Alterations in tricarboxylic acid (TCA) cycle metabolism are associated with hepatic metabolic disorders. Elevated hepatic acetate concentrations, often attributed to high caloric intake, are recognized as a pivotal factor in the etiology of obesity and metabolic syndrome. Therefore, the assessment of acetate breakdown and TCA cycle activity plays a central role in understanding the impact of diet-induced alterations on liver metabolism. Magnetic resonance-based deuterium metabolic imaging (DMI) could help to unravel the underlying mechanisms involved in disease development and progression, however, the application of conventional deuterated glucose does not lead to substantial enrichment in hepatic glutamine and glutamate. This study aimed to demonstrate the feasibility of DMI for tracking deuterated acetate breakdown via the TCA cycle in lean and diet-induced fatty liver (FL) rats using 3D DMI after an intraperitoneal infusion of sodium acetate-d3 at 9.4T. Localized and nonlocalized liver spectra acquired at 10 time points post-injection over a 130-min study revealed similar intrahepatic acetate uptake in both animal groups (AUCFL = 717.9 ± 131.1 mM▯min-1, AUClean = 605.1 ± 119.9 mM▯min-1, p = 0.62). Metabolic breakdown could be observed in both groups with an emerging glutamine/glutamate (Glx) peak as a downstream metabolic product (AUCFL = 113.6 ± 23.8 mM▯min-1, AUClean = 136.7 ± 41.7 mM▯min-1, p = 0.68). This study showed the viability of DMI for tracking substrate flux through the TCA cycle, underscoring its methodological potential for imaging metabolic processes in the body.
- MeSH
- acetáty metabolismus MeSH
- analýza metabolického toku MeSH
- citrátový cyklus * MeSH
- deuterium * MeSH
- játra * metabolismus diagnostické zobrazování MeSH
- krysa rodu rattus MeSH
- magnetická rezonanční tomografie MeSH
- potkani Sprague-Dawley MeSH
- potkani Wistar MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
The molecular mechanisms linking obstructive sleep apnea syndrome (OSA) to obesity and the development of metabolic diseases are still poorly understood. The role of hypoxia (a characteristic feature of OSA) in excessive fat accumulation has been proposed. The present study investigated the possible effects of hypoxia (4% oxygen) on de novo lipogenesis by tracking the major carbon sources in differentiating 3T3-L1 adipocytes. Gas-permeable cultuware was employed to cultivate 3T3-L1 adipocytes in hypoxia (4%) for 7 or 14 days of differentiation. We investigated the contribution of glutamine, glucose or acetate using 13C or 14C labelled carbons to the newly synthesized lipid pool, changes in intracellular lipid content after inhibiting citrate- or acetate-dependent pathways and gene expression of involved key enzymes. The results demonstrate that, in differentiating adipocytes, hypoxia decreased the synthesis of lipids from glucose (44.1 ± 8.8 to 27.5 ± 3.0 pmol/mg of protein, p < 0.01) and partially decreased the contribution of glutamine metabolized through the reverse tricarboxylic acid cycle (4.6% ± 0.2-4.2% ± 0.1%, p < 0.01). Conversely, the contribution of acetate, a citrate- and mitochondria-independent source of carbons, increased upon hypoxia (356.5 ± 71.4 to 649.8 ± 117.5 pmol/mg of protein, p < 0.01). Further, inhibiting the citrate- or acetate-dependent pathways decreased the intracellular lipid content by 58% and 73%, respectively (p < 0.01) showing the importance of de novo lipogenesis in hypoxia-exposed adipocytes. Altogether, hypoxia modified the utilization of carbon sources, leading to alterations in de novo lipogenesis in differentiating adipocytes and increased intracellular lipid content.
- MeSH
- acetáty * metabolismus farmakologie MeSH
- buněčná diferenciace * účinky léků MeSH
- buňky 3T3-L1 * MeSH
- citrátový cyklus MeSH
- glukosa * metabolismus MeSH
- glutamin * metabolismus MeSH
- hypoxie buňky MeSH
- lipidy biosyntéza MeSH
- lipogeneze * účinky léků MeSH
- metabolismus lipidů účinky léků MeSH
- myši MeSH
- tukové buňky * metabolismus účinky léků MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Tumor cells often adapt to amino acid deprivation through metabolic rewiring, compensating for the loss with alternative amino acids/substrates. We have described such a scenario in leukemic cells treated with L-asparaginase (ASNase). Clinical effect of ASNase is based on nutrient stress achieved by its dual enzymatic action which leads to depletion of asparagine and glutamine and is accompanied with elevated aspartate and glutamate concentrations in serum of acute lymphoblastic leukemia patients. We showed that in these limited conditions glutamate uptake compensates for the loss of glutamine availability. Extracellular glutamate flux detection confirms its integration into the TCA cycle and its participation in nucleotide and glutathione synthesis. Importantly, it is glutamate-driven de novo synthesis of glutathione which is the essential metabolic pathway necessary for glutamate's pro-survival effect. In vivo findings support this effect by showing that inhibition of glutamate transporters enhances the therapeutic effect of ASNase. In summary, ASNase induces elevated extracellular glutamate levels under nutrient stress, which leads to a rewiring of intracellular glutamate metabolism and has a negative impact on ASNase treatment.
