ABCD1 dysfunction alters white matter microvascular perfusion

The pathology of X-linked adrenoleukodystrophy: tissue specific changes as a clue to pathophysiology

Although the pathology of X-linked adrenoleukodystrophy (ALD) is well described, it represents the end-stage of neurodegeneration. It is still unclear what cell types are initially involved and what their role is in the disease process. Revisiting the seminal post-mortem studies from the 1970s can generate new hypotheses on pathophysiology. This review describes (histo)pathological changes of the brain and spinal cord in ALD. It aims at integrating older works with current insights and at providing an overarching theory on the pathophysiology of ALD. The data point to an important role for axons and glia in the pathology of both the myelopathy and leukodystrophy of ALD. In-depth pathological analyses with new techniques could help further unravel the sequence of events behind the pathology of ALD.

Ryu J, Akassoglou K, Talebian S, Chu P, Pisani L, Musolino P, Steinman L, Doyle K, Robinson WH, Sharpe O, Cayrol R, Orchard P, Lund T, Vogel H, Lenail M, Han MH, Bonkowsky JL, Van Haren KP. A novel mouse model of cerebral adrenoleukodystrophy highlights NLRP3 activity in lesion pathogenesis

Objective

We sought to create and characterize a mouse model of the inflammatory, cerebral demyelinating phenotype of X-linked adrenoleukodystrophy (ALD) that would facilitate the study of disease pathogenesis and therapy development. We also sought to cross-validate potential therapeutic targets such as fibrin, oxidative stress, and the NLRP3 inflammasome, in post-mortem human and murine brain tissues.

Background

ALD is caused by mutations in the gene ABCD1 encoding a peroxisomal transporter. More than half of males with an ABCD1 mutation develop the cerebral phenotype (cALD). Incomplete penetrance and absence of a genotype-phenotype correlation imply a role for environmental triggers. Mechanistic studies have been limited by the absence of a cALD phenotype in the Abcd1-null mouse.

Methods

We generated a cALD phenotype in 8-week-old, male Abcd1-null mice by deploying a two-hit method that combines cuprizone (CPZ) and experimental autoimmune encephalomyelitis (EAE) models. We employed in vivo MRI and post-mortem immunohistochemistry to evaluate myelin loss, astrogliosis, blood-brain barrier (BBB) disruption, immune cell infiltration, fibrin deposition, oxidative stress, and Nlrp3 inflammasome activation in mice. We used bead-based immunoassay and immunohistochemistry to evaluate IL-18 in CSF and post-mortem human cALD brain tissue.

Results

MRI studies revealed T2 hyperintensities and post-gadolinium enhancement in the medial corpus callosum of cALD mice, similar to human cALD lesions. Both human and mouse cALD lesions shared common histologic features of myelin phagocytosis, myelin loss, abundant microglial activation, T and B-cell infiltration, and astrogliosis. Compared to wild-type controls, Abcd1-null mice had more severe cerebral inflammation, demyelination, fibrin deposition, oxidative stress, and IL-18 activation. IL-18 immunoreactivity co-localized with macrophages/microglia in the perivascular region of both human and mouse brain tissue.

Interpretation

This novel mouse model of cALD suggests loss of Abcd1 function predisposes to more severe cerebral inflammation, oxidative stress, fibrin deposition, and Nlrp3 pathway activation, which parallels the findings seen in humans with cALD. We expect this model to enable long-sought investigations into cALD mechanisms and accelerate development of candidate therapies for lesion prevention, cessation, and remyelination.

