bims-medebr 2023-06-18 papers

bims-medebr

Biomed News

on Metabolism of the developing brain

Issue of 2023‒06‒18
34 papers selected by
Regina F. Fernández
Johns Hopkins University

Modulation of Dietary Choline Uptake in a Mouse Model of Acid Sphingomyelinase Deficiency.
Lactate as a supplemental fuel for synaptic transmission and neuronal network oscillations: Potentials and limitations.
Modulation of the autophagy-lysosomal pathway and endoplasmic reticulum stress by ketone bodies in experimental models of stroke.
Age-related changes in energy metabolism in peripheral mononuclear blood cells (PBMCs) and the brains of cognitively healthy seniors.
Homocysteine May Decrease Glucose Uptake and Alter the Akt/GSK3β/GLUT1 Signaling Pathway in Hippocampal Slices: Neuroprotective Effects of Rivastigmine and Ibuprofen.
Brain glucose metabolism on [18F]-FDG PET/CT: a dynamic biomarker predicting depression and anxiety in cancer patients.
A Targeted Mass Spectrometry Approach to Identify Peripheral Changes in Metabolic Pathways of Patients with Alzheimer's Disease.
Memory deficits in a juvenile rat model of type 1 diabetes are due to excess 11β-HSD1 activity, which is upregulated by high glucose concentrations rather than insulin deficiency.
Fourteen cases of cerebral creatine deficiency syndrome in children: a cohort study in China.
Mass spectrometry imaging as an emerging tool for studying metabolism in human brain organoids.
Brightness and shadows of mitochondrial ROS in the brain.
Folate and Other B Vitamins in Brain Health and Disease.
Substrate binding-induced conformational transitions in the omega-3 fatty acid transporter MFSD2A.
Mitochondria-targeted nanoparticles in treatment of neurodegenerative diseases.
Time-resolved proteomic analyses of senescence highlight metabolic rewiring of mitochondria.
In vitro galactose impairs energy metabolism in the brain of young rats: protective role of antioxidants.
USP30 impairs mitochondrial quality control and aggravates oxidative damage after traumatic brain injury.
Sphingolipid and Phospholipid Levels Are Altered in Human Brain in Chorea-Acanthocytosis.
Ganglioside GM1 and the Central Nervous System.
Brain metabolic derangements examined using 1H MRS and their (in)consistency among different rodent models of depression.
Clinical and Gene Analysis of Fatty Acid Oxidation Disorders Found in Neonatal Tandem Mass Spectrometry Screening.
lThyroid hormone transporter Mct8/Oatp1c1 deficiency compromises proper oligodendrocyte maturation in the mouse CNS.
Cross-talk between DNA damage response and the central carbon metabolic network underlies selective vulnerability of Purkinje neurons in ataxia-telangiectasia.
Metabolic imaging with deuterium labeled substrates.
Maternal Inborn Errors of Metabolism Detected in Expanded Newborn Metabolic Screening.
Is there a role for ketones as alternative fuel in critical illness?
Central and peripheral mechanisms involved in the control of GnRH neuronal function by metabolic factors.
Roles of bile acids signaling in neuromodulation under physiological and pathological conditions.
Prenatal Supplementation of Docosahexaenoic Acid for the Management of Preterm Births: Clinical Information for Practice.
Oxygen-Independent Assays to Measure Mitochondrial Function in Mammals.
Acyl-CoA dehydrogenase substrate promiscuity: Challenges and opportunities for development of substrate reduction therapy in disorders of valine and isoleucine metabolism.
Ex vivo immunocapture and functional characterization of cell-type-specific mitochondria using MitoTag mice.
Untargeted Metabolomics Identifies Biomarkers for MCADD Neonates in Dried Blood Spots.
Purification and Characterization of Mitochondrial Mg2+-Independent Sphingomyelinase from Rat Brain.

Int J Mol Sci. 2023 Jun 05. pii: 9756. [Epub ahead of print]24(11):

Modulation of Dietary Choline Uptake in a Mouse Model of Acid Sphingomyelinase Deficiency.

Ángel Gaudioso, Pilar Moreno-Huguet, Josefina Casas, Edward H Schuchman, María Dolores Ledesma.

  Acid sphingomyelinase deficiency (ASMD) is a lysosomal storage disorder caused by mutations in the gene-encoding acid sphingomyelinase (ASM). ASMD impacts peripheral organs in all patients, including the liver and spleen. The infantile and chronic neurovisceral forms of the disease also lead to neuroinflammation and neurodegeneration for which there is no effective treatment. Cellular accumulation of sphingomyelin (SM) is a pathological hallmark in all tissues. SM is the only sphingolipid comprised of a phosphocholine group linked to ceramide. Choline is an essential nutrient that must be obtained from the diet and its deficiency promotes fatty liver disease in a process dependent on ASM activity. We thus hypothesized that choline deprivation could reduce SM production and have beneficial effects in ASMD. Using acid sphingomyelinase knock-out (ASMko) mice, which mimic neurovisceral ASMD, we have assessed the safety of a choline-free diet and its effects on liver and brain pathological features such as altered sphingolipid and glycerophospholipid composition, inflammation and neurodegeneration. We found that the choline-free diet was safe in our experimental conditions and reduced activation of macrophages and microglia in the liver and brain, respectively. However, there was no significant impact on sphingolipid levels and neurodegeneration was not prevented, arguing against the potential of this nutritional strategy to assist in the management of neurovisceral ASMD patients.

Keywords:  acid sphingomyelinase deficiency; choline; lipidomic; lysosomal storage disorder; phospholipid; sphingomyelin

DOI:  https://doi.org/10.3390/ijms24119756
J Neurochem. 2023 Jun 13.

Lactate as a supplemental fuel for synaptic transmission and neuronal network oscillations: Potentials and limitations.

Oliver Kann.

  Lactate shuttled from the blood circulation, astrocytes, oligodendrocytes or even activated microglia (resident macrophages) to neurons has been hypothesized to represent a major source of pyruvate compared to what is normally produced endogenously by neuronal glucose metabolism. However, the role of lactate oxidation in fueling neuronal signaling associated with complex cortex function, such as perception, motor activity, and memory formation, is widely unclear. This issue has been experimentally addressed using electrophysiology in hippocampal slice preparations (ex vivo) that permit the induction of different neural network activation states by electrical stimulation, optogenetic tools or receptor ligand application. Collectively, these studies suggest that lactate in the absence of glucose (lactate only) impairs gamma (30-70 Hz) and theta-gamma oscillations, which feature high energy demand revealed by the cerebral metabolic rate of oxygen (CMRO2, set to 100%). The impairment comprises oscillation attenuation or moderate neural bursts (excitation-inhibition imbalance). The bursting is suppressed by elevating the glucose fraction in energy substrate supply. By contrast, lactate can retain certain electric stimulus-induced neural population responses and intermittent sharp wave-ripple activity that features lower energy expenditure (CMRO2 of about 65%). Lactate utilization increases the oxygen consumption by about 9% during sharp wave-ripples reflecting enhanced adenosine-5'-triphosphate (ATP) synthesis by oxidative phosphorylation in mitochondria. Moreover, lactate attenuates neurotransmission in glutamatergic pyramidal cells and fast-spiking, γ-aminobutyric acid (GABA)ergic interneurons by reducing neurotransmitter release from presynaptic terminals. By contrast, the generation and propagation of action potentials in the axon is regular. In conclusion, lactate is less effective than glucose and potentially detrimental during neural network rhythms featuring high energetic costs, likely through the lack of some obligatory ATP synthesis by aerobic glycolysis at excitatory and inhibitory synapses. High lactate/glucose ratios might contribute to central fatigue, cognitive impairment, and epileptic seizures partially seen, for instance, during exhaustive physical exercise, hypoglycemia and neuroinflammation.

Keywords:  brain slice technique; concentration gradient; immunometabolism; neuronal activation; nitric oxide; postsynaptic current

DOI:  https://doi.org/10.1111/jnc.15867
J Neurochem. 2023 Jun 16.

Modulation of the autophagy-lysosomal pathway and endoplasmic reticulum stress by ketone bodies in experimental models of stroke.

Teresa Montiel, Juan Carlos Gómora-García, Cristian Gerónimo-Olvera, Yessica Heras-Romero, Berenice N Bernal-Vicente, Xochitl Pérez-Martínez, Luis B Tovar-Y-Romo, Lourdes Massieu.

