Altered Monoamine and Acylcarnitine Metabolites in HIV-Positive and HIV-Negative Subjects With Depression

Metabolomic profiles of 38 acylcarnitines in major depressive episodes before and after treatment

BACKGROUND

Major depression is associated with changes in plasma L-carnitine and acetyl-L-carnitine. But its association with acylcarnitines remains unclear. The aim of this study was to assess metabolomic profiles of 38 acylcarnitines in patients with major depression before and after treatment compared to healthy controls (HCs).

METHODS

Metabolomic profiles of 38 plasma short-, medium-, and long-chain acylcarnitines were performed by liquid chromatography-mass spectrometry in 893 HCs from the VARIETE cohort and 460 depressed patients from the METADAP cohort before and after 6 months of antidepressant treatment.

RESULTS

As compared to HCs, depressed patients had lower levels of medium- and long-chain acylcarnitines. After 6 months of treatment, increased levels of medium- and long-chain acyl-carnitines were observed that no longer differed from those of controls. Accordingly, several medium- and long-chain acylcarnitines were negatively correlated with depression severity.

CONCLUSIONS

These medium- and long-chain acylcarnitine dysregulations argue for mitochondrial dysfunction through fatty acid β-oxidation impairment during major depression.

Bidirectional Relationship between HIV/HBV Infection and Comorbid Depression and/or Anxiety: A Systematic Review on Shared Biological Mechanisms

BACKGROUND

Mental disorders that are comorbid with chronic infectious diseases may worsen clinical outcomes and patients' quality of life. We hypothesized that depression and/or anxiety syndromes or symptoms comorbid with human immunodeficiency virus (HIV) or hepatitis B virus (HBV) infection might stem from shared biological mechanisms.

METHODS

We conducted a systematic review applying the PRISMA statement by searching into the PubMed, APA PsycInfo, and Scopus databases. We examined the literature on HIV/HBV infection comorbid with depression and/or anxiety in adults ≥18 years.

RESULTS

Thirty-one studies on HIV and three on HBV were analyzed. The Tat protein contributed to HIV-associated mood disorders due to the protein's ability to cause neurodegeneration and induce hypothalamic-pituitary-adrenal (HPA) axis dysregulation in response to natural stressors. The decreased brain-derived neurotrophic factor (BDNF) levels also emerged as a mechanism involved in HIV neuropathogenesis and the associated mood symptoms. Neuroinflammation was implicated in depression and/or anxiety onset in patients with HIV/HBV infections. Microglial activation and release of cytokines, in particular, appeared as potential pathogenetic mechanisms. Furthermore, an altered balance between quinolinic acid and kynurenic acid production emerged in HIV patients with comorbid depression, indicating a glutamatergic dysfunction. Inflammatory cytokine production and the downregulation of cellular immune responses contributed to persisting inflammation, delayed healing, and functional decline in patients with chronic hepatitis B (CHB) infection. A shift in type 1-type 2 cytokine balance might be implicated in HBV-related immune pathogenesis, and depression and anxiety might be considered immunomodulatory factors. Cytokines also caused HPA axis hyperactivity, frequently observed in HIV/HBV patients with comorbid depression/anxiety.

CONCLUSIONS

The present systematic review showed, for the first time, that HIV/HBV and depression and/or anxiety might have several biological mechanisms as common denominators. The longitudinal course of the highlighted biological mechanisms should be explored to establish the causative interrelationship among the involved mechanisms. In addition, future research should investigate the possibility that a patient's clinical outcome might improve using pharmacological treatments acting on the biological mechanisms we described as common denominators of chronic inflammatory infective diseases and depression/anxiety.

Depression and HIV: a scoping review in search of neuroimmune biomarkers

People with HIV are at increased risk for depression, though the neurobiological mechanisms underlying this are unclear. In the last decade, there has been a substantial rise in interest in the contribution of (neuro)inflammation to depression, coupled with rapid advancements in the resolution and sensitivity of biomarker assays such as Luminex, single molecular array and newly developed positron emission tomography radioligands. Numerous pre-clinical and clinical studies have recently leveraged these next-generation immunoassays to identify biomarkers that may be associated with HIV and depression (separately), though few studies have explored these biomarkers in co-occurring HIV and depression. Using a systematic search, we detected 33 publications involving a cumulative N = 10 590 participants which tested for associations between depressive symptoms and 55 biomarkers of inflammation and related processes in participants living with HIV. Formal meta-analyses were not possible as statistical reporting in the field was highly variable; future studies must fully report test statistics and effect size estimates. The majority of included studies were carried out in the United States, with samples that were primarily older and primarily men. Substantial further work is necessary to diversify the geographical, age, and sex distribution of samples in the field. This review finds that alterations in concentrations of certain biomarkers of neuroinflammation (interleukin-6, tumour necrosis factor-α, neopterin) may influence the association between HIV and depression. Equally, the chemokines monocyte chemoattractant protein-1 (MCP-1) and interleukin-8 (IL-8) or the metabolic index kynurenine:tryptophan (Kyn:Trp), which have been the focus of several studies, do not appear to be associated with depressive symptoms amongst people living with HIV, as all (MCP-1) or most (IL-8 and Kyn:Trp) available studies of these biomarkers reported non-significant associations. We propose a biomarker-driven hypothesis of the neuroimmunometabolic mechanisms that may precipitate the increased risk of depression among people with HIV. Chronically activated microglia, which trigger key neuroinflammatory cascades shown to be upregulated in people with HIV, may be the central link connecting HIV infection in the central nervous system with depressive symptoms. Findings from this review may inform research design in future studies of HIV-associated depression and enable concerted efforts towards biomarker discovery.

