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Pavlova I, Ruda-Kucerova J. Brain metabolic derangements examined using 1H MRS and their (in)consistency among different rodent models of depression. Prog Neuropsychopharmacol Biol Psychiatry 2023; 127:110808. [PMID: 37301420 DOI: 10.1016/j.pnpbp.2023.110808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 06/01/2023] [Accepted: 06/04/2023] [Indexed: 06/12/2023]
Abstract
Major depressive disorder (MDD) is underlined by neurochemical changes in the brain. Proton magnetic resonance spectroscopy (1H MRS) is a useful tool for their examination as it provides information about the levels of metabolites. This review summarises the current knowledge of 1H MRS findings from rodent models of MDD, assesses the results from both a biological and a technical perspective, and identifies the main sources of bias. From a technical point of view, bias-introducing factors are the diversity of the measured volumes and their positioning in the brain, the data processing, and the metabolite concentration expression. The biological variables are strain, sex, and species, as well as the model itself, and in vivo vs. ex vivo exploration. This review identified some consistency in the 1H MRS findings in the models of MDD: lower levels of glutamine, glutamate + glutamine, and higher levels of myo-inositol and taurine in most of the brain regions of MDD models. This may suggest changes in regional metabolism, neuronal dysregulation, inflammation, and a compensatory effect reaction in the MDD rodent models.
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Affiliation(s)
- Iveta Pavlova
- Institute of Scientific Instruments of the Czech Academy of Sciences, Královopolská 147, 612 00 Brno, Czech Republic; Department of Condensed Matter Physics, Faculty of Science, Masaryk University, Kotlářská 2, 602 00 Brno, Czech Republic.
| | - Jana Ruda-Kucerova
- Department of Pharmacology, Faculty of Medicine, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic.
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2
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Ye C, Greenberg ML. Inositol synthesis regulates the activation of GSK-3α in neuronal cells. J Neurochem 2014; 133:273-83. [PMID: 25345501 DOI: 10.1111/jnc.12978] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 10/10/2014] [Accepted: 10/13/2014] [Indexed: 12/26/2022]
Abstract
The synthesis of inositol provides precursors of inositol lipids and inositol phosphates that are pivotal for cell signaling. Mood stabilizers lithium and valproic acid, used for treating bipolar disorder, cause cellular inositol depletion, which has been proposed as a therapeutic mechanism of action of both drugs. Despite the importance of inositol, the requirement for inositol synthesis in neuronal cells is not well understood. Here, we examined inositol effects on proliferation of SK-N-SH neuroblastoma cells. The essential role of inositol synthesis in proliferation is underscored by the findings that exogenous inositol was dispensable for proliferation, and inhibition of inositol synthesis decreased proliferation. Interestingly, the inhibition of inositol synthesis by knocking down INO1, which encodes inositol-3-phosphate synthase, the rate-limiting enzyme of inositol synthesis, led to the inactivation of GSK-3α by increasing the inhibitory phosphorylation of this kinase. Similarly, the mood stabilizer valproic acid effected transient decreases in intracellular inositol, leading to inactivation of GSK-3α. As GSK-3 inhibition has been proposed as a likely therapeutic mechanism of action, the finding that inhibition of inositol synthesis results in the inactivation of GSK-3α suggests a unifying hypothesis for mechanism of mood-stabilizing drugs. Inositol is an essential metabolite that serves as a precursor for inositol lipids and inositol phosphates. We report that inhibition of the rate-limiting enzyme of inositol synthesis leads to the inactivation of glycogen synthase kinase (GSK) 3α by increasing inhibitory phosphorylation of this kinase. These findings have implications for the therapeutic mechanisms of mood stabilizers and suggest that inositol synthesis and GSK 3α activity are intrinsically related.
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Affiliation(s)
- Cunqi Ye
- Department of Biological Sciences, Wayne State University, Detroit, Michigan, USA
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3
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Phatak P, Shaldivin A, King LS, Shapiro P, Regenold WT. Lithium and inositol: effects on brain water homeostasis in the rat. Psychopharmacology (Berl) 2006; 186:41-7. [PMID: 16572264 DOI: 10.1007/s00213-006-0354-y] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2005] [Accepted: 02/20/2006] [Indexed: 11/30/2022]
Abstract
RATIONALE Since its earliest use in psychiatry, lithium has been known to alter body water homeostasis. Although lithium is also known to decrease the concentration of inositol, an important brain osmolyte, little is known of the effects of lithium on brain water homeostasis. OBJECTIVE To determine whether lithium alters brain water homeostasis, and, if so, whether the mechanism involves changes in inositol concentration. MATERIALS AND METHODS Rats were fed regular food or regular food plus lithium chloride for either 11 days or 5 weeks. Brains were dissected and assayed for tissue water by the wet-dry method and for inositol by gas chromatography-mass spectrometry. RESULTS We found a statistically significant (p=0.05, corrected) 3.1% mean elevation in frontal cortex tissue water in 5-week lithium-fed rats (86.7+/-3.9%), compared to control rats (83.6+/-2.6%). Inositol concentration correlated inversely with percent tissue water (r=-0.50, p=0.003, corrected) in pooled samples of 5-week lithium-fed rats, and was significantly lower in frontal cortex and hippocampus of 5-week lithium-fed rats, compared to controls. Rats fed lithium for 11 days did not differ significantly from controls on either variable. CONCLUSIONS This is the first report of a lithium-induced increase in brain tissue water. Although the mechanism is unclear, it does not appear to result from changes in brain inositol concentration or blood sodium concentration. This finding may have implications for the therapeutic or toxic effects of lithium on brain, because increased tissue water can augment cell excitability.
