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Yu S, Liu L, Bu T, Jiexia Z, Wang W, Wu JP, Liu D. Purification and characterization of hypoglycemic peptides from traditional Chinese soy-fermented douchi. Food Funct 2022; 13:3343-3352. [DOI: 10.1039/d1fo03941e] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Douchi is a popular soy-fermented food originated in China, with documented hypoglycemic effect. However, the responsible molecules and the mechanism underlying its beneficial effects remains unclear. Therefore, in this study,...
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Mandal AK, Leask MP, Estiverne C, Choi HK, Merriman TR, Mount DB. Genetic and Physiological Effects of Insulin on Human Urate Homeostasis. Front Physiol 2021; 12:713710. [PMID: 34408667 PMCID: PMC8366499 DOI: 10.3389/fphys.2021.713710] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2021] [Accepted: 07/02/2021] [Indexed: 12/19/2022] Open
Abstract
Insulin and hyperinsulinemia reduce renal fractional excretion of urate (FeU) and play a key role in the genesis of hyperuricemia and gout, via uncharacterized mechanisms. To explore this association further we studied the effects of genetic variation in insulin-associated pathways on serum urate (SU) levels and the physiological effects of insulin on urate transporters. We found that urate-associated variants in the human insulin (INS), insulin receptor (INSR), and insulin receptor substrate-1 (IRS1) loci associate with the expression of the insulin-like growth factor 2, IRS1, INSR, and ZNF358 genes; additionally, we found genetic interaction between SLC2A9 and the three loci, most evident in women. We also found that insulin stimulates the expression of GLUT9 and increases [14C]-urate uptake in human proximal tubular cells (PTC-05) and HEK293T cells, transport activity that was effectively abrogated by uricosurics or inhibitors of protein tyrosine kinase (PTK), PI3 kinase, MEK/ERK, or p38 MAPK. Heterologous expression of individual urate transporters in Xenopus oocytes revealed that the [14C]-urate transport activities of GLUT9a, GLUT9b, OAT10, OAT3, OAT1, NPT1 and ABCG2 are directly activated by insulin signaling, through PI3 kinase (PI3K)/Akt, MEK/ERK and/or p38 MAPK. Given that the high-capacity urate transporter GLUT9a is the exclusive basolateral exit pathway for reabsorbed urate from the renal proximal tubule into the blood, that insulin stimulates both GLUT9 expression and urate transport activity more than other urate transporters, and that SLC2A9 shows genetic interaction with urate-associated insulin-signaling loci, we postulate that the anti-uricosuric effect of insulin is primarily due to the enhanced expression and activation of GLUT9.
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Affiliation(s)
- Asim K. Mandal
- Renal Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, United States
| | - Megan P. Leask
- Biochemistry Department, University of Otago, Dunedin, New Zealand
- Division of Rheumatology and Clinical Immunology, University of Alabama, Birmingham, AL, United States
| | - Christopher Estiverne
- Renal Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, United States
| | - Hyon K. Choi
- Division of Rheumatology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States
| | - Tony R. Merriman
- Biochemistry Department, University of Otago, Dunedin, New Zealand
- Division of Rheumatology and Clinical Immunology, University of Alabama, Birmingham, AL, United States
| | - David B. Mount
- Renal Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, United States
- Renal Division, VA Boston Healthcare System, Harvard Medical School, Boston, MA, United States
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Matsuzawa T, Morita M, Shimane A, Otsuka R, Mei Y, Irie F, Yamaguchi Y, Yanai K, Yoshikawa T. Heparan sulfate promotes differentiation of white adipocytes to maintain insulin sensitivity and glucose homeostasis. J Biol Chem 2021; 297:101006. [PMID: 34310946 PMCID: PMC8379462 DOI: 10.1016/j.jbc.2021.101006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 07/16/2021] [Accepted: 07/22/2021] [Indexed: 11/29/2022] Open
Abstract
Heparan sulfate (HS), a highly sulfated linear polysaccharide, is involved in diverse biological functions in various tissues. Although previous studies have suggested a possible contribution of HS to the differentiation of white adipocytes, there has been no direct evidence supporting this. Here, we inhibited the synthesis of HS chains in 3T3-L1 cells using CRISPR–Cas9 technology, resulting in impaired differentiation of adipocytes with attenuated bone morphogenetic protein 4 (BMP4)–fibroblast growth factor 1 (FGF1) signaling pathways. HS reduction resulted in reduced glucose uptake and decreased insulin-dependent intracellular signaling. We then made heterozygous mutant mice for the Ext1 gene, which encodes an enzyme essential for the HS biosynthesis, specifically in the visceral white adipose tissue (Fabp4-Cre+::Ext1flox/WT mice, hereafter called Ext1Δ/WT) to confirm the importance of HS in vivo. The expression levels of transcription factors that control adipocyte differentiation, such as peroxisome proliferator–activated receptor gamma, were reduced in Ext1Δ/WT adipocytes, which contained smaller, unilocular lipid droplets, reduced levels of enzymes involved in lipid synthesis, and altered expression of BMP4–FGF1 signaling molecules. Furthermore, we examined the impact of HS reduction in visceral white adipose tissue on systemic glucose homeostasis. We observed that Ext1Δ/WT mice showed glucose intolerance because of insulin resistance. Our results demonstrate that HS plays a crucial role in the differentiation of white adipocytes through BMP4–FGF1 signaling pathways, thereby contributing to insulin sensitivity and glucose homeostasis.
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Affiliation(s)
- Takuro Matsuzawa
- Department of Pharmacology, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Masanobu Morita
- Department of Environmental Medicine and Molecular Toxicology, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Ai Shimane
- Department of Pharmacology, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Rina Otsuka
- Department of Pharmacology, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Yu Mei
- Department of Pharmacology, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Fumitoshi Irie
- Human Genetics Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA
| | - Yu Yamaguchi
- Human Genetics Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA
| | - Kazuhiko Yanai
- Department of Pharmacology, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Takeo Yoshikawa
- Department of Pharmacology, Tohoku University Graduate School of Medicine, Sendai, Japan.
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Gupta A, Beg M, Kumar D, Shankar K, Varshney S, Rajan S, Srivastava A, Singh K, Sonkar S, Mahdi AA, Dikshit M, Gaikwad AN. Chronic hyper-leptinemia induces insulin signaling disruption in adipocytes: Implications of NOS2. Free Radic Biol Med 2017; 112:93-108. [PMID: 28739528 DOI: 10.1016/j.freeradbiomed.2017.07.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Revised: 07/11/2017] [Accepted: 07/20/2017] [Indexed: 01/12/2023]
Abstract
Leptin, following its discovery, has developed a formidable interest in the scientific community to delineate its contribution towards overall metabolic homeostasis. Contradictory reports have been published on leptin administration effects on whole body insulin sensitivity. Following late reports, we surveyed human serum leptin levels along with other metabolic parameters including BMI and HOMA-IR. We found a positive correlation between leptin levels and insulin resistance parameters. Considering the presence of the long form of leptin receptor on adipocytes, we explored the effects of chronic physiological hyper-leptinemic exposure on adipocyte insulin sensitivity. Chronic leptin (50ng/ml) treatment in 3T3-L1 adipocytes decreased insulin-induced phosphorylation of nodal insulin signaling proteins along with reduced glucose uptake. Metabolic flux studies indicated mitochondrial dysfunction and reduced oxygen consumption rate. Leptin treatment also increased both cellular and mitochondrial superoxide levels concomitant to increased expression of nitric oxide synthase-2 (NOS2). Further, pharmacological depletion of NOS2 reversed leptin mediated effects on insulin signaling. In-vivo implantation of leptin osmotic pumps in C57BL/6 mice also decreased insulin responsiveness. Interestingly, these effects were lacking in NOS2 knockout strain. In conclusion, our studies put forward a potential link between leptin and adipocyte insulin responsiveness in an NOS2 dependent manner.
