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Gambioli R, Montanino Oliva M, Nordio M, Chiefari A, Puliani G, Unfer V. New Insights into the Activities of D-Chiro-Inositol: A Narrative Review. Biomedicines 2021; 9:biomedicines9101378. [PMID: 34680494 PMCID: PMC8533370 DOI: 10.3390/biomedicines9101378] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 09/29/2021] [Accepted: 09/30/2021] [Indexed: 12/14/2022] Open
Abstract
D-chiro-inositol (DCI) is a natural compound detectable in cell membranes, which is highly conserved as a biological signaling molecule. In mammals, its function is primarily characterized in the intracellular transduction cascade of insulin. In particular, insulin signal promotes the release of pivotal DCI-containing molecules. In fact, impaired release of DCI is a common feature of insulin-resistant tissues, and insulin-sensitizing pharmaceuticals induce higher concentrations of free DCI. Moreover, it also plays important roles in several other processes. DCI is involved in the regulation of steroidogenesis, due to its regulatory effects on steroidogenic enzymes, including 17α-hydroxylase, 3β-hydroxysteroid dehydrogenase, and aromatase. Such regulation of various enzymes indicates a mechanism by which the body regulates different processes via a single molecule, depending on its concentration. DCI also reduces the expression of integrin β3, which is an adhesion molecule involved in embryo implantation and cellular phenomena such as survival, stemness, and invasiveness. In addition, DCI seems to have important anti-inflammatory activities, like its 3-O-methyl-ether, called pinitol. In vitro evidence demonstrates that treatment with both compounds induces a reduction in pro-inflammatory factors—such as Nf-κB—and cytokines—such as TNF-α. DCI then plays important roles in several fundamental processes in physiology. Therefore, research on such molecule is of primary importance.
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Affiliation(s)
| | - Mario Montanino Oliva
- The Experts Group on Inositol in Basic and Clinical Research (EGOI), 00161 Rome, Italy; (M.M.O.); (M.N.)
- Department of Obstetrics and Gynecology, Santo Spirito Hospital, 00193 Rome, Italy
| | - Maurizio Nordio
- The Experts Group on Inositol in Basic and Clinical Research (EGOI), 00161 Rome, Italy; (M.M.O.); (M.N.)
- Department of Experimental Medicine, Sapienza University, 00185 Rome, Italy
| | - Alfonsina Chiefari
- Oncological Endocrinology Unit, IRCCS Regina Elena National Cancer Institute, 00144 Rome, Italy; (A.C.); (G.P.)
| | - Giulia Puliani
- Oncological Endocrinology Unit, IRCCS Regina Elena National Cancer Institute, 00144 Rome, Italy; (A.C.); (G.P.)
| | - Vittorio Unfer
- The Experts Group on Inositol in Basic and Clinical Research (EGOI), 00161 Rome, Italy; (M.M.O.); (M.N.)
- System Biology Group Lab, 00161 Rome, Italy
- Correspondence:
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López-Gambero AJ, Sanjuan C, Serrano-Castro PJ, Suárez J, Rodríguez de Fonseca F. The Biomedical Uses of Inositols: A Nutraceutical Approach to Metabolic Dysfunction in Aging and Neurodegenerative Diseases. Biomedicines 2020; 8:biomedicines8090295. [PMID: 32825356 PMCID: PMC7554709 DOI: 10.3390/biomedicines8090295] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 08/17/2020] [Accepted: 08/18/2020] [Indexed: 02/05/2023] Open
Abstract
Inositols are sugar-like compounds that are widely distributed in nature and are a part of membrane molecules, participating as second messengers in several cell-signaling processes. Isolation and characterization of inositol phosphoglycans containing myo- or d-chiro-inositol have been milestones for understanding the physiological regulation of insulin signaling. Other functions of inositols have been derived from the existence of multiple stereoisomers, which may confer antioxidant properties. In the brain, fluctuation of inositols in extracellular and intracellular compartments regulates neuronal and glial activity. Myo-inositol imbalance is observed in psychiatric diseases and its use shows efficacy for treatment of depression, anxiety, and compulsive disorders. Epi- and scyllo-inositol isomers are capable of stabilizing non-toxic forms of β-amyloid proteins, which are characteristic of Alzheimer’s disease and cognitive dementia in Down’s syndrome, both associated with brain insulin resistance. However, uncertainties of the intrinsic mechanisms of inositols regarding their biology are still unsolved. This work presents a critical review of inositol actions on insulin signaling, oxidative stress, and endothelial dysfunction, and its potential for either preventing or delaying cognitive impairment in aging and neurodegenerative diseases. The biomedical uses of inositols may represent a paradigm in the industrial approach perspective, which has generated growing interest for two decades, accompanied by clinical trials for Alzheimer’s disease.
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Affiliation(s)
- Antonio J. López-Gambero
- Departamento de Biología Celular, Genética y Fisiología, Campus de Teatinos s/n, Universidad de Málaga, Andalucia Tech, 29071 Málaga, Spain;
- UGC Salud Mental, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Universitario Regional de Málaga, 29010 Málaga, Spain
| | | | - Pedro Jesús Serrano-Castro
- UGC Neurología, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Universitario Regional de Málaga, 29010 Málaga, Spain;
| | - Juan Suárez
- UGC Salud Mental, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Universitario Regional de Málaga, 29010 Málaga, Spain
- Correspondence: (J.S.); (F.R.d.F.); Tel.: +34-952614012 (J.S.)
| | - Fernando Rodríguez de Fonseca
- UGC Salud Mental, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Universitario Regional de Málaga, 29010 Málaga, Spain
- Correspondence: (J.S.); (F.R.d.F.); Tel.: +34-952614012 (J.S.)
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Monastra G, Unfer V, Harrath AH, Bizzarri M. Combining treatment with myo-inositol and D-chiro-inositol (40:1) is effective in restoring ovary function and metabolic balance in PCOS patients. Gynecol Endocrinol 2017; 33:1-9. [PMID: 27898267 DOI: 10.1080/09513590.2016.1247797] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Polycystic ovary syndrome (PCOS), a relevant cause of infertility, is a heterogeneous, endocrine disorder affecting up to 10-15% of women in reproductive age. Besides hyperandrogenism, insulin resistance (IR) plays a key role in such syndrome. Insulin-sensitizing drugs, such as Metformin, are effective in treating hyper-insulinemic PCOS patients. Recently, inositols - myo-inositol (MI) and D-chiro-inositol (DCI) - have shown to be an efficient and safe alternative in PCOS management, as both inositol isoforms are able to counteract downstream consequences of insulin resistance. Yet, whereas DCI contributes in mediating insulin activity mainly on non-ovarian tissues, MI displays specific effects on ovary, chiefly by modulating glucose metabolism and FSH-signaling. Moreover, MI may also improve ovarian functions by modulating steroid metabolism through non-insulin-dependent pathways. As DCI and MI activity likely involves different biological mechanisms, both inositol isoforms can be synergistically integrated according to a multitargeted design, by combining MI and DCI in a ratio corresponding to their physiological plasma relative amount (40:1). New experimental and clinical evidence with MI plus DCI evidenced the suitability of such integrated approach, and provided promising results. Further studies need to investigate thoroughly the molecular mechanism and confirm such preliminary data.
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Affiliation(s)
- Giovanni Monastra
- a Visiting scientist at the Systems Biology Group, Department of Experimental Medicine, University la Sapienza , Rome , Italy
| | - Vittorio Unfer
- b Department of Medical Sciences , IPUS - Institute of Higher Education , Chiasso , Switzerland
| | - Abdel Halim Harrath
- c Department of Zoology , College of Science, King Saud University , Riyadh , Saudi Arabia , and
| | - Mariano Bizzarri
- d Department of Experimental Medicine , Systems Biology Group, University la Sapienza , Rome , Italy
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Dinicola S, Chiu TTY, Unfer V, Carlomagno G, Bizzarri M. The rationale of the myo-inositol and D-chiro-inositol combined treatment for polycystic ovary syndrome. J Clin Pharmacol 2014; 54:1079-92. [PMID: 25042908 DOI: 10.1002/jcph.362] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Accepted: 07/10/2014] [Indexed: 01/11/2023]
Abstract
PCOS is one of the most common endocrine disorders affecting women and it is characterized by a combination of hyper-androgenism, chronic anovulation, and insulin resistance. While a significant progress has recently been made in the diagnosis for PCOS, the optimal infertility treatment remains to be determined. Two inositol isomers, myo-inositol (MI) and D-chiro-inositol (DCI) have been proven to be effective in PCOS treatment, by improving insulin resistance, serum androgen levels and many features of the metabolic syndrome. However, DCI alone, mostly when it is administered at high dosage, negatively affects oocyte quality, whereas the association MI/DCI, in a combination reproducing the plasma physiological ratio (40:1), represents a promising alternative in achieving better clinical results, by counteracting PCOS at both systemic and ovary level.