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Affiliation(s)
- P Phatak
- Division of Geriatric Psychiatry, Department of Psychiatry, University of Maryland School of Medicine and the Research Service, VA Maryland Healthcare System, Baltimore, MD 21201, USA
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Fisher SK, Novak JE, Agranoff BW. Inositol and higher inositol phosphates in neural tissues: homeostasis, metabolism and functional significance. J Neurochem 2002; 82:736-54. [PMID: 12358779 DOI: 10.1046/j.1471-4159.2002.01041.x] [Citation(s) in RCA: 465] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Inositol phospholipids and inositol phosphates mediate well-established functions in signal transduction and in Ca2+ homeostasis in the CNS and non-neural tissues. More recently, there has been renewed interest in other roles that both myo-inositol and its highly phosphorylated forms may play in neural function. We review evidence that myo-inositol serves as a clinically relevant osmolyte in the CNS, and that its hexakisphosphate and pyrophosphorylated derivatives may play roles in such diverse cellular functions as DNA repair, nuclear RNA export and synaptic membrane trafficking.
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Affiliation(s)
- Stephen K Fisher
- Mental Health Research Institute, and Department of Pharmacology, University of Michigan, Ann Arbor, Michigan 48109, USA.
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Porcellati F, Hosaka Y, Hlaing T, Togawa M, Larkin DD, Karihaloo A, Stevens MJ, Killen PD, Greene DA. Alternate splicing in human Na+-MI cotransporter gene yields differentially regulated transport isoforms. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:C1325-37. [PMID: 10362595 DOI: 10.1152/ajpcell.1999.276.6.c1325] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
myo-Inositol is a ubiquitous intracellular organic osmolyte and phosphoinositide precursor maintained at millimolar intracellular concentrations through the action of membrane-associated Na+-myo-inositol cotransporters (SMIT). Functional cloning and expression of a canine SMIT cDNA, which conferred SMIT activity in Xenopus oocytes, predicted a 718-amino acid peptide homologous to the Na+-glucose cotransporter with a potential protein kinase A phosphorylation site and multiple protein kinase C phosphorylation sites. A consistent approximately 1.0- to 13.5-kb array of transcripts hybridizing with this cDNA are osmotically induced in a variety of mammalian cells and species, yet SMIT activity appears to vary among different tissues and species. An open reading frame on human chromosome 21 (SLC5A3) homologous to that of the canine cDNA (96.5%) is thought to comprise an intronless human SMIT gene. Recently, this laboratory ascribed multiply sized, osmotically induced SMIT transcripts in human retinal pigment epithelial cells to the alternate utilization of several 3'-untranslated SMIT exons. This article describes an alternate splice donor site within the coding region that extends the open reading frame into the otherwise untranslated 3' exons, potentially generating novel SMIT isoforms. In these isoforms, the last putative transmembrane domain is replaced with intracellular carboxy termini containing a novel potential protein kinase A phosphorylation site and multiple protein kinase C phosphorylation sites, and this could explain the heterogeneity in the regulation and structure of the SMIT.
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Affiliation(s)
- F Porcellati
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan 48109-0354, USA
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Novak JE, Turner RS, Agranoff BW, Fisher SK. Differentiated human NT2-N neurons possess a high intracellular content of myo-inositol. J Neurochem 1999; 72:1431-40. [PMID: 10098846 DOI: 10.1046/j.1471-4159.1999.721431.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
myo-Inositol plays a key role in signal transduction and osmotic regulation events in the CNS. Despite the known high concentrations of inositol in the human CNS, relatively little is known about its distribution within the different cell types. In this report, inositol homeostasis was studied in NT2-N cells, a unique cell culture model of human CNS neurons. Differentiation of precursor NT2 teratocarcinoma cells into NT2-N neurons by means of retinoic acid treatment resulted in an increase in inositol concentration from 24 to 195 nmol/mg of protein. After measurement of intracellular water spaces, inositol concentrations of 1.6 and 17.4 mM were calculated for NT2 and NT2-N cells, respectively. The high concentrations of inositol in NT2-N neurons could be explained by (1) an increased uptake of inositol (3.7 vs. 1.6 nmol/mg of protein/h, for NT2-N and NT2 cells, respectively) and (2) a decreased efflux of inositol (1.7%/h for NT2-N neurons vs. 9.0%/h for NT2 cells). Activity of inositol synthase, which mediates de novo synthesis of inositol, was not detected in either cell type. The observation that CNS neurons maintain a high intracellular concentration of inositol may be relevant to the regulation of both phosphoinositide signaling and osmotic stress events in the CNS.
