Impaired mitochondrial function in psychiatric disorders

Chronic exposure to neonicotinoids increases neuronal vulnerability to mitochondrial dysfunction in the bumblebee (Bombus terrestris)

The global decline in the abundance and diversity of insect pollinators could result from habitat loss, disease, and pesticide exposure. The contribution of the neonicotinoid insecticides (e.g., clothianidin and imidacloprid) to this decline is controversial, and key to understanding their risk is whether the astonishingly low levels found in the nectar and pollen of plants is sufficient to deliver neuroactive levels to their site of action: the bee brain. Here we show that bumblebees (Bombus terrestris audax) fed field levels [10 nM, 2.1 ppb (w/w)] of neonicotinoid accumulate between 4 and 10 nM in their brains within 3 days. Acute (minutes) exposure of cultured neurons to 10 nM clothianidin, but not imidacloprid, causes a nicotinic acetylcholine receptor-dependent rapid mitochondrial depolarization. However, a chronic (2 days) exposure to 1 nM imidacloprid leads to a receptor-dependent increased sensitivity to a normally innocuous level of acetylcholine, which now also causes rapid mitochondrial depolarization in neurons. Finally, colonies exposed to this level of imidacloprid show deficits in colony growth and nest condition compared with untreated colonies. These findings provide a mechanistic explanation for the poor navigation and foraging observed in neonicotinoid treated bumblebee colonies.—Moffat, C., Pacheco, J. G., Sharp, S., Samson, A. J., Bollan, K. A., Huang, J., Buckland, S. T., Connolly, C. N. Chronic exposure to neonicotinoids increases neuronal vulnerability to mitochondrial dysfunction in the bumblebee (Bombus terrestris).

Teneurins and Alzheimer's disease: a suggestive role for a unique family of proteins

Alzheimer's disease is a debilitating age-related disorder characterized by distinct pathological hallmarks, such as progressive memory loss and cognitive impairment. During the last few years, several cellular signaling pathways have been associated with the pathogenesis of Alzheimer's disease, such as Notch, mTOR and Wnt. However, the potential factors that modulate these pathways and novel molecular mechanisms that might account for the pathogenesis of Alzheimer's disease or for therapy against this disease are still matters of intense research. Teneurins are members of a unique protein system that has recently been proposed as a novel and highly conserved regulatory signaling system in the vertebrate brain, so far related with neurite outgrowth and neuronal matching. The similitude in structure and function of teneurins with other cellular signaling pathways, suggests that they may play a critical role in Alzheimer's disease, either through the modulation of transcription factors due to the nuclear translocation of the teneurins intracellular domain, or through the activity of the corticotrophin releasing factor (CRF)-like peptide sequence, called teneurin C-terminal associated peptide. Moreover, the presence of Ca(2+)-binding motifs within teneurins structure and the Zic2-mediated Wnt/β-catenin signaling modulation, allows hypothesize a potential crosslink between teneurins and the Wnt signaling pathway, particularly. Herein, we aim to highlight the main characteristics of teneurins and propose, based on current knowledge of this family of proteins, an interesting review of their potential involvement in Alzheimer's disease.

Permeabilization of brain tissue in situ enables multiregion analysis of mitochondrial function in a single mouse brain

KEY POINTS

Mitochondrial function in the brain is traditionally assessed through analysing respiration in isolated mitochondria, a technique that possesses significant tissue and time requirements while also disrupting the cooperative mitochondrial reticulum. We permeabilized brain tissue in situ to permit analysis of mitochondrial respiration with the native mitochondrial morphology intact, removing the need for isolation time and minimizing tissue requirements to ∼2 mg wet weight. The permeabilized brain technique was validated against the traditional method of isolated mitochondria and was then further applied to assess regional variation in the mouse brain with ischaemia-reperfusion injuries. A transgenic mouse model overexpressing catalase within mitochondria was applied to show the contribution of mitochondrial reactive oxygen species to ischaemia-reperfusion injuries in different brain regions. This technique enhances the accessibility of addressing physiological questions in small brain regions and in applying transgenic mouse models to assess mechanisms regulating mitochondrial function in health and disease.

ABSTRACT

Mitochondria function as the core energy providers in the brain and symptoms of neurodegenerative diseases are often attributed to their dysregulation. Assessing mitochondrial function is classically performed in isolated mitochondria; however, this process requires significant isolation time, demand for abundant tissue and disruption of the cooperative mitochondrial reticulum, all of which reduce reliability when attempting to assess in vivo mitochondrial bioenergetics. Here we introduce a method that advances the assessment of mitochondrial respiration in the brain by permeabilizing existing brain tissue to grant direct access to the mitochondrial reticulum in situ. The permeabilized brain preparation allows for instant analysis of mitochondrial function with unaltered mitochondrial morphology using significantly small sample sizes (∼2 mg), which permits the analysis of mitochondrial function in multiple subregions within a single mouse brain. Here this technique was applied to assess regional variation in brain mitochondrial function with acute ischaemia-reperfusion injuries and to determine the role of reactive oxygen species in exacerbating dysfunction through the application of a transgenic mouse model overexpressing catalase within mitochondria. Through creating accessibility to small regions for the investigation of mitochondrial function, the permeabilized brain preparation enhances the capacity for examining regional differences in mitochondrial regulation within the brain, as the majority of genetic models used for unique approaches exist in the mouse model.

Is there a "metabolic-mood syndrome"? A review of the relationship between obesity and mood disorders

Obesity and mood disorders are highly prevalent and co-morbid. Epidemiological studies have highlighted the public health relevance of this association, insofar as both conditions and its co-occurrence are associated with a staggering illness-associated burden. Accumulating evidence indicates that obesity and mood disorders are intrinsically linked and share a series of clinical, neurobiological, genetic and environmental factors. The relationship of these conditions has been described as convergent and bidirectional; and some authors have attempted to describe a specific subtype of mood disorders characterized by a higher incidence of obesity and metabolic problems. However, the nature of this association remains poorly understood. There are significant inconsistencies in the studies evaluating metabolic and mood disorders; and, as a result, several questions persist about the validity and the generalizability of the findings. An important limitation in this area of research is the noteworthy phenotypic and pathophysiological heterogeneity of metabolic and mood disorders. Although clinically useful, categorical classifications in both conditions have limited heuristic value and its use hinders a more comprehensive understanding of the association between metabolic and mood disorders. A recent trend in psychiatry is to move toward a domain specific approach, wherein psychopathology constructs are agnostic to DSM-defined diagnostic categories and, instead, there is an effort to categorize domains based on pathogenic substrates, as proposed by the National Institute of Mental Health (NIMH) Research Domain Criteria Project (RDoC). Moreover, the substrates subserving psychopathology seems to be unspecific and extend into other medical illnesses that share in common brain consequences, which includes metabolic disorders. Overall, accumulating evidence indicates that there is a consistent association of multiple abnormalities in neuropsychological constructs, as well as correspondent brain abnormalities, with broad-based metabolic dysfunction, suggesting, therefore, that the existence of a "metabolic-mood syndrome" is possible. Nonetheless, empirical evidence is necessary to support and develop this concept. Future research should focus on dimensional constructs and employ integrative, multidisciplinary and multimodal approaches.

