Measuring mania metabolites: a longitudinal proton spectroscopy study of hypomania

Is brain perfusion correlated to switching mood states and cognitive impairment in bipolar disorder type I? A longitudinal study using perfusion imaging approach

Type I Bipolar disorder (BD-I) is a neuropsychiatric disorder characterized by manic or mixed-featured episodes, impaired cognitive functioning, and persistent work and social functioning impairment. This study aimed to investigate within-subject; (i) differences in brain perfusion using Single-photon emission computed tomography (SPECT) between manic and euthymic states in BD-I patients; (ii) explore potential associations between altered brain perfusion and cognitive status; and (iii) examine the relationship between cerebral perfusion and mania symptom ratings. Seventeen adult patients diagnosed with BD-I in a manic episode were recruited, and clinical assessments, cognitive tests, and brain perfusion studies were conducted at baseline (mania state) and a follow-up visit 6 months later. The results showed cognitive impairment during the manic episode, which persisted during the euthymic state at follow-up. However, no significant changes in brain perfusion were observed between the manic and euthymic states. During mania, trends toward decreased perfusion in the left cerebellum and right superior parietal lobule were noted. Additionally, trends indicated a higher perfusion imbalance in the left superior and middle frontal gyrus during mania and the right superior and middle frontal gyrus during euthymia. No significant correlations existed between brain perfusion, mania symptom ratings, and cognitive performance, indicating that symptomatology might represent more than neural hemodynamics. These findings suggest that cognitive impairment may persist in BD-I patients and highlight the need for therapeutic interventions targeting cognitive deficits. More extensive studies with extended follow-up periods are warranted further to investigate brain perfusion and cognitive functioning in BD-I patients.

Glutamatergic and N-Acetylaspartate Metabolites in Bipolar Disorder: A Systematic Review and Meta-Analysis of Proton Magnetic Resonance Spectroscopy Studies

The exact neurobiological mechanisms of bipolar disorder (BD) remain unknown. However, some neurometabolites could be implicated, including Glutamate (Glu), Glutamine (Gln), Glx, and N-acetylaspartate (NAA). Proton Magnetic Resonance Spectroscopy (¹H-MRS) allows one to quantify these metabolites in the human brain. Thus, we conducted a systematic review and meta-analysis of the literature to compare their levels between BD patients and healthy controls (HC). The main inclusion criteria for inclusion were ¹H-MRS studies comparing levels of Glu, Gln, Glx, and NAA in the prefrontal cortex (PFC), anterior cingulate cortex (ACC), and hippocampi between patients with BD in clinical remission or a major depressive episode and HC. Thirty-three studies were included. NAA levels were significantly lower in the left white matter PFC (wmPFC) of depressive and remitted BD patients compared to controls and were also significantly higher in the left dorsolateral PFC (dlPFC) of depressive BD patients compared to HC. Gln levels were significantly higher in the ACC of remitted BD patients compared to in HC. The decreased levels of NAA of BD patients may be related to the alterations in neuroplasticity and synaptic plasticity found in BD patients and may explain the deep white matter hyperintensities frequently observed via magnetic resonance imagery.

Anterior cingulate cortex neurometabolites in bipolar disorder are influenced by mood state and medication: A meta-analysis of 1H-MRS studies

The anterior cingulate cortex (ACC), a brain region that mediates affect and cognition by connecting the frontal cortex to limbic structures, has been consistently implicated in the neurobiology of Bipolar Disorder (BD). Proton magnetic resonance spectroscopy (¹H-MRS) studies have extensively compared in vivo neurometabolite levels of BD patients and healthy controls (HC) in the ACC. However, these studies have not been analyzed in a systematic review or meta-analysis and nor has the influence of mood state and medication on neurometabolites been examined in this cortical region. A systematic review and a meta-analysis of ¹H-MRS studies comparing ACC neurometabolite profiles of adult BD patients and HC subjects was conducted, retrieving 27 articles published between 2000 and 2018. Overall increased ACC levels of Glx [glutamine (Gln) + glutamate)/Creatine], Gln, choline (Cho) and Cho/Creatine were found in BD compared to HC. Bipolar depression was associated with higher Cho levels, while euthymia correlated with higher glutamine (Gln) and Cho. Mood stabilizers appeared to affect ACC Glu and Gln metabolites. Increased ACC Cho observed in euthymia, depression and in medication-free groups could be considered a trait marker in BD and attributed to increased cell membrane phospholipid turnover. Overall increased ACC Glx was associated with elevated Gln levels, particularly influenced by euthymia, but no abnormality in Glu was detected. Further ¹H-MRS studies, on other voxels, should assess more homogeneous (mood state-specific), larger BD samples and account for medication status using more sensitive ¹H-MRS techniques.

