Association between decreased serum tryptophan concentrations and depressive symptoms in cancer patients undergoing cytokine therapy

Association between peripheral plasma cytokine levels and suicidal ideation in first-episode, drug-naïve major depressive disorder

BACKGROUND

Inflammatory processes could potentially impact both mood and suicide risk, however, the relationship between cytokines and suicidal ideation remains unclear. This study aimed to investigate the association between plasma levels of cytokines and suicidal ideation in population with major depressive disorders (MDD).

METHODS

A cross-sectional study was performed to assess the peripheral plasma levels of interleukin-1β (IL-1β), IL-2, IL-6, IL-8, IL-10 and tumor necrosis factor-α (TNF-α) in 88 Chinese Han first-episode drug-naïve MDD patients. Suicidal ideation in the past week were identified using the Beck Scale for Suicide Ideation-Chinese Version (BSI-CV). The Hamilton Depression Rating Scale-17 (HAMD-17), the Hamilton Anxiety Rating Scale-14 (HAMA-14) and the Childhood Trauma Questionnaire (CTQ) was used to assess depression, anxiety and childhood trauma. Multivariable logistic regression models were used to estimate the association between cytokines and suicidal ideation. Interaction and stratified analyses were conducted according to age, sex, marital status, education, smoking status, BMI and physical activity.

RESULTS

Among the 88 participants, 42 individuals (47.7%) reported suicidal ideation within the past week. In the fully adjusted model, a statistically significant trend was observed in the association between IL-2 level and suicidal ideation (OR: 1.40, 95% CI: 1.00-1.97). The stratified analysis showed a statistically significant association between IL-6 level and suicidal ideation among younger people (OR: 1.17, 95% CI: 1.01-1.36) and a significant positive association between IL-8 (OR: 1.59, 95% CI: 1.03-2.44) and IL-10 (OR: 2.51, 95% CI: 1.27-4.96) levels and suicide ideation among higher educated populations.

LIMITATIONS

The cross-sectional design, residual confounding effects and small sample size CONCLUSION: Our findings indicate a significant positive association between plasma IL-2 level and suicidal ideation in MDD patients. IL-2 has the potential to be a biomarker of suicidal ideation in patients with depression.

Exploring environmental exposomes and the gut-brain nexus: Unveiling the impact of pesticide exposure

This review delves into the escalating concern of environmental pollutants and their profound impact on human health in the context of the modern surge in global diseases. The utilisation of chemicals in food production, which results in residues in food, has emerged as a major concern nowadays. By exploring the intricate relationship between environmental pollutants and gut microbiota, the study reveals a dynamic bidirectional interplay, as modifying microbiota profile influences metabolic pathways and subsequent brain functions. This review will first provide an overview of potential exposomes and their effect to gut health. This paper is then emphasis the connection of gut brain function by analysing microbiome markers with neurotoxicity responses. We then take pesticide as example of exposome to elucidate their influence to biomarkers biosynthesis pathways and subsequent brain functions. The interconnection between neuroendocrine and neuromodulators elements and the gut-brain axis emerges as a pivotal factor in regulating mental health and brain development. Thus, manipulation of gut microbiota function at the onset of stress may offer a potential avenue for the prevention and treatment for mental disorder and other neurodegenerative illness.

Comparison between sub-chronic and chronic sleep deprivation-induced behavioral and neuroimmunological abnormalities in mice: Focusing on glial cell phenotype polarization

BACKGROUND

Sleep disorders, depression, and Alzheimer's disease (AD) are extensively reported as comorbidity. Although neuroinflammation triggered by microglial phenotype M1 activation, leading to neurotransmitter dysfunction and Aβ aggregation, is considered as the leading cause of depression and AD, whether and how sub-chronic or chronic sleep deprivation (SD) contribute to the onset and development of these diseases remains unclear.

METHODS

Memory and depression-like behaviors were evaluated in both SDs, and then circadian markers, glial cell phenotype polarization, cytokines, depression-related neurotransmitters, and AD-related gene/protein expressions were measured by qRT-PCR, enzyme-linked immunosorbent assay, high-performance liquid chromatography, and western-blotting respectively.

RESULTS

Both SDs induced give-up behavior and anhedonia and increased circadian marker period circadian regulator 2 (PER2) expression, which were much worse in chronic than in the sub-chronic SD group, while brain and muscle ARNT-like protein-1 only decreased in the chronic-SD. Furthermore, increased microglial M1 and astrocyte A1 expression and proinflammatory cytokines, interleukin (IL)-1β, IL-6, and tumor necrosis factor-α was observed in both SDs, which were more significant in chronic SD. Similarly, decreased norepinephrine and 5-hydroxytryptamine/5-hydroxyindoleacetic acid ratio were more significant, which corresponds to the worse depression-like behavior in chronic than sub-chronic-SD. With regard to AD, increased amyloid precursor protein (APP) and soluble (s)-APPβ and decreased sAPPα in both SDs were more significant in the chronic. However, sAPPα/sAPPβ ratio was only decreased in chronic SD.

CONCLUSION

These findings suggest that both SDs induce depression-like changes by increasing PER2, leading to neuroinflammation and neurotransmitter dysfunction. However, only chronic SD induced memory impairment likely due to severer circadian disruption, higher neuroinflammation, and dysregulation of APP metabolism.

Multi-omics analysis of the gut microbiome and metabolites associated with the psychoneurological symptom cluster in children with cancer receiving chemotherapy

BACKGROUND

Children with cancer receiving chemotherapy commonly report a cluster of psychoneurological symptoms (PNS), including pain, fatigue, anxiety, depression, and cognitive dysfunction. The role of the gut microbiome and its functional metabolites in PNS is rarely studied among children with cancer. This study investigated the associations between the gut microbiome-metabolome pathways and PNS in children with cancer across chemotherapy as compared to healthy children.

METHODS

A case-control study was conducted. Cancer cases were recruited from Children's Healthcare of Atlanta and healthy controls were recruited via flyers. Participants reported PNS using the Pediatric Patient-Reported Outcomes Measurement Information System. Data for cases were collected pre-cycle two chemotherapy (T0) and post-chemotherapy (T1), whereas data for healthy controls were collected once. Gut microbiome and its metabolites were measured using fecal specimens. Gut microbiome profiling was performed using 16S rRNA V4 sequencing, and metabolome was performed using an untargeted liquid chromatography-mass spectrometry approach. A multi-omics network integration program analyzed microbiome-metabolome pathways of PNS.

RESULTS

Cases (n = 21) and controls (n = 14) had mean ages of 13.2 and 13.1 years. For cases at T0, PNS were significantly associated with microbial genera (e.g., Ruminococcus, Megasphaera, and Prevotella), which were linked with carnitine shuttle (p = 0.0003), fatty acid metabolism (p = 0.001) and activation (p = 0.001), and tryptophan metabolism (p = 0.008). Megasphaera, clustered with aspartate and asparagine metabolism (p = 0.034), carnitine shuttle (p = 0.002), and tryptophan (p = 0.019), was associated with PNS for cases at T1. Gut bacteria with potential probiotic functions, along with fatty acid metabolism, tryptophan, and carnitine shuttle, were more clustered in cancer cases than the control network and this linkage with PNS needs further studies.

CONCLUSIONS

Using multi-omics approaches, this study indicated specific microbiome-metabolome pathways linked with PNS in children with cancer across chemotherapy. Due to limitations such as antibiotic use in cancer cases, these findings need to be further confirmed in a larger cohort.

Techniques for Measurement of Serotonin: Implications in Neuropsychiatric Disorders and Advances in Absolute Value Recording Methods

Serotonin (5-HT) is a monoamine neurotransmitter in the peripheral, enteric, and central nervous systems (CNS). Within the CNS, serotonin is principally involved in mood regulation and reward-seeking behaviors. It is a critical regulator in CNS pathologies such as major depressive disorder, addiction, and schizophrenia. Consequently, in vivo serotonin measurements within the CNS have emerged as one of many promising approaches to investigating the pathogenesis, progression, and treatment of these and other neuropsychiatric conditions. These techniques vary in methods, ranging from analyte sampling with microdialysis to voltammetry. Provided this diversity in approach, inherent differences between techniques are inevitable. These include biosensor size, temporal/spatial resolution, and absolute value measurement capabilities, all of which must be considered to fit the prospective researcher's needs. In this review, we summarize currently available methods for the measurement of serotonin, including novel voltammetric absolute value measurement techniques. We also detail serotonin's role in various neuropsychiatric conditions, highlighting the role of phasic and tonic serotonergic neuronal firing within each where relevant. Lastly, we briefly review the present clinical application of these techniques and discuss the potential of a closed-loop monitoring and neuromodulation system utilizing deep brain stimulation (DBS).

Inflamed but not impulsive: Acute inflammatory cytokine response does not impact prepotent response inhibition

BACKGROUND

Prior evidence has linked inflammation with impulsivity, but most of this evidence is cross-sectional. In this study, we provoked an acute inflammatory cytokine response to see whether it lowered prepotent response inhibition on three cognitive tasks.

