bims-medebr 2023-03-26 papers

bims-medebr

Biomed News

on Metabolism of the developing brain

Issue of 2023–03–26
23 papers selected by
Regina F. Fernández, Johns Hopkins University

Deletion of CaMKIIα disrupts glucose metabolism, glutamate uptake and synaptic energetics in the cerebral cortex.
Associations of ApoE4 status and DHA supplementation on plasma and CSF lipid profiles and entorhinal cortex thickness.
Loss of fatty acid degradation by astrocytic mitochondria triggers neuroinflammation and neurodegeneration.
Sirtuin3 ensures the metabolic plasticity of neurotransmission during glucose deprivation.
Nrf2 regulates glucose uptake and metabolism in neurons and astrocytes.
Long-term dietary folic acid supplementation attenuated aging-induced hippocampus atrophy and promoted glucose uptake in 25-month-old rats with cognitive decline.
Novel 13C enrichment technique reveals early turnover of DHA in peripheral tissues.
Comprehensive study of metabolic changes induced by a ketogenic diet therapy using GC/MS- and LC/MS-based metabolomics.
Mitochondrial Complex I Inhibition in Dopaminergic Neurons Causes Altered Protein Profile and Protein Oxidation: Implications for Parkinson's disease.
Whole-brain MR spectroscopic imaging reveals regional metabolite abnormalities in perinatally HIV infected young adults.
Oxoglutarate dehydrogenase complex controls glutamate-mediated neuronal death.
Sphingolipid desaturase DEGS1 is essential for mitochondria-associated membrane integrity.
A glucose-sensing mechanism with glucose transporter-1 and pyruvate kinase in the area postrema regulates hepatic glucose production in rats.
Perinatal blockade of neuronal glutamine transport sex-differentially alters glutamatergic synaptic transmission and organization of neurons in the ventrolateral ventral media hypothalamus of adult rats.
Lipid-accumulated reactive astrocytes promote disease progression in epilepsy.
CYP4F2 is a human-specific determinant of circulating N-acyl amino acid levels.
Mitochondrial dysfunction and calcium dysregulation in COQ8A-ataxia Purkinje neurons are rescued by CoQ10 treatment.
Ketogenic therapies for glioblastoma: Understanding the limitations in transitioning from mice to patients.
Low Ankle-Brachial Index Relates to Alzheimer-Signature Cerebral Glucose Metabolism in Cognitively Impaired Older Adults.
Accumulated cholesterol protects tumours from elevated lipid peroxidation in the microenvironment.
Unexpected phenotypic and molecular changes of combined glucocerebrosidase and acid sphingomyelinase deficiency.
Loss of respiratory complex I subunit NDUFB10 affects complex I assembly and supercomplex formation.
A quantitative fluorescence-based approach to study mitochondrial protein import.

J Neurochem. 2023 Mar 22.

Deletion of CaMKIIα disrupts glucose metabolism, glutamate uptake and synaptic energetics in the cerebral cortex.

Jens V Andersen, Emil W Westi, Nane Griem-Krey, Niels H Skotte, Arne Schousboe, Blanca I Aldana, Petrine Wellendorph.

  Ca2+ /calmodulin-dependent protein kinase II alpha (CaMKIIα) is a key regulator of neuronal signaling and synaptic plasticity. Synaptic activity and neurotransmitter homeostasis are closely coupled to the energy metabolism of both neurons and astrocytes. However, it remains unclear whether CaMKIIα function is implicated in brain energy and neurotransmitter metabolism. Here, we explored the metabolic consequences of CaMKIIα deletion in the cerebral cortex using a genetic CaMKIIα knock-out (KO) mouse. Energy and neurotransmitter metabolism was functionally investigated in acutely isolated cerebral cortical slices using stable 13 C isotope tracing, whereas the metabolic function of synaptosomes was assessed by the rates of glycolytic activity and mitochondrial respiration. The oxidative metabolism of [U-13 C]glucose was extensively reduced in cerebral cortical slices of the CaMKIIα KO mice. In contrast, metabolism of [1,2-13 C]acetate, primarily reflecting astrocyte metabolism, was unaffected. Cellular uptake, and subsequent metabolism, of [U-13 C]glutamate was decreased in cerebral cortical slices of CaMKIIα KO mice, whereas uptake and metabolism of [U-13 C]GABA was unaffected, suggesting selective metabolic impairments of the excitatory system. Synaptic metabolic function was maintained during resting conditions in isolated synaptosomes from CaMKIIα KO mice, but both the glycolytic and mitochondrial capacities became insufficient when the synaptosomes were metabolically challenged. Collectively, this study shows that global deletion of CaMKIIα significantly impairs cellular energy and neurotransmitter metabolism, particularly of neurons, suggesting a metabolic role of CaMKIIα signaling in the brain.

Keywords:  Ca2+/calmodulin-dependent protein kinase II alpha; astrocytes; energy and neurotransmitter metabolism; long-term potentiation; mitochondria; neurotransmitter recycling

DOI:  https://doi.org/10.1111/jnc.15814
J Lipid Res. 2023 Mar 21. pii: S0022-2275(23)00027-5. [Epub ahead of print] 100354

Associations of ApoE4 status and DHA supplementation on plasma and CSF lipid profiles and entorhinal cortex thickness.

Mikaila A Bantugan, Haotian Xian, Victoria Solomon, Mitchell Lee, Zhiheng Cai, Shaowei Wang, Marlon V Duro, Bilal E Kerman, Alfred Fonteh, Cristiana Meuret, Meitong Li, Meredith N Braskie, Laura Beth J McIntire, Lucia Jurin, Sarah Oberlin, James Evans, Roderick Davis, Wendy J Mack, Laila Abdullah, Hussein N Yassine.