Sex-specific associations between plasma interleukin-6 and depression in persons with and without HIV

Background

Persons with HIV (PWH) have both more frequent depression and higher levels of plasma inflammatory biomarkers compared to persons without HIV (PWoH). Inflammation and depressive symptoms are linked, including in PWH; however, it is unclear whether these associations differ by HIV serostatus and biological sex.

Methods

Six plasma inflammatory biomarkers were assessed using samples from PWH and PWoH who participated in six NIH-funded studies through the UCSD HIV Neurobehavioral Research Program (HNRP) from 2011 to 2019. Factor analysis was performed to identify intercorrelated groups of biomarkers. Factors and their components were then examined for relationships with Beck Depression Inventory-II (BDI-II) and modifying effects of sex or HIV serostatus using multivariable linear regression, adjusting for demographics, substance use diagnoses, and relevant co-morbidities.

Results

Participants included 150 PWH (age = 48.3 ± 13.1 yr; 88% biologically male) and 138 PWoH (age = 46.3 ± 15.9; 56% male). Two inflammatory factors were identified: Factor 1 loaded on interleukin-6 (IL-6), C-reactive protein (CRP), and D-dimer; Factor 2 loaded on interleukin-8, chemokine C-C ligand 2 (CCL2), and chemokine C-X-C ligand 10 (CXCL10). Sex modified the effect of Factor 1 on BDI-II, with a more positive association for men than women (p = 0.04). No significant association between Factor 2 and BDI-II was found. Of the biomarkers in Factor 1, only IL-6 was significantly associated with BDI-II and was modified by sex (p = 0.003). In sex-stratified analysis, a positive association was found for men (β = 5.42; 95% confidence interval = [1.32, 9.52]) but not women (β = -3.88; 95% C.I. = [-11.02, 3.26]). No HIV-related interactions were detected.

Interpretation

We identified a depression-associated inflammatory factor present in both PWH and PWoH, consistent with prior studies of PWH only. The association was driven by a correlation between IL-6 and depression exclusively in men, suggesting that the depression-inflammation link differs by sex. Future studies of depression etiology or treatment, including those on persons with HIV, should consider the impact of biological sex in both design and analysis.

Effects of (S)-ketamine on depression-like behaviors in a chronic variable stress model: a role of brain lipidome

Introduction: Compelling evidence indicates that a single sub-anesthetic dose of (S)-ketamine elicits rapid and robust antidepressant effects. However, the underlying mechanisms behind the antidepressant effects of (S)-ketamine remain unclear. Methods: Here, using a chronic variable stress (CVS) model in mice, we analyzed changes inthe lipid compositions of the hippocampus and prefrontal cortex (PFC) with a mass spectrometry-based lipidomic approach. Results: Similar to previous research outcomes, the current study also showed that (S)-ketamine reversed depressive-like behaviors in mice produced by CVS procedures. Moreover, CVS induced changes inthe lipid compositions of the hippocampus and PFC, notably in the contents of sphingolipids, glycerolipids, and fatty acyls. With the administration of (S)-ketamine, CVS-induced lipid disturbances were partially normalized, particularly in the hippocampus. Conclusion: Altogether, our results indicated that (S)-ketamine could rescue CVS-induced depressive-like behaviors in mice through region-specific modulation of the brain lipidome, contributing to the understanding of (S)-ketamine's antidepressant effects.

Examining Depression as a Risk Factor for Cardiovascular Disease in People with HIV: A Systematic Review

BACKGROUND

People with human immunodeficiency virus (HIV) have an increased risk of cardiovascular disease (CVD) not fully accounted for by traditional or HIV-specific risk factors. Successful management of HIV does not eliminate this excess risk. Thus, there is a need to identify novel risk factors for CVD among people with HIV (PWH).

PURPOSE

Our objective was to systematically review the literature on one such candidate CVD risk factor in PWH-depression.

METHODS

A systematic literature search of PubMed, PsycINFO, EMBASE, Web of Science, and CINAHL was performed to identify published English-language studies examining associations of depression with clinical CVD, subclinical CVD, and biological mechanisms (immune activation, systemic inflammation, altered coagulation) among PWH between the earliest date and June 22, 2021.

RESULTS

Thirty-five articles were included. For clinical CVD (k = 8), findings suggests that depression is consistently associated with an increased risk of incident CVD. For subclinical CVD (k = 5), one longitudinal analysis reported a positive association, and four cross-sectional analyses reported null associations. For immune activation (k = 13), systemic inflammation (k = 17), and altered coagulation (k = 5), findings were mixed, and there was considerable heterogeneity in sample characteristics and methodological quality across studies.

CONCLUSIONS

Depression may be an independent risk factor for CVD among PWH. Additional research is needed to confirm depression's association with clinical CVD and to determine whether depression is consistently and meaningfully associated with subclinical CVD and biological mechanisms of CVD in HIV. We propose a research agenda for this emerging area.

