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Mo Z, Zhan M, Yang X, Xie P, Xiao J, Cao Y, Xiao H, Song M. Fermented dietary fiber from soy sauce residue exerts antidiabetic effects through regulating the PI3K/AKT signaling pathway and gut microbiota-SCFAs-GPRs axis in type 2 diabetic mellitus mice. Int J Biol Macromol 2024; 270:132251. [PMID: 38729488 DOI: 10.1016/j.ijbiomac.2024.132251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2024] [Revised: 05/06/2024] [Accepted: 05/07/2024] [Indexed: 05/12/2024]
Abstract
The gut plays a crucial role in the development and progression of metabolic disorders, particularly in relation to type 2 diabetes mellitus (T2DM). While a high intake of dietary fiber is inversely associated with the risk of T2DM, the specific effects of various dietary fibers on T2DM are not fully understood. This study investigated the anti-diabetic properties of fermented dietary fiber (FDF) derived from soy sauce residue in T2DM mice, demonstrating its ability to lower blood glucose levels and ameliorate insulin resistance. Our findings revealed that FDF could enhance hepatic glucose metabolism via the IRS-1/PI3K/AKT/mTOR pathway. Additionally, the anti-diabetic effect of FDF was correlated with alterations in gut microbiota composition in T2DM mice, promoting a healthier gut environment. Specifically, FDF increased the abundance of beneficial flora such as Dubosiella, Butyricimonas, Lachnospiraceae_NK4A136_group, Lactobacillus and Osillibacter, while reducing harmful bacteria including Bilophila, Parabacteroides and Enterorhabdus. Further analysis of microbial metabolites, including short-chain fatty acids (SCFAs) and bile acids (BAs), provided evidence of FDF's regulatory effects on cecal contents in T2DM mice. Importantly, FDF treatment significantly restored the G-protein-coupled receptors (GPRs) expression in the colon of T2DM mice. In conclusion, our study suggests that the anti-diabetic effects of FDF are associated with the regulation of both the liver-gut axis and the gut microbiota-SCFAs-GPRs axis.
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Affiliation(s)
- Zheqi Mo
- Guangdong Provincial Key Laboratory of Nutraceuticals and Functional Foods, College of Food Sciences, South China Agricultural University, Guangzhou 510642, China
| | - Minmin Zhan
- Department of Food Science and Nutrition, College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China
| | - Xiaoshuang Yang
- Guangdong Provincial Key Laboratory of Nutraceuticals and Functional Foods, College of Food Sciences, South China Agricultural University, Guangzhou 510642, China
| | - Peichun Xie
- Guangdong Provincial Key Laboratory of Nutraceuticals and Functional Foods, College of Food Sciences, South China Agricultural University, Guangzhou 510642, China
| | - Jie Xiao
- Guangdong Provincial Key Laboratory of Nutraceuticals and Functional Foods, College of Food Sciences, South China Agricultural University, Guangzhou 510642, China
| | - Yong Cao
- Guangdong Provincial Key Laboratory of Nutraceuticals and Functional Foods, College of Food Sciences, South China Agricultural University, Guangzhou 510642, China
| | - Hang Xiao
- Department of Food Science, University of Massachusetts, Amherst, MA 01003, USA
| | - Mingyue Song
- Guangdong Provincial Key Laboratory of Nutraceuticals and Functional Foods, College of Food Sciences, South China Agricultural University, Guangzhou 510642, China.
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Serine Palmitoyltransferase Gene Silencing Prevents Ceramide Accumulation and Insulin Resistance in Muscles in Mice Fed a High-Fat Diet. Cells 2022; 11:cells11071123. [PMID: 35406688 PMCID: PMC8997855 DOI: 10.3390/cells11071123] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 03/15/2022] [Accepted: 03/24/2022] [Indexed: 02/04/2023] Open
Abstract
Skeletal muscles account for ~80% of insulin-stimulated glucose uptake and play a key role in lipid metabolism. Consumption of a high-fat diet (HFD) contributes to metabolic changes in muscles, including the development of insulin resistance. The studies carried out to date indicate that the accumulation of biologically active lipids, such as long-chain acyl-CoA, diacylglycerols and ceramides, play an important role in the development of insulin resistance in skeletal muscles. Unfortunately, it has not yet been clarified which of these lipid groups plays the dominant role in inducing these disorders. In order to explore this topic further, we locally silenced the gene encoding serine palmitoyltransferase (SPT) in the gastrocnemius muscle of animals with HFD-induced insulin resistance. This enzyme is primarily responsible for the first step of de novo ceramide biosynthesis. The obtained results confirm that the HFD induces the development of whole-body insulin resistance, which results in inhibition of the insulin pathway. This is associated with an increased level of biologically active lipids in the muscles. Our results also demonstrate that silencing the SPT gene with the shRNA plasmid reduces the accumulation of ceramides in gastrocnemius muscle, which, in turn, boosts the activity of the insulin signaling pathway. Furthermore, inhibition of ceramide synthesis does not significantly affect the content of other lipids, which suggests the leading role of ceramide in the lipid-related induction of skeletal muscle insulin resistance.
