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Insulin improves cardiac contractile function and oxygen utilization efficiency during moderate ischemia without
J D Tune1, R T Mallet, H F Downey
1Department of Integrative Physiology, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX 76107-2699, USA.
Journal of Molecular and Cellular Cardiology
|November 4, 1998
Summary
Insulin enhances myocardial oxygen utilization efficiency (O2UE) and contractile function during moderate ischemia. This improvement occurs without negatively impacting cellular energy levels, suggesting a protective role for insulin.
Area of Science:
- Cardiovascular Physiology
- Metabolic Regulation
- Myocardial Ischemia Research
Background:
- Insulin's positive effect on myocardial contractile function during ischemia is documented.
- The underlying mechanisms, particularly concerning oxygen utilization efficiency (O2UE), remain unclear.
- Understanding insulin's role is crucial for developing therapeutic strategies for ischemic heart conditions.
Purpose of the Study:
- To investigate the effects of insulin on myocardial oxygen utilization efficiency (O2UE) and cardiac energetics during moderate ischemia.
- To determine if insulin treatment preserves myocardial contractile function under reduced coronary perfusion pressure (CPP).
- To elucidate the impact of insulin on high-energy phosphate levels and phosphorylation potential in ischemic myocardium.
Main Methods:
- Anesthetized open-chest dogs underwent sequential reduction of left coronary perfusion pressure (CPP) to 60, 50, and 40 mmHg.
- Myocardial oxygen consumption (MVO2), regional power index (PI), and O2UE were measured in untreated and insulin-treated groups.
- Cardiac biopsies analyzed high-energy phosphates and cytosolic phosphorylation potential at the lowest CPP (40 mmHg).
Main Results:
- Insulin treatment significantly improved the power index (PI) and O2UE at reduced CPP (50 and 40 mmHg) compared to untreated hearts.
- Myocardial oxygen consumption (MVO2) decreased with reduced CPP in all groups but was not affected by insulin.
- Despite improved function and O2UE, insulin did not alter the significant metabolic changes in high-energy phosphates and phosphorylation potential caused by ischemia.
Conclusions:
- Insulin markedly enhances myocardial power output and oxygen utilization efficiency during moderate ischemia.
- These beneficial effects are achieved without altering the fundamental cytosolic energetics or high-energy phosphate levels.
- Insulin offers a protective mechanism during myocardial ischemia by improving functional efficiency rather than directly altering cellular energy stores.