Energy contribution of octanoate to intact rat brain metabolism measured by 13C nuclear magnetic resonance spectroscopy

Anti-seizure effects of norepinephrine-induced free fatty acid release

The brain's ability to rapidly transition between sleep, quiet wakefulness, and states of high vigilance is remarkable. Cerebral norepinephrine (NE) plays a key role in promoting wakefulness, but how does the brain avoid neuronal hyperexcitability upon arousal? Here, we show that NE exposure results in the generation of free fatty acids (FFAs) within the plasma membrane from both astrocytes and neurons. In turn, FFAs dampen excitability by differentially modulating the activity of astrocytic and neuronal Na+, K+, ATPase. Direct application of FFA to the occipital cortex in awake, behaving mice dampened visual-evoked potential (VEP). Conversely, blocking FFA production via local application of a lipase inhibitor heightened VEP and triggered seizure-like activity. These results suggest that FFA release is a crucial step in NE signaling that safeguards against hyperexcitability. Targeting lipid-signaling pathways may offer a novel therapeutic approach for seizure prevention.

Biomarker identification and risk assessment of cardiovascular disease based on untargeted metabolomics and machine learning

Cardiovascular disease (CVD) is the leading cause of mortality, disability, and healthcare costs, with a significant impact on the elderly and contributing to premature deaths across various age groups, including those below age 70. Despite decades of transformative discoveries and clinical efforts, the challenges of diagnosis, prevention, and treatment of CVD persist on a massive scale. This study aimed to unravel potential CVD-associated biomarkers and establish a machine learning model for the risk assessment of CVD. Untargeted metabolic assay with ultra-high performance liquid chromatography-tandem mass spectrometry and routine clinical biochemistry test were undertaken on the fasting venous blood specimens from 57 subjects. Four relevant clinical traits and 164 CVD-associated metabolites were identified, especially those related to glycerophospholipid metabolism and biosynthesis of unsaturated fatty acids. The machine learning model achieved from an integrated biomarker panel of palmitic amide, oleic acid, 138-pos (the 138th detected metabolomic feature in positive ion mode), phosphatidylcholine, linoleic acid, age, direct bilirubin, and inorganic phosphate, was able to improve the accuracy of CVD risk assessment up to a high satisfactory value of 0.91. The findings indicate that disorders in the metabolic processes of biological membranes and energy are significantly associated with increased risk of vascular damage in CVD patients. With machine learning methods, the pivotal metabolites and clinical biomarkers offer a promising potential for the efficient risk assessment and diagnosis of CVD.

Fatty acid β-oxidation in brain mitochondria: Insights from high-resolution respirometry in mouse, rat and Drosophila brain, ischemia and aging models

Glucose is the main energy source of the brain, yet recent studies demonstrate that fatty acid oxidation (FAO) plays a relevant role in the pathogenesis of central nervous system disorders. We evaluated FAO in brain mitochondria under physiological conditions, in the aging brain, and after stroke. Using high-resolution respirometry we compared medium-chain (MC, octanoylcarnitine) and long-chain (LC, palmitoylcarnitine) acylcarnitines as substrates of β-oxidation in the brain. The protocols developed avoid FAO overestimation by malate-linked anaplerotic activity in brain mitochondria. The capacity of FA oxidative phosphorylation (F-OXPHOS) with palmitoylcarnitine was up to 4 times higher than respiration with octanoylcarnitine. The optimal concentration of palmitoylcarnitine was 10 μM which corresponds to the total concentration of LC acylcarnitines in the brain. Maximal respiration with octanoylcarnitine was reached at 20 μM, however, this concentration exceeds MC acylcarnitine concentrations in the brain 15 times. F-OXPHOS capacity was highest in mouse cerebellum, intermediate in cortex, prefrontal cortex, and hypothalamus, and hardly detectable in hippocampus. F-OXPHOS capacity was 2-fold lower and concentrations of LC acylcarnitines were 2-fold higher in brain of aged rats. A similar trend was observed in the rat model of endothelin-1-induced stroke, but reduction of OXPHOS capacity was not limited to FAO. In conclusion, although FAO is not a dominant pathway in brain bioenergetics, it deserves specific attention in studies of brain metabolism.

Brain Metabolism in Health and Neurodegeneration: The Interplay Among Neurons and Astrocytes

The regulation of energy in the brain has garnered substantial attention in recent years due to its significant implications in various disorders and aging. The brain's energy metabolism is a dynamic and tightly regulated network that balances energy demand and supply by engaging complementary molecular pathways. The crosstalk among these pathways enables the system to switch its preferred fuel source based on substrate availability, activity levels, and cell state-related factors such as redox balance. Brain energy production relies on multi-cellular cooperation and is continuously supplied by fuel from the blood due to limited internal energy stores. Astrocytes, which interface with neurons and blood vessels, play a crucial role in coordinating the brain's metabolic activity, and their dysfunction can have detrimental effects on brain health. This review characterizes the major energy substrates (glucose, lactate, glycogen, ketones and lipids) in astrocyte metabolism and their role in brain health, focusing on recent developments in the field.

Metabolic dysregulation in Huntington's disease: Neuronal and glial perspectives

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by a mutant huntingtin protein with an abnormal CAG/polyQ expansion in the N-terminus of HTT exon 1. HD is characterized by progressive neurodegeneration and metabolic abnormalities, particularly in the brain, which accounts for approximately 20 % of the body's resting metabolic rate. Dysregulation of energy homeostasis in HD includes impaired glucose transporters, abnormal functions of glycolytic enzymes, changes in tricarboxylic acid (TCA) cycle activity and enzyme expression in the basal ganglia and cortical regions of both HD mouse models and HD patients. However, current understanding of brain cell behavior during energy dysregulation and its impact on neuron-glia crosstalk in HD remains limited. This review provides a comprehensive summary of the current understanding of the differences in glucose metabolism between neurons and glial cells in HD and how these differences contribute to disease development compared with normal conditions. We also discuss the potential impact of metabolic shifts on neuron-glia communication in HD. A deeper understanding of these metabolic alterations may reveal potential therapeutic targets for future drug development.

Neuroimmune and neuroinflammation response for traumatic brain injury

Traumatic brain injury (TBI) is one of the major diseases leading to mortality and disability, causing a serious disease burden on individuals' ordinary lives as well as socioeconomics. In primary injury, neuroimmune and neuroinflammation are both responsible for the TBI. Besides, extensive and sustained injury induced by neuroimmune and neuroinflammation also prolongs the course and worsens prognosis of TBI. Therefore, this review aims to explore the role of neuroimmune, neuroinflammation and factors associated them in TBI as well as the therapies for TBI. Thus, we conducted by searching PubMed, Scopus, and Web of Science databases for articles published between 2010 and 2023. Keywords included "traumatic brain injury," "neuroimmune response," "neuroinflammation," "astrocytes," "microglia," and "NLRP3." Articles were selected based on relevance and quality of evidence. On this basis, we provide the cellular and molecular mechanisms of TBI-induced both neuroimmune and neuroinflammation response, as well as the different factors affecting them, are introduced based on physiology of TBI, which supply a clear overview in TBI-induced chain-reacting, for a better understanding of TBI and to offer more thoughts on the future therapies for TBI.

Effect of Dietary Supplementation of Glycerol Monolaurate on Growth Performance, Digestive Enzymes, Serum Immune and Antioxidant Parameters, and Intestinal Morphology in Black Sea Bream

An eight-week feeding trial was conducted to examine the impact of dietary supplementation with glycerol monolaurate (GML) on juvenile black sea bream. A basal diet was formulated containing 24% fish meal, while five additional diets were prepared, each supplemented with varying levels of GML: GML1 (0.01%), GML2 (0.02%), GML3 (0.04%), GML4 (0.08%), and GML5 (0.16%). Triplicate tanks were randomly allocated to each diet, each containing 20 fish with an initial weight of 1.55 ± 0.05 g. By the trial's end, the GML3 group displayed a notably higher final body weight (FBW), weight gain (WG), specific growth rate (SGR), and protein efficiency ratio (PER) compared to the other groups (p < 0.05), but the FCR was significantly higher in the control group. However, no significant differences were observed in the MFI, PPV, CF, HSI, IPF, VSI, or SR among the groups (p > 0.05). Regarding the proximate compositions of the dorsal muscle and whole body, no substantial differences were observed across the groups (p > 0.05). Additionally, there were no significant variations in digestive enzyme activity (p > 0.05), serum immune, or biochemical parameters in the midgut and hindgut among the treatment groups. But in the serum immune response IgM, C3 and C4 were significantly higher in the GML3 group as compared to the other groups (p < 0.05). However, the GML3 group exhibited significantly greater fore-intestinal villus height, crypt depth, villus height per crypt depth, and the number of goblet cells per villus compared to the other groups (p < 0.05). Overall, GML supplementation, particularly GML3, significantly improved growth indicators like the final body weight and intestinal morphology. While certain parameters remained unaffected, these findings suggest GML's potential as a beneficial dietary supplement in fish diets.