Analysis of mitochondrial network by imaging: proof of technique in schizophrenia

Mitochondria, similar to living cells and organelles, have negative membrane potential and can therefore accumulate permeable lipophilic cations. Those cations which exhibit fluorescence activity after accumulation into energized systems are widely used to decipher changes in membrane potential by imaging techniques. Here we describe the use of the lipophilic cation 5,5',6,6'tetrachloro-1,1',3,3'-tetraethylbenzimidazol-carbocyanine iodide (JC-1), which alters reversibly its color from green (J-monomer, at its low concentration in the cytosol) to red (J-aggregates, at its high concentration in active mitochondria) with increasing mitochondrial membrane potential (Δψm). We show that in addition to changes in Δψm, this specific dye can be used to follow alterations in mitochondrial distribution and mitochondrial network connectivity. We suggest that JC-1 is a preferable probe to compare between treatment groups, as the ratio of green to red fluorescence intensities is used for analysis. This ratio depends only on the mitochondrial membrane potential and not on other mitochondrial dependent or independent factors. We demonstrate various applications of JC-1 staining to study mitochondrial abnormalities in different cell types derived from schizophrenia patients and healthy subjects.

Mitochondrial targets for pharmacological intervention in human disease

Over the past several years, mitochondrial dysfunction has been linked to an increasing number of human illnesses, making mitochondrial proteins (MPs) an ever more appealing target for therapeutic intervention. With 20% of the mitochondrial proteome (312 of an estimated 1500 MPs) having known interactions with small molecules, MPs appear to be highly targetable. Yet, despite these targeted proteins functioning in a range of biological processes (including induction of apoptosis, calcium homeostasis, and metabolism), very few of the compounds targeting MPs find clinical use. Recent work has greatly expanded the number of proteins known to localize to the mitochondria and has generated a considerable increase in MP 3D structures available in public databases, allowing experimental screening and in silico prediction of mitochondrial drug targets on an unprecedented scale. Here, we summarize the current literature on clinically active drugs that target MPs, with a focus on how existing drug targets are distributed across biochemical pathways and organelle substructures. Also, we examine current strategies for mitochondrial drug discovery, focusing on genetic, proteomic, and chemogenomic assays, and relevant model systems. As cell models and screening techniques improve, MPs appear poised to emerge as relevant targets for a wide range of complex human diseases, an eventuality that can be expedited through systematic analysis of MP function.

Glutamate metabolism in major depressive disorder

Research on novel treatments for major depressive disorder focuses quite deeply on glutamate function, and this research would benefit from a brain-imaging technique that precisely quantified glutamate function. Signs of a specific form of glutamate-related dysfunction that could be targeted by novel therapies were found using novel, state-of-the-art techniques to address this issue.

N-acetyl-aspartate (NAA) as a correlate of pharmacological treatment in psychiatric disorders: a systematic review

The amino-acid N-acetyl-aspartate (NAA) is located in neurons and the concentration of NAA correlates with neuronal mitochondrial function. The signal of NAA, as measured with proton magnetic resonance spectroscopy (1H-MRS), is considered to reflect both, neuronal density and integrity of neuronal mitochondria. A reduction of the NAA concentrations has been found in several psychiatric disorders. Newer studies report reversal of decreased NAA concentration with treatment. The objective of this review is to summarize the literature on NAA changes in association with psychopharmacological treatment in psychiatric disorders (affective disorders, obsessive-compulsive disorder, schizophrenia and dementia). The majority of studies identified increased NAA concentrations in response to treatment, while a smaller number of studies did not find this effect. The NAA increase seems to be neither specific for a certain disorder nor for a specific intervention. This suggests that the reduction of NAA may represent an altered functional (metabolic) state of neurons common to different psychiatric disorders and the increase after treatment to indicate functional restoration as one general effect of interventions.

A meta-analysis of gene expression quantitative trait loci in brain

Current catalogs of brain expression quantitative trait loci (eQTL) are incomplete and the findings do not replicate well across studies. All existing cortical eQTL studies are small and emphasize the need for a meta-analysis. We performed a meta-analysis of 424 brain samples across five studies to identify regulatory variants influencing gene expression in human cortex. We identified 3584 genes in autosomes and chromosome X with false discovery rate q<0.05 whose expression was significantly associated with DNA sequence variation. Consistent with previous eQTL studies, local regulatory variants tended to occur symmetrically around transcription start sites and the effect was more evident in studies with large sample sizes. In contrast to random SNPs, we observed that significant eQTLs were more likely to be near 5'-untranslated regions and intersect with regulatory features. Permutation-based enrichment analysis revealed that SNPs associated with schizophrenia and bipolar disorder were enriched among brain eQTLs. Genes with significant eQTL evidence were also strongly associated with diseases from OMIM (Online Mendelian Inheritance in Man) and the NHGRI (National Human Genome Research Institute) genome-wide association study catalog. Surprisingly, we found that a large proportion (28%) of ~1000 autosomal genes encoding proteins needed for mitochondrial structure or function were eQTLs (enrichment P-value=1.3 × 10(-9)), suggesting a potential role for common genetic variation influencing the robustness of energy supply in brain and a possible role in the etiology of some psychiatric disorders. These systematically generated eQTL information should be a valuable resource in determining the functional mechanisms of brain gene expression and the underlying biology of associations with psychiatric disorders.

Strategies for successful aging: a research update

Population aging is an enormous public health issue and there is clear need for strategies to maximize opportunities for successful aging. Many psychiatric illnesses are increasingly thought to be associated with accelerated aging, therefore emerging data on individual and policy level interventions that alter typical aging trajectories are relevant to mental health practitioners. Although the determinants and definition of successful aging remain controversial, increasing data indicate that psychiatric illnesses directly impact biological aging trajectories and diminish lifestyle, psychological, and socio-environmental factors that seem to reduce risk of morbidity and mortality. Many interventions designed to enhance the normal course of aging may be adjunctive approaches to management of psychiatric illnesses. We highlight recent data on interventions seeking to promote healthy aging, such as cognitive remediation, physical activity, nutrition, and complementary and alternative treatments for older people with and without psychiatric illnesses.

A mitochondrial bioenergetic basis of depression

Major depressive disorder (MDD) is an important public health problem affecting 350 million people worldwide. After decades of study, the pathophysiology of MDD remains elusive, resulting in treatments that are only 30-60% effective. This review summarizes the emerging evidence that implicates impaired mitochondrial bioenergetics as a basis for MDD. It is suggested that impaired mitochondrial bioenergetic function contributes to the pathophysiology of MDD via several potential pathways including: genetics/genomics, inflammation, oxidative stress, and alterations in neuroplasticity. A discussion of mitochondrial bioenergetic pathways that lead to MDD is provided. Evidence is reviewed regarding the mito-toxic or mito-protective impact of various antidepressant medications currently in use. Opportunities for further research on novel therapeutic approaches, including mitochondrial modulators, as stand-alone or adjunct therapy for reducing depression are suggested. In conclusion, while there is substantial evidence linking mitochondrial bioenergetics and MDD, there are currently no clear mitochondrial phenotypes or biomarkers to use as guides in targeting therapies beyond individuals with MDD and known mitochondrial disorders toward the general population of individuals with MDD. Further study is needed to develop these phenotypes and biomarkers, to identify therapeutic targets, and to test therapies aimed at improving mitochondrial function in individuals whose MDD is to some extent symptomatic of impaired mitochondrial bioenergetics.

