Disturbance in cerebral spinal fluid sphingolipid content is associated with memory impairment in subjects infected with the human immunodeficiency virus

Global Metabolic Shifts in Age and Alzheimer's Disease Mouse Brains Pivot at NAD+/NADH Redox Sites

Age and Alzheimer’s disease (AD) share some common features such as cognitive impairments, memory loss, metabolic disturbances, bioenergetic deficits, and inflammation. Yet little is known on how systematic shifts in metabolic networks depend on age and AD. In this work, we investigated the global metabolomic alterations in non-transgenic (NTg) and triple-transgenic (3xTg-AD) mouse brain hippocampus as a function of age by using untargeted Ultrahigh Performance Liquid Chromatography-tandem Mass Spectroscopy (UPLC-MS/MS). We observed common metabolic patterns with aging in both NTg and 3xTg-AD brains involved in energy-generating pathways, fatty acids oxidation, glutamate, and sphingolipid metabolism. We found age-related downregulation of metabolites from reactions in glycolysis that consumed ATP and in the TCA cycle, especially at NAD⁺/NADH-dependent redox sites, where age- and AD-associated limitations in the free NADH may alter reactions. Conversely, metabolites increased in glycolytic reactions in which ATP is produced. With age, inputs to the TCA cycle were increased including fatty acid β-oxidation and glutamine. Overall age- and AD-related changes were > 2-fold when comparing the declines of upstream metabolites of NAD⁺/NADH-dependent reactions to the increases of downstream metabolites (p = 10^-5, n = 8 redox reactions). Inflammatory metabolites such as ceramides and sphingosine-1-phosphate also increased with age. Age-related decreases in glutamate, GABA, and sphingolipid were seen which worsened with AD genetic load in 3xTg-AD brains, possibly contributing to synaptic, learning- and memory-related deficits. The data support the novel hypothesis that age- and AD-associated metabolic shifts respond to NAD(P)⁺/NAD(P)H redox-dependent reactions, which may contribute to decreased energetic capacity.

Neutral ceramidase is a marker for cognitive performance in rats and monkeys

Background

Ceramides are lipid molecules determining cell integrity and intercellular signaling, and thus, involved in the pathogenesis of several psychiatric and neurodegenerative disorders. However, little is known about the role of particular enzymes of the ceramide metabolism in the mechanisms of normal behavioral plasticity. Here, we studied the contribution of neutral ceramidase (NC), one of the main enzymes mediating ceramide degradation, in the mechanisms of learning and memory in rats and non-human primates.

Methods

Naïve Wistar rats and black tufted-ear marmosets (Callithrix penicillata) were tested in several tests for short- and long-term memory and then divided into groups with various memory performance. The activities of NC and acid ceramidase (AC) were measured in these animals. Additionally, anxiety and depression-like behavior and brain levels of monoamines were assessed in the rats.

Results

We observed a predictive role of NC activity in the blood serum for superior performance of long-term object memory tasks in both species. A brain area analysis suggested that high NC activity in the ventral mesencephalon (VM) predicts better short-term memory performance in rats. High NC activity in the VM was also associated with worse long-term object memory, which might be mediated by an enhanced depression-like state and a monoaminergic imbalance.

Conclusions

Altogether, these data suggest a role for NC in short- and long-term memory of various mammalian species. Serum activity of NC may possess a predictive role in the assessing the performance of certain types of memory.

Electronic supplementary material

The online version of this article (10.1007/s43440-020-00159-2) contains supplementary material, which is available to authorized users.

HIV-Associated Neurocognitive Impairment in the Modern ART Era: Are We Close to Discovering Reliable Biomarkers in the Setting of Virological Suppression?

