bims-medebr 2022-05-08 papers

bims-medebr

Biomed News

on Metabolism of the developing brain

Issue of 2022‒05‒08
twenty-two papers selected by
Regina F. Fernández
Johns Hopkins University

Oxysterols and Oxysterol Sulfates in Alzheimer's Disease Brain and Cerebrospinal Fluid.
Altered Cholesterol Homeostasis in Huntington's Disease.
Proteomics datasets of developing rat brain: Synaptic proteome and SUMO2/3-ylome.
Metabolism Connects Body, Brain, and Behavior.
The sex-specific role of sensory neuron LKB1 on metabolic stress-induced mechanical hypersensitivity and mitochondrial respiration.
Astrocytic BDNF signaling within the ventromedial hypothalamus regulates energy homeostasis.
Brain Endothelial Cells Utilize Glycolysis for the Maintenance of the Transcellular Permeability.
Polyunsaturated fatty acids and fatty acid-derived lipid mediators: Recent advances in the understanding of their biosynthesis, structures, and functions.
Pantothenate kinase 2 interacts with PINK1 to regulate mitochondrial quality control via acetyl-CoA metabolism.
The role of mitochondrial dysfunction in Alzheimer's disease pathogenesis.
First insights into the honey bee (Apis mellifera) brain lipidome and its neonicotinoid-induced alterations associated with reduced self-grooming behavior.
A ketogenic intervention improves dorsal attention network functional and structural connectivity in mild cognitive impairment.
Contributive Role of Hyperglycemia and Hypoglycemia Towards the Development of Alzheimer's Disease.
The LPA-CDK5-tau pathway mediates neuronal injury in an in vitro model of ischemia-reperfusion insult.
Cholesterol determines the cytosolic entry and seeded aggregation of tau.
Extracellular Flux Analysis of Mitochondrial Function in Pluripotent Stem Cells.
Therapeutic potential of deuterium-stabilized (R)-pioglitazone - PXL065 - for X-linked adrenoleukodystrophy.
Regulation of Blood-Brain Barrier Transporters by Transforming Growth Factor-β /Activin Receptor-Like Kinase 1 (TGF-β /ALK1) Signaling: Relevance to the Brain Disposition of 3-Hydroxy-3-Methylglutaryl Coenzyme A (HMG-CoA) Reductase Inhibitors (i.e., Statins).
Fasting or the short-term consumption of a ketogenic diet protects against antipsychotic-induced hyperglycemia in mice.
Peroxisome proliferator-activated receptor-γ ameliorates neuronal ferroptosis after traumatic brain injury in mice by inhibiting cyclooxygenase-2.
Functions of Stress-Induced Lipid Droplets in the Nervous System.
Head circumference in glucose transporter 1 deficiency syndrome: Normal for individuals, abnormal as a group.

J Alzheimers Dis. 2022 Apr 27.

Oxysterols and Oxysterol Sulfates in Alzheimer's Disease Brain and Cerebrospinal Fluid.

Irundika H K Dias, Hala Shokr, Freya Shephard, Lisa Chakrabarti.

  BACKGROUND: Brain cholesterol levels are tightly regulated but increasing evidence indicates that cholesterol metabolism may drive Alzheimer's disease (AD)-associated pathological changes. Recent advances in understanding of mitochondrial dysfunction in AD brain have presented a vital role played by mitochondria in oxysterol biosynthesis and their involvement in pathophysiology. Oxysterol accumulation in brain is controlled by various enzymatic pathways including sulfation. While research into oxysterol is under the areas of active investigation, there is less evidence for oxysterol sulfates levels in human brain.OBJECTIVE: This study investigates the hypothesis that AD brain oxysterols detoxification via sulfation is impaired in later stages of disease resulting in oxysterol accumulation.
METHODS: Lipids were extracted from postmortem frozen brain tissue and cerebrospinal (CSF) from late- (Braak stage III-IV) and early- (Braak stage I-II) stage AD patients. Samples were spiked with internal standards prior to lipid extraction. Oxysterols were enriched with a two-step solid phase extraction using a polymeric SPE column and further separation was achieved by LC-MS/MS.
RESULTS: Oxysterols, 26-hydroxycholesterol (26-OHC), 25-hydroxycholesterol (25-OHC), and 7-oxycholesterol levels were higher in brain tissue and mitochondria extracted from late-stage AD brain tissue except for 24S-hydroxycholesterol, which was decreased in late AD. However, oxysterol sulfates are significantly lower in the AD frontal cortex. Oxysterols, 25-OHC, and 7-oxocholesterol was higher is CSF but 26-OHC and oxysterol sulfate levels were not changed.
CONCLUSION: Our results show oxysterol metabolism is altered in AD brain mitochondria, favoring synthesis of 26-OHC, 25-OHC, and 7-oxocholesterol, and this may influence brain mitochondrial function and acceleration of the disease.

Keywords:  Alzheimer’s disease; brain; cholesterol; mitochondria; oxidative stress; oxysterols

DOI:  https://doi.org/10.3233/JAD-220083
Front Aging Neurosci. 2022 ;14 797220

Altered Cholesterol Homeostasis in Huntington's Disease.

Radhia Kacher, Coline Mounier, Jocelyne Caboche, Sandrine Betuing.