METHOD

This study features secondary analyses from a randomized crossover trial in which 171 postmenopausal breast cancer survivors (Stage I-IIIA) each received a typhoid capsular polysaccharide vaccination and a saline placebo injection in a random sequence at two separate visits at least one month apart. Participants completed the Stroop Color-Discrepant Task, the 2-back, and the Conners Continuous Performance Test (CPT) on the computer between 5 and 7 h after the injections. They had their blood drawn once before and repeatedly after the injection to measure interleukin-1 receptor antagonist and interleukin-6 responses.

RESULTS

Women committed marginally fewer errors on the Stroop color-discrepant trials after the typhoid vaccine (M = 0.36, SE = 0.08), compared to placebo (M = 0.54, SE = 0.09, p = .076). Injection type did not predict 2-back accuracy (p = .80) or CPT commission errors (p = .47). Inflammatory cytokine responses were also unrelated to the outcomes of interest (ps>.16).

CONCLUSION

We found no evidence that an acute inflammatory cytokine response provokes response disinhibition - an important facet of impulsivity. In fact, our only marginally non-significant result suggested that women were better able to inhibit their prepotent responses on the Stroop after receiving the typhoid vaccine, compared to placebo. Further experimental tests of the acute inflammatory cytokine response's effect on other aspects of impulsivity are warranted.

LIMITATIONS

The sample was female, primarily White, highly educated cancer survivors, and recruitment was not premised on impulsive traits or diagnosis with an impulsive-related disorder. Also, there are many facets of impulsivity, and this study only measured response inhibition.

Kynurenine pathway and its role in neurologic, psychiatric, and inflammatory bowel diseases

Tryptophan metabolism along the kynurenine pathway is of central importance for the immune function. It prevents hyperinflammation and induces long-term immune tolerance. Accumulating evidence also demonstrates cytoprotective and immunomodulatory properties of kynurenine pathway in conditions affecting either central or peripheral nervous system as well as other conditions such as inflammatory bowel disease (IBD). Although multilevel association exists between the inflammatory bowel disease (IBD) and various neurologic (e.g., neurodegenerative) disorders, it is believed that the kynurenine pathway plays a pivotal role in the development of both IBD and neurodegenerative disorders. In this setting, there is strong evidence linking the gut-brain axis with intestinal dysfunctions including IBD which is consistent with the fact that the risk of neurodegenerative diseases is higher in IBD patients. This review aims to highlight the role of kynurenine metabolic pathway in various neurologic and psychiatric diseases as well as relationship between IBD and neurodegenerative disorders in the light of the kynurenine metabolic pathway.

Efficacy of Yoga for COVID-19 Stress Prophylaxis

BACKGROUND

The global COVID-19 lockdown restricted daily routines due to the psychological fear of infection, which imposed an unknown universal threat on female college students, affecting physiological health and well-being. However, scant information concerning the efficacy of yogic practice on female college students during the stressful COVID-19 pandemic situation is available.

METHODS

In a randomized controlled trial (n = 74, age = 21.65 [4.05] y), a study was conducted with a well-conceptualized yogic module for 5 days/week for 3 months (40 min daily in the morning) among yogic volunteers. Pre-post analysis of anthropometric, physiological, and biochemical indices in pandemic-stressed female college students was done for the control and yoga groups.

RESULTS

After 3 months of yogic practice, significant reduction (P < .05) in heart rate (d = 0.64, meandiff = 5.43), systolic blood pressure (d = 0.59, meandiff = 5.32), cortisol (d = 0.59, meandiff = 6.354), and triglycerides (P < .01, d = 0.45, meandiff = 13.95) was observed. After yogic follow-up significant improvement (P < .01) in high-frequency (d = 0.56, meandiff = -7.3), total power (d = 0.46, meandiff = -1150) and time domain parameters of heart rate variability led to ameliorate the stress index. Superoxide dismutase (P < .01, d = 0.78, meandiff = 0.69), catalase (P < .05, d = 0.48, meandiff = -7.37), glutathione (P < .001, d = 0.83, meandiff = -4.15), high-density lipoprotein (P < .05, d = 0.48, meandiff = -11.07), and dopamine (P < .001, d = 0.97, meandiff = -135.4) values along with inflammatory markers (P < .001) significantly improved among yogic volunteers after regular practice.

CONCLUSIONS

Our findings suggest that a 3-month well-conceptualized yogic intervention during COVID-19 may be considered as a prophylactic tool to improve female college students' universal psychophysiological health by ameliorating autonomic functions, cardiometabolic risk factors, and immune metabolisms in an economical and environment-friendly manner.

Alteration of Branched-Chain and Aromatic Amino Acid Profile as a Novel Approach in Studying Polycystic Ovary Syndrome Pathogenesis

Polycystic ovary syndrome (PCOS) is a common endocrine disorder that affects reproductive-age women and predisposes them to the development of metabolic disturbances. Recent research has shown that several metabolic factors may play a role in PCOS pathogenesis, and it has been suggested that an alteration in the amino acid profile might be a predictive sign of metabolic disorders. Metabolically healthy obesity (MHO) and metabolically unhealthy obesity (MUO) are concepts that have attracted scientific attention; however, a universal definition has not been established yet for these terms. Already existing definitions of MHO involve the coexistence of obesity with the absence or minimal presence of other metabolic syndrome parameters. A group of 326 women, 209 diagnosed with PCOS and 117 healthy individuals, participated in this study. Multiple parameters were assessed, including anthropometrical, biochemical, and hormonal ones, and gas-liquid chromatography, combined with tandem mass spectrometry, was used to investigate the amino acid profile. Statistical analysis revealed noticeably higher levels of all aromatic amino acids in PCOS women compared to the control group: phenylalanine 47.37 ± 7.0 vs. 45.4 ± 6.09 nmol/mL (p = 0.01), tyrosine 61.69 ± 9.56 vs. 58.08 ± 8.89 nmol/mL (p < 0.01), and tryptophan 53.66 ± 11.42 vs. 49.81 ± 11.18 nmol/mL (p < 0.01); however, there was no significant difference in the "tryptophan ratio" between the PCOS and control group (p = 0.88). A comparison of MHO and MUO PCOS women revealed that LAP, leucine, and isoleucine concentrations were significantly higher among the MUO subgroup: respectively, 101.98 ± 34.74 vs. 55.80 ± 24.33 (p < 0.001); 153.26 ± 22.26 vs. 137.25 ± 25.76 nmol/mL (p = 0.04); and 92.92 ± 16.09 vs. 82.60 ± 18.70 nmol/mL (p = 0.02). No significant differences in BMI, fasting glucose, and HOMA-IR between MHO and MUO were found: respectively, 35.0 ± 4.8 vs. 36.1 ± 4.6 kg/m2 (p = 0.59); 88.0 ± 6.0 vs. 87.73 ± 6.28 mg/dL (p = 0.67); and 3.36 ± 1.70 vs. 4.17 ± 1.77 (p = 0.1). The identification of altered amino acid profiles in PCOS holds potential clinical implications. Amino acids may serve as biomarkers for diagnosing and monitoring the metabolic status of individuals with PCOS. The alteration of BCAAs and AAAs may be involved in PCOS pathogenesis, but the underlying mechanism should be further investigated.

Towards Novel Potential Molecular Targets for Antidepressant and Antipsychotic Pharmacotherapies

Depression and schizophrenia are two highly prevalent and severely debilitating neuropsychiatric disorders. Both conventional antidepressant and antipsychotic pharmacotherapies are often inefficient clinically, causing multiple side effects and serious patient compliance problems. Collectively, this calls for the development of novel drug targets for treating depressed and schizophrenic patients. Here, we discuss recent translational advances, research tools and approaches, aiming to facilitate innovative drug discovery in this field. Providing a comprehensive overview of current antidepressants and antipsychotic drugs, we also outline potential novel molecular targets for treating depression and schizophrenia. We also critically evaluate multiple translational challenges and summarize various open questions, in order to foster further integrative cross-discipline research into antidepressant and antipsychotic drug development.

Genetically engineered bacterium-modified magnetic particles assisted chiral recognition and colorimetric determination of D/L-tryptophan in millets

Chiral recognition of enantiomers has always been a thorny issue since they exhibit the same properties under an achiral environment. Herein, polydopamine-functionalized magnetic particles (MP@PDA) were synthesized to immobilize the genetically engineered bacterium Escherichia coli DH5α (MP@PDA-E. coli). L-tryptophan (Trp) instead of D-Trp can be stereo-specifically degraded by tryptophanase in E. coli. The degradation product indole reacts with 4-dimethylaminobenzaldehyde to generate a rose-red adduct. Thus, MP@PDA-E. coli was employed to fabricate a chiral colorimetric method for chiral recognition and determination of L-Trp. The method averts the purification of tryptophanase. More importantly, tryptophanase demonstrates excellent enantioselective ability for L-Trp. The method can not only quantitatively detect L-Trp but also realize the measurement of the enantiomer percentage in the enantiomeric mixture. The feasibility was verified by detecting L-Trp in millet samples from different origins. Furthermore, a portable device was fabricated to make the method more convenient.

