T-cell immunophenotype correlations with cortical thickness and white matter microstructure in bipolar disorder

BACKGROUND

Inflammation and immunological alterations, such as T-cell and cytokine changes, are implicated in bipolar disorder (BD), with some evidence linking them to brain structural changes (e.g., cortical thickness (CT), gray matter (GM) volume and white matter (WM) microstructure). However, the connection between specific peripheral cell types, such as T-cells, and neuroimaging in BD remains scarcely investigated.

AIMS OF THE STUDY

This study aims to explore the link between T-cell immunophenotype and neuroradiological findings in BD.

METHODS

Our study investigated 43 type I BD subjects (22 depressive, 21 manic) and 26 healthy controls (HC), analyzing T lymphocyte immunophenotype and employing neuroimaging to assess CT for GM and fractional anisotropy (FA) for WM.

RESULTS

In lymphocyte populations, BD patients exhibited elevated CD4+ and CD4+ central memory (TCM) cells frequencies, but lower CD8+ effector memory (TEM) and terminal effector memory (TTEM) cells. Neuroimaging analysis revealed reduced CT in multiple brain regions in BD patients; and significant negative correlations between CD4 + TCM levels and CT of precuneus and fusiform gyrus. Tract-based spatial statistics (TBSS) analysis showed widespread alteration in WM microstructure in BD patients, with negative and positive correlations respectively between FA and radial diffusivity (RD) and CD4 + TCM. Additionally, positive and negative correlations were found respectively between FA and RD and the CD8 + TEM and CD8 + TTEM subsets.

CONCLUSIONS

Our research revealed distinct T lymphocyte changes and brain structure alterations in BD, underscoring possible immune-brain interactions, warranting further study and therapeutic exploration.

Correlations between multimodal neuroimaging and peripheral inflammation in different subtypes and mood states of bipolar disorder: a systematic review

BACKGROUND

Systemic inflammation-immune dysregulation and brain abnormalities are believed to contribute to the pathogenesis of bipolar disorder (BD). However, the connections between peripheral inflammation and the brain, especially the interactions between different BD subtypes and episodes, remain to be elucidated. Therefore, we conducted the present study to provide a comprehensive understanding of the complex association between peripheral inflammation and neuroimaging findings in patients with bipolar spectrum disorders.

METHODS

This systematic review was registered in the International Prospective Register of Systematic Reviews (PROSPERO) database (CRD42023447044) and conducted according to the Population, Intervention, Comparison, Outcomes, and Study Design (PICOS) framework. Online literature databases (PubMed, Web of Science, Scopus, EMBASE, MEDLINE, PsycINFO, and the Cochrane Library) were searched for studies that simultaneously investigated both peripheral inflammation-related factors and magnetic resonance neurography of BD patients up to July 01, 2023. Then, we analysed the correlations between peripheral inflammation and neuroimaging, as well as the variation trends and the shared and specific patterns of these correlations according to different clinical dimensions.

RESULTS

In total, 34 publications ultimately met the inclusion criteria for this systematic review, with 2993 subjects included. Among all patterns of interaction between peripheral inflammation and neuroimaging, the most common pattern was a positive relationship between elevated inflammation levels and decreased neuroimaging measurements. The brain regions most susceptible to inflammatory activation were the anterior cingulate cortex, amygdala, prefrontal cortex, striatum, hippocampus, orbitofrontal cortex, parahippocampal gyrus, postcentral gyrus, and posterior cingulate cortex.

LIMITATIONS

The small sample size, insufficiently explicit categorization of BD subtypes and episodes, and heterogeneity of the research methods limited further implementation of quantitative data synthesis.

CONCLUSIONS

Disturbed interactions between peripheral inflammation and the brain play a critical role in BD, and these interactions exhibit certain commonalities and differences across various clinical dimensions of BD. Our study further confirmed that the fronto-limbic-striatal system may be the central neural substrate in BD patients.

Attention TurkerNeXt: Investigations into Bipolar Disorder Detection Using OCT Images

Background and Aim: In the era of deep learning, numerous models have emerged in the literature and various application domains. Transformer architectures, particularly, have gained popularity in deep learning, with diverse transformer-based computer vision algorithms. Attention convolutional neural networks (CNNs) have been introduced to enhance image classification capabilities. In this context, we propose a novel attention convolutional model with the primary objective of detecting bipolar disorder using optical coherence tomography (OCT) images. Materials and Methods: To facilitate our study, we curated a unique OCT image dataset, initially comprising two distinct cases. For the development of an automated OCT image detection system, we introduce a new attention convolutional neural network named "TurkerNeXt". This proposed Attention TurkerNeXt encompasses four key modules: (i) the patchify stem block, (ii) the Attention TurkerNeXt block, (iii) the patchify downsampling block, and (iv) the output block. In line with the swin transformer, we employed a patchify operation in this study. The design of the attention block, Attention TurkerNeXt, draws inspiration from ConvNeXt, with an added shortcut operation to mitigate the vanishing gradient problem. The overall architecture is influenced by ResNet18. Results: The dataset comprises two distinctive cases: (i) top to bottom and (ii) left to right. Each case contains 987 training and 328 test images. Our newly proposed Attention TurkerNeXt achieved 100% test and validation accuracies for both cases. Conclusions: We curated a novel OCT dataset and introduced a new CNN, named TurkerNeXt in this research. Based on the research findings and classification results, our proposed TurkerNeXt model demonstrated excellent classification performance. This investigation distinctly underscores the potential of OCT images as a biomarker for bipolar disorder.

Structural and functional MRI correlates of inflammation in bipolar disorder: A systematic review

BACKGROUND

Bipolar disorder (BD) is a common affective disorder characterized by recurrent oscillations between mood states and associated with inflammatory diseases and chronic inflammation. However, data on MRI abnormalities in BD and their relationship with inflammation are heterogeneous and no review has recapitulated them.

METHODS

In this pre-registered (PROSPERO: CRD42022308461) systematic review we searched Web of Science Core Collection and PubMed for articles correlating functional or structural MRI measures with immune-related markers in BD.

RESULTS

We included 23 studies (6 on functional, 16 on structural MRI findings, 1 on both, including 1'233 BD patients). Overall, the quality of the studies included was fair, with a low risk of bias.