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Affiliation(s)
- Simona Dinicola
- Dept of Experimental Medicine, Systems Biology Group, University La Sapienza, Roma, Italy
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Croze ML, Soulage CO. Potential role and therapeutic interests of myo-inositol in metabolic diseases. Biochimie 2013; 95:1811-27. [PMID: 23764390 DOI: 10.1016/j.biochi.2013.05.011] [Citation(s) in RCA: 348] [Impact Index Per Article: 31.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Accepted: 05/30/2013] [Indexed: 02/08/2023]
Abstract
Several inositol isomers and in particular myo-inositol (MI) and D-chiro-inositol (DCI), were shown to possess insulin-mimetic properties and to be efficient in lowering post-prandial blood glucose. In addition, abnormalities in inositol metabolism are associated with insulin resistance and with long term microvascular complications of diabetes, supporting a role of inositol or its derivatives in glucose metabolism. The aim of this review is to focus on the potential benefits of a dietary supplement of myo-inositol, by far the most common inositol isomer in foodstuffs, in human disorders associated with insulin resistance (polycystic ovary syndrome, gestational diabetes mellitus or metabolic syndrome) or in prevention or treatment of some diabetic complications (neuropathy, nephropathy, cataract). The relevance of such a nutritional strategy will be discussed for each context on the basis of the clinical and/or animal studies. The dietary sources of myo-inositol and its metabolism from its dietary uptake to its renal excretion will be also covered in this review. Finally, the actual insights into inositol insulin-sensitizing effects will be addressed and in particular the possible role of inositol glycans as insulin second messengers.
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Affiliation(s)
- Marine L Croze
- Université de Lyon, INSA de Lyon, CarMeN, INSERM U1060, Univ Lyon-1, F-69621 Villeurbanne, France.
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Hecht ML, Tsai YH, Liu X, Wolfrum C, Seeberger PH. Synthetic inositol phosphoglycans related to GPI lack insulin-mimetic activity. ACS Chem Biol 2010; 5:1075-86. [PMID: 20825209 DOI: 10.1021/cb1002152] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Insulin signaling has been suggested, at least in part, to be affected by an insulin-mimetic species of low molecular weight. These inositol phosphoglycans (IPGs) are generated upon growth hormone/cytokine stimulation and control the activity of a multitude of insulin effector enzymes. The minimal structural requirements of IPGs for insulin-mimetic action have been debated. Two types of IPGs were suggested, and the IPG-A type resembles the core glycan of glycosylphosphatidylinositol (GPI)-anchors. In fact, purified GPI-anchors of lower eukaryotic origin have been shown to influence glucose homeostasis. To elucidate active IPGs, a collection of synthetic IPGs designed on the basis of previous reports of activity were tested for their insulin-mimetic activity. In vitro and ex vivo assays in rodent adipose tissue as well as in vivo analyses in mice were employed to test the synthetic IPGs. None of the IPGs we tested mimic insulin actions as determined by PKB/Akt phosphorylation and quantification of glucose transport and lipogenesis. Furthermore, none of the IPGs had any effect in in vivo insulin tolerance assays. In stark contrast to previous claims, we conclude that neither of the compounds tested is insulin-mimetic.
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Affiliation(s)
- Marie-Lyn Hecht
- Department of Biomolecular Systems, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
- Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany
- Laboratory of Organic Chemistry, Swiss Federal Institute of Technology (ETH) Zurich, 8093 Zurich, Switzerland
- Competence Center for Systems Physiology and Metabolic Diseases, Zurich, 8093 Zurich, Switzerland
| | - Yu-Hsuan Tsai
- Department of Biomolecular Systems, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
- Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany
| | - Xinyu Liu
- Laboratory of Organic Chemistry, Swiss Federal Institute of Technology (ETH) Zurich, 8093 Zurich, Switzerland
| | - Christian Wolfrum
- Competence Center for Systems Physiology and Metabolic Diseases, Zurich, 8093 Zurich, Switzerland
- Institute of Molecular Systems Biology, Swiss Federal Institute of Technology (ETH) Zurich, 8093 Zurich, Switzerland
| | - Peter H. Seeberger
- Department of Biomolecular Systems, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
- Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany
- Laboratory of Organic Chemistry, Swiss Federal Institute of Technology (ETH) Zurich, 8093 Zurich, Switzerland
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Raikwar NS, Bowen-Deeg RF, Du XS, Low MG, Deeg MA. Glycosylphosphatidylinositol-specific phospholipase D improves glucose tolerance. Metabolism 2010; 59:1413-20. [PMID: 20153004 DOI: 10.1016/j.metabol.2008.11.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2008] [Accepted: 11/18/2008] [Indexed: 01/02/2023]
Abstract
Insulin regulation of energy metabolism is complex and involves numerous signaling cascades. Insulin has been suggested to stimulate a phospholipase that cleaves glycosylphosphatidylinositols resulting in the generation of an inositol glycan that serves as an insulin mediator. To determine if glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) may play a role in glucose metabolism, we examined the effect of overexpressing GPI-PLD using adenovirus-mediated gene transfer in C57BL/6 mice. Overexpressing GPI-PLD was associated with a decrease in fasting glucose as well as an improvement in glucose tolerance as determined by an intraperitoneal glucose tolerance test. This effect to improve glucose tolerance does not result from an increase in insulin sensitivity, as overexpressing GPI-PLD does not alter the response to insulin. In contrast, the insulin response during the glucose tolerance test in GPI-PLD-overexpressing mice was increased. Overexpressing GPI-PLD in an insulinoma cell line enhanced glucose-stimulated insulin secretion, suggesting that enhanced insulin secretion in vivo may have contributed to the improved glucose tolerance.
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Affiliation(s)
- Nandita S Raikwar
- Department of Medicine and of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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Baillargeon JP, Iuorno MJ, Apridonidze T, Nestler JE. Uncoupling between insulin and release of a D-chiro-inositol-containing inositolphosphoglycan mediator of insulin action in obese women With polycystic ovary syndrome. Metab Syndr Relat Disord 2010; 8:127-36. [PMID: 20156067 DOI: 10.1089/met.2009.0052] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Obese women with polycystic ovary syndrome (PCOS) manifest impaired insulin-stimulated release of a d-chiro-inositol-containing inositolphosphoglycan (DCI-IPG) insulin mediator during oral glucose tolerance testing (OGTT), which appears to be restored by the administration of metformin. This suggests that either obesity or PCOS is associated with a defect in the coupling of the stimulation of the insulin receptor by insulin to the release of the DCI-IPG mediator. The objective of this study was to compare the release of bioactive DCI-IPG between normal nonobese women and obese PCOS women during stimulation with two different concentrations of insulin when glucose levels are clamped. METHODS We performed a cross-sectional case-control study at the clinical research center of an academic medical center. A two-step euglycemic-hyperinsulinemic clamp was carried out in 8 nonobese normal and 8 obese PCOS women, during which DCI-IPG bioactivity was monitored. RESULTS At baseline, PCOS women were significantly more obese, hyperinsulinemic, and insulin resistant than the controls. During the clamp studies, DCI-IPG bioactivity increased significantly over the first 45 min of the low-insulin step of the clamp in normal nonobese women (P = 0.046) and then decreased to baseline levels; DCI-IPG increased again after initiation of the high-insulin step (P = 0.029). Despite higher insulin levels during the clamp in PCOS women, DCI-IPG bioactivity remained flat throughout both insulin steps and was thus significantly lower than in controls during the initial periods of both steps. CONCLUSIONS The coupling between insulin action and the release of the DCI-IPG mediator is selectively impaired in obese PCOS women, which may contribute to the insulin resistance in these women.
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Affiliation(s)
- Jean-Patrice Baillargeon
- Department of Medicine, Division of Endocrinology, Université de Sherbrooke, Sherbrooke, Quebec, Canada.
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Scioscia M, Gumaa K, Whitten M, Selvaggi LE, Rodeck CH, Rademacher TW. Inositol phosphoglycan P-type in healthy and preeclamptic pregnancies. J Reprod Immunol 2007; 76:85-90. [PMID: 17493685 DOI: 10.1016/j.jri.2007.03.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2007] [Revised: 03/26/2007] [Accepted: 03/28/2007] [Indexed: 10/23/2022]
Abstract
An association between inositol phosphoglycan P-type (P-IPG) and preeclampsia has been demonstrated over recent years. This molecule can mediate many of the metabolic and growth promoting effects of insulin. Dysregulation of the mediator family is associated with insulin resistance. An increased concentration of P-IPG has been reported in preeclamptic placenta, although its precursor (GPI) was undetectable in those placental samples. Insulin administration, that induces P-IPG release in normal human placenta, was shown not to cause production/release of the mediator from preeclamptic placental tissue as a consequence of a disturbed insulin signalling. Amniotic fluid is enriched of this mediator, with further increase during preeclampsia. We have found that the fetus released increasing amounts of P-IPG in the urine between 13 and 18 weeks of gestation, reaching a plateau beyond 20 weeks. Cord blood of infants of preeclamptic mothers showed an increased content of soluble P-IPG compared to controls and to the mother.
