Challenges and developments in research of the early stages of bipolar disorder

Causal role of immune cells in bipolar disorder: a Mendelian randomization study

Background

The understanding of the immunological mechanisms underlying bipolar disorder (BD) has enhanced in recent years due to the extensive use of high-density genetic markers for genotyping and advancements in genome-wide association studies (GWAS). However, studies on the relationship between immune cells and the risk of BD remain limited, necessitating further investigation.

Methods

Bidirectional two-sample Mendelian Randomization (MR) analysis was employed to investigate the causal association between immune cell morphologies and bipolar disorder. Immune cell traits were collected from a research cohort in Sardinia, whereas the GWAS summary statistics for BD were obtained from the Psychiatric Genomics Consortium. Sensitivity analyses were conducted, and the combination of MR-Egger and MR-Presso was used to assess horizontal pleiotropy. Cochran's Q test was employed to evaluate heterogeneity, and the results were adjusted for false discovery rate (FDR).

Results

The study identified six immune cell phenotypes significantly associated with BD incidence (P< 0.01). These phenotypes include IgD- CD27- %lymphocyte, CD33br HLA DR+ CD14- AC, CD8 on CD28+ CD45RA+ CD8br, CD33br HLA DR+ AC, CD14 on CD14+ CD16+ monocyte, and HVEM on CD45RA- CD4+. After adjusting the FDR to 0.2, two immune cell phenotypes remained statistically significant: IgD-CD27-% lymphocyte (OR=1.099, 95% CI: 1.051-1.149, P = 3.51E-05, FDR=0.026) and CD33br HLA DR+ CD14-AC (OR=0.981, 95% CI: 0.971-0.991, P = 2.17E-04, FDR=0.079). In the reverse MR analysis, BD significantly impacted the phenotypes of four monocytes (P< 0.01), including CD64 on CD14+ CD16+ monocyte, CD64 on monocyte, CX3CR1 on CD14- CD16-, CD64 on CD14+ CD16- monocyte. However, after applying the FDR correction (FDR < 0.2), no statistically significant results were observed.

Conclusions

This MR investigation reveals associations between immune cell phenotypes, bipolar disorder, and genetics, providing novel perspectives on prospective therapeutic targets for bipolar disorder.

Metabolomic Profiling of Bipolar Disorder by 1H-NMR in Serbian Patients

Bipolar disorder (BD) is a brain disorder that causes changes in a person's mood, energy, and ability to function. It has a prevalence of 60 million people worldwide, and it is among the top 20 diseases with the highest global burden. The complexity of this disease, including diverse genetic, environmental, and biochemical factors, and diagnoses based on the subjective recognition of symptoms without any clinical test of biomarker identification create significant difficulties in understanding and diagnosing BD. A ¹H-NMR-based metabolomic study applying chemometrics of serum samples of Serbian patients with BD (33) and healthy controls (39) was explored, providing the identification of 22 metabolites for this disease. A biomarker set including threonine, aspartate, gamma-aminobutyric acid, 2-hydroxybutyric acid, serine, and mannose was established for the first time in BD serum samples by an NMR-based metabolomics study. Six identified metabolites (3-hydroxybutyric acid, arginine, lysine, tyrosine, phenylalanine, and glycerol) are in agreement with the previously determined NMR-based sets of serum biomarkers in Brazilian and/or Chinese patient samples. The same established metabolites (lactate, alanine, valine, leucine, isoleucine, glutamine, glutamate, glucose, and choline) in three different ethnic and geographic origins (Serbia, Brazil, and China) might have a crucial role in the realization of a universal set of NMR biomarkers for BD.

Reduced Cortical Thicknesses of Adolescents with Bipolar Disorder and Relationship with Brain-derived Neurotrophic Factor

Background

Cortical thickness (CT) and brain-derived neurotrophic factor (BDNF) were widely investigated in bipolar disorder (BD). Previous studies focused on the association between the volume of subcortical regions and neurotrophic factor levels.

Objective

In this study, we aimed to evaluate the association of the CT in youth with early-onset BD with BDNF levels as a potential peripheral marker of neuronal integrity.

Method

Twenty-three euthymic patients having a clinical diagnosis of BD and 17 healthy subjects as an age-matched control group with neuroimaging and blood BDNF levels were found eligible for CT measurement. A structural magnetic resonance scan (MRI) and timely blood samples were drawn.

Results

Youth with BD exhibited lower cortical thickness in caudal part of left (L) middle frontal gyrus, right (R) paracentral gyrus, triangular part of R inferior frontal gyrus, R pericalcarine region, R precentral gyrus, L precentral gyrus, R superior frontal gyrus and L superior frontal gyrus when compared to healthy controls. The effect sizes of these differences were moderate to large (d=0.67-0.98) There was a significant correlation between BDNF levels with caudal part of the R anterior cingulate gyrus (CPRACG) in adolescents with BD (r=0.49, p=0.023).

Conclusion

As a special region for mood regulation, the CT of the caudal part of the R anterior cingulate gyrus had a positive correlation with BDNF. Regarding the key role of CPRACG for affective regulation skills, our results should be replicated in future follow-up studies, investigating a predictive neuroimaging biomarker for the early-onset BD.