LIMITATIONS

Heterogeneity in the methods and results of the studies and small sample sizes limit the generalizability of the conclusions.

CONCLUSIONS

A qualitative synthesis suggests that the links between immune traits and functional or structural MRI alterations point toward brain areas involved in affective and somatomotor processing, with a trend toward a negative correlation between peripheral inflammatory markers and brain regions volume. We discuss how disentangling the complex relationship between the immune system and MRI alterations in BD may unveil mechanisms underlying symptoms pathophysiology, potentially with quickly translatable diagnostic, prognostic, and therapeutic implications.

Interleukin-1 receptor antagonist (IL-1RA) and interleukin-4 (IL-4) variable number of tandem repeat polymorphisms in schizophrenia and bipolar disorder: an association study in Turkish population

Background

Pro-inflammatory/anti-inflammatory cytokine imbalance in cerebrospinal fluid or plasma of schizophrenia (SCZ) and bipolar disorder (BD) patients has been documented over the last decade. We aim to examine the interleukin-1 receptor antagonist (IL-1RA) and IL-4 variable number of tandem repeat (VNTR) polymorphisms in SCZ and BD patients by comparing them with healthy controls.

Methods

Two hundred and thirty-four unrelated patients (127 patients with SCZ, 107 patients with BD) and 204 healthy controls were included. The Structured Clinical Interview for DSM-IV Axis I Disorders was used to confirm the diagnosis. In addition, the polymerase chain reaction technique was used to investigate IL-1RA and IL-4 VNTR polymorphisms.

Results

Our results showed that the distributions of IL-1RA and IL-4 genotype and the allele frequencies of SCZ or BD patients were not significantly different from the healthy control group. IL-1RA allele 2 homozygous genotype and IL-1RA allele 2 frequencies were non-significantly higher among SCZ patients than in controls.

Conclusions

Our study indicates that the IL-1RA and IL-4 VNTR polymorphisms are not considered risk factors for developing SCZ and BD among Turkish patients.

Lower pro- to anti-inflammatory ratios associated with reduced neurocognitive flexibility in symptomatic adolescents with bipolar disorder

INTRODUCTION

Peripheral inflammatory markers, such as C-reactive protein (CRP), are elevated among adolescents and adults with bipolar disorder (BD), particularly during symptomatic episodes. Neurocognition, predominantly in the domain of executive function, is also impaired among adults and youth with BD. In adults with BD, CRP is negatively associated with neurocognitive functioning. We aim to investigate this relationship in BD adolescents.

METHODS

Serum levels of CRP and five other inflammatory markers (interleukin (IL)-1β, IL-6, IL-10, IL-4 and tumor necrosis factor α (TNF)) were examined in 60 adolescents with BD (34 symptomatic, 26 asymptomatic) age- and sex-matched to 51 healthy controls (HC). Diagnoses were confirmed using semi-structured interviews. Pro- to anti-inflammatory marker ratios were also examined. Neurocognitive flexibility was assessed via the intra/extradimensional shift (IED) task from the CANTAB battery. Multivariate linear regression controlled for age, sex and race.

RESULTS

Within symptomatic BD adolescents, but not asymptomatic BD or HC adolescents, lower IL-6/IL-10 and lower CRP/IL-10 ratios were significantly associated with worse performance on the neurocognitive flexibility task (p = 0.03 and p = 0.04, respectively). Both models accounted for 13.3% of variance in neurocognitive flexibility. No significant CRP by diagnosis interaction effects were observed on neurocognitive flexibility.

LIMITATIONS

Limited sample-size restricted ability to separate the symptomatic BD adolescents into varying mood states.

CONCLUSION

More balanced pro- to anti-inflammatory ratios were associated with better neurocognitive flexibility in symptomatic BD adolescents. Prospective studies are warranted to assess the direction of these findings.

The functional polymorphisms linked with interleukin-1β gene expression are associated with bipolar disorder

BACKGROUND

Bipolar disorder (BD) is a severe psychiatric illness attributable to multifactorial risk components (e.g. environmental stimuli, neuroinflammation, etc.), and genetic variations affecting these risk components are considered pivotal predisposing factors. The interleukin-1β (IL-1β) gene and its protein product have been repeatedly highlighted in the pathogenesis of BD. As functional polymorphisms and haplotypes linked with IL-1β mRNA expression have been reported, whether they are correlated with the risk of developing BD remains to be tested.

METHODS

To examine whether variations in the IL-1β gene locus confer genetic risk of BD, we recruited 930 BD patients and 912 healthy controls for the current study. All subjects were Han Chinese, and were age- and gender-matched. We tested seven functional single nucleotide polymorphisms (SNPs) spanning the IL-1β gene and one haplotype composed of three SNPs for their associations with risk of BD.

RESULTS

We found that the functional SNPs in the promoter region of IL-1β gene were significantly associated with risk of BD. The haplotype analyses further supported the involvement of IL-1β promoter SNPs in BD. The BD risk SNPs in our study have been previously reported to predict higher IL-1β levels in the brain and peripheral blood, which is consistent with the clinical observation of elevated IL-1β levels in the lymphocytes or peripheral blood of patients with BD compared with healthy subjects.

CONCLUSION

Our results support the contention that IL-1β is likely a risk gene for BD, and further investigations on this gene may promote our understanding and clinical management of this illness.

Influence of genetic variations in IL1B on brain region volumes in bipolar patients and controls

Involvement of the immune system has been implicated in the etiology and pathophysiology of mood disorders, including bipolar disorder. Neuroimaging studies have reported structural brain pathology in bipolar disorder patients, and both levels of and genetic variants in cytokines have been associated with altered volumes of brain regions. The aim of this study was to investigate associations between single nucleotide polymorphisms in the gene coding for the pro-inflammatory cytokine interleukin-1 beta (IL1B) and whole brain grey matter volume, as well as volumes of several brain regions shown to be of importance in mood disorders. Structural magnetic resonance imaging and vertex-based morphometry were used to obtain volume of different brain regions in subjects with bipolar disorder (n=188) and healthy controls (n=54). Four IL1B polymorphisms were genotyped: rs1143623, rs1143627, and rs16944 in the promoter region together with the synonymous variant rs1143634 in the IL1B gene. The genotype distribution did not differ between bipolar subjects and controls. The T allele at rs16944 and the C allele at rs1143627 were associated with increased volumes of the putamen of the left hemisphere in patients and controls, which lends support to the role of this immune system mediator for brain structure.