The prevalence of the most severe forms of HIV-associated neurocognitive disorders (HAND) is decreasing due to worldwide availability and high efficacy of antiretroviral treatment (ART). However, several grades of HIV-related cognitive impairment persist with effective ART and remain a clinical concern for people with HIV (PWH). The pathogenesis of these cognitive impairments has yet to be fully understood and probably multifactorial. In PWH with undetectable peripheral HIV-RNA, the presence of viral escapes in cerebrospinal fluid (CSF) might explain a proportion of cases, but not all. Many other mechanisms have been hypothesized to be involved in disease progression, in order to identify possible therapeutic targets. As potential indicators of disease staging and progression, numerous biomarkers have been used to characterize and implicate chronic inflammation in the pathogenesis of neuronal injuries, such as certain phenotypes of activated monocytes/macrophages, in the context of persistent immune activation. Despite none of them being disease-specific, the correlation of several CSF cellular biomarkers to HIV-induced neuronal damage has been investigated. Furthermore, recent studies have been evaluating specific microRNA (miRNA) profiles in the CSF of PWH with neurocognitive impairment (NCI). The aim of the present study is to review the body of evidence on different biomarkers use in research and clinical settings, focusing on PWH on ART with undetectable plasma HIV-RNA.

Ceramide Accumulation Is Associated with Declining Verbal Memory in Coronary Artery Disease Patients: An Observational Study

Background:

Biomarkers in cognitively vulnerable populations, like those with coronary artery disease (CAD), may inform earlier intervention in vascular neurodegeneration. Circulating ceramide C18:0 (CerC18:0) is associated with changes in verbal memory in early neurodegeneration and CAD progression.

Objective:

To investigate whether plasma CerC18:0 accumulation is associated with longitudinal declines in verbal memory performance in CAD.

Methods:

In addition to total CerC18:0, we assessed its relative abundance to its precursors as ratios: CerC18:0 to monohexosylceramide C18:0 (MHxCer18:0), CerC18:0 to sphingomyelin C18:0 (SM18:0), and CerC18:0 to sphingosine-1-phosphate (S1P). Verbal memory was assessed using the California Verbal Learning Test 2^nd Ed. Using mixed models in 60 CAD participants, we evaluated associations between baseline CerC18:0 ratios and changes in verbal memory performance, adjusting for age, body mass index, and education. Given that cognitive decline is more rapid following onset of deficits, these associations were compared between those with possible mild vascular neurocognitive disorder (MVND).

Results:

Increased baseline CerC18:0 concentrations correlated with worse verbal memory performance over time (b[SE] = – 0.91[0.30], p = 0.003). Increased baseline CerC18:0/SM18:0 (b[SE] = – 1.11[`], p = 0.03) were associated with worse verbal memory performance over time. These associations were not mediated by whether or not patients had possible MVND at baseline.

Conclusion:

These findings support aberrant CerC18:0 metabolism as an early neurobiological change in vascular neurodegeneration. Future studies should measure enzymes responsible for conversion of sphingolipid precursors into CerC18:0 to assess enzymatic activity.

Changing clinical phenotypes of HIV-associated neurocognitive disorders

HIV-associated neurocognitive disorder (HAND) remains a common cause of cognitive impairment and persists in 15-55% of HIV+ individuals in the combination antiretroviral therapy (CART) era. CART is now the primary treatment for HAND, but it is effective in only a subset of patients. In the pre-CART era, HIV-associated dementia was the most common form of HAND. However, in CART-treated patients, the prevalence of HIV-associated dementia has declined substantially, and milder stages of HAND, i.e., ANI and MND predominate. HIV+ patients with mild neurocognitive disorder (MND) can still have significant functional impairment in some activities of daily living. There have been several other significant changes in the clinical features of HAND in the CART era. The mean survival for an individual diagnosed with HIV dementia has increased dramatically. In HIV+ individuals on CART with a suppressed systemic viral load, the majority of individuals with HAND remain stable, with a small proportion showing deterioration. Extrapyramidal signs are now less common in patients with HAND on CART. In the CART era, HAND may have a mixed pattern of both cortical and subcortical features with greater deficits in executive functioning and working memory. Despite the milder clinical phenotype, in the CART era, patients with HAND still have persistent laboratory and neuroimaging abnormalities in the central nervous system even with systemic viral suppression. As the HIV+ patient population ages, cerebrovascular disease risk factors such as hypertension, diabetes, and hypercholesterolemia are increasingly recognized as risk factors for cognitive impairment in HIV+ patients on CART. HAND remains a common neurological condition globally in the CART era, necessitating the need for new animal models to examine pathogenesis and potential treatments for HAND.

