bims-medebr 2022-04-10 papers

bims-medebr

Biomed News

on Metabolism of the developing brain

Issue of 2022‒04‒10
twenty papers selected by
Regina F. Fernández
Johns Hopkins University

Recent behavioral findings of pathophysiological involvement of lactate in the central nervous system.
Glycolytic metabolism supports microglia training during age-related neurodegeneration.
Chronic microglial inflammation promotes neuronal lactate supply but impairs its utilization in primary rat astrocyte-neuron co-cultures.
Impact of medium-chain triglycerides on gait performance and brain metabolic network in healthy older adults: a double-blind, randomized controlled study.
Activated glia cells cause bioenergetic impairment of neurons that can be rescued by knock-down of the mitochondrial calcium uniporter.
UBIAD1 alleviates ferroptotic neuronal death by enhancing antioxidative capacity by cooperatively restoring impaired mitochondria and Golgi apparatus upon cerebral ischemic/reperfusion insult.
Glycolytic and Oxidative Phosphorylation Defects Precede the Development of Senescence in Primary Human Brain Microvascular Endothelial Cells.
A Ca2+-dependent mechanism boosting glycolysis and OXPHOS by activating Aralar-malate-aspartate shuttle, upon neuronal stimulation.
Brain glycogen content is increased in the acute and interictal chronic stages of the mouse pilocarpine model of epilepsy.
ER-Mitochondria contacts modulate ROS-mediated signaling and oxidative stress in brain disorders: the key role of Sigma-1 receptor.
Lipidomics and Transcriptomics in Neurological Diseases.
Nervonic Acid Attenuates Accumulation of Very Long-Chain Fatty Acids and is a Potential Therapy for Adrenoleukodystrophy.
Metabolic changes favor the activity and heterogeneity of reactive astrocytes.
Fatty acid balance regulates α-synuclein pathology.
Comparative metabolomics in the Pahenu2 classical PKU mouse identifies cerebral energy pathway disruption and oxidative stress.
α-Lipoic Acid Strengthens the Antioxidant Barrier and Reduces Oxidative, Nitrosative, and Glycative Damage, as well as Inhibits Inflammation and Apoptosis in the Hypothalamus but Not in the Cerebral Cortex of Insulin-Resistant Rats.
Dietary restriction modulates mitochondrial DNA damage and oxylipins profile in aged rats.
Sequencing RNA isoforms in brain tissue.
Serine/Threonine Protein Phosphatase 2A Regulates the Transport of Axonal Mitochondria.
CB2R Activation Regulates TFEB-Mediated Autophagy and Affects Lipid Metabolism and Inflammation of Astrocytes in POCD.

Biochim Biophys Acta Gen Subj. 2022 Apr 03. pii: S0304-4165(22)00055-1. [Epub ahead of print] 130137

Recent behavioral findings of pathophysiological involvement of lactate in the central nervous system.

Yuki Kambe.

  Lactate was initially thought of as a fatigue substance. In recent years, however, lactate not only functions as an energy carrier and contributes to ATP production, but also its role as a signal transmitter has been attracting attention due to the identification of lactate receptors. Lactate is synthesized from glucose and glycogen through the glycolytic system. The central nervous system is a major organ of glucose metabolism and is rich in glycogen. Therefore, this review summarizes the recent findings on the contribution of lactate to the pathophysiology of the central nervous system.

Keywords:  Animal behavior; Astrocytes; Lactate; Neurons

DOI:  https://doi.org/10.1016/j.bbagen.2022.130137
Pharmacol Rep. 2022 Apr 03.

Glycolytic metabolism supports microglia training during age-related neurodegeneration.

Alberto Camacho-Morales.

  Glucose is a major energy source for the brain, necessary to preserve proper neurophysiological functions; aberrant glucose metabolism in the brain has been documented in chronic neurodegenerative pathologies. In addition, glucose-dependent metabolic pathways, including substrates of the Krebs cycle, are involved in peripheral and central innate immune activation through a molecular program known as trained immunity. Notably, it seems that defective glucose metabolism favors trained immunity in the brain, leading to neuronal damage and neurodegeneration. In addition, defective glucose metabolism in the brain correlates with a positive proinflammatory profile and microglia activation, as was found in postmortem samples of neurodegenerative pathologies. We hypothesized that fluctuations in glucose supply or metabolism in the brain during aging may alter microglial training, turning these cells to unresponsive or overresponsive to a challenge during age-related neurodegeneration. This review will cover the most significant advances in glucose-dependent metabolic pathways that favor innate trained immunity of microglia and their contribution to neurodegeneration.

Keywords:  Glucose; Immunometabolism; Microglia; Neurodegeneration; Trained immunity

DOI:  https://doi.org/10.1007/s43440-022-00363-2
Biochem Biophys Res Commun. 2022 Mar 26. pii: S0006-291X(22)00467-3. [Epub ahead of print]607 28-35

Chronic microglial inflammation promotes neuronal lactate supply but impairs its utilization in primary rat astrocyte-neuron co-cultures.

Yi Wang, Jie Li, Meng-Yue Wang, Zhi-Yong Pan, Zhi-Qiang Li, Ze-Fen Wang.