Assessing regional cerebral blood flow in depression using 320-slice computed tomography

While there is evidence that the development and course of major depressive disorder (MDD) symptomatology is associated with vascular disease, and that there are changes in energy utilization in the disorder, the extent to which cerebral blood flow is changed in this condition is not clear. This study utilized a novel imaging technique previously used in coronary and stroke patients, 320-slice Computed-Tomography (CT), to assess regional cerebral blood flow (rCBF) in those with MDD and examine the pattern of regional cerebral perfusion. Thirty nine participants with depressive symptoms (Hamilton Depression Rating Scale 24 (HAMD24) score > 20, and Self-Rating Depression Scale (SDS) score > 53) and 41 healthy volunteers were studied. For all subjects, 3 ml of venous blood was collected to assess hematological parameters. Transcranial Doppler (TCD) ultrasound was utilized to measure parameters of cerebral artery rCBFV and analyse the Pulsatility Index (PI). 16 subjects (8 =  MDD; 8 =  healthy) also had rCBF measured in different cerebral artery regions using 320-slice CT. Differences among groups were analyzed using ANOVA and Pearson's tests were employed in our statistical analyses. Compared with the control group, whole blood viscosity (including high\middle\low shear rate)and hematocrit (HCT) were significantly increased in the MDD group. PI values in different cerebral artery regions and parameters of rCBFV in the cerebral arteries were decreased in depressive participants, and there was a positive relationship between rCBFV and the corresponding vascular rCBF in both gray and white matter. rCBF of the left gray matter was lower than that of the right in MDD. Major depression is characterized by a wide range of CBF impairments and prominent changes in gray matter blood flow. 320-slice CT appears to be a valid and promising tool for measuring rCBF, and could thus be employed in psychiatric settings for biomarker and treatment response purposes.

Brain metabolite clearance: impact on Alzheimer's disease

Alzheimer's Disease (AD) is a complex neurodegenerative disorder often associated with aging and characterized by several critical molecular changes that take place in the brain. Among the molecular hallmarks of AD, increased levels of amyloid β-peptide (Aβ) and the subsequent Aβ-derived damage are the most well-studied factors; however, despite the large amounts of effort and resources devoted to the study of AD and AD pathophysiology, the scientific community still awaits therapeutic alternatives capable of ensuring a better outcome for AD patients. In 2012, Cramer et al. (Science 335:1503-1506 2012) astonished the scientific community by rescuing behavioral and cognitive impairments in AD mouse models via oral administration of bexarotene, a drug used to treat some types of skin cancer. Moreover, these authors demonstrated that bexarotene, a retinoid X receptor (RXR) agonist, exerts major effects on Aβ levels, mainly through increased apolipoprotein E (ApoE) expression. Apart from the valid questions addressed in Cramer's work, only a few attempts have been made to explain the effects of bexarotene. Most of these explanations have been solely based on the ability of bexarotene to reduce Aβ levels and not on the mechanisms that lead to such a reduction. Although it is well known that an imbalance in the Aβ production/excretion rate is the basis of increased Aβ levels in AD, no further explanations have been proposed to address the potential involvement of the blood-brain barrier (BBB), a critical Aβ-clearance structure, in the bexarotene-mediated effects. Moreover, no attempt has been made to explain how the different effects observed after bexarotene administration are connected to each other. Based on current information and on our own experience with nuclear receptors (NR), we offer new perspectives on the mechanisms of bexarotene action, which should help to improve our knowledge of NRs.

Effects of oxidative stress on fatty acid- and one-carbon-metabolism in psychiatric and cardiovascular disease comorbidity

OBJECTIVE

Cardiovascular disease (CVD) is the leading cause of death in severe psychiatric disorders (depression, schizophrenia). Here, we provide evidence of how the effects of oxidative stress on fatty acid (FA) and one-carbon (1-C) cycle metabolism, which may initially represent adaptive responses, might underlie comorbidity between CVD and psychiatric disorders.

METHOD

We conducted a literature search and integrated data in a narrative review.

RESULTS

Oxidative stress, mainly generated in mitochondria, is implicated in both psychiatric and cardiovascular pathophysiology. Oxidative stress affects the intrinsically linked FA and 1-C cycle metabolism: FAs decrease in chain length and unsaturation (particularly omega-3 polyunsaturated FAs), and lipid peroxidation products increase; the 1-C cycle shifts from the methylation to transsulfuration pathway (lower folate and higher homocysteine and antioxidant glutathione). Interestingly, corresponding alterations were reported in psychiatric disorders and CVD. Potential mechanisms through which FA and 1-C cycle metabolism may be involved in brain (neurocognition, mood regulation) and cardiovascular system functioning (inflammation, thrombosis) include membrane peroxidizability and fluidity, eicosanoid synthesis, neuroprotection and epigenetics.

CONCLUSION

While oxidative-stress-induced alterations in FA and 1-C metabolism may initially enhance oxidative stress resistance, persisting chronically, they may cause damage possibly underlying (co-occurrence of) psychiatric disorders and CVD. This might have implications for research into diagnosis and (preventive) treatment of (CVD in) psychiatric patients.

Towards mapping the brain connectome in depression: functional connectivity by perfusion SPECT

Several studies have demonstrated altered brain functional connectivity in the resting state in depression. However, no study has investigated interregional networking in patients with persistent depressive disorder (PDD). The aim of this study was to assess differences in brain perfusion distribution and connectivity between large groups of patients and healthy controls. Participants comprised 91 patients with PDD and 65 age- and sex-matched healthy controls. Resting state perfusion was investigated by single photon emission computed tomography, and group differences were assessed by Statistical Parametric Mapping. Brain connectivity was explored through a voxel-wise interregional correlation analysis using as covariate of interest the normalized values of clusters of voxels in which perfusion differences were found in group analysis. Significantly increased regional brain perfusion distribution covering a large part of the cerebellum was observed in patients as compared with controls. Patients showed a significant negative functional connectivity between the cerebellar cluster and caudate, bilaterally. This study demonstrated inverse relative perfusion between the cerebellum and the caudate in PDD. Functional uncoupling may be associated with a dysregulation between the role of the cerebellum in action control and of the caudate in action selection, initiation and decision making in the patients. The potential impact of the resting state condition and the possibility of mitochondrial impairment are discussed.

NMDA receptor-dependent LTD is required for consolidation but not acquisition of fear memory

NMDA receptor-dependent long-term depression (NMDAR-LTD) is a form of synaptic plasticity leading to long-lasting decreases in synaptic strength. NMDAR-LTD is essential for spatial and working memory, but its role in hippocampus-dependent fear memory has yet to be determined. Induction of NMDAR-LTD requires the activation of caspase-3 by cytochrome c. Cytochrome c normally resides in mitochondria and during NMDAR-LTD is released from mitochondria, a process promoted by Bax (Bcl-2-associated X protein). Bax induces cell death in apoptosis, but it plays a nonapoptotic role in NMDAR-LTD. Here, we investigated the role of NMDAR-LTD in fear memory in CA1-specific Bax knock-out mice. In hippocampal slices from these knock-out mice, while long-term potentiation of synaptic transmission, basal synaptic transmission, and paired-pulse ratio are intact, LTD in both young and fear-conditioned adult mice is obliterated. Interestingly, in CA1-specific Bax knock-out mice, long-term contextual fear memory is impaired, but the acquisition of fear memory and innate fear are normal. Moreover, these conditional Bax knock-out mice exhibit less behavioral despair. These findings indicate that NMDAR-LTD is required for consolidation, but not the acquisition of fear memory. Our study also shows that Bax plays an important role in depressive behavior.

