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Hypoxia-inducible factor-1 (HIF-1) is an $\alpha$/$\beta$ heterodimeric transcription factor. In normal mammalian cells, HIF-1$\alpha$ is hydroxylated and degraded upon biosynthesis. However, HIF-1$\alpha$ is frequently expressed in cancer and adds to cancer malignancy. In this study, we investigated whether green tea-derived epigallocatechin-3-gallate (EGCG) decreased HIF-1$\alpha$ in pancreatic cancer cells. After MiaPaCa-2 and PANC-1 pancreatic cancer cells were exposed to EGCG in vitro, we performed a Western blot to determine native and hydroxylated HIF-1$\alpha$, which was in turn used to assess HIF-1$\alpha$ production. In order to assess HIF-1$\alpha$ stability, we determined the HIF-1$\alpha$ after MiaPaCa-2 and PANC-1 cells were switched from hypoxia to normoxia. We found that EGCG decreased both production and stability of HIF-1$\alpha$. Further, the EGCG-induced decrease in HIF-1$\alpha$ reduced intracellular glucose transporter-1 and glycolytic enzymes and attenuated glycolysis, ATP production, and cell growth. Because EGCG is known to inhibit cancer-induced insulin receptor (IR) and insulin-like growth factor-1 receptor (IGF1R), we created three MiaPaCa-2 sublines whose IR, IGF1R, and HIF-1$\alpha$ were decreased using RNA interference. From wild-type MiaPaCa-2 cells and these sublines, we found evidence that suggested that the EGCG-induced inhibition of HIF-1$\alpha$ was both dependent on and independent of IR and IGF1R. In vivo, we transplanted wild-type MiaPaCa-2 cells in athymic mice and treated the mice with EGCG or vehicle. When the resulting tumors were analyzed, we found that EGCG decreased tumor-induced HIF-1$\alpha$ and tumor growth. In conclusion, EGCG decreased HIF-1$\alpha$ in pancreatic cancer cells and sabotaged the cells. The anticancer effects of EGCG were both dependent on and independent of IR and IGF1R.

Solasonine (SS) is a natural glycoalkaloid compound that has been reported to possess a significant anticancer function. However, its anticancer effects and related mechanisms in osteosarcoma (OS) have not been studied. This study sought to investigate the impact of SS on the growth of OS cells. OS cells were treated with different concentrations of SS for 24h, and the results showed that SS attenuated the survival of OS cells in a dose-dependent manner. Additionally, SS suppressed cancer stem-like properties and epithelial–mesenchymal transition (EMT) by inhibiting aerobic glycolysis in OS cells in an ALDOA-dependent manner. Additionally, SS reduced the levels of Wnt3a, $\beta$-catenin, and Snail in OS cells in vitro. Furthermore, Wnt3a activation reversed the SS-induced inhibition of glycolysis in OS cells. Collectively, this study discovered a novel effect of SS in inhibiting aerobic glycolysis, in addition to cancer stem-like features and EMT, implying that SS could be a therapeutic candidate for OS treatment.

Hexokinase 2 (HK2), the first glycolytic rate-limiting enzyme, is closely correlated with the occurrence and progression of tumors. Effective therapeutic agents targeting HK2 are urgently needed. Bergenin has exhibited various pharmacological activities, such as antitumor properties. However, the effects of bergenin on the abnormal glucose metabolism of cancer cells are yet unclear. In this study, HK2 was overexpressed in OSCC tissues, and the depletion of HK2 inhibited the growth of OSCC cells in vitro and in vivo. Moreover, these results showed that the natural compound, bergenin, exerted a robust antitumor effect on OSCC cells. Bergenin inhibited cancer cell proliferation, suppressed glycolysis, and induced intrinsic apoptosis in OSCC cells by downregulating HK2. Notably, bergenin restored the antitumor efficacy of irradiation in the radioresistant OSCC cells. A mechanistic study revealed that bergenin upregulated the protein level of phosphatase and the tensin homolog deleted on chromosome 10 (PTEN) by enhancing the interaction between PTEN and ubiquitin-specific protease 13 (USP13) and stabilizing PTEN; this eventually inhibited AKT phosphorylation and HK2 expression. Bergenin was identified as a novel therapeutic agent against glycolysis to inhibit OSCC and overcome radioresistance. Targeting PTEN/AKT/HK2 signaling could be a promising option for clinical OSCC treatment.

