bims-glucam Biomed News
on Glutamine cancer metabolism
Issue of 2023‒08‒20
fifteen papers selected by
Sreeparna Banerjee
Middle East Technical University
  1. YAP governs cellular adaptation to perturbation of glutamine metabolism by regulating ATF4-mediated stress response.
  2. Glutamine metabolism in diseases associated with mitochondrial dysfunction.
  3. Co-inhibition of glutaminolysis and one-carbon metabolism promotes ROS accumulation leading to enhancement of chemotherapeutic efficacy in anaplastic thyroid cancer.
  4. FASN deficiency induces a cytosol-to-mitochondria citrate flux to mitigate detachment-induced oxidative stress.
  5. Loss of RACK1 promotes glutamine addiction via activating AKT/mTOR/ASCT2 axis to facilitate tumor growth in gastric cancer.
  6. m5C-methylated lncRNA NR_033928 promotes gastric cancer proliferation by stabilizing GLS mRNA to promote glutamine metabolism reprogramming.
  7. Loss of CD4+ T cell-intrinsic arginase 1 accelerates Th1 response kinetics and reduces lung pathology during influenza infection.
  8. Glutamine production by Glul promotes thermogenic adipocyte differentiation through Prdm9-mediated H3K4me3 and transcriptional reprogramming.
  9. Modulating the polyamine-hypusine axis controls generation of CD8+ tissue resident memory T cells.
  10. Recent advances microRNAs and metabolic reprogramming in colorectal cancer research.
  11. Characterizing cancer metabolism from bulk and single-cell RNA-seq data using METAFlux.
  12. Effects of glutamine, glutamate, and aspartate on intestinal barrier integrity and amino acid pool of the small intestine in piglets with normal or low energy diet.
  13. Hyperpolarized [1-13C]Acetyl-l-Carnitine Probes Tricarboxylic Acid Cycle Activity In Vivo.
  14. Assessment of histologic risk factors for hepatocellular carcinoma in patients with chronic hepatitis B of advanced stage.
  15. Paclitaxel Induces Neurotoxicity by Disrupting Tricarboxylic Acid Cycle Metabolic Balance in the Mouse Hippocampus.
  1. Oncogene. 2023 Aug 17.
    YAP governs cellular adaptation to perturbation of glutamine metabolism by regulating ATF4-mediated stress response.
    Minjoong Kim, Sunsook Hwang, Byungjoo Kim, Seungmin Shin, Seungyeon Yang, Jihye Gwak, Seung Min Jeong.
      Proliferating cells have metabolic dependence on glutamine to fuel anabolic pathways and to refill the mitochondrial carbon pool. The Hippo pathway is essential for coordinating cell survival and growth with nutrient availability, but no molecular connection to glutamine deprivation has been reported. Here, we identify a non-canonical role of YAP, a key effector of the Hippo pathway, in cellular adaptation to perturbation of glutamine metabolism. Whereas YAP is inhibited by nutrient scarcity, enabling cells to restrain proliferation and to maintain energy homeostasis, glutamine shortage induces a rapid YAP dephosphorylation and activation. Upon glutaminolysis inhibition, an increased reactive oxygen species production inhibits LATS kinase via RhoA, leading to YAP dephosphorylation. Activated YAP promotes transcriptional induction of ATF4 to induce the expression of genes involved in amino acid homeostasis, including Sestrin2. We found that YAP-mediated Sestrin2 induction is crucial for cell viability during glutamine deprivation by suppressing mTORC1. Thus, a critical relationship between YAP, ATF4, and mTORC1 is uncovered by our findings. Finally, our data indicate that targeting the Hippo-YAP pathway in combination with glutaminolysis inhibition may provide potential therapeutic approaches to treat tumors.
    DOI:  https://doi.org/10.1038/s41388-023-02811-6
  2. Mol Cell Neurosci. 2023 Aug 15. pii: S1044-7431(23)00081-7. [Epub ahead of print]126 103887
    Glutamine metabolism in diseases associated with mitochondrial dysfunction.