From BBB to PPP: Bioenergetic requirements and challenges for oligodendrocytes in health and disease

Mature myelinating oligodendrocytes, the cells that produce the myelin sheath that insulates axons in the central nervous system, have distinct energetic and metabolic requirements compared to neurons. Neurons require substantial energy to execute action potentials, while the energy needs of oligodendrocytes are directed toward building the lipid-rich components of myelin and supporting neuronal metabolism by transferring glycolytic products to axons as additional fuel. The utilization of energy metabolites in the brain parenchyma is tightly regulated to meet the needs of different cell types. Disruption of the supply of metabolites can lead to stress and oligodendrocyte injury, contributing to various neurological disorders, including some demyelinating diseases. Understanding the physiological properties, structures, and mechanisms involved in oligodendrocyte energy metabolism, as well as the relationship between oligodendrocytes and neighboring cells, is crucial to investigate the underlying pathophysiology caused by metabolic impairment in these disorders. In this review, we describe the particular physiological properties of oligodendrocyte energy metabolism and the response of oligodendrocytes to metabolic stress. We delineate the relationship between oligodendrocytes and other cells in the context of the neurovascular unit, and the regulation of metabolite supply according to energetic needs. We focus on the specific bioenergetic requirements of oligodendrocytes and address the disruption of metabolic energy in demyelinating diseases. We encourage further studies to increase understanding of the significance of metabolic stress on oligodendrocyte injury, to support the development of novel therapeutic approaches for the treatment of demyelinating diseases.

Fatty acid preference for beta-oxidation in mitochondria of murine cultured astrocytes

The brain utilizes glucose as a primary energy substrate but also fatty acids for the β-oxidation in mitochondria. The β-oxidation is reported to occur mainly in astrocytes, but its capacity and efficacy against different fatty acids remain unknown. Here, we show the fatty acid preference for the β-oxidation in mitochondria of murine cultured astrocytes. Fatty acid oxidation assay using an extracellular flux analyzer showed that saturated or monosaturated fatty acids, palmitic acid and oleic acid, are preferred substrates over polyunsaturated fatty acids like arachidonic acid and docosahexaenoic acid. We also report that fatty acid binding proteins expressed in the astrocytes contribute less to fatty acid transport to mitochondria for β-oxidation. Our results could give insight into understanding energy metabolism through fatty acid consumption in the brain.

SGLT2 Inhibitor Dapagliflozin Increases Skeletal Muscle and Brain Fatty Acid Uptake in Individuals With Type 2 Diabetes: A Randomized Double-Blind Placebo-Controlled Positron Emission Tomography Study

OBJECTIVE

The aim of this study was to investigate the impact of the sodium-glucose cotransporter 2 (SGLT2) inhibitor dapagliflozin on tissue fatty acid (FA) uptake in the skeletal muscle, brain, small intestine, and subcutaneous and visceral adipose tissue of individuals with type 2 diabetes by using positron emission tomography (PET).

RESEARCH DESIGN AND METHODS

In a 6-week randomized double-blind placebo-controlled trial, 53 patients with type 2 diabetes treated with metformin received either 10 mg dapagliflozin or placebo daily. Tissue FA uptake was quantified at baseline and end of treatment with PET and the long-chain FA analog radiotracer 14(R,S)-[18F]fluoro-6-thia-heptadecanoic acid. Treatment effects were assessed using ANCOVA, and the results are reported as least square means and 95% CIs for the difference between groups.

RESULTS

A total of 38 patients (dapagliflozin n = 21; placebo n = 17) completed the study. After 6 weeks, skeletal muscle FA uptake was increased by dapagliflozin compared with placebo (1.0 [0.07, 2.0] μmol ⋅ 100 g-1 ⋅ min-1; P = 0.032), whereas uptake was not significantly changed in the small intestine or visceral or subcutaneous adipose tissue. Dapagliflozin treatment significantly increased whole-brain FA uptake (0.10 [0.02, 0.17] μmol ⋅ 100 g-1 ⋅ min-1; P = 0.01), an effect observed in both gray and white matter regions.

CONCLUSIONS

Six weeks of treatment with dapagliflozin increases skeletal muscle and brain FA uptake, partly driven by a rise in free FA availability. This finding is in accordance with previous indirect measurements showing enhanced FA metabolism in response to SGLT2 inhibition and extends the notion of a shift toward increased FA use to muscle and brain.

The role of amino acid metabolism alterations in acute ischemic stroke: From mechanism to application

Acute ischemic stroke (AIS) is the most prevalent type of stroke, and due to its high incidence, disability rate, and mortality rate, it imposes a significant burden on the health care system. Amino acids constitute one of the most crucial metabolic products within the human body, and alterations in their metabolic pathways have been identified in the microenvironment of AIS, thereby influencing the pathogenesis, severity, and prognosis of AIS. The amino acid metabolism characteristics in AIS are complex. On one hand, the dynamic progression of AIS continuously reshapes the amino acid metabolism pattern. Conversely, changes in the amino acid metabolism pattern also exert a double-edged effect on AIS. This interaction is bidirectional, dynamic, heterogeneous, and dose-specific. Therefore, the distinctive metabolic reprogramming features surrounding amino acids during the AIS process are systematically summarized in this paper, aiming to provide potential investigative strategies for the early diagnosis, treatment approaches, and prognostic enhancement of AIS.

Metabolic Reprogramming of Astrocytes in Pathological Conditions: Implications for Neurodegenerative Diseases

Astrocytes play a pivotal role in maintaining brain energy homeostasis, supporting neuronal function through glycolysis and lipid metabolism. This review explores the metabolic intricacies of astrocytes in both physiological and pathological conditions, highlighting their adaptive plasticity and diverse functions. Under normal conditions, astrocytes modulate synaptic activity, recycle neurotransmitters, and maintain the blood-brain barrier, ensuring a balanced energy supply and protection against oxidative stress. However, in response to central nervous system pathologies such as neurotrauma, stroke, infections, and neurodegenerative diseases like Alzheimer's and Huntington's disease, astrocytes undergo significant morphological, molecular, and metabolic changes. Reactive astrocytes upregulate glycolysis and fatty acid oxidation to meet increased energy demands, which can be protective in acute settings but may exacerbate chronic inflammation and disease progression. This review emphasizes the need for advanced molecular, genetic, and physiological tools to further understand astrocyte heterogeneity and their metabolic reprogramming in disease states.

Lipases are differentially regulated by hormones to maintain free fatty acid homeostasis for insect brain development

BACKGROUND

Free fatty acids (FFAs) play vital roles as energy sources and substrates in organisms; however, the molecular mechanism regulating the homeostasis of FFA levels in various circumstances, such as feeding and nonfeeding stages, is not fully clarified. Holometabolous insects digest dietary triglycerides (TAGs) during larval feeding stages and degrade stored TAGs in the fat body during metamorphosis after feeding cessation, which presents a suitable model for this study.

RESULTS

This study reported that two lipases are differentially regulated by hormones to maintain the homeostasis of FFA levels during the feeding and nonfeeding stages using the lepidopteran insect cotton bollworm Helicoverpa armigera as a model. Lipase member H-A-like (Lha-like), related to human pancreatic lipase (PTL), was abundantly expressed in the midgut during the feeding stage, while the monoacylglycerol lipase ABHD12-like (Abhd12-like), related to human monoacylglycerol lipase (MGL), was abundantly expressed in the fat body during the nonfeeding stage. Lha-like was upregulated by juvenile hormone (JH) via the JH intracellular receptor methoprene-tolerant 1 (MET1), and Abhd12-like was upregulated by 20-hydroxyecdysone (20E) via forkhead box O (FOXO) transcription factor. Knockdown of Lha-like decreased FFA levels in the hemolymph and reduced TAG levels in the fat body. Moreover, lipid droplets (LDs) were small, the brain morphology was abnormal, the size of the brain was small, and the larvae showed the phenotype of delayed pupation, small pupae, and delayed tissue remodeling. Knockdown of Abhd12-like decreased FFA levels in the hemolymph; however, TAG levels increased in the fat body, and LDs remained large. The development of the brain was arrested at the larval stage, and the larvae showed a delayed pupation phenotype and delayed tissue remodeling.

