bims-medebr 2024-08-18 papers

bims-medebr

Biomed News

on Metabolism of the developing brain

Issue of 2024‒08‒18
twenty-two papers selected by
Regina F. Fernández, Johns Hopkins University

The Regulation of Frontal Cortex Cholesterol Metabolism Abnormalities by NR3C1/NRIP1/NR1H2 Is Involved in the Occurrence of Stress-Induced Depression.
Alternate-day fasting improves cognitive and brain energy deficits by promoting ketone metabolism in the 3xTg mouse model of Alzheimer's disease.
Impaired microglial glycolysis promotes inflammatory responses after intracerebral haemorrhage via HK2-dependent mitochondrial dysfunction.
A lactate-dependent shift of glycolysis mediates synaptic and cognitive processes in male mice.
Plasma lipidomics in early APP/PS1 female mouse model and its relationship with brain: Is it affected by the estrous cycle?
HSP60 chaperone deficiency disrupts the mitochondrial matrix proteome and dysregulates cholesterol synthesis.
Cerebral glucose metabolism in Alzheimer's disease.
Omics-derived biological modules reflect metabolic brain changes in Alzheimer's disease.
Effects of Atorvastatin and Simvastatin on the Bioenergetic Function of Isolated Rat Brain Mitochondria.
A high-resolution 13C NMR approach for profiling fatty acid unsaturation in lipid extracts and in live C. elegans.
Mitochondrial network reorganization and transient expansion during oligodendrocyte generation.
Creation of a novel zebrafish model with low DHA status to study the role of maternal nutrition during neurodevelopment.
Phosphorylation of Insig-2 mediates inhibition of fatty acid synthesis by polyunsaturated fatty acids.
Maternal n-3 enriched diet reprograms the offspring neurovascular transcriptome and blunts inflammation induced by endotoxin in the neonate.
Mitochondrial Transfer in the Neurovascular Unit, Not Only for Energy Rescue: A Systematic Review.
Microglia are not necessary for maintenance of blood-brain barrier properties in health, but PLX5622 alters brain endothelial cholesterol metabolism.
Mitochondrial-derived compartments remove surplus proteins from the outer mitochondrial membrane.
Differential utilization of vitamin B12-dependent and independent pathways for propionate metabolism across human cells.
Effects of a high-fat diet on cognition and brain distribution of intranasal insulin in E3 and E4 male and female mice.
PSMF1 variants cause a phenotypic spectrum from early-onset Parkinson's disease to perinatal lethality by disrupting mitochondrial pathways.
Huanshaodan regulates microglial glucose metabolism reprogramming to alleviate neuroinflammation in AD mice through mTOR/HIF-1α signaling pathway.
3D Reconstruction of the Mitochondrial Network within the Neuronal Soma from SBF-SEM Volume Data.

Int J Mol Sci. 2024 Jul 24. pii: 8075. [Epub ahead of print]25(15):

The Regulation of Frontal Cortex Cholesterol Metabolism Abnormalities by NR3C1/NRIP1/NR1H2 Is Involved in the Occurrence of Stress-Induced Depression.

Rui Shi, Yingmin Li, Weihao Zhu, Hongjian Xin, Huihuang Yang, Xiaowei Feng, Zhen Wang, Shujin Li, Bin Cong, Weibo Shi.

  Stress-induced alterations in central neuron metabolism and function are crucial contributors to depression onset. However, the metabolic dysfunctions of the neurons associated with depression and specific molecular mechanisms remain unclear. This study initially analyzed the relationship between cholesterol and depression using the NHANES database. We then induced depressive-like behaviors in mice via restraint stress. Applying bioinformatics, pathology, and molecular biology, we observed the pathological characteristics of brain cholesterol homeostasis and investigated the regulatory mechanisms of brain cholesterol metabolism disorders. Through the NHANES database, we initially confirmed a significant correlation between cholesterol metabolism abnormalities and depression. Furthermore, based on successful stress mouse model establishment, we discovered the number of cholesterol-related DEGs significantly increased in the brain due to stress, and exhibited regional heterogeneity. Further investigation of the frontal cortex, a brain region closely related to depression, revealed stress caused significant disruption to key genes related to cholesterol metabolism, including HMGCR, CYP46A1, ACAT1, APOE, ABCA1, and LDLR, leading to an increase in total cholesterol content and a significant decrease in synaptic proteins PSD-95 and SYN. This indicates cholesterol metabolism affects neuronal synaptic plasticity and is associated with stress-induced depressive-like behavior in mice. Adeno-associated virus interference with NR3C1 in the prefrontal cortex of mice subjected to short-term stress resulted in reduced protein levels of NRIP1, NR1H2, ABCA1, and total cholesterol content. At the same time, it increased synaptic proteins PSD95 and SYN, effectively alleviating depressive-like behavior. Therefore, these results suggest that short-term stress may induce cholesterol metabolism disorders by activating the NR3C1/NRIP1/NR1H2 signaling pathway. This impairs neuronal synaptic plasticity and consequently participates in depressive-like behavior in mice. These findings suggest that abnormal cholesterol metabolism in the brain induced by stress is a significant contributor to depression onset.

Keywords:  NR3C1/NRIP1/NR1H2 pathway; cholesterol metabolism; depression; frontal cortex

DOI:  https://doi.org/10.3390/ijms25158075
Exp Neurol. 2024 Aug 12. pii: S0014-4886(24)00246-2. [Epub ahead of print] 114920

Alternate-day fasting improves cognitive and brain energy deficits by promoting ketone metabolism in the 3xTg mouse model of Alzheimer's disease.

Yucai Ye, Chaojing Fu, Yan Li, Junli Sun, Xinru Li, Shifan Chai, Shuo Li, Meng Hou, Hongyan Cai, Meina Wu, Zhaojun Wang.

