bims-medica 2024-07-07 papers

bims-medica

Biomed News

on Metabolism and diet in cancer

Issue of 2024–07–07
twenty-one papers selected by
Brett Chrest, East Carolina University

Deuterium MRI of serine metabolism in mouse models of glioblastoma.
SLC25A19 is required for NADH homeostasis and mitochondrial respiration.
Long-term ketogenic diet causes hyperlipidemia, liver dysfunction, and glucose intolerance from impaired insulin trafficking and secretion in mice.
Bioenergetic myths of energy transduction in eukaryotic cells.
Metagenomic and metabolomic analysis showing the adverse risk-benefit trade-off of the ketogenic diet.
Interactions of Fatty Acid and Cholesterol Metabolism with Cellular Stress Response Pathways in Cancer.
Towards nutrition with precision: unlocking biomarkers as dietary assessment tools.
Perturbations in mitochondrial metabolism associated with defective cardiolipin biosynthesis: An in-organello real-time NMR study.
Less is more: An analysis of venetoclax and hypomethylating agent post-induction treatment modifications in AML.
Venetoclax resistance in acute lymphoblastic leukemia is characterized by increased mitochondrial activity and can be overcome by co-targeting oxidative phosphorylation.
Bridging lipid metabolism and mitochondrial genome maintenance.
The metabolic consequences of 'yo-yo' dieting are markedly influenced by genetic diversity.
Low thiamine status in adults following low-carbohydrate / ketogenic diets: a cross-sectional comparative study of micronutrient intake and status.
Physiology of malate dehydrogenase and how dysregulation leads to disease.
A genome-wide CRISPR screen reveals that antagonism of glutamine metabolism sensitizes head and neck squamous cell carcinoma to ferroptotic cell death.
The mitochondrial aspartate/glutamate carrier does not transport GABA.
Significance and Amplification Methods of the Purine Salvage Pathway in Human Brain Cells.
Mitochondrial Alpha-Keto Acid Dehydrogenase Complexes: Recent Developments on Structure and Function in Health and Disease.
Asparagine Dependency is a Targetable Metabolic Vulnerability in TP53-Altered Castration-Resistant Prostate Cancer.
Inborn errors of the malate aspartate shuttle - Update on patients and cellular models.
Expression of PD-L1 Is Increased by Methionine Restriction Using Recombinant Methioninase in Human Colorectal Cancer Cells.

Magn Reson Med. 2024 Jun 30.

Deuterium MRI of serine metabolism in mouse models of glioblastoma.

Friederike Hesse, Jacob Low, Jianbo Cao, Flaviu Bulat, Felix Kreis, Alan J Wright, Kevin M Brindle.

   PURPOSE: Serine is a major source of one-carbon units needed for the synthesis of nucleotides and the production of intramitochondrial nicotinamide adenine dinucleotide phosphate (NADPH), and it plays an important role in cancer cell proliferation. The aim of this study was to develop a deuterium (2H) MRS imaging method for imaging tumor serine metabolism.
METHODS: Sequential (2H) spectra and spectroscopic images were used to monitor the metabolism of [2,3,3-2H3]serine in patient-derived glioblastoma cells in vitro and in tumors obtained by their orthotopic implantation in mouse brain.
RESULTS: [14,14-2H2] 5,10-methylene-tetrahydrofolate, [2H]glycine, [2H]formate, and labeled water were detected in cell suspensions and water labeling in spectroscopic images of tumors. Studies in cells and tumors with variable mitochondrial content and inhibitor studies in cells demonstrated that most of the labeled serine was metabolized in the mitochondria. Water labeling in the cell suspensions was correlated with formate labeling; therefore, water labeling observed in tumors could be used to provide a surrogate measure of flux in the pathway of one-carbon metabolism in vivo.
CONCLUSION: The method has the potential to be used clinically to select patients for treatment with inhibitors of one-carbon metabolism and subsequently to detect their early responses to such treatment.

Keywords:  folate cycle; one‐carbon metabolism; serine; tumor

DOI:  https://doi.org/10.1002/mrm.30198
Free Radic Biol Med. 2024 Jun 27. pii: S0891-5849(24)00536-7. [Epub ahead of print]222 317-330

SLC25A19 is required for NADH homeostasis and mitochondrial respiration.

Zongsheng Jiang.

  Mitochondrial transporters facilitate the translocation of metabolites between the cytoplasm and mitochondria and are critical for mitochondrial functional integrity. Although many mitochondrial transporters are associated with metabolic diseases, how they regulate mitochondrial function and their metabolic contributions at the cellular level are largely unknown. Here, we show that mitochondrial thiamine pyrophosphate (TPP) transporter SLC25A19 is required for mitochondrial respiration. SLC25A19 deficiency leads to reduced cell viability, increased integrated stress response (ISR), enhanced glycolysis and elevated cell sensitivity to 2-deoxyglucose (2-DG) treatment. Through a series of biochemical assays, we found that the depletion of mitochondrial NADH is the primary cause of the impaired mitochondrial respiration in SLC25A19 deficient cells. We also showed involvement of SLC25A19 in regulating the enzymatic activities of complexes I and III, the tricarboxylic acid (TCA) cycle, malate-aspartate shuttle and amino acid metabolism. Consistently, addition of idebenone, an analog of coenzyme Q10, restores mitochondrial respiration and cell viability in SLC25A19 deficient cells. Together, our findings provide new insight into the functions of SLC25A19 in mitochondrial and cellular physiology, and suggest that restoring mitochondrial respiration could be a novel strategy for treating SLC25A19-associated disorders.

