Etomoxir Actions on Regulatory and Memory T Cells Are Independent of Cpt1a-Mediated Fatty Acid Oxidation

Emerging roles for fatty acid oxidation in cancer

Fatty acid oxidation (FAO) denotes the mitochondrial aerobic process responsible for breaking down fatty acids (FAs) into acetyl-CoA units. This process holds a central position in the cancer metabolic landscape, with certain tumor cells relying primarily on FAO for energy production. Over the past decade, mounting evidence has underscored the critical role of FAO in various cellular processes such as cell growth, epigenetic modifications, tissue-immune homeostasis, cell signal transduction, and more. FAO is tightly regulated by multiple evolutionarily conserved mechanisms, and any dysregulation can predispose to cancer development. In this view, we summarize recent findings to provide an updated understanding of the multifaceted roles of FAO in tumor development, metastasis, and the response to cancer therapy. Additionally, we explore the regulatory mechanisms of FAO, laying the groundwork for potential therapeutic interventions targeting FAO in cancers within the metabolic landscape.

Mitochondrial fatty acid oxidation regulates adult muscle stem cell function through modulating metabolic flux and protein acetylation

During homeostasis and regeneration, satellite cells, the resident stem cells of skeletal muscle, have distinct metabolic requirements for fate transitions between quiescence, proliferation and differentiation. However, the contribution of distinct energy sources to satellite cell metabolism and function remains largely unexplored. Here, we uncover a role of mitochondrial fatty acid oxidation (FAO) in satellite cell integrity and function. Single-cell RNA sequencing revealed progressive enrichment of mitochondrial FAO and downstream pathways during activation, proliferation and myogenic commitment of satellite cells. Deletion of Carnitine palmitoyltransferase 2 (Cpt2), the rate-limiting enzyme in FAO, hampered muscle stem cell expansion and differentiation upon acute muscle injury, markedly delaying regeneration. Cpt2 deficiency reduces acetyl-CoA levels in satellite cells, impeding the metabolic flux and acetylation of selective proteins including Pax7, the central transcriptional regulator of satellite cells. Notably, acetate supplementation restored cellular metabolic flux and partially rescued the regenerative defects of Cpt2-null satellite cells. These findings highlight an essential role of fatty acid oxidation in controlling satellite cell function and suggest an integration of lipid metabolism and protein acetylation in adult stem cells.

Mitochondrial CCN1 drives ferroptosis via fatty acid β-oxidation

Ferroptosis is a type of oxidative cell death, although its key metabolic processes remain incompletely understood. Here, we employ a comprehensive multiomics screening approach that identified cellular communication network factor 1 (CCN1) as a metabolic catalyst of ferroptosis. Upon ferroptosis induction, CCN1 relocates to mitochondrial complexes, facilitating electron transfer flavoprotein subunit alpha (ETFA)-dependent fatty acid β-oxidation. Compared with a traditional carnitine O-palmitoyltransferase 2 (CPT2)-ETFA pathway, the CCN1-ETFA pathway provides additional substrates for mitochondrial reactive oxygen species production, thereby stimulating ferroptosis through lipid peroxidation. A high-fat diet can enhance the anticancer efficacy of ferroptosis in lung cancer mouse models, depending on CCN1. Furthermore, primary lung cancer cells derived from patients with hypertriglyceridemia or high CCN1 expression demonstrate increased susceptibility to ferroptosis in vitro and in vivo. These findings do not only identify the metabolic role of mitochondrial CCN1 but also establish a strategy for enhancing ferroptosis-based anticancer therapies.

Impact of mitochondrial metabolism on T-cell dysfunction in chronic lymphocytic leukemia

T cells play a central role in anti-tumor immunity, yet their function is often compromised within the immunosuppressive tumor microenvironment, leading to cancer progression and resistance to immunotherapies. T-cell activation and differentiation require dynamic metabolic shifts, with mitochondrial metabolism playing a crucial role in sustaining their function. Research in cancer immunometabolism has revealed key mitochondrial abnormalities in tumor-infiltrating lymphocytes, including reduced mitochondrial capacity, depolarization, structural defects, and elevated reactive oxygen species. While these mitochondrial disruptions are well-characterized in solid tumors and linked to T-cell exhaustion, their impact on T-cell immunity in lymphoproliferative disorders remains underexplored. Chronic lymphocytic leukemia (CLL), the most prevalent chronic adult leukemia, is marked by profound T-cell dysfunction that limits the success of adoptive cell therapies. Emerging studies are shedding light on the role of mitochondrial disturbances in CLL-related T-cell dysfunction, but significant knowledge gaps remain. This review explores mitochondrial metabolism in T-cell exhaustion, emphasizing recent findings in CLL. We also discuss therapeutic strategies to restore T-cell mitochondrial function and identify key research gaps.

Carnitine palmitoyltransferase 2 as a novel prognostic biomarker and immunoregulator in colorectal cancer

BACKGROUND

Metabolic interventions are critical for enhancing immunotherapy efficacy, but reliable metabolic targets remain absent for colorectal cancer (CRC). This study aims to investigate the interplay between metabolic and immunological factors in CRC, identify metabolic immunoregulatory molecules, and propose targets for prognostic and therapeutic applications.

METHODS

Immune infiltration and metabolic pathways in CRC were analyzed using CIBERSORT and gene set variation analyses. Cox regression identified survival-related metabolic genes, forming a metabolic-related gene prognostic index (MRGPI), which was validated through survival analysis, timeROC, GSEA, CIBERSORT, and TIDE. Hub genes in the MRGPI were assessed using enrichment and co-expression network analyses. The expression of carnitine palmitoyltransferase 2 (CPT2) was validated through multiplex immunofluorescence of tissue microarrays. While its role was examined by western blot, CCK-8 assay, flow cytometry, qRT-PCR, Elisa, chemotaxis assays, etc. RESULTS: Fatty acid oxidation (FAO) pathways were significantly altered in CRC and correlated with immune cell infiltration and patient survival. The MRGPI, constructed from five survival-related metabolic genes, demonstrated strong prognostic and immunotherapeutic predictive value. Moreover, CPT2, a key hub gene in the MRGPI, whose lower expression in plasma cells predicts unfavorable patients' survival and could be an independent prognostic indicator, while its knockout in tumor cells significantly increases the infiltrating levels of CD8+ T cells via promoting the release of CCL25.

CONCLUSION

The FAO-dominated MRGPI is a promising biomarker for predicting patient outcomes and immunotherapy response. CPT2 holds potential as a prognostic marker and therapeutic target for CRC metabolic immunotherapy.

ACC1 is a dual metabolic-epigenetic regulator of Treg stability and immune tolerance

OBJECTIVE

Regulatory T cells (Tregs) are essential in maintaining immune tolerance and controlling inflammation. Treg stability relies on transcriptional and post-translational mechanisms, including histone acetylation at the Foxp3 locus and FoxP3 protein acetylation. Additionally, Tregs depend on specific metabolic programs for differentiation, yet the underlying molecular mechanisms remain elusive. We aimed to investigate the role of acetyl-CoA carboxylase 1 (ACC1) in the differentiation, stability, and function of regulatory T cells (Tregs).

METHODS

We used either T cell-specific ACC1 knockout mice or ACC1 inhibition via a pharmacological agent to examine the effects on Treg differentiation and stability. The impact of ACC1 inhibition on Treg function was assessed in vivo through adoptive transfer models of Th1/Th17-driven inflammatory diseases.

RESULTS

Inhibition or genetic deletion of ACC1 led to an increase in acetyl-CoA availability, promoting enhanced histone and protein acetylation, and sustained FoxP3 transcription even under inflammatory conditions. Mice with T cell-specific ACC1 deletion exhibited an enrichment of double positive RORγt+FoxP3+ cells. Moreover, Tregs treated with an ACC1 inhibitor demonstrated superior long-term stability and an enhanced capacity to suppress Th1/Th17-driven inflammatory diseases in adoptive transfer models.

CONCLUSIONS

We identified ACC1 as a metabolic checkpoint in Treg biology. Our data demonstrate that ACC1 inhibition promotes Treg differentiation and long-term stability in vitro and in vivo. Thus, ACC1 serves as a dual metabolic and epigenetic hub, regulating immune tolerance and inflammation by balancing de novo lipid synthesis and protein acetylation.

