Structural brain changes in bipolar disorder using deformation field morphometry

Assessing the interaction effects of brain structure longitudinal changes and life environmental factors on depression and anxiety

Disrupted brain structures and several life environmental factors have been shown to influence depression and anxiety, but their interactions with anxiety and depression remain elusive. Genome-wide association study datasets of 15 brain structure longitudinal changes (N = 15,640) were obtained from the published study. Genotype and phenotype-related data of depression, anxiety, and life environmental factors (including smoking, alcohol drinking, coffee intake, maternal smoking, physical activity, vitamin D, insomnia, sleep duration, and family satisfaction) were collected from UK Biobank. We calculated the polygenic risk scores (PRS) of 15 brain structure changes and then conducted linear regression analyses to explore the interactions of brain structure changes and life environmental factors on depression and anxiety using 15 brain structure change-related PRS, life environmental factors and interactions of them as instrumental variables, and depression score or anxiety score as outcomes. Sex stratification in all analyses was performed to reveal sex-specific differences in the interactions. We found 14 shared interactions related to both depression and anxiety in total sample, such as alcohol drinking × cerebellum white matter 3 (WM; beta = -.003, p = .018 for depression; beta = -003, p = .008 for anxiety) and maternal smoking × nucleus accumbens 2 (beta = .088, p = .002 for depression; beta = .070, p = .008 for anxiety). We also observed sex-specific differences in the interactions, for instance, alcohol drinking × cerebellum WM 3 was negatively associated with depression and anxiety in males (beta = -.004, p = .020 for depression; beta = -.005, p = .002 for anxiety). Our study results reveal the important interactions between brain structure changes and several life environmental factors on depression and anxiety, which may help to explore the pathogenesis of depression and anxiety.

The Potential Influence of the Bacterial Microbiome on the Development and Progression of ADHD

The latest research cumulates staggering information about the correlation between the microbiota-gut-brain axis and neurodevelopmental disorders. This review aims to shed light on the potential influence of the microbiome on the development of the most prevalent neurodevelopmental disease, attention-deficit-hyperactive disorder (ADHD). As the etiology and pathophysiology of ADHD are still unclear, finding viable biomarkers and effective treatment still represent a challenge. Therefore, we focused on factors that have been associated with a higher risk of developing ADHD, while simultaneously influencing the microbial composition. We reviewed the effect of a differing microbial makeup on neurotransmitter concentrations important in the pathophysiology of ADHD. Additionally, we deduced factors that correlate with a high prevalence of ADHD, while simultaneously affecting the gut microbiome, such as emergency c-sections, and premature birth as the former leads to a decrease of the gut microbial diversity and the latter causes neuroprotective Lactobacillus levels to be reduced. Also, we assessed nutritional influences, such as breastfeeding, ingestion of short-chain fatty acids (SCFAs) and polyunsaturated fatty acids (PUFAs) on the host′s microbiome and development of ADHD. Finally, we discussed the potential significance of Bifidobacterium as a biomarker for ADHD, the importance of preventing premature birth as prophylaxis and nutrition as a prospective therapeutic measurement against ADHD.

Further Evidence of Accelerated Aging in Bipolar Disorder: Focus on GDF-15

Background

Bipolar disorder (BD) is a mood disorder associated with cardiovascular and metabolic diseases and premature aging. Growth differentiation factor 15 (GDF-15) has emerged as a biomarker for cardiovascular risk and aging. Our aim was to compare plasma levels of GDF-15 between BD patients and controls, and to evaluate whether they were associated with clinical parameters.

Methods

Forty-six patients with type I BD (23 in euthymia and 23 in mania) and 33 healthy controls were recruited for this study. Plasma levels of GDF-15 were measured by immunoassay.

Results

The levels of GDF-15 were significantly higher (p < 0.001) in patients with BD in comparison with controls. In patients, GDF-15 levels correlated with age (rho = 0.434; p = 0.003) and illness duration (rho = 0.502; p = 0.001).

Conclusion

Our findings corroborate the view that BD is an illness associated with accelerated aging.

Altered prefrontal cortex activity during working memory task in Bipolar Disorder: A functional Magnetic Resonance Imaging study in euthymic bipolar I and II patients

BACKGROUND

Working memory (WM) deficits are among the most frequently impaired cognitive domains in patients with Bipolar Disorder (BD), being considered promising cognitive endophenotype of the disorder. However, the related neurobiological correlates still deserve further investigation. The present study was aimed to explore whether dorsolateral prefrontal cortex (DLPFC) activity during WM processing was abnormal in euthymic bipolar patients and may represent a potential trait-related phenotype associated with the disorder.

