Bcl-2 rs956572 polymorphism is associated with increased anterior cingulate cortical glutamate in euthymic bipolar I disorder

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.

Transdiagnostic role of glutamate and white matter damage in neuropsychiatric disorders: A Systematic Review

Neuropsychiatric disorders including generalized anxiety disorder (GAD), obsessive-compulsive disorder (OCD), major depressive disorder (MDD), bipolar disorder (BD), and schizophrenia (SZ) have been considered distinct categories of diseases despite their overlapping characteristics and symptomatology. We aimed to provide an in-depth review elucidating the role of glutamate/Glx and white matter (WM) abnormalities in these disorders from a transdiagnostic perspective. The PubMed online database was searched for studies published between 2010 and 2021. After careful screening, 401 studies were included. The findings point to decreased levels of glutamate in the Anterior Cingulate Cortex in both SZ and BD, whereas Glx is elevated in the Hippocampus in SZ and MDD. With regard to WM abnormalities, the Corpus Callosum and superior Longitudinal Fascicle were the most consistently identified brain regions showing decreased fractional anisotropy (FA) across all the reviewed disorders, except GAD. Additionally, the Uncinate Fasciculus displayed decreased FA in all disorders, except OCD. Decreased FA was also found in the inferior Longitudinal Fasciculus, inferior Fronto-Occipital Fasciculus, Thalamic Radiation, and Corona Radiata in SZ, BD, and MDD. Decreased FA in the Fornix and Corticospinal Tract were found in BD and SZ patients. The Cingulum and Anterior Limb of Internal Capsule exhibited decreased FA in MDD and SZ patients. The results suggest a gradual increase in severity from GAD to SZ defined by the number of brain regions with WM abnormality which may be partially caused by abnormal glutamate levels. WM damage could thus be considered a potential marker of some of the main neuropsychiatric disorders.

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.

Psychiatric neuroimaging research in Brazil: historical overview, current challenges, and future opportunities

The last four decades have witnessed tremendous growth in research studies applying neuroimaging methods to evaluate pathophysiological and treatment aspects of psychiatric disorders around the world. This article provides a brief history of psychiatric neuroimaging research in Brazil, including quantitative information about the growth of this field in the country over the past 20 years. Also described are the various methodologies used, the wealth of scientific questions investigated, and the strength of international collaborations established. Finally, examples of the many methodological advances that have emerged in the field of in vivo neuroimaging are provided, with discussion of the challenges faced by psychiatric research groups in Brazil, a country of limited resources, to continue incorporating such innovations to generate novel scientific data of local and global relevance.

Pharmacological Treatment for Comorbid Bipolar Disorder and Obsessive-Compulsive Disorder in Adults

Comorbidity between bipolar disorder (BD) and obsessive-compulsive disorder (OCD) is fairly common, and the treatment of these conditions when comorbid is challenging. Serotonin reuptake inhibitors, the first option for treatment of OCD, can worsen BD symptoms, and mood stabilizers are generally not efficacious for OCD. Our goal in this article is to assess the clinical effectiveness of pharmacotherapies for comorbid BD-OCD in adults. We searched the Medline, Embase, and Cochrane Central Register of Controlled Trials databases on April 30, 2017, and we also searched the reference lists of identified articles. Studies published beginning January 1, 2007 were included, without language restrictions. Narrative and systematic reviews, letters to the editor, and book chapters were excluded. Two authors independently assessed the quality of the studies and extracted data. Seven studies met our inclusion criteria. Findings from double-blind, randomized, placebo-controlled trials were pooled for analysis. Findings from this pooled analysis indicated that augmentation of mood-stabilizer treatment with glutamate modulator agents (topiramate or memantine) may favor full response of obsessive-compulsive symptoms (risk ratio: 2.62, 95% confidence interval: 1.45-4.74) in patients with BD type I and OCD in the manic phase, and that it does not significantly induce adverse effects (risk ratio: 1.26, 95% confidence interval: 0.53-3.01). Results of a narrative synthesis of observational studies indicated greater efficacy of mood-stabilizer treatment, with serotonin reuptake inhibitors less used. Findings from studies employing different designs were not compared, and our results should be interpreted cautiously.

Bcl-2 Overexpression Induces Neurite Outgrowth via the Bmp4/Tbx3/NeuroD1 Cascade in H19-7 Cells

Bcl-2 is overexpressed in the nervous system during neural development and plays an important role in modulating cell survival. In addition to its anti-apoptotic function, it has been suggested previously that Bcl-2 might act as a mediator of neuronal differentiation. However, the mechanism by which Bcl-2 might influence neurogenesis is not sufficiently understood. In this study, we aimed to determine the non-apoptotic functions of Bcl-2 during neuronal differentiation. First, we used microarrays to analyze the whole-genome expression patterns of rat neural stem cells overexpressing Bcl-2 and found that Bcl-2 overexpression induced the expression of various neurogenic genes. Moreover, Bcl-2 overexpression increased the neurite length as well as expression of Bmp4, Tbx3, and proneural basic helix-loop-helix genes, such as NeuroD1, NeuroD2, and Mash1, in H19-7 rat hippocampal precursor cells. To determine the hierarchy of these molecules, we selectively depleted Bmp4, Tbx3, and NeuroD1 in Bcl-2-overexpressing cells. Bmp4 depletion suppressed the upregulation of Tbx3 and NeuroD1 as well as neurite outgrowth, which was induced by Bcl-2 overexpression. Although Tbx3 knockdown repressed Bcl-2-mediated neurite elaboration and downregulated NeuroD1 expression, it did not affect Bcl-2-induced Bmp4 expression. While the depletion of NeuroD1 had no effect on the expression of Bcl-2, Bmp4, or Tbx3, Bcl-2-mediated neurite outgrowth was suppressed. Taken together, these results demonstrate that Bcl-2 regulates neurite outgrowth through the Bmp4/Tbx3/NeuroD1 cascade in H19-7 cells, indicating that Bcl-2 may have a direct role in neuronal development in addition to its well-known anti-apoptotic function in response to environmental insults.