Modifications in acute phase and complement systems predict shifts in cognitive status of HIV-infected patients

BACKGROUND

The prevalence of HIV-associated neurocognitive disorders (HAND) has not changed considerably in the last two decades. Potent antiretroviral therapy has shifted the severity of HAND to milder phenotypes, but excess morbidity and mortality continue to be associated with HAND. Changes in numerous markers of immune function, inflammation, and cellular stress have been repeatedly associated with HAND, but the underlying systems that drive these changes have not been identified.

METHOD

In this study, we used systems informatics to interrogate the cerebrospinal fluid proteomic content of longitudinal samples obtained from HIV-infected adults with stably unimpaired, stably impaired, worsening, or improving neurocognitive performance.

RESULTS AND CONCLUSION

The patterns of change in cerebrospinal fluid protein content implicated the induction of acute phase and complement systems as important regulators of neurocognitive status. Worsening neurocognitive performance was preceded by induction of acute phase and complement systems, whereas improving neurocognitive performance was preceded by a downregulation of these systems.

HIV-associated neurocognitive disorder--pathogenesis and prospects for treatment

In the past two decades, several advancements have improved the care of HIV-infected individuals. Most importantly, the development and deployment of combination antiretroviral therapy (CART) has resulted in a dramatic decline in the rate of deaths from AIDS, so that people living with HIV today have nearly normal life expectancies if treated with CART. The term HIV-associated neurocognitive disorder (HAND) has been used to describe the spectrum of neurocognitive dysfunction associated with HIV infection. HIV can enter the CNS during early stages of infection, and persistent CNS HIV infection and inflammation probably contribute to the development of HAND. The brain can subsequently serve as a sanctuary for ongoing HIV replication, even when systemic viral suppression has been achieved. HAND can remain in patients treated with CART, and its effects on survival, quality of life and everyday functioning make it an important unresolved issue. In this Review, we describe the epidemiology of HAND, the evolving concepts of its neuropathogenesis, novel insights from animal models, and new approaches to treatment. We also discuss how inflammation is sustained in chronic HIV infection. Moreover, we suggest that adjunctive therapies--treatments targeting CNS inflammation and other metabolic processes, including glutamate homeostasis, lipid and energy metabolism--are needed to reverse or improve HAND-related neurological dysfunction.

Annotation of the human cerebrospinal fluid lipidome using high resolution mass spectrometry and a dedicated data processing workflow

INTRODUCTION

Due to its proximity with the brain, cerebrospinal fluid (CSF) could be a medium of choice for the discovery of biomarkers of neurological and psychiatric diseases using untargeted analytical approaches.

OBJECTIVES

This study explored the CSF lipidome in order to generate a robust mass spectral database using an untargeted lipidomic approach.

METHODS

Cerebrospinal fluid samples from 45 individuals were analyzed by liquid chromatography coupled to high-resolution mass spectrometry method (LC-HRMS). A dedicated data processing workflow was implemented using XCMS software and adapted filters to select reliable features. In addition, an automatic annotation using an in silico lipid database and several MS/MS experiments were performed to identify CSF lipid species.

RESULTS

Using this complete workflow, 771 analytically relevant monoisotopic lipid species corresponding to 550 unique lipids which represent five major lipid families (i.e., free fatty acids, sphingolipids, glycerophospholipids, glycerolipids, and sterol lipids) were detected and annotated. In addition, MS/MS experiments enabled to improve the annotation of 304 lipid species. Thanks to LC-HRMS, it was possible to discriminate between isobaric and also isomeric lipid species; and interestingly, our study showed that isobaric ions represent about 50 % of the total annotated lipid species in the human CSF.

