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Concerto C, Chiarenza C, Di Francesco A, Natale A, Privitera I, Rodolico A, Trovato A, Aguglia A, Fisicaro F, Pennisi M, Bella R, Petralia A, Signorelli MS, Lanza G. Neurobiology and Applications of Inositol in Psychiatry: A Narrative Review. Curr Issues Mol Biol 2023; 45:1762-1778. [PMID: 36826058 PMCID: PMC9955821 DOI: 10.3390/cimb45020113] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2023] [Revised: 02/07/2023] [Accepted: 02/15/2023] [Indexed: 02/22/2023] Open
Abstract
Inositol is a natural sugar-like compound, commonly present in many plants and foods. It is involved in several biochemical pathways, most of them controlling vital cellular mechanisms, such as cell development, signaling and nuclear processes, metabolic and endocrine modulation, cell growth, signal transduction, etc. In this narrative review, we focused on the role of inositol in human brain physiology and pathology, with the aim of providing an update on both potential applications and current limits in its use in psychiatric disorders. Overall, imaging and biomolecular studies have shown the role of inositol levels in the pathogenesis of mood disorders. However, when administered as monotherapy or in addition to conventional drugs, inositol did not seem to influence clinical outcomes in both mood and psychotic disorders. Conversely, more encouraging results have emerged for the treatment of panic disorders. We concluded that, despite its multifaceted neurobiological activities and some positive findings, to date, data on the efficacy of inositol in the treatment of psychiatric disorders are still controversial, partly due to the heterogeneity of supporting studies. Therefore, systematic use of inositol in routine clinical practice cannot be recommended yet, although further basic and translational research should be encouraged.
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Affiliation(s)
- Carmen Concerto
- Department of Clinical and Experimental Medicine, Psychiatry Unit, University of Catania, 95123 Catania, Italy
| | - Cecilia Chiarenza
- Department of Clinical and Experimental Medicine, Psychiatry Unit, University of Catania, 95123 Catania, Italy
| | - Antonio Di Francesco
- Department of Clinical and Experimental Medicine, Psychiatry Unit, University of Catania, 95123 Catania, Italy
| | - Antimo Natale
- Department of Clinical and Experimental Medicine, Psychiatry Unit, University of Catania, 95123 Catania, Italy
| | - Ivan Privitera
- Department of Clinical and Experimental Medicine, Psychiatry Unit, University of Catania, 95123 Catania, Italy
| | - Alessandro Rodolico
- Department of Clinical and Experimental Medicine, Psychiatry Unit, University of Catania, 95123 Catania, Italy
| | - Antonio Trovato
- Department of Clinical and Experimental Medicine, Psychiatry Unit, University of Catania, 95123 Catania, Italy
| | - Andrea Aguglia
- Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, Section of Psychiatry, University of Genoa, 16132 Genoa, Italy
- Istituto di Ricovero e Cura a Carattere Scientifico, Ospedale Policlinico San Martino, 16132 Genoa, Italy
| | - Francesco Fisicaro
- Department of Biomedical and Biotechnological Sciences, University of Catania, Via Santa Sofia 97, 95123 Catania, Italy
| | - Manuela Pennisi
- Department of Biomedical and Biotechnological Sciences, University of Catania, Via Santa Sofia 97, 95123 Catania, Italy
| | - Rita Bella
- Department of Medical, Surgical, and Advanced Technology, University of Catania, Via Santa Sofia 87, 95123 Catania, Italy
| | - Antonino Petralia
- Department of Clinical and Experimental Medicine, Psychiatry Unit, University of Catania, 95123 Catania, Italy
| | - Maria Salvina Signorelli
- Department of Clinical and Experimental Medicine, Psychiatry Unit, University of Catania, 95123 Catania, Italy
| | - Giuseppe Lanza
- Department of Surgery and Medical-Surgical Specialties, University of Catania, Via Santa Sofia 78, 95123 Catania, Italy