Effects of adjunctive inflammatory modulation on IL-1β in treatment resistant bipolar depression

BACKGROUND

Adjunctive inflammatory modulation improved remission rates in treatment-resistant bipolar depression (TRBDD), but reliable biomarkers must be established to characterize the biosignature of TRBDD and the mechanisms underlying treatment response. In this molecular profiling study, we describe TRBDD and treatment response from the standpoint of interleukin-1 Beta (IL-1β) and KYN/TRP.

METHODS

47 TRBDD patients with moderately severe HAMD-17 scores were randomized to receive either escitalopram (ESC) (10 mg-40 mg daily dose range) + celecoxib (CBX) (200 mg twice daily), or ESC (10 mg-40 mg daily dose range) + placebo (PBO) (twice daily). Plasma cytokine levels were measured in both treatment arms at baseline and week 8, and in a healthy control (HC) group of subjects (N = 43) once. A linear mixed model (LMM) was applied to evaluate whether clinical outcome is related to CBX and changes to biomarkers throughout treatment. A binary logistic regression model was formulated from this series to predict both the primary outcome of treatment response to CBX, and the secondary outcome of diagnosis of TRBDD using age, BMI, gender, and IL-1β at baseline.

RESULTS

Patients receiving ESC + CBX had 4.278 greater odds of responding (p = 0.021) with NNT = 3, and 15.300 times more likely to remit (p < 0.001) with NNT = 2, compared with ESC + PBO patients. Patient BMI (p = 0.003), baseline IL-1β (p = 0.004), and baseline KYN/TRP (p = 0.001) were most predictive of TRBDD diagnosis. By Week 8, responders showed a downtrend in IL-1β compared to non-responders in the ESC + CBX treatment arm. However, there was no statistical difference in the IL-1β or KYN/TRP change after treatment between placebo and ESC + CBX group responders/non-responders (p = 0.239, and p = 0.146, respectively). While baseline IL-1β was elevated in TRBDD compared to HC (p < 0.001), there was no difference in IL-1β between treatment responders at Week 8 compared to HC (p = 0.067).

CONCLUSIONS

Elevated IL-1β and low KYN/TRP at baseline are components of the TRBDD molecular signature. CBX but not baseline IL-1β or KYN/TRP predict treatment response. Change in IL-1β and KYN/TRP did not predict treatment response.

Preliminary study of structural magnetic resonance imaging phenotypes related to genetic variation in Interleukin-1β rs16944 in adolescents with Bipolar Disorder

BACKGROUND

Bipolar disorder (BD), among the most heritable psychiatric conditions, is associated with increased pro-inflammatory blood markers and pro-inflammatory gene expression in post-mortem brain. We therefore examined the effects of pro-inflammatory single nucleotide polymorphism interleukin-1β (IL-1β) rs16944 on brain structure in adolescents with BD and healthy control (HC) adolescents.

METHODS

T₁-weighted 3-T magnetic resonance imaging data were acquired for 38 adolescents with BD and 32 HC adolescents (14-20 years). Using FreeSurfer, a priori regions of interest analyses, examining hippocampus, amygdala, dorsolateral prefrontal cortex (DLPFC), and caudal anterior cingulate cortex, were complemented by exploratory whole-brain vertex-wise analyses. General linear models assessed the association between IL-1β rs16944 and the ROIs, controlling for sex, age, and intracranial volume.

RESULTS

There was an IL-1β rs16944 polymorphism-by-diagnosis interaction effect on the DLPFC; T-carriers with BD had greater surface area compared to non-carriers with BD. Whereas, HC T-carriers had smaller DLPFC volume compared to HC non-carriers. In vertex-wise analyses, similar interactions were evident in a pars triangularis surface area cluster and a lateral occipital cortex volume cluster. Whole-brain analyses also yielded a main effect of IL-1β rs16944 polymorphism, whereby T-carriers had greater lateral occipital cortex surface area and volume.

CONCLUSIONS

The IL-1β rs16944 polymorphism is associated with neurostructural phenotypes in cognitive and visual regions that subserve functions, including facial recognition and response inhibition, which are known to be aberrant in BD. Future studies are warranted to evaluate whether the observed rs16944-related structural differences are relevant to neurocognitive function, functional neuroimaging phenotypes and IL-1β protein levels.

Genome-wide QTL analysis for anxiety trait in bipolar disorder type I

BACKGROUND

Genetic studies have been consistent that bipolar disorder type I (BPI) runs in families and that this familial aggregation is strongly influenced by genes. In a preliminary study, we proved that anxiety trait meets endophenotype criteria for BPI.

METHODS

We assessed 619 individuals from the Central Valley of Costa Rica (CVCR) who have received evaluation for anxiety following the same methodological procedure used for the initial pilot study. Our goal was to conduct a multipoint quantitative trait linkage analysis to identify quantitative trait loci (QTLs) related to anxiety trait in subjects with BPI. We conducted the statistical analyses using Quantitative Trait Loci method (Variance-components models), implemented in Sequential Oligogenic Linkage Analysis Routines (SOLAR), using 5606 single nucleotide polymorphism (SNPs).

RESULTS

We identified a suggestive linkage signal with a LOD score of 2.01 at chromosome 2 (2q13-q14).

LIMITATIONS

Since confounding factors such as substance abuse, medical illness and medication history were not assessed in our study, these conclusions should be taken as preliminary.

CONCLUSIONS

We conclude that region 2q13-q14 may harbor a candidate gene(s) with an important role in the pathophysiology of BPI and anxiety.

Infectious and immunogenetic factors in bipolar disorder

OBJECTIVE

Despite the evidence supporting the association between infection and bipolar disorder (BD), the genetic vulnerability that mediates its effects has yet to be clarified. A genetic origin for the immune imbalance observed in BD, possibly involved in the mechanisms of pathogen escape, has, however, been suggested in recent studies.

METHOD

Here, we present a critical review based on a systematic literature search of articles published until December 2016 on the association between BD and infectious/immunogenetic factors.

