Elevated serum measures of lipid peroxidation and abnormal prefrontal white matter in euthymic bipolar adults: toward peripheral biomarkers of bipolar disorder

Mitochondrial DNA copy number is significantly increased in bipolar disorder patients and is correlated with long-term lithium treatment

Mitochondrial dysfunctions have been reported in bipolar disorder (BD), but their role in the etiopathogenesis of BD as well as their implications in modulating response to pharmacological treatments with psychotropic medications have been scarcely explored. Mitochondrial DNA copy number (mtDNA-cn) has been linked to mitochondria functioning, and, despite some degree of inconsistence, previous findings showed that BD patients present significant differences in mtDNA-cn compared to healthy controls. Here we measured mtDNA-cn in a sample of 89 patients with BD and 78 healthy controls (HC). Patients in the BD sample were treated either with lithium (n = 47) and characterized as responders (n = 22) or non-responders (n = 25), or with other mood stabilizers (n = 42). BD patients had larger mtDNA-cn compared to HC (adjusted model: F2=9.832; p = 0.000095; contribution of diagnosis F1= 10.798; p = 0.001). When the BD sample was stratified for treatment exposure, mtDNA-cn was lower in patients treated with lithium compared to those treated with other mood stabilizers (adjusted model: F4=23.770, p = 7.0929E-13; contribution of treatment: F1=54.300, p = 1.55E-10). Moreover mtDNA-cn was higher in patients treated with other mood stabilizers compared to controls and Li-treated BD patients (F3=28.125, p = 1.36E-14; contribution of groups F2=36.156, p = 1.25E-13). Finally, there was no difference in mtDNA-cn levels in lithium responders compared to non-responders and neither between the two diagnostic groups (BD type 1 and 2). Our findings suggest that BD may be associated with mitochondrial dysfunctions, and that exposure to lithium but not to other mood stabilizers may restore these abnormalities, though this does not appear correlated with the clinical efficacy of lithium.

The association of blood biomarkers with cerebral white matter and myelin content in bipolar disorder: a systematic review

OBJECTIVES

Evidence from diffusion tensor imaging (DTI) and postmortem studies has demonstrated white-matter (WM) deficits in bipolar disorder (BD). Changes in peripheral blood biomarkers have also been observed; however, studies evaluating the potential relationship between brain alterations and the periphery are scarce. The objective of this systematic review is to investigate the relationship between blood-based biomarkers and WM in BD.

METHODS

PubMed, Embase, and PsycINFO were used to conduct literature searches. Cross-sectional or longitudinal studies reporting original data which investigated both a blood-based biomarker and WM (by neuroimaging) in BD were included.

RESULTS

Of 3,750 studies retrieved, 23 were included. Several classes of biomarkers were found to have a significant relationship with WM in BD. These included cytokines and growth factors (interleukin-8 [IL-8], tumor necrosis factor alpha [TNF-a], and insulin-like growth factor binding protein 3 [IGFBP-3]), innate immune system (natural killer cells [NK]), metabolic markers (lipid hydroperoxidase, cholesterol, triglycerides), the kynurenine (Kyn) pathway (5-hydroxyindoleacetic acid, kynurenic acid [Kyna]), and various gene polymorphisms (serotonin-transporter-linked promoter region).

CONCLUSION

This systematic review revealed that blood-based biomarkers are associated with markers of WM deficits observed in BD. Longitudinal studies investigating the potential clinical utility of these specific biomarkers are encouraged.

White matter microstructural integrity is associated with retinal vascular caliber in adolescents with bipolar disorder

OBJECTIVE

Reduced white matter integrity is observed in bipolar disorder (BD), and is associated with cardiovascular risk in adults. This topic is underexplored in youth, and in BD, where novel microvascular measures may help to inform understanding of the vascular-brain connection. We therefore examined the association of retinal vascular caliber with white matter integrity in a cross-sectional sample of adolescents with and without BD.

METHODS

Eighty-four adolescents (n = 42 BD, n = 42 controls) completed retinal imaging, yielding arteriolar and venular caliber. Diffusion tensor imaging measured white matter fractional anisotropy (FA). Multiple linear regression tested associations between retinal vascular caliber and FA in regions-of-interest; corpus callosum, anterior thalamic radiation, uncinate fasciculus, and superior longitudinal fasciculus. Complementary voxel-wise analyses were performed.

RESULTS

Arteriolar caliber was elevated in adolescents with BD relative to controls (F(1,79) = 6.15, p = 0.02, η2p = 0.07). In the overall sample, higher venular caliber was significantly associated with lower corpus callosum FA (β = -0.24, puncorrected = 0.04). In voxel-wise analyses, higher arteriolar caliber was significantly associated with lower corpus callosum and forceps minor FA in the overall sample (β = -0.46, p = 0.03). A significant diagnosis-by-venular caliber interaction on FA was noted in 5 clusters including the right retrolenticular internal capsule (β = 0.72, p = 0.03), corticospinal tract (β = 0.72, p = 0.04), and anterior corona radiata (β = 0.63, p = 0.04). In each instance, venular caliber was more positively associated with FA in BD vs. controls.

CONCLUSION

Retinal microvascular measures are associated with white matter integrity in BD, particularly in the corpus callosum. This study was proof-of-concept, designed to guide future studies focused on the vascular-brain interface in BD.

CaMKK2 as an emerging treatment target for bipolar disorder

Current pharmacological treatments for bipolar disorder are inadequate and based on serendipitously discovered drugs often with limited efficacy, burdensome side-effects, and unclear mechanisms of action. Advances in drug development for the treatment of bipolar disorder remain incremental and have come largely from repurposing drugs used for other psychiatric conditions, a strategy that has failed to find truly revolutionary therapies, as it does not target the mood instability that characterises the condition. The lack of therapeutic innovation in the bipolar disorder field is largely due to a poor understanding of the underlying disease mechanisms and the consequent absence of validated drug targets. A compelling new treatment target is the Ca2+-calmodulin dependent protein kinase kinase-2 (CaMKK2) enzyme. CaMKK2 is highly enriched in brain neurons and regulates energy metabolism and neuronal processes that underpin higher order functions such as long-term memory, mood, and other affective functions. Loss-of-function polymorphisms and a rare missense mutation in human CAMKK2 are associated with bipolar disorder, and genetic deletion of Camkk2 in mice causes bipolar-like behaviours similar to those in patients. Furthermore, these behaviours are ameliorated by lithium, which increases CaMKK2 activity. In this review, we discuss multiple convergent lines of evidence that support targeting of CaMKK2 as a new treatment strategy for bipolar disorder.

White matter modifications of corpus callosum in bipolar disorder: A DTI tractography review

BACKGROUND

The recent widespread use of diffusion tensor imaging (DTI) tractography allowed researchers to investigate the diffusivity modifications and neuroanatomical changes of white matter (WM) fascicles in major psychiatric disorders, including bipolar disorder (BD). In BD, corpus callosum (CC) seems to have a crucial role in explaining the pathophysiology and cognitive impairment of this psychiatric disorder. This review aims to provide an overview on the latest results emerging from studies that investigated neuroanatomical changes of CC in BD using DTI tractography.

METHODS

Bibliographic research was conducted on PubMed, Scopus and Web of Science datasets until March 2022. Ten studies fulfilled our inclusion criteria.

RESULTS

From the reviewed DTI tractography studies a significant decrease of fractional anisotropy emerged in the genu, body and splenium of CC of BD patients compared to controls. This finding is coupled with reduction of fiber density and modification in fiber tract length. Finally, an increase of radial and mean diffusivity in forceps minor and in the entire CC was also reported.

LIMITATIONS

Small sample size, heterogeneity in terms of methodological (diffusion gradient) and clinical (lifetime comorbidity, BD status, pharmacological treatments) characteristics.

CONCLUSIONS

Overall, these findings suggest the presence of structural modifications in CC in BD patients, which may in turn explain the cognitive impairments often observed in this psychiatric disorder, especially in executive processing, motor control and visual memory. Finally, structural modifications may suggest an impairment in the amount of functional information and a morphological impact within those brain regions connected by CC.

Dysfunctional mitochondrial processes contribute to energy perturbations in the brain and neuropsychiatric symptoms

Mitochondria are complex endosymbionts that evolved from primordial purple nonsulfur bacteria. The incorporation of bacteria-derived mitochondria facilitates a more efficient and effective production of energy than what could be achieved based on previous processes alone. In this case, endosymbiosis has resulted in the seamless coupling of cytochrome c oxidase and F-ATPase to maximize energy production. However, this mechanism also results in the generation of reactive oxygen species (ROS), a phenomenon that can have both positive and negative ramifications on the host. Recent studies have revealed that neuropsychiatric disorders have a pro-inflammatory component in which ROS is capable of initiating damage and cognitive malfunction. Our current understanding of cognition suggests that it is the product of a neuronal network that consumes a substantial amount of energy. Thus, alterations or perturbations of mitochondrial function may alter not only brain energy supply and metabolite generation, but also thought processes and behavior. Mitochondrial abnormalities and oxidative stress have been implicated in several well-known psychiatric disorders, including schizophrenia (SCZ) and bipolar disorder (BPD). As cognition is highly energy-dependent, we propose that the neuronal pathways underlying maladaptive cognitive processing and psychiatric symptoms are most likely dependent on mitochondrial function, and thus involve brain energy translocation and the accumulation of the byproducts of oxidative stress. We also hypothesize that neuropsychiatric symptoms (e.g., disrupted emotional processing) may represent the vestiges of an ancient masked evolutionary response that can be used by both hosts and pathogens to promote self-repair and proliferation via parasitic and/or symbiotic pathways.