  Ischemic stroke is a leading cause of disability worldwide. There is no simple treatment to alleviate ischemic brain injury, as thrombolytic therapy is applicable within a narrow time window. During the last years, the ketogenic diet (KD) and the exogenous administration of the ketone body β-hydroxybutyrate (BHB) have been proposed as therapeutic tools for acute neurological disorders and both can reduce ischemic brain injury. However, the mechanisms involved are not completely clear. We have previously shown that the D enantiomer of BHB stimulates the autophagic flux in cultured neurons exposed to glucose deprivation (GD) and in the brain of hypoglycemic rats. Here, we have investigated the effect of the systemic administration of D-BHB, followed by its continuous infusion after middle cerebral artery occlusion (MCAO), on the autophagy-lysosomal pathway and the activation of the unfolded protein response (UPR). Results show for the first time that the protective effect of BHB against MCAO injury is enantiomer selective as only D-BHB, the physiologic enantiomer of BHB, significantly reduced brain injury. D-BHB treatment prevented the cleavage of the lysosomal membrane protein LAMP2 and stimulated the autophagic flux in the ischemic core and the penumbra. In addition, D-BHB notably reduced the activation of the PERK/eIF2α/ATF4 pathway of the UPR and inhibited IRE1α phosphorylation. L-BHB showed no significant effect relative to ischemic animals. In cortical cultures under GD, D-BHB prevented LAMP2 cleavage and decreased lysosomal number. It also abated the activation of the PERK/eIF2α/ATF4 pathway, partially sustained protein synthesis, and reduced pIRE1α. In contrast, L-BHB showed no significant effects. Results suggest that protection elicited by D-BHB treatment post-ischemia prevents lysosomal rupture allowing functional autophagy, preventing the loss of proteostasis and UPR activation.

Keywords:  Beta-hydroxybutyrate; Endoplasmic Reticulum stress; Glucose deprivation; Neuronal death; Proteostasis; Unfolded Protein Response

DOI:  https://doi.org/10.1111/jnc.15852
Geroscience. 2023 Jun 13.

Age-related changes in energy metabolism in peripheral mononuclear blood cells (PBMCs) and the brains of cognitively healthy seniors.

Carmina V Silaidos, Martina Reutzel, Lena Wachter, Fabian Dieter, Nasir Ludin, Werner F Blum, Stefan A Wudy, Silke Matura, Ulrich Pilatus, Elke Hattingen, Johannes Pantel, Gunter P Eckert.

  Mitochondrial dysfunction is a hallmark of cellular senescence and many age-related neurodegenerative diseases. We therefore investigated the relationship between mitochondrial function in peripheral blood cells and cerebral energy metabolites in young and older sex-matched, physically and mentally healthy volunteers. Cross-sectional observational study involving 65 young (26.0 ± 0.49 years) and 65 older (71.7 ± 0.71 years) women and men recruited. Cognitive health was evaluated using established psychometric methods (MMSE, CERAD). Blood samples were collected and analyzed, and fresh peripheral blood mononuclear cells (PBMCs) were isolated. Mitochondrial respiratory complex activity was measured using a Clarke electrode. Adenosine triphosphate (ATP) and citrate synthase activity (CS) were determined by bioluminescence and photometrically. N-aspartyl-aspartate (tNAA), ATP, creatine (Cr), and phosphocreatine (PCr) were quantified in brains using 1H- and 31P-magnetic resonance spectroscopic imaging (MRSI). Levels of insulin-like growth factor 1 (IGF-1) were determined using a radio-immune assay (RIA). Complex IV activity (CIV) (- 15%) and ATP levels (- 11%) were reduced in PBMCs isolated from older participants. Serum levels of IGF-1 were significantly reduced (- 34%) in older participants. Genes involved in mitochondrial activity, antioxidant mechanisms, and autophagy were unaffected by age. tNAA levels were reduced (- 5%), Cr (+ 11%), and PCr (+ 14%) levels were increased, and ATP levels were unchanged in the brains of older participants. Markers of energy metabolism in blood cells did not significantly correlate with energy metabolites in the brain. Age-related bioenergetic changes were detected in peripheral blood cells and the brains of healthy older people. However, mitochondrial function in peripheral blood cells does not reflect energy related metabolites in the brain. While ATP levels in PBMCs may be be a valid marker for age-related mitochondrial dysfunction in humans, cerebral ATP remained constant.

Keywords:  1H-magnetic resonance spectroscopic imaging; 31P magnetic resonance spectroscopic imaging; Adenosine triphosphate; Aging; Brain aging; CAD; Citrate synthase; Creatine; IGF-1; Mitochondria; Mitochondrial dysfunction; PBMCs; Peripheral blood mononuclear cells; Phosphocreatine; Respiration; SOD; TFAM

DOI:  https://doi.org/10.1007/s11357-023-00810-9
Mol Neurobiol. 2023 Jun 14.

Homocysteine May Decrease Glucose Uptake and Alter the Akt/GSK3β/GLUT1 Signaling Pathway in Hippocampal Slices: Neuroprotective Effects of Rivastigmine and Ibuprofen.

Osmar Vieira Ramires Júnior, Josiane Silva Silveira, Tiago Marcon Dos Santos, Fernanda Silva Ferreira, Adriana Fernanda K Vizuete, Carlos Alberto Gonçalves, Angela T S Wyse.

  Homocysteine (Hcy) is a risk factor for neurodegenerative diseases, such as Alzheimer's Disease, and is related to cellular and tissue damage. In the present study, we verified the effect of Hcy on neurochemical parameters (redox homeostasis, neuronal excitability, glucose, and lactate levels) and the Serine/Threonine kinase B (Akt), Glucose synthase kinase-3β (GSK3β) and Glucose transporter 1 (GLUT1) signaling pathway in hippocampal slices, as well as the neuroprotective effects of ibuprofen and rivastigmine alone or in combination in such effects. Male Wistar rats (90 days old) were euthanized and the brains were dissected. The hippocampus slices were pre-treated for 30 min [saline medium or Hcy (30 µM)], then the other treatments were added to the medium for another 30 min [ibuprofen, rivastigmine, or ibuprofen + rivastigmine]. The dichlorofluorescein formed, nitrite and Na+, K+-ATPase activity was increased by Hcy at 30 µM. Ibuprofen reduced dichlorofluorescein formation and attenuated the effect of Hcy. The reduced glutathione content was reduced by Hcy. Treatments with ibuprofen and Hcy + ibuprofen increased reduced glutathione. Hcy at 30 µM caused a decrease in hippocampal glucose uptake and GLUT1 expression, and an increase in Glial Fibrillary Acidic Protein-protein expression. Phosphorylated GSK3β and Akt levels were reduced by Hcy (30 µM) and co-treatment with Hcy + rivastigmine + ibuprofen reversed these effects. Hcy toxicity on glucose metabolism can promote neurological damage. The combination of treatment with rivastigmine + ibuprofen attenuated such effects, probably by regulating the Akt/GSK3β/GLUT1 signaling pathway. Reversal of Hcy cellular damage by these compounds may be a potential neuroprotective strategy for brain damage.

Keywords:  GLUT1; Glucose metabolism; Homocysteine; Ibuprofen; Rivastigmine; via Akt/GSK3β

DOI:  https://doi.org/10.1007/s12035-023-03408-6
Front Oncol. 2023 ;13 1098943

Brain glucose metabolism on [18F]-FDG PET/CT: a dynamic biomarker predicting depression and anxiety in cancer patients.

Xue Yang, Guangxia Yang, Ruojun Wang, Yanjuan Wang, Shengyi Zhang, Jian Wang, Chunjing Yu, Zeqin Ren.

  Objectives: To explore the correlation between the incidence rates of depression and anxiety and cerebral glucose metabolism in cancer patients.Methods: The experiment subjects consisted of patients with lung cancer, head and neck tumor, stomach cancer, intestinal cancer, breast cancer and healthy individuals. A total of 240 tumor patients and 39 healthy individuals were included. All subjects were evaluated by the Hamilton depression scale (HAMD) and Manifest anxiety scale (MAS), and were examined by whole body Positron Emission Tomography/Computed Tomography (PET/CT) with 18F-fluorodeoxyglucose (FDG). Demographic, baseline clinical characteristics, brain glucose metabolic changes, emotional disorder scores and their relations were statistically analyzed.
Results: The incidence rates of depression and anxiety in patients with lung cancer were higher than those in patients with other tumors, and Standard uptake values (SUVs) and metabolic volume in bilateral frontal lobe, bilateral temporal lobe, bilateral caudate nucleus, bilateral hippocampus, left cingulate gyrus were lower than those in patients with other tumors. We also found that poor pathological differentiation, and advanced TNM stage independently associated with depression and anxiety risk. SUVs in the bilateral frontal lobe, bilateral temporal lobe, bilateral caudate nucleus, bilateral hippocampus, left cingulate gyrus were negatively correlated with HAMD and MAS scores.
Conclusion: This study revealed the correlation between brain glucose metabolism and emotional disorders in cancer patients. The changes in brain glucose metabolism were expected to play a major role in emotional disorders in cancer patients as psychobiological markers. These findings indicated that functional imaging can be applied for psychological assessment of cancer patients as an innovative method.