   BACKGROUND: Apolipoprotein ε allele 4 (APOE4) influences the metabolism of polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid (DHA). The entorhinal cortex (EC) area in the brain is affected early in Alzheimer's disease (AD) and is rich in DHA. The purpose of this study is to identify the effect of APOE4 and DHA lipid species on the changes in EC.
METHODS: Plasma and CSF lipidomic measurements were obtained from the DHA Brain Delivery Pilot, a randomized clinical trial of DHA supplementation (n=10) vs. placebo (n=12) for six months in non-demented older adults stratified by APOE4 carrier status. Wild C57B6/J mice were fed a high or low DHA diet for 6 months followed by plasma and brain lipidomic analysis.
RESULTS: Levels of phosphatidylcholine DHA (PC 38:6) and cholesterol ester DHA (CE 22:6) had the largest increases in CSF following supplementation (p<0.001). DHA within triglyceride (TG) lipids in CSF strongly correlated with the corresponding plasma TG lipids, and differed by APOE4, with carriers having a lower increase than non-carriers. Changes in plasma PC DHA had the strongest association with the change in EC thickness in millimeters, independent of APOE4 status (p=0.007). In mice, a high DHA diet increased PUFAs within brain lipids.
CONCLUSION: Our findings demonstrate an exchange of DHA at the CSF-blood barrier and into the brain within all lipid species with APOE genotype having the strongest effect on DHA containing TGs. The correlation of PC DHA with EC suggests a functional consequence of DHA accretion in HDL for the brain.

Keywords:  Alzheimer’s; ApoE; Brain; Lipidomics; Lipids

DOI:  https://doi.org/10.1016/j.jlr.2023.100354
Nat Metab. 2023 Mar 23.

Loss of fatty acid degradation by astrocytic mitochondria triggers neuroinflammation and neurodegeneration.

Yashi Mi, Guoyuan Qi, Francesca Vitali, Yuan Shang, Adam C Raikes, Tian Wang, Yan Jin, Roberta D Brinton, Haiwei Gu, Fei Yin.

Astrocytes provide key neuronal support, and their phenotypic transformation is implicated in neurodegenerative diseases. Metabolically, astrocytes possess low mitochondrial oxidative phosphorylation (OxPhos) activity, but its pathophysiological role in neurodegeneration remains unclear. Here, we show that the brain critically depends on astrocytic OxPhos to degrade fatty acids (FAs) and maintain lipid homeostasis. Aberrant astrocytic OxPhos induces lipid droplet (LD) accumulation followed by neurodegeneration that recapitulates key features of Alzheimer's disease (AD), including synaptic loss, neuroinflammation, demyelination and cognitive impairment. Mechanistically, when FA load overwhelms astrocytic OxPhos capacity, elevated acetyl-CoA levels induce astrocyte reactivity by enhancing STAT3 acetylation and activation. Intercellularly, lipid-laden reactive astrocytes stimulate neuronal FA oxidation and oxidative stress, activate microglia through IL-3 signalling, and inhibit the biosynthesis of FAs and phospholipids required for myelin replenishment. Along with LD accumulation and impaired FA degradation manifested in an AD mouse model, we reveal a lipid-centric, AD-resembling mechanism by which astrocytic mitochondrial dysfunction progressively induces neuroinflammation and neurodegeneration.

DOI: https://doi.org/10.1038/s42255-023-00756-4
bioRxiv. 2023 Mar 10. pii: 2023.03.08.531724. [Epub ahead of print]

Sirtuin3 ensures the metabolic plasticity of neurotransmission during glucose deprivation.

Anupama Tiwari, Arsalan Hashemiaghdam, Marissa A Laramie, Dario Maschi, Tristaan Haddad, Marion I Stunault, Carmen Bergom, Ali Javaheri, Vitaly Klyachko, Ghazaleh Ashrafi.

Neurotransmission is an energetically expensive process that underlies cognition. During intense electrical activity or dietary restrictions, glucose levels in the brain plummet, forcing neurons to utilize alternative fuels. However, the molecular mechanisms of neuronal metabolic plasticity remain poorly understood. Here, we demonstrate that glucose-deprived neurons activate the CREB and PGC1α transcriptional program that induces the expression of the mitochondrial deacetylase Sirtuin 3 (Sirt3) both in vitro and in vivo . We show that Sirt3 localizes to axonal mitochondria and stimulates mitochondrial oxidative capacity in hippocampal nerve terminals. Sirt3 plays an essential role in sustaining synaptic transmission in the absence of glucose by powering the retrieval of synaptic vesicles after release. These results demonstrate that the transcriptional induction of Sirt3 ensures the metabolic plasticity of synaptic transmission.
Highlights: Glucose deprivation drives transcriptional reprogramming of neuronal metabolism via CREB and PGC1α. Glucose or food deprivation trigger the neuronal expression of mitochondrial deacetylase sirtuin 3 (Sirt3) both in vitro and in vivo . Sirt3 stimulates oxidative ATP synthesis in nerve terminals.Sirt3 sustains the synaptic vesicle cycle in the absence of glucose.

DOI: https://doi.org/10.1101/2023.03.08.531724
Redox Biol. 2023 Mar 14. pii: S2213-2317(23)00073-3. [Epub ahead of print]62 102672

Nrf2 regulates glucose uptake and metabolism in neurons and astrocytes.

Noemí Esteras, Thomas S Blacker, Evgeny A Zherebtsov, Olga A Stelmashuk, Ying Zhang, W Christian Wigley, Michael R Duchen, Albena T Dinkova-Kostova, Andrey Y Abramov.

  The transcription factor Nrf2 and its repressor Keap1 mediate cell stress adaptation by inducing expression of genes regulating cellular detoxification, antioxidant defence and energy metabolism. Energy production and antioxidant defence employ NADH and NADPH respectively as essential metabolic cofactors; both are generated in distinct pathways of glucose metabolism, and both pathways are enhanced by Nrf2 activation. Here, we examined the role of Nrf2 on glucose distribution and the interrelation between NADH production in energy metabolism and NADPH homeostasis using glio-neuronal cultures isolated from wild-type, Nrf2-knockout and Keap1-knockdown mice. Employing advanced microscopy imaging of single live cells, including multiphoton fluorescence lifetime imaging microscopy (FLIM) to discriminate between NADH and NADPH, we found that Nrf2 activation increases glucose uptake into neurons and astrocytes. Glucose consumption is prioritized in brain cells for mitochondrial NADH and energy production, with a smaller contribution to NADPH synthesis in the pentose phosphate pathway for redox reactions. As Nrf2 is suppressed during neuronal development, this strategy leaves neurons reliant on astrocytic Nrf2 to maintain redox balance and energy homeostasis.