Effect of vitamin D supplementation on cerebral blood flow in male patients with adrenoleukodystrophy

One-third of boys with X-linked adrenoleukodystrophy (ALD) develop inflammatory demyelinating lesions, typically at the splenium. These lesions share similarities with multiple sclerosis, including cerebral hypoperfusion and links to vitamin D insufficiency. We hypothesized that increasing vitamin D levels would increase cerebral blood flow (CBF) in ALD boys. We conducted an exploratory analysis of vitamin D supplementation and CBF using all available data from participants enrolled in a recent single-arm interventional study of vitamin D supplementation in boys with ALD. We measured whole brain and splenium CBF using arterial spin labeling (ASL) from three study time points (baseline, 6 months, and 12 months). We used linear generalized estimating equations to evaluate CBF changes between time points and to test for an association between CBF and vitamin D. ASL data were available for 16 participants, aged 2-22 years. Mean vitamin D levels increased by 72.7% (p < .001) after 6 months and 88.6% (p < .01) after 12 months. Relative to baseline measures, mean CBF of the whole brain (6 months: +2.5%, p = .57; 12 months: +6.1%, p = .18) and splenium (6 months: +1.2%, p = .80; 12 months: +7.4%, p = .058) were not significantly changed. Vitamin D levels were positively correlated with CBF in the splenium (slope = .59, p < .001). In this exploratory analysis, we observed a correlation between vitamin D levels and splenial CBF in ALD boys. We confirm the feasibility of measuring CBF in this brain region and population, but further work is needed to establish a causal role for vitamin D in modulating CBF.

Fatty acids metabolism affects the therapeutic effect of anti-PD-1/PD-L1 in tumor immune microenvironment in clear cell renal cell carcinoma

BACKGROUND

Clear cell renal cell carcinoma (ccRCC) is a highly invasive and metastatic subtype of kidney malignancy and is correlated with metabolic reprogramming for adaptation to the tumor microenvironment comprising infiltrated immune cells and immunomodulatory molecules. The role of immune cells in the tumor microenvironment (TME) and their association with abnormal fatty acids metabolism in ccRCC remains poorly understood.

METHOD

RNA-seq and clinical data of KIRC from The Cancer Genome Atlas (TCGA) and E-MTAB-1980 from the ArrayExpress dataset. The Nivolumab group and Everolimus group of the CheckMate 025 study, the Atezolizumab arm of IMmotion150 and the Atezolizumab plus Bevacizumab group of IMmotion151 cohort were obtained for subsequent analysis. After differential expression genes identification, the signature was constructed through univariate Cox proportional hazard regression and simultaneously the least absolute shrinkage and selection operator (Lasso) analysis and the predictive performance of our signature was assessed by using receiver operating characteristic (ROC), Kaplan-Meier (KM) survival analysis, nomogram, drug sensitivity analysis, immunotherapeutic effect analysis and enrichment analysis. Immunohistochemistry (IHC), qPCR and western blot were performed to measure related mRNA or protein expression. Biological features were evaluated by wound healing, cell migration and invasion assays and colony formation test and analyzed using coculture assay and flow cytometry.

RESULTS

Twenty fatty acids metabolism-related mRNA signatures were constructed in TCGA and possessed a strong predictive performance demonstrated through time-dependent ROC and KM survival analysis. Notably, the high-risk group exhibited an impaired response to anti-PD-1/PD-L1 (Programmed death-1 receptor/Programmed death-1 receptor-ligand) therapy compared to the low-risk group. The overall levels of the immune score were higher in the high-risk group. Additionally, drug sensitivity analysis observed that the model could effectively predict efficacy and sensitivity to chemotherapy. Enrichment analysis revealed that the IL6-JAK-STAT3 signaling pathway was a major pathway. IL4I1 could promote ccRCC cells' malignant features through JAK1/STAT3 signaling pathway and M2-like macrophage polarization.

CONCLUSION

The study elucidates that targeting fatty acids metabolism can affect the therapeutic effect of PD-1/PD-L1 in TME and related signal pathways. The model can effectively predict the response to several treatment options, underscoring its potential clinical utility.