Keywords:  anxiety disorder; cancer; depression; glucose metabolism; positron emission

DOI:  https://doi.org/10.3389/fonc.2023.1098943
Int J Mol Sci. 2023 Jun 04. pii: 9736. [Epub ahead of print]24(11):

A Targeted Mass Spectrometry Approach to Identify Peripheral Changes in Metabolic Pathways of Patients with Alzheimer's Disease.

Pierluigi Reveglia, Carmela Paolillo, Antonella Angiolillo, Gabriella Ferretti, Ruggero Angelico, Rossana Sirabella, Gaetano Corso, Carmela Matrone, Alfonso Di Costanzo.

  Alzheimer's disease (AD), a neurodegenerative disorder, is the most common cause of dementia in the elderly population. Since its original description, there has been intense debate regarding the factors that trigger its pathology. It is becoming apparent that AD is more than a brain disease and harms the whole-body metabolism. We analyzed 630 polar and apolar metabolites in the blood of 20 patients with AD and 20 healthy individuals, to determine whether the composition of plasma metabolites could offer additional indicators to evaluate any alterations in the metabolic pathways related to the illness. Multivariate statistical analysis showed that there were at least 25 significantly dysregulated metabolites in patients with AD compared with the controls. Two membrane lipid components, glycerophospholipids and ceramide, were upregulated, whereas glutamic acid, other phospholipids, and sphingolipids were downregulated. The data were analyzed using metabolite set enrichment analysis and pathway analysis using the KEGG library. The results showed that at least five pathways involved in the metabolism of polar compounds were dysregulated in patients with AD. Conversely, the lipid pathways did not show significant alterations. These results support the possibility of using metabolome analysis to understand alterations in the metabolic pathways related to AD pathophysiology.

Keywords:  Alzheimer’s disease; lipidomic profile; metabolomic profile; targeted mass spectrometry

DOI:  https://doi.org/10.3390/ijms24119736
Diabetologia. 2023 Jun 10.

Memory deficits in a juvenile rat model of type 1 diabetes are due to excess 11β-HSD1 activity, which is upregulated by high glucose concentrations rather than insulin deficiency.

Julie Brossaud, Clémentine Bosch-Bouju, Nathalie Marissal-Arvy, Marie-Neige Campas-Lebecque, Jean-Christophe Helbling, Scott P Webster, Brian R Walker, Xavier Fioramonti, Guillaume Ferreira, Pascal Barat, Jean-Benoît Corcuff, Marie-Pierre Moisan.

  AIMS/HYPOTHESIS: Children with diabetes may display cognitive alterations although vascular disorders have not yet appeared. Variations in glucose levels together with relative insulin deficiency in treated type 1 diabetes have been reported to impact brain function indirectly through dysregulation of the hypothalamus-pituitary-adrenal axis. We have recently shown that enhancement of glucocorticoid levels in children with type 1 diabetes is dependent not only on glucocorticoid secretion but also on glucocorticoid tissue concentrations, which is linked to 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) activity. Hypothalamus-pituitary-adrenal axis dysfunction and memory alteration were further dissected in a juvenile rat model of diabetes showing that excess 11β-HSD1 activity within the hippocampus is associated with hippocampal-dependent memory deficits. Here, to investigate the causal relationships between diabetes, 11β-HSD1 activity and hippocampus-dependent memory deficits, we evaluated the beneficial effect of 11β-HSD1 inhibition on hippocampal-related memory in juvenile diabetic rats. We also examined whether diabetes-associated enhancement of hippocampal 11β-HSD1 activity is due to an increase in brain glucose concentrations and/or a decrease in insulin signalling.METHODS: Diabetes was induced in juvenile rats by daily i.p. injection of streptozotocin for 2 consecutive days. Inhibition of 11β-HSD1 was obtained by administrating the compound UE2316 twice daily by gavage for 3 weeks, after which hippocampal-dependent object location memory was assessed. Hippocampal 11β-HSD1 activity was estimated by the ratio of corticosterone/dehydrocorticosterone measured by LC/MS. Regulation of 11β-HSD1 activity in response to changes in glucose or insulin levels was determined ex vivo on acute brain hippocampal slices. The insulin regulation of 11β-HSD1 was further examined in vivo using virally mediated knockdown of insulin receptor expression specifically in the hippocampus.
RESULTS: Our data show that inhibiting 11β-HSD1 activity prevents hippocampal-related memory deficits in diabetic juvenile rats. A significant increase (53.0±9.9%) in hippocampal 11β-HSD1 activity was found in hippocampal slices incubated in high glucose conditions (13.9 mmol/l) vs normal glucose conditions (2.8 mmol/l) without insulin. However, 11β-HSD1 activity was not affected by variations in insulin concentration either in the hippocampal slices or after a decrease in hippocampal insulin receptor expression.
CONCLUSIONS/INTERPRETATION: Together, these data demonstrate that an increase in 11β-HSD1 activity contributes to memory deficits observed in juvenile diabetic rats and that an excess of hippocampal 11β-HSD1 activity stems from high glucose levels rather than insulin deficiency. 11β-HSD1 might be a therapeutic target for treating cognitive impairments associated with diabetes.

Keywords:  11β-Hydroxysteroid dehydrogenase; Glucocorticoids; Type 1 diabetes

DOI:  https://doi.org/10.1007/s00125-023-05942-3
Transl Pediatr. 2023 May 30. 12(5): 927-937

Fourteen cases of cerebral creatine deficiency syndrome in children: a cohort study in China.

Weihua Sun, Yi Wang, Mengyuan Wu, Hongjiang Wu, Xiaomin Peng, Yingyan Shi, Feifan Xiao, Bingbing Wu, Wenhao Zhou, Wei Lu.

  Background: This study sought to analyze the clinical characteristics, biochemical metabolic indications, treatment results, and genetic spectrum of cerebral creatine deficiency syndrome (CCDS), estimate the prevalence of CCDS in Chinese children and provide a reference to guide clinical practice.Methods: We performed a retrospective cohort study of 3,568 children with developmental delay at Children's Hospital of Fudan University over a 6-year period (January 2017-December 2022). Metabolites in the blood/urine were detected by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and genetic testing was performed by next-generation sequencing (NGS). The patients with suspected CCDS were ultimately diagnosed by magnetic resonance spectroscopy (MRS). The patients were then treated and followed up. All the reported cases of CCDS, their gene mutations, and treatment results in China were summarized.
Results: Ultimately, 14 patients were diagnosed with CCDS. The age of onset was between 1-2 years. All the patients had developmental delay, 9 had epilepsy, and 8 had movement or behavioral disorders. A total of 17 genetic variants were identified, including 6 novel variants. c.403G>A, c.491dupG of the guanidinoacetate methyltransferase (GAMT) gene had a relatively high frequency. After treatment, patients with GAMT deficiency showed obvious improvements, and brain creatine (Cr) levels recovered to 50-80% of normal, 1 patient achieved normal neurodevelopment, and 3 patients became epilepsy free; however, 6 male patients with X-linked creatine transporter gene (SLC6A8) variants received Cr for 3-6 months with no effect, and 2 patients received combined therapy with few improvements.
Conclusions: The prevalence of CCDS is ~0.39% in Chinese children with developmental delay. A low-protein diet, Cr and, ornithine were useful for patients with GAMT deficiency. Male patients with SLC6A8 deficiency showed only limited improvement on combined therapy.

Keywords:  Cerebral creatine deficiency syndrome (CCDS); creatine (Cr); liquid chromatography-tandem mass spectrometry (LC-MS/MS); magnetic resonance spectroscopy (MRS)

DOI:  https://doi.org/10.21037/tp-23-164
Front Mol Biosci. 2023 ;10 1181965

Mass spectrometry imaging as an emerging tool for studying metabolism in human brain organoids.