METHODS

Using 3 Tesla functional Magnetic Resonance Imaging (3T fMRI), we studied 28 euthymic bipolar patients (15 BDI and 13 BDII), and 27 healthy controls (HCs), matched for a series of socio-demographic variables, while performing the N-back task for WM assessment.

RESULTS

We found that euthymic bipolar patients showed increased right middle frontal gyrus engagement compared with HCs (FWE-corrected p = 1 × 10(-3)), regardless of WM load, and in spite of similar WM behavioral performance between groups. In particular, BDI patients had greater BOLD signal change compared to HCs (post-hoc Tukey HSD, p = 1 × 10(-3)), while BDII patients expressed an intermediate pattern of activation between BDI patients and HCs. No other significant effects were detected in the corrected whole-brain analysis.

LIMITATIONS

Sample size, cross-sectional assessment and potential influence of some clinical variables.

CONCLUSIONS

Results provide direct evidence of a primary physiological abnormality in DLPFC function in BDI and II, even in the absence of behavioral differences with HCs. Such exaggerated fMRI response suggests inefficient WM processing in prefrontal circuitry, and further studies are warranted to investigate whether the dysfunction is related to the genetic risk for the disorder.

Biomarkers and staging of bipolar disorder: a systematic review

INTRODUCTION

A growing body of evidence suggests that bipolar disorder (BD) is a progressive disease according to clinical, biochemical and neuroimaging findings. This study reviewed the literature on the relationship between specific biomarkers and BD stages.

METHODS

A comprehensive literature search of MEDLINE and PubMed was conducted to identify studies in English and Portuguese using the keywords biomarker, neurotrophic factors, inflammation, oxidative stress, neuroprogression and staging models cross-referenced with bipolar disorder.

RESULTS

Morphometric studies of patients with BD found neuroanatomic abnormalities, such as ventricular enlargement, grey matter loss in the hippocampus and cerebellum, volume decreases in the prefrontal cortex and variations in the size of the amygdala. Other studies demonstrated that serum concentrations of neurotrophic factors, inflammatory mediators and oxidative stress may be used as BD biomarkers.

CONCLUSIONS

The analysis of neurobiological changes associated with BD progression and activity may confirm the existence of BD biomarkers, which may be then included in staging models that will lead to improvements in treatment algorithms and more effective, individually tailored treatment regimens. Biomarkers may also be used to define early interventions to control disease progression.

A longitudinal study of fronto-limbic brain structures in patients with bipolar I disorder during lithium treatment

In order to assess the association between therapeutic response to lithium treatment and fronto-limbic brain structures' volumes in bipolar I patients (BPI) 24 BPI and 11 healthy comparisons underwent MRI scans at baseline and 4 weeks later. The BPIs received lithium during the 4 week period with a goal of achieving therapeutic blood levels of >0.5 mEq/L (mean level 0.67 mEq/L). Mood symptoms were rated with the Hamilton Depression and the Young Mania Rating Scales at baseline and after 4 weeks, and response was defined as >50% decrease on either scale. Hippocampus, amygdala, prefrontal (PFC), dorsolateral prefrontal (DLPFC), and anterior cingulate cortex (ACC) volumes were obtained by Freesurfer image analysis suite. According to baseline symptoms and treatment response, patients were assigned to three groups: euthymics (n=6), responders (n=12) and non-responders (n=6). Taken over both time periods, non-responders had smaller right amygdala than healthy comparisons and euthymic BPI (p=0.035 and p=0.003, respectively). When baseline and after treatment volumes were compared, there was a significant enlargement in left PFC and left DLPFC in BPI who responded to treatment (p=0.002 and p=0.006, respectively). Left hippocampus and right ACC volumes decreased in non-responders (p=0.02 and p=0.0001, respectively). According to the findings decreased left hippocampus and right ACC volumes may be markers of non-response to lithium amongst BPI. Smaller right amygdala may reflect symptomatic remission and be a marker of treatment non-response. Increases in left PFC and left DLPFC as a result of lithium treatment may relate to lithium's neurotrophic effects.