Hematopoietic stem-cell gene therapy is associated with restored white matter microvascular function in cerebral adrenoleukodystrophy

Blood-brain barrier disruption marks the onset of cerebral adrenoleukodystrophy (CALD), a devastating cerebral demyelinating disease caused by loss of ABCD1 gene function. The underlying mechanism are not well understood, but evidence suggests that microvascular dysfunction is involved. We analyzed cerebral perfusion imaging in boys with CALD treated with autologous hematopoietic stem-cells transduced with the Lenti-D lentiviral vector that contains ABCD1 cDNA as part of a single group, open-label phase 2-3 safety and efficacy study (NCT01896102) and patients treated with allogeneic hematopoietic stem cell transplantation. We found widespread and sustained normalization of white matter permeability and microvascular flow. We demonstrate that ABCD1 functional bone marrow-derived cells can engraft in the cerebral vascular and perivascular space. Inverse correlation between gene dosage and lesion growth suggests that corrected cells contribute long-term to remodeling of brain microvascular function. Further studies are needed to explore the longevity of these effects.

The physiological functions of human peroxisomes

Peroxisomes are subcellular organelles that play a central role in human physiology by catalyzing a range of unique metabolic functions. The importance of peroxisomes for human health is exemplified by the existence of a group of usually severe diseases caused by an impairment in one or more peroxisomal functions. Among others these include the Zellweger spectrum disorders, X-linked adrenoleukodystrophy, and Refsum disease. To fulfill their role in metabolism, peroxisomes require continued interaction with other subcellular organelles including lipid droplets, lysosomes, the endoplasmic reticulum, and mitochondria. In recent years it has become clear that the metabolic alliance between peroxisomes and other organelles requires the active participation of tethering proteins to bring the organelles physically closer together, thereby achieving efficient transfer of metabolites. This review intends to describe the current state of knowledge about the metabolic role of peroxisomes in humans, with particular emphasis on the metabolic partnership between peroxisomes and other organelles and the consequences of genetic defects in these processes. We also describe the biogenesis of peroxisomes and the consequences of the multiple genetic defects therein. In addition, we discuss the functional role of peroxisomes in different organs and tissues and include relevant information derived from model systems, notably peroxisomal mouse models. Finally, we pay particular attention to a hitherto underrated role of peroxisomes in viral infections.

An in-silico approach to studying a very rare neurodegenerative disease using a disease with higher prevalence with shared pathways and genes: Cerebral adrenoleukodystrophy and Alzheimer’s disease

Cerebral adrenoleukodystrophy (cALD) is a rare neurodegenerative disease characterized by inflammatory demyelination in the central nervous system. Another neurodegenerative disease with a high prevalence, Alzheimer’s disease (AD), shares many common features with cALD such as cognitive impairment and the alleviation of symptoms by erucic acid. We investigated cALD and AD in parallel to study the shared pathological pathways between a rare disease and a more common disease. The approach may expand the biological understandings and reveal novel therapeutic targets. Gene set enrichment analysis (GSEA) and weighted gene correlation network analysis (WGCNA) were conducted to identify both the resemblance in gene expression patterns and genes that are pathologically relevant in the two diseases. Within differentially expressed genes (DEGs), GSEA identified 266 common genes with similar up- or down-regulation patterns in cALD and AD. Among the interconnected genes in AD data, two gene sets containing 1,486 genes preserved in cALD data were selected by WGCNA that may significantly affect the development and progression of cALD. WGCNA results filtered by functional correlation via protein–protein interaction analysis overlapping with GSEA revealed four genes (annexin A5, beta-2-microglobulin, CD44 molecule, and fibroblast growth factor 2) that showed robust associations with the pathogeneses of cALD and AD, where they were highly involved in inflammation, apoptosis, and the mitogen-activated protein kinase pathway. This study provided an integrated strategy to provide new insights into a rare disease with scant publicly available data (cALD) using a more prevalent disorder with some pathological association (AD), which suggests novel druggable targets and drug candidates.

Leukodystrophies

PURPOSE OF REVIEW

This article reviews the most common leukodystrophies and is focused on diagnosis, clinical features, and emerging therapeutic options.