  Neuronal activity is closely associated with energy metabolism. In addition to glucose, astrocyte-derived lactate serves as an energy source for neurons. Chronic inflammation is a common pathological event that is associated with aging and neurodegenerative diseases. However, the mechanisms underlying inflammation-induced neuronal injury are not fully understood. Both microglia and astrocytes participate in the regulation of neuronal functions; therefore, we used astrocyte-neuron co-cultures to investigate the effects of chronic microglial activation on neuronal lactate metabolism. Chronic low-grade inflammation was induced by repeated stimulation of primary rat microglia with low-dose lipopolysaccharide (LPS, 10 ng/mL). The medium from the LPS-activated microglia was collected and used to mimic the inflammatory environment in primary cultures. In monocultures exposed to an inflammatory environment, intracellular lactate decreased in neurons but increased in astrocytes. However, astrocyte-neuron co-cultures exhibited increased lactate levels in neurons and decreased lactate levels in astrocytes when exposed to an inflammatory environment. Inhibition of lactate transporters expressed on neurons or astrocytes reduced the intracellular lactate in co-cultured neurons exposed to inflammation, but not in those exposed to physiological conditions. Adenosine triphosphate (ATP) production was reduced in both mono-cultured and co-cultured neurons. These results indicate that a chronic inflammatory environment increases neuronal lactate supply by promoting the astrocyte-neuron lactate shuttle, but it impairs lactate oxidation in neurons. Additionally, chronic inflammation disrupts the neuronal cytoskeleton. This study highlights the importance of glial cells in regulating neuroenergetics and neuronal function and provides a comprehensive explanation for the neurotoxic effects of neuroinflammation.

Keywords:  Astrocyte; Energy metabolism; Lactate shuttle; Microglia; Neuron

DOI:  https://doi.org/10.1016/j.bbrc.2022.03.122
Geroscience. 2022 Apr 05.

Impact of medium-chain triglycerides on gait performance and brain metabolic network in healthy older adults: a double-blind, randomized controlled study.

Tatsushi Mutoh, Keiko Kunitoki, Yasuko Tatewaki, Shuzo Yamamoto, Benjamin Thyreau, Izumi Matsudaira, Ryuta Kawashima, Yasuyuki Taki.

  Nutritional supplementation with medium-chain triglycerides (MCTs) has the potential to increase memory function in elderly patients with frailty and dementia. Our aim was to investigate the effects of MCT on cognitive and gait functions and their relationships with focal brain metabolism and functional connectivity even in healthy older adults. Participants were blindly randomized and allocated to two groups: 18 g/day of MCT oil and matching placebo formula (control) administered as a jelly stick (6 g/pack, ingested three times a day). Gait analysis during the 6-m walk test, cognition, brain focal glucose metabolism quantified by 18F-fluorodeocyglucose positron emission tomography, and magnetic resonance imaging-based functional connectivity were assessed before and after a 3-month intervention. Sixty-three healthy, normal adults (females and males) were included. Compared with the control group, the MCT group showed better balance ability, as represented by the lower Lissajous index (23.1 ± 14.4 vs. 31.3 ± 18.9; P < 0.01), although no time × group interaction was observed in cognitive and other gait parameters. Moreover, MCT led to suppressed glucose metabolism in the right sensorimotor cortex compared with the control (P < 0.001), which was related to improved balance (r = 0.37; P = 0.04) along with increased functional connectivity from the ipsilateral cerebellar hemisphere. In conclusion, a 3-month MCT supplementation improves walking balance by suppressing glucose metabolism, which suggests the involvement of the cerebro-cerebellar network. This may reflect, at least in part, the inverse reaction of the ketogenic switch as a beneficial effect of long-term MCT dietary treatment.

Keywords:  Brain glucose metabolism; Cognition; Elderly; Gait; Ketone; Medium-chain triglyceride

DOI:  https://doi.org/10.1007/s11357-022-00553-z
Biochem Biophys Res Commun. 2022 Mar 25. pii: S0006-291X(22)00465-X. [Epub ahead of print]608 45-51

Activated glia cells cause bioenergetic impairment of neurons that can be rescued by knock-down of the mitochondrial calcium uniporter.

Angela Maria Casaril, Athanasios Katsalifis, Rolf M Schmidt, Carlos Bas-Orth.

  Neuroinflammation is a hallmark of various neurological disorders including autoimmune-, neurodegenerative and neuropsychiatric diseases. In neuroinflammation, activated microglia and astrocytes release soluble mediators such as cytokines, glutamate, and reactive oxygen species that negatively affect neuronal function and viability, and thus contribute to neurodegeneration during disease progression. Therefore, the development of neuroprotective strategies might be important in addition to treating inflammation in these diseases. Mitochondria are promising cellular targets for neuroprotective interventions: They are among the first structures affected in many neuroinflammatory diseases, with mitochondrial impairment ranging from impaired respiratory activity and reduced mitochondrial membrane potential to mitochondrial oxidation and fragmentation. Therefore, we developed a cell culture model that resembles an early state of inflammation-induced neuronal mitochondrial dysfunction preceding neuronal cell death, and can be used to test mito- and neuroprotective strategies. Rat primary cortical neurons were challenged with conditioned medium from mixed primary cultures of rat microglia and astrocytes that had been activated with lipopolysaccharide and ATP. When sublethal amounts of glia-conditioned medium were added to neurons for 24 h, mitochondrial membrane potential and ATP levels were decreased, whereas mitochondrial redox state remained unaffected. Effects on mitochondrial membrane potential and ATP levels were ameliorated by knock-down of the mitochondrial calcium uniporter in neurons. This study suggests that neuronal bioenergetic failure is an early event during neuroinflammation and it identifies the mitochondrial calcium uniporter as a candidate target for neuroprotection in this context.

