bims-medebr 2022-05-15 papers

bims-medebr

Biomed News

on Metabolism of the developing brain

Issue of 2022‒05‒15
35 papers selected by
Regina F. Fernández
Johns Hopkins University

Unpredictable chronic mild stress differentially impacts resting brain glucose metabolism in fatty acid-binding protein 7 deficient mice.
Monocarboxylate Transporter 1 May Benefit Cerebral Ischemia via Facilitating Lactate Transport From Glial Cells to Neurons.
Low Glucose Induced Alzheimer's Disease Phenotype in Induced Pluripotent Stem Cell-Derived Neurons is Due to Decreased O-GlcNAcylation.
Metabolic disorders on cognitive dysfunction after traumatic brain injury.
Exposure to the Brominated Flame Retardant Hexabromocyclododecane Results in Systemic Changes in Polyunsaturated Fatty Acid Metabolism Within Phospholipids of Mice.
A Low-carbohydrate, Ketogenic Diet Enhances Hippocampal Mitochondrial Bioenergetics and Efficiency.
Elucidating the Role of Glycogen in Glucose Transporter 1 Deficiency Syndrome.
Sex-dependent Regulation of Mitochondrial Respiratory Function in Mouse Brain Microvessels by Peroxynitrite Decomposition Catalyst.
Metabolic Alterations in Aorta Induces Brain Cholesterolemia, Memory Loss and Cognitive Dysfunction in Diabetic Mice.
Alcohol binge drinking decreases brain glucose metabolism and functional connectivity in adolescent rats.
Walnut Oil Reduces Aβ Levels and Increases Neurite Length in a Cellular Model of Early Alzheimer Disease.
Global Proteome Profiling of the Temporal Cortex of Female Rats Exposed to Chronic Stress and the Western Diet.
Variability of regional glucose metabolism and the topology of functional networks in the human brain.
Hitchhiker's guide through the axon: transport and local translation of Pink1 mRNA support axonal mitophagy.
Microglial lactate metabolism as a potential therapeutic target for Alzheimer's disease.
Analysis of Content of 2-Oxoacids in Rat Brain Extracts Using High-Performance Liquid Chromatography.
Domestic crickets (Acheta domesticus) as an animal model to study Parkinson's disease.
Revealing Sex and Alzheimer's Disease-related Changes in the Spatial Localization of Brain Lipids in Mice using Mass Spectrometry Imaging.
Metabolism and the Effect of Animal-Derived Oxysterols in the Diet on the Development of Alzheimer's Disease.
Lipid pathway dysfunction is prevalent in patients with Parkinson's disease.
Glutamate-aspartate transporter 1 attenuates oxygen-glucose deprivation-induced injury by promoting glutamate metabolism in primary cortical neurons.
A negative-solvatochromic fluorescent probe for visualizing intracellular distributions of fatty acid metabolites.
Phosphorylation-based regulation of mitochondrial metabolism.
Mitochondrial Fission is Essential to Maintain Cristae Morphology and Bioenergetics.
Inositol-requiring enzyme 1 alpha (IRE1α) regulates astrocyte metabolic and inflammatory phenotypes: Implications in (METH)amphetamine use disorder and HIV-associated neurocognitive disorders.
Molecular and Signaling Mechanisms for Docosahexaenoic Acid-Derived Neurodevelopment and Neuroprotection.
NGF Modulates Cholesterol Metabolism and Stimulates ApoE Secretion in Glial Cells Conferring Neuroprotection against Oxidative Stress.
Neuronal STAT3/HIF-1α/PTRF axis-mediated bioenergetic disturbance exacerbates cerebral ischemia-reperfusion injury via PLA2G4A.
A New Hypothesis for Alzheimer's Disease: The Lipid Invasion Model.
Roles for Mitochondrial Complex I Subunits in Regulating Synaptic Transmission and Growth.
Developing a Pipeline for Personalized Diagnoses of Glut1 Deficiency Syndrome.
DHA-Enriched Fish Oil Ameliorates Deficits in Cognition Associated with Menopause and the APOE4 Genotype in Rodents.
Serum metabolome associated with severity of acute traumatic brain injury.
Carboxylesterase 1 (Ces1) Releases Oxylipins From Oxidized Triacylglycerols: Examination of Its Substrate Selectivity.
An endogenous polyunsaturated fatty acid, dihomo-gamma-linoleic acid, induces neurodegeneration in C. elegans via ferroptosis.

Psychiatry Res Neuroimaging. 2022 Apr 26. pii: S0925-4927(22)00047-6. [Epub ahead of print]323 111486

Unpredictable chronic mild stress differentially impacts resting brain glucose metabolism in fatty acid-binding protein 7 deficient mice.

John Hamilton, Nicole Roeder, Brittany Richardson, Nikki Hammond, Munawwar Sajjad, Rutao Yao, Yuji Owada, Yoshiteru Kagawa, Panayotis K Thanos.

  Fatty acid-binding proteins (FABPs) are intracellular chaperone proteins involved in the trafficking of n-3 polyunsaturated fatty acids and endocannabinoids. Inhibiting two of the main FABP subtypes found in the brain (FABP5 and FABP7) hinders endocannabinoid uptake and hydrolysis. Prior data indicates that cannabinoid receptor stimulation can ameliorate the consequences associated with chronic stress. To this end, FABP expression may play a similar role in response to stressful conditions. Male C57BL/6 J (WT) and FABP7 knockout (KO) mice were assigned to either a non-stress cohort or an unpredictable chronic mild stress (UCMS) cohort for a period of 4 weeks. Immediately after 4 weeks, mice were injected with [18F]2-fluoro-2-deoxy-d-glucose (FDG) and scanned using micro positron emission tomography (mPET) to examine brain glucose metabolism (BGluM). WT mice exposed to UCMS showed reduced BGluM in striatal, cortical, and hypothalamic regions and showed increased BGluM in the hippocampus, thalamus, periaqueductal gray, superior colliculi, inferior colliculi, and cerebellum. In contrast, there were limited effects of UCMS on BGluM in FABP7 KO mice, with a reduction in the thalamus, periaqueductal gray, and superior colliculi. These findings provide novel insight into FABP7 expression and indicate this gene to play an important role in response to aversive stimuli.

Keywords:  Fatty acid-binding protein; Positron emission tomography; Unpredictable chronic mild stress

DOI:  https://doi.org/10.1016/j.pscychresns.2022.111486
Front Neurol. 2022 ;13 781063

Monocarboxylate Transporter 1 May Benefit Cerebral Ischemia via Facilitating Lactate Transport From Glial Cells to Neurons.

Mao Zhang, Yanyan Wang, Yun Bai, Limeng Dai, Hong Guo.

  Monocarboxylate transporter 1 (MCT1) is expressed in glial cells and some populations of neurons. MCT1 facilitates astrocytes or oligodendrocytes (OLs) in the energy supplement of neurons, which is crucial for maintaining the neuronal activity and axonal function. It is suggested that MCT1 upregulation in cerebral ischemia is protective to ischemia/reperfusion (I/R) injury. Otherwise, its underlying mechanism has not been clearly discussed. In this review, it provides a novel insight that MCT1 may protect brain from I/R injury via facilitating lactate transport from glial cells (such as, astrocytes and OLs) to neurons. It extensively discusses (1) the structure and localization of MCT1; (2) the regulation of MCT1 in lactate transport among astrocytes, OLs, and neurons; and (3) the regulation of MCT1 in the cellular response of lactate accumulation under ischemic attack. At last, this review concludes that MCT1, in cerebral ischemia, may improve lactate transport from glial cells to neurons, which subsequently alleviates cellular damage induced by lactate accumulation (mostly in glial cells), and meets the energy metabolism of neurons.

Keywords:  astrocytes; cerebral ischemia; lactate transport; monocarboxylate transporter 1 (MCT1); oligodendrocytes (OLs)

DOI:  https://doi.org/10.3389/fneur.2022.781063
FASEB J. 2022 May;36 Suppl 1

Low Glucose Induced Alzheimer's Disease Phenotype in Induced Pluripotent Stem Cell-Derived Neurons is Due to Decreased O-GlcNAcylation.

Chia-Wei Huang, Gerald Hart.

Sporadic Alzheimer's disease (sAD) is the most common type of neurodegenerative disease. Recent studies show that detectable impairment of brain glucose metabolism occurs years before onset of AD symptoms, and the dysregulated O-GlcNAc levels likely arisen from impaired glucose metabolism correlates with AD pathogenesis. So far, the mechanism of sAD and the role of OGN in AD pathology remained largely unknown due to a lack of human sAD model. We have established a human sAD model in which the pathological features are reproduced by glucose deficiency that better represents sAD as a metabolic disease. We generated human cortical neurons from human induced pluripotent stem cell and treated mature neuron with glucose reduction media to study the effect of low glucose on the degenerative status of neuron. Fluoro JADE C staining and cell viability assays reveals low glucose treatment at 2mM leads to dramatic increases of degeneration cell on day 3 and 5 of treatment and decreased cell viability on day 7. Interestingly, western blotting and immunofluorescent staining results demonstrate that long-term low glucose treatment induces two major AD features in cortical neuron, including accumulation of abnormal hyperphosphorylated tau and increasing amyloid beta production. In addition, glucose deficiency also causes decreased neurite coverage, synapse loss, and neuron network activity disruption detected by immunofluorescent staining and multi-electrode array electrophysiological analyses. Furthermore, we find that O-GlcNAc levels are significantly reduced soon after low glucose treatment and last till the end of experiment. Artificially increasing O-GlcNAc level by thiamet-G (TMG) in low glucose treated neurons, rescues low glucose-induced AD phenotypes. Moreover, our data show that O-GlcNAc dysregulation results in mitochondrial dysfunction, which occurs before any other degenerative phenotype appeared, and may be one of the underlying mechanisms of sAD onset and pathogenesis. Taken together, we established a human sAD model that mimics the main features of AD pathogenesis, which agrees with clinical observations of sAD patients. Therefore, this platform can serve as a tool to better understand molecular processes involved in sAD. Our results also suggest that dysregulated O-GlcNAc levels by glucose deficiency is involved in the onset and progression of sAD.