MIER2/PGC1A elicits sunitinib resistance via lipid metabolism in renal cell carcinoma

INTRODUCTION

Renal cell carcinoma (RCC) is one of the most common malignant tumors of the urinary system and accounts for more than 90 % of all renal tumors. Resistance to targeted therapy has emerged as a pivotal factor that contributes to the progressive deterioration of patients with advanced RCC. Metabolic reprogramming is a hallmark of tumorigenesis and progression, with an increasing body of evidence indicating that abnormal lipid metabolism plays a crucial role in the advancement of renal clear cell carcinoma.

OBJECTIVES

Clarify the precise mechanisms underlying abnormal lipid metabolism and drug resistance.

METHODS

Bioinformatics screening and analyses were performed to identify hub gene. qRT-PCR, western blot, chromatin immunoprecipitation (ChIP) assays, and other biological methods were used to explore and verify related pathways. Various cell line models and animal models were used to perform biological functional experiments.

RESULTS

In this study, we identified Mesoderm induction early response 2 (MIER2) as a novel biomarker for RCC, demonstrating its role in promoting malignancy and sunitinib resistance by influencing lipid metabolism in RCC. Mechanistically, MIER2 facilitated P53 deacetylation by binding to HDAC1. Acetylation modification augmented the DNA-binding stability and transcriptional function of P53, while deacetylation of P53 hindered the transcriptional process of PGC1A, leading to intracellular lipid accumulation in RCC. Furthermore, Trichostatin A (TSA), an inhibitor of HDAC1, was found to impede the MIER2/HDAC1/P53/PGC1A pathway, offering potential benefits for patients with sunitinib-resistant renal cell cancer.

CONCLUSION

Our findings highlight MIER2 as a key player in anchoring HDAC1 and inhibiting PGC1A expression through the deacetylation of P53, thereby inducing lipid accumulation in RCC and promoting drug resistance. Lipid-rich RCC cells compensate for energy production and sustain their own growth in a glycolysis-independent manner, evading the cytotoxic effects of targeted drugs and ultimately culminating in the development of drug resistance.

Targeting lipid metabolism in regulatory T cells for enhancing cancer immunotherapy

As immunosuppressive cells, Regulatory T cells (Tregs) exert their influence on tumor immune escape within the tumor microenvironment (TME) by effectively suppressing the activity of other immune cells, thereby significantly impeding the anti-tumor immune response. In recent years, the metabolic characteristics of Tregs have become a focus of research, especially the important role of lipid metabolism in maintaining the function of Tregs. Consequently, targeted interventions aimed at modulating lipid metabolism in Tregs have been recognized as an innovative and promising approach to enhance the effectiveness of tumor immunotherapy. This review presents a comprehensive overview of the pivotal role of lipid metabolism in regulating the function of Tregs, with a specific focus on targeting Tregs lipid metabolism as an innovative approach to augment anti-tumor immune responses. Furthermore, we discuss potential opportunities and challenges associated with this strategy, aiming to provide novel insights for enhancing the efficacy of cancer immunotherapy.

The immune mechanism of the mTOR/ACC1/CPT1A fatty acid oxidation signaling pathway in Hashimoto's thyroiditis

BACKGROUND

Hashimoto's thyroiditis (HT) is the most common autoimmune thyroid disease (AITD), which is distinguished by high thyroid peroxidase antibody (TPOAb) or thyroglobulin antibody (TgAb). The differentiation of CD4+T cell subsets in patients with HT is imbalanced, with Treg cells decreased and Th17 cells abnormally activated. Fatty acid oxidation supports the differentiation of Th17 cells and induces inflammation, but the specific mechanism is still unknown. This study aimed to explore the role of fatty acid oxidation and its pathway in the pathogenesis of autoimmune thyroiditis and the immune mechanism.

METHODS

In in vitro experiments, a total of 60 HT patients and 20 healthy controls were selected and their CD4+T cells were sorted by magnetic beads. All 80 samples were divided into 4 groups on average: HC group (Healthy control group), HT group (Hashimoto thyroiditis CD4+T cell inactive group), TCC group(Hashimoto thyroiditis CD4+T cell activation), TCC + ETO group(Hashimoto thyroiditis CD4+T cell activation + Etomoxir group). In in vivo experiments, the mice were randomly divided into 3 groups: Con group(Control group), mTg group (CBA/J mice were injected with mTg for modeling, that is EAT mice group), and mTg + ETO group (Etomoxir intervention in EAT mice group). Fatty acid oxidation substrates of CD4+T cells in human peripheral blood were detected by targeted metabolomics. The expressions of key fatty acid oxidation proteins mTOR, ACC1 and CPT1A were detected by Western blotting. The proportion of CD4+T cell subtype differentiation in human and mouse models was detected by flow cytometry. The severity of EAT was detected by HE staining.

RESULTS

Compared with healthy controls, the level of CPT1A in CD4+T cells of HT patients was increased, and the intracellular fatty acid content was significantly decreased, indicating that the level of fatty acid oxidation was enhanced in HT patients. After adding Etomoxir, the level of fatty acid oxidation was significantly inhibited, and the imbalance of CD4+T cell subpopulation differentiation in HT patients was reversed. In EAT mice, the mTOR/ACC1/CPT1A pathway was significantly activated, and its expression level was decreased after adding Etomoxir. At the same time, Etomoxir could reverse the reprogramming of abnormal metabolism in EAT mice cells, reduce the spleen index, and improve lymphocyte infiltration in the thyroid.

CONCLUSIONS

The mTOR/ACC1/CPT1A fatty acid oxidation pathway of CD4+T cells in Hashimoto's thyroiditis was increased, and treatment with Etomoxir could inhibit the activation of this pathway, and reverse the reprogramming of abnormal metabolism in CD4+T cells, thereby reducing Hashimoto's thyroiditis.

Metabolic reprogram and T cell differentiation in inflammation: current evidence and future perspectives

T cell metabolism and differentiation significantly shape the initiation, progression, and resolution of inflammatory responses. Upon activation, T cells undergo extensive metabolic shifts to meet distinct functional demands across various inflammatory stages. These metabolic alterations are not only critical for defining different T cell subsets, but also for sustaining their activity in inflammatory environments. Key signaling pathways-including mTOR, HIF-1α, and AMPK regulate these metabolic adaptions, linking cellular energy states with T cell fate decisions. Insights into the metabolic regulation of T cells offer potential therapeutic strategies to manipulate T cell function, with implications for treating autoimmune diseases, chronic inflammation, and cancer by targeting specific metabolic pathways.

Etomoxir suppresses the expression of PPARγ2 and inhibits the thermogenic gene induction of brown adipocytes through pathways other than β-oxidation inhibition

Brown adipocytes are characterized by a high abundance of mitochondria, allowing them to consume fatty acids for heat production. Increasing the number of brown adipocytes is considered a promising strategy for combating obesity. However, the molecular mechanisms underlying their differentiation remain poorly understood. In this study, we demonstrate that etomoxir, an inhibitor of Carnitine Palmitoyltransferase 1 (CPT1), inhibits their differentiation through mechanisms independent of β-oxidation inhibition. In the presence of etomoxir during brown adipocyte differentiation, reduced expression of the thermogenic gene UCP1 and decreased lipid droplets formation were observed. Furthermore, a transient reduction in the expression of PPARγ2, a critical factor in adipocyte differentiation, was also observed in the presence of etomoxir. These findings suggest the presence of a regulatory mechanism that specifically enhances PPARγ2 expression during brown adipocyte differentiation, thereby modulating thermogenic gene expression.

Targeting metabolic dysfunction of CD8 T cells and natural killer cells in cancer

The importance of metabolic pathways in regulating immune responses is now well established, and a mapping of the bioenergetic metabolism of different immune cell types is under way. CD8 T cells and natural killer (NK) cells contribute to cancer immunosurveillance through their cytotoxic functions and secretion of cytokines and chemokines, complementing each other in target recognition mechanisms. Several immunotherapies leverage these cell types by either stimulating their activity or redirecting their specificity against tumour cells. However, the anticancer activity of CD8 T cells and NK cells is rapidly diminished in the tumour microenvironment, closely linked to a decline in their metabolic capacities. Various strategies have been developed to restore cancer immunosurveillance, including targeting bioenergetic metabolism or genetic engineering. This Review provides an overview of metabolic dysfunction in CD8 T cells and NK cells within the tumour microenvironment, highlighting current therapies aiming to overcome these issues.

