Glutamate level detection by magnetic resonance spectroscopy in patients with post-stroke depression

Innate immunity-mediated neuroinflammation promotes the onset and progression of post-stroke depression

Post-stroke depression (PSD) is a prevalent psychiatric disorder after stroke, with the incidence of approximately one-third among stroke survivors. It is classified as an organic mental disorder and has a well-documented association with stroke affecting various aspects of patients, such as the recovery of limb motor function, daily living self-care ability, and increasing the mortality of stroke survivors. However, the pathogenesis of PSD is not yet fully understood. Currently, immune inflammation is a research hotspot. This review focuses on the pathogenesis of PSD, particularly elucidating the role of inflammation in mediating neuroinflammation through innate immunity. Simultaneously, we highlight that peripheral inflammation following a stroke may trigger a detrimental cycle of neuroinflammation by activating innate immune pathways within the central nervous system, which could potentially contribute to the development of PSD. Lastly, we summarize potential treatments for PSD and propose targeting cytokines and innate immune pathways as novel therapeutic approaches.

Association between post-stroke depression and functional outcomes: A systematic review

BACKGROUND

Post-stroke depression (PSD) is a frequent problem in stroke patients, affecting their rehabilitation process and functional outcomes. Several studies have investigated the relationship between PSD and functional outcomes, but the results have been inconsistent.

OBJECTIVE

This systematic review of non-experimental studies aims to investigate the prevalence of post-stroke depression and the association between post-stroke depression and functional outcomes.

METHOD

A search of PubMed, MEDLINE, Web of Science, and CINAHL Plus with Full Text was carried out from inception until January 2024. The literature was screened using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, with relevant papers included. We extracted data from non-experimental studies that examined associations between PSD and functional outcomes. The Joanna Briggs Institute for systematic reviews was used for critical appraisal.

RESULTS

Twenty-one studies met the study criteria, including sixteen cohort studies, four cross-sectional studies, and one case-control study. PSD prevalences ranged from 12.2% to 32.2% in the first two weeks, 17.9 to 35.5% in the first month, and 10.4% to 32.0% in the third month following a stroke. Functional outcomes were evaluated in four domains: degree of dependence, basic activity of daily living, instrumental activity of daily living, and physical and cognitive function. Significant associations between PSD and functional outcomes were identified after controlling potential factors such as age, comorbidities, and stroke severity. PSD had negative associations with functional outcomes in all four measure domains from one month to five years after a stroke. Depression treatment showed positive results on functional outcomes in stroke patients.

CONCLUSION

PSD prevalence was high in the first three months after stroke. PSD is significantly associated with poor functional outcomes. PSD assessment and management should be performed on a frequent basis in the early stages of stroke to achieve the best possible functional recovery.

Association between baseline high-sensitive C-reactive protein, homocysteine levels, and post-stroke depression among stroke patients: a systematic review, meta-analysis, and meta-regression

BACKGROUND

Post-stroke depression (PSD) is a prevalent neuropsychiatric sequelae following stroke, often associated with diminished functional recovery and heightened mortality risk. Emerging evidence suggests neuroinflammation, triggered in response to stroke events, may be instrumental in precipitating PSD.

AIM

This study aims to assess the significance of high-sensitivity C-reactive protein (Hs-CRP) and homocysteine (Hcy) in post-stroke individuals with PSD.

METHODS

We systematically searched all electronic databases from inception until May 30, 2023. Outcomes were reported as standard mean difference (SMD), and their corresponding 95% confidence interval (95% CI).

RESULTS

A total of 12 studies with 3,230 patients were included in this study. The mean age of the overall cohort was 65.7 years, and patients with PSD were observed to be older than patients without PSD (68.3 years versus 63.1 years). We observed a higher female prevalence in the PSD group (44.4% versus 40.7%). PSD patients were more likely to be widowed (19.4% versus 8.4%) and more likely to have a family history of psychiatric disorder (11.3% versus 4.9%) compared to non-PSD patients. We also observed that patients with PSD had higher levels of baseline Hs-CRP [SMD 0.16, (95% CI 0.08 to 0.25), p<0.001], and Hcy [SMD 0.14, (95% CI 0.05 to 0.22), p<0.001] than patients without PSD. Meta-regression analysis did not reveal any effect modifier for higher Hs-CRP in the study group, however, history of widowhood was a significant effect modifier when assessing Hcy levels between the two groups (coefficient 1.998, p=0.038).

CONCLUSION

Baseline levels of Hs-CRP and Hcy were significantly higher in patients with PSD, highlighting the role of recognizing demographic and biochemical markers in understanding the complexities of post-stroke depression.

Astrocytes in Post-Stroke Depression: Roles in Inflammation, Neurotransmission, and Neurotrophin Signaling

Post-stroke depression (PSD) is a frequent and disabling complication of stroke that affects up to one-third of stroke survivors. The pathophysiology of PSD involves multiple mechanisms, including neurochemical, neuroinflammatory, neurotrophic, and neuroplastic changes. Astrocytes are a type of glial cell that is plentiful and adaptable in the central nervous system. They play key roles in various mechanisms by modulating neurotransmission, inflammation, neurogenesis, and synaptic plasticity. This review summarizes the latest evidence of astrocyte involvement in PSD from human and animal studies, focusing on the alterations of astrocyte markers and functions in relation to monoamine neurotransmitters, inflammatory cytokines, brain-derived neurotrophic factor, and glutamate excitotoxicity. We also discuss the potential therapeutic implications of targeting astrocytes for PSD prevention and treatment. Astrocytes could be new candidates for antidepressant medications and other interventions that aim to restore astrocyte homeostasis and function in PSD. Astrocytes could be new candidates for antidepressant medications and other interventions that aim to restore astrocyte homeostasis and function in PSD.

Altered neurotransmission in stress-induced depressive disorders: The underlying role of the amygdala in depression

Depression is the second leading cause of disability in the world population, for which currently available pharmacological therapies either have poor efficacy or have some adverse effects. Accumulating evidence from clinical and preclinical studies demonstrates that the amygdala is critically implicated in depressive disorders, though the underlying pathogenesis mechanism needs further investigation. In this literature review, we overviewed depression and the key role of Gamma-aminobutyric acid (GABA) and Glutamate neurotransmission in depression. Notably, we discussed a new cholecystokinin-dependent plastic changes mechanism under stress and a possible antidepressant response of cholecystokinin B receptor (CCKBR) antagonist. Moreover, we discussed the fundamental role of the amygdala in depression, to discuss and understand the pathophysiology of depression and the inclusive role of the amygdala in this devastating disorder.

