The effect of atypical antipsychotics on brain N-acetylaspartate levels in antipsychotic-naïve first-episode patients with schizophrenia: a preliminary study

Reduction of N-acetyl aspartate (NAA) in association with relapse in early-stage psychosis: a 7-Tesla MRS study

Understanding the biological underpinning of relapse could improve the outcomes of patients with psychosis. Relapse is elicited by multiple reasons/triggers, but the consequence frequently accompanies deteriorations of brain function, leading to poor prognosis. Structural brain imaging studies have recently been pioneered to address this question, but a lack of molecular investigations is a knowledge gap. Following a criterion used for recent publications by others, we defined the experiences of relapse by hospitalization(s) due to psychotic exacerbation. We hypothesized that relapse-associated molecules might be underscored from the neurometabolites whose levels have been different between overall patients with early-stage psychosis and healthy subjects in our previous report. In the present study, we observed a significant decrease in the levels of N-acetyl aspartate in the anterior cingulate cortex and thalamus in patients who experienced relapse compared to patients who did not. Altogether, decreased N-acetyl aspartate levels may indicate relapse-associated deterioration of neuronal networks in patients.

Associations between N-Acetylaspartate and white matter integrity in individuals with schizophrenia and unaffected relatives

Compromised white matter has been reported in schizophrenia; however, few studies have investigated neurochemical abnormalities underlying microstructural differences. N-acetylaspartate (NAA) is used to synthesize myelin and is often reduced in persons with schizophrenia (PSZ) and their unaffected first-degree relatives (REL). Low levels of NAA could affect white matter by preventing the synthesis or repair of myelin. We used magnetic resonance spectroscopy and diffusion tensor imaging to investigate the relationship between NAA and white matter integrity in PSZ. REL were included to examine whether putative relationships are associated with symptom expression or illness liability. 52 controls, 23 REL and 25 PSZ underwent 7T proton magnetic resonance spectroscopy and/or 3T diffusion tensor imaging. NAA in the visual cortex and basal ganglia were measured and compared across groups. Diffusivity measures were compared across groups using tract-based spatial statistics and related to NAA concentrations. Visual cortex NAA was significantly reduced in PSZ compared to controls. White matter integrity did not differ between groups. Reduced cortical and subcortical NAA were associated with diffusivity measures of poor white matter microstructure. These data suggest that levels of neural NAA may be related to white matter integrity similarly across individuals with schizophrenia, those at genetic risk, and controls.

Treatment effects on neurometabolite levels in schizophrenia: A systematic review and meta-analysis of proton magnetic resonance spectroscopy studies

BACKGROUND

Although there is growing evidence of alterations in the neurometabolite status associated with the pathophysiology of schizophrenia, how treatments influence these metabolite levels in patients with schizophrenia remains poorly studied.

METHODS

We conducted a literature search using Embase, Medline, and PsycINFO to identify proton magnetic resonance spectroscopy studies that compared neurometabolite levels before and after treatment in patients with schizophrenia. Six neurometabolites (glutamate, glutamine, glutamate + glutamine, gamma-aminobutyric acid, N-acetylaspartate, myo-inositol) and six regions of interest (frontal cortex, temporal cortex, parieto-occipital cortex, thalamus, basal ganglia, hippocampus) were investigated.

RESULTS

Thirty-two studies (n = 773 at follow-up) were included in our meta-analysis. Our results demonstrated that the frontal glutamate + glutamine level was significantly decreased (14 groups; n = 292 at follow-up; effect size = -0.35, P = 0.0003; I² = 22%) and the thalamic N-acetylaspartate level was significantly increased (7 groups; n = 184 at follow-up; effect size = 0.47, P < 0.00001; I² = 0%) after treatment in schizophrenia patients. No significant associations were found between neurometabolite changes and age, gender, duration of illness, duration of treatment, or baseline symptom severity.

CONCLUSIONS

The current results suggest that glutamatergic neurometabolite levels in the frontal cortex and neuronal integrity in the thalamus in schizophrenia might be modified following treatment.