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Abstract
Non-alcoholic fatty liver disease (NAFLD) is the most common form of liver disease and leading cause of cirrhosis in the United States and developed countries. NAFLD is closely associated with obesity, insulin resistance and metabolic syndrome, significantly contributing to the exacerbation of the latter. Although NAFLD represents the hepatic component of metabolic syndrome, it can also be found in patients prior to their presentation with other manifestations of the syndrome. The pathogenesis of NAFLD is complex and closely intertwined with insulin resistance and obesity. Several mechanisms are undoubtedly involved in its pathogenesis and progression. In this review, we bring together the current understanding of the pathogenesis that makes NAFLD a systemic disease.
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Affiliation(s)
- Isabella Reccia
- Department of Surgery and Cancer Faculty of Medicine, Hammersmith Hospital, Imperial College London, UK.
| | - Jayant Kumar
- Department of Surgery and Cancer Faculty of Medicine, Hammersmith Hospital, Imperial College London, UK.
| | - Cherif Akladios
- Department of Surgery and Cancer Faculty of Medicine, Hammersmith Hospital, Imperial College London, UK.
| | - Francesco Virdis
- Department of Surgery and Cancer Faculty of Medicine, Hammersmith Hospital, Imperial College London, UK.
| | - Madhava Pai
- Department of Surgery and Cancer Faculty of Medicine, Hammersmith Hospital, Imperial College London, UK.
| | - Nagy Habib
- Department of Surgery and Cancer Faculty of Medicine, Hammersmith Hospital, Imperial College London, UK.
| | - Duncan Spalding
- Department of Surgery and Cancer Faculty of Medicine, Hammersmith Hospital, Imperial College London, UK.
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4
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Cieniewicz AM, Cooper PR, McGehee J, Lingham RB, Kihm AJ. Novel method demonstrates differential ligand activation and phosphatase-mediated deactivation of insulin receptor tyrosine-specific phosphorylation. Cell Signal 2016; 28:1037-47. [PMID: 27155325 DOI: 10.1016/j.cellsig.2016.05.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 04/14/2016] [Accepted: 05/02/2016] [Indexed: 10/21/2022]
Abstract
Insulin receptor signaling is a complex cascade leading to a multitude of intracellular functional responses. Three natural ligands, insulin, IGF1 and IGF2, are each capable of binding with different affinities to the insulin receptor, and result in variable biological responses. However, it is likely these affinity differences alone cannot completely explain the myriad of diverse cellular outcomes. Ligand binding initiates activation of a signaling cascade resulting in phosphorylation of the IR itself and other intracellular proteins. The direct catalytic activity along with the temporally coordinated assembly of signaling proteins is critical for insulin receptor signaling. We hypothesized that determining differential phosphorylation among individual tyrosine sites activated by ligand binding or dephosphorylation by phosphatases could provide valuable insight into insulin receptor signaling. Here, we present a sensitive, novel immunoassay adapted from Meso Scale Discovery technology to quantitatively measure changes in site-specific phosphorylation levels on endogenous insulin receptors from HuH7 cells. We identified insulin receptor phosphorylation patterns generated upon differential ligand activation and phosphatase-mediated deactivation. The data demonstrate that insulin, IGF1 and IGF2 elicit different insulin receptor phosphorylation kinetics and potencies that translate to downstream signaling. Furthermore, we show that insulin receptor deactivation, regulated by tyrosine phosphatases, occurs distinctively across specific tyrosine residues. In summary, we present a novel, quantitative and high-throughput assay that has uncovered differential ligand activation and site-specific deactivation of the insulin receptor. These results may help elucidate some of the insulin signaling mechanisms, discriminate ligand activity and contribute to a better understanding of insulin receptor signaling. We propose this methodology as a powerful approach to characterize agonists and antagonists of the insulin receptor and can be adapted to serve as a platform to evaluate ligands of alternate receptor systems.