  Alzheimer's disease (AD) is characterized by disorders in brain energy. The lack of sufficient energy for nerve function leads to cognitive dysfunction and massive neuronal loss in AD. Ketone bodies are an alternative to glucose as a source of energy in the brain, and alternate-day fasting (ADF) promotes the production of the ketone body β-hydroxybutyric acid (βOHB). In this study, 7-month-old male WT mice and 3xTg mice underwent dietary control for 20 weeks. We found that ADF increased circulating βOHB concentrations in 3xTg mice, improved cognitive function, reduced anxiety-like behaviors, improved hippocampal synaptic plasticity, and reduced neuronal loss, Aβ oligomers and tau hyperphosphorylation. In addition, ADF improved mitochondrial bioenergetic function by promoting brain ketone metabolism and rescued brain energy deficits in 3xTg mice. A safety evaluation showed that ADF improved exercise endurance and liver and kidney function in 3xTg mice without negatively affecting muscle motor and heart functions. This study provides a theoretical basis and strong support for the application of ADF as a non-drug strategy for preventing and treating brain energy defects in the early stage of AD.

Keywords:  Alternate-day fasting; Alzheimer's disease; Brain energy disorders; Brain ketone metabolism; Mitochondrial bioenergetics; Synaptic plasticity

DOI:  https://doi.org/10.1016/j.expneurol.2024.114920
J Adv Res. 2024 Aug 12. pii: S2090-1232(24)00359-X. [Epub ahead of print]

Impaired microglial glycolysis promotes inflammatory responses after intracerebral haemorrhage via HK2-dependent mitochondrial dysfunction.

Yin Li, Hang Zhou, Xuchao He, Lingji Jin, Yuhan Zhu, Libin Hu, Majing Feng, Jun Zhu, Liang Wang, Yonghe Zheng, Shiwei Li, Zhiyuan Yan, Peili Cen, Junwen Hu, Zihang Chen, Xiaobo Yu, Xiongjie Fu, Chaoran Xu, Shenglong Cao, Yang Cao, Gao Chen, Lin Wang.

  INTRODUCTION: Intracerebral haemorrhage (ICH) is a devastating disease that leads to severe neurological deficits. Microglia are the first line of defence in the brain and play a crucial role in neurological recovery after ICH, whose activities are primarily driven by glucose metabolism. However, little is known regarding the status of glucose metabolism in microglia and its interactions with inflammatory responses after ICH.OBJECTIVES: This study investigated microglial glycolysis and its mechanistic effects on microglial inflammation after ICH.
METHODS: We explored the status of glucose metabolism in the ipsilateral region and in fluorescence-activated-cell-sorting-isolated (FACS-isolated) microglia via 2-deoxy-[18F]fluoro-D-glucose positron emission tomography (FDG-PET) analyses and gamma emission, respectively. Energy-related targeted metabolomics, along with 13C-glucose isotope tracing, was utilised to analyse glycolytic products in microglia. Mitochondrial membrane potential and mitochondrial reactive oxygen species (MitoROS) accumulation was assessed by flow cytometry. Behavioural, western blotting, gene regulation, and enzymatic activity analyses were conducted with a focus on microglia.
RESULTS: Neurological dysfunction was strongly correlated with decreased FDG-PET signals in the perihaematomal region, where microglial uptake of FDG was reduced. The decreased quantity of glucose-6-phosphate (G-6-P) in microglia was attributed to the downregulation of glucose transporter 1 (GLUT1) and hexokinase 2 (HK2). Enhanced inflammatory responses were driven by HK2 suppression via decreased mitochondrial membrane potential, which could be rescued by MitoROS scavengers. HK inhibitors aggravated neurological injury by suppressing FDG uptake and enhancing microglial inflammation in ICH mice.
CONCLUSION: These findings indicate an unexpected metabolic status in pro-inflammatory microglia after ICH, consisting of glycolysis impairment caused by the downregulation of GLUT1 and HK2. Additionally, HK2 suppression promotes inflammatory responses by disrupting mitochondrial function, providing insight into the mechanisms by which inflammation may be facilitated after ICH and indicating that metabolic enzymes as potential targets for ICH treatment.

Keywords:  Glycolysis; Hexokinase 2; Inflammation; Intracerebral haemorrhage; Microglia; Mitochondria

DOI:  https://doi.org/10.1016/j.jare.2024.08.016
Nat Commun. 2024 Aug 09. 15(1): 6842

A lactate-dependent shift of glycolysis mediates synaptic and cognitive processes in male mice.

Ignacio Fernández-Moncada, Gianluca Lavanco, Unai B Fundazuri, Nasrin Bollmohr, Sarah Mountadem, Tommaso Dalla Tor, Pauline Hachaguer, Francisca Julio-Kalajzic, Doriane Gisquet, Roman Serrat, Luigi Bellocchio, Astrid Cannich, Bérénice Fortunato-Marsol, Yusuke Nasu, Robert E Campbell, Filippo Drago, Carla Cannizzaro, Guillaume Ferreira, Anne-Karine Bouzier-Sore, Luc Pellerin, Juan P Bolaños, Gilles Bonvento, L Felipe Barros, Stephane H R Oliet, Aude Panatier, Giovanni Marsicano.

Astrocytes control brain activity via both metabolic processes and gliotransmission, but the physiological links between these functions are scantly known. Here we show that endogenous activation of astrocyte type-1 cannabinoid (CB1) receptors determines a shift of glycolysis towards the lactate-dependent production of D-serine, thereby gating synaptic and cognitive functions in male mice. Mutant mice lacking the CB1 receptor gene in astrocytes (GFAP-CB1-KO) are impaired in novel object recognition (NOR) memory. This phenotype is rescued by the gliotransmitter D-serine, by its precursor L-serine, and also by lactate and 3,5-DHBA, an agonist of the lactate receptor HCAR1. Such lactate-dependent effect is abolished when the astrocyte-specific phosphorylated-pathway (PP), which diverts glycolysis towards L-serine synthesis, is blocked. Consistently, lactate and 3,5-DHBA promoted the co-agonist binding site occupancy of CA1 post-synaptic NMDA receptors in hippocampal slices in a PP-dependent manner. Thus, a tight cross-talk between astrocytic energy metabolism and gliotransmission determines synaptic and cognitive processes.

DOI: https://doi.org/10.1038/s41467-024-51008-2
Alzheimers Res Ther. 2024 Aug 14. 16(1): 183

Plasma lipidomics in early APP/PS1 female mouse model and its relationship with brain: Is it affected by the estrous cycle?

