Serine Synthesis via PHGDH Is Essential for Heme Production in Endothelial Cells

The role of tumor-associated endothelial cells in malignant progression and immune evasion of liver cancer

Recent studies have revealed that the malignant progression of hepatocellular carcinoma (HCC) not only stems from tumor cell-intrinsic genetic alterations but is dynamically regulated by the tumor microenvironment (TME). As a pivotal component of TME, tumor-associated endothelial cells (TECs) critically drive HCC progression through dual mechanisms of vascular abnormality and immune modulation. TECs establish a pro-tumorigenic niche by constructing disordered vascular networks while concurrently secreting immunosuppressive factors that induce immune cell dysfunction. This review systematically examines the molecular mechanisms underlying the dynamic transition from hepatic endothelial cells to TECs, identifies key TEC subtypes mediating tumor angiogenesis and immune evasion, and elucidates their crosstalk with immunosuppressive components. Additionally, we highlight TEC-specific biomarkers associated with clinical HCC progression and synthesize current clinical trials targeting TEC-mediated pathways. These findings provide novel insights for developing precision therapies that disrupt the TEC-TME-immune axis in HCC.

PHGDH-mediated serine synthesis in astrocytes supports neuroinflammation by sustaining NADH level to promote histone acetylation

Neuroinflammation contributes to the loss of dopamine neurons and motor dysfunctions in Parkinson's disease (PD). How cell metabolism regulates neuroinflammation by modulating epigenetic modifications is largely unknown. In this study, we found that the expression of phosphoglycerate dehydrogenase (PHGDH) which catalyzes the first step of the de novo serine synthesis pathway was mainly expressed in astrocytes and l-methyl-4-phenyl-l,2,3,6-tetrahydropyridine (MPTP) injection triggered the upregulation of PHGDH in astrocytes in substantia nigra. PHGDH inhibition or knockdown reduced proinflammatory cytokine production in primary astrocytes after LPS (lipopolysaccharide) stimulation which was not due to suppressed inflammatory signaling transduction. Mechanistically, PHGDH promotes proinflammatory cytokine transcription by sustaining nicotinamide adenine dinucleotide (NADH) accumulation to facilitate histone acetylation of cytokine promoters. Moreover, PHGDH inhibition-induced inflammatory response decreased neurotoxicity in vitro and alleviated astrocytes-mediated neuroinflammation and neurotoxicity in an MPTP mice model. This study reveals the role and mechanism of PHGDH-mediated serine synthesis in promoting the inflammatory response of astrocytes which may provide a potential target for neurological diseases involving neuroinflammation.

De novo serine biosynthesis is protective in mitochondrial disease

The importance of serine as a metabolic regulator is well known for tumors and is also gaining attention in degenerative diseases. Recent data indicate that de novo serine biosynthesis is an integral component of the metabolic response to mitochondrial disease, but the roles of the response have remained unknown. Here, we report that glucose-driven de novo serine biosynthesis maintains metabolic homeostasis in energetic stress. Pharmacological inhibition of the rate-limiting enzyme, phosphoglycerate dehydrogenase (PHGDH), aggravated mitochondrial muscle disease, suppressed oxidative phosphorylation and mitochondrial translation, altered whole-cell lipid profiles, and enhanced the mitochondrial integrated stress response (ISRmt) in vivo in skeletal muscle and in cultured cells. Our evidence indicates that de novo serine biosynthesis is essential to maintain mitochondrial respiration, redox balance, and cellular lipid homeostasis in skeletal muscle with mitochondrial dysfunction. Our evidence implies that interventions activating de novo serine synthesis may protect against mitochondrial failure in skeletal muscle.

Mitochondrial Dysfunction: Unraveling the Elusive Biology Behind Anti-TNF Response During Ulcerative Colitis

BACKGROUND

Recent studies hint at mitochondrial genes influencing UC patient response to anti-TNF treatment. We evaluated this hypothesis by following a targeted strategy to identify gene expression that captures the relationship between mitochondrial dysregulation and response to treatment. Our objective was to initially examine this relationship in colon samples and subsequently assess whether the resulting signal persists in the bloodstream.

METHODS

We analyzed the transcriptome of colon samples from an anti-TNF-treated murine model characterized by impaired mitochondrial activity and treatment resistance. We then transferred the findings that linked mitochondrial dysfunction and compromised treatment response to an anti-TNF-treated UC human cohort. We next matched differential expression in the blood using monocytes from the peripheral blood of controls and IBD patients, and we evaluated a classification process at baseline with whole blood samples from UC patients.

RESULTS

In human colon samples, the derived gene set from the murine model showed differential expression, primarily enriched metabolic pathways, and exhibited similar classification capacity as genes enriching inflammatory pathways. Moreover, the evaluation of the classification signal using blood samples from UC patients at baseline highlighted the involvement of mitochondrial homeostasis in treatment response.

CONCLUSIONS

Our results highlight the involvement of metabolic pathways and mitochondrial homeostasis in determining treatment response and their ability to provide promising classification signals with detection levels in both the colon and the bloodstream.

YY2 mediates transcriptional repression of PHGDH and expedites oxidative stress in retinal pigment epithelial cells in diabetic retinopathy

AIMS/INTRODUCTION

Phosphoglycerate dehydrogenase (PHGDH), which controls serine synthesis, has been linked to retinal disease. However, there are no clues about its involvement in the diabetic retinopathy (DR) progression. Therefore, we aimed to investigate the relationship between PHGDH, serine synthesis, and DR and their underlying molecular mechanisms.

METHOD

Differentially expressed genes in DR were screened using bioinformatics tools. DR mice were induced, and retinal histopathology was observed in mice. Overexpression of PHGDH was induced in the DR mice to measure l-serine, ROS, and MDA content in the retinas of DR mice. ARPE-19 cells were transfected with overexpression of PHGDH and exposed to high glucose to induce a DR in vitro model, and cell viability and apoptosis assays, serine content, and oxidative stress factor measurement were conducted. The transcriptional regulation of PHGDH by YY2 was explored by ChIP and dual-luciferase reporter assays. Finally, the combined role of YY2 and PHGDH in regulating serine synthesis, oxidative stress, and ferroptosis was investigated.

RESULTS

PHGDH expression was reduced in DR mice, and overexpression of PHGDH alleviated DR progression by promoting serine synthesis and attenuating oxidative stress. YY2 bound to the promoter of PHGDH and mediated its transcriptional repression. YY2-mediated transcriptional repression of PHGDH caused disturbances in serine synthesis, leading to oxidative stress-triggered ferroptosis.

CONCLUSIONS

Our data prove that YY2 plays a vital role in modulating PHGDH expression, impairing serine synthesis, and expediting oxidative stress and ferroptosis.

Metabolic reprogramming and interventions in angiogenesis

BACKGROUND

Endothelial cell (EC) metabolism plays a crucial role in the process of angiogenesis. Intrinsic metabolic events such as glycolysis, fatty acid oxidation, and glutamine metabolism, support secure vascular migration and proliferation, energy and biomass production, as well as redox homeostasis maintenance during vessel formation. Nevertheless, perturbation of EC metabolism instigates vascular dysregulation-associated diseases, especially cancer.

AIM OF REVIEW

In this review, we aim to discuss the metabolic regulation of angiogenesis by EC metabolites and metabolic enzymes, as well as prospect the possible therapeutic opportunities and strategies targeting EC metabolism.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this work, we discuss various aspects of EC metabolism considering normal and diseased vasculature. Of relevance, we highlight that the implications of EC metabolism-targeted intervention (chiefly by metabolic enzymes or metabolites) could be harnessed in orchestrating a spectrum of pathological angiogenesis-associated diseases.