Keywords:  Astrocytes; Brain; Glucose metabolism; Mitochondria; NADH; NADPH; Neurons; Nrf2

DOI:  https://doi.org/10.1016/j.redox.2023.102672
J Nutr Biochem. 2023 Mar 21. pii: S0955-2863(23)00061-X. [Epub ahead of print] 109328

Long-term dietary folic acid supplementation attenuated aging-induced hippocampus atrophy and promoted glucose uptake in 25-month-old rats with cognitive decline.

Dezheng Zhou, Yue Sun, Zhiyong Qian, Zehao Wang, Dalong Zhang, Zhenshu Li, Jing Zhao, Cuixia Dong, Wen Li, Guowei Huang.

  The brain has high energy demand making it sensitive to changes in energy fuel supply. Aging shrinks brain volume, decreases glucose uptake availability of the brain, and finally, causes cognitive dysfunction. Folic acid supplementation delayed cognitive decline and neurodegeneration. However, whether folic acid affects brain energy metabolism and structural changes is unclear. The study aimed to determine if long-term dietary folic acid supplementation could alleviate age-related cognitive decline by attenuating hippocampus atrophy and promoting brain glucose uptake in Sprague-Dawley (SD) rats. According to folic acid levels in diet, three-month-old male SD rats were randomly divided into four intervention groups for 22 months in equal numbers: folic acid-deficient diet (FA-D) group, folic acid-normal diet (FA-N) group, low folic acid-supplemented diet (FA-L) group, and high folic acid-supplemented diet (FA-H) group. The results showed that serum folate concentrations decreased and serum homocysteine (Hcy) concentrations increased with age, and dietary folic acid supplementation increased serum folate concentrations and decreased Hcy concentrations at 11, 18, and 22 months of intervention. Dietary folic acid supplementation attenuated aging-induced hippocampus atrophy, which was showed by higher fractional anisotropy and lower mean diffusivity in the hippocampus, increased brain 18F-Fluorodeoxyglucose (18F-FDG) uptake, then stimulated neuronal survival, and alleviated age-related cognitive decline in SD rats. In conclusion, long-term dietary folic acid supplementation alleviated age-related cognitive decline by attenuating hippocampus atrophy and promoting brain glucose uptake in SD rats.

Keywords:  Age-related cognitive decline; Folic acid; Glucose uptake; Hippocampus atrophy; Long-term

DOI:  https://doi.org/10.1016/j.jnutbio.2023.109328
J Lipid Res. 2023 Mar 20. pii: S0022-2275(23)00030-5. [Epub ahead of print] 100357

Novel 13C enrichment technique reveals early turnover of DHA in peripheral tissues.

Brinley J Klievik, Adam H Metherel, Giulia Cisbani, Rodrigo Valenzuela, Richard P Bazinet.

  The brain is rich in DHA, which plays important roles in regulating neuronal function. Recently, using compound-specific isotope analysis (CSIA) that takes advantage of natural differences in carbon-13 content (13C/12C ratio or δ13C) of the food supply, we determined the brain DHA half-life. However, due to methodological limitations, we were unable to capture DHA turnover rates in peripheral tissues. In the current study, we applied CSIA via high-precision gas chromatography combustion isotope ratio mass spectrometry (GC/C/IRMS) to determine half-lives of brain, liver, and plasma DHA in mice following a dietary switch experiment. To model DHA tissue turnover rates in peripheral tissues, we added earlier timepoints within the diet switch study and took advantage of natural variations in the δ13C-DHA of algal and fish DHA sources to maintain DHA pool sizes and used an enriched (uniformly labeled 13C) DHA treatment. Mice were fed a fish-DHA diet (control) for 3 months, then switched to an algal-DHA treatment diet, the 13C enriched-DHA treatment diet, or they stayed on the control diet for the remainder of the study time course. In mice fed the algal and 13C enriched-DHA diets, the brain DHA half-life was 47 and 46 days, the liver half-life was 5.6 and 7.2 days, and the plasma half-life was 4.7 and 6.4 days respectively. By using improved methodologies, we calculated DHA turnover rates in the liver and plasma, and our study for the first time, by using an artificially enriched DHA source (very high δ13C), validated its utility in diet switch studies.

Keywords:  brain; diet; docosahexaenoic acid; fatty acid metabolism; liver; mass spectrometry; omega-3 fatty acids

DOI:  https://doi.org/10.1016/j.jlr.2023.100357
Seizure. 2023 Mar 16. pii: S1059-1311(23)00075-4. [Epub ahead of print]107 52-59

Comprehensive study of metabolic changes induced by a ketogenic diet therapy using GC/MS- and LC/MS-based metabolomics.

Mari Akiyama, Tomoyuki Akiyama, Daisuke Saigusa, Eiji Hishinuma, Naomi Matsukawa, Takashi Shibata, Hiroki Tsuchiya, Atsushi Mori, Yuji Fujii, Yukiko Mogami, Chiho Tokorodani, Kozue Kuwahara, Yurika Numata-Uematsu, Kenji Inoue, Katsuhiro Kobayashi.

   OBJECTIVE: The ketogenic diet (KD), a high-fat and low-carbohydrate diet, is effective for a subset of patients with drug-resistant epilepsy, although the mechanisms of the KD have not been fully elucidated. The aims of this observational study were to investigate comprehensive short-term metabolic changes induced by the KD and to explore candidate metabolites or pathways for potential new therapeutic targets.
METHODS: Subjects included patients with intractable epilepsy who had undergone the KD therapy (the medium-chain triglyceride [MCT] KD or the modified Atkins diet using MCT oil). Plasma and urine samples were obtained before and at 2-4 weeks after initiation of the KD. Targeted metabolome analyses of these samples were performed using gas chromatography-tandem mass spectrometry (GC/MS/MS) and liquid chromatography-tandem mass spectrometry (LC/MS/MS).
RESULTS: Samples from 10 and 11 patients were analysed using GC/MS/MS and LC/MS/MS, respectively. The KD increased ketone bodies, various fatty acids, lipids, and their conjugates. In addition, levels of metabolites located upstream of acetyl-CoA and propionyl-CoA, including catabolites of branched-chain amino acids and structural analogues of γ-aminobutyric acid and lactic acid, were elevated.
CONCLUSIONS: The metabolites that were significantly changed after the initiation of the KD and related metabolites may be candidates for further studies for neuronal actions to develop new anti-seizure medications.