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Affiliation(s)
- Anne M Cieniewicz
- Biologics Research, Janssen BioTherapeutics, Janssen R & D Spring House, PA 19477, USA.
| | - Philip R Cooper
- Biologics Research, Janssen BioTherapeutics, Janssen R & D Spring House, PA 19477, USA
| | - Jennifer McGehee
- Biologics Research, Janssen BioTherapeutics, Janssen R & D Spring House, PA 19477, USA
| | - Russell B Lingham
- Biologics Research, Janssen BioTherapeutics, Janssen R & D Spring House, PA 19477, USA
| | - Anthony J Kihm
- Biologics Research, Janssen BioTherapeutics, Janssen R & D Spring House, PA 19477, USA.
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5
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Basciano H, Miller A, Baker C, Naples M, Adeli K. LXRalpha activation perturbs hepatic insulin signaling and stimulates production of apolipoprotein B-containing lipoproteins. Am J Physiol Gastrointest Liver Physiol 2009; 297:G323-32. [PMID: 19497957 DOI: 10.1152/ajpgi.90546.2008] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Liver X receptor-alpha (LXRalpha) is considered a master regulator of hepatic lipid metabolism; however, little is known about the link between LXR activation, hepatic insulin signaling, and very low-density lipoprotein (VLDL)-apolipoprotein B (apoB) assembly and secretion. Here, we examined the effect of LXRalpha activation on hepatic insulin signaling and apoB-lipoprotein production. In vivo activation of LXRalpha for 7 days using a synthetic LXR agonist, TO901317, in hamsters led to increased plasma triglyceride (TG; 3.6-fold compared with vehicle-treated controls, P = 0.006), apoB (54%, P < 0.0001), and VLDL-TG (eightfold increase compared with vehicle). As expected, LXR stimulation activated maturation of sterol response element binding protein-1c (SREBP-1c) as well as the SREBP-1c target genes steroyl CoA desaturase (SCD) and fatty acid synthase (FAS). Metabolic pulse-chase labeling experiments in primary hamster hepatocytes showed increased stability and secretion of newly synthesized apoB following LXR activation. Microsomal triglyceride transfer protein (MTP) mRNA and protein were unchanged, however, likely because of the relatively short period of treatment and long half-life of MTP mRNA. Examination of hepatic insulin-signaling molecules revealed LXR-mediated reductions in insulin receptor (IR)beta subunit mass (39%, P = 0.014) and insulin receptor substrate (IRS)-1 tyrosine phosphorylation (24%, P = 0.023), as well as increases in protein tyrosine phosphatase (PTP)1B (29%, P < 0.001) protein mass. In contrast to IRS-1, a twofold increase in IRS-2 mass (228%, P = 0.0037) and a threefold increase in IRS-2 tyrosine phosphorylation (321%, P = 0.012) were observed. In conclusion, LXR activation dysregulates hepatic insulin signaling and leads to a considerable increase in the number of circulating TG-rich VLDL-apoB particles, likely due to enhanced hepatic assembly and secretion of apoB-containing lipoproteins.
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Affiliation(s)
- Heather Basciano
- Molecular Structure and Function, Research Institute, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
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6
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Johnson DR, O'Connor JC, Dantzer R, Freund GG. Inhibition of vagally mediated immune-to-brain signaling by vanadyl sulfate speeds recovery from sickness. Proc Natl Acad Sci U S A 2005; 102:15184-9. [PMID: 16217019 PMCID: PMC1257721 DOI: 10.1073/pnas.0507191102] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2005] [Indexed: 01/04/2023] Open
Abstract
To the ill patient with diabetes, the behavioral symptoms of sickness such as fatigue and apathy are debilitating and can prevent recuperation. Here we report that peripherally administered insulin-like growth factor 1 (IGF-1) attenuates LPS-dependent depression of social exploration (sickness) in nondiabetic (db/+) but not in diabetic (db/db) mice. We show that the insulin/IGF-1 mimetic vanadyl sulfate (VS) is effective at augmenting recovery from sickness in both db/+ and db/db mice. Specifically, peak illness was reached at 2 h for both VS and control animals injected with LPS, and VS mice recovered 50% faster than non-VS-treated animals. Examination of the mechanism of VS action in db/+ mice showed that VS paradoxically augmented peritoneal macrophage responsivity to LPS, increasing both peritoneal and ex vivo macrophage production of IL-1beta and IL-6 but not TNF-alpha. The effects of VS in promoting recovery from sickness were not restricted to LPS, because they were also observed after direct administration of IL-1beta. To explore the possibility that VS impairs immune-to-brain communication via vagal afferents, the vagally mediated satiety-inducing effects of cholecystokinin 8 were tested in db/+ mice. Cholecystokinin decreased food intake in saline-injected mice but not in VS-treated mice. VS also inhibited LPS-dependent up-regulation of IL-1beta and IL-6 mRNA in the brain, while increasing by 50% the cerebral expression of transcripts of the specific antagonist of IL-1 receptors IL-1RA and IL-1R2. Taken together, these data indicate that VS improves recovery from LPS-induced sickness by blocking vagally mediated immune-to-brain signaling and by up-regulating brain expression of IL-1beta antagonists.