    Rebecca Bornstein, Michael T Mulholland, Margaret Sedensky, Phil Morgan, Simon C Johnson.
      Mitochondrial dysfunction can arise from genetic defects or environmental exposures and impact a wide range of biological processes. Among these are metabolic pathways involved in glutamine catabolism, anabolism, and glutamine-glutamate cycling. In recent years, altered glutamine metabolism has been found to play important roles in the pathologic consequences of mitochondrial dysfunction. Glutamine is a pleiotropic molecule, not only providing an alternate carbon source to glucose in certain conditions, but also playing unique roles in cellular communication in neurons and astrocytes. Glutamine consumption and catabolic flux can be significantly altered in settings of genetic mitochondrial defects or exposure to mitochondrial toxins, and alterations to glutamine metabolism appears to play a particularly significant role in neurodegenerative diseases. These include primary mitochondrial diseases like Leigh syndrome (subacute necrotizing encephalopathy) and MELAS (mitochondrial myopathy with encephalopathy, lactic acidosis, and stroke-like episodes), as well as complex age-related neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. Pharmacologic interventions targeting glutamine metabolizing and catabolizing pathways appear to provide some benefits in cell and animal models of these diseases, indicating glutamine metabolism may be a clinically relevant target. In this review, we discuss glutamine metabolism, mitochondrial disease, the impact of mitochondrial dysfunction on glutamine metabolic processes, glutamine in neurodegeneration, and candidate targets for therapeutic intervention.
    Keywords:  Glutamine toxicity; Mitochondrial disease; Neurodegenerative disease
    DOI:  https://doi.org/10.1016/j.mcn.2023.103887
  3. Cell Death Dis. 2023 08 12. 14(8): 515
    Co-inhibition of glutaminolysis and one-carbon metabolism promotes ROS accumulation leading to enhancement of chemotherapeutic efficacy in anaplastic thyroid cancer.
    Yeseong Hwang, Hyeok Jun Yun, Jae Woong Jeong, Minki Kim, Seyeon Joo, Hae-Kyung Lee, Hang-Seok Chang, Seok-Mo Kim, Sungsoon Fang.
      Anaplastic thyroid cancer (ATC) is one of the most aggressive tumors with an extremely poor prognosis. Based on the several biological features related to glutamine metabolism in ATC, we hypothesized glutaminolysis inhibition induces cell death in ATC cells. However, glutamine metabolism inhibition triggered cell growth arrest independent of cell death in ATC, suggesting that other signaling pathways avoid glutamine metabolism inhibition-induced stress exist. To investigate the functional mechanism against glutamine metabolism inhibition, we conducted mRNA and ATAC-Sequencing data analysis and found that glutamine deprivation increased ATF4-mediated one-carbon metabolism. When we inhibited PHGDH, the first rate-limiting enzyme for one-carbon metabolism, cell growth arrest was promoted upon glutamine metabolism inhibition by accumulating intracellular ROS. We next observed that the co-inhibition of glutamine and one-carbon metabolism could augment the anticancer effects of drugs used in patients with ATC. Finally, single-cell RNA sequencing analysis revealed that one-carbon metabolism was strengthened through the evolutionary process from PTC to ATC. Collectively, our data demonstrate that one-carbon metabolism has a potential role of modulation of cell fate in metabolic stress and can be a therapeutic target for enhancing antitumor effects in ATC.
    DOI:  https://doi.org/10.1038/s41419-023-06041-2
  4. Cell Rep. 2023 Aug 12. pii: S2211-1247(23)00982-8. [Epub ahead of print]42(8): 112971
    FASN deficiency induces a cytosol-to-mitochondria citrate flux to mitigate detachment-induced oxidative stress.
    Wenting Dai, Zhichao Wang, Guan Wang, Qiong A Wang, Ralph DeBerardinis, Lei Jiang.