Xanthocillin X Dimethyl Ether Exhibits Anti-Proliferative Effect on Triple-Negative Breast Cancer by Depletion of Mitochondrial Heme

Triple-negative breast cancer (TNBC) presents a significant therapeutic challenge due to the absence of specific targeted treatments. In this study, we explored the therapeutic potential of xanthocillin X dimethyl ether (XanDME), a naturally occurring isocyanide isolated from the marine fungus Scedosporium apiospermum, on TNBC. To elucidate the underlying mechanism, we initially demonstrated that XanDME directly binds to hemin, the oxidized form of heme, in vitro, corroborating previous reports. This interaction led to the depletion of intracellular regulatory heme. We further established that XanDME translocates into the mitochondria, where it interacts with crucial hemoproteins, namely cytochromes. The binding of XanDME with mitochondrial cytochromes disrupts the electron transport chain (ETC), inhibits the activity of mitochondrial complexes, and inactivates mitochondrial respiration. The inhibitory activity of XanDME on mitochondrial function significantly contributes to its anti-TNBC effects, as observed both in vitro and in vivo. Our study underscores the potential of XanDME against TNBC, warranting further investigations.

Glycometabolic Regulation of Angiogenesis: Mechanisms and Therapeutic Strategies

Angiogenesis, the process by which new blood vessels emerge from pre-existing vasculature, forms the fundamental biological basis for therapeutic angiogenesis. In recent years, this field has garnered significant attention, particularly in the context of understanding the mechanisms of angiogenesis through the lens of glycometabolism. The potential clinical applications of this research have been widely acknowledged within the medical community. In this article, the role of angiogenesis and the principal molecular mechanisms that govern it are first delineated. The influence of glycometabolism on angiogenesis is then explored, with a focus on glycolysis. Finally, research on therapeutic angiogenesis based on the regulation of glycometabolism is presented, offering novel perspectives for ongoing research and clinical applications.

The influence of endothelial metabolic reprogramming on the tumor microenvironment

Endothelial cells (ECs) that line blood vessels act as gatekeepers and shape the metabolic environment of every organ system. In normal conditions, endothelial cells are relatively quiescent with organ-specific expression signatures and metabolic profiles. In cancer, ECs are metabolically reprogrammed to promote the formation of new blood vessels to fuel tumor growth and metastasis. In addition to EC's role on tumor cells, the tortuous tumor vasculature contributes to an immunosuppressive environment by limiting T lymphocyte infiltration and activity while also promoting the recruitment of other accessory pro-angiogenic immune cells. These elements aid in the metastatic spreading of cancer cells and contribute to therapeutic resistance. The concept of restoring a more stabilized vasculature in concert with cancer immunotherapy is emerging as a potential approach to overcoming barriers in cancer treatment. This review summarizes the metabolism of endothelial cells, their regulation of nutrient uptake and delivery, and their impact in shaping the tumor microenvironment and anti-tumor immunity. We highlight new therapeutic approaches that target the tumor vasculature and harness the immune response. Appreciating the integration of metabolic state and nutrient levels and the crosstalk among immune cells, tumor cells, and ECs in the TME may provide new avenues for therapeutic intervention.

Essentiality of SLC7A11-mediated nonessential amino acids in MASLD

Metabolic dysfunction-associated steatotic liver disease (MASLD) remains a rapidly growing global health burden. Here, we report that the nonessential amino acid (NEAA) transporter SLC7A11 plays a key role in MASLD. In patients with MASLD, we found high expression levels of SLC7A11 that were correlated directly with clinical grade. Using both loss-of-function and gain-of-function genetic models, we found that Slc7a11 deficiency accelerated MASLD progression via classic cystine/cysteine deficiency-induced ferroptosis, while serine deficiency and a resulting impairment in de novo cysteine production were attributed to ferroptosis-induced MASLD progression in mice overexpressing hepatic Slc7a11. Consistent with these findings, we found that both serine supplementation and blocking ferroptosis significantly alleviated MASLD, and the serum serine/glutamate ratio was significantly lower in these preclinical disease models, suggesting that it might serve as a prognostic biomarker for MASLD in patients. These findings indicate that defects in NEAA metabolism are involved in the progression of MASLD and that serine deficiency-triggered ferroptosis may provide a therapeutic target for its treatment.

Bilirubin metabolism in early life and respiratory health during preschool age: A combined analysis of two independent birth cohorts

BACKGROUND

Bilirubin has antioxidant properties, and elevated levels within the normal range have been associated with improved lung function and decreased risk of asthma in adults, but studies of young children are scarce. Here, we investigate associations between bilirubin in early life and respiratory health endpoints during preschool age in two independent birth cohorts.

METHODS

Bilirubin metabolites were assessed at ages 0.5, 1.5, and 6 years in COPSAC2010 (Copenhagen Prospective Studies on Asthma in Childhood 2010) and ages 1, 3, and 6 years in the VDAART (The Vitamin D Antenatal Asthma Reduction Trial) cohort. Meta-analyses were done to summarize the relationship between levels of bilirubin metabolites and asthma, infections, lung function, and allergic sensitization until age 6 across the cohorts. Interaction with the glucuronosyltransferase family 1 member A1 (UGT1A) genotype encoding for an enzyme in the bilirubin metabolism was explored, and metabolomics data were integrated to study underlying mechanisms.

FINDINGS

Increasing bilirubin (Z,Z) at ages 1.5-3 years was associated with an increased risk of allergic sensitization (adjusted relative risk [aRR] = 1.85 [1.20-2.85], p = 0.005), and age 6 bilirubin (Z,Z) also showed a trend of association with allergic sensitization at age 6 (aRR = 1.31 [0.97-1.77], p = 0.08), which showed significant interaction for the age 6 bilirubin (Z,Z)xUGT1A genotype. Further, increasing bilirubin (E,E), bilirubin (Z,Z), and biliverdin at ages 1.5-3 years was associated with a lower forced expiratory volume at age 6 (aRR range = 0.81-0.91, p < 0.049) but without a significant interaction with the UGT1A genotype (p interactions > 0.05). Network analysis showed a significant correlation between bilirubin metabolism and acyl carnitines. There were no associations between bilirubin metabolites and the risk of asthma and infections.

CONCLUSIONS

Bilirubin metabolism in early life may play a role in childhood respiratory health, particularly in children with specific UGT1A genotypes.

FUNDING

The Lundbeck Foundation (Grant no R16-A1694), The Ministry of Health (Grant no 903516), Danish Council for Strategic Research (Grant no 0603-00280B), and The Capital Region Research Foundation have provided core support to the COPSAC research center. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 946228). The Vitamin D Antenatal Asthma Reduction Trial (VDDART, ClinicalTrials.gov identifier: NCT00920621) was supported by grant U01HL091528 from NHLBI, U54TR001012 from the National Centers for Advancing Translational Sciences (NCATS). Metabolomics work by VDAART was supported by the National Heart, Lung, and Blood Institute (NHLBI) grant R01HL123915 and R01HL141826. S.T.W. was supported by R01HL091528 from the NHLBI, UG3OD023268 from Office of The Director, National Institute of Health, and P01HL132825 from the NHLBI.

Intracellular endothelial cell metabolism in vascular function and dysfunction

Endothelial cells (ECs) form the inner lining of blood vessels that is crucial for vascular function and homeostasis. They regulate vascular tone, oxidative stress, and permeability. Dysfunction leads to increased permeability, leukocyte adhesion, and thrombosis. ECs undergo metabolic changes in conditions such as wound healing, cancer, atherosclerosis, and diabetes, and can influence disease progression. We discuss recent research that has revealed diverse intracellular metabolic pathways in ECs that are tailored to their functional needs, including lipid handling, glycolysis, and fatty acid oxidation (FAO). Understanding EC metabolic signatures in health and disease will be crucial not only for basic biology but can also be exploited when designing new therapies to target EC-related functions in different vascular diseases.

Piezoelectric stimulation enhances bone regeneration in alveolar bone defects through metabolic reprogramming of macrophages

Immunomodulation has emerged as a promising strategy for promoting bone regeneration. However, designing osteoimmunomodulatory biomaterial that can respond to mechanical stress in the unique microenvironment of alveolar bone under continuous occlusal stress remains a significant challenge. Herein, a wireless piezoelectric stimulation system, namely, piezoelectric hydrogel incorporating BaTiO3 nanoparticles (BTO NPs), is successfully developed to generate piezoelectric potentials for modulating macrophage reprogramming. The piezoelectric stimulation reprograms macrophages towards the M2 phenotype, which subsequently induces osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). RNA sequencing analysis reveals that piezoelectricity-modulated macrophage M2 polarization is closely associated with metabolic reprogramming, including increased amino acid biosynthesis and fatty acid oxidation. The composite hydrogel with excellent biocompatibility exhibits immunomodulatory and osteoinductive activities. In a rat model of alveolar bone defects, the piezoelectric hydrogel effectively promotes endogenous bone regeneration at the load-bearing sites. The piezoelectric-driven osteoimmunomodulation proposed in this study not only broadens understanding of the mechanism underlying piezoelectric biomaterials for tissue regeneration but also provides new insights into the design and development of next-generation immunomodulatory biomaterials.