- MeSH
- akutní lymfatická leukemie farmakoterapie metabolismus patologie MeSH
- antitumorózní látky farmakologie MeSH
- asparaginasa * farmakologie metabolismus MeSH
- citrátový cyklus účinky léků MeSH
- glutamin metabolismus MeSH
- glutathion * metabolismus MeSH
- kyselina glutamová * metabolismus MeSH
- lidé MeSH
- myši MeSH
- nádorové buněčné linie MeSH
- xenogenní modely - testy antitumorózní aktivity MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
V současné době je glukóza považována za zdroj energie, který při nadměrné konzumaci přispívá k obezitě a cukrovce. Produkce energie ve formě ATP však nepředstavuje základní význam tohoto sacharidu. Tím je její neoxidativní metabolismus, který může mít zásadní význam pro živé organismy, a úplná oxidace glukózy nastává pouze tehdy, pokud její množství poskytuje potřeby pro její neoxidační metabolismus. Nedostatek glukózy pro důležité neoxidační procesy se pak stává základem pro inzulinovou rezistenci. Inzulinová rezistence tedy nastává, když existuje relativní nedostatek glukózy během patologických stavů, jako jsou metabolický syndrom, akutní a chronický zánět, ale může být spojena s fyziologickými stavy, jako jsou rychlý růst, regenerace, těhotenství nebo laktace. Protože glukóza je důležitá pro anabolické reakce a nejen zdroj energie ve formě ATP, je logické, že inzulinová rezistence záměrně snižuje jeho nevratnou oxidaci; naopak zvyšuje glukoneogenezi a zvyšuje cyklování glukózy. To znamená, že za výše uvedených podmínek by se příjem uhlohydrátů (glukózy) neměl snížit ani během inzulinové rezistence.
Currently, glucose is considered as the energy source for the formation of ATP. However, the production of energy in the form of ATP does not represent the basic importance of this carbohydrate. It is non-oxidative metabolism that may be of fundamental importance for the function of glucose in living organisms. Complete oxidation is then of secondary importance and if there is a shortage of glucose in the body, then the lack of glucose for non-oxidative metabolism may be the basis for the insulin resistance. Insulin resistance thus occurs in pathological conditions such as metabolic syndrome, acute and chronic inflammation, but at the same time it can be observed in physiological conditions such as rapid growth, regeneration, pregnancy or lactation. Since glucose is important for anabolic reactions, and not just a source of energy in the form of ATP, it is logical that insulin resistance purposefully reduces its irreversible oxidation; on the contrary, it increases gluconeogenesis and increases glucose cycling. This means that during the above states, the intake of carbohydrates (glucose) should not be reduced even during insulin resistance.
- MeSH
- citrátový cyklus MeSH
- glukosa * biosyntéza fyziologie metabolismus MeSH
- inzulinová rezistence MeSH
- lidé MeSH
- Check Tag
- lidé MeSH
Podle definice života – množivost (replikace), metabolismus a energetická potřeba a schopnost reagovat na adekvátní podněty mají základní stavební molekuly života společnou hlavní nosnou strukturu: purinovou bázi – adenin, ribózu a dvě fosfátové skupiny. V tomto smyslu může molekula ATP představovat nosič a donor energie a organizátor molekulární výstavby, obnovy a replikace i signální molekulu v mechanismech reaktivity.
According to the definition of life – reproduction (replication), metabolism and energy requirements and the ability to respond to adequate stimuli, the basic building molecules of life have a common principal structure: the purine base - adenine, ribose and two phosphate groups. In this sense, the ATP molecule can represent a carrier and donor of energy and an organizer of molecular construction, renewal and replication, as well as a signalling molecule in reactivity mechanisms.
