Neurobiology of a Mutation in Glycine Metabolism in Psychotic Disorders
NCT ID: NCT01720316
Last Updated: 2017-09-19
Study Results
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View full resultsBasic Information
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Recruitment Status
COMPLETED
Clinical Phase
PHASE2
Total Enrollment
2 participants
Study Classification
INTERVENTIONAL
Study Start Date
2012-12-10
Study Completion Date
2017-05-31
Brief Summary
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The purpose of this study is to assess the efficacy of oral glycine as an augmentation strategy in two psychotic patients with a triplication (4 copies) of the gene glycine decarboxylase (GLDC). Subjects will first undergo a double-blind placebo-controlled clinical trial in which one 6-week arm will involve glycine (maximum daily dose of 0.8 g/kg, administered on a TID dosing schedule) and one 6-week arm will involve placebo. A 2-week period of no treatment will occur between treatment arms. A 6-week period of open-label glycine (maximum daily dose of 0.8 g/kg, administered on a TID dosing schedule) will follow the double-blind placebo-controlled clinical trial. Prior to the double-blind placebo-controlled clinical trial and at the end of the open-label glycine trial, the following procedures will be carried out: structural MRI (3T), Proton 1H MRS (4T), fMRI (3T), steady-state visual evoked potentials, and EEG. Positive, negative, and affective symptoms and neurocognitive function as well as plasma levels of large neutral and large and small neutral and excitatory amino acids and psychotropic drug levels will be assessed periodically. In addition, 1H MRS (4T) for 2 hours after a single oral dose of a glycine-containing drink will be assessed at baseline. Pharmaceutical grade glycine powder (Ajinomoto) or placebo will be dissolved in 20% solution and prepared by the McLean Hospital Pharmacy.
Because the results of the double-blind placebo-controlled and open-label glycine treatment arms showed substantial clinical benefit to the participants, the study has been extended to include six months of chronic open-label glycine in order to determine 1) whether the clinical benefits achieved within 6 weeks previously recur, 2) the clinical benefits are lasting, and 3) additional clinical benefits occur with longer exposure. The glycine for this extension will be provided by Letco Medical.
The investigators hypothesize that mutation carriers will have reduced endogenous brain glycine and GABA levels and increased brain glutamate and glutamine levels. Glycine administration will increase brain glycine in the two carriers, but to a lesser extent than in non-carrier family members and controls.
The investigators hypothesize reduced activation of magnocellular pathways and abnormal ERPs modulated by NMDA in mutation carriers compared with non-carrier family members and controls.
The investigators hypothesize that glycine, but not placebo, will improve positive, negative and affective symptoms as well as neurocognitive function.
The investigators also hypothesize that open-label glycine will improve clinical and cognitive functioning, will partially normalize decreased baseline glycine and GABA and increased glutamate and glutamine, and will partially normalize magnocellular pathway activation and abnormal evoked potentials.
Because the results of the double-blind placebo-controlled and open-label glycine treatment arms showed substantial clinical benefit to the participants, the study has been extended to include six months of chronic open-label glycine in order to determine 1) whether the clinical benefits achieved within 6 weeks previously recur, 2) the clinical benefits are lasting, and 3) additional clinical benefits occur with longer exposure. The glycine for this extension will be provided by Letco Medical.
The investigators hypothesize that mutation carriers will have reduced endogenous brain glycine and GABA levels and increased brain glutamate and glutamine levels. Glycine administration will increase brain glycine in the two carriers, but to a lesser extent than in non-carrier family members and controls.
The investigators hypothesize reduced activation of magnocellular pathways and abnormal ERPs modulated by NMDA in mutation carriers compared with non-carrier family members and controls.
The investigators hypothesize that glycine, but not placebo, will improve positive, negative and affective symptoms as well as neurocognitive function.
The investigators also hypothesize that open-label glycine will improve clinical and cognitive functioning, will partially normalize decreased baseline glycine and GABA and increased glutamate and glutamine, and will partially normalize magnocellular pathway activation and abnormal evoked potentials.
Detailed Description
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Multiple rare structural variants of relatively recent evolutionary origin are recognized as important risk factors for schizophrenia (SZ) and other neurodevelopmental disorders (e.g., autism spectrum disorders, mental retardation, epilepsy) with odds ratios as high as 7-30 (Sebat et al. 2009; Malhotra et al. 2011; Heinzen et al. 2010; Weiss et al. 2008; McCarthy et al. 2009). We have found a de novo structural rearrangement on chromosome 9p24.1 in two psychotic patients. One of the genes in this region is the gene encoding glycine decarboxylase (GLDC), which affects brain glycine metabolism. GLDC encodes the glycine decarboxylase or glycine cleavage system P-protein, which is involved in degradation of glycine in glia cells. Carriers of the GLDC triplication would be expected to have low levels of brain Gly, resulting in NMDA receptor-mediated hypofunction, which has been strongly implicated in the pathophysiology of schizophrenia (Olney \& Farber, 1995; Coyle, 2006; Javitt, 2007).
