Investigating Cardiac Metabolism in the Isolated Perfused Mouse Heart with Hyperpolarized [1-13C]Pyruvate and 13C/31P NMR Spectroscopy
April 21st, 2023
2.5K views
We describe an experimental setup for administrating hyperpolarized 13C-labeled metabolites in continuous perfusion mode to an isolated perfused mouse heart. A dedicated 13C-NMR acquisition approach enabled the quantification of metabolic enzyme activity in real-time, and a multiparametric 31P-NMR analysis enabled the determination of the tissue ATP content and pH.
Overview
This article details a protocol for real-time assessment of metabolic activity in the perfused mouse heart using hyperpolarized carbon-13 magnetic resonance (MR) spectroscopy combined with 31P NMR spectroscopy. The approach enables quantification of pyruvate metabolism and cardiac energetics under controlled ex vivo conditions, providing valuable insights into heart metabolism in both healthy and diseased states.
Key Study Components
Area of Science
- Cardiac metabolism
- Nuclear magnetic resonance (NMR) spectroscopy
- Hyperpolarized MR imaging
Background
- Metabolism is fundamental to cellular function and disease mechanisms.
- Pyruvate metabolism is central to both aerobic and anaerobic pathways in the heart.
- Real-time metabolic flux measurements in intact tissues are challenging but crucial for understanding cardiac physiology and pathology.
- Hyperpolarized MR techniques enhance sensitivity for tracking metabolic conversions in living tissues.
Purpose of Study
- To establish a protocol for measuring in-cell metabolic activity in the perfused mouse heart using hyperpolarized [1-13C]pyruvate.
- To quantify the rates of lactate dehydrogenase (LDH) and pyruvate dehydrogenase (PDH) activity in real time.
- To monitor cardiac energetics and pH using 31P NMR spectroscopy.
Methods Used
- Isolation and retrograde perfusion of the mouse heart with Krebs-Henseleit buffer.
- Continuous perfusion inside a 10 mm NMR tube within an NMR spectrometer.
- Administration of hyperpolarized [1-13C]pyruvate and acquisition of 13C NMR spectra to monitor pyruvate, lactate, and bicarbonate signals.
- Alternating selective excitation schemes for product-specific signal acquisition.
- 31P NMR spectroscopy to assess ATP, phosphocreatine, inorganic phosphate, and tissue pH.
- Data analysis including baseline correction, signal integration, and correction for T1 decay and excitation effects.
Main Results
- Successful isolation and perfusion of viable mouse hearts suitable for NMR analysis.
- Clear detection of ATP, phosphocreatine, and inorganic phosphate signals indicating tissue viability and energetics.
- Real-time measurement of hyperpolarized [1-13C]pyruvate metabolism, with quantifiable lactate and bicarbonate production rates.
- Calculation of LDH and PDH activity rates during a defined time window of maximal pyruvate concentration.
Conclusions
- The described protocol enables sensitive, real-time assessment of cardiac metabolic fluxes in perfused mouse hearts.
- Combining hyperpolarized 13C and 31P NMR spectroscopy provides comprehensive insights into both metabolic activity and cardiac energetics.
- This system is valuable for studying metabolic alterations in both healthy and diseased cardiac tissue.
Frequently Asked Questions
What is the main advantage of using hyperpolarized [1-13C]pyruvate in this protocol?
Hyperpolarized [1-13C]pyruvate greatly enhances the sensitivity of MR detection, allowing real-time tracking of metabolic conversions such as lactate and bicarbonate production in intact heart tissue.
How is the mouse heart prepared for perfusion and NMR analysis?
The heart is surgically isolated, cannulated via the aorta, and perfused with oxygenated Krebs-Henseleit buffer to maintain viability before being placed in a 10 mm NMR tube for analysis.
What metabolic pathways are assessed in this study?
The protocol quantifies the activities of lactate dehydrogenase (LDH) and pyruvate dehydrogenase (PDH), key enzymes in glycolytic and oxidative metabolism, by measuring the production rates of lactate and bicarbonate from pyruvate.
How is cardiac energetics monitored during the experiment?
31P NMR spectroscopy is used to monitor ATP, phosphocreatine, and inorganic phosphate levels, providing information on tissue energetics and pH.
What are the key steps to ensure heart viability during the protocol?
Maintaining continuous oxygenated perfusion, careful temperature control, and minimizing ischemia during isolation are critical for preserving heart viability throughout the experiment.
How are the metabolic rates calculated from the NMR data?
Signal intensities for pyruvate, lactate, and bicarbonate are integrated and corrected for T1 relaxation and excitation effects; rates are calculated during a time window of maximal, stable pyruvate concentration.
Can this protocol be adapted to study diseased heart models?
Yes, the system is suitable for investigating metabolic changes in both healthy and diseased mouse hearts, enabling studies of disease mechanisms and therapeutic interventions.