Differential association of antioxidative defense genes with white matter integrity in youth bipolar disorder

Oxidative stress is associated with white matter diffusion metrics in adults with bipolar disorder (BD). We examined the association of single-nucleotide polymorphisms in the oxidative stress system, superoxide dismutase-2 (SOD2) rs4880 and glutathione peroxidase-3 (GPX3) rs3792797 with fractional anisotropy (FA) and radial diffusivity (RD) in youth with BD. Participants included 104 youth (age 17.5 ± 1.7 years; 58 BD, 46 healthy controls). Saliva samples were obtained for genotyping, and diffusion tensor imaging was acquired. Voxel-wise whole-brain white matter diffusion analyses controlled for age, sex, and race. There were significant diagnosis-by-SOD2 rs4880 interaction effects for FA and RD in major white matter tracts. Within BD, the group with two copies of the G-allele (GG) showed lower FA and higher RD than A-allele carriers. Whereas within the control group, the GG group showed higher FA and lower RD than A-allele carriers. Additionally, FA was higher and RD was lower within the control GG group compared to the BD GG group. No significant findings were observed for GPX3 rs3793797. The current study revealed that, within matter tracts known to differ in BD, associations of SOD2 rs4880 GG genotype with both FA and RD differed between BD vs healthy control youth. The SOD2 enzyme encoded by the G-allele, has higher antioxidant capacity than the enzyme encoded by the A-allele. We speculate that the current findings of lower FA and higher RD of the BD GG group compared to the other groups reflects attenuation of the salutary antioxidant effects of GG genotype on white matter integrity in youth with BD, in part due to predisposition to oxidative stress. Future studies incorporating other genetic markers and oxidative stress biomarkers are warranted.

Second messengers and their importance for novel drug treatments of patients with bipolar disorder

Second messenger systems, like the cyclic nucleotide, glycogen synthase kinase-3β, phosphoinositide, and arachidonic acid cascades, are involved in bipolar disorder (BD). We investigated their role on the development of novel therapeutic drugs using second messenger mechanisms. PubMed search and narrative review. We used all relevant keywords for each second messenger cascade combining it with BD and related terms and combined all with novel/innovative treatments/drugs. Our search produced 31 papers most were reviews, and focussed on the PI3K/AKT-GSK-3β/Nrf2-NF-ĸB pathways. Only two human randomized clinical trials were identified, of ebselen, an antioxidant, and celecoxib, a cyclooxygenase-2 inhibitor, both with poor unsatisfactory results. Despite the fact that all second messenger systems are involved in the pathophysiology of BD, there are few experiments with novel drugs using these mechanisms. These mechanisms are a neglected and potentially major opportunity to transform the treatment of bipolar illness.

Is SARS-CoV-2 a Risk Factor of Bipolar Disorder?-A Narrative Review

For 2.5 years we have been facing the coronavirus disease (COVID-19) and its health, social and economic effects. One of its known consequences is the development of neuropsychiatric diseases such as anxiety and depression. However, reports of manic episodes related to COVID-19 have emerged. Mania is an integral part of the debilitating illness-bipolar disorder (BD). Due to its devastating effects, it is therefore important to establish whether SARS-CoV-2 infection is a causative agent of this severe mental disorder. In this narrative review, we discuss the similarities between the disorders caused by SARS-CoV-2 and those found in patients with BD, and we also try to answer the question of whether SARS-CoV-2 infection may be a risk factor for the development of this affective disorder. Our observation shows that disorders in COVID-19 showing the greatest similarity to those in BD are cytokine disorders, tryptophan metabolism, sleep disorders and structural changes in the central nervous system (CNS). These changes, especially intensified in severe infections, may be a trigger for the development of BD in particularly vulnerable people, e.g., with family history, or cause an acute episode in patients with a pre-existing BD.

Predictive value of oxidative stress biomarkers in drug-free patients with bipolar disorder

OBJECTIVE

Oxidative stress is one of the primary etiological mechanisms of bipolar disorder (BD).

METHODS

The present study was conducted over a period of 24 months on Tunisian on 34 drug‑free male patients with BD (mean age: 34.5 years) and 101 age and gender matched controls (mean age: 34.20 years) were enrolled in the study.

RESULTS

Plasma reduced glutathione (GSH) and total thiols levels were significantly decreased in patients compared to controls (respectively p < .001; p = .009). In addition, malondialdehyde (MDA), advanced oxidation protein products (AOPP), protein carbonyls (PC) and homocysteine (Hcys) concentrations and glutathione peroxidase (GSH-Px) activity were significantly increased in patients compared to controls (p = .002; p < .001; p = .001; p < .001 and p = .016, respectively). The binary logistic regression analysis revealed that MDA, AOPP and Hcys could be considered as independent risk factors for BD. When using CombiROC analysis, a remarkable increase in the area under the curve (AUC) with higher sensitivity (Se) and specificity (Sp) for MDA, AOPP, PC, GSH-Px and Hcys combined markers was observed.

CONCLUSIONS

Overall, the identification of the predictive value of these five selected biomarkers related to oxidative stress in drug free patients should lead to a better identification of the etiological mechanism of BD.

White Matter Correlates of Early-Onset Bipolar Illness and Predictors of One-Year Recurrence of Depression in Adults with Bipolar Disorder

Diffusion Magnetic Resonance Imaging (dMRI) studies have reported abnormalities in emotion regulation circuits in BD; however, no study has examined the contribution of previous illness on these mechanisms. Using global probabilistic tractography, we aimed to identify neural correlates of previous BD illness and the extent to which these can help predict one-year recurrence of depressive episodes. dMRI data were collected in 70 adults with early-onset BD who were clinically followed for up to 18 years and 39 healthy controls. Higher number of depressive episodes during childhood/adolescence and higher percentage of time with syndromic depression during longitudinal follow-up was associated with lower fractional anisotropy (FA) in focal regions of the forceps minor (left, F = 4.4, p = 0.003; right, F = 3.1, p = 0.021) and anterior cingulum bundle (left, F = 4.7, p = 0.002; right, F = 7.0, p < 0.001). Lower FA in these regions was also associated with higher depressive and anxiety symptoms at scan. Remarkably, those having higher FA in the right cluster of the forceps minor (AOR = 0.43, p = 0.017) and in a cluster of the posterior cingulum bundle (right, AOR = 0.50, p = 0.032) were protected against the recurrence of depressive episodes. Previous depressive symptomatology may cause neurodegenerative effects in the forceps minor that are associated with worsening of BD symptomatology in subsequent years. Abnormalities in the posterior cingulum may also play a role.

White matter predictors of worsening of subthreshold hypomania severity in non-bipolar young adults parallel abnormalities in individuals with bipolar disorder

BACKGROUND

Identifying neural predictors of worsening subthreshold hypomania severity can help identify risk of progression to BD. While diffusion Magnetic Resonance Imaging (dMRI) studies reported white matter microstructural abnormalities in tracts supporting emotional regulation in individuals with BD, it remains unknown whether similar patterns of white matter microstructure predict worsening of subthreshold hypomania severity in non-BD individuals.

METHODS

dMRI data were collected in: 81 non-BD individuals recruited across a range of subthreshold depression and hypomania, and followed for six months; and independent samples of 75 BD and 58 healthy individuals. All individuals were assessed using standardized diagnostic assessments, mood and anxiety symptom rating scales. Global probabilistic tractography and a tract-profile approach examined fractional anisotropy (FA), a measure of fiber collinearity, in tracts supporting emotional regulation shown to have abnormalities in BD: forceps minor (FMIN), anterior thalamic radiation (ATR), cingulum bundle (CB), and uncinate fasciculus (UF).

RESULTS

Lower FA in left CB (middle, β = -0.22, P = 0.022; posterior, β = -0.32, P < 0.001), right CB (anterior, β = -0.30, P = 0.003; posterior, β = -0.27, P = 0.005), and right UF (frontal, β = -0.29, P = 0.002; temporal, β = -0.40, P < 0.001) predicted worsening of subthreshold hypomania severity in non-BD individuals. BD versus healthy individuals showed lower FA in several of these segments: middle left CB (F = 8.7, P = 0.004), anterior right CB (F = 9.8, P = 0.002), and frontal right UF (F = 7.0, P = 0.009). Non-BD individuals with worsening 6-month hypomania had lower FA in these three segments versus HC and non-BD individuals without worsening hypomania, but similar FA to BD individuals.