Machine learning algorithms assisted identification of post-stroke depression associated biological features

Objectives

Post-stroke depression (PSD) is a common and serious psychiatric complication which hinders functional recovery and social participation of stroke patients. Stroke is characterized by dynamic changes in metabolism and hemodynamics, however, there is still a lack of metabolism-associated effective and reliable diagnostic markers and therapeutic targets for PSD. Our study was dedicated to the discovery of metabolism related diagnostic and therapeutic biomarkers for PSD.

Methods

Expression profiles of GSE140275, GSE122709, and GSE180470 were obtained from GEO database. Differentially expressed genes (DEGs) were detected in GSE140275 and GSE122709. Functional enrichment analysis was performed for DEGs in GSE140275. Weighted gene co-expression network analysis (WGCNA) was constructed in GSE122709 to identify key module genes. Moreover, correlation analysis was performed to obtain metabolism related genes. Interaction analysis of key module genes, metabolism related genes, and DEGs in GSE122709 was performed to obtain candidate hub genes. Two machine learning algorithms, least absolute shrinkage and selection operator (LASSO) and random forest, were used to identify signature genes. Expression of signature genes was validated in GSE140275, GSE122709, and GSE180470. Gene set enrichment analysis (GSEA) was applied on signature genes. Based on signature genes, a nomogram model was constructed in our PSD cohort (27 PSD patients vs. 54 controls). ROC curves were performed for the estimation of its diagnostic value. Finally, correlation analysis between expression of signature genes and several clinical traits was performed.

Results

Functional enrichment analysis indicated that DEGs in GSE140275 enriched in metabolism pathway. A total of 8,188 metabolism associated genes were identified by correlation analysis. WGCNA analysis was constructed to obtain 3,471 key module genes. A total of 557 candidate hub genes were identified by interaction analysis. Furthermore, two signature genes (SDHD and FERMT3) were selected using LASSO and random forest analysis. GSEA analysis found that two signature genes had major roles in depression. Subsequently, PSD cohort was collected for constructing a PSD diagnosis. Nomogram model showed good reliability and validity. AUC values of receiver operating characteristic (ROC) curve of SDHD and FERMT3 were 0.896 and 0.964. ROC curves showed that two signature genes played a significant role in diagnosis of PSD. Correlation analysis found that SDHD (r = 0.653, P &lt; 0.001) and FERM3 (r = 0.728, P &lt; 0.001) were positively related to the Hamilton Depression Rating Scale 17-item (HAMD) score.

Conclusion

A total of 557 metabolism associated candidate hub genes were obtained by interaction with DEGs in GSE122709, key modules genes, and metabolism related genes. Based on machine learning algorithms, two signature genes (SDHD and FERMT3) were identified, they were proved to be valuable therapeutic and diagnostic biomarkers for PSD. Early diagnosis and prevention of PSD were made possible by our findings.

Peripheral blood and urine metabolites and biological functions in post-stroke depression

Post-stroke depression (PSD) is the most common and severe neuropsychiatric complication after stroke. However, the molecular mechanism of PSD is still unclear. Previous studies have identified peripheral blood and urine metabolites associated with PSD using metabolomics techniques. We searched and systematically summarized metabolites that may be involved in metabolic changes in peripheral blood and urine of patients with PSD from the Metabolite Network of Depression Database (MENDA) and other biomedical databases. MetaboAnalyst5.0 software was used for pathway analysis and enrichment analysis of differential metabolites, and subgroup analyses were performed according to tissue types and metabolomics techniques. We identified 47 metabolites that were differentially expressed between patients with and without PSD. Five differential metabolites were found in both plasma and urine, including L-glutamic acid, pyroglutamic acid, palmitic acid, L-phenylalanine, and L-tyrosine. We integrated these metabolites into metabolic pathways, and six pathways were significantly altered. These pathways could be roughly divided into three modules including amino acid metabolism, nucleotide metabolism, and glucose metabolism. Among them, the most significantly altered pathway was "phenylalanine metabolism" and the pathway containing the most associated metabolites was "aminoacyl-tRNA biosynthesis", which deserve further study to elucidate their role in the molecular mechanism of PSD. In summary, metabolic changes in peripheral blood and urine are associated with PSD, especially the disruption of "phenylalanine metabolism" and "aminoacyl-tRNA biosynthesis" pathways. This study provides clues to the metabolic characteristics of patients with PSD, which may help to elucidate the molecular pathogenesis of PSD.

Childhood trauma history is linked to abnormal brain metabolism of non-medicated adult patients with major depressive disorder

OBJECTIVES

Childhood trauma is a risk factor that may lead to persistent brain metabolic abnormalities, predisposing individuals to major depressive disorder (MDD). To better elucidate the pathogenesis of MDD, we investigated the neurometabolic changes in unmedicated MDD patients who had experienced childhood trauma (CT).

METHODS

In this study, 37 unmedicated MDD patients with CT, 35 unmedicated MDD patients without CT, and 30 healthy control participants underwent high-resolution proton magnetic resonance spectroscopy (¹H-MRS) examination. Bilateral metabolic ratios of N-acetylaspartate (NAA)/creatine (Cr) and choline (Cho)/Cr in the prefrontal white matter (PWM), anterior cingulate cortex (ACC), putamen, and cerebellum were obtained.

RESULTS

MDD patients showed neurometabolic changes in the cortico-striato-cerebellar (CSC) circuit. Furthermore, MDD patients showed significantly lower NAA/Cr and higher Cho/Cr ratio in the bilateral ACC and putamen, and higher NAA/Cr and lower Cho/Cr ratio in the cerebellum. Childhood trauma reduced the Cho/Cr ratio in the left ACC, which played an important role in longer and more episodes of depression.