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Affiliation(s)
- J E Novak
- Mental Health Research Institute, and Department of Pharmacology, University of Michigan, Ann Arbor 48104-1687, USA
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7
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Karihaloo A, Kato K, Greene DA, Thomas TP. Protein kinase and Ca2+ modulation of myo-inositol transport in cultured retinal pigment epithelial cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1997; 273:C671-8. [PMID: 9277365 DOI: 10.1152/ajpcell.1997.273.2.c671] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The acute regulation of inwardly directed Na(+)-myo-inositol (MI) cotransporter activity and basal and volume-sensitive MI efflux by protein kinases C (PKC) and A (PKA), cytosolic Ca2+, and phosphoinositide (PI) turnover were characterized in cultured human retinal pigment epithelial cells using 2-[3H]MI and liquid scintillation spectrometry. Kinetic analysis revealed two distinct Na(+)-MI cotransporter components differing in apparent Michaelis constant and maximal velocity. Composite Na(+)-MI cotransport activity was stimulated by PKA activation, the muscarinic agonist carbachol, and the Ca2+ ionophore A-23187 and was inhibited by PKC activation. PKC activation also increased MI efflux, but only the volume-sensitive component, whereas PKA activation increased both basal and volume-sensitive MI efflux. These studies implicate PKC as a negative modulator of MI content through Na(+)-MI cotransport inhibition and potentiation of volume-sensitive MI efflux. PKA is a positive modulator of both Na(+)-MI cotransport and basal and volume-sensitive MI efflux. Cytosolic Ca2+ release through receptor-mediated PI hydrolysis may facilitate Na(+)-MI cotransport activity.
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Affiliation(s)
- A Karihaloo
- Department of Internal Medicine, University of Michigan, Ann Arbor 48109-0678, USA
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8
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Berry GT, Mallee JJ, Kwon HM, Rim JS, Mulla WR, Muenke M, Spinner NB. The human osmoregulatory Na+/myo-inositol cotransporter gene (SLC5A3): molecular cloning and localization to chromosome 21. Genomics 1995; 25:507-13. [PMID: 7789985 DOI: 10.1016/0888-7543(95)80052-n] [Citation(s) in RCA: 99] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A human Na+/myo-inositol cotransporter (SLC5A3) gene was cloned; sequencing revealed a single intron-free open reading frame of 2157 nucleotides. Containing 718 amino acid residues, the predicted protein is highly homologous to the product of the canine osmoregulatory SLC5A3 gene. The SLC5A3 protein is number 3 of the solute carrier family 5 and was previously designated SMIT. Using fluorescence in situ hybridization, the human SLC5A3 gene was localized to band q22 on chromosome 21. Many tissues including brain demonstrate gene expression. The inability of a trisomic 21 cell to downregulate expression of three copies of this osmoregulatory gene could result in increased flux of both myo-inositol and Na+ across the plasma membrane. The potential consequences include perturbations in the cell membrane potential and tissue osmolyte levels. The SLC5A3 gene may play a role in the pathogenesis of Down syndrome.
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Affiliation(s)
- G T Berry
- Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, USA
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9
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Shetty HU, Holloway HW. Assay of myo-inositol in cerebrospinal fluid and plasma by chemical ionization mass spectrometry of the hexaacetate derivative. BIOLOGICAL MASS SPECTROMETRY 1994; 23:440-4. [PMID: 8068740 DOI: 10.1002/bms.1200230710] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The paper describes a capillary gas chromatographic/mass spectrometric technique to quantitate myo-inositol in cerebrospinal fluid (CSF) and plasma. A highly abundant fragment ion, m/z 373, for the hexaacetate derivative of myo-inositol was generated by chemical ionization (CI). This ion and the analogous ion of hexadeuterated myo-inositol (the internal standard), m/z 379, were both monitored in the assay. CI was performed with acetonitrile vapor in an ion trap mass spectrometer. Microliter quantities of CSF or plasma were mixed with the internal standard, dried and acetylated. After a post-derivatization clean-up, samples were analyzed on a capillary gas chromatograph interfaced with a Finnigan ion trap. Standard curves constructed for both CSF and plasma were linear and reproducible. Absence of matrix effects and good precision in the results indicate the suitability of the technique for critical assays. Results from the determination of myo-inositol in the CSF and plasma of healthy subjects and those with neurological deficits are reported.