HTR1A, TPH2, and 5-HTTLPR Polymorphisms and Their Impact on the Severity of Depressive Symptoms and on the Concentration of Tryptophan Catabolites during Hepatitis C Treatment with Pegylated Interferon-α2a and Oral Ribavirin (PEG-IFN-α2a/RBV)

BACKGROUND

Seeing that there are no data about associations between serotonin gene polymorphism and tryptophan catabolite concentration during PEG-IFN-α2a treatment, the aim of the current study is to examine (a) the associations between polymorphisms within the HTR1A, TPH2, and 5-HTT genes and the severity of depression symptoms and (b) the relationships among rs6295, rs4570625, and 5-HTTLPR rs25531polymorphisms and indoleamine 2,3-dioxygenase (IDO) activity, as well as kynurenine (KYN), tryptophan (TRP), kynurenic acid (KA), and anthranilic acid (AA) concentrations.

MATERIALS AND METHODS

The study followed a prospective, longitudinal, single-center cohort design. The severity of the depressive symptoms of 101 adult patients with chronic HCV infections was measured during PEG-IFN-α2a/RBV treatment. We used the Montgomery-Åsberg Depression Rating Scale (MADRS) to assess the severity of depressive symptoms. The subjects were evaluated six times-at baseline and at weeks 2, 4, 8, 12, and 24. At all the time points, MADRS score, as well as KYN, TRP, KA, and AA concentrations, and IDO activity were measured. At baseline, rs6295, rs4570625, and 5-HTTLPR rs25531polymorphisms were assessed.

RESULTS

Subjects with C/C genotypes of 5-HT1A and lower-expressing alleles (S/S, L_G/L_G, and S/L_G) of 5-HTTLPR scored the highest total MADRS scores and recorded the highest increase in MADRS scores during treatment. We found associations between TRP concentrations and the TPH-2 and 5-HTTLPR rs25531 genotypes.

CONCLUSIONS

Our findings provide new data that we believe can help better understand infection-induced depression as a distinct type of depression.

Indoleamine 2, 3-dioxygenase is responsible for low stress tolerance after intracerebral hemorrhage

In the chronic phase after intracerebral hemorrhage (ICH), the aftereffect-associated lowering of motivation burdens many patients; however, the pathogenic mechanism is unclear. Here, we revealed for the first time that indoleamine 2, 3-dioxygenase (IDO) expression and enzyme activity are increased in the collagenase-induced murine ICH model. IDO is a rate-limiting enzyme situated at the beginning of the kynurenine pathway and converts tryptophan, a source of serotonin (5-hydroxytryptamine; 5-HT), to kynurenine. In this study, we showed that IDO is localized in 5-HTergic neurons. After ICH, the synaptosomal 5-HT level decreased, but this effect was neutralized by subcutaneous injections of 1-methyl tryptophan (MT), a specific IDO inhibitor. These results suggest that ICH-induced IDO weakens the activity of 5-HTergic neurons. Accordingly, we next investigated whether the IDO increase contributes to the depression-like behaviors of ICH mice. The immobility times of tail suspension and forced swimming tests were significantly prolonged after ICH but shortened by the administration of 1-MT. In conclusion, the increased IDO after ICH was found to decrease 5-HT levels and subsequently reduce stress tolerance. These findings indicate that IDO is a novel therapeutic target for the ICH aftereffect-associated lowering of motivation.

Breaking down the cellular responses to type I interferon neurotoxicity in the brain

Since their original discovery, type I interferons (IFN-Is) have been closely associated with antiviral immune responses. However, their biological functions go far beyond this role, with balanced IFN-I activity being critical to maintain cellular and tissue homeostasis. Recent findings have uncovered a darker side of IFN-Is whereby chronically elevated levels induce devastating neuroinflammatory and neurodegenerative pathologies. The underlying causes of these 'interferonopathies' are diverse and include monogenetic syndromes, autoimmune disorders, as well as chronic infections. The prominent involvement of the CNS in these disorders indicates a particular susceptibility of brain cells to IFN-I toxicity. Here we will discuss the current knowledge of how IFN-Is mediate neurotoxicity in the brain by analyzing the cell-type specific responses to IFN-Is in the CNS, and secondly, by exploring the spectrum of neurological disorders arising from increased IFN-Is. Understanding the nature of IFN-I neurotoxicity is a crucial and fundamental step towards development of new therapeutic strategies for interferonopathies.

Depression trajectories and cytokines in schizophrenia spectrum disorders - A longitudinal observational study

Depression occurs frequently in all phases of schizophrenia spectrum disorders. Altered activity in the immune system is seen in both depression and schizophrenia. We aimed to uncover depressive trajectories in a sample of 144 adult individuals with schizophrenia spectrum disorders followed for one year, in order to identify possible cytokine profile differences. Patients were assessed longitudinally with the Positive and Negative Syndrome Scale (PANSS) and the Calgary Depression Scale for Schizophrenia (CDSS), where a score above 6 predicts depression. The serum cytokine concentrations for tumor necrosis factor (TNF)-alpha, interferon (IFN)-gamma, interleukin (IL)-1beta, IL-2, IL-4, IL-6, IL-10, IL-12p70 and IL-17A were measured using immunoassays. Latent growth curve models, multilevel models and latent class growth analysis (LCGA) were applied. The LCGA model supported three latent classes (trajectories) with differing CDSS profiles during the one-year follow-up: a high CDSS group (40.8 % of participants), a moderate CDSS group (43.9 %) and a low CDSS group (15.3 %). Five single PANSS items predicted affiliation to depressive trajectory: hallucinations, difficulty in abstract thinking, anxiety, guilt feelings and tension. In the high CDSS group, despite diminishing psychotic symptoms, depressive symptoms persisted throughout one year. The pro-inflammatory cytokines IFN-γ, IL-1β and TNF-α were differentially distributed between the depressive trajectories, although levels remained remarkably stable throughout 12 months. Significant changes were found for the anti-inflammatory cytokine IL-10 at baseline with an accompanying difference in change over time. More research is required to optimize future treatment stratification and investigate the contribution of inflammation in depressed patients with schizophrenia spectrum disorders.

Moxibustion alleviates depression-like behavior in rats with Crohn's disease by inhibiting the kynurenine pathway metabolism in the gut-brain axis

Background

Moxibustion is a potential therapy for inflammatory bowel disease-related depression, but its specific mechanism of action is unclear. This study aimed to investigate the molecular mechanism by which moxibustion alleviates depressive behavior in rats with Crohn's disease (CD).

Methods

The CD rat model was established with 2,4,6-trinitrobenzenesulfonic acid. Treatment with moxibustion was applied to Tianshu (ST25, bilateral), Qihai (CV6), and Baihui (GV20) acupoints, and the effect of moxibustion was compared with that of the combination of moxibustion plus indoleamine-2,3-dioxygenase 1 (IDO1) inhibitor, 1-methyltryptophan (1-MT). The effects of moxibustion and moxibustion plus 1-MT combination on colonic inflammation and depressive behavior (assessed by forced swimming test, sucrose preference test, and open field test) were investigated. The changes in IDO1, TNF-α, and IL-1β in rat colon and hippocampus were assessed by Western blot (WB). Gas chromatography-mass spectrometry, immunofluorescence staining, and WB were applied to detect kynurenine pathway (KP) metabolites, hippocampal neuronal activity, and microglia activation, respectively.

Results

Both moxibustion and moxibustion plus 1-MT combination significantly alleviated intestinal inflammation and depressive behavior, downregulated the levels of IDO1 in the colon and hippocampus, and inhibited inflammation-inducing factors IL-1β and TNF-α, as well as the kynurenine/tryptophan (KYN/TRP) ratio of KP metabolites, and upregulated the kynurenic acid (KYNA)/KYN ratio and the KYNA/quinolinic acid (QUIN) ratio in the hippocampus in rats with CD; Hippocampal ionized calcium-binding adaptor molecule-1 (Iba-1), c-fos protein expression, activated microglia, and neuronal activation was also significantly reduced by moxibustion and moxibustion plus 1-MT. The addition of 1-MT did not significantly increase the therapeutic effect of moxibustion.

Conclusion

Moxibustion can improve depressive behavior in rats with CD, which may be related to its regulation of KP metabolism in the gut-brain axis and inhibition of hippocampal microglia activation and neuronal activation.

Biomarker opportunities in the treatment of cancer-related depression

Depression comorbid with cancer is common and associated with a host of negative health outcomes. The inflammatory basis of depression is a growing area of research in cancer, focused on how stressors transduce into inflammation and contribute to the emergence of depression. In this review, we synthesize inflammatory biomarker associations with both depression and the currently available pharmacotherapies and psychotherapies in cancer, underscoring the need for expanding research on anti-inflammatory agents with antidepressant effects. Modulation of inflammatory neuroimmune pathways can slow tumor progression and reduce metastases. Biomarkers associated with depression in cancer may help with diagnosis and treatment monitoring, as well as inform research on novel drug targets to potentially improve cancer survival.