LIMITATIONS

Relatively short follow-up.

CONCLUSIONS

White matter predictors of worsening subthreshold hypomania in non-BD individuals parallel abnormalities in BD individuals, and can guide early risk identification and interventions.

Metabolomic Identification of Serum Exosome-Derived Biomarkers for Bipolar Disorder

Background

Exosomes are extracellular vesicles that play important roles in various physiological and pathological functions. Previous studies have demonstrated that exosome-derived contents are promising biomarkers to inform the pathogenesis and diagnosis of major depressive disorder and schizophrenia.

Methods

We used ultraperformance liquid chromatography-tandem mass spectrometry to analyze the differentially expressed metabolites in serum exosomes of patients with bipolar disorder (BD) and evaluated the potential of exosomal metabolites as biomarkers for BD.

Results

Our results showed 26 differentially expressed serum exosomal metabolites in patients with BD (n = 32) when compared with healthy control (HC) subjects (n = 40), and these differentially expressed metabolites were enriched in pathways related to sugar metabolism. We then utilized random forest classifier and identified 15 exosomal metabolites that can be used to classify samples from patients with BD and HC subjects with 0.838 accuracy (95% CI, 0.604–1.00) in the training set of participants. These 15 metabolites showed excellent performance in differentiating between patients with BD and HC subjects in the testing set of participants, with 0.971 accuracy (95% CI, 0.865–1.00). Importantly, the 15 exosomal metabolites also showed good to excellent performance in differentiating between BD patients and other major psychiatric diseases (major depressive disorder and schizophrenia).

Conclusion

Collectively, our findings for the first time revealed a potential role of exosomal metabolite dysregulations in the onset and/or development of BD and suggested that blood exosomal metabolites are strong candidates to inform the diagnosis of BD.

Malondialdehyde as a candidate biomarker for bipolar disorder: A meta-analysis

Malondialdehyde (MDA) represents one of the final products of lipid peroxidation that is thought to be enhanced and accelerated in patients affected by bipolar disorder (BD). Purpose of the present article is to critically summarize the available data about MDA as a candidate biomarker for BD. First, we carried out a systematic review of the literature selecting those papers that evaluated MDA levels in BD. Then, we performed two separate meta-analyses: one of the studies that compared healthy controls (HC) with unmedicated BD and one with the studies that assessed MDA levels before and after treatment in BD, showing that bipolar patients experience more oxidative stress than healthy subjects and that treatment is effective in reducing MDA levels. In the first set of studies, we also explored through a meta-regression whether age, gender and experiencing an episode specifically influenced the difference between BD and HC in MDA levels. Bipolar patients compared to healthy subjects had higher MDA levels (SMD: 0.94, 95% CI: 0.23-1.64). Age (p < 0.01), gender (p < 0.01) and the presence of a current mood episode (p < 0.01) significantly influenced MDA plasma/serum levels. Specifically, studies that included more female, older subjects and more BD in euthymia were more likely to have higher MDA levels. Finally, patients after treatment had lower levels of MDA compared to baseline (SMD: -0.52, 95% CI: -0.85 -0.19). More studies are needed to draw definitive conclusions.

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

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

Therapeutic Interventions to Mitigate Mitochondrial Dysfunction and Oxidative Stress–Induced Damage in Patients with Bipolar Disorder

Bipolar disorder (BD) is characterized by mood changes, including recurrent manic, hypomanic, and depressive episodes, which may involve mixed symptoms. Despite the progress in neurobiological research, the pathophysiology of BD has not been extensively described to date. Progress in the understanding of the neurobiology driving BD could help facilitate the discovery of therapeutic targets and biomarkers for its early detection. Oxidative stress (OS), which damages biomolecules and causes mitochondrial and dopamine system dysfunctions, is a persistent finding in patients with BD. Inflammation and immune dysfunction might also play a role in BD pathophysiology. Specific nutrient supplements (nutraceuticals) may target neurobiological pathways suggested to be perturbed in BD, such as inflammation, mitochondrial dysfunction, and OS. Consequently, nutraceuticals may be used in the adjunctive treatment of BD. This paper summarizes the possible roles of OS, mitochondrial dysfunction, and immune system dysregulation in the onset of BD. It then discusses OS-mitigating strategies that may serve as therapeutic interventions for BD. It also analyzes the relationship between diet and BD as well as the use of nutritional interventions in the treatment of BD. In addition, it addresses the use of lithium therapy; novel antipsychotic agents, including clozapine, olanzapine, risperidone, cariprazine, and quetiapine; and anti-inflammatory agents to treat BD. Furthermore, it reviews the efficacy of the most used therapies for BD, such as cognitive–behavioral therapy, bright light therapy, imagery-focused cognitive therapy, and electroconvulsive therapy. A better understanding of the roles of OS, mitochondrial dysfunction, and inflammation in the pathogenesis of bipolar disorder, along with a stronger elucidation of the therapeutic functions of antioxidants, antipsychotics, anti-inflammatory agents, lithium therapy, and light therapies, may lead to improved strategies for the treatment and prevention of bipolar disorder.

The uncinate fasciculus in individuals with and at risk for bipolar disorder: A meta-analysis

BACKGROUND

Bipolar disorder (BD) is a severe mental disorder, characterized by prominent mood swings and emotion regulation (ER) deficits. The uncinate fasciculus (UF), a white matter tract connecting the amygdala and the ventral prefrontal cortex, has been implicated in ER. Aberrancies in UF microstructure may be an endophenotype associated with increased risk for BD. However, studies in individuals with BD and their first-degree relatives (REL) have yielded inconsistent findings. This meta-analysis takes a region-of-interest approach to consolidate the available evidence and elucidate the role of the UF in the risk-architecture of BD.

METHODS

Using web-based search engines, we identified diffusion tensor imaging (DTI) studies focusing on the left and right UF and conducted meta-analyses comparing fractional anisotropy (FA) and radial diffusivity (RD) between BD or REL and healthy control participants (HC).

RESULTS

We included 32 studies (n_BD=1186, n_REL=289, n_HC=2315). Compared to HC, individuals with BD showed lower FA in the right (WMD=-0.31, p<0.0001) and left UF (WMD=-0.21, p = 0.010), and higher RD in the right UF (WMD=0.32, p = 0.009). We found no significant differences between REL and HC. In the right but not left UF, REL showed higher FA than BD (p = 0.043).

CONCLUSION

Our findings support aberrant UF microstructure, potentially related to alterations in myelination, as a mechanism, but not as an endophenotype of BD. However, given the limited power in the REL subsample, the latter finding must be considered preliminary. Studies examining the role of the UF in individuals at familial risk for BD are warranted.

The Elusive "Switch Process" in Bipolar Disorder and Photoperiodism: A Hypothesis Centering on NADPH Oxidase-Generated Reactive Oxygen Species Within the Bed Nucleus of the Stria Terminalis

One of the most striking and least understood aspects of mood disorders involves the "switch process" which drives the dramatic state changes characteristic of bipolar disorder. In this paper we explore the bipolar switch mechanism as deeply grounded in forms of seasonal switching (for example, from summer to winter phenotypes) displayed by many mammalian species. Thus we develop a new and unifying hypothesis that involves four specific claims, all converging to demonstrate a deeper affinity between the bipolar switch process and the light-sensitive (photoperiodic) nonhuman switch sequence than has been appreciated. First, we suggest that rapid eye movement (REM) sleep in both human and nonhuman plays a key role in probing for those seasonal changes in length of day that trigger the organism's characteristic involutional response (in certain animals, hibernation) to shorter days. Second, we claim that this general mammalian response requires the integrity of a neural circuit centering on the anterior bed nucleus of the stria terminalis. Third, we propose that a key molecular mediator of the switch process in both nonhumans and seasonal humans involves reactive oxygen species (ROS) of a particular provenance, namely those created by the enzyme NADPH oxidase (NOX). This position diverges from one currently prominent among students of bipolar disorder. In that tradition, the fact that patients afflicted with bipolar-spectrum disorders display indices of oxidative damage is marshaled to support the conclusion that ROS, escaping adventitiously from mitochondria, have a near-exclusive pathological role. Instead, we believe that ROS, originating instead in membrane-affiliated NOX enzymes upstream from mitochondria, take part in an eminently physiological signaling process at work to some degree in all mammals. Fourth and finally, we speculate that the diversion of ROS from that purposeful, genetically rooted seasonal switching task into the domain of human pathology represents a surprisingly recent phenomenon. It is one instigated mainly by anthropogenic modifications of the environment, especially "light pollution."