Gerarda Cappuccio, Saleh M Khalil, Sivan Osenberg, Feng Li, Mirjana Maletic-Savatic.

  Human brain organoids are emerging models to study human brain development and pathology as they recapitulate the development and characteristics of major neural cell types, and enable manipulation through an in vitro system. Over the past decade, with the advent of spatial technologies, mass spectrometry imaging (MSI) has become a prominent tool for metabolic microscopy, providing label-free, non-targeted molecular and spatial distribution information of the metabolites within tissue, including lipids. This technology has never been used for studies of brain organoids and here, we set out to develop a standardized protocol for preparation and mass spectrometry imaging of human brain organoids. We present an optimized and validated sample preparation protocol, including sample fixation, optimal embedding solution, homogenous deposition of matrices, data acquisition and processing to maximize the molecular information derived from mass spectrometry imaging. We focus on lipids in organoids, as they play critical roles during cellular and brain development. Using high spatial and mass resolution in positive- and negative-ion modes, we detected 260 lipids in the organoids. Seven of them were uniquely localized within the neurogenic niches or rosettes as confirmed by histology, suggesting their importance for neuroprogenitor proliferation. We observed a particularly striking distribution of ceramide-phosphoethanolamine CerPE 36:1; O2 which was restricted within rosettes and of phosphatidyl-ethanolamine PE 38:3, which was distributed throughout the organoid tissue but not in rosettes. This suggests that ceramide in this particular lipid species might be important for neuroprogenitor biology, while its removal may be important for terminal differentiation of their progeny. Overall, our study establishes the first optimized experimental pipeline and data processing strategy for mass spectrometry imaging of human brain organoids, allowing direct comparison of lipid signal intensities and distributions in these tissues. Further, our data shed new light on the complex processes that govern brain development by identifying specific lipid signatures that may play a role in cell fate trajectories. Mass spectrometry imaging thus has great potential in advancing our understanding of early brain development as well as disease modeling and drug discovery.

Keywords:  brain organoids; mass spectrometry imaging method; metabolome; neurons; neuroprogenitors

DOI:  https://doi.org/10.3389/fmolb.2023.1181965
Neurobiol Dis. 2023 Jun 13. pii: S0969-9961(23)00214-0. [Epub ahead of print] 106199

Brightness and shadows of mitochondrial ROS in the brain.

Daniel Jimenez-Blasco, Angeles Almeida, Juan P Bolaños.

  Mitochondrial reactive oxygen species (mROS) have been generally considered harmful byproducts wanted to clear when elevated to avoid brain damage. However, the abundance of mROS in astrocytes is very high -about one order of magnitude above that in neurons-, despite they are essential to preserve cell metabolism and animal behavior. Here, we have focused on this apparent ambiguity by discussing (i) the intrinsic mechanisms accounting for the higher production of mROS by the mitochondrial respiratory chain in astrocytes than in neurons, (ii) the specific molecular targets of astrocytic beneficial mROS, and (iii) how decreased astrocytic mROS causes excess neuronal mROS leading to cellular and organismal damage. We hope that this mini-review serves to clarifying the apparent controversy on the beneficial versus deleterious faces of ROS in the brain from molecular to higher-order organismal levels.

Keywords:  Astrocytes; Glutathione; Mitochondria; Neurons; Reactive oxygen species; Supercomplexes

DOI:  https://doi.org/10.1016/j.nbd.2023.106199
Nutrients. 2023 May 29. pii: 2525. [Epub ahead of print]15(11):

Folate and Other B Vitamins in Brain Health and Disease.

Edward V Quadros.

B vitamins as a group play essential roles in a multitude of metabolic reactions involved in cellular replication, energy production, the synthesis of intermediary compounds, and neurotransmitters [...].

DOI: https://doi.org/10.3390/nu15112525
Nat Commun. 2023 Jun 09. 14(1): 3391

Substrate binding-induced conformational transitions in the omega-3 fatty acid transporter MFSD2A.

Shana Bergman, Rosemary J Cater, Ambrose Plante, Filippo Mancia, George Khelashvili.

Major Facilitator Superfamily Domain containing 2 A (MFSD2A) is a transporter that is highly enriched at the blood-brain and blood-retinal barriers, where it mediates Na+-dependent uptake of ω-3 fatty acids in the form of lysolipids into the brain and eyes, respectively. Despite recent structural insights, it remains unclear how this process is initiated, and driven by Na+. Here, we perform Molecular Dynamics simulations which demonstrate that substrates enter outward facing MFSD2A from the outer leaflet of the membrane via lateral openings between transmembrane helices 5/8 and 2/11. The substrate headgroup enters first and engages in Na+ -bridged interactions with a conserved glutamic acid, while the tail is surrounded by hydrophobic residues. This binding mode is consistent with a "trap-and-flip" mechanism and triggers transition to an occluded conformation. Furthermore, using machine learning analysis, we identify key elements that enable these transitions. These results advance our molecular understanding of the MFSD2A transport cycle.

DOI: https://doi.org/10.1038/s41467-023-39088-y
Exploration (Beijing). 2021 Dec;1(3): 20210115

Mitochondria-targeted nanoparticles in treatment of neurodegenerative diseases.

Yue Zhang, Han Yang, Daohe Wei, Xinhui Zhang, Jian Wang, Xiaoli Wu, Jin Chang.

  Neurodegenerative diseases (NDs) are a class of heterogeneous diseases that includes Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. Mitochondria play an important role in oxidative balance and metabolic activity of neurons; therefore, mitochondrial dysfunction is associated with NDs and mitochondria are considered a potential treatment target for NDs. Several obstacles, including the blood-brain barrier (BBB) and cell/mitochondrial membranes, reduce the efficiency of drug entry into the target lesions. Therefore, a variety of neuron mitochondrial targeting strategies has been developed. Among them, nanotechnology-based treatments show especially promising results. Owing to their adjustable size, appropriate charge, and lipophilic surface, nanoparticles (NPs) are the ideal theranostic system for crossing the BBB and targeting the neuronal mitochondria. In this review, we discussed the role of dysfunctional mitochondria in ND pathogenesis as well as the physiological barriers to various treatment strategies. We also reviewed the use and advantages of various NPs (including organic, inorganic, and biological membrane-coated NPs) for the treatment and diagnosis of NDs. Finally, we summarized the evidence and possible use for the promising role of NP-based theranostic systems in the treatment of mitochondrial dysfunction-related NDs.

Keywords:  mitochondrial dysfunction; nanoparticles; neurodegenerative diseases; oxidative stress; target

DOI:  https://doi.org/10.1002/EXP.20210115
Life Sci Alliance. 2023 Sep;pii: e202302127. [Epub ahead of print]6(9):

Time-resolved proteomic analyses of senescence highlight metabolic rewiring of mitochondria.

Jun Yong Kim, Ilian Atanassov, Frederik Dethloff, Lara Kroczek, Thomas Langer.

Mitochondrial dysfunction and cellular senescence are hallmarks of aging. However, the relationship between these two phenomena remains incompletely understood. In this study, we investigated the rewiring of mitochondria upon development of the senescent state in human IMR90 fibroblasts. Determining the bioenergetic activities and abundance of mitochondria, we demonstrate that senescent cells accumulate mitochondria with reduced OXPHOS activity, resulting in an overall increase of mitochondrial activities in senescent cells. Time-resolved proteomic analyses revealed extensive reprogramming of the mitochondrial proteome upon senescence development and allowed the identification of metabolic pathways that are rewired with different kinetics upon establishment of the senescent state. Among the early responding pathways, the degradation of branched-chain amino acid was increased, whereas the one carbon folate metabolism was decreased. Late-responding pathways include lipid metabolism and mitochondrial translation. These signatures were confirmed by metabolic flux analyses, highlighting metabolic rewiring as a central feature of mitochondria in cellular senescence. Together, our data provide a comprehensive view on the changes in mitochondrial proteome in senescent cells and reveal how the mitochondrial metabolism is rewired in senescent cells.

DOI: https://doi.org/10.26508/lsa.202302127
Nucleosides Nucleotides Nucleic Acids. 2023 Jun 15. 1-19

In vitro galactose impairs energy metabolism in the brain of young rats: protective role of antioxidants.