Differential levels of prefrontal cortex glutamate+glutamine in adults with antisocial personality disorder and bipolar disorder: A proton magnetic resonance spectroscopy study

As the main excitatory neurotransmitter in the central nervous system, glutamate, as measured in combination with glutamine (Glx), is implicated in several psychopathologies when levels are aberrant. One illness that shows heightened Glx levels is bipolar disorder (BD), an illness characterized by high impulsivity. In addition, although animal studies have reported elevated levels of Glx in aggressive and impulsive phenotypes, no study, to our knowledge, has reported Glx in the human cortex in relation to aggression. Here, we addressed the question of whether elevated levels of Glx would be present in patients with BD and antisocial personality disorder (ASPD), a condition associated with aggression and, like BD, also presents high impulsivity. We recruited individuals with ASPD (n = 18), individuals with BD (n = 16), and a healthy control group (n = 24). We used proton magnetic resonance spectroscopy to measure relative neurometabolite concentrations in the left dorsolateral prefrontal cortex (dlPFC) and supra-genual anterior cingulate cortex (ACC), two brain regions associated with impulsivity and behavior control. We found significantly elevated levels of Glx in the ASPD group relative to the BD and healthy control groups in the dlPFC (p = .014), and a positive correlation between Glx levels and aggression in the dlPFC in the ASPD group alone (r = .59, p = .026). These findings suggest a link between aggression in ASPD and Glx levels.

Genetic variant in SLC1A2 is associated with elevated anterior cingulate cortex glutamate and lifetime history of rapid cycling

Glutamatergic dysregulation is implicated in the neurobiology of mood disorders. This study investigated the relationship between the anterior cingulate cortex (AC) glutamate, as measured by proton magnetic resonance spectroscopy (¹H-MRS), and single-nucleotide polymorphisms (SNPs) from four genes (GLUL, SLC1A3, SLC1A2, and SLC1A7) that regulate the extracellular glutamate in 26 depressed patients with major depressive disorder (MDD; n = 15) and bipolar disorder (BD; n = 11). Two SNPs (rs3812778 and rs3829280), in perfect linkage disequilibrium, in the 3' untranslated region of the EAAT2 gene SLC1A2, were associated with AC glutamate, with minor allele carriers having significantly higher glutamate levels (p < 0.001) in comparison with common allele homozygotes. In silico analysis revealed an association of minor allele carriers of rs3812778/rs382920 with an upregulation of the astrocytic marker CD44 localized downstream of SLC1A2 on chromosome 11. Finally, we tested the disease relevance of these SNPs in a large group of depressed patients [MDD (n = 458); BD (n = 1473)] and found that minor allele carriers had a significantly higher risk for rapid cycling (p = 0.006). Further work is encouraged to delineate the functional impact of excitatory amino acid transporter genetic variation on CD44 associated physiology and glutamatergic neurotransmission, specifically glutamate-glutamine cycling, and its contribution to subphenotypes of mood disorders.

Lithium-associated anterior cingulate neurometabolic profile in euthymic Bipolar I disorder: A 1H-MRS study

OBJECTIVE

In the treatment of Bipolar disorder (BD), achieving euthymia is highly complex and usually requires a combination of mood stabilizers. The mechanism of action in stabilizing mood has not been fully elucidated, but alterations in N-Acetylaspartate (NAA), Myo-Inositol (mI) and Choline (Cho) have been implicated. Proton magnetic resonance spectroscopy (¹H-MRS) is the gold standard technique for measuring brain NAA, Cho and mI in vivo. The objective of this study was to investigate the association of lithium use in BD type I and brain levels of NAA, mI and Cho in the (anterior cingulate cortex) ACC.

METHODS

129 BD type I subjects and 79 healthy controls (HC) were submitted to a 3-Tesla brain magnetic resonance imaging scan (¹H-MRS) using a PRESS ACC single voxel (8cm³) sequence.

RESULTS

BD patients exhibited higher NAA and Cho levels compared to HC. Lithium prescription was associated with lower mI (combination + monotherapy) and higher NAA levels (monotherapy).

CONCLUSION

The results observed add to the knowledge about the mechanisms of action of mood stabilizers on brain metabolites during euthymia. Additionally, the observed decrease in mI levels associated with lithium monotherapy is an in vivo finding that supports the inositol-depletion hypothesis of lithium pharmacodynamics.

Lithium, Stress, and Resilience in Bipolar Disorder: Deciphering this key homeostatic synaptic plasticity regulator

BACKGROUND

Lithium is the lightest metal and the only mood stabilizer that has been used for over half a century for the treatment of bipolar disorder (BD). As a small ion, lithium is omnipresent, and consequently, its molecular mechanisms and targets are widespread. Currently, lithium is a crucial pharmacotherapy for the treatment of acute mood episodes, prophylactic therapy, and suicide prevention in BD. Besides, lithium blood level is the most widely used biomarker in clinical psychiatry. The concept of stress in BD characterizes short- and long-term deleterious effects at multiple levels (from genes to behaviors) and the ability to establish homeostatic regulatory mechanisms to either prevent or reverse these effects. Within this concept, lithium has consistently shown anti-stress effects, by normalizing components across several levels associated with BD-induced impairments in cellular resilience and plasticity.

