A model for determining cardiac mitochondrial substrate utilisation using stable ¹³C-labelled metabolites

Area of Science:

• Biochemistry
• Metabolic research
• Cardiac physiology

Background:

• Cardiac metabolism relies on oxidizing various substrates to meet energy demands.
• ¹³C-labeled substrates are crucial for studying substrate utilization.
• Accurate models are needed to analyze complex isotopologue data from the Krebs cycle.

Purpose of the Study:

• To develop a network model for quantitative analysis of Krebs cycle intermediate isotopologue distributions.
• To determine the ¹³C-labeled proportion of acetyl-CoA entering the Krebs cycle.
• To quantify the relative oxidation of glucose and triacylglycerol in the heart.

Main Methods:

• Generated a network model for Krebs cycle analysis.
• Validated the model ex vivo using isolated hearts perfused with ¹³C-labeled glucose.
• Determined substrate oxidation using mass spectrometry and isotopologue distributions.

Main Results:

• Glucose contributed 79.1% to Krebs cycle oxidation when perfused alone.
• In the presence of Intralipid, glucose and triglyceride contributed 58% and 35.6% of acetyl-CoA, respectively.
• Model accuracy was confirmed, independent of labeling fraction or assessed intermediate.

Conclusions:

• The developed model accurately quantifies cardiac substrate metabolism.
• This model enables the determination of therapeutic and pathological effects on cardiac substrate utilization.
• The findings support a functional understanding of Krebs cycle metabolism in the heart.