- Clinical Neurophysiology Research Unit, Oasi Research Institute-IRCCS, Via Conte Ruggero 73, 94018 Troina, Italy
- CERNUT–Research Centre for Nutraceuticals and Health Products, University of Catania, Viale A. Doria 6, 95125 Catania, Italy
- Correspondence: ; Tel.: +39-095-3782448
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Das TK, Dey A, Sabesan P, Javadzadeh A, Théberge J, Radua J, Palaniyappan L. Putative Astroglial Dysfunction in Schizophrenia: A Meta-Analysis of 1H-MRS Studies of Medial Prefrontal Myo-Inositol. Front Psychiatry 2018; 9:438. [PMID: 30298023 PMCID: PMC6160540 DOI: 10.3389/fpsyt.2018.00438] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2018] [Accepted: 08/24/2018] [Indexed: 11/22/2022] Open
Abstract
Background: Several lines of evidence support a role for astroglial pathology in schizophrenia. Myo-inositol is particularly abundant in astroglia. Many small sized studies have reported on myo-inositol concentration in schizophrenia, but to date these have not been pooled to estimate a collective effect size. Methods: We reviewed all proton magnetic resonance spectroscopy (1H-MRS) studies reporting myo-inositol values for patients satisfying DSM or ICD based criteria for schizophrenia in comparison to a healthy controls group in the medial prefrontal cortex published until February 2018. A random-effects model was used to calculate the pooled effect size using metafor package. A meta-regression analysis of moderator variables was also undertaken. Results: The literature search identified 19 studies published with a total sample size of 585 controls, 561 patients with schizophrenia. Patients with schizophrenia had significantly reduced medial prefrontal myo-inositol compared to controls (RFX standardized mean difference = 0.19, 95% CI [0.05-0.32], z = 2.72, p = 0.0067; heterogeneity p = 0.09). Studies with more female patients reported more notable schizophrenia-related reduction in myo-inositol (z = 2.53, p = 0.011). Discussion: We report a small, but significant reduction in myo-inositol concentration in the medial prefrontal cortex in schizophrenia. The size of the reported effect indicates that the biological pathways affecting the astroglia are likely to operate only in a subset of patients with schizophrenia. MRS myo-inositol could be a useful tool to stratify and investigate such patients.
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Affiliation(s)
- Tushar Kanti Das
- Department of Psychiatry, University of Western Ontario, London, ON, Canada.,Robarts Research Institute, London, ON, Canada.,Lawson Health Research Institute, London, ON, Canada
| | - Avyarthana Dey
- Department of Psychiatry, University of Western Ontario, London, ON, Canada.,Robarts Research Institute, London, ON, Canada
| | | | - Alborz Javadzadeh
- Department of Psychiatry, University of Western Ontario, London, ON, Canada
| | - Jean Théberge
- Lawson Health Research Institute, London, ON, Canada.,Department of Medical Biophysics, University of Western Ontario, London, ON, Canada
| | - Joaquim Radua
- FIDMAG Germanes Hospitalàries, CIBERSAM, Sant Boi de Llobregat & Institut d'Investigacions Biomediques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Lena Palaniyappan
- Department of Psychiatry, University of Western Ontario, London, ON, Canada.,Robarts Research Institute, London, ON, Canada.,Lawson Health Research Institute, London, ON, Canada.,Department of Medical Biophysics, University of Western Ontario, London, ON, Canada
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Firth J, Stubbs B, Sarris J, Rosenbaum S, Teasdale S, Berk M, Yung AR. The effects of vitamin and mineral supplementation on symptoms of schizophrenia: a systematic review and meta-analysis. Psychol Med 2017; 47:1515-1527. [PMID: 28202095 DOI: 10.1017/s0033291717000022] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