Quantitative analysis of live-cell growth at the shoot apex of Arabidopsis thaliana: algorithms for feature measurement and temporal alignment

Study of the molecular control of organ growth requires establishment of the causal relationship between gene expression and cell behaviors. We seek to understand this relationship at the shoot apical meristem (SAM) of model plant Arabidopsis thaliana. This requires the spatial mapping and temporal alignment of different functional domains into a single template. Live-cell imaging techniques allow us to observe real-time organ primordia growth and gene expression dynamics at cellular resolution. In this paper, we propose a framework for the measurement of growth features at the 3D reconstructed surface of organ primordia, as well as algorithms for robust time alignment of primordia. We computed areas and deformation values from reconstructed 3D surfaces of individual primordia from live-cell imaging data. Based on these growth measurements, we applied a multiple feature landscape matching (LAM-M) algorithm to ensure a reliable temporal alignment of multiple primordia. Although the original landscape matching (LAM) algorithm motivated our alignment approach, it sometimes fails to properly align growth curves in the presence of high noise/distortion. To overcome this shortcoming, we modified the cost function to consider the landscape of the corresponding growth features. We also present an alternate parameter-free growth alignment algorithm which performs as well as LAM-M for high-quality data, but is more robust to the presence of outliers or noise. Results on primordia and guppy evolutionary growth data show that the proposed alignment framework performs at least as well as the LAM algorithm in the general case, and significantly better in the case of increased noise.

Towards a multifactorial approach for prediction of bipolar disorder in at risk populations

BACKGROUND

The high prevalence, recurrence rate, chronicity, and illness burden in bipolar disorder (BD) are well documented. Moreover, insufficient response with conventional pharmacological and manual-based psychosocial interventions, as well as evidence of illness progression and acceleration, invite the need for early detection and primary prevention.

METHODS

Herein we comprehensively review extant studies reporting on a bipolar prodrome. The overarching aim is to propose a predictive algorithm (i.e. prediction of BD in at-risk populations) integrating genetic (i.e. family history), environmental (e.g. childhood maltreatment) and biological markers (i.e. BDNF, inflammatory and oxidative stress markers). Computerized databases i.e. Pubmed, PsychInfo, Cochrane Library and Scielo were searched using the followed terms: bipolar disorder cross-referenced with prodromal, preclinical, at risk mental states, clinical high risk, ultra high risk, biomarkers, brain-derived neurotrophic factor, inflammation, cytokines, oxidative stress, prediction and predictive model.

RESULTS

Available evidence indicates that a prodrome to bipolar disorder exists. Commonly encountered features preceding the onset of a manic episode are affective lability, irritability, anger, depression, anxiety, substance use disorders, sleep disorders, as well as disturbances in attention and cognition. Non-specificity and insufficient sensitivity have hampered the development of an adequate prediction algorithm.

LIMITATIONS

Limitations include biases associated with retrospective studies, poor characterization of clinical high risk, inadequacy of prospective studies regarding sample selection and absence of specificity of risk states.

CONCLUSION

We propose a hypothetical prediction algorithm that is combinatorial in approach that attempts to integrate family history, early adversity, and selected biomarkers.

Neurobiological correlates of illness progression in the recurrent affective disorders

Some clinical aspects of affective illness progression, such as episode-, stress-, and substance-induced sensitization, have been well documented in the literature, but others have received less attention. These include cognitive deficits, treatment-refractoriness, and neurobiological correlates of illness progression, which are the primary focus of this paper. We review the evidence that cognitive dysfunction, treatment resistance, medical comorbidities, and neurobiological abnormalities increase as a function of the number of prior episodes or duration of illness in the recurrent unipolar and bipolar disorders. Substantial evidence supports the view that cognitive dysfunction and vulnerability to a diagnosis of dementia in old age increases as a function of number of prior mood episodes as does non-response to many therapeutic interventions as well as naturalistic treatment. Neurobiological abnormalities that correlate with the number of mood episodes or duration of illness include: anatomical, functional, and biochemical deficits in the prefrontal cortex and hippocampus, as well as amygdala hyperactivity and cortisol hyper-secretion. Some neurotrophic factors and inflammatory markers may also change with greater illness burden. Causality cannot be inferred from these correlative relationships. Nonetheless, given the potentially grave consequences of episode recurrence and progression for morbidity and treatment non-responsiveness, it is clinically wise to assume episodes are causing some of the progressive cognitive and neurobiological abnormalities. As such, earlier and more sustained long-term prophylaxis to attempt to reduce these adverse outcomes is indicated.

The T allele of the interferon-gamma +874A/T polymorphism is associated with bipolar disorder

BACKGROUND

Previous studies have shown that patients with bipolar disorder (BD) tend to have altered immune system function. Several studies have reported that changes in interferon-gamma (IFN-γ) may play an important role in the development of BD.