Keywords:  Electron transport chain; Idebenone; Mitochondrial respiration; Mitochondrial transporter; NADH; SLC25A19; TPP

DOI:  https://doi.org/10.1016/j.freeradbiomed.2024.06.019
bioRxiv. 2024 Jun 17. pii: 2024.06.14.599117. [Epub ahead of print]

Long-term ketogenic diet causes hyperlipidemia, liver dysfunction, and glucose intolerance from impaired insulin trafficking and secretion in mice.

Molly R Gallop, Renan F L Vieira, Elijah T Matsuzaki, Peyton D Mower, Willisa Liou, Faith E Smart, Seth Roberts, Kimberley J Evason, William L Holland, Amandine Chaix.

A ketogenic diet (KD) is a very low-carbohydrate, very high-fat diet proposed to treat obesity and type 2 diabetes. While KD grows in popularity, its effects on metabolic health are understudied. Here we show that, in male and female mice, while KD protects against weight gain and induces weight loss, over long-term, mice develop hyperlipidemia, hepatic steatosis, and severe glucose intolerance. Unlike high fat diet-fed mice, KD mice are not insulin resistant and have low levels of insulin. Hyperglycemic clamp and ex vivo GSIS revealed cell-autonomous and whole-body impairments in insulin secretion. Major ER/Golgi stress and disrupted ER-Golgi protein trafficking was indicated by transcriptomic profiling of KD islets and confirmed by electron micrographs showing a dilated Golgi network likely responsible for impaired insulin granule trafficking and secretion. Overall, our results suggest long-term KD leads to multiple aberrations of metabolic parameters that caution its systematic use as a health promoting dietary intervention.

DOI: https://doi.org/10.1101/2024.06.14.599117
Front Mol Biosci. 2024 ;11 1402910

Bioenergetic myths of energy transduction in eukaryotic cells.

Guy C Brown.

  The study of energy transduction in eukaryotic cells has been divided between Bioenergetics and Physiology, reflecting and contributing to a variety of Bioenergetic myths considered here: 1) ATP production = energy production, 2) energy transduction is confined to mitochondria (plus glycolysis and chloroplasts), 3) mitochondria only produce heat when required, 4) glycolysis is inefficient compared to mitochondria, and 5) mitochondria are the main source of reactive oxygen species (ROS) in cells. These myths constitute a 'mitocentric' view of the cell that is wrong or unbalanced. In reality, mitochondria are the main site of energy dissipation and heat production in cells, and this is an essential function of mitochondria in mammals. Energy transduction and ROS production occur throughout the cell, particularly the cytosol and plasma membrane, and all cell membranes act as two-dimensional energy conduits. Glycolysis is efficient, and produces less heat per ATP than mitochondria, which might explain its increased use in muscle and cancer cells.

Keywords:  Warburg effect; bioenergetics; cancer; cell metabolism; energetics; glycolysis; mitochondria; oxidative stress

DOI:  https://doi.org/10.3389/fmolb.2024.1402910
Lipids Health Dis. 2024 Jun 29. 23(1): 207

Metagenomic and metabolomic analysis showing the adverse risk-benefit trade-off of the ketogenic diet.

Hongyan Qiu, Chengxia Kan, Fang Han, Youhong Luo, Na Qu, Kexin Zhang, Yanhui Ma, Ningning Hou, Di Wu, Xiaodong Sun, Junfeng Shi.

   BACKGROUND: Ketogenic diets are increasingly popular for addressing obesity, but their impacts on the gut microbiota and metabolome remain unclear. This paper aimed to investigate how a ketogenic diet affects intestinal microorganisms and metabolites in obesity.
METHODS: Male mice were provided with one of the following dietary regimens: normal chow, high-fat diet, ketogenic diet, or high-fat diet converted to ketogenic diet. Body weight and fat mass were measured weekly using high-precision electronic balances and minispec body composition analyzers. Metagenomics and non-targeted metabolomics data were used to analyze differences in intestinal contents.
RESULTS: Obese mice on the ketogenic diet exhibited notable improvements in weight and body fat. However, these were accompanied by a significant decrease in intestinal microbial diversity, as well as an increase in Firmicutes abundance and a 247% increase in the Firmicutes/Bacteroidetes ratio. The ketogenic diet also altered multiple metabolic pathways in the gut, including glucose, lipid, energy, carbohydrate, amino acid, ketone body, butanoate, and methane pathways, as well as bacterial secretion and colonization pathways. These changes were associated with increased intestinal inflammation and dysbiosis in obese mice. Furthermore, the ketogenic diet enhanced the secretion of bile and the synthesis of aminoglycoside antibiotics in obese mice, which may impair the gut microbiota and be associated with intestinal inflammation and immunity.
CONCLUSIONS: The study suggest that the ketogenic diet had an unfavorable risk-benefit trade-off and may compromise metabolic homeostasis in obese mice.