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Affiliation(s)
- H U Shetty
- Laboratory of Neurosciences, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892
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10
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Heacock AM, Seguin EB, Agranoff BW. Measurement of receptor-activated phosphoinositide turnover in rat brain: nonequivalence of inositol phosphate and CDP-diacylglycerol formation. J Neurochem 1993; 60:1087-92. [PMID: 8382261 DOI: 10.1111/j.1471-4159.1993.tb03258.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Two methods for the measurement of receptor-activated phosphoinositide turnover were evaluated for their degree of correspondence in slices of rat brain; they involved the Li(+)-dependent accumulations of either [3H]-inositol-labeled inositol phosphates or [3H]cytidine-labeled CDP-diacylglycerol. In contrast to the expectation that the ratio of these two responses would remain approximately constant, varying degrees of correspondence were obtained. The two extremes are exemplified by carbachol, which elicited large increases in both inositol phosphate and CDP-diacylglycerol labeling, and endothelin, which gave a robust inositol phosphate response with little or no accumulation of 3H-CDP-diacylglycerol. No instance of the presence of the latter response in the absence of 3H-inositol phosphate accumulation was observed. Measurement of 3H-CDP-diacylglycerol accumulation thus may add additional insight into the regulation of phosphoinositide turnover and the complex action of Li+.
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Affiliation(s)
- A M Heacock
- Neuroscience Laboratory, University of Michigan, Ann Arbor 48104-1687
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11
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Measurement of Inositol Trisphosphate by Gas Chromatography/Mas s Spectrometry: Femtomole Sensitivity Provided by Negative-Ion Chemical Ionization Mass Spectrometry in Submilligram Quantities of Tissue. ACTA ACUST UNITED AC 1993. [DOI: 10.1016/b978-0-12-185285-6.50025-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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12
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Fruen BR, Lester BR. High-affinity [3H]inositol uptake by dissociated brain cells and cultured fibroblasts from fetal mice. Neurochem Res 1991; 16:913-8. [PMID: 1787879 DOI: 10.1007/bf00965541] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The accumulation of [3H]inositol by mechanically dissociated brain cells and cultured skin fibroblasts from fetal mice was examined. Uptake by both tissues was strongly dependent on temperature and the presence of sodium ions. Brain and fibroblast uptake also responded similarly to inhibition by inositol isomers and phloridzin. At lower concentrations of inositol, both tissues exhibited high-affinity uptake kinetics with apparent Km values near 30 microM, similar to values observed previously in human fibroblasts and other cultured cells. The activity of brain high-affinity uptake was nearly an order of magnitude lower than that of fibroblasts, however, and was in part confounded by the presence of a low-affinity or simple diffusion system operating at inositol concentrations above 100 microM. Brain preparation from adult mice also showed evidence of high-affinity, Na+ dependent uptake, but its activity was significantly diminished relative to that of fetal brain preparations. Our results demonstrate that a high-affinity inositol transport system closely resembling that found in cultured cells is expressed in the developing mouse brain.
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Affiliation(s)
- B R Fruen
- Department of Genetics and Cell Biology, University of Minnesota, Minneapolis 55455
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13
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DaTorre SD, Corr PB, Creer MH. A sensitive method for the quantification of the mass of inositol phosphates using gas chromatography-mass spectrometry. J Lipid Res 1990. [DOI: 10.1016/s0022-2275(20)42336-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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McLaurin J, Hew C, Moscarello MA. Myelin basic protein does not contain a phosphatidylinositol anchor. Biochem J 1990; 269:278-9. [PMID: 1695845 PMCID: PMC1131567 DOI: 10.1042/bj2690278] [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: 12/28/2022]
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15
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Bailyes EM, Ferguson MA, Colaco CA, Luzio JP. Inositol is a constituent of detergent-solubilized immunoaffinity-purified rat liver 5'-nucleotidase. Biochem J 1990; 265:907-9. [PMID: 2306224 PMCID: PMC1133719 DOI: 10.1042/bj2650907] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
myo-Inositol analysis of detergent-solubilized immunoaffinity-purified rat liver 5'-nucleotidase showed the presence of 1 mol of myo-inositol/mol of enzyme monomer. This provides unequivocal evidence that the ectoenzyme 5'-nucleotidase is attached to liver membranes by a glycosyl-phosphatidylinositol lipid anchor.
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Affiliation(s)
- E M Bailyes
- Department of Clinical Biochemistry, University of Cambridge, Addenbrooke's Hospital, U.K
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16
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Hasegawa M, Doi K, Baba S. Measurement of myo-inositol in diabetic sera by GC/MS/SIM using n-butylboronate derivatives. Clin Chim Acta 1988; 176:207-12. [PMID: 3180469 DOI: 10.1016/0009-8981(88)90209-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- M Hasegawa
- Second Department of Internal Medicine, Kobe University School of Medicine, Japan
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17
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Ferguson MA, Homans SW, Dwek RA, Rademacher TW. Glycosyl-phosphatidylinositol moiety that anchors Trypanosoma brucei variant surface glycoprotein to the membrane. Science 1988; 239:753-9. [PMID: 3340856 DOI: 10.1126/science.3340856] [Citation(s) in RCA: 574] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Two forms of protein-membrane anchor have been described for the externally disposed glycoproteins of eukaryotic plasma membranes; namely, the hydrophobic transmembrane polypeptide and the complex glycosylphosphatidylinositol (G-PI) moiety. The chemical structures of the major species of G-PI anchors found on a single variant surface glycoprotein (VSG) of the parasitic protozoan Trypanosoma brucei were determined by a combination of nuclear magnetic resonance spectroscopy, mass spectrometry, chemical modification, and exoglycosidase digestions. The G-PI anchor was found to be heterogeneous with respect to monosaccharide sequence, and several novel glycosidic linkages were present. The results are pertinent to the mechanism of the biosynthesis of G-PI anchors.