RESULTS

We provide evidence suggesting that infectious insults could act as triggers of maladaptive immune responses in BD and that immunogenetic vulnerability may amplify the effects of such environmental risk factors, increasing susceptibility to subsequent environmental encounters. Quality of evidence was generally impaired by scarce attempt of replication, small sample sizes and lack of high-quality environmental measures.

CONCLUSION

Infection has emerged as a potential preventable cause of morbidity in BD, urging the need to better investigate components of the host-pathogen interaction in patients and at-risk subjects, and thus opening the way to novel therapeutic opportunities.

A systematic review of evidence for the role of inflammatory biomarkers in bipolar patients

Bipolar disorder (BD) is a neuropsychiatric disorder that is characterized by a phasic course of affective episodes interspersed with a euthymic state. Epidemiological, clinical, genetic, post-mortem and preclinical studies have shown that inflammatory reactions and immune modulation play a pivotal role in the pathophysiology of BD. It is conceptualized that biomarkers of inflammation and immune responses should be employed to monitor the disease process in bipolar patients. The objective of this systematic review is to analyse the inflammatory markers involved in human studies and to explore each individual marker for its potential clinical application and summarize evidence regarding their role in BD. A systematic review of human studies to measure inflammatory markers was conducted, and the studies were identified by searching PubMed/MEDLINE, PsycINFO, EMBASE, and Web of Science databases for peer-reviewed journals that were published until September 2015. In this review, we included peripheral markers, genetic, post-mortem and cell studies with inflammatory biomarker analysis in BD. One hundred and two (102) papers met the inclusion criteria. The pro-inflammatory cytokines were elevated and the anti-inflammatory cytokines were reduced in BD patients, particularly during manic and depressive phases when compared to the controls. These changes tend to disappear in euthymia, indicating that inflammation may be associated with acute phases of BD. Even though there are promising findings in this field, further clinical studies using more established detection techniques are needed to clearly show the benefit of using inflammatory markers in the diagnosis, follow-up and prognosis of patients with BD.

Optical coherence tomography findings in patients with bipolar disorder

BACKGROUND

Research in bipolar disorder suggests the presence of structural brain abnormalities. It is not clear whether these findings are trait markers or operate with the onset and progress with disease severity and duration. Optical coherence tomography (OCT) is a non-invasive technique that detects degenerative changes in the retina reflecting brain degeneration. This study aimed at detecting these changes and relating them to disease severity and clinical characteristics.

METHODS

A case-control study conducted in Psychiatry and Addiction Medicine hospital, Faculty of Medicine at Cairo University. Forty inpatients with bipolar disorder -according to the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) - were compared to forty matched healthy controls. Patients were subjected to the Structured Clinical Interview of DSM-IV (SCID-I), Hamilton Depression Rating Scale (HAM-D) and Young Mania Rating Scale (YMRS). Both patients and controls were subjected to OCT.

RESULTS

Patients showed thinning of Retinal Nerve Fiber Layer (RNFL) relative to control subjects in most of the OCT parameters including Right average (p<.001 and 95% CI [14.39, 19.84]), Lt average (p<.001 and 95% CI [13.03, 19.42]). Patients also showed decreased Ganglionic Cell Complex (GCC) significantly in Rt average (p=.002 and 95% CI [2.33, 9.78]), Lt average (p<.001) and 95% CI [4.47, 11.63]. Age at onset, number of episodes, and severity did not significantly correlate with OCT parameters.

LIMITATIONS

The small sample and absence of follow-up.

CONCLUSIONS

Patients with bipolar disorder show degenerative changes detected by OCT in relation to healthy controls.

The Effects of Histone Deacetylase Inhibition on the Levels of Cerebral Cytokines in an Animal Model of Mania Induced by Dextroamphetamine

Studies have suggested the involvement of inflammatory processes in the physiopathology of bipolar disorder. Preclinical evidences have shown that histone deacetylase inhibitors may act as mood-stabilizing agents and protect the brain in models of mania and depression. The aim of the present study was to evaluate the effects of sodium butyrate (SB) and valproate (VPA) on behavioral changes, histone deacetylase activity, and the levels of cytokines in an animal model of mania induced by dextroamphetamine (d-AMPH). Wistar rats were first given d-AMPH or saline (Sal) for a period of 14 days, and then, between the 8th and 14th days, the rats were treated with SB, VPA, or Sal. The activity of histone deacetylase and the levels of cytokines (interleukin (IL) IL-4, IL-6, and IL-10 and tumor necrosis factor-alpha (TNF-α)) were evaluated in the frontal cortex and striatum of the rats. The administration of d-AMPH increased the activity of histone deacetylase in the frontal cortex. Administration of SB or VPA decreased the levels of histone deacetylase activity in the frontal cortex and striatum of rats. SB per se increased the levels of cytokines in both of the brain structures evaluated. AMPH increased the levels of cytokines in both of the brain structures evaluated, and VPA reversed this alteration. The effects of SB on d-AMPH-induced cytokine alterations were dependent on the brain structure and the cytokine evaluated. Despite VPA and SB having a similar mechanism of action, both being histone deacetylase inhibitors, they showed different effects on the levels of cytokines. The present study reinforces the need for more research into histone deacetylase inhibitors being used as a possible target for new medications in the treatment of bipolar disorder.

Genetic effect of interleukin-1 beta (C-511T) polymorphism on the structural covariance network and white matter integrity in Alzheimer's disease

Background

Inflammatory processes play a pivotal role in the degenerative process of Alzheimer’s disease. In humans, a biallelic (C/T) polymorphism in the promoter region (position-511) (rs16944) of the interleukin-1 beta gene has been significantly associated with differences in the secretory capacity of interleukin-1 beta. In this study, we investigated whether this functional polymorphism mediates the brain networks in patients with Alzheimer’s disease.

Methods

We enrolled a total of 135 patients with Alzheimer’s disease (65 males, 70 females), and investigated their gray matter structural covariance networks using 3D T1 magnetic resonance imaging and their white matter macro-structural integrities using fractional anisotropy. The patients were classified into two genotype groups: C-carriers (n = 108) and TT-carriers (n = 27), and the structural covariance networks were constructed using seed-based analysis focusing on the default mode network medial temporal or dorsal medial subsystem, salience network and executive control network. Neurobehavioral scores were used as the major outcome factors for clinical correlations.

