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Background: Bipolar disorder is highly heritable and polygenic. The polygenic risk for bipolar disorder overlaps with that of schizophrenia, and polygenic scores are normally distributed in the population. Bipolar disorder has been associated with structural brain abnormalities, but it is unknown how these are linked to genetic risk factors for psychotic disorders. Methods: We tested whether polygenic risk scores for bipolar disorder and schizophrenia predict structural brain alterations in 98 patients with bipolar disorder and 81 healthy controls. We derived brain cortical thickness, surface area and volume from structural MRI scans. In post-hoc analyses, we correlated polygenic risk with functional hub strength, derived from resting-state functional MRI and brain connectomics. Results: Higher polygenic risk scores for both bipolar disorder and schizophrenia were associated with a thinner ventromedial prefrontal cortex (vmPFC). We found these associations in the combined group, and separately in patients and drug-naive controls. Polygenic risk for bipolar disorder was correlated with the functional hub strength of the vmPFC within the default mode network. Limitations: Polygenic risk is a cumulative measure of genomic burden. Detailed genetic mechanisms underlying brain alterations and their cognitive consequences still need to be determined. Conclusion: Our multimodal neuroimaging study linked genomic burden and brain endophenotype by demonstrating an association between polygenic risk scores for bipolar disorder and schizophrenia and the structure and function of the vmPFC. Our findings suggest that genetic factors might confer risk for psychotic disorders by influencing the integrity of the vmPFC, a brain region involved in self-referential processes and emotional regulation. Our study may also provide an imaging-genetics vulnerability marker that can be used to help identify individuals at risk for developing bipolar disorder., Introduction Bipolar disorder is a highly heritable (1) and severe psychiatric disorder characterized by recurrent episodes of (hypo)mania and depression. (2) Psychotic symptoms similar to those seen in schizophrenia are [...]

Background: The CACNA1C gene encodes the 1C subunit of L-type voltage-gated calcium channels and has been associated with several psychiatric syndromes--including bipolar disorder--in many genome-wide association studies. Experimental and clinical studies have reported changes with respect to behaviour and biomarkers in risk allele carriers, corroborating the essential role of the CACNA1C gene in neurons, during development and in the mature brain. However, the association of this gene with regional cortical thickness has not been evaluated in patients with bipolar disorder. Methods: Using magnetic resonance imaging, we measured the average cortical thickness of 68 brain regions in 87 patients genotyped for the single-nucleotide polymorphism rs1006737 in CACNA1C. Results: We found associations with the mean thickness of several cortical areas: the left lateral orbitofrontal and rostral anterior cingulate cortices, as well as other parts of the frontal and parietal cortices. Limitations: This cross-sectional cohort study could not fully differentiate correlation from causation. Conclusion: The CACNA1C polymorphism rs1006737 is associated with the mean thickness of cortical brain areas that have been shown to be altered in bipolar disorder., Introduction Bipolar disorder is a serious mental disorder that affects approximately 1% of the population; (1) people with bipolar disorder experience both decreased mood (depression) and increased mood (mania). (2) [...]