International Union of Basic and Clinical Pharmacology: Fundamental insights and clinical relevance regarding the carnitine palmitoyltransferase family of enzymes

The carnitine palmitoyltransferases (CPTs) play a key role in controlling the oxidation of long-chain fatty acids and are potential therapeutic targets for diseases with a strong metabolic component, such as obesity, diabetes, and cancer. Four distinct proteins are CPT1A, CPT1B, CPT1C, and CPT2, differing in tissue expression and catalytic activity. CPT1s are finely regulated by malonyl-CoA, a metabolite whose intracellular levels reflect the cell's nutritional state. Although CPT1C does not exhibit significant catalytic activity, it is capable of modulating the functioning of other neuronal proteins. Structurally, all CPTs share a Y-shaped catalytic tunnel that allows the entry of 2 substrates and accommodation of the acyl group in a hydrophobic pocket. Several molecules targeting these enzymes have been described, some showing potential in normalizing blood glucose levels in diabetic patients, and others that, through a central mechanism, are anorexigenic and enhance energy expenditure. However, given the critical roles that CPTs play in certain tissues, such as the heart, liver, and brain, it is essential to fully understand the differences between the various isoforms. We analyze in detail the structure of these proteins, their cellular and physiological functions, and their potential as therapeutic targets in diseases such as obesity, diabetes, and cancer. We also describe drugs identified to date as having inhibitory or activating capabilities for these proteins. This knowledge will support the design of new drugs specific to each isoform, and the development of nanomedicines that can selectively target particular tissues or cells. SIGNIFICANCE STATEMENT: Carnitine palmitoyltransferase (CPT) proteins, as gatekeepers of fatty acid oxidation, have great potential as pharmacological targets to treat metabolic diseases like obesity, diabetes, and cancer. In recent years, significant progress has been made in understanding the 3-dimensional structure of CPTs and their pathophysiological functions. A deeper understanding of the differences between the various CPT family members will enable the design of selective drugs and therapeutic approaches with fewer side effects.

Different effects of fatty acid oxidation on hematopoietic stem cells based on age and diet

Fatty acid oxidation is of uncertain importance in most stem cells. We show by 14C-palmitate tracing and metabolomic analysis that hematopoietic stem/progenitor cells (HSPCs) engage in long-chain fatty acid oxidation that depends upon carnitine palmitoyltransferase 1a (CPT1a) and hydroxyacyl-CoA dehydrogenase (HADHA) enzymes. CPT1a or HADHA deficiency had little or no effect on HSPCs or hematopoiesis in young adult mice. Young HSPCs had the plasticity to oxidize other substrates, including glutamine, and compensated for loss of fatty acid oxidation by decreasing pyruvate dehydrogenase phosphorylation, which should increase function. This metabolic plasticity declined as mice aged, when CPT1a or HADHA deficiency altered hematopoiesis and impaired hematopoietic stem cell (HSC) function upon serial transplantation. A high-fat diet increased fatty acid oxidation and reduced HSC function. This was rescued by CPT1a or HADHA deficiency, demonstrating that increased fatty acid oxidation can undermine HSC function. Long-chain fatty acid oxidation is thus dispensable in young HSCs but necessary during aging and deleterious with a high-fat diet.

Regulatory T Cell Metabolism: A Promising Therapeutic Target for Cancer Treatment?

Regulatory T (Treg) cells are essential for maintaining immune homeostasis by suppressing excessive immune responses. In the context of cancer, however, Tregs promote immune evasion and tumor progression, particularly through their unique adaptations within the tumor microenvironment (TME). Recent research has emphasized how metabolic characteristics shape Treg activation, migration, and immunosuppressive function, revealing the impact of metabolic pathways on Treg fitness in homeostasis and within the TME. In this review, we first provide an overview of Tregs in cancer immunology, discussing their immunosuppressive roles and properties specific to the TME. We then examine the metabolic requirements for Treg activation and migration under normal conditions, followed by a discussion of how hypoxia, lactate accumulation, nutrient limitation, oxidative stress, and other TME-specific factors alter Treg metabolism and contribute to cancer immune evasion. Finally, we explore therapeutic strategies that target Treg metabolism within the TME, including pharmacological modulation of specific metabolic pathways to diminish Treg-mediated immunosuppression. Thus, we could suggest future directions and clinical implications for Treg-targeted metabolic modulation as a complementary approach in cancer treatment, setting the stage for novel strategies in immunotherapy.

Immune-metabolic shifts in acute liver failure caused by HEV infection during pregnancy and their association with obstetric outcomes

BACKGROUND

Hepatitis-E virus (HEV)-induced liver failure during pregnancy leads to maternal and fetal complications. This study investigates the HEV-associated metabolomic and immunological changes to elucidate the worsening of obstetric outcomes in patients with acute liver failure (ALF) due to HEV.

METHODS

Pregnant women with (i) acute viral hepatitis, IgM HEV positive (AVH-E, n = 31, Gr.I), (ii) acute liver failure (ALF-E, n = 15, Gr.II), (iii) acute hepatitis but negative for viral infections (non-HEV, n = 30, Gr.III), and healthy (HC, n = 21, Gr.IV) were evaluated at delivery for plasma untargeted metabolomics, cytokine, and immune profiling.

RESULTS

AVH-E and ALF-E (Gr.I, II) showed elevated TNF-α, IL-1β, IL-9, IL-22, and IL-33 compared to HC. In addition, in ALF-E, IFN-γ and IL-12p70 were decreased, but MIP-1α, fractalkine, SDF-1α, IL-22, and IL-33 were increased compared to AVH-E. Both AVH-E and ALF-E had decreased choline, sn-glycero-3-phosphocholine, O-palmitoyl-r-carnitine, and increased taurocholic acid. However, patients with ALF-E had a 2-5-fold decline in these metabolites with raised taurochenodeoxycholic acid. ALF-E showed increased naive T/B cells, decreased CD4, CD8 Tcm, Tem, and plasmablasts, compared to AVH-E contributing to higher failed inductions, preterm births, maternal complications like eclampsia, disseminated intravascular coagulation, preterm premature rupture of membranes, small-for-gestational-age infants, higher rates of intrauterine death, abortion, and mortality.

CONCLUSIONS

HEV infection reduces choline, phosphocholine, and palmitoyl carnitine, enhancing inflammation in ALF-E, while increasing taurocholic and taurochenodeoxycholic acids impairs the immune response. These factors together likely contribute to severe obstetric complications, including higher failed inductions, intrauterine death, and maternal and fetal mortality in ALF-E.

Pivotal role of exogenous pyruvate in human natural killer cell metabolism

Resting natural killer (NK) cells display immediate effector functions after recognizing transformed or infected cells. The environmental nutrients and metabolic requirements to sustain these functions are not fully understood. Here, we show that NK cells rely on the use of extracellular pyruvate to support effector functions, signal transduction and cell viability. Glucose-derived carbons do not generate endogenous pyruvate. Consequently, NK cells import extracellular pyruvate that is reduced to lactate to regenerate glycolytic NAD+ and is oxidized in the tricarboxylic acid (TCA) cycle to produce ATP. This supports serine production through phosphoglycerate dehydrogenase, a pathway required for optimal proliferation following cytokine stimulation but dispensable for effector functions. In addition, like mouse NK cells, human NK cells rely on a citrate-malate configuration of the TCA cycle that is not fed by glutamine. Moreover, supraphysiologic pyruvate concentrations dose-dependently increase the effector functions of NK cells. Overall, this study highlights the role of exogenous pyruvate in NK cell biology, providing knowledge that could be exploited to boost NK cell potential in therapeutic settings.

Metabolic reprogramming and immunological changes in the microenvironment of esophageal cancer: future directions and prospects

Background

Esophageal cancer (EC) is the seventh-most prevalent cancer worldwide and is a significant contributor to cancer-related mortality. Metabolic reprogramming in tumors frequently coincides with aberrant immune function alterations, and extensive research has demonstrated that perturbations in energy metabolism within the tumor microenvironment influence the occurrence and progression of esophageal cancer. Current treatment modalities for esophageal cancer primarily include encompass chemotherapy and a limited array of targeted therapies, which are hampered by toxicity and drug resistance issues. Immunotherapy, particularly immune checkpoint inhibitors (ICIs) targeting the PD-1/PD-L1 pathway, has exhibited promising results; however, a substantial proportion of patients remain unresponsive. The optimization of these immunotherapies requires further investigation. Mounting evidence underscores the importance of modulating metabolic traits within the tumor microenvironment (TME) to augment anti-tumor immunotherapy.