Keywords:  Astrocytes; Energy depletion; Microglia; Mitochondria; Neuroinflammation

DOI:  https://doi.org/10.1016/j.bbrc.2022.03.120
Cell Biosci. 2022 Apr 04. 12(1): 42

UBIAD1 alleviates ferroptotic neuronal death by enhancing antioxidative capacity by cooperatively restoring impaired mitochondria and Golgi apparatus upon cerebral ischemic/reperfusion insult.

Yan Huang, Jianyang Liu, Jialin He, Zhiping Hu, Fengbo Tan, Xuelin Zhu, Fulai Yuan, Zheng Jiang.

  BACKGROUND: Neuronal death due to over-oxidative stress responses defines the pathology of cerebral ischemic/reperfusion (I/R) insult. Ferroptosis is a form of oxidative cell death that is induced by disruption of the balance between antioxidants and pro-oxidants in cells. However, the potential mechanisms responsible for cerebral I/R-induced ferroptotic neuronal death have not been conclusively determined. UBIAD1, is a newly identified antioxidant enzyme that catalyzes coenzyme Q10 (CoQ10) and vitamin K2 biosynthesis in the Golgi apparatus membrane and mitochondria, respectively. Even though UBIAD1 is a significant mediator of apoptosis in cerebral I/R challenge, its roles in ferroptotic neuronal death remain undefined. Therefore, we investigated whether ferroptotic neuronal death is involved in cerebral I/R injury. Further, we evaluated the functions and possible mechanisms of UBIAD1 in cerebral I/R-induced ferroptotic neuronal death, with a major focus on mitochondrial and Golgi apparatus dysfunctions.RESULTS: Ferroptosis occurred in cerebral I/R. Ferroptotic neuronal death promoted cerebral I/R-induced brain tissue injury and neuronal impairment. UBIAD1 was expressed in cerebral tissues and was localized in neurons, astrocytes, and microglia. Under cerebral I/R conditions overexpressed UBIAD1 significantly suppressed lipid peroxidation and ferroptosis. Moreover, upregulated UBIAD1 protected against brain tissue damage and neuronal death by alleviating I/R-mediated lipid peroxidation and ferroptosis. However, UBIAD1 knockdown reversed these changes. Enhanced UBIAD1-mediated ferroptosis elevated the antioxidative capacity by rescuing mitochondrial and Golgi apparatus dysfunction in cerebral I/R-mediated neuronal injury. They improved the morphology and biofunctions of the mitochondria and Golgi apparatus, thereby elevating the levels of SOD, T-AOC and production of CoQ10, endothelial nitric oxide synthase (eNOS)-regulated nitric oxide (NO) generation as well as suppressed MDA generation.
CONCLUSIONS: The neuroprotective agent, UBIAD1, modulates I/R-mediated ferroptosis by restoring mitochondrial and Golgi apparatus dysfunction in damaged brain tissues and neurons, thereby enhancing antioxidative capacities. Moreover, the rescue of impaired mitochondrial and Golgi apparatus as a possible mechanism of regulating ferroptotic neuronal death is a potential treatment strategy for ischemic stroke.

Keywords:  Cerebral ischemia/reperfusion; Ferroptotic neuronal death; Golgi apparatus; Mitochondria; UBIAD1

DOI:  https://doi.org/10.1186/s13578-022-00776-9
Geroscience. 2022 Apr 04.

Glycolytic and Oxidative Phosphorylation Defects Precede the Development of Senescence in Primary Human Brain Microvascular Endothelial Cells.

Siva S V P Sakamuri, Venkata N Sure, Lahari Kolli, Ning Liu, Wesley R Evans, Jared A Sperling, David W Busija, Xiaoying Wang, Sarah H Lindsey, Walter L Murfee, Ricardo Mostany, Prasad V G Katakam.