CONCLUSION

Early childhood trauma has a long-lasting impact on the metabolism of adult MDD patients, leading to abnormal choline metabolism of the left ACC. Abnormal biochemical metabolism in the CSC circuit may be an underlying pathophysiology of MDD.

LIMITATION

As this is a small cross-sectional study, the impact of childhood trauma on the different stages of depression has not been observed.

Repetitive xenon treatment improves post-stroke sensorimotor and neuropsychiatric dysfunction

Stroke is a life-changing event as stroke survivors experience changes in personality, emotions and mood. We investigated the effect of xenon gas encapsulated in liposomes on stroke-generated sensorimotor impairments, and anxiety- and depression-like phenotypes. Ischemic stroke was created by the intraluminal middle cerebral artery occlusion (MCAO) for 6 h followed by reperfusion in rats. Xenon-liposome (6 mg/kg, intravenous) treatment was given multiple times starting at 2 h post-ischemia through 6 h (5X), and once-daily for next 3 days. Rats underwent ischemic injury displayed sensorimotor deficits in the adhesive removal, vibrissae-evoked forelimb placement and rotarod tests. These animals also made lesser entries and spent less time on open arms of the elevated-plus maze and swam more in passive mode in the forced swimming test, indicating anxiety- and depression-like behaviors at 28- and 35-days post-injury, respectively. Repeated intravenous treatment with xenon-liposomes ameliorated these behavioral aberrations (p < 0.05). Gut microbiome analysis (16S ribosomal-RNA gene sequencing) showed a decrease in the Clostridium clusters XI, XIVa, XVIII and Lactobacillus bacterium, and increase of the Prevotella in the xenon-liposome group. No microbiota communities were majorly affected across the treatments. Moreover, xenon treatment group showed augmented plasma levels of IL-6 cytokines (∼5 fold) on day-35 post-ischemia, while no change was noticed in the IL-1β, IL-4, IL-10, IL-13 and MCP-1 levels. Our data highlights the safety, behavioral recovery and reversal of post-stroke brain injury following xenon-liposome treatment in an extended ischemic model. These results show the potential for this treatment strategy to be translated to patients with stroke.

Depression after stroke

Stroke treatment has dramatically improved in recent decades. However, although new treatments have reduced its mortality and the severity of its physical and cognitive sequelae, many people still have incapacitating disabilities following a stroke. Depression is the most common psychiatric disorder following stroke; it is important to recognise and treat as it limits motor and cognitive rehabilitation. Antidepressant medication is an effective treatment and can improve adherence to clinically recommended physical and cognitive tasks, thereby enhancing functional remodelling of neuronal pathways and improving rehabilitation outcomes.

Decreased Serum Netrin-1 as a Predictor for Post-Stroke Depression in Chinese Patients with Acute Ischemic Stroke

BACKGROUND AND AIMS

Experimental studies demonstrated that netrin-1 (NT-1) is an important factor influencing the recovery after ischemic stroke. However, whether NT-1 levels were associated with the post-stroke depression (PSD) remains unclear. We aimed to evaluate the relationship between NT-1 levels and PSD at 3 months in patients with ischemic stroke.

METHODS

From January 2018 to December 2019, consecutive Chinese patients with first-ever ischemic stroke were prospectively recruited. Serum NT-1 levels were measured at admission. Patients with a 17-item Hamilton Depression Scale score of ≥7 were given the Structured Clinical Interview of the Diagnostic and Statistical Manual of Mental Disorders, 4th edition, for diagnosis of PSD.

RESULTS

A total of 238 patients (mean age, 62.5 years; 45.4% female) were enrolled. The median NT-1 concentrations were 467.8 pg/mL (interquartile range, 351.8-581.0 pg/mL). During the 3-month follow-up period, 64 patients (26.9%) experienced PSD. Serum NT-1 levels were significantly lower in PSD patients than in patients without PSD (median, 380.3 pg/mL versus 478.5 pg/mL; P = 0.001). After adjusting for demographic characteristic, National Institutes of Health stroke score, and other potential confounders by multiple logistic regression analysis, patients with NT-1 levels in the first quartile were more likely to have 3-month PSD (as compared with the fourth quartile, odds ratio 3.83, 95% confidence intervals, 1.53-9.63, P = 0.004). Similar significant findings were observed when the NT-1 levels were added as a continuous variable.

CONCLUSIONS

Our data demonstrated that decreased serum NT-1 levels, in a Chinese population, were significantly associated with PSD at 3 months.

Amino acid metabolism, lipid metabolism, and oxidative stress are associated with post-stroke depression: a metabonomics study

Background

Post-stroke depression (PSD) is a mood disorder characterized by depression and anhedonia caused by stroke. Metabolomics identified metabolites associated with PSD, but previous studies are based on gas chromatography (GC)/mass spectrometry (MS). This study aimed to perform a liquid chromatography (LC)-MS-based metabolomics study of the plasma metabolite profiles between patients with PSD and controls.

Methods

This was a prospective study of patients with stroke enrolled between July and December 2017 at the Second Affiliated Hospital of Nanchang University. Patients were grouped as Hamilton Depression Rating Scale > 7 (PSD) or < 7 (controls). Metabonomics profiling of plasma sampled was conducted by LC-MS. By combining multivariable and univariable statistical analyses, significant differential metabolites between the two groups were screened. The threshold for significant differences was VIP ≥1 and P < 0.05. Log₂FC is the logarithm of the mean ratio between the two groups.

Results

There were no significant difference with respect to age, NIHSS score, and MMSE between the two groups (all P > 0.05). There were six differential metabolites between the PSD and stroke groups, of which three metabolites were increased and three were decreased. Compared with the control group, p-chlorophenylalanine (Log₂FC = 1.37, P = 0.03), phenylacetyl glutamine (Log₂FC = 0.21, P = 0.048), and DHA (Log₂FC = 0.77, P = 0.01) levels were higher in the PSD group, while betaine (trimethylglycine) (Log₂FC = − 0.79, P = 0.04), palmitic acid (Log₂FC = − 0.51, P = 0.001), and MHPG-SO₄ (Log₂FC = − 2.37, P = 0.045) were decreased.