      Fatty acid synthase (FASN) maintains de novo lipogenesis (DNL) to support rapid growth in most proliferating cancer cells. Lipogenic acetyl-coenzyme A (CoA) is primarily produced from carbohydrates but can arise from glutamine-dependent reductive carboxylation. Here, we show that reductive carboxylation also occurs in the absence of DNL. In FASN-deficient cells, reductive carboxylation is mainly catalyzed by isocitrate dehydrogenase-1 (IDH1), but IDH1-generated cytosolic citrate is not utilized for supplying DNL. Metabolic flux analysis (MFA) shows that FASN deficiency induces a net cytosol-to-mitochondria citrate flux through mitochondrial citrate transport protein (CTP). Previously, a similar pathway has been shown to mitigate detachment-induced oxidative stress in anchorage-independent tumor spheroids. We further report that tumor spheroids show reduced FASN activity and that FASN-deficient cells acquire resistance to oxidative stress in a CTP- and IDH1-dependent manner. Collectively, these data indicate that by inducing a cytosol-to-mitochondria citrate flux, anchorage-independent malignant cells can gain redox capacity by trading off FASN-supported rapid growth.
    Keywords:  CP: Metabolism; CP: Molecular biology; DNL; FASN inhibitor; IDH1 inhibitor; MFA; SLC25A1; anchorage-independent growth; cytosol-to-mitochondria citrate flux; de novo lipogenesis; metabolic flux analysis; redox; reductive carboxylation
    DOI:  https://doi.org/10.1016/j.celrep.2023.112971
  5. Cell Oncol (Dordr). 2023 Aug 14.
    Loss of RACK1 promotes glutamine addiction via activating AKT/mTOR/ASCT2 axis to facilitate tumor growth in gastric cancer.
    Mengqian Chen, Gaojia Wang, Zhijian Xu, Jie Sun, Bo Liu, Lei Chang, Jianxin Gu, Yuanyuan Ruan, Xiaodong Gao, Shushu Song.
      BACKGROUND: Metabolic reprogramming is closely related to the development of gastric cancer (GC), which remains as the fourth leading cause of cancer-related death worldwide. As a tumor suppressor for GC, whether receptor for activated C-kinase 1 (RACK1) play a modulatory role in metabolic reprogramming remains largely unclear.METHODS: GC cell lines and cell-derived xenograft mouse model were used to identify the biological function of RACK1. Flow cytometry and Seahorse assays were applied to examine cell cycle and oxygen consumption rate (OCR), respectively. Western blot, real-time PCR and autophagy double fluorescent assays were utilized to explore the signaling. Immunohistochemistry was performed to detect the expression of RACK1 and other indicators in tissue sections.
    RESULTS: Loss of RACK1 facilitated the viability, colony formation, cell cycle progression and OCR of GC cells in a glutamine-dependent manner. Further investigation revealed that RACK1 knockdown inhibited the lysosomal degradation of Alanine-serine-cysteine amino acid transporter 2 (ASCT2). Mechanistically, depletion of RACK1 remarkably decreased PTEN expression through up-regulating miR-146b-5p, leading to the activation of AKT/mTOR signaling pathway which dampened autophagy flux subsequently. Moreover, knockdown of ASCT2 could reverse the promotive effect of RACK1 depletion on GC tumor growth both in vitro and in vivo. Tissue microarray confirmed that RACK1 was negatively correlated with the expression of ASCT2 and p62, as well as the phosphorylation of mTOR.
    CONCLUSION: Together, our results demonstrate that the suppressive function of RACK1 in GC is associated with ASCT2-mediated glutamine metabolism, and imply that targeting RACK1/ASCT2 axis provides potential strategies for GC treatment.
    Keywords:  ASCT2; Autophagy; Gastric cancer; Glutamine addiction; RACK1
    DOI:  https://doi.org/10.1007/s13402-023-00854-1
  6. Cell Death Dis. 2023 08 15. 14(8): 520
    m5C-methylated lncRNA NR_033928 promotes gastric cancer proliferation by stabilizing GLS mRNA to promote glutamine metabolism reprogramming.