Daniela Delwing-de Lima, Simone Sasso, Débora Delwing-Dal Magro, Nariana Regina Pereira, André Felipe Rodrigues, Felipe Schmitz, Eduardo Manoel Pereira, Maria Augusta Schramm do Nascimento, Angela T S Wyse.

  We, herein, investigated the in vitro effects of galactose on the activity of pyruvate kinase, succinate dehydrogenase (SDH), complex II and IV (cytochrome c oxidase) of the respiratory chain and Na+K+-ATPase in the cerebral cortex, cerebellum and hippocampus of 30-day-old rats. We also determined the influence of the antioxidants, trolox, ascorbic acid and glutathione, on the effects elicited by galactose. Galactose was added to the assay at concentrations of 0.1, 3.0, 5.0 and 10.0 mM. Control experiments were performed without galactose. Galactose, at 3.0, 5.0 and 10.0 mM, decreased pyruvate kinase activity in the cerebral cortex and at 10.0 mM in the hippocampus. Galactose, at 10.0 mM, reduced SDH and complex II activities in the cerebellum and hippocampus, and reduced cytochrome c oxidase activity in the hippocampus. Additionally, decreased Na+K+-ATPase activity in the cerebral cortex and hippocampus; conversely, galactose, at 3.0 and 5.0 mM, increased this enzyme's activity in the cerebellum. Data show that galactose disrupts energy metabolism and trolox, ascorbic acid and glutathione addition prevented the majority of alterations in the parameters analyzed, suggesting the use of antioxidants as an adjuvant therapy in Classic galactosemia.

Keywords:  Antioxidants; Na+K+-ATPase; brain; energy metabolism; galactose

DOI:  https://doi.org/10.1080/15257770.2023.2222776
Biochem Biophys Res Commun. 2023 May 19. pii: S0006-291X(23)00639-3. [Epub ahead of print]671 58-66

USP30 impairs mitochondrial quality control and aggravates oxidative damage after traumatic brain injury.

Yang Wu, Qing Hu, Hongbo Cheng, Jiegang Yu, Li Gao, Guodong Gao.

  Clinical progress in the treatment of traumatic brain injury (TBI) is hindered by the poor understanding of the molecular mechanisms that underlie secondary brain injury (SBI). USP30, a mitochondrial deubiquitinase, has been implicated in the pathological progress of various diseases. However, the precise role of USP30 in TBI-induced SBI remains unclear. In this study, we found that USP30 was differentially upregulated after TBI in humans and mice. Immunofluorescence staining further revealed that the enhanced USP30 mainly localized in neurons. Neuron-specific knockout of USP30 reduced lesion volumes, mitigated brain edema, and attenuated neurological deficits after TBI in mice. Additionally, we found that USP30 deficiency effectively suppressed oxidative stress and neuronal apoptosis in TBI. Those protective effects of USP30 loss may be attributed, at least partially, to the reduction of TBI-induced impairment of mitochondrial quality control, including mitochondrial dynamics, function, and mitophagy. Collectively, our findings identify a previously undisclosed role of USP30 in the pathophysiology of TBI and lay a preliminary foundation for future research in this field.

Keywords:  Apoptosis; Mitochondrial quality control; Oxidative stress; Traumatic brain injury; USP30

DOI:  https://doi.org/10.1016/j.bbrc.2023.05.069
Mov Disord. 2023 Jun 12.

Sphingolipid and Phospholipid Levels Are Altered in Human Brain in Chorea-Acanthocytosis.

Gabriel Miltenberger-Miltenyi, Attila Jones, Amber M Tetlow, Vasco A Conceição, John F Crary, Ricky Michael Ditzel, Kurt Farrell, Renu Nandakumar, Brandon Barton, Barbara I Karp, Alana Kirby, Debra J Lett, Karin Mente, Susan Morgello, David K Simon, Ruth H Walker.

  BACKGROUND: Chorea-acanthocytosis (ChAc) is associated with mutations of VPS13A, which encodes for chorein, a protein implicated in lipid transport at intracellular membrane contact sites.OBJECTIVES: The goal of this study was to establish the lipidomic profile of patients with ChAc.
METHODS: We analyzed 593 lipid species in the caudate nucleus (CN), putamen, and dorsolateral prefrontal cortex (DLPFC) from postmortem tissues of four patients with ChAc and six patients without ChAc.
RESULTS: We found increased levels of bis(monoacylglycerol)phosphate, sulfatide, lysophosphatidylserine, and phosphatidylcholine ether in the CN and putamen, but not in the DLPFC, of patients with ChAc. Phosphatidylserine and monoacylglycerol were increased in the CN and N-acyl phosphatidylserine in the putamen. N-acyl serine was decreased in the CN and DLPFC, whereas lysophosphatidylinositol was decreased in the DLPFC.
CONCLUSIONS: We present the first evidence of altered sphingolipid and phospholipid levels in the brains of patients with ChAc. Our observations are congruent with recent findings in cellular and animal models, and implicate defects of lipid processing in VPS13A disease pathophysiology. © 2023 International Parkinson and Movement Disorder Society. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Keywords:  VPS13A; brain; chorea-acanthocytosis; phospholipids; sphingolipids

DOI:  https://doi.org/10.1002/mds.29445
Int J Mol Sci. 2023 May 31. pii: 9558. [Epub ahead of print]24(11):

Ganglioside GM1 and the Central Nervous System.

Zhongwu Guo.

  GM1 is one of the major glycosphingolipids (GSLs) on the cell surface in the central nervous system (CNS). Its expression level, distribution pattern, and lipid composition are dependent upon cell and tissue type, developmental stage, and disease state, which suggests a potentially broad spectrum of functions of GM1 in various neurological and neuropathological processes. The major focus of this review is the roles that GM1 plays in the development and activities of brains, such as cell differentiation, neuritogenesis, neuroregeneration, signal transducing, memory, and cognition, as well as the molecular basis and mechanisms for these functions. Overall, GM1 is protective for the CNS. Additionally, this review has also examined the relationships between GM1 and neurological disorders, such as Alzheimer's disease, Parkinson's disease, GM1 gangliosidosis, Huntington's disease, epilepsy and seizure, amyotrophic lateral sclerosis, depression, alcohol dependence, etc., and the functional roles and therapeutic applications of GM1 in these disorders. Finally, current obstacles that hinder more in-depth investigations and understanding of GM1 and the future directions in this field are discussed.

Keywords:  central nervous system; function; glycan; glycolipid; glycosphingolipid; neurological disease

DOI:  https://doi.org/10.3390/ijms24119558
Prog Neuropsychopharmacol Biol Psychiatry. 2023 Jun 08. pii: S0278-5846(23)00094-5. [Epub ahead of print] 110808

Brain metabolic derangements examined using 1H MRS and their (in)consistency among different rodent models of depression.

Iveta Pavlova, Jana Ruda-Kucerova.

  Major depressive disorder (MDD) is underlined by neurochemical changes in the brain. Proton magnetic resonance spectroscopy (1H MRS) is a useful tool for their examination as it provides information about the levels of metabolites. This review summarises the current knowledge of 1H MRS findings from rodent models of MDD, assesses the results from both a biological and a technical perspective, and identifies the main sources of bias. From a technical point of view, bias-introducing factors are the diversity of the measured volumes and their positioning in the brain, the data processing, and the metabolite concentration expression. The biological variables are strain, sex, and species, as well as the model itself, and in vivo vs. ex vivo exploration. This review identified some consistency in the 1H MRS findings in the models of MDD: lower levels of glutamine, glutamate + glutamine, and higher levels of myo-inositol and taurine in most of the brain regions of MDD models. This may suggest changes in regional metabolism, neuronal dysregulation, inflammation, and a compensatory effect reaction in the MDD rodent models.

Keywords:  Animal models; Depression; Metabolites; Proton magnetic resonance spectroscopy

DOI:  https://doi.org/10.1016/j.pnpbp.2023.110808
Pharmgenomics Pers Med. 2023 ;16 577-587

Clinical and Gene Analysis of Fatty Acid Oxidation Disorders Found in Neonatal Tandem Mass Spectrometry Screening.

Xiaoxia Wang, Haining Fang.