Decreased occipital cortical glutamate levels in response to successful cognitive-behavioral therapy and pharmacotherapy for major depressive disorder

BACKGROUND

Previous studies have demonstrated that antidepressant medication and electroconvulsive therapy increase occipital cortical γ-aminobutyric acid (GABA) in major depressive disorder (MDD), but a small pilot study failed to show a similar effect of cognitive-behavioral therapy (CBT) on occipital GABA. In light of these findings we sought to determine if baseline GABA levels predict treatment response and to broaden the analysis to other metabolites and neurotransmitters in this larger study.

METHODS

A total of 40 MDD outpatients received baseline proton magnetic resonance spectroscopy (1H-MRS), and 30 subjects completed both pre- and post-CBT 1H-MRS; 9 CBT nonresponders completed an open-label medication phase followed by an additional/3rd 1H-MRS. The magnitude of treatment response was correlated with occipital amino acid neurotransmitter levels.

RESULTS

Baseline GABA did not predict treatment outcome. Furthermore, there was no significant effect of CBT on GABA levels. However, we found a significant group × time interaction (F1, 28 = 6.30, p = 0.02), demonstrating reduced glutamate in CBT responders, with no significant glutamate change in CBT nonresponders.

CONCLUSIONS

These findings corroborate the lack of effect of successful CBT on occipital cortical GABA levels in a larger sample. A reduction in glutamate levels following treatment, on the other hand, correlated with successful CBT and antidepressant medication response. Based on this finding and other reports, decreased occipital glutamate may be an antidepressant response biomarker. Healthy control comparator and nonintervention groups may shed light on the sensitivity and specificity of these results.

Synaptic proteins in the postmortem anterior cingulate cortex in schizophrenia: relationship to treatment and treatment response

The anterior cingulate cortex (ACC) is one of several brain regions that are abnormal in schizophrenia (SZ). Here we compared markers of synapse and mitochondrial function using western blots of postmortem ACC in: 1) normal controls (NCs, n=13) vs subjects with SZ (n=25); NC, treatment-resistant SZ, and treatment-responsive SZ; and 3) NC and SZ treated with typical or atypical antipsychotic drugs (APDs). Protein levels of synaptophysin, mitofusin-2, vGLUT1, and calcineurin did not differ between the NC and SZ group as a whole, or the NCs vs the SZ group divided by treatment response or type of APDs. In several cases, the levels of vGLUT1 were minuscule or absent. The proportion of NCs lacking vGLUT1 was significantly less than that of the SZ groups. There were several positive correlations across all subjects between: 1) synaptophysin and vGLUT1; 2) synaptophysin and calcineurin; 3) synaptophysin and mitofusin; and 4) calcineurin and mitofusin. Synaptophysin and calcineurin were positively correlated in responders, and this correlation was significantly stronger than that in treatment-resistant SZ subjects or in NCs. Synaptophysin and calcineurin were positively correlated in SZ patients on atypical APDs; this correlation was significantly stronger than that in SZ patients on typical APDs or in NCs. Mitofusin-2 and calcineurin were positively correlated in SZ patients on atypical APDs and in NCs; this correlation was stronger in SZ patients on atypical rather than typical APDs or in NCs. The correlation between these proteins, which have roles in synaptic vesicle cycling, glutamate transmission, mitochondrial fusion, and calcium buffering, is complex and was differentially regulated among the groups.

Altered plasma glutathione levels in bipolar disorder indicates higher oxidative stress; a possible risk factor for illness onset despite normal brain-derived neurotrophic factor (BDNF) levels

BACKGROUND

Oxidative stress and neurotrophic factors have been implicated in the pathophysiology of bipolar disorder. Our objective was to determine whether plasma glutathione or brain-derived neurotrophic factor (BDNF) levels were abnormal in bipolar disorder and therefore useful as possible biomarkers.

METHOD

Blood samples were collected from subsyndromal, medicated bipolar I patients (n = 50), recruited from OXTEXT, University of Oxford, and from 50 matched healthy controls. Total and oxidized glutathione levels were measured using an enzymatic recycling method and used to calculate reduced, percentage oxidized, ratio of reduced:oxidized and redox state. BDNF was measured using an enzyme-linked immunoassay. Self-monitored mood scores for the bipolar group were available (Quick Inventory of Depressive Symptomatology and the Altman Self-Rating Mania Scale) over an 8-week period.

RESULTS

Compared with controls, bipolar patients had significantly lower levels of total glutathione and it was more oxidized. BDNF levels were not different. Age of illness onset but not current mood state correlated with total glutathione levels and its oxidation status, so that lower levels of total and reduced glutathione were associated with later onset of disease, not length of illness.

CONCLUSIONS

Plasma glutathione levels and redox state detect oxidative stress even in subsyndromal patients with normal BDNF. It may relate to the onset and development of bipolar disorder. Plasma glutathione appears to be a suitable biomarker for detecting underlying oxidative stress and for evaluating the efficacy of antioxidant intervention studies.

Alzheimer's disease: relevant molecular and physiopathological events affecting amyloid-β brain balance and the putative role of PPARs

Alzheimer’s disease (AD) is the most common form of age-related dementia. With the expected aging of the human population, the estimated morbidity of AD suggests a critical upcoming health problem. Several lines of research are focused on understanding AD pathophysiology, and although the etiology of the disease remains a matter of intense debate, increased brain levels of amyloid-β (Aβ) appear to be a critical event in triggering a wide range of molecular alterations leading to AD. It has become evident in recent years that an altered balance between production and clearance is responsible for the accumulation of brain Aβ. Moreover, Aβ clearance is a complex event that involves more than neurons and microglia. The status of the blood-brain barrier (BBB) and choroid plexus, along with hepatic functionality, should be considered when Aβ balance is addressed. Furthermore, it has been proposed that exposure to sub-toxic concentrations of metals, such as copper, could both directly affect these secondary structures and act as a seeding or nucleation core that facilitates Aβ aggregation. Recently, we have addressed peroxisomal proliferator-activated receptors (PPARs)-related mechanisms, including the direct modulation of mitochondrial dynamics through the PPARγ-coactivator-1α (PGC-1α) axis and the crosstalk with critical aging- and neurodegenerative-related cellular pathways. In the present review, we revise the current knowledge regarding the molecular aspects of Aβ production and clearance and provide a physiological context that gives a more complete view of this issue. Additionally, we consider the different structures involved in AD-altered Aβ brain balance, which could be directly or indirectly affected by a nuclear receptor (NR)/PPAR-related mechanism.

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.

Copy number variation in schizophrenia in Sweden

Schizophrenia (SCZ) is a highly heritable neuropsychiatric disorder of complex genetic etiology. Previous genome-wide surveys have revealed a greater burden of large, rare copy number variations (CNVs) in SCZ cases and identified multiple rare recurrent CNVs that increase risk of SCZ although with incomplete penetrance and pleiotropic effects. Identification of additional recurrent CNVs and biological pathways enriched for SCZ CNVs requires greater sample sizes. We conducted a genome-wide survey for CNVs associated with SCZ using a Swedish national sample (4719 cases and 5917 controls). High-confidence CNV calls were generated using genotyping array intensity data, and their effect on risk of SCZ was measured. Our data confirm increased burden of large, rare CNVs in SCZ cases as well as significant associations for recurrent 16p11.2 duplications, 22q11.2 deletions and 3q29 deletions. We report a novel association for 17q12 duplications (odds ratio=4.16, P=0.018), previously associated with autism and mental retardation but not SCZ. Intriguingly, gene set association analyses implicate biological pathways previously associated with SCZ through common variation and exome sequencing (calcium channel signaling and binding partners of the fragile X mental retardation protein). We found significantly increased burden of the largest CNVs (>500 kb) in genes present in the postsynaptic density, in genomic regions implicated via SCZ genome-wide association studies and in gene products localized to mitochondria and cytoplasm. Our findings suggest that multiple lines of genomic inquiry--genome-wide screens for CNVs, common variation and exonic variation--are converging on similar sets of pathways and/or genes.

