bims-medebr 2023-09-03 papers

bims-medebr

Biomed News

on Metabolism of the developing brain

Issue of 2023–09–03
twenty papers selected by
Regina F. Fernández, Johns Hopkins University

The translational potential of cholesterol-based therapies for neurological disease.
Generation and characterization of a knock-in mouse model for spastic tetraplegia, thin corpus callosum, and progressive microcephaly (SPATCCM).
Metabolic partitioning in the brain and its hijacking by glioblastoma.
The Effects of CYP27A1 and CYP7B1 on cognitive function: two mouse models in Comparison.
Astrocytic FoxO1 in the hypothalamus regulates metabolic homeostasis by coordinating neuropeptide Y neuron activity.
Dietary fatty acids differentially impact phagocytosis, inflammatory gene expression, and mitochondrial respiration in microglial and neuronal cell models.
Hyperpolarized 13C metabolic imaging detects long-lasting metabolic alterations following mild repetitive traumatic brain injury.
A defect in mitochondrial fatty acid synthesis impairs iron metabolism and causes elevated ceramide levels.
Several dementia subtypes and mild cognitive impairment share brain reduction of neurotransmitter precursor amino acids, impaired energy metabolism, and lipid hyperoxidation.
The malate-aspartate shuttle is important for de novo serine biosynthesis.
Flow cytometric analysis of phosphatidylcholine metabolism using organelle-selective click labeling.
Mitochondrial vulnerability to oxidation in human brain organoids modelling Alzheimer's disease.
Gestational stress decreases postpartum mitochondrial respiration in the prefrontal cortex of female rats.
Hyperpolarized [2-13C]pyruvate MR molecular imaging with whole brain coverage.
Sialic acid biosynthesis pathway blockade disturbs neuronal network formation in human iPSC-derived excitatory neurons.
Mitochondrial phospholipid metabolism in health and disease.
A G1528C Hadha knock-in mouse model recapitulates aspects of human clinical phenotypes for long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency.
Mass Spectrometry-based Lipidomics, Lipid Bioenergetics, and Web Tool for Lipid Profiling and Quantification in Human Cells.
Interactions of Cellular Energetic Gene Clusters in the Alzheimer's Mouse Brain.
Insertases Scramble Lipids: Molecular Simulations of MTCH2.

Nat Rev Neurol. 2023 Aug 29.

The translational potential of cholesterol-based therapies for neurological disease.

Marta Valenza, Giulia Birolini, Elena Cattaneo.

Cholesterol is an important metabolite and membrane component and is enriched in the brain owing to its role in neuronal maturation and function. In the adult brain, cholesterol is produced locally, predominantly by astrocytes. When cholesterol has been used, recycled and catabolized, the derivatives are excreted across the blood-brain barrier. Abnormalities in any of these steps can lead to neurological dysfunction. Here, we examine how precise interactions between cholesterol production and its use and catabolism in neurons ensures cholesterol homeostasis to support brain function. As an example of a neurological disease associated with cholesterol dyshomeostasis, we summarize evidence from animal models of Huntington disease (HD), which demonstrate a marked reduction in cholesterol biosynthesis with clinically relevant consequences for synaptic activity and cognition. In addition, we examine the relationship between cholesterol loss in the brain and cognitive decline in ageing. We then present emerging therapeutic strategies to restore cholesterol homeostasis, focusing on evidence from HD mouse models.

DOI: https://doi.org/10.1038/s41582-023-00864-5
Mamm Genome. 2023 Aug 29.

Generation and characterization of a knock-in mouse model for spastic tetraplegia, thin corpus callosum, and progressive microcephaly (SPATCCM).

Megan L Ratz-Mitchem, Greg Leary, Andrea Grindeland, Derek Silvius, Joseph Guter, Michael P Kavanaugh, Teresa M Gunn.

Solute carrier family 1 member 4 (SLC1A4), also referred to as Alanine/Serine/Cysteine/Threonine-preferring Transporter 1 (ASCT1), is a sodium-dependent neutral amino acid transporter. It is expressed in many tissues, including the brain, where it is expressed primarily on astrocytes and plays key roles in neuronal differentiation and development, maintaining neurotransmitter homeostasis, and N-methyl-D-aspartate neurotransmission, through regulation of L- and D-serine. Mutations in SLC1A4 are associated with the rare autosomal recessive neurodevelopmental disorder spastic tetraplegia, thin corpus callosum, and progressive microcephaly (SPATCCM, OMIM 616657). Psychomotor development and speech are significantly impaired in these patients, and many develop seizures. We generated and characterized a knock-in mouse model for the most common mutant allele, which results in a single amino acid change (p.Glu256Lys, or E256K). Homozygous mutants had increased D-serine uptake in the brain, microcephaly, and thin corpus callosum and cortex layer 1. While p.E256K homozygotes showed some significant differences in exploratory behavior relative to wildtype mice, their performance in assays for motor coordination, endurance, learning, and memory was normal, and they showed no significant differences in long-term potentiation. Taken together, these results indicate that the impact of the p.E256K mutation on cognition and motor function is minimal in mice, but other aspects of SLC1A4 function in the brain are conserved. Mice homozygous for p.E256K may be a good model for understanding the developmental basis of the corpus callosum and microcephaly phenotypes observed in SPATCCM patients and assessing whether they are rescued by serine supplementation.