  Objective: To investigate the clinical and gene mutation characteristics of fatty acid oxidative metabolic diseases found in neonatal screening.Methods: A retrospective analysis was performed on 29,948 neonatal blood tandem mass spectrometry screening samples from January 2018 to December 2021 in our neonatal screening centre. For screening positive, recall review is still suspected of fatty acid oxidation metabolic disorders in children as soon as possible to improve the genetic metabolic disease-related gene detection package to confirm the diagnosis. All diagnosed children were followed up to the deadline.
Results: Among 29,948 neonates screened by tandem mass spectrometry, 14 cases of primary carnitine deficiency, six cases of short-chain acyl coenzyme A dehydrogenase deficiency, two cases of carnitine palmitoyltransferase-I deficiency and one case of multiple acyl coenzyme A dehydrogenase deficiency were recalled. Except for two cases of multiple acyl coenzyme A dehydrogenase deficiency that exhibited [manifestations], the other 21 cases were diagnosed pre-symptomatically. Eight mutations of SLC22A5 gene were detected, including c.51C>G, c.403G>A, c.506G>A, c.1400C>G, c.1085C>T, c.706C>T, c.1540G>C and c.338G>A. Compound heterozygous mutation of CPT1A gene c.2201T>C, c.1318G>A, c.2246G>A, c.2125G>A and ETFA gene c.365G>A and c.699_701delGTT were detected, and new mutation sites were found.
Conclusion: Neonatal tandem mass spectrometry screening is an effective method for identifying fatty acid oxidative metabolic diseases, but it should be combined with urine gas chromatography-mass spectrometry and gene sequencing technology. Our findings enrich the gene mutation profile of fatty acid oxidative metabolic disease and provide evidence for genetic counselling and prenatal diagnosis in families.

Keywords:  carnitine palmitoyltransferase-I deficiency; fatty acid oxidative metabolic disorder; multiple acyl coenzyme A dehydrogenase deficiency; primary carnitine deficiency; short-chain acyl-coenzyme A dehydrogenase deficiency

DOI:  https://doi.org/10.2147/PGPM.S402760
Neurobiol Dis. 2023 Jun 10. pii: S0969-9961(23)00210-3. [Epub ahead of print] 106195

lThyroid hormone transporter Mct8/Oatp1c1 deficiency compromises proper oligodendrocyte maturation in the mouse CNS.

Steffen Mayerl, Heike Heuer.

  Proper CNS myelination depends on the timed availability of thyroid hormone (TH) that induces differentiation of oligodendrocyte precursor cells (OPCs) to mature, myelinating oligodendrocytes. Abnormal myelination is frequently observed in Allan-Herndon-Dudley syndrome caused by inactivating mutations in the TH transporter MCT8. Likewise, persistent hypomyelination is a key CNS feature of the Mct8/Oatp1c1 double knockout (Dko) mouse model, a well-established mouse model for human MCT8 deficiency that exhibits diminished TH transport across brain barriers and thus a TH deficient CNS. Here, we explored whether decreased myelin content is caused by an impairment in oligodendrocyte maturation. To that end, we studied OPC and oligodendrocyte populations in Dko mice versus wild-type and single TH transporter knockout animals at different developmental time points (at postnatal days P12, P30, and P120) using multi-marker immunostaining and confocal microscopy. Only in Dko mice we observed a reduction in cells expressing the oligodendroglia marker Olig2, encompassing all stages between OPCs and mature oligodendrocytes. Moreover, Dko mice exhibited at all analysed time points an increased portion of OPCs and a reduced number of mature oligodendrocytes both in white and grey matter regions indicating a differentiation blockage in the absence of Mct8/Oatp1c1. We also assessed cortical oligodendrocyte structural parameters by visualizing and counting the number of mature myelin sheaths formed per oligodendrocyte. Again, only Dko mice displayed a reduced number of myelin sheaths that in turn exhibited an increase in length indicating a compensatory response to the reduced number of mature oligodendrocyte. Altogether, our studies underscore an oligodendrocyte differentiation impairment and altered oligodendrocyte structural parameters in the global absence of Mct8 and Oatp1c1. Both mechanisms most likely do not only cause the abnormal myelination state but also contribute to compromised neuronal functionality in Mct8/Oatp1c1 deficient animals.

Keywords:  CNS; Mct8; Myelin; Oatp1c1; Oligodendroglia; Slc16a2; Slco1c1; T3; T4; Thyroid hormone

DOI:  https://doi.org/10.1016/j.nbd.2023.106195
J Neurochem. 2023 Jun 15.

Cross-talk between DNA damage response and the central carbon metabolic network underlies selective vulnerability of Purkinje neurons in ataxia-telangiectasia.

Jacquelyne Ka-Li Sun, Genper Chi-Ngai Wong, Kim Hei-Man Chow.

  Cerebellar ataxia is often the first and irreversible outcome in the disease of ataxia-telangiectasia (A-T), as a consequence of selective cerebellar Purkinje neuronal degeneration. A-T is an autosomal recessive disorder resulting from the loss-of-function mutations of the ataxia-telangiectasia-mutated ATM gene. Over years of research, it now becomes clear that functional ATM-a serine/threonine kinase protein product of the ATM gene-plays critical roles in regulating both cellular DNA damage response and central carbon metabolic network in multiple subcellular locations. The key question arises is how cerebellar Purkinje neurons become selectively vulnerable when all other cell types in the brain are suffering from the very same defects in ATM function. This review intended to comprehensively elaborate the unexpected linkages between these two seemingly independent cellular functions and the regulatory roles of ATM involved, their integrated impacts on both physical and functional properties, hence the introduction of selective vulnerability to Purkinje neurons in the disease will be addressed.

Keywords:  DNA damage response; ataxia-telangiectasia; central carbon metabolism; fuel metabolism

DOI:  https://doi.org/10.1111/jnc.15881
Prog Nucl Magn Reson Spectrosc. 2023 Apr-Jun;134-135:pii: S0079-6565(23)00002-X. [Epub ahead of print]134-135 39-51

Metabolic imaging with deuterium labeled substrates.

Jacob Chen Ming Low, Alan J Wright, Friederike Hesse, Jianbo Cao, Kevin M Brindle.

  Deuterium metabolic imaging (DMI) is an emerging clinically-applicable technique for the non-invasive investigation of tissue metabolism. The generally short T1 values of 2H-labeled metabolites in vivo can compensate for the relatively low sensitivity of detection by allowing rapid signal acquisition in the absence of significant signal saturation. Studies with deuterated substrates, including [6,6'-2H2]glucose, [2H3]acetate, [2H9]choline and [2,3-2H2]fumarate have demonstrated the considerable potential of DMI for imaging tissue metabolism and cell death in vivo. The technique is evaluated here in comparison with established metabolic imaging techniques, including PET measurements of 2-deoxy-2-[18F]fluoro-d-glucose (FDG) uptake and 13C MR imaging of the metabolism of hyperpolarized 13C-labeled substrates.

Keywords:  Deuterium; Hyperpolarized-(13)C; Metabolism; PET

DOI:  https://doi.org/10.1016/j.pnmrs.2023.02.002
Turk Arch Pediatr. 2023 Jun 15.

Maternal Inborn Errors of Metabolism Detected in Expanded Newborn Metabolic Screening.

Oğuzhan Tin, Tanyel Zübarioğlu, Mehmet Şerif Cansever, Ertuğrul Kıykım, Çiğdem Aktuğlu-Zeybek.

OBJECTIVE: Pathologic results in expanded metabolic screening tests may be due to the medications, inappropriate sampling methods, or the maternal originated inborn errors of metabolism. The aim of this study is to identify mothers with inborn errors of metabolism through the pathologic expanded metabolic screening results of their babies.MATERIALS AND METHODS: Babies who were under 1 year of age and had a pathologic result of an expanded newborn screening for inborn errors of metabolism and their mothers were included in this retrospective single-centered study. Data of expanded metabolic screening results of both babies and their mothers were recorded. Clinical and laboratory findings relevant to suspected inborn errors of metabolism due to the pathologic screening results analysis were also noted for the mothers.
RESULTS: Seventeen babies and their mothers were enrolled. Expanded metabolic screening results were found compatible with inborn errors of metabolism in 4 (23.5%) of 17 mothers. Two of these mothers were diagnosed with 3-methylcrotonyl-CoA carboxylase deficiency and 2 mothers were diagnosed with glutaric aciduria type 1.
CONCLUSION: Inborn errors of metabolism can present in any period of life, and this is the first study to address the importance of metabolic screening via tandem mass spectrometry in terms of early diagnosis of inborn errors of metabolism not only in pediatric aged patients but also in adulthood in Turkey. The performance of expanded metabolic screening tests may be an important step in terms of detecting maternal inborn errors of metabolism that are not diagnosed until adulthood.