A comparison of neurometabolites between remitted bipolar disorder and depressed bipolar disorder: A proton magnetic resonance spectroscopy study

BACKGROUND

Recent many studies found the abnormal neurometabolites in the acute bipolar disorder (BD). However, limited studies were to detect neurometabolites in remitted BD, comparison between acute and remitted BD is conductive to understand the outcome of neurometabolites. This study sought to investigate the differences in neurometabolites between remitted and depressed BD patients using proton magnetic resonance spectroscopy (¹H-MRS).

METHODS

Three subject groups were enrolled: 22 remitted BD patients, 22 depressed BD patients and 24 healthy controls. All subjects underwent ¹H-MRS to measure N-acetylaspartate (NAA), Choline (Cho), myo-Inositol (mI) and Creatine (Cr) of several bilateral areas potentially involved in BD: prefrontal whiter matter (PWM), thalamus and putamen. The neurometabolite ratios were compared among three groups. The correlations between abnormal neurometabolite ratios and clinical data were computed.

RESULTS

The lower bilateral PWM NAA/Cr ratios were found in depressed BD patients than remitted BD patients and healthy controls, no differences were found between the remitted BD patients and controls. For depressed BD patients, left PWM NAA/Cr ratios showed negative correlation with age of onset, right PWM NAA/Cr ratios showed positive correlation with duration of illness.

CONCLUSIONS

Our findings suggest the abnormal neurometabolites in the prefrontal lobe whiter may occur in the depressed BD. The remitted BD may resemble healthy subjects in terms of neurometabolites. In addition, abnormal neurometabolites in prefrontal lobe whiter may correlate with the age of onset and illness length.

Trait-related alterations of N-acetylaspartate in euthymic bipolar patients: A longitudinal proton magnetic resonance spectroscopy study

BACKGROUND

Neurochemical changes are responsible for bipolar disorder (BD) pathophysiology. Despite current progress in BD research, mood- and trait-related alterations in BD continue to elicit further investigation.

METHODS

In this study, we report a longitudinal proton magnetic resonance spectroscopy study evaluating dorsomedial prefrontal cortex (DMPFC) metabolites N-acetylaspartate (NAA), creatine plus phosphocreatine (total creatine [tCr]), phosphorylcholine plus glycerophosphocholine, myo-inositol, and glutamate plus glutamine levels of manic and euthymic adult BD type I patients (n=48) treated with standard antimanic medicines, compared to matching healthy controls (n=44).

RESULTS

DMPFC NAA values and NAA/tCr ratio were significantly lower in euthymic BD patients when compared with healthy controls with similar levels of other metabolites in all groups, indicating a trait-related NAA abnormality in euthymic BD patients.

LIMITATIONS

of our study include a relatively low (1.5T) magnetic resonance field strength and variable drugs administered to achieve euthymia despite the best efforts to standardize the open fashion treatment.

CONCLUSIONS

Our study contributes to the integrating models of trait-related metabolite alterations observed in euthymia since NAA is considered as a marker of neuronal viability and mitochondrial energy metabolism. In light of supporting and conflicting results reported previously, future studies with longitudinal designs and larger patient groups are warranted to better define both state- and trait-related cerebral metabolic alterations associated with BD pathophysiology.