Non-canonical function of PHGDH promotes HCC metastasis by interacting with METTL3

PURPOSE

Phosphoglycerate dehydrogenase (PHGDH), a pivotal enzyme in serine synthesis, plays a key role in the malignant progression of tumors through both its metabolic activity and moonlight functions. This study aims to elucidate the non-canonical function of PHGDH in promoting hepatocellular carcinoma (HCC) metastasis through its interaction with methyltransferase-like 3 (METTL3), potentially uncovering a novel therapeutic target.

METHODS

Western blot was used to study PHGDH expression changes under anoikis and cellular functional assays were employed to assess its role in HCC metastasis. PHGDH-METTL3 interactions were explored using GST pull-down, Co-immunoprecipitation and immunofluorescence assays. Protein stability and ubiquitination assays were performed to understand PHGDH's impact on METTL3. Flow cytometry, cellular assays and nude mice model were used to confirm PHGDH's effects on anoikis resistance and HCC metastasis in vitro and in vivo.

RESULTS

PHGDH is upregulated under anoikis conditions, thereby enhancing the metastatic potential of HCC cells. By interacting with METTL3, PHGDH prevents its ubiquitin-dependent degradation, resulting in higher METTL3 protein levels. This interaction upregulates epithelial-mesenchymal transition related genes, contributing to anoikis resistance and HCC metastasis. Nude mice model confirms that PHGDH's interaction with METTL3 is crucial for driving HCC metastasis.

CONCLUSION

Our research presents the first evidence that PHGDH promotes HCC metastasis by interacting with METTL3. The PHGDH-METTL3 axis may serve as a potential clinical therapeutic target, offering new insights into the multifaceted roles of PHGDH in HCC metastasis.

Angiogenesis of Avascular Necrosis of the Femoral Head: A Classic Treatment Strategy

Avascular necrosis of the femoral head (ANFH) is a type of osteonecrosis due to the cessation of blood supply, characterized by persistent local pain and collapse of the joint. The etiology of ANFH is multifaceted, and while its precise pathogenesis remains elusive, it is currently widely believed that the femoral head is highly dependent on the vascular system. A large number of studies have shown that vascular injury is the initial factor in the onset of ANFH. In this review, we briefly introduced the process of angiogenesis and the blood supply to the femoral head, with a focus on summarizing the existing research on promoting angiogenesis for the treatment of ANFH. We conclude that providing alternative pathways through angiogenesis to resolve the problem of the obstructed free flow of the blood is an important means of treating ANFH. Moreover, we also looked forward to the mechanism of endothelial metabolism, which has not yet been studied in femoral head necrosis models, providing potential strategies for more effective use of angiogenesis for the treatment of femoral head necrosis.

Endothelial metabolic control of insulin sensitivity through resident macrophages

Endothelial cells (ECs) not only form passive blood conduits but actively contribute to nutrient transport and organ homeostasis. The role of ECs in glucose homeostasis is, however, poorly understood. Here, we show that, in skeletal muscle, endothelial glucose transporter 1 (Glut1/Slc2a1) controls glucose uptake via vascular metabolic control of muscle-resident macrophages without affecting transendothelial glucose transport. Lowering endothelial Glut1 via genetic depletion (Glut1ΔEC) or upon a short-term high-fat diet increased angiocrine osteopontin (OPN/Spp1) secretion. This promoted resident muscle macrophage activation and proliferation, which impaired muscle insulin sensitivity. Consequently, co-deleting Spp1 from ECs prevented macrophage accumulation and improved insulin sensitivity in Glut1ΔEC mice. Mechanistically, Glut1-dependent endothelial glucose metabolic rewiring increased OPN in a serine metabolism-dependent fashion. Our data illustrate how the glycolytic endothelium creates a microenvironment that controls resident muscle macrophage phenotype and function and directly links resident muscle macrophages to the maintenance of muscle glucose homeostasis.

Mitochondrial control of hypoxia-induced pathological retinal angiogenesis

OBJECTIVE

Pathological retinal neovascularization is vision-threatening. In mouse oxygen-induced retinopathy (OIR) we sought to define mitochondrial respiration changes longitudinally during hyperoxia-induced vessel loss and hypoxia-induced neovascularization, and to test interventions addressing those changes to prevent neovascularization.

METHODS

OIR was induced in C57BL/6J mice and retinal vasculature was examined at maximum neovessel formation. We assessed total proteome changes and the ratio of mitochondrial to nuclear DNA copy numbers (mtDNA/nDNA) of OIR vs. control retinas, and mitochondrial oxygen consumption rates (OCR) in ex vivo OIR vs. control retinas (BaroFuse). Pyruvate vs. vehicle control was supplemented to OIR mice either prior to or during neovessel formation.

RESULTS

In OIR vs. control retinas, global proteomics showed decreased retinal mitochondrial respiration at peak neovascularization. OCR and mtDNA/nDNA were also decreased at peak neovascularization suggesting impaired mitochondrial respiration. In vivo pyruvate administration during but not prior to neovessel formation (in line with mitochondrial activity time course) suppressed NV.

CONCLUSIONS

Mitochondrial energetics were suppressed during retinal NV in OIR. Appropriately timed supplementation of pyruvate may be a novel approach in neovascular retinal diseases.

Protein O-GlcNAcylation coupled to Hippo signaling drives vascular dysfunction in diabetic retinopathy

Metabolic disorder significantly contributes to diabetic vascular complications, including diabetic retinopathy, the leading cause of blindness in the working-age population. However, the molecular mechanisms by which disturbed metabolic homeostasis causes vascular dysfunction in diabetic retinopathy remain unclear. O-GlcNAcylation modification acts as a nutrient sensor particularly sensitive to ambient glucose. Here, we observe pronounced O-GlcNAc elevation in retina endothelial cells of diabetic retinopathy patients and mouse models. Endothelial-specific depletion or pharmacological inhibition of O-GlcNAc transferase effectively mitigates vascular dysfunction. Mechanistically, we find that Yes-associated protein (YAP) and Transcriptional co-activator with PDZ-binding motif (TAZ), key effectors of the Hippo pathway, are O-GlcNAcylated in diabetic retinopathy. We identify threonine 383 as an O-GlcNAc site on YAP, which inhibits its phosphorylation at serine 397, leading to its stabilization and activation, thereby promoting vascular dysfunction by inducing a pro-angiogenic and glucose metabolic transcriptional program. This work emphasizes the critical role of the O-GlcNAc-Hippo axis in the pathogenesis of diabetic retinopathy and suggests its potential as a therapeutic target.

Unlocking the potential: Targeting metabolic pathways in the tumor microenvironment for Cancer therapy

Cancer incidence and mortality are increasing and impacting global life expectancy. Metabolic reprogramming in the tumor microenvironment (TME) is intimately related to tumorigenesis, progression, metastasis and drug resistance. Tumor cells drive metabolic reprogramming of other cells in the TME through metabolic induction of cytokines and metabolites, and metabolic substrate competition. Consequently, this boosts tumor cell growth by providing metabolic support and facilitating immunosuppression and angiogenesis. The metabolic interplay in the TME presents potential therapeutic targets. Here, we focus on the metabolic reprogramming of four principal cell subsets in the TME: CAFs, TAMs, TILs and TECs, and their interaction with tumor cells. We also summarize medications and therapies targeting these cells' metabolic pathways, particularly in the context of immune checkpoint blockade therapy.