  Alterations of mitochondrial and glycolytic energy pathways related to aging could contribute to cerebrovascular dysfunction. We studied the impact of aging on energetics of primary human brain microvascular endothelial cells (HBMECs) by comparing the young (passages 7-9), pre-senescent (passages 13-15), and senescent (passages 20-21) cells. Pre-senescent HBMECs displayed decreased telomere length and undetectable telomerase activity although markers of senescence were unaffected. Bioenergetics in HBMECs were determined by measuring the oxygen consumption (OCR) and extracellular acidification (ECAR) rates. Cellular ATP production in young HBMECs was predominantly dependent on glycolysis with glutamine as the preferred fuel for mitochondrial oxidative phosphorylation (OXPHOS). In contrast, pre-senescent HBMECs displayed equal contribution to ATP production rate from glycolysis and OXPHOS with equal utilization of glutamine, glucose, and fatty acids as mitofuels. Compared to young, pre-senescent HBMECs showed a lower overall ATP production rate that was characterized by diminished contribution from glycolysis. Impairments of glycolysis displayed by pre-senescent cells included reduced basal glycolysis, compensatory glycolysis, and non-glycolytic acidification. Furthermore, impairments of mitochondrial respiration in pre-senescent cells involved the reduction of maximal respiration and spare respiratory capacity but intact basal and ATP production-related OCR. Proton leak and non-mitochondrial respiration, however, were unchanged in the pre-senescent HBMECs. HBMECS at passages 20-21 displayed expression of senescence markers and continued similar defects in glycolysis and worsened OXPHOS. Thus, for the first time, we characterized the bioenergetics of pre-senescent HBMECs comprehensively to identify the alterations of the energy pathways that could contribute to aging.

Keywords:  ATP; Extracellular acidification rate; Glycolysis; Oxidative phosphorylation; Oxygen consumption rate

DOI:  https://doi.org/10.1007/s11357-022-00550-2
J Neurosci. 2022 Apr 06. pii: JN-RM-1463-21. [Epub ahead of print]

A Ca2+-dependent mechanism boosting glycolysis and OXPHOS by activating Aralar-malate-aspartate shuttle, upon neuronal stimulation.

Irene Pérez-Liébana, Inés Juaristi, Paloma González-Sánchez, Luis González-Moreno, Eduardo Rial, Maša Podunavac, Armen Zakarian, Jordi Molgó, Ainara Vallejo-Illarramendi, Laura Mosqueira-Martín, Adolfo López de Munain, Beatriz Pardo, Jorgina Satrústegui, Araceli Del Arco.

  Calcium is an important second messenger regulating a bioenergetic response to the workloads triggered by neuronal activation. In embryonic mouse cortical neurons using glucose as only fuel, activation by NMDA elicits a strong workload (ATP demand) dependent on Na+ and Ca2+ entry, and stimulates glucose uptake, glycolysis, pyruvate and lactate production and OXPHOS in a Ca2+-dependent way. We find that Ca2+-upregulation of glycolysis, pyruvate levels and respiration, but not glucose uptake, all depend on Aralar/AGC1/Slc25a12, the mitochondrial aspartate-glutamate carrier, component of the malate-aspartate shuttle (MAS). MAS activation increases glycolysis, pyruvate production and respiration, a process inhibited in the presence of BAPTA-AM suggesting that the Ca2+ binding motifs in Aralar may be involved in the activation. MCU silencing had no effect indicating that none of these processes required MCU-dependent mitochondrial Ca2+ uptake. The neuronal respiratory response to carbachol was also dependent on Aralar, but not on MCU. We find that mouse cortical neurons are endowed with a constitutive ER-to-mitochondria Ca2+ flow maintaining basal cell bioenergetics in which Ryanodine receptors, RyR2, rather than InsP3R, are responsible for Ca2+ release, and in which MCU does not participate. The results reveal that in neurons using glucose MCU does not participate in OXPHOS regulation under basal or stimulated conditions, while Aralar-MAS appears as the major Ca2+-dependent pathway tuning simultaneously glycolysis and OXPHOS to neuronal activation.SIGNIFICANT STATEMENTSNeuronal activation increases cell workload to restore ion gradients altered by activation. Ca2+ is involved in matching increased workload with ATP production, but the mechanisms are still unknown. We find that glycolysis, pyruvate production and neuronal respiration are stimulated upon neuronal activation in a Ca2+ dependent way, independently of effects of Ca2+ as workload inducer. MCU does not play a relevant role in Ca2+ stimulated pyruvate production and oxygen consumption as both are unchanged in MCU silenced neurons. However, Ca2+ stimulation is blunt in the absence of Aralar, a Ca2+-binding mitochondrial carrier component of Malate-Aspartate Shuttle (MAS). The results suggest that Ca2+-regulated Aralar-MAS activation upregulates glycolysis and pyruvate production which fuels mitochondrial respiration, through regulation of cytosolic NAD+/NADH ratio.

Keywords:  Aralar/AGC1/Slc25a12; Neuronal metabolism; calcium regulation; glycolysis; malate aspartate shuttle; mitochondrial calcium uniporter

DOI:  https://doi.org/10.1523/JNEUROSCI.1463-21.2022
Epilepsia Open. 2022 Apr 04.

Brain glycogen content is increased in the acute and interictal chronic stages of the mouse pilocarpine model of epilepsy.

Gi Young Seo, Elliott S Neal, Felicity Han, Diana Vidovic, Fathima Nooru-Mohamed, Gerald A Dienel, Mitchell A Sullivan, Karin Borges.

