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Nature Metabolism Sep 2020The mechanistic target of rapamycin complex 1 (mTORC1) kinase regulates cell growth by setting the balance between anabolic and catabolic processes. To be active, mTORC1...
The mechanistic target of rapamycin complex 1 (mTORC1) kinase regulates cell growth by setting the balance between anabolic and catabolic processes. To be active, mTORC1 requires the environmental presence of amino acids and glucose. While a mechanistic understanding of amino acid sensing by mTORC1 is emerging, how glucose activates mTORC1 remains mysterious. Here, we used metabolically engineered human cells lacking the canonical energy sensor AMP-activated protein kinase to identify glucose-derived metabolites required to activate mTORC1 independent of energetic stress. We show that mTORC1 senses a metabolite downstream of the aldolase and upstream of the GAPDH-catalysed steps of glycolysis and pinpoint dihydroxyacetone phosphate (DHAP) as the key molecule. In cells expressing a triose kinase, the synthesis of DHAP from DHA is sufficient to activate mTORC1 even in the absence of glucose. DHAP is a precursor for lipid synthesis, a process under the control of mTORC1, which provides a potential rationale for the sensing of DHAP by mTORC1.
Topics: AMP-Activated Protein Kinases; Dihydroxyacetone; Dihydroxyacetone Phosphate; Energy Metabolism; Fructose-Bisphosphate Aldolase; Glucose; Glycolysis; HEK293 Cells; Humans; Lipid Metabolism; Phosphotransferases (Alcohol Group Acceptor); TOR Serine-Threonine Kinases
PubMed: 32719541
DOI: 10.1038/s42255-020-0250-5 -
Nature Communications Jul 2023Neutrophils rely predominantly on glycolytic metabolism for their biological functions, including reactive oxygen species (ROS) production. Although pyruvate kinase M2...
Neutrophils rely predominantly on glycolytic metabolism for their biological functions, including reactive oxygen species (ROS) production. Although pyruvate kinase M2 (PKM2) is a glycolytic enzyme known to be involved in metabolic reprogramming and gene transcription in many immune cell types, its role in neutrophils remains poorly understood. Here, we report that PKM2 regulates ROS production and microbial killing by neutrophils. Zymosan-activated neutrophils showed increased cytoplasmic expression of PKM2. Pharmacological inhibition or genetic deficiency of PKM2 in neutrophils reduced ROS production and Staphylococcus aureus killing in vitro. In addition, this also resulted in phosphoenolpyruvate (PEP) accumulation and decreased dihydroxyacetone phosphate (DHAP) production, which is required for de novo synthesis of diacylglycerol (DAG) from glycolysis. In vivo, PKM2 deficiency in myeloid cells impaired the control of infection with Staphylococcus aureus. Our results fill the gap in the current knowledge of the importance of lower glycolysis for ROS production in neutrophils, highlighting the role of PKM2 in regulating the DHAP and DAG synthesis to promote ROS production in neutrophils.
Topics: Pyruvate Kinase; Reactive Oxygen Species; Neutrophils; Phosphorylation; Glycolysis
PubMed: 37460614
DOI: 10.1038/s41467-023-40021-6 -
Polymers May 2023Bacterial immobilization is regarded as an enabling technology to improve the stability and reusability of biocatalysts. Natural polymers are often used as...
Bacterial immobilization is regarded as an enabling technology to improve the stability and reusability of biocatalysts. Natural polymers are often used as immobilization matrices but present certain drawbacks, such as biocatalyst leakage and loss of physical integrity upon utilization in bioprocesses. Herein, we prepared a hybrid polymeric matrix that included silica nanoparticles for the unprecedented immobilization of the industrially relevant (Gfr). This biocatalyst can valorize glycerol, an abundant by-product of the biodiesel industry, into glyceric acid (GA) and dihydroxyacetone (DHA). Different concentrations of siliceous nanosized materials, such as biomimetic Si nanoparticles (SiNps) and montmorillonite (MT), were added to alginate. These hybrid materials were significantly more resistant by texture analysis and presented a more compact structure as seen by scanning electron microscopy. The preparation including 4% alginate with 4% SiNps proved to be the most resistant material, with a homogeneous distribution of the biocatalyst in the beads as seen by confocal microscopy using a fluorescent mutant of Gfr. It produced the highest amounts of GA and DHA and could be reused for up to eight consecutive 24 h reactions with no loss of physical integrity and negligible bacterial leakage. Overall, our results indicate a new approach to generating biocatalysts using hybrid biopolymer supports.