Assessment of cytochrome C oxidase dysfunction in the substantia nigra/ventral tegmental area in schizophrenia

Perturbations in metabolism are a well-documented but complex facet of schizophrenia pathology. Optimal cellular performance requires the proper functioning of the electron transport chain, which is constituted by four enzymes located within the inner membrane of mitochondria. These enzymes create a proton gradient that is used to power the enzyme ATP synthase, producing ATP, which is crucial for the maintenance of cellular functioning. Anomalies in a single enzyme of the electron transport chain are sufficient to cause disruption of cellular metabolism. The last of these complexes is the cytochrome c oxidase (COX) enzyme, which is composed of thirteen different subunits. COX is a major site for oxidative phosphorylation, and anomalies in this enzyme are one of the most frequent causes of mitochondrial pathology. The objective of the present report was to assess if metabolic anomalies linked to COX dysfunction may contribute to substantia nigra/ventral tegmental area (SN/VTA) pathology in schizophrenia. We tested COX activity in postmortem SN/VTA from schizophrenia and non-psychiatric controls. We also tested the protein expression of key subunits for the assembly and activity of the enzyme, and the effect of antipsychotic medication on subunit expression. COX activity was not significantly different between schizophrenia and non-psychiatric controls. However, we found significant decreases in the expression of subunits II and IV-I of COX in schizophrenia. Interestingly, these decreases were observed in samples containing the entire rostro-caudal extent of the SN/VTA, while no significant differences were observed for samples containing only mid-caudal regions of the SN/VTA. Finally, rats chronically treated with antipsychotic drugs did not show significant changes in COX subunit expression. These findings suggest that COX subunit expression may be compromised in specific sub-regions of the SN/VTA (i.e. rostral regions), which may lead to a faulty assembly of the enzyme and a greater vulnerability to metabolic insult.

Differential expression of synaptic proteins in unilateral 6-OHDA lesioned rat model-A comparative proteomics approach

Parkinson's disease (PD) is characterized as a movement disorder due to lesions in the basal ganglia. As the major input region of the basal ganglia, striatum plays a vital role in coordinating movements. It receives afferents from the cerebral cortex and projects afferents to the internal segment of the globus pallidus and substantia nigra pars reticulate. Additionally, accumulating evidences support a role for synaptic dysfunction in PD. Therefore, the present study explores the changes in protein abundance involved in synaptic disorders in unilateral lesioned 6-OHDA rat model. Based on (18) O/(16) O-labeling technique, striatal proteins were separated using online 2D-LC, and identified by nano-ESI-quadrupole-TOF. A total of 370 proteins were identified, including 76 significantly differentially expressed proteins. Twenty-two downregulated proteins were found in composition of vesicle, ten of which were involved in neuronal transmission and recycling across synapses. These include N-ethylmaleimide-sensitive fusion protein attachment receptor proteins (SNAP-25, syntaxin-1A, syntaxin-1B, VAMP2), synapsin-1, septin-5, clathrin heavy chain 1, AP-2 complex subunit beta, dynamin-1, and endophilin-A1. Moreover, MS result for syntaxin-1A was confirmed by Western blot analysis. Overall, these synaptic changes induced by neurotoxin may serve as a reference for understanding the functional mechanism of striatum in PD.

Mitochondrial dysfunction as a neurobiological subtype of autism spectrum disorder: evidence from brain imaging

IMPORTANCE

Impaired mitochondrial function impacts many biological processes that depend heavily on energy and metabolism and can lead to a wide range of neurodevelopmental disorders, including autism spectrum disorder (ASD). Although evidence that mitochondrial dysfunction is a biological subtype of ASD has grown in recent years, no study, to our knowledge, has demonstrated evidence of mitochondrial dysfunction in brain tissue in vivo in a large, well-defined sample of individuals with ASD.

OBJECTIVES

To assess brain lactate in individuals with ASD and typically developing controls using high-resolution, multiplanar spectroscopic imaging; to map the distribution of lactate in the brains of individuals with ASD; and to assess correlations of elevated brain lactate with age, autism subtype, and intellectual ability.

DESIGN, SETTING, AND PARTICIPANTS

Case-control study at Columbia University Medical Center and New York State Psychiatric Institute involving 75 children and adults with ASD and 96 age- and sex-matched, typically developing controls.

MAIN OUTCOMES AND MEASURES

Lactate doublets (present or absent) on brain magnetic resonance spectroscopic imaging.

RESULTS

Lactate doublets were present at a significantly higher rate in participants with ASD (13%) than controls (1%) (P = .001). In the ASD group, the presence of lactate doublets correlated significantly with age (P = .004) and was detected more often in adults (20%) than in children (6%), though it did not correlate with sex, ASD subtype, intellectual ability, or the Autism Diagnostic Observation Schedule total score or subscores. In those with ASD, lactate was detected most frequently within the cingulate gyrus but it was also present in the subcortical gray matter nuclei, corpus callosum, superior temporal gyrus, and pre- and postcentral gyri.

CONCLUSIONS AND RELEVANCE

In vivo brain findings provide evidence for a possible neurobiological subtype of mitochondrial dysfunction in ASD.

A review of MR spectroscopy studies of pediatric bipolar disorder

Pediatric bipolar disorder is a severe mental illness whose pathophysiology is poorly understood and for which there is an urgent need for improved diagnosis and treatment. MR spectroscopy is a neuroimaging method capable of in vivo measurement of neurochemicals relevant to bipolar disorder neurobiology. MR spectroscopy studies of adult bipolar disorder provide consistent evidence for alterations in the glutamate system and mitochondrial function. In bipolar disorder, these 2 phenomena may be linked because 85% of glucose in the brain is consumed by glutamatergic neurotransmission and the conversion of glutamate to glutamine. The purpose of this article is to review the MR spectroscopic imaging literature in pediatric bipolar disorder, at-risk samples, and severe mood dysregulation, with a focus on the published findings that are relevant to glutamatergic and mitochondrial functioning. Potential directions for future MR spectroscopy studies of the glutamate system and mitochondrial dysfunction in pediatric bipolar disorder are discussed.

Changes in mitochondrial function are pivotal in neurodegenerative and psychiatric disorders: how important is BDNF?

The brain is at the very limit of its energy supply and has evolved specific means of adapting function to energy supply, of which mitochondria form a crucial link. Neurotrophic and inflammatory processes may not only have opposite effects on neuroplasticity, but also involve opposite effects on mitochondrial oxidative phosphorylation and glycolytic processes, respectively, modulated by stress and glucocorticoids, which also have marked effects on mood. Neurodegenerative processes show marked disorders in oxidative metabolism in key brain areas, sometimes decades before symptoms appear (Parkinson's and Alzheimer's diseases). We argue that brain-derived neurotrophic factor couples activity to changes in respiratory efficiency and these effects may be opposed by inflammatory cytokines, a key factor in neurodegenerative processes.

Oxidative stress in early stage Bipolar Disorder and the association with response to lithium

BACKGROUND

Several studies have described increased oxidative stress (OxS) parameters and imbalance of antioxidant enzymes in Bipolar Disorder (BD) but few is know about the impact of treatment at these targets. However, no study has evaluated OxS parameters in unmedicated early stage BD and their association with lithium treatment in bipolar depression.