  Huntington's disease (HD) is an autosomal dominant genetic disorder caused by an expansion of the CAG repeat in the first exon of Huntingtin's gene. The associated neurodegeneration mainly affects the striatum and the cortex at early stages and progressively spreads to other brain structures. Targeting HD at its earlier stages is under intense investigation. Numerous drugs were tested, with a rate of success of only 3.5% approved molecules used as symptomatic treatment. The restoration of cholesterol metabolism, which is central to the brain homeostasis and strongly altered in HD, could be an interesting disease-modifying strategy. Cholesterol is an essential membrane component in the central nervous system (CNS); alterations of its homeostasis have deleterious consequences on neuronal functions. The levels of several sterols, upstream of cholesterol, are markedly decreased within the striatum of HD mouse model. Transcription of cholesterol biosynthetic genes is reduced in HD cell and mouse models as well as post-mortem striatal and cortical tissues from HD patients. Since the dynamic of brain cholesterol metabolism is complex, it is essential to establish the best method to target it in HD. Cholesterol, which does not cross the blood-brain-barrier, is locally synthesized and renewed within the brain. All cell types in the CNS synthesize cholesterol during development but as they progress through adulthood, neurons down-regulate their cholesterol synthesis and turn to astrocytes for their full supply. Cellular levels of cholesterol reflect the dynamic balance between synthesis, uptake and export, all integrated into the context of the cross talk between neurons and glial cells. In this review, we describe the latest advances regarding the role of cholesterol deregulation in neuronal functions and how this could be a determinant factor in neuronal degeneration and HD progression. The pathways and major mechanisms by which cholesterol and sterols are regulated in the CNS will be described. From this overview, we discuss the main clinical strategies for manipulating cholesterol metabolism in the CNS, and how to reinstate a proper balance in HD.

Keywords:  CYP46A1; astrocytes; cholesterol; cholesterol 24-hydroxylase; neurons; therapy

DOI:  https://doi.org/10.3389/fnagi.2022.797220
Data Brief. 2022 Jun;42 108151

Proteomics datasets of developing rat brain: Synaptic proteome and SUMO2/3-ylome.

Félicie Kieffer, Marie Pronot, Anne-Sophie Gay, Delphine Debayle, Carole Gwizdek.

  During brain development, synapses undergo structural rearrangements and functional changes mediated by many molecular processes including post-translational modifications by the Small Ubiquitin-like MOdifier (SUMO). To get an overview of the endogenous SUMO-modified proteins in the developing rat brain synapses, our first aim was to characterize the synaptic proteome from rat at 14 postnatal days (PND14), a period that combines intense synaptogenesis, neurotransmission and high levels of SUMO2/3-ylation. In this purpose, we isolated the synaptosomal fraction by differential centrifugation on sucrose percoll gradient and characterized the synaptosomal proteome by nanoLC-MS/MS. Our second aim was to provide a comprehensive list of the SUMO2/3-modified protein in this compartment. We thus performed an enrichment in SUMO2/3-ylated proteins from the synaptosomal fraction by denaturing immunoprecipitation using specific anti-SUMO2/3 antibodies prior to proteomics analysis. The information presented in this article complement the publication "Proteomic Identification of an Endogenous Synaptic SUMOylome in the Developing Rat Brain" [1], by focusing on the characterization of the synaptic proteome of PND14 rat brain. Altogether, these data can inform future experiments focused on studying the functional consequences of synaptic SUMOylation regarding synapses structure and function. In addition, they can provide the basis for future mechanistic studies investigating brain pathologies involving altered SUMOylation levels.

Keywords:  Brain development; SUMOylome; Subcellular fractionation; Synapses

DOI:  https://doi.org/10.1016/j.dib.2022.108151
Biol Psychiatry. 2022 May 15. pii: S0006-3223(22)01134-9. [Epub ahead of print]91(10): 854-855

Metabolism Connects Body, Brain, and Behavior.

Tamas L Horvath.

DOI: https://doi.org/10.1016/j.biopsych.2022.03.015
Am J Physiol Regul Integr Comp Physiol. 2022 May 03.

The sex-specific role of sensory neuron LKB1 on metabolic stress-induced mechanical hypersensitivity and mitochondrial respiration.

Katherine Marie Garner, Michael D Burton.

  Pain disorders induce metabolic stress in peripheral sensory neurons by reducing mitochondrial output, shifting cellular metabolism, and altering energy use. These processes implicate neuronal metabolism as an avenue for creating novel therapeutics. Liver kinase B1 (LKB1) mediates the cellular response to metabolic stress by inducing the AMPK pathway. The LKB1-AMPK pathway increases energy producing processes, including mitochondrial output. These processes inhibit pain by directly or indirectly restoring energetic balance within a cell. Although the LKB1-AMPK pathway has been linked to pain relief, it is not yet known which cell is responsible for this property, as well any direct ties to cellular metabolism. To elucidate this, we developed a genetic mouse model where LKB1 is selectively removed from Nav1.8-pain sensory neurons and metabolically stressed them by fasting for 24 hours. We found females, but not males, had neuron-specific, LKB1-dependent restoration of metabolic stress-induced mitochondrial metabolism. This was reflected in mechanical hypersensitivity, where the absence of LKB1 led to hypersensitivity in female, but not male, animals. This discrepancy suggests a sex- and cell-specific contribution to LKB1-depdendent fasting-induced mechanical hypersensitivity. While our data represent a potential role for LKB1 in anti-pain pathways in a metabolic-specific manner, more must be done to investigate these sex differences.