Methods

We selected relevant studies on the metabolism of the esophageal cancer tumor microenvironment and immune cells based on our searches of MEDLINE and PubMed, focusing on screening experimental articles and reviews related to glucose metabolism, amino acid metabolism, and lipid metabolism, as well their interactions with tumor cells and immune cells, published within the last five years. We analyzed and discussed these studies, while also expressing our own insights and opinions.

Results

A total of 137 articles were included in the review: 21 articles focused on the tumor microenvironment of esophageal cancer, 33 delved into research related to glucose metabolism and tumor immunology, 30 introduced amino acid metabolism and immune responses, and 17 focused on the relationship between lipid metabolism in the tumor microenvironment and both tumor cells and immune cells.

Conclusion

This article delves into metabolic reprogramming and immune alterations within the TME of EC, systematically synthesizes the metabolic characteristics of the TME, dissects the interactions between tumor and immune cells, and consolidates and harnesses pertinent immunotherapy targets, with the goal of enhancing anti-tumor immunotherapy for esophageal cancer and thereby offering insights into the development of novel therapeutic strategies.

Relationship between metabolomics of T2DM patients and the anti-diabetic effects of Phellodendri Chinensis Cortex-Anemarrhenae Rhizoma herb pair in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Type 2 diabetes mellitus (T2DM) poses significant threats to public health. In Traditional Chinese Medicine (TCM), the Phellodendri Chinensis Cortex-Anemarrhenae Rhizoma (PCC/AR) herb pair has long been used for T2DM treatment, although its specific anti-diabetic mechanisms remain unclear.

AIM OF THE STUDY

This study aimed to elucidate the relationship between metabolomics of T2DM patients and the anti-diabetic effects of PCC/AR herb pair in mice through clinical metabolomics and both in vitro and in vivo experiments.

MATERIALS AND METHODS

In this study, a T2DM mouse model was established via high-fat feeding (HFD) and streptozotocin (STZ) injection. The effects of PCC/AR on blood glucose, lipid metabolism, and inflammatory markers were evaluated. High-performance liquid chromatography-mass spectrometry (HPLC-MS) was performed for metabolomics analysis of T2DM patients.

RESULTS

Serum metabolomics analysis identified significant alterations in metabolites linked to the biosynthesis of unsaturated fatty acids and purine metabolism in T2DM patients, with elevated 2-hydroxyvaleric acid (2HB) levels. In T2DM mice, PCC/AR intervention normalized FBG, GHbA1c, TC, TG, LDL-C, HDL-C, TNF-α and IL-1β levels, while improving insulin sensitivity and pancreatic β-cell function in T2DM mice. Notably, PCC/AR reduced key enzymes in gluconeogenesis and fatty acid synthesis, PEPCK and ACC1.

CONCLUSION

PCC/AR herb pair exerts an anti-diabetes effect in T2DM mice by regulating 2HB through ACC1 inhibition, thereby reducing FFA and TG synthesis. Additionally, PCC/AR may also exert its effects by modulating glucose and lipid metabolism and reducing inflammation. These results support further investigation into the PCC/AR herb pair as a complementary therapy for T2DM.

Unlocking the full potential of memory T cells in adoptive T cell therapy for hematologic malignancies

In recent years, immune cell therapy, particularly adoptive cell therapy (ACT), has shown superior therapeutic effects on hematologic malignancies. However, a challenge lies in ensuring that genetically engineered specific T cells maintain lasting anti-tumor effects within the host. The enduring success of ACT therapy hinges on the persistence of memory T (TM) cells, a diverse cell subset crucial for tumor immune response and immune memory upkeep. Notably, TM cell subsets at varying differentiation stages exhibit distinct biological traits and anti-tumor capabilities. Poorly differentiated TM cells are pivotal for favorable clinical outcomes in ACT. The differentiation of TM cells is influenced by multiple factors, including metabolism and cytokines. Consequently, current research focuses on investigating the differentiation patterns of TM cells and enhancing the production of poorly differentiated TM cells with potent anti-tumor properties in vitro, which is a prominent area of interest globally. This review delves into the differentiation features of TM cells, outlining their distribution in patients and their impact on ACT treatment. It comprehensively explores cutting-edge strategies to boost ACT efficacy through TM cell differentiation induction, aiming to unlock the full potential of TM cells in treating hematologic malignancies and offering novel insights for tumor immune cell therapy.

Exploring the role of metabolic pathways in TNBC immunotherapy: insights from single-cell and spatial transcriptomics

The article provides an overview of the current understanding of the interplay between metabolic pathways and immune function in the context of triple-negative breast cancer (TNBC). It highlights recent advancements in single-cell and spatial transcriptomics technologies, which have revolutionized the analysis of tumor heterogeneity and the immune microenvironment in TNBC. The review emphasizes the crucial role of metabolic reprogramming in modulating immune cell function, discussing how specific metabolic pathways, such as glycolysis, lipid metabolism, and amino acid metabolism, can directly impact the activity and phenotypes of various immune cell populations within the TNBC tumor microenvironment. Furthermore, the article explores the implications of these metabolic-immune interactions for the efficacy of immune checkpoint inhibitor (ICI) therapies in TNBC, suggesting that strategies targeting metabolic pathways may enhance the responsiveness to ICI treatments. Finally, the review outlines future directions and the potential for combination therapies that integrate metabolic modulation with immunotherapeutic approaches, offering promising avenues for improving clinical outcomes for TNBC patients.

Loss of Cpt1a results in elevated glucose-fueled mitochondrial oxidative phosphorylation and defective hematopoietic stem cells

Hematopoietic stem cells (HSCs) rely on self-renewal to sustain stem cell potential and undergo differentiation to generate mature blood cells. Mitochondrial fatty acid β-oxidation (FAO) is essential for HSC maintenance. However, the role of carnitine palmitoyl transferase 1a (CPT1A), a key enzyme in FAO, remains unclear in HSCs. Using a Cpt1a hematopoiesis-specific conditional-KO (Cpt1aΔ/Δ) mouse model, we found that loss of Cpt1a led to HSC defects, including loss of HSC quiescence and self-renewal and increased differentiation. Mechanistically, we found that loss of Cpt1a resulted in elevated levels of mitochondrial respiratory chain complex components and their activity, as well as increased ATP production and accumulation of mitochondrial ROS in HSCs. Taken together, this suggests hyperactivation of mitochondria and metabolic rewiring via upregulated glucose-fueled oxidative phosphorylation (OXPHOS). In summary, our findings demonstrate an essential role for Cpt1a in HSC maintenance and provide insight into the regulation of mitochondrial metabolism via control of the balance between FAO and glucose-fueled OXPHOS.

Tissue specific roles of fatty acid oxidation

Mitochondrial long chain fatty acid β-oxidation is a critical central carbon catabolic process. The importance of fatty acid oxidation is made evident by the life-threatening disease associated with diverse inborn errors in the pathway. While inborn errors show multisystemic requirements for fatty acid oxidation, it is not clear from the clinical presentation of these enzyme deficiencies what the tissue specific roles of the pathway are compared to secondary systemic effects. To understand the cell or tissue specific contributions of fatty acid oxidation to systemic physiology, conditional knockouts in mice have been employed to determine the requirements of fatty acid oxidation in disparate cell types. This has produced a host of surprising results that sometimes run counter to the canonical view of this metabolic pathway. The rigor of conditional knockouts has also provided clarity over previous research utilizing cell lines in vitro or small molecule inhibitors with dubious specificity. Here we will summarize current research using mouse models of Carnitine Palmitoyltransferases to determine the tissue specific roles and requirements of long chain mitochondrial fatty acid β-oxidation.

Carnitine palmitoyltransferase 1 facilitates fatty acid oxidation in a non-cell-autonomous manner

Mitochondrial fatty acid oxidation is facilitated by the combined activities of carnitine palmitoyltransferase 1 (Cpt1) and Cpt2, which generate and utilize acylcarnitines, respectively. We compare the response of mice with liver-specific deficiencies in the liver-enriched Cpt1a or the ubiquitously expressed Cpt2 and discover that they display unique metabolic, physiological, and molecular phenotypes. The loss of Cpt1a or Cpt2 results in the induction of the muscle-enriched isoenzyme Cpt1b in hepatocytes in a Pparα-dependent manner. However, hepatic Cpt1b does not contribute substantively to hepatic fatty acid oxidation when Cpt1a is absent. Liver-specific double knockout of Cpt1a and Cpt1b or Cpt2 eliminates the mitochondrial oxidation of non-esterified fatty acids. However, Cpt1a/Cpt1b double knockout mice retain fatty acid oxidation by utilizing extracellular long-chain acylcarnitines that are dependent on Cpt2. These data demonstrate the non-cell-autonomous intercellular metabolism of fatty acids in hepatocytes.