DOI: https://doi.org/10.1096/fasebj.2022.36.S1.R2271
Trends Endocrinol Metab. 2022 May 07. pii: S1043-2760(22)00060-1. [Epub ahead of print]

Metabolic disorders on cognitive dysfunction after traumatic brain injury.

Jin-Qing Lai, Yan-Chuan Shi, Shu Lin, Xiang-Rong Chen.

  Cognitive dysfunction is a common adverse consequence of traumatic brain injury (TBI). After brain injury, the brain and other organs trigger a series of complex metabolic changes, including reduced glucose metabolism, enhanced lipid peroxidation, disordered neurotransmitter secretion, and imbalanced trace element synthesis. In recent years, several research and clinical studies have demonstrated that brain metabolism directly or indirectly affects cognitive dysfunction after TBI, but the mechanisms remain unclear. Drugs that improve the symptoms of cognitive dysfunction caused by TBI are under investigation and treatments that target metabolic processes are expected to improve cognitive function in the future. This review explores the impact of metabolic disorders on cognitive dysfunction after TBI and provides new strategies for the treatment of metabolic disorders.

Keywords:  cognitive dysfunction; metabolic disorder; metabolic therapy; traumatic brain injury

DOI:  https://doi.org/10.1016/j.tem.2022.04.003
FASEB J. 2022 May;36 Suppl 1

Exposure to the Brominated Flame Retardant Hexabromocyclododecane Results in Systemic Changes in Polyunsaturated Fatty Acid Metabolism Within Phospholipids of Mice.

Naomi E Kramer, Lillie Barnett, Hannah Xu, Tai Guo, John Wagner, Brian Cummings.

Brominated flame retardants are used in many household products to reduce flammability, but often leach into the surrounding environment over time. Hexabromocyclododecane (HBCD) is one brominated flame retardant detected in human blood across the world. HBCD exposure can result in neurological problems and altered lipid metabolism, but to date the two remain unlinked. As lipids constitute ~50% of brain dry weight, lipid metabolism plays a critical role in neuronal function and homeostasis. To determine the effect of HBCD exposure on brain lipid metabolism, young adult male mice were exposed to 1 mg/kg HBCD every 3 days for 28 days. HBCD exposure altered lipid abundance of 8 major lipid classes in the dorsal striatum, including fatty acids (FA), lysophosphatidylcholines (LPC), lysophosphatidylethanolamines (LPE), phosphatidylcholines (PC), phosphatidylethanolamines (PE) alkylphosphatidylethanolamines (PEO), phosphatidylethanolamine plasmalogens (PEP), and sphingomyelins (SM). The liver, as a major lipid metabolism hub, and blood were also examined to determine whether these alterations correlated to systemic changes in lipid metabolism. Although several lipid classes changed in the liver and blood, only PE was consistently altered between organs. Despite the lack of commonalities between lipid class alterations of differing organs, phospholipid fatty acid tails displayed a consistent enrichment of Polyunsaturated Fatty Acids (PUFAs) such as Arachidonic Acid (AA) and Docosahexaenoic Acid (DHA) across lipid classes and organs. Free AA was enriched in the blood as well as AA contained within phospholipids of the liver (in PE), blood (in LPC, PEO, and PEP), and dorsal striatum (in PE, PEO). Additionally, although free DHA was unchanged in the blood, DHA-containing phospholipids were enriched in the liver (in PE), blood (in LPC, LPE), and dorsal striatum (in PE, PEO, PEP, PS). These studies indicate that HBCD can cause systemic alterations in PUFA metabolism. Further study is necessary to determine the mechanisms underlying the lipid alterations and their functional consequences.

DOI: https://doi.org/10.1096/fasebj.2022.36.S1.R4045
FASEB J. 2022 May;36 Suppl 1

A Low-carbohydrate, Ketogenic Diet Enhances Hippocampal Mitochondrial Bioenergetics and Efficiency.

Erin R Saito, Cali E Warren, Rachel J Campbell, Gavin Miller, Johannes D du Randt, Mio E Cannon, Jeremy Y Saito, Cameron M Hanegan, Colin M Kemberling, Jeffrey G Edwards, Benjamin T Bikman.

Mitochondrial dysfunction and cognitive impairment are common symptoms in many neurologic and psychiatric disorders, as well as in nonpathological aging. Ketones have been suggested as therapeutic for their relevance in epilepsy as well as other neurodegenerative diseases such as Alzheimer's and Parkinson's disease. Here we explored whether a low-carbohydrate, ketogenic diet (KD) alters recognition memory, hippocampal mitochondrial bioenergetics, and expression of proteins involved in mitochondrial dynamics. Mature-to-middle-aged adult male and female mice were placed on a lard-based KD supplemented with an exogenous ketone ester for eight weeks. Changes in behavioral recognition memory were measured in a two-object novel object recognition test. Hippocampal mitochondrial physiology was assessed using high-resolution respirometry to measure changes in oxygen flux, biochemical assays to quantify ATP production, and western blot to measure changes in Drp1 expression. Here we demonstrate that the KD reduces hippocampal oxygen consumption (p=0.013), but does not alter ATP production (p=0.42) or Drp1 expression (p=0.51). These results indicate an enhancement of mitochondrial coupling and efficiency independent of mitochondrial dynamics, as changes in oxygen flux occurred without changes in Drp1 expression. Together, these findings add to growing support for the use of ketones and KDs in pathological brain states in which mitochondrial function is compromised, especially within the hippocampus.

DOI: https://doi.org/10.1096/fasebj.2022.36.S1.R5607
FASEB J. 2022 May;36 Suppl 1

Elucidating the Role of Glycogen in Glucose Transporter 1 Deficiency Syndrome.

Meredith Williams, Kia H Markussen, Madison Webb, Annette Mestas, Juan Pascual, Matthew S Gentry.

Glucose Transporter 1 Deficiency Syndrome (G1D) is a rare genetic disorder characterized by impaired brain glucose metabolism caused by mutations in the SLC2A1 gene. Mutations in the SLC2A1 gene lead to reduced or loss of function in the glucose transporter protein type 1 (GLUT-1), affecting its ability to deliver glucose across the blood brain barrier. This lack of glucose in the brain affects brain function and development, causing people with the disorder to suffer from seizures, learning disabilities, and struggle for independence. While decreased levels of glucose in G1D is recognized, glycogen levels in the brain have not been studied in human or animal models of the disease. We employed a mouse model of G1D syndrome characterized by a loss of function in the SLC2A1 gene to study glycogen levels. Wildtype and G1D animals of the same sex at 14 weeks old were utilized for this study. Immunohistochemical (IHC) staining with IV58B6 and an amyloglucosidase glycogen assay were used to determine regional and total glycogen levels, respectively. HALO software was employed to quantify IHC staining, and the enzymatic glycogen determination was measured with a spectrophotometric microplate reader. Through these techniques, it was determined that G1D mice had perturbed glycogen levels present in multiple regions of the brain. These data suggest that the G1D phenotype could be affected by perturbed levels of glycogen in the brain. Further research into the effect of glycogen levels in G1D may be important for determining disease modalities, defining disease progression, and understanding preclinical data and drug treatment.

DOI: https://doi.org/10.1096/fasebj.2022.36.S1.0R303
FASEB J. 2022 May;36 Suppl 1

Sex-dependent Regulation of Mitochondrial Respiratory Function in Mouse Brain Microvessels by Peroxynitrite Decomposition Catalyst.

Siva S Sakamuri, Venkata N Sure, Lahari Kolli, William P Wisen, Wesley R Evans, Sarah H Lindsey, Ricardo Mostany, Prasad V Katakam.