CONCLUSIONS

The differential regulation of lipases expression by different hormones determines FFAs homeostasis and different TAG levels in the fat body during the feeding larval growth and nonfeeding stages of metamorphosis in the insect. The homeostasis of FFAs supports insect growth, brain development, and metamorphosis.

Brain lipid sensing and the neural control of energy balance

The central nervous system continuously detects circulating concentrations of lipids such as fatty acids and troglycerides. Once information has been detected, the central nervous system can in turn participate in the control of energy balance and blood sugar levels and in particular regulate the secretion and action of insulin. Neurons capable of detecting circulating lipid variations are located in the hypothalamus and in other regions such as the nucleus accumbens, the striatum or the hippocampus. An excess of lipids will have deleterious effects and may induce central lipotoxicity, in particular following local production of ceramides and the appearance of neuroinflammation which may lead to metabolic diseases such as obesity and type 2 diabetes.

Case for supporting astrocyte energetics in glucose transporter 1 deficiency syndrome

In glucose transporter 1 deficiency syndrome (Glut1DS), glucose transport into brain is reduced due to impaired Glut1 function in endothelial cells at the blood-brain barrier. This can lead to shortages of glucose in brain and is thought to contribute to seizures. Ketogenic diets are the first-line treatment and, among many beneficial effects, provide auxiliary fuel in the form of ketone bodies that are largely metabolized by neurons. However, Glut1 is also the main glucose transporter in astrocytes. Here, we review data indicating that glucose shortage may also impact astrocytes in addition to neurons and discuss the expected negative biochemical consequences of compromised astrocytic glucose transport for neurons. Based on these effects, auxiliary fuels are needed for both cell types and adding medium chain triglycerides (MCTs) to ketogenic diets is a biochemically superior treatment for Glut1DS compared to classical ketogenic diets. MCTs provide medium chain fatty acids (MCFAs), which are largely metabolized by astrocytes and not neurons. MCFAs supply energy and contribute carbons for glutamine and γ-aminobutyric acid synthesis, and decanoic acid can also block α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid glutamate receptors. MCTs do not compete with metabolism of ketone bodies mostly occurring in neurons. Triheptanoin, an anaplerotic but also gluconeogenic uneven MCT, may be another potential addition to ketogenic diets, although maintenance of "ketosis" can be difficult. Gene therapy has also targeted both endothelial cells and astrocytes. Other approaches to increase fuel delivery to the brain currently investigated include exchange of Glut1DS erythrocytes with healthy cells, infusion of lactate, and pharmacological improvement of glucose transport. In conclusion, although it remains difficult to assess impaired astrocytic energy metabolism in vivo, astrocytic energy needs are most likely not met by ketogenic diets in Glut1DS. Thus, we propose prospective studies including monitoring of blood MCFA levels to find optimal doses for add-on MCT to ketogenic diets and assessing of short- and long-term outcomes.

Polar Lipids Supplementation Enhances Basal Excitatory Synaptic Transmission in Primary Cortical Neuron

SCOPE

Polar lipids, such as gangliosides and phospholipids, are fundamental structural components that play critical roles in the development and maturation of neurons in the brain. Recent evidence has demonstrated that dietary intakes of polar lipids in early life are associated with improved cognitive outcomes during infancy and adolescence. However, the specific mechanisms through which these lipids impact cognition remain unclear.

METHODS AND RESULTS

This study examines the direct physiological impact of polar lipid supplementation, in the form of buttermilk powder, on primary cortical neuron growth and maturation. The changes are measured with postsynaptic current response recordings, immunohistochemical examination of functional synapse localization and numbers, and the biochemical quantification of receptors responsible for neuronal synaptic neurotransmission. Chronic exposure to polar lipids increases primary mouse cortical neuron basal excitatory synapse response strength attributed to enhanced dendritic complexity and an altered expression of the excitatory α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunit 2 (GluR2).

CONCLUSION

The present finding suggests that dietary polar lipids improve human cognition through an enhancement of neuronal maturation and/or function.

Lipidomic analysis identifies long-chain acylcarnitine as a target for ischemic stroke

INTRODUCTION

Lipid metabolism dysfunction is widely involved in the pathological process of acute ischemic stroke (AIS). The coordination of lipid metabolism between neurons and astrocytes is of great significance. However, the full scope of lipid dynamic changes and the function of key lipids during AIS remain unknown. Hence, identifying lipid alterations and characterizing their key roles in AIS is of great importance.

METHODS

Untargeted and targeted lipidomic analyses were applied to profile lipid changes in the ischemic penumbra and peripheral blood of transient middle cerebral artery occlusion (tMCAO) mice as well as the peripheral blood of AIS patients. Infarct volume and neurological deficits were assessed after tMCAO. The cell viability and dendritic complexity of primary neurons were evaluated by CCK8 assay and Sholl analysis. Seahorse, MitoTracker Green, tetramethyl rhodamine methyl ester (TMRM), 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) and MitoSOX were used as markers of mitochondrial health. Fluorescent and isotopic free fatty acid (FFA) pulse-chase assays were used to track FFA flux in astrocytes.

RESULTS

Long-chain acylcarnitines (LCACs) were the lipids with the most dramatic changes in the ischemic penumbra and peripheral blood of tMCAO mice. LCACs were significantly elevated on admission in AIS patients and associated with poor outcomes in AIS patients. Increasing LCACs through a bolus administration of palmitoylcarnitine amplified stroke injury, while decreasing LCACs by overexpressing carnitine palmitoyltransferase 2 (CPT2) ameliorated stroke injury. Palmitoylcarnitine aggravated astrocytic mitochondrial damage after OGD/R, while CPT2 overexpression in astrocytes ameliorated cocultured neuron viability. Further study revealed that astrocytes stimulated by OGD/R liberated FFAs from lipid droplets into mitochondria to form LCACs, resulting in mitochondrial damage and lowered astrocytic metabolic support and thereby aggravated neuronal damage.

CONCLUSION

LCACs could accumulate and damage neurons by inducing astrocytic mitochondrial dysfunction in AIS. LCACs play a crucial role in the pathology of AIS and are novel promising diagnostic and prognostic biomarkers for AIS.

Brain organoid as a model to study the role of mitochondria in neurodevelopmental disorders: achievements and weaknesses

Mitochondrial diseases are a group of severe pathologies that cause complex neurodegenerative disorders for which, in most cases, no therapy or treatment is available. These organelles are critical regulators of both neurogenesis and homeostasis of the neurological system. Consequently, mitochondrial damage or dysfunction can occur as a cause or consequence of neurodevelopmental or neurodegenerative diseases. As genetic knowledge of neurodevelopmental disorders advances, associations have been identified between genes that encode mitochondrial proteins and neurological symptoms, such as neuropathy, encephalomyopathy, ataxia, seizures, and developmental delays, among others. Understanding how mitochondrial dysfunction can alter these processes is essential in researching rare diseases. Three-dimensional (3D) cell cultures, which self-assemble to form specialized structures composed of different cell types, represent an accessible manner to model organogenesis and neurodevelopmental disorders. In particular, brain organoids are revolutionizing the study of mitochondrial-based neurological diseases since they are organ-specific and model-generated from a patient's cell, thereby overcoming some of the limitations of traditional animal and cell models. In this review, we have collected which neurological structures and functions recapitulate in the different types of reported brain organoids, focusing on those generated as models of mitochondrial diseases. In addition to advancements in the generation of brain organoids, techniques, and approaches for studying neuronal structures and physiology, drug screening and drug repositioning studies performed in brain organoids with mitochondrial damage and neurodevelopmental disorders have also been reviewed. This scope review will summarize the evidence on limitations in studying the function and dynamics of mitochondria in brain organoids.