Keywords:  LKB1; cell metabolism; fasting; mechanical hypersensitivity; sensory neuron

DOI:  https://doi.org/10.1152/ajpregu.00279.2021
Nat Metab. 2022 May 02.

Astrocytic BDNF signaling within the ventromedial hypothalamus regulates energy homeostasis.

Dominique Ameroso, Alice Meng, Stella Chen, Jennifer Felsted, Chris G Dulla, Maribel Rios.

Brain-derived neurotrophic factor (BDNF) is essential for maintaining energy and glucose balance within the central nervous system. Because the study of its metabolic actions has been limited to effects in neuronal cells, its role in other cell types within the brain remains poorly understood. Here we show that astrocytic BDNF signaling within the ventromedial hypothalamus (VMH) modulates neuronal activity in response to changes in energy status. This occurs via the truncated TrkB.T1 receptor. Accordingly, either fasting or central BDNF depletion enhances astrocytic synaptic glutamate clearance, thereby decreasing neuronal activity in mice. Notably, selective depletion of TrkB.T1 in VMH astrocytes blunts the effects of energy status on excitatory transmission, as well as on responses to leptin, glucose and lipids. These effects are driven by increased astrocytic invasion of excitatory synapses, enhanced glutamate reuptake and decreased neuronal activity. We thus identify BDNF/TrkB.T1 signaling in VMH astrocytes as an essential mechanism that participates in energy and glucose homeostasis.

DOI: https://doi.org/10.1038/s42255-022-00566-0
Mol Neurobiol. 2022 May 05.

Brain Endothelial Cells Utilize Glycolysis for the Maintenance of the Transcellular Permeability.

Eun Seon Kim, Kyu-Sung Kim, Chan Hee Lee, Min-Tae Jeon, Sung Bae Lee, Jong Hwa Lee, Do-Geun Kim.

  Among the components of the blood-brain barrier (BBB), endothelial cells (ECs) play an important role in supplying limited materials, especially glucose, to the brain. However, the mechanism by which glucose is metabolized in brain ECs is still elusive. To address this topic, we assessed the metabolic signature of glucose utilization using live-cell metabolic assays and liquid chromatography-tandem mass spectrometry metabolomic analysis. We found that brain ECs are highly dependent on aerobic glycolysis, generating lactate as its final product with minimal consumption of glucose. Glucose treatment decreased the oxygen consumption rate in a dose-dependent manner, indicating the Crabtree effect. Moreover, when glycolysis was inhibited, brain ECs showed impaired permeability to molecules utilizing transcellular pathway. In addition, we found that the blockade of glycolysis in mouse brain with 2-deoxyglucose administration resulted in decreased transcellular permeability of the BBB. In conclusion, utilizing glycolysis in brain ECs has critical roles in the maintenance and permeability of the BBB. Overall, we could conclude that brain ECs are highly glycolytic, and their energy can be used to maintain the transcellular permeability of the BBB.

Keywords:  BBB; Endothelial cells; Energy metabolism; Glucose; Transcytosis

DOI:  https://doi.org/10.1007/s12035-022-02778-7
Prog Lipid Res. 2022 May 01. pii: S0163-7827(22)00020-0. [Epub ahead of print] 101165

Polyunsaturated fatty acids and fatty acid-derived lipid mediators: Recent advances in the understanding of their biosynthesis, structures, and functions.

Simon C Dyall, Laurence Balas, Nicolas G Bazan, J Thomas Brenna, Nan Chiang, Felipe da Costa Souza, Jesmond Dalli, Thierry Durand, Jean-Marie Galano, Pamela J Lein, Charles N Serhan, Ameer Y Taha.

  Polyunsaturated fatty acids (PUFAs) are structural components of membrane phospholipids, and influence cellular function via effects on membrane properties, and also by acting as a precursor pool for lipid mediators. These lipid mediators are formed via activation of pathways involving at least one step of dioxygen-dependent oxidation, and are consequently called oxylipins. Their biosynthesis can be either enzymatically-dependent, utilising the promiscuous cyclooxygenase, lipoxygenase, or cytochrome P450 mixed function oxidase pathways, or nonenzymatic via free radical-catalyzed pathways. The oxylipins include the classical eicosanoids, comprising prostaglandins, thromboxanes, and leukotrienes, and also more recently identified lipid mediators. With the advent of new technologies there is growing interest in identifying these different lipid mediators and characterising their roles in health and disease. This review brings together contributions from some of those at the forefront of research into lipid mediators, who provide brief introductions and summaries of current understanding of the structure and functions of the main classes of nonclassical oxylipins. The topics covered include omega-3 and omega-6 PUFA biosynthesis pathways, focusing on the roles of the different fatty acid desaturase enzymes, oxidized linoleic acid metabolites, omega-3 PUFA-derived specialized pro-resolving mediators, elovanoids, nonenzymatically oxidized PUFAs, and fatty acid esters of hydroxy fatty acids.