Východiska: Společným rysem metabolizmu nádorových buněk je schopnost získávat potřebné živiny z poměrně chudého prostředí a využívat je k udržení životaschopnosti a tvorbě nové biomasy. Změny v intracelulárních a extracelulárních metabolitech, které doprovází metabolické přeprogramování spojené s růstem nádoru, mají následně zásadní účinek na genovou expresi, buněčnou diferenciaci a mikroprostředí nádoru. V průběhu kancerogeneze čelí nádorové buňky selekčním tlakům, které je nutí neustále optimalizovat dominantní metabolické dráhy a nádorové buňky tak procházejí zásadními metabolickými reorganizacemi. Obecně platí, že vyšší flexibilita metabolických drah zvyšuje schopnost nádorových buněk sladit metabolické potřeby s měnícím se prostředím. Cíl: V tomto přehledovém článku pojednáváme o metabolických vlastnostech nádorových buněk a popisujeme účinek transformovaného metabolizmu na progresi nádoru. Domníváme se, že metabolické změny jsou pro rozvoj nádorů zásadní a mohly by poskytnout zajímavé cíle pro léčbu.
Background: A general characteristic of cancer metabolism is the skill to gain the essential nutrients from a relatively poor environment and use them effectively to maintain viability and create new biomass. The changes in intracellular and extracellular metabolites that accompany metabolic reprogramming associated with tumor growth subsequently affect gene expression, cell differentiation, and tumor microenvironment. During carcinogenesis, cancer cells face huge selection pressures that force them to constantly optimize dominant metabolic pathways and undergo major metabolic reorganizations. In general, greater flexibility of metabolic pathways increases the ability of tumor cells to satisfy their metabolic needs in a changing environment. Purpose: In this review, we discuss the metabolic properties of cancer cells and describe the tumor promoting effect of the transformed metabolism. We assume that changes in metabolism are significant enough to facilitate tumorigenesis and may provide interesting targets for cancer therapy.
Obstructive sleep apnea syndrome, characterized by repetitive episodes of tissue hypoxia, is associated with several metabolic impairments. Role of fatty acids and lipids attracts attention in its pathogenesis for their metabolic effects. Parallelly, hypoxia-induced activation of reverse tricarboxylic acid cycle (rTCA) with reductive glutamine metabolism provides precursor molecules for de novo lipogenesis. Gas-permeable cultureware was used to culture L6-myotubes in chronic hypoxia (12%, 4% and 1% O2) with 13C labelled glutamine and inhibitors of glutamine uptake or rTCA-mediated lipogenesis. We investigated changes in lipidomic profile, 13C appearance in rTCA-related metabolites, gene and protein expression of rTCA-related proteins and glutamine transporters, glucose uptake and lactate production. Lipid content increased by 308% at 1% O2, predominantly composed of saturated fatty acids, while triacylglyceroles containing unsaturated fatty acids and membrane lipids (phosphatidylcholines, phosphatidylethanolamines, phosphatidylinositol) decreased by 20-70%. rTCA labelling of malate, citrate and 2-hydroxyglutarate increased by 4.7-fold, 2.2-fold and 1.9-fold in 1% O2, respectively. ATP-dependent citrate lyase inhibition in 1% O2 decreased lipid amount by 23% and increased intensity of triacylglyceroles containing unsaturated fatty acids by 56-80%. Lactate production increased with hypoxia. Glucose uptake dropped by 75% with progression of hypoxia from 4% to 1% O2. Protein expression remained unchanged. Altogether, hypoxia modified cell metabolism leading to lipid composition alteration and rTCA activation.
Psychosis is a state of altered thoughts which often accompanies schizophrenia. It was suggested that changes in energetic metabolism accompany psychosis and post-psychosis states. Here, we use the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 to experimentally induce psychosis-like behavior in rats. We addressed an effect of single and repeated (5×) MK-801 application (0.3 mg/kg; i.p.) on the energy metabolism in homogenates and crude mitochondrial fraction (CMF) of the striatum (STR), prefrontal cortex (PFC), and the hippocampus (HIP) of the adult male Wistar rat (n = 39). In each brain region, we assessed activity of glycolytic (hexokinase (HK) and lactate dehydrogenase (LDH)) and Krebs cycle enzymes (citrate synthase (CS) and malate dehydrogenase (MDH)) 2 h and 3 days (3d) after the last MK-801 application together with relative respiratory rates assessment in tissue homogenate. In STR, a single MK-801 application led to a decrease in the LDH (p = 0.0035) and the increase of the MDH (p = 0.0043) activities following 3d. Therein, repeated MK-801 doses evoked increased LDH (p = 0.0204) and CS (p = 0.0019) activities in the homogenate 2 h and increased HK (p = 0.0007) 3d after the last application. Elevated HK activity within CMF was observed after 3d (p = 0.0054). In PFC, repeated MK-801 application decreased HK activity in the homogenate 3d after the final application (p = 0.0234). Correspondingly, PFC HK activity in CMF of repeated administration samples dropped (p = 0.003). In HIP, repeated MK-801 administration led to increased respiration of SDH (p = 0.0475) only 2 h after the last application and decreased CS activity (p = 0.0160) was observed 3d after the last application. Our results indicate a progressive metabolic dysregulation of glycolytic and Krebs cycle enzymes following repeated inhibition of NMDA receptors activity in a region-specific manner. Energetic alterations may form a basis for persisting cognitive problems during and following a psychosis in schizophrenia patients.