Animal Models of Retinopathy of Prematurity: Advances and Metabolic Regulators

Retinopathy of prematurity (ROP) is a primary cause of visual impairment and blindness in premature newborns, characterized by vascular abnormalities in the developing retina, with microvascular alteration, neovascularization, and in the most severe cases retinal detachment. To elucidate the pathophysiology and develop therapeutics for ROP, several pre-clinical experimental models of ROP were developed in different species. Among them, the oxygen-induced retinopathy (OIR) mouse model has gained the most popularity and critically contributed to our current understanding of pathological retinal angiogenesis and the discovery of potential anti-angiogenic therapies. A deeper comprehension of molecular regulators of OIR such as hypoxia-inducible growth factors including vascular endothelial growth factors as primary perpetrators and other new metabolic modulators such as lipids and amino acids influencing pathological retinal angiogenesis is also emerging, indicating possible targets for treatment strategies. This review delves into the historical progressions that gave rise to the modern OIR models with a focus on the mouse model. It also reviews the fundamental principles of OIR, recent advances in its automated assessment, and a selected summary of metabolic investigation enabled by OIR models including amino acid transport and metabolism.

Tumor Metabolism: A New Field for the Treatment of Glioma

The clinical treatment of glioma remains relatively immature. Commonly used clinical treatments for gliomas are surgery combined with chemotherapy and radiotherapy, but there is a problem of drug resistance. In addition, immunotherapy and targeted therapies also suffer from the problem of immune evasion. The advent of metabolic therapy holds immense potential for advancing more efficacious and tolerable therapies against this aggressive disease. Metabolic therapy alters the metabolic processes of tumor cells at the molecular level to inhibit tumor growth and spread, and lead to better outcomes for patients with glioma that are insensitive to conventional treatments. Moreover, compared with conventional therapy, it has less impact on normal cells, less toxicity and side effects, and higher safety. The objective of this review is to examine the changes in metabolic characteristics throughout the development of glioma, enumerate the current methodologies employed for studying tumor metabolism, and highlight the metabolic reprogramming pathways of glioma along with their potential molecular mechanisms. Importantly, it seeks to elucidate potential metabolic targets for glioblastoma (GBM) therapy and summarize effective combination treatment strategies based on various studies.

The significant role of amino acid metabolic reprogramming in cancer

Amino acid metabolism plays a pivotal role in tumor microenvironment, influencing various aspects of cancer progression. The metabolic reprogramming of amino acids in tumor cells is intricately linked to protein synthesis, nucleotide synthesis, modulation of signaling pathways, regulation of tumor cell metabolism, maintenance of oxidative stress homeostasis, and epigenetic modifications. Furthermore, the dysregulation of amino acid metabolism also impacts tumor microenvironment and tumor immunity. Amino acids can act as signaling molecules that modulate immune cell function and immune tolerance within the tumor microenvironment, reshaping the anti-tumor immune response and promoting immune evasion by cancer cells. Moreover, amino acid metabolism can influence the behavior of stromal cells, such as cancer-associated fibroblasts, regulate ECM remodeling and promote angiogenesis, thereby facilitating tumor growth and metastasis. Understanding the intricate interplay between amino acid metabolism and the tumor microenvironment is of crucial significance. Expanding our knowledge of the multifaceted roles of amino acid metabolism in tumor microenvironment holds significant promise for the development of more effective cancer therapies aimed at disrupting the metabolic dependencies of cancer cells and modulating the tumor microenvironment to enhance anti-tumor immune responses and inhibit tumor progression.

Central carbon metabolism exhibits unique characteristics during the handling of fungal patterns by monocyte-derived dendritic cells

Monocyte-derived dendritic cells (MDDCs) are key players in the defense against fungal infection because of their outstanding capacity for non-opsonic phagocytosis and phenotypic plasticity. Accordingly, MDDCs rewire metabolism to meet the energetic demands for microbial killing and biomass synthesis required to restore homeostasis. It has been commonplace considering the metabolic reprogramming a mimicry of the Warburg effect observed in tumor cells. However, this may be an oversimplification since the offshoots of glycolysis and the tricarboxylic acid (TCA) cycle are connected in central carbon metabolism. Zymosan, the external wall of Saccharomyces cerevisiae, contains β-glucan and α-mannan chains that engage the C-type lectin receptors dectin-1/2 and Toll-like receptors. This makes it an optimal fungal surrogate for experimental research. Using real-time bioenergetic assays and [U-13C]glucose labeling, central hubs connected to cytokine expression were identified. The pentose phosphate pathway (PPP) exhibited a more relevant capacity to yield ribose-5-phosphate than reducing equivalents of NADPH, as judged from the high levels of isotopologues showing 13C-labeling in the ribose moiety and the limited contribution of the oxidative arm of the PPP to the production of ROS by NADPH oxidases (NOX). The finding of 13C-label in the purine ring and in glutathione unveiled the contribution of serine-derived glycine to purine ring and glutathione synthesis. Serine synthesis also supported the TCA cycle. Zymosan exhausted NAD+ and ATP, consistent with intracellular consumption and/or extracellular export. Poly-ADP-ribosylated proteins detected in the nuclear fractions of MDDCs did not show major changes upon zymosan stimulation, which suggests its dependence on constitutive Fe(II)/2-oxoglutarate-dependent demethylation of 5-methylcytosine by TET translocases and/or demethylation of histone H3 lysine 27 by JMJD demethylases rather than on NOX activities. These results disclose a unique pattern of central carbon metabolism following fungal challenge, characterized by the leverage of glycolysis offshoots and an extensive recycling of NAD+ and poly(ADP-ribose).

Prognostic value and potential function of a novel heme-related LncRNAs signature in gastric cancer

Heme is a coordination complex formed by the binding of iron ions and porphyrin rings. Its metabolic processes are associated with various cancers, including gastric cancer (GC). In recent years, long non-coding RNAs (LncRNAs) have been identified as key regulatory factors in GC. However, the role of LncRNAs associated with heme metabolism in GC and their relationship with prognosis have not been reported. In this study, we constructed a novel LncRNAs signature related to heme metabolism (HMlncSig) and validated its prognostic value for predicting the survival of GC patients through training, test, and entire cohorts. Kaplan-Meier analysis demonstrated that patients in the high-risk group had shorter survival times. Univariate and multivariate Cox regression analysis showed that HMlncSig was an independent prognostic indicator for GC patients, regardless of other clinical pathological features. Gene ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis and gene set variation analysis pathways showed that the activation of these markers may be involved in tumor progression, influencing the survival of GC patients. The nomogram, based on HMlncSig score and clinical features, demonstrated the strong predictive ability of this signature. Additionally, significant differences were observed between the high-risk and low-risk groups in terms of immune cell subtypes, expression of immune checkpoint genes, and response to chemotherapy and immunotherapy. Through clinical validation, we found that the risk score and heme levels of GC patients were both significantly elevated and correlated with the degree of malignancy. Furthermore, we found that AP000692.1, a key gene in this signature, promoted the proliferation, migration, and invasion of GC cells. In conclusion, our HMlncSig model has significant predictive value for the prognosis of GC patients and can provide clinical guidance for personalized immunotherapy.

The gluconeogenesis enzyme PCK2 has a non-enzymatic role in proteostasis in endothelial cells

Endothelial cells (ECs) are highly glycolytic, but whether they generate glycolytic intermediates via gluconeogenesis (GNG) in glucose-deprived conditions remains unknown. Here, we report that glucose-deprived ECs upregulate the GNG enzyme PCK2 and rely on a PCK2-dependent truncated GNG, whereby lactate and glutamine are used for the synthesis of lower glycolytic intermediates that enter the serine and glycerophospholipid biosynthesis pathways, which can play key roles in redox homeostasis and phospholipid synthesis, respectively. Unexpectedly, however, even in normal glucose conditions, and independent of its enzymatic activity, PCK2 silencing perturbs proteostasis, beyond its traditional GNG role. Indeed, PCK2-silenced ECs have an impaired unfolded protein response, leading to accumulation of misfolded proteins, which due to defective proteasomes and impaired autophagy, results in the accumulation of protein aggregates in lysosomes and EC demise. Ultimately, loss of PCK2 in ECs impaired vessel sprouting. This study identifies a role for PCK2 in proteostasis beyond GNG.

