Hyperglycemia results in an increase in myocardial interstitial glucose and glucose uptake during ischemia

The purpose of this investigation was to assess the effects of hyperglycemia, in the absence of changes in plasma insulin and arterial free fatty acid (FFA) levels, on interstitial glucose levels and glucose uptake across the left ventricular wall during ischemia in domestic swine. Insulin secretion was suppressed with a continuous infusion of somatostatin. Arterial FFA levels remained stable due to the suppression of insulin. Microdialysis probes were used to estimate changes in interstitial glucose and lactate, and were placed in the subepicardium and the subendocardium of the left anterior descending ([LAD] ischemic) coronary artery perfusion bed and in the midmyocardium of the circumflex ([CFX] nonischemic) perfusion bed. The LAD coronary artery was cannulated and perfused with blood from the femoral artery through an extracorporal perfusion circuit. Ischemia was induced in the LAD perfusion bed by reducing the flow of the LAD perfusion pump by 60% for 50 minutes, and was followed by 30 minutes of reperfusion. Twenty minutes into the ischemic period, seven animals were given a bolus injection of 50% glucose (200 mg/kg) followed by a glucose infusion (10 mg/kg/min), resulting in an increase in arterial glucose levels from 5 to 13 mmol/L in the hyperglycemic group. Hyperglycemia resulted in a marked increase in dialysate glucose during ischemia and a greater than twofold increase in glucose extraction and uptake. Dialysate glucose correlated with plasma glucose in all three perfusion beds. In conclusion, hyperglycemia, in the absence of an increase in insulin and a decrease in arterial FFA, resulted in a doubling of glucose extraction, delivery, and uptake, which corresponded to the twofold elevation in interstitial glucose during ischemia.