Acute Glycine Pharmacodynamic Study

Schizophrenia Clinical Trial

Official title:

Acute Glycine Pharmacodynamic Study

Clinical Trial Details — Status: Completed

Administrative data

• NCT number: NCT01610011
• Other study ID #: 2010P001576
• Status: Completed
• Phase: N/A
• First received: May 28, 2012
• Last updated: September 25, 2015
• Start date: July 2010
• Est. completion date: December 2013

Study information

• Verified date: September 2015
• Source: Mclean Hospital
• Contact: n/a
• Is FDA regulated: No
• Health authority: United States: Institutional Review Board
• Study type: Interventional

Clinical Trial Summary

The purpose of this study is to use proton magnetic resonance spectroscopy (MRS) at 4 Tesla to measure brain glycine levels noninvasively at baseline and for 2 hours after a single oral dose of a concentrated glycine-containing beverage, and to compare MRS glycine measurements to glycine blood levels in samples obtained after each MRS spectrum.

The investigators hypothesize that they will observe a high correlation between the magnitude increases in brain and plasma glycine levels over this time frame.

The investigators also hypothesize that we will observe large intersubject variability in glycine uptake rates into brain and blood.

The investigators also hypothesize that subjects with a glycine decarboxylase (GLDC) mutation (triplication) will have lower baseline plasma and brain glycine levels and will experience smaller brain and plasma glycine increases after glycine consumption than controls or family members without the GLDC mutation.

Description:

High doses of glycine (0.4-0.8 g/kg/day) administered orally along with certain antipsychotic medications can improve negative symptoms of schizophrenia (e.g., Heresco-Levy et al., 1999). The therapeutic effect appears to be due to glycine's co-agonist activity at glutamatergic N-methyl-D-aspartate receptors, which may correct the glutamatergic hypofunction associated with schizophrenia (e.g., Bergeron et al., 1998). Unfortunately, the therapeutic benefits of orally administered glycine are variable, in part because gut glycine absorption and resultant plasma (and presumably brain) glycine increases are variable (Silk et al., 1974). Even with intravenous glycine administration, which bypasses variability contributed by gut absorption and metabolism, between-subject variability in cerebrospinal fluid (CSF) glycine increments is large (D'Souza et al., 2000), suggesting that brain glycine uptake, metabolism, and turnover differ substantially among individuals.

If brain glycine increments after oral glycine dosing are highly variable, those manifesting smaller or more transient brain glycine increments may not experience clinically significant effects. As a result, glycine's therapeutic efficacy could be underappreciated. Indeed, a multi-site glycine trial in schizophrenia subjects concluded that glycine is not a "…generally effective therapeutic option for treating negative symptoms or cognitive impairments", but included the caveat that "…it is not known if efficacy would have been achieved at substantially higher serum glycine levels" (Buchanan et al., 2007).

Accordingly, we believe that it is important to fully characterize glycine's brain and plasma pharmacodynamic variability, which we will do in healthy subjects and in several members of a family with some members possessing a mutation in their glycine decarboxylase gene (GLDC), which may be associated with abnormal baseline brain and plasma glycine levels and increments after glycine administration. We will use an MRS method we developed to detect brain glycine increases after high-dose oral glycine administration (Prescot et al., 2006; Kaufman et al., 2009) along with standard analytical methods to determine plasma glycine levels.

Recruitment information / eligibility

• Status: Completed
• Enrollment: 21
• Est. completion date: December 2013
• Est. primary completion date: December 2013
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: Both
• Age group: 18 Years to 55 Years

Eligibility

Inclusion Criteria:

• Healthy Adult males

• Members of a family known to the research team with some members possessing a GLDC genetic mutation

Exclusion Criteria:

• Contraindications to magnetic resonance scanning including metallic surgical implants or claustrophobia

• History of head injury with loss of consciousness > 5 minutes

• Brain structural abnormalities identified on MRI scan

• Known sensitivity or allergy to glycine

• History of taking glycine or other dietary supplements

• Healthy controls: history of psychiatric or substance use disorders; individuals taking prescription medications