DOI: https://doi.org/10.1007/s00335-023-10013-4
Genes Dev. 2023 Aug 30.

Metabolic partitioning in the brain and its hijacking by glioblastoma.

Jed de Ruiter Swain, Evdokia Michalopoulou, Evan K Noch, Michael J Lukey, Linda Van Aelst.

  The different cell types in the brain have highly specialized roles with unique metabolic requirements. Normal brain function requires the coordinated partitioning of metabolic pathways between these cells, such as in the neuron-astrocyte glutamate-glutamine cycle. An emerging theme in glioblastoma (GBM) biology is that malignant cells integrate into or "hijack" brain metabolism, co-opting neurons and glia for the supply of nutrients and recycling of waste products. Moreover, GBM cells communicate via signaling metabolites in the tumor microenvironment to promote tumor growth and induce immune suppression. Recent findings in this field point toward new therapeutic strategies to target the metabolic exchange processes that fuel tumorigenesis and suppress the anticancer immune response in GBM. Here, we provide an overview of the intercellular division of metabolic labor that occurs in both the normal brain and the GBM tumor microenvironment and then discuss the implications of these interactions for GBM therapy.

Keywords:  IDH mutation; brain metabolism; cancer metabolism; glioblastoma; glioma; glioma therapy; immune suppression; tumor microenvironment

DOI:  https://doi.org/10.1101/gad.350693.123
J Steroid Biochem Mol Biol. 2023 Aug 28. pii: S0960-0760(23)00142-5. [Epub ahead of print] 106387

The Effects of CYP27A1 and CYP7B1 on cognitive function: two mouse models in Comparison.

Julen Goikolea, Maria Latorre-Leal, Christina Tsagkogianni, Sonja Pikkupeura, Balazs Gulyas, Angel Cedazo Minguez, Raul Loera-Valencia, Ingemar Björkhem, Patricia Rodriguez Rodriguez, Silvia Maioli.

  The oxysterol 27-hydroxycholesterol (27OHC) is produced by the enzyme sterol 27-hydroxylase (Cyp27A1) and is mainly catabolized to 7α-Hydroxy-3-oxo-4-cholestenoic acid (7-HOCA) by the enzyme cytochrome P-450 oxysterol 7α-hydroxylase (Cyp7B1). 27OHC is mostly produced in the liver and can reach the brain by crossing the blood-brain barrier. A large body of evidence shows that CYP27A1 overexpression and high levels of 27OHC have a detrimental effect on the brain, causing cognitive and synaptic dysfunction together with a decrease in glucose uptake in mice. In this work, we analyzed two mouse models with high levels of 27OHC: Cyp7B1 knock-out mice and CYP27A1 overexpressing mice. Despite the accumulation of 27OHC in both models, Cyp7B1 knock-out mice maintained intact learning and memory capacities, neuronal morphology, and brain glucose uptake over time. Neurons treated with the Cyp7B1 metabolite 7-HOCA did not show changes in synaptic genes and 27OHC-treated Cyp7B1 knock-out neurons could not counteract 27OHC detrimental effects. This suggests that 7-HOCA and Cyp7B1 deletion in neurons do not mediate the neuroprotective effects observed in Cyp7B1 knock-out animals. RNA-seq of neuronal nuclei sorted from Cyp7B1 knock-out brains revealed upregulation of genes likely to confer neuroprotection to these animals. Differently from Cyp7B1 knock-out mice, transcriptomic data from CYP27A1 overexpressing neurons showed significant downregulation of genes associated with synaptic function and several metabolic processes. Our results suggest that the differences observed in the two models may be mediated by the higher levels of Cyp7B1 substrates such as 25-hydroxycholesterol and 3β-Adiol in the knock-out mice and that CYP27A1 overexpressing mice may be a more suitable model for studying 27-OHC-specific signaling. We believe that future studies on Cyp7B1 and Cyp27A1 will contribute to a better understanding of the pathogenic mechanisms of neurodegenerative diseases like Alzheimer's disease and may lead to potential new therapeutic approaches.

Keywords:  27-hydroxycholesterol; CYP27A1; CYP7B1; cholesterol metabolism; memory

DOI:  https://doi.org/10.1016/j.jsbmb.2023.106387
Glia. 2023 Sep 01.

