The lipid paradox in neuroprogressive disorders: Causes and consequences

Inflammation molecular network alterations in a depressive-like primate model

At present, there are no definitive biomarkers for major depressive disorder (MDD). Previous studies prompted that neuroimmunoinflammation is involved in the pathogenesis of depression and its factors become potential diagnostic biomarkers. Non-human primates exhibit depression-like behavior similar to humans in chronically stressed environments. Therefore, in the present study, after completing Whole transcriptome sequencing of peripheral blood, neurology-related and inflammatory molecules in plasma and cerebrospinal fluid were measured by Olink proximity extension assay technology simultaneously in 4 natural depressive-like (DL) cynomolgus monkeys and 4 normal controls to screen potential biological markers. Further, postmortem brain tissues and peripheral blood RNA sequencing data from MDD patients available in the Gene Expression Omnibus (GEO) database were used for cross-species validation. Compared to control monkeys, depressive-like monkeys exhibited elevated levels of neurocan (NCAN). RNA sequencing revealed Toll-like receptor 4 (TLR4) and the interacting S100 calcium-binding protein A family as key molecules in the inflammatory gene network. GEO brain tissue data showed up-regulation of S100A8 and S100A9 in the anterior cingulate cortex of MDD patients. These findings suggest that depressive-like monkeys are in a state of chronic low-grade inflammation and identify NCAN and TLR4 inflammatory network molecules as potential biomarkers of MDD.

Elevated levels of apolipoprotein A4 in umbilical cord serum from the maternal major depressive disorder

AIM

Prenatal maternal depression is known to affect the neurodevelopment of offspring. This study aimed to investigate the profile of umbilical cord serum in mothers with major depressive disorder (MDD).

METHODS

Liquid chromatography-tandem mass spectrometry (LC-MS) was conducted using umbilical cord serum from mothers with MDD (n = 5) and controls (control, n = 5). The levels of several differentially expressed proteins in umbilical cord serum were compared between the MDD (n = 10) and control groups (n = 10) by enzyme-linked immunosorbent assay.

RESULTS

The proteomic profiles in the umbilical cord serum were different between the MDD and control groups, including the pathways of regulation of plasma lipoprotein particle levels, and synapse organization. Only apolipoprotein A4 (APOA4) was significantly higher in the cord blood of MDD group. APOA4 levels in maternal serum were also significantly higher in the MDD group than those in the control group. The APOA4 levels in the umbilical cord serum were higher than that in the maternal serum.

CONCLUSIONS

The levels of APOA4, a biomarker of depression, in the umbilical cord serum at birth were elevated in the neonates of MDD mothers. It is, therefore, likely that fetuses of MDD mothers were exposed to higher APOA4 levels in utero and this could have developmental and mental health implications for the offspring.

Identification of significant biomarkers for predicting the risk of bipolar disorder with arteriosclerosis based on integrative bioinformatics and machine learning

Introduction

Increasing evidence has indicated a connection between bipolar disorder (BD) and arteriosclerosis (AS), yet the specific molecular mechanisms remain unclear. This study aims to investigate the hub genes and molecular pathways for BD with AS.

Methods

BD-related dataset GSE12649 were downloaded from the Gene Expression Omnibus database and differentially expressed genes (DEGs) and key module genes derived from Limma and weighted gene co-expression network analyses (WGCNA) were identified. AS-related genes were sourced from the DisGeNET database, and the overlapping genes between DEGs and AS-related genes were characterized as differentially expressed arteriosclerosis-related genes (DE-ASRGs). The functional enrichment analysis, protein-protein interaction (PPI) network and three machine learning algorithms were performed to explore the hub genes, which were validated with two external validation sets. Additionally, immune infiltration was performed in BD.