Differentiating white matter measures that protect against vs. predispose to bipolar disorder and other psychopathology in at-risk youth

Bipolar disorder (BD) is highly heritable. Identifying objective biomarkers reflecting pathophysiological processes predisposing to, versus protecting against BD, can help identify BD risk in offspring of BD parents. We recruited 21 BD participants with a first-degree relative with BD, 25 offspring of BD parents, 27 offspring of comparison parents with non-BD psychiatric disorders, and 32 healthy offspring of healthy parents. In at-risk groups, 23 had non-BD diagnoses and 29, no Axis-I diagnoses(healthy). Five at-risk offspring who developed BD post scan(Converters) were included. Diffusion imaging(dMRI) analysis with tract segmentation identified between-group differences in the microstructure of prefrontal tracts supporting emotional regulation relevant to BD: forceps minor, anterior thalamic radiation(ATR), cingulum bundle(CB), and uncinate fasciculus(UF). BD participants showed lower fractional anisotropy (FA) in the right CB (anterior portion) than other groups (q < 0.05); and in bilateral ATR (posterior portion) versus at-risk groups (q < 0.001). Healthy, but not non-BD, at-risk participants showed significantly higher FA in bilateral ATR clusters than healthy controls (qs < 0.05). At-risk groups showed higher FA in these clusters than BD participants (qs < 0.05). Non-BD versus healthy at-risk participants, and Converters versus offspring of BD parents, showed lower FA in the right ATR cluster (qs < 0.05). Low anterior right CB FA in BD participants versus other groups might result from having BD. High bilateral ATR FA in at-risk groups, and in healthy at-risk participants, versus healthy controls might protect against BD/other psychiatric disorders. Absence of elevated right ATR FA in non-BD versus healthy at-risk participants, and in Converters versus non-converter offspring of BD parents, might lower protection against BD in at-risk groups.

Association of antioxidant deficiency and the level of products of protein and lipid peroxidation in patients with the first episode of schizophrenia

Schizophrenia is considered a multifactorial disease, where one of the pathogenetic links is oxidative stress; however, the results of studies are often contradictory, largely due to significant heterogeneity among study methods. The present study was undertaken to compare the levels of oxidative stress markers in the peripheral blood of patients with a first episode of schizophrenia (FES) and in healthy volunteers (HV). The study included 50 patients with FES and 37 HV. Blood samples were collected for spectrophotometric assessment of reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), aldehyde-2,4-dinitrophenylhydrazone (ADNPH), and ketone-2,4-dinitrophenylhydrazone (KDNPH) in blood plasma. Results showed that in patients with FES compared with HV, a significant decrease in CAT activity and an increase in oxidative modification of proteins (OMP) were found. In both groups, a significant increase in the level of MDA with age was revealed. In patients, the GSH plasma level was inversely proportional to the ADNPH level, and SOD activity was directly proportional to the KDNPH level. In volunteers there was no such correlation; however, there was a direct correlation between CAT activity and the levels of OMP and MDA. In both groups, a moderate direct correlation between peroxidation products was observed. The results confirm that a redox imbalance (a deficiency of antioxidants, in particular CAT, and excess OMP) may be a pathogenetic link in schizophrenia, which is manifested already at an early stage of the disease.

Association of altered thyroid hormones and neurometabolism to cognitive dysfunction in unmedicated bipolar II depression

BACKGROUND

The underlying mechanism of cognitive impairment in bipolar II depression (BD II) remains unclear. Studies show disturbances of the hypothalamus-pituitary-thyroid (HPT) axis are suspected of correlating to brain neurometabolic alterations and cognitive deficits in psychiatric disorders. While, the nature of their inter-relationships in BD II depression remain enigmatic.

METHODS

106 patients with unmedicated BD II depression and 100 healthy controls underwent cognitive function assessment using Trail Making Test, Part-A (TMT-A), Digit Symbol Substitution Test (DSST), and Semantic Verbal Fluency testing (SVF). Of those, 69 patients and 53 healthy controls had serum thyroid hormone levels measured including free tri-iodothyronine (FT3), total tri-iodothyronine (TT3), free thyroxin (FT4), total thyroxin (TT4) and thyroid-stimulating hormone (TSH). Additionally, 79 of the patients and 76 of the healthy controls underwent proton magnetic resonance spectroscopy (H-MRS) to obtain ratios of N-acetyl aspartate to creatine (NAA/Cr) and choline-containing compounds to creatine (Cho/Cr) in the prefrontal cortex (PFC), anterior cingulate cortex (ACC) and thalamus. Finally, association and multiple regression analysis were conducted to investigate their inter-relationships.

RESULTS

Patients with BD II depression showed significantly lower DSST and verbal fluency scores and longer completion time of TMT-A than did healthy controls. The FT3, TT3, and TSH levels of the BD cohort significantly decreased, while their FT4 levels increased. We also found significantly lower NAA/Cr ratios in the PFC and higher NAA/Cr ratios in the left thalamus of patients with BD II depression than in healthy controls. Furthermore, association analysis showed that increased FT4 negatively correlated to DSST and SVF, while increased FT4 correlation significantly with increasing TSH and DSST. Multiple regression analyses revealed relationships between TSH and NAA in the left PFC and the left thalamus, while correlating to SVF testing within the BD II depression cohort.

CONCLUSIONS

Our results demonstrate coinciding thyroid hormone abnormalities, cognitive dysfunction, and neurometabolic alterations of the PFC-thalamic circuitry occur in an early course of BD II depression. Further understanding of the interaction between thyroid-stimulating hormone and NAA/Cr of PFC-thalamic circuitry may shed light on the etiology of associated cognitive impairment.

White matter integrity in young medication-naïve bipolar II depressed adults

It is unknown if young medication-naïve bipolar II (BPII) depressed patients have increased white matter (WM) disruptions. 27 each of young (average 23 years) and treatment-naïve BPII depressed, unipolar depressed (UD) patients and age–sex–education matched healthy controls (HC) underwent 3 T MRIs with diffusion tensor imaging. Diagnostic ratings included Structured Clinical Interview for DSM Disorders (SCID), Montgomery-Åsberg Depression Rating Scale (MADRS), Young Mania Rating Scale (YMRS) and Hamilton Anxiety Rating Scale (HAM-A). Patients were clinically depressed (MADRS-BPII: 26.15 [SD9.25], UD: 25.56 [5.24], p = 0.86). Compared to UD, BPII had increased family bipolarity (BPII 13.6% vs UD 2.5%, p = 0.01, φc = 0.28), hypomanic symptoms (YMRS-BPII: 4.22 [4.24], UD: 1.33 [2], p = 0.02, d = 0.87), lifetime number of depressive episodes (BPII: 2.37 [1.23], UD: 1.44 [0.75], p = 0.02, d = 0.91), lifetime and current-year number of episodes (lifetime BPII: 50.85 [95.47], UD: 1.7 [1.03]; current-year BPII: 9.93 [16.29], UD: 1.11 [0.32], ps = 0.04, ds = 0.73–0.77) and longer illness duration (BPII: 4.96 years [3.96], UD: 2.99 [3.33], p = 0.15, d = 0.54). BPII showed no increased WM disruptions vs UD or HC in any of the 15 a priori WM tracts. UD had lower right superior longitudinal fasciculus (SLF) (temporal) axial diffusivity (AD) (1.14 vs 1.17 (BPII), 1.16 (HC); F = 6.93, 95% CI of\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${F}_{B}$$\end{document}FB: 0.00073, 5.22, ηp² = 0.15). Principal component analysis followed by exploratory linear discriminant analysis showed that increased R-SLF (temporal) AD, YMRS and family bipolarity distinguished BPII from UD (81.5% sensitivity, 85.2% specificity) independent of episode number and frequency. Young, medication-naïve adults with BPII depression did not show the WM disruptions distinguishing more chronically ill BP patients from UD. These WM disruptions may therefore be partly attributable to illness chronicity. Longitudinal studies should examine the trajectory of WM changes in BPII and UD and predictive validity of these baseline clinical and imaging parameters.

The activity and connectivity of the facial emotion processing neural circuitry in bipolar disorder: a systematic review

BACKGROUND

Facial emotion processing abnormalities may be a trait feature of bipolar disorder (BD). These social cognitive impairments may be due to alterations in the neural processing of facial affective information in visual ("core"), and limbic and prefrontal ("extended") networks, however, the precise neurobiological mechanism(s) underlying these symptoms are unclear.

METHODS

We conducted a systematic review to appraise the literature on the activity and connectivity of the facial emotion processing neural circuitry in BD. Two reviewers undertook a search of the electronic databases PubMed, Scopus and PsycINFO, to identify relevant literature published since inception up until September 2019. Study eligibility criteria included; BD participants, neuroimaging, and facial emotion processing tasks.

RESULTS

Out of an initial yield of 6121 articles, 66 were eligible for inclusion in this review. We identified differences in neural activity and connectivity within and between occipitotemporal, limbic, and prefrontal regions, in response to facial affective stimuli, in BD compared to healthy controls.

LIMITATIONS

The methodologies used across studies varied considerably.

CONCLUSIONS

The findings from this review suggest abnormalities in both the activity and connectivity of facial emotion processing neural circuitry in BD. It is recommended that future research aims to further define the connectivity and spatiotemporal course of neural events within and between occipitotemporal, limbic, and prefrontal regions.