Astrocytic FoxO1 in the hypothalamus regulates metabolic homeostasis by coordinating neuropeptide Y neuron activity.

Khanh Van Doan, Le Trung Tran, Dong Joo Yang, Thu Thi Anh Ha, Thi Dang Mai, Seul Ki Kim, Ronald A DePinho, Dong-Min Shin, Yun-Hee Choi, Ki Woo Kim.

  The forkhead box transcription factor O1 (FoxO1) is expressed ubiquitously throughout the central nervous system, including in astrocytes, the most prevalent glial cell type in the brain. While the role of FoxO1 in hypothalamic neurons in controlling food intake and energy balance is well-established, the contribution of astrocytic FoxO1 in regulating energy homeostasis has not yet been determined. In the current study, we demonstrate the essential role of hypothalamic astrocytic FoxO1 in maintaining normal neuronal activity in the hypothalamus and whole-body glucose metabolism. Inhibition of FoxO1 function in hypothalamic astrocytes shifts the cellular metabolism from glycolysis to oxidative phosphorylation, enhancing astrocyte ATP production and release meanwhile decreasing astrocytic export of lactate. As a result, specific deletion of astrocytic FoxO1, particularly in the hypothalamus, causes a hyperactivation of hypothalamic neuropeptide Y neurons, which leads to an increase in acute feeding and impaired glucose regulation and ultimately results in diet-induced obesity and systemic glucose dyshomeostasis.

Keywords:  FoxO1; astrocyte; energy homeostasis; glucose metabolism; hypothalamus

DOI:  https://doi.org/10.1002/glia.24448
Front Cell Neurosci. 2023 ;17 1227241

Dietary fatty acids differentially impact phagocytosis, inflammatory gene expression, and mitochondrial respiration in microglial and neuronal cell models.

Michael J Butler, Sabrina E Mackey-Alfonso, Nashali Massa, Kedryn K Baskin, Ruth M Barrientos.

  The consumption of diets high in saturated fatty acids and/or refined carbohydrates are associated with neuroinflammation, cognitive dysfunction, and neurodegenerative disease. In contrast, diets high in polyunsaturated fatty acids are associated with anti-inflammatory and neuroprotective effects. We have previously shown that high fat diet (HFD) consumption increases saturated fatty acids and decreases polyunsaturated fatty acids in the hippocampus. We have further shown that HFD elicits exaggerated neuroinflammation and reduced synaptic elements, and results in robust memory deficits in aged rats. Here, we examined the impact of palmitate, an abundant dietary saturated fat, on a variety of cellular responses in BV2 microglia and HippoE-14 neurons, and the extent to which the omega-3 fatty acid, docosahexaenoic acid (DHA), would buffer against these responses. Our data demonstrate that DHA pretreatment prevents or partially attenuates palmitate-induced alterations in proinflammatory, endoplasmic reticulum stress, and mitochondrial damage-associated gene expression in both cell types. Furthermore, we show that synaptoneurosomes isolated from aged, HFD-fed mice are engulfed by BV2 microglia at a faster rate than synaptoneurosomes isolated from aged, chow-fed mice, suggesting HFD alters signaling at synapses to hasten their engulfment by microglia. Consistent with this notion, we found modest increases in complement proteins and a decrease in CD47 protein expression on synaptoneurosomes isolated from the hippocampus of aged, HFD-fed mice. Interestingly, palmitate reduced BV2 microglial phagocytosis, but only of synaptoneurosomes isolated from chow-fed mice, an effect that was prevented by DHA pretreatment. Lastly, we measured the impact of palmitate and DHA on mitochondrial function in both microglial and neuronal cell models using the Seahorse XFe96 Analyzer. These data indicate that DHA pretreatment does not mitigate palmitate-induced reductions in mitochondrial respiration in BV2 microglia and HippoE-14 neurons, suggesting DHA may be acting downstream of mitochondrial function to exert its protective effects. Together, this study provides evidence that DHA can ameliorate the negative impact of palmitate on a variety of cellular functions in microglia- and neuron-like cells.

Keywords:  inflammation; lipids; metabolism; nutrition; synapse

DOI:  https://doi.org/10.3389/fncel.2023.1227241
Res Sq. 2023 Aug 14. pii: rs.3.rs-3166656. [Epub ahead of print]

Hyperpolarized 13C metabolic imaging detects long-lasting metabolic alterations following mild repetitive traumatic brain injury.

Myriam Chaumeil, Caroline Guglielmetti, Kai Qiao, Brice Tiret, Mustafa Ozen, Karen Krukowski, Amber Nolan, Maria Serena Paladini, Carlos Lopez, Susanna Rosi.