PubMed: 37299313
DOI: 10.3390/polym15112514 -
Chemical Research in Toxicology Apr 2022Dihydroxyacetone (DHA) is a major byproduct of e-cigarette combustion and is the active ingredient in sunless tanning products. Mounting evidence points to its damaging...
Dihydroxyacetone (DHA) is a major byproduct of e-cigarette combustion and is the active ingredient in sunless tanning products. Mounting evidence points to its damaging effects on cellular functions. While developing a simple synthetic route to monomeric [C]DHA for flux metabolic studies that compared DHA and glyceraldehyde (GA) metabolism, we uncovered that solid DHA ages upon storage and differences in the relative abundance of each of its isomer occur when reconstituted in an aqueous solution. While all three of the dimeric forms of DHA ultimately resolve to the ketone and hydrated forms of monomeric DHA once in water at room temperature, these species require hours rather than minutes to reach an equilibrium favoring the monomeric species. Consequently, when used in bolus or flux experiments, the relative abundance of each isomer and its effects at the time of application is dependent on the initial DHA isomeric composition and concentration, and time of equilibration in solution before use. Here, we make recommendations for the more consistent handling of DHA as we report conditions that ensure that DHA is present in its monomeric form while in solutions, conditions used in an isotopic tracing study that specifically compared monomeric DHA and GA metabolism in cells.
Topics: Dihydroxyacetone; Electronic Nicotine Delivery Systems; Isomerism; Solutions
PubMed: 35324152
DOI: 10.1021/acs.chemrestox.1c00403 -
NMR in Biomedicine Oct 2019Glycolysis is a fundamental metabolic process in all organisms. Anomalies in glucose metabolism are linked to various pathological conditions. In particular, elevated... (Review)
Review
Glycolysis is a fundamental metabolic process in all organisms. Anomalies in glucose metabolism are linked to various pathological conditions. In particular, elevated aerobic glycolysis is a characteristic feature of rapidly growing cells. Glycolysis and the closely related pentose phosphate pathway can be monitored in real time by hyperpolarized C-labeled metabolic substrates such as C-enriched, deuterated D-glucose derivatives, [2- C]-D-fructose, [2- C] dihydroxyacetone, [1- C]-D-glycerate, [1- C]-D-glucono-δ-lactone and [1- C] pyruvate in healthy and diseased tissues. Elevated glycolysis in tumors (the Warburg effect) was also successfully imaged using hyperpolarized [U- C , U- H ]-D-glucose, while the size of the preexisting lactate pool can be measured by C MRS and/or MRI with hyperpolarized [1- C]pyruvate. This review summarizes the application of various hyperpolarized C-labeled metabolites to the real-time monitoring of glycolysis and related metabolic processes in normal and diseased tissues.
Topics: Animals; Carbohydrate Metabolism; Carbon Isotopes; Glycolysis; Humans; Magnetic Resonance Spectroscopy; Metabolome; Time Factors
PubMed: 30474153
DOI: 10.1002/nbm.4018 -
Cell Stress & Chaperones Nov 2023Plants trigger endoplasmic reticulum (ER) pathways to survive stresses, but the assistance of ER in plant tolerance still needs to be explored. Thus, we selected...