DOI: https://doi.org/10.5152/TurkArchPediatr.2023.23009
Curr Opin Crit Care. 2023 Jun 01.

Is there a role for ketones as alternative fuel in critical illness?

Naomi Watson, Thomas J McClelland, Zudin Puthucheary.

PURPOSE OF REVIEW: The evidence base advocating ketones as an alternative substrate for critically ill patients is expanding. We discuss the rationale for investigating alternatives to the traditional metabolic substrates (glucose, fatty acids and amino acids), consider evidence relating to ketone-based nutrition in a variety of contexts, and suggest the necessary future steps.RECENT FINDINGS: Hypoxia and inflammation inhibit pyruvate dehydrogenase, diverting glucose to lactate production. Skeletal muscle beta-oxidation activity falls, decreasing acetyl-CoA generation from fatty acids and subsequent ATP generation reduction.The benefits of induced ketosis are well established in epilepsy, whilst the evidence base for ketogenic diet therapy in other neurological pathology, such as traumatic brain injury and neurodegenerative diseases, is expanding. Evidence of upregulation of ketone metabolism in the hypertrophied and failing heart suggests that ketones may be utilized as an alternative fuel source to sustain myocardial function. Ketogenic diets stabilize immune cell homeostasis, promote cell survival following bacterial infection and inhibit the NLRP3 inflammasome, preventing the release of pro-inflammatory cytokines - interleukin (IL)-1β and IL-18.
SUMMARY: Whilst ketones provide an attractive nutritional option, further research is required to determine whether the proposed benefits are translatable to critically unwell patients.

DOI: https://doi.org/10.1097/MCC.0000000000001061
Curr Opin Pharmacol. 2023 Jun 10. pii: S1471-4892(23)00035-8. [Epub ahead of print]71 102382

Central and peripheral mechanisms involved in the control of GnRH neuronal function by metabolic factors.

Miguel Ruiz-Cruz, Carmen Torres-Granados, Manuel Tena-Sempere, Juan Roa.

  Gonadotropin-releasing hormone (GnRH) neurons are the final output pathway for the brain control of reproduction. The activity of this neuronal population, mainly located at the preoptic area of the hypothalamus, is controlled by a plethora of metabolic signals. However, it has been documented that most of these signal impact on GnRH neurons through indirect neuronal circuits, Kiss1, proopiomelanocortin, and neuropeptide Y/agouti-related peptide neurons being some of the most prominent mediators. In this context, compelling evidence has been gathered in recent years on the role of a large range of neuropeptides and energy sensors in the regulation of GnRH neuronal activity through both direct and indirect mechanisms. The present review summarizes some of the most prominent recent advances in our understanding of the peripheral factors and central mechanisms involved in the metabolic control of GnRH neurons.

Keywords:  GnRH; Gonadal function; Kiss1; Kisspeptins; Melanocortins; Metabolic hormones; Metabolism; NPY/AgRP neurons; Neuropeptides; Obesity; POMC neurons; Puberty; Reproduction

DOI:  https://doi.org/10.1016/j.coph.2023.102382
Cell Biosci. 2023 Jun 12. 13(1): 106

Roles of bile acids signaling in neuromodulation under physiological and pathological conditions.

Chen Xing, Xin Huang, Dongxue Wang, Dengjun Yu, Shaojun Hou, Haoran Cui, Lung Song.

  Bile acids (BA) are important physiological molecules not only mediating nutrients absorption and metabolism in peripheral tissues, but exerting neuromodulation effect in the central nerve system (CNS). The catabolism of cholesterol to BA occurs predominantly in the liver by the classical and alternative pathways, or in the brain initiated by the neuronal-specific enzyme CYP46A1 mediated pathway. Circulating BA could cross the blood brain barrier (BBB) and reach the CNS through passive diffusion or BA transporters. Brain BA might trigger direct signal through activating membrane and nucleus receptors or affecting activation of neurotransmitter receptors. Peripheral BA may also provide the indirect signal to the CNS via farnesoid X receptor (FXR) dependent fibroblast growth factor 15/19 (FGF15/19) pathway or takeda G protein coupled receptor 5 (TGR5) dependent glucagon-like peptide-1 (GLP-1) pathway. Under pathological conditions, alterations in BA metabolites have been discovered as potential pathogenic contributors in multiple neurological disorders. Attractively, hydrophilic ursodeoxycholic acid (UDCA), especially tauroursodeoxycholic acid (TUDCA) can exert neuroprotective roles by attenuating neuroinflammation, apoptosis, oxidative or endoplasmic reticulum stress, which provides promising therapeutic effects for treatment of neurological diseases. This review summarizes recent findings highlighting the metabolism, crosstalk between brain and periphery, and neurological functions of BA to elucidate the important role of BA signaling in the brain under both physiological and pathological conditions.

Keywords:  Bile acids; Blood brain barrier; Cholesterol; FXR; Neurodegenerative diseases; TGR5; TUDCA; UDCA

DOI:  https://doi.org/10.1186/s13578-023-01053-z
Curr Pediatr Rev. 2023 Jun 15.

Prenatal Supplementation of Docosahexaenoic Acid for the Management of Preterm Births: Clinical Information for Practice.

Shubham Thakur, Ritika Sharma, Subheet Kumar Jain.

  Unhealthy pregnancy and the resultant abnormalities in newborns exhibit a significant drawback. Each year, an estimated 15 million babies are born prematurely, accounting for the majority of deaths among children under the age of 5. India accounts for about a quarter of all preterm birth (PTB) incidences, with few therapeutic options available. However, research shows that consuming more marine foods (rich in omega-3 fatty acids (Ω-3), particularly Docosahexaenoic acid (DHA), helps to maintain a healthy pregnancy and can manage or prevent the onset of PTB and its accompanying difficulties. Present circumstances raise concerns about the use of DHA as a medication due to a lack of evidence on the dosage requirements, safety profile, molecular route, and commercially accessible strength for their therapeutic response. Several clinical experiments have been done over the last decade; however, the mixed outcomes have resulted in discrepancies. Most scientific organizations suggest a daily DHA consumption of 250-300 mg. However, this may differ from person to person. As a result, before prescribing a dosage, one should check the DHA concentrations in the individual's blood and then propose a dose that will benefit both the mother and the unborn. Thus, the review focuses on the favourable benefits of Ω-3, particularly DHA during pregnancy and postpartum, therapeutic dose recommendations, safety considerations, particularly during pregnancy, and the mechanistic pathway that might prevent or reduce the frequency of PTB accidents.

Keywords:  Cognitive disorders; Docosahexaenoic acid; Dose recommendation; Eicosapentaenoic acid; Omega-3 fatty acid; Prenatal supplementation; Preterm birth

DOI:  https://doi.org/10.2174/1573396320666230615090527
J Vis Exp. 2023 May 19.

Oxygen-Independent Assays to Measure Mitochondrial Function in Mammals.

Tenzin Tseyang, Jonathan Valeros, Paula Vo, Jessica B Spinelli.

The flow of electrons in the mitochondrial electron transport chain (ETC) supports multifaceted biosynthetic, bioenergetic, and signaling functions in mammalian cells. As oxygen (O2) is the most ubiquitous terminal electron acceptor for the mammalian ETC, the O2 consumption rate is frequently used as a proxy for mitochondrial function. However, emerging research demonstrates that this parameter is not always indicative of mitochondrial function, as fumarate can be employed as an alternative electron acceptor to sustain mitochondrial functions in hypoxia. This article compiles a series of protocols that allow researchers to measure mitochondrial function independently of the O2 consumption rate. These assays are particularly useful when studying mitochondrial function in hypoxic environments. Specifically, we describe methods to measure mitochondrial ATP production, de novo pyrimidine biosynthesis, NADH oxidation by complex I, and superoxide production. In combination with classical respirometry experiments, these orthogonal and economical assays will provide researchers with a more comprehensive assessment of mitochondrial function in their system of interest.

DOI: https://doi.org/10.3791/65184
J Inherit Metab Dis. 2023 Jun 12.

Acyl-CoA dehydrogenase substrate promiscuity: Challenges and opportunities for development of substrate reduction therapy in disorders of valine and isoleucine metabolism.

Sander M Houten, Tetyana Dodatko, William Dwyer, Sara Violante, Hongjie Chen, Brandon Stauffer, Robert J DeVita, Frédéric M Vaz, Justin R Cross, Chunli Yu, João Leandro.