  Glucose is the main brain fuel in fed conditions, while astrocytic glycogen is used as supplemental fuel when the brain is stimulated. Brain glycogen levels are decreased after induced seizures in rodents, but little is known about how glycogen levels are affected interictally in chronic models of epilepsy. Reduced glutamine synthetase activity has been suggested to lead to increased brain glycogen levels in humans with chronic epilepsy. Here, we used the mouse pilocarpine model of epilepsy to investigate if brain glycogen levels are altered, both acutely and in the chronic stage of the model. One day after pilocarpine-induced convulsive status epilepticus (CSE), glycogen levels were higher in the hippocampal formation, cerebral cortex and cerebellum. Opposite to expected, this was accompanied by elevated glutamine synthetase activity in the hippocampus but not cortex. Increased interictal glycogen amounts were seen in the hippocampal formation and cerebral cortex in the chronic stage of the model (21 days post-CSE), suggesting long-lasting alterations in glycogen metabolism. Glycogen solubility in the cerebral cortex was unaltered in this epilepsy mouse model. Glycogen synthase kinase 3 beta (Gsk3b) mRNA levels were reduced in the hippocampal formations of mice in the chronic stage, which may underlie the elevated brain glycogen content in this model. This is the first report of elevated interictal glycogen levels in a chronic epilepsy model. Increased glycogen amounts in the brain may influence seizure susceptibility in this model and this warrants further investigation.

Keywords:  Gsk3b; glutamine synthetase; status epilepticus; temporal lobe epilepsy

DOI:  https://doi.org/10.1002/epi4.12599
Antioxid Redox Signal. 2022 Apr 04.

ER-Mitochondria contacts modulate ROS-mediated signaling and oxidative stress in brain disorders: the key role of Sigma-1 receptor.

Rosa Resende, Tânia Fernandes, Ana Catarina Pereira, Ana Patrícia Marques, Cláudia Fragão Pereira.

SIGNIFICANCE: Mitochondria-Associated Membranes (MAMs) are highly dynamic endoplasmic reticulum (ER)-mitochondria contact sites that, due to the transfer of lipids and Ca2+ between these organelles, modulate several physiologic processes, such as ER stress response, mitochondrial bioenergetics and fission/fusion events, autophagy and inflammation. In addition, these contacts are implicated in the modulation of the cellular redox status since several MAMs-resident proteins are involved in the generation of reactive oxygen species (ROS), which can act both as signaling mediators or deleterious molecules, depending on their intracellular levels.RECENT ADVANCES: In the last years, structural and functional alterations of MAMs have been associated with the pathophysiology of several neurodegenerative diseases that are closely associated with impairment of several MAMs-associated events, including perturbation of the redox state upon accumulation of high ROS levels.
CRITICAL ISSUES: Inter-organelle contacts must be tightly regulated to preserve cellular functioning by maintaining Ca2+ and protein homeostasis, lipid metabolism, mitochondrial dynamics and energy production, as well as ROS signaling. Simultaneously, these contacts should avoid mitochondrial Ca2+ overload, which might lead to energetic deficits and deleterious ROS accumulation, culminating in oxidative stress-induced activation of apoptotic cell death pathways, which are common features of many neurodegenerative diseases.
FUTURE DIRECTIONS: Given that Sig-1R is an ER resident chaperone highly enriched at the MAMs and controls ER to mitochondria Ca2+ flux, as well as oxidative and ER stress responses, its potential as a therapeutic target for neurodegenerative diseases such as Amyotrophic Lateral Sclerosis, Alzheimer, Parkinson and Huntington diseases should be further explored.

DOI: https://doi.org/10.1089/ars.2020.8231
J Vis Exp. 2022 Mar 18.

Lipidomics and Transcriptomics in Neurological Diseases.

Julia M Post, Raissa Lerner, Claudia Schwitter, Beat Lutz, Ermelinda Lomazzo, Laura Bindila.

Lipids serve as the primary interface to brain insults or stimuli conducive to neurological diseases and are a reservoir for the synthesis of lipids with various signaling or ligand function that can underscore the onset and progression of diseases. Often changing at the presymptomatic level, lipids are an emerging source of drug targets and biomarkers. Many neurological diseases exhibit neuroinflammation, neurodegeneration, and neuronal excitability as common hallmarks, partly modulated by specific lipid signaling systems. The interdependence and interrelation of synthesis of various lipids prompts a multilipid, multienzyme, and multireceptor analysis in order to derive the commonalities and specificities of neurological contexts and to expedite the unravelling of mechanistic aspects of disease onset and progression. Ascribing lipid roles to distinct brain regions advances the determination of lipid molecular phenotype and morphology associated with a neurological disease. Presented here is a modular protocol suitable for the analysis of membrane lipids and downstream lipid signals along with mRNA of enzymes and mediators underlying their functionality, extracted from discrete brain regions that are relevant for a particular neurological disease and/or condition. To ensure accurate comparative lipidomic profiling, the workflows and operating criteria were optimized and standardized for: i) brain sampling and dissection of regions of interest, ii) co-extraction of multiple lipid signals and membrane lipids, iii) dual lipid/mRNA extraction, iv) quantification by liquid chromatography multiple reaction monitoring (LC/MRM), and v) standard mRNA profiling. This workflow is amenable for the low tissue amounts obtained by sampling of the functionally discrete brain subregions (i.e. by brain punching), thus preventing bias in multimolecular analysis due to tissue heterogeneity and/or animal variability. To reveal peripheral consequences of neurological diseases and establish translational molecular readouts of neurological disease states, peripheral organ sampling, processing, and their subsequent lipidomic analysis, as well as plasma lipidomics, are also pursued and described. The protocol is demonstrated on an acute epilepsy mouse model.