Metabolic parameters as possible diagnostic predictors in first-episode psychosis: An exploratory retrospective cohort study

AIM

Patients in early phases of schizophrenia or mood disorders with psychotic symptoms have a wide array of metabolic abnormalities. We analysed the potential predictive value of uric acid (UA) levels and other metabolic parameters in first-episode psychosis patients to differentiate between non-affective and affective psychosis.

METHODS

Retrospective chart review of all patients referenced to a first-episode psychosis unit (n = 149), between 2012 and 2017, with available UA levels. Patients included (n = 37) were compared according to the follow-up diagnosis of schizophrenia or mood disorder.

RESULTS

Mood disorder patients presented higher UA levels (p = .030) and lower fasting blood glucose levels (p = .020) compared with schizophrenia patients. The remaining variables did not show significant intergroup differences.

CONCLUSIONS

Findings in this first-episode psychosis cohort support previous evidence suggesting higher UA levels as a predictor of affective psychosis and glucose dysfunction as predictive of schizophrenia. Further studies are needed to explore metabolic parameters as possible diagnostic predictors in first-episode psychosis.

Neuroinflammation and neuroprogression produced by oxidative stress in euthymic bipolar patients with different onset disease times

Bipolar disorder (BD) is associated with systemic toxicity, represented by changes in biomarkers associated with mood episodes, leading to neurological damage, which may reflect cognitive functions and functionality and the progression of the disease. We aimed to analyze the effect of four biomarkers, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and thiobarbituric acid reactive substances (TBA-RS), related to oxidative stress in BD and to correlate them with cognitive functions and functionality. We studied 50 bipolar types I/II patients in the euthymic phase, which was divided into two subgroups with 25 patients each (≤ 3 years and ≥ 10 years of diagnosis, from the first episode of mania) and 25 control patients. To analyze frontal cognitive functions and functionality, we used the Frontal Assessment Battery (FAB) and Functioning Assessment Short Test (FAST) tests, respectively. The scores of the FAST and FAB tests showed an increase and decrease respectively, in both bipolar groups, when compared to the control group, demonstrating impairment in cognitive functions and functionality since the disease onset. In addition, changes occurred in all six domains of the FAST test, and in four domains of the FAB test in bipolar patients when compared to the control group. Regarding oxidative stress biomarkers, we did not find changes in SOD and GSH-Px activities; however, a significant increase in CAT activity and lipid peroxidation was observed in both groups, although the patients were euthymic and medicated. These results allow us to raise the hypothesis that since the beginning of the disease, the euthymic bipolar patient has presented a level of oxidative stress, which gets worse with the evolution of the disease, promoting impairments in the frontal cognitive functions and functionality gradually.

[The staging model (or evolutionary stages) applied to bipolar disorder]

In psychiatry, clinical staging raises awareness of the need to understand disease trajectories and heterotypic continuity; it draws attention to individuals at risk of developing disorders, such as those with a family history or subsyndromal presentations; and it actively promotes greater attention to prevention strategies and interventions for individuals at ultra-high risk of developing a severe mental disorder. Staging paradigms have been increasingly applied in early intervention in psychoses, but there are issues in broadening the scope of clinical staging to the more prevalent affective disorders. For example, it is potentially more complex to devise a model that considers the varying clinical presentations of the late prodromal stage of bipolar disorder and where to locate depressive episodes that precede the first manic episode and how to describe subthreshold manic syndromes, especially hypomania. The above issues might be resolved if we had a greater understanding of the risk factors, biomarkers or endophenotypes for the onset and progression of bipolar disorder. This level of understanding is not yet available in psychiatry, but clinical staging may help us improve our knowledge of the pathophysiological correlates of disease progression and reduce our over-reliance on cross-sectional assessments of symptoms in bipolar disorders.

Illness, at-risk and resilience neural markers of early-stage bipolar disorder

BACKGROUND

Current knowledge on objective and specific neural markers for bipolar risk and resilience-related processes is lacking, partly due to not subdividing high-risk individuals manifesting different levels of subclinical symptoms who possibly possess different levels of resilience.

METHODS

We delineated grey matter markers for bipolar illness, genetic high risk (endophenotype) and resilience, through comparing across 42 young non-comorbid bipolar patients, 42 healthy controls, and 72 diagnosis-free, medication-naive high-genetic-risk individuals subdivided into a combined-high-risk group who additionally manifested bipolar risk-relevant subsyndromes (N = 38), and an asymptomatic high-risk group (N = 34). Complementary analyses assessed the additional predictive and classification values of grey matter markers beyond those of clinical scores, through using logistic regression and support vector machine analyses.

RESULTS

Illness-related effects manifested as reduced grey matter volumes of bilateral temporal limbic-striatal and cerebellar regions, which significantly differentiated bipolar patients from healthy controls and improved clinical classification specificity by 20%. Reduced bilateral cerebellar grey matter volume emerged as a potential endophenotype and (along with parieto-occipital grey matter changes) separated combined-high-risk individuals from healthy and high-risk individuals, and increased clinical classification specificity by approximately 10% and 27%, respectively, while the relatively normalized cerebellar grey matter volumes in the high-risk sample may confer resilience.