Keywords:  Amino acids; Biomarkers; Intractable epilepsy; Ketone bodies; Organic acids

DOI:  https://doi.org/10.1016/j.seizure.2023.03.014
Neurochem Res. 2023 Mar 25.

Mitochondrial Complex I Inhibition in Dopaminergic Neurons Causes Altered Protein Profile and Protein Oxidation: Implications for Parkinson's disease.

Yogeshachar Chithra, Gourav Dey, Vivek Ghose, Vivek Chandramohan, Niya Gowthami, V Vasudev, M M Srinivas Bharath.

  Mitochondrial dysfunction and oxidative stress are critical to neurodegeneration in Parkinson's disease (PD). Mitochondrial dysfunction in PD entails inhibition of the mitochondrial complex I (CI) in the dopaminergic neurons of substantia nigra. The events contributing to CI inhibition and downstream pathways are not completely elucidated. We conducted proteomic analysis in a dopaminergic neuronal cell line exposed individually to neurotoxic CI inhibitors: rotenone (Rot), paraquat (Pq) and 1-methyl-4-phenylpyridinium (MPP+). Mass spectrometry (MS) revealed the involvement of biological processes including cell death pathways, structural changes and metabolic processes among others, most of which were common across all models. The proteomic changes induced by Pq were significantly higher than those induced by Rot and MPP+. Altered metabolic processes included downregulated mitochondrial proteins such as CI subunits. MS of CI isolated from the models revealed oxidative post-translational modifications with Tryptophan (Trp) oxidation as the predominant modification. Further, 62 peptides in 22 subunits of CI revealed Trp oxidation with 16 subunits common across toxins. NDUFV1 subunit had the greatest number of oxidized Trp and Rot model displayed the highest number of Trp oxidation events compared to the other models. Molecular dynamics simulation (MDS) of NDUFV1 revealed that oxidized Trp 433 altered the local conformation thereby changing the distance between the Fe-S clusters, Fe-S 301(N1a) to Fe-S 502 (N3) and Fe-S 802 (N4) to Fe-S 801 (N5), potentially affecting the efficiency of electron transfer. The events triggered by the neurotoxins represent CI damage, mitochondrial dysfunction and neurodegeneration in PD.

Keywords:  MPP+ (1-methyl-4-phenylpyridinium); Mass spectrometry; Molecular dynamics; Paraquat; Post-translational Modifications; Rotenone; Tryptophan

DOI:  https://doi.org/10.1007/s11064-023-03907-x
Front Neurosci. 2023 ;17 1134867

Whole-brain MR spectroscopic imaging reveals regional metabolite abnormalities in perinatally HIV infected young adults.

Teddy Salan, Elizabeth J Willen, Anai Cuadra, Sulaiman Sheriff, Andrew A Maudsley, Varan Govind.

  Perinatally acquired HIV (PHIV) has been associated with brain structural and functional deficiencies, and with poorer cognitive performance despite the advent of antiretroviral therapy (ART). However, investigation of brain metabolite levels in PHIV measured by proton magnetic resonance spectroscopy (MRS) methods, is still limited with often inconclusive or contradictory findings. In general, these MRS-based methods have used a single voxel approach that can only evaluate metabolite concentrations in a few select brain anatomical regions. Additionally, most of the published data have been on children perinatally infected with HIV with only a few studies examining adult populations, though not exclusively. Therefore, this prospective and cross-sectional study aims to evaluate metabolite differences at the whole-brain level, using a unique whole-brain proton magnetic resonance spectroscopy imaging (MRSI) method, in a group of PHIV infected young adults (N = 28) compared to age and gender matched control sample (N = 28), and to find associations with HIV clinical factors and neurocognitive scores. MRSI data were acquired on a 3T scanner with a TE of 70 ms. Brain metabolites levels of total N-acetylaspartate (tNAA), total choline (tCho) and total creatine (tCre), as well as ratios of tNAA/tCre, tCho/tCre, and tNAA/tCho, were obtained from the whole brain level and evaluated at the level of gray matter (GM) and white matter (WM) tissue types and anatomical regions of interest (ROI). Our results indicate extensive metabolic abnormalities throughout the brains of PHIV infected subjects with significantly elevated levels of tCre and tCho, notably in GM regions. Decreases in tNAA and ratios of tNAA/tCre and tNAA/tCho were also found mostly in WM regions. These metabolic alterations indicate increased glial activation, inflammation, neuronal dysfunction, and energy metabolism in PHIV infected individuals, which correlated with a reduction in CD4 cell count, and lower cognitive scores. Our findings suggest that significant brain metabolite alterations and associated neurological complications persist in the brains of those with PHIV on long-term ART, and advocates the need for continued monitoring of their brain health.

Keywords:  MRSI; brain; metabolites; perinatal HIV; young adults

DOI:  https://doi.org/10.3389/fnins.2023.1134867
Redox Biol. 2023 Mar 11. pii: S2213-2317(23)00070-8. [Epub ahead of print]62 102669

Oxoglutarate dehydrogenase complex controls glutamate-mediated neuronal death.

Adelheid Weidinger, Nadja Milivojev, Arthur Hosmann, J Catharina Duvigneau, Csaba Szabo, Gabor Törö, Laurin Rauter, Annette Vaglio-Garro, Garik V Mkrtchyan, Lidia Trofimova, Rinat R Sharipov, Alexander M Surin, Irina A Krasilnikova, Vsevolod G Pinelis, Laszlo Tretter, Rudolf Moldzio, Hülya Bayır, Valerian E Kagan, Victoria I Bunik, Andrey V Kozlov.