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Affiliation(s)
- M A Ferguson
- Oxford Oligosaccharide Group, Department of Biochemistry, University of Oxford, England
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18
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Smith R, Braun PE, Ferguson MA, Low MG, Sherman WR. Direct measurement of inositol in bovine myelin basic protein. Biochem J 1987; 248:285-8. [PMID: 2449164 PMCID: PMC1148533 DOI: 10.1042/bj2480285] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Myelin basic protein has been isolated from bovine central-nervous-system myelin by four methods, none of which exposes the protein to acid. After purification the inositol content of both hydrolysed and unhydrolysed protein was quantified by g.c.-m.s. Basic protein prepared by all methods contained less than 4 mol % of inositol. It is concluded, contrary to a previous proposal, that covalent binding to phosphoinositides does not represent a general mechanism for attachment of this cytoplasmically-oriented protein to its membrane.
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Affiliation(s)
- R Smith
- Department of Biochemistry, McGill University, Montreal PQ, Canada
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19
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Wong YH, Kalmbach SJ, Hartman BK, Sherman WR. Immunohistochemical staining and enzyme activity measurements show myo-inositol-1-phosphate synthase to be localized in the vasculature of brain. J Neurochem 1987; 48:1434-42. [PMID: 2435847 DOI: 10.1111/j.1471-4159.1987.tb05682.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Rabbit anti-bovine myo-inositol-1-phosphate synthase was used to examine the distribution of that enzyme in perfused and immersion-fixed bovine brain and testis. In brain, intense and specific staining was found in the walls of all the vascular elements including cerebral capillaries. The remainder of brain parenchyma exhibited only low levels of background staining. In testis, an organ rich in the enzyme, blood vessels showed no specific staining. Instead, the enzyme was found in the seminiferous epithelium of the seminiferous tubules, perhaps localized in spermatozoa. To confirm the brain finding, the activity of myo-inositol-1-phosphate synthase was measured in bovine brain microvessel preparations and brain pial vessels. In these preparations the activity of the enzyme was found on average to be 7 and 22 times enriched over that in whole brain, respectively. The activities of two other enzymes of inositol metabolism, myo-inosose reductase and myo-inositol-1-phosphatase, were also examined for their distribution in brain. Those enzymes were found to be generally distributed. The surprising finding of a vascular localization of myo-inositol-1-phosphate synthase in brain raises new questions about the mechanism by which myo-inositol is concentrated to such high cellular levels in the principal substance of that organ.
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20
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Eisenberg F, Parthasarathy R. Measurement of biosynthesis of myo-inositol from glucose 6-phosphate. Methods Enzymol 1987; 141:127-43. [PMID: 3600356 DOI: 10.1016/0076-6879(87)41061-6] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Turk J, Wolf BA, McDaniel ML. Quantitation of myo-inositol as its hexakis(trifluoroacetyl) derivative with negative ion chemical ionization mass spectrometry. BIOMEDICAL & ENVIRONMENTAL MASS SPECTROMETRY 1986; 13:237-44. [PMID: 2941090 DOI: 10.1002/bms.1200130506] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Highly volatile hexakis(trifluoroacetyl) derivatives of myo-inositol and hexadeutero-myo-inositol have been prepared and analysed by capillary column gas chromatography/mass spectrometry. The electron impact and negative ion (methane) chemical ionization mass spectra of these compounds have been determined. Negative ion chemical ionization mass spectrometric analysis of hexakis(trifluoroacetyl)-myo-inositol achieves a sensitivity one order of magnitude greater than electron impact mass spectrometric analysis of hexakis(trimethylsilyl)-myo-inositol at appropriate selected ions. Stable isotope dilution measurement of myo-inositol versus hexadeutero-myo-inositol employing gas chromatography/negative ion chemical ionization mass spectrometry of the hexakis(trifluoroacetyl) derivatives is demonstrated, and this method is applied to the detection of inositol derived from hydrolysis of water-soluble inositol phosphates obtained from isolated pancreatic islets.
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23
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Swahn CG. Gas chromatographic-mass spectrometric determination of myo-inositol in human cerebrospinal fluid. J Neurochem 1985; 45:331-4. [PMID: 4009166 DOI: 10.1111/j.1471-4159.1985.tb03992.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The concentration of free myo-inositol in CSF was determined with a gas chromatographic-mass spectrometric method using deuterated myo-inositol as an internal standard after conversion to the hexa-O-acetyl derivative with acetic anhydride and pyridine. Twenty microliters of CSF is sufficient for the analysis which has a coefficient of variation of 9%. Identical analytical results were obtained on two different mass numbers. Schizophrenic patients were compared with healthy control persons. In addition, patients with rheumatoid arthritis or with neurological illnesses were studied. No consistent differences related to the illness could be found. The mean concentration of myo-inositol was about 25 micrograms/ml. Treatment of schizophrenic patients with chlorpromazine or sulpiride had no significant effect on the concentration of myo-inositol in CSF.