BACKGROUND: Peroxynitrite (PN) is a strong oxidizing and nitrating molecule. PN is a potent inhibitor of mitochondrial respiration and promotes ischemia-reperfusion injury following stroke. In isolated mouse brain mitochondria, we observed that PN donors inhibit mitochondrial respiratiory function whereas the PN decomposition catalyst, Fe (III) tetrakis (1-methyl-4-pyridyl) porphyrin pentachlorideporphyrin pentachloride (FeTMPyP), enhances mitochondrial state III and state IVo mitochondrial respiration. In addition, we demonstrated that mitochondrial respiration is the primary contributor of cellular energy in brain microvessels (BMVs). The present study tested the hypothesis that FeTMPyP negatively regulates mitochondrial respiration in the mouse BMVs.METHODS: BMVs were isolated from male and female mice (C57Bl/6, 2-4 months) using a combination of filters with pore sizes of 300μm and 40μm followed by gradient centrifugation. BMVs were treated with FeTMPyP at 37o C for 60 minutes. Oxygen consumption rates (OCR) were measured using the Agilent Seahorse XFe24 analyzer and various respiratory parameters were determined following Mitostress test.
RESULTS: In male BMVs, basal respiration, ATP production, and non-mitochondrial respiration were not altered by FeTMPyP treatment. Contrary to our hypothesis, in male BMVs, PN decomposition catalyst decreased the mitochondrial maximal respiration by 24.6% (2.1 ± 0.4 vs 2.8 ± 0.3 picomoles of O2 /min/µg protein;) whereas the spare respiratory capacity was reduced by 33.3% (1.2 ± 0.3 vs 1.8 ± 0.3 picomoles of O2 /min/µg protein; n=17 each, p<0.05). Proton leak was elevated by 70% (0.7 ± 0.1 vs 0.4 ± 0.1 picomoles of O2 /min/µg protein) by PN decomposition catalyst in male BMVs. In contrast, in the female BMVs, the PN decomposition catalyst failed to alter mitochondrial respiratory parameters (n=15 each, p=NS). Interestingly, FeTMPyP increased non-mitochondrial respiration by 63.8% (0.95 ± 0.2 vs 0.58 ± 0.1 picomoles of O2 /min/µg protein) in the female BMVs (n=17 each, p<0.05).
CONCLUSION: BMVs display sex-dependent respenses to endogenous PN. Notably, in female mouse BMVs, PN appears to act as an antioxidant as PN inhibited the non-mitochondrial respiration which mostly contributes to extramitochondrial superoxide generation.

DOI: https://doi.org/10.1096/fasebj.2022.36.S1.R5105
FASEB J. 2022 May;36 Suppl 1

Metabolic Alterations in Aorta Induces Brain Cholesterolemia, Memory Loss and Cognitive Dysfunction in Diabetic Mice.

Chandrakala Aluganti Narasimhulu, Dinender Singla.

  AIM: Diabetic hyperlipidemia and associated cognitive dysfunction are of major concern and is essential to understand the mechanism and pathophysiology of diabetic brains, which remains unknown. In this study, we investigated whether hypercholesterolemia induces apoptosis and cognitive dysfunction, in diabetic apolipoprotein E (APOE) and paraoxonase 1 (PON1) double knockout (DKO) mice brains.HYPOTHESIS: We hypothesize that hypercholesterolemia induces apoptosis that involves cognitive dysfunction and furthers to Alzheimer's.
METHODS: ApoE-PON1 DKO mice (6±2 months) were divided into control and STZ groups. At Day-28, brain function, blood glucose, and serum lipids were measured followed by subjecting animals to Glucose Tolerance Test. Echocardiography was performed, and mice aortas were isolated. Brain-parameters were examined using RT-PCR, immunohistochemistry, and histologically.
RESULTS: We observed a significant (p<0.05) increase in blood glucose levels, serum lipids, increased aortic lesions, as well as increased cholesterol loading and apoptotic markers in brains of diabetic mice as compared to control. A significant reduction in reverse cholesterol transport, and HDL-associated proteins were observed. A significant (p<0.05) decrease in brain weight, size, and brain function were observed in diabetic mice. Furthermore, a significant (p<0.05) increase in PTEN and decrease in AKT levels were observed in diabetic mice. In addition, a significant (p<0.05) increase in Alzheimer's specific markers were also observed.
CONCLUSION: In conclusion, our data suggest that hyperlipidemia induces apoptosis, that leads to neuronal cell death, memory-loss, and cognitive dysfunction, which furthers Alzheimer's in diabetic ApoE and PON1 DKO mice. Further therapeutic approaches require to be developed to target hyperlipidemia in diabetic brains.

Keywords:  cognitive dysfunction; hyperglycemia; hyperlipidemia; inflammation

DOI:  https://doi.org/10.1096/fasebj.2022.36.S1.R3629
Metab Brain Dis. 2022 May 14.

Alcohol binge drinking decreases brain glucose metabolism and functional connectivity in adolescent rats.

Cecilia Rapp, John Hamilton, Kaleigh Richer, Munawwar Sajjad, Rutao Yao, Panayotis K Thanos.

  Alcohol misuse represents a serious health concern, especially during adolescence, with approximately 18% of high school students engaging in binge drinking. Despite widespread misuse of alcohol, its effects on how the brain functions is not fully understood. This study utilized a binge drinking model in adolescent rats to examine effects on brain function as measured by brain glucose metabolism (BGluM). Following an injection of [18 FDG] fluro-2-deoxy-D-glucose, rats had voluntary access to either water or various concentrations of ethanol to obtain the following targeted doses: water (no ethanol), low dose ethanol (0.29 ± 0.03 g/kg), moderate dose ethanol (0.98 ± 0.05), and high dose ethanol (2.19 ± 0.23 g/kg). Rats were subsequently scanned using positron emission tomography. All three doses of ethanol were found to decrease BGluM in the restrosplenial cortex, visual cortex, jaw region of the somatosensory cortex, and cerebellum. For both the LD and MD ethanol dose, decreased BGluM was seen in the superior colliculi. The MD ethanol dose also decreased BGluM in the subiculum, frontal association area, as well as the primary motor cortex. Lastly, the HD ethanol dose decreased BGluM in the hippocampus, thalamus, raphe nucleus, inferior colliculus, and the primary motor cortex. Similar decreases in the hippocampus were also seen in the LD group. Taken together, these results highlight the negative consequences of acute binge drinking on BGluM in many regions of the brain involved in sensory, motor, and cognitive processes. Future studies are needed to assess the long-term effects of alcohol binge drinking on brain function as well as its cessation.

Keywords:  Addiction; Alcohol; Binge drinking; Brain glucose metabolism; Positron emission tomography

DOI:  https://doi.org/10.1007/s11011-022-00977-8
Nutrients. 2022 Apr 19. pii: 1694. [Epub ahead of print]14(9):

Walnut Oil Reduces Aβ Levels and Increases Neurite Length in a Cellular Model of Early Alzheimer Disease.

Carsten Esselun, Fabian Dieter, Nadine Sus, Jan Frank, Gunter P Eckert.

  (1) Background: Mitochondria are the cells' main source of energy. Mitochondrial dysfunction represents a key hallmark of aging and is linked to the development of Alzheimer's disease (AD). Maintaining mitochondrial function might contribute to healthy aging and the prevention of AD. The Mediterranean diet, including walnuts, seems to prevent age-related neurodegeneration. Walnuts are a rich source of α-linolenic acid (ALA), an essential n3-fatty acid and the precursor for n3-long-chain polyunsaturated fatty acids (n3-PUFA), which might potentially improve mitochondrial function. (2) Methods: We tested whether a lipophilic walnut extract (WE) affects mitochondrial function and other parameters in human SH-SY5Y cells transfected with the neuronal amyloid precursor protein (APP695). Walnut lipids were extracted using a Soxhlet Extraction System and analyzed using GC/MS and HPLC/FD. Adenosine triphosphate (ATP) concentrations were quantified under basal conditions in cell culture, as well as after rotenone-induced stress. Neurite outgrowth was investigated, as well as membrane integrity, cellular reactive oxygen species, cellular peroxidase activity, and citrate synthase activity. Beta-amyloid (Aβ) was quantified using homogenous time-resolved fluorescence. (3) Results: The main constituents of WE are linoleic acid, oleic acid, α-linolenic acid, and γ- and δ-tocopherol. Basal ATP levels following rotenone treatment, as well as citrate synthase activity, were increased after WE treatment. WE significantly increased cellular reactive oxygen species but lowered peroxidase activity. Membrane integrity was not affected. Furthermore, WE treatment reduced Aβ1-40 and stimulated neurite growth. (4) Conclusions: WE might increase ATP production after induction of mitochondrial biogenesis. Decreased Aβ1-40 formation and enhanced ATP levels might enhance neurite growth, making WE a potential agent to enhance neuronal function and to prevent the development of AD. In this sense, WE could be a promising agent for the prevention of AD.

Keywords:  PUFA; aging; mitochondria; neurodegeneration; poly-unsaturated fatty acids; vitamin E; walnut

DOI:  https://doi.org/10.3390/nu14091694
Nutrients. 2022 May 05. pii: 1934. [Epub ahead of print]14(9):

Global Proteome Profiling of the Temporal Cortex of Female Rats Exposed to Chronic Stress and the Western Diet.

Maria Marta Nowacka-Chmielewska, Daniela Liśkiewicz, Arkadiusz Liśkiewicz, Marta Przybyła, Łukasz Marczak, Anna Wojakowska, Konstancja Grabowska, Mateusz Grabowski, Jarosław Jerzy Barski, Andrzej Małecki.