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Affiliation(s)
- Abhishek Gupta
- Division of Pharmacology, CSIR-Central Drug Research Institute, Lucknow 226031, India
| | - Muheeb Beg
- Division of Pharmacology, CSIR-Central Drug Research Institute, Lucknow 226031, India
| | - Durgesh Kumar
- Division of Pharmacology, CSIR-Central Drug Research Institute, Lucknow 226031, India; Academy of Scientific and Innovative Research, CSIR-Central Drug Research Institute, Lucknow 226031, India
| | - Kripa Shankar
- Division of Pharmacology, CSIR-Central Drug Research Institute, Lucknow 226031, India
| | - Salil Varshney
- Division of Pharmacology, CSIR-Central Drug Research Institute, Lucknow 226031, India; Academy of Scientific and Innovative Research, CSIR-Central Drug Research Institute, Lucknow 226031, India
| | - Sujith Rajan
- Division of Pharmacology, CSIR-Central Drug Research Institute, Lucknow 226031, India; Academy of Scientific and Innovative Research, CSIR-Central Drug Research Institute, Lucknow 226031, India
| | - Ankita Srivastava
- Division of Pharmacology, CSIR-Central Drug Research Institute, Lucknow 226031, India; Academy of Scientific and Innovative Research, CSIR-Central Drug Research Institute, Lucknow 226031, India
| | - Kalpana Singh
- Department of Biochemistry, King George's Medical University, Lucknow 226003, India
| | - Satyendra Sonkar
- Department of Internal Medicine, King George's Medical University, Lucknow 226003, India
| | - Abbas Ali Mahdi
- Department of Biochemistry, King George's Medical University, Lucknow 226003, India
| | - Madhu Dikshit
- Division of Pharmacology, CSIR-Central Drug Research Institute, Lucknow 226031, India
| | - Anil Nilkanth Gaikwad
- Division of Pharmacology, CSIR-Central Drug Research Institute, Lucknow 226031, India.
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Wang Y, Shao J, Zaro JL, Shen WC. Proinsulin-transferrin fusion protein as a novel long-acting insulin analog for the inhibition of hepatic glucose production. Diabetes 2014; 63:1779-88. [PMID: 24353179 PMCID: PMC3994961 DOI: 10.2337/db13-0973] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Proinsulin-transferrin (ProINS-Tf) fusion protein was evaluated for its in vivo pharmacokinetics, efficacy, and mechanism. Our previous studies have shown that ProINS-Tf was converted to active insulin-transferrin (INS-Tf) via the transferrin (Tf)-receptor-mediated pathway in hepatoma cells. We hypothesized that this fusion protein can be administered as a prodrug and be converted to a biologically active protein with specificity for the liver versus other insulin (INS)-sensitive tissues (muscle and adipose). Administration as an inactive prodrug with liver-specific action compared with other INS-sensitive tissues conceivably reduces negative side effects seen with other INS analogs. In this report, the data show that ProINS-Tf exhibited a slow, but sustained, in vivo hypoglycemic efficacy and long plasma half-life. The fusion protein showed activity in the liver, as evidenced by decreased expression of two key hepatic glucose production (HGP) enzymes, PEPCK and glucose-6-phosphatase, and increased glycogen levels under feeding conditions. Furthermore, the INS receptor (IR) phosphorylation (activation) in liver and muscle tissues was compared with postinjection of INS or ProINS-Tf. While INS activated IR in both the liver and muscle, ProINS-Tf only showed activation in the liver. Thus, ProINS-Tf fusion protein can potentially be administered as a prodrug with sustained Tf-mediated activation and selectivity in inhibiting HGP.
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Stall R, Ramos J, Kent Fulcher F, Patel YM. Regulation of myosin IIA and filamentous actin during insulin-stimulated glucose uptake in 3T3-L1 adipocytes. Exp Cell Res 2013; 322:81-8. [PMID: 24374234 DOI: 10.1016/j.yexcr.2013.12.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Revised: 12/04/2013] [Accepted: 12/08/2013] [Indexed: 11/18/2022]
Abstract
Insulin stimulated glucose uptake requires the colocalization of myosin IIA (MyoIIA) and the insulin-responsive glucose transporter 4 (GLUT4) at the plasma membrane for proper GLUT4 fusion. MyoIIA facilitates filamentous actin (F-actin) reorganization in various cell types. In adipocytes F-actin reorganization is required for insulin-stimulated glucose uptake. What is not known is whether MyoIIA interacts with F-actin to regulate insulin-induced GLUT4 fusion at the plasma membrane. To elucidate the relationship between MyoIIA and F-actin, we examined the colocalization of MyoIIA and F-actin at the plasma membrane upon insulin stimulation as well as the regulation of this interaction. Our findings demonstrated that MyoIIA and F-actin colocalized at the site of GLUT4 fusion with the plasma membrane upon insulin stimulation. Furthermore, inhibition of MyoII with blebbistatin impaired F-actin localization at the plasma membrane. Next we examined the regulatory role of calcium in MyoIIA-F-actin colocalization. Reduced calcium or calmodulin levels decreased colocalization of MyoIIA and F-actin at the plasma membrane. While calcium alone can translocate MyoIIA it did not stimulate F-actin accumulation at the plasma membrane. Taken together, we established that while MyoIIA activity is required for F-actin localization at the plasma membrane, it alone is insufficient to localize F-actin to the plasma membrane.
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Affiliation(s)
- Richard Stall
- Department of Biology, University of North Carolina at Greensboro, 312 Eberhart Building, Greensboro, NC 27412, USA
| | - Joseph Ramos
- Department of Biology, University of North Carolina at Greensboro, 312 Eberhart Building, Greensboro, NC 27412, USA
| | - F Kent Fulcher
- Department of Biology, University of North Carolina at Greensboro, 312 Eberhart Building, Greensboro, NC 27412, USA
| | - Yashomati M Patel
- Department of Biology, University of North Carolina at Greensboro, 312 Eberhart Building, Greensboro, NC 27412, USA.