Keywords:  Elovanoids; FAHFA; Fatty acid destaturase; Lipid mediators; Maresins; Omega-3 PUFA; Oxylipins; Protectins; Resolvins; SPM

DOI:  https://doi.org/10.1016/j.plipres.2022.101165
Nat Commun. 2022 May 03. 13(1): 2412

Pantothenate kinase 2 interacts with PINK1 to regulate mitochondrial quality control via acetyl-CoA metabolism.

Yunpeng Huang, Zhihui Wan, Yinglu Tang, Junxuan Xu, Bretton Laboret, Sree Nallamothu, Chenyu Yang, Boxiang Liu, Rongze Olivia Lu, Bingwei Lu, Juan Feng, Jing Cao, Susan Hayflick, Zhihao Wu, Bing Zhou.

Human neurodegenerative disorders often exhibit similar pathologies, suggesting a shared aetiology. Key pathological features of Parkinson's disease (PD) are also observed in other neurodegenerative diseases. Pantothenate Kinase-Associated Neurodegeneration (PKAN) is caused by mutations in the human PANK2 gene, which catalyzes the initial step of de novo CoA synthesis. Here, we show that fumble (fbl), the human PANK2 homolog in Drosophila, interacts with PINK1 genetically. fbl and PINK1 mutants display similar mitochondrial abnormalities, and overexpression of mitochondrial Fbl rescues PINK1 loss-of-function (LOF) defects. Dietary vitamin B5 derivatives effectively rescue CoA/acetyl-CoA levels and mitochondrial function, reversing the PINK1 deficiency phenotype. Mechanistically, Fbl regulates Ref(2)P (p62/SQSTM1 homolog) by acetylation to promote mitophagy, whereas PINK1 regulates fbl translation by anchoring mRNA molecules to the outer mitochondrial membrane. In conclusion, Fbl (or PANK2) acts downstream of PINK1, regulating CoA/acetyl-CoA metabolism to promote mitophagy, uncovering a potential therapeutic intervention strategy in PD treatment.

DOI: https://doi.org/10.1038/s41467-022-30178-x
Alzheimers Dement. 2022 May 06.

The role of mitochondrial dysfunction in Alzheimer's disease pathogenesis.

Theophania Ashleigh, Russell H Swerdlow, M Flint Beal.

  To promote new thinking of the pathogenesis of Alzheimer's disease (AD), we examine the central role of mitochondrial dysfunction in AD. Pathologically, AD is characterized by progressive neuronal loss and biochemical abnormalities including mitochondrial dysfunction. Conventional thinking has dictated that AD is driven by amyloid beta pathology, per the Amyloid Cascade Hypothesis. However, the underlying mechanism of how amyloid beta leads to cognitive decline remains unclear. A model correctly identifying the pathogenesis of AD is critical and needed for the development of effective therapeutics. Mitochondrial dysfunction is closely linked to the core pathological feature of AD: neuronal dysfunction. Targeting mitochondria and associated proteins may hold promise for new strategies for the development of disease-modifying therapies. According to the Mitochondrial Cascade Hypothesis, mitochondrial dysfunction drives the pathogenesis of AD, as baseline mitochondrial function and mitochondrial change rates influence the progression of cognitive decline. HIGHLIGHTS: The Amyloid Cascade Model does not readily account for various parameters associated with Alzheimer's disease (AD). A unified model correctly identifying the pathogenesis of AD is greatly needed to inform the development of successful therapeutics. Mitochondria play a key and central role in the maintenance of optimal neuronal and synaptic function, the core pathological feature of AD. Mitochondrial dysfunction may be the primary cause of AD, and is a promising target for new therapeutic strategies.

Keywords:  Alzheimer's disease; bioenergetics; mitochondrial cascade hypothesis; mitochondrial dysfunction; oxidative stress

DOI:  https://doi.org/10.1002/alz.12683
J Adv Res. 2022 03;37 75-89

First insights into the honey bee (Apis mellifera) brain lipidome and its neonicotinoid-induced alterations associated with reduced self-grooming behavior.

Nuria Morfin, Tiffany A Fillier, Thu Huong Pham, Paul H Goodwin, Raymond H Thomas, Ernesto Guzman-Novoa.

  Introduction: Honey bees (Apis mellifera) play key roles in food production performing complex behaviors, like self-grooming to remove parasites. However, the lipids of their central nervous system have not been examined, even though they likely play a crucial role in the performance of cognitive process to perform intricate behaviors. Lipidomics has greatly advanced our understanding of neuropathologies in mammals and could provide the same for honey bees.Objectives: The objectives of this study were to characterize the brain lipidome of adult honey bees and to assess the effect of clothianidin (a neurotoxic insecticide) on the brain lipid composition, gene expression, and performance of self-grooming behavior under controlled conditions (cage experiments).
Methods: After seven days of exposure to oral sublethal doses of clothianidin, the bees were assessed for self-grooming behavior; their brains were dissected to analyze the lipidome using an untargeted lipidomics approach and to perform a high throughput RNAseq analysis.
Results: Compared to all other organisms, healthy bee brain lipidomes contain unusually high levels of alkyl-ether linked (plasmanyl) phospholipids (51.42%) and low levels of plasmalogens (plasmenyl phospholipids; 3.46%). This could make it more susceptible to the effects of toxins in the environment. A positive correlation between CL 18:3/18:1/14:0/22:6, TG 6:0/11:2/18:1, LPE 18:0e and intense self-grooming was found. Sublethal doses of a neonicotinoid altered PC 20:3e/15:0, PC 16:0/18:3, PA 18:0/24:1, and TG 18:1/18:1/18/1 levels, and affected gene expression linked to GPI-anchor biosynthesis pathway and energy metabolism that may be partially responsible for the altered lipid composition.
Conclusion: This study showed that lipidomics can reveal honey bee neuropathologies associated with reduced grooming behavior due to sublethal neonicotinoid exposure. The ease of use, unusual brain lipidome as well as characterized behaviors that are affected by the environment make honey bees a promising model organism for studying the neurolipidome and associations with neurobehavioral disorders.