Results

Overall, 67 DE-ASRGs were found to be overlapping between the DEGs and AS-related genes. Functional enrichment analysis highlighted the cancer pathways between BD and AS. We identified seven candidate hub genes (CTSD, IRF3, NPEPPS, ST6GAL1, HIF1A, SOX9 and CX3CR1). Eventually, two hub genes (CX3CR1 and ST6GAL1) were identified as BD and AS co-biomarkers by using machine learning algorithms. Immune infiltration had revealed the disorder of immunocytes.

Discussion

This study identified the hub genes CX3CR1 and ST6GAL1 in BD and AS, providing new insights for further research on the bioinformatic mechanisms of BD with AS and contributing to the diagnosis and prevention of AS in psychiatric clinical practice.

Inflammation and lipid metabolism as potential biomarkers of memory impairment across type 2 diabetes mellitus and severe mental disorders

INTRODUCTION

Neurocognitive impairment is a transdiagnostic feature across several psychiatric and cardiometabolic conditions. The relationship between inflammatory and lipid metabolism biomarkers and memory performance is not fully understood. This study aimed to identify peripheral biomarkers suitable to signal memory decline from a transdiagnostic and longitudinal perspective.

METHODS

Peripheral blood biomarkers of inflammation, oxidative stress and lipid metabolism were assessed twice over a 1-year period in 165 individuals, including 30 with schizophrenia (SZ), 42 with bipolar disorder (BD), 35 with major depressive disorder (MDD), 30 with type 2 diabetes mellitus (T2DM), and 28 healthy controls (HCs). Participants were stratified by memory performance quartiles, taking as a reference their global memory score (GMS) at baseline, into categories of high memory (H; n = 40), medium to high memory (MH; n = 43), medium to low memory (ML; n = 38) and low memory (L; n = 44). Exploratory and confirmatory factorial analysis, mixed one-way analysis of covariance and discriminatory analyses were performed.

RESULTS

L group was significantly associated with higher levels of tumor necrosis factor-alpha (TNF-α) and lower levels of apolipoprotein A1 (Apo-A1) compared to those from the MH and H groups (p < 0.05; η2p = 0.06-0.09), with small to moderate effect sizes. Moreover, the combination of interleukin-6 (IL-6), TNF-α, c-reactive protein (CRP), Apo-A1 and Apo-B compounded the transdiagnostic model that best discriminated between groups with different degrees of memory impairment (χ2 = 11.9-49.3, p < 0.05-0.0001).

CONCLUSIONS

Inflammation and lipid metabolism seem to be associated with memory across T2DM and severe mental illnesses (SMI). A panel of biomarkers may be a useful approach to identify individuals at greater risk of neurocognitive impairment. These findings may have a potential translational utility for early intervention and advance precision medicine in these disorders.

Albumin and Associated Biomarkers in Severe Neuropsychiatric Disorders: Acute-Phase Schizophrenia and Bipolar Disorder

Background

Inflammation is relevant to the pathophysiology of severe neuropsychiatric disorders, schizophrenia (SCZ) and bipolar disorders (BD). Multiple pathophysiological biomarkers are valuable for the study of inflammatory processes. This study investigated albumin-related biomarkers in SCZ and BD to explore their roles in disease.

Methods

A total of 5,577 SCZ, 3442 BD-manic (BD-M) and 1405 BD-depression (BD-D) in acute stage and 5000 health controls (HCs) were enrolled. The differences in these biomarker levels among different groups were compared, and the contributing factors for the occurrence of SCZ, BD, and subgroups of BD were analyzed.

Results

Both SCZ and BD exhibit lower prognostic nutritional index (PNI), but higher neutrophil percentage-to-albumin ratio (NPAR) and creatinine-albumin ratio (CRA) compared with HC. Compared with BD-D, BD-M had higher NPAR and platelet-to-albumin ratio (PAR) and lower CRA. In logistic regression, lower prognostic nutritional index (PNI) and higher CRA were associated with both SCZ and BD, while higher NPAR was associated with BD. In the subgroup of BD, higher NPAR, CRA and lower PNI were associated with BD-M; lower PAR, PNI and higher CRA were associated with BD-D.

