Glutamatergic Metabolites, Volume and Cortical Thickness in Antipsychotic-Naïve Patients

Glutamatergic metabolites, volume and cortical thickness in antipsychotic-naïve patients with first-episode psychosis: implications for excitotoxicity

Plitman et al

Neuropsychopharmacology

Supplementary Material

Patients and Methods

Participants

Approval for this study was received from the Ethics and Scientific Committees of the National Institute of Neurology and Neurosurgery of Mexico (INNN). For inclusion, individuals successfully completed an informed consent procedure; for participants under 18 years old, written consent was obtained from both parents.

The present study included participants previously reported upon by our group (de la Fuente-Sandoval et al, 2013b; de la Fuente-Sandoval et al, 2011; Plitman et al, 2016). In total, 64right-handed FEP patients were recruited during their first non-affective psychosis episode from inpatient or outpatient services at the INNN. The Structured Clinical Interview for DSM-IV was used to assess participants’ inclusion into this study. Patients satisfied inclusion criteria if they were antipsychotic-naïve; all but 3 patients had less than 2 years of psychotic symptoms. Exclusion criteria included a high risk for suicide, a concomitant medical or neurological illness, current substance abuse or history of substance dependence (excluding nicotine), comorbidity with other Axis I disorders, and psychomotor agitation. Sixty-three right-handed, age- and sex-matched healthy controls were also included. Any control with a history of psychiatric illness or a family history of psychosis was excluded. Participants from both groups were screened for drugs of abuse at inclusion and 1 hour prior to the magnetic resonance imaging (MRI) scan.

Clinical Assessment

The Positive and Negative Syndrome Scale (PANSS) was used by research psychiatrists (C.d.l.F.-S., F.R.-M., P.L.-O.) to measure patients’ psychopathology (Kay et al, 1987).

Magnetic Resonance Studies

MRI parameters were carried out in accordance with previous publications (de la Fuente-Sandoval et al, 2013a; de la Fuente-Sandoval et al, 2013b; de la Fuente-Sandoval et al, 2011; Plitman et al, 2016). Briefly, MRI scans were performed at the Neuroimaging Department of the INNN in a 3T GE whole-body scanner (Signa Excite HDxt; GE Healthcare, Milwaukee, WI) with a high-resolution 8-channel head coil. The participant’s head was positioned along the canthomeatal line and immobilized using a forehead strap. MRI scans included a T1-weighted spoiled gradient-echo 3-dimensional axial acquisition (SPGR, TE=5.7 ms, TR=13.4 ms, TI=450 ms, flip angle=20°, FOV=25.6 cm, ≥256 × ≥256 matrix, slice thickness≤1.2 mm), oriented parallel to the anterior-posterior commissure line. Three patterns of voxel dimensions existed across the dataset: 0.47mm × 0.47mm × 1.2mm; 0.47mm × 0.47mm × 0.6mm; 1mm × 1mm × 1mm. T1-weighted SPGR images were reformatted to sagittal and coronal views and were utilized for 1H-MRS voxel placement.

1H-MRS spectra were acquired using point-resolved spectroscopy (PRESS, TE=35 ms, TR=2000 ms, spectral width=5000 Hz, 4096 data points used, 128 water-suppressed, and 16 water-unsuppressed averages) centered on the right dorsal-caudate nucleus in volume elements (voxels) of 8 mℓ (2×2×2 cm). The lower end of the dorsal-caudate voxel (associative striatum) was located 3 mm dorsal to the anterior commissure so that the maximum amount of gray matter (GM) was included and with a dorsal extension (thickness) of 2 cm. 1H-MRS spectra were shimmed during the acquisition to achieve a full-width at half maximum (FWHM) of 12 Hz or less, measured on the unsuppressed water signal from the voxel.

