Anaerobic Glycolysis Research Articles

Inversion of the Warburg Effect: Unraveling the Metabolic Nexus between Obesity and Cancer.

Obesity is a well-established risk factor for cancer, significantly impacting both cancer incidence and mortality. However, the intricate molecular mechanisms connecting adipose tissue to cancer cell metabolism are not fully understood. This Review explores the historical context of tumor energy metabolism research, tracing its origins to Otto Warburg's pioneering work in 1920. Warburg's discovery of the "Warburg effect", wherein cancer cells prefer anaerobic glycolysis even in the presence of oxygen, laid the foundation for understanding cancer metabolism. Building upon this foundation, the "reverse Warburg effect" emerged in 2009, elucidating the role of aerobic glycolysis in cancer-associated fibroblasts (CAFs) and its contribution to lactate accumulation in the tumor microenvironment, subsequently serving as a metabolic substrate for cancer cells. In contrast, within high-adiposity contexts, cancer cells exhibit a unique metabolic shift termed the "inversion of the Warburg effect". This phenomenon, distinct from the stromal-dependent reverse Warburg effect, relies on increased nutrient abundance in obesity environments, leading to the generation of glucose from lactate as a metabolic substrate. This Review underscores the heightened tumor proliferation and aggressiveness associated with obesity, introducing the "inversion of the Warburg effect" as a novel mechanism rooted in the altered metabolic landscape within an obese milieu. The insights presented here open promising avenues for therapeutic exploration, offering fresh perspectives and opportunities for the development of innovative cancer treatment strategies.

Systematic analysis of the role of LDHs subtype in pan-cancer demonstrates the importance of LDHD in the prognosis of hepatocellular carcinoma patients

BackgroundLactate dehydrogenase (LDHs) is an enzyme involved in anaerobic glycolysis, including LDHA, LDHB, LDHC and LDHD. Given the regulatory role in the biological progression of certain tumors, we analyzed the role of LDHs in pan-cancers.MethodsCox regression, Kaplan–Meier curves, Receiver Operating Characteristic (ROC) curves, and correlation of clinical indicators in tumor patients were used to assess the prognostic significance of LDHs in pan-cancer. The TCGA, HPA, TIMER, UALCAN, TISIDB, and Cellminer databases were used to investigate the correlation between the expression of LDHs and immune subtypes, immune checkpoint genes, methylation levels, tumor mutational load, microsatellite instability, tumor-infiltrating immune cells and drug sensitivity. The cBioPortal database was also used to identify genomic abnormalities of LDHs in pan-cancer. A comprehensive assessment of the biological functions of LDHs was performed using GSEA. In vitro, HepG2 and Huh7 cells were transfected with LDHD siRNA and GFP-LDHD, the proliferation capacity of cells was examined using CCK-8, EdU, and colony formation assays; the migration and invasion of cells was detected by wound healing and transwell assays; western blotting was used to detect the levels of MMP-2, MMP-9, E-cadherin, N-cadherin and Akt phosphorylation.ResultsLDHs were differentially expressed in a variety of human tumor tissues. LDHs subtypes can act as pro-oncogenes or anti-oncogenes in different types of cancer and have an impact on the prognosis of patients with tumors by influencing their clinicopathological characteristics. LDHs were differentially expressed in tumor immune subtypes and molecular subtypes. In addition, LDHs expression correlated with immune checkpoint genes, tumor mutational load, and microsatellite instability. LDHD was identified to play an important role in the prognosis of HCC patients, according to a comprehensive analysis of LDHs in pan-cancer. In HepG2 and Huh7 cells, knockdown of LDHD promoted cell proliferation, migration, and invasion, promoted the protein expression levels of MMP-2, MMP-9, N-cadherin, and Akt phosphorylation, but inhibited the protein expression level of E-cadherin. In addition, LDHD overexpression showed the opposite changes.ConclusionLDHs subtypes can be used as potential prognostic markers for certain cancers. Prognostic and immunotherapeutic analysis indicated that LDHD plays an important role in the prognosis of HCC patients. In vitro experiments revealed that LDHD can affect HCC proliferation, migration, and invasion by regulating MMPs expression and EMT via Akt signaling pathway, which provides a new perspective on the anti-cancer molecular mechanism of LDHD in HCC.

Lactic acid promotes nucleus pulposus cell senescence and corresponding intervertebral disc degeneration via interacting with Akt.