Carnitine and Depression

Depression has become one of the most common mental diseases in the world, but the understanding of its pathogenesis, diagnosis and treatments remains insufficient. Carnitine is a natural substance that exists in organisms, which can be synthesized in vivo or supplemented by intake. Relationships of carnitine with depression, bipolar disorder and other mental diseases have been reported in different studies. Several studies show that the level of acylcarnitines (ACs) changes significantly in patients with depression compared with healthy controls while the supplementation of acetyl-L-carnitine is beneficial to the treatment of depression. In this review, we aimed to clarify the effects of ACs in depressive patients and to explore whether ACs might be the biomarkers for the diagnosis of depression and provide new ideas to treat depression.

The Impact of Electroacupuncture Early Intervention on the Brain Lipidome in a Mouse Model of Post-traumatic Stress Disorder

The neuroprotective effect of electroacupuncture (EA) treatment has been well studied; growing evidence suggests that changes in lipid composition may be involved in the pathogenesis of post-traumatic stress disorder (PTSD) and may be a target for treatment. However, the influence of early EA intervention on brain lipid composition in patients with PTSD has never been investigated. Using a modified single prolonged stress (mSPS) model in mice, we assessed the anti-PTSD-like effects of early intervention using EA and evaluated changes in lipid composition in the hippocampus and prefrontal cortex (PFC) using a mass spectrometry-based lipidomic approach. mSPS induced changes in lipid composition in the hippocampus, notably in the content of sphingolipids, glycerolipids, and fatty acyls. These lipid changes were more robust than those observed in the PFC. Early intervention with EA after mSPS ameliorated PTSD-like behaviors and partly normalized mSPS-induced lipid changes, notably in the hippocampus. Cumulatively, our data suggest that EA may reverse mSPS-induced PTSD-like behaviors due to region-specific regulation of the brain lipidome, providing new insights into the therapeutic mechanism of EA.

Unbiased Metabolomics Links Fatty Acid Pathways to Psychiatric Symptoms in People Living with HIV

Psychiatric symptoms are prevalent in people living with HIV (PLWH), especially depression, anxiety, impulsivity, and substance use. Various biological mechanisms might play a role in the occurrence of psychiatric symptoms in this population. A hypothesis free, data-driven metabolomics approach can further our understanding of these mechanisms. In this study, we identified metabolic pathways associated with impulsivity, depression and substance use in 157 PLWH. First, Spearman’s rank correlations between metabolite feature intensities and psychiatric symptom levels were calculated, while controlling for age, gender and body mass index. Subsequently, a mummichog pathway analysis was performed. Finally, we analyzed which individual metabolites drove the observed effects. In our cohort of PLWH, fatty acid-related pathways were associated with both depressive as well as impulsive symptomatology. Substance use showed most extensive metabolic associations, and was positively associated with short chain fatty acids (SCFA’s), and negatively associated with glutamate levels. These findings suggest that PUFA metabolism might be associated with both internalising and externalising symptomatology in PLWH. Furthermore, glutamate and SCFA’s—microbiome derivatives with known neuroactive properties—might be involved in substance use in these patients. Future studies should explore potential causal mechanisms involved and whether these findings are HIV-specific.

HIV-Associated Neurocognitive Disorder (HAND): Relative Risk Factors

This chapter will address the issue of risk for HIV-associated neurocognitive disorder (HAND), focusing on HIV-associated dementia (HAD), among persons living with HIV in relationship to the risk for other dementias. Advances in effective antiretroviral therapy (ART) have led to an increase in the prevalence of older persons surviving with HIV - in addition to older persons who become infected by HIV later in life. Hence, HIV is no longer a disease of younger persons, and additional attention has been brought to bear against the plight of older persons living with HIV - not only as it pertains to treatment but also to prevention. The additional risk caused by aging among older persons living with HIV is complex to asses, and HIV infection is a research area that requires a robust approach to multiple other factors causing neurocognitive impairment with older age. The long-term and potentially neurotoxic exposure to ART and the deleterious consequences of chronic infection with HIV and its associated neuro-inflammation have been described for health. This aids in the understanding of dementia risk factors in this patient population, but the comorbidities (HIV- and non-HIV-associated) occurring among older persons living with HIV must also be addressed to properly assess the overall impact on dementia risk in this group. This need also warrants our examination of the risk factors for other dementias (and comorbid dementias) in persons living with HIV versus the general population through the assessment and quantification of modifiable and non-modifiable risk factors identified as major contributors toward dementia.

Metabolomics and computational analysis of the role of monoamine oxidase activity in delirium and SARS-COV-2 infection

Delirium is an acute change in attention and cognition occurring in ~ 65% of severe SARS-CoV-2 cases. It is also common following surgery and an indicator of brain vulnerability and risk for the development of dementia. In this work we analyzed the underlying role of metabolism in delirium-susceptibility in the postoperative setting using metabolomic profiling of cerebrospinal fluid and blood taken from the same patients prior to planned orthopaedic surgery. Distance correlation analysis and Random Forest (RF) feature selection were used to determine changes in metabolic networks. We found significant concentration differences in several amino acids, acylcarnitines and polyamines linking delirium-prone patients to known factors in Alzheimer's disease such as monoamine oxidase B (MAOB) protein. Subsequent computational structural comparison between MAOB and angiotensin converting enzyme 2 as well as protein-protein docking analysis showed that there potentially is strong binding of SARS-CoV-2 spike protein to MAOB. The possibility that SARS-CoV-2 influences MAOB activity leading to the observed neurological and platelet-based complications of SARS-CoV-2 infection requires further investigation.