Conclusion

Plasma metabolomics showed that amino acid metabolism (phenylacetyl glutamine, p-chlorophenylalanine, trimethylglycine), lipid metabolism (DHA, palmitic acid, trimethylglycine), and oxidative stress (DHA, palmitic acid, trimethylglycine) were associated with PSD. These results could help to reveal the pathophysiological mechanism of PSD and eventually identify treatment targets.

An early increase in glutamate is critical for the development of depression-like behavior in a chronic restraint stress (CRS) model

Dysfunction in glutamate homeostasis contributes to the pathology of depression-like behavior. Using a chronic restraint stress (CRS) model of depression in C57BL/6 mice, we measured glutamate levels in the cerebrospinal fluid at different restraint time points (CRS 1 d, CRS 3 d, CRS 5 d, CRS 7 d, CRS 14 d, and CRS 21 d). Glutamate levels were increased in the early stage of stress (CRS 1 d and CRS 5 d) but returned to basal levels at the other time points (CRS 7 d-21 d). We hypothesized that glutamate-induced excitotoxicity is critical for the development of depression-like behavior in the CRS model. Treatment with sodium valproate (VPA) or lamotrigine (LTG), two drugs that prevent excitotoxicity in neurons by increasing inhibitory inputs or blocking sodium channels, in the early stage (CRS 1 d-5 d) was sufficient to correct depression-like behavior. In contrast, treatment with the classic antidepressant fluoxetine (FLX) during the same time period was not sufficient to correct depressive behavior. Western blot of two markers of dendritic spines PSD95 and VGluT1 showed that restraining mice for 5 d resulted in the loss of dendritic spines, which was rescued by VPA or LTG. In conclusion, an initial increase in glutamate levels plays an important role in the development of depression-like behavior in the CRS model.

Multimodal Magnetic Resonance Imaging and Therapeutic Intervention With Yi-nao-jie-yu Decoction in a Rat Model of Post-stroke Depression

Post-stroke depression (PSD) is the most common neuropsychiatric complication after a stroke, though its neuropathological characteristics have not been fully elucidated. Comprehensive and non-invasive magnetic resonance (MR) assessment techniques are urgently needed for current research, as diffusion tensor imaging (DTI), arterial spin labeling (ASL), and magnetic resonance spectroscopy (MRS) can allow for a comprehensive assessment of neuropathological changes in the brain. These techniques can provide information about microscopic tissue integrity, cerebral perfusion, and cerebral metabolism, and can serve as powerful tools for investigating neurophysiological changes associated with PSD. Yi-nao-jie-yu decoction (YNJYD) is a Chinese herbal formulation based on the theory of traditional Chinese medicine, with demonstrated clinical efficacy in the treatment of PSD. The aim of this study was to use these MR techniques to evaluate changes in PSD and YNJYD-treated rats. This is the first experimental study in animals to investigate neuropathological changes associated with PSD using a combination of multiple MR techniques, including DTI, ASL, and MRS. In addition, we investigated the effect of YNJYD in a rat model of PSD by assessing changes in brain tissue microstructure, brain metabolism, and cerebral perfusion. First, depressive-like behaviors of PSD rats were assessed by the open field test (OFT), sucrose preference test (SPT), and Morris water maze (MWM) test, and then the integrity of the rats' microstructure was assessed by DTI, the levels of regional cerebral perfusion were assessed by ASL, and changes in the relative concentrations of brain metabolites were determined by MRS. The results showed that OFT and SPT scores were significantly reduced in PSD rats, as was performance in the MWM; these PSD-associated changes were attenuated in rats administered YNJYD, with improved depressive-like behaviors evidenced by increased OFT and SPT scores and improved performance in the MWM task. Furthermore, we found that PSD rats had lower perfusion levels in the prefrontal cortex (PFC) and hippocampus (HP), microstructural damage, and abnormal changes in the concentrations of brain metabolites; YNJYD exerted therapeutic effects on PSD rats by improving microcirculation in the PFC and HP, regulating glutamatergic systems and membrane phospholipid metabolism, and repairing microstructural damage.

Mitochondria: A Connecting Link in the Major Depressive Disorder Jigsaw

Background

Depression is a widespread phenomenon with varying degrees of pathology in different patients. Various hypotheses have been proposed for the cause and continuance of depression. Some of these include, but not limited to, the monoamine hypothesis, the neuroendocrine hypothesis, and the more recent epigenetic and inflammatory hypotheses.

Objective

In this article, we review all the above hypotheses with a focus on the role of mitochondria as the connecting link. Oxidative stress, respiratory activity, mitochondrial dynamics and metabolism are some of the mitochondria-dependent factors which are affected during depression. We also propose exogenous ATP as a contributing factor to depression.

Result

Literature review shows that pro-inflammatory markers are elevated in depressive individuals. The cause for elevated levels of cytokines in depression is not completely understood. We propose exogenous ATP activates purinergic receptors which in turn increase the levels of various pro-inflammatory factors in the pathophysiology of depression.

Conclusion

Mitochondria are integral to the function of neurons and undergo dysfunction in major depressive disorder patients. This dysfunction is reflected in all the various hypotheses that have been proposed for depression. Among the newer targets identified, which also involve mitochondria, includes the role of exogenous ATP. The diversity of purinergic receptors, and their differential expression among various individuals in the population, due to genetic and environmental (prenatal) influences, may influence the susceptibility and severity of depression. Identifying specific receptors involved and using patient-specific purinergic receptor antagonist may be an appropriate therapeutic course in the future.

Astrocyte-Conditioned Medium Protects Prefrontal Cortical Neurons from Glutamate-Induced Cell Death by Inhibiting TNF-α Expression

OBJECTIVE

Both excitotoxicity and neurotrophin deficiency may contribute to the etiology of depression and neurodegeneration. Astrocytes not only regulate glutamate metabolism and clearance, they also produce neurotrophins in the brain. However, the direct interaction between neurons and astrocytes remains unknown.

METHODS

This study evaluated the cellular mechanisms by which astrocyte-conditioned medium (ACM) protects prefrontal cortical neurons from glutamate-induced death by measuring cell viability and morphology as well as mRNA and protein expression of brain-derived neurotrophic factor (BDNF), BDNF receptors, glial cell line-derived neurotrophic factor (GDNF), and the proinflammatory cytokine, tumor necrosis factor (TNF)-α. Neurons and astrocytes were purified from the brains of neonatal 1-day-old Sprague-Dawley rats. ACM was harvested after exposing astrocytes to culture medium containing 100 μM glutamate for 48 h.