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Affiliation(s)
- Marco Scioscia
- Department of Immunology and Molecular Pathology, Molecular Medicine Unit, Royal Free and University College London Medical School, London, UK.
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Scioscia M, Gumaa K, Kunjara S, Paine MA, Selvaggi LE, Rodeck CH, Rademacher TW. Insulin resistance in human preeclamptic placenta is mediated by serine phosphorylation of insulin receptor substrate-1 and -2. J Clin Endocrinol Metab 2006; 91:709-17. [PMID: 16332940 DOI: 10.1210/jc.2005-1965] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Preeclampsia is a severe complication of human pregnancy often associated with maternal risk factors. Insulin resistance represents a major risk for developing preeclampsia during pregnancy. OBJECTIVE A putative second messenger of insulin, inositol phosphoglycan P type (P-IPG), was previously shown to be highly increased during active preeclampsia. Its association with insulin resistance was investigated. DESIGN AND SETTING A cross-sectional study was carried out in a referral center. PATIENTS Nine preeclamptic (PE) and 18 healthy women were recruited and matched for maternal age, body mass index, parity, and ethnicity in a 1:2 ratio. Placental specimens were collected immediately after delivery. INTERVENTION Placental tissue was incubated with insulin and P-IPG production assessed. Insulin signaling proteins were subsequently studied by immunoblotting. RESULTS P-IPG extracted from human term placentas upon incubation with insulin was found to be far lower in those with preeclampsia than controls (P < 0.001). Immunoblotting studies revealed serine phosphorylation of insulin receptor substrate-1 and -2 in PE placentas (P < 0.001) with downstream impairment of insulin signaling. The activation of the p85 regulatory subunit of phosphatidylinositol 3- kinase was markedly decreased in PE samples (P < 0.001). CONCLUSIONS These findings highlight the importance of P-IPG in active preeclampsia and demonstrate a substantially different response to the insulin stimulus of human PE placentas. Acquired alterations in activation of proteins involved in insulin signaling may play a role in the complex pathogenesis of preeclampsia, probably as a consequence of the immunological dysfunction that occurs in this syndrome. These results seem to confirm an insulin-resistant state in PE placenta and shed a different light on its role in the pathogenesis of this disease with potential therapeutic implications.
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Affiliation(s)
- Marco Scioscia
- Department of Obstetrics and Gynaecology, University of Bari, Policlinico di Bari, Piazza Giulio Cesare 11, 70125 Bari, Italy.
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Chevalier F, Lopez-Prados J, Perez S, Martín-Lomas M, Nieto PM. Conformational Study of GPI Anchors: the Common Oligosaccharide GPI Anchor Backbone. European J Org Chem 2005. [DOI: 10.1002/ejoc.200500171] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Martini CN, Vaena de Avalos SG, del Carmen Vila M. ACTH stimulates the release of alkaline phosphatase through Gi-mediated activation of a phospholipase C and the release of inositol-phosphoglycan. Mol Cell Biochem 2004; 258:191-9. [PMID: 15030184 DOI: 10.1023/b:mcbi.0000012855.94291.dd] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We have previously reported that ACTH activates a phospholipase C that hydrolyzes glycosylphosphatidylinositol (GPI), which would release inositolphosphoglycan (IPG) to the extracellular medium, and that an IPG purified from Trypanosoma cruzi is able to inhibit ACTH-mediated steroid production in adrenocortical cells. In the present paper, it was found that anti-inositolphosphoglycan antibodies (anti-CRD) increased ACTH-mediated corticosterone production, which indicates that an endogenous IPG is a physiological inhibitor of ACTH response. On the other hand, we investigated the release to the extracellular medium of the GPI-anchored enzyme, alkaline phosphatase, by ACTH. We found that: (a) the released enzyme appeared in the aqueous phase after Triton X-114 partitioning, consistent with loss of the GPI, (b) the phospholipase C inhibitor, U73122, impaired the release of the enzyme by the hormone and (c) two inhibitors of IPG uptake, inositol 2-monophosphate and 2 M NaCl, increased the amount of alkaline phosphatase in the extracellular medium. These results suggest that ACTH releases alkaline phosphatase by activation of a phospholipase C. Dibutyryladenosine-3',5'-cyclic monophosphate (db-cAMP) was able to increase the release of alkaline phosphatase from adrenocortical cells and this effect was inhibited by U73122, suggesting that cAMP is involved in the activation of phospholipase C. In addition, it was found that a pertussis-toxin sensitive G-protein is required for ACTH- and db-cAMP-mediated release of alkaline phosphatase and that incorporation of anti-Gi antibodies in adrenocortical cells inhibited the release of alkaline phosphatase by ACTH. Our results suggest that ACTH increases the release of alkaline phosphatase by activation of a phospholipase C through cAMP and Gi which would contribute to produce IPG It was also found that the two inhibitors of IPG uptake, inositol-2-monophosphate and 2 M NaCl, increased the amount of alkaline phosphatase in the extracellular medium of ACTH-treated cells more than in control cells, indicating that ACTH also stimulates the uptake of IPG These data support a role of GPI and the involvement of Gi in ACTH action.
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Affiliation(s)
- Claudia N Martini
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón 2, Ciudad Universitaria, 1428, Buenos Aires, Argentina
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Stanciu IN, Pitale S, Prinz RA, Jakate S, Webb G, Steiner D, Braithwaite S, Gordon D, Emanuele MA. Insulinoma presenting with hyperandrogenism: a case report and a literature review. J Intern Med 2003; 253:484-9. [PMID: 12653879 DOI: 10.1046/j.1365-2796.2003.01132.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
An 18-year-old woman presented with a 6-month history of amenorrhoea and hyperandrogenism. Three months later she developed several episodes of fasting hypoglycaemia and was subsequently diagnosed with an insulinoma. Hyperinsulinaemia was observed in association with an elevated serum testosterone level. Surgical removal of the insulinoma resulted in resolution of the clinical and biochemical features of the polycystic ovarian syndrome (PCOS). Polycystic ovarian syndrome is unusual in a patient having an insulinoma. The rarity of this association may be the result of the late age of onset of this type of tumour, intermittent secretion of excessive insulin by the tumour, the degree of hyperinsulinism or other factors extrinsic to the insulin receptor that may facilitate insulin activity. However, we could not discover how our patient differs in having had PCOS from the majority of women with insulinoma who do not. If other patients with insulinoma are subsequently found to have hyperandrogenism, then this tumour might be added to the differential diagnosis of causes of anovulatory cycles and hyperandrogenaemia, although rare the association would be uncommon.
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Affiliation(s)
- I N Stanciu
- Department of Endocrinology and Metabolism, Loyola University Medical Center and Hines VA Hospital, Maywood, IL, USA
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Rizzo MA, Kraft CA, Watkins SC, Levitan ES, Romero G. Agonist-dependent traffic of raft-associated Ras and Raf-1 is required for activation of the mitogen-activated protein kinase cascade. J Biol Chem 2001; 276:34928-33. [PMID: 11466321 DOI: 10.1074/jbc.m105918200] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Stimulation of HIRcB fibroblasts with insulin leads to accumulation of active components of the mitogen-activated protein kinase cascade in endocytic compartments. However, the factors that regulate the mobilization of these components through the endocytic pathway and the relevance of this event to cellular signaling remain unclear. Here we report that Ras proteins are associated with lipid rafts in resting HIRcB fibroblasts. Ras is rapidly internalized into the endocytic compartment following stimulation with insulin. The redistribution of Ras is independent of its activation. Attachment of the C-terminal 20 amino acids of Ha-Ras to green fluorescent protein was sufficient to target this construct to the same loci as the endogenous Ras protein, indicating that Ras distribution is a consequence of the association of its lipid modified C terminus with membranes. Depletion of plasma membrane cholesterol delocalized Ras and blocked insulin-dependent Ras traffic. Cholesterol depletion also blocked insulin-dependent phosphorylation of MEK and mitogen-activated protein kinase (MAPK) but had no effects on the translocation and activation of Raf-1. A second inhibitor of endocytosis, cytochalasin D, also blocked insulin-dependent MAPK phosphorylation. Taken together, these results suggest that mobilization of active Raf-1 through the endocytic compartment is required for completion of the MAPK cascade.