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Futerman AH, Low MG, Ackermann KE, Sherman WR, Silman I. Identification of covalently bound inositol in the hydrophobic membrane-anchoring domain of Torpedo acetylcholinesterase. Biochem Biophys Res Commun 1985; 129:312-7. [PMID: 4004881 DOI: 10.1016/0006-291x(85)91439-1] [Citation(s) in RCA: 134] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The hydrophobic, membrane-bound form of Torpedo acetylcholinesterase is specifically solubilized by a phosphatidylinositol-specific phospholipase C, suggesting that acetylcholinesterase is bound to the membrane via a direct and specific interaction with phosphatidylinositol (Futerman et al., Biochem. J. (1985) 226, 369-377). Here we demonstrate the presence of covalently bound inositol in the membrane-anchoring domain of purified Torpedo acetylcholinesterase. Upon removal of this domain, levels of inositol are reduced to only 15-20% of those found in the intact enzyme. The results presented strongly support our suggestion that phosphatidylinositol is indeed involved in anchoring acetylcholinesterase to the plasma membrane.
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Abstract
An enzymatic assay for myo-inositol (MI) is described. The method is based on the oxidation of MI by NAD+-dependent myo-inositol dehydrogenase, coupled to reoxidation of NADH with oxalacetate and malate dehydrogenase. The resultant malate is measured fluorimetrically. Several variations of the assay are described for measuring MI in serum and in tissues in amounts ranging from 0.2 pmol to 8 nmol. Highest sensitivity is achieved by applying an oil-well technique for handling small droplets, and by using the principle of enzymatic cycling. The potential of the technique is illustrated by MI measurements in several tissues of normal and diabetic rats and Chinese hamsters.
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Hallman M. Effect of extracellular myo-inositol on surfactant phospholipid synthesis in the fetal rabbit lung. ACTA ACUST UNITED AC 1984; 795:67-78. [PMID: 6547857 DOI: 10.1016/0005-2760(84)90105-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In the present investigation, myo-inositol was elevated in fetal serum by dietary manipulation. The myo-inositol-containing diet doubled the already high fetal serum myo-inositol between fetal days 26 and 28 but had no detectable effects on the lung. However, myo-inositol decreased betamethasone-induced (0.2 mg/kg, days 26.3 and 27.3, to the doe) inhibition in lung growth and potentiated the hormone-induced increase in alveolar space saturated phosphatidylcholine. This effect could not be explained by alteration of glucocorticoid-stimulated enzyme activity (phosphatidate cytidylyltransferase, phosphatidic acid phosphohydrolase, choline phosphate cytidylyltransferase) in the lung. Lung explants from 26-day-old fetuses were grown in a serum-free medium for 4 days. myo-Inositol (1.5 mM) had only a small effect on the phospholipid incorporation. Dexamethasone and thyroxine increased the incorporation of the precursors into surfactant phosphatidylglycerol and saturated phosphatidylcholine. myo-Inositol, in the presence of the hormones, switched the acidic surfactant phospholipid from phosphatidylglycerol to phosphatidylinositol and further increased the incorporation of surfactant-associated saturated phosphatidylcholine. myo-Inositol-excess preferentially increased the incorporation of NADPH (derived from glucose) and acetate into the fatty acid moiety of surfactant phosphatidylcholine. It is proposed that the high extracellular myo-inositol in immature fetuses provides an environment that promotes both the hormone-stimulated differentiation and the growth.
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Greene DA, Lattimer SA. Sodium- and energy-dependent uptake of myo-inositol by rabbit peripheral nerve. Competitive inhibition by glucose and lack of an insulin effect. J Clin Invest 1982; 70:1009-18. [PMID: 6813354 PMCID: PMC370313 DOI: 10.1172/jci110688] [Citation(s) in RCA: 130] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Experimental diabetes consistently reduces the concentration of free myo-inositol in peripheral nerve, which usually exceeds that of plasma by 90-100-fold. This phenomenon has been explicitly linked to the impairment of nerve conduction in the acutely diabetic streptozocin-treated rat. However, the mechanism by which acute experimental diabetes lowers nerve myo-inositol content and presumably alters nerve myo-inositol content and presumably alters nerve myo-inositol metabolism is unknown. Therefore, the effects of insulin and elevated medium glucose concentration of 2-[3H]myo-inositol uptake were studied in a metabolically-defined in vitro peripheral nerve tissue preparation derived from rabbit sciatic nerve, whose free myo-inositol content is reduced by experimental diabetes. The results demonstrate that myo-inositol uptake occurs by at least two distinct transport systems in the normal endoneurial preparation. A sodium- and energy-dependent saturable transport system is responsible for at least 94% of the measured uptake at medium myo-inositol concentrations approximating that present in plasma. This carrier-mediated transport system has a high affinity for myo-inositol (Kt = 63 microM), and is not influenced acutely by physiological concentrations of insulin; it is, however, inhibited by hyperglycemic concentrations of glucose added to the incubation medium in a primarily competitive fashion. Thus, competitive inhibition of peripheral nerve myo-inositol uptake by glucose may constitute a mechanism by which diabetes produces physiologically significant alterations in peripheral nerve myo-inositol metabolism.