The accumulation of metabolites in the intervertebral disc is considered an important cause of intervertebral disc degeneration (IVDD). Lactic acid, which is a metabolite that is produced by cellular anaerobic glycolysis, has been proven to be closely associated with IVDD. However, little is known about the role of lactic acid in nucleus pulposus cells (NPCs) senescence and oxidative stress. The aim of this study was to investigate the effect of lactic acid on NPCs senescence and oxidative stress as well as the underlying mechanism. A puncture-induced disc degeneration (PIDD) model was established in rats. Metabolomics analysis revealed that lactic acid levels were significantly increased in degenerated intervertebral discs. Elimination of excessive lactic acid using a lactate oxidase (LOx)-overexpressing lentivirus alleviated the progression of IVDD. In vitro experiments showed that high concentrations of lactic acid could induce senescence and oxidative stress in NPCs. High-throughput RNA sequencing results and bioinformatic analysis demonstrated that the induction of NPCs senescence and oxidative stress by lactic acid may be related to the PI3K/Akt signaling pathway. Further study verified that high concentrations of lactic acid could induce NPCs senescence and oxidative stress by interacting with Akt and regulating its downstream Akt/p21/p27/cyclin D1 and Akt/Nrf2/HO-1 pathways. Utilizing molecular docking, site-directed mutation and microscale thermophoresis assays, we found that lactic acid could regulate Akt kinase activity by binding to the Lys39 and Leu52 residues in the PH domain of Akt. These results highlight the involvement of lactic acid in NPCs senescence and oxidative stress, and lactic acid may become a novel potential therapeutic target for the treatment of IVDD.

Transcriptome analysis of anaerobic glycolysis effects on Jurkat T cell proliferation.

To explore the effects of anaerobic glycolysis on Jurkat T cell proliferation and clarify the possible mechanism via transcriptomic analysis. The monocarboxylate transporter 1 inhibitor AZD3965 was used to target and block the transmembrane transport of lactate, thereby inhibiting anaerobic glycolysis in Jurkat T cells. Then, genes with differential expression between treated and untreated cells were detected by transcriptomic analysis, and constructs were generated. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses as well as protein-protein interaction (PPI) network analysis were performed to explore the potential mechanism. Inhibition of anaerobic glycolysis reduced Jurkat T-cell proliferation. RNA sequencing identified 1723 transcripts that were differentially expressed, including 1460 upregulated genes and 263 downregulated genes. GO functional enrichment analysis showed that the differentially expressed genes were mainly involved in the biological processes of response to unfolded protein, response to topologically incorrect protein, and protein folding. KEGG pathway analysis of differentially expressed genes or hub genes from the PPI network analysis revealed enrichment in the estrogen signaling and PI3K-Akt pathways. Anaerobic glycolysis contributes to the regulation of Jurkat T-cell proliferation. The underlying mechanism may involve the estrogen signaling pathway or PI3K-Akt signaling pathway as well as protein metabolism.

Nanotech-Driven Activation of Glycolysis in Stored Red Blood Cells through Innovative Resuspension Solution Processing

At present, nanotechnology offers fresh possibilities for influencing anaerobic glycolysis processes and hexose monophosphate reactions in preserved red blood cells. We investigated components containing red blood cells donated with the CPDA-1 preservative. We utilized modified solutions consisting of 0.9% NaCl and 5% glucose for resuspension. The solutions underwent treatment with magnetite nanoparticles (specifically, ICNB brand) using the Belousov’s method. Spectrophotometry was employed to determine the levels of 2,3-DPG, ATP, reduced glutathione, and glutathione peroxidase. This research presents promising avenues for extending the shelf life and maintaining the functional activity of preserved red blood cells. Our findings demonstrated a significant increase in ATP and reduced glutathione, accompanied by a reduction in 2,3-DPG and glutathione peroxidase. It was evident that the enhancement of anaerobic glycolysis was less pronounced in experiments involving modified physiological saline compared to those using a glucose solution. Instead, the pentose glucose oxidation cycle prevailed. A comprehensive analysis of the collected data suggests that the modified resuspension solutions possess membrane-protective properties, which can be attributed to the rise in ATP and reduced glutathione, maintaining the cell's redox potential in equilibrium. The introduction of magnetite nanoparticles (ICNB) induces changes in the mobility and orientation of hydrogen protons within the resuspension solutions. This results in polarization of the aqueous environment surrounding the erythrocytes due to van der Waals forces. This polarization constitutes the primary cause behind the activation of ATP phosphate residue hydrolysis and the activation of intracellular enzymes that regulate anaerobic glycolysis and the pentose phosphate cycle. As a consequence, transmembrane metabolism and metabolic processes are altered, leading to a shift in the energy state of erythrocytes and the activation of enzymes. All of these changes exert a substantial influence on the energy supply of preserved red blood cells, thus preserving their functional capabilities under storage conditions at temperatures ranging from 2 to 6℃.

Cardiac Metabolism.