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Affiliation(s)
- Daniel R Johnson
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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7
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Mingo-Sion AM, Ferguson HA, Koller E, Reyland ME, Van Den Berg CL. PKCdelta and mTOR interact to regulate stress and IGF-I induced IRS-1 Ser312 phosphorylation in breast cancer cells. Breast Cancer Res Treat 2005; 91:259-69. [PMID: 15952059 DOI: 10.1007/s10549-005-0669-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
IRS-1 (Insulin Receptor Substrate-1) is an adaptor protein important for insulin and IGF-I receptor (Insulin-like Growth Factor-IR) transduction to downstream targets. One mechanism recently identified to downregulate IGF-I or insulin receptor signaling in diabetic models is IRS-1 Ser(312) phosphorylation. To date, the importance of this residue in cancer is unknown. This paper identifies mechanisms leading to Ser(312) regulation in MCF-7 breast cancer cells. Whereas IGF-I phosphorylation of IRS(312) is PI (phosphatidylinositol) 3-kinase dependent, anisomycin stress treatment requires JNK activation to induce phosphorylation of IRS(312). We show that both IGF-I and anisomycin stress treatment converge downstream onto mTOR (Mammalian Target of Rapamycin) and PKCdelta (Protein Kinase C-delta) to induce IRS-1 Ser(312) phosphorylation. mTOR associates with IRS-1 and is primarily required for Ser(312) phosphorylation in response to stress or IGF-I treatment. PKCdelta binds to mTOR and its activity is also important for stress or IGF-I mediated Ser(312) phosphorylation. Thus, mTOR and PKCdelta convey diverse signals to regulate IRS-1 function.
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Affiliation(s)
- Amy M Mingo-Sion
- School of Pharmacy, School of Medicine, University of Colorado Health Sciences Center, Denver, CO 80272, USA
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8
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Huang C, Thirone ACP, Huang X, Klip A. Differential contribution of insulin receptor substrates 1 versus 2 to insulin signaling and glucose uptake in l6 myotubes. J Biol Chem 2005; 280:19426-35. [PMID: 15764603 DOI: 10.1074/jbc.m412317200] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Insulin receptor substrates-1 and 2 (IRS-1 and IRS-2) are pivotal in relaying insulin signaling in insulin-responsive tissues such as muscle. However, the precise contribution of IRS-1 vis-a-vis IRS-2 in insulin-mediated metabolic and mitogenic responses has not been compared directly in differentiated muscle cells. This study aimed to determine the relative contribution of IRS-1 versus IRS-2 in these responses, using small interfering RNA (siRNA)-mediated specific gene silencing. In L6 myotubes, transfection of siRNA targeted specifically against IRS-1 (siIRS-1) or IRS-2 (siIRS-2) reduced the cognate protein expression by 70-75%. Insulin-induced ERK phosphorylation was much more sensitive to IRS-2 than IRS-1 ablation, whereas p38MAPK phosphorylation was reduced by 43 or 62% in myotubes treated with siIRS-1 or siIRS-2, respectively. Insulin-induced Akt1 and Akt2 phosphorylation was reduced in myotubes treated with siIRS-1, but only Akt2 phosphorylation was reduced in myotubes treated with siIRS-2. In contrast, siIRS-1 treatment caused a marked reduction in insulin-induced actin remodeling, glucose uptake, and GLUT4 translocation, and siIRS-2 was without effect on these responses. Notably, combined siIRS-1 and siIRS-2, although reducing each IRS by around 75%, caused no further drop in glucose uptake than that achieved with siIRS-1 alone, but abolished p38MAPK phosphorylation. We conclude that insulin-stimulated Akt1 phosphorylation, actin remodeling, GLUT4 translocation, and glucose uptake are regulated mainly by IRS-1, whereas IRS-2 contributes selectively to ERK signaling, and Akt2 and p38MAPK lie downstream of both IRS in muscle cells.