  The increasing consumption of highly processed foods with high amounts of saturated fatty acids and simple carbohydrates is a major contributor to the burden of overweight and obesity. Additionally, an unhealthy diet in combination with chronic stress exposure is known to be associated with the increased prevalence of central nervous system diseases. In the present study, the global brain proteome approach was applied to explore protein alterations after exposure to the Western diet and/or stress. Female adult rats were fed with the Western diet with human snacks and/or subjected to chronic stress induced by social instability for 12 weeks. The consumption of the Western diet resulted in an obese phenotype and induced changes in the serum metabolic parameters. Consuming the Western diet resulted in changes in only 5.4% of the proteins, whereas 48% of all detected proteins were affected by chronic stress, of which 86.3% were down-regulated due to this exposure to chronic stress. However, feeding with a particular diet modified stress-induced changes in the brain proteome. The down-regulation of proteins involved in axonogenesis and mediating the synaptic clustering of AMPA glutamate receptors (Nptx1), as well as proteins related to metabolic processes (Atp5i, Mrps36, Ndufb4), were identified, while increased expression was detected for proteins involved in the development and differentiation of the CNS (Basp1, Cend1), response to stress, learning and memory (Prrt2), and modulation of synaptic transmission (Ncam1, Prrt2). In summary, global proteome analysis provides information about the impact of the combination of the Western diet and stress exposure on cerebrocortical protein alterations and yields insight into the underlying mechanisms and pathways involved in functional and morphological brain alterations as well as behavioral disturbances described in the literature.

Keywords:  Western diet; brain proteome; chronic stress; female rats

DOI:  https://doi.org/10.3390/nu14091934
Neuroimage. 2022 May 04. pii: S1053-8119(22)00401-3. [Epub ahead of print]257 119280

Variability of regional glucose metabolism and the topology of functional networks in the human brain.

Alessandro Palombit, Erica Silvestri, Tommaso Volpi, Marco Aiello, Diego Cecchin, Alessandra Bertoldo, Maurizio Corbetta.

  The brain consumes the most energy per relative mass amongst the organs in the human body. Theoretical and empirical studies have shown that behavioral processes are relatively inexpensive metabolically, and that most energy goes to maintaining the status quo, i.e., the balance of cell membranes' resting potentials and subthreshold spontaneous activity. Spontaneous activity fluctuates across brain regions in a correlated fashion that defines multi-scale hierarchical networks called resting-state networks (RSNs). Different regions of the brain display different metabolic consumption, but the relationship between regional brain metabolism and RSNs is still under investigation. Here, we examine the variability of glucose metabolism across brain regions, measured with the relative standard uptake value (SUVR) using 18F-FDG PET, and the topology of RSNs, measured through graph analysis applied to fMRI resting-state functional connectivity (FC). We found a moderate linear relationship between the strength (STR) of pairwise regional FC and metabolism. Moreover, the linear correlation between SUVR and STR grew stronger as we considered more connected regions (hubs). Regions connecting different RSNs, or connector hubs, showed higher SUVR than regions connecting nodes within the same RSN, or provincial hubs. Our results show that functional connections as probed by fMRI are related to glucose metabolism, especially in a system of provincial and connector hubs.

Keywords:  (18)F-FDG; Brain metabolism; Brain networks; Functional connectivity (FC); Hubs; Resting state

DOI:  https://doi.org/10.1016/j.neuroimage.2022.119280
Autophagy. 2022 May 09. 1-2

Hitchhiker's guide through the axon: transport and local translation of Pink1 mRNA support axonal mitophagy.

Shree Padma Metur, Daniel J Klionsky.

  The unique cellular organization and metabolic demands of neurons pose a challenge in the maintenance of neuronal homeostasis. A critical element in maintaining neuronal health and homeostasis is mitochondrial quality control via replacement and rejuvenation at the axon. Dysregulation of mitochondrial quality control mechanisms such as mitophagy has been implicated in neurodegenerative diseases including Parkinson disease and amyotrophic lateral sclerosis. To sustain mitophagy at the axon, a continuous supply of PINK1 is required; however, how do neurons maintain a steady supply of this protein at the distal axons? In the study highlighted here, Harbauer et al. show that axonal mitophagy is supported by local translation of Pink1 mRNA that is co-transported with mitochondria to the distal ends of the neuron. This neuronal-specific pathway provides a continuous supply of PINK1 to sustain mitophagy.

Keywords:  Autophagy; mitochondria; neurodegeneration; neuron; stress

DOI:  https://doi.org/10.1080/15548627.2022.2071081
Mol Neurodegener. 2022 May 12. 17(1): 36

Microglial lactate metabolism as a potential therapeutic target for Alzheimer's disease.

Yingjun Zhao, Huaxi Xu.

DOI: https://doi.org/10.1186/s13024-022-00541-z
Biochemistry (Mosc). 2022 Apr;87(4): 356-365

Analysis of Content of 2-Oxoacids in Rat Brain Extracts Using High-Performance Liquid Chromatography.

Vadim N Tashlitsky, Artem V Artiukhov, Natalia V Fedorova, Maxim A Sukonnikov, Alexander L Ksenofontov, Victoria I Bunik, Ludmila A Baratova.

  2-Oxoacids are involved in a number of important metabolic processes and can be used as biomarkers in some human diseases. A new optimized method for quantification of 2,4-dinitrophenylhydrazine derivatives of 2-oxoacids using high-performance liquid chromatography was developed based on available techniques for quantification of 2-oxoacids in mammalian brain. The use of the 2,4-dinitrophenylhydrazine derivatives of 2-oxoacids was shown to be more advantageous in comparison with the previously used phenylhydrazine derivatives, due to a high chemical stability of the former. Here, we determined the concentrations of pyruvate, glyoxylate, 2-oxoglutarate, 2-oxomalonate, and 4-methylthio-2-oxobutyrate in the methanol/acetic acid extracts of the rat brain using the developed method, as well discussed the procedures for the sample preparation in analysis of mammalian brain extracts. The validation parameters of the method demonstrated that the quantification limits for each of the analyzed of 2-oxoacids was 2 nmol/mg tissue. The developed method facilitates identification of subtle changes in the tissue and cellular content of 2-oxoacids as (patho)physiological biomarkers of metabolism in mammalian tissues.

Keywords:  2,4-dinitrophenylhydrazine; 2-oxoacids; HPLC; method validation; rat brain extract

DOI:  https://doi.org/10.1134/S0006297922040058
FASEB J. 2022 May;36 Suppl 1

Domestic crickets (Acheta domesticus) as an animal model to study Parkinson's disease.

Christian Arias-Reyes, Andrés Rojas-Ruiz, Jorge Soliz.

Impaired glutamatergic neurotransmission and neuronal metabolic dysfunction are classic alterations in the pathophysiology of Parkinson's disease (PD). The substantia nigra compacta of the brain (the area where the primary pathological lesion is located) is particularly exposed to oxidative stress and metabolic damage. A reduced ability to cope with metabolic demands, possibly related to impaired mitochondrial function, may make the substantia nigra highly vulnerable to the effects of glutamate, which acts as a neurotoxin in the presence of impaired cellular energy metabolism. Taking into account that insects and mammals share a similar molecular architecture in terms of brain function, this work investigated whether domestic crickets (Acheta domesticus) can be used as an animal model for the study of PD. For this, the crickets received an intra-lymphatic injection (between the second and third tergit of the ventral abdominal segment) of glutamate (10 µl; 2M). Control animals received a similar volume of PBS solution. Twenty-four hours after treatment, the brains of the animals were dissected. We use our oxygraph-2K system (OROBOROS Instruments) to determine mitochondrial respiration by activating mitochondrial complexes (CI, CII, CI&II, and CIV) and the production of reactive oxygen species (ROS). Our preliminary results showed that glutamate treatment significantly reduced the respiration of mitochondrial complexes CI, CII, and CI&II, even though the activity of complex IV (an indicator of the number of mitochondria) was not reduced between treatments. On the other hand, mitochondrial production of reactive oxygen species (ROS) in glutamate-treated animals was significantly increased when both mitochondrial complexes I&II were active, but this pattern was reversed when only one of the complexes I or II was active. Because similar alterations have been observed in the brains of mammals with Parkinson's disease, these results strongly suggest that domestic crickets can be used as an animal model to investigate the mitochondrial mechanisms involved in this disease.

DOI: https://doi.org/10.1096/fasebj.2022.36.S1.L7978
FASEB J. 2022 May;36 Suppl 1

Revealing Sex and Alzheimer's Disease-related Changes in the Spatial Localization of Brain Lipids in Mice using Mass Spectrometry Imaging.

Herana K Seneviratne, Abigail Wheeler, Colten Eberhard, Bindu Paul, Namandjé Bumpus.