RECENT FINDINGS

In the past decade, the recognition of leukodystrophies has exponentially increased, and now this class includes more than 30 distinct disorders. Classically recognized as progressive and fatal disorders affecting young children, it is now understood that leukodystrophies are associated with an increasing spectrum of neurologic trajectories and can affect all ages. Next-generation sequencing and newborn screening allow the opportunity for the recognition of presymptomatic and atypical cases. These new testing opportunities, in combination with growing numbers of natural history studies and clinical consensus guidelines, have helped improve diagnosis and clinical care. Additionally, a more granular understanding of disease outcomes informs clinical trial design and has led to several recent therapeutic advances. This review summarizes the current understanding of the clinical manifestations of disease and treatment options for the most common leukodystrophies.

SUMMARY

As early testing becomes more readily available through next-generation sequencing and newborn screening, neurologists will better understand the true incidence of the leukodystrophies and be able to diagnose children within the therapeutic window. As targeted therapies are developed, it becomes increasingly imperative that this broad spectrum of disorders is recognized and diagnosed. This work summarizes key advances in the leukodystrophy field.

Cerebral hemodynamics and capillary dysfunction in late-onset major depressive disorder

In major depressive disorder (MDD), perfusion changes in cortico-limbic pathways are interpreted as altered neuronal activity, but they could also signify changes in neurovascular coupling due to altered capillary function. To examine capillary function in late-onset MDD, 22 patients and 22 age- and gender-matched controls underwent perfusion MRI. We measured normalized cerebral blood flow (nCBF), cerebral blood volume (nCBV), and relative transit-time heterogeneity (RTH). Resulting brain oxygenation was estimated in terms of oxygen tension and normalized metabolic rate of oxygen (nCMRO₂). Patients revealed signs of capillary dysfunction (elevated RTH) in the anterior prefrontal cortex and ventral anterior cingulate cortex bilaterally and in the left insulate cortex compared to controls, bilateral hypometabolism (parallel reductions of nCBV, nCBF, and CMRO₂) but preserved capillary function in the subthalamic nucleus and globus pallidus bilaterally, and hyperactivity with preserved capillary function (increased nCBF) in the cerebellum and brainstem. Our data support that perfusion changes in deep nuclei and cerebellum reflect abnormally low and high activity, respectively, in MDD patients, but suggest that microvascular pathology affects neurovascular coupling in ventral circuits. We speculate that microvascular pathology is important for our understanding of etiology of late-onset MDD as well as infererences about resulting brain activity changes.

Imaging in X-Linked Adrenoleukodystrophy

Magnetic resonance imaging (MRI) is the gold standard for the detection of cerebral lesions in X-linked adrenoleukodystrophy (ALD). ALD is one of the most common peroxisomal disorders and is characterized by a defect in degradation of very long chain fatty acids (VLCFA), resulting in accumulation of VLCFA in plasma and tissues. The clinical spectrum of ALD is wide and includes adrenocortical insufficiency, a slowly progressive myelopathy in adulthood, and cerebral demyelination in a subset of male patients. Cerebral demyelination (cerebral ALD) can be treated with hematopoietic cell transplantation (HCT) but only in an early (pre- or early symptomatic) stage and therefore active MRI surveillance is recommended for male patients, both pediatric and adult. Although structural MRI of the brain can detect the presence and extent of cerebral lesions, it does not predict if and when cerebral demyelination will occur. There is a great need for imaging techniques that predict onset of cerebral ALD before lesions appear. Also, imaging markers for severity of myelopathy as surrogate outcome measure in clinical trials would facilitate drug development. New quantitative MRI techniques are promising in that respect. This review focuses on structural and quantitative imaging techniques-including magnetic resonance spectroscopy, diffusion tensor imaging, MR perfusion imaging, magnetization transfer (MT) imaging, neurite orientation dispersion and density imaging (NODDI), and myelin water fraction imaging-used in ALD and their role in clinical practice and research opportunities for the future.