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Godfrey DA, Hallcher LM, Laird MH, Matschinsky FM, Sherman WR. Distribution of myo-inositol in the cat cochlear nucleus. J Neurochem 1982; 38:939-47. [PMID: 7062042 DOI: 10.1111/j.1471-4159.1982.tb05333.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The distribution of myo-inositol, a substance that has been implicated in synaptic transmission, has been mapped within sections of the cat cochlear nucleus as well as some nearby regions. Highest values in the cochlear nucleus were found in regions of granule cells along the periphery of the anteroventral subdivision of the nucleus. Highest values overall were found in the molecular layer of the cerebellar flocculus. A fairly good correlation was found between myo-inositol levels and activities of the enzymes of acetylcholine metabolism in the cat cochlear nucleus, supporting the possibility that myo-inositol may be involved in cholinergic synaptic transmission. No positive correlation was found between myo-inositol levels and the levels of glutamate, aspartate, glycine, or gamma-aminobutyric acid (GABA). The most striking gradient of myo-inositol levels within a region was found in the auditory nerve, where different myo-inositol levels might be related to nerve fibers innervating different parts of the cochlea. The distribution of scyllo-inositol, a stereoisomer of myo-inositol, was also examined, and found to parallel closely the distribution of myo-inositol, with levels 4--5% as high.
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Andersen JR, Larsen E, Harbo H, Bertelsen B, Christensen JE, Gregersen G. Gas chromatographic mass spectrometric determination of myo-inositol in humans utilizing a deuterated internal standard. BIOMEDICAL MASS SPECTROMETRY 1982; 9:135-40. [PMID: 7046826 DOI: 10.1002/bms.1200090402] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The isotopic dilution technique was used for determining the content of myo-inositol in human urine, plasma and haemolysed erythrocyte samples. A deuterated myo-inositol, synthesized from inosose-2 by base-catalysed exchange of hydrogens by deuterium, followed by reduction of the inosose with 2H2, was added as internal standard to the samples at an early stage in the analytical procedure. After separation and derivatization to the hexa-acetate, the gas chromatographic mass spectrometric analysis was carried out. A 25 m fused silica capillary column coated with methyl silicone was used, and the ions selected for monitoring were m/z 210 and m/z 214, which are characteristic and abundant fragment ions from unlabelled and hexadeuterated myo-inositolhexa-acetate, respectively. Calibration curves from water, urine, plasma and haemolysed erythrocytes show parallel, linear responses in the ratio between analyte and internal standard in the area of interest (0.2-2.0).
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Holub BJ. The nutritional significance, metabolism, and function of myo-inositol and phosphatidylinositol in health and disease. ADVANCES IN NUTRITIONAL RESEARCH 1982; 4:107-41. [PMID: 6278902 DOI: 10.1007/978-1-4613-9934-6_5] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Recent advances in nutritional and biochemical research have substantiated the importance of inositol as a dietary and cellular constituent. The processes involved in the metabolism of inositol and its derivatives in mammalian tissues have been characterized both in vivo and at the enzyme level. Biochemical functions elucidated for phosphatidylinositol in biological membranes include the mediation of cellular responses to external stimuli, nerve transmission, and the regulation of enzyme activity through specific interactions with various proteins. Inositol deficiency in animals has been shown to produce an accumulation of triglyceride in liver, intestinal lipodystrophy, and other abnormalities. The metabolic mechanisms giving rise to these latter phenomena have been extensively studied as a function of dietary inositol. Altered metabolism of inositol has been documented in patients with diabetes mellitus, chronic renal failure, galactosemia, and multiple sclerosis. A moderate increase in plasma and nerve inositol levels by dietary supplementation has been suggested as a means of treating diabetic neuropathy, although excessively high levels, such as are found in uremic patients, may be neurotoxic. A thorough consideration of the biochemical functions of inositol and a further characterization of various diseases with the aid of appropriate animal models may suggest a possible role for inositol and other dietary components in their prevention and treatment
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[2] Determination of inositol phosphates by gas chromatography. Methods Enzymol 1982. [DOI: 10.1016/s0076-6879(82)89004-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