Ovarian cancer is a common, highly lethal tumor. Herein, we reported that S-phase kinase-associated protein 2 (Skp2) is essential for the growth and aerobic glycolysis of ovarian cancer cells. Skp2 was upregulated in ovarian cancer tissues and associated with poor clinical outcomes. Using a customized natural product library screening, we found that xanthohumol inhibited aerobic glycolysis and cell viability of ovarian cancer cells. Xanthohumol facilitated the interaction between E3 ligase Cdh1 and Skp2 and promoted the Ub-K48-linked polyubiquitination of Skp2 and degradation. Cdh1 depletion reversed xanthohumol-induced Skp2 downregulation, enhancing HK2 expression and glycolysis in ovarian cancer cells. Finally, a xenograft tumor model was employed to examine the antitumor efficacy of xanthohumol in vivo. Collectively, we discovered that xanthohumol promotes the binding between Skp2 and Cdh1 to suppress the Skp2/AKT/HK2 signal pathway and exhibits potential antitumor activity for ovarian cancer cells.

Glycolysis is one of the key metabolic reprogramming characteristics of ovarian cancer. Ursolic Acid (UA), as a natural compound, exerts a beneficial regulatory effect on tumor metabolism. In this study, we have confirmed through RNA-seq analysis and a series of in vitro and in vivo functional experiments that UA significantly inhibits ovarian cancer cell proliferation, promotes tumor apoptosis, and reduces glycolysis levels. Additionally, it demonstrates synergistic therapeutic effects with cisplatin in both in vitro and in vivo experiments. Furthermore, at the molecular level, we found that UA inhibits glycolysis in ovarian cancer by binding to the transcription factor KLF5 and blocking the transcriptional expression of the downstream PI3K/AKT signaling pathway, thereby exerting its therapeutic effect. In conclusion, our research indicates that UA can inhibit the proliferation, apoptosis, and glycolysis levels of ovarian cancer cells through the KLF5/PI3K/AKT signaling axis. Our findings offer a new perspective on the therapeutic application of the natural compound UA in ovarian cancer and support its potential development as a candidate for chemotherapy.

Glycolysis is the most important cellular process yielding ATP, the universal energy carrier molecule in all living organisms. The characteristic oscillations of the intermediates of glycolysis have been the subject of extensive experimental and theoretical research over the last four decades. A conspicuous property of the glycolytic oscillations is their critical control by the substrate injection rate. In this brief review, we trace its experimental background and explore the essential underlying theoretical models to elucidate a number of nonlinear dynamical phenomena observed in the weak noise limit of the substrate injection rate. Simultaneous oscillations of glycolytic intermediates and insulin have also been discussed within the framework of a phenomenological model in the context of basic experimental issues.

First developed in the case of a stationary flux, the notion of control strength inside a metabolic pathway is extended here to the case of a periodic flux. In this case, the control strength is no more defined on the stationary flux, but on other characteristics of the dynamics like the period or the amplitude, depending on the characteristic whose evolution we wished to describe.

We simulated a subsystem of the glycolysis where a periodic behaviour exists and calculated the control strength on the period and on the amplitude of the ATP concentration. The results showed the value of the control coefficients were different on both characteristics: some steps exerts more control on the period than on the amplitude and conversely for other steps. Then, in a given step of the metabolic chain, we tried to relate the control coefficient obtained in the stationary flux situation to the one obtained for the flux amplitude in the periodic situation. We did not observe any continuity phenomenon and we explain that it is due to the qualitative properties of the system. Finally, we think the extension of the notion of control strength to periodic or chaotic motion is a good approach to analyze the way a metabolic step influences specific characteristics of the dynamics.