The heart is composed of a heterogeneous mixture of cellular components perfectly intermingled and able to integrate common environmental signals to ensure proper cardiac function and performance. Metabolism defines a cell context-dependent signature that plays a critical role in survival, proliferation, or differentiation, being a recognized master piece of organ biology, modulating homeostasis, disease progression, and adaptation to tissue damage. The heart is a highly demanding organ, and adult cardiomyocytes require large amount of energy to fulfill adequate contractility. However, functioning under oxidative mitochondrial metabolism is accompanied with a concomitant elevation of harmful reactive oxygen species that indeed contributes to the progression of several cardiovascular pathologies and hampers the regenerative capacity of the mammalian heart. Cardiac metabolism is dynamic along embryonic development and substantially changes as cardiomyocytes mature and differentiate within the first days after birth. During early stages of cardiogenesis, anaerobic glycolysis is the main energetic program, while a progressive switch toward oxidative phosphorylation is a hallmark of myocardium differentiation. In response to cardiac injury, different signaling pathways participate in a metabolic rewiring to reactivate embryonic bioenergetic programs or the utilization of alternative substrates, reflecting the flexibility of heart metabolism and its central role in organ adaptation to external factors. Despite the well-established metabolic pattern of fetal, neonatal, and adult cardiomyocytes, our knowledge about the bioenergetics of other cardiac populations like endothelial cells, cardiac fibroblasts, or immune cells is limited. Considering the close intercellular communication and the influence of nonautonomous cues during heart development and after cardiac damage, it will be fundamental to better understand the metabolic programs in different cardiac cells in order to develop novel interventional opportunities based on metabolic rewiring to prevent heart failure and improve the limited regenerative capacity of the mammalian heart.

Predictive role of lactate in dogs with acute pancreatitis advanced to systemic inflammatory response syndrome.

Acute pancreatitis (AP) can develop into life-threatening conditions such as systemic inflammatory response syndrome (SIRS) or multiple organ dysfunction syndrome. Thirty-nine of 54 client-owned dogs admitted to the Referral Animal Medical Center and diagnosed with AP within 24 hr of onset were retrospectively reviewed to assess early predictors of progression from AP to SIRS. The patients were divided into SIRS (SIRS occurring after AP) and non-SIRS (AP occurring but no SIRS) groups. The population and mean values of laboratory variables within 24 hr of admission were assessed and compared between both groups. There were significantly more dogs with abnormal lactate levels in the SIRS group (80.00%) than non-SIRS group (11.10%). Other parameters did not differ significantly. Mean lactate level values were significantly higher at 3.64 ± 1.75 mmol in the SIRS group compared to 1.68 ± 0.52 mmol in the non-SIRS group. The increased energy required by activated immune cells may lead to metabolic changes characterized by anaerobic glycolysis and increased lactate production. This study's results suggest blood lactate monitoring in the early stages of progression from AP to SIRS in small animal clinical practice. Measuring lactate levels at the early stages of pancreatitis could lead to rapid therapeutic intervention for SIRS and ultimately reduce mortality.

Spinal manipulation techniques in the treatment of arterial hypertension. (A literature review)

There is a long-observed relationship between the pathology of the spine and arterial hypertension. There are a number of explanations for this, including one based on reflex effects and obstruction of blood flow to the cerebral vasodilatory centre localized in the rhomboid fossa projection. Obstruction can be absolute and relative, preventing the increase of blood flow during stress, when the brain turns on additional energy demand (phenomenon of «selfish brain»). In conditions of insufficient blood supply anaerobic metabolism is included, requiring in the future, the addition of anaerobic glycolysis products. This leads to the persistence of an elevated level of AD and is part of the theory of centralized compensation of aerobic-anaerobic balance (theoretical aerobic-anaerobic energy concept, TAAEBC). The existing methods of manual manipulation and physical action on the spine, mainly the atlantoacral section of the cervical spine, have, according to existing publications, varying degrees of effectiveness. The modern approach to treatment of arterial hypertension and correction of metabolic disorders by A. Shishonin is promising. It is based on the TAAEBC concept and assumes a system approach and long-term effect through a consistent three-step manual and physical interventions aimed at restoring, retaining and long-term support of the vertebral blood flow.

Spiny dogfish, Squalus suckleyi, shows a good tolerance for hypoxia but need long recovery times.