METHODS

A literature search for biomarkers associated with lithium effects at multiple targets, with a particular focus on those related to clinical outcomes was performed. An extensive search of the published literature using PubMed, Medline and Google Scholar was performed. Example search terms included lithium, plasticity, stress, efficacy, and neuroimaging. Articles determined by the author to focus on lithium's impact on neural plasticity markers (central and periphery) and clinical outcomes were examined in greater depth. Relevant papers were evaluated, selected and included in this review.

RESULTS

Lithium induces neurotrophic and neuroprotective effects in a wide range of preclinical and translational models. Lithium's neurotrophic effects are related to the enhancement of cellular proliferation, differentiation, growth, and regeneration, whereas its neuroprotective effects limit the progression of neuronal atrophy or cell death following the onset of BD. Lithium's neurotrophic and neuroprotective effects seem most pronounced in the presence of pathology, which again supports its pivotal role as an active homeostatic regulator.

LIMITATIONS

Few studies associated with clinical outcomes. Due to space limitations, the author was unable to detail all findings, in special those originated from preclinical studies.

CONCLUSIONS

These results support a potential role for biomarkers involved in neuroprotection and activation of plasticity pathways in lithium's clinical response. Evidence supporting this model comes from results evaluating macroscopic and microscopic brain structure as well neurochemical findings in vivo from cellular to sub-synaptic (molecules and intracellular signaling) compartments using central and peripheral biomarkers. Challenges to precisely decipher lithium's biological mechanisms involved in its therapeutic profile include the complex nature of the illness and clinical subtypes, family history and comorbid conditions. In the context of personalized medicine, it is necessary to validate predictive biomarkers of response to lithium by designing longitudinal clinical studies during mood episodes and associated clinical dimensions in BD.

Anterior Cingulate Cortex Glutamatergic Metabolites and Mood Stabilizers in Euthymic Bipolar I Disorder Patients: A Proton Magnetic Resonance Spectroscopy Study

BACKGROUND

Bipolar disorder is a chronic and recurrent illness characterized by depressive and manic episodes. Proton magnetic resonance spectroscopy (¹H-MRS) studies have demonstrated glutamate (Glu) system abnormalities in BD, but it is unclear how Glu varies among mood states and how medications modulate it. The objective of this study was to investigate the influence of mood stabilizers on anterior cingulate cortex Glu levels using ¹H-MRS during euthymia.

METHODS

One hundred twenty-eight bipolar I disorder (BDI) euthymic subjects and 80 healthy control subjects underwent 3T brain ¹H-MRS imaging examination including acquisition of an anterior cingulate cortex single voxel (8 cm³) ¹H-MRS, based on a point resolved spectroscopy (PRESS) sequence with an echo time of 80 ms and a repetition time of 1500 ms (BIPUSP MRS study). The Glu system was described by measuring Glu and the sum of Glu and glutamine (Glx) using creatine (Cre) as a reference.

RESULTS

Euthymic BDI subjects presented with higher ratios of Glu/Cre and Glx/Cre compared to healthy control subjects. Glu/Cre ratios were lower among patients using anticonvulsants, while Glx/Cre did not differ between the two groups. Lithium, antipsychotics, and antidepressants did not influence Glu/Cre or Glx/Cre.

CONCLUSIONS

We reported Glu/Cre and Glx abnormalities in the largest sample of euthymic BDI patients studied by ¹H-MRS to date. Our data indicate that both Glu/Cre and Glx/Cre are elevated in BDI during euthymia regardless of medication effects, reinforcing the hypothesis of glutamatergic abnormalities in BD. Furthermore, we found an effect of anticonvulsants on Glu/Cre during euthymia, which might indicate a mechanism of mood stabilization in BD.

Associations of Bcl-2 rs956572 genotype groups in the structural covariance network in early-stage Alzheimer's disease

Background

Alzheimer’s disease (AD) is a complex neurodegenerative disease, and genetic differences may mediate neuronal degeneration. In humans, a single-nucleotide polymorphism in the B-cell chronic lymphocytic leukemia/lymphoma-2 (Bcl-2) gene, rs956572, has been found to significantly modulate Bcl-2 protein expression in the brain. The Bcl-2 AA genotype has been associated with reduced Bcl-2 levels and lower gray matter volume in healthy populations. We hypothesized that different Bcl-2 genotype groups may modulate large-scale brain networks that determine neurobehavioral test scores.

Methods

Gray matter structural covariance networks (SCNs) were constructed in 104 patients with AD using T1-weighted magnetic resonance imaging with seed-based correlation analysis. The patients were stratified into two genotype groups on the basis of Bcl-2 expression (G carriers, n = 76; A homozygotes, n = 28). Four SCNs characteristic of AD were constructed from seeds in the default mode network, salience network, and executive control network, and cognitive test scores served as the major outcome factor.

Results

For the G carriers, influences of the SCNs were observed mostly in the default mode network, of which the peak clusters anchored by the posterior cingulate cortex seed determined the cognitive test scores. In contrast, genetic influences in the A homozygotes were found mainly in the executive control network, and both the dorsolateral prefrontal cortex seed and the interconnected peak clusters were correlated with the clinical scores. Despite a small number of cases, the A homozygotes showed greater covariance strength than the G carriers among all four SCNs.