- MeSH
- citrátový cyklus MeSH
- citrátsynthasa metabolismus farmakologie MeSH
- dizocilpinmaleát * farmakologie MeSH
- hexokinasa metabolismus farmakologie MeSH
- hipokampus MeSH
- krysa rodu rattus MeSH
- L-laktátdehydrogenasa metabolismus MeSH
- lidé MeSH
- N-methylaspartát * farmakologie MeSH
- potkani Wistar MeSH
- prefrontální mozková kůra MeSH
- receptory N-methyl-D-aspartátu metabolismus MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- lidé MeSH
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Fluorescein is a fluorescent dye used as a diagnostic tool in various fields of medicine. Although fluorescein itself possesses low toxicity, after photoactivation, it releases potentially toxic molecules, such as singlet oxygen (1O2) and, as we demonstrate in this work, also carbon monoxide (CO). As both of these molecules can affect physiological processes, the main aim of this study was to explore the potential biological impacts of fluorescein photochemistry. In our in vitro study in a human hepatoblastoma HepG2 cell line, we explored the possible effects on cell viability, cellular energy metabolism, and the cell cycle. We observed markedly lowered cell viability (≈30%, 75-2400 μM) upon irradiation of intracellular fluorescein and proved that this decrease in viability was dependent on the cellular oxygen concentration. We also detected a significantly decreased concentration of Krebs cycle metabolites (lactate and citrate < 30%; 2-hydroxyglutarate and 2-oxoglutarate < 10%) as well as cell cycle arrest (decrease in the G2 phase of 18%). These observations suggest that this photochemical reaction could have important biological consequences and may account for some adverse reactions observed in fluorescein-treated patients. Additionally, the biological activities of both 1O2 and CO might have considerable therapeutic potential, particularly in the treatment of cancer.
- MeSH
- angiografie MeSH
- antitumorózní látky chemie farmakologie MeSH
- buňky Hep G2 MeSH
- citrátový cyklus účinky léků účinky záření MeSH
- fluorescein chemie farmakologie MeSH
- fotochemické procesy MeSH
- kontrolní body buněčného cyklu účinky léků účinky záření MeSH
- lidé MeSH
- oxid uhelnatý analýza MeSH
- plynová chromatografie s hmotnostně spektrometrickou detekcí MeSH
- singletový kyslík analýza MeSH
- světlo MeSH
- viabilita buněk účinky léků MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Metabolic transformation of cancer cells leads to the accumulation of lactate and significant acidification in the tumor microenvironment. Both lactate and acidosis have a well-documented impact on cancer progression and negative patient prognosis. Here, we report that cancer cells adapted to acidosis are significantly more sensitive to oxidative damage induced by hydrogen peroxide, high-dose ascorbate, and photodynamic therapy. Higher lactate concentrations abrogate the sensitization. Mechanistically, acidosis leads to a drop in antioxidant capacity caused by a compromised supply of nicotinamide adenine dinucleotide phosphate (NADPH) derived from glucose metabolism. However, lactate metabolism in the Krebs cycle restores NADPH supply and antioxidant capacity. CPI-613 (devimistat), an anticancer drug candidate, selectively eradicates the cells adapted to acidosis through inhibition of the Krebs cycle and induction of oxidative stress while completely abrogating the protective effect of lactate. Simultaneous cell treatment with tetracycline, an inhibitor of the mitochondrial proteosynthesis, further enhances the cytotoxic effect of CPI-613 under acidosis and in tumor spheroids. While there have been numerous attempts to treat cancer by neutralizing the pH of the tumor microenvironment, we alternatively suggest considering tumor acidosis as the Achilles' heel of cancer as it enables selective therapeutic induction of lethal oxidative stress.
- MeSH
- acidóza patofyziologie MeSH
- antitumorózní látky farmakologie MeSH
- citrátový cyklus účinky léků MeSH
- energetický metabolismus MeSH
- fyziologická adaptace MeSH
- glukosa metabolismus MeSH
- glykolýza MeSH
- kapryláty farmakologie MeSH
- koncentrace vodíkových iontů MeSH
- kyselina mléčná metabolismus MeSH
- lidé MeSH
- mitochondrie účinky léků metabolismus patologie MeSH
- nádorové buňky kultivované MeSH
- nádorové mikroprostředí * MeSH
- nádory farmakoterapie metabolismus patologie MeSH
- oxidační stres MeSH
- sulfidy farmakologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