    Lang Fang, Hongxin Huang, Jialun Lv, Zetian Chen, Chen Lu, Tianlu Jiang, Penghui Xu, Ying Li, Sen Wang, Bowen Li, Zheng Li, Weizhi Wang, Zekuan Xu.
      Abnormal 5-methylcytosine (m5C) methylation has been proved to be closely related to gastric carcinogenesis, progression, and prognosis. Dysregulated long noncoding RNAs (lncRNAs) participate in a variety of biological processes in cancer. However, to date, m5C-methylated lncRNAs are rarely researched in gastric cancer (GC). Here, we found that RNA cytosine-C(5)-methyltransferase (NSUN2) was upregulated in GC and high NSUN2 expression was associated with poor prognosis. NR_033928 was identified as an NSUN2-methylated and upregulated lncRNA in GC. Functionally, NR_033928 upregulated the expression of glutaminase (GLS) by interacting with IGF2BP3/HUR complex to promote GLS mRNA stability. Increased glutamine metabolite, α-KG, upregulated NR_033928 expression by enhancing its promoter 5-hydroxymethylcytosine (hm5C) demethylation. In conclusion, our results revealed that NSUN2-methylated NR_033928 promoted GC progression and might be a potential prognostic and therapeutic target for GC.
    DOI:  https://doi.org/10.1038/s41419-023-06049-8
  7. Immunity. 2023 Aug 03. pii: S1074-7613(23)00327-8. [Epub ahead of print]
    Loss of CD4+ T cell-intrinsic arginase 1 accelerates Th1 response kinetics and reduces lung pathology during influenza infection.
    Erin E West, Nicolas S Merle, Marcin M Kamiński, Gustavo Palacios, Dhaneshwar Kumar, Luopin Wang, Jack A Bibby, Kirsten Overdahl, Alan K Jarmusch, Simon Freeley, Duck-Yeon Lee, J Will Thompson, Zu-Xi Yu, Naomi Taylor, Marc Sitbon, Douglas R Green, Andrea Bohrer, Katrin D Mayer-Barber, Behdad Afzali, Majid Kazemian, Sabine Scholl-Buergi, Daniela Karall, Martina Huemer, Claudia Kemper.
      Arginase 1 (Arg1), the enzyme catalyzing the conversion of arginine to ornithine, is a hallmark of IL-10-producing immunoregulatory M2 macrophages. However, its expression in T cells is disputed. Here, we demonstrate that induction of Arg1 expression is a key feature of lung CD4+ T cells during mouse in vivo influenza infection. Conditional ablation of Arg1 in CD4+ T cells accelerated both virus-specific T helper 1 (Th1) effector responses and its resolution, resulting in efficient viral clearance and reduced lung pathology. Using unbiased transcriptomics and metabolomics, we found that Arg1-deficiency was distinct from Arg2-deficiency and caused altered glutamine metabolism. Rebalancing this perturbed glutamine flux normalized the cellular Th1 response. CD4+ T cells from rare ARG1-deficient patients or CRISPR-Cas9-mediated ARG1-deletion in healthy donor cells phenocopied the murine cellular phenotype. Collectively, CD4+ T cell-intrinsic Arg1 functions as an unexpected rheostat regulating the kinetics of the mammalian Th1 lifecycle with implications for Th1-associated tissue pathologies.
    Keywords:  IFN-γ; IL-10; Th1 immunity; arginase 1; arginase 1 deficiency; autoimmunity; cell metabolism; complement; glutamine; influenza infection
    DOI:  https://doi.org/10.1016/j.immuni.2023.07.014
  8. Diabetes. 2023 Aug 14. pii: db230162. [Epub ahead of print]
    Glutamine production by Glul promotes thermogenic adipocyte differentiation through Prdm9-mediated H3K4me3 and transcriptional reprogramming.