Pacific spiny dogfish, Squalus suckleyi, move to shallow coastal waters during critical reproductive life stages and are thus at risk of encountering hypoxic events which occur more frequently in these areas. For effective conservation management, we need to fully understand the consequences of hypoxia on marine key species such as elasmobranchs. Because of their benthic life style, we hypothesized that S. suckleyi are hypoxia tolerant and able to efficiently regulate oxygen consumption, and that anaerobic metabolism is supported by a broad range of metabolites including ketones, fatty acids and amino acids. Therefore, we studied oxygen consumption rates, ventilation frequency and amplitude, blood gasses, acid-base regulation, and changes in plasma and tissue metabolites during progressive hypoxia. Our results show that critical oxygen levels (P crit) where oxyregulation is lost were indeed low (18.1% air saturation or 28.5Torr at 13°C). However, many dogfish behaved as oxyconformers rather than oxyregulators. Arterial blood PO2 levels mostly decreased linearly with decreasing environmental PO2. Blood gases and acid-base status were dependent on open versus closed respirometry but in both set-ups ventilation frequency increased. Hypoxia below Pcrit resulted in an up-regulation of anaerobic glycolysis, as evidenced by increased lactate levels in all tissues except brain. Elasmobranchs typically rely on ketone bodies as oxidative substrates, and decreased concentrations of acetoacetate and β-hydroxybutyrate were observed in white muscle of hypoxic and/or recovering fish. Furthermore, reductions in isoleucine, glutamate, glutamine and other amino acids were observed. After 6hours of normoxic recovery, changes persisted and only lactate returned to normal in most tissues. This emphasizes the importance of using suitable bioindicators adjusted to preferred metabolic pathways of the target species in conservation physiology. We conclude that Pacific spiny dogfish can tolerate severe transient hypoxic events, but recovery is slow and negative impacts can be expected when hypoxia persists.

Plant-Derived Exosomes as Novel Nanotherapeutics Contrive Glycolysis Reprogramming-Mediated Angiogenesis for Diabetic Ulcer Healing.

Reversal of endothelial cell (EC) dysfunction under high-glucose (HG) conditions to achieve angiogenesis has remained a big challenge in diabetic ulcers. Herein, exosomes derived from medicinal plant ginseng (GExos) were shown as excellent nanotherapeutics with biomimetic cell membrane-like structures to be able to efficiently transfer the encapsulated active substances to ECs, resulting in a marked reprogramming of glycolysis by up-regulating anaerobic glycolysis and down-regulating oxidative stress, which further restore the proliferation, migration, and tubule formation abilities of ECs under HG conditions. Invivo, GExos enhance the angiogenesis and nascent vessel network reconstruction in full-thickness diabetic complicated skin ulcer wounds in mice with high biosafety. GExos were shown as promising nanotherapeutics in stimulating glycolysis reprogramming-mediated angiogenesis in diabetic ulcers, possessing wide application potential for reversing hyperglycemic dysangiogenesis and stimulating vascular regeneration.

A New Role for Lactate in Breast Cancer

Lactate dehydrogenase (LDH) is an enzyme that plays a key role in cellular metabolism by converting pyruvate to lactate during anaerobic glycolysis. LDH has been implicated in various cancer types, including breast cancer, where increased LDH activity is associated with tumor growth, invasion, and resistance to therapy. LDH inhibitors are being investigated as potential therapeutic agents in cancer treatment, including breast cancer. Khajah and colleagues investigated the role of LDH inhibitors in both estrogen receptor (ER)+ and ER‑ breast cancer cell lines and in normal breast epithelial cells. A significant reduction in extracellular lactate level, cell proliferation, motility, and invasion was observed after treatment with LDH inhibitors. Subsequently, changes in the levels of vimentin, E‑cadherin, p38 MAPK, ERK1/2, and AKT were also observed. Cancer cell proliferation was preferentially blocked compared with normal epithelial cell inhibition by LDH inhibitors such as quercetin and lonidamine. These results further highlight the role of lactate in breast cancer progression and indicate the practical use of various commercially available LDH inhibitors as promising therapeutic agents to oppose the processes leading to cancer progression. While LDH inhibitors show promise, challenges include achieving selectivity for cancer cells and minimizing toxicity to normal tissues. The development of specific LDH inhibitors with favorable pharmacokinetic properties is an ongoing area of research. Mol Med Rep. 2024 Jan;29(1):12. doi: 10.3892/mmr.2023.1313.

A comprehensive metabolite fingerprint of fibrostenosis in patients with Crohn’s disease

Intestinal fibrostenosis in patients with Crohn’s disease (CD) is a common and untreatable comorbidity that is notoriously difficult to monitor. We aimed to find metabolites associated with the presence of fibrostenosis in patients with CD using targeted and untargeted metabolomics analyses of serum and primary cell cultures using hyphenated ultra-high performance liquid chromatography high-resolution mass spectrometry. Targeted metabolomics revealed 11 discriminating metabolites in serum, which were enriched within the arginine and proline metabolism pathway. Based on untargeted metabolomics and discriminant analysis, 166 components showed a high predictive value. In addition, human intestinal fibroblasts isolated from stenotic tissue were characterized by differential levels of medium-chain dicarboxylic acids, which are proposed as an energy source through beta-oxidation, when oxidative phosphorylation is insufficient. Another energy providing pathway in such situations is anaerobic glycolysis, a theory supported by increased expression of hexokinase 2 and solute carrier family 16 member 1 in stenotic fibroblasts. Of interest, four (unannotated) metabolic components showed a negative correlation with hexokinase 2 gene expression. Together, this study provides a discriminative metabolic fingerprint in the serum and in intestinal fibroblasts of stenotic and non-stenotic patients with CD suggestive for increased production of building blocks for collagen synthesis and increased glycolysis.