Serine synthesis controls mitochondrial biogenesis in macrophages

Mitochondrial dysfunction is the pivotal driving factor of multiple inflammatory diseases, and targeting mitochondrial biogenesis represents an efficacious approach to ameliorate such dysfunction in inflammatory diseases. Here, we demonstrated that phosphoglycerate dehydrogenase (PHGDH) deficiency promotes mitochondrial biogenesis in inflammatory macrophages. Mechanistically, PHGDH deficiency boosts mitochondrial reactive oxygen species (mtROS) by suppressing cytoplasmic glutathione synthesis. mtROS provokes hypoxia-inducible factor-1α signaling to direct nuclear specificity protein 1 and nuclear respiratory factor 1 transcription. Moreover, myeloid Phgdh deficiency reverses diet-induced obesity. Collectively, this study reveals that a mechanism involving de novo serine synthesis orchestrates mitochondrial biogenesis via mitochondrial-to-nuclear communication, and provides a potential therapeutic target for tackling inflammatory diseases and mitochondria-mediated diseases.

Targeting PHGDH reverses the immunosuppressive phenotype of tumor-associated macrophages through α-ketoglutarate and mTORC1 signaling

Phosphoglycerate dehydrogenase (PHGDH) has emerged as a crucial factor in macromolecule synthesis, neutralizing oxidative stress, and regulating methylation reactions in cancer cells, lymphocytes, and endothelial cells. However, the role of PHGDH in tumor-associated macrophages (TAMs) is poorly understood. Here, we found that the T helper 2 (Th2) cytokine interleukin-4 and tumor-conditioned media upregulate the expression of PHGDH in macrophages and promote immunosuppressive M2 macrophage activation and proliferation. Loss of PHGDH disrupts cellular metabolism and mitochondrial respiration, which are essential for immunosuppressive macrophages. Mechanistically, PHGDH-mediated serine biosynthesis promotes α-ketoglutarate production, which activates mTORC1 signaling and contributes to the maintenance of an M2-like macrophage phenotype in the tumor microenvironment. Genetic ablation of PHGDH in macrophages from tumor-bearing mice results in attenuated tumor growth, reduced TAM infiltration, a phenotypic shift of M2-like TAMs toward an M1-like phenotype, downregulated PD-L1 expression and enhanced antitumor T-cell immunity. Our study provides a strong basis for further exploration of PHGDH as a potential target to counteract TAM-mediated immunosuppression and hinder tumor progression.

Decoding Serine Metabolism: Unveiling Novel Pathways for Evolving Cancer Therapies

Serine metabolism plays a pivotal role in cancer, making it an appealing therapeutic target. Two recent studies published in Nature Metabolism and Science Translational Medicine uncovered novel players and therapeutic opportunities within this crucial metabolic pathway. Papalazarou and colleagues employed genetic tools coupled with metabolomics and high-throughput imaging to identify and characterize membrane transporters involved in serine uptake and mitochondrial import in colorectal cancer. Notably, they showed that dual inhibition of these transporters in combination with impaired serine biosynthesis reduced tumor growth in xenograft models. In a parallel study, Zhang and colleagues identified isocitrate dehydrogenase I (IDH1) as a novel regulator of serine biosynthesis in non-small cell lung cancer. Through extensive mechanistic studies, they demonstrated that IDH1 enhances the expression of the key enzymes phosphoglycerate dehydrogenase and phosphoserine aminotransferase 1 via a noncanonical function independent of its enzymatic activity. Strikingly, pharmacologic disruption of this novel function of IDH1 not only diminished tumor growth but also enhanced the anticancer efficacy of dietary serine restriction in mouse models of lung cancer. Together, these studies advance our mechanistic understanding of how cancer cells fulfill their serine requirements and reveal innovative therapeutic avenues to deprive tumors of this vital nutrient.

TIE2 expression in hypertensive ICH and its therapeutic modulation with AKB-9778: Implications for brain vascular health

Hypertensive intracerebral hemorrhage (ICH) is a devastating condition, the molecular underpinnings of which remain not fully understood. By leveraging high-throughput transcriptome sequencing and network pharmacology analysis, this study unveils the significant role of the tyrosine kinase with immunoglobulin-like and EGF-like domains 2 (TIE2) in ICH pathogenesis. Compared to controls, a conspicuous downregulation of TIE2 was observed in the cerebral blood vessels of hypertensive ICH mice. In vitro assays with human brain microvascular endothelial cells (HBMEC), HBEC-5i revealed that modulation of TIE2 expression significantly influences cellular proliferation, migration, and angiogenesis, mediated via the Rap1/MEK/ERK signaling pathway. Notably, the small molecule AKB-9778 was identified to target and activate TIE2, affecting the functional attributes of HBEC-5i. In vivo experiments further demonstrated that combining AKB-9778 with antihypertensive drugs could mitigate the incidence and volume of bleeding in hypertensive ICH mouse models, suggesting potential therapeutic implications.

Serine Metabolism Regulates the Replicative Senescence of Human Dental Pulp Cells through Histone Methylation

Tissue regeneration therapy based on human dental pulp cells (hDPCs) faces the distinct challenge of cellular senescence during massive expansion in vitro. To further explore the regulatory mechanism of cellular senescence in hDPCs, we conduct experiments on young cells (Passage 5, P5) and replicative senescent (Passage 12, P12) hDPCs. The results confirm that hDPCs undergo replicative senescence with passaging, during which their ability to proliferate and osteogenic differentiation decreases. Notably, during replicative senescence, phosphoglycerate dehydrogenase (PHGDH), the key enzyme of the serine synthesis pathway (SSP), is significantly downregulated, as well as S-adenosylmethionine (SAM) levels, resulting in reduced H3K36me3 modification on Sirtuin 1 (SIRT1)and Runt-related transcription factor 2 (RUNX2) promoters. Inhibition of PHGDH leads to the same phenotype as replicative senescence. Serine supplementation fails to rescue the senescence phenotype caused by replicative senescence and inhibitors, in which folate metabolism-related genes, including serine hydroxymethyl transferase 2 (SHMT2), methylenetetrahydrofolate dehydrogenase 1(MTHFD1), methylenetetrahydrofolate dehydrogenase 2(MTHFD2), are notably decreased. Our research raised a possibility that PHGDH may be involved in cellular senescence by affecting folate metabolism and histone methylation in addition to serine biosynthesis, providing potential targets to prevent senescence.

A comprehensive review on signaling attributes of serine and serine metabolism in health and disease

Serine is a metabolite with ever-expanding metabolic and non-metabolic signaling attributes. By providing one‑carbon units for macromolecule biosynthesis and functional modifications, serine and serine metabolism largely impinge on cellular survival and function. Cancer cells frequently have a preference for serine metabolic reprogramming to create a conducive metabolic state for survival and aggressiveness, making intervention of cancer-associated rewiring of serine metabolism a promising therapeutic strategy for cancer treatment. Beyond providing methyl donors for methylation in modulation of innate immunity, serine metabolism generates formyl donors for mitochondrial tRNA formylation which is required for mitochondrial function. Interestingly, fully developed neurons lack the machinery for serine biosynthesis and rely heavily on astrocytic l-serine for production of d-serine to shape synaptic plasticity. Here, we recapitulate recent discoveries that address the medical significance of serine and serine metabolism in malignancies, mitochondrial-associated disorders, and neurodegenerative pathologies. Metabolic control and epigenetic- and posttranslational regulation of serine metabolism are also discussed. Given the metabolic similarities between cancer cells, neurons and germ cells, we further propose the relevance of serine metabolism in testicular homeostasis. Our work provides valuable hints for future investigations that will lead to a deeper understanding of serine and serine metabolism in cellular physiology and pathology.