Results

There were no differences between the two genotype groups in the cognitive test scores, seed, or peak cluster volumes and white matter fractional anisotropy. The covariance strength showing C-carriers > TT-carriers was the entorhinal-cingulum axis. There were two peak clusters (Brodmann 6 and 10) in the salience network and four peak clusters (superior prefrontal, precentral, fusiform, and temporal) in the executive control network that showed C-carriers < TT-carriers in covariance strength. The salience network and executive control network peak clusters in the TT group and the default mode network peak clusters in the C-carriers strongly predicted the cognitive test scores.

Conclusions

Interleukin-1 beta C-511 T polymorphism modulates the structural covariance strength on the anterior brain network and entorhinal-interconnected network which were independent of the white matter tract integrity. Depending on the specific C-511 T genotype, different network clusters could predict the cognitive tests.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0791-z) contains supplementary material, which is available to authorized users.

Association between the serotonin transporter and cytokines: Implications for the pathophysiology of bipolar disorder

BACKGROUND

Reduced brain serotonin transporter (SERT) has been demonstrated in bipolar disorder (BD). The aim of this study was to explore the potential role of cytokines on reduced SERT in BD.

METHODS

Twenty-eight BD type I patients and 28 age- and gender-matched healthy controls (HCs) were recruited. Single photon emission computed tomography with the radiotracer 123I ADAM was used for SERT imaging. Regions of interest included the midbrain, thalamus, putamen and caudate. Seven cytokines, including tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-1α (IL-1α), IL-1β, IL-4, IL-6 and IL-10, were measured using an enzyme linked immune-sorbent assay.

RESULTS

SERT availability in the midbrain and caudate was significantly lower in BD compared to HCs. IL-1β was significantly lower, whereas IL-10 was significantly higher in BD compared to HCs. Multiple linear regression analyses revealed that there were associations between cytokines, IL-1α, IL-1β, IL-6 and SERT availability in the midbrain but not in the thalamus, putamen and caudate. Furthermore, linear mixed effect analyses demonstrated that these associations were not different between HCs and BD.

CONCLUSION

While many cytokines have been proposed to be important in the pathophysiology of BD, our results demonstrated that significant associations between cytokines and SERT availability may explain the role of cytokines in mood regulation. However, these associations were not different between HCs and BD, which imply the role of these cytokines is not specific for BD.

Peripapillary retinal nerve fiber layer thickness in bipolar disorder

BACKGROUND

To compare peripapillary retinal nerve fiber layer thickness (RNFLT) between patients with bipolar disorder and a control group by optical coherence tomography (OCT).

METHODS

This prospective comparative case series included 60 eyes of 30 patients with bipolar disorder and 60 eyes of 30 age-matched healthy control subjects. Using OCT, peripapillary RNFLT of the 4 quadrants and the mean of them was compared between the two groups. Variables such as age of onset, duration, smoking, psychosis, mania and depression episodes in the case group and their relationships with RNFLT were evaluated by OCT.

RESULTS

Mean RNFLT was 99 ± 8 in the case group, significantly less than the 106 ± 8 mμ in the control group (p = 0.001). The inferior, superior, and nasal quadrants in the case and control groups showed significant difference in RNFLT (p < 0.001) (p = 0.040) (p = 0.005); however, the temporal quadrant was not reduced significantly, compared to the control value (p = 0.907). Moreover, the only variable showing significant relation with RNFLT was duration of bipolar disorder (p = 0.040).

CONCLUSION

Reduction of peripapilary RNFLT occurs in patients with bipolar disorder, and is related to the duration of disease. RNFLT can be a beneficial value for studying neurodegenerative changes over time towards detecting the severity and duration of disorder.

Common biological mechanisms between bipolar disorder and type 2 diabetes: Focus on inflammation

INTRODUCTION

Bipolar disorder (BD) patients present a 3-5 fold greater risk of developing type 2 diabetes (T2D) compared to general population. The underlying mechanisms for the increased prevalence of T2D in BD population are poorly understood.

OBJECTIVES

The purpose of this review is to critically review evidence suggesting that inflammation may have an important role in the development of both BD and T2D.

RESULTS

The literature covered in this review suggests that inflammatory dysregulation take place among many BD patients. Such dysregulated and low grade chronic inflammatory process may also increase the prevalence of T2D in BD population. Current evidence supports the hypothesis of dysregulated inflammatory processes as a critical upstream event in BD as well as in T2D.

CONCLUSIONS

Inflammation may be a factor for the development of T2D in BD population. The identification of inflammatory markers common to these two medical conditions will enable researchers and clinicians to better understand the etiology of BD and develop treatments that simultaneously target all aspects of this multi-system condition.

Cytokines in bipolar disorder: paving the way for neuroprogression

Bipolar disorder (BD) is a severe, chronic, and recurrent psychiatric illness. It has been associated with high prevalence of medical comorbidities and cognitive impairment. Its neurobiology is not completely understood, but recent evidence has shown a wide range of immune changes. Cytokines are proteins involved in the regulation and the orchestration of the immune response. We performed a review on the involvement of cytokines in BD. We also discuss the cytokines involvement in the neuroprogression of BD. It has been demonstrated that increased expression of cytokines in the central nervous system in postmortem studies is in line with the elevated circulating levels of proinflammatory cytokines in BD patients. The proinflammatory profile and the immune imbalance in BD might be regarded as potential targets to the development of new therapeutic strategies.

A genome-wide linkage scan of bipolar disorder in Latino families identifies susceptibility loci at 8q24 and 14q32

A genome-wide nonparametric linkage screen was performed to localize Bipolar Disorder (BP) susceptibility loci in a sample of 3757 individuals of Latino ancestry. The sample included 963 individuals with BP phenotype (704 relative pairs) from 686 families recruited from the US, Mexico, Costa Rica, and Guatemala. Non-parametric analyses were performed over a 5 cM grid with an average genetic coverage of 0.67 cM. Multipoint analyses were conducted across the genome using non-parametric Kong & Cox LOD scores along with Sall statistics for all relative pairs. Suggestive and significant genome-wide thresholds were calculated based on 1000 simulations. Single-marker association tests in the presence of linkage were performed assuming a multiplicative model with a population prevalence of 2%. We identified two genome-wide significant susceptibly loci for BP at 8q24 and 14q32, and a third suggestive locus at 2q13-q14. Within these three linkage regions, the top associated single marker (rs1847694, P = 2.40 × 10(-5)) is located 195 Kb upstream of DPP10 in Chromosome 2. DPP10 is prominently expressed in brain neuronal populations, where it has been shown to bind and regulate Kv4-mediated A-type potassium channels. Taken together, these results provide additional evidence that 8q24, 14q32, and 2q13-q14 are susceptibly loci for BP and these regions may be involved in the pathogenesis of BP in the Latino population.