Glutathione-Responsive Organosilica Hybrid Nanosystems for Targeted Dual-Starvation Therapy in Luminal Breast Cancer.

Starvation therapy is an innovative approach in cancer treatment aimed at depriving cancer cells of necessary resources by impeding tumor angiogenesis or blocking the energy supply. In addition to the commonly observed anaerobic glycolysis energy supply mode, adipocyte-rich tumor tissue triggers the fatty acid energy supply pathway, which fuels the proliferation and metastasis of cancer cells. To completely disrupt these dual-energy-supply pathways, we developed an exceptional nanoreactor. This nanoreactor consisted of yolk-shell mesoporous organosilica nanoparticles (YSMONs) loaded with a fatty acid transport inhibitor (Dox), conjugated with a luminal breast-cancer-specific targeting aptamer, and integrated with a glucose oxidation catalyst (GOx). Upon reaching cancer cells with the assistance of the aptamer, the nanoreactor underwent a structural collapse of the shell triggered by the high concentration of glutathione within cancer cells. This collapse led to the release of GOx and Dox, achieving targeted delivery and exhibiting significant efficacy in starving therapy. Additionally, the byproducts of glucose metabolism, gluconic acid and H2O2, enhanced the acidity and reactive oxygen species levels of the intracellular microenvironment, inducing oxidative damage to cancer cells. Simultaneously, released Dox acted as a potent broad-spectrum anticancer drug, inhibiting the activity of carnitine palmitoyltransferase 1A and exerting marked effects. Combining these effects ensures high anticancer efficiency, and the "dual-starvation" nanoreactor has the potential to establish a novel synergistic therapy paradigm with considerable clinical significance. Furthermore, this approach minimizes damage to normal organs, making it highly valuable in the field of cancer treatment.

SNHG17 alters anaerobic glycolysis by resetting phosphorylation modification of PGK1 to foster pro-tumor macrophage formation in pancreatic ductal adenocarcinoma

BackgroundWithin the tumor immune microenvironment (TME), tumor-associated macrophages (TAMs) are crucial in modulating polarization states to influence cancer development through metabolic reprogramming. While long non-coding RNAs (lncRNAs) have been shown to play a pivotal role in the progression of various cancers, the underlying mechanisms by which lncRNAs alter M2 polarization through macrophage metabolism remodeling remain unelucidated.MethodsRNA sequencing was used to screen for differentially expressed lncRNAs in TAMs and normal tissue-resident macrophages (NTRMs) isolated from pancreatic ductal adenocarcinoma (PDAC) tissues, whilst RT-qPCR and FISH were employed to detect the expression level of SNHG17. Moreover, a series of in vivo and in vitro experiments were conducted to assess the functions of SNHG17 from TAMs in the polarization and glycolysis of M2-like macrophages and in the proliferation and metastasis of pancreatic cancer cells (PCs). Furthermore, Western blotting, RNA pull-down, mass spectrometry, RIP, and dual-luciferase assays were utilized to explore the underlying mechanism through which SNHG17 induces pro-tumor macrophage formation.ResultsSNHG17 was substantially enriched in TAMs and was positively correlated with a worse prognosis in PDAC. Meanwhile, functional assays determined that SNHG17 promoted the malignant progression of PCs by enhancing M2 macrophage polarization and anaerobic glycolysis. Mechanistically, SNHG17 could sponge miR-628-5p to release PGK1 mRNA and concurrently interact with the PGK1 protein, activating the pro-tumorigenic function of PGK1 by enhancing phosphorylation at the T168A site of PGK1 through ERK1/2 recruitment. Lastly, SNHG17 knockdown could reverse the polarization status of macrophages in PDAC.ConclusionsThe present study illustrated the essential role of SNHG17 and its molecular mechanism in TAMs derived from PDAC, indicating that SNHG17 might be a viable target for PDAC immunotherapy.

Features of the respiratory burst state of neutrophils and the activity of NAD(P)-dependent dehydrogenases in patients with widespread purulent peritonitis in the prognosis of the development of sepsis