In a previous paper [26] the emergence of irreversible transitions between alternative branches of stationary states in a bistable dynamical regime of the phosphofructokinase/fructose 1,6-bisphosphatase model cycle was shown to exist in addition to reversible hysteretic transitions. In the case of irreversible transitions, all these transitions lead to only one of the branches of stationary states, and hence no hysteretic loop can take place. In the present report we demonstrate that for some parameters a situation may arise where, in a bistable dynamic regime, both limit points are not accessible by changes of the respective parameters. Then the system behaves like a monostable device although, depending upon its history, alternative stationary states related to distinct functional properties, e.g., the direction of fluxes or the energetic charge of the states, may be approached. Transitions from one branch of stationary solutions to another one would require adequate tuning of other parameters which could drive the system out of the domain in which non-connected bands of stationary states arise. In the investigated model system, the adenylate energy charge influx and the rate of the influx in the hexosemonophosphates may serve as parameters causing the emergence of non-connected bands of stationary solutions.

The steady-state and dynamic behavior of a partial glycolytic reaction sequence are investigated in cell-free extracts of yeast. Pyruvate kinase, adenylate kinase and glucose 6-phosphate isomerase cooperate to a multi-enzyme system centered around the 6-phosphofructose 1-kinase (6-PFK) and fructose 1,6-bisphosphatase (FBPase) cycle. The reaction system operates under thermodynamically open conditions maintained by a continuous supply of substrates, i.e. glucose 6-phosphate (Glc6P), ATP and phospho-enolpyruvate (PPrv) in a flow-through reaction chamber. Appropriate parametric conditions lead to the occurence of (two) coexisting and markedly different time-independent states in the metabolite concentrations and fluxes. It was already shown that for particular experimental conditions, changes of the influx adenylate energy charge, [AEC]_IN, may cause transitions between these alternative steady states which are either reversible as it occurs in classical hysteresis phenomena, or irreversible (irreversible transitions) where the system is not able to switch back to its previous state even when the perturbation is reverted.

It was also shown numerically from the same qualitative model, that changes in the [AEC]_IN, could also lead to the occurence of non-connected branches of alternative steady states [27]. In the present article, we propose the first experimental demonstration for the existence of such dynamic structures related to bistability and where no transition between the two coexisting stable branches of the bistable are physically possible and defining thus functionally non-equivalent states with distinct metabolite pattern.

Different genes of an organism are expressed to different levels at different times during the life cycle and in response to various environmental stresses. Elucidating the network of gene-gene interactions responsible for the expression helps understand living processes. Microarray technology allows concurrent genomic scale measurement of an organism's mRNA levels. We describe a power-law formalism to model the combinatorial effect of regulators on gene transcription. The dynamic model allows delayed transcription. We employ a principled network reconstruction approach that accounts for the high noise and low replicate characteristics of present day microarray data. An important feature of our approach is that the detail of the reconstructed network is limited to the noise level of the data. We apply the methodology to a microarray dataset of yeast cells grown in glucose and experiencing a diauxic transition upon glucose depletion. The reconstructed transcriptional regulations of yeast glycolytic genes are consistent with published findings.

Metal ions have a major effect on the metabolic processes in cells either as inhibitors or as integral components of enzymes. The inhibition of enzymes can take place either through the inhibition of gene expression or through inhibition of protein function. A particularly interesting example of the effect of a metal ion on metabolism is the observed inhibition of Krebs cycle and alteration of energy metabolism by zinc (II) cations. In this particular case metal ion inhibition of enzyme is linked to one of the major functions of prostate cells of accumulation and excretion of citrate. Experimental results have shown that increase in concentration of zinc (II) in prostate cells effectively blocks progression of a part of the Krebs cycle leading to change in the concentration of several metabolites with largest effect in the accumulation of citrate. Based on previously reported experimental results, several distinct mechanisms for zinc (II) inhibition of Krebs cycle were proposed. In order to determine the precise mechanism of inhibition in this system, a mathematical model of glycolysis and Krebs cycle was constructed. Three different types of inhibition were analyzed, including competitive and uncompetitive inhibition as well as inhibition through the alteration of the expression level of m-aconitase. The effects of different inhibition models on metabolite concentrations were investigated as a time course simulation of the system of reactions. Several kinetic parameters in the model were optimized in order to best resemble experimental measurements. The simulation shows that only competitive inhibition leads to an agreement with experimental data.