Acute administration of ibuprofen increases serum concentration of the neuroprotective kynurenine pathway metabolite, kynurenic acid: a pilot randomized, placebo-controlled, crossover study

RATIONALE

At least six different types of antidepressant treatments have been shown to either increase the neuroprotective kynurenine pathway (KP) metabolite, kynurenic acid (KynA), or decrease the neurotoxic KP metabolite, quinolinic acid (QA). Nonsteroidal anti-inflammatory drugs (NSAIDs) including ibuprofen have shown some efficacy in the treatment of depression but their effects on the KP have not been studied in humans.

OBJECTIVES

To evaluate the effect of ibuprofen on circulating KP metabolites.

METHODS

In a randomized, placebo-controlled, crossover study, 20 healthy adults (10 women) received a single oral dose of 200-mg ibuprofen, 600-mg ibuprofen, or placebo in a counterbalanced order (NCT02507219). Serum samples were drawn in the mid-afternoon, 5 h after ibuprofen/placebo administration. KP metabolites were measured blind to visit by tandem mass spectrometry. Data were analyzed with linear mixed effect models. The primary outcome was KynA/QA and the secondary outcome was KynA.

RESULTS

After Bonferroni correction, there was a significant effect of treatment on KynA/QA. The effect was driven by an increase in KynA concentration after the 600-mg dose but not the 200-mg dose relative to placebo (Cohen's d = 1.71). In contrast, both the 200-mg (d = 1.03) and 600-mg (d = 2.05) doses of ibuprofen decreased tryptophan concentrations relative to placebo.

CONCLUSIONS

Given its KynA-elevating effects, ibuprofen could have neuroprotective effects in the context of depression as well as other neuroinflammatory disorders that are characterized by a reduction in KynA.

Exploration for biomarkers of postpartum depression based on metabolomics: A systematic review

BACKGROUND

Postpartum depression (PPD) is the most frequent psychiatric complication during the postnatal period and its mechanisms are not fully understood. Metabolomics, can quantitatively measure metabolites in a high-throughput method, and thus uncover the underlying pathophysiology of disease.

OBJECTIVES

In this study, we reviewed metabolomics studies conducted on PPD, aiming to understand the changes of metabolites in PPD patients and analyze the potential application of metabolomics in PPD prediction and diagnosis.

METHODS

Relevant articles were searched in PubMed, Google scholar, and Web of Science databases from January 2011 to July 2022. The metabolites involved were systematically examined and compared. MetaboAnalyst online software was applied to analyze metabolic pathways.

RESULTS

A total of 14 papers were included in this study. There were several highly reported metabolites, such as kynurenine, kynurenic acid, and eicosapentaenoic acid. Dysregulation of metabolic pathways involved amino acids metabolism, fatty acids metabolism, and steroids metabolism.

LIMITATIONS

The included studies are relatively inadequate, and further work is needed.

CONCLUSIONS

This study summarized significant metabolic alterations that provided clues for the prediction, diagnosis, and pathogenesis of PPD.

Evaluation of Inflammatory Response System (IRS) and Compensatory Immune Response System (CIRS) in Adolescent Major Depression

Purpose

Nowadays, the role of two tightly interconnected systems, the inflammatory response system (IRS) and the compensatory immune response system (CIRS) in depression, is increasingly discussed. Various studies indicate pro-inflammatory activity in adolescent depression; however, there is an almost complete lack of findings about IRS and CIRS balance. Thus, we aimed to assess different IRS and CIRS indices, profiles, and IRS/CIRS ratios in drug-naïve MDD patients at adolescent age, with respect to sex.

Patients and Methods

One hundred MDD adolescents (40 boys, average age: 15.4±1.2 yrs.) and 60 controls (28 boys, average age: 15.3±1.5 yrs.) were examined. Evaluated parameters were 1. plasma levels of interleukin (IL)-1α, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, interferon gamma, tumor necrosis factor alpha (TNF-α), soluble receptor of IL-6 (sIL-6R), soluble receptors of TNF-α (sTNF-R1, sTNF-R2); 2. profiles: IL-6 trans-signaling, M1 macrophage signaling, helper T lymphocytes (Th) 1 profile, regulatory T lymphocytes (Treg)+Th2, allIRS, and allCIRS; 3. IRS vs CIRS activity ratios: TNF-α/TNF-R1, TNF-α/TNF-R2, TNF-α/sTNF-Rs (ie sTNF-R1+sTNF-R2), Th1/Th2, Th1/Treg, Th1/Th2+Treg, M1/Th2, M1/Treg, M1/Treg+Th2, allIRS/allCIRS.

Results

MDD patients showed increased IL-4, IL-10, TNF-α, sIL-6R, Treg+Th2, allIRS, allCIRS, and TNF-α/sTNF-Rs, and decreased Th1/Th2+Treg. MDD females showed increased IL-10 and TNF-α compared to control females. MDD males showed increased IL-4, IL-10, sIL-6R, Treg+Th2, and TNF-α/TNF-R1 compared to control males. Increased sTNF-R1 was found in MDD males compared to MDD females. Positive correlations were found between CDI score and sIL-6R and IL-10 in the total group and between CDI score and IL-10 in adolescent males.

Conclusion

Our study for the first time extensively evaluated IRS and CIRS interactions revealing enhanced pro-inflammatory TNF-α signaling and IL-6 trans-signaling in association with increased IL-10- and IL-4-mediated anti-inflammatory activity in first-episode depression at the adolescent age. Moreover, results reflect the sex-specific simultaneous activation of IRS and CIRS pathways in adolescent depression.

The relationship between depressive symptoms and BMI: 2005-2018 NHANES data

BACKGROUND

Depression is one of the most common diseases in the world, and severe depression is the second leading cause of disability in the world. However, the relationship between depressive symptoms and body mass index (BMI) is still unclear. The purpose of this study was to explore the relationship between BMI and depressive symptoms.

METHODS

We conducted a cross-sectional study involving 35,407 participants, all data collected from NHANES 2005-2018. A multivariable logistic regression model was used to analyze the relationship between depressive symptoms (outcome variables) and BMI levels (independent variables). The Patient Health Questionnaire (PHQ-9) was the primary measure of depressive symptoms. We also performed sensitivity analyses, including multiple sensitivity analyses.

RESULTS

After adjusting for covariates, the ORS (95 % CI) of depressive symptoms from the lowest to the highest levels of BMI were 1.14 (1.00-1.30), 1.00 (Reference), 1.19 (1.05-1.35) and 1.45 (1.29-1.64), respectively. However, stratified analysis and sensitivity analysis showed that there was no U-shaped relationship between non-Hispanic black race and depressive symptoms.

LIMITATION

Self-reporting questionnaire may lead to recall bias or reporting bias; Cross-sectional studies failed to verify causality.

CONCLUSION

There is a U-shaped relationship between depression and BMI. However, no such relationship was found among non-Hispanic blacks. More researches are needed to confirm the relationship between weight and depression, as well as the causal relationship between them.

The role and mechanism of tryptophan - kynurenine metabolic pathway in depression

Major depressive disorder (MDD) is a common mental illness characterized by persistent low mood and anhedonia, normally accompanied with cognitive impairment. Due to its rising incidence and high rate of recurrence and disability, MDD poses a substantial threat to patients' physical and mental health, as well as a significant economic cost to society. However, the etiology and pathogenesis of MDD are still unclear. Chronic inflammation may cause indoleamine-2,3-dioxygenase (IDO) to become overactive throughout the body and brain, resulting in excess quinolinic acid (QUIN) and less kynuric acid (KYNA) in the brain. QUIN's neurotoxicity damages glial cells and neurons, accelerates neuronal apoptosis, hinders neuroplasticity, and causes depression due to inflammation. Therefore, abnormal TRP-KYN metabolic pathway and its metabolites have been closely related to MDD, suggesting changes in the TRP-KYN metabolic pathway might contribute to MDD. In addition, targeting TRP-KYN with traditional Chinese medicine showed promising treatment effects for MDD. This review summarizes the recent studies on the TRP-KYN metabolic pathway and its metabolites in depression, which would provide a theoretical basis for exploring the etiology and pathogenesis of depression.

Morinda officinalis oligosaccharides mitigate chronic mild stress-induced inflammation and depression-like behaviour by deactivating the MyD88/PI3K pathway via E2F2

Morinda officinalis oligosaccharides (MOs) are natural herbal extracts that have been shown to exert antidepressant effects. However, the mechanism of this effect remains unclear. Here, we explored the mechanism by which MOs improved experimental depression. Using a chronic mild stress (CMS) murine model, we examined whether MOs could protect against depressive-like behaviour. Lipopolysaccharide (LPS)- and ATP-treated BV2 cells were used to examine the potential mechanism by which MOs mediate the inflammatory response. We found that MOs prevented the CMS-induced reduction in the sucrose preference ratio in the sucrose preference test (SPT) and shortened the immobility durations in both the tail suspension test (TST) and forced swim test (FST). We also noticed that MOs suppressed inflammatory effects by deactivating the MyD88/PI3K pathway via E2F2 in CMS mice or LPS- and ATP-stimulated BV2 cells. Furthermore, overexpression of E2F2 blunted the beneficial effects of MOs in vitro. Collectively, these data showed that MOs exerted antidepressant effects in CMS mice by targeting E2F2-mediated MyD88/PI3K signalling pathway.