White Matter Correlates of Suicidality in Adults With Bipolar Disorder Who Have Been Prospectively Characterized Since Childhood

BACKGROUND

Prevention of suicide in individuals with early-onset bipolar disorder (BD) remains a challenge. Diffusion magnetic resonance imaging studies in BD have identified neural correlates of emotional dysregulation implicated in BD and suicide. Using diffusion magnetic resonance imaging, we sought to identify neural signatures of suicide attempts in adults with childhood-onset BD who have been clinically followed for up to 19 years as part of the COBY (Course and Outcome of Bipolar Youth) study.

METHODS

Diffusion magnetic resonance imaging data were collected in 68 adults with BD: 20 in the suicide attempter (SA+) group and 48 in the non-suicide attempter (SA-) group. Multivariate analysis of covariance was used to identify the effect of group (SA+, SA-) on mean fractional anisotropy (indirect index of fiber collinearity) in key white matter tracts of emotional regulation. The effect of suicidal ideation and other clinical factors was further explored. False discovery rate was used to account for multiple comparison. Forty healthy control subjects were included.

RESULTS

Analyses revealed a main effect of group on fractional anisotropy (F5,59 = 3.0, p = .017). Specifically, the SA+ group showed lower fractional anisotropy than the SA- and healthy control groups in the middle portion of the forceps minor (FMIN) (F1,63 = 8.5, p = .010) and in the anterior (F1,63 = 7.8, p = .010) and posterior (F1,63 = 8.7, p = .006) portion of the right cingulum bundle (CB). Abnormalities in the FMIN, but not CB, were also associated with suicidal ideation (F1,64 = 10.6, p = .002) and levels of emotional distress at scan.

CONCLUSIONS

FMIN and CB abnormalities have been associated with emotional dysregulation in BD. Our findings suggest that the FMIN may represent a generic marker of suicidal ideation and, more broadly, emotional distress, while CB may represent a specific marker of attempted suicide.

Comparison of White Matter Structure of Drug-Naïve Patients With Bipolar Disorder and Major Depressive Disorder Using Diffusion Tensor Tractography

BACKGROUND

The presence of microstructural white matter (WM) abnormalities in individuals with bipolar disorder (BD) has previously been reported. However, the interpretation of data is challenging because pharmacological treatment has a potential effect on WM integrity. To date, no study has compared the differences in WM structure among drug-naïve BD patients, drug-naïve major depression disorder (MDD) patients, and healthy controls (HC) using the visual evaluation method of diffusion tensor tractography (DTT).

METHODS

This retrospective study included 12 drug-naïve patients with BD, 15 drug-naïve patients with MDD, and 27 age- and sex-matched HC individuals. Visual evaluation, fractional anisotropy (FA), and apparent diffusion coefficient (ADC) were analysed in the anterior thalamic radiation (ATR) as a tract of interest using the optimal follow-up truncation threshold. They were also analysed in the cingulate fasciculus, superior longitudinal fasciculus, inferior longitudinal fasciculus, inferior fronto-occipital fasciculus, uncinate fasciculus, and fornix.

RESULTS

No significant differences were found in the FA or ADC of any tract. However, visual evaluation revealed poorer depiction of ATR in patients with BD than in patients with MDD and HC individuals (p = 0.004). Our post-hoc analysis showed a significant difference between BD and HC patients (p = 0.018).

CONCLUSIONS

The visual evaluation method of DTT revealed poor depiction of ATR in patients with BD compared with HC individuals and MDD patients, suggesting microstructural WM abnormalities of ATR in BD.

Peripheral Markers of Depression

Major Depressive Disorder (MDD) is a leading cause of disability worldwide, creating a high medical and socioeconomic burden. There is a growing interest in the biological underpinnings of depression, which are reflected by altered levels of biological markers. Among others, enhanced inflammation has been reported in MDD, as reflected by increased concentrations of inflammatory markers-C-reactive protein, interleukin-6, tumor necrosis factor-α and soluble interleukin-2 receptor. Oxidative and nitrosative stress also plays a role in the pathophysiology of MDD. Notably, increased levels of lipid peroxidation markers are characteristic of MDD. Dysregulation of the stress axis, along with increased cortisol levels, have also been reported in MDD. Alterations in growth factors, with a significant decrease in brain-derived neurotrophic factor and an increase in fibroblast growth factor-2 and insulin-like growth factor-1 concentrations have also been found in MDD. Finally, kynurenine metabolites, increased glutamate and decreased total cholesterol also hold promise as reliable biomarkers for MDD. Research in the field of MDD biomarkers is hindered by insufficient understanding of MDD etiopathogenesis, substantial heterogeneity of the disorder, common co-morbidities and low specificity of biomarkers. The construction of biomarker panels and their evaluation with use of new technologies may have the potential to overcome the above mentioned obstacles.

The P2X7 Receptor: Central Hub of Brain Diseases

The P2X7 receptor is a cation channel activated by high concentrations of adenosine triphosphate (ATP). Upon long-term activation, it complexes with membrane proteins forming a wide pore that leads to cell death and increased release of ATP into the extracellular milieu. The P2X7 receptor is widely expressed in the CNS, such as frontal cortex, hippocampus, amygdala and striatum, regions involved in neurodegenerative diseases and psychiatric disorders. Despite P2X7 receptor functions in glial cells have been extensively studied, the existence and roles of this receptor in neurons are still controversially discussed. Regardless, P2X7 receptors mediate several processes observed in neuropsychiatric disorders and brain tumors, such as activation of neuroinflammatory response, stimulation of glutamate release and neuroplasticity impairment. Moreover, P2X7 receptor gene polymorphisms have been associated to depression, and isoforms of P2X7 receptors are implicated in neuropsychiatric diseases. In view of that, the P2X7 receptor has been proposed to be a potential target for therapeutic intervention in brain diseases. This review discusses the molecular mechanisms underlying P2X7 receptor-mediated signaling in neurodegenerative diseases, psychiatric disorders, and brain tumors. In addition, it highlights the recent advances in the development of P2X7 receptor antagonists that are able of penetrating the central nervous system.

Deficits of white matter axial diffusivity in bipolar disorder relative to major depressive disorder: No relationship to cerebral perfusion or body mass index

OBJECTIVE

To compare white matter integrity (WMI) in bipolar disorder (BD) relative to healthy volunteers (HVs) and major depressive disorder (MDD). To determine the relationship of bipolar-specific differences in WMI to cerebral perfusion, body mass index (BMI), and blood pressure as indices of cardiovascular function.

METHODS

Thirty-two participants with BD, 44 with MDD, and 41 HV were recruited. All BD and MDD participants were in a major depressive episode, and all but 12 BD participants were medication-free. 64-direction diffusion tensor imaging (DTI) and arterial spin labeling (ASL) sequences were obtained. Tract-based spatial statistics (TBSS) on four DTI indices were employed to distinguish patterns of DTI in BD relative to HV and MDD groups. BMI, blood pressure, and medical histories were also obtained for the BD participants.

RESULTS

A cluster of lower axial diffusivity (AD) was found in BD participants in comparison to the HVs in the left posterior thalamic radiation, superior longitudinal fasciculus, inferior longitudinal fasciculus, fronto-occipital fasciculus, and internal capsule. Mean AD in the significant cluster was not associated with cerebral blood flow (CBF) in the region as measured by ASL, and was not associated with BMI or blood pressure. A cluster of lower AD was also found in the BD group when compared to MDD that had spatial overlap with the HV comparison.

CONCLUSIONS

The results indicate a deficit of AD in BD when compared to MDD and HV groups. No association between AD values and either cerebral perfusion, BMI, or blood pressure was found in BD.

Region-specific effects of maternal separation on oxidative stress accumulation in parvalbumin neurons of male and female rats

Early life adversity in humans is linked to cognitive deficits and increased risk of mental illnesses, including depression, bipolar disorder, and schizophrenia, with evidence for different vulnerabilities in men versus women. Modeling early life adversity in rodents shows similar neuropsychological deficits that may partially be driven by sex-dependent dysfunction in parvalbumin (PV) interneurons in the prefrontal cortex (PFC), hippocampus (HPC), and basolateral amygdala (BLA). Research demonstrates that PV interneurons are particularly susceptible to oxidative stress; therefore, accumulation of oxidative damage may drive PV dysfunction following early life adversity. The goal of this study was to quantify oxidative stress accumulation in PV neurons in rats exposed to maternal separation (MS). Pups were separated from their dam and littermates for 4 h per day from postnatal day (P)2 to 20. Serial sections from the PFC, HPC, and BLA of juvenile (P20) rats of both sexes were immunohistochemically stained with antibodies against PV and 8-oxo-dG, a marker for oxidative DNA damage. PV cell counts, colocalization with 8-oxo-dG, and intensity of each signal were measured in each region to determine the effects of MS and establish whether MS-induced oxidative damage varies between sexes. A significant increase in colocalization of PV and 8-oxo-dG was found in the PFC and HPC, indicating increased oxidative stress in that cell population following MS. Region-specific sex differences were also revealed in the PFC, BLA, and HPC. These data identify oxidative stress during juvenility as a potential mechanism mediating PV dysfunction in individuals with a history of early life adversity.