Lipids are essential biomolecules in the brain, as they have important roles in signaling and structural integrity. Of note, the central nervous system has a high concentration of lipids, second only to adipose tissue. Recently, it has been shown that abnormalities in lipid levels play a critical role in the onset of neurodegenerative diseases including Alzheimer's disease (AD). AD is a progressive and severe neurodegenerative disease and the leading cause for dementia, affecting millions worldwide. However, the spatial localization of individual lipid molecules in normal brain tissues, as well as region-specific lipid alterations during AD are yet to be explored. Additionally, current understanding of potential sexual dimorphisms in lipid localization in brain is incomplete. With these in mind, we employed high-resolution matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) coupled to ion mobility mass spectrometry to characterize region-specific lipid distribution in brain obtained from age- and sex-matched wild type and AD mice (18-month-old female C57BL/6J and 3xTg-AD mice, which exhibits both amyloid and tau pathology, n=3 per group). Additionally, the spatial distributions of lipids were investigated in male and female mice within two different age groups (4 and 12-week-old, n=3 per group). From these experiments, we were able to detect more than one thousand ions in brain tissue sections. Following detection, we annotated an approximate 100 lipid molecules with high confidence. Tissue imaging results revealed region-specific distributions of specific lipids representing a range of classes including phosphatidylcholines, lysophosphatidylcholines, phosphatidylethanolamines, ceramide phosphates, sphingomyelins, sulfated hexosyl ceramides, and ceramide phosphoinositols across male and female mice. Interestingly, ceramide phosphate (30:7), lysophosphatidylcholine (16:0), and phosphatidylcholine (36:5) molecules exhibited sex-specific localization patterns restricted to the cerebellum in 4-week-old male mice. Further, ceramide phosphoinositol (42:6) was localized to the cerebellum region of 12-week-old male and female mice whereas 4-week-old male and female mice showed relative homogeneous spatial distribution. Notably, we observed region-specific alterations in the spatial localization of several lipid molecules including phosphatidylcholine [(40:6), and (40:7)] and sulfated hexosyl ceramide [(16:1;2O/22:2;O), (24:2;2O/12:1;O), and (19:0;2O/15:0;O)] in AD mice as compared to age- and sex-matched controls. These observed changes occurred in the hippocampus region and were further confirmed using receiver operating characteristic analysis. Taken together, the above results reveal highly localized patterns of alterations in lipid molecules across male and female mice, as well as during AD.

DOI: https://doi.org/10.1096/fasebj.2022.36.S1.R4131
Ann Nutr Metab. 2022 May 11. 1-8

Metabolism and the Effect of Animal-Derived Oxysterols in the Diet on the Development of Alzheimer's Disease.

Mikołaj Choroszyński, Maria Barcikowska, Anna Barczak.

  BACKGROUND: The rapid worldwide increase in the incidence of Alzheimer's disease is associated with changing nutrition patterns. Recently, some articles have highlighted the link between Alzheimer's disease and dietary cholesterol. It was found that elevated levels of some of its fractions in the brain and circulation affect metabolism.SUMMARY: Previous studies have considered the relationship between Alzheimer's disease and oxidized cholesterol molecules in the brain. To date, there are limited data available on the relationship between oxidized cholesterol in the brain and Alzheimer's disease. There is a link between a diet high in cholesterol and its oxidized forms, leading to hypercholesterolemia, which is one of significant risk factors of dementia, and Alzheimer's disease. Oxidized cholesterol can be absorbed in the small intestine and cross the blood-brain barrier, leading to increased inflammation and endogenous oxidative process. Animal-origin foods are sources of oxidized cholesterol, with cholesterol oxidation beginning already after slaughter and occurring during storage and processing.
KEY MESSAGES: High-heat food preparation and storage of cooked products in the refrigerator followed by subsequent heating may significantly increase the amount of oxidized cholesterol products. Therefore, a diet low in cholesterol oxidation products and high in plants with antioxidative properties seems to be most preventable and should be implemented as early as possible.

Keywords:  Alzheimer’s disease; Cholesterol; Diet; Metabolism; Oxysterols

DOI:  https://doi.org/10.1159/000520514
Brain. 2022 May 13. pii: awac176. [Epub ahead of print]

Lipid pathway dysfunction is prevalent in patients with Parkinson's disease.

Jasmin Galper, Nicholas J Dean, Russell Pickford, Simon J G Lewis, Glenda M Halliday, Woojin S Kim, Nicolas Dzamko.

  Many genetic risk factors for Parkinson's disease have lipid-related functions and lipid-modulating drugs such as statins may be protective against Parkinson's disease. Moreover, the hallmark Parkinson's disease pathological protein, α-synuclein, has lipid membrane function and pathways dysregulated in Parkinson's disease such as the endosome-lysosome system and synaptic signaling rely heavily on lipid dynamics. Despite the potential role for lipids in Parkinson's disease, most research to date has been protein-centric, with large-scale, untargeted serum and CSF lipidomic comparisons between genetic and idiopathic Parkinson's disease and neurotypical controls limited. In particular, the extent to which lipid dysregulation occurs in mutation carriers of one of the most common Parkinson's disease risk genes, LRRK2, is unclear. Further, the functional lipid pathways potentially dysregulated in idiopathic and LRRK2 mutation Parkinson's disease is underexplored. To better determine the extent of lipid dysregulation in Parkinson's disease, untargeted high performance liquid chromatography-tandem mass spectrometry was performed on serum (N = 221) and CSF (N = 88) obtained from a multiethnic population from the Michael J Fox Foundation LRRK2 Clinical Cohort Consortium. The cohort consisted of controls, asymptomatic LRRK2 G2019S carriers, LRRK2 G2019S carriers with Parkinson's disease and Parkinson's disease patients without a LRRK2 mutation. Age and sex were adjusted for in analyses where appropriate. Approximately one thousand serum lipid species per participant were analyzed. The main serum lipids that distinguished both Parkinson's disease patients and LRRK2 mutation carriers from controls included species of ceramide, triacylglycerol, sphingomyelin, acylcarnitine, phosphatidylcholine and lysophosphatidylethanolamine. Significant alterations in sphingolipids and glycerolipids were also reflected in Parkinson's disease and LRRK2 mutation carrier CSF, although no correlations were observed between lipids identified in both serum and CSF. Pathway analysis of altered lipid species indicated that sphingolipid metabolism, insulin signaling and mitochondrial function were the major metabolic pathways dysregulated in Parkinson's disease. Importantly, these pathways were also found to be dysregulated in serum samples from a second Parkinson's disease cohort (N = 315). Results from this study demonstrate that dysregulated lipids in Parkinson's disease generally, and in LRRK2 mutation carriers, are from functionally and metabolically related pathways. These findings provide new insight into the extent of lipid dysfunction in Parkinson's disease and therapeutics manipulating these pathways may potentially be beneficial for Parkinson's disease patients. Moreover, serum lipid profiles may be novel biomarkers for both genetic and idiopathic Parkinson's disease.

Keywords:  LRRK2; Parkinson’s disease; biomarker; lipid; sphingolipid

DOI:  https://doi.org/10.1093/brain/awac176
J Cell Physiol. 2022 May 12.

Glutamate-aspartate transporter 1 attenuates oxygen-glucose deprivation-induced injury by promoting glutamate metabolism in primary cortical neurons.

Yun-Zhi Zhao, Jun Wei, Ke-Xin Song, Chen Zhou, Zhen Chai.

  Ischemic stroke is a common cerebral disease. However, the treatment for the disease is limited. Daurian ground squirrel (GS; Spermophilus dauricus), a hibernating mammalian species, is highly tolerant to ischemia. In the present study, GS neurons in a non-hibernating state were found to be more resistant to oxygen-glucose deprivation (OGD), an ischemic model in vitro. We leveraged the differences in the endurance capacity of GS and rats to investigate the mechanisms of resistance to ischemia in GS neurons. We first identified glutamate-aspartate transporter 1 (GLAST) as a cytoprotective factor that contributed to tolerance against OGD injury of GS neurons. The expression of GLAST in GS neurons was much higher than that in rat neurons. Overexpression of GLAST rescued viability in rat neurons, and GS neurons exhibited decreased viability following GLAST knockdown under OGD conditions. Mechanistically, more glutamate was transported into neurons after GLAST overexpression and served as substrates for ATP production. Furthermore, eukaryotic transcription initiation factor 4E binding protein 1 was downregulated by GLAST to rescue neuronal viability. Our findings not only revealed an important molecular mechanism underlying the survival of hibernating mammals but also suggested that neuronal GLAST may be a potential target for ischemic stroke therapy.

Keywords:  glutamate; glutamate-aspartate transporter 1; hibernation; ischemia; neuroprotection

DOI:  https://doi.org/10.1002/jcp.30768
Nat Commun. 2022 May 09. 13(1): 2533

A negative-solvatochromic fluorescent probe for visualizing intracellular distributions of fatty acid metabolites.

Keiji Kajiwara, Hiroshi Osaki, Steffen Greßies, Keiko Kuwata, Ju Hyun Kim, Tobias Gensch, Yoshikatsu Sato, Frank Glorius, Shigehiro Yamaguchi, Masayasu Taki.

Metabolic distribution of fatty acid to organelles is an essential biological process for energy homeostasis as well as for the maintenance of membrane integrity, and the metabolic pathways are strictly regulated in response to environmental stimuli. Herein, we report a fluorescent fatty acid probe, which bears an azapyrene dye that changes its absorption and emission features depending on the microenvironment polarity of the organelle into which it is transported. Owing to the environmental sensitivity of this dye, the distribution of the metabolically incorporated probe in non-polar lipid droplets, medium-polarity membranes, and the polar aqueous regions, can be visualized in different colors. Based on density scatter plots of the fluorophore, we demonstrate that the degradation of triacylglycerols in lipid droplets occurs predominantly via lipolysis rather than lipophagy in nutrition-starved hepatocytes. This tool can thus be expected to significantly advance our understanding of the lipid metabolism in living organisms.

DOI: https://doi.org/10.1038/s41467-022-30153-6
FASEB J. 2022 May;36 Suppl 1

Phosphorylation-based regulation of mitochondrial metabolism.