CONCLUSION

This work provides an extensive LC/HRMS database of the human CSF lipidome which constitutes a relevant foundation for future studies aimed at finding biomarkers of neurological disorders.

Low serum sphingolipids in children with attention deficit-hyperactivity disorder

Background: Attention deficit-hyperactivity disorder (ADHD) is the most prevalent neuropsychiatric condition in childhood. ADHD is a multifactorial trait with a strong genetic component. One neurodevelopmental hypothesis is that ADHD is associated with a lag in brain maturation. Sphingolipids are essential for brain development and neuronal functioning, but their role in ADHD pathogenesis is unexplored. We hypothesized that serum sphingolipid levels distinguish ADHD patients from unaffected subjects.

Methods: We characterized serum sphingolipid profiles of ADHD patients and two control groups: non-affected relatives and non-affected subjects without a family history of ADHD. Sphingolipids were measured by LC-MS/MS in 77 participants (28 ADHD patients, 28 related controls, and 21 unrelated controls). ADHD diagnosis was based on the Diagnostic and Statistical Manual of Mental Disorders (DSM IV-TR). Diagnostic criteria were assessed by two independent observers. Groups were compared by parametrical statistics.

Results: Serum sphingomyelins C16:0, C18:0, C18:1, C24:1, ceramide C24:0, and deoxy-ceramide C24:1 were significantly decreased in ADHD patients at 20–30% relative reductions. In our sample, decreased serum sphingomyelin levels distinguished ADHD patients with 79% sensitivity and 78% specificity.

Conclusions: Our results showed lower levels of all major serum sphingomyelins in ADHD. These findings may reflect brain maturation and affect neuro-functional pathways characteristic for ADHD.

Cambinol, a novel inhibitor of neutral sphingomyelinase 2 shows neuroprotective properties

Ceramide is a bioactive lipid that plays an important role in stress responses leading to apoptosis, cell growth arrest and differentiation. Ceramide production is due in part to sphingomyelin hydrolysis by sphingomyelinases. In brain, neutral sphingomyelinase 2 (nSMase2) is expressed in neurons and increases in its activity and expression have been associated with pro-inflammatory conditions observed in Alzheimer's disease, multiple sclerosis and human immunodeficiency virus (HIV-1) patients. Increased nSMase2 activity translates into higher ceramide levels and neuronal cell death, which can be prevented by chemical or genetic inhibition of nSMase2 activity or expression. However, to date, there are no soluble, specific and potent small molecule inhibitor tool compounds for in vivo studies or as a starting point for medicinal chemistry optimization. Moreover, the majority of the known inhibitors were identified using bacterial, bovine or rat nSMase2. In an attempt to identify new inhibitor scaffolds, two activity assays were optimized as screening platform using the recombinant human enzyme. First, active hits were identified using a fluorescence-based high throughput compatible assay. Then, hits were confirmed using a 14C sphingomyelin-based direct activity assay. Pharmacologically active compounds and approved drugs were screened using this strategy which led to the identification of cambinol as a novel uncompetitive nSMase2 inhibitor (Ki = 7 μM). The inhibitory activity of cambinol for nSMase2 was approximately 10-fold more potent than for its previously known target, silence information regulator 1 and 2 (SIRT1/2). Cambinol decreased tumor necrosis factor-α or interleukin-1 β-induced increases of ceramide and cell death in primary neurons. A preliminary study of cambinol structure and activity allowed the identification of the main structural features required for nSMase2 inhibition. Cambinol and its analogs may be useful as nSMase2 inhibitor tool compounds to prevent ceramide-dependent neurodegeneration.