Personalized and precision medicine as informants for treatment management of bipolar disorder

DSM-5 diagnostic categories, defined by a set of psychopathological symptoms are heterogeneous conditions that may include different biological entities, with distinct etiopathogenesis, different courses and requiring different treatment management. For bipolar disorder the major evidences for this lack of validity are the long paths before a proper diagnosis, the inconsistence of treatment guidelines, the long phases of pharmacological adjustment and the low average of long-term treatment response rates. Personalized medicine for mental disorders aims to couple established clinical-pathological indexes with new molecular profiling to create diagnostic, prognostic and therapeutic strategies precisely tailored to each patient. Regarding bipolar disorder, the clinical history and presentation are still the most reliable markers in stratifying patients and guiding therapeutic management, despite the research goes to great lengths to develop new neuropsychological or biological markers that can reliably predict individual therapy effectiveness. We provide an overview of the advancements in personalized medicine in bipolar disorder, with particular attention to how psychopathology, age at onset, comorbidity, course and staging, genetic and epigenetic, imaging and biomarkers can influence treatment management and provide an integration to the conventional treatment guidelines. This approach may offer a new and rational path for the development of treatments for targeted subgroups of patients with bipolar disorder.

Carotid Artery Stiffness and Incident Depressive Symptoms: The Paris Prospective Study III

BACKGROUND

Arterial stiffness may contribute to late-life depression via cerebral microvascular damage, but evidence is scarce. No longitudinal study has evaluated the association between arterial stiffness and risk of depressive symptoms. Therefore, we investigated the association between carotid artery stiffness and incident depressive symptoms in a large community-based cohort study.

METHODS

This longitudinal study included 7013 participants (mean age 59.7 ± 6.3 years; 35.8% women) free of depressive symptoms at baseline. Carotid artery stiffness (high-resolution echo tracking) was determined at baseline. Presence of depressive symptoms was determined at baseline and at 4 and 6 years of follow-up, and was defined as a score ≥7 on the validated Questionnaire of Depression, Second Version, Abridged and/or new use of antidepressant medication. Logistic regression and generalized estimating equations were used.

RESULTS

In total, 6.9% (n = 484) of the participants had incident depressive symptoms. Individuals in the lowest tertile of carotid distensibility coefficient (indicating greater carotid artery stiffness) compared with those in the highest tertile had a higher risk of incident depressive symptoms (odds ratio: 1.43; 95% confidence interval: 1.10-1.87), after adjustment for age, sex, living alone, education, lifestyle, cardiovascular risk factors, and baseline Questionnaire of Depression, Second Version, Abridged scores. Results were qualitatively similar when we used carotid Young's elastic modulus as a measure of carotid stiffness instead of carotid distensibility coefficient, and when we used generalized estimating equations instead of logistic regression.

CONCLUSIONS

Greater carotid stiffness is associated with a higher incidence of depressive symptoms. This supports the hypothesis that carotid stiffness may contribute to the development of late-life depression.

Peripheral Oxidative Stress Markers in Patients with Bipolar Disorder during Euthymia and in Siblings

AIMS

Oxidative stress is increased during the acute phases of bipolar disorder (BD). Our aim here was to analyze oxidative stress biomarkers in patients with BD during euthymia and their siblings.

METHOD

A cross-sectional study was performed in euthymic patients with BD-I (n=48), unaffected siblings (n=23) and genetically unrelated healthy controls (n=21). Protein carbonyl content (PCC), total antioxidant capacity (TRAP), lipid peroxidation (TBARS) and uric acid were measured as biomarkers of oxidative stress in blood.

RESULTS

The antioxidant capacity (TRAP) was lower (p<0.001) in patients with BD compared to their siblings and controls, whereas no differences were observed in PCC, TBARS or uric acid. In patients, the concentrations of TRAP and TBARS were positively associated with the dose of valproic acid (p<0.05 and p<0.001, respectively). The concentrations of these biomarkers were not significantly associated with any of socio-demographic and clinical variables.

CONCLUSION

A selective reduction in antioxidant capacity is present in BD during euthymia state, whereas other markers of oxidative stress are unaltered during euthymia. Siblings did not show any alterations in oxidative stress biomarkers. Oxidative stress might represent a state-dependent marker in BD. The association between treatment with valproic acid and oxidative stress markers in euthymia deserves further studies.

Protein biomarkers of epileptogenicity after traumatic brain injury

Traumatic brain injury (TBI) is a major risk factor for acquired epilepsy. Post-traumatic epilepsy (PTE) develops over time in up to 50% of patients with severe TBI. PTE is mostly unresponsive to traditional anti-seizure treatments suggesting distinct, injury-induced pathomechanisms in the development of this condition. Moderate and severe TBIs cause significant tissue damage, bleeding, neuron and glia death, as well as axonal, vascular, and metabolic abnormalities. These changes trigger a complex biological response aimed at curtailing the physical damage and restoring homeostasis and functionality. Although a positive correlation exists between the type and severity of TBI and PTE, there is only an incomplete understanding of the time-dependent sequelae of TBI pathobiologies and their role in epileptogenesis. Determining the temporal profile of protein biomarkers in the blood (serum or plasma) and cerebrospinal fluid (CSF) can help to identify pathobiologies underlying the development of PTE, high-risk individuals, and disease modifying therapies. Here we review the pathobiological sequelae of TBI in the context of blood- and CSF-based protein biomarkers, their potential role in epileptogenesis, and discuss future directions aimed at improving the diagnosis and treatment of PTE.

White matter - emotion processing activity relationships in youth offspring of bipolar parents

BACKGROUND

Early detection of Bipolar Disorder (BD) is critical for targeting interventions to delay or prevent illness onset. Yet, the absence of objective BD biomarkers makes accurately identifying at-risk youth difficult. In this study, we examined how relationships between white matter tract (WMT) structure and activity in emotion processing neural circuitry differentiate youth at risk for BD from youth at risk for other psychiatric disorders.

METHODS

Offspring (ages 8-17) of parents with BD (OBP, n = 32), offspring of comparison parents with non-BD psychopathology (OCP, n = 30), and offspring of healthy parents (OHP, n = 24) underwent diffusion tensor and functional magnetic resonance imaging while performing an emotional face processing task. Penalized and multiple regression analyses included GROUP(OBP,OCP)xWMT interactions as main independent variables, and emotion processing activity as dependent variables, to determine significant group differences in WMT-activity relationships.

RESULTS

8 GROUPxWMT interaction variables contributed to 16.5% of the variance in amygdala and prefrontal cortical activity to happy faces. Of these, significant group differences in slopes (inverse for OBP, positive for OCP) existed for the relationship between forceps minor radial diffusivity and rostral anterior cingulate activity (p = 0.014). Slopes remained significantly different in unmedicated youth without psychiatric disorders (p = 0.017) and were moderated by affective lability symptoms (F(1,29) = 5.566, p = 0.036).

LIMITATIONS

Relatively small sample sizes were included.

CONCLUSIONS

Forceps minor radial diffusivity-rostral anterior cingulate activity relationships may reflect underlying neuropathological processes that contribute to affectively labile youth at risk for BD and may help differentiate them from youth at risk for other psychiatric disorders.

Longitudinal associations between 4-hydroxynonenal and depression in coronary artery disease patients

Depressive symptoms in patients with coronary artery disease (CAD) attenuate the cardiovascular benefits of cardiac rehabilitation (CR). Given that oxidative stress may be an important mechanism underlying depression, this study aimed to understand the longitudinal relationship between lipid peroxidation markers and depression in CAD. Serum levels of early (lipid hydroperoxides, LPH) and late (4‑hydroxy‑2-nonenal, 4-HNE; 8-isoprotane, 8-ISO) lipid peroxidation markers were measured in 120 CAD patients undergoing CR. The Structured Clinical Interview for DSM Axis I Disorders - Depression Module (SCID) was used to diagnose depression at baseline and the Center for Epidemiological Studies Depression Scale (CES-D) was used to measure depressive symptom severity. Multivariate mixed models compared the trajectories of serum LPH, 4-HNE, and 8-ISO between depressed and non-depressed CAD patients undergoing 6 months of CR. Similar models evaluated the associations between serum LPH, 4-HNE, and 8-ISO and CES-D score over the course of CR. Serum 4-HNE decreased less in CAD patients with depression compared to those without. In addition, a decrease in 4-HNE concentrations was significantly associated with a decrease in CES-D scores over 6 months. These findings suggest that 4-HNE may be an important marker of depressive symptoms in CAD and may be involved in its progression.

