Central Carbon Metabolic Pathways Research Articles

Predicting plasticity of rosette growth and metabolic fluxes in Arabidopsis thaliana.

Plants can rapidly mitigate the effects of suboptimal growth environments by phenotypic plasticity of fitness-traits. While genetic variation for phenotypic plasticity offers the means for breeding climate-resilient crop lines, accurate genomic prediction models for plasticity of fitness-related traits are still lacking. Here, we employed condition- and accession-specific metabolic models for 67 Arabidopsis thaliana accessions to dissect and predict plasticity of rosette growth to changes in nitrogen availability. We showed that specific reactions in photorespiration, linking carbon and nitrogen metabolism, as well as key pathways of central carbon metabolism exhibited substantial genetic variation for flux plasticity. We also demonstrated that, in comparison with a genomic prediction model for fresh weight (FW), genomic prediction of growth plasticity improves the predictability of FW under low nitrogen by 58.9% and by additional 15.4% when further integrating data on plasticity of metabolic fluxes. Therefore, the combination of metabolic and statistical modeling provides a stepping stone in understanding the molecular mechanisms and improving the predictability of plasticity for fitness-related traits.

Coordinated Regulation of Central Carbon Metabolism in Pyroligneous Acid-Treated Tomato Plants under Aluminum Stress

Aluminum (Al) toxicity is a major threat to global crop production in acidic soils, which can be mitigated by natural substances such as pyroligneous acid (PA). However, the effect of PA in regulating plant central carbon metabolism (CCM) under Al stress is unknown. In this study, we investigated the effects of varying PA concentrations (0, 0.25 and 1% PA/ddH2O (v/v)) on intermediate metabolites involved in CCM in tomato (Solanum lycopersicum L., ‘Scotia’) seedlings under varying Al concentrations (0, 1 and 4 mM AlCl3). A total of 48 differentially expressed metabolites of CCM were identified in the leaves of both control and PA-treated plants under Al stress. Calvin–Benson cycle (CBC) and pentose phosphate pathway (PPP) metabolites were considerably reduced under 4 mM Al stress, irrespective of the PA treatment. Conversely, the PA treatment markedly increased glycolysis and tricarboxylic acid cycle (TCA) metabolites compared to the control. Although glycolysis metabolites in the 0.25% PA-treated plants under Al stress were comparable to the control, the 1% PA-treated plants exhibited the highest accumulation of glycolysis metabolites. Furthermore, all PA treatments increased TCA metabolites under Al stress. Electron transport chain (ETC) metabolites were higher in PA-treated plants alone and under 1 mM, Al but were reduced under a higher Al treatment of 4 mM. Pearson correlation analysis revealed that CBC metabolites had a significantly strong positive (r = 0.99; p < 0.001) association with PPP metabolites. Additionally, glycolysis metabolites showed a significantly moderate positive association (r = 0.76; p < 0.05) with TCA metabolites, while ETC metabolites exhibited no association with any of the determined pathways. The coordinated association between CCM pathway metabolites suggests that PA can stimulate changes in plant metabolism to modulate energy production and biosynthesis of organic acids under Al stress conditions.

Functional Degeneracy in Paracoccus denitrificans Pd1222 Is Coordinated via RamB, Which Links Expression of the Glyoxylate Cycle to Activity of the Ethylmalonyl-CoA Pathway.