Metabolic Pathways Associated With Psychoneurological Symptoms in Children With Cancer Receiving Chemotherapy

CONTEXT

Children with cancer undergoing chemotherapy experience a cluster of psychoneurological symptoms (PNS), including pain, fatigue, anxiety, and depressive symptoms. Metabolomics is promising to differentiate metabolic pathways associated with the PNS cluster.

OBJECTIVES

Identify metabolic pathways associated with the PNS cluster in children with cancer before and after chemotherapy.

METHODS

Pain, fatigue, anxiety, and depressive symptoms were assessed using the Pediatric PROMIS scales. T-scores were computed and divided dichotomously by a cutoff point of 50; the PNS cluster was a sum of the four symptoms ranging from 0 (all T-scores <50) to 4 (all T-scores ≥50). Serum metabolites were processed using liquid chromatography mass-spectrometry untargeted metabolomics approach. Linear regression models examined metabolites associated with the PNS cluster. Metabolic pathway enrichment analysis was performed.

RESULTS

Participant demographics (n = 40) were 55% female, 60% white, 62.5% aged 13-19 years, and 62.5% diagnoses of Hodgkin's lymphoma and B-cell acute lymphocytic leukemia. Among 9276 unique metabolic features, 454 were associated with pain, 281 with fatigue, 596 with anxiety, 551 with depressive symptoms, and 300 with the PNS cluster across one chemotherapy cycle. Fatty acids pathways were associated with pain: de novo fatty acid biosynthesis (p < .001), fatty acid metabolism (p = .001), fatty acid activation (p = .004), and omega-3 fatty acid metabolism (p = .009). Tryptophan amino acid pathway was associated with fatigue (p < .001), anxiety (p = .015), and the PNS cluster (p = .037). Carnitine shuttle was associated with the PNS cluster (p = .015).

CONCLUSION

Fatty acids and amino acids pathways were associated with PNS in children undergoing chemotherapy. These findings require further investigation in a larger sample.

Effects of stress on endophenotypes of suicide across species: A role for ketamine in risk mitigation

Suicide is a leading cause of death and morbidity worldwide, yet few interventions are available to mitigate its risk. Barriers to effective treatments involve a limited understanding of factors that predict the onset of suicidal thoughts and behaviors. In the context of suicide risk, stress is a precipitating factor that is largely overlooked in the literature. Indeed, the pathophysiology of stress and suicide are heavily interconnected, underscoring the need to target the stress system in suicide prevention. In this review, we integrate findings from the preclinical and clinical literature that links stress and suicide. We focus specifically on the effects of stress on underlying biological functions and processes associated with suicide, allowing for the review of research using animal models. Owing to the rapid anti-suicidal effects of (R,S)-ketamine, we discuss its ability to modulate various stress-related endophenotypes of suicide, as well as its potential role in preventing suicide in those with a history of chronic life stress (e.g., early life adversity). We highlight future research directions that could advance our understanding of stress-related effects on suicide risk, advocating a dimensional, endophenotype approach to suicide research.

•

Suicide and chronic stress pathophysiology are interconnected.

•

Chronic stress has profound impacts on several endophenotypes of suicide.

•

Animal and human research points to stress as a precipitating factor in suicide.

•

Ketamine modulates specific biological processes associated with stress and suicide.

•

Suicide research into endophenotypes can help inform risk-mitigation strategies.

Regulation of the kynurenine/serotonin pathway by berberine and the underlying effect in the hippocampus of the chronic unpredictable mild stress mice

BACKGROUND

Depression is a common mental disorder and is one of the main causes of disability. Berberine (BBR), the major constituent alkaloid originally from the famous Chinese herb Huanglian (Coptis chinensis), has been shown to exert antidepressant-like effects. This study was to investigate the hypothesis that BBR treats depressive-like behavior by shifting the balance of the kynurenine (KYN)/serotonin (5-HT) pathway toward the 5-HT pathway through downregulated indoleamine 2,3-dioxygenase 1 (IDO1), monoamine oxidase A (MAOA) and upregulated dopamine decarboxylase (DDC) in hippocampus.

METHOD

A chronic unpredictable mild stress (CUMS) mice model of depression was established via 21 days unpredictable stimulation. Then the mice were randomly assigned into six groups, namely control, model, fluoxetine [FLU, (10 mg/kg)], BBRL (25 mg/kg), BBRM (50 mg/kg), and BBRH (100 mg/kg) groups. Behavioral assessments were conducted to evaluate the antidepressant effects of BBR. The levels of 5-HT, KYN, tryptophan (TRP), and 5-hydroxyindoleacetic acid (5-HIAA) in hippocampus were estimated using high performance liquid chromatography (HPLC). The mRNA and protein levels of DDC, MAOA and IDO1 in hippocampus were detected by real-time quantitative polymerase chain reaction (qRT-PCR) and western blot (WB), respectively.

RESULT

The results showed that a successful CUMS mice model was established through 21 days of continuous unpredictable stimulation, as indicated by the significant decrease in locomotor activity and increase in immobility time, reduction in body weight and sucrose preference rate etc. Compared with the normal group, the concentrations of KYN/TRP had significantly increased (p^## <0.01) and 5-HT/5-HIAA had decreased (p^#<0.05) at day 21 in the control group, but then improved after drug treatment with FLU and BBR. Compared with the normal group, the mRNA of IDO1 and MAOA were significantly upregulated (p^#<0.05) in the control group, MAOA and IDO1 gene were downregulated by FLU and BBR treatment. Protein expressions of IDO1 and MAOA was significantly increased (p^#<0.05) and DDC downregulated (p^##<0.01). BBR treatment downregulated IDO1 and MAOA, upregulated DDC.

CONCLUSIONS

BBR reversed the abnormalities of the KYN/5-HT pathway in depressed mice and achieved an excellent antidepressant effect. Its direct impact may be observed as changes in biological indicators in mice hippocampus tissue.

Association between the indole pathway of tryptophan metabolism and subclinical depressive symptoms in obesity: a preliminary study

Converging data support the role of chronic low-grade inflammation in depressive symptomatology in obesity. One mechanism likely to be involved relies on the effects of inflammation on tryptophan (TRP) metabolism. While recent data document alterations in the indole pathway of TRP metabolism in obesity, the relevance of this mechanism to obesity-related depressive symptoms has not been investigated. The aim of this preliminary study was to assess the association between plasma levels of TRP and indole metabolites and depressive symptoms in 44 subjects with severe or morbid obesity, free of clinically relevant neuropsychiatric disorders. The interaction effect of inflammation, reflected in serum high-sensitive C-reactive protein (hsCRP) levels, and indoles on depressive symptoms was also determined. Higher serum levels of hsCRP and lower concentrations of TRP and indoles, particularly indole-3-carboxaldehyde (IAld), correlated with more severe depressive symptoms. Interestingly, the effect of high hsCRP levels in predicting greater depressive symptoms was potentiated by low IAld levels. These results comfort the link between inflammation, the indole pathway of TRP metabolism, and obesity-related depressive symptoms.

Unlocking the potential of Escherichia coli modified magnetic particles for chiral discrimination of racemic tryptophan

Enzymes possess a highly specific affinity toward their substrates. In this study, an enzyme-based biological method was established for chiral discrimination of D/L-tryptophan (Trp). The polydopamine modified magnetic particles (PDA@Fe₃O₄) were prepared for immobilization of the genetically engineered bacterium Escherichia coli (E. coli) DH5α. The bacteria-magnetic particles conjugates (bacteria@PDA@Fe₃O₄) demonstrate excellent chiral discrimination performance toward D/L-Trp at pH 7.0 and 45 °C. The investigation for the principle exhibits that the immobilized E. coli DH5α can produce tryptophanase, and the enzyme can selectively recognize and degrade L-Trp. The Michaelis constant of tryptophanase produced by bacteria@PDA@Fe₃O₄ was measured to be 25.7 µg mL^-1. This method avoids the purification of tryptophanase and unlocks the potential of bacteria modified magnetic particles for chiral discrimination of racemic tryptophan.