T cell metabolism in kidney immune homeostasis

Kidney immune homeostasis is intricately linked to T cells. Inappropriate differentiation, activation, and effector functions of T cells lead to a spectrum of kidney disease. While executing immune functions, T cells undergo a series of metabolic rewiring to meet the rapid energy demand. The key enzymes and metabolites involved in T cell metabolism metabolically and epigenetically modulate T cells' differentiation, activation, and effector functions, thereby being capable of modulating kidney immune homeostasis. In this review, we first summarize the latest advancements in T cell immunometabolism. Second, we outline the alterations in the renal microenvironment under certain kidney disease conditions. Ultimately, we highlight the metabolic modulation of T cells within kidney immune homeostasis, which may shed light on new strategies for treating kidney disease.

Control of T-cell immunity by fatty acid metabolism

Fatty acids play critical roles in maintaining the cellular functions of T cells and regulating T-cell immunity. This review synthesizes current research on the influence of fatty acids on T-cell subsets, including CD8+ T cells, TH1, TH17, Treg (regulatory T cells), and TFH (T follicular helper) cells. Fatty acids impact T cells by modulating signaling pathways, inducing metabolic changes, altering cellular structures, and regulating gene expression epigenetically. These processes affect T-cell activation, differentiation, and function, with implications for diseases such as autoimmune disease and cancer. Based on these insights, fatty acid pathways can potentially be modulated by novel therapeutics, paving the way for novel treatment approaches for immune-mediated disorders and cancer immunotherapy.

Tumor energy metabolism: implications for therapeutic targets

Tumor energy metabolism plays a crucial role in the occurrence, progression, and drug resistance of tumors. The study of tumor energy metabolism has gradually become an emerging field of tumor treatment. Recent studies have shown that epigenetic regulation is closely linked to tumor energy metabolism, influencing the metabolic remodeling and biological traits of tumor cells. This review focuses on the primary pathways of tumor energy metabolism and explores therapeutic strategies to target these pathways. It covers key areas such as glycolysis, the Warburg effect, mitochondrial function, oxidative phosphorylation, and the metabolic adaptability of tumors. Additionally, this article examines the role of the epigenetic regulator SWI/SNF complex in tumor metabolism, specifically its interactions with glucose, lipids, and amino acids. Summarizing therapeutic strategies aimed at these metabolic pathways, including inhibitors of glycolysis, mitochondrial-targeted drugs, exploitation of metabolic vulnerabilities, and recent developments related to SWI/SNF complexes as potential targets. The clinical significance, challenges, and future directions of tumor metabolism research are discussed, including strategies to overcome drug resistance, the potential of combination therapy, and the application of new technologies.

Etomoxir Sodium Salt Promotes Imidazole Ketone Erastin-Induced Myeloid-Derived Suppressor Cell Ferroptosis and Enhances Cancer Therapy

Although ferroptosis inducers trigger ferroptotic tumor cells and immune cells in the tumor microenvironment (TME), imidazole ketone erastin (IKE)'s induction of ferroptosis shows no effect on tumor growth in immunocompetent tumor-bearing mice due to the presence of myeloid-derived suppressor cells (MDSCs). Treatment of the carnitine palmitoyltransferase 1a (CPT1A)-specific inhibitor decreases the immunosuppressive function of MDSCs and enhances ferroptotic inducer-initiated tumor cell ferroptosis. However, whether blocking CPT1A could enhance IKE-induced MDSC ferroptosis and thereby inhibit tumor growth is still unclear. Here, we report that a CPT1A-specific inhibitor, etomoxir sodium salt (Eto), and IKE combined treatment increased MDSC ferroptosis. Interestingly, the combination treatment of Eto and IKE blocked MDSCs' immunosuppressive function and accumulation by downregulating the expression of SLC7A11, GPX4, and ARG1 while promoting T-cell proliferation and infiltration into tumor tissues to enhance cancer therapy. These data provide a rationale for the combination therapy of a specific CPT1A inhibitor, Eto, with IKE in clinical settings.

Size of lipid emulsion droplets influences metabolism in human CD4+ T cells

SCOPE

Triglyceride-based lipid emulsions are critical for total parenteral nutrition (TPN), but their long-term use has adverse effects, such as severe liver dysfunction necessitating improved formulations. This study compares the uptake mechanism and intracellular fate of novel glycerol-stabilized nano-sized lipid emulsions with conventional emulsions in CD4+ T cells, focusing on their impact on cellular metabolism.

METHODS AND RESULTS

Nanoemulsions were formulated with increased glycerol content. Uptake of emulsions in primary human CD4+ T cells was investigated using different endocytic blockers, then quantified by flow cytometry, and visualized by confocal microscopy. To investigate emulsion intracellular fate, fatty acids in membrane phospholipids were quantified by GC-MS/MS and cellular metabolism was assessed by Seahorse technology. Results show T cells internalize both conventional and nano-sized emulsions using macropinocytosis. Fatty acids from emulsions are stored as neutral lipids in intracellular vesicles and are incorporated into phospholipids of cellular membranes. However, only nanoemulsions additionally use clathrin-mediated endocytosis and deliver fatty acids to mitochondria for increased β-oxidation.

CONCLUSIONS

Size of lipid emulsion droplets significantly influences their uptake and subsequent metabolism in CD4+ T cells. Our results highlight the potential for improved nutrient utilization with nanoemulsions in TPN formulations possibly leading to less adverse effects.

Enhanced fatty acid oxidation by selective activation of PPARα alleviates autoimmunity through metabolic transformation in T-cells

While fatty acid oxidation (FAO) in mitochondria is a primary energy source for quiescent lymphocytes, the impact of promoting FAO in activated lymphocytes undergoing metabolic reprogramming remains unclear. Here, we demonstrate that pemafibrate, a selective PPARα modulator used clinically for the treatment of hypertriglyceridemia, transforms metabolic system of T-cells and alleviates several autoimmune diseases. Pemafibrate suppresses Th17 cells but not Th1 cells, through the inhibition of glutaminolysis and glycolysis initiated by enhanced FAO. In contrast, a conventional PPARα agonist fenofibrate significantly inhibits cell growth by restraining overall metabolisms even at a dose insufficient to induce fatty acid oxidation. Clinically, patients receiving pemafibrate showed a significant decrease of Th17/Treg ratio in peripheral blood. Our results suggest that augmented FAO by pemafibrate-mediated selective activation of PPARα restrains metabolic programs of Th17 cells and could be a viable option for the treatment of autoimmune diseases.

Precise targeting of lipid metabolism in the era of immuno-oncology and the latest advances in nano-based drug delivery systems for cancer therapy

Over the past decade, research has increasingly identified unique dysregulations in lipid metabolism within the tumor microenvironment (TME). Lipids, diverse biomolecules, not only constitute biological membranes but also function as signaling molecules and energy sources. Enhanced synthesis or uptake of lipids in the TME significantly promotes tumorigenesis and proliferation. Moreover, lipids secreted into the TME influence tumor-resident immune cells (TRICs), thereby aiding tumor survival against chemotherapy and immunotherapy. This review aims to highlight recent advancements in understanding lipid metabolism in both tumor cells and TRICs, with a particular emphasis on exogenous lipid uptake and endogenous lipid de novo synthesis. Targeting lipid metabolism for intervention in anticancer therapies offers a promising therapeutic avenue for cancer treatment. Nano-drug delivery systems (NDDSs) have emerged as a means to maximize anti-tumor effects by rewiring tumor metabolism. This review provides a comprehensive overview of recent literature on the development of NDDSs targeting tumor lipid metabolism, particularly in the context of tumor immunotherapy. It covers four key aspects: reprogramming lipid uptake, reprogramming lipolysis, reshaping fatty acid oxidation (FAO), and reshuffling lipid composition on the cell membrane. The review concludes with a discussion of future prospects and challenges in this burgeoning field of research.