Career athletes, active military, and head trauma victims are at increased risk for mild repetitive traumatic brain injury (rTBI), a condition that contributes to the development of epilepsy and neurodegenerative diseases. Standard clinical imaging fails to identify rTBI-induced lesions, and novel non-invasive methods are needed. Here, we evaluated if hyperpolarized 13 C magnetic resonance spectroscopic imaging (HP 13 C MRSI) could detect long-lasting changes in brain metabolism 3.5 months post-injury in a rTBI mouse model. Our results show that this metabolic imaging approach can detect changes in cortical metabolism at that timepoint, whereas multimodal MR imaging did not detect any structural or contrast alterations. Using Machine Learning, we further show that HP 13 C MRSI parameters can help classify rTBI vs. Sham and predict long-term rTBI-induced behavioral outcomes. Altogether, our study demonstrates the potential of metabolic imaging to improve detection, classification and outcome prediction of previously undetected rTBI.

DOI: https://doi.org/10.21203/rs.3.rs-3166656/v1
Nat Metab. 2023 Aug 31.

A defect in mitochondrial fatty acid synthesis impairs iron metabolism and causes elevated ceramide levels.

Undiagnosed Diseases Network

In most eukaryotic cells, fatty acid synthesis (FAS) occurs in the cytoplasm and in mitochondria. However, the relative contribution of mitochondrial FAS (mtFAS) to the cellular lipidome is not well defined. Here we show that loss of function of Drosophila mitochondrial enoyl coenzyme A reductase (Mecr), which is the enzyme required for the last step of mtFAS, causes lethality, while neuronal loss of Mecr leads to progressive neurodegeneration. We observe a defect in Fe-S cluster biogenesis and increased iron levels in flies lacking mecr, leading to elevated ceramide levels. Reducing the levels of either iron or ceramide suppresses the neurodegenerative phenotypes, indicating an interplay between ceramide and iron metabolism. Mutations in human MECR cause pediatric-onset neurodegeneration, and we show that human-derived fibroblasts display similar elevated ceramide levels and impaired iron homeostasis. In summary, this study identifies a role of mecr/MECR in ceramide and iron metabolism, providing a mechanistic link between mtFAS and neurodegeneration.

DOI: https://doi.org/10.1038/s42255-023-00873-0
Front Aging Neurosci. 2023 ;15 1237469

Several dementia subtypes and mild cognitive impairment share brain reduction of neurotransmitter precursor amino acids, impaired energy metabolism, and lipid hyperoxidation.

Roberto Aquilani, Matteo Cotta Ramusino, Roberto Maestri, Paolo Iadarola, Mirella Boselli, Giulia Perini, Federica Boschi, Maurizia Dossena, Anna Bellini, Daniela Buonocore, Enrico Doria, Alfredo Costa, Manuela Verri.

   Objective: Dementias and mild cognitive impairment (MCI) are associated with variously combined changes in the neurotransmitter system and signaling, from neurotransmitter synthesis to synaptic binding. The study tested the hypothesis that different dementia subtypes and MCI may share similar reductions of brain availability in amino acid precursors (AAPs) of neurotransmitter synthesis and concomitant similar impairment in energy production and increase of oxidative stress, i.e., two important metabolic alterations that impact neurotransmission.
Materials and methods: Sixty-five demented patients (Alzheimer's disease, AD, n = 44; frontotemporal disease, FTD, n = 13; vascular disease, VaD, n = 8), 10 subjects with MCI and 15 control subjects (CTRL) were recruited for this study. Cerebrospinal fluid (CSF) and plasma levels of AAPs, energy substrates (lactate, pyruvate), and an oxidative stress marker (malondialdehyde, MDA) were measured in all participants.
Results: Demented patients and subjects with MCI were similar for age, anthropometric parameters, biohumoral variables, insulin resistance (HOMA index model), and CSF neuropathology markers. Compared to age-matched CTRL, both demented patients and MCI subjects showed low CSF AAP tyrosine (precursor of dopamine and catecholamines), tryptophan (precursor of serotonin), methionine (precursor of acetylcholine) limited to AD and FTD, and phenylalanine (an essential amino acid largely used for protein synthesis) (p = 0.03 to <0.0001). No significant differences were found among dementia subtypes or between each dementia subtype and MCI subjects. In addition, demented patients and MCI subjects, compared to CTRL, had similar increases in CSF and plasma levels of pyruvate (CSF: p = 0.023 to <0.0001; plasma: p < 0.002 to <0.0001) and MDA (CSF: p < 0.035 to 0.002; plasma: p < 0.0001). Only in AD patients was the CSF level of lactate higher than in CTRL (p = 0.003). Lactate/pyruvate ratios were lower in all experimental groups than in CTRL.
Conclusion: AD, FTD, and VaD dementia patients and MCI subjects may share similar deficits in AAPs, partly in energy substrates, and similar increases in oxidative stress. These metabolic alterations may be due to AAP overconsumption following high brain protein turnover (leading to phenylalanine reductions), altered mitochondrial structure and function, and an excess of free radical production. All these metabolic alterations may have a negative impact on synaptic plasticity and activity.