AIMS

To investigate the relationship between IFN-γ and BD, 156 patients with BD and 175 control subjects were genotyped for the IFN-γ +874A/T single nucleotide polymorphism.

RESULTS

We detected significant differences in the genotype distributions and allele frequencies of the IFN-γ +874A/T single nucleotide polymorphism (rs2430561) between patients with BD and normal controls. The T allele was found to be significantly more common among patients with BD than in controls. Additionally, significant differences in scores on the Young Mania Rating Scale (YMRS) were found between the three genotypes of this polymorphism.

CONCLUSIONS

Our results suggest that the IFN-γ +874A/T polymorphism may have important effects related to susceptibility to BD and that the T allele may be associated with an increased risk of developing BD.

The co-occurrence of cigarette smoking and bipolar disorder: phenomenology and treatment considerations

OBJECTIVES

  Despite recent advances in understanding the causes and treatment of nicotine dependence among individuals with psychiatric disorders, smoking among individuals with bipolar disorder (BD) has received little attention. The goal of this review is to synthesize the literature on the epidemiology, consequences, and treatment of smoking and nicotine dependence among individuals with BD and to delineate a future research agenda.

METHODS

  We conducted a PubMed search of English-language articles using the search terms bipolar disorder, mania, tobacco, nicotine, and smoking, followed by a manual search of the literature cited in the identified articles. Articles were chosen by the authors on the basis of their relevance to the topic areas covered in this selective review.

RESULTS

  Adults with BD are two to three times more likely to have started smoking and, on the basis of epidemiological data, may be less likely to initiate and/or maintain smoking abstinence than individuals without psychiatric disorders. Smoking cessation is achievable for individuals with BD, but challenges such as chronic mood dysregulation, high prevalence of alcohol and drug use, more severe nicotine dependence, and limited social support can make quitting more difficult. Effective treatments for tobacco cessation are available, but no controlled trials in smokers with BD have been conducted.

CONCLUSIONS

  Cigarette smoking is a prevalent and devastating addiction among individuals with BD and should be addressed by mental health providers. Additional research on the mechanisms of, and optimal treatment for, smoking and nicotine dependence in this population is desperately needed.

Structural equation modeling and principal component analysis of gray matter volumes in major depressive and bipolar disorders: differences in latent volumetric structure

Abnormalities of the cortico-striatal-thalamic-cortical (CSTC) and the limbic-cortico-striatal-thalamic-cortical (LCSTC) circuits have been hypothesized in mood disorders. We performed principal component analysis (PCA) to identify latent volumetric systems on regional brain volumes and correlated these patterns with clinical characteristics; further, we performed exploratory structural equation modeling (SEM) to test a priori hypotheses about the organization among the structures comprising the CSTC and LCSTC circuits, and to investigate differences among subjects with bipolar disorder (BD), major depressive disorder (MDD), and healthy controls (HC). Participants included 45 BD and 31 MDD patients, and 72 HC. Regional MR brain volumes were used to calculate patterns of volumetric covariance. The identified latent volumetric systems were related to the depression severity and the duration of illness. BD differed from HC on the estimated parameters describing the paths of cortico-striatal, thalamo-striatal and intrastriatal loops of the CSTC circuit, and the paths between anterior and posterior cingulate cortex (PCC), and hippocampus to amygdala of the LCSTC circuit. MDD differed from HC on the paths between putamen and thalamus, and PCC to hippocampus. This study provides evidence to suggest different organizational patterns among structures within the CSTC and LCSTC circuits for BD, MDD, and HC, which may point to structural abnormalities underlying mood disorders.

The structural neuroimaging of bipolar disorder

There is an increasing body of literature fuelled by advances in high-resolution structural MRI acquisition and image processing techniques which implicates subtle neuroanatomical abnormalities in the aetiopathogenesis of bipolar disorder. This account reviews the main findings from structural neuroimaging research into regional brain abnormalities, the impact of genetic liability and mood stabilizing medication on brain structure in bipolar disorder, and the overlapping structural deviations found in the allied disorders of schizophrenia and depression. The manifold challenges extant within neuroimaging research are highlighted with accompanying recommendations for future studies. The most consistent findings include preservation of total cerebral volume with regional grey and white matter structural changes in prefrontal, midline and anterior limbic networks, non-contingent ventriculomegaly and increased rates of white matter hyperintensities, with more pronounced deficits in juveniles suffering from the illness. There is increasing evidence that medication has observable effects on brain structure, whereby lithium status is associated with volumetric increase in the medial temporal lobe and anterior cingulate gyrus. However, research continues to be confounded by the use of highly heterogeneous methodology and clinical populations, in studies employing small scale, low-powered, cross-sectional designs. Future work should investigate larger, clinically homogenous groups of patients and unaffected relatives, combining both categorical and dimensional approaches to illness classification in cross-sectional and longitudinal designs in order to elucidate trait versus state mechanisms, genetic effects and medication/illness progression effects over time.