Regulation of CD8+ T cells by lipid metabolism in cancer progression

Dysregulation of lipid metabolism is a key characteristic of the tumor microenvironment, where tumor cells utilize lipids for proliferation, survival, metastasis, and evasion of immune surveillance. Lipid metabolism has become a critical regulator of CD8+ T-cell-mediated antitumor immunity, with excess lipids in the tumor microenvironment impeding CD8+ T-cell activities. Considering the limited efficacy of immunotherapy in many solid tumors, targeting lipid metabolism to enhance CD8+ T-cell effector functions could significantly improve immunotherapy outcomes. In this review, we examine recent findings on how lipid metabolic processes, including lipid uptake, synthesis, and oxidation, regulate CD8+ T cells within tumors. We also assessed the impact of different lipids on CD8+ T-cell-mediated antitumor immunity, with a particular focus on how lipid metabolism affects mitochondrial function in tumor-infiltrating CD8+ T cells. Furthermore, as cancer is a systemic disease, we examined systemic factors linking lipid metabolism to CD8+ T-cell effector function. Finally, we summarize current therapeutic approaches that target lipid metabolism to increase antitumor immunity and enhance immunotherapy. Understanding the molecular and functional interplay between lipid metabolism and CD8+ T cells offers promising therapeutic opportunities for cancer treatment.

Ginseng aconitum decoction (Shenfu Tang) provides neuroprotection by ameliorating impairment of blood-brain barrier in cerebral ischemia-reperfusion injury

Ischemic stroke (IS) remains one of the most serious threats to human life. Early blood-brain barrier damage (BBB) is the cause of parenchymal cell damage. Repair of the structure and function of the BBB is beneficial for the treatment of IS. The traditional prescription ginseng aconitum decoction (GAD) has a long history in the treatment of cardiovascular and cerebrovascular diseases, however, the effect of GAD on the BBB disruption and underlying mechanisms remains largely unknown. To address these issues, in vitro models of BBB were established with brain endothelial cells (bEnd.3). We found that GAD reduced the leakage of the fluorescent probe FITC-dextran (P < 0.01) and increased the expression of tight junction proteins (Claudin-5, ZO-1) (P < 0.05) in the BBB model in vitro. Furthermore, to investigate the BBB protective effects of GAD in vivo. A total of 25 male C57/BL6 mice (20 - 22 g) were randomly divided into 5 groups (n = 5 per group): (1) Sham group (saline), (2) MCAO group (saline), (3) MCAO + CG group (Chinese ginseng 8 mg/kg/day), (4) MCAO + AC group (aconite 8 mg/kg/day), (5) MCAO + GAD group (GAD 8 mg/kg/day).We constructed IS model in mice and found that GAD treatment reduced IgG leakage (P < 0.05), up-regulated the expression of tight junction proteins Claudin-5, Occludin, and ZO-1 (P < 0.05). Further mechanism study showed that fatty acid oxidation (FAO) of vascular endothelial cells is involved in the protection of the BBB after IS, and GAD regulates FAO (P < 0.05) to protect BBB. In addition, we found the effect of GAD was stronger than that of Chinese ginseng (CG) (P < 0.05) and aconite (AC) (P < 0.01) alone. We concluded that GAD ameliorated the BBB dysfunction by regulating FAO involving vascular endothelial cells after IS. At the same time, the prescription is more effective than single traditional Chinese medicine.

CPT2-mediated Fatty Acid Oxidation Is Dispensable for Humoral Immunity

B cell activation is accompanied by dynamic metabolic reprogramming, supported by a multitude of nutrients that include glucose, amino acids, and fatty acids. Although several studies have indicated that fatty acid mitochondrial oxidation is critical for immune cell functions, contradictory findings have been reported. Carnitine palmitoyltransferase II (CPT2) is a critical enzyme for long-chain fatty acid oxidation in mitochondria. In this study, we test the requirement of CPT2 for humoral immunity using a mouse model with a lymphocyte-specific deletion of CPT2. Stable [13C] isotope tracing reveals highly reduced fatty acid-derived citrate production in CPT2-deficient B cells. Yet, CPT2 deficiency has no significant impact on B cell development, B cell activation, germinal center formation, and Ab production upon either thymus-dependent or -independent Ag challenges. Together, our findings indicate that CPT2-mediated fatty acid oxidation is dispensable for humoral immunity, highlighting the metabolic flexibility of lymphocytes.

Complex Interplay Between Metabolism and CD4+ T-Cell Activation, Differentiation, and Function: a Novel Perspective for Atherosclerosis Immunotherapy

Atherosclerosis is a complex pathological process that results from the chronic inflammatory reaction of the blood vessel wall and involves various immune cells and cytokines. An imbalance in the proportion and function of the effector CD4+ T-cell (Teff) and regulatory T-cell (Treg) subsets is an important cause of the occurrence and development of atherosclerotic plaques. Teff cells depend on glycolytic metabolism and glutamine catabolic metabolism for energy, while Treg cells mainly rely on fatty acid oxidation (FAO), which is crucial for determining the fate of CD4+ T cells during differentiation and maintaining their respective immune functions. Here, we review recent research achievements in the field of immunometabolism related to CD4+ T cells, focusing on the cellular metabolic pathways and metabolic reprogramming involved in the activation, proliferation, and differentiation of CD4+ T cells. Subsequently, we discuss the important roles of mTOR and AMPK signaling in regulating CD4+ T-cell differentiation. Finally, we evaluated the links between CD4+ T-cell metabolism and atherosclerosis, highlighting the potential of targeted modulation of CD4+ T-cell metabolism in the prevention and treatment of atherosclerosis in the future.

Oligodendroglial fatty acid metabolism as a central nervous system energy reserve

Brain function requires a constant supply of glucose. However, the brain has no known energy stores, except for glycogen granules in astrocytes. In the present study, we report that continuous oligodendroglial lipid metabolism provides an energy reserve in white matter tracts. In the isolated optic nerve from young adult mice of both sexes, oligodendrocytes survive glucose deprivation better than astrocytes. Under low glucose, both axonal ATP levels and action potentials become dependent on fatty acid β-oxidation. Importantly, ongoing oligodendroglial lipid degradation feeds rapidly into white matter energy metabolism. Although not supporting high-frequency spiking, fatty acid β-oxidation in mitochondria and oligodendroglial peroxisomes protects axons from conduction blocks when glucose is limiting. Disruption of the glucose transporter GLUT1 expression in oligodendrocytes of adult mice perturbs myelin homeostasis in vivo and causes gradual demyelination without behavioral signs. This further suggests that the imbalance of myelin synthesis and degradation can underlie myelin thinning in aging and disease.

Fatty acid metabolism in neutrophils promotes lung damage and bacterial replication during tuberculosis

Mycobacterium tuberculosis (Mtb) infection induces a marked influx of neutrophils into the lungs, which intensifies the severity of tuberculosis (TB). The metabolic state of neutrophils significantly influences their functional response during inflammation and interaction with bacterial pathogens. However, the effect of Mtb infection on neutrophil metabolism and its consequent role in TB pathogenesis remain unclear. In this study, we examined the contribution of glycolysis and fatty acid metabolism on neutrophil responses to Mtb HN878 infection using ex-vivo assays and murine infection models. We discover that blocking glycolysis aggravates TB pathology, whereas inhibiting fatty acid oxidation (FAO) yields protective outcomes, including reduced weight loss, immunopathology, and bacterial burden in lung. Intriguingly, FAO inhibition preferentially disrupts the recruitment of a pathogen-permissive immature neutrophil population (Ly6Glo/dim), known to accumulate during TB. Targeting carnitine palmitoyl transferase 1a (Cpt1a)-a crucial enzyme in mitochondrial β-oxidation-either through chemical or genetic methods impairs neutrophils' ability to migrate to infection sites while also enhancing their antimicrobial function. Our findings illuminate the critical influence of neutrophil immunometabolism in TB pathogenesis, suggesting that manipulating fatty acid metabolism presents a novel avenue for host-directed TB therapies by modulating neutrophil functions.