Lipid Droplets and Neurodegeneration

Energy metabolism in the brain has been considered one of the critical research areas of neuroscience for ages. One of the most vital parts of brain metabolism cascades is lipid metabolism, and fatty acid plays a crucial role in this process. The fatty acid breakdown process in mitochondria undergoes through a conserved pathway known as β-oxidation where acetyl-CoA and shorter fatty acid chains are produced along with a significant amount of energy molecule. Further, the complete breakdown of fatty acids occurs when they enter the mitochondrial oxidative phosphorylation. Cells store energy as neutral lipids in organelles known as Lipid Droplets (LDs) to prepare for variations in the availability of nutrients. Fatty acids are liberated by lipid droplets and are transported to various cellular compartments for membrane biogenesis or as an energy source. Current research shows that LDs are important in inflammation, metabolic illness, and cellular communication. Lipid droplet biology in peripheral organs like the liver and heart has been well investigated, while the brain's LDs have received less attention. Recently, there has been increased awareness of the existence and role of these dynamic organelles in the central nervous system, mainly connected to neurodegeneration. In this review, we discussed the role of beta-oxidation and lipid droplet formation in the oxidative phosphorylation process, which directly affects neurodegeneration through various pathways.

Effects of environmentally relevant concentration of short-chain chlorinated paraffins on BV2 microglia activation and lipid metabolism, implicating altered neurogenesis

Short-chain chlorinated paraffins (SCCPs), a class of persistent organic pollutants, have been found to cause diverse organ and systemic toxicity. However, little is known about their neurotoxic effects. In this study, we exposed BV2, a mouse microglia cell line, to environmentally relevant concentration of SCCPs (1 μg/L, 10 μg/L, 100 μg/L) for 24 h to investigate their impacts on the nervous system. Our observations revealed that SCCPs induced the activation of BV2 microglia, as indicated by altered morphology, stimulated cell proliferation, enhanced phagocytic and migratory capabilities. Analysis at the mRNA level confirmed the activation status, with the downregulation of TMEM119 and Tgfbr1, and upregulation of Iba1 and CD11b. The upregulated expression of genes such as cenpe, mki67, Axl, APOE and LPL also validated alterations in cell functions. Moreover, BV2 microglia presented an M2 alternative phenotype upon SCCPs exposure, substantiated by the reduction of NF-κB, TNF-α, IL-1β, and the elevation of TGF-β. Additionally, SCCPs caused lipid metabolic changes in BV2 microglia, characterized by the upregulations of long-chain fatty acids and acylcarnitines, reflecting an enhancement of β-oxidation. This aligns with our findings of increased ATP production upon SCCPs exposure. Intriguingly, cell activation coincided with elevated levels of omega-3 polyunsaturated fatty acids. Furthermore, activated microglial medium remarkably altered the proliferation and differentiation of mouse neural stem cells. Collectively, exposure to environmentally relevant concentrations of SCCPs resulted in activation and lipid metabolic alterations in BV2 microglia, potentially impacting neurogenesis. These findings provide valuable insights for further research on the neurotoxic effect of SCCPs.

In the Brain, It Is Not All about Sugar

The maintenance of energetic homeostasis relies on a tight balance between glycolysis and mitochondrial oxidative phosphorylation. The case of the brain is a peculiar one, as although entailing a constant demand for energy, it is believed to rely mostly on glucose, particularly at the level of neurons. Nonetheless, this has been challenged by studies that show that alternatives such as lactate, ketone bodies, and glutamate can be used as fuels to sustain neuronal activity. The importance of fatty acid (FA) metabolism to this extent is still unclear, albeit sustaining a significant energetic output when compared to glucose. While several authors postulate a possible role of FA for the energetic homeostasis of the brain, several others point out the intrinsic features of this pathway that make its contribution difficult to explain in the context of neuronal bioenergetics. Moreover, fueling preference at the synapse level is yet to be uncovered. In this review, we discuss in detail the arguments for and against the brain usage of FA. Furthermore, we postulate that the importance of this fuel may be greater at the synapse, where local mitochondria possess a set of features that enable a more effective usage of this fuel source.

Biological Insights and Radiation-Immuno-Oncology Developments in Primary and Secondary Brain Tumors

Malignant central nervous system (CNS) cancers include a group of heterogeneous dis-eases characterized by a relative resistance to treatments and distinguished as either primary tumors arising in the CNS or secondary tumors that spread from other organs into the brain. Despite therapeutic efforts, they often cause significant mortality and morbidity across all ages. Radiotherapy (RT) remains the main treatment for brain cancers, improving associated symptoms, improving tumor control, and inducing a cure in some. However, the ultimate goal of cancer treatment, to improve a patient's survival, remains elusive for many CNS cancers, especially primary tumors. Over the years, there have thus been many preclinical studies and clinical trials designed to identify and overcome mechanisms of resistance to improve outcomes after RT and other therapies. For example, immunotherapy delivered concurrent with RT, especially hypo-fractionated stereotactic RT, is synergistic and has revolutionized the clinical management and outcome of some brain tumors, in particular brain metastases (secondary brain tumors). However, its impact on gliomas, the most common primary malignant CNS tumors, remains limited. In this review, we provide an overview of radioresistance mechanisms, the emerging strategies to overcome radioresistance, the role of the tumor microenviroment (TME), and the selection of the most significant results of radiation-immuno-oncological investigations. We also identify novel therapeutic opportunities in primary and secondary brain tumors with the purpose of elucidating current knowledge and stimulating further research to improve tumor control and patients' survival.

Metabolic Contrasts: Fatty Acid Oxidation and Ketone Bodies in Healthy Brains vs. Glioblastoma Multiforme

The metabolism of glucose and lipids plays a crucial role in the normal homeostasis of the body. Although glucose is the main energy substrate, in its absence, lipid metabolism becomes the primary source of energy. The main means of fatty acid oxidation (FAO) takes place in the mitochondrial matrix through β-oxidation. Glioblastoma (GBM) is the most common form of primary malignant brain tumor (45.6%), with an incidence of 3.1 per 100,000. The metabolic changes found in GBM cells and in the surrounding microenvironment are associated with proliferation, migration, and resistance to treatment. Tumor cells show a remodeling of metabolism with the use of glycolysis at the expense of oxidative phosphorylation (OXPHOS), known as the Warburg effect. Specialized fatty acids (FAs) transporters such as FAT, FABP, or FATP from the tumor microenvironment are overexpressed in GBM and contribute to the absorption and storage of an increased amount of lipids that will provide sufficient energy used for tumor growth and invasion. This review provides an overview of the key enzymes, transporters, and main regulatory pathways of FAs and ketone bodies (KBs) in normal versus GBM cells, highlighting the need to develop new therapeutic strategies to improve treatment efficacy in patients with GBM.

Brain energy metabolism: A roadmap for future research

Although we have learned much about how the brain fuels its functions over the last decades, there remains much still to discover in an organ that is so complex. This article lays out major gaps in our knowledge of interrelationships between brain metabolism and brain function, including biochemical, cellular, and subcellular aspects of functional metabolism and its imaging in adult brain, as well as during development, aging, and disease. The focus is on unknowns in metabolism of major brain substrates and associated transporters, the roles of insulin and of lipid droplets, the emerging role of metabolism in microglia, mysteries about the major brain cofactor and signaling molecule NAD+, as well as unsolved problems underlying brain metabolism in pathologies such as traumatic brain injury, epilepsy, and metabolic downregulation during hibernation. It describes our current level of understanding of these facets of brain energy metabolism as well as a roadmap for future research.