Laura Ferré-González, Ángel Balaguer, Marta Roca, Artemis Ftara, Ana Lloret, Consuelo Cháfer-Pericás.

  BACKGROUND: Alzheimer's disease (AD) is the most prevalent dementia, showing higher incidence in women. Besides, lipids play an essential role in brain, and they could be dysregulated in neurodegeneration. Specifically, impaired plasma lipid levels could predict early AD diagnosis. This work aims to identify the main plasma lipids altered in early AD female mouse model and evaluate their relationship with brain lipidome. Also, the possible involvement of the estrous cycle in lipid metabolism has been evaluated.METHODS: Plasma samples of wild-type (n = 10) and APP/PS1 (n = 10) female mice of 5 months of age were collected, processed, and analysed using a lipidomic mass spectrometry-based method. A statistical analysis involving univariate and multivariate approaches was performed to identify significant lipid differences related to AD between groups. Also, cytology tests were conducted to confirm estrous cycle phases.
RESULTS: Three hundred thirty lipids were detected in plasma, 18 of them showed significant differences between groups; specifically, some triacylglycerols, cholesteryl esters, lysophosphatidylcholines, phosphatidylcholines, and ether-linked phosphatidylcholines, increased in early AD; while other phosphatidylcholines, phosphatidylethanolamines, ceramides, and ether-linked phosphatidylethanolamines decreased in early AD. A multivariate approach was developed from some lipid variables, showing high diagnostic indexes (70% sensitivity, 90% specificity, 80% accuracy). From brain and plasma lipidome, some significant correlations were observed, mainly in the glycerophospholipid family. Also, some differences were found in both plasma and brain lipids, according to the estrous cycle phase.
CONCLUSIONS: Therefore, lipid alterations can be identified in plasma at early AD stages in mice females, with a relationship with brain lipid metabolism for most of the lipid subfamilies, suggesting some lipids as potential AD biomarkers. In addition, the estrous cycle monitoring could be relevant in female studies.

Keywords:  Alzheimer; Brain; Early; Estrous cycle; Lipid; Mouse model; Plasma

DOI:  https://doi.org/10.1186/s13195-024-01549-x
Mol Metab. 2024 Aug 13. pii: S2212-8778(24)00140-6. [Epub ahead of print] 102009

HSP60 chaperone deficiency disrupts the mitochondrial matrix proteome and dysregulates cholesterol synthesis.

Cagla Cömert, Kasper Kjær-Sørensen, Jakob Hansen, Jasper Carlsen, Jesper Just, Brandon F Meaney, Elsebet Østergaard, Yonglun Luo, Claus Oxvig, Lisbeth Schmidt-Laursen, Johan Palmfeldt, Paula Fernandez-Guerra, Peter Bross.

  OBJECTIVE: Mitochondrial proteostasis is critical for cellular function. The molecular chaperone HSP60 is essential for cell function and dysregulation of HSP60 expression has been implicated in cancer and diabetes. The few reported patients carrying HSP60 gene variants show neurodevelopmental delay and brain hypomyelination. Hsp60 interacts with more than 260 mitochondrial proteins but the mitochondrial proteins and functions affected by HSP60 deficiency are poorly characterized.METHODS: We studied two model systems for HSP60 deficiency: (1) engineered HEK cells carrying an inducible dominant negative HSP60 mutant protein, (2) zebrafish HSP60 knockout larvae. Both systems were analyzed by RNASeq, proteomics, and targeted metabolomics, and several functional assays relevant for the respective model. In addition, skin fibroblasts from patients with disease-associated HSP60 variants were analyzed by proteomics.
RESULTS: We show that HSP60 deficiency leads to a differentially downregulated mitochondrial matrix proteome, transcriptional activation of stress responses, and dysregulated cholesterol biosynthesis. This leads to lipid accumulation in zebrafish knockout larvae.
CONCLUSIONS: Our data provide a compendium of the effects of HSP60 deficiency on the mitochondrial matrix proteome. We show that HSP60 is a master regulator and modulator of mitochondrial functions and metabolic pathways. HSP60 dysfunction also affects cellular metabolism and disrupts the integrated stress response. The effect on cholesterol synthesis explains the effect of HSP60 dysfunction on myelination observed in patients carrying genetic variants of HSP60.

Keywords:  HSP60; HSPD1; chaperone; cholesterol; folding; mitochondria; myelination; proteomics; transcriptomics; zebrafish

DOI:  https://doi.org/10.1016/j.molmet.2024.102009
Cortex. 2024 Aug 03. pii: S0010-9452(24)00206-5. [Epub ahead of print]179 50-61

Cerebral glucose metabolism in Alzheimer's disease.

Eric Salmon, Fabienne Collette, Christine Bastin.

  18F-fluoro-deoxy-glucose positron emission tomography (FDG-PET) is a useful paraclinical exam for the diagnosis of Alzheimer's disease (AD). In this narrative review, we report seminal studies in clinically probable AD that have shown the importance of posterior brain metabolic decrease and the paradoxical variability of the hippocampal metabolism. The FDG-PET pattern was a sensitive indicator of AD in pathologically confirmed cases and it was used for differential diagnosis of dementia conditions. In prodromal AD, the AD FDG-PET pattern was observed in converters and predicted conversion. Automated data analysis techniques provided variable accuracy according to the reported indices and machine learning methods showed variable reliability of results. FDG-PET could confirm AD clinical heterogeneity and image data driven analyses identified hypometabolic subtypes with variable involvement of the hippocampus, reminiscent if the paradoxical FDG uptake. In studies dedicated to clinical and metabolic correlations, episodic memory was related to metabolism in the default mode network (and Papez's circuit) in prodromal and mild AD stages, and specific cognitive processes were associated to precisely distributed brain metabolism. Cerebral metabolic correlates of anosognosia could also be related to current neuropsychological models. AD FDG-PET pattern was reported in preclinical AD stages and related to cognition or to conversion to mild cognitive impairment (MCI). Using other biomarkers, the AD FDG-PET pattern was confirmed in AD participants with positive PET-amyloid. Intriguing observations reported increased metabolism related to brain amyloid and/or tau deposition. Preserved glucose metabolism sometimes appear as a compensation, but it was frequently detrimental and the nature of such a preservation of glucose metabolism remains an open question. Limbic metabolic involvement was frequently related to non-AD biomarkers profile and clinical stability, and it was reported in non-AD pathologies, such as the limbic predominant age-related encephalopathy (LATE). FDG-PET abnormalities observed in the absence of classical AD proteinopathies can be useful to search for pathological mechanisms and differential diagnosis of AD.