Normal Metabolic Levels in Prefrontal Cortex in Euthymic Bipolar I Patients with and without Suicide Attempts

Introduction/Objective. Evidence suggests that the prefrontal cortex has been implicated in the pathophysiology of bipolar disorder (BD), but few neurochemical studies have evaluated this region in bipolar patients and there is no information from BD suicide attempters using Proton Magnetic Resonance Spectroscopy (H⁺MRS). The objective was to evaluate the metabolic function of the medial orbital frontal cortex in euthymic BD type I suicide and nonsuicide attempters compared to healthy subjects by H⁺MRS. Methods. 40 euthymic bipolar I outpatients, 19 without and 21 with history of suicide attempt, and 22 healthy subjects were interviewed using the Structured Clinical Interview with the DSM-IV axis I, the Hamilton Depression Rating Scale, the Young Mania Rating Scale, and the Barratt Impulsiveness Scale-11 and underwent H⁺MRS. Results. We did not find any metabolic abnormality in medial orbital frontal regions of suicide and nonsuicide BD patients and BD patients as a group compared to healthy subjects. Conclusions. The combined chronic use of psychotropic drugs with neuroprotective or neurotrophic effects leading to a euthymic state for longer periods of time may improve neurometabolic function, at least measured by H⁺MRS, even in suicide attempters. Besides, these results may implicate mood dependent alterations in brain metabolic activity. However, more studies with larger sample sizes of this heterogeneous disorder are warranted to clarify these data.

(1)H-MRS of hippocampus in patients after first manic episode

OBJECTIVES

The investigation of the pathophysiology of bipolar disorder in patients at disease onset is a strategy to avoid the confounding effect of progression of disease or duration of treatment. Our purpose was to investigate in vivo neuronal metabolites in the hippocampus of bipolar disorder patients using proton magnetic resonance spectroscopy ((1)H-MRS) within 3 months after their first manic episode.

METHODS

Fifty-eight BD I patients meeting DSM-IV criteria following their first episode of mania and 27 healthy subjects were studied using (1)H-MRS with a 3.0 T Philips Achieva scanner. Voxels with 30 × 15 × 15 mm were placed in the hippocampus on both sides of the brain and the signal was collected using a PRESS sequence with TE = 35 ms and TR = 2000 ms. Data analysis was performed using the LC Model software.

RESULTS

N-Acetyl-aspartate (NAA), choline (Cho), myo-inositol (mI), creatine (Cre) and glutamine + glutamate (Glx) levels were compared between the groups and no statistically significant differences were found.

CONCLUSIONS

Our results suggest that early in the course of BD there are no alterations in neuronal metabolism or vulnerability in the hippocampus after the first manic episode.

Neurobiology of mood-state shifts in bipolar disorder: a selective review and a hypothesis

OBJECTIVE

Neuroimaging techniques have begun to elucidate the neurophysiology of bipolar disorder (BPD). Several features of BPD have hindered understanding of how mood-state changes are reflected in changes in brain physiology. Longitudinal studies have advantages in isolating state-related changes and in studying the instability, inherent in these disorders, that gives rise to pathological mood states.

METHODS

To assess the state of the art in longitudinal neuroimaging studies in BPD, we conducted a literature review, searching MEDLINE for articles that included the key words bipolar disorder and magnetic resonance spectroscopy (MRS), magnetic resonance imaging (MRI), or emission tomography. The search was limited to studies with multiple subjects at two distinct and defined mood states. This search yielded eight MRS studies, four functional MRI studies, and three positron emission tomography studies.

RESULTS

Although longitudinally designed studies allow for the isolation of biomarkers of mood state (including euthymia), the current literature is hampered by a lack of replication between studies.

CONCLUSIONS

The current body of longitudinal BPD imaging studies is heterogeneous and incomplete, and does not lend itself to the construction of an explanatory model of mood-state transitions. Drawing on extant studies, we propose a hypothetical framework for future experiments combining multimodal imaging with a longitudinal study design.