Keywords:  Gut microbiota; High-fat diet; Ketogenic diet; Metabolome; Metagenome; Obesity

DOI:  https://doi.org/10.1186/s12944-024-02198-7
Cold Spring Harb Perspect Med. 2024 Jul 01. pii: a041548. [Epub ahead of print]

Interactions of Fatty Acid and Cholesterol Metabolism with Cellular Stress Response Pathways in Cancer.

Alina M Winkelkotte, Kamal Al-Shami, Adriano B Chaves-Filho, Felix C E Vogel, Almut Schulze.

Lipids have essential functions as structural components of cellular membranes, as efficient energy storage molecules, and as precursors of signaling mediators. While deregulated glucose and amino acid metabolism in cancer have received substantial attention, the roles of lipids in the metabolic reprogramming of cancer cells are less well understood. However, since the first description of de novo fatty acid biosynthesis in cancer tissues almost 70 years ago, numerous studies have investigated the complex functions of altered lipid metabolism in cancer. Here, we will summarize the mechanisms by which oncogenic signaling pathways regulate fatty acid and cholesterol metabolism to drive rapid proliferation and protect cancer cells from environmental stress. The review also discusses the role of fatty acid metabolism in metabolic plasticity required for the adaptation to changing microenvironments during cancer progression and the connections between fatty acid and cholesterol metabolism and ferroptosis.

DOI: https://doi.org/10.1101/cshperspect.a041548
Nat Metab. 2024 Jul 02.

Towards nutrition with precision: unlocking biomarkers as dietary assessment tools.

Cătălina Cuparencu, Tuğçe Bulmuş-Tüccar, Jan Stanstrup, Giorgia La Barbera, Henrik M Roager, Lars O Dragsted.

Precision nutrition requires precise tools to monitor dietary habits. Yet current dietary assessment instruments are subjective, limiting our understanding of the causal relationships between diet and health. Biomarkers of food intake (BFIs) hold promise to increase the objectivity and accuracy of dietary assessment, enabling adjustment for compliance and misreporting. Here, we update current concepts and provide a comprehensive overview of BFIs measured in urine and blood. We rank BFIs based on a four-level utility scale to guide selection and identify combinations of BFIs that specifically reflect complex food intakes, making them applicable as dietary instruments. We discuss the main challenges in biomarker development and illustrate key solutions for the application of BFIs in human studies, highlighting different strategies for selecting and combining BFIs to support specific study designs. Finally, we present a roadmap for BFI development and implementation to leverage current knowledge and enable precision in nutrition research.

DOI: https://doi.org/10.1038/s42255-024-01067-y
bioRxiv. 2024 Jun 22. pii: 2024.06.18.599628. [Epub ahead of print]

Perturbations in mitochondrial metabolism associated with defective cardiolipin biosynthesis: An in-organello real-time NMR study.

Antonio J Rua, Wayne Mitchell, Steven M Claypool, Nathan N Alder, Andrei T Alexandrescu.

Mitochondria are central to cellular metabolism; hence, their dysfunction contributes to a wide array of human diseases including cancer, cardiopathy, neurodegeneration, and heritable pathologies such as Barth syndrome. Cardiolipin, the signature phospholipid of the mitochondrion promotes proper cristae morphology, bioenergetic functions, and directly affects metabolic reactions carried out in mitochondrial membranes. To match tissue-specific metabolic demands, cardiolipin typically undergoes an acyl tail remodeling process with the final step carried out by the phospholipid-lysophospholipid transacylase tafazzin. Mutations in the tafazzin gene are the primary cause of Barth syndrome. Here, we investigated how defects in cardiolipin biosynthesis and remodeling impact metabolic flux through the tricarboxylic acid cycle and associated pathways in yeast. Nuclear magnetic resonance was used to monitor in real-time the metabolic fate of 13 C 3 -pyruvate in isolated mitochondria from three isogenic yeast strains. We compared mitochondria from a wild-type strain to mitochondria from a Δ taz1 strain that lacks tafazzin and contains lower amounts of unremodeled cardiolipin, and mitochondria from a Δ crd1 strain that lacks cardiolipin synthase and cannot synthesize cardiolipin. We found that the 13 C-label from the pyruvate substrate was distributed through about twelve metabolites. Several of the identified metabolites were specific to yeast pathways, including branched chain amino acids and fusel alcohol synthesis. Most metabolites showed similar kinetics amongst the different strains but mevalonate and α-ketoglutarate, as well as the NAD+/NADH couple measured in separate nuclear magnetic resonance experiments, showed pronounced differences. Taken together, the results show that cardiolipin remodeling influences pyruvate metabolism, tricarboxylic acid cycle flux, and the levels of mitochondrial nucleotides.

DOI: https://doi.org/10.1101/2024.06.18.599628
Leuk Res. 2024 Jun 21. pii: S0145-2126(24)00111-5. [Epub ahead of print]143 107545

Less is more: An analysis of venetoclax and hypomethylating agent post-induction treatment modifications in AML.

Stephanie Boisclair, Edward Zhou, Phyu Naing, Richa Thakur, Erin Jou, Bradley Goldberg, Douglas E Gladstone, Steven L Allen, Jonathan E Kolitz, David W Chitty.