Conclusion

Our study reaffirmed the role of inflammation in the pathophysiology of SCZ and BD. Diagnostic value has been demonstrated in NPAR, PAR, PNI and CRA for BD and SCZ.

The pharmacological bases for repurposing statins in depression: a review of mechanistic studies

Statins are commonly prescribed medications widely investigated for their potential actions on the brain and mental health. Pre-clinical and clinical evidence suggests that statins may play a role in the treatment of depressive disorders, but only the latter has been systematically assessed. Thus, the physiopathological mechanisms underlying statins' putative antidepressant or depressogenic effects have not been established. This review aims to gather available evidence from mechanistic studies to strengthen the pharmacological basis for repurposing statins in depression. We used a broad, well-validated search strategy over three major databases (Pubmed/MEDLINE, Embase, PsychINFO) to retrieve any mechanistic study investigating statins' effects on depression. The systematic search yielded 8068 records, which were narrowed down to 77 relevant papers. The selected studies (some dealing with more than one bodily system) described several neuropsychopharmacological (44 studies), endocrine-metabolic (17 studies), cardiovascular (6 studies) and immunological (15 studies) mechanisms potentially contributing to the effects of statins on mood. Numerous articles highlighted the beneficial effect of statins on depression, particularly through positive actions on serotonergic neurotransmission, neurogenesis and neuroplasticity, hypothalamic-pituitary axis regulation and modulation of inflammation. The role of other mechanisms, especially the association between statins, lipid metabolism and worsening of depressive symptoms, appears more controversial. Overall, most mechanistic evidence supports an antidepressant activity for statins, likely mediated by a variety of intertwined processes involving several bodily systems. Further research in this area can benefit from measuring relevant biomarkers to inform the selection of patients most likely to respond to statins' antidepressant effects while also improving our understanding of the physiopathological basis of depression.

Network analysis of plasma proteomes in affective disorders

The conventional differentiation of affective disorders into major depressive disorder (MDD) and bipolar disorder (BD) has insufficient biological evidence. Utilizing multiple proteins quantified in plasma may provide critical insight into these limitations. In this study, the plasma proteomes of 299 patients with MDD or BD (aged 19-65 years old) were quantified using multiple reaction monitoring. Based on 420 protein expression levels, a weighted correlation network analysis was performed. Significant clinical traits with protein modules were determined using correlation analysis. Top hub proteins were determined using intermodular connectivity, and significant functional pathways were identified. Weighted correlation network analysis revealed six protein modules. The eigenprotein of a protein module with 68 proteins, including complement components as hub proteins, was associated with the total Childhood Trauma Questionnaire score (r = -0.15, p = 0.009). Another eigenprotein of a protein module of 100 proteins, including apolipoproteins as hub proteins, was associated with the overeating item of the Symptom Checklist-90-Revised (r = 0.16, p = 0.006). Functional analysis revealed immune responses and lipid metabolism as significant pathways for each module, respectively. No significant protein module was associated with the differentiation between MDD and BD. In conclusion, childhood trauma and overeating symptoms were significantly associated with plasma protein networks and should be considered important endophenotypes in affective disorders.

Differences in plasma lipoprotein profiles between patients with chronic peripheral neuropathic pain and healthy controls: an exploratory pilot study

Supplemental Digital Content is Available in the Text.

Lipoprotein profiles were significantly different between patients with chronic peripheral neuropathic pain and healthy controls, indicative of ongoing systemic low-grade inflammation among the patients.

Introduction:

Little is still known about the underlying mechanisms that drive and maintain neuropathic pain (NeuP). Recently, lipids have been implicated as endogenous proalgesic ligands affecting onset and maintenance of pain; however, in the case of NeuP, the relationship is largely unexplored.

Objectives:

The aim of this study was to investigate the lipoprotein profile in patients with chronic peripheral NeuP compared with healthy controls.