Volume of the hippocampal subfields in healthy adults: differential associations with age and a pro-inflammatory genetic variant

The hippocampus is one of the most age-sensitive brain regions, yet the mechanisms of hippocampal shrinkage remain unclear. Recent studies suggest that hippocampal subfields are differentially vulnerable to aging and differentially sensitive to vascular risk. Promoters of inflammation are frequently proposed as major contributors to brain aging and vascular disease but their effects on hippocampal subfields are unknown. We examined the associations of hippocampal subfield volumes with age, a vascular risk factor (hypertension), and genetic polymorphisms associated with variation in pro-inflammatory cytokines levels (IL-1β C-511T and IL-6 C-174G) and risk for Alzheimer's disease (APOEε4) in healthy adult volunteers (N = 80; age = 22-82 years). Volumes of three hippocampal subfields, cornu ammonis (CA) 1-2, CA3-dentate gyrus, and the subiculum were manually measured on high-resolution magnetic resonance images. Advanced age was differentially associated with smaller volume of CA1-2, whereas carriers of the T allele of IL-1β C-511T polymorphism had smaller volume of all hippocampal subfields than CC homozygotes did. Neither of the other genetic variants, nor diagnosis of hypertension, was associated with any of the measured volumes. The results support the notion that volumes of age-sensitive brain regions may be affected by pro-inflammatory factors that may be targeted by therapeutic interventions.

Relationship between clinical features and inflammation-related monocyte gene expression in bipolar disorder - towards a better understanding of psychoimmunological interactions

OBJECTIVES

Existing and previously published datasets were examined for associations between illness and treatment characteristics and monocyte pro-inflammatory gene expression in patients with bipolar disorder (BD). We hypothesized a priori that increased monocyte pro-inflammatory gene expression would be found more frequently in patients with a lifetime history of psychotic symptoms.

METHODS

Monocyte quantitative polymerase chain reaction and symptom data from 64 patients with BD were collected from three Dutch studies. Regression analyses were performed to analyze the various associations between pro-inflammatory gene expression and clinical features, from which feature-expression heat maps were drawn.

RESULTS

No associations were found between pro-inflammatory gene expression and lifetime psychotic symptoms, whereas a positive association was identified between subcluster 2 genes and manic symptoms. For several subcluster 1a genes, a negative association was found with age at onset. For most subcluster 2 genes, a positive association was found with the duration of illness. Current use of antidepressants and of anti-epileptic agents was associated with subcluster 2 gene expression, and current use of lithium and antipsychotic agents with subcluster 1a gene expression.

CONCLUSIONS

Our hypothesis that lifetime psychotic features would be associated with pro-inflammatory monocyte gene expression was not confirmed. In an explorative analysis we found: (i) a possible relationship between pro-inflammatory gene expression and manic symptomatology; (ii) a differential immune activation related to age at onset and duration of illness; and (iii) support for the concept of an immune suppressive action of some of the mood-regulating medications.

Polymorphism of Toll-like receptor 4 gene in bipolar disorder

BACKGROUND

Bipolar disorder (BD) is considered as a multifactorial disorder involving complex interactions between genetic and environmental factors, where immune dysfunction is thought to play a key etiopathogenic role. In particular, excess of winter births associated with early-life infections raise the possibility of the implication of innate immunity. Given the pivotal role of Toll-like receptor 4 (TLR-4), a major innate immune sensor molecule, we hypothesized that genetic variations of TLR-4 may be associated to BD.

METHODS

Genomic DNAs from 572 BD patients and 202 healthy controls (HC) were analyzed for the distribution of six single nucleotides polymorphisms (SNPs) scattered along the TLR-4 locus (rs1927914, rs10759932, rs4986790, rs4986791, rs11536889 and rs11536891). Associations between BD and these polymorphisms were examined using the Chi-square test.

RESULTS

We found that rs1927914 AA and rs11536891 TT genotype are more frequent in BD patients than in controls (corrected p; pc=.02 and .02 respectively) particularly in early-onset BD patients (pc=.004 and .006) born during the summer season (pc=.02 and .002 respectively). We also found that rs4986790 AG and rs4986791 CT genotypes were significantly associated with presence of autoimmune thyroiditis (pc=.002).

LIMITATIONS

Our results are to be confirmed by replication in independent BD cohorts.

CONCLUSIONS

We report for the first time a genetic association between BD and TLR-4 a major player of innate immunity. Possible mechanisms underlying bipolar disorders linking altered TLR-4 expression and increased susceptibility to infections and/or autoimmunity are discussed.

Influence of IL-1RN intron 2 variable number of tandem repeats (VNTR) polymorphism on bipolar disorder

BACKGROUND/AIMS

Several lines of evidence point to the role of neurobiological mechanisms and genetic background in bipolar disorder (BD). The interleukin-1 receptor antagonist (IL-1Ra) is the principal regulator of IL-1α and IL-1β bioactivities. This study aimed to investigate the potential role of the variable number of tandem repeats (VNTR) polymorphisms of the IL-1Ra gene (IL1RN) in conferring susceptibility to BD.

METHODS

In total, 217 patients meeting DSM-IV-TR criteria for BD and 212 controls were recruited for the study. Genotyping of IL1RN was determined by polymerase chain reaction amplification of VNTR of 86 base pairs in intron 2 of IL1RN.

RESULTS

The genotype distribution of IL1RN polymorphism was significantly different between BD patients and controls. The IL1RN*1/2 genotype was more prevalent in BD patients than in controls (44.2 vs. 30.2%, p = 0.003). Multiple logistic regression analysis demonstrated that IL1RN*1/2 heterozygotes had a significantly higher risk for BD (OR 1.83 and 95% CI 1.22-2.74, p = 0.003). Further stratification of the BD patients into IL1RN*2 allele carrier and noncarrier subgroups revealed a strong association between IL1RN*2 carriage and prolongation of the disease (p = 0.02).