  Venetoclax (Ven) combined with a hypomethylating agent (HMA) enhances survival in elderly/unfit acute myeloid leukemia (AML) patients, yet often necessitates regimen modifications due to intolerance. However, it is unclear how these modifications affect patient outcome. This retrospective cohort study evaluates the impact of post-induction HMA/Ven regimen modifications on disease progression and survival. This study reviewed 142 AML patients treated with HMA/Ven within the Northwell Health System from January 2019 to December 2022. To assess the impact of post-induction regimen modifications, patients were grouped according to median days between cycles (≤34 or ≥35 days cycle intervals) and median Ven days per cycle (≤14 or ≥15 days/cycle) based on only cycle 3 and beyond. Kaplan-Meier and Cox proportional hazard regression analyses were employed for univariate and multivariate assessments, respectively. There was no significant difference in median progression-free survival (mPFS)(11.6 vs 11.8 months, p = 0.73) or median overall survival (mOS)(15.1 vs 21.8 months, p = 0.16) between cycle interval groups. However, there was a clinically and statistically significant advantage in mPFS (15.8 vs 8.7 months, p = 0.01) and mOS (24.7 vs 11.3 months, p = 0.006) for patients with a median of ≤14 Ven days/cycle compared to ≥15 Ven days/cycle. Multivariate analysis demonstrated that ≤14 days of Ven for cycle 3 and beyond was an independent predictor of decreased mortality (HR 0.18, CI 0.07-0.48, p = 0.0007). Extended cycle intervals did not adversely affect mortality while reduced Ven duration per cycle post-induction was associated with improved survival in elderly AML patients.

Keywords:  Acute myeloid leukemia; Hypomethylating agents; Survival outcomes; Venetoclax

DOI:  https://doi.org/10.1016/j.leukres.2024.107545
Cell Death Dis. 2024 Jul 03. 15(7): 475

Venetoclax resistance in acute lymphoblastic leukemia is characterized by increased mitochondrial activity and can be overcome by co-targeting oxidative phosphorylation.

Stefanie Enzenmüller, Alexandra Niedermayer, Felix Seyfried, Vera Muench, Daniel Tews, Ulrich Rupp, Eugen Tausch, Alexander Groß, Pamela Fischer-Posovszky, Paul Walther, Stephan Stilgenbauer, Hans A Kestler, Klaus-Michael Debatin, Lüder Hinrich Meyer.

Deregulated apoptosis signaling is characteristic for many cancers and contributes to leukemogenesis and treatment failure in B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Apoptosis is controlled by different pro- and anti-apoptotic molecules. Inhibition of anti-apoptotic molecules like B-cell lymphoma 2 (BCL-2) has been developed as therapeutic strategy. Venetoclax (VEN), a selective BCL-2 inhibitor has shown clinical activity in different lymphoid malignancies and is currently evaluated in first clinical trials in BCP-ALL. However, insensitivity to VEN has been described constituting a major clinical concern. Here, we addressed and modeled VEN-resistance in BCP-ALL, investigated the underlying mechanisms in cell lines and patient-derived xenograft (PDX) samples and identified potential strategies to overcome VEN-insensitivity. Leukemia lines with VEN-specific resistance were generated in vitro and further characterized using RNA-seq analysis. Interestingly, gene sets annotated to the citric/tricarboxylic acid cycle and the respiratory electron transport chain were significantly enriched and upregulated, indicating increased mitochondrial metabolism in VEN-resistant ALL. Metabolic profiling showed sustained high mitochondrial metabolism in VEN-resistant lines as compared to control lines. Accordingly, primary PDX-ALL samples with intrinsic VEN-insensitivity showed higher oxygen consumption and ATP production rates, further highlighting that increased mitochondrial activity is a characteristic feature of VEN-resistant ALL. VEN-resistant PDX-ALL showed significant higher mitochondrial DNA content and differed in mitochondria morphology with significantly larger and elongated structures, further corroborating our finding of augmented mitochondrial metabolism upon VEN-resistance. Using Oligomycin, an inhibitor of the complex V/ATPase subunit, we found synergistic activity and apoptosis induction in VEN-resistant BCP-ALL cell lines and PDX samples, demonstrating that acquired and intrinsic VEN-insensitivity can be overcome by co-targeting BCL-2 and the OxPhos pathway. These findings of reprogrammed, high mitochondrial metabolism in VEN-resistance and synergistic activity upon co-targeting BCL-2 and oxidative phosphorylation strongly suggest further preclinical and potential clinical evaluation in VEN-resistant BCP-ALL.

DOI: https://doi.org/10.1038/s41419-024-06864-7
J Biol Chem. 2024 Jun 27. pii: S0021-9258(24)01999-9. [Epub ahead of print] 107498

Bridging lipid metabolism and mitochondrial genome maintenance.

Casadora Boone, Samantha C Lewis.