Sphingolipid metabolism correlates with cerebrospinal fluid Beta amyloid levels in Alzheimer's disease

Sphingolipids are important in many brain functions but their role in Alzheimer’s disease (AD) is not completely defined. A major limit is availability of fresh brain tissue with defined AD pathology. The discovery that cerebrospinal fluid (CSF) contains abundant nanoparticles that include synaptic vesicles and large dense core vesicles offer an accessible sample to study these organelles, while the supernatant fluid allows study of brain interstitial metabolism. Our objective was to characterize sphingolipids in nanoparticles representative of membrane vesicle metabolism, and in supernatant fluid representative of interstitial metabolism from study participants with varying levels of cognitive dysfunction. We recently described the recruitment, diagnosis, and CSF collection from cognitively normal or impaired study participants. Using liquid chromatography tandem mass spectrometry, we report that cognitively normal participants had measureable levels of sphingomyelin, ceramide, and dihydroceramide species, but that their distribution differed between nanoparticles and supernatant fluid, and further differed in those with cognitive impairment. In CSF from AD compared with cognitively normal participants: a) total sphingomyelin levels were lower in nanoparticles and supernatant fluid; b) levels of ceramide species were lower in nanoparticles and higher in supernatant fluid; c) three sphingomyelin species were reduced in the nanoparticle fraction. Moreover, three sphingomyelin species in the nanoparticle fraction were lower in mild cognitive impairment compared with cognitively normal participants. The activity of acid, but not neutral sphingomyelinase was significantly reduced in the CSF from AD participants. The reduction in acid sphingomylinase in CSF from AD participants was independent of depression and psychotropic medications. Acid sphingomyelinase activity positively correlated with amyloid β₄₂ concentration in CSF from cognitively normal but not impaired participants. In dementia, altered sphingolipid metabolism, decreased acid sphingomyelinase activity and its lost association with CSF amyloid β₄₂ concentration, underscores the potential of sphingolipids as disease biomarkers, and acid sphingomyelinase as a target for AD diagnosis and/or treatment.

Understanding the MIND phenotype: macrophage/microglia inflammation in neurocognitive disorders related to human immunodeficiency virus infection

Tissue macrophages play important roles in maintaining homeostasis in most organs of the body including the brain where microglia represent the resident phagocytic cells of this compartment. The possibility of one day harnessing macrophage plasticity to treat or ameliorate disorders including obesity, cancer, organ damage, intestinal disorders, neurodegeneration, and cardiovascular disease in which these cells play a role, is a very exciting prospect. Inflammatory signaling is required for regenerative repair, healing, and pathogen clearance functions. However, when the inflammatory response persists in a chronic fashion over an extended period of time, damage to neurons is followed by neuronal injury and dysfunction. Macrophages in the brain are heterogeneous arising from tissues during embryogenesis, and in the adult, from bone marrow derived monocytes that enter through the blood-brain-barrier. While much of our insight regarding macrophage functional subtypes has been garnered through elegant studies in mice, which are amenable to genetic manipulation, far less is known about such cells in human tissues, and particularly in the brain under normal, disease, or injurious conditions. In this regard, non-human primate models for human immunodeficiency virus have been extremely useful for understanding the contribution of bone marrow-derived monocytes in neurological disease and their interaction and impact on the activation state of resident microglia in the brain. This review will focus on what has been learned from the rhesus macaque models about the types of macrophages present in the brains of animals with encephalitis. In vitro studies, which have used human blood monocytes differentiated into macrophages to address the question of macrophage subsets in HIV infection will be highlighted. Recent insights on macrophage phenotype and persistent inflammation in the brain in HIV-associated neurocognitive disorder from immunohistochemical studies on human autopsy tissue will be examined.

Activation of TRPML1 clears intraneuronal Aβ in preclinical models of HIV infection