1H-MRS Data Analysis

Each participant’s water suppressed spectra were analyzed with LCModel version 6.3-0E (Provencher, 2001), using a standard basis set of metabolites acquired with the same sequence parameters as used in the present study. Spectra were normalized to the unsuppressed water signal, allowing for the quantification of neurometabolite levels, expressed in institutional units. The standard basis set of metabolites included L-alanine, aspartate, creatine (Cr), Cr methylene group, γ-aminobutyric acid, glucose, glutamate, glutamine, glutathione, glycerophosphocholine (GPC), guanidinoacetate, L-lactate, myo-inositol, N-acetylaspartate (NAA), N-acetylaspartylglutamate acid (NAAG), phosphocholine (PCh), phosphocreatine, scyllo-inositol, taurine, GPC+PCh, glutamate+glutamine, NAA+NAAG, along with the following lipids (Lip) and macromolecules (MM): Lip09, Lip13a, Lip13b, Lip20, MM09, MM12, MM14, MM17 and MM20. Participants with %SD values of 20% or greater for any neurometabolite of interest were interpreted as poor quality and were excluded from statistical analyses (Jiru et al, 2006; Provencher, 2012). Four patients with FEP and 3 healthy controls were removed as a result of either rejection by LCModel analysis or due to a FWHM exceeding 12Hz(Wijtenburg et al, 2015). Thus, 60 patients with FEP and 60 healthy controls progressed to statistical analysis.

T1-weighted MRI scans utilized for voxel localization were segmented into GM, white matter (WM), and cerebrospinal fluid (CSF) with Statistical Parametric Mapping 8 (SPM8, Wellcome Department of Imaging Neuroscience, University College London, UK). The size and location of each area were obtained from the spectra file headers to determine the percentage of GM, WM, and CSF content within the 1H-MRS voxel using an in-house software, which allowed spectroscopic values to be corrected for CSF fraction (de la Fuente-Sandoval et al, 2011).

Subcortical Structure Volume Analysis

These analyses were performed in the same manner as those described for the PCV in the main text of the manuscript. To determine volumes of the postcommissural caudate, precommissural putamen, postcommissural putamen, nucleus accumbens/ventral striatum, total striatum, globus pallidus, and thalamus, the Colin-27 Subcortical Atlas (Chakravarty et al, 2006) referred to in the main text of the manuscript was utilized. To determine volumes of the hippocampus, the hippocampal subfields atlas (Winterburn et al, 2013) was used. Notably, 1 healthy control was excluded from hippocampal analyses due to failed subfield segmentation.

References

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Table S1. Demographic and Clinical Characteristics of Study Participants

Variable / FEP Group (n=60) / HC Group (n=60)
Age, mean (SD) [range], y / 24.67 (7.68) [13-47] / 23.03 (4.87) [15-42]
Educational level, mean (SD), y / 11.48 (3.13)* / 15.00 (2.88)
Sex, No.
Male / 37 / 38
Female / 23 / 22
Ever used, No./total No.
Tobacco / 17/60* / 7/60
Cannabis / 4/60 / 0/60
Handedness, No.
Right / 60 / 60
Left / 0 / 0
PANSS subscale total, mean (SD), score
Positive / 24.13 (4.97) / NA
Negative / 24.33 (5.66) / NA
General
Psychopathology / 48.75 (8.38) / NA
Duration of untreated psychosis, mean (SD) [range], wk / 33.03 (52.70) [1-312] / NA

Abbreviations: FEP, first-episode psychosis; HC, healthy control; NA, not applicable; No., number; PANSS, Positive and Negative Syndrome Scale.

*Denotes p<0.05.

Table S2. Glutamatergic Neurometabolite Levels and Cramer-Rao Lower Bound Values

Mean (SD)
Glu / Glx / CRLB – Glu / CRLB – Glx / %SD – Glu / %SD – Glx
FEP Group / 13.10 (1.31)* / 16.61 (1.69) / 0.75 (0.11) / 0.83 (0.18) / 6.48 (1.16) / 5.67 (1.17)
HC Group / 12.39 (0.95) / 16.21 (1.50) / 0.74 (0.12) / 0.83 (0.17) / 6.69 (1.44) / 5.72 (1.33)

Abbreviations: CRLB, Cramer-Rao lower bound; FEP, first-episode psychosis; Glu, glutamate; Glx, glutamate+glutamine; HC, healthy control.

*Denotes p<0.05.