Keywords:  cerebrospinal fluid amino acid precursors of neurotransmitters; dementias; energetic substrates; mild cognitive impairment; oxidative stress

DOI:  https://doi.org/10.3389/fnagi.2023.1237469
Cell Rep. 2023 Aug 29. pii: S2211-1247(23)01054-9. [Epub ahead of print]42(9): 113043

The malate-aspartate shuttle is important for de novo serine biosynthesis.

Melissa H Broeks, Nils W F Meijer, Denise Westland, Marjolein Bosma, Johan Gerrits, Hannah M German, Jolita Ciapaite, Clara D M van Karnebeek, Ronald J A Wanders, Fried J T Zwartkruis, Nanda M Verhoeven-Duif, Judith J M Jans.

  The malate-aspartate shuttle (MAS) is a redox shuttle that transports reducing equivalents across the inner mitochondrial membrane while recycling cytosolic NADH to NAD+. We genetically disrupted each MAS component to generate a panel of MAS-deficient HEK293 cell lines in which we performed [U-13C]-glucose tracing. MAS-deficient cells have reduced serine biosynthesis, which strongly correlates with the lactate M+3/pyruvate M+3 ratio (reflective of the cytosolic NAD+/NADH ratio), consistent with the NAD+ dependency of phosphoglycerate dehydrogenase in the serine synthesis pathway. Among the MAS-deficient cells, those lacking malate dehydrogenase 1 (MDH1) show the most severe metabolic disruptions, whereas oxoglutarate-malate carrier (OGC)- and MDH2-deficient cells are less affected. Increasing the NAD+-regenerating capacity using pyruvate supplementation resolves most of the metabolic disturbances. Overall, we show that the MAS is important for de novo serine biosynthesis, implying that serine supplementation could be used as a therapeutic strategy for MAS defects and possibly other redox disorders.

Keywords:  CP: Metabolism; NADH shuttle; central carbon metabolism; glycolysis; isotope-tracer analysis; malate dehydrogenase; malate-aspartate shuttle; metabolomics; serine biosynthesis

DOI:  https://doi.org/10.1016/j.celrep.2023.113043
STAR Protoc. 2023 Aug 26. pii: S2666-1667(23)00492-6. [Epub ahead of print]4(3): 102525

Flow cytometric analysis of phosphatidylcholine metabolism using organelle-selective click labeling.

Masaki Tsuchiya, Nobuhiko Tachibana, Itaru Hamachi.

  Here, we present a protocol to analyze phosphatidylcholine (PC) metabolism in mammalian cells using organelle-selective click labeling coupled with flow cytometry (O-ClickFC). We describe steps for the metabolic incorporation of azide-choline into PC. We then detail fluorescent labeling of the azide-modified PC with organelle-targeting clickable dyes in the ER-Golgi, plasma membrane, and mitochondria, and by flow cytometry. This protocol is optimized for flow cytometric quantification of the labeled PC at the organelle level within single live cells. For complete details on the use and execution of this protocol, please refer to Tsuchiya et al. (2023).1.

Keywords:  Chemistry; Flow Cytometry/Mass Cytometry; Metabolism; Molecular/Chemical Probes

DOI:  https://doi.org/10.1016/j.xpro.2023.102525
Free Radic Biol Med. 2023 Aug 30. pii: S0891-5849(23)00608-1. [Epub ahead of print]

Mitochondrial vulnerability to oxidation in human brain organoids modelling Alzheimer's disease.

Mariana I Holubiec, Matias Alloatti, Bianchelli Julieta, Greloni Francisco, Arnaiz Cayetana, Gonzalez Prinz Melina, Fernandez Bessone Ivan, Pozo Devoto Victorio, Tomas L Falzone.

  Reactive Oxygen Species (ROS) and mitochondrial dysfunction are implicated in the pathogenesis of Alzheimer's disease (AD), a common neurodegenerative disorder characterized by abnormal metabolism of the amyloid precursor protein (APP) in brain tissue. However, the exact mechanism by which abnormal APP leads to oxidative distress remains unclear. Damage to mitochondrial membrane and inhibition of mitochondrial respiration are thought to contribute to the progression of the disease. However, the lack of suitable human models that replicate pathological features, together with impaired cellular pathways, constitutes a major challenge in AD studies. In this work, we induced pluripotency in patient-derived skin fibroblasts carrying the Swedish mutation in App (APPswe), to generate human brain organoids that model AD, and studied redox regulation and mitochondrial homeostasis. We found time-dependent increases in AD-related pathological hallmarks in APPswe brain organoids, including elevated Aβ levels, increased extracellular amyloid deposits, and enhanced tau phosphorylation. Interestingly, using live-imaging spinning-disk confocal microscopy, we found an increase in mitochondrial fragmentation and a significant loss of mitochondrial membrane potential in APPswe brain organoids when subjected to oxidative conditions. Moreover, ratiometric dyes in a live imaging setting revealed a selective increase in mitochondrial superoxide anion and hydrogen peroxide levels in APPswe brain organoids that were coupled to impairments in cytosolic and mitochondrial redoxin expression. Our results suggest a selective increase in mitochondrial vulnerability to oxidative conditions in APPswe organoids, indicating that the abnormal metabolism of APP leads to specific changes in mitochondrial homeostasis that enhance the vulnerability to oxidation in AD.