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Affiliation(s)
- Carol Huang
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada
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9
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Huang SS, Leal SM, Chen CL, Liu IH, Huang JS. Cellular growth inhibition by TGF-β1involves IRS proteins. FEBS Lett 2004; 565:117-21. [PMID: 15135063 DOI: 10.1016/j.febslet.2004.03.082] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2004] [Revised: 03/24/2004] [Accepted: 03/24/2004] [Indexed: 11/17/2022]
Abstract
In Mv1Lu cells, insulin partially reverses transforming growth factor-beta1 (TGF-beta1) growth inhibition in the presence of alpha5beta1 integrin antagonists. TGF-beta1 appears to induce phosphorylation of IRS-2 in these cells; this is inhibited by a TGF-beta antagonist known to reverse TGF-beta growth inhibition. Stable transfection of 32D myeloid cells (which lack endogenous IRS proteins and are insensitive to growth inhibition by TGF-beta1) with IRS-1 or IRS-2 cDNA confers sensitivity to growth inhibition by TGF-beta1; this IRS-mediated growth inhibition can be partially reversed by insulin in 32D cells stably expressing IRS-2 and the insulin receptor (IR). These results suggest that growth inhibition by TGF-beta1 involves IRS proteins.
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Affiliation(s)
- Shuan Shian Huang
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, 1402 South Grand Boulevard, St. Louis, MO 63104, USA.
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10
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Suryawan A, Nguyen HV, Orellana RA, Bush JA, Davis TA. Insulin/insulin-like growth factor-I hybrid receptor abundance decreases with development in suckling pigs. J Nutr 2003; 133:2783-7. [PMID: 12949365 DOI: 10.1093/jn/133.9.2783] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The activation of the insulin signaling pathway that leads to translation initiation is enhanced in skeletal muscle of neonates, and decreases with development in parallel with the developmental decline in muscle protein synthesis. Because the elevated expression of insulin receptor (IR)/insulin-like growth factor-I receptor (IGF-IR) hybrids has been associated with insulin resistance in some studies, we hypothesized that IR/IGF-IR hybrid abundance and binding affinity increase with development. To test this hypothesis, we determined the abundances and binding affinities of the IR, IGF-IR and hybrid receptor in skeletal muscle of 7- and 26-d-old pigs. We found that the abundances of IR, IGF-IR and hybrid receptor were higher in muscle of 7- than 26-d-old pigs. However, the relative proportions of hybrid receptor abundance compared with IR abundance and IGF-IR abundance were similar at both ages. The binding affinities of the IR, IGF-IR and hybrid receptor also were similar at both ages. Overall, the results suggest that insulin/IGF-I hybrid receptor abundance and binding affinity do not contribute to the developmental decline in the activation of the insulin signaling pathway.
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Affiliation(s)
- Agus Suryawan
- US Department of Agriculture/Agriculture Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA
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11
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Abstract
Tyrosine dephosphorylation, serine phosphorylation, and proteasomal degradation of insulin receptor substrates (IRSs) are implicated in the negative regulation of insulin action. Here we show that simultaneous inhibition of IRS-1 tyrosine dephosphorylation and proteasomal degradation synergistically augments insulin-responsive glucose uptake. L6 skeletal muscle cells (L6 cells) were treated with inhibitors of protein-tyrosine phosphatases, proteasomal degradation, and mammalian target of rapamycin (mTOR), and the effects of insulin on glucose uptake, IRS-1 tyrosine phosphorylation, phosphatidylinositol (PI) 3-kinase activity, and IRS-1 mass were examined. Pretreatment of L6 cells with sodium orthovanadate (Na(3)VO(4)) plus the mTOR inhibitor rapamycin caused a 5-fold increase in insulin-responsive glucose uptake at 2 hours when compared to insulin alone. Evaluation of IRS-1 associated PI 3-kinase activity, IRS-1-associated p85 mass, and IRS-1 tyrosine phosphorylation showed that 2 hours after insulin addition they were reduced by 70% from maximal activity. Likewise, IRS-1 mass was reduced by 50%. When L6 cells were pretreated with Na(3)VO(4) plus the proteasome inhibitor MG-132 or the mTOR inhibitor rapamycin prior to insulin addition, IRS-1 mass loss as well as IRS-1/PI-3 kinase complex decay was blocked at 2 hours and PI 3-kinase activity was increased 2.5-fold and 4-fold, respectively, over insulin alone. Finally, treatment of L6 cells with subtherapeutic amounts of vanadyl sulfate and rapamycin induced a synergistic 3-fold increase in insulin-induced glucose uptake at 2 hours. These findings indicate that vanadium and rapamycin synergize to enhance glucose uptake by preventing IRS-1 mass loss and IRS-1/PI 3-kinase complex decay and may offer a new approach to enhance glucose transport in diabetes.