    Xiaowen Pan, Lingxia Ye, Xiaozhen Guo, Weihua Wang, Ziyin Zhang, Qintao Wang, Jingjing Huang, Jingya Xu, Yanhan Cai, Xinxin Shou, Yuting Wang, Yu Feng, Cen Xie, Pengfei Shan, Zhuo-Xian Meng.
      Thermogenic adipocytes have been extensively investigated due to their energy dissipating property and therapeutic potential for obesity and diabetes. Besides serving as fuel sources, accumulating evidence suggests that intermediate metabolites play critical roles in multiple biological processes. However, their role in adipocyte differentiation and thermogenesis remains unexplored. Here, we report that human and mouse obesity is associated with marked downregulation of glutamine synthetase (Glul) expression and activity in thermogenic adipose tissues. Glul is robustly upregulated during brown adipocyte (BAC) differentiation and in brown adipose tissue (BAT) upon cold exposure and Cl316,243 stimulation. Further genetic, pharmacologic, or metabolic manipulations of Glul and glutamine levels reveal that glutamine cell-autonomously stimulates BAC differentiation and function, BAT tissue remodeling, and improves systemic energy homeostasis in mice. Mechanistically, glutamine promotes transcriptional induction of adipogenic and thermogenic gene programs through histone modification-mediated chromatin remodeling. Among all the glutamine-regulated writer and eraser genes responsible for histone methylation and acetylation, only Prdm9, a histone lysine methyltransferase, is robustly induced during BAC differentiation. Importantly, Prdm9 inactivation by shRNA knockdown or a selective inhibitor attenuates glutamine-triggered adipogenic and thermogenic induction. Further, Prdm9 gene transcription is regulated by glutamine through the recruitment of C/EBPb to its enhancer region. This work reveals glutamine as a novel activator of thermogenic adipocyte differentiation and uncovers an unexpected role of C/EBPb-Prdm9-mediated H3K4me3 and transcriptional reprogramming in adipocyte differentiation and thermogenesis.
    DOI:  https://doi.org/10.2337/db23-0162
  9. JCI Insight. 2023 Aug 15. pii: e169308. [Epub ahead of print]
    Modulating the polyamine-hypusine axis controls generation of CD8+ tissue resident memory T cells.
    Aya G Elmarsafawi, Rebecca S Hesterberg, Mario R Fernandez, Chunying Yang, Lancia Nf Darville, Min Liu, John M Koomen, Otto Phanstiel Iv, Reginald Atkins, John E Mullinax, Shari A Pilon-Thomas, Frederick L Locke, Pearlie K Epling-Burnette, John L Cleveland.
      Glutaminolysis is a hallmark of the activation and metabolic reprogramming of T cells. Isotopic tracer analyses of antigen-activated effector CD8+ T cells revealed that glutamine is the principal carbon source for the biosynthesis of polyamines putrescine, spermidine and spermine. These metabolites play critical roles in activation-induced T-cell proliferation, as well as for the production of hypusine, which is derived from spermidine and is covalently linked to the translation elongation factor eIF5A. Here, we demonstrated that the glutamine-polyamine-hypusine axis controls the expression of CD69, an important regulator of tissue resident memory T cells (TRM). Inhibition of this circuit augmented the development of TRM cells ex vivo and in vivo in the bone marrow, a well-established niche for TRM cells. Furthermore, blocking the polyamine-hypusine axis augmented CD69 expression and IFN-γ and TNF-α production in human CD8+ T cells from peripheral blood and sarcoma tumor infiltrating lymphocytes, as well as in human CD8+ CAR-T cells. Collectively, these findings support the notion that the polyamine-hypusine circuit can be exploited to modulate TRM cells for therapeutic benefit.
    Keywords:  Immunology; Metabolism; Polyamines; T cells
    DOI:  https://doi.org/10.1172/jci.insight.169308
  10. Front Oncol. 2023 ;13 1165862
    Recent advances microRNAs and metabolic reprogramming in colorectal cancer research.
    Bin Xiong, Qiaoyi Huang, Huida Zheng, Shu Lin, Jianhua Xu.