Metabolic degeneracy describes the phenomenon that cells can use one substrate through different metabolic routes, while metabolic plasticity, refers to the ability of an organism to dynamically rewire its metabolism in response to changing physiological needs. A prime example for both phenomena is the dynamic switch between two alternative and seemingly degenerate acetyl-CoA assimilation routes in the alphaproteobacterium Paracoccus denitrificans Pd1222: the ethylmalonyl-CoA pathway (EMCP) and the glyoxylate cycle (GC). The EMCP and the GC each tightly control the balance between catabolism and anabolism by shifting flux away from the oxidation of acetyl-CoA in the tricarboxylic acid (TCA) cycle toward biomass formation. However, the simultaneous presence of both the EMCP and GC in P. denitrificans Pd1222 raises the question of how this apparent functional degeneracy is globally coordinated during growth. Here, we show that RamB, a transcription factor of the ScfR family, controls expression of the GC in P. denitrificans Pd1222. Combining genetic, molecular biological and biochemical approaches, we identify the binding motif of RamB and demonstrate that CoA-thioester intermediates of the EMCP directly bind to the protein. Overall, our study shows that the EMCP and the GC are metabolically and genetically linked with each other, demonstrating a thus far undescribed bacterial strategy to achieve metabolic plasticity, in which one seemingly degenerate metabolic pathway directly drives expression of the other. IMPORTANCE Carbon metabolism provides organisms with energy and building blocks for cellular functions and growth. The tight regulation between degradation and assimilation of carbon substrates is central for optimal growth. Understanding the underlying mechanisms of metabolic control in bacteria is of importance for applications in health (e.g., targeting of metabolic pathways with new antibiotics, development of resistances) and biotechnology (e.g., metabolic engineering, introduction of new-to-nature pathways). In this study, we use the alphaproteobacterium P. denitrificans as model organism to study functional degeneracy, a well-known phenomenon of bacteria to use the same carbon source through two different (competing) metabolic routes. We demonstrate that two seemingly degenerate central carbon metabolic pathways are metabolically and genetically linked with each other, which allows the organism to control the switch between them in a coordinated manner during growth. Our study elucidates the molecular basis of metabolic plasticity in central carbon metabolism, which improves our understanding of how bacterial metabolism is able to partition fluxes between anabolism and catabolism.

Yeast increases glycolytic flux to support higher growth rates accompanied by decreased metabolite regulation and lower protein phosphorylation

Supply of Gibbs free energy and precursors are vital for cellular function and cell metabolism have evolved to be tightly regulated to balance their supply and consumption. Precursors and Gibbs free energy are generated in the central carbon metabolism (CCM), and fluxes through these pathways are precisely regulated. However, how fluxes through CCM pathways are affected by posttranslational modification and allosteric regulation remains poorly understood. Here, we integrated multi-omics data collected under nine different chemostat conditions to explore how fluxes in the CCM are regulated in the yeast Saccharomyces cerevisiae. We deduced a pathway- and metabolism-specific CCM flux regulation mechanism using hierarchical analysis combined with mathematical modeling. We found that increased glycolytic flux associated with an increased specific growth rate was accompanied by a decrease in flux regulation by metabolite concentrations, including the concentration of allosteric effectors, and a decrease in the phosphorylation level of glycolytic enzymes.

Engineering acetyl-CoA metabolism to enhance stress tolerance of yeast by regulating membrane functionality

Zygosaccharomyces rouxii has excellent fermentation performance and good tolerance to osmotic stress. Acetyl-CoA is a crucial intermediate precursor in the central carbon metabolic pathway of yeast. This study investigated the effect of engineering acetyl-CoA metabolism on the membrane functionality and stress tolerance of yeast. Firstly, exogenous supplementation of acetyl-CoA improved the biomass and the ability of unsaturated fatty acid synthesis of Z. rouxii under salt stress. Q-PCR results suggested that the gene ACSS (coding acetyl-CoA synthetase) was significantly up-expressed. Subsequently, the gene ACSS from Z. rouxii was transformed and heterologously expressed in S. cerevisiae. The recombinant cells exhibited better multiple stress (salt, acid, heat, and cold) tolerance, higher fatty acid contents, membrane integrity, and fluidity. Our findings may provide a suitable means to enhance the stress tolerance and fermentation efficiency of yeast under harsh fermentation environments.

BPA exposure enhances the metastatic aggression of ovarian cancer through the ERα/AKT/mTOR/HIF-1α signaling axis.