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Affiliation(s)
- Jason C O'Connor
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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12
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Hasan RN, Phukan S, Harada S. Differential regulation of early growth response gene-1 expression by insulin and glucose in vascular endothelial cells. Arterioscler Thromb Vasc Biol 2003; 23:988-93. [PMID: 12689920 DOI: 10.1161/01.atv.0000071351.07784.19] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Early growth response gene (Egr)-1 is a key transcription factor involved in vascular pathophysiology. Its role in diabetic vascular complications, however, remains unclear. Because hyperinsulinemia and hyperglycemia are major risk factors leading to diabetic vascular complications, we examined the effect of insulin and glucose on Egr-1 expression in murine glomerular vascular endothelial cells. METHODS AND RESULTS Insulin or glucose, when added separately, increased egr-1 mRNA levels and promoter activity, as well as Egr-1 protein levels in nuclear extracts. When insulin was added to cells preincubated with glucose, the two had an additive effect on Egr-1 expression. Furthermore, vascular endothelial growth factor receptor-1 (flt-1) and plasminogen activator inhibitor-1, two known Egr-1-responsive genes, were also upregulated in the presence of insulin or glucose. An investigation into the underlying molecular mechanisms demonstrated that insulin, but not glucose, increased Egr-1 expression through extracellular signal-regulated kinase 1/2 activation, which is consistent with our previous reports. In contrast, inhibition of protein kinase C by phorbol ester or by the specific protein kinase C inhibitor chelerythrine chloride downregulated glucose-induced, but not insulin-induced, Egr-1 expression. CONCLUSIONS Differential regulation of Egr-1 expression by insulin and glucose in vascular cells may be one of the initial key events that plays a crucial role in the development of diabetic vascular complications.
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Affiliation(s)
- Rukhsana N Hasan
- Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pa 19104, USA
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13
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Bifulco G, Di Carlo C, Caruso M, Oriente F, Di Spiezio Sardo A, Formisano P, Beguinot F, Nappi C. Glucose regulates insulin mitogenic effect by modulating SHP-2 activation and localization in JAr cells. J Biol Chem 2002; 277:24306-14. [PMID: 11983706 DOI: 10.1074/jbc.m202962200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The glucose effect on cell growth has been investigated in the JAr human choriocarcinoma cells. When JAr cells were cultured in the presence of 6 mm glucose (LG), proliferation and thymidine incorporation were induced by serum, epidermal growth factor, and insulin-like growth factor 1 but not by insulin. In contrast, at 25 mm glucose (HG), proliferation and thymidine incorporation were stimulated by insulin, serum, epidermal growth factor, and insulin-like growth factor 1 to a comparable extent, whereas basal levels were 25% lower than those in LG. HG culturing also enhanced insulin-stimulated insulin receptor and insulin receptor substrate 1 (IRS1) tyrosine phosphorylations while decreasing basal phosphorylations. These actions of glucose were accompanied by an increase in cellular tyrosine phosphatase activity. The activity of SHP-2 in HG-treated JAr cells was 400% of that measured in LG-treated cells. SHP-2 co-precipitation with IRS1 was also increased in HG-treated cells. SHP-2 was mainly cytosolic in LG-treated cells. However, HG culturing largely redistributed SHP-2 to the internal membrane compartment, where tyrosine-phosphorylated IRS1 predominantly localizes. Further exposure to insulin rescued SHP-2 cytosolic localization, thereby preventing its interaction with IRS1. Antisense inhibition of SHP-2 reverted the effect of HG on basal and insulin-stimulated insulin receptor and IRS1 phosphorylation as well as that on thymidine incorporation. Thus, in JAr cells, glucose modulates insulin mitogenic action by modulating SHP-2 activity and intracellular localization.