Etomoxir repurposed as a promiscuous fatty acid mimetic chemoproteomic probe

Etomoxir has been used for decades as a popular small molecule inhibitor of carnitine palmitoyltransferase I, Cpt1, to block mitochondrial fatty acid β-oxidation. To test the specificity of etomoxir, we generated click chemistry-enabled reagents to label etomoxir binding proteins in situ. Etomoxir bound to Cpt1, but also bound to a large array of diverse proteins that metabolize and transport fatty acids in the cytoplasm, peroxisome, and mitochondria. Many of the most abundant proteins identified in primary hepatocytes were peroxisomal proteins. The loss of Pex5, required for the import of peroxisomal matrix proteins, eliminated many of these etomoxir-labeled proteins. By utilizing the promiscuous, covalent, and fatty acid mimetic properties of etomoxir, etomoxir targets of fatty acid ω-oxidation were revealed following the loss of Pex5. These data demonstrate that etomoxir is not specific for Cpt1 and is not appropriate as a tool to distinguish the biological effects of fatty acid oxidation.

Gut Microbiota-Derived Butyrate Induces Epigenetic and Metabolic Reprogramming in Myeloid-Derived Suppressor Cells to Alleviate Primary Biliary Cholangitis

BACKGROUND & AIMS

Gut dysbiosis and myeloid-derived suppressor cells (MDSCs) are implicated in primary biliary cholangitis (PBC) pathogenesis. However, it remains unknown whether gut microbiota or their metabolites can modulate MDSCs homeostasis to rectify immune dysregulation in PBC.

METHODS

We measured fecal short-chain fatty acids levels using targeted gas chromatography-mass spectrometry and analyzed circulating MDSCs using flow cytometry in 2 independent PBC cohorts. Human and murine MDSCs were differentiated in vitro in the presence of butyrate, followed by transcriptomic, epigenetic (CUT&Tag-seq and chromatin immunoprecipitation-quantitative polymerase chain reaction), and metabolic (untargeted liquid chromatography-mass spectrometry, mitochondrial stress test, and isotope tracing) analyses. The in vivo role of butyrate-MDSCs was evaluated in a 2-octynoic acid-bovine serum albumin-induced cholangitis murine model.

RESULTS

Decreased butyrate levels and defective MDSC function were found in patients with incomplete response to ursodeoxycholic acid, compared with those with adequate response. Butyrate induced expansion and suppressive activity of MDSCs in a manner dependent on PPARD-driven fatty acid β-oxidation (FAO). Pharmaceutical inhibition or genetic knockdown of the FAO rate-limiting gene CPT1A abolished the effect of butyrate. Furthermore, butyrate inhibited HDAC3 function, leading to enhanced acetylation of lysine 27 on histone H3 at promoter regions of PPARD and FAO genes in MDSCs. Therapeutically, butyrate administration alleviated immune-mediated cholangitis in mice via MDSCs, and adoptive transfer of butyrate-treated MDSCs also displayed protective efficacy. Importantly, reduced expression of FAO genes and impaired mitochondrial physiology were detected in MDSCs from ursodeoxycholic acid nonresponders, and their impaired suppressive function was restored by butyrate.

CONCLUSIONS

We identify a critical role for butyrate in modulation of MDSC homeostasis by orchestrating epigenetic and metabolic crosstalk, proposing a novel therapeutic strategy for treating PBC.

Etomoxir-carnitine, a novel pharmaco-metabolite of etomoxir, inhibits phospholipases A2 and mitochondrial respiration

Mitochondrial fatty acid oxidation serves as an essential process for cellular survival, differentiation, proliferation, and energy metabolism. Numerous studies have utilized etomoxir (ETO) for the irreversible inhibition of carnitine palmitoylcarnitine transferase 1 (CPT1), which catalyzes the rate-limiting step for mitochondrial long-chain fatty acid β-oxidation to examine the bioenergetic roles of mitochondrial fatty acid metabolism in many tissues in multiple diverse disease states. Herein, we demonstrate that intact mitochondria robustly metabolize ETO to etomoxir-carnitine (ETO-carnitine) prior to nearly complete ETO-mediated inhibition of CPT1. The novel pharmaco-metabolite, ETO-carnitine, was conclusively identified by accurate mass, fragmentation patterns, and isotopic fine structure. On the basis of these data, ETO-carnitine was successfully differentiated from isobaric structures (e.g., 3-hydroxy-C18:0 carnitine and 3-hydroxy-C18:1 carnitine). Mechanistically, generation of ETO-carnitine from mitochondria required exogenous Mg2+, ATP or ADP, CoASH, and L-carnitine, indicating that thioesterification by long-chain acyl-CoA synthetase to form ETO-CoA precedes its conversion to ETO-carnitine by CPT1. CPT1-dependent generation of ETO-carnitine was substantiated by an orthogonal approach using ST1326 (a CPT1 inhibitor), which effectively inhibits mitochondrial ETO-carnitine production. Surprisingly, purified ETO-carnitine potently inhibited calcium-independent PLA2γ and PLA2β as well as mitochondrial respiration independent of CPT1. Robust production and release of ETO-carnitine from HepG2 cells incubated in the presence of ETO was also demonstrated. Collectively, this study identifies the chemical mechanism for the biosynthesis of a novel pharmaco-metabolite of ETO, ETO-carnitine, that is generated by CPT1 in mitochondria and likely impacts multiple downstream (non-CPT1 related) enzymes and processes in multiple subcellular compartments.

T-Cell Metabolic Reprogramming in Atherosclerosis

Atherosclerosis is a key pathological basis for cardiovascular diseases, significantly influenced by T-cell-mediated immune responses. T-cells differentiate into various subtypes, such as pro-inflammatory Th1/Th17 and anti-inflammatory Th2/Treg cells. The imbalance between these subtypes is critical for the progression of atherosclerosis (AS). Recent studies indicate that metabolic reprogramming within various microenvironments can shift T-cell differentiation towards pro-inflammatory or anti-inflammatory phenotypes, thus influencing AS progression. This review examines the roles of pro-inflammatory and anti-inflammatory T-cells in atherosclerosis, focusing on how their metabolic reprogramming regulates AS progression and the associated molecular mechanisms of mTOR and AMPK signaling pathways.

Targeting fatty acid oxidation enhances response to HER2-targeted therapy

Metabolic reprogramming, a hallmark of tumorigenesis, involves alterations in glucose and fatty acid metabolism. Here, we investigate the role of Carnitine palmitoyl transferase 1a (Cpt1a), a key enzyme in long-chain fatty acid (LCFA) oxidation, in ErbB2-driven breast cancers. In ErbB2+ breast cancer models, ablation of Cpt1a delays tumor onset, growth, and metastasis. However, Cpt1a-deficient cells exhibit increased glucose dependency that enables survival and eventual tumor progression. Consequently, these cells exhibit heightened oxidative stress and upregulated nuclear factor erythroid 2-related factor 2 (Nrf2) activity. Inhibiting Nrf2 or silencing its expression reduces proliferation and glucose consumption in Cpt1a-deficient cells. Combining the ketogenic diet, composed of LCFAs, or an anti-ErbB2 monoclonal antibody (mAb) with Cpt1a deficiency significantly perturbs tumor growth, enhances apoptosis, and reduces lung metastasis. Using an immunocompetent model, we show that Cpt1a inhibition promotes an antitumor immune microenvironment, thereby enhancing the efficacy of anti-ErbB2 mAbs. Our findings underscore the importance of targeting fatty acid oxidation alongside HER2-targeted therapies to combat resistance in HER2+ breast cancer patients.

Potential Application of the Myocardial Scintigraphy Agent [123I]BMIPP in Colon Cancer Cell Imaging

[123I]β-methyl-p-iodophenyl-pentadecanoic acid ([123I]BMIPP), which is used for nuclear medicine imaging of myocardial fatty acid metabolism, accumulates in cancer cells. However, the mechanism of accumulation remains unknown. Therefore, this study aimed to elucidate the accumulation and accumulation mechanism of [123I]BMIPP in cancer cells. We compared the accumulation of [123I]BMIPP in cancer cells with that of [18F]FDG and found that [123I]BMIPP was a much higher accumulation than [18F]FDG. The accumulation of [123I]BMIPP was evaluated in the presence of sulfosuccinimidyl oleate (SSO), a CD36 inhibitor, and lipofermata, a fatty acid transport protein (FATP) inhibitor, under low-temperature conditions and in the presence of etomoxir, a carnitine palmitoyl transferase I (CPT1) inhibitor. The results showed that [123I]BMIPP accumulation was decreased in the presence of SSO and lipofermata in H441, LS180, and DLD-1 cells, suggesting that FATPs and CD36 are involved in [123I]BMIPP uptake in cancer cells. [123I]BMIPP accumulation in all cancer cell lines was significantly decreased at 4 °C compared to that at 37 °C and increased in the presence of etomoxir in all cancer cell lines, suggesting that the accumulation of [123I]BMIPP in cancer cells is metabolically dependent. In a biological distribution study conducted using tumor-bearing mice transplanted with LS180 cells, [123I]BMIPP highly accumulated in not only LS180 cells but also normal tissues and organs (including blood and muscle). The tumor-to-intestine or large intestine ratios of [123I]BMIPP were similar to those of [18F]FDG, and the tumor-to-large-intestine ratios exceeded 1.0 during 30 min after [123I]BMIPP administration in the in vivo study. [123I]BMIPP is taken up by cancer cells via CD36 and FATP and incorporated into mitochondria via CPT1. Therefore, [123I]BMIPP may be useful for imaging cancers with activated fatty acid metabolism, such as colon cancer. However, the development of novel imaging radiotracers based on the chemical structure analog of [123I]BMIPP is needed.