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Thomas DW, Parkhurst RM, Negi DS, Lunan KD, Wen AC, Brandt AE, Stephens RJ. Improved assay for alpha-tocopherol in the picogram range, using gas chromatography--mass spectrometry. JOURNAL OF CHROMATOGRAPHY 1981; 225:433-9. [PMID: 7298777 DOI: 10.1016/s0378-4347(00)80291-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Dyck PJ, Lambert EH, Windebank AJ, Lais AA, Sparks MF, Karnes J, Sherman WR, Hallcher LM, Low PA, Service FJ. Acute hyperosmolar hyperglycemia causes axonal shrinkage and reduced nerve conduction velocity. Exp Neurol 1981; 71:507-14. [PMID: 7461077 DOI: 10.1016/0014-4886(81)90028-5] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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Dyck PJ, Sherman WR, Hallcher LM, Service FJ, O'Brien PC, Grina LA, Palumbo PJ, Swanson CJ. Human diabetic endoneurial sorbitol, fructose, and myo-inositol related to sural nerve morphometry. Ann Neurol 1980; 8:590-6. [PMID: 7212646 DOI: 10.1002/ana.410080608] [Citation(s) in RCA: 364] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Fascicles of the sural nerve from each of 20 diabetic patients, mostly with maturity-onset diabetes, were studied by biochemical and pathological techniques, and results were compared to values found in nerve specimens from 15 healthy persons. The sorbitol and fructose content was much more variable in diabetic than in healthy nerves. More than one-third of the diabetic nerves had sorbitol and fructose values above the highest levels for controls. myo-Inositol and scyllo-inositol content was not reduced in diabetic nerves. The sorbitol, fructose, and inositol concentrations could not be related to clinical, neurophysiological, or pathological severity of neuropathy. A comparison of scored symptoms and signs and clinical neurophysiological studies against morphometric and teased fiber studies of sural nerve demonstrated that the former three provide sensitive and reliable measures of severity of neuropathy that can be used for controlled clinical trials of diabetic neuropathy. The presence and type of teased fiber abnormalities could be related to the duration of diabetes and to symptoms of neuropathy. In untreated diabetics without symptoms of neuropathy, a higher than normal frequency of teased fibers showing segmental demyelination and remyelination was found. Untreated diabetics with symptomatic neuropathy showed two kinds of abnormalities: fibers with segmental demyelination and remyelination and fibers undergoing axonal degeneration. In treated diabetics, who often had longstanding neuropathy, the most common abnormalities were fibers undergoing axonal degeneration.
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Allison JH, Boshans RL, Hallcher LM, Packman PM, Sherman WR. The effects of lithium on myo-inositol levels in layers of frontal cerebral cortex, in cerebellum, and in corpus callosum of the rat. J Neurochem 1980; 34:456-8. [PMID: 7411156 DOI: 10.1111/j.1471-4159.1980.tb06619.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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Brown MJ, Iwamori M, Kishimoto Y, Ostroff SM, Moser HW, Asbury AK. Endoneurial lipid composition of normal human sural nerve. Ann Neurol 1979; 5:239-44. [PMID: 443756 DOI: 10.1002/ana.410050305] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The endoneurial lipid composition was determined in 7 human sural nerves from subjects without known neurological disease. The nerves were morphologically normal, with myelinated fiber density of 7,710 +/- 1,210/mm2 (mean +/- SD). Endoneurium contained 30.7 +/- 1.5 mg total lipid per 100 mg of dry weight. Cholesterol was the predominant lipid (9.1 +/- 1.0 mg). Cholesterol ester was present only in very small quantities (0.2 +/- 0.1 mg). Cerebroside concentration was 4.5 +/- 0.3 mg, and sulfatide was 1.5 +/- 0.3 mg. The most abundant phospholipid was sphingomyelin (4.3 +/- 0.3 mg), followed by phosphatidylethanolamine (4.1 +/- 0.2 mg), phosphatidylcholine (3.8 +/- 0.2 mg), and phosphatidylinositol-phosphatidylserine (1.7 +/- 0.2 mg). Eighty-one percent of cerebroside nonhydroxy fatty acids were long chain (C20 to C26), and 67% were saturated. Technological advances now permit microchemical lipid analysis of human sural nerve biopsies in cases of neuropathy. When compared with our normative data, such studies may further the understanding of peripheral nerve disorders.
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Brown MJ, Iwamori M, Kishimoto Y, Rapoport B, Moser HW, Asbury AK. Nerve lipid abnormalities in human diabetic neuropathy: a correlative study. Ann Neurol 1979; 5:245-52. [PMID: 443757 DOI: 10.1002/ana.410050306] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
To study endoneurial lipid composition in human diabetic neuropathy, we biopsied sural nerves from 3 middleaged men with adult-onset diabetes mellitus. Magnitude of electrophysiological abnormalities and myelinated fiber loss paralleled the clinical severity of neuropathy in all cases. Cholesterol ester concentration was elevated to about 800% of normal in diabetic nerves. Reduction in total endoneurial lipid concentration correlated best with decrease in myelin volume as calculated from measured fiber diameters. Cholesterol, cerebroside, and most phospholipids were reduced in keeping with the severity of fiber loss in each nerve. The phosphatidylinositol-phosphatidylserine fraction was most reduced in the least affected nerves. Cerebroside nonhydroxy fatty acids in diabetic nerves were of shorter chain length and more saturated than normal. It is not yet clear whether the abnormalities of phosphatidylinositol-phosphatidylserine and cerebroside fatty acids are of pathogenetic importance or whether these changes may be the nonspecific consequence of axonal degeneration.
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