Variable / FEP Group (n=60) / HC Group (n=60)
FWHM, mean (SD), ppm / 0.08 (0.02) / 0.08 (0.02)
SNR, mean (SD) / 14.32 (2.45) / 14.68 (2.63)
1H-MRS Voxel, mean (SD), %
GM / 0.43 (0.06) / 0.43 (0.04)
WM / 0.47 (0.08) / 0.48 (0.06)
CSF / 0.11 (0.08) / 0.09 (0.06)

Table S3. Full-Width at Half Maximum Values, Signal-to-Noise Ratios, and1H-MRS Voxel Tissue Composition

Abbreviations: CSF, cerebrospinal fluid; FEP, first-episode psychosis; FWHM, full-width at half maximum; GM, gray matter; HC, healthy control; SNR, signal-to-noise ratio; WM, white matter.

Table S4. Relationships Between Glutamatergic Neurometabolite Levels and Precommissural Caudate Volume

Variable / Glu / Glx
FEP
PCV / =-0.08, t=-0.81, p=0.42a / =-0.25, t=-2.44, p=0.018b*
HC
PCV / =0.11, t=0.88, p=0.38c / =0.01, t=0.09, p=0.93d

Abbreviations: FEP, first-episode psychosis; Glu, glutamate; Glx, glutamate+glutamine; HC, healthy control; PCV, precommissural caudate volume.

*Denotes p<0.05.

Model statistics: aadjusted R2=0.558, F5,54=15.92, p<0.001; badjusted R2=0.597, F5,54=18.51, p<0.001;
cadjusted R2=0.264, F6,52=4.46, p=0.001; dadjusted R2=0.254, F6,53=4.34, p=0.001

Variable / PCV
PANSS Subscale
Positive / =-0.08, t=-0.92, p=0.36a
Negative / =-0.07, t=-0.77, p=0.44b
General Psychopathology / =-0.11, t=-1.25, p=0.22c

Table S5. Relationships Between Precommissural Caudate Volume and PANSS Subscale Total Scores

Abbreviations: PANSS, Positive and Negative Syndrome Scale; PCV, precommissural caudate volume.

Model statistics: aadjusted R2=0.560, F5,54=16.02, p<0.001; badjusted R2=0.558, F5,54=15.89, p0.001;

cadjusted R2=0.566, F5,54=16.36, p0.001

Table S6. Relationships Between Glutamatergic Neurometabolite Levels and SubcorticalStructure Volumes in Patients With First-Episode Psychosis

Variable / Glu / Glx
FEP
Rpostcau / =0.19, t=1.80, p=0.08 / =0.11, t=0.98, p=0.33
Rpreput / =-0.06, t=-0.49, p=0.63 / =-0.17, t=-1.33, p=0.19
Rpostput / =0.03, t=0.27, p=0.79 / =-0.04, t=-0.32, p=0.75
RNA/VS / =-0.13, t=-1.38, p=0.17 / =-0.21, t=-2.25, p=0.029
Lpostcau / =0.17, t=1.64, p=0.11 / =0.05, t=0.50, p=0.62
Lpreput / =-0.03, t=-0.25, p=0.80 / =-0.16, t=-1.24, p=0.22
Lpostput / =-0.01, t=-0.05, p=0.96 / =-0.08, t=-0.72, p=0.48
LNA/VS / =-0.17, t=-1.70, p=0.09 / =-0.21, t=-2.11, p=0.040
RS / =-0.002, t=-0.03, p=0.98 / =-0.12, t=-1.31, p=0.20
RGP / =-0.01, t=-0.11, p=0.92 / =-0.06, t=-0.51, p=0.61
RT / =-0.02, t=-0.22, p=0.83 / =0.50, t=0.52, p=0.60
LS / =-0.01, t=-0.15, p=0.88 / =-0.14, t=-1.55, p=0.13
LGP / =0.02, t=0.21, p=0.83 / =0.03, t=0.30, p=0.77
LT / =-0.06, t=-0.62, p=0.54 / =-0.03, t=-0.28, p=0.78
RHIP / =0.13, t=1.26, p=0.21 / =0.07, t=0.64, p=0.52
LHIP / =0.15, t=1.33, p=0.19 / =0.08, t=0.67, p=0.51