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Woody S, Stall R, Ramos J, Patel YM. Regulation of myosin light chain kinase during insulin-stimulated glucose uptake in 3T3-L1 adipocytes. PLoS One 2013; 8:e77248. [PMID: 24116218 PMCID: PMC3792908 DOI: 10.1371/journal.pone.0077248] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Accepted: 09/09/2013] [Indexed: 11/25/2022] Open
Abstract
Myosin II (MyoII) is required for insulin-responsive glucose transporter 4 (GLUT4)-mediated glucose uptake in 3T3-L1 adipocytes. Our previous studies have shown that insulin signaling stimulates phosphorylation of the regulatory light chain (RLC) of MyoIIA via myosin light chain kinase (MLCK). The experiments described here delineate upstream regulators of MLCK during insulin-stimulated glucose uptake. Since 3T3-L1 adipocytes express two MyoII isoforms, we wanted to determine which isoform was required for insulin-stimulated glucose uptake. Using a siRNA approach, we demonstrate that a 60% decrease in MyoIIA protein expression resulted in a 40% inhibition of insulin-stimulated glucose uptake. We also show that insulin signaling stimulates the phosphorylation of MLCK. We further show that MLCK can be activated by calcium as well as signaling pathways. We demonstrate that adipocytes treated with the calcium chelating agent, 1,2-b (iso-aminophenoxy) ethane-N,N,N',N'-tetra acetic acid, (BAPTA) (in the presence of insulin) impaired the insulin-induced phosphorylation of MLCK by 52% and the RLC of MyoIIA by 45% as well as impairing the recruitment of MyoIIA to the plasma membrane when compared to cells treated with insulin alone. We further show that the calcium ionophore, A23187 alone stimulated the phosphorylation of MLCK and the RLC associated with MyoIIA to the same extent as insulin. To identify signaling pathways that might regulate MLCK, we examined ERK and CaMKII. Inhibition of ERK2 impaired phosphorylation of MLCK and insulin-stimulated glucose uptake. In contrast, while inhibition of CaMKII did inhibit phosphorylation of the RLC associated with MyoIIA, inhibition of CAMKIIδ did not impair MLCK phosphorylation or translocation to the plasma membrane or glucose uptake. Collectively, our results are the first to delineate a role for calcium and ERK in the activation of MLCK and thus MyoIIA during insulin-stimulated glucose uptake in 3T3-L1 adipocytes.
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Affiliation(s)
- Shelly Woody
- Department of Biology, University of North Carolina at Greensboro, Greensboro, North Carolina, United States of America
| | - Richard Stall
- Department of Biology, University of North Carolina at Greensboro, Greensboro, North Carolina, United States of America
| | - Joseph Ramos
- Department of Biology, University of North Carolina at Greensboro, Greensboro, North Carolina, United States of America
| | - Yashomati M. Patel
- Department of Biology, University of North Carolina at Greensboro, Greensboro, North Carolina, United States of America
- * E-mail:
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Fan B, Gu JQ, Yan R, Zhang H, Feng J, Ikuyama S. High glucose, insulin and free fatty acid concentrations synergistically enhance perilipin 3 expression and lipid accumulation in macrophages. Metabolism 2013; 62:1168-79. [PMID: 23566650 DOI: 10.1016/j.metabol.2013.02.013] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Revised: 02/27/2013] [Accepted: 02/28/2013] [Indexed: 01/03/2023]
Abstract
OBJECTIVE Perilipin (PLIN) 3, an intracellular lipid droplet (LD)-associated protein, is implicated in foam cell formation. Since metabolic derangements found in metabolic syndrome, such as high serum levels of glucose, insulin and free fatty acids (FFAs), are major risk factors promoting atherosclerosis, we investigated whether PLIN3 expression is affected by glucose, insulin and oleic acid (OA) using RAW264.7 cells. METHODS Real-time PCR and Western blotting were performed to detect PLIN3 or PLIN2 expression. Oil-red O staining and Lipid Analysis were employed to measure cellular content of triacylglycerides (TAG) and cholesterol. RESULTS PLIN3 mRNA was stimulated by high glucose or insulin concentrations individually, but not by OA. A combination of any two factors did not enhance PLIN3 expression any more than that evoked by glucose alone at 24h. Interestingly, however, simultaneous addition of all three factors synergistically enhanced the PLIN3 expression. This synergistic effect was not apparent for PLIN2 mRNA expression. Inhibitors of Src family tyrosine kinase and/or phosphatidylinositol 3-kinase, both of which are activated by insulin and FFA signaling, partially suppressed PLIN3 expression induced by the combination of the three factors. While simultaneous addition of glucose, insulin and OA remarkably increased the cellular content of TAG and cholesterol, knocking-down of PLIN3 predominantly reduced TAG content. CONCLUSIONS These results indicate that PLIN3 expression is synergistically stimulated by high glucose, insulin and FFA concentrations, in parallel with TAG accumulation in macrophages. This finding raises new evidence of PLIN3 involvement in conversion of macrophages into foam cells.
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Affiliation(s)
- Bin Fan
- Department of Neurology, Shengjing Hospital, China Medical University, Shenyang 11004, China
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Kappel VD, Cazarolli LH, Pereira DF, Postal BG, Zamoner A, Reginatto FH, Silva FRMB. Involvement of GLUT-4 in the stimulatory effect of rutin on glucose uptake in rat soleus muscle. J Pharm Pharmacol 2013; 65:1179-86. [DOI: 10.1111/jphp.12066] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Accepted: 03/06/2013] [Indexed: 01/08/2023]
Abstract
Abstract
Objectives
The aim of this study was to investigate the in-vitro effect of rutin on glucose uptake in an insulin target (soleus muscle) and the mechanism of action involved.
Methods
Isolated soleus muscles from rats were treated with rutin (500 μm) with or without the following inhibitors; hydroxy-2-naphthalenylmethylphosphonic acid trisacetoxymethyl ester (HNMPA(AM)3), an insulin receptor tyrosine kinase activity inhibitor, wortmannin, an inhibitor of phosphatidylinositol 3-kinase (PI3K), RO318220, an inhibitor of protein kinase C, colchicine, a microtubule-depolymerizing agent, PD98059, an inhibitor of mitogen-activated protein kinase kinase (MEK), and cycloheximide, an inhibitor of protein synthesis on fresh Krebs Ringer-bicarbonate plus [U-14C]-2-deoxy-d-glucose (0.1 μCi/ml). Samples of tissue medium were used for the radioactivity measurements.
Key findings
Rutin increased the glucose uptake in rat soleus muscle. In addition, the effect of rutin on glucose uptake was completely inhibited by pretreatment with HNMPA(AM)3, wortmannin, RO318220, colchicine, PD98059, and cycloheximide. These results suggested that rutin stimulated glucose uptake in the rat soleus muscle via the PI3K, atypical protein kinase C and mitogen-activated protein kinase (MAPK) pathways. Also, rutin may have influenced glucose transporter translocation and may have directly activated the synthesis of the transporter GLUT-4.