There is an extensive literature on the effects of NMDA enhancing agents on positive, negative, and depressive symptoms and on neurocognitive function (see Tsai \& Lin, 2010; Lin et al. 2011 for reviews). Although many studies have reported positive results in at least one symptom domain (Heresco-Levy et al. 1996, 1999, 2004; Tsai et al. 1998, 1999, 2004, 2006; Javitt et al. 2001; Goff et al. 1996; Lane et al. 2008), the results of other studies have been negative or ambiguous (Goff et al. 1999; Evins et al. 2000; Duncan et al. 2004; van Berckel et al. 1999). Factors likely to contribute to this variability include: mechanism of action of the agent, compliance, concurrent treatment with first- vs second generation antipsychotic drugs, baseline glycine blood levels, presence/absence of kynurenine pathway metabolic abnormalities (Wonodi et al. 2010; Erhardt et al. 2007) and individual differences in brain glycine uptake and metabolism (Kaufman et al. 2009; Buchanan et al. 2007). Genetic variants that impact the synthesis and breakdown of glycine, glutamate, or other modulators of NMDA receptor function are also likely to have significant effects. Although glycine augmentation has shown variable efficacy in patients unselected for having a mutation that would be expected to lower brain glycine levels, the GLDC triplication in the two carriers in this study would be expected to result in unusually low brain glycine levels, supporting its therapeutic potential as an augmentation strategy.
Thus, it is important to evaluate the therapeutic efficacy of glycine augmentation in individuals in whom there is a high prior probability of therapeutic benefit and to characterize the neurobiology of this mutation in terms of brain metabolites, brain function, and the pharmacokinetics of glycine metabolism using well-established methods (Kaufman et al. 2009; Prescot et al. 2006; Martinez et al. 2008; Butler et al. 2001; Jensen et al. 2009; Ongur et al. 2008).
There is an extensive literature on the effects of NMDA enhancing agents on positive, negative, and depressive symptoms and on neurocognitive function (see Tsai \& Lin, 2010; Lin et al. 2011 for reviews). Although many studies have reported positive results in at least one symptom domain (Heresco-Levy et al. 1996, 1999, 2004; Tsai et al. 1998, 1999, 2004, 2006; Javitt et al. 2001; Goff et al. 1996; Lane et al. 2008), the results of other studies have been negative or ambiguous (Goff et al. 1999; Evins et al. 2000; Duncan et al. 2004; van Berckel et al. 1999). Factors likely to contribute to this variability include: mechanism of action of the agent, compliance, concurrent treatment with first- vs second generation antipsychotic drugs, baseline glycine blood levels, presence/absence of kynurenine pathway metabolic abnormalities (Wonodi et al. 2010; Erhardt et al. 2007) and individual differences in brain glycine uptake and metabolism (Kaufman et al. 2009; Buchanan et al. 2007). Genetic variants that impact the synthesis and breakdown of glycine, glutamate, or other modulators of NMDA receptor function are also likely to have significant effects. Although glycine augmentation has shown variable efficacy in patients unselected for having a mutation that would be expected to lower brain glycine levels, the GLDC triplication in the two carriers in this study would be expected to result in unusually low brain glycine levels, supporting its therapeutic potential as an augmentation strategy.
Thus, it is important to evaluate the therapeutic efficacy of glycine augmentation in individuals in whom there is a high prior probability of therapeutic benefit and to characterize the neurobiology of this mutation in terms of brain metabolites, brain function, and the pharmacokinetics of glycine metabolism using well-established methods (Kaufman et al. 2009; Prescot et al. 2006; Martinez et al. 2008; Butler et al. 2001; Jensen et al. 2009; Ongur et al. 2008).
Conditions
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Schizo-affective Disorder
Bipolar Disorder
Study Design
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Allocation Method
RANDOMIZED
Intervention Model
CROSSOVER
Primary Study Purpose
TREATMENT
Blinding Strategy
QUADRUPLE
Participants
Caregivers
Investigators
Outcome Assessors
Study Groups
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glycine
Glycine, up to 0.8 g/kg, administered with TID dosing for 6 weeks Double-blind
Group Type
ACTIVE_COMPARATOR
Glycine
Intervention Type
DRUG
Double-blind placebo controlled trial of glycine or placebo, followed by open-label glycine
Placebo
placebo, TID dosing, 6 weeks Double-blind
Group Type
PLACEBO_COMPARATOR
placebo
Intervention Type
DRUG
glycine, open-label
glycine, up to 0.8 g/kg, administered with TID dosing for 6 weeks
Group Type
ACTIVE_COMPARATOR
Glycine
Intervention Type
DRUG
Double-blind placebo controlled trial of glycine or placebo, followed by open-label glycine
Interventions
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Glycine
Double-blind placebo controlled trial of glycine or placebo, followed by open-label glycine
Intervention Type
DRUG
placebo
Intervention Type
DRUG
Eligibility Criteria
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Inclusion Criteria
* Triplication of glycine decarboxylase gene
Exclusion Criteria
* Normal glycine decarboxylase copy number
Minimum Eligible Age
18 Years
Maximum Eligible Age
65 Years
Eligible Sex
ALL
Accepts Healthy Volunteers
No
Sponsors
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National Institute of Mental Health (NIMH)
NIH
Sponsor Role
collaborator
Mclean Hospital
OTHER
Sponsor Role
lead
Responsible Party
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Deborah L. Levy
Associate Professor
Responsibility Role
PRINCIPAL_INVESTIGATOR
Principal Investigators
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Deborah L Levy, PhD
Role: PRINCIPAL_INVESTIGATOR
Mclean Hospital
Locations
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McLean Hospital
Belmont, Massachusetts, United States
Site Status
Countries
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United States
References
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DERIVED
Provided Documents
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Document Type: Informed Consent Form
Document Type: Statistical Analysis Plan
Document Type: Study Protocol
Other Identifiers
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2012p001597
Identifier Type: -
Identifier Source: org_study_id