Intersection of Immunology and Metabolism in Myocardial Disease

Immunometabolism is an emerging field at the intersection of immunology and metabolism. Immune cell activation plays a critical role in the pathogenesis of cardiovascular diseases and is integral for regeneration during cardiac injury. We currently possess a limited understanding of the processes governing metabolic interactions between immune cells and cardiomyocytes. The impact of this intercellular crosstalk can manifest as alterations to the steady state flux of metabolites and impact cardiac contractile function. Although much of our knowledge is derived from acute inflammatory response, recent work emphasizes heterogeneity and flexibility in metabolism between cardiomyocytes and immune cells during pathological states, including ischemic, cardiometabolic, and cancer-associated disease. Metabolic adaptation is crucial because it influences immune cell activation, cytokine release, and potential therapeutic vulnerabilities. This review describes current concepts about immunometabolic regulation in the heart, focusing on intercellular crosstalk and intrinsic factors driving cellular regulation. We discuss experimental approaches to measure the cardio-immunologic crosstalk, which are necessary to uncover unknown mechanisms underlying the immune and cardiac interface. Deeper insight into these axes holds promise for therapeutic strategies that optimize cardioimmunology crosstalk for cardiac health.

CPT2 mediated fatty acid oxidation is dispensable for humoral immunity

B cell activation is accompanied by dynamic metabolic reprogramming, supported by a multitude of nutrients that include glucose, amino acids and fatty acids. While several studies have indicated that fatty acid mitochondrial oxidation is critical for immune cell functions, contradictory findings have been reported. Carnitine palmitoyltransferase II (CPT2) is a critical enzyme for long-chain fatty acid oxidation in mitochondria. Here, we test the requirement of CPT2 for humoral immunity using a mouse model with a lymphocyte specific deletion of CPT2. Stable 13C isotope tracing reveals highly reduced fatty acid-derived citrate production in CPT2 deficient B cells. Yet, CPT2 deficiency has no significant impact on B cell development, B cell activation, germinal center formation, and antibody production upon either thymus-dependent or -independent antigen challenges. Together, our findings indicate that CPT2 mediated fatty acid oxidation is dispensable for humoral immunity, highlighting the metabolic flexibility of lymphocytes.

The role of lymphatic endothelial cell metabolism in lymphangiogenesis and disease

Lymphatic endothelial cells (LECs) line lymphatic vessels, which play an important role in the transport of lymph fluid throughout the human body. An organized lymphatic network develops via a process termed "lymphangiogenesis." During development, LECs respond to growth factor signaling to initiate the formation of a primary lymphatic vascular network. These LECs display a unique metabolic profile, preferring to undergo glycolysis even in the presence of oxygen. In addition to their reliance on glycolysis, LECs utilize other metabolic pathways such as fatty acid β-oxidation, ketone body oxidation, mitochondrial respiration, and lipid droplet autophagy to support lymphangiogenesis. This review summarizes the current understanding of metabolic regulation of lymphangiogenesis. Moreover, it highlights how LEC metabolism is implicated in various pathological conditions.

Metabolic programming of organ-specific natural killer cell responses

Cells of the mammalian innate immune system have evolved to protect the host from various environmental or internal insults and injuries which perturb the homeostatic state of the organism. Among the lymphocytes of the innate immune system are natural killer (NK) cells, which circulate and survey host tissues for signs of stress, including infection or transformation. NK cells rapidly eliminate damaged cells in the blood or within tissues through secretion of cytolytic machinery and production of proinflammatory cytokines. To perform these effector functions while traversing between the blood and tissues, patrolling NK cells require sufficient fuel to meet their energetic demands. Here, we highlight the ability of NK cells to metabolically adapt across tissues, during times of nutrient deprivation and within tumor microenvironments. Whether at steady state, or during viral infection and cancer, NK cells readily shift their nutrient uptake and usage in order to maintain metabolism, survival, and function.

Cellular metabolism regulates the differentiation and function of T-cell subsets

T cells are an important component of adaptive immunity and protect the host from infectious diseases and cancers. However, uncontrolled T cell immunity may cause autoimmune disorders. In both situations, antigen-specific T cells undergo clonal expansion upon the engagement and activation of antigens. Cellular metabolism is reprogrammed to meet the increase in bioenergetic and biosynthetic demands associated with effector T cell expansion. Metabolites not only serve as building blocks or energy sources to fuel cell growth and expansion but also regulate a broad spectrum of cellular signals that instruct the differentiation of multiple T cell subsets. The realm of immunometabolism research is undergoing swift advancements. Encapsulating all the recent progress within this concise review in not possible. Instead, our objective is to provide a succinct introduction to this swiftly progressing research, concentrating on the metabolic intricacies of three pivotal nutrient classes-lipids, glucose, and amino acids-in T cells. We shed light on recent investigations elucidating the roles of these three groups of metabolites in mediating the metabolic and immune functions of T cells. Moreover, we delve into the prospect of "editing" metabolic pathways within T cells using pharmacological or genetic approaches, with the aim of synergizing this approach with existing immunotherapies and enhancing the efficacy of antitumor and antiinfection immune responses.

Bromocriptine protects perilesional spinal cord neurons from lipotoxicity after spinal cord injury

Recent studies have revealed that lipid droplets accumulate in neurons after brain injury and evoke lipotoxicity, damaging the neurons. However, how lipids are metabolized by spinal cord neurons after spinal cord injury remains unclear. Herein, we investigated lipid metabolism by spinal cord neurons after spinal cord injury and identified lipid-lowering compounds to treat spinal cord injury. We found that lipid droplets accumulated in perilesional spinal cord neurons after spinal cord injury in mice. Lipid droplet accumulation could be induced by myelin debris in HT22 cells. Myelin debris degradation by phospholipase led to massive free fatty acid production, which increased lipid droplet synthesis, β-oxidation, and oxidative phosphorylation. Excessive oxidative phosphorylation increased reactive oxygen species generation, which led to increased lipid peroxidation and HT22 cell apoptosis. Bromocriptine was identified as a lipid-lowering compound that inhibited phosphorylation of cytosolic phospholipase A2 by reducing the phosphorylation of extracellular signal-regulated kinases 1/2 in the mitogen-activated protein kinase pathway, thereby inhibiting myelin debris degradation by cytosolic phospholipase A2 and alleviating lipid droplet accumulation in myelin debris-treated HT22 cells. Motor function, lipid droplet accumulation in spinal cord neurons and neuronal survival were all improved in bromocriptine-treated mice after spinal cord injury. The results suggest that bromocriptine can protect neurons from lipotoxic damage after spinal cord injury via the extracellular signal-regulated kinases 1/2-cytosolic phospholipase A2 pathway.

Metabolic basis of cardiac dysfunction in cancer patients

PURPOSE OF REVIEW

The relationship between metabolism and cardiovascular diseases is complex and bidirectional. Cardiac cells must adapt metabolic pathways to meet biosynthetic demands and energy requirements to maintain contractile function. During cancer, this homeostasis is challenged by the increased metabolic demands of proliferating cancer cells.

RECENT FINDINGS

Tumors have a systemic metabolic impact that extends beyond the tumor microenvironment. Lipid metabolism is critical to cancer cell proliferation, metabolic adaptation, and increased cardiovascular risk. Metabolites serve as signals which provide insights for diagnosis and prognosis in cardio-oncology patients.

SUMMARY

Metabolic processes demonstrate a complex relationship between cancer cell states and cardiovascular remodeling with potential for therapeutic interventions.