BACKGROUND When used as an adjunctive with antipsychotics, certain vitamins and minerals may be effective for improving symptomatic outcomes of schizophrenia, by restoring nutritional deficits, reducing oxidative stress, or modulating neurological pathways. METHOD We conducted a systematic review of all randomized controlled trials (RCTs) reporting effects of vitamin and/or mineral supplements on psychiatric symptoms in people with schizophrenia. Random-effects meta-analyses were used to calculate the standardized mean difference between nutrient and placebo treatments. RESULTS An electronic database search in July 2016 identified 18 eligible RCTs, with outcome data for 832 patients. Pooled effects showed that vitamin B supplementation (including B6, B8 and B12) reduced psychiatric symptoms significantly more than control conditions [g = 0.508, 95% confidence interval (CI) 0.01-1.01, p = 0.047, I 2 = 72.3%]. Similar effects were observed among vitamin B RCTs which used intention-to-treat analyses (g = 0.734, 95% CI 0.00-1.49, p = 0.051). However, no effects of B vitamins were observed in individual domains of positive and negative symptoms (both p > 0.1). Meta-regression analyses showed that shorter illness duration was associated with greater vitamin B effectiveness (p = 0.001). There were no overall effects from antioxidant vitamins, inositol or dietary minerals on psychiatric symptoms. CONCLUSIONS There is preliminary evidence that certain vitamin and mineral supplements may reduce psychiatric symptoms in some people with schizophrenia. Further research is needed to examine how the benefits of supplementation relate to nutrient deficits and the impact upon underlying neurobiological pathways, in order to establish optimal nutrient formulations for improving clinical outcomes in this population. Future studies should also explore the effects of combining beneficial nutrients within multi-nutrient formulas.
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Affiliation(s)
- J Firth
- Division of Psychology and Mental Health,University of Manchester,Manchester,UK
| | - B Stubbs
- Physiotherapy Department,South London and Maudsley NHS Foundation Trust, London,UK
| | - J Sarris
- Department of Psychiatry,University of Melbourne, The Melbourne Clinic,Melbourne,Australia
| | - S Rosenbaum
- Department of Exercise Physiology,School of Medical Sciences,Faculty of Medicine,University of New South Wales,Sydney,Australia
| | - S Teasdale
- Keeping the Body in Mind Program,South Eastern Sydney Local Health District,Sydney,Australia
| | - M Berk
- Deakin University, IMPACT Strategic Research Centre, School of Medicine,Victoria,Australia
| | - A R Yung
- Division of Psychology and Mental Health,University of Manchester,Manchester,UK
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Vadnal R, Parthasarathy L, Parthasarathy R. Promising Psychotherapeutic Effects of the Natural Sugar: Myo-Inositol. Nutr Neurosci 2016; 1:21-33. [DOI: 10.1080/1028415x.1998.11747210] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Azab AN, Agam G, Kaplanski J, Delbar V, Greenberg ML. Inositol depletion: a good or bad outcome of valproate treatment? FUTURE NEUROLOGY 2008. [DOI: 10.2217/14796708.3.3.275] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Bipolar affective disorder is a severe and chronic disabling illness affecting 1.5% of the general population. Lithium, valproate and other mood stabilizers are used to treat bipolar disorder; however, these are ineffective for, and not tolerated by, a significant percentage of patients, underscoring the urgent need for better medications. Although not universally accepted, the inositol-depletion hypothesis is one of the main hypotheses suggested to explain the therapeutic mechanism of mood-stabilizing drugs. This paper reviews the relevance of the inositol-depletion hypothesis, paying special attention to the inhibition of inositol de novo synthesis by valproate. It also discusses inositol supplementation as a treatment strategy for multiple neurological disorders, including prophylactic use against valproate-induced neural tube defects.