Acrolein and other toxicant exposures in relation to cardiovascular disease among marijuana and tobacco smokers in a longitudinal cohort of HIV-positive and negative adults

BACKGROUND

Marijuana smoke contains some of the same toxicants present in tobacco smoke. Marijuana smoking is prevalent among HIV+ individuals, but few studies have characterized smoke-related toxicants or associated health outcomes in exclusive marijuana users.

METHODS

This longitudinal study included 245 participants over age 40 (76% HIV+). 33 plasma and 28 urine metabolites of nicotine, ∆-9-trans-tetrahydrocannabinol, polycyclic aromatic hydrocarbons, and volatile organic compounds were assayed by liquid or gas chromatography/mass spectrometry. Exposures and health outcomes were assessed from surveys and medical records.

FINDINGS

At baseline, 18% of participants were marijuana-only smokers, 20% tobacco-only smokers, and 24% dual marijuana-tobacco smokers (median (IQR) age 53 (47-60) years, 78% male, 54% white race). Marijuana smoking was independently associated with elevated plasma naphthalenes, 2-hydroxyfluorene sulfate, 4-vinylphenol sulfate, and o-cresol sulfate (p<0·05) and urine acrylonitrile and acrylamide metabolites (p<0·05), but levels were lower than those associated with tobacco smoking. Acrolein metabolite N-Acetyl-S-(3-hydroxypropyl)-l-cysteine (3HPMA) was significantly elevated in plasma and urine in tobacco-only and dual but not marijuana-only smokers, and correlated with nicotine metabolites (p<0·05). The highest tertile of 3HPMA was associated with increased cardiovascular disease diagnoses independent of tobacco smoking, traditional risk factors, and HIV status (odds ratio [95% CI] 3·34 [1·31-8·57]; p = 0·012).

INTERPRETATION

Smoke-related toxicants, including acrylonitrile and acrylamide metabolites, are detectable in exclusive marijuana smokers, but exposures are lower compared with tobacco or dual smokers. Acrolein exposure is increased by tobacco smoking but not exclusive marijuana smoking in HIV+ and HIV- adults, and contributes to cardiovascular disease in tobacco smokers.

FUNDING

U.S. NIH.

A metabolome-wide association study in the general population reveals decreased levels of serum laurylcarnitine in people with depression

Depression constitutes a leading cause of disability worldwide. Despite extensive research on its interaction with psychobiological factors, associated pathways are far from being elucidated. Metabolomics, assessing the final products of complex biochemical reactions, has emerged as a valuable tool for exploring molecular pathways. We conducted a metabolome-wide association analysis to investigate the link between the serum metabolome and depressed mood (DM) in 1411 participants of the KORA (Cooperative Health Research in the Augsburg Region) F4 study (discovery cohort). Serum metabolomics data comprised 353 unique metabolites measured by Metabolon. We identified 72 (5.1%) KORA participants with DM. Linear regression tests were conducted modeling each metabolite value by DM status, adjusted for age, sex, body-mass index, antihypertensive, cardiovascular, antidiabetic, and thyroid gland hormone drugs, corticoids and antidepressants. Sensitivity analyses were performed in subcohorts stratified for sex, suicidal ideation, and use of antidepressants. We replicated our results in an independent sample of 968 participants of the SHIP-Trend (Study of Health in Pomerania) study including 52 (5.4%) individuals with DM (replication cohort). We found significantly lower laurylcarnitine levels in KORA F4 participants with DM after multiple testing correction according to Benjamini/Hochberg. This finding was replicated in the independent SHIP-Trend study. Laurylcarnitine remained significantly associated (p value < 0.05) with depression in samples stratified for sex, suicidal ideation, and antidepressant medication. Decreased blood laurylcarnitine levels in depressed individuals may point to impaired fatty acid oxidation and/or mitochondrial function in depressive disorders, possibly representing a novel therapeutic target.

Methamphetamine and Cannabis: A Tale of Two Drugs and their Effects on HIV, Brain, and Behavior

HIV infection and drug use intersect epidemiologically, and their combination can result in complex effects on brain and behavior. The extent to which drugs affect the health of persons with HIV (PWH) depends on many factors including drug characteristics, use patterns, stage of HIV disease and its treatment, comorbid factors, and age. To consider the range of drug effects, we have selected two that are in common use by PWH: methamphetamine and cannabis. We compare the effects of methamphetamine with those of cannabis, to illustrate how substances may potentiate, worsen, or even buffer the effects of HIV on the CNS. Data from human, animal, and ex vivo studies provide insights into how these drugs have differing effects on the persistent inflammatory state that characterizes HIV infection, including effects on viral replication, immune activation, mitochondrial function, gut permeability, blood brain barrier integrity, glia and neuronal signaling. Moving forward, we consider how these mechanistic insights may inform interventions to improve brain outcomes in PWH. This review summarizes literature from clinical and preclinical studies demonstrating the adverse effects of METH, as well as the potentially beneficial effects of cannabis, on the interacting systemic (e.g., gut barrier leakage/microbial translocation, immune activation, inflammation) and CNS-specific (e.g., glial activation/neuroinflammation, neural injury, mitochondrial toxicity/oxidative stress) mechanisms underlying HIV-associated neurocognitive disorders.