Antiretroviral therapy extends the lifespan of human immunodeficiency virus (HIV)-infected patients, but many survivors develop premature impairments in cognition. These residual cognitive impairments may involve aberrant deposition of amyloid β-peptides (Aβ). By unknown mechanisms, Aβ accumulates in the lysosomal and autophagic compartments of neurons in the HIV-infected brain. Here we identify the molecular events evoked by the HIV coat protein gp120 that facilitate the intraneuronal accumulation of Aβ. We created a triple transgenic gp120/APP/PS1 mouse that recapitulates intraneuronal deposition of Aβ in a manner reminiscent of the HIV-infected brain. In cultured neurons, we found that the HIV coat protein gp120 increased the transcriptional expression of BACE1 through repression of PPARγ, and increased APP expression by promoting interaction of the translation-activating RBP heterogeneous nuclear ribonucleoprotein C with APP mRNA. APP and BACE1 were colocalized into stabilized membrane microdomains, where the β-cleavage of APP and Aβ formation were enhanced. Aβ-peptides became localized to lysosomes that were engorged with sphingomyelin and calcium. Stimulating calcium efflux from lysosomes with a TRPM1 agonist promoted calcium efflux, luminal acidification, and cleared both sphingomyelin and Aβ from lysosomes. These findings suggest that therapeutics targeted to reduce lysosomal pH in neurodegenerative conditions may protect neurons by facilitating the clearance of accumulated sphingolipids and Aβ-peptides.

Cerebrospinal fluid metabolomics reveals altered waste clearance and accelerated aging in HIV patients with neurocognitive impairment

Objective(s):

HIV-associated neurocognitive disorders (HAND) remain prevalent in HIV-infected patients on antiretroviral therapy (ART), but the underlying mechanisms are unclear. Some features of HAND resemble those of age-associated cognitive decline in the absence of HIV, suggesting that overlapping mechanisms may contribute to neurocognitive impairment.

Design:

Cross-sectional analysis of cerebrospinal fluid (CSF) from 100 individuals (46 HIV-positive patients and 54 HIV-negative controls).

Methods:

Untargeted CSF metabolite profiling was performed using liquid/gas chromatography followed by mass spectrometry. Cytokine profiling was performed by Bioplex. Bioinformatic analyses were performed in Metaboanalyst and R.

Results:

Alterations in the CSF metabolome of HIV patients on ART mapped to pathways associated with neurotransmitter production, mitochondrial function, oxidative stress, and metabolic waste. Many CSF metabolites altered in HIV overlapped with those altered with advanced age in HIV-negative controls, suggesting a pattern indicative of accelerated aging. Machine learning models identified neurotransmitters (glutamate, N-acetylaspartate), markers of glial activation (myo-inositol), and ketone bodies (beta-hydroxybutyric acid, 1,2-propanediol) as top-ranked classifiers of HAND. These CSF metabolites correlated with worse neurocognitive test scores, plasma inflammatory biomarkers [interferon (IFN)-α, IFN-γ, interleukin (IL)-8, IL-1β, IL-6, IL-2Ra], and intrathecal IFN responses (IFN-γ and kynurenine : tryptophan ratio), suggesting inter-relationships between systemic and intrathecal inflammation and metabolic alterations in CSF.

Conclusions:

Alterations in the CSF metabolome of HIV patients on ART suggest that persistent inflammation, glial responses, glutamate neurotoxicity, and altered brain waste disposal systems contribute to mechanisms involved in HAND that may be augmented with aging.

Antiretroviral drugs induce oxidative stress and neuronal damage in the central nervous system

HIV-associated neurocognitive disorder (HAND), characterized by a wide spectrum of behavioral, cognitive, and motor dysfunctions, continues to affect approximately 50 % of HIV(+) patients despite the success of combination antiretroviral drug therapy (cART) in the periphery. Of note, potential toxicity of antiretroviral drugs in the central nervous system (CNS) remains remarkably underexplored and may contribute to the persistence of HAND in the cART era. Previous studies have shown antiretrovirals (ARVs) to be neurotoxic in the peripheral nervous system in vivo and in peripheral neurons in vitro. Alterations in lipid and protein metabolism, mitochondrial damage, and oxidative stress all play a role in peripheral ARV neurotoxicity. We hypothesized that ARVs also induce cellular stresses in the CNS, ultimately leading to neuronal damage and contributing to the changing clinical and pathological picture seen in HIV-positive patients in the cART era. In this report, we show that ARVs are neurotoxic in the CNS in both pigtail macaques and rats in vivo. Furthermore, in vitro, ARVs lead to accumulation of reactive oxygen species (ROS), and ultimately induction of neuronal damage and death. Whereas ARVs alone caused some activation of the endogenous antioxidant response in vitro, augmentation of this response by a fumaric acid ester, monomethyl fumarate (MMF), blocked ARV-induced ROS generation, and neuronal damage/death. These findings implicate oxidative stress as a contributor to the underlying mechanisms of ARV-induced neurotoxicity and will provide an access point for adjunctive therapies to complement ARV therapy and reduce neurotoxicity in this patient population.