Prospective neurochemical characterization of child offspring of parents with bipolar disorder

We wished to determine whether decreases in N-acetyl aspartate (NAA) and increases in myoinositol (mI) concentrations as a ratio of creatine (Cr) occurred in the dorsolateral prefrontal cortex (DLPFC) of pediatric offspring of parents with bipolar disorder (BD) and a healthy comparison group (HC) over a 5-year period using proton magnetic resonance spectroscopy ((1)H-MRS). Paticipants comprised 64 offspring (9-18 years old) of parents with BD (36 with established BD, and 28 offspring with symptoms subsyndromal to mania) and 28 HCs, who were examined for group differences in NAA/Cr and mI/Cr in the DLPFC at baseline and follow-up at either 8, 10, 12, 52, 104, 156, 208, or 260 weeks. No significant group differences were found in metabolite concentrations at baseline or over time. At baseline, BD offspring had trends for higher mI/Cr concentrations in the right DLPFC than the HC group. mI/Cr concentrations increased with age, but no statistically significant group differences were found between groups on follow-up. It may be the case that with intervention youth at risk for BD are normalizing otherwise potentially aberrant neurochemical trajectories in the DLPFC. A longer period of follow-up may be required before observing any group differences.

Neurometabolites in schizophrenia and bipolar disorder - a systematic review and meta-analysis

This meta-analysis evaluates alterations of neurometabolites in schizophrenia and bipolar disorder. PubMed was searched to find controlled studies evaluating N-acetylaspartate (NAA), Choline (Cho) and Creatine (Cr) assessed with ((1))H-MRS (proton magnetic resonance spectroscopy) in patients with schizophrenia and bipolar disorder up to September 2010. Random effects meta-analyses were conducted to estimate pooled standardized mean differences. The statistic was used to quantify inconsistencies. Subgroup analyses were conducted to explore potential explanations for inconsistencies. The systematic review included 146 studies with 5643 participants. NAA levels were affected in schizophrenia and bipolar disorder. Decreased levels in the basal ganglia and frontal lobe were the most consistent findings in schizophrenia; decreased levels in the basal ganglia were the most consistent findings in bipolar disorder. Cho and Cr levels were not altered in either disorder. Findings for Cr were most consistent in the thalamus, frontal lobe and dorsolateral prefrontal cortex in schizophrenia and the basal ganglia and frontal lobe in bipolar disorder. Findings for Cho were most consistent in the thalamus, frontal lobe and anterior cingulate cortex in schizophrenia and basal ganglia in bipolar disorder. Large, carefully designed studies are needed to better estimate the extent of alterations in neurometabolites.

Brain GABA levels in patients with bipolar disorder

PURPOSE

A growing body of research supports an important role for GABA in the pathophysiology of bipolar and other mood disorders. The purpose of the current study was to directly examine brain GABA levels in a clinical sample of bipolar patients.

GENERAL METHODS

We used magnetic resonance spectroscopy (MRS) to examine whole brain and regional GABA, glutamate and glutamine in 13 patients with bipolar disorder compared to a matched group of 11 healthy controls.

FINDINGS

There were no significant differences in GABA, glutamate or glutamine between patients and controls.

CONCLUSIONS

Further research is needed to better characterize the GABAergic and glutamatergic effects of pharmacotherapy, anxiety comorbidity and clinical state in bipolar disorder.

Elevated metabolites within dorsolateral prefrontal cortex in rapid cycling bipolar disorder

Metabolites within the left dorsolateral prefrontal cortex (DLPFC) of six inpatients with bipolar II rapid cycling (RC) during various mood states (depressed, hypomanic, and euthymic), six depressed inpatients with non-RC bipolar disorder (BIPD), and six healthy controls (HC) were assessed by proton magnetic resonance spectroscopy (MRS). We hypothesized that glutamate/glutamine levels should be altered in RC compared with HC. Patients with RC in contrast to BIPD and HC exhibited elevated levels of N-acetylaspartate (NAA), choline (Cho), creatine (Cr), and glutamate/glutamine (Glx) during all mood states. The Glx levels of BIPD compared with HC did not differ significantly; the other metabolites were increased, though less than in RC patients. Our findings of elevated metabolites in patients with RC, especially Glx as a possible marker of cortical activity, indicate that increased neuronal activity may constitute an important neurobiological feature of RC.