Conclusion
The similarities of rutin action on glucose uptake compared with the signalling pathways of insulin constitute strong evidence for the insulin-mimetic role of rutin in glucose homeostasis.
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Affiliation(s)
- Virginia Demarchi Kappel
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, Brazil
| | - Luisa Helena Cazarolli
- Campus Universitário Laranjeiras do Sul, Universidade Federal da Fronteira Sul, Laranjeiras do Sul, Brazil
| | - Danielle Fontana Pereira
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, Brazil
| | - Bárbara Graziela Postal
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, Brazil
| | - Ariane Zamoner
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, Brazil
| | - Flávio Henrique Reginatto
- Departamento de Ciências Farmacêuticas, Centro de Ciências da Saúde, Universidade Federal de Santa Catarina, Florianópolis, Brazil
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Gupta A, Dey CS. PTEN, a widely known negative regulator of insulin/PI3K signaling, positively regulates neuronal insulin resistance. Mol Biol Cell 2012; 23:3882-98. [PMID: 22875989 PMCID: PMC3459864 DOI: 10.1091/mbc.e12-05-0337] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Lipid and protein tyrosine phosphatase, phosphatase and tension homologue (PTEN), is a widely known negative regulator of insulin/phosphoinositide 3-kinase signaling. Down-regulation of PTEN is thus widely documented to ameliorate insulin resistance in peripheral tissues such as skeletal muscle and adipose. However, not much is known about its exact role in neuronal insulin signaling and insulin resistance. Moreover, alterations of PTEN in neuronal systems have led to discovery of several unexpected outcomes, including in the neurodegenerative disorder Alzheimer's disease (AD), which is increasingly being recognized as a brain-specific form of diabetes. In addition, contrary to expectations, its neuron-specific deletion in mice resulted in development of diet-sensitive obesity. The present study shows that PTEN, paradoxically, positively regulates neuronal insulin signaling and glucose uptake. Its down-regulation exacerbates neuronal insulin resistance. The positive role of PTEN in neuronal insulin signaling is likely due to its protein phosphatase actions, which prevents the activation of focal adhesion kinase (FAK) and extracellular signal-regulated kinase (ERK), the kinases critically involved in neuronal energy impairment and neurodegeneration. Results suggest that PTEN acting through FAK, the direct protein substrate of PTEN, prevents ERK activation. Our findings provide an explanation for unexpected outcomes reported earlier with PTEN alterations in neuronal systems and also suggest a novel molecular pathway linking neuronal insulin resistance and AD, the two pathophysiological states demonstrated to be closely linked.
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Affiliation(s)
- Amit Gupta
- Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Punjab, India
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Olianas MC, Dedoni S, Onali P. δ-Opioid receptors stimulate GLUT1-mediated glucose uptake through Src- and IGF-1 receptor-dependent activation of PI3-kinase signalling in CHO cells. Br J Pharmacol 2011; 163:624-37. [PMID: 21250979 DOI: 10.1111/j.1476-5381.2011.01234.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
BACKGROUND AND PURPOSE Although opioids have been reported to affect glucose homeostasis, relatively little is known on the role of δ-opioid receptors. We have investigated the regulation of glucose transport by human δ-opioid receptors expressed in Chinese hamster ovary cells. EXPERIMENTAL APPROACH The uptake of [(3)H]-2-deoxy-D-glucose and 3-O-[methyl-[(3)H]]-D-glucose in response to δ-opioid receptor ligands and the expression of GLUT1, GLUT3 and GLUT4 glucose transporters were examined. Moreover, the effects of intracellular signal transduction inhibitors on δ-opioid receptor-regulated [(3)H]-2-deoxy-D-glucose uptake and protein phosphorylation were investigated. KEY RESULTS Activation of δ-opioid receptors rapidly stimulated [(3)H]-2-deoxy-D-glucose and 3-O-[methyl-[(3)H]]-D-glucose uptakes, which were blocked by the GLUT inhibitors cytochalasin B and phloretin. The stimulation of [(3)H]-2-deoxy-D-glucose uptake that occurred without a change in plasma membrane GLUT1 - required the coupling to G(i) /G(o) proteins - was independent of cAMP and extracellular signal-regulated protein kinases, and was suppressed by blockade of Src and insulin-like growth factor-1 receptor (IGF-1R) tyrosine kinases. Inhibition of phosphatidylinositol 3-kinase (PI3K) by wortmannin or LY294002 and by PI3Kα, but not γ, isoform-selective inhibitors greatly reduced the δ-opioid receptor stimulation of glucose uptake. Moreover, the response was attenuated by overexpressing a dominant-negative kinase-deficient Akt form and by chemical inhibition of Akt. Stimulation of δ-opioid receptors increased protein kinase Cζ/λ (PKCζ/λ) phosphorylation and a selective PKCζ/λ inhibitor slightly reduced opioid stimulation of glucose uptake. CONCLUSIONS AND IMPLICATIONS δ-Opioid receptors stimulated glucose transport probably by enhancing GLUT1 intrinsic activity through a signalling cascade involving G(i)/G(o), Src, IGF-1R, PI3Kα, Akt and, to a minor extent, PKCζ/λ. This effect may contribute to the opioid regulation of glucose homeostasis in physio-pathological conditions.
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Affiliation(s)
- Maria C Olianas
- Section of Biochemical Pharmacology, Department of Neuroscience, University of Cagliari, Monserrato, Italy
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Shoham N, Gottlieb R, Sharabani-Yosef O, Zaretsky U, Benayahu D, Gefen A. Static mechanical stretching accelerates lipid production in 3T3-L1 adipocytes by activating the MEK signaling pathway. Am J Physiol Cell Physiol 2011; 302:C429-41. [PMID: 22012328 DOI: 10.1152/ajpcell.00167.2011] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Understanding mechanotransduction in adipocytes is important for research of obesity and related diseases. We cultured 3T3-L1 preadipocytes on elastic substrata and applied static tensile strains of 12% to the substrata while inducing differentiation. Using an image processing method, we monitored lipid production for a period of 3-4 wk. The ratio of %-lipid area per field of view (FOV) in the stretched over nonstretched cultures was significantly greater than unity (P < 0.05), reaching ∼1.8 on average starting from experimental day ∼10. The superior coverage of the FOV by lipids in the stretched cultures was due to significantly greater sizes of lipid droplets (LDs) with respect to nonstretched cultures, starting from experimental day ∼10 (P < 0.05), and due to significantly more LDs per cell between days ∼10 and ∼17 (P < 0.05). The statically stretched cells also differentiated significantly faster than the nonstretched cells within the first ∼10 days (P < 0.05). Adding peroxisome proliferator-activated receptor-γ (PPARγ) antagonist did not change these trends, as the %-lipid area per FOV in the stretched cultures that received this treatment was still significantly greater than in the nonstretched cultures without the PPARγ antagonist (14.44 ± 1.96% vs. 10.21 ± 3%; P < 0.05). Hence, the accelerated adipogenesis in the stretched cultures was not mediated through PPARγ. Nonetheless, inhibiting the MEK/MAPK signaling pathway reduced the extent of adipogenesis in the stretched cultures (13.53 ± 5.63%), bringing it to the baseline level of the nonstretched cultures without the MEK inhibitor (10.21 ± 3.07%). Our results hence demonstrate that differentiation of adipocytes can be enhanced by sustained stretching, which activates the MEK signaling pathway.