Exploring mania-associated white matter injury by comparison with multiple sclerosis: a diffusion tensor imaging study

Bipolar disorder (BD), especially in its active phases, has shown some neuroimaging and immunological similarities with multiple sclerosis (MS). The objective of this study was to compare white matter (WM) alterations in BD patients in manic phase (M-BD) and MS patients at early stage of disease and with low lesion burden. We compared diffusion tensor imaging (DTI)-derived fractional anisotropy (FA), mean diffusivity (MD) and radial diffusivity (RD) in a priori selected WM regions (i.e., corpus callosum and cingulum) betwixt 23 M-BD, 23 MS patients and 46 healthy controls. Both M-BD and MS showed WM changes in the corpus callosum, which, however, showed a greater impairment in MS patients. However, considering the different sub-regions of corpus callosum separately (i.e., genu, body, splenium), M-BD and MS presented an opposite pattern in spatial distribution of WM microstructure alterations, with a greater impairment in the anterior region in M-BD and in the posterior region in MS. Common features as well as divergent patterns in DTI changes are detected in M-BD and early MS, prompting a deeper investigation of analogies and differences in WM and immunological alterations of these disorders.

White matter microstructure alterations correlate with terminally differentiated CD8+ effector T cell depletion in the peripheral blood in mania: Combined DTI and immunological investigation in the different phases of bipolar disorder

BACKGROUND

White matter (WM) microstructural abnormalities and, independently, signs of immunological activation were consistently demonstrated in bipolar disorder (BD). However, the relationship between WM and immunological alterations as well as their occurrence in the various phases of BD remain unclear.

METHOD

In 60 type I BD patients - 20 in manic, 20 in depressive, 20 in euthymic phases - and 20 controls we investigated: (i) diffusion tensor imaging (DTI)-derived fractional anisotropy (FA), radial diffusivity (RD) and axial diffusivity (AD) using a tract-based spatial statistics (TBSS) approach; (ii) circulating T cell subpopulations frequencies, as well as plasma levels of different cytokines; (iii) potential relationships between WM and immunological data.

RESULTS

We found: (i) a significant widespread combined FA-RD alteration mainly in mania, with involvement of the body of corpus callosum (BCC) and superior corona radiata (SCR); (ii) significant increase in CD4+ T cells as well as significant decrease in CD8+ T cells and their subpopulations effector memory (CD8+ CD28-CD45RA-), terminal effector memory (CD8+ CD28-CD45RA+) and CD8+ IFNγ+ in mania; (iii) a significant relationship between WM and immunological alterations in the whole cohort, and a significant correlation of FA-RD abnormalities in the BCC and SCR with reduced frequencies of CD8+ terminal effector memory and CD8+ IFNγ+ T cells in mania only.

CONCLUSIONS

Our data show a combined occurrence of WM and immunological alterations in mania. WM abnormalities highly correlated with reduction in circulating CD8+ T cell subpopulations that are terminally differentiated effector cells prone to tissue migration, suggesting that these T cells could play a role in WM alteration in BD.

Fractional anisotropy of the uncinate fasciculus and cingulum in bipolar disorder type I, type II, unaffected siblings and healthy controls

BACKGROUND

Fractional anisotropy in the uncinate fasciculus and the cingulum may be biomarkers for bipolar disorder and may even be distinctly affected in different subtypes of bipolar disorder, an area in need of further research.AimsThis study aims to establish if fractional anisotropy in the uncinate fasciculus and cingulum shows differences between healthy controls, patients with bipolar disorder type I (BD-I) and type II (BD-II), and their unaffected siblings.

METHOD

Fractional anisotropy measures from the uncinate fasciculus, cingulum body and parahippocampal cingulum were compared with tractography methods in 40 healthy controls, 32 patients with BD-I, 34 patients with BD-II, 17 siblings of patients with BD-I and 14 siblings of patients with BD-II.

RESULTS

The main effects were found in both the right and left uncinate fasciculus, with patients with BD-I showing significantly lower fractional anisotropy than both patients with BD-II and healthy controls. Participants with BD-II did not differ from healthy controls. Siblings showed similar effects in the left uncinate fasciculus. In a subsequent complementary analysis, we investigated the association between fractional anisotropy in the uncinate fasciculus and polygenic risk for bipolar disorder and psychosis in a large cohort (n = 570) of healthy participants. However, we found no significant association.

CONCLUSIONS

Fractional anisotropy in the uncinate fasciculus differs significantly between patients with BD-I and patients with BD-II and healthy controls. This supports the hypothesis of differences in the physiological sub-tract between bipolar disorder subtypes. Similar results were found in unaffected siblings, suggesting the potential for this biomarker to represent an endophenotype for BD-I. However, fractional anisotropy in the uncinate fasciculus seems unrelated to polygenic risk for bipolar disorder or psychosis.Declaration of interestNone.

Neurotrophins, cytokines, oxidative stress mediators and mood state in bipolar disorder: systematic review and meta-analyses

BACKGROUND

A reliable biomarker signature for bipolar disorder sensitive to illness phase would be of considerable clinical benefit. Among circulating blood-derived markers there has been a significant amount of research into inflammatory markers, neurotrophins and oxidative stress markers.AimsTo synthesise and interpret existing evidence of inflammatory markers, neurotrophins and oxidative stress markers in bipolar disorder focusing on the mood phase of illness.

METHOD

Following PRISMA (Preferred Reporting Items for Systematic reviews and Meta-analyses) guidelines, a systematic review was conducted for studies investigating peripheral biomarkers in bipolar disorder compared with healthy controls. We searched Medline, Embase, PsycINFO, SciELO and Web of Science, and separated studies by bipolar mood phase (mania, depression and euthymia). Extracted data on each biomarker in separate mood phases were synthesised using random-effects model meta-analyses.

RESULTS

In total, 53 studies were included, comprising 2467 cases and 2360 controls. Fourteen biomarkers were identified from meta-analyses of three or more studies. No biomarker differentiated mood phase in bipolar disorder individually. Biomarker meta-analyses suggest a combination of high-sensitivity C-reactive protein/interleukin-6, brain derived neurotrophic factor/tumour necrosis factor (TNF)-α and soluble TNF-α receptor 1 can differentiate specific mood phase in bipolar disorder. Several other biomarkers of interest were identified.

CONCLUSIONS

Combining biomarker results could differentiate individuals with bipolar disorder from healthy controls and indicate a specific mood-phase signature. Future research should seek to test these combinations of biomarkers in longitudinal studies.Declaration of interestNone.

Examining redox modulation pathways in the post-mortem frontal cortex in patients with bipolar disorder through data mining of microRNA expression datasets

The etiology of redox (reduction and oxidation) alterations in bipolar disorder (BD) is largely unknown. To explore whether microRNAs targeting redox enzymes may have a role in BD, we examined 3 frontal cortex microRNA expression datasets (Perkins [2007], Vladimirov [2009], and Miller [2009]; N for BD = 30-36 per dataset, N for controls = 28-34 per dataset) from the Stanley Neuropathology Consortium. Each dataset was analyzed separately because they were generated using different high-throughput platforms. Following the selection of only redox modulator-targeting microRNAs, microRNAs in the top 10th percentile in feature selection could together discriminate BD and controls at a greater frequency than expected by chance in classification analysis. In pathway enrichment analysis of all three datasets, these classifying microRNAs targeted the cellular nitrogen compound metabolic process pathway, which includes redox enzymes of the mitochondrial electron transport chain and the glutathione system. To see if this pathway would still emerge as significant if all microRNAs (not just redox-targeting) were analyzed, all analyses were repeated with the complete set of microRNAs. Cellular nitrogen compound metabolic process pathway was enriched in all 3 datasets in this analysis as well, demonstrating that preselection of redox microRNAs was not a requirement to identify this pathway for the discrimination of BD and controls. While preliminary, our findings suggest that microRNAs that target redox enzymes in this pathway may be good candidates for the exploration of causative factors contributing to redox alterations in BD. Future studies validating these findings in a separate set of central and peripheral samples are warranted.

Metabolic/inflammatory/vascular comorbidity in psychiatric disorders; soluble epoxide hydrolase (sEH) as a possible new target

The common and severe psychiatric disorders, including major depressive disorder (MDD) and bipolar disorder (BD), are associated with inflammation, oxidative stress and changes in peripheral and brain lipid metabolism. Those pathways are implicated in the premature development of vascular and metabolic comorbidities, which account for considerable morbidity and mortality, including increased dementia risk. During endoplasmic reticulum stress, the soluble epoxide hydrolase (sEH) enzyme converts anti-inflammatory fatty acid epoxides generated by cytochrome p450 enzymes into their corresponding and generally less anti-inflammatory, or even pro-inflammatory, diols, slowing the resolution of inflammation. The sEH enzyme and its oxylipin products are elevated post-mortem in MDD, BD and schizophrenia. Preliminary clinical data suggest that oxylipins increase with symptoms in seasonal MDD and anorexia nervosa, requiring confirmation in larger studies and other cohorts. In rats, a soluble sEH inhibitor mitigated the development of depressive-like behaviors. We discuss sEH inhibitors under development for cardiovascular diseases, post-ischemic brain injury, neuropathic pain and diabetes, suggesting new possibilities to address the mood and cognitive symptoms of psychiatric disorders, and their most common comorbidities.