      Colorectal cancer (CRC) is a cancer with the highest incidence and mortality. Alteration of gene expression is the main pathophysiological mechanism of CRC, which results in disturbed signaling pathways and cellular metabolic processes. MicroRNAs are involved in almost all pathophysiological processes and are correlative with colorectal cancer metabolism, proliferation, and chemotherapy resistance. Metabolic reprogramming, an important feature of cancer, is strongly correlative with the development and prognosis of cancers, including colorectal cancer. MicroRNAs can target enzymes involved in metabolic processes, thus playing a regulatory role in tumor metabolism. The disorder of the signaling pathway is another characteristic of tumor, which induces the occurrence and proliferation of tumors, and is closely correlative with the prognosis and chemotherapy resistance of tumor patients. MicroRNAs can target the components of the signaling pathways to regulate their transduction. Understanding the function of microRNAs in the occurrence and proliferation of CRC provides novel insights into the optimal treatment strategies, prognosis, and development of diagnosis in CRC. This article reviews the relationship between CRC and microRNA expression and hopes to provide new options for the diagnosis and treatment of CRC.
    Keywords:  chemotherapy resistance; colorectal cancer; metabolism reprogramming; miRNA; signaling/signaling pathways
    DOI:  https://doi.org/10.3389/fonc.2023.1165862
  11. Nat Commun. 2023 Aug 12. 14(1): 4883
    Characterizing cancer metabolism from bulk and single-cell RNA-seq data using METAFlux.
    Yuefan Huang, Vakul Mohanty, Merve Dede, Kyle Tsai, May Daher, Li Li, Katayoun Rezvani, Ken Chen.
      Cells often alter metabolic strategies under nutrient-deprived conditions to support their survival and growth. Characterizing metabolic reprogramming in the tumor microenvironment (TME) is of emerging importance in cancer research and patient care. However, recent technologies only measure a subset of metabolites and cannot provide in situ measurements. Computational methods such as flux balance analysis (FBA) have been developed to estimate metabolic flux from bulk RNA-seq data and can potentially be extended to single-cell RNA-seq (scRNA-seq) data. However, it is unclear how reliable current methods are, particularly in TME characterization. Here, we present a computational framework METAFlux (METAbolic Flux balance analysis) to infer metabolic fluxes from bulk or single-cell transcriptomic data. Large-scale experiments using cell-lines, the cancer genome atlas (TCGA), and scRNA-seq data obtained from diverse cancer and immunotherapeutic contexts, including CAR-NK cell therapy, have validated METAFlux's capability to characterize metabolic heterogeneity and metabolic interaction amongst cell types.
    DOI:  https://doi.org/10.1038/s41467-023-40457-w
  12. Front Vet Sci. 2023 ;10 1202369
    Effects of glutamine, glutamate, and aspartate on intestinal barrier integrity and amino acid pool of the small intestine in piglets with normal or low energy diet.
    Yuankun Deng, Hao Cheng, Junyao Li, Hui Han, Ming Qi, Nan Wang, Bi'e Tan, Jianjun Li, Jing Wang.