Keywords:  Brain; Grooming; Honey bees; Lipidome; Neonicotinoids; Social immunity

DOI:  https://doi.org/10.1016/j.jare.2021.08.007
Neurobiol Aging. 2022 Apr 12. pii: S0197-4580(22)00074-4. [Epub ahead of print]115 77-87

A ketogenic intervention improves dorsal attention network functional and structural connectivity in mild cognitive impairment.

Maggie Roy, Manon Edde, Mélanie Fortier, Etienne Croteau, Christian-Alexandre Castellano, Valérie St-Pierre, Camille Vandenberghe, François Rheault, Mahsa Dadar, Simon Duchesne, Christian Bocti, Tamas Fulop, Stephen C Cunnane, Maxime Descoteaux.

  Ketones, the brain's alternative fuel to glucose, bypass the brain glucose deficit and improve cognition in mild cognitive impairment (MCI). Our goal was to assess the impact of a 6-month ketogenic intervention on the functional connectivity within eight major brain resting-state networks, and its possible relationship to improved cognitive outcomes in the BENEFIC trial. MCI participants were randomized to a placebo (n = 15) or ketogenic medium chain triglyceride (kMCT; n = 17) intervention. kMCT was associated with increased functional connectivity within the dorsal attention network (DAN), which correlated to improvement in cognitive tests targeting attention. Ketone uptake (11C-acetoacetate PET) specifically in DAN cortical regions was highly increased in the kMCT group and was directly associated with the improved DAN functional connectivity. Analysis of the structural connectome revealed increased fiber density within the DAN following kMCT. Our findings suggest that ketones in MCI may prove beneficial for cognition at least in part because they improve brain network energy status, functional connectivity and axonal integrity.

Keywords:  Dorsal attention network; Functional connectivity; Ketone; Medium chain triglyceride; Mild cognitive impairment; Structural connectivity

DOI:  https://doi.org/10.1016/j.neurobiolaging.2022.04.005
Mol Neurobiol. 2022 May 03.

Contributive Role of Hyperglycemia and Hypoglycemia Towards the Development of Alzheimer's Disease.

Riya Chakrabarty, Sumaira Yousuf, Mahendra P Singh.

  Alzheimer's disease (AD) is one of the causes of dementia that results from several infections/biological conditions leading to either cell disruption or loss of neuronal communication. Studies have documented the accumulation of two proteins, beta-amyloid (Aβ), which accumulates on the exteriors of neurons, and tau (Tau), which assembles at the interiors of brain cells and is chiefly liable for the progression of the disease. Several molecular and cellular pathways account for the accumulation of amyloid-β and the formation of neurofibrillary tangles, which are phosphorylated variants of Tau protein. Moreover, research has revealed a potential connection between AD and diabetes. It has also been demonstrated that both hypoglycemia and hyperglycemia have a significant role in the development of AD. In addition, SUMO (small ubiquitin-like modifier protein) plays a crucial role in the pathogenesis of AD. SUMOylation is the process by which modification of amyloid precursor protein (APP) and Tau takes place. Furthermore, Drosophila melanogaster has proven to be an efficient model organism in studies to establish the relationship between AD and variations in blood glucose levels. In addition, the review successfully identifies the common pathway that links the effects of fluctuations in glucose levels on AD pathogenesis and advancements.

Keywords:  Alzheimer’s disease; Amyloid Precursor Protein; Hyperglycemia; Hypoglycemia; SUMOylation of APP and Tau protein

DOI:  https://doi.org/10.1007/s12035-022-02846-y
BMC Neurol. 2022 May 02. 22(1): 166

The LPA-CDK5-tau pathway mediates neuronal injury in an in vitro model of ischemia-reperfusion insult.

Yaya Wang, Jie Zhang, Liqin Huang, Yanhong Mo, Changyu Wang, Yiyi Li, Yangyang Zhang, Zhaohui Zhang.

  Lysophosphatidic acid (LPA) is a common glycerol phospholipid and an important extracellular signaling molecule. LPA binds to its receptors and mediates a variety of biological effects, including the pathophysiological process underlying ischemic brain damage and traumatic brain injury. However, the molecular mechanisms mediating the pathological role of LPA are not clear. Here, we found that LPA activates cyclin-dependent kinase 5 (CDK5). CDK5 phosphorylates tau, which leads to neuronal cell death. Inhibition of LPA production or blocking its receptors reduced the abnormal activation of CDK5 and phosphorylation of tau, thus reversing the death of neurons. Our data indicate that the LPA-CDK5-Tau pathway plays an important role in the pathophysiological process after ischemic stroke. Inhibiting the LPA pathway may be a potential therapeutic target for treating ischemic brain injury.