Background: Bipolar disorder (BD) is a common chronic psychiatric disorder mainly characterized by episodes of mania, hypomania and depression. The disorder is associated with cognitive impairments and structural brain abnormalities, such as lower cortical volumes in primarily frontal brain regions than healthy controls. Although bipolar disorder types I (BDI) and II (BDII) exhibit different symptoms and severity, previous studies have focused on BDI. Furthermore, the most frequently investigated measure in this population is cortical volume. The aim of our study was to investigate abnormalities in patients with BDI and BDII by simultaneously analyzing cortical volume, thickness and surface area, which yields more information about disease- and symptom-related neurobiology. Methods: We used MRI to measure cortical volume, thickness and area in patients with BDI and BDII as well as in healthy controls. The large study cohort enabled us to adjust for important confounding factors. Results: We included 81 patients with BDI, 59 with BDII and 85 controls in our analyses. Cortical volume, thickness and surface area abnormalities were present in frontal, temporal and medial occipital regions in patients with BD. Lithium and antiepileptic drug use had an effect on the observed differences in medial occipital regions. Patients with the subtypes BDI and BDII displayed common cortical abnormalities, such as lower volume, thickness and surface area than healthy controls in frontal brain regions but differed in temporal and medial prefrontal regions, where only those with BDI had abnormally low cortical volume and thickness. Limitations: The group differences can be explained by progressive changes, but also by premorbid conditions. They could also have been influenced by unknown factors, such as social, environmental or genetic factors. Conclusion: Our findings suggest diagnosis-related neurobiological differences between the BD subtypes, which could explain distinct symptoms and point to potential biomarkers that could inform the subtype diagnosis of BD., Introduction Bipolar disorder (BD) is a common chronic psychiatric disorder characterized by mood disturbances with recurrent episodes of mania, hypomania and depression interspersed by euthymic periods. The disorder is not [...]

Background: Bipolar disorder is associated with medical comorbidities that have been linked to systemic inflammatory mechanisms. There is, however, limited evidence supporting a role of neuroinflammation in bipolar disorder. Here we tested whether microglial activation and associated tissue remodelling processes are related to bipolar disorder by analyzing markers in cerebrospinal fluid (CSF) and serum from patients and healthy controls. Methods: Serum was sampled from euthymic patients with bipolar disorder and healthy controls, and CSF was sampled from a large subset of these individuals. The levels of monocyte chemoattractant protein-1 (MCP-1), YKL-40, soluble cluster of differentiation 14 (sCD14), tissue inhibitor of metalloproteinases-1 (TIMP-1) and tissue inhibitor of metalloproteinases-2 (TIMP-2), were measured, and we adjusted comparisons between patients and controls for confounding factors. Results: We obtained serum samples from 221 patients and 112 controls and CSF samples from 125 patients and 87 controls. We found increased CSF levels of MCP-1 and YKL-40 and increased serum levels of sCD14 and YKL-40 in patients compared with controls; these differences remained after controlling for confounding factors, such as age, sex, smoking, blood-CSF barrier function, acute-phase proteins and body mass index. The CSF levels of MCP-1 and YKL-40 correlated with the serum levels, whereas the differences between patients and controls in CSF levels of MCP-1 and YKL-40 were independent of serum levels. Limitations: The cross-sectional study design precludes conclusions about causality. Conclusion: Our results suggest that both neuroinflammatory and systemic inflammatory processes are involved in the pathophysiology of bipolar disorder. Importantly, markers of immunological processes in the brain were independent of peripheral immunological activity., Introduction Bipolar disorder is a severe psychiatric condition characterized by recurrent episodes of elevated (mania or hypomania) or depressed mood and interepisodic periods with no or few symptoms. (1,2) The [...]

Background: Bipolar disorder is a common psychiatric mood disorder that is defined by recurrent episodes of abnormally elevatedmood and depression. Progressive structural brain changes in individuals with bipolar disorder have been suggested to be associated with defects in the secretion of neurotrophic factors. We sought to assess how the regulated secretory pathway in the brain is affected inpatients with bipolar disorder by measuring chromogranin B and secretogranin II, which are 2 cerebrospinal fluid (CSF) biological markers for this process. Methods: We measured the concentrations of chromogranin B (peptide 439-451) and secretogranin II (peptide 154-165) in the CSF of patients with well-defined bipolar disorder and healthy controls. The lifetime severity of bipolar disorder was rated using the Clinical Global Impression (CGI) scale. Results: We included 126 patients with bipolar disorder and 71 healthy controls in our analysis. Concentrations of secretogranin II were significantly lower in patients with bipolar disorder type I than in healthy controls. The reduction was most pronounced in patients with high CGI scores (i.e., severe disease). Limitations: The cross-sectional design of the current study limits the ability to pinpoint the causalities behind the observed associations. Conclusion: This study shows that the CSF marker secretogranin II has the potential to act as a biological marker for severe forms of bipolar disorder. Our findings indicate that patients with bipolar disorder possess defects in the regulatory secretory pathway, which may be of relevance to the progressive structural brain changes seen in those with severe forms of the disease., Introduction Bipolar disorder is a common psychiatric mood disorder that is defined by recurrent episodes of abnormally elevated mood and depression. (1,2) Although the neurobiology of bipolar disorder is mainly [...]