DOI: https://doi.org/10.3791/59423
Neurotherapeutics. 2022 Apr 04.

Nervonic Acid Attenuates Accumulation of Very Long-Chain Fatty Acids and is a Potential Therapy for Adrenoleukodystrophy.

Marcia R Terluk, Julianne Tieu, Siddhee A Sahasrabudhe, Ann Moser, Paul A Watkins, Gerald V Raymond, Reena V Kartha.

  Adrenoleukodystrophy (ALD) is an X-linked inherited peroxisomal disorder due to mutations in the ALD protein and characterized by accumulation of very long-chain fatty acids (VLCFA), specifically hexacosanoic acid (C26:0). This can trigger other pathological processes such as mitochondrial dysfunction, oxidative stress, and inflammation, which if involves the brain tissues can result in a lethal form of the disease called childhood cerebral ALD. With the recent addition of ALD to the Recommended Uniform Screening Panel, there is an increase in the number of individuals who are identified with ALD. However, currently, there is no approved treatment for pre-symptomatic individuals that can arrest or delay symptom development. Here, we report our observations investigating nervonic acid, a monounsaturated fatty acid as a potential therapy for ALD. Using ALD patient-derived fibroblasts, we examined whether nervonic acid can reverse VLCFA accumulation similar to erucic acid, the active ingredient in Lorenzo's oil, a dietary intervention believed to alter disease course. We have shown that nervonic acid can reverse total lipid C26:0 accumulation in a concentration-dependent manner in ALD cell lines. Further, we show that nervonic acid can protect ALD fibroblasts from oxidative insults, presumably by increasing intracellular ATP production. Thus, nervonic acid can be a potential therapeutic for individuals with ALD, which can alter cellular biochemistry and improve its function.

Keywords:  Adrenoleukodystrophy; Dietary lipids; Fibroblasts; Monounsaturated fatty acids; Peroxisomes; Sphingomyelin; Very long-chain fatty acids

DOI:  https://doi.org/10.1007/s13311-022-01226-7
Trends Endocrinol Metab. 2022 Apr 05. pii: S1043-2760(22)00053-4. [Epub ahead of print]

Metabolic changes favor the activity and heterogeneity of reactive astrocytes.

Xiao-Yi Xiong, Yong Tang, Qing-Wu Yang.

  Reactive astrocytes undergo morphological, molecular, metabolic, and functional remodeling in response to central nervous system (CNS) damage. However, we still know very little about how the metabolic switching of astrocytes influences, or is influenced by, reactive astrocytes in response to neurological diseases. In this review, we initially cover a brief introduction into reactive astrocyte function under pathological conditions. Subsequently, we summarize the emerging roles of glucose and lipid metabolism in reactive astrocytes in the context of CNS injury to provide a new insight into metabolic mechanisms of reactive astrocyte-mediated neuroprotection or damage. Finally, we propose that deciphering the mechanistic link between astrocyte heterogeneity metabolism and improved methods is an emerging frontier for the therapeutic investigation of CNS injury and disease.

Keywords:  astrocyte; fatty acid; glycolysis; heterogeneity; metabolism; mitochondria

DOI:  https://doi.org/10.1016/j.tem.2022.03.001
Trends Neurosci. 2022 Apr 01. pii: S0166-2236(22)00057-1. [Epub ahead of print]

Fatty acid balance regulates α-synuclein pathology.

Stav Cohen-Adiv, Avraham Ashkenazi.

  A recent study by Triphati et al. used a protein engineering approach to demonstrate that cellular stress caused by familial α-synuclein mutations can be alleviated by altering the monounsaturated fatty acid equilibrium in neuronal cells. This work supports the notion that metabolic perturbation of lipids may be involved in the pathogenesis of Parkinson's disease.

Keywords:  Parkinson's disease; aggregation-prone proteins; cellular membrane; monounsaturated fatty acid; α-synuclein

DOI:  https://doi.org/10.1016/j.tins.2022.03.006
Mol Genet Metab. 2022 Mar 18. pii: S1096-7192(22)00155-X. [Epub ahead of print]

Comparative metabolomics in the Pahenu2 classical PKU mouse identifies cerebral energy pathway disruption and oxidative stress.

Steven F Dobrowolski, Yu Leng Phua, Cayla Sudano, Kayla Spridik, Pascal O Zinn, Yudong Wang, Sivakama Bharathi, Jerry Vockley, Eric Goetzman.