RESULTS

Glutamate insult (100 μM for 6 h) significantly reduced neuronal cell viability and increased the mRNA expression of BDNF. Glutamate (24 h) decreased neuronal viability and the expression of BDNF, but increased mRNA expression of GFAP, p75 neurotrophin receptor (p75NTR), and TNF-α. ACM pretreatment (2 h) reversed glutamate-decreased cell viability and increased BDNF, but reduced the expression of GDNF, P75NTR, and TNF-α at the mRNA level. Western blotting generally confirmed the mRNA expression following 24 glutamate insults. Furthermore, the glutamate-induced decrease in the protein expression of BDNF and full-length TrkB receptor and increase in pro-BDNF, truncated TrkB isoform 1 receptor, p75NTR, GDNF, and TNF-α were significantly attenuated by ACM pretreatment.

CONCLUSIONS

The study demonstrates that ACM exerts neuroprotective effects on cell viability, and this effect is most likely mediated through the modulation of neurotrophin and TNF-α expression.

Brain choline in major depression: A review of the literature

The focus of this review is to provide a synthesis of the current literature on the role of brain choline, as measured by proton magnetic resonance spectroscopy (1H-MRS), in major depressive disorder (MDD). The most recent ¹H-MRS literature review took place over 10 years ago and, reflecting the high level of research on this topic, much has been learned since then. Higher brain choline levels have been linked to an increase in depression, and a cholinergic model for MDD development has been postulated. However, current ¹H-MRS studies have been inconclusive regarding the role of choline in depression. Data from eighty-six peer-reviewed studies were analyzed for a random-effects model meta-analysis. Two significant findings are reported. Papers that did not report segmentation had a significant, moderate effect size. Higher choline concentrations in the frontal lobe were found in depressed patients, both in those who responded to treatment and those who did not, after treatment with psychiatric medication, repetitive transcranial magnetic stimulation, or electroconvulsive therapy. Findings from this review may add to existing information regarding the role of brain choline in MDD. This may provide a future target for treatment and drug development. It also may serve as a biomarker for treatment progress.

Diversiform Etiologies for Post-stroke Depression

After the onset of stroke, many patients suffer from emotional behavior changes. Approximately, one-third of stroke survivors are affected by post-stroke depression (PSD), making it a serious social and public health problem. Post-stroke depression (PSD) has an important impact on the course, recovery, and prognosis of stroke. The pathogenesis of PSD is very complex, involving many factors such as biological mechanism and social psychological mechanisms. This article provides a brief review of the hot issues related to etiologies of PSD.

Yi-nao-jie-yu Prescription Exerts a Positive Effect on Neurogenesis by Regulating Notch Signals in the Hippocampus of Post-stroke Depression Rats

Post-stroke depression (PSD) is one of the most frequent complications of stroke. The Yi-nao-jie-yu prescription (YNJYP) is an herbal prescription widely used as a therapeutic agent against PSD in traditional Chinese medicine. Disruption of adult neurogenesis has attracted attention as a potential cause of cognitive pathophysiology in neurological and psychiatric disorders. The Notch signaling pathway plays an important role in neurogenesis. This study investigated the effects of YNJYP on adult neurogenesis and explored its underlying molecular mechanism in a rat model of PSD that is established by middle cerebral artery occlusion and accompanied by chronic immobilization stress for 1 week. At 2, 4, and 8 weeks, depression-like behavior was evaluated by a forced swim test (FST) and sucrose consumption test (SCT). Neurogenesis was observed by double immunofluorescence staining. Notch signals were detected by real-time polymerase chain reaction. The results show that, at 4 weeks, the immobility time in the FST for rats in the PSD group increased and the sucrose preference in the SCT decreased compared with that in the stroke group. Therefore, YNJYP decreased the immobility time and increased the sucrose preference of the PSD rats. Further, PSD interfered with neurogenesis and decreased the differentiation toward neurons of newly born cells in the hippocampal dentate gyrus, and increased the differentiation toward astrocytes, effects that were reversed by YNJYP, particularly at 4 weeks. At 2 weeks, compared with the stroke group, expression of target gene Hes5 mRNA transcripts in the PSD group decreased, but increased after treatment with YNJYP. At 4 weeks, compared with the stroke group, the expression of Notch receptor Notch1 mRNA transcripts in the PSD group decreased, but also increased after treatment with YNJYP. Overall, this study indicated that disturbed nerve regeneration, including the increased numbers of astrocytes and decrease numbers of neurons, is a mechanism of PSD, and Notch signaling genes dynamically regulate neurogenesis. Moreover, YNJYP can relieve depressive behavior in PSD rats, and exerts a positive effect on neurogenesis by dynamically regulating the expression of Notch signaling genes.

Imaging Markers of Post-Stroke Depression and Apathy: a Systematic Review and Meta-Analysis

Several brain imaging markers have been studied in the development of post-stroke depression (PSD) and post-stroke apathy (PSA), but inconsistent associations have been reported. This systematic review and meta-analysis aims to provide a comprehensive and up-to-date evaluation of imaging markers associated with PSD and PSA. Databases (Medline, Embase, PsycINFO, CINAHL, and Cochrane Database of Systematic Reviews) were searched from inception to July 21, 2016. Observational studies describing imaging markers of PSD and PSA were included. Pooled odds ratios (OR) and 95% confidence intervals (CI) were calculated to examine the association between PSD or PSA and stroke lesion laterality, type, and location, also stratified by study phase (acute, post-acute, chronic). Other imaging markers were reviewed qualitatively. The search retrieved 4502 studies, of which 149 studies were included in the review and 86 studies in the meta-analyses. PSD in the post-acute stroke phase was significantly associated with frontal (OR 1.72, 95% CI 1.34–2.19) and basal ganglia lesions (OR 2.25, 95% CI 1.33–3.84). Hemorrhagic stroke related to higher odds for PSA in the acute phase (OR 2.58, 95% CI 1.18–5.65), whereas ischemic stroke related to higher odds for PSA in the post-acute phase (OR 0.20, 95% CI 0.06–0.69). Frequency of PSD and PSA is modestly associated with stroke type and location and is dependent on stroke phase. These findings have to be taken into consideration for stroke rehabilitation programs, as this could prevent stroke patients from developing PSD and PSA, resulting in better clinical outcome.