Staging bipolar disorder

The purpose of this study was to analyze the evidence supporting a staging model for bipolar disorder. The authors conducted an extensive Medline and Pubmed search of the published literature using a variety of search terms (staging, bipolar disorder, early intervention) to find relevant articles, which were reviewed in detail. Only recently specific proposals have been made to apply clinical staging to bipolar disorder. The staging model in bipolar disorder suggests a progression from prodromal (at-risk) to more severe and refractory presentations (Stage IV). A staging model implies a longitudinal appraisal of different aspects: clinical variables, such as number of episodes and subsyndromal symptoms, functional and cognitive impairment, comorbidity, biomarkers, and neuroanatomical changes. Staging models are based on the fact that response to treatment is generally better when it is introduced early in the course of the illness. It assumes that earlier stages have better prognosis and require simpler therapeutic regimens. Staging may assist in bipolar disorder treatment planning and prognosis, and emphasize the importance of early intervention. Further research is required in this exciting and novel area.

Sex dependence of brain size and shape in bipolar disorder: an exploratory study

OBJECTIVES

Anomalies of asymmetry and sex differences in brain structure have frequently been described in schizophrenic illnesses but have seldom been explored in bipolar disorder.

METHODS

We measured volumes of the left and right frontal, temporal, parietal, and occipital lobes and computed the magnitude of brain torque (i.e., rightward frontal and leftward occipital asymmetry) for 49 patients with bipolar disorder and 47 healthy controls and performed an exploratory analysis of sex differences in patients and controls.

RESULTS

Patients had significantly greater cerebrospinal fluid volume than controls, but no difference in total brain volume. There were no main effects of diagnosis in gray matter lobe volume or brain torque, but when analyses were performed separately for male and female subjects, significant sex-by-diagnosis interactions were found in the volume of the left frontal, left temporal, right parietal, and right occipital lobes, such that male patients with bipolar disorder tend toward larger, more symmetric brains than male controls, whereas female patients tend toward smaller, more asymmetric brains than female controls.

CONCLUSION

The lateralised nature of these interactions was such that the normal sex difference in volume was significantly accentuated, whilst the normal sex difference in asymmetry tended to be diminished in patients with bipolar disorder. We conclude that bipolar disorder in part reflects an interaction between brain growth and sex along the anterior-posterior axis of the human brain.

The potential use of biomarkers as an adjunctive tool for staging bipolar disorder

Recent data show that biomarkers differ in early and late-stage bipolar disorder (BD). Here we propose a model of staging for bipolar disorder that emphasizes the potential use of biomarkers for differentiating early and late-stage BD patients in the inter-episodic period. The proposed model includes a Latent phase: patients at "ultra-high-risk" for developing BD, characterized by a family history of BD, temperament traits, mood, and anxiety symptoms as well as genetic vulnerability for developing the disorder; Stage I: patients who return to their baseline level of functioning when mood episodes resolve; Stage II: biomarkers and functioning impairment are related to comorbidities or rapid-cycling presentations; Stage III: persistent cognitive and functioning impairment in the inter-episode period as well as changes in biomarkers; and Stage IV: same findings as in Stage III associated with extreme cognitive and functioning impairment, to the point that patients are unable to live autonomously. Empirical testing will determine the ability of the present model to inform patients and clinicians about both prognosis and response to treatment.

Dorsolateral and dorsomedial prefrontal gray matter density changes associated with bipolar depression

Mood states are associated with alterations in cerebral blood flow and metabolism, yet changes in cerebral structure are typically viewed in the context of enduring traits, genetic predispositions, or the outcome of chronic psychiatric illness. Magnetic resonance imaging (MRI) scans were obtained from two groups of patients with bipolar disorder. In one group, patients met criteria for a current major depressive episode whereas in the other no patient did. No patient in either group met criteria for a current manic, hypomanic, or mixed episode. Groups were matched with respect to age and illness severity. Analyses of gray matter density were performed with Statistical Parametric Mapping software (SPM5). Compared with non-depressed bipolar subjects, depressed bipolar subjects exhibited lower gray matter density in the right dorsolateral and bilateral dorsomedial prefrontal cortices and portions of the left parietal lobe. In addition, gray matter density was greater in the left temporal lobe and right posterior cingulate cortex/parahippocampal gyrus in depressed than in non-depressed subjects. Our findings highlight the importance of mood state in structural studies of the brain-an issue that has received insufficient attention to date. Moreover, our observed differences in gray matter density overlap metabolic areas of change and thus have implications for the conceptualization and treatment of affective disorders.