Biomarkers of Post-COVID Depression

The COVID-19 pandemic is spreading around the world and 187 million people have already been affected. One of its after-effects is post-COVID depression, which, according to the latest data, affects up to 40% of people who have had SARS-CoV-2 infection. A very important issue for the mental health of the general population is to look for the causes of this complication and its biomarkers. This will help in faster diagnosis and effective treatment of the affected patients. In our work, we focused on the search for major depressive disorder (MDD) biomarkers, which are also present in COVID-19 patients and may influence the development of post-COVID depression. For this purpose, we searched PubMed, Scopus and Google Scholar scientific literature databases using keywords such as 'COVID-19', 'SARS-CoV-2', 'depression', 'post-COVID', 'biomarkers' and others. Among the biomarkers found, the most important that were frequently described are increased levels of interleukin 6 (IL-6), soluble interleukin 6 receptor (sIL-6R), interleukin 1 β (IL-1β), tumor necrosis factor α (TNF-α), interferon gamma (IFN-γ), interleukin 10 (IL-10), interleukin 2 (IL-2), soluble interleukin 2 receptor (sIL-2R), C-reactive protein (CRP), Monocyte Chemoattractant Protein-1 (MCP-1), serum amyloid a (SAA1) and metabolites of the kynurenine pathway, as well as decreased brain derived neurotrophic factor (BDNF) and tryptophan (TRP). The biomarkers identified by us indicate the etiopathogenesis of post-COVID depression analogous to the leading inflammatory hypothesis of MDD.

Neuromodulation by the immune system: a focus on cytokines

Interactions between the immune system and the nervous system have been described mostly in the context of diseases. More recent studies have begun to reveal how certain immune cell-derived soluble effectors, the cytokines, can influence host behaviour even in the absence of infection. In this Review, we contemplate how the immune system shapes nervous system function and how it controls the manifestation of host behaviour. Interactions between these two highly complex systems are discussed here also in the context of evolution, as both may have evolved to maximize an organism's ability to respond to environmental threats in order to survive. We describe how the immune system relays information to the nervous system and how cytokine signalling occurs in neurons. We also speculate on how the brain may be hardwired to receive and process information from the immune system. Finally, we propose a unified theory depicting a co-evolution of the immune system and host behaviour in response to the evolutionary pressure of pathogens.

Aiding and Abetting Anhedonia: Impact of Inflammation on the Brain and Pharmacological Implications

Exogenous administration of inflammatory stimuli to humans and laboratory animals and chronic endogenous inflammatory states lead to motivational deficits and ultimately anhedonia, a core and disabling symptom of depression present in multiple other psychiatric disorders. Inflammation impacts neurotransmitter systems and neurocircuits in subcortical brain regions including the ventral striatum, which serves as an integration point for reward processing and motivational decision-making. Many mechanisms contribute to these effects of inflammation, including decreased synthesis, release and reuptake of dopamine, increased synaptic and extrasynaptic glutamate, and activation of kynurenine pathway metabolites including quinolinic acid. Neuroimaging data indicate that these inflammation-induced neurotransmitter effects manifest as decreased activation of ventral striatum and decreased functional connectivity in reward circuitry involving ventral striatum and ventromedial prefrontal cortex. Neurocircuitry changes in turn mediate nuanced effects on motivation that include decreased willingness to expend effort for reward while maintaining the ability to experience reward. Taken together, the data reveal an inflammation-induced pathophysiologic phenotype that is agnostic to diagnosis. Given the many mechanisms involved, this phenotype represents an opportunity for development of novel and/or repurposed pharmacological strategies that target inflammation and associated cellular and systemic immunometabolic changes and their downstream effects on the brain. To date, clinical trials have failed to capitalize on the unique nature of this transdiagnostic phenotype, leaving the field bereft of interpretable data for meaningful clinical application. However, novel trial designs incorporating established targets in the brain and/or periphery using relevant outcome variables (e.g., anhedonia) are the future of targeted therapy in psychiatry. SIGNIFICANCE STATEMENT: Emerging understanding of mechanisms by which peripheral inflammation can affect the brain and behavior has created unprecedented opportunities for development of pharmacological strategies to treat deficits in motivation including anhedonia, a core and disabling symptom of depression well represented in multiple psychiatric disorders. Mechanisms include inflammation and cellular and systemic immunometabolism and alterations in dopamine, glutamate, and kynurenine metabolites, revealing a target-rich environment that nevertheless has yet to be fully exploited by current clinical trial designs and drugs employed.

Tryptophan-kynurenine metabolism: a link between the gut and brain for depression in inflammatory bowel disease

Inflammatory bowel disease (IBD), which mainly includes ulcerative colitis (UC) and Crohn's disease (CD), is a group of chronic bowel diseases that are characterized by abdominal pain, diarrhea, and bloody stools. IBD is strongly associated with depression, and its patients have a higher incidence of depression than the general population. Depression also adversely affects the quality of life and disease prognosis of patients with IBD. The tryptophan-kynurenine metabolic pathway degrades more than 90% of tryptophan (TRP) throughout the body, with indoleamine 2,3-dioxygenase (IDO), the key metabolic enzyme, being activated in the inflammatory environment. A series of metabolites of the pathway are neurologically active, among which kynerunic acid (KYNA) and quinolinic acid (QUIN) are molecules of great interest in recent studies on the mechanisms of inflammation-induced depression. In this review, the relationship between depression in IBD and the tryptophan-kynurenine metabolic pathway is overviewed in the light of recent publications.

Early Life Stress and the Fate of Kynurenine Pathway Metabolites

Early life stress (ELS) precedes alterations to neuro-immune activation, which may mediate an increased risk for stress-related psychiatric disorders, potentially through alterations of central kynurenine pathway (KP) metabolites, the latter being relatively unexplored. We hypothesized that ELS in a non-human primate model would lead to a reduction of neuroprotective and increases of neurotoxic KP metabolites. Twelve adult female bonnet macaques reared under conditions of maternal variable foraging demand (VFD) were compared to 27 age- and weight-matched non-VFD-exposed female controls. Baseline behavioral observations of social affiliation were taken over a 12-week period followed by the first cerebrospinal fluid (CSF) sample. Subjects were then either exposed to a 12-week repeated separation paradigm (RSP) or assigned to a “no-RSP” condition followed by a second CSF. We used high-performance liquid chromatography for kynurenine (KYN), tryptophan, 5-hydroxyindoleacetic acid, kynurenic acid (KYNA), and anthranilic acid (ANTH) as a proxy for quinolinic acid determination. At baseline, social affiliation scores were reduced in VFD-reared versus control subjects. CSF log KYNA and log KYNA/KYN ratio were lower in VFD-reared versus control subjects. CSF log KYNA/KYN was positively correlated with CSF log ANTH in VFD only (r = 0.82). Controlling for log KYNA/KYN, log ANTH was elevated in VFD-reared subjects versus controls. CSF log KYNA/KYN obtained post-RSP was positively correlated with mean social affiliation scores during RSP, specifically in VFD. ELS is associated with a reduced neuroprotective and increased neurotoxic pathway products. That the two contrasting processes are paradoxically correlated following ELS suggests a cross-talk between two opposing KP enzymatic systems.

Anhedonia and Increased Evoked Immune Response

There is a growing body of evidence supporting the association between immune processes and psychopathology, including major depressive disorder (MDD). However, lack of diagnostic specificity has given rise to a search for specific symptom types, as opposed to more heterogeneous categorical diagnoses, linked to increased inflammation. One such symptom could be anhedonia, which is not only a key feature of MDD, but also a pervasive and persistent transdiagnostic symptom. To evaluate the specific role of anhedonia as well as categorical MDD diagnoses, we examined endotoxin-evoked immune responses in vitro in relation to current levels of anhedonia and history of recurrent MDD (rMDD) in a sample of adults recruited from the community. A total of 39 participants either had a history of rMDD (n ​= ​20) or no lifetime history of any MDD episodes (n ​= ​19). The average age of participants was 36.81 years and the majority were women (87.2%) and Caucasian (76.3%). We found that higher levels of current anhedonia, but not history of rMDD, were associated with increased lipopolysaccharide-stimulated levels of inflammatory markers even after we statistically adjusted for the potential influence of participants’ demographic (age, sex, ethnicity, income) and physiological (body temperature, BMI) characteristics, current symptoms of depression and anxiety, and the time of day of the sample collection. These findings highlight the relation of anhedonia specifically, rather than rMDD more generally, with inflammatory processes and identify endotoxin-stimulated cytokine production as a plausible biological marker of current anhedonia.

Diet, Obesity, and Depression: A Systematic Review

BACKGROUND

Obesity and depression co-occur in a significant proportion of the population. Mechanisms linking the two disorders include the immune and the endocrine system, psychological and social mechanisms. The aim of this systematic review was to ascertain whether weight loss through dietary interventions has the additional effect of ameliorating depressive symptoms in obese patients.

METHODS

We systematically searched three databases (Pubmed, Medline, Embase) for longitudinal clinical trials testing a dietary intervention in people with obesity and depression or symptoms of depression.

RESULTS

Twenty-four longitudinal clinical studies met the eligibility criteria with a total of 3244 included patients. Seventeen studies examined the effects of calorie-restricted diets and eight studies examined dietary supplements (two studies examined both). Only three studies examined people with a diagnosis of both obesity and depression. The majority of studies showed that interventions using a calorie-restricted diet resulted in decreases in depression scores, with effect sizes between ≈0.2 and ≈0.6. The results were less clear for dietary supplements.