  Mitochondria are the nexus of cellular energy metabolism and major signaling hubs that integrate information from within and without the cell to implement cell function. Mitochondria harbor a distinct polyploid genome, mitochondrial DNA (mtDNA), that encodes respiratory chain components required for energy production. MtDNA mutation and depletion have been linked to obesity and metabolic syndrome in humans. At the cellular and subcellular levels, mtDNA synthesis is coordinated by membrane contact sites implicated in lipid transfer from the endoplasmic reticulum, tying genome maintenance to lipid storage and homeostasis. Here, we examine the relationship between mtDNA and lipid trafficking, the influence of lipotoxicity on mtDNA integrity, and how lipid metabolism may be disrupted in primary mtDNA disease.

Keywords:  Mitochondria; lipid metabolism; lipotoxicity; mitochondrial DNA (mtDNA); mitochondrial metabolism

DOI:  https://doi.org/10.1016/j.jbc.2024.107498
Int J Obes (Lond). 2024 Jul 03.

The metabolic consequences of 'yo-yo' dieting are markedly influenced by genetic diversity.

Senthil Thillainadesan, Aaron Lambert, Kristen C Cooke, Jacqueline Stöckli, Belinda Yau, Stewart W C Masson, Anna Howell, Meg Potter, Oliver K Fuller, Yi Lin Jiang, Melkam A Kebede, Grant Morahan, David E James, Søren Madsen, Samantha L Hocking.

BACKGROUND: Weight loss can improve the metabolic complications of obesity. However, it is unclear whether insulin resistance persists despite weight loss and whether any protective benefits are preserved following weight regain (weight cycling). The impact of genetic background on weight cycling is undocumented. We aimed to investigate the effects of weight loss and weight cycling on metabolic outcomes and sought to clarify the role of genetics in this relationship.
METHOD: Both C57BL/6 J and genetically heterogeneous Diversity Outbred Australia (DOz) mice were alternately fed high fat Western-style diet (WD) and a chow diet at 8-week intervals. Metabolic measures including body composition, glucose tolerance, pancreatic beta cell activity, liver lipid levels and adipose tissue insulin sensitivity were determined.
RESULTS: After diet switch from WD (8-week) to chow (8-week), C57BL/6 J mice displayed a rapid normalisation of body weight, adiposity, hyperinsulinemia, liver lipid levels and glucose uptake into adipose tissue comparable to chow-fed controls. In response to the same dietary intervention, genetically diverse DOz mice conversely maintained significantly higher fat mass and insulin levels compared to chow-fed controls and exhibited much more profound interindividual variability than C57BL/6 J mice. Weight cycled (WC) animals were re-exposed to WD (8-week) and compared to age-matched controls fed 8-week WD for the first time (LOb). In C57BL/6 J but not DOz mice, WC animals had significantly higher blood insulin levels than LOb controls. All WC animals exhibited significantly greater beta cell activity than LOb controls despite similar fat mass, glucose tolerance, liver lipid levels and insulin-stimulated glucose uptake in adipose tissue.
CONCLUSION: Following weight loss, metabolic outcomes return to baseline in C57BL/6 J mice with obesity. However, genetic diversity significantly impacts this response. A period of weight loss does not provide lasting benefits after weight regain, and weight cycling is detrimental and associated with hyperinsulinemia and elevated basal insulin secretion.

DOI: https://doi.org/10.1038/s41366-024-01542-2
Eur J Nutr. 2024 Jul 05.

Low thiamine status in adults following low-carbohydrate / ketogenic diets: a cross-sectional comparative study of micronutrient intake and status.

Chaitong Churuangsuk, Anthony Catchpole, Dinesh Talwar, Paul Welsh, Naveed Sattar, Michael E J Lean, Emilie Combet.

   BACKGROUND: Low-carbohydrate diets (LCD) are popular for weight loss but lack evidence about micronutrient sufficiency in real-life use. This study assessed the intake and biochemical status of selected micronutrients in people voluntarily following LCDs.
METHODS: A cross-sectional study was conducted (2018-20) among 98 adults recruited as self-reporting either LCD (n = 49) or diets not restricting carbohydrates (controls; n = 49). Diets were assessed using the 130-item EPIC-Norfolk food-frequency questionnaire. Red-blood-cell thiamine diphosphate (TDP) was measured for thiamine status using HPLC. Plasma magnesium, zinc, copper, and selenium were measured using inductively coupled plasma mass spectrometry. Between-group biomarker comparisons were conducted using ANCOVA and adjusted for age, sex, body mass index (BMI), and diabetes status.
RESULTS: LCD-followers (26% male, median age 36 years, median BMI 24.2 kg/m2) reported adhering to LCDs for a median duration of 9 months (IQR 4-36). The most followed LCD type was 'their own variations of LCD' (30%), followed by ketogenic (23%), 'palaeolithic' (15%), and Atkins diets (8%). Among controls, 41% were male (median age 27 years, median BMI 23 kg/m2). Median macronutrient intakes for LCD vs control groups were carbohydrate 16%Energy (E) vs. 50%E; protein 25%E vs. 19%E; and fat 55%E vs 34%E (saturated fat 18%E vs. 11%E). Two-thirds of LCD followers (32/49) and half of the controls (24/49) reported some use of dietary supplements (p = 0.19). Among LCD-followers, assessing from food data only, 21 (43%) failed to meet the reference nutrient intake (RNI) for thiamine (vs.14% controls, p = 0.002). When thiamine from supplementation (single- or multivitamin) was included, there appeared to be no difference in thiamine intake between groups. Still, red-blood-cell TDP was lower in LCD-followers than controls (407 ± 91 vs. 633 ± 234 ng/gHb, p < 0.001). Three LCD-followers were thiamine-deficient (RBC thiamine < 275 ng/gHb) vs. one control. There were no significant differences in dietary intakes or plasma concentrations of magnesium, zinc, copper, and selenium between groups.
CONCLUSIONS: Following LCDs is associated with lower thiamine intake and TDP status than diets without carbohydrate restriction, incompletely corrected by supplement use. These data, coupled with a lack of RCT evidence on body weight control, do not support recommending LCDs for weight management without appropriate guidance and diet supplementation.

