Metabolic and hemodynamic effects of insulin on human hearts

Myocardial muscle is considered to be a target tissue for insulin action, but direct measurements of insulin's effects on cardiac hemodynamics and intermediary metabolism in humans are scarce. We combined great vein (GCV)/arterial catheterization with the euglycemic insulin clamp technique and thermodilution in six healthy middle-aged (53 +/- 2 yr) volunteers. In the fasting state, the extracted free fatty acid (FFA), lactate, pyruvate, glycerol, and beta-hydroxybutyrate (6.4 +/- 0.8, 6.2 +/- 1.0, 0.58 +/- 0.12, 0.44 and 11 +/- 2 mumol/min, respectively) and consumed 0.26 +/- 0.02 oxygen. As fasting plasma insulin (73 +/- 6 pmol/l) was raised and clamped at 503 +/- 16 pmol/l for 100 min while maintaining euglycemia (approximately 5 mmol/l), arterial levels of lactate and rose (by 121 and 159%, respectively), whereas FFA, glycerol, and beta-hydroxybutyrate fell (by 69, 48, and 85%, respectively, all P \textless Correspondingly, net myocardial uptake of glucose, lactate, and increased to 18.9 +/- 3.5, 32.0 +/- 2.3, and 2.7 +/- 0.5 mumol/min, respectively, whereas net extraction of circulating FFA, glycerol, beta-hydroxybutyrate was abolished (all P \textless 0.001). The stimulation lactate and pyruvate uptake was the result of both increased arterial and enhanced myocardial extraction ratio (from 19 +/- 3 to 51 +/- 6% lactate, from 26 +/- 5 to 44 +/- 5% for pyruvate, P \textless 0.001 for shift from fat to carbohydrate fuel usage occurred in the absence of in oxygen consumption, heart rate, GCV blood flow, aortic pressures, coronary vascular resistance, and left ventricular end- pressure.(ABSTRACT TRUNCATED AT 250 WORDS)