Nataile Niemi.

Phosphorylation has long been appreciated to influence mitochondrial metabolism via the regulation of pyruvate dehydrogenase. However, the extent to which phosphorylation broadly influences mitochondrial function remains unclear, despite the presence of multiple protein phosphatases within the organelle. We recently demonstrated that deletion of the mitochondrial matrix phosphatase Pptc7 unexpectedly caused perinatal lethality in mice, suggesting that the regulation of mitochondrial phosphorylation is essential in mammalian development. Pptc7-/- mice exhibit severe metabolic deficiencies, including hypoglycemia and lactic acidosis, and die within one day of birth. Biochemical and proteomic approaches revealed that Pptc7-/- tissues have decreased mitochondrial function concomitant with a post-transcriptional downregulation of mitochondrial proteins. Multiple elevated mitochondrial protein phosphorylation sites in Pptc7-/- tissues suggest novel functional connections between Pptc7-mediated dephosphorylation and these observed metabolic consequences. Interestingly, these modifications occur on components of the import machinery of the mitochondria and within the mitochondrial targeting sequences of select nuclear-encoded precursor proteins. Collectively, our data reveal an unappreciated role for a matrix-localized phosphatase in the post-translational regulation of the mitochondrial proteome and organismal metabolic homeostasis.

DOI: https://doi.org/10.1096/fasebj.2022.36.S1.R6264
FASEB J. 2022 May;36 Suppl 1

Mitochondrial Fission is Essential to Maintain Cristae Morphology and Bioenergetics.

Gabriella Robertson, Mira Patel, Stellan Riffle, Andrea Marshall, Heather Beasley, Edgar Garza-Lopez, Antentor O Hinton, Maria Stoll, Jason Mears, Vivian Gama.

Mitochondria and peroxisomes are both dynamic signaling organelles that constantly undergo fission. While mitochondrial fission and fusion are known to coordinate cellular metabolism, proliferation, and apoptosis, the physiological relevance of peroxisome dynamics and the implications for cell fate are not fully understood. DRP1 (dynamin-related protein 1) is an essential GTPase that executes both mitochondrial and peroxisomal fission. Patients with de novo heterozygous missense mutations in the gene that encodes DRP1, DNM1L, present with encephalopathy due to mitochondrial and peroxisomal elongation (EMPF). EMPF is a devastating neurodevelopmental disease with no effective treatment. To interrogate the molecular mechanisms by which DRP1 mutations cause developmental defects, we are using patient-derived fibroblasts and iPSC-derived models from patients with mutations in different domains of DRP1 who present with clinically disparate conditions. Using super resolution imaging, we find that patient cells, in addition to displaying elongated mitochondrial and peroxisomal morphology, present with aberrant cristae structure. Given the direct link between cristae morphology and oxidative phosphorylation efficiency, we explored the impact of these mutations on cellular energy production. Patient cells display a lower coupling efficiency of the electron transport chain, increased proton leak, and Complex III deficiency. In addition to these metabolic abnormalities, mitochondrial hyperfusion results in hyperpolarized mitochondrial membrane potential. Intriguingly, human fibroblasts are capable of cellular reprogramming into iPSCs and appear to display peroxisome-mediated mitochondrial adaptations that could help sustain these cell fate transitions. Understanding the mechanism by which DRP1 mutations cause cellular dysfunction will give insight into the role of mitochondrial and peroxisome dynamics in neurodevelopment.

DOI: https://doi.org/10.1096/fasebj.2022.36.S1.R3665
FASEB J. 2022 May;36 Suppl 1

Inositol-requiring enzyme 1 alpha (IRE1α) regulates astrocyte metabolic and inflammatory phenotypes: Implications in (METH)amphetamine use disorder and HIV-associated neurocognitive disorders.

Jessica M Proulx, Kathleen Borgmann.

Human immunodeficiency virus 1 (HIV-1) invades the central nervous system (CNS) early during infection and can persist in the CNS for life despite effective antiretroviral treatment. Infection and activation of residential glial cells leads to low viral replication and chronic inflammation, which damage neurons contributing to a spectrum of HIV-associated neurocognitive disorders (HAND). Astrocytes are the most numerous glial cells in the CNS and provide essential support to neurons. During a neuropathological challenge, such as HIV-1 infection, astrocytes can shift their neurotrophic functions to become neurotoxic and even serve as latent reservoirs for HIV-1 infection. Notably, substance use disorders, including methamphetamine (METH) are disproportionately elevated among people living with HIV-1. METH use can induce neurotoxic and neurodegenerative consequences, which can increase one's risk and severity of HAND. Thus, a better understanding of HIV-1 infection and METH exposure both alone and in combination on astrocyte function could help identify key cellular or molecular targets that can regulate astrocyte neuroprotective versus neurotoxic phenotypes to optimize astrocyte and neuronal coupling and combat CNS pathology. Direct contact sites between the endoplasmic reticulum (ER) and the mitochondria, termed mitochondria-associated ER membranes (MAMs), are central hubs for regulating several cellular processes, including inflammation and mitochondrial function and dynamics. In fact, the transfer of calcium from the ER to mitochondria is essential for mitochondrial bioenergetics. Interestingly, increasing evidence supports that the three arms of the unfolded protein response (UPR) are key cell signaling messengers within the ER-mitochondrial interface, beyond their classical ER stress functions. Briefly, protein kinase RNA-like endoplasmic reticulum kinase (PERK) has been determined as a regulator for MAM tethering and mitochondrial morphology. Inositol-requiring enzyme 1 alpha (IRE1α) is implicated in regulating MAM-mediated calcium transfer. Activating transcription factor 6 (ATF6) is suspected to participate in MAM formation as it is known to mediate ER elongation and lipid homeostasis. However, these regulatory mechanisms have not yet been fully elucidated. Our studies specifically highlight IRE1α as a key regulator of astrocyte metabolic and inflammatory phenotypes. Using primary human astrocytes infected with pseudotyped HIV and/or exposed to low doses of METH for seven days, astrocytes have increased protein expression of select UPR/MAM mediators. Under the same paradigms, we see increased cytosolic calcium flux and mitochondrial oxygen consumption rate, which were associated with increased mitochondria calcium uptake. Manipulation of IRE1α using both pharmacological inhibitors and an overexpression plasmid, confirms IRE1α modulates astrocyte calcium signaling, metabolic activity, glutamate clearance, and cytokine release. These findings identify a novel target for regulating astrocyte metabolic and inflammatory phenotypes, which could help combat astrocyte-mediated neurotoxicity and potentially promote a neurotrophic phenotype during CNS pathologies.

DOI: https://doi.org/10.1096/fasebj.2022.36.S1.R3764
Int J Mol Sci. 2022 Apr 22. pii: 4635. [Epub ahead of print]23(9):

Molecular and Signaling Mechanisms for Docosahexaenoic Acid-Derived Neurodevelopment and Neuroprotection.

Hee-Yong Kim, Bill X Huang, Arthur A Spector.

  The neurodevelopmental and neuroprotective actions of docosahexaenoic acid (DHA) are mediated by mechanisms involving membrane- and metabolite-related signal transduction. A key characteristic in the membrane-mediated action of DHA results from the stimulated synthesis of neuronal phosphatidylserine (PS). The resulting DHA-PS-rich membrane domains facilitate the translocation and activation of kinases such as Raf-1, protein kinase C (PKC), and Akt. The activation of these signaling pathways promotes neuronal development and survival. DHA is also metabolized in neural tissues to bioactive mediators. Neuroprotectin D1, a docosatriene synthesized by the lipoxygenase activity, has an anti-inflammatory property, and elovanoids formed from DHA elongation products exhibit antioxidant effects in the retina. Synaptamide, an endocannabinoid-like lipid mediator synthesized from DHA in the brain, promotes neurogenesis and synaptogenesis and exerts anti-inflammatory effects. It binds to the GAIN domain of the GPR110 (ADGRF1) receptor, triggers the cAMP/protein kinase A (PKA) signaling pathway, and activates the cAMP-response element binding protein (CREB). The DHA status in the brain influences not only the PS-dependent signal transduction but also the metabolite formation and expression of pre- and post-synaptic proteins that are downstream of the CREB and affect neurotransmission. The combined actions of these processes contribute to the neurodevelopmental and neuroprotective effects of DHA.

Keywords:  ADGRF1; Akt; GPR110; N-docosahexaenoylethanolamine; N-docosahexaenoylphosphatidylethanolamine; PKA; cAMP; docosahexaenoic acid; phosphatidylserine; synaptamide; synaptic membrane proteins

DOI:  https://doi.org/10.3390/ijms23094635
Int J Mol Sci. 2022 Apr 27. pii: 4842. [Epub ahead of print]23(9):

NGF Modulates Cholesterol Metabolism and Stimulates ApoE Secretion in Glial Cells Conferring Neuroprotection against Oxidative Stress.

Mayra Colardo, Michele Petraroia, Letizia Lerza, Daniele Pensabene, Noemi Martella, Valentina Pallottini, Marco Segatto.