Brain injury is accompanied by neuroinflammation, accumulation of extracellular glutamate and mitochondrial dysfunction, all of which cause neuronal death. The aim of this study was to investigate the impact of these mechanisms on neuronal death. Patients from the neurosurgical intensive care unit suffering aneurysmal subarachnoid hemorrhage (SAH) were recruited retrospectively from a respective database. In vitro experiments were performed in rat cortex homogenate, primary dissociated neuronal cultures, B35 and NG108-15 cell lines. We employed methods including high resolution respirometry, electron spin resonance, fluorescent microscopy, kinetic determination of enzymatic activities and immunocytochemistry. We found that elevated levels of extracellular glutamate and nitric oxide (NO) metabolites correlated with poor clinical outcome in patients with SAH. In experiments using neuronal cultures we showed that the 2-oxoglutarate dehydrogenase complex (OGDHC), a key enzyme of the glutamate-dependent segment of the tricarboxylic acid (TCA) cycle, is more susceptible to the inhibition by NO than mitochondrial respiration. Inhibition of OGDHC by NO or by succinyl phosphonate (SP), a highly specific OGDHC inhibitor, caused accumulation of extracellular glutamate and neuronal death. Extracellular nitrite did not substantially contribute to this NO action. Reactivation of OGDHC by its cofactor thiamine (TH) reduced extracellular glutamate levels, Ca2+ influx into neurons and cell death rate. Salutary effect of TH against glutamate toxicity was confirmed in three different cell lines. Our data suggest that the loss of control over extracellular glutamate, as described here, rather than commonly assumed impaired energy metabolism, is the critical pathological manifestation of insufficient OGDHC activity, leading to neuronal death.

DOI: https://doi.org/10.1016/j.redox.2023.102669
J Clin Invest. 2023 Mar 23. pii: e162957. [Epub ahead of print]

Sphingolipid desaturase DEGS1 is essential for mitochondria-associated membrane integrity.

Laura Planas-Serra, Nathalie Launay, Leire Goicoechea, Bénédicte Heron, Cristina Jou, Natalia Juliá-Palacios, Montserrat Ruiz, Stéphane Fourcade, Carlos Casasnovas, Carolina De La Torre, Antoinette Gelot, Maria Marsal, Pablo Loza-Alvarez, Àngels García-Cazorla, Ali Fatemi, Isidre Ferrer, Manuel Portero-Otin, Estela Area-Gómez, Aurora Pujol.

  Sphingolipids function as membrane constituents and signaling molecules, with crucial roles in human diseases, from neurodevelopmental to cancer, best exemplified in the inborn errors of sphingolipid metabolism in lysosomes. The dihydroceramide desaturase DEGS1 acts in the last step of a sector of the sphingolipid pathway, de novo ceramide biosynthesis. Defects in DEGS1 cause the recently described hypomyelinating leukodystrophy-18 (HLD18, OMIM #618404). Here, we reveal that DEGS1 is a mitochondria-associated endoplasmic reticulum membrane (MAM)-resident enzyme, refining previous reports locating DEGS1 at the endoplasmic reticulum only. Using patient fibroblasts, multi-omics and enzymatic assays, we show that DEGS1 deficiency disrupts the main core functions of the MAM: i) mitochondrial dynamics, with a hyperfused mitochondrial network associated with decreased activation of dynamin-related protein 1; ii) cholesterol metabolism, with impaired sterol O-acyltransferase activity and decreased cholesteryl esters; iii) phospholipid metabolism, with increased phosphatidic acid and phosphatidylserine and decreased phosphatidylethanolamine; iv) biogenesis of lipid droplets, with increased size and numbers. Moreover, we detected increased mitochondrial superoxide species production in fibroblasts and mitochondrial respiration impairment in patient muscle biopsy tissues. Our findings shed light on the pathophysiology of HLD18 and broaden our understanding of the role of sphingolipid metabolism in MAMs function.

Keywords:  Bioenergetics; Demyelinating disorders; Lipid rafts; Metabolism; Neuroscience

DOI:  https://doi.org/10.1172/JCI162957
J Biol Chem. 2023 Mar 22. pii: S0021-9258(23)00275-2. [Epub ahead of print] 104633

A glucose-sensing mechanism with glucose transporter-1 and pyruvate kinase in the area postrema regulates hepatic glucose production in rats.

Rosa J W Li, Jennifer F M Chiu, Kyla Bruce, Song-Yang Zhang, Daniel R Barros, Jessica T Y Yue, Tony K T Lam.

  The area postrema (AP) of the brain is exposed to circulating metabolites and hormones. However, whether AP detects glucose changes to exert biological responses remains unknown. Its neighboring nuclei, the nucleus tractus solitarius (NTS), responds to acute glucose infusion by inhibiting hepatic glucose production, but the mechanism also remains elusive. Herein, we characterized AP and NTS glucose-sensing mechanisms. Infusion of glucose into the AP, like the NTS, of chow rats suppressed glucose production during the pancreatic (basal insulin)-euglycemic clamps. Glucose transporter-1 or pyruvate kinase lentiviral-mediated knockdown in the AP negated AP glucose infusion to lower glucose production, while the glucoregulatory effect of NTS glucose infusion was also negated by knocking down glucose transporter-1 or pyruvate kinase in the NTS. Furthermore, we determined that high-fat (HF) feeding disrupts glucose infusion to lower glucose production in association with a modest reduction in expression of glucose transporter-1, but not pyruvate kinase, in the AP and NTS. However, pyruvate dehydrogenase activator dichloroacetate infusion into the AP or NTS that enhanced downstream pyruvate metabolism and recapitulated the glucoregulatory effect of glucose in chow rats still failed to lower glucose production in HF rats. We discovered that a glucose transporter-1 and pyruvate kinase-dependent glucose-sensing mechanism in the AP (as well as the NTS) lowers glucose production in chow rats, and that HF disrupts the glucose-sensing mechanism that is downstream of pyruvate metabolism in the AP and NTS. These findings highlight the role of AP and NTS in mediating glucose to regulate hepatic glucose production.