Long-term exposure to bisphenol A (BPA) in humans may promote ovarian cancer development. In present study, the mechanisms by which BPA mediates the aggression metastatic behavior of ovarian cancer were investigated in vitro/in vivo. The results showed that BPA (10μM) significantly promoted the proliferation, migration and invasion of human ovarian cancer cells (ES-2 and OVCAR-3cells); moreover, it promoted ES-2 and OVCAR-3cell glucose uptake, lactic acid release and intracellular ATP synthesis. After administration of 5μg/kg/day BPA, tumor volume was increased compared with that in control group. KEGG and GO enrichment analyses showed that the genes from ES-2cell in 10μM BPA-treated group were enriched mainly in central carbon metabolism and PI3K-AKT signaling pathway. Then, qRT‒PCR and western blotting results showed that BPA (10μM) increased the mRNA and protein expression levels of glycolysis-related genes and mTOR, p-AKT HIF-1α and ERα in vitro/vivo; whereas this effect was reduced after treatment with the ERα inhibitor methyl-piperidino-pyrazole. Furthermore, coimmunoprecipitation and mass spectrometry showed that BPA promoted the direct interaction of ERα with lactate dehydrogenase A. These results show that BPA directly promoted the proliferation, migration and invasion of ovarian cancer cells through the ERα/AKT/mTOR/HIF-1α signaling axis to enhance glycolysis.

Chemical isotope labeling assisted liquid chromatography-mass spectrometry method for simultaneous analysis of central carbon metabolism intermediates

Central carbon metabolism pathway (CCM) is one of the most important metabolic pathways in all living organisms and play crucial function in aspect of organism life. However, the simultaneous detection of CCM intermediates remains challenging. Here, we developed a chemical isotope labeling combined with LC-MS method for simultaneous determination of CCM intermediates with high coverage and accuracy. By chemical derivatization with 2-(diazo-methyl)-N-methyl-N-phenyl-benzamide (2-DMBA) and d5-2-DMBA, all CCM intermediates obtain better separation and accurate quantification at a single LC-MS run. The obtained limits of detection of CCM intermediates ranged from 5 to 36 pg/mL. Using this method, we achieved simultaneous and accurate quantification of 22 CCM intermediates in different biological samples. Take account of the high detection sensitivity of the developed method, this method was further applied to the quantification of CCM intermediates at single-cell level. Finally, 21 CCM intermediates were detected in 1000 HEK-293T cells and 9 CCM intermediates were detected in mouse kidney glomeruli optical slice samples (10∼100 cells).

Alpha-Tocopherol Significantly Improved Squalene Production Yield of Aurantiochytrium sp. TWZ-97 through Lowering ROS levels and Up-Regulating Key Genes of Central Carbon Metabolism Pathways.

Media supplementation has proven to be an effective technique for improving byproduct yield during microbial fermentation. This study explored the impact of different concentrations of bioactive compounds, namely alpha-tocopherol, mannitol, melatonin, sesamol, ascorbic acid, and biotin, on the Aurantiochytrium sp. TWZ-97 culture. Our investigation revealed that alpha-tocopherol was the most effective compound in reducing the reactive oxygen species (ROS) burden, both directly and indirectly. Adding 0.7 g/L of alpha-tocopherol led to an 18% improvement in biomass, from 6.29 g/L to 7.42 g/L. Moreover, the squalene concentration increased from 129.8 mg/L to 240.2 mg/L, indicating an 85% improvement, while the squalene yield increased by 63.2%, from 19.82 mg/g to 32.4 mg/g. Additionally, our comparative transcriptomics analysis suggested that several genes involved in glycolysis, pentose phosphate pathway, TCA cycle, and MVA pathway were overexpressed following alpha-tocopherol supplementation. The alpha-tocopherol supplementation also lowered ROS levels by binding directly to ROS generated in the fermentation medium and indirectly by stimulating genes that encode antioxidative enzymes, thereby decreasing the ROS burden. Our findings suggest that alpha-tocopherol supplementation can be an effective method for improving squalene production in Aurantiochytrium sp. TWZ-97 culture.

Comparative Genomic Analysis of a Methylorubrum rhodesianum MB200 Isolated from Biogas Digesters Provided New Insights into the Carbon Metabolism of Methylotrophic Bacteria.