  Cholesterol plays a crucial role in the brain, where its metabolism is particularly regulated by astrocytic activity. Indeed, adult neurons suppress their own cholesterol biosynthesis and import this sterol through ApoE-rich particles secreted from astrocytes. Recent evidence suggests that nerve growth factor (NGF) may exert neurotrophic activity by influencing cell metabolism. Nevertheless, the effect of NGF on glial cholesterol homeostasis has still not been elucidated. Thus, the aim of this project is to assess whether NGF could influence cholesterol metabolism in glial cells. To reach this objective, the U373 astrocyte-derived cell line was used as an experimental model. Immunoblot and ELISA analysis showed that proteins and enzymes belonging to the cholesterol metabolism network were increased upon NGF treatment in glial cells. Furthermore, NGF significantly increased ApoE secretion and the amount of extracellular cholesterol in the culture medium. Co-culture and U373-conditioned medium experiments demonstrated that NGF treatment efficiently counteracted rotenone-mediated cytotoxicity in N1E-115 neuronal cells. Conversely, neuroprotection mediated by NGF treatment was suppressed when N1E-115 were co-cultured with ApoE-silenced U373 cells. Taken together, these data suggest that NGF controls cholesterol homeostasis in glial cells. More importantly, NGF exerts neuroprotection against oxidative stress, which is likely associated with the induction of glial ApoE secretion.

Keywords:  ApoE; astrocyte; cholesterol; differentiation; metabolism; nerve growth factor; neuron; reactive oxygen species; rotenone

DOI:  https://doi.org/10.3390/ijms23094842
Theranostics. 2022 ;12(7): 3196-3216

Neuronal STAT3/HIF-1α/PTRF axis-mediated bioenergetic disturbance exacerbates cerebral ischemia-reperfusion injury via PLA2G4A.

Weili Jin, Jixing Zhao, Eryan Yang, Yunfei Wang, Qixue Wang, Ye Wu, Fei Tong, Yanli Tan, Junhu Zhou, Chunsheng Kang.

  Ischemic stroke is an acute and severe neurological disease with high mortality and disability rates worldwide. Polymerase I and transcript release factor (PTRF) plays a pivotal role in regulating cellular senescence, glucose intolerance, lipid metabolism, and mitochondrial bioenergetics, but its mechanism, characteristics, and functions in neuronal cells following the cerebral ischemia-reperfusion (I/R) injury remain to be determined. Methods: Transcription factor motif analysis, chromatin immunoprecipitation (ChIP), luciferase and co-Immunoprecipitation (co-IP) assays were performed to investigate the mechanisms of PTRF in neuronal cells after I/R injury. Lentiviral-sgRNA against PTRF gene was introduced to HT22 cells, and adeno-associated virus (AAV) encoding a human synapsin (hSyn) promoter-driven construct was transduced a short hairpin RNA (shRNA) against PTRF mRNA in primary neuronal cells and the cortex of the cerebral I/R mice for investigating the role of PTRF in neuronal damage and PLA2G4A change induced by the cerebral I/R injury. Results: Here, we reported that neuronal PTRF was remarkably increased in the cerebral penumbra after I/R injury, and HIF-1α and STAT3 regulated the I/R-dependent expression of PTRF via binding to its promoter in neuronal cells. Moreover, overexpression of neuronal PTRF enhanced the activity and stability of PLA2G4A by decreasing its proteasome-mediated degradation pathway. Subsequently, PTRF promoted reprogramming of lipid metabolism and altered mitochondrial bioenergetics, which could lead to oxidative damage, involving autophagy, lipid peroxidation, and ferroptosis via PLA2G4A in neuronal cells. Furthermore, inhibition of neuronal PTRF/PLA2G4A-axis markedly reduced the neurological deficits, cerebral infarct volumes, and mortality rates in the mice following cerebral I/R injury. Conclusion: Our results thus identify that the STAT3/HIF-1α/PTRF-axis in neurons, aggravating cerebral I/R injury by regulating the activity and stability of PLA2G4A, might be a novel therapeutic target for ischemic stroke.

Keywords:  cerebral ischemia-reperfusion (I/R) injury; lipid metabolism; mitochondrial bioenergetics; oxidative damage; polymerase I and transcript release factor (PTRF)

DOI:  https://doi.org/10.7150/thno.71029
J Alzheimers Dis Rep. 2022 ;6(1): 129-161

A New Hypothesis for Alzheimer's Disease: The Lipid Invasion Model.

Jonathan D'Arcy Rudge.

  This paper proposes a new hypothesis for Alzheimer's disease (AD)-the lipid invasion model. It argues that AD results from external influx of free fatty acids (FFAs) and lipid-rich lipoproteins into the brain, following disruption of the blood-brain barrier (BBB). The lipid invasion model explains how the influx of albumin-bound FFAs via a disrupted BBB induces bioenergetic changes and oxidative stress, stimulates microglia-driven neuroinflammation, and causes anterograde amnesia. It also explains how the influx of external lipoproteins, which are much larger and more lipid-rich, especially more cholesterol-rich, than those normally present in the brain, causes endosomal-lysosomal abnormalities and overproduction of the peptide amyloid-β (Aβ). This leads to the formation of amyloid plaques and neurofibrillary tangles, the most well-known hallmarks of AD. The lipid invasion model argues that a key role of the BBB is protecting the brain from external lipid access. It shows how the BBB can be damaged by excess Aβ, as well as by most other known risk factors for AD, including aging, apolipoprotein E4 (APOE4), and lifestyle factors such as hypertension, smoking, obesity, diabetes, chronic sleep deprivation, stress, and head injury. The lipid invasion model gives a new rationale for what we already know about AD, explaining its many associated risk factors and neuropathologies, including some that are less well-accounted for in other explanations of AD. It offers new insights and suggests new ways to prevent, detect, and treat this destructive disease and potentially other neurodegenerative diseases.

Keywords:  Alzheimer’s disease; anesthesia; anterograde amnesia; apolipoproteins; blood-brain barrier; cholesterol; ethanol; lipids; lipoproteins; nonesterified fatty acids

DOI:  https://doi.org/10.3233/ADR-210299
Front Neurosci. 2022 ;16 846425

Roles for Mitochondrial Complex I Subunits in Regulating Synaptic Transmission and Growth.

Bhagaban Mallik, C Andrew Frank.

  To identify conserved components of synapse function that are also associated with human diseases, we conducted a genetic screen. We used the Drosophila melanogaster neuromuscular junction (NMJ) as a model. We employed RNA interference (RNAi) on selected targets and assayed synapse function and plasticity by electrophysiology. We focused our screen on genetic factors known to be conserved from human neurological or muscle functions (300 Drosophila lines screened). From our screen, knockdown of a Mitochondrial Complex I (MCI) subunit gene (ND-20L) lowered levels of NMJ neurotransmission. Due to the severity of the phenotype, we studied MCI function further. Knockdown of core MCI subunits concurrently in neurons and muscle led to impaired neurotransmission. We localized this neurotransmission function to the muscle. Pharmacology targeting MCI phenocopied the impaired neurotransmission phenotype. Finally, MCI subunit knockdowns or pharmacological inhibition led to profound cytological defects, including reduced NMJ growth and altered NMJ morphology. Mitochondria are essential for cellular bioenergetics and produce ATP through oxidative phosphorylation. Five multi-protein complexes achieve this task, and MCI is the largest. Impaired Mitochondrial Complex I subunits in humans are associated with disorders such as Parkinson's disease, Leigh syndrome, and cardiomyopathy. Together, our data present an analysis of Complex I in the context of synapse function and plasticity. We speculate that in the context of human MCI dysfunction, similar neuronal and synaptic defects could contribute to pathogenesis.

Keywords:  Drosophila; Mitochondrial Complex I; NMJ – neuromuscular junction; neurodevelopment; neurotransmission; synapse; synaptic development; synaptic dysfunction

DOI:  https://doi.org/10.3389/fnins.2022.846425
FASEB J. 2022 May;36 Suppl 1

Developing a Pipeline for Personalized Diagnoses of Glut1 Deficiency Syndrome.

Laiken Griffith, Katherine Donohue, Maya Abul-Khoudoud, Matthew Gentry.

Glut1 deficiency syndrome (Glut1DS) is a brain metabolic disorder, caused by the impairment of glucose transport in the brain. Glut1DS occurs when there is a mutation in the SLC2A1 gene, which encodes for the protein glucose transporter protein type 1. Around 500 people worldwide suffer from this disease, and most deal with symptoms such as seizures, movement disorders, and in more severe cases, microcephaly. A common treatment for Glut1DS is the ketogenic diet, which provides the brain with an alternate energy source. Patients suffering from Glut1DS have been shown to respond more positively to this treatment when they are able to start it early in life. Unfortunately, due to the variety of phenotypes associated with Glut1DS, there is often a large gap between onset of symptoms and diagnosis. This is problematic because a delay in diagnosis means a delay in treatment, leading to more severe disease progression. In order to bridge the gap, our lab applied a suite of bioinformatics techniques to characterize novel mutations and help patients achieve faster diagnoses. Because Glut1DS patients with different mutations experience varying loss of function of the Glut1 transporter, linking mutation type to phenotype could help patients receive a faster diagnosis, allowing them to start treatment earlier. In order to do this, we analyzed and classified different mutations in the SLC2A1 gene based on predicted pathogenicity. By comparing these data to known Glut1DS patient phenotypes, we were able to able to define five mutation classes based on severity. This type of analysis can be used to provide a faster diagnosis and personalized treatment plans for patients based on their mutation class. As personalized medicine for rare genetic diseases progresses, a database of mutations and severity class could help patients start life-changing treatment much earlier. Additionally, this model for pipeline development could be expanded to assist in the diagnosis of other rare genetic diseases.