The differential effects of palmitic acid and oleic acid on the metabolic response of hypothalamic astrocytes from male and female mice

Diets rich in saturated fats are more detrimental to health than those containing mono- or unsaturated fats. Fatty acids are an important source of energy, but they also relay information regarding nutritional status to hypothalamic metabolic circuits and when in excess can be detrimental to these circuits. Astrocytes are the main site of central fatty acid β-oxidation, and hypothalamic astrocytes participate in energy homeostasis, in part by modulating hormonal and nutritional signals reaching metabolic neurons, as well as in the inflammatory response to high-fat diets. Thus, we hypothesized that how hypothalamic astrocytes process-specific fatty acids participates in determining the differential metabolic response and that this is sex dependent as males and females respond differently to high-fat diets. Male and female primary hypothalamic astrocyte cultures were treated with oleic acid (OA) or palmitic acid (PA) for 24 h, and an untargeted metabolomics study was performed. A clear predictive model for PA exposure was obtained, while the metabolome after OA exposure was not different from controls. The observed modifications in metabolites, as well as the expression levels of key metabolic enzymes, indicate a reduction in the activity of the Krebs and glutamate/glutamine cycles in response to PA. In addition, there were specific differences between the response of astrocytes from male and female mice, as well as between hypothalamic and cerebral cortical astrocytes. Thus, the response of hypothalamic astrocytes to specific fatty acids could result in differential impacts on surrounding metabolic neurons and resulting in varied systemic metabolic outcomes.

Identification of the abnormalities in astrocytic functions as potential drug targets for neurodegenerative disease

INTRODUCTION

Historically, astrocytes were seen primarily as a supportive cell population within the brain; with neurodegenerative disease research focusing exclusively on malfunctioning neurons. However, astrocytes perform numerous tasks that are essential for maintenance of the central nervous system`s complex processes. Disruption of these functions can have negative consequences; hence, it is unsurprising to observe a growing amount of evidence for the essential role of astrocytes in the development and progression of neurodegenerative diseases. Targeting astrocytic functions may serve as a potential disease-modifying drug therapy in the future.

AREAS COVERED

The present review emphasizes the key astrocytic functions associated with neurodegenerative diseases and explores the possibility of pharmaceutical interventions to modify these processes. In addition, the authors provide an overview of current advancement in this field by including studies of possible drug candidates.

EXPERT OPINION

Glial research has experienced a significant renaissance in the last quarter-century. Understanding how disease pathologies modify or are caused by astrocyte functions is crucial when developing treatments for brain diseases. Future research will focus on building advanced models that can more precisely correlate to the state in the human brain, with the goal of routinely testing therapies in these models.

The Role of Astrocytic Mitochondria in the Pathogenesis of Brain Ischemia

The morbidity rate of ischemic stroke is increasing annually with the growing aging population in China. Astrocytes are ubiquitous glial cells in the brain and play a crucial role in supporting neuronal function and metabolism. Increasing evidence shows that the impairment or loss of astrocytes contributes to neuronal dysfunction during cerebral ischemic injury. The mitochondrion is increasingly recognized as a key player in regulating astrocyte function. Changes in astrocytic mitochondrial function appear to be closely linked to the homeostasis imbalance defects in glutamate metabolism, Ca2+ regulation, fatty acid metabolism, reactive oxygen species, inflammation, and copper regulation. Here, we discuss the role of astrocytic mitochondria in the pathogenesis of brain ischemic injury and their potential as a therapeutic target.

A randomized feasibility trial of the modified Atkins diet in older adults with mild cognitive impairment due to Alzheimer's disease

Background

Alzheimer's disease (AD) is increasing in prevalence, but effective treatments for its cognitive impairment remain severely limited. This study investigates the impact of ketone body production through dietary manipulation on memory in persons with mild cognitive impairment due to early AD and explores potential mechanisms of action.

Methods

We conducted a 12-week, parallel-group, controlled feasibility trial of a ketogenic diet, the modified Atkins diet (MAD), compared to a control diet in patients with cognitive impairments attributed to AD. We administered neuropsychological assessments, including memory tests, and collected blood samples at baseline and after 12 weeks of intervention. We performed untargeted lipidomic and targeted metabolomic analyses on plasma samples to detect changes over time.

Results

A total of 839 individuals were screened to yield 38 randomized participants, with 20 assigned to receive MAD and 18 assigned to receive a control diet. Due to attrition, only 13 in the MAD arm and nine in the control arm were assessed for the primary endpoint, with two participants meeting ketosis levels used to define MAD adherence criteria. The average change from baseline in the Memory Composite Score was 1.37 (95% CI: -0.87, 4.90) points higher in the MAD group compared to the control group. The effect size of the intervention on baseline MAD change was moderate (Cohen's D = 0.57, 95% CI: -0.67, 1.33). In the 15 participants (nine MAD, six control) assessed for lipidomic and metabolomic-lipidomics and metabolomics, 13 metabolites and 10 lipids showed significant changes from baseline to 12 weeks, including triacylglycerols (TAGs, 50:5, 52:5, and 52:6), sphingomyelins (SM, 44:3, 46:0, 46:3, and 48:1), acetoacetate, fatty acylcarnitines, glycerol-3-phosphate, and hydroxy fatty acids.

Conclusions

Attrition was greatest between baseline and week 6. All participants retained at week 6 completed the study. Despite low rates of adherence by criteria defined a priori, lipidomic and metabolomic analyses indicate significant changes from baseline in circulating lipids and metabolites between MAD and control participants at 12-week postrandomization, and MAD participants showed greater, albeit nonsignificant, improvement in memory.

Tracing the path of disruption: 13C isotope applications in traumatic brain injury-induced metabolic dysfunction

Cerebral metabolic dysfunction is a critical pathological hallmark observed in the aftermath of traumatic brain injury (TBI), as extensively documented in clinical investigations and experimental models. An in-depth understanding of the bioenergetic disturbances that occur following TBI promises to reveal novel therapeutic targets, paving the way for the timely development of interventions to improve patient outcomes. The 13C isotope tracing technique represents a robust methodological advance, harnessing biochemical quantification to delineate the metabolic trajectories of isotopically labeled substrates. This nuanced approach enables real-time mapping of metabolic fluxes, providing a window into the cellular energetic state and elucidating the perturbations in key metabolic circuits. By applying this sophisticated tool, researchers can dissect the complexities of bioenergetic networks within the central nervous system, offering insights into the metabolic derangements specific to TBI pathology. Embraced by both animal studies and clinical research, 13C isotope tracing has bolstered our understanding of TBI-induced metabolic dysregulation. This review synthesizes current applications of isotope tracing and its transformative potential in evaluating and addressing the metabolic sequelae of TBI.

Caprylic acid attenuates amyloid-β proteotoxicity by supplying energy via β-oxidation in an Alzheimer's disease model of the nematode Caenorhabditis elegans

Computer-based analysis of motility was used as a measure of amyloid-β (Aβ) proteotoxicity in the transgenic strain GMC101, expressing human Aβ1-42 in body wall muscle cells. Aβ-aggregation was quantified to relate the effects of caprylic acid (CA) to the amount of the proteotoxic protein. Gene knockdowns were induced through RNA-interference (RNAi). Moreover, the estimation of adenosine triphosphate (ATP) levels, the mitochondrial membrane potential (MMP) and oxygen consumption served the evaluation of mitochondrial function. CA improved the motility of GMC101 nematodes and reduced Aβ aggregation. Whereas RNAi for orthologues encoding key enzymes for α-lipoic acid and ketone bodies synthesis did not affect motility stimulation by CA, knockdown of orthologues involved in β-oxidation of fatty acids diminished its effects. The efficient energy gain by application of CA was finally proven by the increase of ATP levels in association with increased oxygen consumption and MMP. In conclusion, CA attenuates Aβ proteotoxicity by supplying energy via FAO. Since especially glucose oxidation is disturbed in Alzheimer´s disease, CA could potentially serve as an alternative energy fuel.

Metabolic dynamics in astrocytes and microglia during post-natal development and their implications for autism spectrum disorders

Autism Spectrum Disorder (ASD) is a complex neurodevelopmental condition characterized by elusive underlying mechanisms. Recent attention has focused on the involvement of astrocytes and microglia in ASD pathology. These glial cells play pivotal roles in maintaining neuronal homeostasis, including the regulation of metabolism. Emerging evidence suggests a potential association between ASD and inborn errors of metabolism. Therefore, gaining a comprehensive understanding of the functions of microglia and astrocytes in ASD is crucial for the development of effective therapeutic interventions. This review aims to provide a summary of the metabolism of astrocytes and microglia during post-natal development and the evidence of disrupted metabolic pathways in ASD, with particular emphasis on those potentially important for the regulation of neuronal post-natal maturation by astrocytes and microglia.