Keywords:  Area postrema; Glucose production; Glucose transporter-1; Nucleus tractus solitarius; Pyruvate metabolism

DOI:  https://doi.org/10.1016/j.jbc.2023.104633
J Neuroendocrinol. 2023 Mar 11. e13253

Perinatal blockade of neuronal glutamine transport sex-differentially alters glutamatergic synaptic transmission and organization of neurons in the ventrolateral ventral media hypothalamus of adult rats.

Shu-Ling Liang, Wen-Lin Liao, Rou-Shayn Chen.

  Compared to male pups, perinatal female rats rely heavily on neuronal glutamine (Gln) transport for sustaining glutamatergic synaptic release in neurons of the ventrolateral ventral media nucleus of the hypothalamus (vlVMH). VMH mainly regulates female sexual behavior and increases glutamate release of perinatal hypothalamic neurons, permanently enhances dendrite spine numbers and is associated with brain and behavioral defeminization. We hypothesized that perinatal interruption of neuronal Gln transport may alter the glutamatergic synaptic transmission during adulthood. Perinatal rats of both sexes received an intracerebroventricular injection of a neuronal Gln uptake blocker, alpha-(methylamino) isobutyric acid (MeAIB, 5 mM), and were raised until adulthood. Whole-cell voltage-clamp recordings of miniature excitatory postsynaptic currents (mEPSCs) and evoked EPSCs (eEPSCs) of vlVMH neurons in adult rats with the perinatal pretreatment were conducted and neuron morphology was subjected to post hoc examination. Perinatal MeAIB treatment sex-differentially increased mEPSC frequency in males, but decreased mEPSC amplitude and synaptic Glu release in females. The pretreatment sex-differentially decreased eEPSC amplitude in males but increased AMPA/NMDA current ratio in females, and changed the morphology of vlVMH neurons of adult rats to that of the opposite sex. Most alterations in the glutamatergic synaptic transmission resembled the changes occurring during MeAIB acute exposure in perinatal rats of both sexes. We conclude that perinatal blockade of neuronal Gln transport mediates changes via different presynaptic and postsynaptic mechanisms to induce sex-differential alterations of the glutamatergic synaptic transmission and organization of vlVMH neurons in adult rats. These changes may be permanent and associated with brain and behavior feminization and/or defeminization in rats.

Keywords:  Sex differentiation; electrophysiology; glutamatergic neuron; hypothalamus; synaptic plasticity

DOI:  https://doi.org/10.1111/jne.13253
Nat Neurosci. 2023 Mar 20.

Lipid-accumulated reactive astrocytes promote disease progression in epilepsy.

Zhang-Peng Chen, Suji Wang, Xiansen Zhao, Wen Fang, Zhengge Wang, Haojie Ye, Meng-Ju Wang, Ling Ke, Tengfei Huang, Pin Lv, Xiaohong Jiang, Qipeng Zhang, Liang Li, Shu-Tao Xie, Jing-Ning Zhu, Chunhua Hang, Dijun Chen, Xiangyu Liu, Chao Yan.

Reactive astrocytes play an important role in neurological diseases, but their molecular and functional phenotypes in epilepsy are unclear. Here, we show that in patients with temporal lobe epilepsy (TLE) and mouse models of epilepsy, excessive lipid accumulation in astrocytes leads to the formation of lipid-accumulated reactive astrocytes (LARAs), a new reactive astrocyte subtype characterized by elevated APOE expression. Genetic knockout of APOE inhibited LARA formation and seizure activities in epileptic mice. Single-nucleus RNA sequencing in TLE patients confirmed the existence of a LARA subpopulation with a distinct molecular signature. Functional studies in epilepsy mouse models and human brain slices showed that LARAs promote neuronal hyperactivity and disease progression. Targeting LARAs by intervention with lipid transport and metabolism could thus provide new therapeutic options for drug-resistant TLE.

DOI: https://doi.org/10.1038/s41593-023-01288-6
bioRxiv. 2023 Mar 09. pii: 2023.03.09.531581. [Epub ahead of print]

CYP4F2 is a human-specific determinant of circulating N-acyl amino acid levels.

Julia T Tanzo, Veronica L Li, Amanda L Wiggenhorn, Maria Dolores Moya-Garzon, Wei Wei, Xuchao Lyu, Wentao Dong, Usman A Tahir, Zsu-Zsu Chen, Daniel E Cruz, Shuliang Deng, Xu Shi, Shuning Zheng, Yan Guo, Mario Sims, Monther Abu-Remaileh, James G Wilson, Robert E Gerszten, Jonathan Z Long, Mark D Benson.

N-acyl amino acids are a large family of circulating lipid metabolites that modulate energy expenditure and fat mass in rodents. However, little is known about the regulation and potential cardiometabolic functions of N-acyl amino acids in humans. Here, we analyze the cardiometabolic phenotype associations and genetic regulation of four plasma N-fatty acyl amino acids (N-oleoyl-leucine, N-oleoyl-phenylalanine, N-oleoyl-serine, and N-oleoyl-glycine) in 2,351 individuals from the Jackson Heart Study. N-oleoyl-leucine and N-oleoyl-phenylalanine were positively associated with traits related to energy balance, including body mass index, waist circumference, and subcutaneous adipose tissue. In addition, we identify the CYP4F2 locus as a human-specific genetic determinant of plasma N-oleoyl-leucine and N-oleoyl-phenylalanine levels. In vitro, CYP4F2-mediated hydroxylation of N-oleoyl-leucine and N-oleoyl-phenylalanine results in metabolic diversification and production of many previously unknown lipid metabolites with varying characteristics of the fatty acid tail group, including several that structurally resemble fatty acid hydroxy fatty acids (FAHFAs). By contrast, FAAH-regulated N-oleoyl-glycine and N-oleoyl-serine were inversely associated with traits related to glucose and lipid homeostasis. These data uncover a human-specific enzymatic node for the metabolism of a subset of N-fatty acyl amino acids and establish a framework for understanding the cardiometabolic roles of individual N-fatty acyl amino acids in humans.