Pathology of the neurovascular unit in leukodystrophies

The blood-brain barrier is a dynamic endothelial cell barrier in the brain microvasculature that separates the blood from the brain parenchyma. Specialized brain endothelial cells, astrocytes, neurons, microglia and pericytes together compose the neurovascular unit and interact to maintain blood-brain barrier function. A disturbed brain barrier function is reported in most common neurological disorders and may play a role in disease pathogenesis. However, a comprehensive overview of how the neurovascular unit is affected in a wide range of rare disorders is lacking. Our aim was to provide further insights into the neuropathology of the neurovascular unit in leukodystrophies to unravel its potential pathogenic role in these diseases. Leukodystrophies are monogenic disorders of the white matter due to defects in any of its structural components. Single leukodystrophies are exceedingly rare, and availability of human tissue is unique. Expression of selective neurovascular unit markers such as claudin-5, zona occludens 1, laminin, PDGFRβ, aquaporin-4 and α-dystroglycan was investigated in eight different leukodystrophies using immunohistochemistry. We observed tight junction rearrangements, indicative of endothelial dysfunction, in five out of eight assessed leukodystrophies of different origin and an altered aquaporin-4 distribution in all. Aquaporin-4 redistribution indicates a general astrocytic dysfunction in leukodystrophies, even in those not directly related to astrocytic pathology or without prominent reactive astrogliosis. These findings provide further evidence for dysfunction in the orchestration of the neurovascular unit in leukodystrophies and contribute to a better understanding of the underlying disease mechanism.

GIT1 protects traumatically injured spinal cord by prompting microvascular endothelial cells to clear myelin debris

The clearance of myelin debris is a critical step in the functional recovery following spinal cord injury (SCI). As phagocytes do, microvascular endothelial cells (MECs) participate in myelin debris clearance at the injury site within one week. Our group has verified that G protein-coupled receptor kinase 2 interacting protein-1 (GIT1) is essential in autophagy and angiogenesis, both of which are tightly related to the uptake and degradation of myelin debris by MECs. Here, we analyzed the performance and mechanism of GIT1 in myelin debris clearance after SCI. The SCI contusion model was established and in vitro MECs were treated with myelin debris. Better recovery from traumatic SCI was observed in the GIT1 WT mice than in the GIT1 KO mice. More importantly, we found that GIT1 prompted MECs to clear myelin debris and further enhanced MECs angiogenesis in vivo and in vitro. Mechanistically, GIT1-mediated autophagy contributed to the clearance of myelin debris by MECs. In this study, we demonstrated that GIT1 may prompt MECs to clear myelin debris via autophagy and further stimulate MECs angiogenesis via upregulating VEGF. Our results indicate that GITI may serve as a promising target for accelerating myelin debris clearance and improving SCI recovery.

Blood flow, capillary transit times, and tissue oxygenation: the centennial of capillary recruitment

The transport of oxygen between blood and tissue is limited by blood's capillary transit time, understood as the time available for diffusion exchange before blood returns to the heart. If all capillaries contribute equally to tissue oxygenation at all times, this physical limitation would render vasodilation and increased blood flow insufficient means to meet increased metabolic demands in the heart, muscle, and other organs. In 1920, Danish physiologist August Krogh was awarded the Nobel Prize in Physiology or Medicine for his mathematical and quantitative, experimental demonstration of a solution to this conceptual problem: capillary recruitment, the active opening of previously closed capillaries to meet metabolic demands. Today, capillary recruitment is still mentioned in textbooks. When we suspect symptoms might represent hypoxia of a vascular origin, however, we search for relevant, flow-limiting conditions in our patients and rarely ascribe hypoxia or hypoxemia to short capillary transit times. This review describes how natural changes in capillary transit-time heterogeneity (CTH) and capillary hematocrit (HCT) across open capillaries during blood flow increases can account for a match of oxygen availability to metabolic demands in normal tissue. CTH and HCT depend on a number of factors: on blood properties, including plasma viscosity, the number, size, and deformability of blood cells, and blood cell interactions with capillary endothelium; on anatomical factors including glycocalyx, endothelial cells, basement membrane, and pericytes that affect the capillary diameter; and on any external compression. The review describes how risk factor- and disease-related changes in CTH and HCT interfere with flow-metabolism coupling and tissue oxygenation and discusses whether such capillary dysfunction contributes to vascular disease pathology.