Keywords:  Ketogenic diet; Low carbohydrate; Magnesium; Micronutrient; Obesity; Thiamine

DOI:  https://doi.org/10.1007/s00394-024-03459-y
Essays Biochem. 2024 Jul 04. pii: EBC20230085. [Epub ahead of print]

Physiology of malate dehydrogenase and how dysregulation leads to disease.

Amy D Parente, Danielle E Bolland, Kathryn L Huisinga, Joseph J Provost.

  Malate dehydrogenase (MDH) is pivotal in mammalian tissue metabolism, participating in various pathways beyond its classical roles and highlighting its adaptability to cellular demands. This enzyme is involved in maintaining redox balance, lipid synthesis, and glutamine metabolism and supports rapidly proliferating cells' energetic and biosynthetic needs. The involvement of MDH in glutamine metabolism underlines its significance in cell physiology. In contrast, its contribution to lipid metabolism highlights its role in essential biosynthetic processes necessary for cell maintenance and proliferation. The enzyme's regulatory mechanisms, such as post-translational modifications, underscore its complexity and importance in metabolic regulation, positioning MDH as a potential target in metabolic dysregulation. Furthermore, the association of MDH with various pathologies, including cancer and neurological disorders, suggests its involvement in disease progression. The overexpression of MDH isoforms MDH1 and MDH2 in cancers like breast, prostate, and pancreatic ductal adenocarcinoma, alongside structural modifications, implies their critical role in the metabolic adaptation of tumor cells. Additionally, mutations in MDH2 linked to pheochromocytomas, paragangliomas, and other metabolic diseases emphasize MDH's role in metabolic homeostasis. This review spotlights MDH's potential as a biomarker and therapeutic target, advocating for further research into its multifunctional roles and regulatory mechanisms in health and disease.

Keywords:  MDH; OAA; TCA; disease; malate dehydrogenase; metabolism

DOI:  https://doi.org/10.1042/EBC20230085
Cancer Lett. 2024 Jul 02. pii: S0304-3835(24)00484-1. [Epub ahead of print] 217089

A genome-wide CRISPR screen reveals that antagonism of glutamine metabolism sensitizes head and neck squamous cell carcinoma to ferroptotic cell death.

Michael M Allevato, Sally Trinh, Keiichi Koshizuka, Daniela Nachmanson, Thien-Tu C Nguyen, Yumi Yokoyama, Xingyu Wu, Allen Andres, Zhiyong Wang, Jeramie Watrous, Alfredo A Molinolo, Prashant Mali, Olivier Harismendy, Mohit Jain, Robert Wild, J Silvio Gutkind.

  Glutamine is a conditionally essential amino acid for the growth and survival of rapidly proliferating cancer cells. Many cancers are addicted to glutamine, and as a result, targeting glutamine metabolism has been explored clinically as a therapeutic approach. Glutamine-catalyzing enzymes are highly expressed in primary and metastatic head and neck squamous cell carcinoma (HNSCC). However, the nature of the glutamine-associated pathways in this aggressive cancer type has not been elucidated. Here, we explored the therapeutic potential of a broad glutamine antagonist, DRP-104 (sirpiglenastat), in HNSCC tumors and aimed at shedding light on glutamine-dependent pathways in this disease. We observed a potent antitumoral effect of sirpiglenastat in HPV- and HPV+ HNSCC xenografts. We conducted a whole-genome CRISPR screen and metabolomics analyses to identify mechanisms of sensitivity and resistance to glutamine metabolism blockade. These approaches revealed that glutamine metabolism blockade results in the rapid buildup of polyunsaturated fatty acids (PUFAs) via autophagy nutrient-sensing pathways. Finally, our analysis demonstrated that GPX4 mediates the protection of HNSCC cells from accumulating toxic lipid peroxides; hence, glutamine blockade sensitizes HNSCC cells to ferroptosis cell death upon GPX4 inhibition. These findings demonstrate the therapeutic potential of sirpiglenastat in HNSCC and establish a novel link between glutamine metabolism and ferroptosis, which may be uniquely translated into targeted glutamine-ferroptosis combination therapies.

Keywords:  Glutamine; autophagy; ferroptosis; head and neck squamous cell carcinoma; poly-unsaturated fatty acids; precision medicine; targeted therapy

DOI:  https://doi.org/10.1016/j.canlet.2024.217089
Biochim Biophys Acta Bioenerg. 2024 Jun 28. pii: S0005-2728(24)00457-2. [Epub ahead of print]1865(4): 149487

The mitochondrial aspartate/glutamate carrier does not transport GABA.

