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Synthesis of [1-¹³ C-5-¹² C]-alpha-ketoglutarate enables noninvasive detection of 2-hydroxyglutarate.

ABSTRACT: Isocitrate dehydrogenase 1 (IDH1) mutations that generate the oncometabolite 2-hydroxyglutarate (2-HG) from α-ketoglutarate (α-KG) have been identified in many types of tumors and are an important prognostic factor in gliomas. 2-HG production can be determined by hyperpolarized carbon-13 magnetic resonance spectroscopy (HP-¹³ C-MRS) using [1-¹³ C]-α-KG as a probe, but peak contamination from naturally occurring [5-¹³ C]-α-KG overlaps with the [1-¹³ C]-2-HG peak. Via a newly developed oxidative-Stetter reaction, [1-¹³ C-5-¹² C]-α-KG was synthesized. α-KG metabolism was measured via HP-¹³ C-MRS using [1-¹³ C-5-¹² C]-α-KG as a probe. [1-¹³ C-5-¹² C]-α-KG was synthesized in high yields, and successfully eliminated the signal from C5 of α-KG in the HP-¹³ C-MRS spectra. In HCT116 IDH1 R132H cells, [1-¹³ C-5-¹² C]-α-KG allowed for unimpeded detection of [1-¹³ C]-2-HG. ¹² C-enrichment represents a novel method to circumvent spectral overlap, and [1-¹³ C-5-¹² C]-α-KG shows promise as a probe to study IDH1 mutant tumors and α-KG metabolism.

SUBMITTER: Miura N

PROVIDER: S-EPMC8492538 | biostudies-literature | 2021 Nov

REPOSITORIES: biostudies-literature

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Synthesis of [1-13 C-5-12 C]-alpha-ketoglutarate enables noninvasive detection of 2-hydroxyglutarate.

Miura Natsuko N Mushti Chandrasekhar C Sail Deepak D AbuSalim Jenna E JE Yamamoto Kazutoshi K Brender Jeffrey R JR Seki Tomohiro T AbuSalim Deyaa I DI Matsumoto Shingo S Camphausen Kevin A KA Krishna Murali C MC Swenson Rolf E RE Kesarwala Aparna H AH

NMR in biomedicine 20210714 11

Isocitrate dehydrogenase 1 (IDH1) mutations that generate the oncometabolite 2-hydroxyglutarate (2-HG) from α-ketoglutarate (α-KG) have been identified in many types of tumors and are an important prognostic factor in gliomas. 2-HG production can be determined by hyperpolarized carbon-13 magnetic resonance spectroscopy (HP-13 C-MRS) using [1-13 C]-α-KG as a probe, but peak contamination from naturally occurring [5-13 C]-α-KG overlaps with the [1-13 C]- ...[more]

PMID: 34263489

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Project description:α-Ketoglutarate is a key biomolecule involved in a number of metabolic pathways─most notably the TCA cycle. Abnormal α-ketoglutarate metabolism has also been linked with cancer. Here, isotopic labeling was employed to synthesize [1-13C,5-12C,D4]α-ketoglutarate with the future goal of utilizing its [1-13C]-hyperpolarized state for real-time metabolic imaging of α-ketoglutarate analytes and its downstream metabolites in vivo. The signal amplification by reversible exchange in shield enables alignment transfer to heteronuclei (SABRE-SHEATH) hyperpolarization technique was used to create 9.7% [1-13C] polarization in 1 minute in this isotopologue. The efficient 13C hyperpolarization, which utilizes parahydrogen as the source of nuclear spin order, is also supported by favorable relaxation dynamics at 0.4 μT field (the optimal polarization transfer field): the exponential 13C polarization buildup constant Tb is 11.0 ± 0.4 s whereas the 13C polarization decay constant T1 is 18.5 ± 0.7 s. An even higher 13C polarization value of 17.3% was achieved using natural-abundance α-ketoglutarate disodium salt, with overall similar relaxation dynamics at 0.4 μT field, indicating that substrate deuteration leads only to a slight increase (∼1.2-fold) in the relaxation rates for 13C nuclei separated by three chemical bonds. Instead, the gain in polarization (natural abundance versus [1-13C]-labeled) is rationalized through the smaller heat capacity of the "spin bath" comprising available 13C spins that must be hyperpolarized by the same number of parahydrogen present in each sample, in line with previous 15N SABRE-SHEATH studies. Remarkably, the C-2 carbon was not hyperpolarized in both α-ketoglutarate isotopologues studied; this observation is in sharp contrast with previously reported SABRE-SHEATH pyruvate studies, indicating that the catalyst-binding dynamics of C-2 in α-ketoglutarate differ from that in pyruvate. We also demonstrate that 13C spectroscopic characterization of α-ketoglutarate and pyruvate analytes can be performed at natural 13C abundance with an estimated detection limit of 80 micromolar concentration × *%P13C. All in all, the fundamental studies reported here enable a wide range of research communities with a new hyperpolarized contrast agent potentially useful for metabolic imaging of brain function, cancer, and other metabolically challenging diseases.

Dataset Information

Synthesis of [1-¹³ C-5-¹² C]-alpha-ketoglutarate enables noninvasive detection of 2-hydroxyglutarate.

Publications

Synthesis of [1-<sup>13</sup> C-5-<sup>12</sup> C]-alpha-ketoglutarate enables noninvasive detection of 2-hydroxyglutarate.

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