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Affiliation(s)
- Abed N Azab
- Ben-Gurion University of the Negev, School for Community Health Professions, Faculty of Health Sciences, PO Box 653, Beer-Sheva 84105, Israel
| | - Galila Agam
- Ben-Gurion University of the Negev, Psychiatry Research Unit & Department of Clinical Biochemistry, Faculty of Health Sciences, PO Box 4600, Beer-Sheva 84170, Israel
| | - Jacob Kaplanski
- Ben-Gurion University of the Negev, Department of Clinical Pharmacology, Faculty of Health Sciences, PO Box 653, Beer-Sheva 84105, Israel
| | - Vered Delbar
- Ben-Gurion University of the Negev, School for Community Health Professions, Faculty of Health Sciences, PO Box 653, Beer-Sheva 84105, Israel
| | - Miriam L Greenberg
- Wayne State University, Department of Biological Sciences, Detroit, MI 48202, USA
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Parthasarathy LK, Seelan RS, Tobias C, Casanova MF, Parthasarathy RN. Mammalian inositol 3-phosphate synthase: its role in the biosynthesis of brain inositol and its clinical use as a psychoactive agent. Subcell Biochem 2006; 39:293-314. [PMID: 17121280 DOI: 10.1007/0-387-27600-9_12] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Affiliation(s)
- Latha K Parthasarathy
- Molecular Neuroscience Laboratory, Autism Research Unit, Mental Health, Behavioral Science and Research Services, VA Medical Center (151), Louisville, Kentucky 40206, USA
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Kim H, McGrath BM, Silverstone PH. A review of the possible relevance of inositol and the phosphatidylinositol second messenger system (PI-cycle) to psychiatric disorders--focus on magnetic resonance spectroscopy (MRS) studies. Hum Psychopharmacol 2005; 20:309-26. [PMID: 15880397 DOI: 10.1002/hup.693] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Myo-inositol is an important part of the phosphatidylinositol second messenger system (PI-cycle). Abnormalities in nerve cell myo-inositol levels and/or PI-cycle regulation has been suggested as being involved in the pathophysiology and/or treatment of many psychiatric disorders including bipolar disorder, major depressive disorder, panic disorder, obsessive-compulsive disorder, eating disorders and schizophrenia. This review examines the metabolism and biochemical importance of myo-inositol and the PI-cycle. It relates this to the current in vivo evidence for myo-inositol and PI-cycle involvement in these psychiatric disorders, particularly focusing upon the magnetic resonance spectroscopy (MRS) findings in patient studies to date. From this review it is concluded that while the evidence suggests probable relevance to the pathophysiology and/or treatment of bipolar disorder, there is much less support for a significant role for the PI-cycle or myo-inositol in any other psychiatric disorder. More definitive investigation is required before PI-cycle dysfunction can be considered specific to bipolar disorder.
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Affiliation(s)
- Hyeonjin Kim
- Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada
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Skosnik PD, Yao JK. From membrane phospholipid defects to altered neurotransmission: is arachidonic acid a nexus in the pathophysiology of schizophrenia? Prostaglandins Leukot Essent Fatty Acids 2003; 69:367-84. [PMID: 14623490 DOI: 10.1016/j.plefa.2003.08.008] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Schizophrenia (SZ) is a devastating neuropsychiatric disorder affecting 1% of the general population, and is characterized by symptoms such as delusions, hallucinations, and blunted affect. While many ideas regarding SZ pathogenesis have been put forth, the majority of research has focused on neurotransmitter function, particularly in relation to altered dopamine activity. However, treatments based on this paradigm have met with only modest success, and current medications fail to alleviate symptoms in 30-60% of patients. An alternative idea postulated a quarter of a century ago by Feldberg (Psychol. Med. 6 (1976) 359) and Horrobin (Lancet 1 (1977) 936) involves the theory that SZ is associated in part with phospholipid/fatty acid abnormalities. Since then, it has been repeatedly shown that in both central and peripheral tissue, SZ patients demonstrate increased phospholipid breakdown and decreased levels of various polyunsaturated fatty acids (PUFAs), particularly arachidonic acid (AA). Given the diverse physiological function of membrane phospholipids and PUFAs, an elucidation of their role in SZ pathophysiology may provide novel strategies in the treatment of this disorder. The purpose of this review is to summarize the relevant data on membrane phospholipid/PUFA defects in SZ, the physiological consequence of altered AA signaling, and how they relate to the neurobiological manifestations of SZ and therapeutic outcome.