Vito Porcelli, Serena Barile, Loredana Capobianco, Simona Nicole Barile, Ruggiero Gorgoglione, Giuseppe Fiermonte, Barbara Monti, Francesco Massimo Lasorsa, Luigi Palmieri.

  ɣ-aminobutyric acid (GABA) is a four‑carbon amino acid acting as the main inhibitory transmitter in the invertebrate and vertebrate nervous systems. The metabolism of GABA is well compartmentalized in the cell and the uptake of cytosolic GABA into the mitochondrial matrix is required for its degradation. A previous study carried out in the fruit fly Drosophila melanogaster indicated that the mitochondrial aspartate/glutamate carrier (AGC) is responsible for mitochondrial GABA accumulation. Here, we investigated the transport of GABA catalysed by the human and D. melanogaster AGC proteins through a well-established method for the study of the substrate specificity and the kinetic parameters of the mitochondrial carriers. In this experimental system, the D. melanogaster spliced AGC isoforms (Aralar1-PA and Aralar1-PE) and the human AGC isoforms (AGC1/aralar1 and AGC2/citrin) are unable to transport GABA both in homo- and in hetero-exchange with either glutamate or aspartate, i.e. the canonical substrates of AGC. Moreover, GABA has no inhibitory effect on the exchange activities catalysed by the investigated AGCs. Our data demonstrate that AGC does not transport GABA and the molecular identity of the GABA transporter in human and D. melanogaster mitochondria remains unknown.

Keywords:  AGC; Aralar; Citrin; GABA; Mitochondrial carriers

DOI:  https://doi.org/10.1016/j.bbabio.2024.149487
J Biol Chem. 2024 Jul 01. pii: S0021-9258(24)02025-8. [Epub ahead of print] 107524

Significance and Amplification Methods of the Purine Salvage Pathway in Human Brain Cells.

Mai Sekine, Megumi Fujiwara, Ken Okamoto, Kimiyoshi Ichida, Koji Nagata, Russ Hille, Takeshi Nishino.

  Previous studies suggest that uric acid or reactive oxygen species, products of xanthine oxidoreductase (XOR), may associate with neurodegenerative diseases. However, neither relationship has ever been firmly established. Here, we analyzed human brain samples, obtained under protocols approved by research ethics committees, and found no expression of XOR and only low levels of uric acid in various regions of the brain. In the absence of XOR, hypoxanthine will be preserved and available for incorporation into the purine salvage pathway. To clarify the importance of salvage in the brain, we tested using human induced pluripotent stem cell-derived neuronal cells. Stable isotope analyses showed that the purine salvage pathway was more effective for ATP synthesis than purine de novo synthesis. Blood uric acid levels were related to the intracellular adenylate pool (ATP + ADP + AMP), and reduced levels of this pool result in lower uric acid levels. XOR inhibitors are related to extracellular hypoxanthine levels available for uptake into the purine salvage pathway by inhibiting the oxidation of hypoxanthine to xanthine and uric acid in various organs where XOR is present and can prevent further decreases in the intracellular adenylate pool under stress. Furthermore, adding precursors of the pentose phosphate pathway enhanced hypoxanthine uptake, indicating that purine salvage is activated by PRPP replenishment. These findings resolve previous contradictions regarding XOR products and provide new insights into clinical studies. It is suggested that therapeutic strategies maximizing maintenance of intracellular adenylate levels may effectively treat pathological conditions associated with ischemia and energy depletion.

Keywords:  HPRT; XOR; brain; pentose phosphate pathway; purine metabolism; salvage

DOI:  https://doi.org/10.1016/j.jbc.2024.107524
Subcell Biochem. 2024 ;104 295-381

Mitochondrial Alpha-Keto Acid Dehydrogenase Complexes: Recent Developments on Structure and Function in Health and Disease.

Eszter Szabo, Balint Nagy, Andras Czajlik, Timea Komlodi, Oliver Ozohanics, Laszlo Tretter, Attila Ambrus.

  The present work delves into the enigmatic world of mitochondrial alpha-keto acid dehydrogenase complexes discussing their metabolic significance, enzymatic operation, moonlighting activities, and pathological relevance with links to underlying structural features. This ubiquitous family of related but diverse multienzyme complexes is involved in carbohydrate metabolism (pyruvate dehydrogenase complex), the citric acid cycle (α-ketoglutarate dehydrogenase complex), and amino acid catabolism (branched-chain α-keto acid dehydrogenase complex, α-ketoadipate dehydrogenase complex); the complexes all function at strategic points and also participate in regulation in these metabolic pathways. These systems are among the largest multienzyme complexes with at times more than 100 protein chains and weights ranging up to ~10 million Daltons. Our chapter offers a wealth of up-to-date information on these multienzyme complexes for a comprehensive understanding of their significance in health and disease.

Keywords:  Alpha-ketoadipate dehydrogenase complex; Alpha-ketoglutarate dehydrogenase complex; Branched-chain α-keto acid dehydrogenase complex; Metabolic disease; Mitochondrion; Pathogenic mutation; Pyruvate dehydrogenase complex; ROS; α-keto acid dehydrogenase complexes

DOI:  https://doi.org/10.1007/978-3-031-58843-3_13
Cancer Res. 2024 Jul 03.