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Affiliation(s)
- Naama Shoham
- Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University, Israel
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14
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Wang Y, Chen YS, Zaro JL, Shen WC. Receptor-mediated activation of a proinsulin-transferrin fusion protein in hepatoma cells. J Control Release 2011; 155:386-92. [PMID: 21756950 DOI: 10.1016/j.jconrel.2011.06.029] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2011] [Revised: 06/02/2011] [Accepted: 06/18/2011] [Indexed: 11/19/2022]
Abstract
A proinsulin-transferrin (ProINS-Tf) recombinant fusion protein was designed and characterized for the sustained release of an active form of insulin (INS) by hepatoma cells. During incubation with H4IIE hepatoma cells, a gradual decline of ProINS-Tf concentration, with a concomitant generation of the immuno-reactive insulin-transferrin (irINS-Tf), was detected in the culture medium by using INS- or proinsulin (ProINS)-specific radioimmunoassay (RIA) system. Further studies indicated that the conversion of ProINS-Tf to irINS-Tf was a transferrin receptor (TfR) mediated process that was pH-sensitive, and temperature- and microtubule-dependent. These results suggest that the conversion occurred during the slow recycling route of transferrin (Tf)-TfR pathway, possibly processed by proteases in the slow recycling compartments juxtaposed to the trans-Golgi network (TGN). ProINS-Tf exhibited little activity in the short-term promotion of glucose uptake in adipocytes, indicating that it was in an inactive form similar to ProINS. Stimulation of Akt phosphorylation by ProINS-Tf was detected only after prolonged incubation with H4IIE cells. On the other hand, ProINS-Tf pre-incubated with H4IIE cells for 24h acquired an immediate activity of stimulating Akt phosphorylation. Furthermore, ProINS-Tf elicited a strong activity in the inhibition of glucose production following 24h incubation with H4IIE cells. Based on these findings, we conclude that the Tf-TfR endocytosis and recycling pathway enables the conversion and release of ProINS-Tf in an active form of irINS-Tf. Results from this study suggest that the Tf-TfR pathway can be exploited for the design of prohormone-Tf fusion proteins as protein prodrugs for their sustained and targeted activation.
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Affiliation(s)
- Yan Wang
- Department of Pharmacology and Pharmaceutical Sciences, University of Southern California, Los Angeles, United States
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15
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Hsu HF, Tsou TC, Chao HR, Kuo YT, Tsai FY, Yeh SC. Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on adipogenic differentiation and insulin-induced glucose uptake in 3T3-L1 cells. JOURNAL OF HAZARDOUS MATERIALS 2010; 182:649-655. [PMID: 20633992 DOI: 10.1016/j.jhazmat.2010.06.081] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2010] [Revised: 06/02/2010] [Accepted: 06/19/2010] [Indexed: 05/29/2023]
Abstract
Dioxin exposure has been positively associated with human type II diabetes. Because lipophilic dioxins accumulate mainly in adipose tissue, this study aimed to determine if dioxins induce metabolic dysfunction in fat cells. Using 3T3-L1 cells as an in vitro model, we analyzed the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a model dioxin, on adipogenic differentiation, glucose uptake, and lipolysis. TCDD inhibited adipogenic differentiation, as determined by using oil droplet formation and adipogenic marker gene expression, including PPARgamma (peroxisome proliferator-activated receptor gamma), C/EBPalpha (CCAAT/enhancer-binding protein alpha), and Glut4 (glucose transporter type 4). Effects of TCDD on glucose uptake were evaluated using fully differentiated 3T3-L1 adipocytes, revealing that TCDD significantly attenuated insulin-induced glucose uptake dose dependently. Inhibition of aryl hydrocarbon receptor (AhR) by alpha-naphthoflavone (alpha-NF), an AhR inhibitor, did not prevent the inhibitory effect of TCDD on glucose uptake, suggesting that TCDD attenuates insulin-induced glucose uptake in an AhR-independent manner. Effects of TCDD on lipolysis were determined using glycerol release assay. We found that TCDD had no marked effect on isoproterenol-induced glycerol release in fully differentiated 3T3-L1 adipocytes. These results provide in vitro evidence of TCDD's effects on fat cell metabolism, suggesting dioxin exposure in development of insulin resistance and type II diabetes.
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Affiliation(s)
- Hsin-Fen Hsu
- Division of Environmental Health and Occupational Medicine, National Health Research Institutes, Zhunan, Miaoli County 35053, Taiwan
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16
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Bouraoui L, Capilla E, Gutiérrez J, Navarro I. Insulin and insulin-like growth factor I signaling pathways in rainbow trout (Oncorhynchus mykiss) during adipogenesis and their implication in glucose uptake. Am J Physiol Regul Integr Comp Physiol 2010; 299:R33-41. [DOI: 10.1152/ajpregu.00457.2009] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Primary cultures of rainbow trout ( Oncorhynchus mykiss ) adipocytes were used to examine the main signaling pathways of insulin and insulin-like growth factor I (IGF-I) during adipogenesis. We first determined the presence of IGF-I receptors (IGF-IR) and insulin receptors (IR) in trout preadipocytes ( day 5) and adipocytes ( day 14). IGF-IRs were more abundant and appeared to be in higher levels in differentiated cells than in preadipocytes, whereas IRs were detected in lower but constant levels throughout the culture. The cells were immunoreactive against ERK1/2 MAPK, and AKT/PI3K, components of the two main signal transduction pathways for insulin and IGF-I receptors. Stimulation of MAPK phosphorylation by IGF-I was higher in preadipocytes than in adipocytes, while no effects were observed in MAPK phosphorylation after incubation of cells with insulin. AKT phosphorylation increased in the presence of both insulin and IGF-I, with higher levels of stimulation in adipocytes than in preadipocytes. Activation of both pathways was blocked by the use of specific inhibitors of MAPK (PD98059) and AKT (wortmannin). We describe here, for the first time, the effects of IGF-I and insulin on 2-deoxyglucose uptake in primary culture of trout adipocytes. IGF-I was more potent in stimulating glucose uptake than insulin, and PD98059 and wortmannin inhibited the stimulation of glucose uptake by this growth factor, suggesting that IGF-I plays an important metabolic role in trout adipocytes. Our results suggest that differential activation of the MAPK and AKT pathways are involved in the IGF-I- and insulin-induced effects of trout adipocytes during the various stages of adipogenesis.