Nicotinamide adenine dinucleotide (NADH) is a cofactor that serves to shuttle electrons during metabolic processes such as glycolysis, the tricarboxylic acid cycle, and oxidative phosphorylation (OXPHOS). NADH is autofluorescent, and its fluorescence lifetime can be used to infer metabolic dynamics in living cells. Fiber-coupled time-correlated single photon counting (TCSPC) equipped with an implantable needle probe can be used to measure NADH lifetime in vivo, enabling investigation of changing metabolic demand during muscle contraction or tissue regeneration. This study illustrates a proof of concept for point-based, minimally-invasive NADH fluorescence lifetime measurement in vivo. Volumetric muscle loss (VML) injuries were created in the left tibialis anterior (TA) muscle of male Sprague Dawley rats. NADH lifetime measurements were collected before, during, and after a 30s tetanic contraction in the injured and uninjured TA muscles, which was subsequently fit to a biexponential decay model to yield a metric of NADH utilization (cytoplasmic vs protein-bound NADH, the A${}_1{\tau }_1$/A${}_2{\tau }_2$ ratio). On average, this ratio was higher during and after contraction in uninjured muscle compared to muscle at rest, suggesting higher levels of free NADH in contracting and recovering muscle, indicating increased rates of glycolysis. In injured muscle, this ratio was higher than uninjured muscle overall but decreased over time, which is consistent with current knowledge of inflammatory response to injury, suggesting tissue regeneration has occurred. These data suggest that fiber-coupled TCSPC has the potential to measure changes in NADH binding in vivo in a minimally invasive manner that requires further investigation.

Metabolism is one of the best studied fields of biochemistry, but its regulation involves processes on many different levels, some of which are still not understood well enough to allow for quantitative modeling and prediction. Glycolysis in yeast is a good example: although high-quality quantitative data are available, well-established mathematical models typically only cover direct regulation of the involved enzymes by metabolite binding. The effect of various metabolites on the enzyme kinetics is summarized in carefully developed mathematical formulae. However, this approach implicitly assumes that the enzyme concentrations themselves are constant, thus neglecting other regulatory levels – e.g. transcriptional and translational regulation – involved in the regulation of enzyme activities. It is believed, however, that different experimental conditions result in different enzyme activities regulated by the above mechanisms. Detailed modeling of all regulatory levels is still out of reach since some of the necessary data – e.g. quantitative large scale enzyme concentration data sets – are lacking or rare. Nevertheless, a viable approach is to include the regulation of enzyme concentrations into an established model and to investigate whether this improves the predictive capabilities. Proteome data are usually hard to obtain, but levels of mRNA transcripts may be used instead as clues for changes in enzyme concentrations. Here we investigate whether including mRNA data into an established model of yeast glycolysis allows to predict the steady state metabolic concentrations for different experimental conditions. To this end, we modified an established ODE model for the glycolytic pathway of yeast to include changes of enzyme concentrations. Presumable changes were inferred from mRNA transcript level measurement data. We investigate how this approach can be used to predict metabolite concentrations for steady-state yeast cultures at five different oxygen levels ranging from anaerobic to fully aerobic conditions. We were partly able to reproduce the experimental data and present a number of changes that were necessary to improve the modeling result.

The sun is the only source of renewable energy available to us, if geothermal energy is not taken into account. In the form of radiation (UV light, visible light, infrared light, Section 1.1) it sends us annually 178,000 terawatts (1 TW = 10¹² W; unit of power 1 W = 1 J s^–1 = 859.85 calories per hour), that is to say 15,000 times the energy consumed annually by humanity. Only 0.1% of the solar energy received by planet Earth is converted into plant biomass, i.e. 100 × 10⁹ tons per year which corresponds to ca. 180 × 10⁹ tons per year of CO₂ captured from the atmosphere. This CO₂ returns to the biosphere after the death of the plants. Consumption of fossil carbon emits ca. 35 × 10⁹ tons of CO₂ yearly. Biomass is the material produced by all living organisms (plants, animals, microorganisms, fungi)…