Aim: Studying of the respiratory burst state and NAD(P)-dependent dehydrogenases activities in blood neutrophils features in the forecast of the development of abdominal sepsis in patients with widespread purulent peritonitis (WPP).
 Materials and methods. The study involved 50 patients with WPP in the preoperative period. Abdominal sepsis was developed by 35 patients (70.0%) from 5 to 10 days postoperative period, 15 patients (30.0%) hadn’t complications. The respiratory burst condition of blood neutrophils was examined using a chemiluminescent assay. Intracellular activity of the NAD- and NADP-dependent dehydrogenases was researched with using bioluminescent methods.
 Results. It was found that patients with WPP whose dynamics of the preoperative period will develop sepsis the chemiluminescent activity of blood neutrophils was characterized by a reduced level of spontaneous synthesis of the primary reactive oxygen species (ROS) and elevated levels of spontaneous synthesis of secondary ROS relative of the indicators identified in patients without subsequent complications. The feature of neutrophil metabolism in WPP patients without subsequent development of sepsis was high activity of the anaerobic lactate dehydrogenase reaction and decrease in activity of the NADP-dependent decarboxylating malate dehydrogenase. In patients with WPP and the subsequent development of sepsis was found high level of NAD-dependent substrates outflow citric acid cycle in the reaction of amino acid metabolism via glutamate dehydrogenase that may affect the activity of aerobic respiration in the neutrophils. Using correlation analysis was found that the intensity of the neutrophils respiratory burst in patients with no subsequent complications depends on the activity of anaerobic glycolysis.
 Conclusion. The established differences in the state of the respiratory burst and the activity of enzymes in neutrophils in patients with WPP, in depending on the subsequent development of the sepsis, determine the possibility of developing the method of forecasting complications and developing immunoactive therapy in the postoperative period of WPP.

Lactate-induced histone lactylation by p300 promotes osteoblast differentiation.

Lactate, which is synthesized as an end product by lactate dehydrogenase A (LDHA) from pyruvate during anaerobic glycolysis, has attracted attention for its energy metabolism and oxidant effects. A novel histone modification-mediated gene regulation mechanism termed lactylation by lactate was recently discovered. The present study examined the involvement of histone lactylation in undifferentiated cells that underwent differentiation into osteoblasts. C2C12 cells cultured in medium with a high glucose content (4500 mg/L) showed increases in marker genes (Runx2, Sp7, Tnap) indicating BMP-2-induced osteoblast differentiation and ALP staining activity, as well as histone lactylation as compared to those cultured in medium with a low glucose content (900 mg/L). Furthermore, C2C12 cells stimulated with the LDH inhibitor oxamate had reduced levels of BMP-2-induced osteoblast differentiation and histone lactylation, while addition of lactate to C2C12 cells cultured in low glucose medium resulted in partial restoration of osteoblast differentiation and histone lactylation. These results indicate that lactate synthesized by LDHA during glucose metabolism is important for osteoblast differentiation of C2C12 cells induced by BMP-2. Additionally, silencing of p300, a possible modifier of histone lactylation, also inhibited osteoblast differentiation and reduced histone lactylation. Together, these findings suggest a role of histone lactylation in promotion of undifferentiated cells to undergo differentiation into osteoblasts.

Glycolytic Metabolism of the Tissue Stem Cells in the Maculae Flavae of the Human Vocal Fold

Metabolic programs in the stem cells are essential for maintaining homeostasis and protecting against stem cell aging. There is growing evidence that the tissue stem cells reside in the anterior and posterior maculae flavae of the human vocal fold mucosa. Our previous studies observed that the glycolysis of the cell in the human maculae flavae seems to rely more on anaerobic glycolysis for energy supply in comparison with oxidative phosphorylation. However, previous studies showed only the metabolic enzymes of glycolysis and functional morphology of the mitochondria, therefore, it has not yet been determined whether anaerobic glycolysis actually took place. The purpose of this study is to investigate the glycolytic metabolites of the cells in the maculae flavae of the human vocal fold in vitro. Four normal human vocal folds were used. After extraction of the anterior maculae flavae, cells in the maculae flavae were cultured and proliferated. Glucose transporter-1 was assessed using immunocytochemistry and metabolites of glycolysis (lactate and NADPH) were measured. The cells in the maculae flavae expressed glucose transporter-1 in the cytoplasm and the cell membranes. In addition, the cultured cells produced lactate (metabolites of anaerobic glycolysis) and NADPH (metabolites of the pentose phosphate pathway). The cells in the maculae flavae of the human vocal folds were found to undergo anaerobic glycolysis via the pentose phosphate pathway. This suggests that the cells in the maculae flavae of the human vocal fold have a metabolism that favors the maintenance of stemness and undifferentiated states.

