Hyperpolarized Sodium [1-¹³C]-Glycerate as a Probe for Assessing Glycolysis In Vivo

Abstract

Hyperpolarized 13C magnetic resonance spectroscopy (MRS) provides unprecedented opportunities to obtain clinical diagnostic information through in vivo monitoring of metabolic pathways. The continuing advancement of this field relies on the identification of molecular probes that can effectively interrogate pathways critical to disease. In this report, we describe the synthesis, development, and in vivo application of sodium [1-13C]-glycerate ([13C]-Glyc) as a novel probe for evaluating glycolysis using hyperpolarized 13C MRS. This agent was prepared by a concise synthetic route and formulated for dynamic nuclear polarization. [13C]-Glyc displayed a high level of polarization and long spin–lattice relaxation time—both of which are necessary for future clinical investigations. In vivo spectroscopic studies with hyperpolarized [13C]-Glyc in rat liver furnished metabolic products, [13C]-labeled pyruvate and lactate, originating from glycolysis. The levels of production and relative intensities of these metabolites were directly correlated with the induced glycolytic state (fasted versus fed groups). This work establishes hyperpolarized [13C]-Glyc as a novel agent for clinically relevant 13C MRS studies of energy metabolism and further provides opportunities for evaluating intracellular redox states in biochemical investigations.

Emerging Technologies to Image Tissue Metabolism

“…GGT is overexpressed in several different tumor types, including those arising in tissues that do not normally express the enzyme, such as ovarian adenocarcinoma, and it therefore has the potential to act as a tumor biomarker. 13 C-dihydroxyacetone has been used to probe glycolysis and gluconeogenesis in perfused mouse liver (Moreno et al, 2014), which led to labeling of glucose, glycerol 3-phosphate, phosphoenolpyruvate, pyruvate, alanine, and lactate; [1-13 C]glycerate has been used to probe glycolysis in rat liver in vivo, which led to labeling of pyruvate and lactate (Park et al, 2017). Flux in the pentose phosphate pathway (PPP) in perfused mouse liver has been assessed using hyperpolarized d-[1-13 C]gluconolactone, which resulted in the production of hyperpolarized 13 CO 2 (subsequently rapidly converted to H 13 CO 3 -) in the reaction catalyzed by the PPP enzyme 6-phosphogluconate dehydrogenase (Moreno et al, 2017).…”

Probing carbohydrate metabolism using hyperpolarized 13C‐labeled molecules

“…The recently reported hyperpolarized [1‐ 13 C]‐D‐glycerate is another interesting and potentially useful probe for glycolysis, because glycerate is expected to be transported into cells by monocarboxyate transporters and converted into PEP and triose phosphates . The labeled compound was polarized to a high level using a commercial polarizer and the T 1 of the C1 labeled carbonyl was measured as 59.9 ± 3.0 s at 3 T. The probe was investigated in healthy Wistar rat liver under glycolytic (fed) and gluconeogenic (fasted) conditions.…”

“…The [1‐ 13 C]lactate/[1‐ 13 C] pyruvate ratio was higher in fed animals, consistent with a more highly reduced redox state (Figure ). [ 13 C] Bicarbonate (161.4 ppm) was also observed, albeit with a poor signal to noise ratio . Other metabolites such as alanine and phosphoglycerates could not be detected because the chemical shift of the C1 carbon of those metabolites overlapped with the intense glycerate signal.…”

“…The data were collected at 3 T with a custom‐built 13 C transmit/receive surface coil (diameter = 28 mm) placed over the liver. (Reproduced with permission from Reference )…”

Proximity hybridization-mediated isothermal exponential amplification for ultrasensitive electrochemical protein detection

“…1,2 In general, the common detection methods rely on commercialized antibody-based assays, for example, enzyme-linked immune sorbent assay (ELISA), whereas the moderate sensitivity and tedious procedures of ELISA make it urgent to develop better methods for the detection of biomarkers. Aptamers, since its first report in 1990s, have received extensive interests as a rival of antibody due to the high affinity and specificity.…”