Conclusions

Our results suggest that the Bcl-2 rs956572 polymorphism is associated with different strengths of structural covariance in AD that determine clinical outcomes. The greater covariance strength in the four SCNs shown in the A homozygotes suggests that different Bcl-2 polymorphisms play different modulatory roles.

Electronic supplementary material

The online version of this article (10.1186/s13195-018-0344-4) contains supplementary material, which is available to authorized users.

Disrupted Cerebellar Connectivity With the Central Executive Network and the Default-Mode Network in Unmedicated Bipolar II Disorder

Objective: Bipolar disorder (BD) is a common psychiatric disease. Although structural and functional abnormalities of the cerebellum in BD patients have been reported by recent neuroimaging studies, the cerebellar-cerebral functional connectivity (FC) has not yet been examined. The present study aims to investigate the FC between the cerebellum and cerebrum, particularly the central executive network (CEN) and the default-mode network (DMN) in bipolar II disorder (BD II). Methods: Ninety-four patients with unmedicated BD II depression and 100 healthy controls (HCs) underwent the resting-state functional magnetic resonance imaging. Seed-based connectivity analyses were performed using cerebellar seeds previously identified as being involved in the CEN (bilateral Crus Ia) and DMN (bilateral Crus Ib). Results: Compared with HCs, BD II depression patients appeared decreased FC in the right Crus Ia-left dorsal lateral prefrontal cortex (dlPFC) and -left anterior cingulate cortex (ACC), the right Crus Ib-left medial prefrontal cortex (mPFC), -left middle temporal gyrus (MTG), and -left inferior temporal gyrus (ITG). No altered FC between the left Crus Ia or Crus Ib and the cerebral regions was found. Conclusions: Patients with BD II depression showed disrupted FC between the cerebellum and the CEN (mainly in the left dlPFC and ACC) and DMN (mainly in the left mPFC and temporal lobe), suggesting the significant role of the cerebellum-CEN and -DMN connectivity in the pathogenesis of BD.

Unique prefrontal GABA and glutamate disturbances in co-occurring bipolar disorder and alcohol dependence

Bipolar disorder (BD) and alcohol dependence (AD) frequently co-occur, and co-occurring BD and AD are associated with devastating public health costs. Minimal neurobiological research exists to guide the development of effective treatments for this treatment-resistant population. We believe the present study represents the first investigation of prefrontal gamma-aminobutyric acid (GABA) and glutamate levels in co-occurring BD and current AD. The participants were 78 individuals who met DSM-IV criteria for BD I/II and current AD (n=20), BD I/II alone (n=19), current AD alone (n=20) or no diagnosis (n=19). The participants completed a baseline diagnostic visit, then returned approximately 4 days later for a two-dimensional J-resolved proton magnetic resonance spectroscopy (¹H-MRS) acquisition in dorsal anterior cingulate cortex (dACC). All participants were required to demonstrate ⩾1 week of abstinence from alcohol/drugs via serial biomarker testing before ¹H-MRS. A 2 × 2 factorial analysis of variance of cerebrospinal fluid (CSF)-corrected GABA/water concentrations demonstrated a significant BD × AD interaction (F=2.91, P<0.05), signifying uniquely low levels of GABA in BD+AD; this effect doubled when the sample was restricted to individuals who consumed alcohol within 2 weeks of ¹H-MRS. There were no overall effects of BD/AD on CSF-corrected glutamate/water levels. However, the BD × AD interaction, signifying uniquely low levels of glutamate in BD+AD, approached statistical significance (F=3.83, P=0.06) in individuals who consumed alcohol within 2 weeks of ¹H-MRS. The dACC GABA levels were significantly, negatively associated with Barratt Impulsiveness Scale (r=-0.28, P=0.02) and Obsessive Compulsive Drinking Scale (r=-0.35, P<0.01) scores. If replicated, these results may suggest that future treatment studies should preferentially evaluate therapeutics in BD+AD known to increase prefrontal GABA and glutamate levels.

The CACNA1C risk allele rs1006737 is associated with age-related prefrontal cortical thinning in bipolar I disorder

Calcium channels control the inflow of calcium ions into cells and are involved in diverse cellular functions. The CACNA1C gene polymorphism rs1006737 A allele has been strongly associated with increased risk for bipolar disorder (BD) and with modulation of brain morphology. The medial prefrontal cortex (mPFC) has been widely associated with mood regulation in BD, but the role of this CACNA1C polymorphism in mPFC morphology and brain aging has yet to be elucidated. One hundred seventeen euthymic BD type I subjects were genotyped for CACNA1C rs1006737 and underwent 3 T three-dimensional structural magnetic resonance imaging scans to determine cortical thickness of mPFC components (superior frontal cortex (sFC), medial orbitofrontal cortex (mOFC), caudal anterior cingulate cortex (cACC) and rostral anterior cingulate cortex (rACC)). Carriers of the CACNA1C allele A exhibited greater left mOFC thickness compared to non-carriers. Moreover, CACNA1C A carriers showed age-related cortical thinning of the left cACC, whereas among A non-carriers there was not an effect of age on left cACC cortical thinning. In the sFC, mOFC and rACC (left or right), a negative correlation was observed between age and cortical thickness, regardless of CACNA1C rs1006737 A status. Further studies investigating the direct link between cortical thickness, calcium channel function, apoptosis mechanism and their underlying relationship with aging-associated cognitive decline in BD are warranted.