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Affiliation(s)
- Megan A Rizzo
- Department of Pharmacology and Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
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15
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Shashkin PN, Wasner HK, Ortmeyer HK, Hansen BC. Prostaglandylinositol cyclic phosphate (cPIP): a novel second messenger of insulin action. Comparative analysis of two kinds of "insulin mediators". Diabetes Metab Res Rev 2001; 17:273-84. [PMID: 11544611 DOI: 10.1002/dmrr.218] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Insulin induces a broad spectrum of effects over a wide time interval. It also stimulates the phosphorylation of some cellular proteins, while decreasing the state of phosphorylation of others. These observations indicate the presence of different, but not necessarily mutually exclusive, pathways of insulin action. One well-known pathway represents a phosphorylation cascade initiated by the tyrosine kinase activity of the insulin receptor followed by involvement of different MAP-kinases. Another pathway suggests the existence of low molecular weight insulin mediators whose synthesis and/or release is initiated by insulin. Comparable analysis of two kinds of insulin mediators, namely inositolphosphoglycans and prostaglandylinositol cyclic phosphate (cPIP), has been carried out. It has been shown that the expression of a number of enzymes, such as phospholipase A(2), phospholipase C, cyclo-oxygenase and IRS-1-like enzyme, could regulate the biosynthesis of cPIP in both normal and diabetes-related conditions. Data on the activity of a key enzyme of cPIP biosynthesis termed cPIP synthase (IRS-1-like enzyme) in various monkey tissues before and twice during an euglycemic hyperinsulinemic clamp have been presented. It has been concluded that in vivo insulin increases cPIP synthase activity in both liver and subcutaneous adipose tissue of lean normal monkeys. It has been also suggested that abnormal production of cPIP could be related to several pathologies including glucocorticoid-induced insulin resistance and diabetic embryopathy. Further studies on cPIP and other types of insulin mediators are necessary to aid our understanding of insulin action.
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Affiliation(s)
- P N Shashkin
- Obesity and Diabetes Research Center, Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
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16
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Martín-Lomas M, Flores-Mosquera M, Chiara J. Attempted Synthesis of Type-A Inositolphosphoglycan Mediators – Synthesis of a Pseudohexasaccharide Precursor. European J Org Chem 2000. [DOI: 10.1002/(sici)1099-0690(200004)2000:8<1547::aid-ejoc1547>3.0.co;2-c] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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17
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Tachado SD, Mazhari-Tabrizi R, Schofield L. Specificity in signal transduction among glycosylphosphatidylinositols of Plasmodium falciparum, Trypanosoma brucei, Trypanosoma cruzi and Leishmania spp. Parasite Immunol 1999; 21:609-17. [PMID: 10583863 DOI: 10.1046/j.1365-3024.1999.00268.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Glycosylphosphatidylinositols (GPIs) and related glycoconjugates of parasite origin have been shown to regulate both the innate and acquired immune systems of the host. This is achieved through the activation of novel GPI-dependent signalling pathways in macrophages, lymphocytes and other cell types. Parasite GPIs impart at least two distinct signals to host cells through the structurally distinct inositolphosphoglycan (IPG) and fatty acid domains. Binding of IPG to as yet uncharacterized cell surface receptor(s) leads to activation of src-family protein tyrosine kinases: depending upon structure, GPI-derived fatty acids can either activate or antagonize protein kinase C, and may enter the sphingomyelinase pathway. The degree of fatty acid saturation may also contribute to signalling activity. Thus, variation in structure of parasite GPIs imparts different properties of signal transduction upon this class of glycolipid. The divergent activities of GPIs from various protozoal taxa reflect global aspects of the host/parasite relationship, suggesting that GPI signalling is a central determinant of disease in malaria, leishmaniasis and both American and African trypanosomiases.
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Affiliation(s)
- S D Tachado
- The Walter and Eliza Hall Institute of Medical Research, Post Office, Royal Melbourne Hospital, Parkville 3050 Victoria, Australia
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18
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Kunjara S, Wang DY, Greenbaum AL, McLean P, Kurtz A, Rademacher TW. Inositol phosphoglycans in diabetes and obesity: urinary levels of IPG A-type and IPG P-type, and relationship to pathophysiological changes. Mol Genet Metab 1999; 68:488-502. [PMID: 10607479 DOI: 10.1006/mgme.1999.2936] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Measurements have been made, in adult male diabetic patients and control subjects, of the urinary content of inositol phosphoglycans (IPGs), the IPG A-type and IPG P-type forms, which, among other actions, regulate pathways of glucose utilization, lipogenesis, triglyceride formation, and pyruvate dehydrogenase (PDH) activity. Urine samples from the entire diabetic group showed a 2- to 3-fold increase in IPG A-type, and a fall in the IPG P-type:IPG A-type ratio relative to the control group. Subdivision of the diabetic patients into lean IDDM and obese NIDDM groups revealed significant differences in the IPG P-type:IPG A-type ratio between these groups, this ratio decreasing with increases in the body mass index (BMI). Analysis of the relationships among IPGs and HbA1, blood pressure, and BMI indicated that a fall in the IPG P-type:IPG A-type ratio correlated with a rise in the HbA1 (indicative of impaired glycemic control), with increased systolic blood pressure and increased obesity, all factors linked to Syndrome X. There was a parallism between the profile of the IPG P-type:IPG A-type ratio and the well-established pattern of insulin resistance and BMI. In vitro studies of the effects of alterations in the IPG P-type:IPG A-type ratio on the activation of the pyruvate dehydrogenase complex (PDH complex) at the PDH phosphatase reaction demonstrated that IPG A-type forms antagonized the stimulation of the PDH phosphatase by IPG P-type forms, thus having a negative effect on the conversion of PDH to the active, dephosphorylated, form. This observation could provide a mechanism whereby the shifts in the IPG P-type:IPG A-type ratio reported above could change the metabolic pattern from one directed to glucose oxidation to one more directed toward energy conservation and lipid storage.
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Affiliation(s)
- S Kunjara
- Department of Molecular Pathology, Molecular Medicine Unit, University College London Medical School, The Windeyer Building, 46, Cleveland Street, London, W1P 6DB, United Kingdom
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19
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Nestler JE. Inositolphosphoglycans (IPGs) as mediators of insulin's steroidogenic actions. J Basic Clin Physiol Pharmacol 1999; 9:197-204. [PMID: 10212834 DOI: 10.1515/jbcpp.1998.9.2-4.197] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
PCOS is a unique model of insulin resistance in which one tissue (skeletal muscle) is resistant to insulin in terms of glucose metabolism whereas another tissue (ovarian thecal cells) maintains its responsiveness to insulin in terms of testosterone biosynthesis. During the past decade, a series of in vitro studies conducted in human placental cells /25/, swine granulosa cells /28/, and most recently, human thecal cells /17/, have provided compelling evidence that one factor involved in this apparent clinical paradox is the clear demonstration of the utilization of the IPG signal transduction system for insulin's effects on steroidogenesis. Nonetheless, many questions remain to be addressed. For example, it would be instructive to determine simultaneously the effects of insulin on glucose disposal and testosterone biosynthesis in isolated thecal cells. In other words, is the thecal cell itself resistant to insulin in terms of glucose disposal while remaining sensitive to insulin in terms of testosterone biosynthesis? Is the IPG content of human thecal cells from women with PCOS decreased compared with that in matched healthy women? There is substantial evidence to suggest that some IPGs may also be responsible in part for mediating insulin's stimulation of glucose disposal (see paper by Dr. Joseph Larner in this issue)--this raises the question as to whether specific forms of IPGs are responsible for glucose metabolism in vivo, whereas other IPGs are responsible for mediating insulin's effects on steroidogenesis. Is there a disparity in the ratio of different types of IPGs among various tissues (e.g., muscle, liver, ovary), and does that ratio determine the tissue's responsiveness to one or another action of insulin? These questions and others leave IPGs and insulin signal transduction a fruitful area for both clinical and laboratory investigations.
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Affiliation(s)
- J E Nestler
- Division of Endocrinology and Metabolism Medical College of Virginia, Virginia Commonwealth University, USA.
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20
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León Y, Sanz C, Giráldez F, Varela-Nieto I. Induction of cell growth by insulin and insulin-like growth factor-I is associated with Jun expression in the otic vesicle. J Comp Neurol 1998; 398:323-32. [PMID: 9714146 DOI: 10.1002/(sici)1096-9861(19980831)398:3<323::aid-cne2>3.0.co;2-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The present report investigates the cellular mechanisms involved in the regulation of cell proliferation by insulin and insulin-like growth factor-I (IGF-I) in the developing inner ear. The results show that insulin and IGF-I stimulate cell proliferation in the otic vesicle. This effect is associated with the induction of the expression of the nuclear proto-oncogene c-jun. The temporal profile of Jun expression coincided with the proliferative period of growth of the otic vesicle. IGF-I promoted the hydrolysis of a membrane glycosyl-phosphatidylinositol, which was characterised as the endogenous precursor for inositol phosphoglycan (IPG). Both purified IPG and a synthetic analogue, 6-O-(2-amino-2-deoxy-alpha-D-glucopyranosyl)-D-myoinositol-1,2-cyclic phosphate (C3), were able to mimic the effects of IGF-I on Jun expression. Anti-IPG antibodies blocked the effects of IGF-I, which were rescued by the addition of IPG or its analogue. These results suggest that the sequence involving the hydrolysis of membrane glycolipids and the expression of c-jun and c-fos proto-oncogenes is part of the mechanism that activates cell division in response to insulin and IGF-I during early organogenesis of the avian inner ear. The implications of these observations for otic development and regeneration are briefly discussed.