Abbreviations: FEP, first-episode psychosis; Glu, glutamate; Glx, glutamate+glutamine; LGP, left globus pallidus; LHIP, left hippocampus; LNA/VS, left nucleus accumbens/ventral striatum; Lpreput, left precommissural putamen; Lpostcau, left postcommissural caudate; Lpostput, left postcommissural putamen; LS, left striatum; LT, left thalamus; RGP, right globus pallidus; RHIP, right hippocampus; RNA/VS, right nucleus accumbens/ventral striatum; Rpreput, right precommissural putamen; Rpostcau, right postcommissural caudate; Rpostput, right postcommissural putamen; RS, right striatum; RT, right thalamus.

Model statistics range: adjusted R2=0.296-0.676, F5,54=5.96-25.62, all p<0.001

Table S7. Relationships Between Glutamatergic Neurometabolite Levels and SubcorticalStructure Volumes in Healthy Controls

Variable / Glu / Glx
HC
Rpostcau / =0.11, t=0.97, p=0.33a / =0.09, t=0.76, p=0.45a
Rpreput / =-0.09, t=-0.69, p=0.49a / =-0.20, t=-1.47, p=0.15a
Rpostput / =-0.09, t=-0.73, p=0.47a / =-0.14, t=-1.07, p=0.29a
RNA/VS / =0.18, t=1.46, p=0.15a / =0.04, t=0.30, p=0.77a
Lpostcau / =0.11, t=0.95, p=0.35a / =0.08, t=0.63, p=0.53a
Lpreput / =-0.07, t=-0.50, p=0.62a / =-0.05, t=-0.36, p=0.72a
Lpostput / =-0.12, t=-1.03, p=0.31a / =-0.16, t=-1.31, p=0.20a
LNA/VS / =0.18, t=1.48, p=0.15a / =0.06, t=0.42, p=0.67a
RS / =0.03, t=0.24, p=0.81a / =-0.06, t=-0.49, p=0.62a
RGP / =-0.04, t=-0.30, p=0.76a / =-0.10, t=-0.83, p=0.41a
RT / =0.03, t=0.34, p=0.74a / =-0.02, t=-0.20, p=0.84a
LS / =0.05, t=0.48, p=0.64a / =-0.03, t=-0.29, p=0.77a
LGP / =-0.02, t=-0.21, p=0.83a / =-0.16, t=-1.36, p=0.18a
LT / =-0.05, t=-0.69, p=0.50a / =-0.06, t=-0.71, p=0.48a
RHIP / =-0.07, t=-0.57, p=0.57b / =-0.05, t=-0.38, p=0.71b
LHIP / =-0.09, t=-0.65, p=0.52b / =-0.14, t=-0.99, p=0.33b

Abbreviations: Glu, glutamate; Glx, glutamate+glutamine; HC, healthy control; LGP, left globus pallidus; LHIP, left hippocampus; LNA/VS, left nucleus accumbens/ventral striatum; Lpreput, left precommissural putamen; Lpostcau, left postcommissural caudate; Lpostput, left postcommissural putamen; LS, left striatum; LT, left thalamus; RGP, right globus pallidus; RHIP, right hippocampus; RNA/VS, right nucleus accumbens/ventral striatum; Rpreput, right precommissural putamen; Rpostcau, right postcommissural caudate; Rpostput, right postcommissural putamen; RS, right striatum; RT, right thalamus.

Model statistics range: aadjusted R2=0.156-0.712, Glutamate: F6,52=2.79-24.87; Glx: F6,53=2.90-24.63, p<0.001-0.02

Model statistics range: badjusted R2=0.227-0.406, Glutamate: F6,51=3.79-7.45; Glx: F6,52=4.21-7.60, p<0.001-0.003

Figure S1. Location of Right Precommissural Dorsal Caudate 1H-MRS Voxel Placement and Delineation of Right Precommissural Caudate Volume Measurea

Abbreviations: R, right.

aDepicted images derived from one randomly selected study participant.

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