Exogenous substrate preference of the post-ischaemic myocardium

Area of Science:

• Biochemistry
• Cardiology
• Physiology

Background:

• Myocardial substrate utilization is crucial for heart function.
• Ischemic stress significantly alters cardiac metabolism.
• Lactate accumulation during ischemia impacts energy substrate preference.

Purpose of the Study:

• To investigate myocardial exogenous substrate preference.
• To assess changes in fatty acid oxidation after ischemic stress.
• To understand metabolic adaptation in the presence of elevated lactate.

Main Methods:

• Studied myocardial substrate preference under increased plasma lactate.
• Induced severe but reversible global ischemia using hypothermic electromechanical arrest.
• Quantified fatty acid oxidation using 1-14C-palmitate under controlled conditions.

Main Results:

• Pre-ischemia: Fatty acid oxidation was 0.62 (0.21) µmol/min/100g, representing 32% of CO2 output.
• Post-ischemia: Fatty acid oxidation increased to 2.67 (0.87) µmol/min/100g, representing 82% of CO2 output.
• Increased plasma lactate concentrations were observed both pre- and post-ischemia.

Conclusions:

• Myocardial substrate preference shifts towards greater oxidation of exogenous free fatty acids after ischemic stress.
• Elevated lactate levels facilitate increased reliance on fatty acids for energy.
• The heart demonstrates metabolic flexibility in substrate utilization post-ischemia.