Asparagine Dependency is a Targetable Metabolic Vulnerability in TP53-Altered Castration-Resistant Prostate Cancer.

Young A Yoo, Songhua Quan, William Yang, Qianyu Guo, Yara Rodríguez, Zachary R Chalmers, Mary F Dufficy, Barbara Lackie, Vinay Sagar, Kenji Unno, Mihai I Truica, Navdeep S Chandel, Sarki A Abdulkadir.

The TP53 tumor suppressor is frequently altered in lethal, castration-resistant prostate cancer (CRPC). However, to date there are no effective treatments that specifically target TP53 alterations. Using transcriptomic and metabolomic analyses, we showed here that TP53-altered prostate cancer (PCa) exhibits an increased dependency on asparagine and overexpresses asparagine synthetase (ASNS), the enzyme catalyzing the synthesis of asparagine. Mechanistically, loss or mutation of TP53 transcriptionally activated ASNS expression, directly as well as via mTORC1-mediated ATF4 induction, driving de novo asparagine biosynthesis to support CRPC growth. TP53-altered CRPC cells were sensitive to asparagine restriction by knockdown of ASNS or L-asparaginase treatment to deplete the intracellular and extracellular sources of asparagine, respectively, and cell viability was rescued by asparagine addition. Notably, pharmacological inhibition of intracellular asparagine biosynthesis using a glutaminase inhibitor and depletion of extracellular asparagine with L-asparaginase significantly reduced asparagine production and effectively impaired CRPC growth. This study highlights the significance of ASNS-mediated metabolic adaptation as a synthetic vulnerability in CRPC with TP53 alterations, providing a rationale for targeting asparagine production to treat these lethal prostate cancers.

DOI: https://doi.org/10.1158/0008-5472.CAN-23-2910
Mol Genet Metab. 2024 Jun 24. pii: S1096-7192(24)00404-9. [Epub ahead of print]142(4): 108520

Inborn errors of the malate aspartate shuttle - Update on patients and cellular models.

Jasmine Koch, Melissa H Broeks, Matthias Gautschi, Judith Jans, Alexander Laemmle.

The malate aspartate shuttle (MAS) plays a pivotal role in transporting cytosolic reducing equivalents - electrons - into the mitochondria for energy conversion at the electron transport chain (ETC) and in the process of oxidative phosphorylation. The MAS consists of two pairs of cytosolic and mitochondrial isoenzymes (malate dehydrogenases 1 and 2; and glutamate oxaloacetate transaminases 1 and 2) and two transporters (malate-2-oxoglutarate carrier and aspartate glutamate carrier (AGC), the latter of which has two tissue-dependent isoforms AGC1 and AGC2). While the inner mitochondrial membrane is impermeable to NADH, the MAS forms one of the main routes for mitochondrial electron uptake by promoting uptake of malate. Inherited bi-allelic pathogenic variants in five of the seven components of the MAS have been described hitherto and cause a wide spectrum of symptoms including early-onset epileptic encephalopathy. This review provides an overview of reported patients suffering from MAS deficiencies. In addition, we give an overview of diagnostic procedures and research performed on patient-derived cellular models and tissues. Current cellular models are briefly discussed and novel ways to achieve a better understanding of MAS deficiencies are highlighted.

DOI: https://doi.org/10.1016/j.ymgme.2024.108520
Cancer Genomics Proteomics. 2024 Jul-Aug;21(4):21(4): 395-398

Expression of PD-L1 Is Increased by Methionine Restriction Using Recombinant Methioninase in Human Colorectal Cancer Cells.

Kohei Mizuta, Byung Mo Kang, Qinghong Han, Yutaro Kubota, Sei Morinaga, Motokazu Sato, Michael Bouvet, Yasunori Tome, Kotaro Nishida, Robert M Hoffman.

   BACKGROUND/AIM: It has been recently demonstrated that a methionine-restricted diet increases the response to immune checkpoint inhibitors (ICIs) via an increase in PD-L1 in a syngeneic mouse colorectal-cancer model. Our laboratory has developed recombinant methioninase (rMETase) to restrict methionine. The aim of the present study was to determine if rMETase can increase PD-L1 expression in a human colorectal cancer cell line in vitro.
MATERIALS AND METHODS: We evaluated the half-maximal inhibitory concentration (IC50) value of rMETase on HCT-116 human colorectal cancer cells. HCT-116 cells were treated with rMETase at the IC50 Western immunoblotting was used to compare PD-L1 expression in HCT-116 cells treated with and without rMETase.
RESULTS: The IC50 value of rMETase on HCT-116 was 0.79 U/ml. Methionine restriction using rMETase increased PD-L1 expression compared to the untreated control (p<0.05).
CONCLUSION: Methionine restriction with rMETase up-regulates PD-L1 expression in human colorectal cancer cells and the combination of rMETase and ICIs may have the potential to improve immunotherapy in human colorectal cancer.

Keywords:  Colorectal cancer; PD-L1; immune checkpoints; methionine restriction; recombinant methioninase (rMETase)

DOI:  https://doi.org/10.21873/cgp.20457