Methods:

The concentrations of 112 lipoprotein fractions in plasma from patients with NeuP (n = 16) and healthy controls (n = 13) were analyzed using proton nuclear magnetic resonance spectroscopy. A multiplex immunoassay based on an electrochemiluminescent detection method was used to measure the concentration of 71 cytokines in plasma from patients with NeuP (n = 10) and healthy controls (n = 11). Multivariate data analysis was used to identify patterns of protein intercorrelations and proteins significant for group discrimination.

Results:

We found 23 lipoproteins that were significantly upregulated in patients with NeuP compared with healthy controls. When the influence of cytokines was included in a regression model, 30 proteins (8 cytokines and 22 lipoprotein fractions) were significantly upregulated or downregulated in patients with NeuP. Both conditions presented lipoprotein profiles consistent with inflammation. Body mass index did not affect lipoprotein profiles in either group. No relationship between age and lipoprotein pattern was found in NeuP, but a significant relationship was found in healthy controls.

Conclusion:

Patients with NeuP presented a lipoprotein profile consistent with systemic low-grade inflammation, like that seen in autoimmune, cardiometabolic, and neuroprogressive diseases. These preliminary results emphasize the importance of chronic low-grade inflammation in NeuP.

Relationship between Brain Metabolic Disorders and Cognitive Impairment: LDL Receptor Defect

The low-density-lipoprotein receptor (LDLr) removes low-density lipoprotein (LDL), an endovascular transporter that carries cholesterol from the bloodstream to peripheral tissues. The maintenance of cholesterol content in the brain, which is important to protect brain function, is affected by LDLr. LDLr co-localizes with the insulin receptor and complements the internalization of LDL. In LDLr deficiency, LDL blood levels and insulin resistance increase, leading to abnormal cholesterol control and cognitive deficits in atherosclerosis. Defects in brain cholesterol metabolism lead to neuroinflammation and blood–brain-barrier (BBB) degradation. Moreover, interactions between endoplasmic reticulum stress (ER stress) and mitochondria are induced by ox-LDL accumulation, apolipoprotein E (ApoE) regulates the levels of amyloid beta (Aβ) in the brain, and hypoxia is induced by apoptosis induced by the LDLr defect. This review summarizes the association between neurodegenerative brain disease and typical cognitive deficits.

Shared postulations between bipolar disorder and polycystic ovary syndrome pathologies

INTRODUCTION

Women with bipolar disorder (BD) present a high prevalence of polycystic ovary syndrome (PCOS) and other reproductive disorders even before diagnosis or treatment of the disease. Postulations on the potential molecular mechanisms of comorbid PCOS in women with BD remain limited to influence of medications and need further extension.

OBJECTIVES

This review focuses on evidence suggesting that common metabolic and immune disorders may play an important role in the development of BD and PCOS.

RESULTS

The literature covered in this review suggests that metabolic and immune disorders, including the dysfunction of the hypothalamic-pituitary-adrenal axis, chronic inflammatory state, gut microbial alterations, adipokine alterations and circadian rhythm disturbance, are observed in patients with BD and PCOS. Such disorders may be responsible for the increased prevalence of PCOS in the BD population and indicate a susceptibility gene overlap between the two diseases. Current evidence supports postulations of common metabolic and immune disorders as endophenotype in BD as well as in PCOS.

CONCLUSIONS

Metabolic and immune disorders may be responsible for the comorbid PCOS in the BD population. The identification of hallmark metabolic and immune features common to these two diseases will contribute to the clarification of the effect of BD on the reproductive endocrine function and development of symptomatic treatments targeting the biomarkers of the two diseases.

Lipoprotein oxidation may underlie the paradoxical association of low cholesterol with coronary atherosclerotic risk in rheumatoid arthritis

OBJECTIVE

To compare coronary plaque burden, proatherogenic cytokines, oxidized low-density lipoprotein (oxLDL), anti-oxLDL antibodies, lipoprotein(a)-cholesterol, and their relationships in patients with rheumatoid arthritis with low-density lipoprotein cholesterol (LDL-C)<1.8 mmol/L versus ≥1.8 mmol/L. Also, to study differences in inflammation and proprotein convertase subtilisin/kexin type-9 (PCSK9), which impacts LDL clearance, in patients with low versus high LDL-C.