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Affiliation(s)
- P D Skosnik
- Department of Psychology, Indiana University, Bloomington, IN, USA
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Einat H, Clenet F, Shaldubina A, Belmaker RH, Bourin M. The antidepressant activity of inositol in the forced swim test involves 5-HT(2) receptors. Behav Brain Res 2001; 118:77-83. [PMID: 11163636 DOI: 10.1016/s0166-4328(00)00314-4] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The effect of inositol as an antidepressant was previously demonstrated in both animal models of depression-like behavior and in clinical trials. Unlike most antidepressant drugs, inositol does not have a clear target in the synapse and was not demonstrated to alter monoamine levels in the brain. The present study attempted to draw a psychopharmacological profile of inositol's behavioral effects by exploring the interactions between the drug and specific receptor agonists and antagonists in the forced swim test. Rats received inositol treatment (or control) in combination with the serotonergic metabolism inhibitor PCPA or with the noradrenergic neurotoxin DSP-4. Results indicated that PCPA but not DSP-4 abolished the ability of inositol to cause a reduction in immobility time in the forced swim test. In mice, the specific 5-HT(2A)/5-HT(2C) antagonist ritanserin, but not the 5-HT(1A)/5-HT(1B)/beta adrenergic antagonist pindolol, abolished inositol's effect in the forced swim test. The 5-HT(2A)/5-HT(2C) agonist DOI and the 5-HT(1A) agonist 8-OH-DPAT did not have any significant effects on inositol's activity. The present data indicates that the antidepressant effect of inositol may involve 5-HT(2) receptors. It is thus possible that the effects of reuptake antidepressant drugs and the effects of inositol may have a common final pathway.
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Affiliation(s)
- H Einat
- Beer Sheva Mental Health Center, Faculty of Health Sciences, Ben Gurion University of the Negev, P.O. Box 4600, Beer Sheva, Israel.
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Abstract
Clinical trials indicate that inositol may be effective in the treatment of patients with depression, panic disorder and obsessive compulsive disorder (OCD), but not in the treatment of patients with schizophrenia, Alzheimer's disease, ADHD or autism. This spectrum of clinical action parallels that of serotonin selective reuptake inhibitors (SSRIs), but inositol is a precursor in the phosphatidylinositol cycle, a second messenger system distal to the receptor for 5HT-2. To study its mechanism of therapeutic action there is a need to test inositol's activity in animal models of psychopathology. In rats, chronic inositol was demonstrated to increase activity levels, reduce immobility time in the forced swim test and in the reserpine-induced hypoactivity models of depression, and reduce anxiety-like behaviors in the elevated plus-maze. The reduction in anxiety-like behaviors appears to be related to baseline levels of activity. Inositol treatment was not observed to have any effect on amphetamine-induced hyperactivity, apomorphine-induced stereotypy, or on the performance of memory tasks by monkeys. Clinical controlled trials of inositol in patients with depression, panic disorder, and OCD were small, and positive psychoactive effects in animals clearly strengthen the case for further clinical trials and potential for general therapeutic use in humans.
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Affiliation(s)
- H Einat
- Ministry of Health Mental Health Center, Faculty of Health Sciences, Ben Gurion University of the Negev, Beersheva, Israel
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Yao JK, van Kammen DP. Incorporation of 3H-arachidonic acid into platelet phospholipids of patients with schizophrenia. Prostaglandins Leukot Essent Fatty Acids 1996; 55:21-6. [PMID: 8888119 DOI: 10.1016/s0952-3278(96)90141-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Incorporation of 3H-arachidonic acid (AA) into resting platelets was carried out in normal control subjects as well as in schizophrenic patients before and after haloperidol (HD) withdrawal. Metabolic turnover of membrane phospholipids was subsequently evaluated in prelabelled platelets at various time intervals after thrombin activation. 3H-AA was mainly incorporated into phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylinositol (PI) and phosphatidylserine (PS) of resting platelets. Very minute amounts of 3H-labelling were found in phosphatidic acid (PA). Following thrombin activation, however, substantial amounts of 3H-labelling were found in PA. Such an increase in thrombin-induced PA formation was not reduced in schizophrenic patients both receiving and not receiving HD treatment. Increased labelling has been found in platelet diacylglycerol (DAG) after thrombin activation. It is therefore not likely that a decreased DAG kinase activity contributes to the accumulation of DAG. However, the thrombin-induced PA production was temporally associated with a decreased 3H-labelling in PI, but not in PC, PS and PE. The present data taken together with our previous findings suggest that the increased production of second messengers (DAG, PA and inositol phosphates) in schizophrenia may result from an increased phospholipase C (PLC) activity in schizophrenia, because thrombin-induced platelet activation is mediated by polyphosphoinositide hydrolysis through the G-protein activation.