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Affiliation(s)
- Giuseppe Bifulco
- Dipartimento di Ginecologia, Ostetricia e Fisiopatologia della Riproduzione Umana, Università degli Studi di Napoli Federico II, 80131 Naples, Italy
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14
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Hirose M, Martyn JAJ, Kuroda Y, Marunaka Y, Tanaka Y. Mechanism of suppression of insulin signalling with lignocaine. Br J Pharmacol 2002; 136:76-80. [PMID: 11976270 PMCID: PMC1762118 DOI: 10.1038/sj.bjp.0704691] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Lignocaine suppresses insulin-stimulated glucose transport into the cells and insulin-stimulated glycogenesis at doses equivalent to that used in the treatment of muscle pain disorder. We evaluated the direct effect of lignocaine on insulin receptor (IR) kinase activity. After lignocaine (40 mM, approximately equivalent to 1%) or an equal volume (100 microl) saline had been injected into the tibialis anterior muscle of rat, insulin (50 mM g-1 body weight) was administered into the portal vein in vivo. Immunoprecipitation and immunoblotting were used to detect insulin-mediated tyrosine phosphorylation of both IR-beta and insulin receptor substrate (IRS)-1, and insulin-stimulated binding of IRS-1 to p85 regulatory subunit of phosphatidylinositol 3-kinase (PI3-K) in the extracted muscle. In the in vitro study, purified IR from rat liver and/or recombinant IRS-1 protein with adenosine triphosphate were incubated with lignocaine (4 or 40 mM). Lignocaine reduced insulin-stimulated tyrosine phosphorylation of IR-beta to 12.6+/-5.7% (P<0.001), and IRS-1 to 32.1+/-18.8% (P<0.01), and also reduced insulin-stimulated binding of IRS-1 to p85 to 27.4+/-12.7% (P<0.001) relative to control (100%) in muscle in vivo. The in vitro study revealed that lignocaine directly inhibited both basal and insulin-stimulated tyrosine phosphorylation of IR. These results indicate that clinically used doses of lignocaine inhibit insulin signalling in skeletal muscle. The inhibitory effect of lignocaine on tyrosine kinase activity of the IR underlies the suppression of insulin signalling with lignocaine.
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Affiliation(s)
- Munetaka Hirose
- Department of Anaesthesiology, Kyoto Prefectural University of Medicine, Kamigyoku, Kyoto 602-8566, Japan.
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15
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Suryawan A, Nguyen HV, Bush JA, Davis TA. Developmental changes in the feeding-induced activation of the insulin-signaling pathway in neonatal pigs. Am J Physiol Endocrinol Metab 2001; 281:E908-15. [PMID: 11595645 DOI: 10.1152/ajpendo.2001.281.5.e908] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In neonatal animals, feeding stimulates skeletal muscle protein synthesis, a response that declines with development. Both the magnitude of the feeding response and its developmental decline can be reproduced by insulin infusion, suggesting that an altered responsiveness to insulin is a primary determinant of the developmental decline in the stimulation of protein synthesis by feeding. In this study, 7- and 26-day-old pigs were either fasted overnight or fed porcine milk after an overnight fast. We examined the abundance and degree of tyrosine phosphorylation of the insulin receptor (IR), insulin receptor substrate-1 (IRS-1), and IRS-2 in skeletal muscle and, for comparison, liver. We also evaluated the association of IRS-1 and IRS-2 with phosphatidylinositol 3-kinase (PI 3-kinase). The abundance of IR protein in muscle was twofold higher at 7 than at 26 days, but IRS-1 and IRS-2 abundances were similar in muscle of 7- and 26-day-old pigs. The feeding-induced phosphorylations were greater at 7 than at 26 days of age for IR (28- vs. 13-fold), IRS-1 (14- vs. 8-fold), and IRS-2 (21- vs. 12-fold) in muscle. The associations of IRS-1 and IRS-2 with PI 3-kinase were also increased by refeeding to a greater extent at 7 than at 26 days (9- vs. 5-fold and 6- vs. 4-fold, respectively). In liver, the abundance of IR, IRS-1, and IRS-2 was similar at 7 and 26 days of age. Feeding increased the activation of IR, IRS-1, IRS-2, and PI 3-kinase in liver only twofold, and these responses were unaffected by age. Thus our findings demonstrate that the feeding-induced activation of IR, IRS-1, IRS-2, and PI 3-kinase in skeletal muscle decreases with development. Further study is needed to ascertain whether the developmental decline in the feeding-induced activation of early insulin-signaling components contributes to the developmental decline in translation initiation in skeletal muscle.