Toxicity of accumulating substrates is a significant problem in several disorders of valine and isoleucine degradation notably short-chain enoyl-CoA hydratase (ECHS1 or crotonase) deficiency, 3-hydroxyisobutyryl-CoA hydrolase (HIBCH) deficiency, propionic acidemia (PA) and methylmalonic aciduria (MMA). Isobutyryl-CoA dehydrogenase (ACAD8) and short/branched-chain acyl-CoA dehydrogenase (SBCAD, ACADSB) function in the valine and isoleucine degradation pathways, respectively. Deficiencies of these acyl-CoA dehydrogenase (ACAD) enzymes are considered biochemical abnormalities with limited or no clinical consequences. We investigated whether substrate reduction therapy through inhibition of ACAD8 and SBCAD can limit the accumulation of toxic metabolic intermediates in disorders of valine and isoleucine metabolism. Using analysis of acylcarnitine isomers, we show that 2-methylenecyclopropaneacetic acid (MCPA) inhibited SBCAD, isovaleryl-CoA dehydrogenase, short-chain acyl-CoA dehydrogenase and medium-chain acyl-CoA dehydrogenase, but not ACAD8. MCPA treatment of wild-type and PA HEK-293 cells caused a pronounced decrease in C3-carnitine. Furthermore, deletion of ACADSB in HEK-293 cells led to an equally strong decrease in C3-carnitine when compared to wild-type cells. Deletion of ECHS1 in HEK-293 cells caused a defect in lipoylation of the E2 component of the pyruvate dehydrogenase complex, which was not rescued by ACAD8 deletion. MCPA was able to rescue lipoylation in ECHS1 KO cells, but only in cells with prior ACAD8 deletion. SBCAD was not the sole ACAD responsible for this compensation, which indicates substantial promiscuity of ACADs in HEK-293 cells for the isobutyryl-CoA substrate. Substrate promiscuity appeared less prominent for 2-methylbutyryl-CoA at least in HEK-293 cells. We suggest that pharmacological inhibition of SBCAD to treat PA should be investigated further. This article is protected by copyright. All rights reserved.

DOI: https://doi.org/10.1002/jimd.12642
Nat Protoc. 2023 Jun 16.

Ex vivo immunocapture and functional characterization of cell-type-specific mitochondria using MitoTag mice.

Natalia Prudente de Mello, Caroline Fecher, Adrian Marti Pastor, Fabiana Perocchi, Thomas Misgeld.

Mitochondria are key bioenergetic organelles involved in many biosynthetic and signaling pathways. However, their differential contribution to specific functions of cells within complex tissues is difficult to dissect with current methods. The present protocol addresses this need by enabling the ex vivo immunocapture of cell-type-specific mitochondria directly from their tissue context through a MitoTag reporter mouse. While other available methods were developed for bulk mitochondria isolation or more abundant cell-type-specific mitochondria, this protocol was optimized for the selective isolation of functional mitochondria from medium-to-low-abundant cell types in a heterogeneous tissue, such as the central nervous system. The protocol has three major parts: First, mitochondria of a cell type of interest are tagged via an outer mitochondrial membrane eGFP by crossing MitoTag mice to a cell-type-specific Cre-driver line or by delivery of viral vectors for Cre expression. Second, homogenates are prepared from relevant tissues by nitrogen cavitation, from which tagged organelles are immunocaptured using magnetic microbeads. Third, immunocaptured mitochondria are used for downstream assays, e.g., to probe respiratory capacity or calcium handling, revealing cell-type-specific mitochondrial diversity in molecular composition and function. The MitoTag approach enables the identification of marker proteins to label cell-type-specific organelle populations in situ, elucidates cell-type-enriched mitochondrial metabolic and signaling pathways, and reveals functional mitochondrial diversity between adjacent cell types in complex tissues, such as the brain. Apart from establishing the mouse colony (6-8 weeks without import), the immunocapture protocol takes 2 h and functional assays require 1-2 h.

DOI: https://doi.org/10.1038/s41596-023-00831-w
Int J Mol Sci. 2023 Jun 02. pii: 9657. [Epub ahead of print]24(11):

Untargeted Metabolomics Identifies Biomarkers for MCADD Neonates in Dried Blood Spots.

Rajaa Sebaa, Maha AlMogren, Wafaa Alseraty, Anas M Abdel Rahman.

  Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is the most common inherited mitochondrial metabolic disease of fatty acid β-oxidation, especially in newborns. MCADD is clinically diagnosed using Newborn Bloodspot Screening (NBS) and genetic testing. Still, these methods have limitations, such as false negatives or positives in NBS and the variants of uncertain significance in genetic testing. Thus, complementary diagnostic approaches for MCADD are needed. Recently, untargeted metabolomics has been proposed as a diagnostic approach for inherited metabolic diseases (IMDs) due to its ability to detect a wide range of metabolic alterations. We performed an untargeted metabolic profiling of dried blood spots (DBS) from MCADD newborns (n = 14) and healthy controls (n = 14) to discover potential metabolic biomarkers/pathways associated with MCADD. Extracted metabolites from DBS samples were analyzed using UPLC-QToF-MS for untargeted metabolomics analyses. Multivariate and univariate analyses were used to analyze the metabolomics data, and pathway and biomarker analyses were also performed on the significantly identified endogenous metabolites. The MCADD newborns had 1034 significantly dysregulated metabolites compared to healthy newborns (moderated t-test, no correction, p-value ≤ 0.05, FC 1.5). A total of 23 endogenous metabolites were up-regulated, while 84 endogenous metabolites were down-regulated. Pathway analyses showed phenylalanine, tyrosine, and tryptophan biosynthesis as the most affected pathways. Potential metabolic biomarkers for MCADD were PGP (a21:0/PG/F1alpha) and glutathione, with an area under the curve (AUC) of 0.949 and 0.898, respectively. PGP (a21:0/PG/F1alpha) was the first oxidized lipid in the top 15 biomarker list affected by MCADD. Additionally, glutathione was chosen to indicate oxidative stress events that could happen during fatty acid oxidation defects. Our findings suggest that MCADD newborns may have oxidative stress events as signs of the disease. However, further validations of these biomarkers are needed in future studies to ensure their accuracy and reliability as complementary markers with established MCADD markers for clinical diagnosis.

Keywords:  DBS; MCADD; glutathione; mass-spectrometry; metabolic biomarkers; newborns; oxidized lipids; untargeted metabolomics

DOI:  https://doi.org/10.3390/ijms24119657
Mol Cells. 2023 Jun 12.

Purification and Characterization of Mitochondrial Mg2+-Independent Sphingomyelinase from Rat Brain.

Jong Min Choi, Yongwei Piao, Kyong Hoon Ahn, Seok Kyun Kim, Jong Hoon Won, Jae Hong Lee, Ji Min Jang, In Chul Shin, Zhicheng Fu, Sung Yun Jung, Eui Man Jeong, Dae Kyong Kim.

  Sphingomyelinase (SMase) catalyzes ceramide production from sphingomyelin. Ceramides are critical in cellular responses such as apoptosis. They enhance mitochondrial outer membrane permeabilization (MOMP) through self-assembly in the mitochondrial outer membrane to form channels that release cytochrome c from intermembrane space (IMS) into the cytosol, triggering caspase-9 activation. However, the SMase involved in MOMP is yet to be identified. Here, we identified a mitochondrial Mg2+-independent SMase (mt-iSMase) from rat brain, which was purified 6,130-fold using a Percoll gradient, pulled down with biotinylated sphingomyelin, and subjected to Mono Q anion exchange. A single peak of mt-iSMase activity was eluted at a molecular mass of approximately 65 kDa using Superose 6 gel filtration. The purified enzyme showed optimal activity at pH of 6.5 and was inhibited by dithiothreitol and Mg2+, Mn2+, N2+, Cu2+, Zn2+, Fe2+, and Fe3+ ions. It was also inhibited by GW4869, which is a non-competitive inhibitor of Mg2+-dependent neutral SMase 2 (encoded by SMPD3), that protects against cytochrome c release-mediated cell death. Subfractionation experiments showed that mt-iSMase localizes in the IMS of the mitochondria, implying that mt-iSMase may play a critical role in generating ceramides for MOMP, cytochrome c release, and apoptosis. These data suggest that the purified enzyme in this study is a novel SMase.

Keywords:  Mg2+-independent sphingomyelinase; brain; mitochondria; purification

DOI:  https://doi.org/10.14348/molcells.2023.0074