Classical phenylketonuria (PKU, OMIM 261600) owes to hepatic deficiency of phenylalanine hydroxylase (PAH) that enzymatically converts phenylalanine (Phe) to tyrosine (Tyr). PKU neurologic phenotypes include impaired brain development, decreased myelination, early onset mental retardation, seizures, and late-onset features (neuropsychiatric, Parkinsonism). Phe over-representation is systemic; however, tissue response to hyperphenylalaninemia is not consistent. To characterize hyperphenylalaninemia tissue response, metabolomics was applied to Pahenu2 classical PKU mouse blood, liver, and brain. In blood and liver over-represented analytes were principally Phe, Phe catabolites, and Phe-related analytes (Phe-conjugates, Phe-containing dipeptides). In addition to Phe and Phe-related analytes, the metabolomic profile of Pahenu2 brain tissue evidenced oxidative stress responses and energy dysregulation. Glutathione and homocarnosine anti-oxidative responses are apparent Pahenu2 brain. Oxidative stress in Pahenu2 brain was further evidenced by increased reactive oxygen species. Pahenu2 brain presents an increased NADH/NAD ratio suggesting respiratory chain complex 1 dysfunction. Respirometry in Pahenu2 brain mitochondria functionally confirmed reduced respiratory chain activity with an attenuated response to pyruvate substrate. Glycolysis pathway analytes are over-represented in Pahenu2 brain tissue. PKU pathologies owe to liver metabolic deficiency; yet, Pahenu2 liver tissue shows neither energy disruption nor anti-oxidative response. Unique aspects of metabolomic homeostasis in PKU brain tissue along with increased reactive oxygen species and respiratory chain deficit provide insight to neurologic disease mechanisms. While some elements of assumed, long standing PKU neuropathology are enforced by metabolomic data (e.g. reduced tryptophan and serotonin representation), energy dysregulation and tissue oxidative stress expand mechanisms underlying neuropathology.

DOI: https://doi.org/10.1016/j.ymgme.2022.03.004
Oxid Med Cell Longev. 2022 ;2022 7450514

α-Lipoic Acid Strengthens the Antioxidant Barrier and Reduces Oxidative, Nitrosative, and Glycative Damage, as well as Inhibits Inflammation and Apoptosis in the Hypothalamus but Not in the Cerebral Cortex of Insulin-Resistant Rats.

Mateusz Maciejczyk, Ewa Żebrowska, Miłosz Nesterowicz, Małgorzata Żendzian-Piotrowska, Anna Zalewska.

The research determined the role of α-lipoic acid (ALA) in reducing the brain manifestations of insulin resistance. The mechanism of ALA action is mainly based on its ability to "scavenge" oxygen free radicals and stimulate biosynthesis of reduced glutathione (GSH), considered the most critical brain antioxidant. Although the protective effect of ALA is widely documented in various diseases, there are still no studies assessing the influence of ALA on brain metabolism in the context of insulin resistance and type 2 diabetes. The experiment was conducted on male Wistar rats fed a high-fat diet for ten weeks with intragastric administration of ALA for four weeks. We are the first to demonstrate that ALA improves the function of enzymatic and nonenzymatic brain antioxidant systems, but the protective effects of ALA were mainly observed in the hypothalamus of insulin-resistant rats. Indeed, ALA caused a significant increase in superoxide dismutase, catalase, peroxidase, and glutathione reductase activities, as well as GSH concentration and redox potential ([GSH]2/[GSSG]) in the hypothalamus of HFD-fed rats. A consequence of antioxidant barrier enhancement by ALA is the reduction of oxidation, glycation, and nitration of brain proteins, lipids, and DNA. The protective effects of ALA result from hypothalamic activation of the transcription factor Nrf2 and inhibition of NF-κB. In the hypothalamus of insulin-resistant rats, we demonstrated reduced levels of oxidation (AOPP) and glycation (AGE) protein products, 4-hydroxynoneal, 8-isoprostanes, and 3-nitrotyrosine and, in the cerebral cortex, lower levels of 8-hydroxydeoxyguanosine and peroxynitrite. In addition, we demonstrated that ALA decreases levels of proinflammatory TNF-α but also increases the synthesis of anti-inflammatory IL-10 in the hypothalamus of insulin-resistant rats. ALA also prevents neuronal apoptosis, confirming its multidirectional effects within the brain. Interestingly, we have shown no correlation between brain and serum/plasma oxidative stress biomarkers, indicating the different nature of redox imbalance at the central and systemic levels. To summarize, ALA improves antioxidant balance and diminishes oxidative/glycative stress, protein nitrosative damage, inflammation, and apoptosis, mainly in the hypothalamus of insulin-resistant rats. Further studies are needed to determine the molecular mechanism of ALA action within the brain.

DOI: https://doi.org/10.1155/2022/7450514
FEBS J. 2022 Apr 03.

Dietary restriction modulates mitochondrial DNA damage and oxylipins profile in aged rats.

Artem P Gureev, Nadezda V Andrianova, Irina B Pevzner, Ljubava D Zorova, Ekaterina V Chernyshova, Irina S Sadovnikova, Dmitry V Chistyakov, Vasily A Popkov, Dmitry S Semenovich, Valentina A Babenko, Denis N Silachev, Dmitry B Zorov, Egor Y Plotnikov, Vasily N Popov.