A longitudinal magnetic resonance spectroscopy study investigating effects of risperidone in the anterior cingulate cortex and hippocampus in schizophrenia

Magnetic Resonance Spectroscopy is a popular approach to probe brain chemistry in schizophrenia (SZ), but no consensus exists as to the extent of alterations. This may be attributable to differential effects of populations studied, brain regions examined, or antipsychotic medication effects. Here, we measured neurometabolites in the anterior cingulate cortex (ACC) and hippocampus, two structurally dissimilar brain regions implicated in the SZ pathophysiology. We enrolled 61 SZ with the goal to scan them before and after six weeks of treatment with risperidone. We also scanned 31 matched healthy controls twice, six weeks apart. Using mixed effect repeated measures linear models to examine the effect of group and time on metabolite levels in each voxel, we report an increase in hippocampal glutamate + glutamine (Glx) in SZ compared to controls (p = 0.043), but no effect of antipsychotic medication (p = 0.330). In the ACC, we did not find metabolite alterations or antipsychotic medication related changes after six weeks of treatment with risperidone. The coefficients for the discriminant function (differentiating SZ from HC) in the ACC were greatest for NAA (-0.83), and in the hippocampus for Glx (0.76), the same metabolites were associated with greater treatment response in patients at trend level. Taken together, our data extends the existing literature by demonstrating regionally distinct metabolite alterations in the same patient group and suggests that antipsychotic medications may have limited effects on metabolite levels in these regions.

Proton magnetic resonance spectroscopy changes in a longitudinal schizophrenia study: a pilot study in eleven patients

PURPOSE

Investigation of the longitudinal effect of schizophrenia on changes in various brain-metabolite levels and their relationships with cognitive deficits that have not been fully explained yet.

METHODS

Five years subsequent to their first examination for their first episode of schizophrenia, eleven patients from an original group of 30 were reexamined. Their cognitive functions were assessed with the Wisconsin Card Sorting Test. Magnetic resonance imaging and proton magnetic resonance spectroscopy were performed on a 1.5 T scanner. Voxels of 8 cm³ were positioned in the left frontal lobe, left temporal lobe, and the left thalamus. The study had a naturalistic design, and patients were treated with various antipsychotics.

RESULTS

No significant statistical differences between the baseline and follow-up in N-acetylaspartate (NAA:creatine plus phosphocreatine [Cr] and NAA/H₂O) levels were observed in any region of interest. We found a significant statistical correlation between 5-year difference in frontal NAA/Cr levels and duration of the last antipsychotic treatment in this period (R=0.908, P=0.012). We found a trend (P=0.068) toward lower choline-containing compounds (Cho/Cr ratio) in the temporal lobe over 5 years and a trend (P=0.079) in higher glutamate-glutamine- GABA (Glx/H₂O) levels in the left thalamus. The patients showed social and clinical improvement at follow-up examination, and there were no changes in Wisconsin Card Sorting Test results.

CONCLUSION

The observed tendency toward decline in choline ratio might have been due to decreased temporal cell density or impaired neuron-membrane or myelin functions. A tendency for higher Glx levels suggest the involvement of thalamus dysfunction in the chronic schizophrenia process. The lack of NAA decrease might have been due to effective antipsychotic treatment. Further longitudinal studies on large patient groups are required to confirm these metabolic changes in schizophrenia.

Effect of Adjuvant Electroconvulsive Therapy Compared to Antipsychotic Medication Alone on the Brain Metabolites of Patients with Chronic Schizophrenia: A Proton Magnetic Resonance Spectroscopy Study