Executive Industry Relevance
Real-time metabolic flux analysis in perfused mouse hearts using hyperpolarized 13C and 31P NMR spectroscopy enables precise interrogation of cardiac metabolic pathways under controlled conditions. This approach supports mechanistic de-risking and predictive confidence for early-stage target validation in cardiovascular drug discovery. The methodology provides a robust platform for evaluating metabolic alterations relevant to disease models and therapeutic intervention strategies.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables direct measurement of lactate dehydrogenase and pyruvate dehydrogenase activity in intact cardiac tissue.
- Supports mechanistic de-risking by quantifying metabolic fluxes in real time.
- Facilitates functional target validation for metabolic and cardiovascular research portfolios.
- Provides a controlled system for hypothesis testing of metabolic pathway modulation.
Screening & Assay Development
- Establishes a reproducible ex vivo platform for metabolic assay development.
- Delivers quantitative outputs for lactate, bicarbonate, and ATP production rates.
- Enables standardization of metabolic readouts for compound screening workflows.
- Supports scalability and platform reuse for multiple cardiac models.
Translational & Preclinical Research
- Aligns metabolic measurements with disease-relevant cardiac models.
- Provides translational continuity from discovery to preclinical validation of metabolic targets.
- Enables risk-adjusted advancement decisions based on quantitative metabolic endpoints.
- Supports biomarker alignment for cardiac energetics and pH monitoring.
Pipeline & Workflow Integration
This NMR-based metabolic analysis integrates into the discovery-to-preclinical continuum, bridging early mechanistic studies with translational research in cardiovascular metabolism.
- Discovery Biology: Quantifies metabolic pathway activity to clarify target function and biological relevance.
- Screening: Provides validated, quantitative metabolic readouts for assay development and compound evaluation.
- Analytics: Delivers real-time, model-free measurements of substrate and metabolite fluxes for robust data comparison.
- Translational Research: Connects ex vivo metabolic findings to disease models and preclinical endpoints.
- Enterprise Reuse: Offers a reusable platform for diverse cardiac metabolic investigations across R&D teams.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence and reduces mechanistic ambiguity in cardiac metabolism studies.
- Operational Value: Enhances standardization, reproducibility, and scalability of metabolic assays.
- Strategic Value: Improves go/no-go decision-making and capital efficiency by providing quantitative metabolic endpoints.
- Portfolio Impact: Enables risk-adjusted prioritization of metabolic targets and disease models.
Implementation Considerations
- Requires expertise in NMR spectroscopy and cardiac perfusion techniques.
- Demands access to hyperpolarization equipment and compatible NMR infrastructure.
- Necessitates rigorous cross-team standardization of perfusion and data analysis protocols.
- Adaptation may be needed for different cardiac disease models or metabolic substrates.
- Practical limitations include the need for precise temperature and perfusion control to maintain tissue viability.
Biopharma FAQs
Why does null hypothesis testing matter for LDH and PDH activity quantification?
Null hypothesis testing ensures that observed changes in lactate and bicarbonate production rates reflect true metabolic modulation rather than experimental variability, supporting robust target validation in cardiac metabolism studies.
How does independent variable isolation in perfused heart NMR support discovery?
Isolating the perfused mouse heart allows precise control of substrate delivery and environmental conditions, enabling unambiguous assessment of metabolic pathway responses to experimental interventions in early discovery workflows.
What do quantitative dependent variable measurements of lactate and bicarbonate enable?
Quantitative measurement of lactate and bicarbonate production rates provides actionable data on LDH and PDH activity, facilitating comparison across conditions and supporting data-driven advancement decisions in R&D pipelines.
Why are replication requirements critical for cross-functional metabolic assay development?
Replication ensures that metabolic flux measurements are reproducible and reliable, enabling cross-team confidence in assay outputs and supporting collaborative development of standardized screening platforms.
What statistical analysis capabilities are required before implementing NMR-based metabolic assays?
Robust statistical analysis is needed to correct for T1 relaxation, excitation effects, and signal integration, ensuring that calculated metabolic rates are accurate and suitable for decision-making in biopharma R&D.
Chapters in this video
0:03
Introduction
1:17
Krebs-Henseleit Buffer Preparation
1:45
Perfusion System Preparation
2:29
Calibration and Preparation of the NMR Spectrometer for Acquisition
3:22
Animal Preparation, Surgical Procedure, and Perfusion of the Heart in the NMR Tube
9:23
Acquiring Data for Cardiac Energetics and pH
10:09
DNP Spin Polarization and Dissolution
11:25
Hyperpolarized 13C Spectroscopy
12:07
Representative Results
14:40
Conclusion
![Measuring the Spin-Lattice Relaxation Magnetic Field Dependence of Hyperpolarized [1-13C]pyruvate](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F59399.jpg%3Fv%3D2026-08-30T10%253A42%253A00.000Z&w=384&q=75)