Keywords:  Brain metabolism; Dementia; FDG-PET; Memory; Mild cognitive impairment

DOI:  https://doi.org/10.1016/j.cortex.2024.07.004
Alzheimers Dement. 2024 Aug 14.

Omics-derived biological modules reflect metabolic brain changes in Alzheimer's disease.

Alzheimer's Disease Neuroimaging Initiative

  INTRODUCTION: Brain glucose hypometabolism, indexed by the fluorodeoxyglucose positron emission tomography ([18F]FDG-PET) imaging, is a metabolic signature of Alzheimer's disease (AD). However, the underlying biological pathways involved in these metabolic changes remain elusive.METHODS: Here, we integrated [18F]FDG-PET images with blood and hippocampal transcriptomic data from cognitively unimpaired (CU, n = 445) and cognitively impaired (CI, n = 749) individuals using modular dimension reduction techniques and voxel-wise linear regression analysis.
RESULTS: Our results showed that multiple transcriptomic modules are associated with brain [18F]FDG-PET metabolism, with the top hits being a protein serine/threonine kinase activity gene cluster (peak-t(223) = 4.86, P value < 0.001) and zinc-finger-related regulatory units (peak-t(223) = 3.90, P value < 0.001).
DISCUSSION: By integrating transcriptomics with PET imaging data, we identified that serine/threonine kinase activity-associated genes and zinc-finger-related regulatory units are highly associated with brain metabolic changes in AD.
HIGHLIGHTS: We conducted an integrated analysis of system-based transcriptomics and fluorodeoxyglucose positron emission tomography ([18F]FDG-PET) at the voxel level in Alzheimer's disease (AD). The biological process of serine/threonine kinase activity was the most associated with [18F]FDG-PET in the AD brain. Serine/threonine kinase activity alterations are associated with brain vulnerable regions in AD [18F]FDG-PET. Zinc-finger transcription factor targets were associated with AD brain [18F]FDG-PET metabolism.

Keywords:  Alzheimer's disease; fluorodeoxyglucose positron emission tomography; systems biology; transcriptomics

DOI:  https://doi.org/10.1002/alz.14095
Int J Mol Sci. 2024 Aug 03. pii: 8494. [Epub ahead of print]25(15):

Effects of Atorvastatin and Simvastatin on the Bioenergetic Function of Isolated Rat Brain Mitochondria.

Krzysztof Wojcicki, Adrianna Budzinska, Wieslawa Jarmuszkiewicz.

  Little is known about the effects of statins, which are cholesterol-lowering drugs, on the bioenergetic functions of mitochondria in the brain. This study aimed to elucidate the direct effects of atorvastatin and simvastatin on the bioenergetics of isolated rat brain mitochondria by measuring the statin-induced changes in respiratory chain activity, ATP synthesis efficiency, and the production of reactive oxygen species (ROS). Our results in isolated brain mitochondria are the first to demonstrate that atorvastatin and simvastatin dose-dependently significantly inhibit the activity of the mitochondrial respiratory chain, resulting in a decreased respiratory rate, a decreased membrane potential, and increased ROS formation. Moreover, the tested statins reduced mitochondrial coupling parameters, the ADP/O ratio, the respiratory control ratio, and thus, the oxidative phosphorylation efficiency in brain mitochondria. Among the oxidative phosphorylation complexes, statin-induced mitochondrial impairment concerned complex I, complex III, and ATP synthase activity. The calcium-containing atorvastatin had a significantly more substantial effect on isolated brain mitochondria than simvastatin. The higher inhibitory effect of atorvastatin was dependent on calcium ions, which may lead to the disruption of calcium homeostasis in mitochondria. These findings suggest that while statins are effective in their primary role as cholesterol-lowering agents, their use may impair mitochondrial function, which may have consequences for brain health, particularly when mitochondrial energy efficiency is critical.

Keywords:  atorvastatin; brain mitochondria; membrane potential; reactive oxygen species; respiration; simvastatin

DOI:  https://doi.org/10.3390/ijms25158494
J Lipid Res. 2024 Aug 08. pii: S0022-2275(24)00123-8. [Epub ahead of print] 100618

A high-resolution 13C NMR approach for profiling fatty acid unsaturation in lipid extracts and in live C. elegans.

Bruno Hernández Cravero, Gastón Prez, Verónica A Lombardo, Florencia V Guastaferri, Carla B Delprato, Silvia Altabe, Diego de Mendoza, Andres Binolfi.

  Unsaturated fatty acids (UFA) play a crucial role in central cellular processes in animals, including membrane function, development, and disease. Disruptions in UFA homeostasis can contribute to the onset of metabolic, cardiovascular, and neurodegenerative disorders. Consequently, there is a high demand for analytical techniques to study lipid compositions in live cells and multicellular organisms. Conventional analysis of UFA compositions in cells, tissues and organisms involves solvent extraction procedures coupled with analytical techniques such as gas chromatography,mass spectrometry (MS) and/or nuclear magnetic resonance (NMR) spectroscopy. As a non-destructive and non-targeted technique, NMR spectroscopy is uniquely capable of characterizing the chemical profiling of living cells and multicellular organisms. Here we use NMR spectroscopy to analyze C. elegans, enabling the determination of their lipid compositions and fatty acid unsaturation levels both in cell-free lipid extracts and in vivo. The NMR spectra of lipid extracts from wild-type and fat-3 mutant C. elegans strains revealed notable differences due to the absence of Δ-6 fatty acid desaturase activity, including the lack of arachidonic and eicosapentaenoic acyl chains. Uniform 13C-isotope labeling and high-resolution 2D solution-state NMR of live worms confirmed these findings, indicating that the signals originated from fast-tumbling lipid molecules within lipid droplets. Overall, this strategy permits the analysis of lipid storage in intact worms and has enough resolution and sensitivity to identify differences between wild type and mutant animals with impaired fatty acid desaturation. Our results establish methodological benchmarks for future investigations of fatty acid regulation in live C. elegans using NMR.