Maternal Dietary Intake of Omega-3 Fatty Acids Correlates Positively with Regional Brain Volumes in 1-Month-Old Term Infants

Maternal nutrition is an important factor for infant neurodevelopment. However, prior magnetic resonance imaging (MRI) studies on maternal nutrients and infant brain have focused mostly on preterm infants or on few specific nutrients and few specific brain regions. We present a first study in term-born infants, comprehensively correlating 73 maternal nutrients with infant brain morphometry at the regional (61 regions) and voxel (over 300 000 voxel) levels. Both maternal nutrition intake diaries and infant MRI were collected at 1 month of life (0.9 ± 0.5 months) for 92 term-born infants (among them, 54 infants were purely breastfed and 19 were breastfed most of the time). Intake of nutrients was assessed via standardized food frequency questionnaire. No nutrient was significantly correlated with any of the volumes of the 61 autosegmented brain regions. However, increased volumes within subregions of the frontal cortex and corpus callosum at the voxel level were positively correlated with maternal intake of omega-3 fatty acids, retinol (vitamin A) and vitamin B12, both with and without correction for postmenstrual age and sex (P < 0.05, q < 0.05 after false discovery rate correction). Omega-3 fatty acids remained significantly correlated with infant brain volumes after subsetting to the 54 infants who were exclusively breastfed, but retinol and vitamin B12 did not. This provides an impetus for future larger studies to better characterize the effect size of dietary variation and correlation with neurodevelopmental outcomes, which can lead to improved nutritional guidance during pregnancy and lactation.

X-linked adrenoleukodystrophy: Pathology, pathophysiology, diagnostic testing, newborn screening and therapies

Adrenoleukodystrophy (ALD) is a rare X‐linked disease caused by a mutation of the peroxisomal ABCD1 gene. This review summarizes our current understanding of the pathogenic cell‐ and tissue‐specific roles of lipid species in the context of experimental therapeutic strategies and provides an overview of critical historical developments, therapeutic trials and the advent of newborn screening in the USA. In ALD, very long‐chain fatty acid (VLCFA) chain length‐dependent dysregulation of endoplasmic reticulum stress and mitochondrial radical generating systems inducing cell death pathways has been shown, providing the rationale for therapeutic moiety‐specific VLCFA reduction and antioxidant strategies. The continuing increase in newborn screening programs and promising results from ongoing and recent therapeutic investigations provide hope for ALD.

Bioinformatic Profiling Identifies a Fatty Acid Metabolism-Related Gene Risk Signature for Malignancy, Prognosis, and Immune Phenotype of Glioma

Cancer cells commonly have metabolic abnormalities. Aside from altered glucose and amino acid metabolism, cancers cells often share the attribute of fatty acid metabolic alterations. However, fatty acid metabolism related-gene set has not been systematically investigated in gliomas. Here, we provide a bioinformatic profiling of the fatty acid catabolic metabolism-related gene risk signature for the malignancy, prognosis and immune phenotype of glioma. In this study, a cohort of 325 patients with whole genome RNA-seq expression data from the Chinese Glioma Genome Atlas (CGGA) dataset was used as training set, while another cohort of 667 patients from The Cancer Genome Atlas (TCGA) dataset was used as validating set. After confirmed that fatty acid catabolic metabolism-related gene set could distinguish clinicopathological features of gliomas, we used LASSO regression analysis to develop a fatty-acid metabolism-related gene risk signature for glioma. This 8-gene risk signature was found to be a good predictor of clinical and molecular features involved in the malignancy of gliomas. We also identified that this 8-gene risk signature had high prognostic values in patients with gliomas. Correlation analysis showed that our risk signature was closely associated with the immune cells involved in the microenvironment of glioma. Furthermore, the fatty acid catabolic metabolism-related gene risk signature was also found to be significantly correlated with immune checkpoint members B7-H3 and Tim-3. In summary, we have identified a fatty acid metabolism-related gene risk signature for malignancy, prognosis, and immune phenotype of glioma; and our study might contribute to better understanding of metabolic pathways and further developing of novel therapeutic approaches for gliomas.