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Affiliation(s)
- Y León
- Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain
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21
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Convergence and Divergence of the Signaling Pathways for Insulin and Phosphoinositolglycans. Mol Med 1998. [DOI: 10.1007/bf03401738] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
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22
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Müller G, Wied S, Piossek C, Bauer A, Bauer J, Frick W. Convergence and divergence of the signaling pathways for insulin and phosphoinositolglycans. Mol Med 1998; 4:299-323. [PMID: 9642681 PMCID: PMC2230381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Phosphoinositolglycan molecules isolated from insulin-sensitive mammalian tissues have been demonstrated in numerous in vitro studies to exert partial insulin-mimetic activity on glucose and lipid metabolism in insulin-sensitive cells. However, their ill-defined structures, heterogeneous nature, and limited availability have prohibited the analysis of the underlying molecular mechanism. Phosphoinositolglycan-peptide (PIG-P) of defined and homogeneous structure prepared in large scale from the core glycan of a glycosyl-phosphatidylinositol-anchored membrane protein from Saccharomyces cerevisiae has recently been shown to stimulate glucose transport as well as a number of glucose-metabolizing enzymes and pathways to up to 90% (at 2 to 10 microns) of the maximal insulin effect in isolated rat adipocytes, cardiomyocytes, and diaphragms (G. Müller et al., 1997, Endocrinology 138: 3459-3476). Consequently, we used this PIG-P for the present study in which we compare its intracellular signaling with that of insulin. The activation of glucose transport by both PIG-P and insulin in isolated rat adipocytes and diaphragms was found to require stimulation of phosphatidylinositol (PI) 3-kinase but to be independent of functional p70S6kinase and mitogen-activated protein kinase. The increase in glycerol-3-phosphate acyltransferase activity in rat adipocytes in response to PIG-P and insulin was dependent on both PI 3-kinase and p70S6kinase. This suggest that the signaling pathways for PIG-P and insulin to glucose transport and metabolism converage at the level of PI 3-kinase. A component of the PIG-P signaling pathway located up-stream of PI 3-kinase was identified by desensitization of isolated rat adipocytes for PIG-P action by combined treatment with trypsin and NaCl under conditions that preserved cell viability and the insulin-mimetic activity of sodium vanadate but completely blunted the insulin response. Incubation of the cells with either trypsin or NaCl alone was ineffective. The desensitized adipocytes were reconstituted for stimulation of lipogenesis by PIG-P by addition of the concentrated trypsin/salt extract. The reconstituted adipocytes exhibited 65-75% of the maximal PIG-P response and similar EC50 values for PIG-P (2 to 5 microns) compared with control cells. A proteinaceous N-ethylmaleimide (NEM)-sensitive component contained in the trypsin/salt extract was demonstrated to bind in a functional manner to the adipocyte plasma membrane of desensitized adipocytes via bipolar interactions. An excess of trypsin/salt extract inhibited PIG-P action in untreated adipocytes in a competitive fashion compatible with a receptor function for PIG-P of this protein. The presence of the putative PIG-P receptor protein in detergent-insoluble complexes prepared from isolated rat adipocytes suggests that caveolae/detergent-insoluble complexes of the plasma membrane may play a role in insulin-mimetic signaling by PIG-P. Furthermore, treatment of isolated rat diaphragms and adipocytes with PIG-P as well as with other agents exerting partially insulin-mimetic activity, such as PI-specific phospholipase C (PLC) and the sulfonylurea glimepiride, triggered tyrosine phosphorylation of the caveolar marker protein caveolin, which was apparently correlated with stimulation of lipogenesis. Strikingly, in adipocytes subjected to combined trypsin/salt treatment, PIG-P, PI-specific PLC, and glimepiride failed completely to provoke insulin-mimetic effects. A working model is presented for a signaling pathway in insulin-sensitive cells used by PIG(-P) molecules which involves GPI structures, the trypsin/salt- and NEM-sensitive receptor protein for PIG-P, and additional proteins located in caveolae/detergent-insoluble complexes.
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Affiliation(s)
- G Müller
- Hoechst Marion Roussel Deutschland GmbH, Frankfurt am Main, Germany.
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23
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Jones DR, Varela-Nieto I. The role of glycosyl-phosphatidylinositol in signal transduction. Int J Biochem Cell Biol 1998; 30:313-26. [PMID: 9611774 DOI: 10.1016/s1357-2725(97)00144-1] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Glycosyl-phosphatidylinositol (GPI) lipids have a structural role as protein anchors to the cell surface. In addition, they are implicated in hormone, growth factor and cytokine signal transduction. Their phosphodiesteric hydrolysis mediated by an activated phospholipase results in the generation of water soluble oligosaccharide species termed the inositol phosphoglycan (IPG). This product has been demonstrated to possess biological properties when added exogenously to cells mimicking the biological effects of a variety of extracellular ligands. This may be accomplished since IPG is generic for a family of closely related species which are released in a tissue-specific manner and additionally have cell-specific targets. Micro-organic synthesis has recently been able to shed new light on this topic by the introduction of defined oligosaccharide analogues of IPG for the assessment of their biological activity. These have complemented the findings observed with purified IPG from biological sources thus strengthening the belief that the GPI/IPG signalling system represents a truly novel aspect of transmembrane signalling.
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Affiliation(s)
- D R Jones
- Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
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24
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Kessler A, Müller G, Wied S, Crecelius A, Eckel J. Signalling pathways of an insulin-mimetic phosphoinositolglycan-peptide in muscle and adipose tissue. Biochem J 1998; 330 ( Pt 1):277-86. [PMID: 9461521 PMCID: PMC1219138 DOI: 10.1042/bj3300277] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A novel phosphoinositolglycan-peptide (PIG-P) from the yeast Saccharomyces cerevisiae potently mimicks insulin action on glucose transport and metabolism in rat muscle and adipose tissue. The aim of the present study was to elucidate the cellular signalling pathways of this insulin-mimetic compound. Rapid onset and reversibility of PIG-P action on glucose transport were observed in isolated adipocytes with a half-time of transport stimulation of 6-8 min (insulin less than 5 min). Combined treatment with PIG-P and insulin indicated additive stimulation of glucose transport at submaximal concentrations and non-additive action of both agents at maximal doses. The tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) was markedly increased in response to PIG-P in rat cardiomyocytes without any effect on the tyrosine phosphorylation of the insulin receptor beta-subunit. PIG-P action in these cells was accompanied by phosphorylation/dephosphorylation of several proteins with molecular masses of 15-30 kDa, a response not detected with insulin. Downstream signalling of IRS-1 was then analysed by monitoring IRS-1-associated phosphatidylinositol 3-kinase (PI 3-kinase) activity in cardiomyocytes. A stable (2 and 15 min incubation with PIG-P) 7-fold stimulation corresponding to about 50% of insulin action could be detected. Increased tyrosine phosphorylation of IRS-1 and enhanced PI 3-kinase activity in response to PIG-P independent of the insulin receptor was also observed in isolated adipocytes. Involvement of PI 3-kinase in PIG-P action was subsequently confirmed by the dose-dependent inhibition of PIG-P-activated glucose transport in rat diaphragm and adipocytes by the PI 3-kinase inhibitors wortmannin and LY294002. These data suggest divergent upstream signalling by insulin and PIG-P involving phosphoproteins not affected by insulin. However, PIG-P and insulin action converge at the level of IRS-1 inducing insulin-independent PI 3-kinase-mediated signalling to glucose transport.
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Affiliation(s)
- A Kessler
- Department of Molecular Cardiology, Diabetes Research Institute, Düsseldorf, Germany
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25
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Movahedi S, Hooper NM. Insulin stimulates the release of the glycosyl phosphatidylinositol-anchored membrane dipeptidase from 3T3-L1 adipocytes through the action of a phospholipase C. Biochem J 1997; 326 ( Pt 2):531-7. [PMID: 9291128 PMCID: PMC1218701 DOI: 10.1042/bj3260531] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Membrane dipeptidase (MDP; EC 3.4.13.19) enzymic activity that was inhibited by cilastatin has been detected on the surface of 3T3-L1 cells. On differentiation of the cells from fibroblasts to adipocytes the activity of MDP increased 12-fold. Immunoelectrophoretic blot analysis indicated that on adipogenesis the increase in the amount of MDP preceded the appearance of GLUT-4. MDP on 3T3-L1 adipocytes was anchored in the bilayer by a glycosyl phosphatidylinositol (GPI) moiety as evidenced by its release into the medium in a hydrophilic form on treatment of the cells with bacterial phosphatidylinositol-specific phospholipase C and the appearance of the inositol 1,2-cyclic monophosphate cross-reacting determinant. Incubation of 3T3-L1 adipocytes with either insulin or the sulphonylurea glimepiride led to a rapid concentration- and time-dependent release of MDP from the cell surface. The hydrophilic form of MDP released from the cells on stimulation with insulin was recognized by antibodies against the inositol 1,2-cyclic monophosphate cross-reacting determinant, indicating that it had been generated by cleavage of its GPI anchor through the action of a phospholipase C.