Comparative analysis of glucose and fructose tolerance in two marine fishes: effects on insulin secretion and acute hypoxia tolerance

Carbohydrates are a common and economical energy source in animal feeds. However, most fish show a persistent postprandial hyperglycemia after intake of a high-carbohydrate diet. Unfortunately, the mechanism of glucose metabolism in fish is still unclear. In the present study, tiger puffer (Takifugu rubripes) and turbot (Scophthalmus maximus) were intraperitoneally injected or orally administered with glucose or fructose (500 mg/kg body weight) to evaluate the ability of fish to utilize carbohydrates. Afterwards, serum glucose, fructose, pyruvate, insulin levels, and acute hypoxia tolerance were measured. Our results showed increased serum glucose level and then decreased post intraperitoneal injection with glucose, and reached a peak after 0.5 hours in turbot and 1 hour in tiger puffer. Tiger puffer had significantly lower liver glycogen, serum glucose, fructose, pyruvate, and insulin contents than turbot. Glucose and fructose only induced insulin secretion in turbot, but did not change serum insulin level in tiger puffer. Glucose was a stronger stimulator of insulin than fructose in the two marine species. Both intraperitoneal injection and oral fructose intake increased serum glucose level, while intraperitoneal or oral glucose also increased serum fructose level. Intraperitoneal injection of glucose promoted absorption and utilization of glucose in the blood more effectively than oral glucose intake. In addition, turbot and tiger puffer were intolerant to acute hypoxia, whereas supplementation with glucose or fructose improved hypoxia tolerance in the two marine fishes by activating anaerobic glycolysis. Taken together, our results provide important scientific information for understanding the mechanism for glucose and fructose utilization and improving hypoxia tolerance in fish.

Intracellular Iron Controls HSC Metabolism By Affecting Mitochondrial Fitness

Iron is an important source of reactive oxygen species (ROS) within the cell and recent evidence highlighted its role in regulating HSC self-renewal and differentiation. However, whether and how iron influences HSC metabolism is still undetermined. Cellular metabolism is a key regulator of HSC maintenance and HSCs adapt their metabolic state to their function. Quiescent HSCs have low energy requirements and depend on anaerobic glycolysis, whereas active HSCs require high energy for proliferation and differentiation thus enhancing oxidative phosphorylation (OXPHOS), glycolysis and fatty acid oxidation (FAO). To explore which metabolic pathways are triggered by intracellular iron levels, we took advantage of the thalassemic Hbb th3/+mice ( th3), characterized by chronic iron overload (IO). We previously demonstrated an impaired function of th3 HSCs due to persistence into altered BM niche ( Aprile et al., 2020). Th3 HSCs showed higher levels of intracellular free reactive iron (1.7±0.2 calcein MFI fold to wt, p<0.0001) and interestingly iron specifically accumulated in the mitochondria. As a result, mitochondria are impaired, with low mass and activity, as assessed by decreased mitochondrial membrane potential ( th3 1068±167 vs. wt 3215±686 MFI TMRE, p<0.05). These data, together with a reduced expression of mitochondrial biogenesis and mitophagy genes, indicate an accumulation of damaged mitochondria. To demonstrate a direct effect of iron on mitochondrial fitness in HSCs, we treated wt mice with iron dextran. Consistently, IO wt HSCs showed reduced mitochondrial activity following intracellular iron accumulation. Since mitochondria are the major site of cellular ATP production mostly through OXPHOS, we measured the metabolic state of HSCs in ß-thalassemia. ATP levels in sorted th3 HSCs was halved than the one in wt mice ( th3 3.7±0.3 vs. wt 9.8±2.6 ATP nM, p<0.01). Inhibition of OXPHOS by oligomycin lowered the ATP content in wt cells with a minor effect in th3 HSCs, thus indicating a reduced OXPHOS-dependent metabolism, despite their active cycling profile. Since mitochondria are damaged and OXPHOS and glycolysis are the two main metabolic pathways involved in cellular ATP generation, we hypothesized increased glycolytic dependency to compensate for reduced OXPHOS in th3 HSCs. Indeed, in these cells we observed a positive enrichment of glycolytic genes, such as Tpi1, Gapdh and Pklr, and a 1.4-fold higher glucose uptake ( th3 2401±85 vs. wt 1639±163 MFI 2NBDG, p<0.05). In vivo administration of the iron chelator DFO normalized intracellular iron content and rescued mitochondrial dysfunction in th3 mice, indicating the reversibility of mitochondrial defects. Moreover, HSCs from DFO-treated mice showed reduced glucose uptake, thus demonstrating that IO causes mitochondrial defects and metabolic adaptations of HSCs. Excess iron is expected to give rise to ROS and, consistently, th3 HSCs displayed high mitochondrial ROS (mtROS) levels ( th3 5205±459 vs. wt 2507±756 MFI MitoSOX, p<0.01). I n vivo reduction of mtROS by MitoQ administration restored mitochondrial activity and decreased glucose uptake. Remarkably, MitoQ rescued the quiescence and self-renewal ability of th3 HSCs, as shown by superior chimerism in secondary transplantation of HSCs from MitoQ-treated th3 donors in lethally irradiated recipients ( th3 HSC+MitoQ 81.7±1.6 vs. untreated th3 HSC 34.9±14.6 vs. % of chimerism, p<0.05), thus indicating that IO-derived ROS impair HSC function by affecting mitochondrial fitness and bioenergetics. Preliminary results confirmed intracellular IO and mitochondrial defects also in HSCs from Townes mice, a model of sickle cell anemia characterized by IO. Collectively, our study revealed that increased intracellular iron and ROS levels alter HSC metabolic programs by inducing mitochondrial dysfunction. Since mitochondria are defective, IO HSCs are unable to produce appropriate levels of ATP through OXPHOS and rely on glycolysis, despite their active cycling activity. Finally, the rescue of mitochondrial activity can restore the functional defects of th3 HSCs.