Bipolar and major depressive disorder: neuroimaging the developmental-degenerative divide

Both major depressive disorder and bipolar disorder are the subject of a voluminous imaging and genetics literature. Here, we attempt a comprehensive review of MRI and metabolic PET studies conducted to date on these two disorders, and interpret our findings from the perspective of developmental and degenerative models of illness. Elevated activity and volume loss of the hippocampus, orbital and ventral prefrontal cortex are recurrent themes in the literature. In contrast, dorsal aspects of the PFC tend to display hypometabolism. Ventriculomegaly and white matter hyperintensities are intimately associated with depression in elderly populations and likely have a vascular origin. Important confounding influences are medication, phenotypic and genetic heterogeneity, and technological limitations. We suggest that environmental stress and genetic risk variants interact with each other in a complex manner to alter neural circuitry and precipitate illness. Imaging genetic approaches hold out promise for advancing our understanding of affective illness.

Chronic administration of mood stabilizers upregulates BDNF and bcl-2 expression levels in rat frontal cortex

Brain-derived neurotrophic factor (BDNF) and B-cell lymphoma-2 (Bcl-2) proteins are neuroprotective factors involved in neuronal signaling, survival and plasticity. Both can be regulated by cyclic AMP response element binding (CREB) protein. Decreased levels of BDNF and Bcl-2 are implicated in the pathogenesis of bipolar disorder. The present study investigated whether chronically administered mood stabilizers would increase BDNF and/or Bcl-2 levels in rat brain. Real time RT-PCR, sandwich ELISA and Western blotting were used to measure BDNF and Bcl-2 mRNA and protein levels in the frontal cortex of rats chronically administered carbamazepine (CBZ) or lamotrigine (LTG) to produce plasma concentrations therapeutically relevant to bipolar disorder. Chronic CBZ and LTG significantly increased BDNF and Bcl-2 mRNA and protein levels in the frontal cortex. A common mechanism of action of mood stabilizers in the treatment of bipolar disorder may involve neuroprotection mediated by upregulation of brain BDNF and Bcl-2 expression.

TNF-alpha as a molecular target in bipolar disorder

The pathophysiology of bipolar disorder (BD) is poorly understood. An emerging body of evidence points to impairments in neuroplasticity, cell resilience and neuronal survival as the main neuropathological correlates of BD. It has been suggested that inflammatory cytokines, particularly TNF-alpha may play a critical role in this process. In the present review we examine the evidence suggesting that TNF-alpha regulates apoptotic cascades which may be related to neuronal and glial loss in BD. Current evidence suggests that an increase in serum levels of TNF-alpha takes place during manic and depressive episodes. The present article reviews the therapeutic implications of TNF-alpha signaling pathways involvement in the pathophysiology of BD.

Volumetric neuroimaging investigations in mood disorders: bipolar disorder versus major depressive disorder

BACKGROUND

As patients with mood disorders manifest heterogeneity in phenomenology, pathophysiology, etiology, and treatment response, a biological classification of mental disease is urgently needed to advance research. Patient and methodological variability complicates the comparison of neuroimaging study results and limits heuristic model development and a biologically-based diagnostic schema.

OBJECTIVE

We have critically reviewed and compared the magnetic resonance neuroimaging literature to determine the degree and directionality of volumetric changes in brain regions putatively implicated in the pathophysiology of major depressive disorder (MDD) versus bipolar disorder (BD).

METHODS

A total of 140 published magnetic resonance imaging investigations evaluating subjects with BD or MDD were selected to provide a summary and interpretation of volumetric neuroimaging results in MDD and BD. Further commentary on the pathophysiological implications, and putative cellular and pharmacological mechanisms, is also provided.

RESULTS

While whole brain volumes of patients with mood disorders do not differ from those of healthy controls, regional deficits in the frontal lobe, particularly in the anterior cingulate and the orbitofrontal cortex, appear to consistently differentiate subjects with mood disorders from the general population. Preliminary findings also suggest that subcortical structures, particularly the striatum, amygdala, and hippocampus, may be differentially affected in MDD and BD.