The combination of plasma glutamate and physical impairment after acute stroke as a potential indicator for the early-onset post-stroke depression

OBJECTS

The present study aimed to investigate the relationship of plasma glutamate levels with the early-onset of post-stroke depression (PSD) and to further explore the prognostic value of plasma glutamate combined with clinical characteristics for the early-onset PSD in the acute ischemic stroke patients.

METHODS

Seventy-four patients who admitted to the hospital within 24h of acute ischemic stroke were consecutively recruited and followed up for 2weeks. The Beck Depression Inventory (BDI) and 17-item Hamilton Depression Rating Scale (HAMD-17) were used to screen for depressive symptoms 14days after stroke. Diagnoses of depression were made in accordance with DSM-IV. Plasma glutamate levels were determined by High Performance Liquid Chromatography (HPLC) on days 1 and 14 after stroke for all patients.

RESULTS

Plasma glutamate levels were significantly lower in PSD patients than those of non-PSD patients on day 1 after stroke. ROC curve analyses revealed an AUC (area under the ROC curve) of 0.724 (95% CI: 0.584-0.863, p=0.004) and of 0.669 (95% CI: 0.523-0.814, p=0.030) for National Institute of Health Stroke Scale (NIHSS) scores and plasma glutamate levels on day 1 respectively. Combined ROC analyses using the two factors revealed the highest AUC of 0.804 (95% CI: 0.685-0.922, P<0.0001).

CONCLUSIONS

These results indicated an association between the early-onset PSD and a low plasma glutamate level following acute ischemic stroke. The combination of reduced plasma glutamate levels and physical impairment (determined by NIHSS) 1day after acute ischemic stroke was a potential diagnostic indicator for early-onset PSD.

Neuropsychiatric sequelae of stroke

Stroke survivors are often affected by psychological distress and neuropsychiatric disturbances. About one-third of stroke survivors experience depression, anxiety or apathy, which are the most common neuropsychiatric sequelae of stroke. Neuropsychiatric sequelae are disabling, and can have a negative influence on recovery, reduce quality of life and lead to exhaustion of the caregiver. Despite the availability of screening instruments and effective treatments, neuropsychiatric disturbances attributed to stroke are currently underdiagnosed and undertreated. Stroke severity, stroke-related disabilities, cerebral small vessel disease, previous psychiatric disease, poor coping strategies and unfavourable psychosocial environment influence the presence and severity of the psychiatric sequelae of stroke. Although consistent associations between psychiatric disturbances and specific stroke locations have yet to be confirmed, functional MRI studies are beginning to unveil the anatomical networks that are disrupted in stroke-associated psychiatric disorders. Evidence regarding biochemical and genetic biomarkers for stroke-associated psychiatric disorders is still limited, and better understanding of the biological determinants and pathophysiology of these disorders is needed. Investigation into the management of these conditions must be continued, and should include pilot studies to assess the benefits of innovative behavioural interventions and large-scale cooperative randomized controlled pharmacological trials of drugs that are safe to use in patients with stroke.

Serum Levels of High-sensitivity C-Reactive Protein at Admission Are More Strongly Associated with Poststroke Depression in Acute Ischemic Stroke than Homocysteine Levels

Inflammatory processes have fundamental roles in depression. The primary purpose of this study was to assess the serum levels of high-sensitivity C-reactive protein (Hs-CRP) and homocysteine (HCY) at admission to the presence of poststroke depression (PSD). From December 2012 to December 2013, first-ever acute ischemic stroke patients who were admitted to the hospital within the first 24 h after stroke onset were consecutively recruited and followed up for 6 months. Serum levels of Hs-CRP and HCY were tested at admission. Based on the symptoms, diagnoses of depression were made in accordance with DSM-IV criteria for depression at 6 months after stroke. Ninety-five patients (42.0%) showed depression (major + minor) at 6 months after admission, and in 69 patients (30.5%), this depression was classified as major. In the 69 patients with major depression, our results showed significantly higher Hs-CRP and HCY levels at admission than patients without major depression. After adjusting all other possible covariates, Hs-CRP and HCY still were independent predicators of PSD with adjusted OR of 1.332 (95% CI, 1.230-1.452; P < 0.001) and 1.138 (95% CI, 1.072-1.274; P < 0.001), respectively. The area under the receiver operating characteristic curve values of Hs-CRP and HCY were 0.765 (95% CI, 0.701-0.9825) and 0.684 (95% CI, 0.610-0.757) for PSD, respectively. The prognostic accuracy of combined model (HCY and Hs-CRP) was higher compared to those biomarkers alone and other markers. Elevated serum levels of Hs-CRP and HCY at admission were found to be associated with depression 6 months after stroke, suggesting that these alterations might participate in the pathophysiology of depression symptoms in stroke patients.

Ex vivo (1)H nuclear magnetic resonance spectroscopy reveals systematic alterations in cerebral metabolites as the key pathogenetic mechanism of bilirubin encephalopathy

BACKGROUND

Bilirubin encephalopathy (BE) is a severe neurologic sequelae induced by hyperbilirubinemia in newborns. However, the pathogenetic mechanisms underlying the clinical syndromes of BE remain ambiguous. Ex vivo (1)H nuclear magnetic resonance (NMR) spectroscopy was used to measure changes in the concentrations of cerebral metabolites in various brain areas of newborn 9-day-old rats subjected to bilirubin to explore the related mechanisms of BE.

RESULTS

When measured 0.5 hr after injection of bilirubin, levels of the amino acid neurotransmitters glutamate (Glu), glutamine (Gln), and γ-aminobutyric acid (GABA) in hippocampus and occipital cortex significantly decreased, by contrast, levels of aspartate (Asp) considerably increased. In the cerebellum, Glu and Gln levels significantly decreased, while GABA, and Asp levels showed no significant differences. In BE 24 hr rats, all of the metabolic changes observed returned to normal in the hippocampus and occipital cortex; however, levels of Glu, Gln, GABA, and glycine significantly increased in the cerebellum.