Methylotrophic bacteria are widely distributed in nature and can be applied in bioconversion because of their ability to use one-carbon source. The aim of this study was to investigate the mechanism underlying utilization of high methanol content and other carbon sources by Methylorubrum rhodesianum strain MB200 via comparative genomics and analysis of carbon metabolism pathway. The genomic analysis revealed that the strain MB200 had a genome size of 5.7 Mb and two plasmids. Its genome was presented and compared with that of the 25 fully sequenced strains of Methylobacterium genus. Comparative genomics revealed that the Methylorubrum strains had closer collinearity, more shared orthogroups, and more conservative MDH cluster. The transcriptome analysis of the strain MB200 in the presence of various carbon sources revealed that a battery of genes was involved in the methanol metabolism. These genes are involved in the following functions: carbon fixation, electron transfer chain, ATP energy release, and resistance to oxidation. Particularly, the central carbon metabolism pathway of the strain MB200 was reconstructed to reflect the possible reality of the carbon metabolism, including ethanol metabolism. Partial propionate metabolism involved in ethyl malonyl-CoA (EMC) pathway might help to relieve the restriction of the serine cycle. In addition, the glycine cleavage system (GCS) was observed to participate in the central carbon metabolism pathway. The study revealed the coordination of several metabolic pathways, where various carbon sources could induce associated metabolic pathways. To the best of our knowledge, this is the first study providing a more comprehensive understanding of the central carbon metabolism in Methylorubrum. This study provided a reference for potential synthetic and industrial applications of this genus and its use as chassis cells.

Quantitative proteomics reveals reduction in central carbon and energy metabolisms contributes to gentamicin resistance in Staphylococcus aureus

The emergence of antibiotic resistance greatly increases the difficulty of treating bacterial infections. In order to develop effective treatments, the underlying mechanisms of antibiotic resistance must be understood. In this study, Staphylococcus aureus ATCC6538 strain was passaged in medium with and without gentamicin and obtained lab-evolved gentamicin-resistant S. aureus (RGEN) and gentamicin-sensitive S. aureus (SGEN) strains, respectively. Data-Independent Acquisition (DIA)-based proteomics approach was applied to compare the two strains. A total of 1426 proteins were identified, of which 462 were significantly different: 126 were upregulated and 336 were downregulated in RGEN compared to SGEN. Further analysis found that reduced protein biosynthesis was a characteristic feature in RGEN, related to metabolic suppression. The most differentially expressed proteins were involved in metabolic pathways. In RGEN, central carbon metabolism was dysregulated and energy metabolism decreased. After verification, it was found that the levels of NADH, ATP, and reactive oxygen species (ROS) decreased, and superoxide dismutase and catalase activities increased. These findings suggest that inhibition of central carbon and energy metabolic pathways may play an important role in the resistance of S. aureus to gentamicin, and that gentamicin resistance is associated with oxidative stress.Significance: The overuse and misuse of antibiotics have led to bacterial antibiotic resistance, which is a serious threat to human health. Understanding the mechanisms of antibiotic resistance will help better control these antibiotic-resistant pathogens in the future. The present study characterized the differential proteome of gentamicin-resistant Staphylococcus aureus using the most advanced DIA-based proteomics technology. Many of the differential expressed proteins were related to metabolism, specifically, reduced central carbon and energy metabolism. Lower levels of NADH, ROS, and ATP were detected as a consequence of the reduced metabolism. These results reveal that downregulation of protein expression affecting central carbon and energy metabolisms may play an important role in the resistance of S. aureus to gentamicin.

Porcine reproductive and respiratory syndrome virus infection manipulates central carbon metabolism

The metabolic pathways of central carbon metabolism (CCM), glycolysis and the tricarboxylic acid (TCA) cycle, are important host factors determining the outcome of viral infection. Thus, it is not surprising that viruses easily manipulate CCM for optimized replication. Porcine reproductive and respiratory syndrome virus (PRRSV) is an Arterivirus that has devastated the swine industry worldwide for over 30 years. However, whether PRRSV reprograms CCM is still unclear. In this study, we found that PRRSV infection increased the intensity of cellular uptake of glucose and glutamine, two main carbon sources for mammalian cells. Deprivation of glucose and/or glutamine significantly reduced PRRSV replication; restricted entry of glucose and glutamine into CCM inhibited PRRSV proliferation. We further found that PRRSV infection elevated glycolysis and maintained the TCA cycle flux. Furthermore, preventing the flow of glycolysis or the TCA cycle led to a reduction in PRRSV proliferation. The anaplerotic usage of glutamine in the TCA cycle partially rescued PRRSV growth by replacing glutamine with α-ketoglutarate (α-KG), an intermediate of the TCA cycle. Interestingly, the addition of α-KG in replete medium also promoted PRRSV proliferation. Taken together, these results reveal that PRRSV infection promotes cellular uptake of glucose and glutamine to provide the energy and macromolecules required for PRRSV replication, and optimal PRRSV replication occurs in cells dependent on glycolysis and the TCA cycle.