  Age-related impairment of coordination of the processes of maintaining mitochondrial homeostasis is associated with a decrease in the functionality of cells and leads to degenerative processes. Mitochondrial DNA (mtDNA) can be a marker of oxidative stress and tissue degeneration. However, the mechanism of accumulation of age-related damage in mtDNA remains unclear. In this study, we analyzed the accumulation of mtDNA damage in several organs of rats during aging, as well as the possibility of reversing these alterations by dietary restriction (DR). We showed that mtDNA of brain compartments (with the exception of the cerebellum), along with kidney mtDNA, was the most susceptible to accumulation of age-related damage, while liver, testis, and lung were the least susceptible organs. DR prevented age-related accumulation of mtDNA damage in the cortex and led to its decrease in the lung and testis. Changes in mtDNA copy number and expression of genes involved in the regulation of mitochondrial biogenesis and mitophagy were also tissue-specific. There was a tendency for an age-related decrease in the copy number of mtDNA in the striatum and its increase in the kidney. DR promoted an increase in the amount of mtDNA in the cerebellum and hippocampus. mtDNA damage may be associated not only with the metabolic activity of organs but also with the lipid composition and activity of processes associated with the isoprostanes pathway of lipid peroxidation. The comparison of polyunsaturated fatty acids (PUFAs) and oxylipins profiles in old rats showed that DR decreased the synthesis of arachidonic acid and its metabolites synthesized by the cyclooxygenase (COX), cytochrome P450 monooxygenases (CYP), and lipoxygenase (LOX) metabolic pathways.

Keywords:  caloric restriction; mitochondria; oxidative stress; oxylipins; quality control

DOI:  https://doi.org/10.1111/febs.16451
Nat Methods. 2022 Apr 08.

Sequencing RNA isoforms in brain tissue.

Lei Tang.

DOI: https://doi.org/10.1038/s41592-022-01473-8
Front Cell Neurosci. 2022 ;16 852245

Serine/Threonine Protein Phosphatase 2A Regulates the Transport of Axonal Mitochondria.

Keunjung Heo, Himanish Basu, Amos Gutnick, Wei Wei, Evgeny Shlevkov, Thomas L Schwarz.

  Microtubule-based transport provides mitochondria to distant regions of neurons and is essential for neuronal health. To identify compounds that increase mitochondrial motility, we screened 1,641 small-molecules in a high-throughput screening platform. Indirubin and cantharidin increased mitochondrial motility in rat cortical neurons. Cantharidin is known to inhibit protein phosphatase 2A (PP2A). We therefore tested two other inhibitors of PP2A: LB-100 and okadaic acid. LB-100 increased mitochondrial motility, but okadaic acid did not. To resolve this discrepancy, we knocked down expression of the catalytic subunit of PP2A (PP2CA). This long-term inhibition of PP2A more than doubled retrograde transport of axonal mitochondria, confirming the importance of PP2A as a regulator of mitochondrial motility and as the likely mediator of cantharidin's effect.

Keywords:  cantharidin; high-throughput screen; indirubin; mitochondrial transport; protein phosphatase 2A

DOI:  https://doi.org/10.3389/fncel.2022.852245
Front Immunol. 2022 ;13 836494

CB2R Activation Regulates TFEB-Mediated Autophagy and Affects Lipid Metabolism and Inflammation of Astrocytes in POCD.

Lieliang Zhang, Xifeng Wang, Wen Yu, Jun Ying, Pu Fang, Qingcui Zheng, Xiaojin Feng, Jialing Hu, Fan Xiao, Shoulin Chen, Gen Wei, Yue Lin, Xing Liu, Danying Yang, Yang Fang, Guohai Xu, Fuzhou Hua.

  Evidence suggests that the accumulation of lipid drots (LDs) accelerates damage to mitochondria and increases the release of inflammatory factors. These have been implicated as a mechanism underlying neurodegenerative diseases or tumors and aging-related diseases such as postoperative cognitive dysfunction (POCD), nevertheless, accumulation of lipid droplets has not been extensively studied in the central nervous system (CNS). Here, we found that after surgery, there was activation of astrocytes and lipid accumulation in the hippocampus. However, cannabinoid receptor type II (CB2R) activation significantly reduced lipid accumulation in astrocytes and change the expression of genes related to lipid metabolism. CB2R reduces the release of the inflammatory factors interleukin-1 beta (IL-1β) and interleukin 6 (IL-6) in peripheral serum and simultaneously improves cognitive ability in mice with POCD. Further research on mechanisms indicates that CB2R activation promotes the nuclear entry of the bHLH-leucine zipper transcription factor, the transcription factor EB (TFEB), and which is a master transcription factor of the autophagy-lysosomal pathway, also reduces TFEB-S211 phosphorylation. When CB2R promotes TFEB into the nucleus, TFEB binds at two sites within promoter region of PGC1α, promoting PGC1α transcription and accelerating downstream lipid metabolism. The aforementioned process leads to autophagy activation and decreases cellular lipid content. This study uncovers a new mechanism allowing CB2R to regulate lipid metabolism and inflammation in POCD.

Keywords:  astrocytes; autophagy; cannabinoid type 2 receptor; inflammation; lipid accumulation; mitochondrial damage; postoperative cognitive dysfunction

DOI:  https://doi.org/10.3389/fimmu.2022.836494