The impact of repetitive transcranial magnetic stimulation and fluoxetine on the brain lipidome in a rat model of chronic unpredictable stress

The antidepressant effect of repetitive transcranial magnetic stimulation (rTMS) has been extensively studied; growing evidence suggests that changes in lipid composition may be involved in the pathogenesis of depression and may be a targeted mechanism for treatment. However, the influence of rTMS on lipid composition and the differences between these effects compared to antidepressants like fluoxetine (Flx) have never been investigated. Using a chronic unpredictable stress (CUS) model in rats, we assessed the antidepressive effects of rTMS and Flx treatments and evaluated changes in lipid composition in the hippocampus and prefrontal cortex (PFC) using a mass spectrometry-based lipidomic approach. Both rTMS and Flx treatments ameliorated depressive-like behaviors induced by CUS. Moreover, changes in lipid composition, especially glycerophospholipids, sphingolipids, and glycerolipids induced by CUS in the hippocampus were more robust than those observed in the PFC. CUS led to decreased levels of 20 carbon-containing fatty acyls and polyunsaturated fatty acyls in the PFC, and decreased levels of acyl carnitines (AcCa) in both the hippocampus and PFC. Notably, rTMS treatment had higher impact than Flx on composition of glycerophospholipids and sphingolipids in the hippocampus that were altered by CUS, while Flx attenuated CUS-induced changes in the PFC to a greater extent than rTMS. However, neither was able to restore fatty acyls and AcCa to baseline levels. Altogether, modulation of the brain lipidome may be involved in the antidepressant action of rTMS and Flx, and the degree to which these treatments induce changes in lipid composition within the hippocampus and PFC might explain their differential antidepressant effects.

Pathogenesis of Aging and Age-related Comorbidities in People with HIV: Highlights from the HIV ACTION Workshop

People with HIV (PWH) experience accentuated biological aging, as defined by markers of inflammation, immune dysfunction, and the epigenetic clock. They also have an elevated risk of multiple age-associated comorbidities. To discuss current knowledge, research gaps, and priorities in aging and age-related comorbidities in treated HIV infection, the NIH program staff organized a workshop held in Bethesda, Maryland in September 2019. This review article describes highlights of discussions led by the Pathogenesis/Basic Science Research working group that focused on three high priority topics: immunopathogenesis; the microbiome/virome; and aging and senescence. We summarize knowledge in these fields and describe key questions for research on the pathogenesis of aging and age-related comorbidities in PWH. Understanding the drivers and mechanisms underlying accentuated biological aging is a high priority that will help identify potential therapeutic targets to improve healthspan in older PWH.

Impaired mitochondrial complex I function as a candidate driver in the biological stress response and a concomitant stress-induced brain metabolic reprogramming in male mice

Mitochondria play a critical role in bioenergetics, enabling stress adaptation, and therefore, are central in biological stress responses and stress-related complex psychopathologies. To investigate the effect of mitochondrial dysfunction on the stress response and the impact on various biological domains linked to the pathobiology of depression, a novel mouse model was created. These mice harbor a gene trap in the first intron of the Ndufs4 gene (Ndufs4^GT/GT mice), encoding the NDUFS4 protein, a structural component of complex I (CI), the first enzyme of the mitochondrial electron transport chain. We performed a comprehensive behavioral screening with a broad range of behavioral, physiological, and endocrine markers, high-resolution ex vivo brain imaging, brain immunohistochemistry, and multi-platform targeted mass spectrometry-based metabolomics. Ndufs4^GT/GT mice presented with a 25% reduction of CI activity in the hippocampus, resulting in a relatively mild phenotype of reduced body weight, increased physical activity, decreased neurogenesis and neuroinflammation compared to WT littermates. Brain metabolite profiling revealed characteristic biosignatures discriminating Ndufs4^GT/GT from WT mice. Specifically, we observed a reversed TCA cycle flux and rewiring of amino acid metabolism in the prefrontal cortex. Next, exposing mice to chronic variable stress (a model for depression-like behavior), we found that Ndufs4^GT/GT mice showed altered stress response and coping strategies with a robust stress-associated reprogramming of amino acid metabolism. Our data suggest that impaired mitochondrial CI function is a candidate driver for altered stress reactivity and stress-induced brain metabolic reprogramming. These changes result in unique phenomic and metabolomic signatures distinguishing groups based on their mitochondrial genotype.

Improved metabolomic data-based prediction of depressive symptoms using nonlinear machine learning with feature selection

To solve major limitations in algorithms for the metabolite-based prediction of psychiatric phenotypes, a novel prediction model for depressive symptoms based on nonlinear feature selection machine learning, the Hilbert-Schmidt independence criterion least absolute shrinkage and selection operator (HSIC Lasso) algorithm, was developed and applied to a metabolomic dataset with the largest sample size to date. In total, 897 population-based subjects were recruited from the communities affected by the Great East Japan Earthquake; 306 metabolite features (37 metabolites identified by nuclear magnetic resonance measurements and 269 characterized metabolites based on the intensities from mass spectrometry) were utilized to build prediction models for depressive symptoms as evaluated by the Center for Epidemiologic Studies-Depression Scale (CES-D). The nested fivefold cross-validation was used for developing and evaluating the prediction models. The HSIC Lasso-based prediction model showed better predictive power than the other prediction models, including Lasso, support vector machine, partial least squares, random forest, and neural network. L-leucine, 3-hydroxyisobutyrate, and gamma-linolenyl carnitine frequently contributed to the prediction. We have demonstrated that the HSIC Lasso-based prediction model integrating nonlinear feature selection showed improved predictive power for depressive symptoms based on metabolome data as well as on risk metabolites based on nonlinear statistics in the Japanese population. Further studies should use HSIC Lasso-based prediction models with different ethnicities to investigate the generality of each risk metabolite for predicting depressive symptoms.

