Correlations between amygdala volumes and serum levels of BDNF and NGF as a neurobiological markerin adolescents with bipolar disorder

Gray matter alterations in adolescent major depressive disorder and adolescent bipolar disorder

BACKGROUND

Gray matter volume (GMV) alterations in several emotion-related brain areas are implicated in mood disorders, but findings have been inconsistent in adolescents with major depressive disorder (MDD) or bipolar disorder (BD).

METHODS

We conducted a comprehensive meta-analysis of 35 region-of-interest (ROI) and 18 whole-brain voxel-based morphometry (VBM) MRI studies in adolescent MDD and adolescent BD, and indirectly compared the results in the two groups. The effects of age, sex, and other demographic and clinical scale scores were explored using meta-regression analysis.

RESULTS

In the ROI meta-analysis, right putamen volume was decreased in adolescents with MDD, while bilateral amygdala volume was decreased in adolescents with BD compared to healthy controls (HC). In the whole-brain VBM meta-analysis, GMV was increased in right middle frontal gyrus and decreased in left caudate in adolescents with MDD compared to HC, while in adolescents with BD, GMV was increased in left superior frontal gyrus and decreased in limbic regions compared with HC. MDD vs BD comparison revealed volume alteration in the prefrontal-limbic system.

LIMITATION

Different clinical features limit the comparability of the samples, and small sample size and insufficient clinical details precluded subgroup analysis or meta-regression analyses of these variables.

CONCLUSIONS

Distinct patterns of GMV alterations in adolescent MDD and adolescent BD could help to differentiate these two populations and provide potential diagnostic biomarkers.

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.

Elevated Epidermal Growth Factor (EGF) as Candidate Biomarker of Mood Disorders-Longitudinal Study in Adolescent and Young Adult Patients

Bipolar disorder (BD) is a chronic mental disorder that affects more than 1% of the population worldwide. Over 65% of patients experience early onset of the disease. Most cases of juvenile bipolar disorder begin with a depressed mood episode, and up to 50% of youth initially diagnosed with major depression go onto developing a BD. Our study aimed to find biomarkers of diagnosis conversion in young patients with mood disorders. We performed a two-year follow-up study on 79 adolescent patients diagnosed with MDD or BD, with a detailed clinical assessment at five visits. We monitored diagnosis change from MDD to BD. The control group consisted of 31 healthy youths. According to the neurodevelopmental and neuroimmunological hypotheses of mood disorders, we analyzed serum levels of brain-derived neurotrophic factor (BDNF), proBDNF, epidermal growth factor (EGF), migration inhibitory factor (MIF), stem cell factor (SCF), and correlations with clinical factors. We detected a significant disease-dependent increase in EGF level in MDD and BP patients at baseline exacerbation of depressive or hypomanic/manic episodes as well as in euthymic state compared to healthy controls. No potential biological predictors of disease conversion were found. Replication studies on a larger cohort of patients are needed.

The Amygdala in Schizophrenia and Bipolar Disorder: A Synthesis of Structural MRI, Diffusion Tensor Imaging, and Resting-State Functional Connectivity Findings