Keywords:  CDK5; Ischemia reperfusion; LPA; Tau

DOI:  https://doi.org/10.1186/s12883-022-02694-2
Cell Rep. 2022 05 03. pii: S2211-1247(22)00540-X. [Epub ahead of print]39(5): 110776

Cholesterol determines the cytosolic entry and seeded aggregation of tau.

Benjamin J Tuck, Lauren V C Miller, Taxiarchis Katsinelos, Annabel E Smith, Emma L Wilson, Sophie Keeling, Shi Cheng, Marina J Vaysburd, Claire Knox, Lucy Tredgett, Emmanouil Metzakopian, Leo C James, William A McEwan.

  Assemblies of tau can transit between neurons, seeding aggregation in a prion-like manner. To accomplish this, tau must cross cell-limiting membranes, a process that is poorly understood. Here, we establish assays for the study of tau entry into the cytosol as a phenomenon distinct from uptake, in real time, and at physiological concentrations. The entry pathway of tau is cell type specific and, in neurons, highly sensitive to cholesterol. Depletion of the cholesterol transporter Niemann-Pick type C1 or extraction of membrane cholesterol renders neurons highly permissive to tau entry and potentiates seeding even at low levels of exogenous tau assemblies. Conversely, cholesterol supplementation reduces entry and almost completely blocks seeded aggregation. Our findings establish entry as a rate-limiting step to seeded aggregation and demonstrate that dysregulated cholesterol, a feature of several neurodegenerative diseases, potentiates tau aggregation by promoting entry of tau assemblies into the cell interior.

Keywords:  Alzheimer’s disease; CP: Metabolism; CP: Neuroscience; Niemann-Pick disease; cholesterol; endocytosis; neurodegeneration; seeded aggregation; tau

DOI:  https://doi.org/10.1016/j.celrep.2022.110776
Methods Mol Biol. 2022 ;2429 85-102

Extracellular Flux Analysis of Mitochondrial Function in Pluripotent Stem Cells.

Enkhtuul Tsogtbaatar, Katherine Minter-Dykhouse, Alicia Saarinen, Clifford D L Folmes.

  Mitochondrial function and energy metabolism are increasingly recognized not only as regulators of pluripotent stem cell function and fate, but also as critical targets in disease pathogenesis and aging. Therefore across the downstream applications of pluripotent stem cells, including development and disease modeling, drug screening, and cell-based therapies, it is crucial to be able to measure mitochondrial function and metabolism in a high-throughput, real-time and label-free manner. Here we describe the application of Seahorse extracellular flux analysis to measure mitochondrial function in pluripotent stem cells and their derivatives. Specifically, we highlight two assays, the Mitochondrial Stress Test, which quantifies overall mitochondrial function including basal, maximal and ATP-couple oxygen consumption rates, and the Electron Transport Chain Complex Specific assay, that quantifies function of individual complexes within the electron transport chain.

Keywords:  Differentiation; Embryonic stem cells; Induced pluripotent stem cells; Mitochondrial respiration; Oxidative metabolism; Oxidative phosphorylation

DOI:  https://doi.org/10.1007/978-1-0716-1979-7_7
J Inherit Metab Dis. 2022 May 05.

Therapeutic potential of deuterium-stabilized (R)-pioglitazone - PXL065 - for X-linked adrenoleukodystrophy.

Pierre-Axel Monternier, Jaspreet Singh, Parveen Parasar, Pierre Theurey, Sheila DeWitt, Vincent Jacques, Eric Klett, Navtej Kaur, Tavarekere N Nagaraja, David E Moller, Sophie Hallakou-Bozec.

X-linked adrenoleukodystrophy (ALD) results from ABCD1 gene mutations which impair Very Long Chain Fatty Acids (VLCFA; C26:0 and C24:0) peroxisomal import and β-oxidation, leading to accumulation in plasma and tissues. Excess VLCFA drives impaired cellular functions (e.g. disrupted mitochondrial function), inflammation, and neurodegeneration. Major disease phenotypes include: adrenomyeloneuropathy (AMN), progressive spinal cord axonal degeneration, and cerebral ALD (C-ALD), inflammatory white matter demyelination and degeneration. No pharmacological treatment is available to-date for ALD. Pioglitazone, an anti-diabetic thiazolidinedione, exerts potential benefits in ALD models. Its mechanisms are genomic (PPARγ agonism) and non-genomic (mitochondrial pyruvate carrier - MPC, long chain acyl-CoA synthetase 4 - ACSL4, inhibition). However, its use is limited by PPARγ driven side effects (e.g. weight gain, edema). PXL065 is a clinical-stage deuterium-stabilized (R)-enantiomer of pioglitazone which lacks PPARγ agonism but retains MPC activity. Here, we show that incubation of ALD patient-derived cells (both AMN and C-ALD) and glial cells from Abcd1-null mice with PXL065 resulted in: normalization of elevated VLCFA, improved mitochondrial function, and attenuated indices of inflammation. Compensatory peroxisomal transporter gene expression was also induced. Additionally, chronic treatment of Abcd1-null mice lowered VLCFA in plasma, brain and spinal cord and improved both neural histology (sciatic nerve) and neurobehavioral test performance. Several in vivo effects of PXL065 exceeded those achieved with pioglitazone. PXL065 was confirmed to lack PPARγ agonism but retained ACSL4 activity of pioglitazone. PXL065 has novel actions and mechanisms and exhibits a range of potential benefits in ALD models; further testing of this molecule in ALD patients is warranted. This article is protected by copyright. All rights reserved.