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Affiliation(s)
- S Movahedi
- Department of Biochemistry and Molecular Biology, University of Leeds, U.K
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26
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Müller G, Wied S, Crecelius A, Kessler A, Eckel J. Phosphoinositolglycan-peptides from yeast potently induce metabolic insulin actions in isolated rat adipocytes, cardiomyocytes, and diaphragms. Endocrinology 1997; 138:3459-75. [PMID: 9231801 DOI: 10.1210/endo.138.8.5308] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Polar headgroups of free glycosyl-phosphatidylinositol (GPI) lipids or protein-bound GPI membrane anchors have been shown to exhibit insulin-mimetic activity in different cell types. However, elucidation of the molecular mode of action of these phospho-inositolglycan (PIG) molecules has been hampered by 1) lack of knowledge of their exact structure; 2) variable action profiles; and 3) rather modest effects. In the present study, these problems were circumvented by preparation of PIG-peptides (PIG-P) in sufficient quantity by sequential proteolytic (V8 protease) and lipolytic (phosphatidylinositol-specific phospholipase C) cleavage of the GPI-anchored plasma membrane protein, Gce1p, from the yeast Saccharomyces cerevisiae. The structure of the resulting PIG-P, NH2-Tyr-Cys-Asn-ethanolamine-PO4-6(Man1-2)Man1-2Man1-+ ++6Man1-4GlcNH(2)1-6myo-inositol-1,2-cyclicPO4, was revealed by amino acid analysis and Dionex exchange chromatography of fragments generated enzymatically or chemically from the neutral glycan core and is in accordance with the known consensus structures of yeast GPI anchors. PIG-P stimulated glucose transport and lipogenesis in normal, desensitized and receptor-depleted isolated rat adipocytes, increased glycerol-3-phosphate acyltransferase activity and translocation of the glucose transporter isoform 4, and inhibited isoproterenol-induced lipolysis and protein kinase A activation in adipocytes. Furthermore, PIG-P was found to stimulate glucose transport in isolated rat cardiomyocytes and glycogenesis and glycogen synthase in isolated rat diaphragms. The concentration-dependent effects of the PIG-P reached 70-90% of the maximal insulin activity with EC50-values of 0.5-5 microM. Chemical or enzymic cleavages within the glycan or peptide portion of the PIG-P led to decrease or loss of activity. The data demonstrate that PIG-P exhibits a potent insulin-mimetic activity which covers a broad spectrum of metabolic insulin actions on glucose transport and metabolism.
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Affiliation(s)
- G Müller
- Hoechst AG, Hoechst Marion Roussel, Frankfurt am Main, Germany
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27
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Caro HN, Kunjara S, Rademacher TW, León Y, Jones DR, Avila MA, Varela-Nieto I. Isolation and partial characterisation of insulin-mimetic inositol phosphoglycans from human liver. BIOCHEMICAL AND MOLECULAR MEDICINE 1997; 61:214-28. [PMID: 9259987 DOI: 10.1006/bmme.1997.2607] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Extracts of human liver were found to contain activities which copurified and coeluted with the two major subtypes of mediators (type A and type P) isolated from insulin-stimulated rat liver. The putative type A mediator from human liver inhibited cAMP-dependent protein kinase from bovine heart, decreased phosphoenolypyruvate carboxykinase mRNA levels in rat hepatoma cells, and stimulated lipogenesis in rat adipocytes. The putative type P mediator stimulated bovine heart pyruvate dehydrogenase phosphatase. Both fractions were able to stimulate proliferation of EGFR T17 fibroblasts and the type A was able to support growth in organotypic cultures of chicken embryo cochleovestibular ganglia. Both activities were resistant to Pronase treatment and the presence of carbohydrates, phosphate, and free-amino groups were confirmed in the two fractions. These properties are consistent with the structure/ function characteristics of the type A and P inositolphosphoglycans (IPG) previously characterized from rat liver. Further, the ability of the human-derived mediators to interact with rat adipocytes and bovine-derived metabolic enzymes suggests similarity in structure between the mediators purified from different species. Galactose oxidase-susceptible membrane-associated glycosylphosphatidylinositols (GPI) have been proposed to be the precursors of IPG. GPI was purified from human liver membranes followed by treatment with galactose oxidase and reduction with NaB3H4. Serial t.l.c. revealed three radiolabeled bands which comigrated with the putative GPI precursors found in rat liver. These galactose-oxidase-reactive lipidic compounds, however, were only partially susceptible to hydrolysis with phosphatidylinositol-specific phospholipase C from Bacillus thuringiensis and were resistant to glycosylphosphatidylinositol-specific phospholipase C from Trypanosoma brucei. These data indicate that IPG molecules with insulin-like biological activities are present in human liver.
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Affiliation(s)
- H N Caro
- Department of Molecular Pathology, University College London Medical School, United Kingdom
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28
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Jones DR, Avila MA, Sanz C, Varela-Nieto I. Glycosyl-phosphatidylinositol-phospholipase type D: a possible candidate for the generation of second messengers. Biochem Biophys Res Commun 1997; 233:432-7. [PMID: 9144552 DOI: 10.1006/bbrc.1997.6475] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Membrane associated glycosyl-phosphatidylinositols have been shown to be the precursors of inositol phosphoglycan second messengers. Extraction of human liver membranes and purification by serial thin layer chromatography revealed three glycolipids which co-migrated with glycosyl-phosphatidylinositol from rat liver. These lipidic fractions were partially sensitive to treatment with nitrous acid and to hydrolysis by glycosyl-phosphatidylinositol-specific phospholipase D from bovine serum. In parallel, glycosyl-phosphatidylinositol isolated from rat liver was found to be a substrate for the enzyme generating a biologically active inositol phosphoglycan species (determined by measuring inhibition of protein kinase A activity and stimulation of cell proliferation within the chicken embryo cochleovestibular ganglion). This molecule was recognised by an anti-inositol phosphoglycan antibody. Hence, we propose that glycosyl-phosphatidylinositol-specific phospholipase D could be implicated in cellular signalling.
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Affiliation(s)
- D R Jones
- Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain
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29
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Abstract
The molecular pathways for insulin's signal transduction from its cell surface receptor to the cell's interior metabolic machinery remain in many ways uncharted. Lately two molecules have been proposed as second messengers transducing the insulin signal into the target cell. One is a phospho-oligosaccharide/inositolphosphoglycan and the other is diacylglycerol, both deriving from the same plasma membrane glycolipid, which is hydrolysed in response to insulin treatment. The phospho-oligosaccharide appears to mediate many metabolic effects of insulin through control of the phosphorylation state of key regulatory metabolic enzymes. Diacylglycerol may mediate insulin's stimulation of glucose transport over the plasma membrane. The glycolipid precursor of these putative second messengers, as well as the receptor for insulin, appear to be localized in caveolae microdomains of the plasma membrane, and glucose transporters accumulate in caveolae in response to insulin treatment, suggesting a focal role for caveolae in insulin signalling.
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Affiliation(s)
- P Strålfors
- Department of Cell Biology, Faculty of Health Sciences, University of Linköping, Sweden
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30
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Schofield L, Tachado SD. Regulation of host cell function by glycosylphosphatidylinositols of the parasitic protozoa. Immunol Cell Biol 1996; 74:555-63. [PMID: 8989594 DOI: 10.1038/icb.1996.89] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Antigenic variation, antigenic drift, molecular mimicry, intracellular localization and sequestration in privileged sites are important mechanisms of immune evasion by infectious organisms. Added to this however is the phenomenon by which pathogens deliberately regulate host cell function by the production of glycolipids with agonistic or antagonistic signal transduction capacity. Such pro-active glycolipids are often pathogenicity factors, but they also serve as immunomodulators and immunosuppressants, and these activities may serve as mechanisms of immune evasion. Here we review glycosylphosphatidylinositols and related structures, a novel class of glycolipid common to eukaryotic parasites and their hosts, which recent studies suggest may play a role in immune evasion and immunosuppression by regulating host cell function via the activation or suppression of endogenous host signalling pathways.
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Affiliation(s)
- L Schofield
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.
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31
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Galera C, Clemente F, Alcantara A, Trapote MA, Perea A, Lopez-Delgado MI, Villanueva-Penacarrillo ML, Valverde I. Inositolphosphoglycans and diacyglycerol are possible mediators in the glycogenic effect of GLP-1(7-36)amide in BC3H-1 myocytes. Cell Biochem Funct 1996; 14:43-8. [PMID: 8907253 DOI: 10.1002/cbf.639] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A potent glycogenic effect of GLP-1(7-36)amide has been found in rat hepatocytes and skeletal muscle, and specific receptors for this peptide, which do not seem to be associated with the adenylate cyclase-cAMP system, have been detected in these tissue membranes. On the other hand, inositolphosphoglycan molecules (IPGs) have been implicated as second messengers of the action of insulin. In this work, we have found, in differentiated BC3H-1 myocytes, specific binding of [125I]GLP-1(7-36)amide, and a stimulatory effect of the peptide on glycogen synthesis, confirming the findings in rat skeletal muscle. Also, GLP-1(7-36)amide modulates the cell content of radiolabelled glycosylphosphatidylinositols (GPIs) and increases the production of diacylglycerol (DAG), in the same manner as insulin acts, indicating hydrolysis of GPIs and an immediate and short-lived generation of IPGs. Thus, IPGs and DAG could be mediators in the glycogenic action of GLP-1(7-36)amide in skeletal muscle.