Evaluation of neuron-glia integrity by in vivo proton magnetic resonance spectroscopy: Implications for psychiatric disorders

Proton magnetic resonance spectroscopy (¹H-MRS) has been widely applied in human studies. There is now a large literature describing findings of brain MRS studies with mental disorder patients including schizophrenia, bipolar disorder, major depressive disorder, and anxiety disorders. However, the findings are mixed and cannot be reconciled by any of the existing interpretations. Here we proposed the new theory of neuron-glia integrity to explain the findings of brain ¹H-MRS stuies. It proposed the neurochemical correlates of neuron-astrocyte integrity and axon-myelin integrity on the basis of update of neurobiological knowledge about neuron-glia communication and of experimental MRS evidence for impairments in neuron-glia integrity from the authors and the other investigators. Following the neuron-glia integrity theories, this review collected evidence showing that glutamate/glutamine change is a good marker for impaired neuron-astrocyte integrity and that changes in N-acetylaspartate and lipid precursors reflect impaired myelination. Moreover, this new theory enables us to explain the differences between MRS findings in neuropsychiatric and neurodegenerative disorders.

Differential neurometabolite alterations in brains of medication-free individuals with bipolar disorder and those with unipolar depression: a two-dimensional proton magnetic resonance spectroscopy study

OBJECTIVES

Bipolar disorder (BD) is a mental disorder characterized by periods of elevated mood and depression. Many individuals with BD are initially misdiagnosed and treated for unipolar depression (UD). In this study, we report direct comparisons between medication-free individuals with BD and those with UD in terms of the neurometabolites in the anterior cingulate cortex (ACC), medial prefrontal cortex (mPFC), parietal cortex (PC), and posterior cingulate cortex (PCC) of the brain.

METHODS

Participants included medication-free patients with BD or UD, and matched healthy controls. All patients were in the depressive state and had similar symptoms. All subjects were subjected to a multi-voxel proton magnetic resonance spectroscopy procedure with a 3.0 T GE Signa MR scanner. After post-processing, the absolute concentrations of glycerophosphocholine + phosphocholine (GPC + PC), phosphocreatine + creatine (PCr + Cr), Glx (glutamate + glutamine), myo-inositol (MI), and N-acetyl aspartate (NAA) from the above brain regions were compared across the three groups.

RESULTS

Patients with BD showed significantly higher levels of Glx in their ACC, lower GPC + PC, PCr + Cr, MI, and NAA in their PC, and lower NAA in their mPFC, compared to healthy controls; patients with UD presented significantly lower levels of GPC + PC, PCr + Cr, and NAA in their PCC, and lower Glx in their mPFC. All analyzed brain metabolites, except Glx, were significantly lower in the PC of patients with BD, whereas levels of GPC + PC, PCr + Cr, and NAA were significantly reduced in the PCC of patients with UD.

CONCLUSIONS

These results add to the evidence of brain metabolite differences in brains of patients with UD and BD which may be of help in differentiating these two mood disorders.

CACNA1C SNP rs1006737 associates with bipolar I disorder independent of the Bcl-2 SNP rs956572 variant and its associated effect on intracellular calcium homeostasis

OBJECTIVES

Intracellular calcium (Ca(2+)) dyshomeostasis (ICDH) has been implicated in bipolar disorder (BD) pathophysiology. We previously showed that SNP rs956572 in the B-cell CLL/lymphoma 2 (Bcl-2) gene associates with elevated B lymphoblast (BLCL) intracellular Ca(2+) concentrations ([Ca(2+)]B) differentially in BD-I. Genome-wide association studies strongly support the association between BD and the SNP rs1006737, located within the L-type voltage-dependent Ca(2+) channel α1C subunit gene (CACNA1C). Here we investigated whether this CACNA1C variant also associates with ICDH and interacts with SNP rs956572 on [Ca(2+)]B in BD-I.

METHODS

CACNA1C SNP rs1006737 was genotyped in 150 BD-I, 65 BD-II, 30 major depressive disorder patients, and 70 healthy subjects with available BLCL [Ca(2+)]B and Bcl-2 SNP rs956572 genotype measures.

RESULTS

SNP rs1006737 was significantly associated with BD-I. The [Ca(2+)]B was significantly higher in BD-I rs1006737 A compared with healthy A allele carriers and also in healthy GG compared with A allele carriers. There was no significant interaction between SNP rs1006737 and SNP rs956572 on [Ca(2+)]B.

CONCLUSIONS

Our study further supports the association of SNP rs1006737 with BD-I and suggests that CACNA1C SNP rs1006737 and Bcl-2 SNP rs956572, or specific causal variants in LD with these proxies, act independently to increase risk and ICDH in BD-I.

Bipolar disorder, a precursor of Parkinson's disease?

Parkinson's disease is a neurodegenerative disorder predominantly resulting from dopamine depletion in the substantia nigra pars compacta. Some psychiatric disorders may have dopaminergic dysfunction as their substrate. We describe a well-documented case of Parkinson's disease associated with Bipolar Disorder. Although there is some knowledge about the association between these diseases, little is known about its pathophysiology and correlation. We believe that among various hypotheses, many neurotransmitters are linked to this pathophysiology.