DOI: https://doi.org/10.1101/2023.03.09.531581
Brain. 2023 Mar 24. pii: awad099. [Epub ahead of print]

Mitochondrial dysfunction and calcium dysregulation in COQ8A-ataxia Purkinje neurons are rescued by CoQ10 treatment.

Ioannis Manolaras, Andrea Del Bondio, Olivier Griso, Laurence Reutenauer, Aurélie Eisenmann, Bianca H Habermann, Hélène Puccio.

  COQ8A-Ataxia is a rare form of neurodegenerative disorder due to mutations in the COQ8A gene. The encoded mitochondrial protein is involved in the regulation of Coenzyme Q10 biosynthesis. Previous studies on the constitutive Coq8a-/-mice indicated specific alterations of cerebellar Purkinje neurons involving altered electrophysiological function and dark cell degeneration. In the present manuscript, we extend our understanding of the contribution of Purkinje neuron dysfunction to the pathology. By generating a Purkinje specific conditional COQ8A knockout, we demonstrate that loss of COQ8A in Purkinje neurons is the main cause of cerebellar ataxia. Furthermore, through in vivo and in vitro approaches, we show that COQ8A-depleted Purkinje neurons have abnormal dendritic arborizations, altered mitochondria function and intracellular calcium dysregulation. Furthermore, we demonstrate that oxidative phosphorylation, in particular Complex IV, is primarily altered at pre-symptomatic stages of the disease. Finally, the morphology of primary Purkinje neurons as well as the mitochondrial dysfunction and calcium dysregulation could be rescued by CoQ10 treatment, suggesting that CoQ10 could be a beneficial treatment for COQ8A-Ataxia.

Keywords:  Purkinje neurons; ataxia; calcium; coenzyme Q10; mitochondria

DOI:  https://doi.org/10.1093/brain/awad099
Front Nutr. 2023 ;10 1110291

Ketogenic therapies for glioblastoma: Understanding the limitations in transitioning from mice to patients.

Angela D Clontz.

  Glioblastoma Multiforme is an aggressive brain cancer affecting children and adults frequently resulting in a short life expectancy. Current cancer therapies include surgery and radiation followed by chemotherapy, which due to their ineffectiveness, requires repeated exposure to the same therapies. Since the 1990s, researchers and doctors have explored other therapies, such as diet therapies, to aid in combating gliomas. The ketogenic diet has gained popularity due to Otto Warburg's theory that tumor cells prefer "aerobic glycolysis" and cannot metabolize ketones. The inability of gliomas to use ketones provides an excellent opportunity to weaken the tumor while protecting healthy cells during cancer treatments. This review will examine some of the current research using the ketogenic diet as a form of cancer therapy to determine if this intervention is manageable and effective in patients with glioblastoma. Peer-reviewed articles from 2009 to 2019 were used. The primary objective is to distinguish differences between pre-clinical and clinical research to determine if the ketogenic diet is reproducible from mouse models into humans to determine its effectiveness. The analysis revealed several limitations of the ketogenic diet as an intervention. The effectiveness is more robust in mice than in human studies. Furthermore, tolerability is marginally supported in human studies requiring more reproducible research to validate that the intervention is manageable and effective in patients with glioblastoma.

Keywords:  calorie restriction; diet intervention; glioblastoma; ketogenic diet; low carbohydrate diet

DOI:  https://doi.org/10.3389/fnut.2023.1110291
J Alzheimers Dis. 2023 Mar 13.

Low Ankle-Brachial Index Relates to Alzheimer-Signature Cerebral Glucose Metabolism in Cognitively Impaired Older Adults.

and for the KBASE Research Group

   BACKGROUND: Ankle-brachial index (ABI), an indicator of atherosclerosis or arterial stiffness, has been associated with Alzheimer's disease (AD) dementia and related cognitive impairment. Nevertheless, only limited information is available regarding its contribution to brain alterations leading to cognitive decline in late-life.
OBJECTIVE: We aimed to investigate the relationship of ABI with in vivo AD pathologies and cerebrovascular injury in cognitively impaired older adults.
METHODS: Total 127 cognitively impaired (70 mild cognitive impairment and 57 AD dementia) individuals, who participated in an ongoing prospective cohort study, were included. All participants underwent comprehensive clinical and neuropsychological assessment, ABI measurement, apolipoprotein E (APOE) ɛ4 genotyping, and multi-modal brain imaging including [11C] Pittsburgh Compound B (PiB)-positron emission tomography (PET) and [18F] fludeoxyglucose (FDG)-PET, and MRI.
RESULTS: General linear model analysis showed significant relationship between ABI strata (low ABI: <1.00, normal ABI: 1.00-1.29, and high ABI: ≥1.30) and AD-signature region cerebral glucose metabolism (AD-CM), even after controlling age, sex, clinical dementia rating-sum of box, and APOE ɛ4 positivity (p = 0.029). Post hoc comparison revealed that low ABI had significantly lower AD-CM than middle and high ABI, while no difference of AD-CM was found between middle and high ABI. There was no significant difference of global Aβ deposition, AD-signature region cortical thickness, and white matter hyperintensity volume between the three ABI strata.
CONCLUSION: Our findings suggest that lower ABI, likely related to atherosclerosis, may contribute to the aggravation of AD-related regional neurodegeneration in cognitively impaired older adults.

Keywords:  Alzheimer’s disease; ankle-brachial index; cerebral Aβ deposition; mild cognitive impairment; neurodegeneration

DOI:  https://doi.org/10.3233/JAD-220911
Redox Biol. 2023 Mar 15. pii: S2213-2317(23)00079-4. [Epub ahead of print]62 102678

Accumulated cholesterol protects tumours from elevated lipid peroxidation in the microenvironment.

Xi Zhao, Xinyu Lian, Jianlan Xie, Guoquan Liu.