METHODS

Computed tomography angiography evaluated coronary plaque (noncalcified, partially calcified, fully calcified, and high-risk plaque) in 150 patients from a single-center observational cohort. Ox-LDL, anti-oxLDL IgG, lipoprotein(a)-cholesterol, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), interleukin-6, tumor necrosis factor-α (TNF-α) and PCSK9 were measured. Analyses adjusted for Framingham general cardiovascular risk score, statin use, and high-density lipoprotein cholesterol.

RESULTS

Patients with LDL-C<1.8 mmol/L versus ≥1.8 mmol/L demonstrated: 1) higher likelihood of per-segment plaque (adjusted-OR = 1.67 [95%CI = 1.10-2.55], p = 0.017) and high-risk plaque presence (adjusted-OR 2.78 [95%CI = 1.06-7.29], p = 0.038); 2) greater anti-oxLDL titers (p = 0.020), which positively associated with TNF-α and likelihood of noncalcified, partially calcified and high-risk plaque presence only in patients with LDL-C<1.8 mmol/L (all p-for-interaction≤0.046); 3) increased lipoprotein(a)-cholesterol content (10.33% [8.11-12.54] versus 6.68% [6.10-7.25], p < 0.001), which positively associated with oxLDL (p < 0.001) and anti-oxLDL (p = 0.036); 4) higher interleukin-6 and PCSK9. No differences in CRP, ESR, or oxLDL were observed.

CONCLUSION

RA patients with LDL-C<1.8 mmol/L had more coronary plaque, higher anti-oxLDL titers and anti-oxLDL associated with plaque only in this group. It is possible the observed paradoxical association of low LDL-C with greater atherosclerosis may be related to higher production of the oxidation-prone lipoprotein(a)-cholesterol and anti-oxLDL antibodies, resulting in increased vascular LDL uptake and plaque formation.

Hypoxic and Hyperoxic Breathing as a Complement to Low-Intensity Physical Exercise Programs: A Proof-of-Principle Study

Inflammation is an adaptive response to both external and internal stimuli including infection, trauma, surgery, ischemia-reperfusion, or malignancy. A number of studies indicate that physical activity is an effective means of reducing acute systemic and low-level inflammation occurring in different pathological conditions and in the recovery phase after disease. As a proof-of-principle, we hypothesized that low-intensity workout performed under modified oxygen supply would elicit a "metabolic exercise" inducing a hormetic response, increasing the metabolic load and oxidative stress with the same overall effect expected after a higher intensity or charge exercise. Herein, we report the effect of a 5-week low-intensity, non-training, exercise program in a group of young healthy subjects in combination with the exposure to hyperoxia (30% and 100% pO₂, respectively) or light hypoxia (15% pO₂) during workout sessions on several inflammation and oxidative stress parameters, namely hemoglobin (Hb), redox state, nitric oxide metabolite (NOx), inducible nitric oxide synthase (iNOS), inflammatory cytokine expression (TNF-α, interleukin (IL)-6, IL-10), and renal functional biomarkers (creatinine, neopterin, and urates). We confirmed our previous reports demonstrating that intermittent hyperoxia induces the normobaric oxygen paradox (NOP), a response overlapping the exposure to hypoxia. Our data also suggest that the administration of modified air composition is an expedient complement to a light physical exercise program to achieve a significant modulation of inflammatory and immune parameters, including cytokines expression, iNOS activity, and oxidative stress parameters. This strategy can be of pivotal interest in all those conditions characterized by the inability to achieve a sufficient workload intensity, such as severe cardiovascular alterations and articular injuries failing to effectively gain a significant improvement of physical capacity.