Multi-omics analysis reveals GAPDH posttranscriptional regulation of IFN-γ and PHGDH as a metabolic checkpoint of microglia polarization

A "switch" in the metabolic pattern of microglia is considered to be required to meet the metabolic demands of cell survival and functions. However, how metabolic switches regulate microglial function remains controversial. We found here that exposure to amyloid-β triggers microglial inflammation accompanied by increasing GAPDH levels. The increase of GAPDH, a glycolysis enzyme, leads to the reduced release of interferon-γ (IFN-γ) from inflammatory microglia. Such alternation is translational and is regulated by the binding of glycolysis enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) to IFN-γ mRNA. GAPDH, by engaging/disengaging glycolysis and through influencing IFN-γ expression, regulates microglia functions, including phagocytosis and cytokine production. Phosphoglycerate dehydrogenase (PHGDH), screened from different state microglia by metabolomics combined with METARECON analysis, is a metabolic enzyme adjacent downstream of GAPDH and synthesizes serine on the collateral pathway derived from glycolysis. Polarization of microglial with PHGDH as a metabolic checkpoint can be bidirectionally regulated by adding IL-4 or giving PHGDH inhibitors. Therefore, regulation of metabolic enzymes not only reprograms metabolic patterns, but also manipulates microglia functions. Further study should be performed to explore the mechanism of metabolic checkpoints in human microglia or more in vivo animal experiments, and may expand to the effects of various metabolic substrates or enzyme, such as lipids and amino acids, on the functions of microglia.

ZSWIM4 inhibition improves chemosensitivity in epithelial ovarian cancer cells by suppressing intracellular glycine biosynthesis

BACKGROUND

Zinc finger SWIM-type containing 4 (ZSWIM4) induces drug resistance in breast cancer cells. However, its role in epithelial ovarian cancer (EOC) remains unknown. In this study, we aimed to investigate the clinical significance of ZSWIM4 expression in EOC and develop new clinical therapeutic strategies for EOC.

METHODS

ZSWIM4 expression in control and EOC tumor tissues was examined using immunohistochemistry. Lentiviral transduction, Cell Counting Kit-8 assay, tumorsphere formation assay, flow cytometry, western blotting, and animal xenograft model were used to assess the role of ZSWIM4 in chemotherapy. Cleavage Under Targets and Tagmentation (CUT&Tag) assays, chromatin immunoprecipitation assays, and luciferase reporter assays were used to confirm FOXK1-mediated upregulation of ZSWIM4 expression. The mechanism by which ZSWIM4 inhibition improves chemosensitivity was evaluated using RNA-sequencing. A ZSWIM4-targeting inhibitor was explored by virtual screening and surface plasmon resonance analysis. Patient-derived organoid (PDO) models were constructed from EOC tumor tissues with ZSWIM4 expression.

RESULTS

ZSWIM4 was overexpressed in EOC tumor tissues and impaired patient prognoses. Its expression correlated positively with EOC recurrence. ZSWIM4 expression was upregulated following carboplatin treatment, which, in turn, contributed to chemoresistance. Silencing ZSWIM4 expression sensitized EOC cells to carboplatin treatment in vitro and in vivo. FOXK1 could bind to the GTAAACA sequence of the ZSWIM4 promoter region to upregulate ZSWIM4 transcriptional activity and FOXK1 expression increased following carboplatin treatment, leading to an increase in ZSWIM4 expression. Mechanistically, ZSWIM4 knockdown downregulated the expression of several rate-limiting enzymes involved in glycine synthesis, causing a decrease in intracellular glycine levels, thus enhancing intracellular reactive oxygen species production induced by carboplatin treatment. Compound IPN60090 directly bound to ZSWIM4 protein and exerted a significant chemosensitizing effect in both EOC cells and PDO models.

CONCLUSIONS

ZSWIM4 inhibition enhanced EOC cell chemosensitivity by ameliorating intracellular glycine metabolism reprogramming, thus providing a new potential therapeutic strategy for EOC.

FLVCR1a Controls Cellular Cholesterol Levels through the Regulation of Heme Biosynthesis and Tricarboxylic Acid Cycle Flux in Endothelial Cells

Feline leukemia virus C receptor 1a (FLVCR1a), initially identified as a retroviral receptor and localized on the plasma membrane, has emerged as a crucial regulator of heme homeostasis. Functioning as a positive regulator of δ-aminolevulinic acid synthase 1 (ALAS1), the rate-limiting enzyme in the heme biosynthetic pathway, FLVCR1a influences TCA cycle cataplerosis, thus impacting TCA flux and interconnected metabolic pathways. This study reveals an unexplored link between FLVCR1a, heme synthesis, and cholesterol production in endothelial cells. Using cellular models with manipulated FLVCR1a expression and inducible endothelial-specific Flvcr1a-null mice, we demonstrate that FLVCR1a-mediated control of heme synthesis regulates citrate availability for cholesterol synthesis, thereby influencing cellular cholesterol levels. Moreover, alterations in FLVCR1a expression affect membrane cholesterol content and fluidity, supporting a role for FLVCR1a in the intricate regulation of processes crucial for vascular development and endothelial function. Our results underscore FLVCR1a as a positive regulator of heme synthesis, emphasizing its integration with metabolic pathways involved in cellular energy metabolism. Furthermore, this study suggests that the dysregulation of heme metabolism may have implications for modulating lipid metabolism. We discuss these findings in the context of FLVCR1a's potential heme-independent function as a choline importer, introducing additional complexity to the interplay between heme and lipid metabolism.

Serine synthesis pathway enzyme PHGDH is critical for muscle cell biomass, anabolic metabolism, and mTORC1 signaling

Cells use glycolytic intermediates for anabolism, e.g., via the serine synthesis and pentose phosphate pathways. However, we still understand poorly how these metabolic pathways contribute to skeletal muscle cell biomass generation. The first aim of this study was therefore to identify enzymes that limit protein synthesis, myotube size, and proliferation in skeletal muscle cells. We inhibited key enzymes of glycolysis, the pentose phosphate pathway, and the serine synthesis pathway to evaluate their importance in C2C12 myotube protein synthesis. Based on the results of this first screen, we then focused on the serine synthesis pathway enzyme phosphoglycerate dehydrogenase (PHGDH). We used two different PHGDH inhibitors and mouse C2C12 and human primary muscle cells to study the importance and function of PHGDH. Both myoblasts and myotubes incorporated glucose-derived carbon into proteins, RNA, and lipids, and we showed that PHGDH is essential in these processes. PHGDH inhibition decreased protein synthesis, myotube size, and myoblast proliferation without cytotoxic effects. The decreased protein synthesis in response to PHGDH inhibition appears to occur mainly mechanistic target of rapamycin complex 1 (mTORC1)-dependently, as was evident from experiments with insulin-like growth factor 1 and rapamycin. Further metabolomics analyses revealed that PHGDH inhibition accelerated glycolysis and altered amino acid, nucleotide, and lipid metabolism. Finally, we found that supplementing an antioxidant and redox modulator, N-acetylcysteine, partially rescued the decreased protein synthesis and mTORC1 signaling during PHGDH inhibition. The data suggest that PHGDH activity is critical for skeletal muscle cell biomass generation from glucose and that it regulates protein synthesis and mTORC1 signaling.NEW & NOTEWORTHY The use of glycolytic intermediates for anabolism was demonstrated in both myoblasts and myotubes, which incorporate glucose-derived carbon into proteins, RNA, and lipids. We identify phosphoglycerate dehydrogenase (PHGDH) as a critical enzyme in those processes and also for muscle cell hypertrophy, proliferation, protein synthesis, and mTORC1 signaling. Our results thus suggest that PHGDH in skeletal muscle is more than just a serine-synthesizing enzyme.

Serine metabolism in macrophage polarization

OBJECTIVE

Emerging studies have revealed that macrophages possess different dependences on the uptake, synthesis, and metabolism of serine for their activation and functionalization, necessitating our insight into how serine availability and utilization impact macrophage activation and inflammatory responses.

METHODS

This article summarizes the reports published domestically and internationally about the serine uptake, synthesis, and metabolic flux by the macrophages polarizing with distinct stimuli and under different pathologic conditions, and particularly analyzes how altered serine metabolism rewires the metabolic behaviors of polarizing macrophages and their genetic and epigenetic reprogramming.

RESULTS

Macrophages dynamically change serine metabolism to orchestrate their anabolism, redox balance, mitochondrial function, epigenetics, and post-translation modification, and thus match the distinct needs for both classical and alternative activation.

CONCLUSION

Serine metabolism coordinates multiple metabolic pathways to tailor macrophage polarization and their responses to different pathogenic attacks and thus holds the potential as therapeutic target for types of acute and chronic inflammatory diseases.