Low Neuroactive Steroids Identifies a Biological Subtype of Depression in Adults with Human Immunodeficiency Virus on Suppressive Antiretroviral Therapy

Background

The prevalence and mortality risk of depression in people with human immunodeficiency virus (HIV) infection receiving antiretroviral therapy (ART) is higher than in the general population, yet biomarkers for therapeutic targeting are unknown. In the current study, we aimed to identify plasma metabolites associated with depressive symptoms in people with HIV receiving ART.

Methods

This is a prospective study of ART-treated HIV-infected adults with or without depressive symptoms assessed using longitudinal Beck Depression Inventory scores. Plasma metabolite profiling was performed in 2 independent cohorts (total n = 99) using liquid and gas chromatography and tandem mass spectrometry.

Results

Participants with depressive symptoms had lower neuroactive steroids (dehydroepiandrosterone sulfate [DHEA-S], androstenediols, and pregnenolone sulfate) compared with those without depressive symptoms. The cortisol/DHEA-S ratio, an indicator of hypothalamic-pituitary-adrenal axis imbalance, was associated with depressive symptoms (P < .01) because of low DHEA-S levels, whereas cortisol was similar between groups. The odds of having depressive symptoms increased with higher cortisol/DHEA-S ratios (adjusted odds ratio, 2.5 per 1-unit increase in z score; 95% confidence interval, 1.3–4.7), independent of age and sex. The kynurenine-to-tryptophan ratio showed no significant associations.

Conclusions

These findings suggest that altered neuroactive steroid metabolism may contribute to the pathophysiological mechanisms of depression in ART-treated HIV-infected adults, representing a potential biological pathway for therapeutic targeting.

Host Metabolic Response in Early Lyme Disease

Lyme disease is a tick-borne bacterial illness that occurs in areas of North America, Europe, and Asia. Early infection typically presents as generalized symptoms with an erythema migrans (EM) skin lesion. Dissemination of the pathogen Borrelia burgdorferi can result in multiple EM skin lesions or in extracutaneous manifestations such as Lyme neuroborreliosis. Metabolic biosignatures of patients with early Lyme disease can potentially provide diagnostic targets as well as highlight metabolic pathways that contribute to pathogenesis. Sera from well-characterized patients diagnosed with either early localized Lyme disease (ELL) or early disseminated Lyme disease (EDL), plus healthy controls (HC), from the United States were analyzed by liquid chromatography-mass spectrometry (LC-MS). Comparative analyses were performed between ELL, or EDL, or ELL combined with EDL, and the HC to develop biosignatures present in early Lyme disease. A direct comparison between ELL and EDL was also performed to develop a biosignature for stages of early Lyme disease. Metabolic pathway analysis and chemical identification of metabolites with LC-tandem mass spectrometry (LC-MS/MS) demonstrated alterations of eicosanoid, bile acid, sphingolipid, glycerophospholipid, and acylcarnitine metabolic pathways during early Lyme disease. These metabolic alterations were confirmed using a separate set of serum samples for validation. The findings demonstrated that infection of humans with B. burgdorferi alters defined metabolic pathways that are associated with inflammatory responses, liver function, lipid metabolism, and mitochondrial function. Additionally, the data provide evidence that metabolic pathways can be used to mark the progression of early Lyme disease.

Tenofovir disoproxil fumarate induces peripheral neuropathy and alters inflammation and mitochondrial biogenesis in the brains of mice

Mounting evidence suggests that antiretroviral therapy (ART) drugs may contribute to the prevalence of HIV-associated neurological dysfunction. The HIV envelope glycoprotein (gp120) is neurotoxic and has been linked to alterations in mitochondrial function and increased inflammatory gene expression, which are common neuropathological findings in HIV+ cases on ART with neurological disorders. Tenofovir disproxil fumarate (TDF) has been shown to affect neurogenesis in brains of mice and mitochondria in neurons. In this study, we hypothesized that TDF contributes to neurotoxicity by modulating mitochondrial biogenesis and inflammatory pathways. TDF administered to wild-type (wt) and GFAP-gp120 transgenic (tg) mice caused peripheral neuropathy, as indicated by nerve conduction slowing and thermal hyperalgesia. Conversely TDF protected gp120-tg mice from cognitive dysfunction. In the brains of wt and gp120-tg mice, TDF decreased expression of mitochondrial transcription factor A (TFAM). However, double immunolabelling revealed that TFAM was reduced in neurons and increased in astroglia in the hippocampi of TDF-treated wt and gp120-tg mice. TDF also increased expression of GFAP and decreased expression of IBA1 in the wt and gp120-tg mice. TDF increased tumor necrosis factor (TNF) α in wt mice. However, TDF reduced interleukin (IL) 1β and TNFα mRNA in gp120-tg mouse brains. Primary human astroglia were exposed to increasing doses of TDF for 24 hours and then analyzed for mitochondrial alterations and inflammatory gene expression. In astroglia, TDF caused a dose-dependent increase in oxygen consumption rate, extracellular acidification rate and spare respiratory capacity, changes consistent with increased metabolism. TDF also reduced IL-1β-mediated increases in IL-1β and TNFα mRNA. These data demonstrate that TDF causes peripheral neuropathy in mice and alterations in inflammatory signaling and mitochondrial activity in the brain.