Knocking out central metabolism genes to identify new targets and alternating substrates to improve lipid synthesis in Y. lipolytica.

Introduction: Systematic gene knockout studies may offer us novel insights on cell metabolism and physiology. Specifically, the lipid accumulation mechanism at the molecular or cellular level is yet to be determined in the oleaginous yeast Y. lipolytica. Methods: Herein, we established ten engineered strains with the knockout of important genes involving in central carbon metabolism, NADPH generation, and fatty acid biosynthetic pathways. Results: Our result showed that NADPH sources for lipogenesis include the OxPP pathway, POM cycle, and a trans-mitochondrial isocitrate-α-oxoglutarate NADPH shuttle in Y. lipolytica. Moreover, we found that knockout of mitochondrial NAD+ isocitrate dehydrogenase IDH2 and overexpression of cytosolic NADP+ isocitrate dehydrogenase IDP2 could facilitate lipid synthesis. Besides, we also demonstrated that acetate is a more favorable carbon source for lipid synthesis when glycolysis step is impaired, indicating the evolutionary robustness of Y. lipolytica. Discussion: This systematic investigation of gene deletions and overexpression across various lipogenic pathways would help us better understand lipogenesis and engineer yeast factories to upgrade the lipid biomanufacturing platform.

Post-pollination sepal longevity of female flower co-regulated by energy-associated multiple pathways in dioecious spinach.

Reproductive growth is a bioenergetic process with high energy consumption. Pollination induces female flower longevity in spinach by accelerating sepal retention and development. Cellular bioenergetics involved in cellular growth is at the foundation of all developmental activities. By contrast, how pollination alter the sepal cells bioenergetics to support energy requirement and anabolic biomass accumulation for development is less well understood. To investigate pollination-induced energy-associated pathway changes in sepal tissues after pollination, we utilized RNA-sequencing to identify transcripts that were differentially expressed between unpollinated (UNP) and pollinated flower sepals at 12, 48, and 96HAP. In total, over 6756 non-redundant DEGs were identified followed by pairwise comparisons (i.e. UNP vs 12HAP, UNP vs 48HAP, and UNP vs 96HAP). KEGG enrichment showed that the central carbon metabolic pathway was significantly activated after pollination and governed by pivotal energy-associated regulation pathways such as glycolysis, the citric acid cycle, oxidative phosphorylation, photosynthesis, and pentose phosphate pathways. Co-expression networks confirmed the synergistically regulation interactions among these pathways. Gene expression changes in these pathways were not observed after fertilization at 12HAP, but started after fertilization at 48HAP, and significant changes in gene expression occurred at 96HAP when there is considerable sepal development. These results were also supported by qPCR validation. Our results suggest that multiple energy-associated pathways may play a pivotal regulatory role in post-pollination sepal longevity for developing the seed coat, and proposed an energy pathway model regulating sepal retention in spinach.

Ribitol alters multiple metabolic pathways of central carbon metabolism with enhanced glycolysis: A metabolomics and transcriptomics profiling of breast cancer.

Breast cancer is heterogenous in development and cell population with prognoses being highly dependent on numerous factors from driving mutations, biomarker expression and variation in extracellular environment, all affecting response to therapies. Recently, much attention has been given to the role of metabolic alteration in cancers, expanding from the Warburg effect to highlight unique patterns in different cancer cell populations for improving diagnostic and therapeutic approaches. We recently reported on modulation of mannosylation of α-dystroglycan with the metabolite ribitol in breast cancer lines. Here we investigate the effects of pentose sugars ribitol, ribose, and xylitol media supplementation in breast cancer cells by metabolomics and differential gene expression profiling. This combined approach revealed distinctive patterns of alterations in metabolic pathways by ribitol, contrasted with the closely related pentose ribose and pentitol xylitol. Significantly, ribitol supplementation enhances utilization of glucose by glycolysis, whereas ribose improves oxidative phosphorylation and fatty acid synthesis. Ribitol supplementation also increased levels of reduced glutathione (associated with a decrease in oxidative phosphorylation, gluconeogenesis), where ribose supplementation elevated levels of oxidized glutathione (GSSG) indicating an increase in oxidative stress. Treatment with ribitol also enhanced nucleotide biosynthesis. The apparent TCA cycle dysregulation, with distinctive pattern in response to the individual pentitol and pentose, such as ribitol increasing succinate and fumarate while decreasing citrate, demonstrate the adaptive capability of cancer cells to nutritional environment. This metabolic reprogramming presents new avenues for developing targeted therapies to cancers with metabolites, especially in combination with other drug treatments.

