Insulin improves contractile function during moderate ischemia in canine left ventricle

Area of Science:

• Cardiovascular Physiology
• Metabolic Regulation
• Myocardial Ischemia Research

Background:

• Moderate coronary hypoperfusion can impair myocardial contractile function and alter glucose metabolism.
• Insulin's role in supporting cardiac function during ischemia requires further elucidation.

Purpose of the Study:

• To investigate the effects of insulin on myocardial contractile function and glucose metabolism under conditions of moderate coronary hypoperfusion.
• To assess whether insulin administration influences glucose uptake and anaerobic metabolism byproducts in ischemic myocardium.

Main Methods:

• Anesthetized, open-chest dogs underwent controlled reduction of coronary perfusion pressure (CPP) in the left anterior descending coronary artery.
• Regional glucose uptake, lactate uptake, myocardial O2 consumption, and percent segment shortening (%SS) were measured.
• Insulin was administered intravenously or intracoronary, with measurements taken at varying CPP levels and in myocardial biopsies.

Main Results:

• Insulin significantly increased myocardial glucose uptake (GU) regardless of administration route (intravenous or intracoronary).
• Reduced CPP did not affect GU but decreased lactate uptake and myocardial O2 consumption.
• Myocardial contractile function (%SS) was preserved with insulin treatment during hypoperfusion, unlike in untreated controls.

Conclusions:

• Insulin markedly improves regional contractile function in moderately ischemic canine myocardium.
• Insulin enhances glucose utilization without significantly increasing anaerobic glucose metabolism products during hypoperfusion.
• These findings highlight insulin's potential therapeutic role in managing myocardial ischemia.