Plasma acylcarnitines and progression of carotid artery atherosclerosis in HIV infection

OBJECTIVE

To evaluate plasma acylcarnitine profiles and their relationships with progression of carotid artery atherosclerosis among individuals with and without HIV infection.

DESIGN

Prospective cohort studies of 499 HIV-positive and 206 HIV-negative individuals from the Women's Interagency HIV Study and the Multicenter AIDS Cohort Study.

METHODS

Twenty-four acylcarnitine species were measured in plasma samples of participants at baseline. Carotid artery plaque was assessed using repeated B-mode carotid artery ultrasound imaging in 2004-2013. We examined the associations of individual and aggregate short-chain (C2-C7), medium-chain (C8-C14) and long-chain acylcarnitines (C16-C26) with incident carotid artery plaque over 7 years.

RESULTS

Among 24 acylcarnitine species, C8-carnitines and C20 : 4-carnitines showed significantly lower levels comparing HIV-positive to HIV-negative individuals (false discovery rate adjusted P < 0.05); and C20-carnitines and C26-carnitines showed significantly higher levels in HIV positive using antiretroviral therapy than those without antiretroviral therapy (false discovery rate adjusted P < 0.05). In the univariate analyses, higher aggregated short-chain and long-chain acylcarnitine scores were associated with increased risk of carotid artery plaque [risk ratios (RRs) = 1.22 (95% confidence interval 1.02-1.45) and 1.20 (1.02-1.41) per SD increment, respectively]. The association for the short-chain acylcarnitine score remained significant [RR = 1.23 (1.05-1.44)] after multivariate adjustment (including traditional cardiovascular disease risk factors). This association was more evident in HIV-positive individuals without persistent viral suppression [RR = 1.37 (1.11-1.69)] compared with those with persistent viral suppression during follow-up [RR = 1.03 (0.76-1.40)] or HIV-negative individuals [RR = 1.02 (0.69-1.52)].

CONCLUSION

In two HIV cohorts, plasma levels of most acylcarnitines were not significantly different between HIV-positive and HIV-negative individuals. However, higher levels of aggregated short-chain acylcarnitines were associated with progression of carotid artery atherosclerosis.

Examining Relationships between Metabolism and Persistent Inflammation in HIV Patients on Antiretroviral Therapy

With the advent of antiretroviral therapy (ART), HIV-infected individuals are now living longer and healthier lives. However, ART does not completely restore health and treated individuals are experiencing increased rates of noncommunicable diseases such as dyslipidemia, insulin resistance, type 2 diabetes, cardiovascular disease, and nonalcoholic fatty liver disease. While it is well known that persistent immune activation and inflammation contribute to the development of these comorbid diseases, the mechanisms underlying this chronic activation remain incompletely understood. In this review, we will discuss emerging evidence that suggests that alterations in cellular metabolism may play a central role in driving this immune dysfunction in HIV patients on ART.

Exosome markers associated with immune activation and oxidative stress in HIV patients on antiretroviral therapy

Exosomes are nanovesicles released from most cell types including immune cells. Prior studies suggest exosomes play a role in HIV pathogenesis, but little is known about exosome cargo in relation to immune responses and oxidative stress. Here, we characterize plasma exosomes in HIV patients and their relationship to immunological and oxidative stress markers. Plasma exosome fractions were isolated from HIV-positive subjects on ART with suppressed viral load and HIV-negative controls. Exosomes were characterized by electron microscopy, nanoparticle tracking, immunoblotting, and LC-MS/MS proteomics. Plasma exosomes were increased in HIV-positive subjects compared to controls, and correlated with increased oxidative stress markers (cystine, oxidized cys-gly) and decreased PUFA (DHA, EPA, DPA). Untargeted proteomics detected markers of exosomes (CD9, CD63, CD81), immune activation (CD14, CRP, HLA-A, HLA-B), oxidative stress (CAT, PRDX1, PRDX2, TXN), and Notch4 in plasma exosomes. Exosomal Notch4 was increased in HIV-positive subjects versus controls and correlated with immune activation markers. Treatment of THP-1 monocytic cells with patient-derived exosomes induced expression of genes related to interferon responses and immune activation. These results suggest that exosomes in ART-treated HIV patients carry proteins related to immune activation and oxidative stress, have immunomodulatory effects on myeloid cells, and may have pro-inflammatory and redox effects during pathogenesis.

Neuropsychiatric Aspects of Infectious Diseases: An Update

Among the critically ill, infectious diseases can play a significant role in the etiology of neuropsychiatric disturbances. All critical care physicians are familiar with delirium as a secondary complication of systemic infection. This article focuses on key infectious diseases that commonly and directly produce neuropsychiatric symptoms, including direct infection of the central nervous system, human immunodeficiency virus infection, and AIDS.