Objective: Schizophrenia is a common psychiatric disease and is characterized by changes in several brain metabolites detectable by magnetic resonance spectroscopy (MRS). Electroconvulsive therapy (ECT) is a general method of management for most severe psychiatric conditions that may play a role in changing the brain metabolites. This study examined the effectiveness of adjuvant ECT with oral medication compared to that of oral second generation antipsychotic medication alone on brain metabolites in patients with chronic schizophrenia. Method : This study was conducted on 20 patients with chronic schizophrenia who were admitted to a hospital; of them, 10 underwent ECT as an adjuvant therapy with oral medication at least 8 times, and 10 patients were given a second- generation antipsychotic therapy drug (risperidone and olanzapine) without ECT for at least 4 weeks. MRS was used to assess brain metabolites, including N-acetyl aspartate (NAA), choline (Cho), creatine (Cr), myoinositol (MI), and Glx (glutamate [Glu] and glutamine [Gln]), in the left prefrontal cortex, left thalamus, left hippocampus, and left occipital cortex. Differences between the 2 groups were not significant, except for method of treatment. Results: The NAA/Cr ratio in the left prefrontal cortex was significantly higher in ECT-treated patients (P = 0.035). In addition, the Cho/Cr ratios in the left prefrontal cortex and left thalamus were statisticaly lower in the ECT-treated patients than those treated with oral antipsychotic drugs alone (P = 0.019). No statistically significant changes were observed between the 2 groups in other sites of the brain. In addition, no statistically significant differences were detected between the 2 groups in SAPS and DES scores. Conclusion: Compared to oral antipsychotic drug treatment, ECT had improving effects on at least 2 metabolites in the brains of patients with schizophrenia. Therefore, ECT may have a neuroprotective effect in these patients.

1H-magnetic resonance spectroscopy study of glutamate-related abnormality in bipolar disorder

BACKGROUND

Previous studies of patients with bipolar disorder (BD) using magnetic resonance spectroscopy (MRS) have shown neurophysiological abnormalities related to the glutamate (Glu)-glutamine (Gln) cycle, membrane turnover, and neuronal integrity, although the results were neither consistent nor conclusive. Recently it has been reported the Gln/Glu ratio is the most useful index, quantifying neuronal-glial interactions and the balance of glutamatergic metabolites In this MRS study, we elucidated the abnormalities of metabolites in a larger sample of patients with BD with a high-field MRI system.

METHODS

Sixty-two subjects (31 patients with BD and 31 healthy controls [HC]) underwent 3T proton MRS (1H-MRS) of the anterior cingulate cortex (ACC) and left basal ganglia (ltBG) using a stimulated echo acquisition mode (STEAM) sequence.

RESULTS

After verifying the data quality, 20 patients with BD and 23 age- and gender-matched HCs were compared using repeated-measures analysis of covariance (ANCOVA). Compared to the HC group, the BD group showed increased levels of Gln, creatine (Cr), N-acetyl aspartate (NAA), choline (Cho), and an increased ratio of Gln to Glu in the ACC, and increased Gln and Cho in the ltBG. These findings remained after the participants with BD were limited to only euthymic patients. After removing the influence of lithium (Li) and sodium valproate (VPA), we observed activated glutamatergic neurotransmission in the ACC but not in the ltBG.

LIMITATIONS

The present findings are cross-sectional and metabolites were measured in only two regions.

CONCLUSIONS

Our results support a wide range of metabolite changes in patients with BD involved in glutamatergic neurotransmission, membrane turnover, and neuronal integrity. Moreover, the elevation of Gln/Glu ratio suggested that hyperactivity of glutamatergic neurotransmission in the ACC is a disease marker for BD.

The predictive value of baseline NAA/Cr for treatment response of first-episode schizophrenia: A ¹H MRS study

The study focused on the predictive value of baseline metabolite ratios in bilateral hippocampus of first-episode schizophrenia by using proton magnetic resonance spectroscopy ((1)H MRS). (1)H MRS data were acquired from 23 hallucination and 17 non-hallucination first-episode schizophrenia patients compared with 17 healthy participants. Clinical characteristics of patients were rated using the Positive and Negative Syndrome Scale (PANSS) before and after 3-month treatment. The schizophrenia patients showed lower NAA/Cr ratio than healthy participants respectively (p=0.024; p=0.001), and non-hallucination patients had even lower NAA/Cr ratio than hallucination patients (p=0.033). After 3-month treatment, hallucination patients had greater improvement in negative symptoms than non-hallucination patients (p=0.018). The reduction of PANSS total score and negative factor score was positively correlated with the left NAA/Cr in both group patients (p<0.05). Given that the bilateral hippocampal baseline NAA/Cr had predictive value for the whole treatment response, and the left hippocampal NAA/Cr can predict the prognosis of negative symptoms during acute phase medication in first-episode schizophrenia.