CONCLUSIONS

People with obesity and depression appear to be a specific subgroup of depressed patients in which calorie-restricted diets might constitute a promising personalized treatment approach. The reduction of depressive symptoms may be related to immunoendocrine and psychosocial mechanisms.

Microglia Fighting for Neurological and Mental Health: On the Central Nervous System Frontline of COVID-19 Pandemic

Coronavirus disease 2019 (COVID-19) is marked by cardio-respiratory alterations, with increasing reports also indicating neurological and psychiatric symptoms in infected individuals. During COVID-19 pathology, the central nervous system (CNS) is possibly affected by direct severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) invasion, exaggerated systemic inflammatory responses, or hypoxia. Psychosocial stress imposed by the pandemic further affects the CNS of COVID-19 patients, but also the non-infected population, potentially contributing to the emergence or exacerbation of various neurological or mental health disorders. Microglia are central players of the CNS homeostasis maintenance and inflammatory response that exert their crucial functions in coordination with other CNS cells. During homeostatic challenges to the brain parenchyma, microglia modify their density, morphology, and molecular signature, resulting in the adjustment of their functions. In this review, we discuss how microglia may be involved in the neuroprotective and neurotoxic responses against CNS insults deriving from COVID-19. We examine how these responses may explain, at least partially, the neurological and psychiatric manifestations reported in COVID-19 patients and the general population. Furthermore, we consider how microglia might contribute to increased CNS vulnerability in certain groups, such as aged individuals and people with pre-existing conditions.

The role of anthranilic acid in the increase of depressive symptoms and major depressive disorder during treatment for hepatitis C with pegylated interferon-α2a and oral ribavirin

BACKGROUND

Tryptophan metabolism via the kynurenine pathway is considered the link between the immune and endocrine systems. Dysregulation of serotonergic transmission can stem from the direct influence of interferon-α on the activity of serotonergic receptors 5-HT1A and 5-HT2A, and from its indirect effect on tryptophan metabolism. Induction of the kynurenine pathway increases the concentration of neurotoxic kynurenine metabolites, and the activity of kynurenine derivatives is linked to the onset of depression. The aim of our study was to evaluate the relationships between depressive symptoms and kynurenine, tryptophan, anthranilic acid and kynurenic acid concentrations, indolamine 2,3-dioxygenase (IDO) activity and tryptophan availability to the brain.

METHODS

The study followed a prospective longitudinal cohort design. We evaluated 101 patients with chronic hepatitis C who were treated with pegylated interferon-α2a, and 40 controls who were awaiting treatment. We evaluated the relationships between total score on the Montgomery-Åsberg Depression Rating Scale and kynurenine, tryptophan, anthranilic acid and kynurenic acid concentrations, IDO activity and tryptophan availability to the brain. A logistic regression model was adapted for the diagnosis of major depressive disorder at each time point, taking into account changes in parameters of the kynurenine pathway between a given time point and the baseline measurement.

RESULTS

Of the treated patients, 44% fulfilled the criteria for major depressive disorder at least once during the 24 weeks of treatment. Anthranilic acid concentrations were significantly increased compared to baseline for all time points except week 2. Tryptophan availability showed a significant decrease (β = -0.09, p = 0.01) only in week 12 of treatment. Over time, kynurenine, tryptophan and anthranilic acid concentrations, as well as IDO activity and tryptophan availability to the brain, were significantly associated with total score on the Montgomery-Åsberg Depression Rating Scale. A logistic regression model revealed that participants with decreased tryptophan availability to the brain at 12 weeks of treatment and participants with increased anthranilic acid concentrations at week 24 of treatment were at increased risk for diagnosis of major depressive disorder (odds ratios 2.92 and 3.59, respectively).

LIMITATIONS

This study had an open-label design in a population receiving naturalistic treatment.

CONCLUSION

The present study provides the first direct evidence of the role of anthranilic acid in the pathogenesis of inflammation-induced major depressive disorder during treatment for hepatitis C with pegylated interferon-α2a.

Interaction Mechanisms Between Major Depressive Disorder and Non-alcoholic Fatty Liver Disease

Major depressive disorder (MDD), which is highly associated with non-alcoholic fatty liver disease (NAFLD), has complex pathogenic mechanisms. However, a limited number of studies have evaluated the mutual pathomechanisms involved in MDD and NAFLD development. Chronic stress-mediated elevations in glucocorticoid (GC) levels play an important role in the development of MDD-related NAFLD. Elevated GC levels can induce the release of inflammatory factors and changes in gut permeability. Elevated levels of inflammatory factors activate the hypothalamic-pituitary-adrenal (HPA) axis, which further increases the release of GC. At the same time, changes in gut permeability promote the release of inflammatory factors, which results in a vicious circle among the three, causing disease outbreaks. Even though the specific role of the thyroid hormone (TH) in this pathogenesis has not been fully established, it is highly correlated with MDD and NAFLD. Therefore, changing lifestyles and reducing psychological stress levels are necessary measures for preventing MDD-related NAFLD. Among them, GC inhibitors and receptor antagonists may be key in the alleviation of early and mid-term disease progression. However, combination medications may be important in late-stage diseases, but they are associated with various side effects. Traditional Chinese medicines have been shown to be potential therapeutic alternatives for such complex diseases.

The Link Between Autonomic Nervous System and Rheumatoid Arthritis: From Bench to Bedside

Neuronal stimulation is an emerging field of research focused on the management and treatment of various diseases through the reestablishment of physiological homeostasis. Electrical vagus nerve stimulation has recently been proposed as a revolutionary therapeutic option for rheumatoid arthritis (RA) in combination with or even as a replacement for conventional and biological drugs. In the past few years, disruption of the autonomic system has been linked to RA onset and activity. Novel research on the link between the autonomic nervous system and the immune system (immune-autonomics) has paved the way for the development of innovative RA management strategies. Clinical evidence supports this approach. Cardiovascular involvement, in terms of reduced baroreflex sensitivity and heart rate variability-derived indices, and mood disorders, common comorbidities in patients with RA, have been linked to autonomic nervous system dysfunction, which in turn is influenced by increased levels of circulating pro-inflammatory cytokines. This narrative review provides an overview of the autonomic nervous system and RA connection, discussing most of the common cardiac and mental health-related RA comorbidities and their potential relationships to systemic and joint inflammation.

Peripheral Markers of Depression

Major Depressive Disorder (MDD) is a leading cause of disability worldwide, creating a high medical and socioeconomic burden. There is a growing interest in the biological underpinnings of depression, which are reflected by altered levels of biological markers. Among others, enhanced inflammation has been reported in MDD, as reflected by increased concentrations of inflammatory markers-C-reactive protein, interleukin-6, tumor necrosis factor-α and soluble interleukin-2 receptor. Oxidative and nitrosative stress also plays a role in the pathophysiology of MDD. Notably, increased levels of lipid peroxidation markers are characteristic of MDD. Dysregulation of the stress axis, along with increased cortisol levels, have also been reported in MDD. Alterations in growth factors, with a significant decrease in brain-derived neurotrophic factor and an increase in fibroblast growth factor-2 and insulin-like growth factor-1 concentrations have also been found in MDD. Finally, kynurenine metabolites, increased glutamate and decreased total cholesterol also hold promise as reliable biomarkers for MDD. Research in the field of MDD biomarkers is hindered by insufficient understanding of MDD etiopathogenesis, substantial heterogeneity of the disorder, common co-morbidities and low specificity of biomarkers. The construction of biomarker panels and their evaluation with use of new technologies may have the potential to overcome the above mentioned obstacles.

Indoleamine and tryptophan 2,3-dioxygenases as important future therapeutic targets

Conversion of tryptophan to N-formylkynurenine is the first and rate-limiting step of the tryptophan metabolic pathway (i.e., the kynurenine pathway). This conversion is catalyzed by three enzyme isoforms: indoleamine 2,3-dioxygenase 1 (IDO1), indoleamine 2,3-dioxygenase 2 (IDO2), and tryptophan 2,3-dioxygenase (TDO). As this pathway generates numerous metabolites that are involved in various pathological conditions, IDOs and TDO represent important targets for therapeutic intervention. This pathway has especially drawn attention due to its importance in tumor resistance. Over the last decade, a large number of IDO and TDO inhibitors have been developed, many of which have entered clinical trials. Here, detailed structural comparisons of these three enzymes (with emphasis on their active sites), their involvement in cellular signaling, and their role(s) in pathological conditions are discussed. Furthermore, the most important recent inhibitors described in papers and patents and involved in clinical trials are reviewed, with a focus on both selective and multiple inhibitors. A short overview of the biochemical and cellular assays used for inhibitory potency evaluation is also presented. This review summarizes recent advances on IDO and TDO as potential drug targets, and provides the key features and perspectives for further research and development of potent inhibitors of the kynurenine pathway.

Cognitive assessment in patients with Hepatitis C submitted to treatment with Sofosbuvir and Simeprevir or Daclatasvir

BACKGROUND

Hepatitis C can be defined as an infectious disease that develops an inflammatory activity, which may cause an impairment in the central nervous system, may cause cognitive impairments and symptoms of depression.