Plants trigger endoplasmic reticulum (ER) pathways to survive stresses, but the assistance of ER in plant tolerance still needs to be explored. Thus, we selected sensitive and tolerant contrasting abiotic stress sorghum varieties to test if they present a degree of tolerance to ER stress. Accordingly, this work evaluated crescent concentrations of tunicamycin (TM µg mL): control (0), lower (0.5), mild (1.5), and higher (2.5) on the initial establishment of sorghum seedlings CSF18 and CSF20. ER stress promoted growth and metabolism reductions, mainly in CSF18, from mild to higher TM. The lowest TM increased SbBiP and SbPDI chaperones, as well as SbbZIP60, and SbbIRE1 gene expressions, but mild and higher TM decreased it. However, CSF20 exhibited higher levels of SbBiP and SbbIRE1 transcripts. It corroborated different metabolic profiles among all TM treatments in CSF18 shoots and similarities between profiles of mild and higher TM in CSF18 roots. Conversely, TM profiles of both shoots and roots of CSF20 overlapped, although it was not complete under low TM treatment. Furthermore, ER stress induced an increase of carbohydrates (dihydroxyacetone in shoots, and cellobiose, maltose, ribose, and sucrose in roots), and organic acids (pyruvic acid in shoots, and butyric and succinic acids in roots) in CSF20, which exhibited a higher degree of ER stress tolerance compared to CSF18 with the root being the most affected plant tissue. Thus, our study provides new insights that may help to understand sorghum tolerance and the ER disturbance as significant contributor for stress adaptation and tolerance engineering.
Topics: Tunicamycin; Sorghum; Molecular Chaperones; Endoplasmic Reticulum; Endoplasmic Reticulum Stress
PubMed: 37775652
DOI: 10.1007/s12192-023-01382-5 -
Frontiers in Microbiology 2022Acetic acid bacteria (AAB) are a group of Gram-negative, strictly aerobic bacteria, including 19 reported genera until 2021, which are widely found on the surface of... (Review)
Review
Acetic acid bacteria (AAB) are a group of Gram-negative, strictly aerobic bacteria, including 19 reported genera until 2021, which are widely found on the surface of flowers and fruits, or in traditionally fermented products. Many AAB strains have the great abilities to incompletely oxidize a large variety of carbohydrates, alcohols and related compounds to the corresponding products mainly including acetic acid, gluconic acid, gulonic acid, galactonic acid, sorbose, dihydroxyacetone and miglitol the membrane-binding dehydrogenases, which is termed as AAB oxidative fermentation (AOF). Up to now, at least 86 AOF products have been reported in the literatures, but no any monograph or review of them has been published. In this review, at first, we briefly introduce the classification progress of AAB due to the rapid changes of AAB classification in recent years, then systematically describe the enzymes involved in AOF and classify the AOF products. Finally, we summarize the application of molecular biology technologies in AOF researches.
PubMed: 35685922
DOI: 10.3389/fmicb.2022.879246 -
Molecular Metabolism Dec 2022Glycerol-3-phosphate (Gro3P) phosphatase (G3PP) hydrolyzes Gro3P to glycerol that exits the cell, thereby operating a "glycerol shunt", a metabolic pathway that we...
OBJECTIVE
Glycerol-3-phosphate (Gro3P) phosphatase (G3PP) hydrolyzes Gro3P to glycerol that exits the cell, thereby operating a "glycerol shunt", a metabolic pathway that we identified recently in mammalian cells. We have investigated the role of G3PP and the glycerol shunt in the regulation of glucose metabolism and lipogenesis in mouse liver.
METHODS
We generated hepatocyte-specific G3PP-KO mice (LKO), by injecting AAV8-TBG-iCre to male G3PP mice. Controls received AAV8-TBG-eGFP. Both groups were fed chow diet for 10 weeks. Hyperglycemia (16-20 mM) was induced by glucose infusion for 55 h. Hepatocytes were isolated from normoglycemic mice for ex vivo studies and targeted metabolomics were measured in mice liver after glucose infusion.
RESULTS
LKO mice showed no change in body weight, food intake, fed and fasted glycemia but had increased fed plasma triglycerides. Hepatic glucose production from glycerol was increased in fasted LKO mice. LKO mouse hepatocytes displayed reduced glycerol production, elevated triglyceride and lactate production at high glucose concentration. Hyperglycemia in LKO mice led to increased liver weight and accumulation of triglycerides, glycogen and cholesterol together with elevated levels of Gro3P, dihydroxyacetone phosphate, acetyl-CoA and some Krebs cycle intermediates in liver. Hyperglycemic LKO mouse liver showed elevated expression of proinflammatory cytokines and M1-macrophage markers accompanied by increased plasma triglycerides, LDL/VLDL, urea and uric acid and myocardial triglycerides.