CONCLUSIONS

Structural neuroimaging studies have consistently identified regional abnormalities in subjects with mood disorders. Future studies should strive to definitively establish the influence of age and medication.

Chronic treatment of rats with sodium valproate downregulates frontal cortex NF-kappaB DNA binding activity and COX-2 mRNA

OBJECTIVES

Valproic acid (VPA) is used to treat bipolar disorder, but its mechanism of action is not clear. VPA shares many cellular and molecular targets with lithium, including reducing arachidonic acid turnover in rat brain phospholipids and cyclooxygenase-2 (COX-2) protein level and activity in rat brain.

METHODS

We examined the effect of chronic VPA administration (200 mg/kg body weight for 30 days) to produce therapeutically relevant plasma concentrations, on transcription factors (NF-kappaB, AP-1, AP-2, C/EBP, CREB, and ETS) that are known to regulate the COX-2 gene.

RESULTS

Chronic VPA significantly increased AP-1 DNA binding activity and decreased NF-kappaB DNA binding activity, p50 subunit protein and mRNA expression of COX-2 in frontal cortex compared with untreated control rats. It did not alter AP-2, C/EBP, ETS or CREB DNA binding activity.

CONCLUSIONS

VPA downregulates NF-kappaB DNA binding activity, likely by decreasing the p50 protein levels. This effect may explain its downregulation of COX-2 mRNA. The decrease in NF-kappaB activity by chronic VPA may affect other NF-kappaB-regulated genes and may be related to VPA's action in bipolar disorder. Chronic VPA may decrease the reported increased brain NF-kappaB components in bipolar patients.

Heritability of brain volume, surface area and shape: an MRI study in an extended pedigree of baboons

To evaluate baboons (Papio hamadryas) as a primate model for the study of the genetic control of brain size and internal structure, we performed high resolution (<500 microm) magnetic resonance imaging on 109 pedigreed baboons. Quantitative genetic analysis of these MR images using a variance components approach indicates that native (untransformed) brain volume exhibits significant heritability among these baboons (h(2) = 0.52, P = 0.0049), with age and sex also accounting for substantial variation. Using global spatial normalization, we transformed all images to a standard population-specific reference, and recalculated the heritability of brain volume. The transformed images generated heritability estimates of h(2) = 0.82 (P = 0.00022) for total brain volume, h(2) = 0.86 (P = 0.0006) for cerebral volume, h(2) = 0.73 (P = 0.0069) for exposed surface area of the cerebrum and h(2) = 0.67 (P = 0.01) for gray matter volume. Regional differences in the genetic effects on brain structure were calculated using a voxel-based morphometry (VBM) approach. This analysis of regional variation shows that some areas of motor cortex and the superior temporal gyrus show relatively high heritability while other regions (e.g. superior parietal cortex) exhibit lower heritability. The general pattern of regional differences is similar to that observed in previous studies of humans. The present study demonstrates that there is substantial genetic variation underlying individual variation in brain size and structure among Papio baboons, and that broad patterns of genetic influence on variation in brain structure may be similar in baboons and humans.

Chronic NMDA administration to rats up-regulates frontal cortex cytosolic phospholipase A2 and its transcription factor, activator protein-2

Excessive N-methyl-D-aspartate (NMDA) signaling is thought to contribute to bipolar disorder symptoms. Lithium and carbamazepine, effective against bipolar mania, are reported in rats to reduce brain transcription of an arachidonic acid selective calcium-dependent cytosolic phospholipase A(2) (cPLA(2)), as well as expression of one of its transcription factors, activator protein (AP)-2. In this study, we determined if chronic administration of NMDA (25 mg/kg i.p.) to rats would increase brain cPLA(2) and AP-2 expression, as these antimanic drugs are known to down-regulate excessive NMDA signaling. Administration of a daily subconvulsive dose of NMDA to rats for 21 days decreased frontal cortex NMDA receptor (NR)-1 and NR-3A subunits and increased cPLA(2) activity, phosphorylation, protein, and mRNA levels. The activity and protein levels of secretory phospholipase A(2) or calcium-independent phospholipase A(2) were not changed significantly. Chronic NMDA also increased the DNA-binding activity of AP-2 and the protein levels of its alpha and beta subunits. These changes were absent following acute (3 h earlier) NMDA administration. The changes, opposite to those found following chronic lithium or carbamazepine, are consistent with up-regulated arachidonic acid release due to excessive NR signaling and may be a contributing factor to bipolar mania.