CONCLUSIONS

These findings suggest a positive association between VNTR polymorphism in IL1RN and BD. Additional studies, particularly with a prospective approach, are necessary to clarify the precise role of the VNTR polymorphism on the disease in different ethnic populations.

Immunity, inflammation, and bipolar disorder: diagnostic and therapeutic implications

Bipolar disorder is now known to be associated not only with highly prevalent co-occurring psychiatric and substance use disorders but also with medical comorbidities, such as cardiovascular diseases, diabetes mellitus, obesity and thyroid dysfunction. Inflammatory disturbances repeatedly observed in bipolar disorder, can explain some of the comorbidity between bipolar disorder and medical disorder. This revised perspective of bipolar disorders should promote the development of therapeutic tools. Immuno-inflammatory dysfunction may well represent a significant component of the underlying pathophysiology of the disorder. We therefore propose to review the immuno-inflammatory hypothesis in bipolar disorder considering the co-occurence with autoimmune diseases, immunological and inflammatory markers, as well as immuno-genetic markers which could lead to personalized treatments.

Cytokine alterations in bipolar disorder: a meta-analysis of 30 studies

BACKGROUND

We conducted a meta-analysis of studies comparing cytokine concentrations between patients with bipolar disorder (BD) and healthy control subjects (HCs).

METHODS

We searched ISI Web of Science, MEDLINE, BIOSIS Previews, Scopus, Current Contents Connect, and Biological Abstracts for relevant studies. Based on heterogeneity status, we used fixed-effect or restricted maximal likelihood model to perform meta-analysis.

RESULTS

Thirty studies with a total of 2599 participants (1351 BD and 1248 HCs) were eligible for the analysis. Concentrations of interleukin (IL)-4 (p = .008), IL-6 (p = .073), IL-10 (p = .013), soluble IL-2 receptor (sIL-2R; p < .001), sIL-6R (p = .021), tumor necrosis factor (TNF)-α (p = .010), soluble TNF receptor-1 (sTNFR1; p < .001), and IL-1 receptor antagonist (p value in mania < .001 and euthymia = .021) were significantly elevated in patients compared with HCs. Moreover, IL-1β (p = .059), and IL-6 (p = .073) tended to show higher values in patients. Levels of IL-2 (p = .156), interferon (INF)-γ (p = .741), C-C motif ligand 2 (p = .624), and IL-8 (p = .952) did not significantly differ between patients and HCs. Subgroup analysis based on mitogen stimulation status partially or completely resolved heterogeneity for most of the cytokines. Concentrations of IL-2, IL-4, sIL-6R, and INF-γ were unrelated to medication status. Phasic difference was present for TNF-α, sTNFR1, sIL-2R, IL-6, and IL-1RA, whereas it was absent for IL-4 and IL-10.

CONCLUSIONS

This meta-analysis provides evidence for significant elevation of proinflammatory, anti-inflammatory, and regulatory cytokines in BD.

Interleukin-1 beta C-511T polymorphism modulates functional connectivity of anterior midcingulate cortex in non-demented elderly Han males

Recent resting fMRI studies have suggested that the functional connectivity of the brain's large-scale networks is associated with the cognitive decline of aging and is modulated by genetic factors. Our previous study found a significant association between interleukin-1 (IL-1 beta) C-511T polymorphism and working memory performance among elderly people. This study investigates the effects of IL-1 beta C-511T polymorphism on the functional connectivity of the cognitive division of the cingulate cortex [i.e., the anterior midcingulate (aMCC)] in non-demented Han elderly people and tests the hypothesis that T/T carriers are associated with lowered FC. Non-demented elderly males (n = 95) received resting MRI scanning, genotyping, and cognitive evaluation using the cognitive abilities screening instrument (CASI) and the Wechsler digit span task test. The functional connectivity map in each subject was derived based on positive correlations of low-frequency fMRI fluctuations with a seed in the aMCC according to structural definition. Between-group difference was compared by random effect analysis. Compared to the C/C or C/T carriers, the T/T carriers had a significantly worse CASI performance, especially in the abstraction scores. For the functional connectivity analysis, the T/T carriers exhibited significantly lower functional connectivity with several prefrontal areas and the left putamen. The cortico-striatal connection between the aMCC and left putamen was correlated with the CASI abstraction and attention scores. The results were consistent with our hypothesis and supported that the brains' functional connectivity in elderly people may be modulated by genetic polymorphism associated with local inflammation processes.

Haplotypes in the expression quantitative trait locus of interleukin-1β gene are associated with schizophrenia

Recent genome-wide association study (GWAS) and gene expression analyses have revealed that single nucleotide polymorphisms (SNPs) associated with complex diseases such as schizophrenia are significantly more likely to be associated with expression quantitative trait loci (eQTL). The interleukin-1β (IL1B) gene has been strongly implicated in the susceptibility to schizophrenia. In order to test this association, we selected five tag SNPs in the eQTL of the IL1B gene and conducted a case-control study using two independent samples. The first sample comprised 528 schizophrenic patients and 709 controls and the second sample comprised 576 schizophrenic patients and 768 controls. We identified two SNPs and several haplotypes as being significantly associated with schizophrenia. Previous reports indicated that one major haplotype that was protective against schizophrenia reduced IL1B transcription, while two risk haplotypes for schizophrenia enhanced IL1B transcription. Therefore, we measured IL1B mRNA expression in PAXgene-stabilized whole blood from 40 schizophrenic patients and 40 controls to explore the possibility of using five tag SNPs as schizophrenic trait markers. A multiple regression analysis taking confounding factors into account revealed that the T allele of rs4848306 SNP, which is a protective allele for schizophrenia, predicted reduced change in IL1B mRNA expression, regardless of phenotype. Our results appear to support the previous hypothesis that IL1B contributes to the genetic risk of schizophrenia and warrant further research on the association of eQTL SNPs with schizophrenia.