Keywords:  Alzheimer's disease; Amyloid precursor protein; Human brain organoids; Mitochondrial homeostasis; Oxidative distress; Swedish mutation; Thioredoxins

DOI:  https://doi.org/10.1016/j.freeradbiomed.2023.08.028
Neurobiol Stress. 2023 Sep;26 100563

Gestational stress decreases postpartum mitochondrial respiration in the prefrontal cortex of female rats.

Erin Gorman-Sandler, Breanna Robertson, Jesseca Crawford, Gabrielle Wood, Archana Ramesh, Olufunke O Arishe, R Clinton Webb, Fiona Hollis.

  Postpartum depression (PPD) is a major psychiatric complication of childbirth, affecting up to 20% of mothers, yet remains understudied. Mitochondria, dynamic organelles crucial for cell homeostasis and energy production, share links with many of the proposed mechanisms underlying PPD pathology. Brain mitochondrial function is affected by stress, a major risk factor for development of PPD, and is linked to anxiety-like and social behaviors. Considering the importance of mitochondria in regulating brain function and behavior, we hypothesized that mitochondrial dysfunction is associated with behavioral alterations in a chronic stress-induced rat model of PPD. Using a validated and translationally relevant chronic mild unpredictable stress paradigm during late gestation, we induced PPD-relevant behaviors in adult postpartum Wistar rats. In the mid-postpartum, we measured mitochondrial function in the prefrontal cortex (PFC) and nucleus accumbens (NAc) using high-resolution respirometry. We then measured protein expression of mitochondrial complex proteins and 4-hydroxynonenal (a marker of oxidative stress), and Th1/Th2 cytokine levels in PFC and plasma. We report novel findings that gestational stress decreased mitochondrial function in the PFC, but not the NAc of postpartum dams. However, in groups controlling for the effects of either stress or parity alone, no differences in mitochondrial respiration measured in either brain regions were observed compared to nulliparous controls. This decrease in PFC mitochondrial function in stressed dams was accompanied by negative behavioral consequences in the postpartum, complex-I specific deficits in protein expression, and increased Tumor Necrosis Factor alpha cytokine levels in plasma and PFC. Overall, we report an association between PFC mitochondrial respiration, PPD-relevant behaviors, and inflammation following gestational stress, highlighting a potential role for mitochondrial function in postpartum health.

Keywords:  Chronic unpredictable stress; Mitochondria; Postpartum; Prefrontal cortex; Pregnancy; Susceptibility

DOI:  https://doi.org/10.1016/j.ynstr.2023.100563
Neuroimage. 2023 Aug 25. pii: S1053-8119(23)00501-3. [Epub ahead of print]280 120350

Hyperpolarized [2-13C]pyruvate MR molecular imaging with whole brain coverage.

Brian T Chung, Yaewon Kim, Jeremy W Gordon, Hsin-Yu Chen, Adam W Autry, Philip M Lee, Jasmine Y Hu, Chou T Tan, Chris Suszczynski, Susan M Chang, Javier E Villanueva-Meyer, Robert A Bok, Peder E Z Larson, Duan Xu, Yan Li, Daniel B Vigneron.

  Hyperpolarized (HP) 13C Magnetic Resonance Imaging (MRI) was applied for the first time to image and quantify the uptake and metabolism of [2-13C]pyruvate in the human brain to provide new metabolic information on cerebral energy metabolism. HP [2-13C]pyruvate was injected intravenously and imaged in 5 healthy human volunteer exams with whole brain coverage in a 1-minute acquisition using a specialized spectral-spatial multi-slice echoplanar imaging (EPI) pulse sequence to acquire 13C-labeled volumetric and dynamic images of [2-13C]pyruvate and downstream metabolites [5-13C]glutamate and [2-13C]lactate. Metabolic ratios and apparent conversion rates of pyruvate-to-lactate (kPL) and pyruvate-to-glutamate (kPG) were quantified to investigate simultaneously glycolytic and oxidative metabolism in a single injection.