Dietary n-3 PUFA deprivation alters expression of enzymes of the arachidonic and docosahexaenoic acid cascades in rat frontal cortex

The enzymes that regulate the brain arachidonic acid (AA) cascade have been implicated in bipolar disorder and neuroinflammation. Fifteen weeks of dietary n-3 polyunsaturated fatty acid (PUFA) deprivation in rats decreases the concentration of docosahexaenoic acid (DHA) and increases its half-life within the brain. Based on this, we hypothesized that such dietary deprivation would decrease expression of enzymes responsible for the metabolic loss of DHA while increasing expression of those responsible for the metabolism of AA. Fifteen weeks of n-3 PUFA deprivation significantly decreased the activity, protein and mRNA expression of the DHA regulatory phospholipase A2 (PLA2), calcium-independent iPLA2, in rat frontal cortex. In contrast the activities, protein and mRNA levels of the AA selective calcium-dependent cytosolic phospholipase (cPLA2) and secretory sPLA2 were increased. Cyclooxygenase (COX)-1 protein but not mRNA was decreased in the n-3 PUFA-deprived rats whereas COX-2 protein and mRNA were increased. This study suggests that n-3 PUFA deprivation increases the half-live of brain DHA by downregulating iPLA2. The finding that n-3 PUFA deprivation increases cPLA2, sPLA2 and COX-2 is opposite to what has been reported after chronic administration of anti-manic agents to rats and suggests that n-3 PUFA deprivation may increase susceptibility to bipolar disorder.

n-3 polyunsaturated fatty acid deprivation in rats decreases frontal cortex BDNF via a p38 MAPK-dependent mechanism

Decreased docosahexaenoic acid (DHA) and brain-derived neurotrophic factor (BDNF) have been implicated in bipolar disorder. It also has been reported that dietary deprivation of n-3 polyunsaturated fatty acids (PUFAs) for 15 weeks in rats, increased their depression and aggression scores. Here, we show that n-3 PUFA deprivation for 15 weeks decreased the frontal cortex DHA level and reduced frontal cortex BDNF expression, cAMP response element binding protein (CREB) transcription factor activity and p38 mitogen-activated protein kinase (MAPK) activity. Activities of other CREB activating protein kinases were not significantly changed. The addition of DHA to rat primary cortical astrocytes in vitro, induced BDNF protein expression and this was blocked by a p38 MAPK inhibitor. DHA's ability to regulate BDNF via a p38 MAPK-dependent mechanism may contribute to its therapeutic efficacy in brain diseases having disordered cell survival and neuroplasticity.

Cortical sulci and bipolar disorder

The width of cortical sulci in bipolar patients (n=19) and healthy controls (n=35) was examined using a novel automated technique involving magnetic resonance imaging. All sulci were wider for bipolar patients than for healthy controls. Bipolar-control differences were largest for the superior and intermediate frontal sulci, smallest for the occipital and cingulate sulci, and intermediate in magnitude for the other sulci (intraparietal, inferior frontal, and central sulci). The results were interpreted in terms of neurodegenerative-illness-related processes, which could produce cortical atrophy and result in wider sulci.

The neurophysiology of childhood and adolescent bipolar disorder

INTRODUCTION

Children and adolescents with bipolar disorder often present with higher rates of mixed episodes, rapid cycling, and co-occurring attention-deficit/hyperactivity disorder than adults with bipolar disorder. It is unclear whether the differences in clinical presentation between youth and adults with bipolar disorder are due to differences in underlying etiologies or developmental differences in symptom manifestation. Neuroimaging studies of children and adolescents with bipolar disorder may clarify whether neurobiological abnormalities associated with early- and adult-onset bipolar disorder are distinct. Moreover, children and adolescents with bipolar disorder are typically closer to their illness onset than bipolar adults, providing a window of opportunity for identifying core neurobiological characteristics of the illness (ie, disease biomarkers) that are independent of repeated affective episodes and other confounding factors associated with illness course.

METHODS

Peer-reviewed publications of neuroimaging studies of bipolar children and adolescents were reviewed.

RESULTS

Structural, neurochemical, and neurofunctional abnormalities in prefrontal and medical temporal and subcortical limbic structures, including the striatum, amygdala, and possibly hippocampus, are present in children and adolescents with bipolar disorder.

CONCLUSION

Differences between neurobiological abnormalities in bipolar youth and adults as well as recommendations for future research directions are discussed.