Dorsal Anterior Cingulate Lactate and Glutathione Levels in Euthymic Bipolar I Disorder: 1H-MRS Study

OBJECTIVE

Oxidative stress and mitochondrial dysfunction are 2 closely integrated processes implicated in the physiopathology of bipolar disorder. Advanced proton magnetic resonance spectroscopy techniques enable the measurement of levels of lactate, the main marker of mitochondrial dysfunction, and glutathione, the predominant brain antioxidant. The objective of this study was to measure brain lactate and glutathione levels in bipolar disorder and healthy controls.

METHODS

Eighty-eight individuals (50 bipolar disorder and 38 healthy controls) underwent 3T proton magnetic resonance spectroscopy in the dorsal anterior cingulate cortex (2x2x4.5cm(3)) using a 2-D JPRESS sequence. Lactate and glutathione were quantified using the ProFit software program.

RESULTS

Bipolar disorder patients had higher dorsal anterior cingulate cortex lactate levels compared with controls. Glutathione levels did not differ between euthymic bipolar disorder and controls. There was a positive correlation between lactate and glutathione levels specific to bipolar disorder. No influence of medications on metabolites was observed.

CONCLUSION

This is the most extensive magnetic resonance spectroscopy study of lactate and glutathione in bipolar disorder to date, and results indicated that euthymic bipolar disorder patients had higher levels of lactate, which might be an indication of altered mitochondrial function. Moreover, lactate levels correlated with glutathione levels, indicating a compensatory mechanism regardless of bipolar disorder diagnosis.

Anterior cingulate Glutamate-Glutamine cycle metabolites are altered in euthymic bipolar I disorder

Bipolar disorder (BD) has been consistently associated with abnormalities in the Glutamate/GABA-Glutamine cycle. Magnetic resonance spectroscopy (MRS) studies have reported increased brain Glutamate (Glu) and Glx (Glu+Glutamine) in subjects with BD. However, data on separate measures of GABA and Glutamine (Gln) in BD are sparse due to overlapping resonant signals. The development of new sequence methods in the quantification of these metabolites has allowed a better understanding of the Glu/GABA-Gln cycle but data on this field of research remains sparse in BD. Eighty-eight subjects (50 euthymic BD and 38 HC) underwent 3T proton magnetic resonance spectroscopy (1H MRS) in the anterior cingulate cortex (ACC; 2×2×4.5cm(3)) using a two-dimensional JPRESS sequence. GABA, Glutamine (Gln) and Glutamate (Glu) were quantified with the ProFit program. Using image segmentation and known creatine (Cre) concentrations for white and grey matter, metabolite concentrations were calculated for the excited MRS voxel. GABA levels did not differ between groups. Gln level was higher in euthymic BD patients than in healthy controls. The Glu level and Glu/Gln ratio were lower in BD patients than in controls. The use of anticonvulsants was associated with Gln increase but did not affect Glu or Glu/Gln. Neither lithium nor antipsychotic use influenced metabolite levels. The ACC MRS findings indicate that the glutamatergic function in euthymic medicated BD patients is altered relative to controls. Whether this feature is a metabolic signature of euthymic BD subjects should be the focus of future studies.

A Longitudinal (6-week) 3T (1)H-MRS Study on the Effects of Lithium Treatment on Anterior Cingulate Cortex Metabolites in Bipolar Depression

The anterior cingulate cortex (ACC) is a key area in mood regulation. To date, no longitudinal study has specifically evaluated lithium׳s effects on ACC metabolites using (1)H-MRS, as well as its association with clinical improvement in bipolar depression. This (1)H-MRS (TE=35ms) study evaluated 24 drug-free BD patients during depressive episodes and after lithium treatment at therapeutic levels. Brain metabolite levels (N-acetyl aspartate (NAA), creatine (tCr), choline, myo-inositol, and glutamate levels) were measured in the ACC at baseline (week 0) and after lithium monotherapy (week 6). The present investigation showed that ACC glutamate (Glu/tCr) and glutamate+glutamine (Glx/tCr) significantly increased after six weeks of lithium therapy. Regarding the association with clinical improvement, remitters showed an increase in myoinositol levels (mI/tCr) after lithium treatment compared to non-remitters. The present findings reinforce a role for ACC glutamate-glutamine cycling and myoinositol pathway as key targets for lithium׳s therapeutic effects in BD.

Cellular models to study bipolar disorder: A systematic review

BACKGROUND

There is an emerging interest in the use of cellular models to study psychiatric disorders. We have systematically reviewed the application of cellular models to understand the biological basis of bipolar disorder (BD).

METHOD

Published scientific literature in MEDLINE, PsychINFO and SCOPUS databases were identified with the following search strategy: [(Lymphoblastoid OR Lymphoblast OR Fibroblast OR Pluripotent OR Olfactory epithelium OR Olfactory mucosa) AND (Bipolar disorder OR Lithium OR Valproate OR Mania)]. Studies were included if they had used cell cultures derived from BD patients.

RESULTS

There were 65 articles on lymphoblastoid cell lines, 14 articles on fibroblasts, 4 articles on olfactory neuronal epithelium (ONE) and 2 articles on neurons reprogrammed from induced pluripotent stem cell lines (IPSC). Several parameters have been studied, and the most replicated findings are abnormalities in calcium signaling, endoplasmic reticulum (ER) stress response, mitochondrial oxidative pathway, membrane ion channels, circadian system and apoptosis related genes. These, although present in basal state, seem to be accentuated in the presence of cellular stressors (e.g. oxidative stress--rotenone; ER stress--thapsigargin), and are often reversed with in-vitro lithium.