METHODS

Patients with BD I or II (n = 29) in a depressive episode were treated for 6 weeks with lithium. Plasma samples were collected at baseline and endpoint, and were also compared to age-matched controls (n = 28). The thiobarbituric acid reactive substances (TBARS), and the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities were measured.

RESULTS

Subjects with BD depression at baseline presented a significant increase in CAT (p = 0.005) and GPx (p < 0.001) levels, with lower SOD/CAT ratio (p = 0.001) and no changes on SOD or TBARS compared to healthy controls. Regarding therapeutics, lithium only induced a decrease in TBARS (p = 0.023) and SOD (p = 0.029) levels, especially in BDII. Finally, TBARS levels were significantly lower at endpoint in lithium responders compared to non-responders (p = 0.018) with no difference in any biomarker regarding remission.

CONCLUSION

The present findings suggest a reactive increase in antioxidant enzymes levels during depressive episodes in early stage BD with minimal prior treatment. Also, decreased lipid peroxidation (TBARS) levels were observed, associated with lithium's clinical efficacy. Overall, these results reinforce the role for altered oxidative stress in the pathophysiology of BD and the presence of antioxidant effects of lithium in the prevention of illness progression and clinical efficacy.

Pathway analyses implicate glial cells in schizophrenia

BACKGROUND

The quest to understand the neurobiology of schizophrenia and bipolar disorder is ongoing with multiple lines of evidence indicating abnormalities of glia, mitochondria, and glutamate in both disorders. Despite high heritability estimates of 81% for schizophrenia and 75% for bipolar disorder, compelling links between findings from neurobiological studies, and findings from large-scale genetic analyses, are only beginning to emerge.

METHOD

Ten publically available gene sets (pathways) related to glia, mitochondria, and glutamate were tested for association to schizophrenia and bipolar disorder using MAGENTA as the primary analysis method. To determine the robustness of associations, secondary analyses were performed with: ALIGATOR, INRICH, and Set Screen. Data from the Psychiatric Genomics Consortium (PGC) were used for all analyses. There were 1,068,286 SNP-level p-values for schizophrenia (9,394 cases/12,462 controls), and 2,088,878 SNP-level p-values for bipolar disorder (7,481 cases/9,250 controls).

RESULTS

The Glia-Oligodendrocyte pathway was associated with schizophrenia, after correction for multiple tests, according to primary analysis (MAGENTA p = 0.0005, 75% requirement for individual gene significance) and also achieved nominal levels of significance with INRICH (p = 0.0057) and ALIGATOR (p = 0.022). For bipolar disorder, Set Screen yielded nominally and method-wide significant associations to all three glial pathways, with strongest association to the Glia-Astrocyte pathway (p = 0.002).

CONCLUSIONS

Consistent with findings of white matter abnormalities in schizophrenia by other methods of study, the Glia-Oligodendrocyte pathway was associated with schizophrenia in our genomic study. These findings suggest that the abnormalities of myelination observed in schizophrenia are at least in part due to inherited factors, contrasted with the alternative of purely environmental causes (e.g. medication effects or lifestyle). While not the primary purpose of our study, our results also highlight the consequential nature of alternative choices regarding pathway analysis, in that results varied somewhat across methods, despite application to identical datasets and pathways.

Mitochondrial homeostasis: the interplay between mitophagy and mitochondrial biogenesis

Mitochondria are highly dynamic organelles and their proper function is crucial for the maintenance of cellular homeostasis. Mitochondrial biogenesis and mitophagy are two pathways that regulate mitochondrial content and metabolism preserving homeostasis. The tight regulation between these opposing processes is essential for cellular adaptation in response to cellular metabolic state, stress and other intracellular or environmental signals. Interestingly, imbalance between mitochondrial proliferation and degradation process results in progressive development of numerous pathologic conditions. Here we review recent studies that highlight the intricate interplay between mitochondrial biogenesis and mitophagy, mainly focusing on the molecular mechanisms that govern the coordination of these processes and their involvement in age-related pathologies and ageing.

In vivo evidence for cerebral bioenergetic abnormalities in schizophrenia measured using 31P magnetization transfer spectroscopy

IMPORTANCE

Abnormalities in neural activity and cerebral bioenergetics have been observed in schizophrenia (SZ). Further defining energy metabolism anomalies would provide crucial information about molecular mechanisms underlying SZ and may be valuable for developing novel treatment strategies.

OBJECTIVE

To investigate cerebral bioenergetics in SZ via measurement of creatine kinase activity using in vivo 31P magnetization transfer spectroscopy.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional case-control study in the setting of clinical services and a brain imaging center of an academic psychiatric hospital. Twenty-six participants with chronic SZ (including a subgroup diagnosed as having schizoaffective disorder) and 26 age-matched and sex-matched healthy control subjects (25 usable magnetic resonance spectroscopy data sets from the latter).

INTERVENTION

31P magnetization transfer spectroscopy.

MAIN OUTCOMES AND MEASURES

The primary outcome measure was the forward rate constant (k(f)) of the creatine kinase enzyme in the frontal lobe. We also collected independent measures of brain intracellular pH and steady-state metabolite ratios of high-energy phosphate-containing compounds (phosphocreatine and adenosine triphosphate [ATP]), inorganic phosphate, and the 2 membrane phospholipids phosphodiester and phosphomonoester.

RESULTS

A substantial (22%) and statistically significant (P = .003) reduction in creatine kinase kf was observed in SZ. In addition, intracellular pH was significantly reduced (7.00 in the SZ group vs 7.03 in the control group, P = .007) in this condition. The phosphocreatine to ATP ratio, inorganic phosphate to ATP ratio, and phosphomonoester to ATP ratio were not substantially altered in SZ, but a significant (P = .02) reduction was found in the phosphodiester to ATP ratio. The abnormalities were similar between SZ and schizoaffective disorder.

CONCLUSIONS AND RELEVANCE

Using a novel 31P magnetization transfer magnetic resonance spectroscopy approach, we provide direct and compelling evidence for a specific bioenergetic abnormality in SZ. Reduced kf of the creatine kinase enzyme is consistent with an abnormality in storage and use of brain energy. The intracellular pH reduction suggests a relative increase in the contribution of glycolysis to ATP synthesis, providing convergent evidence for bioenergetic abnormalities in SZ. The similar phosphocreatine to ATP ratios in SZ and healthy controls suggest that the underlying bioenergetics abnormality is not associated with change in this metabolite ratio.

The neurobiology of autism spectrum disorders

Data is progressively and robustly accumulating regarding the biological basis of autism. Autism spectrum disorders (ASD) are currently considered a group of neurodevelopmental disorders with onset very early in life and a complex, heterogeneous, multifactorial aetiology. A comprehensive search of the last five years of the Medline database was conducted in order to summarize recent evidence on the neurobiological bases of autism. The main findings on genetic influence, neuropathology, neurostructure and brain networks are summarized. In addition, findings from peripheral samples of subjects with autism and animal models, which show immune, oxidative, mitochondrial dysregulations, are reported. Then, other biomarkers from very different systems associated with autism are reported. Finally, an attempt is made to try and integrate the available evidence, which points to a oligogenetic, multifactorial aetiology that converges in an aberrant micro-organization of the cortex, with abnormal functioning of the synapses and abnormalities in very general physiological pathways (such as inflammatory, immune and redox systems).

