The aim of this work was to investigate the use of 13C‐labelled acetoacetate and β‐hydroxybutyrate as novel hyperpolarized substrates in the study of cardiac metabolism. [1‐13C]Acetoacetate was synthesized by catalysed hydrolysis, and both it and [1‐13C]β‐hydroxybutyrate were hyperpolarized by dissolution dynamic nuclear polarization (DNP). Their metabolism was studied in isolated, perfused rat hearts. Hyperpolarized [1‐13C]acetoacetate metabolism was also studied in the in vivo rat heart in the fed and fasted states. Hyperpolarization of [1‐13C]acetoacetate and [1‐13C]β‐hydroxybutyrate provided liquid state polarizations of 8 ± 2% and 3 ± 1%, respectively. The hyperpolarized T1 values for the two substrates were 28 ± 3 s (acetoacetate) and 20 ± 1 s (β‐hydroxybutyrate). Multiple downstream metabolites were observed within the perfused heart, including acetylcarnitine, citrate and glutamate. In the in vivo heart, an increase in acetylcarnitine production from acetoacetate was observed in the fed state, as well as a potential reduction in glutamate. In this work, methods for the generation of hyperpolarized [1‐13C]acetoacetate and [1‐13C]β‐hydroxybutyrate were investigated, and their metabolism was assessed in both isolated, perfused rat hearts and in the in vivo rat heart. These preliminary investigations show that DNP can be used as an effective in vivo probe of ketone body metabolism in the heart. 相似文献
Reprogramming of energy metabolism in the development of prostate cancer can be exploited for a better diagnosis and treatment of the disease. The goal of this study was to determine whether differences in glucose and pyruvate metabolism of human prostate cancer cells with dissimilar aggressivenesses can be detected using hyperpolarized [1‐13C]pyruvate MRS and [18F]FDG‐PET imaging, and to evaluate whether these measures correlate. For this purpose, we compared murine xenografts of human prostate cancer LNCaP cells with those of more aggressive PC3 cells. [1‐13C]pyruvate was hyperpolarized by dissolution dynamic nuclear polarization (dDNP) and [1‐13C]pyruvate to lactate conversion was followed by 13C MRS. Subsequently [18F]FDG uptake was investigated by static and dynamic PET measurements. Standard uptake values (SUVs) for [18F]FDG were significantly higher for xenografts of PC3 compared with those of LNCaP. However, we did not observe a difference in the average apparent rate constant kpl of 13C label exchange from pyruvate to lactate between the tumor variants. A significant negative correlation was found between SUVs from [18F]FDG PET measurements and kpl values for the xenografts of both tumor types. The kpl rate constant may be influenced by various factors, and studies with a range of prostate cancer cells in suspension suggest that LDH inhibition by pyruvate may be one of these. Our results indicate that glucose and pyruvate metabolism in the prostate cancer cell models differs from that in other tumor models and that [18F]FDG‐PET can serve as a valuable complementary tool in dDNP studies of aggressive prostate cancer with [1‐13C]pyruvate. 相似文献
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 13C‐labeled metabolic substrates such as 13C‐enriched, deuterated D‐glucose derivatives, [2‐13C]‐D‐fructose, [2‐13C] dihydroxyacetone, [1‐13C]‐D‐glycerate, [1‐13C]‐D‐glucono‐δ‐lactone and [1‐13C] pyruvate in healthy and diseased tissues. Elevated glycolysis in tumors (the Warburg effect) was also successfully imaged using hyperpolarized [U‐13C6, U‐2H7]‐D‐glucose, while the size of the preexisting lactate pool can be measured by 13C MRS and/or MRI with hyperpolarized [1‐13C]pyruvate. This review summarizes the application of various hyperpolarized 13C‐labeled metabolites to the real‐time monitoring of glycolysis and related metabolic processes in normal and diseased tissues. 相似文献
Dynamic nuclear polarization (DNP) provides the opportunity to boost liquid state magnetic resonance (MR) signals from selected nuclear spins by several orders of magnitude. A cryostat running at a temperature of ~ 1 K and a superconducting magnet set to between 3 and 10 T are required to efficiently hyperpolarize nuclear spins. Several DNP polarizers have been implemented for the purpose of hyperpolarized MR and recent systems have been designed to avoid the need for user input of liquid cryogens. We herein present a zero boil‐off DNP polarizer that operates at 1.35 ± 0.01 K and 7 T, and which can polarize two samples in parallel. The samples are cooled by a static helium bath thermally connected to a 1 K closed‐cycle 4He refrigerator. Using a modified version of the commercial fluid path developed for the SPINlab polarizer, we demonstrate that, within a 12‐minute interval, the system can produce two separate hyperpolarized 13C solutions. The 13C liquid‐state polarization of [1‐13C]pyruvate measured 26 seconds after dissolution was 36%, which can be extrapolated to a 55% solid state polarization. The system is well adapted for in vitro and in vivo preclinical hyperpolarized MR experiments and it can be modified to polarize up to four samples in parallel. 相似文献