CONCLUSION

Cellular modeling has proven useful in BD, and potential pathways, especially in cellular resilience related mechanisms have been identified. These findings show consistency with other study designs (genome-wide association, brain-imaging, and post-mortem brain expression). ONE cells and IPSC reprogrammed neurons represent the next generation of cell models in BD. Future studies should focus on family-based study designs and combine cell models with deep sequencing and genetic manipulations.

Alterations of cerebral glutamate in the euthymic state of patients with bipolar disorder

The pathophysiology of bipolar disorder (BD) mostly remains unclear. However, some findings argue for a dysfunction in glutamatergic neurotransmission in BD. Proton magnetic resonance spectroscopy at 3T was used to determine glutamate concentrations in the anterior cingulate cortex (ACC) and the hippocampus (HC) of euthymic outpatients with BP-I disorder and age- and sex-matched healthy controls. In patients with BD, glutamate concentrations were significantly increased in the ACC and decreased in the HC compared with concentrations in controls. Significant group differences were also measured for N-acetyl aspartate and choline; no differences were found for other metabolites examined. An inverse correlation was observed for glutamate concentrations in the ACC and number of episodes. The findings of the study add to the concept of abnormalities in glutamatergic regulation in the ACC and HC in patients with BD.

Decreased AKT1/mTOR pathway mRNA expression in short-term bipolar disorder

Strong evidence implicates intracellular signaling cascades dysfunction in the pathophysiology of Bipolar Disorder (BD). Regulation of AKT/mTOR pathway is a critical signaling pathway in synaptic neurotransmission and plasticity, also modulating cell proliferation and migration. Gene expression of the AKT/mTOR pathway was assessed in 25 BD (DSM-IV-TR criteria) unmedicated depressed individuals at baseline and after 6 weeks of lithium therapy and 31 matched healthy controls. Decreases in blood AKT1 and mTOR mRNA expression, as well as in BAD/BCL-2 expression ratio were observed in short-term BD patients during depressive episodes in comparison to healthy controls. There was no significant change in the expression of AKT1, mTOR, BCL-2, BAD and NDUFA6 after lithium therapy in the total group of BD subjects. However, the changes in AKT1 expression after lithium treatment were positively correlated with depression improvement. An integrated activity within this pathway was observed at both baseline and post-treatment. The present results support an integrated AKT/mTOR signaling pathway activity in a similar fashion to the described in previous human postmortem and rodents brain studies. Overall, the results reinforce a role for AKT1 and mTOR in the pathophysiology of BD and support the relevance of blood mRNA expression as a valid surrogate biological source to study brain intracellular signaling cascades changes and convergent molecular pathways in psychiatric disorders.

Bcl-2 associated with severity of manic symptoms in bipolar patients in a manic phase

B cell lymphoma protein-2 (Bcl-2) may contribute to the pathophysiology of bipolar disorder, and may be involved in the therapeutic action of anti-manic drugs. The aim of this study was to investigate serum levels of Bcl-2 in bipolar patients in a manic phase, and evaluate the Bcl-2 changes after treatment. We consecutively enrolled 23 bipolar inpatients in a manic phase and 40 healthy subjects; 20 bipolar patients were followed up with treatment. Serum Bcl-2 levels were measured with assay kits. All 20 patients were evaluated by examining the correlation between Bcl-2 levels and Young Mania Rating Scale (YMRS) scores, using Spearman׳s correlation coefficients. The serum Bcl-2 levels in bipolar patients in a manic phase were higher than in healthy subjects, but without a significant difference. The YMRS scores were significantly negatively associated with serum Bcl-2 levels (p=0.042). Bcl-2 levels of the 20 bipolar patients were measured at the end of treatment. Using the Wilcoxon Signed Rank test, we found no significant difference in the Bcl-2 levels of bipolar patients after treatment. Our results suggest that Bcl-2 levels might be an indicator of severity of manic symptoms in bipolar patients in a manic phase.

Investigation of Heschl's gyrus and planum temporale in patients with schizophrenia and bipolar disorder: a proton magnetic resonance spectroscopy study

BACKGROUND

Superior temporal cortices include brain regions dedicated to auditory processing and several lines of evidence suggest structural and functional abnormalities in both schizophrenia and bipolar disorder within this brain region. However, possible glutamatergic dysfunction within this region has not been investigated in adult patients.

METHODS

Thirty patients with schizophrenia (38.67±12.46years of age), 28 euthymic patients with bipolar I disorder (35.32±9.12years of age), and 30 age-, gender- and education-matched healthy controls were enrolled. Proton magnetic resonance spectroscopy data were acquired using a 3.0T Siemens MAGNETOM TIM Trio MR system and single voxel Point REsolved Spectroscopy Sequence (PRESS) in order to quantify brain metabolites within the left and right Heschl's gyrus and planum temporale of superior temporal cortices.

RESULTS

There were significant abnormalities in glutamate (Glu) (F(2,78)=8.52, p<0.0001), N-acetyl aspartate (tNAA) (F(2,81)=5.73, p=0.005), creatine (tCr) (F(2,83)=5.91, p=0.004) and inositol (Ins) (F(2,82)=8.49, p<0.0001) concentrations in the left superior temporal cortex. In general, metabolite levels were lower for bipolar disorder patients when compared to healthy participants. Moreover, patients with bipolar disorder exhibited significantly lower tCr and Ins concentrations when compared to schizophrenia patients. In addition, we have found significant correlations between the superior temporal cortex metabolites and clinical measures.

CONCLUSION

As the left auditory cortices are associated with language and speech, left hemisphere specific abnormalities may have clinical significance. Our findings are suggestive of shared glutamatergic abnormalities in schizophrenia and bipolar disorder.