LIMITATIONS

The cross-validation procedure was not performed on an independent sample using independently-derived features. The BD group had different age and sex distributions than some other groups which may not be fully addressable statistically.

CONCLUSIONS

Our framework can be applied in other measurement domains to derive complete profiles for bipolar patients and at-risk individuals, towards forming strategies for promoting resilience and preclinical intervention.

The differential association between history of childhood sexual abuse and body mass index in early and late stages of bipolar disorder

BACKGROUND

History of distal stressors such as childhood trauma is a well-established, non-specific vulnerability factor for multiple mental illnesses. The objective of this study was to investigate the possible association between history of childhood trauma and body mass index (BMI) in individuals in early and late stages of bipolar disorder (BD) and to verify is there was any difference in the association of sexual abuse history and obesity in early versus late stages of BD.

METHODS

Seventy-one euthymic BD-type I patients and eighty-one healthy controls were evaluated using the Childhood Trauma Questionnaire (CTQ) and body mass index (BMI). The association between BMI and CTQ total and subscores were evaluated dividing BD population in early-stage BD-I (less than 10 years since onset of disease) or late-stage BD (more than 10 years).

RESULTS

BD individuals had higher rates of history of childhood trauma than HC, especially sexual and emotional abuse, after adjusting for confounders. We observed a moderating effect of group on the association between BMI and sexual abuse (SA), but not on other modalities of childhood trauma, after adjustments for age, gender, ethnicity, education, alcohol and tobacco use.

LIMITATIONS

Our sample included a predominance of female individuals. The study cross-sectional design does not allow concluding a cause-effect relationship. In dividing the BD subgroups in relation with the time since the onset, we supposed that the natural course of BD is linear. The CTQ is subject to recall bias.

CONCLUSION

There is a relationship between childhood sexual abuse and BMI, but the direction of the association varies across the different stages of BD-I.

BDNF and BMI effects on brain structures of bipolar offspring: results from the global mood and brain science initiative

OBJECTIVE

To compare brain-derived neurotrophic factor (BDNF) levels between offspring of individuals with bipolar disorders (BD) and healthy controls (HCs) and investigate the effects of BDNF levels and body mass index (BMI) on brain structures.

METHOD

Sixty-seven bipolar offspring and 45 HCs were included (ages 8-28). Structural images were acquired using 3.0 Tesla magnetic resonance imaging. Serum BDNF levels were measured using enzyme-linked immunosorbent assay. Multivariate and univariate analyses of covariance were conducted.

RESULTS

Significantly higher BDNF levels were observed among bipolar offspring, relative to HCs (P > 0.025). Offspring status moderated the association between BDNF and BMI (F₁ =4.636, P = 0.034). After adjustment for relevant covariates, there was a trend for a significant interaction of group and BDNF on neuroimaging parameters (Wilks'λ F_56,94 =1.463, P = 0.052), with significant effects on cerebellar white matter and superior and middle frontal regions. Brain volume and BDNF were positively correlated among HCs and negatively correlated among bipolar offspring. Interactions between BDNF and BMI on brain volumes were non-significant among HCs (Wilks'λ F_28,2 =2.229, P = 0.357), but significant among bipolar offspring (Wilks'λ F_28,12 =2.899, P = 0.028).

CONCLUSION

Offspring status and BMI moderate the association between BDNF levels and brain structures among bipolar offspring, underscoring BDNF regulation and overweight/obesity as key moderators of BD pathogenesis.

1H-NMR, 1H-NMR T2-edited, and 2D-NMR in bipolar disorder metabolic profiling

Background

The objective of this study was to identify molecular alterations in the human blood serum related to bipolar disorder, using nuclear magnetic resonance (NMR) spectroscopy and chemometrics.

Methods

Metabolomic profiling, employing ¹H-NMR, ¹H-NMR T₂-edited, and 2D-NMR spectroscopy and chemometrics of human blood serum samples from patients with bipolar disorder (n = 26) compared with healthy volunteers (n = 50) was performed.

Results

The investigated groups presented distinct metabolic profiles, in which the main differential metabolites found in the serum sample of bipolar disorder patients compared with those from controls were lipids, lipid metabolism-related molecules (choline, myo-inositol), and some amino acids (N-acetyl-l-phenyl alanine, N-acetyl-l-aspartyl-l-glutamic acid, l-glutamine). In addition, amygdalin, α-ketoglutaric acid, and lipoamide, among other compounds, were also present or were significantly altered in the serum of bipolar disorder patients. The data presented herein suggest that some of these metabolites differentially distributed between the groups studied may be directly related to the bipolar disorder pathophysiology.

Conclusions

The strategy employed here showed significant potential for exploring pathophysiological features and molecular pathways involved in bipolar disorder. Thus, our findings may contribute to pave the way for future studies aiming at identifying important potential biomarkers for bipolar disorder diagnosis or progression follow-up.

Electronic supplementary material

The online version of this article (doi:10.1186/s40345-017-0088-2) contains supplementary material, which is available to authorized users.