DOI: https://doi.org/10.1002/jimd.12510
Drug Metab Dispos. 2022 May 03. pii: DMD-AR-2021-000781. [Epub ahead of print]

Regulation of Blood-Brain Barrier Transporters by Transforming Growth Factor-β /Activin Receptor-Like Kinase 1 (TGF-β /ALK1) Signaling: Relevance to the Brain Disposition of 3-Hydroxy-3-Methylglutaryl Coenzyme A (HMG-CoA) Reductase Inhibitors (i.e., Statins).

Robert D Betterton, Wazir Abdullahi, Erica I Williams, Jeffrey L Lochhead, Hrvoje Brzica, Joshua A Stanton, Elizabeth Reddell, Chidinma Ogbonnaya, Thomas P Davis, Patrick T Ronaldson.

  Our laboratory has shown that activation of transforming growth factor-b (TGF-b)/Activin receptor-like kinase 1 (ALK1) signaling can increase protein expression and transport activity of organic anion transporting polypeptide 1a4 (Oatp1a4) at the blood-brain barrier (BBB). These results are relevant to treatment of ischemic stroke because Oatp transport substrates such as 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors (i.e., statins) improve functional neurological outcomes in patients. Advancement of our work requires determination if TGF-b/ALK1 signaling alters Oatp1a4 functional expression differently across brain regions and if such disparities affect CNS statin disposition. Therefore, we studied regulation of Oatp1a4 by the TGF-b/ALK1 pathway, in vivo, in rat brain microvessels isolated from cerebral cortex, hippocampus, and cerebellum using the ALK1 agonist bone morphogenetic protein 9 (BMP-9) and the ALK1 inhibitor LDN193189. We showed that Oatp1a4 protein expression and brain distribution of three currently marketed statin drugs (i.e., atorvastatin, pravastatin, rosuvastatin) were increased in cortex relative to hippocampus and cerebellum. Additionally, BMP-9 treatment enhanced Oatp-mediated statin transport in cortical tissue but not in hippocampus or cerebellum. While brain drug delivery is also dependent upon efflux transporters such as P-glycoprotein (P-gp) and/or Breast Cancer Resistance Protein (Bcrp), our data showed that administration of BMP-9 did not alter the relative contribution of these transporters to CNS disposition of statins. Overall, this study provides evidence for differential regulation of Oatp1a4 by TGF-b/ALK1 signaling across brain regions, knowledge that is critical for development of therapeutic strategies to target Oatps at the BBB for CNS drug delivery. Significance Statement Organic anion transporting polypeptides (Oatps) represent transporter targets for CNS delivery of drugs. We have shown that brain statin uptake via Oatp1a4 is higher in cortex versus hippocampus and cerebellum. Additionally, we have shown that the TGF-b/ALK1 agonist BMP-9 increases Oatp1a4 functional expression, but not that of efflux transporters P-gp and Bcrp, in brain microvessels isolated from cortical tissue. Our in vivo approach provides critical data that will advance therapeutic strategies for neurological diseases where drug development has been challenging.

Keywords:  HMG-CoA reductase inhibitors; Organic anion uptake / efflux (OATs, OATPs); blood-brain barrier; drug delivery; efflux transporters (P-gp, BCRP, MRP, MATE, BSEP, etc); transforming growth factor (TGF); vascular permeability

DOI:  https://doi.org/10.1124/dmd.121.000781
J Physiol. 2022 May 04.

Fasting or the short-term consumption of a ketogenic diet protects against antipsychotic-induced hyperglycemia in mice.

Hesham Shamshoum, Kyle D Medak, Greg L McKie, Margaret K Hahn, David C Wright.

  KEY POINTS: Antipsychotic medications cause rapid and robust increases in blood glucose Cotreatment approaches to offset these harmful metabolic side effects have not been identified We demonstrate that fasting or the consumption or a short-term ketogenic diet, but not treatment with βHB or oral ketone esters, protects against acute antipsychotic induced hyperglycemia Protective effects of fasting and ketogenic diets were paralleled by reductions in serum glucagon, but not improvements in whole body insulin action ABSTRACT: Antipsychotic (AP) medications, such as olanzapine (OLZ), are used in the treatment of schizophrenia and a growing number of "off-label" conditions. A single dose of OLZ causes robust increases in blood glucose within minutes following treatment. The purpose of the current study was to investigate if interventions which increase circulating ketone bodies (fasting, βHB, ketone esters or a ketogenic diet) would be sufficient to protect against acute metabolic side effects of OLZ. We demonstrate that fasting or the short-term consumption of a ketogenic diet (KD) protects against OLZ-induced hyperglycemia, independent of alterations in whole body insulin action, and in parallel with a blunted rise in serum glucagon. Interestingly, the effects of fasting and ketogenic diets were not recapitulated by acutely increasing circulating concentrations of ketone bodies through treatment with βHB or oral ketone esters, approaches which increase ketone bodies to physiological or supra-physiological levels respectively. Collectively our findings demonstrate that fasting and the short-term consumption of a KD can protect against acute AP-induced perturbations in glucose homeostasis, whereas manipulations which acutely increase circulating ketone bodies do not elicit the same beneficial effects. Abstract figure legend Model for fasting and ketogenic diet to protect against OLZ-induced hyperglycemia. This article is protected by copyright. All rights reserved.