Effects of medication on neuroimaging findings in bipolar disorder: an updated review

OBJECTIVE

Neuroimaging is an important tool for better understanding the neurobiological underpinnings of bipolar disorder (BD). However, potential study participants are often receiving psychotropic medications which can possibly confound imaging data. To better interpret the results of neuroimaging studies in BD, it is important to understand the impact of medications on structural magnetic resonance imaging (sMRI), functional MRI (fMRI), and diffusion tensor imaging (DTI).

METHODS

To better understand the impact of medications on imaging data, we conducted a literature review and searched MEDLINE for papers that included the key words bipolar disorder and fMRI, sMRI, or DTI. The search was limited to papers that assessed medication effects and had not been included in a previous review by Phillips et al. (Medication effects in neuroimaging studies of bipolar disorder. Am J Psychiatry 2008; 165: 313-320). This search yielded 74 sMRI studies, 46 fMRI studies, and 15 DTI studies.

RESULTS

Medication appeared to influence many sMRI studies, but had limited impact on fMRI and DTI findings. From the structural studies, the most robust finding (20/45 studies) was that lithium was associated with increased volumes in areas important for mood regulation, while antipsychotic agents and anticonvulsants were generally not. Regarding secondary analysis of the medication effects of fMRI and DTI studies, few showed significant effects of medication, although rigorous analyses were typically not possible when the majority of subjects were medicated. Medication effects were more frequently observed in longitudinal studies designed to assess the impact of particular medications on the blood oxygen level-dependent (BOLD) signal. With a few exceptions, the observed effects were normalizing, meaning that the medicated individuals with BD were more similar than their unmedicated counterparts to healthy subjects.

CONCLUSIONS

The effects of psychotropic medications, when present, are predominantly normalizing and thus do not seem to provide an alternative explanation for differences in volume, white matter tracts, or BOLD signal between BD participants and healthy subjects. However, the normalizing effects of medication could obfuscate differences between BD and healthy subjects, and thus might lead to type II errors.

Volume of white matter hyperintensities in healthy adults: contribution of age, vascular risk factors, and inflammation-related genetic variants

Aging is associated with appearance of white matter hyperintensities (WMH) on MRI scans. Vascular risk and inflammation, which increase with age, may contribute to white matter deterioration and proliferation of WMH. We investigated whether circulating biomarkers and genetic variants associated with elevated vascular risk and inflammation are associated with WMH volume in healthy adults (144 volunteers, 44-77 years of age). We examined association of WMH volume with age, sex, hypertension, circulating levels of total plasma homocysteine (tHcy), cholesterol (low-density lipoprotein), and C-reactive protein (CRP), and four polymorphisms related to vascular risk and inflammation: Apolipoprotein ε (ApoE ε2,3,4), Angiotensin-Converting Enzyme insertion/deletion (ACE I/D), methylenetetrahydrofolate reductase (MTHFR) C677T, C-reactive protein (CRP)-286C>A>T, and interleukin-1β (IL-1β) C-511T. We found that larger WMH volume was associated with advanced age, hypertension, and elevated levels of homocysteine and CRP but not with low-density lipoprotein levels. Homozygotes for IL-1β-511T allele and carriers of CRP-286T allele that are associated with increased inflammatory response had larger WMH than the other allelic combinations. Carriers of the APOE ε2 allele had larger frontal WMH than ε3 homozygotes and ε4 carriers did. Thus, in healthy adults, who are free of neurological and vascular disease, genetic variants that promote inflammation and elevated levels of vascular risk biomarkers can contribute to brain abnormalities. This article is part of a Special Issue entitled: Imaging Brain Aging and Neurodegenerative disease.

Pathways underlying neuroprogression in bipolar disorder: focus on inflammation, oxidative stress and neurotrophic factors

There is now strong evidence of progressive neuropathological processes in bipolar disorder (BD). On this basis, the current understanding of the neurobiology of BD has shifted from an initial focus on monoamines, subsequently including evidence of changes in intracellular second messenger systems and more recently to, incorporating changes in inflammatory cytokines, corticosteroids, neurotrophins, mitochondrial energy generation, oxidative stress and neurogenesis into a more comprehensive model capable of explaining some of the clinical features of BD. These features include progressive shortening of the inter-episode interval with each recurrence, occurring in consort with reduced probability of treatment response as the illness progresses. To this end, emerging data shows that these biomarkers may differ between early and late stages of BD in parallel with stage-related structural and neurocognitive alterations. This understanding facilitates identification of rational therapeutic targets, and the development of novel treatment classes. Additionally, these pathways provide a cogent explanation for the efficacy of seemingly diverse therapies used in BD, that appear to share common effects on oxidative, inflammatory and neurotrophic pathways.

Similar immune profile in bipolar disorder and schizophrenia: selective increase in soluble tumor necrosis factor receptor I and von Willebrand factor

BACKGROUND

Alterations in the inflammatory system have been associated with schizophrenia and major depression, while bipolar disorder has been less studied. Most previous studies examined small samples, and the literature is inconsistent with regard to specific underlying immune mechanisms. In the present study, we examined markers representing different inflammatory pathways, and the aim was to investigate whether the levels of inflammatory parameters in a representative sample of bipolar disorder and schizophrenia are elevated compared to healthy controls, and to investigate whether the inflammatory profile is different between the groups.

METHODS

Plasma levels of soluble tumor necrosis factor receptor 1 (sTNF-R1), interleukin-1 receptor antagonist (IL-1Ra), interleukin-6 (IL-6), high-sensitivity CRP (hs-CRP), soluble CD40L ligand (sCD40L), and von Willebrand factor (vWf) were measured with ELISA techniques in a catchment area based sample of consecutively referred patients with severe mental disorders [N = 311, comprising bipolar disorder (n = 125) and schizophrenia (n = 186)] and in healthy volunteers (n = 244).

RESULTS

Plasma levels of sTNF-R1 and vWf were statistically significantly increased in both bipolar disorder and schizophrenia compared to controls (p < 0.00001), and were also increased in unmedicated patients, but there were no major differences between the two diagnostic groups. Controlling for age, gender, ethnicity, cardiovascular disorders, kidney and liver function, and other confounders did not affect the results. There were no differences in other inflammation factors between the groups.

CONCLUSION

The present results indicate specific alterations of endothelium-related inflammation processes in both bipolar disorder and schizophrenia.