MRS Measurement of Glutamate and GABA Metabolism in Brain

Not Applicable

Recruiting

• Conditions: Normal Physiology
• Interventions: Device: 3T and 7T device

• Registration Number: NCT00109174
• Lead Sponsor: National Institute of Mental Health (NIMH)

Brief Summary

This study will use magnetic resonance spectroscopy (MRS) to measure in the brain the transfer of \[13\]C as it is naturally metabolized from glucose to specific chemical transmitters. From this method, we can measure the rate of production of an important excitatory neurotransmitter (glutamate) as well as an inhibitory neurotransmitter (GABA).

Detailed Description

13C is a stable (i.e., non-radioactive) isotope of carbon with a natural abundance of \~1%. Following infusion of \[13C\]glucose and/or \[13C\]acetate, in vivo MRS (magnetic resonance spectroscopy) can monitor the rate of flux of the 13C atom from glucose and/or acetate to glutamate to glutamine. Thus, this procedure can provide measure of glutamate (GLU) and glutamine (GLN) turnover in brain. We have established parameters to obtain these measurements in nonhuman primate brain. The current protocol seeks approval to optimize MRS parameters and to develop new MRS techniques for human brain using the GE 3T, the Siemens 3T, and the Siemens 7T device.

Study population: All subjects will be aged 18 65 years, without serious medical illnesses and meet criteria listed in Section VI A.

Design: Subjects will receive either oral administration of \[13C\]glucose or an intravenous infusion of \[13C\]glucose and/or \[13C\]acetate to approximately double their plasma glucose levels. The plasma acetate level will remain within the physiological range observed in humans (Lebon et al, 2002). While lying in the 3T or 7T device, serial data acquisitions will be obtained over \~2 h to optimize the experimental conditions so as to measure the 13C signals from GLU, GLN and other metabolisms in brain.

Outcome measures: The primary goal of this study is to measure GLU/GLN turnover in brain. With no additional data acquisition, we can also obtain information on the synthesis of GABA, the major inhibitory neurotransmitter in brain. GLU is converted to GABA via the enzyme glutamic acid decarboxylase (GAD). While monitoring the transfer of 13C signal from GLU to GLN, we can simultaneously measure the transfer of 13C signal from GLU to GABA and thereby measure the activity of GAD (Li et al 2005). In addition to directly measure 13C signals, 13C labeling to brain metabolites can also be measured indirectly by detecting proton MRS during infusion of \[13C\]glucose and/or \[13C\]acetate.

Study Timeline

• Study First Submitted: 2005-04-22
• Study First Submitted QC: 2005-04-22
• Study First Posted: 2005-04-25
• Study Start: 2006-09-06
• Status Verified: 2025-03-21
• Last Update Submitted: 2025-05-17
• Last Update Posted: 2025-05-20
• Primary Completion: 2030-01-11
• Study Completion: 2030-03-11

Recruitment & Eligibility

• Status: RECRUITING
• Sex: All
• Target Recruitment: 200

Inclusion Criteria

Not provided

Exclusion Criteria

Not provided

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: SINGLE_GROUP

Arm && Interventions

Group	Intervention	Description
One arm	3T and 7T device	Subjects receive the same test

Primary Outcome Measures

Name	Time	Method
The primary outcome is the quality of the MR spectroscopy which includes spectrum signal-to-noise (SNR)\ ratio, spectral lineshape, linewidth, and resolution.	prospective and ongoing	To obtain more accurate and reliable MRS data from the human brain

Secondary Outcome Measures

Name	Time	Method
The secondary outcome is the performance improvements of the scanner hardware, software and methodology	prospective and ongoing	To obtain more accurate and reliable MRS data from the human brain.

Trial Locations

Locations (1)

National Institutes of Health Clinical Center; 🇺🇸 Bethesda, Maryland, United States