      Aspartate (asp), glutamate (glu), and glutamine (gln) are the major energy fuels for the small intestine, and it had been indicated in our previous study that the mix of these three amino acid supplementations could maintain intestinal energy homeostasis. This study aimed to further investigate whether the treatment of gln, glu, and asp in low energy diet affects the intestinal barrier integrity and amino acid pool in weaning piglets. A total of 198 weaned piglets were assigned to 3 treatments: control (basal diet + 1.59% L-Ala); T1 (basal diet + 1% L-Gln + 0.5% L-Glu + 0.1% L-Asp); and T2 (low energy diet + 1% L-Gln + 0.5% L-Glu + 0.1% L-Asp). The blood, jejunum, and ileum were obtained on day 5 or on day 21 post-weaning, respectively. Our results showed that T1 and T2 treatments increased the abundances of occludin, claudin-1, and claudin-3 in the small intestine while decreasing the serum diamine oxidase (DAO) and D-lactate levels in weaning piglets. Meanwhile, T1 and T2 treatments significantly increased the positive rate of proliferating cell nuclear antigen (PCNA) of the small intestine, promoting intestinal cell proliferation. We also found that supplementation with glu, gln, and asp improved the serum amino acid pool and promoted ileal amino acid transporter gene expression of slc3a2, slc6a14, and slc7a11 in weaned piglets. Additionally, on day 21 post-weaning, T1 and T2 treatments stimulated the phosphorylation of the mTOR-S6K1-4EBP1 signaling pathway in the small intestine, which may implicate the enhanced protein synthesis rate. In summary, dietary supplementation of gln, glu, and asp was beneficial to the intestinal barrier function and amino acid pool regulation, while the benefits of gln, glu, and asp treatment might be diminished by the low-energy diet. The results demonstrated that the supplementation of gln, glu, and asp under low energy levels was preferentially supplied as the energy fuel to restore the gut barrier function in piglets on day 5 post-weaning. With the increase in age and intestinal maturation (on day 21 post-weaning), gln, glu, and asp supplementation could also show an effect on the regulation of the amino acid pool and protein synthesis.
    Keywords:  amino acid pool; aspartate; glutamate; glutamine; intestinal barrier
    DOI:  https://doi.org/10.3389/fvets.2023.1202369
  13. ACS Sens. 2023 Aug 14.
    Hyperpolarized [1-13C]Acetyl-l-Carnitine Probes Tricarboxylic Acid Cycle Activity In Vivo.
    Jun Chen, Tamara K Singh, Sarah Al Nemri, Maheen Zaidi, Kelvin L Billingsley, Jae Mo Park.
      Mitochondrial oxidative phosphorylation (OXPHOS) is sensitive to a variety of biological factors, and dysregulated OXPHOS is observed during the development of numerous pathological conditions. ATP production via OXPHOS is intrinsically dependent on the availability of acetyl-coenzyme A (CoA), which can enter the tricarboxylic acid (TCA) cycle to drive the oxidative pathway. Acetyl-l-carnitine (ALCAR) is an interchangeable endogenous source of acetyl-CoA, and therefore, ALCAR-derived probes are uniquely positioned for the assessment of OXPHOS. In this report, we develop hyperpolarized (HP) [1-13C]ALCAR as a noninvasive probe to investigate cardiac TCA cycle activity in vivo. We initially synthesized the isotopically labeled substrate and demonstrated that the 13C nucleus maintained a suitable T1 value (50.1 ± 0.8 s at 3 T) and polarization levels (21.3 ± 5.3%) to execute in vivo metabolic measurements. HP [1-13C]ALCAR was employed for cardiac analyses of OXPHOS in rats under fed and fasted conditions. [5-13C]Glutamate was successfully detected, and the metabolite was used to analyze the TCA cycle activity in both nutritional states. These assessments were compared to analogous experiments with the HP [1-13C]pyruvate. Our report represents the first study to demonstrate that HP methods using [1-13C]ALCAR enable direct analyses of mitochondrial function and TCA cycle activity, which are fundamental to cardiac cell homeostasis.
    Keywords:  acetyl-CoA; acetyl-l-carnitine; carbon-13 MRS; cardiac oxidative metabolism; hyperpolarization; oxidative phosphorylation
    DOI:  https://doi.org/10.1021/acssensors.3c01046
  14. Pathol Res Pract. 2023 Aug 05. pii: S0344-0338(23)00441-7. [Epub ahead of print]249 154741
    Assessment of histologic risk factors for hepatocellular carcinoma in patients with chronic hepatitis B of advanced stage.
    Pavlina Pantelidou, Emmanouil Sinakos, Georgios Germanidis, Eirini Pagkalidou, Anna Bettina Haidich, Evangelos Akriviadis, Prodromos Hytiroglou.