Keywords:  Arachidonic acid; C. elegans; Lipid droplets; Lipids; Lipids/Chemistry; Physical biochemistry; in-cell NMR; solution state NMR spectroscopy; unsaturated fatty acids

DOI:  https://doi.org/10.1016/j.jlr.2024.100618
Nat Commun. 2024 Aug 14. 15(1): 6979

Mitochondrial network reorganization and transient expansion during oligodendrocyte generation.

Xhoela Bame, Robert A Hill.

Oligodendrocyte precursor cells (OPCs) give rise to myelinating oligodendrocytes of the brain. This process persists throughout life and is essential for recovery from neurodegeneration. To better understand the cellular checkpoints that occur during oligodendrogenesis, we determined the mitochondrial distribution and morphometrics across the oligodendrocyte lineage in mouse and human cerebral cortex. During oligodendrocyte generation, mitochondrial content expands concurrently with a change in subcellular partitioning towards the distal processes. These changes are followed by an abrupt loss of mitochondria in the oligodendrocyte processes and myelin, coinciding with sheath compaction. This reorganization and extensive expansion and depletion take 3 days. Oligodendrocyte mitochondria are stationary over days while OPC mitochondrial motility is modulated by animal arousal state within minutes. Aged OPCs also display decreased mitochondrial size, volume fraction, and motility. Thus, mitochondrial dynamics are linked to oligodendrocyte generation, dynamically modified by their local microenvironment, and altered in the aging brain.

DOI: https://doi.org/10.1038/s41467-024-51016-2
bioRxiv. 2024 Jul 30. pii: 2024.07.30.605803. [Epub ahead of print]

Creation of a novel zebrafish model with low DHA status to study the role of maternal nutrition during neurodevelopment.

Katherine M Ranard, Bruce Appel.

  Docosahexaenoic acid (DHA), a dietary omega-3 fatty acid, is a major building block of brain cell membranes. Offspring rely on maternal DHA transfer to meet their neurodevelopmental needs, but DHA sources are lacking in the American diet. Low DHA status is linked to altered immune responses, white matter defects, impaired vision, and an increased risk of psychiatric disorders during development. However, the underlying cellular mechanisms involved are largely unknown, and advancements in the field have been limited by the existing tools and animal models. Zebrafish are an excellent model for studying neurodevelopmental mechanisms. Embryos undergo rapid external development and are optically transparent, enabling direct observation of individual cells and dynamic cell-cell interactions in a way that is not possible in rodents. Here, we create a novel DHA-deficient zebrafish model by 1) disrupting elovl2, a key gene in the DHA biosynthesis pathway, via CRISPR-Cas9 genome editing, and 2) feeding mothers a DHA-deficient diet. We show that low DHA status during development is associated with a small eye morphological phenotype and demonstrate that even the morphologically normal siblings exhibit dysregulated gene pathways related to vision and stress response. Future work using our zebrafish model could reveal the cellular and molecular mechanisms by which low DHA status leads to neurodevelopmental abnormalities and provide insight into maternal nutritional strategies that optimize infant brain health.

Keywords:  Nutrition; docosahexaenoic acid; elongation of very long-chain fatty acid 2; maternal diet; neurodevelopment; omega-3 fatty acids; zebrafish

DOI:  https://doi.org/10.1101/2024.07.30.605803
Proc Natl Acad Sci U S A. 2024 Aug 20. 121(34): e2409262121

Phosphorylation of Insig-2 mediates inhibition of fatty acid synthesis by polyunsaturated fatty acids.

Jing Tian, Joseph L Goldstein, Shili Li, Marc M Schumacher, Michael S Brown.

  Insig-1 and Insig-2 are endoplasmic reticulum (ER) proteins that inhibit lipid synthesis by blocking transport of sterol regulatory element-binding proteins (SREBP-1 and SREBP-2) from ER to Golgi. In the Golgi, SREBPs are processed proteolytically to release their transcription-activating domains, which enhance the synthesis of fatty acids, triglycerides, and cholesterol. Heretofore, the two Insigs have redundant functions, and there is no rationale for two isoforms. The current data identify a specific function for Insig-2. We show that eicosapentaenoic acid (EPA), a polyunsaturated fatty acid, inhibits fatty acid synthesis in human fibroblasts and rat hepatocytes by activating adenylate cyclase, which induces protein kinase A (PKA) to phosphorylate serine-106 in Insig-2. Phosphorylated Insig-2 inhibits the proteolytic processing of SREBP-1, thereby blocking fatty acid synthesis. Phosphorylated Insig-2 does not block the processing of SREBP-2, which activates cholesterol synthesis. Insig-1 lacks serine-106 and is not phosphorylated at this site. EPA inhibition of SREBP-1 processing was reduced by the replacement of serine-106 in Insig-2 with alanine or by treatment with KT5720, a PKA inhibitor. Inhibition did not occur in mutant human fibroblasts that possess Insig-1 but lack Insig-2. These data provide an Insig-2-specific mechanism for the long-known inhibition of fatty acid synthesis by polyunsaturated fatty acids.

Keywords:  SREBP-1; cyclic AMP; fatty acid synthesis; mammalian cells; phosphorylated Insig-2

DOI:  https://doi.org/10.1073/pnas.2409262121
J Neuroinflammation. 2024 Aug 11. 21(1): 199

Maternal n-3 enriched diet reprograms the offspring neurovascular transcriptome and blunts inflammation induced by endotoxin in the neonate.

Tetyana Chumak, Amandine Jullienne, C Joakim Ek, Maryam Ardalan, Pernilla Svedin, Ryan Quan, Arjang Salehi, Sirus Salari, Andre Obenaus, Zinaida S Vexler, Carina Mallard.