Dysregulation of the axonal trafficking of nuclear-encoded mitochondrial mRNA alters neuronal mitochondrial activity and mouse behavior

Local translation of nuclear-encoded mitochondrial mRNAs is essential for mitochondrial activity, yet there is little insight into the role that axonal trafficking of these transcripts play in neuronal function and behavior. Previously, we identified a 38 nucleotide stem-loop structure (zipcode) in the 3' untranslated region of the Cytochrome C oxidase IV (COXIV) mRNA that directs the transport of a reporter mRNA to the axon of superior cervical ganglion neurons (SCG). Overexpression of a chimeric reporter mRNA with the COXIV zipcode competed with the axonal trafficking of endogenous COXIV mRNA, and led to attenuated axon growth in SCG neurons. Here, we show that exogenous expression of the COXIV zipcode in cultured SCG neurons also results in the reduction of local ATP levels and increases levels of reactive oxygen species (ROS) in the axon. We took advantage of this "competition" phenotype to investigate the in vivo significance of axonal transport of COXIV mRNA. Toward this end, we generated transgenic mice expressing a fluorescent reporter fused to COXIV zipcode under a forebrain-specific promoter. Immunohistological analyses and RT-PCR analyses of RNA from the transgenic mouse brain showed expression of the reporter in the deep layer neurons in the pre-frontal and frontal cortex. Consistent with the in vitro studies, we observed increased ROS levels in neurons of these transgenic animals. A battery of behavioral tests on transgenic mice expressing the COXIV zipcode revealed an "anxiety-like" behavioral phenotype, suggesting an important role for axonal trafficking of nuclear-encoded mitochondrial mRNAs in neuronal physiology and animal behavior.

A combined metabonomic and proteomic approach identifies frontal cortex changes in a chronic phencyclidine rat model in relation to human schizophrenia brain pathology

Current schizophrenia (SCZ) treatments fail to treat the broad range of manifestations associated with this devastating disorder. Thus, new translational models that reproduce the core pathological features are urgently needed to facilitate novel drug discovery efforts. Here, we report findings from the first comprehensive label-free liquid-mass spectrometry proteomic- and proton nuclear magnetic resonance-based metabonomic profiling of the rat frontal cortex after chronic phencyclidine (PCP) intervention, which induces SCZ-like symptoms. The findings were compared with results from a proteomic profiling of post-mortem prefrontal cortex from SCZ patients and with relevant findings in the literature. Through this approach, we identified proteomic alterations in glutamate-mediated Ca(2+) signaling (Ca(2+)/calmodulin-dependent protein kinase II, PPP3CA, and VISL1), mitochondrial function (GOT2 and PKLR), and cytoskeletal remodeling (ARP3). Metabonomic profiling revealed changes in the levels of glutamate, glutamine, glycine, pyruvate, and the Ca(2+) regulator taurine. Effects on similar pathways were also identified in the prefrontal cortex tissue from human SCZ subjects. The discovery of similar but not identical proteomic and metabonomic alterations in the chronic PCP rat model and human brain indicates that this model recapitulates only some of the molecular alterations of the disease. This knowledge may be helpful in understanding mechanisms underlying psychosis, which, in turn, can facilitate improved therapy and drug discovery for SCZ and other psychiatric diseases. Most importantly, these molecular findings suggest that the combined use of multiple models may be required for more effective translation to studies of human SCZ.

Omega-3 fatty acid deficiency disrupts endocytosis, neuritogenesis, and mitochondrial protein pathways in the mouse hippocampus

Omega-3 fatty acid (n-3 FA) deficiency is an environmental risk factor for schizophrenia, yet characterization of the consequences of deficiency at the protein level in the brain is limited. We aimed to identify the protein pathways disrupted as a consequence of chronic n-3 deficiency in the hippocampus of mice. Fatty acid analysis of the hippocampus following chronic dietary deficiency revealed a 3-fold decrease (p < 0.001) in n-3 FA levels. Label free LC-MS/MS analysis identified and profiled 1008 proteins, of which 114 were observed to be differentially expressed between n-3 deficient and control groups (n = 8 per group). The cellular processes that were most implicated were neuritogenesis, endocytosis, and exocytosis, while specific protein pathways that were most significantly dysregulated were mitochondrial dysfunction and clathrin mediated endocytosis (CME). In order to characterize whether these processes and pathways are ones influenced by antipsychotic medication, we used LC-MS/MS to test the differential expression of these 114 proteins in the hippocampus of mice chronically treated with the antipsychotic agent haloperidol. We observed 23 of the 114 proteins to be differentially expressed, 17 of which were altered in the opposite direction to that observed following n-3 deficiency. Overall, our findings point to disturbed synaptic function, neuritogenesis, and mitochondrial function as a consequence of dietary deficiency in n-3 FA. This study greatly aids our understanding of the molecular mechanism by which n-3 deficiency impairs normal brain function, and provides clues as to how n-3 FA exert their therapeutic effect in early psychosis.

Mitochondrial activity and oxidative stress markers in peripheral blood mononuclear cells of patients with bipolar disorder, schizophrenia, and healthy subjects

Evidence suggests that mitochondrial dysfunction is involved in the pathophysiology of psychiatric disorders such as schizophrenia (SZ) and bipolar disorder (BD). However, the exact mechanisms underlying this dysfunction are not well understood. Impaired activity of electron transport chain (ETC) complexes has been described in these disorders and may reflect changes in mitochondrial metabolism and oxidative stress markers. The objective of this study was to compare ETC complex activity and protein and lipid oxidation markers in 12 euthymic patients with BD type I, in 18 patients with stable chronic SZ, and in 30 matched healthy volunteers. Activity of complexes I, II, and III was determined by enzyme kinetics of mitochondria isolated from peripheral blood mononuclear cells (PBMCs). Protein oxidation was evaluated using the protein carbonyl content (PCC) method, and lipid peroxidation, the thiobarbituric acid reactive substances (TBARS) assay kit. A significant decrease in complex I activity was observed (p = 0.02), as well as an increase in plasma levels of TBARS (p = 0.00617) in patients with SZ when compared to matched controls. Conversely, no significant differences were found in complex I activity (p = 0.17) or in plasma TBARS levels (p = 0.26) in patients with BD vs. matched controls. Our results suggest that mitochondrial complex I dysfunction and oxidative stress play important roles in the pathophysiology of SZ and may be used in potential novel adjunctive therapy for SZ, focusing primarily on cognitive impairment and disorder progression.

Abnormal neuronal differentiation and mitochondrial dysfunction in hair follicle-derived induced pluripotent stem cells of schizophrenia patients

One of the prevailing hypotheses suggests schizophrenia as a neurodevelopmental disorder, involving dysfunction of dopaminergic and glutamatergic systems. Accumulating evidence suggests mitochondria as an additional pathological factor in schizophrenia. An attractive model to study processes related to neurodevelopment in schizophrenia is reprogramming of somatic cells into induced pluripotent stem cells (iPSCs) and differentiating them into different neuronal lineages. iPSCs from three schizophrenia patients and from two controls were reprogrammed from hair follicle keratinocytes, because of their accessibility and common ectodermal origin with neurons. iPSCs were differentiated into Pax6(+)/Nestin(+) neural precursors and then further differentiated into β3-Tubulin(+)/tyrosine hydroxylase(+)/DAT(+) dopaminergic neurons. In addition, iPSCs were differentiated through embryonic bodies into β3-Tubulin(+)/Tbox brain1(+) glutamatergic neurons. Schizophrenia-derived dopaminergic cells showed severely impaired ability to differentiate, whereas glutamatergic cells were unable to maturate. Mitochondrial respiration and its sensitivity to dopamine-induced inhibition were impaired in schizophrenia-derived keratinocytes and iPSCs. Moreover, we observed dissipation of mitochondrial membrane potential (Δψm) and perturbations in mitochondrial network structure and connectivity in dopaminergic along the differentiation process and in glutamatergic cells. Our data unravel perturbations in neural differentiation and mitochondrial function, which may be interconnected, and of relevance to dysfunctional neurodevelopmental processes in schizophrenia.