MRNA levels of tricarboxylic acid cycle genes in Streptomyces coelicolor M145 cultured on glucose.

Streptomyces strains degrade many complex organic compounds and produce secondary metabolites. In aerobic organisms such as Streptomyces species, the tricarboxylic acid (TCA) cycle represents an indispensable central carbon metabolic pathway for energy generation and metabolic intermediary replenishment. Although various precursors for antibiotic biosynthesis are derived from this cycle, relatively few studies have focused on determining how a single carbon source can impact this metabolic pathway at different growth phases. In this study, we identified chromosomal genes involved in the TCA cycle in Streptomyces coelicolor and determined their mRNA levels. We searched the genes involved in the TCA cycle in S. coelicolor through bioinformatic analysis. Growth, glucose concentration quantification and RNA isolation were made from cultures of S. coelicolor grown on minimal medium with glucose along 72h. mRNA levels of all identified genes were obtained by RT-qPCR. Five enzymes encoded by a single gene each were found, while for the rest at least two genes were found. The results showed that all the genes corresponding to the TCA enzymes were transcribed at very different levels and some of them displayed growth-phase dependent expression. All TCA cycle-associated genes, including paralog genes, were differentially transcribed in S. coelicolor grown in minimal medium with glucose as carbon source. Some of them, such as succinyl-CoA synthetase and succinate dehydrogenase, have low mRNA levels, which could limit the carbon flux through the TCA cycle. Our findings suggest that the genetic expansion of TCA cycle genes could confer to S. coelicolor the ability to adapt to diverse nutritional conditions and metabolic changes through different paralog genes expression.

Lactucin, a Bitter Sesquiterpene from Cichorium intybus, Inhibits Cancer Cell Proliferation by Downregulating the MAPK and Central Carbon Metabolism Pathway.

Lung cancer, especially adenocarcinoma, is the second most occurring and highest fatality-causing cancer worldwide. Many natural anticancer compounds, such as sesquiterpene lactones (SLs), show promising anticancer properties. Herein, we examined Lactucin, an SL from the plant Cichorium intybus, for its cytotoxicity, apoptotic-inducing, cell cycle inhibiting capacity, and associated protein expression. We also constructed a biotinylated Lactucin probe to isolate interacting proteins and identified them. We found that Lactucin stops the proliferation of A549 and H2347 lung adenocarcinoma cell lines while not affecting normal lung cell MRC5. It also significantly inhibits the cell cycle at G0/G1 stage and induces apoptosis. The western blot analysis shows that Lactucin downregulates the MAPK pathway, cyclin, and cyclin-dependent kinases, inhibiting DNA repair while upregulating p53, p21, Bax, PTEN, and downregulation of Bcl-2. An increased p53 in response to DNA damage upregulates p21, Bax, and PTEN. In an activity-based protein profiling (ABPP) analysis of A549 cell's protein lysate using a biotinylated Lactucin probe, we found that Lactucin binds PGM, PKM, and LDHA PDH, four critical enzymes in central carbon metabolism in cancer cells, limiting cancer cells in its growth; thus, Lactucin inhibits cancer cell proliferation by downregulating the MAPK and the Central Carbon Metabolism pathway.

Kinetic and data-driven modeling of pancreatic β-cell central carbon metabolism and insulin secretion.