Frequently implicated in psychotic spectrum disorders, the amygdala serves as an important hub for elucidating the convergent and divergent neural substrates in schizophrenia and bipolar disorder, the two most studied groups of psychotic spectrum conditions. A systematic search of electronic databases through December 2017 was conducted to identify neuroimaging studies of the amygdala in schizophrenia and bipolar disorder, focusing on structural MRI, diffusion tensor imaging (DTI), and resting-state functional connectivity studies, with an emphasis on cross-diagnostic studies. Ninety-four independent studies were selected for the present review (49 structural MRI, 27 DTI, and 18 resting-state functional MRI studies). Also selected, and analyzed in a separate meta-analysis, were 33 volumetric studies with the amygdala as the region-of-interest. Reduced left, right, and total amygdala volumes were found in schizophrenia, relative to both healthy controls and bipolar subjects, even when restricted to cohorts in the early stages of illness. No volume abnormalities were observed in bipolar subjects relative to healthy controls. Shape morphometry studies showed either amygdala deformity or no differences in schizophrenia, and no abnormalities in bipolar disorder. In contrast to the volumetric findings, DTI studies of the uncinate fasciculus tract (connecting the amygdala with the medial- and orbitofrontal cortices) largely showed reduced fractional anisotropy (a marker of white matter microstructure abnormality) in both schizophrenia and bipolar patients, with no cross-diagnostic differences. While decreased amygdalar-orbitofrontal functional connectivity was generally observed in schizophrenia, varying patterns of amygdalar-orbitofrontal connectivity in bipolar disorder were found. Future studies can consider adopting longitudinal approaches with multimodal imaging and more extensive clinical subtyping to probe amygdalar subregional changes and their relationship to the sequelae of psychotic disorders.

Brain-derived neurotrophic factor association with amygdala response in major depressive disorder

BACKGROUND

Brain-derived neurotrophic factor (BDNF) has an essential role in synaptic plasticity and neurogenesis. BDNF mediates amygdala-dependent learning for both aversive and appetitive emotional memories. The expression of BDNF in limbic regions is posited to contribute the development of depression, and amygdala responsivity is a potential marker of depressive state.

METHODS

The present study examined the relationship between platelet BDNF levels and amygdala volume and function in major depressive disorder (MDD). Participants were 23 MDD (mean age 38.9 years) and 23 healthy controls (mean age 38.8 years). All participants were recruited from the community. MDD participants were in a current depressive episode of moderate severity and medication-free. Amygdala responses were acquired during a functional MRI task of implicit emotional processing with sad facial expressions.

RESULTS

Significant correlation was observed between platelet BDNF levels and left amygdala responses, but no significant correlations were found with right amygdala responses or with amygdala volumes.

LIMITATIONS

Interactions with neuroprotective as well as neurotoxic metabolites in the kyneurenine pathway were not examined.

CONCLUSIONS

Relationship between BDNF levels and amygdala responsivity to emotionally salient stimuli in MDD could reflect the importance of BDNF in amygdala-dependent learning with clinical implications for potential pathways for treatment.

Structural variation in the glycogen synthase kinase 3β and brain-derived neurotrophic factor genes in Japanese patients with bipolar disorders

Background

Lithium is the first‐line drug for the treatment of bipolar disorders (BDs); however, not all patients responded. Glycogen synthase kinase (GSK) 3β and brain‐derived neurotrophic factor (BDNF) play a role in the therapeutic action of lithium. Since structural variations were reported in these genes, it is possible that these genomic variations may be involved in the therapeutic responses to lithium.

Method

Fifty patients with BDs and 50 healthy subjects (mean age 55.0 ± 15.0 years; M/F 19/31) participated. We examined structural variation of the GSK3β and BDNF genes by real‐time PCR. We examined the influence of structural variation of these genes on the therapeutic responses to lithium and the occurrence of antidepressant‐emergent affective switch (AEAS). The efficacy of lithium was assessed using the Alda scale, and AEAS was evaluated using Young Mania Rating Scale.

Results

Although we examined structural variations within intron II and VII of the GSK3^® gene and from the end of exon IV to intron IV and within exon IX of the BDNF gene, no structural variation was found in BDs. Whereas 5 of 50 patients exhibited three copies of the genomic region within exon IV of the BDNF gene, all healthy subjects had two copies. No difference in the therapeutic efficacy of lithium was found between patients with three and two copies. No difference in the occurrence of AEAS was found between the two groups.

Conclusion

The amplification of the BDNF gene influenced neither the therapeutic responses to lithium nor the occurrence of AEAS.

Five of 50 patients with bipolar disorders exhibited three copies of the genomic region within exon IV of the BDNF gene. But, 50 healthy subjects had two copies. This amplification did not affect the therapeutic responses to lithium.