How might circadian rhythms control mood? Let me count the ways

Mood disorders are serious diseases that affect a large portion of the population. There have been many hypotheses put forth over the years to explain the development of major depression, bipolar disorder, and other mood disorders. These hypotheses include disruptions in monoamine transmission, hypothalamus-pituitary-adrenal axis function, immune function, neurogenesis, mitochondrial dysfunction, and neuropeptide signaling (to name a few). Nearly all people suffering from mood disorders have significant disruptions in circadian rhythms and the sleep/wake cycle. In fact, altered sleep patterns are one of the major diagnostic criteria for these disorders. Moreover, environmental disruptions to circadian rhythms, including shift work, travel across time zones, and irregular social schedules, tend to precipitate or exacerbate mood-related episodes. Recent studies have found that molecular clocks are found throughout the brain and body where they participate in the regulation of most physiological processes, including those thought to be involved in mood regulation. This review will summarize recent data that implicate the circadian system as a vital regulator of a variety of systems that are thought to play a role in the development of mood disorders.

Canonical Wnt signaling protects hippocampal neurons from Aβ oligomers: role of non-canonical Wnt-5a/Ca(2+) in mitochondrial dynamics

Alzheimer's disease (AD) is the most common type of age-related dementia. The disease is characterized by a progressive loss of cognitive abilities, severe neurodegeneration, synaptic loss and mitochondrial dysfunction. The Wnt signaling pathway participates in the development of the central nervous system and growing evidence indicates that Wnts also regulate the function of the adult nervous system. We report here, that indirect activation of canonical Wnt/β-catenin signaling using Bromoindirubin-30-Oxime (6-BIO), an inhibitor of glycogen synthase kinase-3β, protects hippocampal neurons from amyloid-β (Aβ) oligomers with the concomitant blockade of neuronal apoptosis. More importantly, activation with Wnt-5a, a non-canonical Wnt ligand, results in the modulation of mitochondrial dynamics, preventing the changes induced by Aβ oligomers (Aβo) in mitochondrial fission-fusion dynamics and modulates Bcl-2 increases induced by oligomers. The canonical Wnt-3a ligand neither the secreted Frizzled-Related Protein (sFRP), a Wnt scavenger, did not prevent these effects. In contrast, some of the Aβ oligomer effects were blocked by Ryanodine. We conclude that canonical Wnt/β-catenin signaling controls neuronal survival, and that non-canonical Wnt/Ca(2+)signaling modulates mitochondrial dysfunction. Since mitochondrial dysfunction is present in neurodegenerative diseases, the therapeutic possibilities of the activation of Wnt signaling are evident.

Decreased mitochondrial DNA copy number in the hippocampus and peripheral blood during opiate addiction is mediated by autophagy and can be salvaged by melatonin

Drug addiction is a chronic brain disease that is a serious social problem and causes enormous financial burden. Because mitochondrial abnormalities have been associated with opiate addiction, we examined the effect of morphine on mtDNA levels in rat and mouse models of addiction and in cultured cells. We found that mtDNA copy number was significantly reduced in the hippocampus and peripheral blood of morphine-addicted rats and mice compared with control animals. Concordantly, decreased mtDNA copy number and elevated mtDNA damage were observed in the peripheral blood from opiate-addicted patients, indicating detrimental effects of drug abuse and stress. In cultured rat pheochromocytoma (PC12) cells and mouse neurons, morphine treatment caused many mitochondrial defects, including a reduction in mtDNA copy number that was mediated by autophagy. Knockdown of the Atg7 gene was able to counteract the loss of mtDNA copy number induced by morphine. The mitochondria-targeted antioxidant melatonin restored mtDNA content and neuronal outgrowth and prevented the increase in autophagy upon morphine treatment. In mice, coadministration of melatonin with morphine ameliorated morphine-induced behavioral sensitization, analgesic tolerance and mtDNA content reduction. During drug withdrawal in opiate-addicted patients and improvement of protracted abstinence syndrome, we observed an increase of serum melatonin level. Taken together, our study indicates that opioid addiction is associated with mtDNA copy number reduction and neurostructural remodeling. These effects appear to be mediated by autophagy and can be salvaged by melatonin.

Selfish brain and neuroprogression in bipolar disorder

Bipolar disorder is associated with increases in mortality rates due to metabolic complications when compared to the general population. The "selfish brain" theory postulates that the CNS modulates energy metabolism in the periphery in order to prioritize its own demand and offers an heurist value framework to understand how and why metabolic abnormalities develop in the course of BD. Mood episodes, especially those of manic polarity are neurotoxic, because of the acute release of the neurotransmitters dopamine and glutamate, oxidative species, inflammatory cytokines and the deprivation of neuroprotective factors, such as neurotrophins. The cell loss and malfunctioning require from the brain an extra effort to repair itself, which will demand energetic supplies. Application of "selfish brain" theory in BD can potentially offer new insights about how to prevent and treat metabolic complications in BD.

Age-related change of neurochemical abnormality in attention-deficit hyperactivity disorder: a meta-analysis

Prevalence and symptoms of attention-deficit hyperactivity disorder (ADHD) change with advancing age. However, neurochemical background of such age-related change is yet to be elucidated. We therefore conducted a meta-analysis of 16 proton magnetic resonance spectroscopy studies comprising 270 individuals with ADHD and 235 controls. Standardized mean differences were calculated and used as an effect size. Sensitivity analyses and meta-regression to explore the effect of age on neurochemical abnormality were performed. A random effects model identified a significantly higher-than-normal N-acetylaspartate (NAA) in the medial prefrontal cortex (mPFC), but no significant differences of other metabolites in that area. No significant difference in metabolite levels was demonstrated in any other region. Sensitivity analysis of children with ADHD revealed significantly higher-than-normal NAA, whereas no significant difference was found in adults with ADHD. Meta-regression revealed significant correlation between advanced age and normal levels of NAA in the mPFC, suggesting that age-dependent abnormality of NAA level in the mPFC is a potential neural basis of age-related change of symptoms of ADHD.

Mechanisms underlying synaptic vulnerability and degeneration in neurodegenerative disease

Recent developments in our understanding of events underlying neurodegeneration across the central and peripheral nervous systems have highlighted the critical role that synapses play in the initiation and progression of neuronal loss. With the development of increasingly accurate and versatile animal models of neurodegenerative disease it has become apparent that disruption of synaptic form and function occurs comparatively early, preceding the onset of degenerative changes in the neuronal cell body. Yet, despite our increasing awareness of the importance of synapses in neurodegeneration, the mechanisms governing the particular susceptibility of distal neuronal processes are only now becoming clear. In this review we bring together recent developments in our understanding of cellular and molecular mechanisms regulating synaptic vulnerability. We have placed a particular focus on three major areas of research that have gained significant interest over the last few years: (i) the contribution of synaptic mitochondria to neurodegeneration; (ii) the contribution of pathways that modulate synaptic function; and (iii) regulation of synaptic degeneration by local posttranslational modifications such as ubiquitination. We suggest that targeting these organelles and pathways may be a productive way to develop synaptoprotective strategies applicable to a range of neurodegenerative conditions.