The Diverse Roles of Reactive Astrocytes in the Pathogenesis of Amyotrophic Lateral Sclerosis

Astrocytes displaying reactive phenotypes are characterized by their ability to remodel morphologically, molecularly, and functionally in response to pathological stimuli. This process results in the loss of their typical astrocyte functions and the acquisition of neurotoxic or neuroprotective roles. A growing body of research indicates that these reactive astrocytes play a pivotal role in the pathogenesis of amyotrophic lateral sclerosis (ALS), involving calcium homeostasis imbalance, mitochondrial dysfunction, abnormal lipid and lactate metabolism, glutamate excitotoxicity, etc. This review summarizes the characteristics of reactive astrocytes, their role in the pathogenesis of ALS, and recent advancements in astrocyte-targeting strategies.

Novel insights into brain lipid metabolism in Alzheimer's disease: Oligodendrocytes and white matter abnormalities

Alzheimer's disease (AD) is the most common cause of dementia. A genome-wide association study has shown that several AD risk genes are involved in lipid metabolism. Additionally, epidemiological studies have indicated that the levels of several lipid species are altered in the AD brain. Therefore, lipid metabolism is likely changed in the AD brain, and these alterations might be associated with an exacerbation of AD pathology. Oligodendrocytes are glial cells that produce the myelin sheath, which is a lipid-rich insulator. Dysfunctions of the myelin sheath have been linked to white matter abnormalities observed in the AD brain. Here, we review the lipid composition and metabolism in the brain and myelin and the association between lipidic alterations and AD pathology. We also present the abnormalities in oligodendrocyte lineage cells and white matter observed in AD. Additionally, we discuss metabolic disorders, including obesity, as AD risk factors and the effects of obesity and dietary intake of lipids on the brain.

Important roles of linoleic acid and α-linolenic acid in regulating cognitive impairment and neuropsychiatric issues in metabolic-related dementia

Metabolic syndrome (MetS), which is characterized by insulin resistance, high blood glucose, obesity, and dyslipidemia, is known to increase the risk of dementia accompanied by memory loss and depression. The direct pathways and specific mechanisms in the central nervous system (CNS) for addressing fatty acid imbalances in MetS have not yet been fully elucidated. Among polyunsaturated acids, linoleic acid (LA, n6-PUFA) and α-linolenic acid (ALA, n3-PUFA), which are two essential fatty acids that should be provided by food sources (e.g., vegetable oils and seeds), have been reported to regulate various cellular mechanisms including apoptosis, inflammatory responses, mitochondrial biogenesis, and insulin signaling. Furthermore, inadequate intake of LA and ALA is reported to be involved in neuropathology and neuropsychiatric diseases as well as imbalanced metabolic conditions. Herein, we review the roles of LA and ALA on metabolic-related dementia focusing on insulin resistance, dyslipidemia, synaptic plasticity, cognitive function, and neuropsychiatric issues. This review suggests that LA and ALA are important fatty acids for concurrent treatment of both MetS and neurological problems.

Metabolic Reprogramming in Gliocyte Post-cerebral Ischemia/ Reperfusion: From Pathophysiology to Therapeutic Potential

Ischemic stroke is a leading cause of disability and death worldwide. However, the clinical efficacy of recanalization therapy as a preferred option is significantly hindered by reperfusion injury. The transformation between different phenotypes of gliocytes is closely associated with cerebral ischemia/ reperfusion injury (CI/RI). Moreover, gliocyte polarization induces metabolic reprogramming, which refers to the shift in gliocyte phenotype and the overall transformation of the metabolic network to compensate for energy demand and building block requirements during CI/RI caused by hypoxia, energy deficiency, and oxidative stress. Within microglia, the pro-inflammatory phenotype exhibits upregulated glycolysis, pentose phosphate pathway, fatty acid synthesis, and glutamine synthesis, whereas the anti-inflammatory phenotype demonstrates enhanced mitochondrial oxidative phosphorylation and fatty acid oxidation. Reactive astrocytes display increased glycolysis but impaired glycogenolysis and reduced glutamate uptake after CI/RI. There is mounting evidence suggesting that manipulation of energy metabolism homeostasis can induce microglial cells and astrocytes to switch from neurotoxic to neuroprotective phenotypes. A comprehensive understanding of underlying mechanisms and manipulation strategies targeting metabolic pathways could potentially enable gliocytes to be reprogrammed toward beneficial functions while opening new therapeutic avenues for CI/RI treatment. This review provides an overview of current insights into metabolic reprogramming mechanisms in microglia and astrocytes within the pathophysiological context of CI/RI, along with potential pharmacological targets. Herein, we emphasize the potential of metabolic reprogramming of gliocytes as a therapeutic target for CI/RI and aim to offer a novel perspective in the treatment of CI/RI.

A novel splice variant of goat CPT1a gene and their diverse mRNA expression profiles

The Alternative splicing (AS) of Carnitine palmitoyltransferase 1a (CPT1a) and their expression profiles had never been illuminated in goats until now. Herein, a novel splice transcript in the CPT1a gene that is predicted to result in the skipping of exons 6-19 (CPT1a-sv1) has been isolated in addition to the full-length transcript in goats. The result of RT-PCR showed that CPT1a-sv1 is 606 bp in length and consists of 6 exons. A novel exon 6 was consisted of partial exon 5 and partial exon 19, compared to that in CPT1a. RT-qPCR analysis showed that the expression patterns of CPT1a and CPT1a-sv1 are spatially different. In both kid and adult goats, the CPT1a transcript is strongly expressed in the liver, spleen, lung, kidney, and brain tissues. However, CPT1a-sv1 has a strong tissue-specific expression pattern, with moderate RNA levels in the liver and brain of kids, while highly expressed in the liver and minimally expressed in the brain of adults. We observed two transcripts to be involved in brain development. These findings improve our understanding of the function of the CPT1a gene in goats and provide information on the molecular mechanism of AS events.

Paradoxical mTORC1-Dependent microRNA-mediated Translation Repression in the Nucleus Accumbens of Mice Consuming Alcohol Attenuates Glycolysis

mTORC1 promotes protein translation, learning and memory, and neuroadaptations that underlie alcohol use and abuse. We report that activation of mTORC1 in the nucleus accumbens (NAc) of mice consuming alcohol promotes the translation of microRNA (miR) machinery components and the upregulation of microRNAs (miRs) expression including miR34a-5p. In parallel, we detected a paradoxical mTORC1-dependent repression of translation of transcripts including Aldolase A, an essential glycolytic enzyme. We found that miR34a-5p in the NAc targets Aldolase A for translation repression and promotes alcohol intake. Our data further suggest that glycolysis is inhibited in the NAc manifesting in an mTORC1-dependent attenuation of L-lactate, the end product of glycolysis. Finally, we show that systemic administration of L-lactate attenuates mouse excessive alcohol intake. Our data suggest that alcohol promotes paradoxical actions of mTORC1 on translation and glycolysis which in turn drive excessive alcohol use.

Abstract Figure

Systems levels analysis of lipid metabolism in oxygen-induced retinopathy

Hyperoxia induces glutamine-fueled anaplerosis in the Muller cells, endothelial cells, and retinal explants. Anaplerosis takes away glutamine from the biosynthetic pathway to the energy-producing TCA cycle. This process depletes biosynthetic precursors from newly proliferating endothelial cells. The induction of anaplerosis in the hyperoxic retina is a compensatory response, either to decreased glycolysis or decreased flux from glycolysis to the TCA cycle. We hypothesized that by providing substrates that feed into TCA, we could reverse or prevent glutamine-fueled anaplerosis, thereby abating the glutamine wastage for energy generation. Using an oxygen-induced retinopathy (OIR) mouse model, we first compared the difference in fatty acid metabolism between OIR-resistant BALB/cByJ and OIR susceptible C57BL/6J strains to understand if these strains exhibit metabolic difference that protects BALB/cByJ from the hyperoxic conditions and prevents their vasculature in oxygen-induced retinopathy model. Based on our findings from the metabolic comparison between two mouse strains, we hypothesized that the medium-chain fatty acid, octanoate, can feed into the TCA and serve as an alternative energy source in response to hyperoxia. Our systems levels analysis of OIR model shows that the medium chain fatty acid can serve as an alternative source to feed TCA. We here, for the first time, demonstrate that the retina can use medium-chain fatty acid octanoate to replenish TCA in normoxic and at a higher rate in hyperoxic conditions.