  Infection during the perinatal period can adversely affect brain development, predispose infants to ischemic stroke and have lifelong consequences. We previously demonstrated that diet enriched in n-3 polyunsaturated fatty acids (n-3 PUFA) transforms brain lipid composition in the offspring and protects the neonatal brain from stroke, in part by blunting injurious immune responses. Critical to the interface between the brain and systemic circulation is the vasculature, endothelial cells in particular, that support brain homeostasis and provide a barrier to systemic infection. Here, we examined whether maternal PUFA-enriched diets exert reprograming of endothelial cell signalling in postnatal day 9 mice after modeling aspects of infection using LPS. Transcriptome analysis was performed on microvessels isolated from brains of pups from dams maintained on 3 different maternal diets from gestation day 1: standard, n-3 enriched or n-6 enriched diets. Depending on the diet, in endothelial cells LPS produced distinct regulation of pathways related to immune response, cell cycle, extracellular matrix, and angiogenesis. N-3 PUFA diet enabled higher immune reactivity in brain vasculature, while preventing imbalance of cell cycle regulation and extracellular matrix cascades that accompanied inflammatory response in standard diet. Cytokine analysis revealed a blunted LPS response in blood and brain of offspring from dams on n-3 enriched diet. Analysis of cerebral vasculature in offspring in vivo revealed no differences in vessel density. However, vessel complexity was decreased in response to LPS at 72 h in standard and n-6 diets. Thus, LPS modulates specific transcriptomic changes in brain vessels of offspring rather than major structural vessel characteristics during early life. N-3 PUFA-enriched maternal diet in part prevents an imbalance in homeostatic processes, alters inflammation and ultimately mitigates changes to the complexity of surface vessel networks that result from infection. Importantly, maternal diet may presage offspring neurovascular outcomes later in life.

Keywords:  Brain angioarchitecture; Brain vessel transcriptomics; Maternal diet; Neonatal; Neuroinflammation; PUFA

DOI:  https://doi.org/10.1186/s12974-024-03191-8
Aging Dis. 2024 Jul 30.

Mitochondrial Transfer in the Neurovascular Unit, Not Only for Energy Rescue: A Systematic Review.

Daqiang Zhou, Sibo Yang, Jiehong Wu, Yanan Li, Huijuan Jin, Yan Luo, Feng Zhang, Junjie Jiang, Bo Hu, Yifan Zhou.

Despite substantial evidence highlighting molecular communication within the components of neurovascular units (NVU), the interactions at the organelle level have been insufficiently explored in recent decades. Mitochondria, for instance, beyond their traditional role as energy supply for intracellular metabolism and survival, provide a novel perspective on intercellular connections through mitochondrial transfer. These transferred mitochondria not only carry bioactive molecules but also signal to mitigate risks in both healthy and pathological conditions. In this review, we summarized mitochondrial transfer events, relevant routes, and underlying molecular mechanisms originating from diverse cell populations within NVU. We particularly focus on the therapeutic potential of this mechanism in treating central nervous system disorders, notably neurodegenerative diseases marked by mitochondrial dysfunction and then highlight the promising prospects of exogenous mitochondrial supplementation as a treatment target.

DOI: https://doi.org/10.14336/AD.2024.0461
Neuron. 2024 Aug 08. pii: S0896-6273(24)00537-3. [Epub ahead of print]

Microglia are not necessary for maintenance of blood-brain barrier properties in health, but PLX5622 alters brain endothelial cholesterol metabolism.

Caterina P Profaci, Sean S Harvey, Kaja Bajc, Tony Z Zhang, Danielle A Jeffrey, Alexander Z Zhang, Kelsey M Nemec, Hayk Davtyan, Carleigh A O'Brien, Gabriel L McKinsey, Aaron Longworth, Timothy P McMullen, Joia K Capocchi, Jessica G Gonzalez, Devon A Lawson, Thomas D Arnold, Dimitrios Davalos, Mathew Blurton-Jones, Fabrice Dabertrand, F Chris Bennett, Richard Daneman.

  Microglia, the resident immune cells of the central nervous system, are intimately involved in the brain's most basic processes, from pruning neural synapses during development to preventing excessive neuronal activity throughout life. Studies have reported both helpful and harmful roles for microglia at the blood-brain barrier (BBB) in the context of disease. However, less is known about microglia-endothelial cell interactions in the healthy brain. To investigate the role of microglia at a healthy BBB, we used the colony-stimulating factor 1 receptor (CSF1R) inhibitor PLX5622 to deplete microglia and analyzed the BBB ultrastructure, permeability, and transcriptome. Interestingly, we found that, despite their direct contact with endothelial cells, microglia are not necessary for the maintenance of BBB structure, function, or gene expression in the healthy brain. However, we found that PLX5622 treatment alters brain endothelial cholesterol metabolism. This effect was independent from microglial depletion, suggesting that PLX5622 has off-target effects on brain vasculature.

Keywords:  CSF1R; LDLR; PLX5622; blood-brain barrier; cholesterol; endothelial cells; genetic microglial depletion; microglia; off-target effects; vasculature

DOI:  https://doi.org/10.1016/j.neuron.2024.07.015
J Cell Biol. 2024 Nov 04. pii: e202307036. [Epub ahead of print]223(11):

Mitochondrial-derived compartments remove surplus proteins from the outer mitochondrial membrane.

Zachary N Wilson, Sai Sangeetha Balasubramaniam, Sara Wong, Max-Hinderk Schuler, Mitchell J Wopat, Adam L Hughes.

The outer mitochondrial membrane (OMM) creates a boundary that imports most of the mitochondrial proteome while removing extraneous or damaged proteins. How the OMM senses aberrant proteins and remodels to maintain OMM integrity remains unresolved. Previously, we identified a mitochondrial remodeling mechanism called the mitochondrial-derived compartment (MDC) that removes a subset of the mitochondrial proteome. Here, we show that MDCs specifically sequester proteins localized only at the OMM, providing an explanation for how select mitochondrial proteins are incorporated into MDCs. Remarkably, selective sorting into MDCs also occurs within the OMM, as subunits of the translocase of the outer membrane (TOM) complex are excluded from MDCs unless assembly of the TOM complex is impaired. Considering that overloading the OMM with mitochondrial membrane proteins or mistargeted tail-anchored membrane proteins induces MDCs to form and sequester these proteins, we propose that one functional role of MDCs is to create an OMM-enriched trap that segregates and sequesters excess proteins from the mitochondrial surface.