Molecular and metabolic orchestration of the lymphatic vasculature in physiology and pathology

Lymphangiogenesis refers to the generation of new lymphatic vessels from pre-existing ones. During development and particular adult states, lymphatic endothelial cells (LEC) undergo reprogramming of their transcriptomic and signaling networks to support the high demands imposed by cell proliferation and migration. Although there has been substantial progress in identifying growth factors and signaling pathways controlling lymphangiogenesis in the last decades, insights into the role of metabolism in lymphatic cell functions are just emerging. Despite numerous similarities between the main metabolic pathways existing in LECs, blood ECs (BEC) and other cell types, accumulating evidence has revealed that LECs acquire a unique metabolic signature during lymphangiogenesis, and their metabolic engine is intertwined with molecular regulatory networks, resulting in a tightly regulated and interconnected process. Considering the implication of lymphatic dysfunction in cancer and lymphedema, alongside other pathologies, recent findings hold promising opportunities to develop novel therapeutic approaches. In this review, we provide an overview of the status of knowledge in the molecular and metabolic network regulating the lymphatic vasculature in health and disease.

Lycorine eliminates B-cell acute lymphoblastic leukemia cells by targeting PSAT1 through the serine/glycine metabolic pathway

B-cell acute lymphoblastic leukemia (B-ALL) has been confirmed as the most common malignant hematologic neoplasm among children. A novel antitumor mechanism of lycorine was elucidated in this study. As revealed by the result of this study, lycorine significantly inhibited the growth and proliferation of REH and NALM-6 and induced their apoptosis. The result of the RNA-seq analysis suggested that lycorine targeted PSAT1 of serine/glycine metabolism in B-ALL cells. As indicated by the result of the GSEA analysis, the genes enriched in the amino acid metabolic pathways were down-regulated by lycorine. As revealed by the results of ectopic expression, shRNA knockdown assays, and further liquid-phase tandem mass spectrometry (LC-MS) analysis, lycorine reduced serine/glycine metabolites by down-regulating PSAT1, further disrupting carbon metabolism and eliminating B-ALL cells. Furthermore, lycorine showed a synergistic effect with cytarabine in ALL treatments. Lastly, lycorine significantly down-regulated leukemia progression in the cell line-derived xenograft (CDX) model. In brief, this study has suggested for the first time that lycorine is a promising anti-ALL drug, and a novel amino acid metabolism-associated property of lycorine was identified.

Myotube growth is associated with cancer-like metabolic reprogramming and is limited by phosphoglycerate dehydrogenase

The Warburg effect links growth and glycolysis in cancer. A key purpose of the Warburg effect is to generate glycolytic intermediates for anabolic reactions, such as nucleotides → RNA/DNA and amino acids → protein synthesis. The aim of this study was to investigate whether a similar 'glycolysis-for-anabolism' metabolic reprogramming also occurs in hypertrophying skeletal muscle. To interrogate this, we first induced C2C12 myotube hypertrophy with IGF-1. We then added 14C glucose to the differentiation medium and measured radioactivity in isolated protein and RNA to establish whether 14C had entered anabolism. We found that especially protein became radioactive, suggesting a glucose → glycolytic intermediates → non-essential amino acid(s) → protein series of reactions, the rate of which was increased by IGF-1. Next, to investigate the importance of glycolytic flux and non-essential amino acid synthesis for myotube hypertrophy, we exposed C2C12 and primary mouse myotubes to the glycolysis inhibitor 2-Deoxy-d-glucose (2DG). We found that inhibiting glycolysis lowered C2C12 and primary myotube size. Similarly, siRNA silencing of PHGDH, the key enzyme of the serine biosynthesis pathway, decreased C2C12 and primary myotube size; whereas retroviral PHGDH overexpression increased C2C12 myotube size. Together these results suggest that glycolysis is important for hypertrophying myotubes, which reprogram their metabolism to facilitate anabolism, similar to cancer cells.

Dietary fat and lipid metabolism in the tumor microenvironment

Metabolic reprogramming has been considered a core hallmark of cancer, in which excessive accumulation of lipids promote cancer initiation, progression and metastasis. Lipid metabolism often includes the digestion and absorption of dietary fat, and the ways in which cancer cells utilize lipids are often influenced by the complex interactions within the tumor microenvironment. Among multiple cancer risk factors, obesity has a positive association with multiple cancer types, while diets like calorie restriction and fasting improve health and delay cancer. Impact of these diets on tumorigenesis or cancer prevention are generally studied on cancer cells, despite heterogeneity of the tumor microenvironment. Cancer cells regularly interact with these heterogeneous microenvironmental components, including immune and stromal cells, to promote cancer progression and metastasis, and there is an intricate metabolic crosstalk between these compartments. Here, we focus on discussing fat metabolism and response to dietary fat in the tumor microenvironment, focusing on both immune and stromal components and shedding light on therapeutic strategies surrounding lipid metabolic and signaling pathways.

Integrative Analysis of Transcriptomic and Lipidomic Profiles Reveals a Differential Subcutaneous Adipose Tissue Mechanism among Ningxiang Pig and Berkshires, and Their Offspring

Adipose tissue composition contributes greatly to the quality and nutritional value of meat. Transcriptomic and lipidomic techniques were used to investigate the molecular mechanisms of the differences in fat deposition in Ningxiang pigs, Berkshires and F1 offspring. Transcriptomic analysis identified 680, 592, and 380 DEGs in comparisons of Ningxiang pigs vs. Berkshires, Berkshires vs. F1 offspring, and Ningxiang pigs vs. F1 offspring. The lipidomic analysis screened 423, 252, and 50 SCLs in comparisons of Ningxiang pigs vs. Berkshires, Berkshires vs. F1 offspring, and Ningxiang pigs vs. F1 offspring. Lycine, serine, and the threonine metabolism pathway, fatty acid biosynthesis and metabolism-related pathways were significantly enriched in comparisons of Berkshires vs. Ningxiang pigs and Berkshires vs. F1 offspring. The DEGs (PHGDH, LOC110256000) and the SCLs (phosphatidylserines) may have a great impact on the glycine, serine, and the threonine metabolism pathway. Moreover, the DEGs (FASN, ACACA, CBR4, SCD, ELOV6, HACD2, CYP3A46, CYP2B22, GPX1, and GPX3) and the SCLs (palmitoleic acid, linoleic acid, arachidonic acid, and icosadienoic acid) play important roles in the fatty acid biosynthesis and metabolism of fatty acids. Thus, the difference in fat deposition among Ningxiang pig, Berkshires, and F1 offspring may be caused by differences in the expression patterns of key genes in multiple enriched KEGG pathways. This research revealed multiple lipids that are potentially available biological indicators and screened key genes that are potential targets for molecular design breeding. The research also explored the molecular mechanisms of the difference in fat deposition among Ningxiang pig, Berkshires, and F1 pigs, and provided an insight into selection for backfat thickness and the fat composition of adipose tissue for future breeding strategies.

New insights in the targets of action of dimethyl fumarate in endothelial cells: effects on energetic metabolism and serine synthesis in vitro and in vivo

Dimethyl fumarate is an ester from the Krebs cycle intermediate fumarate. This drug is approved and currently used for the treatment of psoriasis and multiple sclerosis, and its anti-angiogenic activity was reported some years ago. Due to the current clinical relevance of this compound and the recently manifested importance of endothelial cell metabolism on the angiogenic switch, we wanted to elucidate whether dimethyl fumarate has an effect on energetic metabolism of endothelial cells. Different experimental approximations were performed in endothelial cells, including proteomics, isotope tracing and metabolomics experimental approaches, in this work we studied the possible role of dimethyl fumarate in endothelial cell energetic metabolism. We demonstrate for the first time that dimethyl fumarate promotes glycolysis and diminishes cell respiration in endothelial cells, which could be a consequence of a down-regulation of serine and glycine synthesis through inhibition of PHGDH activity in these cells. Dimethyl fumarate alters the energetic metabolism of endothelial cells in vitro and in vivo through an unknown mechanism, which could be the cause or the consequence of its pharmacological activity. This new discovery on the targets of this compound could open a new field of study regarding the mechanism of action of dimethyl fumarate.