DOI: https://doi.org/10.1096/fasebj.2022.36.S1.R5375
Nutrients. 2022 Apr 19. pii: 1698. [Epub ahead of print]14(9):

DHA-Enriched Fish Oil Ameliorates Deficits in Cognition Associated with Menopause and the APOE4 Genotype in Rodents.

Matthew G Pontifex, Anneloes Martinsen, Rasha N M Saleh, Glenn Harden, Chris Fox, Michael Muller, David Vauzour, Anne-Marie Minihane.

  Female APOE4 carriers have a greater predisposition to developing Alzheimer's disease (AD) compared to their male counterparts, which may partly be attributed to menopause. We previously reported that a combination of menopause and APOE4 led to an exacerbation of cognitive and neurological deficits, which were associated with reduced brain DHA and DHA:AA ratio. Here, we explored whether DHA-enriched fish oil (FO) supplementation mitigated the detrimental impact of these risk factors. Whilst DHA-enriched fish oil improved recognition memory (NOR) in APOE4 VCD (4-vinylcyclohexene diepoxide)-treated mice (p < 0.05), no change in spatial working memory (Y-maze) was observed. FO supplementation increased brain DHA and nervonic acid and the DHA:AA ratio. The response of key bioenergetic and blood-brain barrier related genes and proteins provided mechanistic insights into these behavioural findings, with increased BDNF protein concentration as well as mitigation of aberrant Erβ, Cldn1 and Glut-5 expression in APOE4 mice receiving fish oil supplementation (p < 0.05). In conclusion, supplementation with a physiologically relevant dose of DHA-enriched fish oil appears to offer protection against the detrimental effects of menopause, particularly in "at-risk" APOE4 female carriers.

Keywords:  4-vinylcyclohexanediepoxide; Alzheimer’s disease; BDNF; Glut-5; apolipoprotein E; arachidonic acid; brain; docosahexaenoic acid; oestrogen; oestrogen receptor

DOI:  https://doi.org/10.3390/nu14091698
Nat Commun. 2022 May 10. 13(1): 2545

Serum metabolome associated with severity of acute traumatic brain injury.

CENTER-TBI Participants and Investigators

Complex metabolic disruption is a crucial aspect of the pathophysiology of traumatic brain injury (TBI). Associations between this and systemic metabolism and their potential prognostic value are poorly understood. Here, we aimed to describe the serum metabolome (including lipidome) associated with acute TBI within 24 h post-injury, and its relationship to severity of injury and patient outcome. We performed a comprehensive metabolomics study in a cohort of 716 patients with TBI and non-TBI reference patients (orthopedic, internal medicine, and other neurological patients) from the Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) cohort. We identified panels of metabolites specifically associated with TBI severity and patient outcomes. Choline phospholipids (lysophosphatidylcholines, ether phosphatidylcholines and sphingomyelins) were inversely associated with TBI severity and were among the strongest predictors of TBI patient outcomes, which was further confirmed in a separate validation dataset of 558 patients. The observed metabolic patterns may reflect different pathophysiological mechanisms, including protective changes of systemic lipid metabolism aiming to maintain lipid homeostasis in the brain.

DOI: https://doi.org/10.1038/s41467-022-30227-5
FASEB J. 2022 May;36 Suppl 1

Carboxylesterase 1 (Ces1) Releases Oxylipins From Oxidized Triacylglycerols: Examination of Its Substrate Selectivity.

Matthew K Ross, Maggie Phillips, Abdolsamad Borazjani.

Triacylglycerols (TAGs) are the most quantitatively important storage form of fat and are found primarily in cytoplasmic lipid droplets within cells. TAGs are broken down to its component free fatty acids by lipolytic enzymes when fuel reserves are required. However, when TAGs possess large quantities of polyunsaturated fatty acids (PUFAs) they are prone to nonenzymatic oxidation reactions, leading to formation of oxylipins (i.e., oxidized forms of fatty acids) that are esterified to the glycerol backbone (termed oxTAGs). Human carboxylesterase (CES1) is a member of the serine hydrolase superfamily and defined by its ability to catalyze the hydrolysis of carboxyl ester bonds in both toxicants and lipids. Although it is known that CES1 is a bona fideTAG hydrolase, it is unclear which specific fatty acids are preferentially released during lipolysis. Moreover, to better understand the biochemical function of CES1 in macrophages, we need to determine its substrate selectivity when it encounters oxidized PUFAs in TAG lipid droplets. Thus, the goal of this study is to systematically identify those oxidized fatty acids that are liberated from oxTAGs by CES1, because their release activates signaling pathways important for the development of lipid-driven inflammation. Gaining this knowledge will fill data gaps that exist between CES1 and the lipid-sensing nuclear receptors, PPARγ and LXRα, that are abundantly expressed in macrophages and are important drivers of lipid metabolism and inflammation. Oxidized forms of triarachidonoylglycerol (oxTAG C20:4) and trilinoleoylglycerol (oxTAG C18:2) - containing physiologically relevant levels of oxidized PUFAs (<5 mol%) - were incubated with recombinant CES1, or Pseudomonaslipase (a positive control), to assess the release of oxylipins and non-oxidized arachidonic acid (AA) and linoleic acid (LA), which were quantified by LC-MS. CES1 was shown to efficiently metabolize oxTAG C20:4 and oxTAG C18:2, yielding several regioisomers of hydroxyeicosatetraenoic acid (5-, 12-, and 15-HETE) and hydroxyoctadecadienoic acid (9- and 13-HODE), respectively. The CES1-catalyzed cumulative release of HODEs was faster than that of HETEs from the respective oxTAGs (7 pmol HODEs/min vs. 1 pmol HETEs/min). Thus, for oxTAGs, hydroxy fatty acids derived from LA are preferred by CES1 to those derived from AA. A similar trend was noted for the release of non-oxidized PUFAs from the respective oxTAGs (470 pmol LA/min vs. 83 pmol AA/min). CES1 also preferentially liberated 5-HETE over 12-HETE and 15-HETE from oxTAG C20:4, whereas no differences were noted between 9-HODE and 13-HODE. This study indicates that CES1 can metabolize oxTAG lipids to release oxylipins and PUFAs. It further specifies the substrate selectivity of CES1 in the metabolism of bioactive lipid mediators that can regulate inflammatory activities of immune cells.

DOI: https://doi.org/10.1096/fasebj.2022.36.S1.R4600
FASEB J. 2022 May;36 Suppl 1

An endogenous polyunsaturated fatty acid, dihomo-gamma-linoleic acid, induces neurodegeneration in C. elegans via ferroptosis.

Kin Sing Stephen Lee, Morteza Sarparast, Fan Zhang, Pourmand Seyedehelham, Roland E Gonzalez, Benjamin Kessler, Benjamin Heasman, Jamie Alan.

Ferroptosis, an iron-dependent non-apoptotic programmed cell death, becomes a novel target and mechanism for age-associated neurodegenerative diseases. Although several ferroptosis regulatory proteins have been identified, the signaling molecules and the pathways of ferroptosis remain largely unknown. Despite membrane lipid peroxidation being one of the molecular hallmarks of ferroptosis, how polyunsaturated fatty acids (PUFAs) involved in the ferroptosis pathway is understudied. Here, we hypothesize that a specific PUFA and/or its downstream metabolites are lipid mediators of ferroptosis. However, it is challenging to identify by which metabolites regulate ferroptosis and to study the associated mechanism due to many different endogenous PUFAs are presented endogenously and each PUFAs can be metabolized to almost a hundred of metabolites. To take on these challenges, we employed Caenorhabditis elegans (C. elegans) as a novel biological model due to the availability of many genetic and imaging tools, conserved ferroptosis pathways between mammal and C. elegans, and adaptability for high-throughput whole animal aging study. Using the well-established fluorescent imaging assay in C. elegans, we showed that treatment of dihomo-gamma-linoleic acid (DGLA), but not other PUFAs, induces significant (>40% as compared to control) degeneration in dopaminergic neurons immediately after 1 day of treatment. We also found that treatment of DGLA does not affect other somatic tissues of the C. elegans. Our lipidomic analysis demonstrated that DGLA is well-absorbed by C. elegans. Besides, our results indicated that DGLA triggers neurodegeneration in dopaminergic neurons, likely through ferroptosis. Using our oxidized lipid metabolites analysis and synthetic chemical probes, we revealed that DGLA likely triggers neurodegeneration viatheir oxidized metabolites. Finally, we will also present the potential ferroptosis signaling pathways triggered by DGLA based on our RNA-seq experiments. Our results will help us identify novel lipid mediators for ferroptosis, which will lead to a better understanding of the molecular mechanism of ferroptosis. Our findings regarding the neuronal specific effects triggered by DGLA also revive a novel cell-specific regulatory mechanism of ferroptosis. Lastly, our study will find novel therapeutic targets for either preventative treatment or cure for neurodegenerative diseases.

DOI: https://doi.org/10.1096/fasebj.2022.36.S1.0R466