      Histologic markers of increased risk for hepatocellular carcinoma can provide useful information for the management of patients with chronic hepatitis B. The expression of epithelial cell adhesion molecule (EpCAM, a marker of hepatic progenitor cells), p21 (a marker of hepatocyte senescence), glutamine synthetase (a marker of perivenular hepatocytes) and CD34 (a marker of sinusoidal capillarization) were assessed by immunohistochemistry in 52 liver biopsy specimens from patients with advanced stage chronic hepatitis B. Nineteen patients developed hepatocellular carcinoma during a follow-up period of 133 months. The findings were compared with those of 18 liver biopsy specimens from patients with early-stage chronic hepatitis B and 6 liver biopsy specimens without significant pathologic findings. EpCAM expression in hepatocytes was significantly increased in specimens with advanced stage, as compared with all other specimens. EpCAM positivity in over 30 % of hepatocytes was only seen in 3 specimens from patients who subsequently developed hepatocellular carcinoma. The expression of p21, glutamine synthetase and CD34 was not associated with hepatocellular carcinoma development. Nevertheless, glutamine synthetase immunostains highlighted zonality abnormalities that were useful in chronic hepatitis B staging. In conclusion, extensive immunopositivity of hepatocytes for EpCAM in chronic hepatitis B may represent a marker of increased hepatocellular carcinoma risk. Glutamine synthetase immunostaining represents a useful adjunct in determining the stage of chronic hepatitis B in diagnostic practice.
    Keywords:  Chronic hepatitis B; Epithelial cell adhesion molecule; Glutamine synthetase; Hepatocellular carcinoma; Risk factor; p21
    DOI:  https://doi.org/10.1016/j.prp.2023.154741
  15. J Toxicol. 2023 ;2023 5660481
    Paclitaxel Induces Neurotoxicity by Disrupting Tricarboxylic Acid Cycle Metabolic Balance in the Mouse Hippocampus.
    Xi Liu, Changmeng Cui, Wenxue Sun, Junjun Meng, Jinxiu Guo, Linlin Wu, Beibei Chen, Dehua Liao, Pei Jiang.
      Objective: It is well known that paclitaxel (PTX)-induced neurotoxicity seriously affects the quality of life of patients and is the main reason for reducing the dose of chemotherapy or even stopping chemotherapy. The current data are limited, and further information is required for practice and verification. The aims of this study were to clarify the molecular mechanism underlying PTX-induced neurotoxicity by combining in vivo and in vitro metabolomics studies and provide new targets for the prevention and treatment of PTX-induced neurotoxicity.Methods: In the in vivo study, a PTX-induced neurotoxicity mouse model was established by intraperitoneal injection of PTX (6 mg/kg every three days) for two consecutive weeks. After verification by water maze tests and HE staining of pathological sections, hippocampal metabolites were measured and the differential metabolites and related metabolic pathways were identified by multivariate statistical analysis. In the in vitro study, we investigated the effects of PTX on mouse hippocampal neuron cells, assessing the concentration and time of administration by MTT assays. After modeling, the relevant metabolites in the TCA cycle were quantified by targeted metabolomics using stable isotope labeling. Finally, the key enzymes of the TCA cycle in tissues and cells were verified by RT-PCR.
    Results: Administration of PTX to model mice resulted in neurological damage, shown by both water-maze tests and hippocampal tissue sections. Twenty-four metabolites and five associated metabolic pathways were found to differ significantly between the hippocampal tissues of the model and control groups. These included metabolites and pathways related to the TCA cycle and pyruvate metabolism. Metabolomics analysis using stable isotope labeling showed significant changes in metabolites associated with the TCA cycle compared with the control group (P < 0.05). Finally, RT-PCR verified that the expression of key enzymes in the TCA cycle was changed to different degrees in both hippocampal tissues and cells.
    Conclusion: Our results showed that PTX neurotoxicity in hippocampal tissue and neuron cells was associated with inhibition of the TCA cycle. This inhibition leads to brain insufficiency and impaired metabolism, resulting in various neurotoxic symptoms.
    DOI:  https://doi.org/10.1155/2023/5660481
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