CONCLUSIONS

These metabolic changes for the neurotransmitters are mostly likely the result of a shift in the steady-state equilibrium of the Gln-Glu-GABA metabolic cycle between astrocytes and neurons, in a region-specific manner. Changes in energy metabolism and the tricarboxylic acid cycle may also be involved in the pathogenesis of BE.

The role of NMDA receptors in the pathophysiology and treatment of mood disorders

Mood disorders such as major depressive disorder and bipolar disorder are chronic and recurrent illnesses that cause significant disability and affect approximately 350 million people worldwide. Currently available biogenic amine treatments provide relief for many and yet fail to ameliorate symptoms for others, highlighting the need to diversify the search for new therapeutic strategies. Here we present recent evidence implicating the role of N-methyl-D-aspartate receptor (NMDAR) signaling in the pathophysiology of mood disorders. The possible role of NMDARs in mood disorders has been supported by evidence demonstrating that: (i) both BPD and MDD are characterized by altered levels of central excitatory neurotransmitters; (ii) NMDAR expression, distribution, and function are atypical in patients with mood disorders; (iii) NMDAR modulators show positive therapeutic effects in BPD and MDD patients; and (iv) conventional antidepressants/mood stabilizers can modulate NMDAR function. Taken together, this evidence suggests the NMDAR system holds considerable promise as a therapeutic target for developing next generation drugs that may provide more rapid onset relief of symptoms. Identifying the subcircuits involved in mood and elucidating the role of NMDARs subtypes in specific brain circuits would constitute an important step toward the development of more effective therapies with fewer side effects.

Plasma levels of glutamate during stroke is associated with development of post-stroke depression

BACKGROUND

Depression is a frequent mood disorder that affects around 33% of stroke patient. Our aim was to test the possible association between plasma glutamate and the development of post-stroke depression (PSD) in Chinese patients.

METHODS

The subjects were first-ever acute ischemic stroke (AIS) patients who were hospitalized during the period from November 2011 to September 2013. Clinical information and stroke severity was collected at admission. Neurological and neuropsychological evaluations were conducted at the 3-month follow-up. Plasma glutamate levels were analyzed at baseline using liquid chromatography followed by tandem mass spectrometry. Glutamate oxaloacetate transaminase (GOT), glutamate-pyruvate transaminase (GPT) and blood markers were also tested. Multivariate analyses were performed using logistic regression models.

RESULTS

During the study period, 209 patients were included in the analysis. Seventy patients (33.5%) were diagnosed as having major depression at 3 month. Patients with major depression showed higher levels of plasma glutamate [299 (235-353) vs. 157 (108-206) μM, P<0.0001] and lower GOT [14 (11-20) vs. 21 (15-32)U/L, P<0.0001] at admission. In multivariate analyses, plasma glutamate and GOT were independent predictors of PSD at 3 months [odds ratio (OR): 1.03 (1.02-1.04), P<0.0001; 0.84 (0.75-0.97), P=0.003]. Plasma levels of glutamate >205 μM were independently associated with PSD (OR, 21.3; 95% CI, 8.28-67.36, P<0.0001), after adjustment for possible variables.

CONCLUSION

The present study demonstrates a strong relationship between plasma glutamate and GOT levels at admission and the development of PSD within 3 months. Further studies are necessary to confirm this association, which may open the way to the proposal of new therapeutic options.

Neurochemical alterations in frontal cortex of the rat after one week of hypobaric hypoxia

Residing at high altitude may lead to reduced blood oxygen saturation in the brain and altered metabolism in frontal cortical brain areas, probably due to chronic hypobaric hypoxia. These changes may underlie the increased rates of depression and suicidal behavior that have been associated with life at higher altitudes. To test the hypothesis that hypobaric hypoxia is responsible for development of mood disorders due to alterations in neurochemistry, we assessed depression-like behavior in parallel to levels of brain metabolites in rats housed at simulated altitude. 32 female Sprague Dawley rats were housed either in a hypobaric hypoxia chamber at 10,000 ft of simulated altitude for 1 week or at local conditions (4500 ft of elevation in Salt Lake City, Utah). Depression-like behavior was assessed using the forced swim test (FST) and levels of neurometabolites were estimated by in vivo proton magnetic resonance spectroscopy in the frontal cortex, the striatum and the hippocampus at baseline and after a week of exposure to hypobaric hypoxia. After hypoxia exposure the animals demonstrated increased immobility behavior and shortened latency to immobility in the FST. Elevated ratios of myo-inositol, glutamate, and the sum of myo-inositol and glycine to total creatine were observed in the frontal cortex of hypoxia treated rats. A decrease in the ratio of alanine to total creatine was also noted. This study shows that hypoxia induced alterations in frontal lobe brain metabolites, aggravated depression-like behavior and might be a factor in increased rates of psychiatric disorders observed in populations living at high altitudes.

The neurobiological pathogenesis of poststroke depression

Poststroke depression (PSD) is an important consequence after stroke, with negative impact on stroke outcome. The pathogenesis of PSD is complicated, with some special neurobiological mechanism, which mainly involves neuroanatomical, neuron, and biochemical factors and neurogenesis which interact in complex ways. Abundant studies suggested that large lesions in critical areas such as left frontal lobe and basal ganglia or accumulation of silent cerebral lesions might interrupt the pathways of monoamines or relevant pathways of mood control, thus leading to depression. Activation of immune system after stroke produces more cytokines which increase glutamate excitotoxicity, results in more cell deaths of critical areas and enlargement of infarctions, and, together with hypercortisolism induced by stress or inflammation after stroke which could decrease intracellular serotonin transporters, might be the key biochemical change of PSD. The interaction among cytokines, glucocorticoid, and neurotrophin results in the decrease of hippocampal neurogenesis which has been proved to be important for mood control and pharmaceutical effect of selective serotonin reuptake inhibitors and might be another promising pathway to understand the pathogenesis of PSD. In order to reduce the prevalence of PSD and improve the outcome of stroke, more relevant studies are still required to clarify the pathogenesis of PSD.