DOI: https://doi.org/10.1083/jcb.202307036
J Biol Chem. 2024 Aug 09. pii: S0021-9258(24)02163-X. [Epub ahead of print] 107662

Differential utilization of vitamin B12-dependent and independent pathways for propionate metabolism across human cells.

Harsha Gouda, Yuanyuan Ji, Sneha Rath, David Watkins, David Rosenblatt, Vamsi Mootha, Jace W Jones, Ruma Banerjee.

Propionic acid links the oxidation of branched-chain amino acids and odd-chain fatty acids to the TCA cycle. Gut microbes ferment complex fiber remnants, generating high concentrations of short chain fatty acids, acetate, propionate and butyrate, which are shared with the host as fuel sources. Analysis of vitamin B12-dependent propionate utilization in skin biopsy samples has been used to characterize and diagnose underlying inborn errors of cobalamin (or B12) metabolism. In these cells, the B12-dependent enzyme, methylmalonyl-CoA mutase (MMUT), plays a central role in funneling propionate to the TCA cycle intermediate, succinate. Our understanding of the fate of propionate in other cell types, specifically, the involvement of the β-oxidation-like and methylcitrate pathways, is limited. In this study, we have used [14C]-propionate tracing in combination with genetic ablation or inhibition of MMUT, to reveal the differential utilization of the B12-dependent and independent pathways for propionate metabolism in fibroblast versus colon cell lines. We demonstrate that itaconate can be used as a tool to investigate MMUT-dependent propionate metabolism in cultured cell lines. While MMUT gates the entry of propionate carbons into the TCA cycle in fibroblasts, colon-derived cell lines exhibit a quantitatively significant or exclusive reliance on the β-oxidation-like pathway. Lipidomics and metabolomics analyses reveal that propionate elicits pleiotropic changes, including an increase in odd-chain glycerophospholipids, and perturbations in the purine nucleotide cycle and arginine/nitric oxide metabolism. The metabolic rationale and the regulatory mechanisms underlying the differential reliance on propionate utilization pathways at a cellular, and possibly tissue level, warrant further elucidation.

DOI: https://doi.org/10.1016/j.jbc.2024.107662
Sci Rep. 2024 08 11. 14(1): 18641

Effects of a high-fat diet on cognition and brain distribution of intranasal insulin in E3 and E4 male and female mice.

Ariel Chaklai, Elizabeth M Rhea, Abigail O'Niel, Alice Babin, Riley Weaver, Sarah Pemberton, William A Banks, Jacob Raber.

  There are genetic and environmental risk factors that contribute to the development of cognitive decline in Alzheimer's disease (AD). Some of these include the genetic predisposition of the apolipoprotein E4 genotype, consuming a high-fat diet (HFD), and the female sex. Brain insulin receptor resistance and deficiency have also been shown to be associated with AD and cognitive impairment. Intranasal (INL) insulin enhances cognition in AD, but the response varies due to genotype, diet, and sex. We investigated here the combination of these risk factors in a humanized mouse model, expressing E3 or E4, following a HFD in males and females on cognitive performance and the brain distribution of insulin following INL delivery. The HFD had a negative effect on survival in male mice only, requiring sex to be collapsed. We found many genotype, diet, and genotype x diet effects in anxiety-related tasks. We further found beneficial effects of INL insulin in our memory tests, with the most important findings showing a beneficial effect of INL insulin in mice on a HFD. We found insulin distribution throughout the brain after INL delivery was largely unaffected by diet and genotype, indicating these susceptible groups can still receive adequate levels of insulin following INL delivery. Our findings support the involvement of brain insulin signaling in cognition and highlight continuing efforts investigating mechanisms resulting from treatment with INL insulin.

Keywords:  Apolipoprotein E; Cognition; High-fat diet; Intranasal insulin; Sex

DOI:  https://doi.org/10.1038/s41598-024-62053-8
medRxiv. 2024 Jun 20. pii: 2024.06.19.24308302. [Epub ahead of print]

PSMF1 variants cause a phenotypic spectrum from early-onset Parkinson's disease to perinatal lethality by disrupting mitochondrial pathways.

Francesca Magrinelli, Christelle Tesson, Plamena R Angelova, Ainara Salazar-Villacorta, Jose A Rodriguez, Annarita Scardamaglia, Brian Hon-Yin Chung, Matthew Jaconelli, Barbara Vona, Noemi Esteras, Anna Ka-Yee Kwong, Thomas Courtin, Reza Maroofian, Shahryar Alavi, Raja Nirujogi, Mariasavina Severino, Patrick A Lewis, Stephanie Efthymiou, Benjamin O'Callaghan, Rebecca Buchert, Linda Sofan, Pawel Lis, Chloé Pinon, Guido J Breedveld, Martin Man-Chun Chui, David Murphy, Vanessa Pitz, Mary B Makarious, Marlene Cassar, Bassem A Hassan, Sana Iftikhar, Clarissa Rocca, Peter Bauer, Michele Tinazzi, Marina Svetel, Bedia Samanci, Haşmet A Hanağası, Basar Bilgiç, José A Obeso, Monica M Kurtis, Guillaume Cogan, Ayşe Nazlı Başak, Güneş Kiziltan, Tuğçe Gül, Gül Yalçın, Bülent Elibol, Nina Barišić, Earny Wei-Sen Ng, Sze-Shing Fan, Tova Hershkovitz, Karin Weiss, Javeria Raza Alvi, Tipu Sultan, Issam Azmi Alkhawaja, Tawfiq Froukh, Hadeel Abdollah E Alrukban, Christine Fauth, Ulrich A Schatz, Thomas Zöggeler, Michael Zech, Karen Stals, Vinod Varghese, Sonia Gandhi, Cornelis Blauwendraat, John A Hardy, Suzanne Lesage, Vincenzo Bonifati, Tobias B Haack, Aida M Bertoli-Avella, Robert Steinfeld, Dario R Alessi, Hermann Steller, Alexis Brice, Andrey Y Abramov, Kailash P Bhatia, Henry Houlden.