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Affiliation(s)
- C Galera
- Department Metabolismo, Nutricion y Hormonas, Fundacion Jimenez Diaz, Madrid, Spain
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Affiliation(s)
- A R Saltiel
- Department of Signal Transduction, Parke-Davis Pharmaceutical Research, Division of Warner-Lambert Co., Ann Arbor, Michigan 48105, USA
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33
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Parpal S, Gustavsson J, Strålfors P. Isolation of phosphooligosaccharide/phosphoinositol glycan from caveolae and cytosol of insulin-stimulated cells. J Cell Biol 1995; 131:125-35. [PMID: 7559770 PMCID: PMC2120598 DOI: 10.1083/jcb.131.1.125] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
A phosphooligosaccharide has been proposed as a second messenger of insulin. It is believed to be structurally related to the carbohydrate moiety of phosphatidylinositol glycan anchors of many cell surface proteins. Herein we demonstrate that [32]phosphate in freshly isolated adipocytes and [3H]galactose in cultured hepatoma cells (H4IIE) labeled the same set of three different glycolipids. With all three, the radiolabel was made water soluble by phosphatidylinositol(glycan)-specific phospholipase C or D catalyzed hydrolysis. We isolated the three phospholipase C-released substances. One of them was susceptible to nitrous acid deamination, indicative of a hexosamine with a free amino group. This phosphooligosaccharide structure had an apparent molecular mass between tetra- and pentaglucose by gel filtration. By anion-exchange chromatography it was separated into two differently charged and interconvertible species. Adipocytes stimulated with insulin accumulated the nitrous acid sensitive phosphooligosaccharide: after stimulation the intracellular level of free phosphooligosaccharide increased threefold within 5 min, fell off during the next few minutes and then remained at a slightly elevated level. After insulin stimulation the intracellular concentration of free phosphooligosaccharide was > 1,000-fold higher than in the incubation medium. When prepared from rat livers on a preparative scale, the oligosaccharide was also found to exhibit insulinomimetic effects on protein phosphorylation of insulin target proteins in intact adipocytes. After subcellular fractionation of adipocytes the lipid-bound [32P]phosphooligosaccharide of the plasma membrane was found to be localized in plasma membrane domains apparently corresponding to caveolae. Lipid-bound [32P]phosphooligosaccharide was found also in the microsomal fraction.
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Affiliation(s)
- S Parpal
- Department of Cell Biology, Faculty of Health Sciences, University of Linköping, Sweden
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34
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Farese RV, Standaert ML, Yamada K, Huang LC, Zhang C, Cooper DR, Wang Z, Yang Y, Suzuki S, Toyota T. Insulin-induced activation of glycerol-3-phosphate acyltransferase by a chiro-inositol-containing insulin mediator is defective in adipocytes of insulin-resistant, type II diabetic, Goto-Kakizaki rats. Proc Natl Acad Sci U S A 1994; 91:11040-4. [PMID: 7972005 PMCID: PMC45162 DOI: 10.1073/pnas.91.23.11040] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Type II diabetic Goto-Kakizaki (GK) rats were insulin-resistant in euglycemic-hyperinsulinemic clamp studies. We therefore examined insulin signaling systems in control Wistar and diabetic GK rats. Glycerol-3-phosphate acyltransferase (G3PAT), which is activated by headgroup mediators released from glycosyl-phosphatidylinositol (GPI), was activated by insulin in intact and cell-free adipocyte preparations of control, but not diabetic, rats. A specific chiro-inositol-containing inositol phosphoglycan (IPG) mediator, prepared from beef liver, bypassed this defect and comparably activated G3PAT in cell-free adipocyte preparations of both diabetic GK and control rats. A myo-inositol-containing IPG mediator did not activate G3PAT. Relative to control adipocytes, labeling of GPI by [3H]glucosamine was diminished by 50% and insulin failed to stimulate GPI hydrolysis in GK adipocytes. In contrast to GPI-dependent G3PAT activation, insulin-stimulated hexose transport was intact in adipocytes and soleus and gastrocnemius muscles of the GK rat, as was insulin-induced activation of mitogen-activated protein kinase and protein kinase C. We conclude that (i) chiro-inositol-containing IPG mediator activates G3PAT during insulin action, (ii) diabetic GK rats have a defect in synthesizing or releasing functional chiro-inositol-containing IPG, and (iii) defective IPG-regulated intracellular glucose metabolism contributes importantly to insulin resistance in diabetic GK rats.
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Affiliation(s)
- R V Farese
- J. A. Haley Veterans' Hospital, Tampa, FL 33612
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35
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Lazar DF, Knez JJ, Medof ME, Cuatrecasas P, Saltiel AR. Stimulation of glycogen synthesis by insulin in human erythroleukemia cells requires the synthesis of glycosyl-phosphatidylinositol. Proc Natl Acad Sci U S A 1994; 91:9665-9. [PMID: 7524086 PMCID: PMC44877 DOI: 10.1073/pnas.91.21.9665] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Although the insulin-dependent hydrolysis of glycosyl-phosphatidylinositol (GPI) may play an important role in insulin action, an absolute requirement for this glycolipid has not been demonstrated. Human K562 cells were mutated to produce a cell line (IA) incapable of the earliest step in PI glycosylation, the formation of PI-GlcNAc. Another cell line (IVD) was deficient in the deacetylation of PI-GlcNAc to form PI-GlcN and subsequent mannosylated species. Each line was transfected with wild-type human insulin receptors. Similar insulin-stimulated receptor autophosphorylation was observed in all three lines, along with a nearly identical increase in the association of phosphorylated insulin receptor substrate 1 with endogenous PI 3-kinase. Both normal and GPI-defective lines also displayed a similar 2- to 3-fold increase in phosphorylation of the Shc protein and its association with growth factor receptor-bound protein 2 in response to insulin. In contrast to these results, striking differences were noted in insulin-stimulated glycogen synthesis. In normal cells, glycogen synthesis was significantly increased by insulin, whereas no insulin stimulation was observed in GPI-deficient IA cells, and only a trace of stimulation was detected in IVD cells. These results indicate that tyrosine phosphorylation produced by insulin is not dependent on GPI synthesis, and this effect is not sufficient to elicit at least some of the metabolic effects of the hormone. In contrast, GPI synthesis is required for the stimulation of glycogen synthesis by insulin in these cells. These findings support the existence of divergent pathways in the action of insulin.
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Affiliation(s)
- D F Lazar
- Department of Signal Transduction, Parke-Davis Pharmaceutical Research Division, Ann Arbor, MI 48105
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36
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Abstract
Plasmalemmal caveolae were first identified as an endocytic compartment in endothelial cells, where they appear to move molecules across the cell by transcytosis. More recently, they have been found to be sites where small molecules are concentrated and internalized by a process called potocytosis. A growing body of biochemical and morphological evidence indicates that a variety of molecules known to function directly or indirectly in signal transduction are enriched in caveolae. This raises the possibility that a third function for caveolae is to process hormonal and mechanical signals for the cell. Insights gained from studying potocytosis suggest several different ways that this membrane specialization might function to integrate incoming and outgoing cellular messages.
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Affiliation(s)
- R G Anderson
- Department of Cell Biology and Neuroscience, University of Texas Southwestern Medical Center, Dallas 75235
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37
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Abstract
The results presented here indicate that GPI lipids are a structurally and functionally diverse molecular family. Despite new detailed information on the structures of GPI-anchored proteins, there is relatively scant information on the structure of free-GPI. Thus, little is known of the relationships between GPI structures and the mechanism of their biological effects. For example, there is no distinction at the structural level between hormone-sensitive free-GPI and those that serve as precursors for protein-GPI. Nor is there precise biochemical data on the mechanism and importance of free-GPI in hormone signaling, or the signaling roles that GPI anchors play in protein function. The T-cell activation cascade is an ideal system for studying both forms of GPI and their derivatives. The study of GPI molecules in T lymphocytes offers the exciting possibility of addressing questions on the structure, function, genesis, and regulation of both free- and protein-GPI molecules in a single cell type. The detection of multiple protein-GPI and free-GPI forms, and of hormone-sensitive GPI, provides the first approach to these issues. For the moment, the potential for biochemical signaling by intact GPI or its metabolites is enormous. If significant progress is to be made, the structures of hormone sensitive free-GPI must be elucidated. Only then can we precisely define the roles of these molecules in the regulation of cell metabolism and proliferation.