Metabolic control of cancer metastasis: role of amino acids at secondary organ sites

Most cancer-related deaths are caused by the metastases, which commonly develop at multiple organ sites including the brain, bone, and lungs. Despite longstanding observations that the spread of cancer is not random, our understanding of the mechanisms that underlie metastatic spread to specific organs remains limited. However, metabolism has recently emerged as an important contributor to metastasis. Amino acids are a significant nutrient source to cancer cells and their metabolism which can serve to fuel biosynthetic pathways capable of facilitating cell survival and tumor expansion while also defending against oxidative stress. Compared to the primary tumor, each of the common metastatic sites exhibit vastly different nutrient compositions and environmental stressors, necessitating the need of cancer cells to metabolically thrive in their new environment during colonization and outgrowth. This review seeks to summarize the current literature on amino acid metabolism pathways that support metastasis to common secondary sites, including impacts on immune responses. Understanding the role of amino acids in secondary organ sites may offer opportunities for therapeutic inhibition of cancer metastasis.

Glioblastomas: Hijacking Metabolism to Build a Flexible Shield for Therapy Resistance

Significance: Glioblastomas (GBMs) are among the most lethal tumors despite the almost exclusive localization to the brain. This is largely due to therapeutic resistance. Radiation and chemotherapy significantly increase the survival for GBM patients, however, GBMs always recur, and the median overall survival is just over a year. Proposed reasons for such intractable resistance to therapy are numerous and include tumor metabolism, in particular, the ability of tumor cells to reconfigure metabolic fluxes on demand (metabolic plasticity). Understanding how the hard-wired, oncogene-driven metabolic tendencies of GBMs intersect with flexible, context-induced metabolic rewiring promises to reveal novel approaches for combating therapy resistance. Recent Advances: Personalized genome-scale metabolic flux models have recently provided evidence that metabolic flexibility promotes radiation resistance in cancer and identified tumor redox metabolism as a major predictor for resistance to radiation therapy (RT). It was demonstrated that radioresistant tumors, including GBM, reroute metabolic fluxes to boost the levels of reducing factors of the cell, thus enhancing clearance of reactive oxygen species that are generated during RT and promoting survival. Critical Issues: The current body of knowledge from published studies strongly supports the notion that robust metabolic plasticity can act as a (flexible) shield against the cytotoxic effects of standard GBM therapies, thus driving therapy resistance. The limited understanding of the critical drivers of such metabolic plasticity hampers the rational design of effective combination therapies. Future Directions: Identifying and targeting regulators of metabolic plasticity, rather than specific metabolic pathways, in combination with standard-of-care treatments have the potential to improve therapeutic outcomes in GBM. Antioxid. Redox Signal. 39, 957-979.

Metabolic regulation of microglial phagocytosis: Implications for Alzheimer's disease therapeutics

Microglia, the resident immune cells of the brain, are increasingly implicated in the regulation of brain health and disease. Microglia perform multiple functions in the central nervous system, including surveillance, phagocytosis and release of a variety of soluble factors. Importantly, a majority of their functions are closely related to changes in their metabolism. This natural inter-dependency between core microglial properties and metabolism offers a unique opportunity to modulate microglial activities via nutritional or metabolic interventions. In this review, we examine the existing scientific literature to synthesize the hypothesis that microglial phagocytosis of amyloid beta (Aβ) aggregates in Alzheimer's disease (AD) can be selectively enhanced via metabolic interventions. We first review the basics of microglial metabolism and the effects of common metabolites, such as glucose, lipids, ketone bodies, glutamine, pyruvate and lactate, on microglial inflammatory and phagocytic properties. Next, we examine the evidence for dysregulation of microglial metabolism in AD. This is followed by a review of in vivo studies on metabolic manipulation of microglial functions to ascertain their therapeutic potential in AD. Finally, we discuss the effects of metabolic factors on microglial phagocytosis of healthy synapses, a pathological process that also contributes to the progression of AD. We conclude by enlisting the current challenges that need to be addressed before strategies to harness microglial phagocytosis to clear pathological protein deposits in AD and other neurodegenerative disorders can be widely adopted.

The Physiological and Pathological Role of Acyl-CoA Oxidation

Fatty acid metabolism, including β-oxidation (βOX), plays an important role in human physiology and pathology. βOX is an essential process in the energy metabolism of most human cells. Moreover, βOX is also the source of acetyl-CoA, the substrate for (a) ketone bodies synthesis, (b) cholesterol synthesis, (c) phase II detoxication, (d) protein acetylation, and (d) the synthesis of many other compounds, including N-acetylglutamate-an important regulator of urea synthesis. This review describes the current knowledge on the importance of the mitochondrial and peroxisomal βOX in various organs, including the liver, heart, kidney, lung, gastrointestinal tract, peripheral white blood cells, and other cells. In addition, the diseases associated with a disturbance of fatty acid oxidation (FAO) in the liver, heart, kidney, lung, alimentary tract, and other organs or cells are presented. Special attention was paid to abnormalities of FAO in cancer cells and the diseases caused by mutations in gene-encoding enzymes involved in FAO. Finally, issues related to α- and ω- fatty acid oxidation are discussed.

Fundamental Neurochemistry Review: Microglial immunometabolism in traumatic brain injury

Traumatic brain injury (TBI) is a devastating neurological disorder caused by a physical impact to the brain that promotes diffuse damage and chronic neurodegeneration. Key mechanisms believed to support secondary brain injury include mitochondrial dysfunction and chronic neuroinflammation. Microglia and brain-infiltrating macrophages are responsible for neuroinflammatory cytokine and reactive oxygen species (ROS) production after TBI. Their production is associated with loss of homeostatic microglial functions such as immunosurveillance, phagocytosis, and immune resolution. Beyond providing energy support, mitochondrial metabolic pathways reprogram the pro- and anti-inflammatory machinery in immune cells, providing a critical immunometabolic axis capable of regulating immunologic response to noxious stimuli. In the brain, the capacity to adapt to different environmental stimuli derives, in part, from microglia's ability to recognize and respond to changes in extracellular and intracellular metabolite levels. This capacity is met by an equally plastic metabolism, capable of altering immune function. Microglial pro-inflammatory activation is associated with decreased mitochondrial respiration, whereas anti-inflammatory microglial polarization is supported by increased oxidative metabolism. These metabolic adaptations contribute to neuroimmune responses, placing mitochondria as a central regulator of post-traumatic neuroinflammation. Although it is established that profound neurometabolic changes occur following TBI, key questions related to metabolic shifts in microglia remain unresolved. These include (a) the nature of microglial mitochondrial dysfunction after TBI, (b) the hierarchical positions of different metabolic pathways such as glycolysis, pentose phosphate pathway, glutaminolysis, and lipid oxidation during secondary injury and recovery, and (c) how immunometabolism alters microglial phenotypes, culminating in chronic non-resolving neuroinflammation. In this basic neurochemistry review article, we describe the contributions of immunometabolism to TBI, detail primary evidence of mitochondrial dysfunction and metabolic impairments in microglia and macrophages, discuss how major metabolic pathways contribute to post-traumatic neuroinflammation, and set out future directions toward advancing immunometabolic phenotyping in TBI.

Microglial Metabolic Reprogramming: Emerging Insights and Therapeutic Strategies in Neurodegenerative Diseases

Microglia, the resident immune cells of the central nervous system, play a critical role in maintaining brain homeostasis. However, in neurodegenerative conditions, microglial cells undergo metabolic reprogramming in response to pathological stimuli, including Aβ plaques, Tau tangles, and α-synuclein aggregates. This metabolic shift is characterized by a transition from oxidative phosphorylation (OXPHOS) to glycolysis, increased glucose uptake, enhanced production of lactate, lipids, and succinate, and upregulation of glycolytic enzymes. These metabolic adaptations result in altered microglial functions, such as amplified inflammatory responses and diminished phagocytic capacity, which exacerbate neurodegeneration. This review highlights recent advances in understanding the molecular mechanisms underlying microglial metabolic reprogramming in neurodegenerative diseases and discusses potential therapeutic strategies targeting microglial metabolism to mitigate neuroinflammation and promote brain health. Microglial Metabolic Reprogramming in Neurodegenerative Diseases This graphical abstract illustrates the metabolic shift in microglial cells in response to pathological stimuli and highlights potential therapeutic strategies targeting microglial metabolism for improved brain health.