A co‐polarization scheme for [1,4‐13C2]fumarate and [1‐13C]pyruvate is presented to simultaneously assess necrosis and metabolism in rats with hyperpolarized 13C magnetic resonance (MR). The co‐polarization was performed in a SPINlab polarizer. In addition, the feasibility of simultaneous positron emission tomography (PET) and MR of small animals with a clinical PET/MR scanner is demonstrated. The hyperpolarized metabolic MR and PET was demonstrated in a rat model of necrosis. The polarization and T1 of the co‐polarized [1,4‐13C2]fumarate and [1‐13C]pyruvate substrates were measured in vitro and compared with those obtained when the substrates were polarized individually. A polarization of 36 ± 4% for fumarate and 37 ± 6% for pyruvate was obtained. We found no significant difference in the polarization and T1 values between the dual and single substrate polarization. Rats weighing about 400 g were injected intramuscularly in one of the hind legs with 200 μL of turpentine to induce necrosis. Two hours later, 13C metabolic maps were obtained with a chemical shift imaging sequence (16 × 16) with a resolution of 3.1 × 5.0 × 25.0 mm3. The 13C spectroscopic images were acquired in 12 s, followed by an 8‐min 18F‐2‐fluoro‐2‐deoxy‐d ‐glucose (18F–FDG) PET acquisition with a resolution of 3.5 mm. [1,4‐13C2]Malate was observed from the tissue injected with turpentine indicating necrosis. Normal [1‐13C]pyruvate metabolism and 18F–FDG uptake were observed from the same tissue. The proposed co‐polarization scheme provides a means to utilize multiple imaging agents simultaneously, and thus to probe various metabolic pathways in a single examination. Moreover, it demonstrates the feasibility of small animal research on a clinical PET/MR scanner for combined PET and hyperpolarized metabolic MR. 相似文献
Arthritic conditions are a major source of chronic pain. Furthering our understanding of disease mechanisms creates the opportunity to develop more targeted therapeutics. In rheumatoid arthritis (RA), measurements of pH in human synovial fluid suggest that acidosis occurs, but that this is highly variable between individuals. Here we sought to determine if tissue acidosis occurs in a widely used rodent arthritis model: complete Freund's adjuvant (CFA)‐induced inflammation. CFA robustly evoked paw and ankle swelling, concomitant with worsening clinical scores over time. We used magnetic resonance spectroscopic imaging of hyperpolarized [1‐13C]pyruvate metabolism to demonstrate that CFA induces an increase in the lactate‐to‐pyruvate ratio. This increase is indicative of enhanced glycolysis and an increased lactate concentration, as has been observed in the synovial fluid from RA patients, and which was correlated with acidosis. We also measured the 13CO2/H13CO3? ratio, in animals injected with hyperpolarized H13CO3?, to estimate extracellular tissue pH and showed that despite the apparent increase in glycolytic activity in CFA‐induced inflammation there was no accompanying decrease in extracellular pH. The pH was 7.23 ± 0.06 in control paws and 7.32 ± 0.09 in inflamed paws. These results could explain why mice lacking acid‐sensing ion channel subunits 1, 2 and 3 do not display any changes in mechanical or thermal hyperalgesia in CFA‐induced inflammation. 相似文献