A lipid storage-like disorder contributes to cognitive decline in HIV-infected subjects

OBJECTIVE

In this multicenter cohort study, we sought to identify prognostic and associative metabolic indicators for HIV-associated neurocognitive disorders (HAND).

METHODS

A quantitative lipidomic analysis was conducted on 524 longitudinal CSF samples collected from 7 different performance sites across the mainland United States, Hawaii, and Puerto Rico. Subjects included HIV-infected individuals with longitudinal clinical and cognitive testing data and cognitively normal HIV-negative healthy controls.

RESULTS

At baseline, HIV+ subjects could be differentiated from HIV- controls by reductions in a single ceramide species and increases in multiple forms of cholesterol. Perturbations in cholesterol metabolism and ceramide were influenced by combined antiretroviral therapy (cART) use. There were no cross-sectional baseline differences in any lipid metabolite when HIV+ subjects were grouped according to cognitive status. However, a single sphingolipid metabolite and reduced levels of esterified cholesterols were prognostic indicators of incident cognitive decline. Longitudinal patterns of these disturbances in sphingolipid and sterol metabolism suggest that a progressive disorder of lipid metabolism that is similar to disorders of lipid storage may contribute to the pathogenesis of HAND.

CONCLUSIONS

These findings suggest that HIV infection and cART are independently associated with a CNS metabolic disturbance, identify surrogate markers that are prognostic for cognitive decline, and implicate a lipid storage-like disorder in the progression of HAND.

Could plasma sphingolipids be diagnostic or prognostic biomarkers for Alzheimer's disease?

Understanding the etiopathological processes of Alzheimer's disease (AD) in the preclinical and early clinical stages will be important in developing new therapeutic targets and biomarkers. There is growing consensus that nonamyloid targets will be necessary to reverse or slow AD progression. Lipidomic, metabolomic and targeted approaches have identified pathways and products of sphingolipid metabolism that are altered early in the course of AD and contribute to the neuropathological alterations associated with AD, including amyloid-β production, tau formation and neurodegeneration. In this article, we briefly review the current literature on the role of sphingolipids in the underlying pathophysiology of AD, and then discuss the current state of translating these findings to clinical populations and the potential utility of plasma sphingolipids as diagnostic and/or prognostic indicators of AD.

Chemotherapy-related changes in central nervous system phospholipids and neurocognitive function in childhood acute lymphoblastic leukemia

Long-term survivors of childhood leukemia are at risk for neurocognitive impairment, although the neurophysiological basis is not well understood. The purpose of this study was to explore associations between changes in cerebrospinal fluid (CSF) phospholipids and neurocognitive function in children undergoing chemotherapy for acute lymphoblastic leukemia. Seventy-six children were followed prospectively from diagnosis. CSF samples were collected during scheduled lumbar punctures and phospholipids were extracted. Neurocognitive evaluations were conducted annually beginning shortly after diagnosis. Concentrations of sphingomyelin (SM) increased following induction (p = 0.03) and consolidation (p = 0.04), while lysophosphatidylcholine (LPC) increased following induction (p = 0.003). Multivariable analyses demonstrated associations between post-induction SM and motor speed at 1 year (p < 0.001), 2 years (p = 0.001) and 3 years (p = 0.02) following diagnosis. Post-induction LPC was associated with verbal working memory (p = 0.007). Results indicate that early changes in phospholipids are related to neurocognitive decline and suggest a chemotherapy impact on white matter integrity.