (COX) pathway in the vascular modifications associated to this pathological context. Endothelial function was evaluated in control and fructose-fed rats (FFR) by i) in vitro study of endothelium-dependent and -independent relaxations of aortic rings, and ii) in vivo telemetric evaluation of pressor response to norepinephrine. After 9 weeks of diet, FFR displayed hypertriglyceridemia, hyperinsulinemia and exaggerated response to glucose overload. Aortic rings from control rats and FFR exhibited comparable endothelium-dependent relaxations to Ach. In the presence of indomethacin, relaxations were significantly reduced. FFR showed exaggerated pressor responses to norepinephrine that were abolished with indomethacin. Urinary nitrites/nitrates, 8-isoprostanes and thromboxane B2 excretion levels were markedly enhanced in FFR, whereas the plasma levels of 6-keto prostaglandin F1α were unchanged. In conclusion, fructose overload in rats induced hypertriglyceridemia and insulin resistance associated with an enhanced oxidative stress. This was associated with COX pathway dysregulation which could be one of the contributors to subsequent vascular dysfunction. Consequently, reduction of oxidative stress and regulation of the COX pathway could represent new potential therapeutic strategies to limit vascular dysfunction and subsequent cardiovascular complications associated with insulin resistance.

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GRP75 Regulates Mitochondrial-Supercomplex Turnover to Modulate Insulin Sensitivity

10.2337/figshare.17026628 ◽

2021 ◽

Author(s):

Qiongya Zhao ◽

Ting Luo ◽

Feng Gao ◽

Yinxu Fu ◽

Bin Li ◽

...

Keyword(s):

Insulin Resistance ◽

Insulin Sensitivity ◽

Metabolic Diseases ◽

Chain Complex ◽

Complex Activity ◽

Insulin Resistant ◽

Mitochondrial Homeostasis ◽

Dna Release

GRP75, defined as a major component of both mitochondrial quality control system and mitochondria-associated membrane, plays a key role in mitochondrial homeostasis. In this study, we assessed the roles of GRP75, other than as a component, in insulin action in both in vitro and in vivo models with insulin resistance. We found that GRP75 was downregulated in HFD-fed mice, and induction of Grp75 in mice could prevent HFD induced obesity and insulin resistance. Mechanistically, GRP75 influenced insulin sensitivity by regulating mitochondrial function through its modulation of mitochondrial-supercomplex turnover rather than MAM communication: GRP75 was negatively associated with respiratory-chain complex activity and was essential for mitochondrial-supercomplex assembly and stabilization. Moreover, mitochondrial dysfunction in Grp75-knockdown cells might further increase mitochondrial fragmentation, thus trigger cytosolic mitochondrial DNA release and activate the cGAS/STING-dependent pro-inflammatory response. Therefore, GRP75 can serve as a potential therapeutic target of insulin resistant-related diabetes or other metabolic diseases.

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Oleanolic Acid Attenuates Insulin Resistance via NF-κB to Regulate the IRS1-GLUT4 Pathway in HepG2 Cells

Evidence-based Complementary and Alternative Medicine ◽

10.1155/2015/643102 ◽

2015 ◽

Vol 2015 ◽

pp. 1-9 ◽

Cited By ~ 35

Author(s):

Ming Li ◽

Zongyu Han ◽

Weijian Bei ◽

Xianglu Rong ◽

Jiao Guo ◽

...

