Correlation between lactate dehydrogenase/pyruvate dehydrogenase activities ratio and tissue pH in the perfused mouse heart: A potential noninvasive indicator of cardiac pH provided by hyperpolarized magnetic resonance. (1st December 2020)

• Record Type: Journal Article
• Authors: Shaul, David; Azar, Assad; Sapir, Gal; Uppala, Sivaranjan; Nardi‐Schreiber, Atara; Gamliel, Ayelet; Sosna, Jacob; Gomori, J. Moshe; Katz‐Brull, Rachel
• Is Part Of: NMR in biomedicine. Volume 34:Number 2(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-12-01
• Subjects: biomarkers -- hyperpolarized 13C MR -- imaging agent -- magnetic resonance spectroscopy -- metabolic imaging -- metabolism; Nuclear magnetic resonance -- Periodicals; Magnetic Resonance Spectroscopy -- Periodicals; 574
• DOI: 10.1002/nbm.4444
• Languages: English
• ISSNs: 0952-3480

Abstract

Abstract : Cardiovascular diseases account for more than 30% of all deaths worldwide and many could be ameliorated with early diagnosis. Current cardiac imaging modalities can assess blood flow, heart anatomy and mechanical function. However, for early diagnosis and improved treatment, further functional biomarkers are needed. One such functional biomarker could be the myocardium pH. Although tissue pH is already determinable via MR techniques, and has been since the early 1990s, it remains elusive to use practically. The objective of this study was to explore the possibility to evaluate cardiac pH noninvasively, using in‐cell enzymatic rates of hyperpolarized [1‐ 13 C]pyruvate metabolism (ie, moles of product produced per unit time) determined directly in real time using magnetic resonance spectroscopy in a perfused mouse heart model. As a gold standard for tissue pH we used 31 P spectroscopy and the chemical shift of the inorganic phosphate (Pi) signal. The nonhomogenous pH distribution of the perfused heart was analyzed using a multi‐parametric analysis of this signal, thus taking into account the heterogeneous nature of this characteristic. As opposed to the signal ratio of hyperpolarized [ 13 C]bicarbonate to [ 13 CO2 ], which has shown correlation to pH in other studies, we investigated here the ratio of two intracellular enzymatic rates: lactate dehydrogenase (LDH) and pyruvate dehydrogenase (PDH), by way of determining the production rates of [1‐ 13 C]lactate and [ 13 C]bicarbonate, respectively. The enzyme activities determined here are intracellular, while the pH determined using the Pi signal may contain an extracellular component, which could not be ruled out. Nevertheless, we report a strong correlation between the tissue pH and the LDH/PDH activities ratio. This work may pave the way for using the LDH/PDH activities ratio as an indicator of cardiac intracellular pH in vivo, in an MRI examination. Abstract : In‐cell enzymatic rates of lactate dehydrogenase (LDH) and pyruvate dehydrogenase (PDH) were quantitatively determined in real time using magnetic resonance spectroscopy (MRS) of hyperpolarized [1‐13C]pyruvate metabolism. The nonhomogenous pH distribution of the heart was determined using 31 P MRS and a multi‐parametric analysis approach. A strong correlation was found between the cardiac pH characteristics and the LDH/PDH activities ratio. This work may pave the way for using the LDH/PDH activities ratio as an indicator of cardiac pH in vivo.