Impact of comorbidity and ageing on health-related quality of life in HIV-positive and HIV-negative individuals

BACKGROUND

HIV-infected individuals may be at risk for the premature onset of age-associated noncommunicable comorbidities. Being HIV-positive, having comorbidities and being of higher age may adversely impact health-related quality of life (HRQL). We investigated the possible contribution of HIV infection, comorbidities and age on HRQL and depression.

METHODS

HIV-infected individuals and uninfected controls from the AGEhIV Cohort Study were screened for the presence of comorbidities. They completed the Short Form 36-item Health Survey to assess HRQL and the nine-item Patient Health Questionnaire to assess depression. Linear and logistic regression were used to investigate to which extent comorbidities, aging and HIV infection were independently associated with HRQL and depression.

RESULTS

HIV-infected individuals (n = 541) reported significantly worse physical and mental HRQL and had a higher prevalence of depression than HIV-uninfected individuals (n = 526). A higher number of comorbidities and HIV-positive status were each independently associated with worse physical HRQL, whereas HIV-positive status and younger age were independently associated with worse mental HRQL and more depression. The difference in physical HRQL between HIV-positive and HIV-negative individuals did not become greater with a higher number of comorbidities or with higher age.

CONCLUSION

In a cohort of largely well suppressed HIV-positive participants and HIV-negative controls, HIV-positive status was significantly and independently associated with worse physical and mental HRQL and with an increased likelihood of depression. Our finding that a higher number of comorbidities was independently associated with worse physical HRQL reinforces the importance to optimize prevention and management of comorbidities as the HIV-infected population continues to age.

Neurobehavioral Manifestations of Human Immunodeficiency Virus/AIDS: Diagnosis and Treatment

Behavioral disorders are common in persons infected with human immunodeficiency virus (HIV). The differential includes preexisting psychiatric diseases, substance abuse, direct effects of HIV infection, opportunistic infection, and the adverse effects of medical therapies. Many patients have more than one contributing or comorbid problem to explain these behavioral changes. The differential should always include consideration of psychosocial, genetic, and medical causes of disease. Treatment strategies must take into account the coadministration of antiretroviral therapy and the specific neurologic problems common in patients infected with HIV.

Impact of Depression and Inflammation on the Progression of HIV Disease

The human immunodeficiency virus type 1 (HIV-1) epidemic has negatively affected over 40 million people worldwide. Antiretroviral therapy (ART) has improved life expectancy and changed the outcome of HIV-1 infection, making it a chronic and manageable disease. However, AIDS and non-AIDS comorbid illnesses persist during the course of infection despite the use of ART. In addition, the development of neuropsychiatric comorbidities (including depression) by HIV-infected subjects significantly affects quality of life, medication adherence, and disease prognosis. The factors associated with depression during HIV-1 infection include altered immune response, the release of pro-inflammatory cytokines, and monoamine imbalance. Elevated plasma pro-inflammatory cytokine levels contribute to the development of depression and depressive-like behaviors in HIV⁺ subjects. In addition, comorbid depression influences the decline rates of CD4⁺ cell counts and increases plasma viral load. Depression can manifest in some subjects despite their adherence to ART. In addition, psychosocial factors related to stigma (negative attitudes, moral issues, and abuse of HIV⁺ subjects) are also associated with depression. Both neurobiological and psychosocial factors are important considerations for the effective clinical management of HIV and the prevention of HIV disease progression.

Polymorphism of Kynurenine Pathway-Related Genes, Kynurenic Acid, and Psychopathological Symptoms in HIV

HIV-infection is associated with neuroinflammation and greater psychopathological symptoms, which may be mediated by imbalances in the kynurenic pathway (KP). Two key KP enzymes that catabolize kynurenine include kynurenine-aminotransferase II (KATII), which yields antioxidative kynurenine acid [KYNA] in astrocytes, and kynurenine-3-monooxygenase (KMO), which produces neurotoxic metabolites in microglia. The relationships between polymorphisms in KMO and KATII, psychopathological symptoms, and cerebrospinal fluid (CSF) [KYNA] were evaluated in subjects with and without HIV-infection. Seventy-two HIV-positive and 72-seronegative (SN) participants were genotyped for KATII-rs1480544 and KMO-rs1053230. Although our participants were not currently diagnosed with depression or anxiety, they were assessed for psychopathological distress with Center for Epidemiologic Studies-Depression scale and Symptom Checklist-90-Revised. CSF-[KYNA] was also measured in 100 subjects (49 HIV/51 SN). HIV-participants had more psychopathological distress than SN, especially for anxiety. KATII-by-HIV interactions were found on anxiety, interpersonal sensitivity and obsessive compulsivity; KATII-C-carriers had lower scores than TT-carriers in SN but not in HIV. In contrast, the KMO-polymorphism had no influence on psychopathological symptoms in both groups. Overall, CSF-[KYNA] increased with age independently of HIV-serostatus, except KATII-TT-carriers tended to show no age-dependent variations. Therefore, the C-allele in KATII-rs1480544 appears to be protective against psychopathological distress in SN but not in HIV individuals, who had more psychopathological symptoms and likely greater neuroinflammation. The age-dependent increase in CSF-[KYNA] may reflect a compensatory response to age-related inflammation, which may be deficient in KATII-TT-carriers. Targeted treatments that decrease neuroinflammation and increase KYNA in at risk KATII-TT-carriers may reduce psychopathological symptoms in HIV.