PCr/ATP ratios and mitochondrial function in the heart. A comparative study in humans

Area of Science:

• Cardiology
• Biochemistry
• Medical Imaging

Background:

• Cardiac energy status, quantified by the phosphocreatine (PCr)/adenosine triphosphate (ATP) ratio via 31P-Magnetic Resonance Spectroscopy (31P-MRS), is a key prognostic indicator in heart failure and is diminished in cardiometabolic diseases.
• The PCr/ATP ratio is hypothesized to reflect cardiac mitochondrial function due to the significant role of oxidative phosphorylation in ATP synthesis.

Purpose of the Study:

• To determine if the in vivo PCr/ATP ratio serves as a reliable marker for cardiac mitochondrial function.

Main Methods:

• Thirty-eight patients undergoing open-heart surgery were assessed using cardiac 31P-MRS prior to their procedure.
• Tissue samples from the right atrial appendage were collected during surgery for high-resolution respirometry to evaluate mitochondrial function.
• Correlations between the PCr/ATP ratio and various measures of mitochondrial respiration were analyzed.

Main Results:

• No significant correlation was found between the PCr/ATP ratio and ADP-stimulated respiration rates with either octanoylcarnitine or pyruvate.
• Similarly, no correlation was observed between the PCr/ATP ratio and maximally uncoupled respiration.
• A correlation was identified between the PCr/ATP ratio and indexed left ventricular end-systolic mass.

Conclusions:

• The study concludes that the cardiac PCr/ATP ratio does not directly correlate with in vivo cardiac mitochondrial function.
• Cardiac energy status is likely influenced by factors beyond mitochondrial function alone.
• Findings emphasize the need for careful contextual interpretation of cardiac energy status in metabolic studies.