  Elevated lipid peroxidation (LPO), usually present in the tumour microenvironment (TME), is profoundly implicated in antitumour immunity and may be targeted for the development of new antitumour therapies. However, tumour cells may also rewire their metabolism to survive elevated LPO. Here, we report a novel and nonantioxidant mechanism by which tumour cells benefit from accumulated cholesterol to restrain LPO and ferroptosis, a nonapoptotic form of cell death characterized by accumulated LPO. Modulating cholesterol metabolism, especially LDLR-mediated cholesterol uptake, shifted the susceptibility of tumour cells to ferroptosis. Elevation of cellular cholesterol content specifically restrained LPO triggered by GSH-GPX4 inhibition or oxidizing factors in the TME. Furthermore, depletion of TME cholesterol by MβCD efficiently enhanced the antitumour efficacy of ferroptosis in a mouse xenograft model. Distinct from the antioxidant effect of its metabolic intermediates, the protective role of cholesterol was ascribed to its ability to decrease membrane fluidity and promote lipid raft formation, which affects the diffusion of LPO substrates. A correlation between LPO and lipid rafts was also found in tumour tissues from renal cancer patients. Together, our ﬁndings have identified a general and nonsacrificial mechanism by which cholesterol suppresses LPO, which can be exploited to enhance the efficacy of ferroptosis-based antitumour strategies.

Keywords:  Cholesterol; Ferroptosis; LDLR; Lipid peroxidation; Lipid raft; Tumour microenvironment

DOI:  https://doi.org/10.1016/j.redox.2023.102678
Dis Model Mech. 2023 Mar 23. pii: dmm.049954. [Epub ahead of print]

Unexpected phenotypic and molecular changes of combined glucocerebrosidase and acid sphingomyelinase deficiency.

Marcus Keatinge, Matthew E Gegg, Lisa Watson, Heather Mortiboys, Nan Li, Mark Dunning, Deepak Ailani, Hai Bui, Astrid van Rens, Dirk J Lefeber, Anthony H V Schapira, Ryan B MacDonald, Oliver Bandmann.

  Heterozygous variants in GBA1 encoding glucocerebrosidase (GCase) are the most common genetic risk factor for Parkinson's disease (PD). Moreover, sporadic PD patients also have a substantial reduction of GCase activity. Genetic variants in SMPD1 are also overrepresented in PD cohorts, whilst a reduction of its encoded enzyme (ASM) activity is linked to an earlier age of PD onset. Despite both converging on the ceramide pathway, how combined deficiencies of both enzymes may interact to modulate PD has yet to be explored. Therefore, we created a double knock out (DKO) zebrafish line for both gba1 and smpd1 to test for an interaction in vivo, hypothesising an exacerbation of phenotypes in the DKO compared to single mutants. Unexpectedly, DKOs maintained conventional swimming behaviour and had normalised neuronal gene expression signatures when compared to single mutants. We further identified rescue of mitochondrial Complexes I and IV in DKOs. Despite having an unexpected rescue effect, our results confirm ASM as a modifier of GBA1 deficiency in vivo. Our study highlights the need for validating how genetic variants and enzymatic deficiencies may interact in vivo.

Keywords:  Acid sphingomyelinase; Gene-gene interaction.; Glucocerebrosidase 1; Parkinson's disease; Zebrafish

DOI:  https://doi.org/10.1242/dmm.049954
Biol Chem. 2023 Mar 24.

Loss of respiratory complex I subunit NDUFB10 affects complex I assembly and supercomplex formation.

Tasnim Arroum, Marie-Theres Borowski, Nico Marx, Frank Schmelter, Martin Scholz, Olympia Ekaterini Psathaki, Michael Hippler, José Antonio Enriquez, Karin B Busch.

  The orchestrated activity of the mitochondrial respiratory or electron transport chain (ETC) and ATP synthase convert reduction power (NADH, FADH2) into ATP, the cell's energy currency in a process named oxidative phosphorylation (OXPHOS). Three out of the four ETC complexes are found in supramolecular assemblies: complex I, III, and IV form the respiratory supercomplexes (SC). The plasticity model suggests that SC formation is a form of adaptation to changing conditions such as energy supply, redox state, and stress. Complex I, the NADH-dehydrogenase, is part of the largest supercomplex (CI + CIII2 + CIVn). Here, we demonstrate the role of NDUFB10, a subunit of the membrane arm of complex I, in complex I and supercomplex assembly on the one hand and bioenergetics function on the other. NDUFB10 knockout was correlated with a decrease of SCAF1, a supercomplex assembly factor, and a reduction of respiration and mitochondrial membrane potential. This likely is due to loss of proton pumping since the CI P P -module is downregulated and the P D -module is completely abolished in NDUFB10 knock outs.

Keywords:  NDUFB10; OXPHOS; complex I; mitochondria; respiratory chain supercomplexes

DOI:  https://doi.org/10.1515/hsz-2022-0309
EMBO Rep. 2023 Mar 20. e55760

A quantitative fluorescence-based approach to study mitochondrial protein import.

Naintara Jain, Ridhima Gomkale, Olaf Bernhard, Peter Rehling, Luis Daniel Cruz-Zaragoza.

  Mitochondria play central roles in cellular energy production and metabolism. Most proteins required to carry out these functions are synthesized in the cytosol and imported into mitochondria. A growing number of metabolic disorders arising from mitochondrial dysfunction can be traced to errors in mitochondrial protein import. The mechanisms underlying the import of precursor proteins are commonly studied using radioactively labeled precursor proteins imported into purified mitochondria. Here, we establish a fluorescence-based import assay to analyze protein import into mitochondria. We show that fluorescently labeled precursors enable import analysis with similar sensitivity to those using radioactive precursors, yet they provide the advantage of quantifying import with picomole resolution. We adapted the import assay to a 96-well plate format allowing for fast analysis in a screening-compatible format. Moreover, we show that fluorescently labeled precursors can be used to monitor the assembly of the F1 F0 ATP synthase in purified mitochondria. Thus, we provide a sensitive fluorescence-based import assay that enables quantitative and fast import analysis.

Keywords:  fluorescent precursor; in vitro import; mitochondria; presequence pathway; protein import

DOI:  https://doi.org/10.15252/embr.202255760