Keywords:  Brain Metabolism; Hyperpolarized carbon-13; Molecular imaging

DOI:  https://doi.org/10.1016/j.neuroimage.2023.120350
J Neurochem. 2023 Aug 31.

Sialic acid biosynthesis pathway blockade disturbs neuronal network formation in human iPSC-derived excitatory neurons.

Rachel Mijdam, Chantal Bijnagte-Schoenmaker, Emma Dyke, Sam J Moons, Thomas J Boltje, Nael Nadif Kasri, Dirk J Lefeber.

  N-acetylneuraminic acid (sialic acid) is present in large quantities in the brain and plays a crucial role in brain development, learning, and memory formation. How sialic acid contributes to brain development is not fully understood. The purpose of this study was to determine the effects of reduced sialylation on network formation in human iPSC-derived neurons (iNeurons). Using targeted mass spectrometry and antibody binding, we observed an increase in free sialic acid and polysialic acid during neuronal development, which was disrupted by treatment of iNeurons with a synthetic inhibitor of sialic acid biosynthesis. Sialic acid inhibition disturbed synapse formation and network formation on microelectrode array (MEA), showing short but frequent (network) bursts and an overall lower firing rate, and higher percentage of random spikes. This study shows that sialic acid is necessary for neuronal network formation during human neuronal development and provides a physiologically relevant model to study the role of sialic acid in patient-derived iNeurons.

Keywords:  induced pluripotent stem cells; neuronal networks; sialic acid; synapse

DOI:  https://doi.org/10.1111/jnc.15934
J Cell Sci. 2023 Sep 01. pii: jcs260857. [Epub ahead of print]136(17):

Mitochondrial phospholipid metabolism in health and disease.

Alaumy Joshi, Travis H Richard, Vishal M Gohil.

  Studies of rare human genetic disorders of mitochondrial phospholipid metabolism have highlighted the crucial role that membrane phospholipids play in mitochondrial bioenergetics and human health. The phospholipid composition of mitochondrial membranes is highly conserved from yeast to humans, with each class of phospholipid performing a specific function in the assembly and activity of various mitochondrial membrane proteins, including the oxidative phosphorylation complexes. Recent studies have uncovered novel roles of cardiolipin and phosphatidylethanolamine, two crucial mitochondrial phospholipids, in organismal physiology. Studies on inter-organellar and intramitochondrial phospholipid transport have significantly advanced our understanding of the mechanisms that maintain mitochondrial phospholipid homeostasis. Here, we discuss these recent advances in the function and transport of mitochondrial phospholipids while describing their biochemical and biophysical properties and biosynthetic pathways. Additionally, we highlight the roles of mitochondrial phospholipids in human health by describing the various genetic diseases caused by disruptions in their biosynthesis and discuss advances in therapeutic strategies for Barth syndrome, the best-studied disorder of mitochondrial phospholipid metabolism.

Keywords:  Barth syndrome; Cardiolipin; Membranes; Mitochondria; Phosphatidylethanolamine; Phospholipids

DOI:  https://doi.org/10.1242/jcs.260857
Commun Biol. 2023 08 29. 6(1): 890

A G1528C Hadha knock-in mouse model recapitulates aspects of human clinical phenotypes for long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency.

Garen Gaston, Shannon Babcock, Renee Ryals, Gabriela Elizondo, Tiffany DeVine, Dahlia Wafai, William Packwood, Sarah Holden, Jacob Raber, Jonathan R Lindner, Mark E Pennesi, Cary O Harding, Melanie B Gillingham.

Long chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) is a fatty acid oxidation disorder (FAOD) caused by a pathogenic variant, c.1528 G > C, in HADHA encoding the alpha subunit of trifunctional protein (TFPα). Individuals with LCHADD develop chorioretinopathy and peripheral neuropathy not observed in other FAODs in addition to the more ubiquitous symptoms of hypoketotic hypoglycemia, rhabdomyolysis and cardiomyopathy. We report a CRISPR/Cas9 generated knock-in murine model of G1528C in Hadha that recapitulates aspects of the human LCHADD phenotype. Homozygous pups are less numerous than expected from Mendelian probability, but survivors exhibit similar viability with wildtype (WT) littermates. Tissues of LCHADD homozygotes express TFPα protein, but LCHADD mice oxidize less fat and accumulate plasma 3-hydroxyacylcarnitines compared to WT mice. LCHADD mice exhibit lower ketones with fasting, exhaust earlier during treadmill exercise and develop a dilated cardiomyopathy compared to WT mice. In addition, LCHADD mice exhibit decreased visual performance, decreased cone function, and disruption of retinal pigment epithelium. Neurological function is affected, with impaired motor function during wire hang test and reduced open field activity. The G1528C knock-in mouse exhibits a phenotype similar to that observed in human patients; this model will be useful to explore pathophysiology and treatments for LCHADD in the future.