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Affiliation(s)
- A Suryawan
- United States Department of Agriculture/Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030, USA
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Ozawa T, Kaihara A, Sato M, Tachihara K, Umezawa Y. Split luciferase as an optical probe for detecting protein-protein interactions in mammalian cells based on protein splicing. Anal Chem 2001; 73:2516-21. [PMID: 11403293 DOI: 10.1021/ac0013296] [Citation(s) in RCA: 187] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We describe a new method for detecting protein-protein interactions in intact mammalian cells; the approach is based on protein splicing-induced complementation of rationally designed fragments of firefly luciferase. The protein splicing is a posttranslational protein modification through which inteins (internal proteins) are excised out from a precursor fusion protein, ligating the flanking exteins (external proteins) into a contiguous polypeptide. As the intein, naturally split DnaE from Synechocystis sp. PCC6803 was used: The N- and C-terminal DnaE, each fused respectively to N- and C-terminal fragments of split luciferase, were connected to proteins of interest. In this approach, protein-protein interactions trigger the folding of DnaE intein, wherein the protein splicing occurs and thereby the extein of ligated luciferase recovers its enzymatic activity. To test the applicability of this split luciferase complementation, we used insulin-induced interaction between known binding partners, phosphorylated insulin receptor substrate 1 (IRS-1) and its target N-terminal SH2 domain of PI 3-kinase. Enzymatic luciferase activity triggered by insulin served to monitor the interaction between IRS-1 and the SH2 domain in an insulin dose-dependent manner, of which amount was assessed by the luminescent intensity. This provides a convenient method to study phosphorylation of any protein or interactions of integral membrane proteins, a class of molecules that has been difficult to study by existing biochemical or genetic methods. High-throughput drug screening and quantitative analysis for a specific pathway in tyrosine phosphorylation of IRS-1 in insulin signaling are also made possible in this system.
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Affiliation(s)
- T Ozawa
- Department of Chemistry, School of Science, The University of Tokyo, Japan
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Poltilove RM, Jacobs AR, Haft CR, Xu P, Taylor SI. Characterization of Drosophila insulin receptor substrate. J Biol Chem 2000; 275:23346-54. [PMID: 10801879 DOI: 10.1074/jbc.m003579200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Insulin receptor substrate (IRS) proteins are phosphorylated by multiple tyrosine kinases, including the insulin receptor. Phosphorylated IRS proteins bind to SH2 domain-containing proteins, thereby triggering downstream signaling pathways. The Drosophila insulin receptor (dIR) C-terminal extension contains potential binding sites for signaling molecules, suggesting that dIR might not require an IRS protein to accomplish its signaling functions. However, we obtained a cDNA encoding Drosophila IRS (dIRS), and we demonstrated expression of dIRS in a Drosophila cell line. Like mammalian IRS proteins, the N-terminal portion of dIRS contains a pleckstrin homology domain and a phosphotyrosine binding domain that binds to phosphotyrosine residues in both human and Drosophila insulin receptors. When coexpressed with dIRS in COS-7 cells, a chimeric receptor (the extracellular domain of human IR fused to the cytoplasmic domain of dIR) mediated insulin-stimulated tyrosine phosphorylation of dIRS. Mutating the juxtamembrane NPXY motif markedly reduced the ability of the receptor to phosphorylate dIRS. In contrast, the NPXY motifs in the C-terminal extension of dIR were required for stable association with dIRS. Coimmunoprecipitation experiments demonstrated insulin-dependent binding of dIRS to phosphatidylinositol 3-kinase and SHP2. However, we did not detect interactions with Grb2, SHC, or phospholipase C-gamma. Taken together with published genetic studies, these biochemical data support the hypothesis that dIRS functions directly downstream from the insulin receptor in Drosophila.
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Affiliation(s)
- R M Poltilove
- Diabetes Branch, NIDDKD, National Institutes of Health, Bethesda, Maryland 20892, USA
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