Longitudinal Diffusion Tensor Imaging Study of Adolescents and Young Adults With Bipolar Disorder

OBJECTIVE

Longitudinal neuroimaging during adolescence/young adulthood, when bipolar disorder (BD) commonly emerges, can help elucidate the neurodevelopmental pathophysiology of BD. Adults with BD have shown reduced structural integrity in the uncinate fasciculus (UF), a white matter (WM) tract providing major connections between the amygdala and ventral prefrontal cortex (vPFC), important in emotion regulation. In this longitudinal diffusion tensor imaging (DTI) study of adolescents/young adults, we hypothesized differences in age- and time-related changes in UF integrity in BD compared to healthy controls (HC).

METHOD

Two DTI scans were obtained in 27 adolescents/young adults with BD and 37 HC adolescents/young adults, on average approximately 2.5 years apart. Interactions between diagnosis with age and with time for UF fractional anisotropy (FA) were assessed. Exploratory analyses were performed including euthymic-only participants with BD, and for potential influences of demographic and clinical factors. Whole-brain analyses were performed to explore for interactions in other regions.

RESULTS

There were significant interactions between diagnosis with age and with time for UF FA (p < .05). Healthy control adolescents/young adults showed significant UF FA increases with age and over time (p < .05), whereas no significant changes with age or over time were observed in the adolescents/young adults with BD. Significant interactions with age and time were also observed in analyses including euthymic-only participants with BD (p < .05).

CONCLUSION

These findings provide neuroimaging evidence supporting differences in UF WM structural development during adolescence/young adulthood, suggesting that differences in the development of an amygdala-vPFC system subserving emotion regulation may be a trait feature of BD neurodevelopment.

Cognitive Impairment In Treatment-Naïve Bipolar II and Unipolar Depression

Cognition dysfunction may reflect trait characteristics of bipolarity but cognitive effects of medications have confounded previous comparisons of cognitive function between bipolar II and unipolar depression, which are distinct clinical disorders with some overlaps. Therefore, we examined the executive function (WCST), attention, cognitive speed (TMT-A) and memory (CAVLT, WMS-Visual reproduction) of 20 treatment-naïve bipolar II patients (BPII), 35 treatment-naïve unipolar depressed (UD) patients, and 35 age/sex/education matched healthy controls. The subjects were young (aged 18–35), and had no history of psychosis or substance use, currently depressed and meeting either RDC criteria for Bipolar II Disorder or DSM-IV-TR criteria for Major Depressive Disorder. The patients were moderately depressed (MADRS) and anxious(HAM-A), on average within 3.44 years of illness onset. Sociodemographic data and IQ were similar between the groups. UD patients had significantly slower cognitive speed and cognitive flexibility (WCST perseverative error). BPII depressed patients showed relatively intact cognitive function. Verbal memory (CAVLT List A total) correlated with illness chronicity only in BPII depression, but not UD. In conclusion, young and treatment-naïve BPII depressed patients differed from unipolar depression by a relatively intact cognitive profile and a chronicity-cognitive correlation that suggested a stronger resemblance to Bipolar I Disorder than Unipolar Depression.

Functional Segmentation of the Anterior Limb of the Internal Capsule: Linking White Matter Abnormalities to Specific Connections

The anterior limb of the internal capsule (ALIC) carries thalamic and brainstem fibers from prefrontal cortical regions that are associated with different aspects of emotion, motivation, cognition processing, and decision-making. This large fiber bundle is abnormal in several psychiatric illnesses and a major target for deep brain stimulation. Yet, we have very little information about where specific prefrontal fibers travel within the bundle. Using a combination of tracing studies and diffusion MRI in male nonhuman primates, as well as diffusion MRI in male and female human subjects, we segmented the human ALIC into five regions based on the positions of axons from different cortical regions within the capsule. Fractional anisotropy (FA) abnormalities in patients with bipolar disorder were detected when FA was averaged in the ALIC segment that carries ventrolateral prefrontal cortical connections. Together, the results set the stage for linking abnormalities within the ALIC to specific connections and demonstrate the utility of applying connectivity profiles of large white matter bundles based on animal anatomic studies to human connections and associating disease abnormalities in those pathways with specific connections. The ability to functionally segment large white matter bundles into their components begins a new era of refining how we think about white matter organization and use that information in understanding abnormalities.SIGNIFICANCE STATEMENT The anterior limb of the internal capsule (ALIC) connects prefrontal cortex with the thalamus and brainstem and is abnormal in psychiatric illnesses. However, we know little about the location of specific prefrontal fibers within the bundle. Using a combination of animal tracing studies and diffusion MRI in animals and human subjects, we segmented the human ALIC into five regions based on the positions of axons from different cortical regions. We then demonstrated that differences in FA values between bipolar disorder patients and healthy control subjects were specific to a given segment. Together, the results set the stage for linking abnormalities within the ALIC to specific connections and for refining how we think about white matter organization in general.

Linking lipid peroxidation and neuropsychiatric disorders: focus on 4-hydroxy-2-nonenal

4-hydroxy-2-nonenal (HNE) is considered to be a strong marker of oxidative stress; the interaction between HNE and cellular proteins leads to the formation of HNE-protein adducts able to alter cellular homeostasis and cause the development of a pathological state. By virtue of its high lipid concentration, oxygen utilization, and the presence of metal ions participating to redox reactions, the brain is highly susceptible to the formation of free radicals and HNE-related compounds. A variety of neuropsychiatric disorders have been associated with elevations of HNE concentration. For example, increased levels of HNE were found in the cortex of bipolar and schizophrenic patients, while HNE plasma concentrations resulted high in patients with major depression. On the same line, high brain concentrations of HNE were found associated with Huntington's inclusions. The incidence of high HNE levels is relevant also in the brain and cerebrospinal fluid of patients suffering from Parkinson's disease. Intriguingly, in this case the increase of HNE was associated with an accumulation of iron in the substantia nigra, a brain region highly affected by the pathology. In the present review we recapitulate the findings supporting the role of HNE in the pathogenesis of different neuropsychiatric disorders to highlight the pathogenic mechanisms ascribed to HNE accumulation. The aim of this review is to offer novel perspectives both for the understanding of etiopathogenetic mechanisms that remain still unclear and for the identification of new useful biological markers. We conclude suggesting that targeting HNE-driven cellular processes may represent a new more efficacious therapeutical intervention.

Therapeutic effects of the mitochondrial ROS-redox modulator KH176 in a mammalian model of Leigh Disease

Leigh Disease is a progressive neurometabolic disorder for which a clinical effective treatment is currently still lacking. Here, we report on the therapeutic efficacy of KH176, a new chemical entity derivative of Trolox, in Ndufs4 -/- mice, a mammalian model for Leigh Disease. Using in vivo brain diffusion tensor imaging, we show a loss of brain microstructural coherence in Ndufs4 -/- mice in the cerebral cortex, external capsule and cerebral peduncle. These findings are in line with the white matter diffusivity changes described in mitochondrial disease patients. Long-term KH176 treatment retained brain microstructural coherence in the external capsule in Ndufs4 -/- mice and normalized the increased lipid peroxidation in this area and the cerebral cortex. Furthermore, KH176 treatment was able to significantly improve rotarod and gait performance and reduced the degeneration of retinal ganglion cells in Ndufs4 -/- mice. These in vivo findings show that further development of KH176 as a potential treatment for mitochondrial disorders is worthwhile to pursue. Clinical trial studies to explore the potency, safety and efficacy of KH176 are ongoing.

Night sleep influences white matter microstructure in bipolar depression

BACKGROUND

Alteration of circadian rhythms and sleep disruption are prominent trait-like features of bipolar disorder (BD). Diffusion tensor imaging (DTI) measures suggest a widespread alteration of white matter (WM) microstructure in patients with BD. Sleep promotes myelination and oligodendrocyte precursor cells proliferation. We hypothesized a possible association between DTI measures of WM microstructure and sleep quantity measures in BD.

METHODS

We studied 69 inpatients affected by a depressive episode in course of type I BD. We used whole brain tract-based spatial statistics on DTI measures of WM microstructure: axial, radial, and mean diffusivity (AD, RD, MD), and fractional anisotropy (FA). Self-assessed measures of time asleep (TA) and total sleep time (TST) were extracted from the Pittsburgh Sleep Quality Index (PSQI). Actigraphic recordings were performed on a subsample of 23 patients.

RESULTS

We observed a positive correlation of DTI measures of FA with actigraphic measures of TA and TST, and with PSQI measure of TA. DTI measures of RD inversely associated with actigraphic measure of TA, and with PSQI measures of TA and TST. Several WM tracts were involved, including corpus callosum, cyngulate gyrus, uncinate fasciculus, left superior and inferior longitudinal and fronto-occipital fasciculi, thalamic radiation, corona radiata, retrolenticular part of internal capsule and corticospinal tract.

LIMITATIONS

The study is correlational in nature, and no conclusion about a causal connection can be drawn.

CONCLUSIONS

Reduced FA with increased RD and MD indicate higher water diffusivity associated with less organized myelin and/or axonal structures. Our findings suggest an association between sleep disruption and these measures of brain microstructure in specific tracts contributing to the functional connectivity in BD.