Keyword(s):

Insulin Resistance ◽

Protein Expression ◽

Oleanolic Acid ◽

Hepg2 Cells ◽

Glucose Transporter ◽

Underlying Mechanism ◽

Pyrrolidine Dithiocarbamate ◽

Glucose Content ◽

Insulin Resistant

The aim of our study is to elucidate the mechanisms of oleanolic acid (OA) on insulin resistance (IR) in HepG2 cells. HepG2 cells were induced with FFA as the insulin resistance model and were treated with OA. Then the glucose content and the levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were analyzed. Moreover, protein expression of nuclear factor kappa B (NF-κB), insulin receptor substrate 1(IRS1), and glucose transporter 4 (GLUT4) in cells treated with OA were measured by Western blot analysis. Additionally, IRS1 protein expression exposed to OA was detected after using pyrrolidine dithiocarbamate (PDTC).Our results revealed that OA decreased the glucose content in HepG2 cells in vitro. Moreover, OA reduced the levels of TNF-α and IL-6 and upregulated IRS1 and GLUT4 protein expression. Furthermore, OA also reduced NF-κB protein expression in insulin-resistant HepG2 cells. After blocking NF-κB, the expression of IRS1 protein had no obvious changes when treated with OA. OA attenuated insulin resistance and decreased the levels of TNF-α and IL-6. Meanwhile, OA decreased NF-κB protein expression and upregulated IRS1 and GLUT4 protein expression. Therefore, regulating the IRS1-GLUT4 pathway via NF-κB was the underlying mechanism of OA on insulin resistance.

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Evidence Coupling Increased Hexosamine Biosynthesis Pathway Activity to Membrane Cholesterol Toxicity and Cortical Filamentous Actin Derangement Contributing to Cellular Insulin Resistance†

Endocrinology ◽

10.1210/en.2011-1295 ◽

2011 ◽

Vol 152 (9) ◽

pp. 3373-3384 ◽

Cited By ~ 16

Author(s):

Padma Bhonagiri ◽

Guruprasad R. Pattar ◽

Kirk M. Habegger ◽

Alicia M. McCarthy ◽

Lixuan Tackett ◽

...

Keyword(s):

Insulin Resistance ◽

Glucose Transporter ◽

Normal Operation ◽

Biosynthesis Pathway ◽

Glucose Transporter 4 ◽

Filamentous Actin ◽

Insulin Resistant ◽

Hexosamine Biosynthesis ◽

Actin Structure ◽

Hexosamine Biosynthesis Pathway

Hyperinsulinemia is known to promote the progression/worsening of insulin resistance. Evidence reveals a hidden cost of hyperinsulinemia on plasma membrane (PM) phosphatidylinositol 4,5-bisphosphate (PIP2)-regulated filamentous actin (F-actin) structure, components critical to the normal operation of the insulin-regulated glucose transport system. Here we delineated whether increased glucose flux through the hexosamine biosynthesis pathway (HBP) causes PIP2/F-actin dysregulation and subsequent insulin resistance. Increased glycosylation events were detected in 3T3-L1 adipocytes cultured under conditions closely resembling physiological hyperinsulinemia (5 nm insulin; 12 h) and in cells in which HBP activity was amplified by 2 mm glucosamine (GlcN). Both the physiological hyperinsulinemia and experimental GlcN challenge induced comparable losses of PIP2 and F-actin. In addition to protecting against the insulin-induced membrane/cytoskeletal abnormality and insulin-resistant state, exogenous PIP2 corrected the GlcN-induced insult on these parameters. Moreover, in accordance with HBP flux directly weakening PIP2/F-actin structure, pharmacological inhibition of the rate-limiting HBP enzyme [glutamine-fructose-6-phosphate amidotransferase (GFAT)] restored PIP2-regulated F-actin structure and insulin responsiveness. Conversely, overexpression of GFAT was associated with a loss of detectable PM PIP2 and insulin sensitivity. Even less invasive challenges with glucose, in the absence of insulin, also led to PIP2/F-actin dysregulation. Mechanistically we found that increased HBP activity increased PM cholesterol, the removal of which normalized PIP2/F-actin levels. Accordingly, these data suggest that glucose transporter-4 functionality, dependent on PIP2 and/or F-actin status, can be critically compromised by inappropriate HBP activity. Furthermore, these data are consistent with the PM cholesterol accrual/toxicity as a mechanistic basis of the HBP-induced defects in PIP2/F-actin structure and impaired glucose transporter-4 regulation.

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