DOI: https://doi.org/10.1038/s42003-023-05268-1
Bio Protoc. 2023 Aug 20. 13(16): e4742

Mass Spectrometry-based Lipidomics, Lipid Bioenergetics, and Web Tool for Lipid Profiling and Quantification in Human Cells.

Liang Cui, Meisam Yousefi, Xin Yap, Clara W T Koh, Kwan Sing Leona Tay, Yaw Shin Ooi, Kuan Rong Chan.

  Lipids can play diverse roles in metabolism, signaling, transport across membranes, regulating body temperature, and inflammation. Some viruses have evolved to exploit lipids in human cells to promote viral entry, fusion, replication, assembly, and energy production through fatty acid beta-oxidation. Hence, studying the virus-lipid interactions provides an opportunity to understand the biological processes involved in the viral life cycle, which can facilitate the development of antivirals. Due to the diversity and complexity of lipids, the assessment of lipid utilization in infected host cells can be challenging. However, the development of mass spectrometry, bioenergetics profiling, and bioinformatics has significantly advanced our knowledge on the study of lipidomics. Herein, we describe the detailed methods for lipid extraction, mass spectrometry, and assessment of fatty acid oxidation on cellular bioenergetics, as well as the bioinformatics approaches for detailed lipid analysis and utilization in host cells. These methods were employed for the investigation of lipid alterations in TMEM41B- and VMP1-deficient cells, where we previously found global dysregulations of the lipidome in these cells. Furthermore, we developed a web app to plot clustermaps or heatmaps for mass spectrometry data that is open source and can be hosted locally or at https://kuanrongchan-lipid-metabolite-analysis-app-k4im47.streamlit.app/. This protocol provides an efficient step-by-step methodology to assess lipid composition and usage in host cells.

Keywords:  Bioenergetics; Clustergram; Lipid profiling; Lipidomics; Mass spectrometry; Seahorse assay; Virus–lipid interactions; Web tool

DOI:  https://doi.org/10.21769/BioProtoc.4742
Mol Neurobiol. 2023 Aug 26.

Interactions of Cellular Energetic Gene Clusters in the Alzheimer's Mouse Brain.

Raghavan Pillai Raju, Lun Cai, Alpna Tyagi, Subbiah Pugazhenthi.

  Alzheimer's disease (AD) is the most common cause of dementia in the aging population. The pathological characteristics include extracellular senile plaques and intracellular neurofibrillary tangles. In addition, mitochondrial dysfunction, oxidative stress, and neuroinflammation contribute to AD pathogenesis. In this study, we sought to determine the crosstalk between different pathways in the brain of 5XFAD mice, a mouse model for amyloid pathology, by RNA-seq analysis. We observed significant changes in the expression of genes (1288 genes; adj p value < 0.05; log2-fold > 1 and < 1) related to pathways including oxidation-reduction, oxidative phosphorylation, innate immune response, ribosomal protein synthesis, and ubiquitin proteosome system. The most striking feature was the downregulation of genes related to oxidation-reduction process with changes in the expression of a large number of mitochondrial genes. We also observed an upregulation of several immune response genes. Gene interaction network of oxidation-reduction related genes further confirmed a tight cluster of mitochondrial genes. Furthermore, gene interaction analysis of all the 1288 genes showed at least three distinct interaction clusters, with the predominant one relating to cellular energetics. In summary, we identified 1288 genes distinctly different in the 5XFAD brain compared to the WT brain and found cellular energetics to be the most distinct gene cluster in the AD mouse brain.

Keywords:  Alzheimer’s disease; Gene expression; Inflammation; Mitochondria; Oxidative stress

DOI:  https://doi.org/10.1007/s12035-023-03551-0
bioRxiv. 2023 Aug 14. pii: 2023.08.14.553169. [Epub ahead of print]

Insertases Scramble Lipids: Molecular Simulations of MTCH2.

Ladislav Bartoš, Anant K Menon, Robert Vácha.

Scramblases play a pivotal role in facilitating bidirectional lipid transport across cell membranes, thereby influencing lipid metabolism, membrane homeostasis, and cellular signaling. MTCH2, a mitochondrial outer membrane protein insertase, has a membrane-spanning hydrophilic groove resembling those that form the lipid transit pathway in known scramblases. Employing both coarse-grained and atomistic molecular dynamics simulations, we now show that MTCH2 significantly reduces the free energy barrier for lipid movement along the groove and therefore can indeed function as a scramblase. Notably, the scrambling rate of MTCH2 in silico is similar to that of VDAC, a recently discovered scramblase of the outer mitochondrial membrane, suggesting a potential complementary physiological role for these mitochondrial proteins. Finally, our findings suggest that other insertases which possess a hydrophilic path across the membrane like MTCH2, can also function as scramblases.
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DOI: https://doi.org/10.1101/2023.08.14.553169