Background: In recent years, a role for the immune system in the pathogenesis of psychiatric diseases has gained increased attention. Although bipolar disorder appears to be associated with altered serum cytokine levels, a putative immunological contribution to its pathophysiology remains to be established. Hitherto, no direct analyses of cerebrospinal fluid (CSF) cytokines in patients with bipolar disorder have been performed. Methods: We analyzed CSF cytokine concentrations in euthymic patients with diagnosed bipolar disorder type I (n = 15) or type II (n = 15) and healthy volunteers (n = 30) using an immunoassay-based protein array multiplex system. Results: The mean interleukin (IL)-1β level (4.2 pg/mL, standard error of the mean [SEM] 0.5) was higher and the IL-6 level (1.5 pg/mL, SEM 0.2) was lower in euthymic bipolar patients than in healthy volunteers (0.8 pg/mL, SEM 0.04, and 2.6 pg/mL, SEM 0.2, respectively). Patients with 1 or more manic/hypomanic episodes during the last year showed significantly higher levels of IL-1β (6.2 pg/mL, SEM 0.8; n = 9) than patients without a recent manic/hypomanic episode (3.1 pg/mL, SEM 1.0; n = 10). Limitations: All patients were in an euthymic state at the time of sampling. Owing to the large variety of drugs prescribed to patients in the present study, influence of medication on the cytokine profile cannot be ruled out. Conclusion: Our findings show an altered brain cytokine profile associated with the manifestation of recent manic/hypomanic episodes in patients with bipolar disorder. Although the causality remains to be established, these findings may suggest a pathophysiological role for IL-1β in bipolar disorder., Introduction Bipolar disorder is characterized by recurrent episodes of manic or depressive mood interspaced with periods of euthymia. The underlying pathophysiology of the disease is poorly understood, although manic symptoms [...]

Background: Patients with schizophrenia show elevated brain levels of the neuroactive tryptophan metabolite kynurenic acid (KYNA). This astrocyte-derived mediator acts as a neuroprotectant and modulates sensory gating and cognitive function. We measured the levels of KYNA in the cerebrospinal fluid (CSF) of patients with bipolar disorder and healthy volunteers to investigate the putative involvement of KYNA in bipolar disorder. Methods: We obtained CSF by lumbar puncture from 23 healthy men and 31 euthymic men with bipolar disorder. We analyzed the samples using high-performance liquid chromatography. Results: Patients with bipolar disorder had increased levels of KYNA in their CSF compared with healthy volunteers (1.71 nM, standard error of the mean [SEM] 0.13 v. 1.13 nM, SEM 0.09; p = 0.002. The levels of KYNA were positively correlated with age among bipolar patients but not healthy volunteers. Limitations: The influence of ongoing drug treatment among patients cannot be ruled out. We conducted our study during the euthymic phase of the disease. Conclusion: Brain KYNA levels are increased in euthymic men with bipolar disorder. In addition, KYNA levels increased with age in these patients. These findings indicate shared mechanisms between bipolar disorder and schizophrenia. Elevated levels of brain KYNA may provide further insight to the pathophysiology and progression of bipolar disorder., Introduction Bipolar disorder is characterized by recurrent episodes of mania and depression, interspersed with euthymic periods when depressive or manic symptoms are absent. Severe manic episodes often feature psychotic symptoms, [...]