The Role of Acyl-CoA β-Oxidation in Brain Metabolism and Neurodegenerative Diseases

This review highlights the complex role of fatty acid β-oxidation in brain metabolism. It demonstrates the fundamental importance of fatty acid degradation as a fuel in energy balance and as an essential component in lipid homeostasis, brain aging, and neurodegenerative disorders.

Refueling the post COVID-19 brain: potential role of ketogenic medium chain triglyceride supplementation: an hypothesis

COVID-19 infection causes cognitive changes in the acute phase, but also after apparent recovery. Over fifty post (long)-COVID symptoms are described, including cognitive dysfunction ("brain fog") precluding return to pre-COVID level of function, with rates twice as high in females. Additionally, the predominant demographic affected by these symptoms is younger and still in the workforce. Lack of ability to work, even for six months, has significant socio-economic consequences. This cognitive dysfunction is associated with impaired cerebral glucose metabolism, assessed using 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET), showing brain regions that are abnormal compared to age and sex matched controls. In other cognitive conditions such as Alzheimer's disease (AD), typical patterns of cerebral glucose hypometabolism, frontal hypometabolism and cerebellar hypermetabolism are common. Similar FDG-PET changes have also been observed in post-COVID-19, raising the possibility of a similar etiology. Ketone bodies (B-hydroxybutyrate, acetoacetate and acetone) are produced endogenously with very low carbohydrate intake or fasting. They improve brain energy metabolism in the face of cerebral glucose hypometabolism in other conditions [mild cognitive impairment (MCI) and AD]. Long-term low carbohydrate intake or prolonged fasting is not usually feasible. Medium chain triglyceride (MCT) is an exogenous route to nutritional ketosis. Research has supported their efficacy in managing intractable seizures, and cognitive impairment in MCI and AD. We hypothesize that cerebral glucose hypometabolism associated with post COVID-19 infection can be mitigated with MCT supplementation, with the prediction that cognitive function would also improve. Although there is some suggestion that post COVID-19 cognitive symptoms may diminish over time, in many individuals this may take more than six months. If MCT supplementation is able to speed the cognitive recovery, this will impact importantly on quality of life. MCT is readily available and, compared to pharmaceutical interventions, is cost-effective. Research shows general tolerability with dose titration. MCT is a component of enteral and parenteral nutrition supplements, including in pediatrics, so has a long record of safety in vulnerable populations. It is not associated with weight gain or adverse changes in lipid profiles. This hypothesis serves to encourage the development of clinical trials evaluating the impact of MCT supplementation on the duration and severity of post COVID-19 cognitive symptoms.

Metabolomic Analysis in Neurocritical Care Patients

Metabolomics is the analytical study of metabolites in biological matrices using high-throughput profiling. Traditionally, the metabolome has been studied to identify various biomarkers for the diagnosis and pathophysiology of disease. Over the last decade, metabolomic research has grown to include the identification of prognostic markers, the development of novel treatment strategies, and the prediction of disease severity. In this review, we summarized the available evidence on the use of metabolome profiling in neurocritical care populations. Specifically, we focused on aneurysmal subarachnoid hemorrhage, traumatic brain injury, and intracranial hemorrhage to identify the gaps in the current literature and to provide direction for future studies. A primary literature search of the Medline and EMBASE databases was conducted. Upon removing duplicate studies, abstract screening and full-text screening were performed. We screened 648 studies and extracted data from 17 studies. Based on the current evidence, the utility of metabolomic profiling has been limited due to inconsistencies amongst studies and a lack of reproducible data. Studies identified various biomarkers for diagnosis, prognosis, and treatment modification. However, studies evaluated and identified different metabolites, resulting in an inability to compare the study results. Future research towards addressing the gaps in the current literature, including reproducing data on the use of specific metabolite panels, is needed.

Global determination of reaction rates and lipid turnover kinetics in Mus musculus

Metabolism is fundamental to life, but measuring metabolic reaction rates remains challenging. Here, we applied C13 fluxomics to monitor the metabolism of dietary glucose carbon in 12 tissues, 9 brain compartments, and over 1,000 metabolite isotopologues over a 4-day period. The rates of 85 reactions surrounding central carbon metabolism are determined with elementary metabolite unit (EMU) modeling. Lactate oxidation, not glycolysis, occurs at a comparable pace with the tricarboxylic acid cycle (TCA), supporting lactate as the primary fuel. We expand the EMU framework to track and quantify metabolite flows across tissues. Specifically, multi-organ EMU simulation of uridine metabolism shows that tissue-blood exchange, not synthesis, controls nucleotide homeostasis. In contrast, isotopologue fingerprinting and kinetic analyses reveal the brown adipose tissue (BAT) having the highest palmitate synthesis activity but no apparent contribution to circulation, suggesting a tissue-autonomous synthesis-to-burn mechanism. Together, this study demonstrates the utility of dietary fluxomics for kinetic mapping in vivo and provides a rich resource for elucidating inter-organ metabolic cross talk.

Blood-based bioenergetic profiling reveals differences in mitochondrial function associated with cognitive performance and Alzheimer's disease

INTRODUCTION

Despite evidence for systemic mitochondrial dysfunction early in Alzheimer's disease (AD) pathogenesis, reliable approaches monitoring these key bioenergetic alterations are lacking. We used peripheral blood mononuclear cells (PBMCs) and platelets as reporters of mitochondrial function in the context of cognitive impairment and AD.

METHODS

Mitochondrial function was analyzed using complementary respirometric approaches in intact and permeabilized cells from older adults with normal cognition, mild cognitive impairment (MCI), and dementia due to probable AD. Clinical outcomes included measures of cognitive function and brain morphology.

RESULTS

PBMC and platelet bioenergetic parameters were lowest in dementia participants. MCI platelets exhibited higher maximal respiration than normocognitives. PBMC and platelet respiration positively associated with cognitive ability and hippocampal volume, and negatively associated with white matter hyperintensities.

DISCUSSION

Our findings indicate blood-based bioenergetic profiling can be used as a minimally invasive approach for measuring systemic bioenergetic differences associated with dementia, and may be used to monitor bioenergetic changes associated with AD risk and progression.

HIGHLIGHTS

Peripheral cell bioenergetic alterations accompanied cognitive decline in older adults with mild cognitive impairment (MCI) and Alzheimer's disease (AD) and related dementia (DEM). Peripheral blood mononuclear cells (PBMC) and platelet glucose-mediated respiration decreased in participants with dementia compared to normocognitive controls (NC). PBMC fatty-acid oxidation (FAO)-mediated respiration progressively declined in MCI and AD compared to NC participants, while platelet FAO-mediated respiration exhibited an inverse-Warburg effect in MCI compared to NC participants. Positive associations were observed between bioenergetics and Modified Preclinical Alzheimer's Cognitive Composite, and bioenergetics and hippocampal volume %, while a negative association was observed between bioenergetics and white matter hyperintensities. Systemic mitochondrial dysfunction is associated with cognitive decline.

Amino acid metabolic reprogramming in tumor metastatic colonization

Metastasis is considered as the major cause of cancer death. Cancer cells can be released from primary tumors into the circulation and then colonize in distant organs. How cancer cells acquire the ability to colonize in distant organs has always been the focus of tumor biology. To enable survival and growth in the new environment, metastases commonly reprogram their metabolic states and therefore display different metabolic properties and preferences compared with the primary lesions. For different microenvironments in various colonization sites, cancer cells must transfer to specific metabolic states to colonize in different distant organs, which provides the possibility of evaluating metastasis tendency by tumor metabolic states. Amino acids provide crucial precursors for many biosynthesis and play an essential role in cancer metastasis. Evidence has proved the hyperactivation of several amino acid biosynthetic pathways in metastatic cancer cells, including glutamine, serine, glycine, branched chain amino acids (BCAAs), proline, and asparagine metabolism. The reprogramming of amino acid metabolism can orchestrate energy supply, redox homeostasis, and other metabolism-associated pathways during cancer metastasis. Here, we review the role and function of amino acid metabolic reprogramming in cancer cells colonizing in common metastatic organs, including lung, liver, brain, peritoneum, and bone. In addition, we summarize the current biomarker identification and drug development of cancer metastasis under the amino acid metabolism reprogramming, and discuss the possibility and prospect of targeting organ-specific metastasis for cancer treatment.