The Landscape of Hematopoietic Stem Cell Transplant and Gene Therapy for X-Linked Adrenoleukodystrophy

PURPOSE OF REVIEW

To present an updated appraisal of hematopoietic stem cell transplant (HSCT) and gene therapy for X-linked adrenoleukodystrophy (ALD) in the setting of a novel, presymptomatic approach to disease.

RECENT FINDINGS

Outcomes in HSCT for ALD have been optimized over time due to early patient detection, improved myeloablative conditioning regimens, and adjunctive treatment for patients with advanced cerebral disease. Gene therapy has arrested disease progression in a cohort of boys with childhood cerebral ALD. New therapeutic strategies have provided the clinical basis for the implementation of Newborn Screening (NBS). With the help of advocacy groups, NBS has been implemented, allowing for MRI screening for the onset of cerebral ALD from birth. Gene therapy and optimized hematopoietic stem cell transplant for childhood CALD have changed the natural history of this previously devastating neurological disease.

X-linked Adrenoleukodystrophy: Pathology, Pathophysiology, Diagnostic Testing, Newborn Screening, and Therapies

Adrenoleukodystrophy (ALD) is a rare X-linked disease caused by a mutation of the peroxisomal ABCD1 gene. This review summarizes our current understanding of the pathogenic cell- and tissue-specific role of lipid species in the context of experimental therapeutic strategies and provides an overview of critical historical developments, therapeutic trials, and the advent of newborn screening in the United States. In ALD, very long chain fatty acid (VLCFA) chain-length-dependent dysregulation of endoplasmic reticulum stress and mitochondrial radical generating systems inducing cell death pathways has been shown, providing the rationale for therapeutic moiety-specific VLCFA reduction and antioxidant strategies. The continuing increase in newborn screening programs and promising results from ongoing and recent therapeutic investigations provide hope for ALD.

Oxygenation differs among white matter hyperintensities, intersected fiber tracts and unaffected white matter

White matter hyperintensities of presumed vascular origin are frequently observed on magnetic resonance imaging in normal aging. They are typically found in cerebral small vessel disease and suspected culprits in the etiology of complex age- and small vessel disease-related conditions, such as late-onset depression. White matter hyperintensities may interfere with surrounding white matter metabolic demands by disrupting fiber tract integrity. Meanwhile, risk factors for small vessel disease are thought to reduce tissue oxygenation, not only by reducing regional blood supply, but also by impairing capillary function. To address white matter oxygen supply–demand balance, we estimated voxel-wise capillary density as an index of resting white matter metabolism, and combined estimates of blood supply and capillary function to calculate white matter oxygen availability. We conducted a cross-sectional study with structural, perfusion- and diffusion-weighted magnetic resonance imaging in 21 patients with late-onset depression and 21 controls. We outlined white matter hyperintensities and used tractography to identify the tracts they intersect. Perfusion data comprised cerebral blood flow, blood volume, mean transit time and relative transit time heterogeneity—the latter a marker of capillary dysfunction. Based on these, white matter oxygenation was calculated as the steady state cerebral metabolic rate of oxygen under the assumption of normal tissue oxygen tension and vice versa. The number, volume and perfusion characteristics of white matter hyperintensities did not differ significantly between groups. Hemodynamic data showed white matter hyperintensities to have lower blood flow and blood volume, but higher relative transit time heterogeneity, than normal-appearing white matter, resulting in either reduced capillary metabolic rate of oxygen or oxygen tension. Intersected tracts showed significantly lower blood flow, blood volume and capillary metabolic rate of oxygen than normal-appearing white matter. Across groups, lower lesion oxygen tension was associated with higher lesion number and volume. Compared with normal-appearing white matter, tissue oxygenation is significantly reduced in white matter hyperintensities as well as the fiber tracts they intersect, independent of parallel late-onset depression. In white matter hyperintensities, reduced microvascular blood volume and concomitant capillary dysfunction indicate a severe oxygen supply–demand imbalance with hypoxic tissue injury. In intersected fiber tracts, parallel reductions in oxygenation and microvascular blood volume are consistent with adaptations to reduced metabolic demands. We speculate, that aging and vascular risk factors impair white matter hyperintensity perfusion and capillary function to create hypoxic tissue injury, which in turn affect the function and metabolic demands of the white matter tracts they disrupt.