Keywords:  antipsychotic; fasting; hyperglycemia; ketone bodies

DOI:  https://doi.org/10.1113/JP282922
Exp Neurol. 2022 Apr 29. pii: S0014-4886(22)00125-X. [Epub ahead of print]354 114100

Peroxisome proliferator-activated receptor-γ ameliorates neuronal ferroptosis after traumatic brain injury in mice by inhibiting cyclooxygenase-2.

Hui Liang, Ting Tang, Hanyu Huang, Tao Li, Chaochao Gao, Yanling Han, Bin Yuan, Shengqing Gao, Handong Wang, Meng-Liang Zhou.

  Among the multiple kinds of neuronal cell death triggered by traumatic brain injury (TBI), ferroptosis, an iron-dependent lipid peroxidative regulatory cell death, has a critical role. Peroxisome proliferator-activated receptor-γ (PPARγ) is a nuclear transcription factor that regulates lipid metabolism and suppresses neuronal inflammation. However, the role of PPARγ in neuronal ferroptosis induced by TBI remains unclear. Here, we investigated the regulatory effect of PPARγ on neuronal ferroptosis in a weight-drop TBI model in vivo and an RAS-selective lethal 3 (RSL3)-activated ferroptotic neuronal model in vitro. PPARγ was mainly localized in the nucleus of neurons and was decreased in both the in vivo TBI model and the in vitro ferroptotic neuronal model. The addition of a specific agonist, pioglitazone, activated PPARγ, which protected neuronal function post-TBI in vivo and increased the viability of ferroptotic neurons in vitro. Further investigation suggested that PPARγ probably attenuates neuronal ferroptosis by downregulating cyclooxygenase-2 (COX2) protein expression levels in vivo and in vitro. This study revealed the relationship among PPARγ, ferroptosis and TBI and identified a potential target for comprehensive TBI treatment.

Keywords:  COX2; Ferroptosis; Neurons; PPARγ; Traumatic brain injury

DOI:  https://doi.org/10.1016/j.expneurol.2022.114100
Front Cell Dev Biol. 2022 ;10 863907

Functions of Stress-Induced Lipid Droplets in the Nervous System.

Eva Islimye, Victor Girard, Alex P Gould.

  Lipid droplets are highly dynamic intracellular organelles that store neutral lipids such as cholesteryl esters and triacylglycerols. They have recently emerged as key stress response components in many different cell types. Lipid droplets in the nervous system are mostly observed in vivo in glia, ependymal cells and microglia. They tend to become more numerous in these cell types and can also form in neurons as a consequence of ageing or stresses involving redox imbalance and lipotoxicity. Abundant lipid droplets are also a characteristic feature of several neurodegenerative diseases. In this minireview, we take a cell-type perspective on recent advances in our understanding of lipid droplet metabolism in glia, neurons and neural stem cells during health and disease. We highlight that a given lipid droplet subfunction, such as triacylglycerol lipolysis, can be physiologically beneficial or harmful to the functions of the nervous system depending upon cellular context. The mechanistic understanding of context-dependent lipid droplet functions in the nervous system is progressing apace, aided by new technologies for probing the lipid droplet proteome and lipidome with single-cell type precision.

Keywords:  cholesteryl esters and triacylglycerols; glia; lipid droplets; lipotoxicity; neural stem cells; neurological disorders; neurons

DOI:  https://doi.org/10.3389/fcell.2022.863907
Eur J Paediatr Neurol. 2022 Apr 27. pii: S1090-3798(22)00061-7. [Epub ahead of print]38 73-76

Head circumference in glucose transporter 1 deficiency syndrome: Normal for individuals, abnormal as a group.

Loes A van Gemert, Wilhelmina G Leen, Jos M Draaisma, Nel Roeleveld, Michèl A Willemsen.

  In the literature, microcephaly is considered as part of the classical phenotype of glucose transporter 1 deficiency syndrome (GLUT1DS), and previous cohort studies reported a prevalence of microcephaly of around 50%. In our clinical experience, however, only very few patients with GLUT1DS appear to have microcephaly. Therefore, we conducted an observational study among a large cohort of Dutch patients with GLUT1DS to investigate the prevalence of microcephaly, defined as < 2 standard deviations (SD) below the mean. We analysed the head circumference of 54 patients and found a prevalence of microcephaly at last known measurement of 6.5%. Notably, none of the patients had a head circumference < -3 SD. However, we learned that 75.9% of the patients had a head circumference below 0 SD. This study shows that microcephaly occurs less often than previously thought in patients with GLUT1DS, and that primary or secondary microcephaly does not seem to be a sign for clinicians to suspect GLUT1DS. As a group, however, patients with GLUT1DS seem to have decreased head circumference compared to healthy individuals and as such, our study suggests that early brain development and brain growth may be compromised in GLUT1DS.

Keywords:  Glucose transporter 1 deficiency syndrome; Head circumference; Microcephaly; Phenotype; Retrospective study; SLC2A1

DOI:  https://doi.org/10.1016/j.ejpn.2022.04.005