Dissecting biological pathways highlighted by Mendelian gene discovery has provided critical insights into the pathogenesis of Parkinson's disease (PD) and neurodegeneration. This approach ultimately catalyzes the identification of potential biomarkers and therapeutic targets. Here, we identify PSMF1 as a new gene implicated in PD and childhood neurodegeneration. We find that biallelic PSMF1 missense and loss-of-function variants co-segregate with phenotypes from early-onset PD and parkinsonism to perinatal lethality with neurological manifestations across 15 unrelated pedigrees with 22 affected subjects, showing clear genotype-phenotype correlation. PSMF1 encodes the proteasome regulator PSMF1/PI31, a highly conserved, ubiquitously expressed partner of the 20S proteasome and neurodegeneration-associated F-box-O 7 and valosin-containing proteins. We demonstrate that PSMF1 variants impair mitochondrial membrane potential, dynamics and mitophagy in patient-derived fibroblasts. Additionally, we develop models of psmf1 knockdown Drosophila and Psmf1 conditional knockout mouse exhibiting age-dependent motor impairment, with diffuse gliosis in mice. These findings unequivocally link defective PSMF1 to early-onset PD and neurodegeneration and suggest mitochondrial dysfunction as a mechanistic contributor.

DOI: https://doi.org/10.1101/2024.06.19.24308302
Front Pharmacol. 2024 ;15 1434568

Huanshaodan regulates microglial glucose metabolism reprogramming to alleviate neuroinflammation in AD mice through mTOR/HIF-1α signaling pathway.

Congcong Shang, Yunfang Su, Jinlian Ma, Zhonghua Li, Pan Wang, Huifen Ma, Junying Song, Zhenqiang Zhang.

  Abnormal glucose metabolism in microglial is closely associated with Alzheimer's disease (AD). Reprogramming of microglial glucose metabolism is centered on regulating the way in which microglial metabolize glucose to alter microglial function. Therefore, reprogramming microglial glucose metabolism is considered as a therapeutic strategy for AD. Huanshaodan (HSD) is a Chinese herbal compound which shows significant efficacy in treating AD, however, the precise mechanism by which HSD treats AD remains unclear. This study is aim to investigate whether HSD exerts anti-AD effects by regulating the metabolic reprogramming of microglial through the mTOR/HIF-1α signaling pathway. SAMP8 mice and BV2 cells were used to explore the alleviative effect of HSD on AD and the molecular mechanism in vivo and in vitro. The pharmacodynamic effects of HSD was evaluated by behavioral tests. The pathological deposition of Aβ in brain of mice was detected by immunohistochemistry. ELISA method was used to measure the activity of HK2 and the expression of PKM2, IL-6 and TNF-α in hippocampus and cortex tissues of mice. Meanwhile, proteins levels of p-mTOR, mTOR, HIF-1α, CD86, Arg1 and IL-1β were detected by Western-blot. LPS-induced BV2 cells were treated with HSD-containing serum. The analysis of the expression profiles of the CD86 and CD206 markers by flow cytometry allows us to distinguish the BV2 polarization. Glucose, lactic acid, ATP, IL-6 and TNF-α levels, as well as lactate dehydrogenase and pyruvate dehydrogenase activities were evaluated in the BV2. Western-blot analysis was employed to detect mTOR, p-mTOR, HIF-1α and IL-1β levels in BV2. And the mTOR agonist MHY1485 (MHY) was chosen to reverse validate. In this study, it is found that HSD improved cognitive impairment in SAMP8 mice and reduced Aβ deposition, suppressed the levels of glycolysis and neuroinflammation in mice. In LPS-induced BV2 cells, HSD also regulated glycolysis and neuroinflammation, and suppressed the mTOR/HIF-1α signaling pathway. More importantly, these effects were reversed by MHY. It is demonstrated that HSD regulated microglial glucose metabolism reprogramming by inhibiting the mTOR/HIF-1α signaling pathway, alleviated neuroinflammation, and exerted anti-AD effects. This study provided scientific evidence for the clinical application of HSD for treating AD.

Keywords:  Alzheimer’s disease; Huanshaodan; mTOR/HIF-1α signaling pathway; microglial glucose metabolism reprogramming; neuroinflammation

DOI:  https://doi.org/10.3389/fphar.2024.1434568
Methods Mol Biol. 2024 ;2831 145-177

3D Reconstruction of the Mitochondrial Network within the Neuronal Soma from SBF-SEM Volume Data.

Jane Tweedy, Ross Laws, George Merces, Tracey Davey, Amy K Reeve, Amy E Vincent.

  Neurons contain three compartments, the soma, long axon, and dendrites, which have distinct energetic and biochemical requirements. Mitochondria feature in all compartments and regulate neuronal activity and survival, including energy generation and calcium buffering alongside other roles including proapoptotic signaling and steroid synthesis. Their dynamicity allows them to undergo constant fusion and fission events in response to the changing energy and biochemical requirements. These events, termed mitochondrial dynamics, impact their morphology and a variety of three-dimensional (3D) morphologies exist within the neuronal mitochondrial network. Distortions in the morphological profile alongside mitochondrial dysfunction may begin in the neuronal soma in ageing and common neurodegenerative disorders. However, 3D morphology cannot be comprehensively examined in flat, two-dimensional (2D) images. This highlights a need to segment mitochondria within volume data to provide a representative snapshot of the processes underpinning mitochondrial dynamics and mitophagy within healthy and diseased neurons. The advent of automated high-resolution volumetric imaging methods such as Serial Block Face Scanning Electron Microscopy (SBF-SEM) as well as the range of image software packages allow this to be performed.We describe and evaluate a method for randomly sampling mitochondria and manually segmenting their whole morphologies within randomly generated regions of interest of the neuronal soma from SBF-SEM image stacks. These 3D reconstructions can then be used to generate quantitative data about mitochondrial and cellular morphologies. We further describe the use of a macro that automatically dissects the soma and localizes 3D mitochondria into the subregions created.

Keywords:  3D reconstruction; Ageing; Mitochondria; Morphology; Neurodegeneration; SBF-SEM; Three-dimensional; Two-dimensional; mtDNA

DOI:  https://doi.org/10.1007/978-1-0716-3969-6_11