Insulin-resistant glucose metabolism in patients with microvascular angina--syndrome X

Studies in patients with microvascular angina (MA) or the cardiologic syndrome X have shown a hyperinsulinemic response to an oral glucose challenge, suggesting insulin resistance and a role for increased serum insulin in coronary microvascular dysfunction. The aim of the present study was to examine whether patients with MA are insulin-resistant. Nine patients with MA and seven control subjects were studied. All were sedentary and glucose-tolerant. Coronary arteriography was normal in all participants, and exercise-induced coronary ischemia was demonstrated in all MA patients. A euglycemic, hyperinsulinemic clamp was performed in combination with indirect calorimetry. Biopsy of vastus lateralis muscle was taken in the basal state and after 4 hours of euglycemia and hyperinsulinemia (2 mU.kg-1.min-1). The fasting level of "true" serum insulin was significantly higher (43 +/- 6 v 22 +/- 3 pmol/L, P < .02) and the rate of insulin-stimulated glucose disposal to peripheral tissues was lower in patients with MA (13.4 +/- 1.0 v 18.2 +/- 1.4 mg.kg fat-free mass [FFM]-1.min-1, P < .02) due to a decrease in nonoxidative glucose metabolism (8.4 +/- 0.9 v 12.5 +/- 1.3 mg.kg FFM-1.min-1, P < .02). No difference was found in glucose or lipid oxidation rates between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)