Pancreatic β-cells respond to increased extracellular glucose levels by initiating a metabolic shift. That change in metabolism is part of the process of glucose-stimulated insulin secretion and is of particular interest in the context of diabetes. However, we do not fully understand how the coordinated changes in metabolic pathways and metabolite products influence insulin secretion. In this work, we apply systems biology approaches to develop a detailed kinetic model of the intracellular central carbon metabolic pathways in pancreatic β-cells upon stimulation with high levels of glucose. The model is calibrated to published metabolomics datasets for the INS1 823/13 cell line, accurately capturing the measured metabolite fold-changes. We first employed the calibrated mechanistic model to estimate the stimulated cell's fluxome. We then used the predicted network fluxes in a data-driven approach to build a partial least squares regression model. By developing the combined kinetic and data-driven modeling framework, we gain insights into the link between β-cell metabolism and glucose-stimulated insulin secretion. The combined modeling framework was used to predict the effects of common anti-diabetic pharmacological interventions on metabolite levels, flux through the metabolic network, and insulin secretion. Our simulations reveal targets that can be modulated to enhance insulin secretion. The model is a promising tool to contextualize and extend the usefulness of metabolomics data and to predict dynamics and metabolite levels that are difficult to measure in vitro. In addition, the modeling framework can be applied to identify, explain, and assess novel and clinically-relevant interventions that may be particularly valuable in diabetes treatment.

Lactucin, a bitter sesquiterpene from Cichorium intybus, inhib-its cancer cell proliferation by downregulating the MAPK and Central Carbon Metabolism pathway

Lactucin, a bitter sesquiterpene from Cichorium intybus, inhib-its cancer cell proliferation by downregulating the MAPK and Central Carbon Metabolism pathway

Folate enzyme MTHFD2 links one-carbon metabolism to unfolded protein response in glioblastoma

The mitochondrial folate enzyme methylenetetrahydrofolate dehydrogenase/cyclohydrolase (MTHFD2) has shown oncogenic roles in various cancers and may have non-metabolic functions. This study investigated the role of MTHFD2 in glioblastoma pathogenesis. We find that MTHFD2 expression is enriched in gliomas by analysing public databases and clinical specimens. RNA interference (RNAi) and inhibitor of MTHFD2 hamper the proliferation of glioblastoma and induce apoptosis in cell lines, glioma stem-like cells (GSCs) and patient-derived xenografts (PDX). Metabolomic analyses show that MTHFD2 depletion suppresses the central carbon metabolic pathways, including glycolysis, the pentose phosphate pathway (PPP), and the tricarboxylic acid (TCA) cycle. GSEA reveals a novel non-metabolic function of MTHFD2 in association with the unfolded protein response (UPR). MTHFD2 depletion activates the PERK/eIF2α axis which contributes to translation inhibition and apoptosis; these effects are attenuated by a PERK inhibitor. Mechanistically, MTHFD2 may be linked to UPR via the post-transcriptionally regulation of chaperone protein GRP78. In conclusion, MTHFD2 could be a promising therapeutic target for glioblastoma. Besides its canonical role, MTHFD2 may contribute to glioblastoma pathogenesis via UPR, highlighting a newly identified functional link between one-carbon metabolism and cell stress response.

Spatially resolved characterization of tissue metabolic compartments in fasted and high-fat diet livers.

Cells adapt their metabolism to physiological stimuli, and metabolic heterogeneity exists between cell types, within tissues, and subcellular compartments. The liver plays an essential role in maintaining whole-body metabolic homeostasis and is structurally defined by metabolic zones. These zones are well-understood on the transcriptomic level, but have not been comprehensively characterized on the metabolomic level. Mass spectrometry imaging (MSI) can be used to map hundreds of metabolites directly from a tissue section, offering an important advance to investigate metabolic heterogeneity in tissues compared to extraction-based metabolomics methods that analyze tissue metabolite profiles in bulk. We established a workflow for the preparation of tissue specimens for matrix-assisted laser desorption/ionization (MALDI) MSI that can be implemented to achieve broad coverage of central carbon, nucleotide, and lipid metabolism pathways. Herein, we used this approach to visualize the effect of nutrient stress and excess on liver metabolism. Our data revealed a highly organized metabolic tissue compartmentalization in livers, which becomes disrupted under high fat diet. Fasting caused changes in the abundance of several metabolites, including increased levels of fatty acids and TCA intermediates while fatty livers had higher levels of purine and pentose phosphate-related metabolites, which generate reducing equivalents to counteract oxidative stress. This spatially conserved approach allowed the visualization of liver metabolic compartmentalization at 30 μm pixel resolution and can be applied more broadly to yield new insights into metabolic heterogeneity in vivo.