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Affiliation(s)
- J C Pratt
- University of Pennsylvania, School of Medicine, Department of Pathology and Laboratory Medicine, Philadelphia 19104-6140
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38
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Sánchez-Arias JA, Sánchez-Gutiérrez JC, Guadaño A, Alvarez JF, Samper B, Mato JM, Felíu JE. Changes in the insulin-sensitive glycosyl-phosphatidyl-inositol signalling system with aging in rat hepatocytes. EUROPEAN JOURNAL OF BIOCHEMISTRY 1993; 211:431-6. [PMID: 8436106 DOI: 10.1111/j.1432-1033.1993.tb17568.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
An inositol-phosphate glycan (InsP glycan), which is the polar head group of an insulin-sensitive glycosyl-phosphatidylinositol (glycosyl-PtdIns), has been reported to mimic some insulin actions when added to different types of cells. In connection with this, a specific, time-dependent and energy-dependent transport system for this InsP glycan has been identified in isolated rat hepatocytes [Alvarez, J. F., Sánchez-Arias, J. A., Guadaño, A., Estevez, F., Varela, I., Felíu, J. E. & Mato, J.M. (1991) Biochem. J. 274, 369-374]. Here we have investigated the glycosyl-PtdIns-dependent insulin-signalling system in hepatocytes isolated from either 3-month-old or 24-month-old rats. Aging reduced the stimulatory effect of insulin on [U-14C]glucose incorporation into glycogen, caused a significant decrease in basal glycosyl-PtdIns levels and blocked the insulin-mediated hydrolysis of this lipid. In 24-month-old rats, we also observed a diminution in the rate of hepatocyte InsP-glycan uptake and a marked reduction of the stimulatory effect of this compound on glycogen synthesis. These results support the hypothesis that insulin resistance associated with aging is accompanied by an impairment of the glycosyl-PtdIns-dependent cellular signalling system.
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Affiliation(s)
- J A Sánchez-Arias
- Servico de Endocrinología Experimental, Hospital Puerta de Hierro, Universidad Autónoma de Madrid, Spain
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Romero G, Larner J. Insulin mediators and the mechanism of insulin action. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 1993; 24:21-50. [PMID: 8504064 DOI: 10.1016/s1054-3589(08)60932-1] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- G Romero
- Department of Pharmacology, University of Pittsburgh School of Medicine, Pennsylvania 15261
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40
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Zapata A, Martín-Lomas M. Building blocks for the synthesis of glycosyl-myo-inositols involved in the insulin intracellular signalling process. Carbohydr Res 1992; 234:93-106. [PMID: 1468083 DOI: 10.1016/0008-6215(92)85041-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Glycosylation of (+/- )-1-O-benzyl-2,3:5,6-di-O-isopropylidene-myo-inositol (4) with 6-O-acetyl-4-O-allyl-2-azido-3-O-benzyl-2-deoxy-beta-D-glucopyranosyl trichloroacetimidate (6) gave the 4-O-(2-amino-2-deoxy-alpha-D-glucopyranosyl)- myo-inositol derivative (9) as a mixture of diastereoisomers which could be resolved by chromatography. Likewise alpha-glycosylation of 4 with 6-O-acetyl-2-azido-3-O-benzoyl-2-deoxy-4-O-(2,3,4,6-tetra-O-acetyl-beta- D- galactopyranosyl)-D-glucopyranosyl trichloroacetimidate (10) gave the corresponding pseudotrisaccharide derivative 16 as a mixture of diastereomers which could be resolved partially by chromatography. alpha-Glycosylation of enantiomerically pure 2,3:5,6- (18) and 2,3:4,5-di-O-isopropylidene-1-O-menthoxycarbonyl-myo-inositol (19) with 3,4,6-tri-O-acetyl-2-azido-2-deoxy-D-glucopyranosyl trichloroacetimidate (20) gave the pseudodisaccharide derivatives 21 and 22, respectively. Likewise, alpha-glycosylation of 18 with 10 afforded a pseudotrisaccharide derivative (23).
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Affiliation(s)
- A Zapata
- Grupo de Carbohidratos, Instituto de Química Orgánica, C.S.I.C., Madrid, Spain
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41
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Misek D, Saltiel A. An inositol phosphate glycan derived from a Trypanosoma brucei glycosyl-phosphatidylinositol mimics some of the metabolic actions of insulin. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)41995-3] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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42
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Avila MA, Clemente R, Varela-Nieto I. A phosphatidylinositol-linkage-deficient T-cell mutant contains insulin-sensitive glycosyl-phosphatidylinositol. Biochem J 1992; 282 ( Pt 3):681-6. [PMID: 1532490 PMCID: PMC1130841 DOI: 10.1042/bj2820681] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Glycosyl-phosphatidylinositol molecules, acting as both signal transduction elements and membrane protein anchors, have been proposed to play a role during T-cell activation. The MVB2 cell line is a mutant, derived from the wild-type T-T hybrid YH.16.33, which has a defect in the biosynthesis of PtdIns-protein linkages. As a consequence, MVB2 mutants are defective in activation through the T-cell receptor. Despite the lack of glycosyl-PtdIns anchors in the mutant MVB2 cells, a comparison of the levels and structural features of the insulin-sensitive glycosyl-PtdIns between the MVB2 and YH.16.33 lineages indicates that both cell lines are identical in this respect. The time course for insulin-responsiveness coincides in both cell lines, with maximal hydrolysis 30 s after insulin addition. The ultimate localization of insulin-regulated glycosyl-PtdIns at the outer surface of the cell membrane is also similar. These data indicate that the glycosyl-PtdIns whose hydrolysis is regulated by insulin is not anchoring proteins at the cell surface of T-lymphocytes.
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Affiliation(s)
- M A Avila
- Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Cientificas, Universidad Autónoma de Madrid, Spain
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43
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Represa J, Avila MA, Miner C, Giraldez F, Romero G, Clemente R, Mato JM, Varela-Nieto I. Glycosyl-phosphatidylinositol/inositol phosphoglycan: a signaling system for the low-affinity nerve growth factor receptor. Proc Natl Acad Sci U S A 1991; 88:8016-9. [PMID: 1654553 PMCID: PMC52436 DOI: 10.1073/pnas.88.18.8016] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Nerve growth factor (NGF) exerts a variety of actions during embryonic development. At the early stages of inner ear development, NGF stimulates cell proliferation, an effect mediated through low-affinity receptors. We have studied the possibility that the glycosyl-phosphatidylinositol/inositol phosphoglycan (glycosyl-PtdIns/IPG) system is involved in transmitting this NGF signal. Endogenous glycosyl-PtdIns was characterized in extracts of cochleovestibular ganglia (CVGs) that incorporated [3H]glucosamine, [3H]galactose, [3H]myristic acid, and [3H]palmitic acid. Incubation of CVG with NGF produced a rapid and transient hydrolysis of glycosyl-PtdIns. Hydrolysis was complete at 100 ng/ml, and the half-maximal effect occurred at 25 ng/ml, overlapping with the concentration dependence of the mitogenic effect of NGF. An IPG was isolated from embryonic extracts. It had biological effects similar to those reported for the insulin-induced IPG in other tissues. It exerted a powerful mitogenic effect on CVG, comparable to that of NGF. Both the IPG- and NGF-induced cell proliferation were blocked by anti-IPG antibodies that recognized the endogenous IPG on a silica plate immunoassay. These results show that CVG possesses a fully active glycosyl-PtdIns/IPG signal transduction system and that the proliferative effects associated with NGF binding to low-affinity receptors require IPG generation.
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Affiliation(s)
- J Represa
- Departamento Ciencias Morfológicas, Facultad de Medicina, Universidad de Valladolid, Spain
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44
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Suzuki S, Sugawara K, Satoh Y, Toyota T. Insulin stimulates the generation of two putative insulin mediators, inositol-glycan and diacylglycerol in BC3H-1 myocytes. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)92949-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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45
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Alvarez JF, Sánchez-Arias JA, Guadaño A, Estévez F, Varela I, Felíu JE, Mato JM. Transport in isolated rat hepatocytes of the phospho-oligosaccharide that mimics insulin action. Effects of adrenalectomy and glucocorticoid treatment. Biochem J 1991; 274 ( Pt 2):369-74. [PMID: 2006906 PMCID: PMC1150146 DOI: 10.1042/bj2740369] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The addition to intact cells of an inositol phospho-oligosaccharide (POS), which is the polar head-group of an insulin-sensitive glycosylphosphatidylinositol, mimics and may mediate some of the biological effects of this hormone. Here we report the existence of a POS transport system in hepatocytes. This POS transport system is specific and time- and dose-dependent. Insulin-resistance caused by dexamethasone administration to rats was accompanied by a decrease in the hepatocyte POS transport system. In contrast, bilateral adrenalectomy provoked a significant increase in the transport of POS. Both the temporal uptake of POS and the regulation of this process by conditions known to modify the sensitivity to insulin suggest that this novel transport system might be involved in the insulin signalling mechanism.
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Affiliation(s)
- J F Alvarez
- Instituto de Investigaciones Biomédicas, C.S.I.C., Madrid, Spain
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46
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Ambrus JL, Chesky L, Chused T, Young KR, McFarland P, August A, Brown EJ. Intracellular signaling events associated with the induction of proliferation of normal human B lymphocytes by two different antigenically related human B cell growth factors (high molecular weight B cell growth factor (HMW-BCGF) and the complement factor Bb). J Biol Chem 1991. [DOI: 10.1016/s0021-9258(19)67851-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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