BDNF, endurance activity, and mechanisms underlying the evolution of hominin brains

OBJECTIVES

As a complex, polygenic trait, brain size has likely been influenced by a range of direct and indirect selection pressures for both cognitive and non-cognitive functions and capabilities. It has been hypothesized that hominin brain expansion was, in part, a correlated response to selection acting on aerobic capacity (Raichlen & Polk, 2013). According to this hypothesis, selection for aerobic capacity increased the activity of various signaling molecules, including those involved in brain growth. One key molecule is brain-derived neurotrophic factor (BDNF), a protein that regulates neuronal development, survival, and plasticity in mammals. This review updates, partially tests, and expands Raichlen and Polk's (2013) hypothesis by evaluating evidence for BDNF as a mediator of brain size.

DISCUSSION

We contend that selection for endurance capabilities in a hot climate favored changes to muscle composition, mitochondrial dynamics and increased energy budget through pathways involving regulation of PGC-1α and MEF2 genes, both of which promote BDNF activity. In addition, the evolution of hairlessness and the skin's thermoregulatory response provide other molecular pathways that promote both BDNF activity and neurotransmitter synthesis. We discuss how these pathways contributed to the evolution of brain size and function in human evolution and propose avenues for future research. Our results support Raichlen and Polk's contention that selection for non-cognitive functions has direct mechanistic linkages to the evolution of brain size in hominins.

The International Society for Bipolar Disorders Task Force report on pediatric bipolar disorder: Knowledge to date and directions for future research

OBJECTIVES

Over the past two decades, there has been tremendous growth in research regarding bipolar disorder (BD) among children and adolescents (ie, pediatric BD [PBD]). The primary purpose of this article is to distill the extant literature, dispel myths or exaggerated assertions in the field, and disseminate clinically relevant findings.

METHODS

An international group of experts completed a selective review of the literature, emphasizing areas of consensus, identifying limitations and gaps in the literature, and highlighting future directions to mitigate these gaps.

RESULTS

Substantial, and increasingly international, research has accumulated regarding the phenomenology, differential diagnosis, course, treatment, and neurobiology of PBD. Prior division around the role of irritability and of screening tools in diagnosis has largely abated. Gold-standard pharmacologic trials inform treatment of manic/mixed episodes, whereas fewer data address bipolar depression and maintenance/continuation treatment. Adjunctive psychosocial treatment provides a forum for psychoeducation and targets primarily depressive symptoms. Numerous neurocognitive and neuroimaging studies, and increasing peripheral biomarker studies, largely converge with prior findings from adults with BD.

CONCLUSIONS

As data have accumulated and controversy has dissipated, the field has moved past existential questions about PBD toward defining and pursuing pressing clinical and scientific priorities that remain. The overall body of evidence supports the position that perceptions about marked international (US vs elsewhere) and developmental (pediatric vs adult) differences have been overstated, although additional research on these topics is warranted. Traction toward improved outcomes will be supported by continued emphasis on pathophysiology and novel therapeutics.

All-Trans-Retinoic Acid Stimulates Overexpression of Tumor Protein D52 (TPD52, Isoform 3) and Neuronal Differentiation of IMR-32 Cells