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Affiliation(s)
- J K Yao
- Department of Veterans Affairs Medical Center, Pittsburgh, PA, USA
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Levine J, Goldberger I, Rapaport A, Schwartz M, Schield C, Elizur A, Belmaker RH, Shapiro J, Agam G. CSF inositol in schizophrenia and high-dose inositol treatment of schizophrenia. Eur Neuropsychopharmacol 1994; 4:487-90. [PMID: 7894259 DOI: 10.1016/0924-977x(94)90297-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Inositol is a key metabolite in the phosphatidylinositol cycle, which is a second messenger system for serotonin-2 receptors that have been implicated in the pathophysiology of schizophrenia. Cerebrospinal fluid inositol levels were measured in 20 schizophrenic patients and 19 age- and sex-matched controls and no difference was found. However, the patients were all neuroleptic-treated. A controlled double-blind crossover trial of 12 g daily of inositol for a month in 12 anergic schizophrenic patients, twice the dose given before in schizophrenia, did not show any beneficial effects. However, the number of patients studied was small and the length of time of inositol administration may not have been sufficient.
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Affiliation(s)
- J Levine
- Abarbanel Mental Health Center, Bat Yam, Israel
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Kofman O, Belmaker RH. Ziskind-Somerfeld Research Award 1993. Biochemical, behavioral, and clinical studies of the role of inositol in lithium treatment and depression. Biol Psychiatry 1993; 34:839-52. [PMID: 8110911 DOI: 10.1016/0006-3223(93)90052-f] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Lithium (Li) reduces brain inositol levels by inhibiting the enzyme inositol monophosphatase. The enzyme inositol-1-phosphatase was measured in human red blood cells of controls, Li-free bipolar patients, and Li-treated bipolar patients and was found to be reduced by 80% in Li-treated bipolars, thus supporting the concept that chronic Li at therapeutic concentrations inhibits this enzyme. Two behaviors in rats caused by Li, reduction of rearing, and Li-pilocarpine seizures, are reversed by intracerebroventricular replenishment of inositol. The reversal is stereospecific to the naturally occurring myo-inositol; whereas the stereoisomer L-chiro-inositol is ineffective. The reversal is dose-dependent, requiring a dose consistent with known quantities of brain inositol depletion; and is time-dependent, as inositol must be given 1-8 h before stimulation. High-dose peripheral inositol also reverses the limbic seizures induced by Li-pilocarpine, and using gas chromatography was shown to increase brain inositol levels that had been reduced by Li treatment. Low-dose inositol could be shown to reverse a peripheral Li-induced side effect, polyuria/polydipsia, in rats and in patients treated with Li. A higher dose of inositol markedly reduced Hamilton Depression Ratings in 9 of 11 unipolar major depressive disorder patients previously unresponsive to tricyclics, in an open design, but had no effect on chronic schizophrenics in a controlled double-blind randomized crossover trial. A new inositol monophosphatase inhibitor, a fungal product originally discovered as a complement inhibitor, was found to act like Li and lower the seizure threshold for subconvulsant doses of pilocarpine. These data suggest that inositol monophosphatase inhibition is a key mechanism of Li's therapeutic action and that design of new inositol monophosphatase inhibitors may be a practical strategy to create new compounds with Li-like therapeutic effects.
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Affiliation(s)
- O Kofman
- Ministry of Health Mental Health Center Faculty of Health Science, Ben Gurion University of the Negev Beersheva, Israel
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