The pentose phosphate pathway (PPP) is thought to be upregulated in trauma (to produce excess NADPH) and in cancer (to provide ribose for nucleotide biosynthesis), but simple methods for detecting changes in flux through this pathway are not available. MRI of hyperpolarized 13C–enriched metabolites offers considerable potential as a rapid, non‐invasive tool for detecting changes in metabolic fluxes. In this study, hyperpolarized δ‐[1‐13C]gluconolactone was used as a probe to detect flux through the oxidative portion of the pentose phosphate pathway (PPPox) in isolated perfused mouse livers. The appearance of hyperpolarized (HP) H13CO3? within seconds after exposure of livers to HP‐δ‐[1‐13C]gluconolactone demonstrates that this probe rapidly enters hepatocytes, becomes phosphorylated, and enters the PPPox pathway to produce HP‐H13CO3? after three enzyme catalyzed steps (6P–gluconolactonase, 6‐phosphogluconate dehydrogenase, and carbonic anhydrase). Livers perfused with octanoate as their sole energy source show no change in production of H13CO3? after exposure to low levels of H2O2, while livers perfused with glucose and insulin showed a twofold increase in H13CO3? after exposure to peroxide. This indicates that flux through the PPPox is stimulated by H2O2 in glucose perfused livers but not in livers perfused with octanoate alone. Subsequent perfusion of livers with non‐polarized [1,2‐13C]glucose followed by 1H NMR analysis of lactate in the perfusate verified that flux through the PPPox is indeed low in healthy livers and modestly higher in peroxide damaged livers. We conclude that hyperpolarized δ‐[1‐13C]gluconolactone has the potential to serve as a metabolic imaging probe of this important biological pathway. 相似文献
Vorinostat is a histone deacetylase (HDAC) inhibitor that inhibits cell proliferation and induces apoptosis in solid tumors, and is in clinical trials for the treatment of glioblastoma (GBM). The goal of this study was to assess whether hyperpolarized 13C MRS and magnetic resonance spectroscopic imaging (MRSI) can detect HDAC inhibition in GBM models. First, we confirmed HDAC inhibition in U87 GBM cells and evaluated real‐time dynamic metabolic changes using a bioreactor system with live vorinostat‐treated or control cells. We found a significant 40% decrease in the 13C MRS‐detectable ratio of hyperpolarized [1‐13C]lactate to hyperpolarized [1‐13C]pyruvate, [1‐13C]Lac/Pyr, and a 37% decrease in the pseudo‐rate constant, kPL, for hyperpolarized [1‐13C]lactate production, in vorinostat‐treated cells compared with controls. To understand the underlying mechanism for this finding, we assessed the expression and activity of lactate dehydrogenase (LDH) (which catalyzes the pyruvate to lactate conversion), its associated cofactor nicotinamide adenine dinucleotide, the expression of monocarboxylate transporters (MCTs) MCT1 and MCT4 (which shuttle pyruvate and lactate in and out of the cell) and intracellular lactate levels. We found that the most likely explanation for our finding that hyperpolarized lactate is reduced in treated cells is a 30% reduction in intracellular lactate levels that occurs as a result of increased expression of both MCT1 and MCT4 in vorinostat‐treated cells. In vivo13C MRSI studies of orthotopic tumors in mice also showed a significant 52% decrease in hyperpolarized [1‐13C]Lac/Pyr when comparing vorinostat‐treated U87 GBM tumors with controls, and, as in the cell studies, this metabolic finding was associated with increased MCT1 and MCT4 expression in HDAC‐inhibited tumors. Thus, the 13C MRSI‐detectable decrease in hyperpolarized [1‐13C]lactate production could serve as a biomarker of response to HDAC inhibitors. 相似文献
Summary: The copolymer of N‐isopropylacrylamide and 3‐(acrylamido)phenylboronic acid (82:18, = 47 000 g · mol?1) was prepared by free radical polymerization. The copolymer showed typical thermal precipitation behavior in aqueous solutions, its precipitation temperature (TP) being increased from 23 to 32 °C by increasing the pH from 6.5 to 9.7, because of ionization of the phenylboronate units. The pKa was evaluated as 8.9 ± 0.1 from the effect of pH on TP. At pH > 9, i.e., in the anionic form of the copolymer, TP was affected by a very low concentration of glucose (5.6 μM , ΔTP = 1–1.5 °C), because of complex formation with a high binding constant. At a higher concentration of polyols (560 μM , pH > 8) the increase of TP was maximal for the copolymer complexes with fructose (7–10 °C) and decreased in the order: fructose > glucose ≈ mannitol > pentaerythritol > galactose > Tris >glycerol. Di‐ and oligosaccharides (lactose, sucrose, and dextran) caused a slight increase of TP at pH 7.5–8.7 while no effect was observed at pH > 9. Isothermal dissolution of the copolymer suspension in water (27 °C, pH 8.5) was possible in the presence of fructose or mannitol but required higher concentrations (1.4–3.6 × 103 μM ) as compared to those which enabled the shift of TP in the soluble copolymer. The dissolution rate increased with fructose concentrations.
Effect of pH on TP of poly(NIPAAM‐co‐AAPBA) in the presence of various monosaccharides. 相似文献