Pyruvate Kinase Thermostability Is Associated with Red Blood Cell Adhesion, Deformability and Oxygen Affinity in Patients with Sickle Cell Disease

Introduction: Sickle cell disease(SCD) is caused by a mutation in the beta globin gene that causes formation of abnormal hemoglobin S (HbS). Red blood cells (RBCs) from patients with SCD are less deformable and take on the shape of sickle upon deoxygenation. This results in multiple downstream effects including RBC adhesion, microvascular occlusion and chronic hemolysis. RBCs rely solely on anaerobic glycolysis to produce adenosine triphosphate (ATP), which is needed to maintain the cell's structure and function. Pyruvate kinase (PK) is a key enzyme involved in the last step of glycolysis. We have previously demonstrated a decrease in PK activity and stability as a novel pathophysiological feature of SCD. Currently there are several clinical trials ongoing investigating the efficacy of PK activation by small molecules such as mitapivat (NL8517, NCT04000165, NCT05031780), AG-946 (NCT04536792) and etavopivat (NCT04624659, NCT04987489). In this study we aim to investigate how PK properties correlate to sickle RBC properties in order to explore if impaired PK function is associated with specific features of the complex SCD pathophysiology. Methods: Homozygous HbS (HbSS) and HbS/ β0 thalassemia patients were eligible to participate. Patients who received blood transfusion (<3 months) were excluded. Dense RBCs (MCHC >41 g/dL, Advia 120/2120 Siemens) and HbF and HbS levels (Tosoh G8) were measured. PK and hexokinase (HK) activity were measured on purified RBCs. PK thermostability (reflected by % residual PK activity) was measured on purified RBCs lysates after one hour of incubation (53°C). RBC adhesion to laminin (Biolamina) was measured using a microfluidic device (IBIDI µ-Slide I 0.4). RBC hydration (Ohyper), RBC deformability (EImax) and point of sickling (PoS) were assessed by osmotic and oxygen gradient ektacytometry using the Laser-Optical Rotational Red Cell Analyzer (Lorrca, RR Mechatronics). Oxygen affinity (P50) was measured with the Hemox-Analyzer (TCS). Statistical analysis was performed in Graphpad Prism (Pearson's correlation). Results: Fifty-seven patients with SCD (53 HbSS, 4 HbS/β 0 thalassemia) were included of which 17 were children (median age 14 years [range 6-17]) and 40 were adults (median age 36 years [range 18-58]). Baseline characteristics are depicted in Table 1. Figure 1 shows a heatmap with correlation coefficients of all laboratory parameters from Table 1 as measured in this cohort. When focusing on PK properties we found that patients with SCD and lower PK thermostability had significantly higher absolute reticulocyte counts (ARC, p<0.0001), lower hemoglobin (p=0.012) and HbF (p=0.020) levels and increased RBC adhesion to laminin (p=0.007). Furthermore, PK thermostability was significantly correlated with EImax (p=0.017) and inversely correlated with PoS (p=0.011) and P50 (p=0.003), indicating that patients with less stable RBC PK had less deformable RBCs which sickled at a higher oxygen tension. RBC adhesion to laminin was significantly correlated with both ARC (p=0.0003) and dense RBCs (p=0.019). To explore whether our findings were a reflection of reticulocytosis we fractionated whole blood samples of HbSS patients according to cell density. We found that more RBCs from the most dense fraction adhered to laminin than from the less dense, reticulocyte enriched, fraction, even though RBCs from this less dense fraction had reduced PK-thermostability. Additionally, the most dense RBCs had the lowest PK activity, were less deformable and had a higher PoS (data not shown). Altogether these findings indicate that the reduced PK thermostability we found in our SCD cohort is associated with an overall functionally impaired RBC population with increased RBC adhesion and ARC. We found no correlation of markers of RBC dehydration (Ohyper and % dense RBCs) with PK thermostability which suggests that RBCs with reduced PK thermostability are not more dehydrated. Discussion/conclusion: This study shows for the first time a significant correlation between PK thermostability in sickle RBCs and RBC functions, such as adhesion, deformability and oxygen affinity. Our results suggest that enhancing the activity and stability of PK, with PK activators, is an attractive target in SCD that might improve other pathophysiological targets outside RBC metabolism. Future studies are needed to explore how activation of PK will affect these altered sickle RBC properties in vivo.