Lithium-induced neuroprotection is associated with epigenetic modification of specific BDNF gene promoter and altered expression of apoptotic-regulatory proteins

Bipolar disorder (BD), one of the most debilitating mental disorders, is associated with increased morbidity and mortality. Lithium is the first line of treatment option for BD and is often used for maintenance therapy. Recently, the neuroprotective action of lithium has gained tremendous attention, given that BD is associated with structural and functional abnormalities of the brain. However, the precise molecular mechanism by which lithium exerts its neuroprotective action is not clearly understood. In hippocampal neurons, the effects of lithium (1 and 2 mM) on neuronal viability against glutamate-induced cytotoxicity, dendritic length and number, and expression and methylation of BDNF promoter exons and expression of apoptotic regulatory genes were studied. In rat hippocampal neurons, lithium not only increased dendritic length and number, but also neuronal viability against glutamate-induced cytotoxicity. While lithium increased the expression of BDNF as well as genes associated with neuroprotection such as Bcl2 and Bcl-XL, it decreased the expression of pro-apoptotic genes Bax, Bad, and caspases 3. Interestingly, lithium activated transcription of specific exon IV to induce BDNF gene expression. This was accompanied by hypomethylation of BDNF exon IV promoter. This study delineates mechanisms by which lithium mediates its effects in protecting neurons.

Bipolar disorder with comorbid binge eating history: a genome-wide association study implicates APOB

BACKGROUND

Bipolar disorder (BD) is a highly heritable disease. While genome-wide association (GWA) studies have identified several genetic risk factors for BD, few of these studies have investigated the genetic etiology of specific disease subtypes. In particular, BD is positively associated with eating dysregulation traits such as binge eating behavior (BE), yet the genetic risk factors underlying BD with comorbid BE have not been investigated.

METHODS

Utilizing data from the Genetic Association Information Network study of BD, which included 729,454 single nucleotide polymorphisms (SNPs) genotyped in 1001 European American bipolar cases and 1034 controls, we performed GWA analyses of bipolar subtypes defined by the presence or absence of BE history, and performed a case-only analysis comparing BD subjects with and without BE history. Association signals were refined using imputation, and network analysis was performed with Ingenuity Pathway Analysis software. Based on these results, candidate SNPs were selected for replication in an independent sample of 855 cases and 857 controls.

RESULTS

Top ranking SNPs in the discovery set included rs6006893 in PRR5, rs17045162 in ANK2, rs13233490 near PER4, rs4665788 and rs10198175 downstream of APOB, rs2367911 in CACNA2D1, and rs7249968 near ZNF536. Rs10198175 in APOB also demonstrated evidence of association in the replication sample and a meta-analysis of the two samples.

LIMITATIONS

Without information of BE history in controls, it is not possible to determine whether the observed association with APOB reflects a risk factor for BE behavior in general or a risk factor for a subtype of BD with BE. Further longitudinal and functional studies are needed to determine the causal pathways underlying the observed associations.

CONCLUSIONS

This study identified new potential BD-susceptibility genes, highlighting the advantages of phenotypic sub-classification in genetic research and clinical practice.

Targeting mitochondrially mediated plasticity to develop improved therapeutics for bipolar disorder

INTRODUCTION

Bipolar disorder (BPD) is a severe illness with few treatments available. Understanding BPD pathophysiology and identifying potential relevant targets could prove useful for developing new treatments. Remarkably, subtle impairments of mitochondrial function may play an important role in BPD pathophysiology.

AREAS COVERED

This article focuses on human studies and reviews evidence of mitochondrial dysfunction in BPD as a promising target for the development of new, improved treatments. Mitochondria are crucial for energy production, generated mainly through the electron transport chain (ETC) and play an important role in regulating apoptosis and calcium (Ca²⁺) signaling as well as synaptic plasticity. Mitochondria move throughout the neurons to provide energy for intracellular signaling. Studies showed polymorphisms of mitochondria-related genes as risk factors for BPD. Postmortem studies in BPD also show decreased ETC activity/expression and increased nitrosative and oxidative stress (OxS) in patient brains. BPD has been also associated with increased OxS, Ca²⁺ dysregulation and increased proapoptotic signaling in peripheral blood. Neuroimaging studies consistently show decreased energy levels and pH in brains of BPD patients.

EXPERT OPINION

Targeting mitochondrial function, and their role in energy metabolism, synaptic plasticity and cell survival, may be an important avenue for development of new mood-stabilizing agents.

Second messenger/signal transduction pathways in major mood disorders: moving from membrane to mechanism of action, part II: bipolar disorder

In this second of two articles on second messenger/signal transduction cascades in major mood disorders, we will review the evidence in support of intracellular dysfunction and its rectification in the etiopathogenesis and treatment of bipolar disorder (BD). The importance of these cascades is highlighted by lithium's (the gold standard in BD psychopharmacology) ability to inhibit multiple critical loci in second messenger/signal transduction cascades including protein kinase C (involved in the IP3/PIP2 pathway) and GSK-3β (canonically identified in the Wnt/Fz/Dvl/GSK-3β cascade). As a result, and like major depressive disorder (MDD), more recent pathophysiological studies and rational therapeutic targets have been directed at these and other intracellular mediators. Even in the past decade, intracellular dysfunction in numerous neuroprotective/apoptotic cascades appears important in the pathophysiology and may be a future target for pharmacological interventions of BD.