• Pregnancy

Study Design

Endpoint Classification: Pharmacodynamics Study, Intervention Model: Single Group Assignment, Masking: Open Label, Primary Purpose: Basic Science

Related Conditions & MeSH terms

• Mental Disorders
• Psychotic Disorders
• Schizophrenia

Intervention

Dietary Supplement:
• Glycine administration
Glycine will be administered once as a 250 cc lemon-flavored beverage based on each subject's body weight. The drink concentration will be 0.4 g/kg glycine (not to exceed 30 grams). Subjects will have 10 minutes to consume the beverage.

Locations

Country	Name	City	State
United States	McLean Imaging Center, McLean Hospital	Belmont	Massachusetts

Sponsors (2)

Lead Sponsor	Collaborator
Mclean Hospital	Brain & Behavior Research Foundation

Country where clinical trial is conducted

United States, 

References & Publications (7)

Bergeron R, Meyer TM, Coyle JT, Greene RW. Modulation of N-methyl-D-aspartate receptor function by glycine transport. Proc Natl Acad Sci U S A. 1998 Dec 22;95(26):15730-4. — View Citation

Buchanan RW, Javitt DC, Marder SR, Schooler NR, Gold JM, McMahon RP, Heresco-Levy U, Carpenter WT. The Cognitive and Negative Symptoms in Schizophrenia Trial (CONSIST): the efficacy of glutamatergic agents for negative symptoms and cognitive impairments. Am J Psychiatry. 2007 Oct;164(10):1593-602. — View Citation

D'Souza DC, Gil R, Cassello K, Morrissey K, Abi-Saab D, White J, Sturwold R, Bennett A, Karper LP, Zuzarte E, Charney DS, Krystal JH. IV glycine and oral D-cycloserine effects on plasma and CSF amino acids in healthy humans. Biol Psychiatry. 2000 Mar 1;47(5):450-62. — View Citation

Heresco-Levy U, Javitt DC, Ermilov M, Mordel C, Silipo G, Lichtenstein M. Efficacy of high-dose glycine in the treatment of enduring negative symptoms of schizophrenia. Arch Gen Psychiatry. 1999 Jan;56(1):29-36. — View Citation

Kaufman MJ, Prescot AP, Ongur D, Evins AE, Barros TL, Medeiros CL, Covell J, Wang L, Fava M, Renshaw PF. Oral glycine administration increases brain glycine/creatine ratios in men: a proton magnetic resonance spectroscopy study. Psychiatry Res. 2009 Aug 30;173(2):143-9. doi: 10.1016/j.pscychresns.2009.03.004. Epub 2009 Jun 24. — View Citation

Prescot AP, de B Frederick B, Wang L, Brown J, Jensen JE, Kaufman MJ, Renshaw PF. In vivo detection of brain glycine with echo-time-averaged (1)H magnetic resonance spectroscopy at 4.0 T. Magn Reson Med. 2006 Mar;55(3):681-6. — View Citation

Silk DB, Kumar PJ, Perrett D, Clark ML, Dawson AM. Amino acid and peptide absorption in patients with coeliac disease and dermatitis herpetiformis. Gut. 1974 Jan;15(1):1-8. — View Citation

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Brain Glycine Increments After Oral Glycine Administration Measured With MRS as Glycine/Total Creatine, Normalized to the Glycine Dose Administered (g/kg).	Brain and plasma glycine levels are measured with proton magnetic resonance spectroscopy at 4T and analytically, respectively. Because glycine doses were limited to 30 g to avoid nausea and vomiting, some subjects with higher weights were administered lower doses per body weight of glycine (g/kg). Therefore, we corrected MRS data by the actual glycine dose administered (g/kg) to account for dosing differences.	For up to 2 hours	No

External Links

•   Brain and Behavior Research Foundation - Awarding NARSAD Grants