ABC Transporters in Neurological Disorders: An Important Gateway for Botanical Compounds Mediated Neuro-Therapeutics

Neurodegeneration is a distinguishing feature of many age related disorders and other vector borne neuroinflammatory diseases. There are a number of factors that can modulate the pathology of these disorders. ATP-binding cassette (ABC) transporters are primarily involved in the maintenance of normal brain homeostasis by eliminating toxic peptides and compounds from the brain. Also, ABC transporters protect the brain from the unwanted effects of endogenous and exogenous toxins that can enter the brain parenchyma. Therefore, these transporters have the ability to determine the pathological outcomes of several neurological disorders. For instance, ABC transporters like P-glycoprotein (ABCB1), and BCRP (ABCG2) have been reported to facilitate the clearance of peptides such as amyloid-β (Aβ) that accumulate in the brain during Alzheimer's disease (AD) progression. Other members such as ABCA1, ABCA2, ABCC8, ABCC9, ABCG1 and ABCG4 also have been reported to be involved in the progression of various brain disorders such as HIV-associated dementia, Multiple sclerosis (MS), Ischemic stroke, Japanese encephalitis (JE) and Epilepsy. However, these defective transporters can be targeted by numerous botanical compounds such as Verapamil, Berberine and Fascalpsyn as a therapeutic target to treat these neurological outcomes. These compounds are already reported to modulate ABC transporter activity in the CNS. Nonetheless, the exact mechanisms involving the ABC transporters role in normal brain functioning, their role in neuronal dysfunction and how these botanical compounds ensure and facilitate their therapeutic action in association with defective transporters still remain elusive. This review therefore, summarizes the role of ABC transporters in neurological disorders, with a special emphasis on its role in AD brains. The prospect of using botanical/natural compounds as modulators of ABC transporters in neurological disorders is discussed in the latter half of the article.

The Natural History of Adrenal Insufficiency in X-Linked Adrenoleukodystrophy: An International Collaboration

CONTEXT

Primary adrenal insufficiency is an important clinical manifestation of X-linked adrenoleukodystrophy (ALD). Other manifestations include spinal cord disease and/or inflammatory demyelinating cerebral disease. Implementation of newborn screening requires natural history data to develop follow-up recommendations.

OBJECTIVE

To delineate the natural history of adrenal insufficiency in male patients with ALD and to assess associations between the risk for developing adrenal insufficiency, spinal cord disease, or cerebral disease and plasma C26:0/C22:0 and C24:0/C22:0 ratios, which are diagnostic biomarkers for ALD.

DESIGN

Retrospective review of medical records.

SETTING

Two international tertiary referral centers of expertise for ALD.

PATIENTS

Male patients with ALD followed at the centers between 2002 and 2016.

MAIN OUTCOME MEASURES

The primary endpoint was adrenal insufficiency; secondary endpoints were spinal cord and cerebral disease.

RESULTS

Data on 159 male patients was available. The probability of developing adrenal insufficiency was described with survival analysis. Median time until adrenal insufficiency was 14 years (95% CI, 9.70 to 18.30 years). The cumulative proportion of patients who developed adrenal insufficiency was age-dependent and highest in early childhood [0 to 10 years, 46.8% (SEM 0.041%); 11 to 40 years, 28.6% (SEM, 0.037%); >40 years, 5.6% (SEM, 0.038%)]. No association between clinical manifestations and plasma ratios was detected with Cox model or Spearman correlation.

CONCLUSIONS

Lifetime prevalence of adrenal insufficiency in male patients with ALD is ~80%. Adrenal insufficiency risk is time-dependent and warrants age-dependent follow-up. Besides on-demand testing if symptoms manifest, we suggest a minimum of adrenal testing every 4 to 6 months for patients age ≤10 years, annual testing for those age 11 to 40 years, and solely on-demand testing for those age >40 years.