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Affiliation(s)
- L. Bouraoui
- Departament de Fisiologia, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain
| | - E. Capilla
- Departament de Fisiologia, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain
| | - J. Gutiérrez
- Departament de Fisiologia, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain
| | - I. Navarro
- Departament de Fisiologia, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain
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17
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Kobashi C, Asamizu S, Ishiki M, Iwata M, Usui I, Yamazaki K, Tobe K, Kobayashi M, Urakaze M. Inhibitory effect of IL-8 on insulin action in human adipocytes via MAP kinase pathway. JOURNAL OF INFLAMMATION-LONDON 2009; 6:25. [PMID: 19709445 PMCID: PMC2746203 DOI: 10.1186/1476-9255-6-25] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2009] [Accepted: 08/27/2009] [Indexed: 11/30/2022]
Abstract
Background Various cytokines and other compounds are produced in human adipose tissue and might have functions in the adipose tissue. They might be involved in complications associated with obesity and diabetes. Recently, interleukin-8 (IL-8) has been shown to be produced and released from human adipose tissue and/or adipocytes, suggesting IL-8 involvement in some obesity-related health complications. Therefore, we found it of interest to investigate whether IL-8 is involved in the insulin action in human adipocytes. Methods The IL-8 levels in the medium were measured using ELISA. The IL-8 mRNA expression was analyzed using Northern blot analysis. The phosphorylation of Akt was analyzed using Western blot analysis. Furthermore, we examined the effect of IL-8 on the phosphorylation of Akt induced by insulin. Results The level of IL-8 in the medium and the IL-8 mRNA expression after stimulation with either TNF-α, IL-1β, or CRP was significantly enhanced in human adipocytes. It is particularly interesting that IL-8 per se also enhanced IL-8 mRNA expression. The IL-8 induced-IL-8 mRNA expression was inhibited by PD98059 (a MEK inhibitor) or SB203580 (a p38 MAPK inhibitor). The IL-8 inhibited insulin-induced Akt phosphorylation. The inhibitory effect of IL-8 was eliminated by either PD 98059 or SB203580. Conclusion These data suggest that IL-8 is a main adipocytokine producing insulin resistance via the inhibition of insulin-induced Akt phosphorylation in adipocytes. The attenuation of IL-8 action might be a target for prevention of diabetes and its complications.
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Affiliation(s)
- Chikaaki Kobashi
- First Department of Internal Medicine, Faculty of Medicine, Toyama University, Toyama, Japan.
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18
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Signaling pathways of kaempferol-3-neohesperidoside in glycogen synthesis in rat soleus muscle. Biochimie 2009; 91:843-9. [DOI: 10.1016/j.biochi.2009.04.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Accepted: 04/07/2009] [Indexed: 11/23/2022]
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19
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Wang Z, Jin H, Li C, Hou Y, Mei Q, Fan D. Heat Shock Protein 72 Protects Kidney Proximal Tubule Cells From Injury Induced by Triptolide by Means of Activation of the MEK/ERK Pathway. Int J Toxicol 2009; 28:177-89. [PMID: 19546256 DOI: 10.1177/1091581809337418] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Triptolide, which has been used to treat inflammatory diseases, has also been reported to inhibit proliferation of cancer cells. However, it can cause severe nephrotoxicity, limiting its clinical use. Here, nephrotoxicity of triptolide was observed in vivo and in vitro. Heat shock protein 72 (HSP72) was upregulated during kidney injury in rats. HSP72 partially protected human kidney proximal tubule cell lines HK-2 and HKC from triptolide-induced injury. Phospho-Raf, phospho-MEK and phospho-ERK were elevated in HK-2 cells that overexpressed HSP72 after either heat shock or triptolide treatment, and downregulated when HSP72 was repressed by siRNA. The participation of the MEK/ERK1/2 pathway was confirmed by exposure of the cells to the MEK inhibitor U0126. Collectively, our results suggested that HSP72 plays a protective role by means of the MEK/ERK pathway, against triptolide-induced kidney injury.
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Affiliation(s)
- Zhipeng Wang
- From the Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; State Key Laboratory of Cancer Biology and Institute of Digestive Diseases, Xijing Hospital, The Fourth Military Medical University, Xi’an, Shaanxi Provine, China; Department of Gastroenterology, Bethune International Peace Hospital, Shijiazhuang, Hebei Province, P.R. China; Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; Department
| | - Haifeng Jin
- From the Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; State Key Laboratory of Cancer Biology and Institute of Digestive Diseases, Xijing Hospital, The Fourth Military Medical University, Xi’an, Shaanxi Provine, China; Department of Gastroenterology, Bethune International Peace Hospital, Shijiazhuang, Hebei Province, P.R. China; Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; Department
| | - Chen Li
- From the Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; State Key Laboratory of Cancer Biology and Institute of Digestive Diseases, Xijing Hospital, The Fourth Military Medical University, Xi’an, Shaanxi Provine, China; Department of Gastroenterology, Bethune International Peace Hospital, Shijiazhuang, Hebei Province, P.R. China; Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; Department
| | - Ying Hou
- From the Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; State Key Laboratory of Cancer Biology and Institute of Digestive Diseases, Xijing Hospital, The Fourth Military Medical University, Xi’an, Shaanxi Provine, China; Department of Gastroenterology, Bethune International Peace Hospital, Shijiazhuang, Hebei Province, P.R. China; Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; Department
| | - Qibing Mei
- From the Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; State Key Laboratory of Cancer Biology and Institute of Digestive Diseases, Xijing Hospital, The Fourth Military Medical University, Xi’an, Shaanxi Provine, China; Department of Gastroenterology, Bethune International Peace Hospital, Shijiazhuang, Hebei Province, P.R. China; Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; Department
| | - Daiming Fan
- From the Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; State Key Laboratory of Cancer Biology and Institute of Digestive Diseases, Xijing Hospital, The Fourth Military Medical University, Xi’an, Shaanxi Provine, China; Department of Gastroenterology, Bethune International Peace Hospital, Shijiazhuang, Hebei Province, P.R. China; Department of Pharmacology, School of Pharmacy, Fourth Military Medical University, Xi’an, Shaanxi, China; Department
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20
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Montagut G, Onnockx S, Vaqué M, Bladé C, Blay M, Fernández-Larrea J, Pujadas G, Salvadó MJ, Arola L, Pirson I, Ardévol A, Pinent M. Oligomers of grape-seed procyanidin extract activate the insulin receptor and key targets of the insulin signaling pathway differently from insulin. J Nutr Biochem 2009; 21:476-81. [PMID: 19443198 DOI: 10.1016/j.jnutbio.2009.02.003] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2008] [Revised: 01/16/2009] [Accepted: 02/03/2009] [Indexed: 10/20/2022]
Abstract
Procyanidins are bioactive flavonoid compounds from fruits and vegetables that possess insulinomimetic properties, decreasing hyperglycaemia in streptozotocin-diabetic rats and stimulating glucose uptake in insulin-sensitive cell lines. Here we show that the oligomeric structures of a grape-seed procyanidin extract (GSPE) interact and induce the autophosphorylation of the insulin receptor in order to stimulate the uptake of glucose. However, their activation differs from insulin activation and results in differences in the downstream signaling. Oligomers of GSPE phosphorylate protein kinase B at Thr308 lower than insulin does, according to the lower insulin receptor activation by procyanidins. On the other hand, they phosphorylate Akt at Ser473 to the same extent as insulin. Moreover, we found that procyanidins phosphorylate p44/p42 and p38 MAPKs much more than insulin does. These results provide further insight into the molecular signaling mechanisms used by procyanidins, pointing to Akt and MAPK proteins as key points for GSPE-activated signaling pathways. Moreover, the differences between GSPE and insulin might help us to understand the wide range of biological effects that procyanidins have.