OBJECTIVE

The objective of this study was to verify the cognitive performance of patients with chronic hepatitis C before and after treatment with simeprevir, sofosbuvir, and daclatasvir.

METHODS

A prospective study was carried out in three stages: before, right after treatment, and six months after. Fifty-eight patients under clinical follow-up were evaluated at the Emílio Ribas Infectology Institute, in São Paulo, Brazil. The following instruments were used: sociodemographic questionnaire, Lawton's Scale, Beck's Depression Inventory, and a battery of neuropsychological tests that evaluated: intellectual function, memory, attention, executive function, and motor and processing speed). For statistical analysis, the analyses described (mean, frequency, and standard deviation), chi-square, and ANOVA were used.

RESULTS

Most of the participants were male (n=30, 51.7%), with a mean of 58.23±8.79 years, mean schooling of 9.75±4.43 years. Comparing the results of neuropsychological evaluations (before, just after completion of drugs, and six months), a significant improvement was observed in relation to the acquisition of new knowledge (p=0.03), late visual memory (p=0.01), and tendency towards alternate attention (p=0.07).

CONCLUSION

The treatment of the hepatitis C virus improved cognitive performance, especially in relation to memory.

Immunotherapy of COVID-19 with poly (ADP-ribose) polymerase inhibitors: starting with nicotinamide

COVID-19 induces a proinflammatory environment that is stronger in patients requiring intensive care. The cytokine components of this environment may determine efficacy or otherwise of glucocorticoid therapy. The immunity modulators, the aryl hydrocarbon receptor (AhR) and the nuclear NAD+-consuming enzyme poly (ADP-ribose) polymerase 1 (PARP 1) may play a critical role in COVID-19 pathophysiology. The AhR is overexpressed in coronaviruses, including COVID-19 and, as it regulates PARP gene expression, the latter is likely to be activated in COVID-19. PARP 1 activation leads to cell death mainly by depletion of NAD+ and adenosine triphosphate (ATP), especially when availability of these energy mediators is compromised. PARP expression is enhanced in other lung conditions: the pneumovirus respiratory syncytial virus (RSV) and chronic obstructive pulmonary disease (COPD). I propose that PARP 1 activation is the terminal point in a sequence of events culminating in patient mortality and should be the focus of COVID-19 immunotherapy. Potent PARP 1 inhibitors are undergoing trials in cancer, but a readily available inhibitor, nicotinamide (NAM), which possesses a highly desirable biochemical and activity profile, merits exploration. It conserves NAD+ and prevents ATP depletion by PARP 1 and Sirtuin 1 (silent mating type information regulation 2 homologue 1) inhibition, enhances NAD+ synthesis, and hence that of NADP+ which is a stronger PARP inhibitor, reverses lung injury caused by ischaemia/reperfusion, inhibits proinflammatory cytokines and is effective against HIV infection. These properties qualify NAM for therapeutic use initially in conjunction with standard clinical care or combined with other agents, and subsequently as an adjunct to stronger PARP 1 inhibitors or other drugs.

The Impact of Chronic Mild Stress and Agomelatine Treatment on the Expression Level and Methylation Status of Genes Involved in Tryptophan Catabolic Pathway in PBMCs and Brain Structures

Depression is the serious mental disorder. Previous studies suggest that the development mechanism of depression may be associated with disorders of the tryptophan catabolic pathway (TRYCAT). Thus, this study investigates the effect of agomelatine treatment on the expression and methylation status of genes involved in TRYCAT in the brain and blood of rats exposed to a chronic mild stress (CMS). Separate groups of rats were exposed to CMS for two or seven weeks; the second group received vehicle or agomelatine for five weeks. After completion of both stress conditions and treatment, the expression levels of messenger RNA (mRNA) and protein, as well as the methylation status of promoters, were measured in peripheral blood mononuclear cells (PBMCs) and in brain structures with the use of TaqMan Gene Expression Assay, Western blot, and methylation-sensitive high-resolution melting techniques. In PBMCs, Kmo mRNA expression increased in the group after CMS, while this effect was normalized by agomelatine therapy. In brain, KatI and KatII expression changed following CMS exposure. Moreover, CMS decreased the methylation status of the second Tdo2 promoter in the amygdala. Protein expression of Tph1, Tph2, Ido1, and KatII changed in the group after CMS and agomelatine administration, most prominently in the basal ganglia, cerebral cortex, hippocampus, and amygdala. The results indicate that CMS and agomelatine affect the mRNA and protein expression, as well as the methylation of promoters of genes involved in the tryptophan catabolic pathway.

Kynurenine pathway metabolites selectively associate with impaired associative memory function in depression

Activation of the kynurenine pathway (KP), an important downstream effect of inflammation, is a driver of depression and neurodegeneration. Damage from the end product of KP activation, quinolinic acid, may be responsible specifically for impairment in hippocampally mediated memory function, among its effects. We hypothesized that associative memory - the ability to recall relationships between items - would be sensitive to KP activation because it is heavily dependent on the hippocampus. We tested a sample of N ​= ​80 adults with unmedicated depression using a face-name task which assesses the ability to recognize, as well as to recall correct pairings, of faces and names. Plasma samples were analyzed for KP metabolites - tryptophan (TRP), kynurenine (KYN), quinolinic acid (QUIN) and kynurenic acid (KYNA). Using linear models we examined whether the KYN/TRP and QUIN/KYNA ratios predicted performance of recognition memory and associative memory, accounting for item type and the number of learning exposures to items (1 vs. 3). We found that for rearranged items viewed three times, associative memory performance was inversely related to the QUIN/KYNA ratio (p ​= ​0.01, p ​= ​0.001 adjusted for age, gender and race/ethnicity). Recognition memory was not associated with KP activation. The results support our hypothesis that KP activation most sensitively impacts hippocampally mediated memory function.

Reductions in anti-inflammatory gut bacteria are associated with depression in a sample of young adults

We assessed the gut microbiota of 90 American young adults, comparing 43 participants with major depressive disorder (MDD) and 47 healthy controls, and found that the MDD subjects had significantly different gut microbiota compared to the healthy controls at multiple taxonomic levels. At the phylum level, participants with MDD had lower levels of Firmicutes and higher levels of Bacteroidetes, with similar trends in the at the class (Clostridia and Bacteroidia) and order (Clostridiales and Bacteroidales) levels. At the genus level, the MDD group had lower levels of Faecalibacterium and other related members of the family Ruminococcaceae, which was also reduced relative to healthy controls. Additionally, the class Gammaproteobacteria and genus Flavonifractor were enriched in participants with MDD. Accordingly, predicted functional differences between the two groups include a reduced abundance of short-chain fatty acid production pathways in the MDD group. We also demonstrated that the magnitude of taxonomic changes was associated with the severity of depressive symptoms in many cases, and that most changes were present regardless of whether depressed participants were taking psychotropic medications. Overall, our results support a link between MDD and lower levels of anti-inflammatory, butyrate-producing bacteria, and may support a connection between the gut microbiota and the chronic, low-grade inflammation often observed in MDD patients.

The Bidirectional Relationship of Depression and Inflammation: Double Trouble

Depression represents the number one cause of disability worldwide and is often fatal. Inflammatory processes have been implicated in the pathophysiology of depression. It is now well established that dysregulation of both the innate and adaptive immune systems occur in depressed patients and hinder favorable prognosis, including antidepressant responses. In this review, we describe how the immune system regulates mood and the potential causes of the dysregulated inflammatory responses in depressed patients. However, the proportion of never-treated major depressive disorder (MDD) patients who exhibit inflammation remains to be clarified, as the heterogeneity in inflammation findings may stem in part from examining MDD patients with varied interventions. Inflammation is likely a critical disease modifier, promoting susceptibility to depression. Controlling inflammation might provide an overall therapeutic benefit, regardless of whether it is secondary to early life trauma, a more acute stress response, microbiome alterations, a genetic diathesis, or a combination of these and other factors.

Psychiatric side effects of interferon-β in multiple sclerosis

Psychiatric disorders, especially depression, are frequent in patients with multiple sclerosis (MS). They are attributed both to the psychosocial impact of a chronic, usually progressive, disabling illness and to cerebral demyelination. Besides, drugs such as corticosteroids and possibly interferon (IFN) may also have depressogenic effects. Major depressive disorders and/or suicidal ideation are a major concern and efforts to identify and minimize these reactions are of much importance. Psychiatric side effects, particularly depression, are widely reported with IFN-α and have been suspected with IFN-β but are not yet fully established. Our review of the literature revealed that most studies discard an association between IFN-β and depression or suicide. However, few patients, especially those with a history of depression, might be at higher risk for depression when treated with IFN-β. Overall, considering the uncertainty of a link between IFN-β and depression and/or suicide, as well as the complete remission of psychiatric complications after IFN discontinuation and/or antidepressant treatment, physicians should closely monitor the psychiatric status of patients, but should not refrain from including them in IFN-β treatment programs, even when they have past or present depression.