CONCLUSIONS
The glycerol shunt orchestrated by G3PP acts as a glucose excess detoxification pathway in hepatocytes by preventing metabolic disturbances that contribute to enhanced liver fat, glycogen storage, inflammation and lipid build-up in the heart. We propose G3PP as a novel therapeutic target for hepatic disorders linked to nutrient excess.
Topics: Animals; Male; Mice; Glucose; Glycerol; Glycogen; Hyperglycemia; Liver; Phosphoric Monoester Hydrolases; Triglycerides
PubMed: 36198384
DOI: 10.1016/j.molmet.2022.101609 -
Dihydroxyacetone suppresses mTOR nutrient signaling and induces mitochondrial stress in liver cells.PloS One 2022Dihydroxyacetone (DHA) is the active ingredient in sunless tanning products and a combustion product from e-juices in electronic cigarettes (e-cigarettes). DHA is...
Dihydroxyacetone (DHA) is the active ingredient in sunless tanning products and a combustion product from e-juices in electronic cigarettes (e-cigarettes). DHA is rapidly absorbed in cells and tissues and incorporated into several metabolic pathways through its conversion to dihydroxyacetone phosphate (DHAP). Previous studies have shown DHA induces cell cycle arrest, reactive oxygen species, and mitochondrial dysfunction, though the extent of these effects is highly cell-type specific. Here, we investigate DHA exposure effects in the metabolically active, HepG3 (C3A) cell line. Metabolic and mitochondrial changes were evaluated by characterizing the effects of DHA in metabolic pathways and nutrient-sensing mechanisms through mTOR-specific signaling. We also examined cytotoxicity and investigated the cell death mechanism induced by DHA exposure in HepG3 cells. Millimolar doses of DHA were cytotoxic and suppressed glycolysis and oxidative phosphorylation pathways. Nutrient sensing through mTOR was altered at both short and long time points. Increased mitochondrial reactive oxygen species (ROS) and mitochondrial-specific injury induced cell cycle arrest and cell death through a non-classical apoptotic mechanism. Despite its carbohydrate nature, millimolar doses of DHA are toxic to liver cells and may pose a significant health risk when higher concentrations are absorbed through e-cigarettes or spray tanning.
Topics: Dihydroxyacetone; Electronic Nicotine Delivery Systems; Reactive Oxygen Species; Mitochondria; Liver
PubMed: 36472985
DOI: 10.1371/journal.pone.0278516 -
Communications Biology Nov 2022Bacteria and Eucarya utilize the non-oxidative pentose phosphate pathway to direct the ribose moieties of nucleosides to central carbon metabolism. Many archaea do not...
Bacteria and Eucarya utilize the non-oxidative pentose phosphate pathway to direct the ribose moieties of nucleosides to central carbon metabolism. Many archaea do not possess this pathway, and instead, Thermococcales utilize a pentose bisphosphate pathway involving ribose-1,5-bisphosphate (R15P) isomerase and ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (Rubisco). Intriguingly, multiple genomes from halophilic archaea seem only to harbor R15P isomerase, and do not harbor Rubisco. In this study, we identify a previously unrecognized nucleoside degradation pathway in halophilic archaea, composed of guanosine phosphorylase, ATP-dependent ribose-1-phosphate kinase, R15P isomerase, RuBP phosphatase, ribulose-1-phosphate aldolase, and glycolaldehyde reductase. The pathway converts the ribose moiety of guanosine to dihydroxyacetone phosphate and ethylene glycol. Although the metabolic route from guanosine to RuBP via R15P is similar to that of the pentose bisphosphate pathway in Thermococcales, the downstream route does not utilize Rubisco and is unique to halophilic archaea.
Topics: Ribulose-Bisphosphate Carboxylase; Ribose; Pentoses; Archaea; Guanosine; Phosphates
PubMed: 36434094
DOI: 10.1038/s42003-022-04247-2