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Affiliation(s)
- Gemma Montagut
- Departament de Bioquímica i Biotecnologia, Universitat Rovira i Virgili, Tarragona 43007, Spain
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21
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Lee DF, Kuo HP, Chen CT, Wei Y, Chou CK, Hung JY, Yen CJ, Hung MC. IKKbeta suppression of TSC1 function links the mTOR pathway with insulin resistance. Int J Mol Med 2009; 22:633-8. [PMID: 18949383 DOI: 10.3892/ijmm_00000065] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The proinflammatory cytokine TNFalpha is one of the factors that links obesity-derived chronic inflammation with insulin resistance. Activation of mTOR signaling pathway has been found to suppress insulin sensitivity through serine phosphorylation and the inhibition of IRS1 by mTOR and its downstream effector, S6K1. It remains elusive that whether the mTOR pathway has a role in TNFalpha-mediated insulin resistance. In the present study, we demonstrated that TNFalpha-IKKbeta-mediated inactivation of TSC1 resulted in increasing phosphorylation of IRS1 serine 307 and serine 636/639, impaired insulin-induced glucose uptake, tyrosine phosphorylation of IRS1, and the association between IRS1 and PI3K p85. Furthermore, a higher expression of pIKKbeta (S181), pTSC1(S511), and pS6(S240/244) was found in livers obtained from both C57BL/6J mice on a high-fat diet and B6.V-Lepob/J mice. Collectively, dysregulation of the TSC1/ TSC2/mTOR signaling pathway by IKKbeta is a common molecular switch for both cancer pathogenesis and diet- and obesity-induced insulin resistance.
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Affiliation(s)
- Dung-Fang Lee
- Department of Molecular and Cellular Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, TX, USA
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22
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Dual role for myosin II in GLUT4-mediated glucose uptake in 3T3-L1 adipocytes. Exp Cell Res 2008; 314:3264-74. [PMID: 18773891 DOI: 10.1016/j.yexcr.2008.08.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2008] [Revised: 08/07/2008] [Accepted: 08/10/2008] [Indexed: 01/15/2023]
Abstract
Insulin-stimulated glucose uptake requires the activation of several signaling pathways to mediate the translocation and fusion of GLUT4 vesicles to the plasma membrane. Our previous studies demonstrated that GLUT4-mediated glucose uptake is a myosin II-dependent process in adipocytes. The experiments described in this report are the first to show a dual role for the myosin IIA isoform specifically in regulating insulin-stimulated glucose uptake in adipocytes. We demonstrate that inhibition of MLCK but not RhoK results in impaired insulin-stimulated glucose uptake. Furthermore, our studies show that insulin specifically stimulates the phosphorylation of the RLC associated with the myosin IIA isoform via MLCK. In time course experiments, we determined that GLUT4 translocates to the plasma membrane prior to myosin IIA recruitment. We further show that recruitment of myosin IIA to the plasma membrane requires that myosin IIA be activated via phosphorylation of the RLC by MLCK. Our findings also reveal that myosin II is required for proper GLUT4-vesicle fusion at the plasma membrane. We show that once at the plasma membrane, myosin II is involved in regulating the intrinsic activity of GLUT4 after insulin stimulation. Collectively, our results are the first to reveal that myosin IIA plays a critical role in mediating insulin-stimulated glucose uptake in 3T3-LI adipocytes, via both GLUT4 vesicle fusion at the plasma membrane and GLUT4 activity.
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23
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Bezy O, Vernochet C, Gesta S, Farmer SR, Kahn CR. TRB3 blocks adipocyte differentiation through the inhibition of C/EBPbeta transcriptional activity. Mol Cell Biol 2007; 27:6818-31. [PMID: 17646392 PMCID: PMC2099230 DOI: 10.1128/mcb.00375-07] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
TRB3 has been implicated in the regulation of several biological processes in mammalian cells through its ability to influence Akt and other signaling pathways. In this study, we investigated the role of TRB3 in regulating adipogenesis and the activity of adipogenic transcription factors. We find that TRB3 is expressed in 3T3-L1 preadipocytes, and this expression is transiently suppressed during the initial days of differentiation concomitant with induction of C/EBPbeta. This event appears to be a prerequisite for adipogenesis. Overexpression of TRB3 blocks differentiation of 3T3-L1 cells at a step downstream of C/EBPbeta. Ectopic expression of TRB3 in mouse fibroblasts also inhibits the C/EBPbeta-dependent induction of PPARgamma2 and blocks their differentiation into adipocytes. This inhibition of preadipocyte differentiation by TRB3 appears to be the result of two complementary effects. First, TRB3 inhibits extracellular signal-regulated kinase activity, which prevents the phosphorylation of regulatory sites on C/EBPbeta. Second, TRB3 directly interacts with the DR1 domain of C/EBPbeta in the nucleus, further inhibiting both its ability to bind its response element and its ability to transactivate the C/EBPalpha and a-FABP promoters. Thus, TRB3 is an important negative regulator of adipogenesis that acts at an early step in the differentiation cascade to block the C/EBPbeta proadipogenic function.
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Affiliation(s)
- Olivier Bezy
- Section on Obesity and Hormone Action, Joslin Diabetes Center, Harvard Medical School, Boston, MA 02215, USA
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24
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Zhou L, Yang Y, Wang X, Liu S, Shang W, Yuan G, Li F, Tang J, Chen M, Chen J. Berberine stimulates glucose transport through a mechanism distinct from insulin. Metabolism 2007; 56:405-12. [PMID: 17292731 DOI: 10.1016/j.metabol.2006.10.025] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2006] [Accepted: 10/30/2006] [Indexed: 12/15/2022]
Abstract
Berberine exerts a hypoglycemic effect, but the mechanism remains unknown. In the present study, the effect of berberine on glucose uptake was characterized in 3T3-L1 adipocytes. It was revealed that berberine stimulated glucose uptake in 3T3-L1 adipocytes in a dose- and time-dependent manner with the maximal effect at 12 hours. Glucose uptake was increased by berberine in 3T3-L1 preadipocytes as well. Berberine-stimulated glucose uptake was additive to that of insulin in 3T3-L1 adipocytes, even at the maximal effective concentrations of both components. Unlike insulin, the effect of berberine on glucose uptake was insensitive to wortmannin, an inhibitor of phosphatidylinositol 3-kinase, and SB203580, an inhibitor of p38 mitogen-activated protein kinase. Berberine activated extracellular signal-regulated kinase (ERK) 1/2, but PD98059, an ERK kinase inhibitor, only decreased berberine-stimulated glucose uptake by 32%. Berberine did not induce Ser473 phosphorylation of Akt nor enhance insulin-induced phosphorylation of Akt. Meanwhile, the expression and cellular localization of glucose transporter 4 (GLUT4) were not altered by berberine. Berberine did not increase GLUT1 gene expression. However, genistein, a tyrosine kinase inhibitor, completely blocked berberine-stimulated glucose uptake in 3T3-L1 adipocytes and preadipocytes, suggesting that berberine may induce glucose transport via increasing GLUT1 activity. In addition, berberine increased adenosine monophosphate-activated protein kinase and acetyl-coenzyme A carboxylase phosphorylation. These findings suggest that berberine increases glucose uptake through a mechanism distinct from insulin, and activated adenosine monophosphate-activated protein kinase seems to be involved in the metabolic effect of berberine.