Postnatal hyperglycemia alters amino acid profile in retinas (model of Phase I ROP)

Nutritional deprivation occurring in most preterm infants postnatally can induce hyperglycemia, a significant and independent risk factor for suppressing physiological retinal vascularization (Phase I retinopathy of prematurity (ROP)), leading to compensatory but pathological neovascularization. Amino acid supplementation reduces retinal neovascularization in mice. Little is known about amino acid contribution to Phase I ROP. In mice modeling hyperglycemia-associated Phase I ROP, we found significant changes in retinal amino acids (including most decreased L-leucine, L-isoleucine, and L-valine). Parenteral L-isoleucine suppressed physiological retinal vascularization. In premature infants, severe ROP was associated with a higher mean intake of parenteral versus enteral amino acids in the first two weeks of life after adjustment for treatment group, gestational age at birth, birth weight, and sex. The number of days with parenteral amino acids support independently predicted severe ROP. Further understanding and modulating amino acids may help improve nutritional intervention and prevent Phase I ROP.

Beyond energy and growth: the role of metabolism in developmental signaling, cell behavior and diapause

Metabolism is crucial for development through supporting cell growth, energy production, establishing cell identity, developmental signaling and pattern formation. In many model systems, development occurs alongside metabolic transitions as cells differentiate and specialize in metabolism that supports new functions. Some cells exhibit metabolic flexibility to circumvent mutations or aberrant signaling, whereas other cell types require specific nutrients for developmental progress. Metabolic gradients and protein modifications enable pattern formation and cell communication. On an organism level, inadequate nutrients or stress can limit germ cell maturation, implantation and maturity through diapause, which slows metabolic activities until embryonic activation under improved environmental conditions.

Multifaceted roles of mitochondria in wound healing and chronic wound pathogenesis

Mitochondria are intracellular organelles that play a critical role in numerous cellular processes including the regulation of metabolism, cellular stress response, and cell fate. Mitochondria themselves are subject to well-orchestrated regulation in order to maintain organelle and cellular homeostasis. Wound healing is a multifactorial process that involves the stringent regulation of several cell types and cellular processes. In the event of dysregulated wound healing, hard-to-heal chronic wounds form and can place a significant burden on healthcare systems. Importantly, treatment options remain limited owing to the multifactorial nature of chronic wound pathogenesis. One area that has received more attention in recent years is the role of mitochondria in wound healing. With regards to this, current literature has demonstrated an important role for mitochondria in several areas of wound healing and chronic wound pathogenesis including metabolism, apoptosis, and redox signalling. Additionally, the influence of mitochondrial dynamics and mitophagy has also been investigated. However, few studies have utilised patient tissue when studying mitochondria in wound healing, instead using various animal models. In this review we dissect the current knowledge of the role of mitochondria in wound healing and discuss how future research can potentially aid in the progression of wound healing research.

Serine Metabolic Reprogramming in Tumorigenesis, Tumor Immunity, and Clinical Treatment

Serine has been recently identified as an essential metabolite for oncogenesis, progression, and adaptive immunity. Influenced by many physiologic or tumor environmental factors, the metabolic pathways of serine synthesis, uptake, and usage are heterogeneously reprogrammed and frequently amplified in tumor or tumor-associated cells. The hyperactivation of serine metabolism promotes abnormal cellular nucleotide/protein/lipid synthesis, mitochondrial function, and epigenetic modifications, which drive malignant transformation, unlimited proliferation, metastasis, immunosuppression, and drug resistance of tumor cells. Dietary restriction of serine or phosphoglycerate dehydrogenase depletion mitigates tumor growth and extends the survival of tumor patients. Correspondingly, these findings triggered a boom in the development of novel therapeutic agents targeting serine metabolism. In this study, recent discoveries in the underlying mechanism and cellular function of serine metabolic reprogramming are summarized. The vital role of serine metabolism in oncogenesis, tumor stemness, tumor immunity, and therapeutic resistance is outlined. Finally, some potential tumor therapeutic concepts, strategies, and limitations of targeting the serine metabolic pathway are described in detail. Taken together, this review underscores the importance of serine metabolic reprogramming in tumorigenesis and progression and highlights new opportunities for dietary restriction or selective pharmacologic intervention.

Sources and Sinks of Serine in Nutrition, Health, and Disease

Amino acid dysregulation has emerged as an important driver of disease progression in various contexts. l-Serine lies at a central node of metabolism, linking carbohydrate metabolism, transamination, glycine, and folate-mediated one-carbon metabolism to protein synthesis and various downstream bioenergetic and biosynthetic pathways. l-Serine is produced locally in the brain but is sourced predominantly from glycine and one-carbon metabolism in peripheral tissues via liver and kidney metabolism. Compromised regulation or activity of l-serine synthesis and disposal occurs in the context of genetic diseases as well as chronic disease states, leading to low circulating l-serine levels and pathogenesis in the nervous system, retina, heart, and aging muscle. Dietary interventions in preclinical models modulate sensory neuropathy, retinopathy, tumor growth, and muscle regeneration. A serine tolerance test may provide a quantitative readout of l-serine homeostasis that identifies patients who may be susceptible to neuropathy or responsive to therapy.

Endothelial cells require functional FLVCR1a during developmental and adult angiogenesis

The Feline Leukemia Virus Subgroup C Receptor 1a (FLVCR1a) is a transmembrane heme exporter essential for embryonic vascular development. However, the exact role of FLVCR1a during blood vessel development remains largely undefined. Here, we show that FLVCR1a is highly expressed in angiogenic endothelial cells (ECs) compared to quiescent ECs. Consistently, ECs lacking FLVCR1a give rise to structurally and functionally abnormal vascular networks in multiple models of developmental and pathologic angiogenesis. Firstly, zebrafish embryos without FLVCR1a displayed defective intersegmental vessels formation. Furthermore, endothelial-specific Flvcr1a targeting in mice led to a reduced radial expansion of the retinal vasculature associated to decreased EC proliferation. Moreover, Flvcr1a null retinas showed defective vascular organization and loose attachment of pericytes. Finally, adult neo-angiogenesis is severely affected in murine models of tumor angiogenesis. Tumor blood vessels lacking Flvcr1a were disorganized and dysfunctional. Collectively, our results demonstrate the critical role of FLVCR1a as a regulator of developmental and pathological angiogenesis identifying FLVCR1a as a potential therapeutic target in human diseases characterized by aberrant neovascularization.

PHGDH promotes esophageal squamous cell carcinoma progression via Wnt/β-catenin pathway

PURPOSE

Esophageal squamous carcinoma (ESCC) with a high incidence in China, lacks effective therapeutic targets. Phosphoglycerate dehydrogenase (PHGDH) is a key enzyme in serine biosynthesis. However, the biological role of PHGDH in ESCC has not been revealed.

METHODS

The expression of PHGDH in ESCC was investigated by UALCAN. The relationship between PHGDH expression and its prognostic value was analyzed by Kaplan-Meier and univariate Cox regression. Further, the potential functions of PHGDH involved in ESCC were explored through DAVID database and GSEA software. In addition, the expression of PHGDH was verified in ESCC. Then, the effects of PHGDH knockdown on ESCC were evaluated in vitro and in vivo by cell proliferation, clone formation, cell cycle, apoptosis, tube formation assays and ESCC cells derived xenograft model. In addition, western blotting and immunohistochemistry were used to detect the expression of Wnt/β-catenin pathway which was associated with PHGDH.

RESULTS

Bioinformatics analysis found that PHGDH was highly expressed in ESCC, and meaningfully, patients with high PHGDH expression had a poor prognosis. Moreover, the overexpression of PHGDH was verified in ESCC. Afterwards, PHGDH knockdown inhibited the cell proliferation, induced cell cycle arrest and apoptosis in ESCC cells, and inhibited the angiogenesis of HUVECs induced by ESCC conditioned medium, as well as inhibited the growth of xenograft tumor. Mechanistically, PHGDH knockdown inhibited Wnt/β-catenin signaling pathway in ESCC.

CONCLUSION

High expression of PHGDH predicts a poor prognosis for ESCC. PHGDH knockdown inhibits ESCC progression by suppressing Wnt/β-catenin signaling pathway, indicating that PHGDH might be a potential target for ESCC therapy.