Tumor protein D52 (TPD52), a proto-oncogene is overexpressed in a variety of epithelial carcinomas and plays an important role in cell proliferation, migration, and cell death. In the present study we found that the treatment of IMR-32 neuroblastoma (NB) cells with retinoic acid (RA) stimulates an increase in expression of TPD52. TPD52 expression is detectable after 72 h, can be maintained till differentiation of NB cells suggesting that TPD52 is involved in differentiation. Here, we demonstrate that TPD52 is essential for RA to promote differentiation of NB cells. Our results show that exogenous expression of EGFP-TPD52 in IMR-32 cells resulted cell differentiation even without RA. RA by itself and with overexpression of TPD52 can increase the ability of NB cells differentiation. Interestingly, transfection of IMR-32 cells with a specific small hairpin RNA for efficient knockdown of TPD52 attenuated RA induced NB cells differentiation. Transcriptional and translational level expression of neurotropic (BDNF, NGF, Nestin) and differentiation (β III tubulin, NSE, TH) factors in NB cells with altered TPD52 expression and/or RA treatment confirmed essential function of TPD52 in cellular differentiation. Furthermore, we show that TPD52 protects cells from apoptosis and arrest cell proliferation by varying expression of p27Kip1, activation of Akt and ERK1/2 thus promoting cell differentiation. Additionally, inhibition of STAT3 activation by its specific inhibitor arrested NB cells differentiation by EGFP-TPD52 overexpression with or without RA. Taken together, our data reveal that TPD52 act through activation of JAK/STAT signaling pathway to undertake NB cells differentiation induced by RA. J. Cell. Biochem. 118: 4358-4369, 2017. © 2017 Wiley Periodicals, Inc.

Peripheral blood nerve growth factor levels in major psychiatric disorders

Nerve growth factor (NGF) plays crucial roles in promoting neural growth and survival, and mediating synaptic and morphological plasticity. Several studies investigated the correlation between peripheral NGF levels and major psychiatric disorders, including schizophrenia (SCZ), major depressive disorder (MDD) and bipolar disorder (BPD); however, the findings were inconsistent. This meta-analysis sought to investigate blood NGF levels in patients with psychiatric disorders compared with healthy subjects and examined potential effects of blood fraction, medication and disease status. A total of 21 eligible studies, encompassing 1342 patients suffering from psychiatric disorders and 1225 healthy subjects, were enrolled in the present meta-analysis. No obvious publication bias was observed either for SCZ, MDD or BPD by the Begg's test (P > 0.05). Random-effects meta-analysis showed that SCZ (Z = 2.14, P = 0.033, SMD = -1.08, 95% CI = -2.07 to -0.09) and MDD (Z = 2.57, P = 0.010, SMD = -0.61, 95% CI = -1.08 to -0.14) patients had significantly reduced NGF levels, compared with healthy controls. Notably, this decrease was enhanced in un-medicated patients of SCZ (P = 0.004) and medicated or chronic patients of MDD (P < 0.001). No significant difference of NGF levels was observed between BPD patients and controls (P > 0.05). These results supported an association between the reduction of NGF levels and psychiatric disorders. It remains unclear whether the change of NGF levels is a prerequisite for its function in psychiatric disorders development or merely an epiphenomenon unrelated to the pathophysiologic mechanisms.

Proteomic analysis of the postsynaptic density implicates synaptic function and energy pathways in bipolar disorder

The postsynaptic density (PSD) contains a complex set of proteins of known relevance to neuropsychiatric disorders such as schizophrenia and bipolar disorder. We enriched for this anatomical structure in the anterior cingulate cortex of 16 bipolar disorder samples and 20 controls from the Stanley Medical Research Institute. Unbiased shotgun proteomics incorporating label-free quantitation was used to identify differentially expressed proteins. Quantitative investigation of the PSD identified 2033 proteins, among which 288 were found to be differentially expressed. Validation of expression changes of DNM1, DTNA, NDUFV2, SEPT11 and SSBP was performed by western blotting. Bioinformatics analysis of the differentially expressed proteins implicated metabolic pathways including mitochondrial function, the tricarboxylic acid cycle, oxidative phosphorylation, protein translation and calcium signaling. The data implicate PSD-associated proteins, and specifically mitochondrial function in bipolar disorder. They relate synaptic function in bipolar disorder and the energy pathways that underpin it. Overall, our findings add to a growing literature linking the PSD and mitochondrial function in psychiatric disorders generally, and suggest that mitochondrial function associated with the PSD is particularly important in bipolar disorder.