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Affiliation(s)
- Libin Zhou
- Shanghai Clinical Center for Endocrine and Metabolic Diseases, Shanghai Institute of Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200025, China
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25
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Maslowska M, Legakis H, Assadi F, Cianflone K. Targeting the signaling pathway of acylation stimulating protein. J Lipid Res 2006; 47:643-52. [PMID: 16333141 DOI: 10.1194/jlr.m500500-jlr200] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Acylation stimulating protein (ASP; C3adesArg) stimulates triglyceride synthesis (TGS) and glucose transport in preadipocytes/adipocytes through C5L2, a G-protein-coupled receptor. Here, ASP signaling is compared with insulin in 3T3-L1 cells. ASP stimulation is not Galpha(s) or Galpha(i) mediated (pertussis and cholera toxin insensitive), suggesting G(alphaq) as a candidate. Phospholipase C (PLC) is required, because the Ca(2+) chelator 1,2-bis(o-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl) ester and the PLC inhibitor U73122 decreased ASP stimulation of TGS by 93.1% (P < 0.0.001) and 86.1% (P < 0.004), respectively. Wortmannin and LY294002 blocked ASP effect by 69% (P < 0.001) and 116.1% (P < 0.003), respectively, supporting phosphatidylinositol 3-kinase (PI3K) involvement. ASP induced rapid, transient Akt phosphorylation (maximal, 5 min; basal, 45 min), which was blocked by Akt inhibition, resembling treatment by insulin. Downstream of PI3K, mamalian target of rapaycin (mTOR) is required for insulin but not ASP action. By contrast, both ASP and insulin activate the mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK(1/2)) pathway, with rapid, pronounced increases in ERK(1/2) phosphorylation, effects partially blocked by PD98059 (64.7% and 65.9% inhibition, respectively; P < 0.001). Time-dependent (maximal, 30 min) transient calcium-dependent phospholipase A(2) (cPLA(2))(-Ser505) phosphorylation (by MAPK/ERK(1/2)) was demonstrated by Western blot analysis. ASP signaling involves sequential activation of PI3K and PLC, with downstream activation of protein kinase C, Akt, MAPK/ERK(1/2), and cPLA(2), all of which leads to an effective and prolonged stimulation of TGS.
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Affiliation(s)
- Magdalena Maslowska
- Mike Rosenbloom Laboratory for Cardiovascular Research, McGill University Health Center, Montreal, Québec, Canada
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26
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Abstract
The mitogen-activated protein kinase (MAPK) ERK5 plays an important role in mammary epithelial proliferation, endothelial cell survival and normal embryonic development. In nonhaematopoietic cells, mitogenic and stress signals activate the ERK5 cascade. Here, we investigated the role of the ERK5 pathway in T-cell activation and show that primary and leukaemic T cells express ERK5, whose activating phosphorylation is induced by antibodies against CD3 but not by phorbol myristate acetate treatment. ERK5 localized in the cytosol and nucleus in quiescent and activated T cells. In the latter, ERK5 phosphorylation was mainly observed in the nucleus. Selective activation of the ERK5 cascade by transfecting constitutively active MEK5 and wildtype ERK5 induced a reporter gene driven by the IL-2 promoter while barely affecting CD69 expression. These results suggest a new role for the ERK5 cascade in intracellular signalling in T cells.
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Affiliation(s)
- J Garaude
- Institut de Génétique Moléculaire de Montpellier, CNRS UMR5535, IFR 122, 34293 Montpellier cedex 5, France
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27
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Steimle PA, Fulcher FK, Patel YM. A novel role for myosin II in insulin-stimulated glucose uptake in 3T3-L1 adipocytes. Biochem Biophys Res Commun 2005; 331:1560-5. [PMID: 15883051 DOI: 10.1016/j.bbrc.2005.04.082] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2005] [Indexed: 11/25/2022]
Abstract
Insulin-stimulated glucose uptake requires the activation of several signaling pathways to mediate the translocation and fusion of GLUT4 vesicles from an intracellular pool to the plasma membrane. The studies presented here show that inhibition of myosin II activity impairs GLUT4-mediated glucose uptake but not GLUT4 translocation to the plasma membrane. We also show that adipocytes express both myosin IIA and IIB isoforms, and that myosin IIA is recruited to the plasma membrane upon insulin stimulation. Taken together, the data presented here represent the first demonstration that GLUT4-mediated glucose uptake is a myosin II-dependent process in adipocytes. Based on our findings, we hypothesize that myosin II is activated upon insulin stimulation and recruited to the cell cortex to facilitate GLUT4 fusion with the plasma membrane. The identification of myosin II as a key component of GLUT4-mediated glucose uptake represents an important advance in our understanding of the mechanisms regulating glucose homeostasis.
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Affiliation(s)
- Paul A Steimle
- Department of Biology, University of North Carolina at Greensboro, Greensboro, NC 27402, USA
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28
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Dokladda K, Green KA, Pan DA, Hardie DG. PD98059 and U0126 activate AMP-activated protein kinase by increasing the cellular AMP:ATP ratio and not via inhibition of the MAP kinase pathway. FEBS Lett 2005; 579:236-40. [PMID: 15620719 DOI: 10.1016/j.febslet.2004.11.084] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2004] [Revised: 11/16/2004] [Accepted: 11/25/2004] [Indexed: 10/26/2022]
Abstract
The MAP kinase pathway inhibitor U0126 caused phosphorylation and activation of AMP-activated protein kinase (AMPK) and increased phosphorylation of its downstream target acetyl-CoA carboxylase, in HEK293 cells. This effect only occurred in cells expressing the upstream kinase, LKB1. Of two other widely used MAP kinase pathway inhibitors not closely related in structure to U0126, PD98059 also activated AMPK but PD184352 did not. U0126 and PD98059, but not PD184352, also increased the cellular ADP:ATP and AMP:ATP ratios, accounting for their ability to activate AMPK. These results suggest the need for caution in interpreting experiments conducted using U0126 and PD98059.
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Affiliation(s)
- Kanchana Dokladda
- Division of Molecular Physiology, Wellcome Trust Biocentre, University of Dundee, Dow Street, Dundee DD1 5EH, UK
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