Ketamine as antidepressant? Current state and future perspectives

Major depressive disorder (MDD) is a serious mental disorder that ranks among the major causes of disease burden. Standard medical treatment targeting cerebral monoamines often provides only insufficient symptom relief and fails in approximately every fifth patient. The complexity of MDD therefore, reflects more than monoaminergic dysregulation. Initial research argues the case for excessive glutamate levels, suggesting that antiglutamatergic drugs might be useful in treating MDD. Ketamine is a non-selective, high-affinity N-methyl-D-aspartate receptor (NMDAR) antagonist most commonly used in pediatric and animal surgery. In the past, ketamine has gained popularity because of its ability to rapidly elevate mood, even in treatment-resistant and bipolar depression. However, there are still many obstacles before widespread clinical approval of ketamine treatment could become reality. In this review, ketamine's powerful antidepressant effects are discussed and further research necessary for therapeutic application is outlined. NMDAR antagonists provide an entirely new way of treating the manifold appearances of depression that should not be left unused.

Increased ratio of glutamate/glutamine to creatine in the right hippocampus contributes to depressive symptoms in patients with epilepsy

PURPOSE

Our study aimed to investigate whether the glutamatergic system in the hippocampus is correlated with depressive symptoms in patients with epilepsy.

METHODS

Fifty patients with epilepsy were recruited and divided into three groups on the basis of their Hamilton Depression Rating Scale (HAMD) scores. Single-voxel proton magnetic resonance spectroscopy ((1)H-MRS) was carried out. Pearson correlation analysis and multiple linear regression analysis were performed to investigate any correlation between the variables of hippocampal metabolites and HAMD scores.

RESULTS

Proton magnetic resonance spectroscopy analysis showed that the ratio of glutamate/glutamine to creatine (Glx/Cr) in the right hippocampus was significantly increased in patients with moderate depression and correlated positively with HAMD scores. Multiple linear regression analysis showed that the ratio of Glx/Cr in the right hippocampus was an independent risk factor relating to depressive symptoms in patients with epilepsy.

CONCLUSION

A disturbance of the hippocampal glutamatergic system may be involved in the pathogenesis of depression in epilepsy.

Phospholipase D-mTOR signaling is compromised in a rat model of depression

Depression is associated with structural and neurochemical changes in limbic structures, including the hippocampus, that control emotion and mood. Structural abnormalities such as decrease in hippocampal cell proliferation, neurogenesis and hippocampal volume, and loss of neurons and glial cells have been widely reported in physical and psychosocial stress paradigms and animal model of depression, but corresponding neurochemical changes are largely unknown. Using neonatal clomipramine (CL)-treated rats as a model to elucidate the association of phospholipase D (PLD) and mammalian target of rapamycin (mTOR) signaling with depressive pathology, we found that the hippocampus of CL-treated rats showed significantly down-regulation of PLD1 expression and attenuation of PLD activity which leads to the less formation of phosphatidic acid (PA), an activator of mTOR, and free choline, a potential biomarker for depression. With lower PA levels which could affect mTOR signaling, we further observed that the phosphorylation of p70S6 kinase, one of the downstream effectors of mTOR, was also significantly decreased in the hippocampus of CL-treated rats compared to the controls. Down-regulation of PLD1 expression, PLD activity and p70S6 phosphorylation was also found in the hypothalamus and frontal cortex with CL-treated rats. Our results indicate that PLD-mTOR signaling is associated with depressive disorder.

Influence of GRIA1, GRIA2 and GRIA4 polymorphisms on diagnosis and response to treatment in patients with major depressive disorder

The present study is aimed to exploring whether some single nucleotide polymorphisms (SNPs) within GRIA1, GRIA2 and GRIA4 could be associated with major depressive disorder (MDD) and whether they could predict clinical outcomes in Korean in-patients, respectively, treated with antidepressants. One hundred forty-five (145) patients with MDD and 170 healthy controls were genotyped for 17 SNPs within GRIA1, GRIA2 and GRIA4. Baseline and final clinical measures, including the Montgomery-Asberg Depression Rating Scale (MADRS) for patients with MDD, were recorded. No association was observed between alleles, genotypes and haplotypes under investigation and clinical and demographical variables. As a secondary finding, a marginal association was observed between rs4302506 and rs4403097 alleles within GRIA2 and age of onset in patients with MDD. Our findings provide evidence for a possible association between rs4302506 and rs4403097 SNPs and age of onset in patients with MDD. However, taking into account that the several limitations of our study including the moderately small sample size of our study, our findings should be considered with caution and further research is needed to draw more definitive conclusions.

Towards a glutamate hypothesis of depression: an emerging frontier of neuropsychopharmacology for mood disorders

Half a century after the first formulation of the monoamine hypothesis, compelling evidence implies that long-term changes in an array of brain areas and circuits mediating complex cognitive-emotional behaviors represent the biological underpinnings of mood/anxiety disorders. A large number of clinical studies suggest that pathophysiology is associated with dysfunction of the predominant glutamatergic system, malfunction in the mechanisms regulating clearance and metabolism of glutamate, and cytoarchitectural/morphological maladaptive changes in a number of brain areas mediating cognitive-emotional behaviors. Concurrently, a wealth of data from animal models have shown that different types of environmental stress enhance glutamate release/transmission in limbic/cortical areas and exert powerful structural effects, inducing dendritic remodeling, reduction of synapses and possibly volumetric reductions resembling those observed in depressed patients. Because a vast majority of neurons and synapses in these areas and circuits use glutamate as neurotransmitter, it would be limiting to maintain that glutamate is in some way 'involved' in mood/anxiety disorders; rather it should be recognized that the glutamatergic system is a primary mediator of psychiatric pathology and, potentially, also a final common pathway for the therapeutic action of antidepressant agents. A paradigm shift from a monoamine hypothesis of depression to a neuroplasticity hypothesis focused on glutamate may represent a substantial advancement in the working hypothesis that drives research for new drugs and therapies. Importantly, despite the availability of multiple classes of drugs with monoamine-based mechanisms of action, there remains a large percentage of patients who fail to achieve a sustained remission of depressive symptoms. The unmet need for improved pharmacotherapies for treatment-resistant depression means there is a large space for the development of new compounds with novel mechanisms of action such as glutamate transmission and related pathways. This article is part of a Special Issue entitled 'Anxiety and Depression'.