Myocardial insulin resistance in patients with syndrome X.
Insulin resistance is common in patients with angina pectoris, a positive exercise electrocardiogram, and normal coronary angiograms (syndrome X). It is still not known whether insulin resistance affects the cardiac muscle itself and, if so, whether insulin resistance involves myocardial hemodynamics and energy metabolism. We investigated hemodynamics as well as metabolite exchanges across the heart and the forearm in eight patients with syndrome X and eight control subjects during a baseline period after an overnight fast and during a hyperinsulinemic-euglycemic clamp. Myocardial hemodynamics and metabolism were studied at rest, during pace stress, and in the recovery period after pacing. Neither coronary sinus blood flow nor forearm blood flow differed between the groups before and during the clamp. Whole body insulin-stimulated glucose uptake was decreased in the patients (15.6+/-2.1 vs. 23.1+/-2.0 micromol x kg-1 x min-1). Insulin-stimulated glucose uptake in the forearm and the cardiac muscle was equally reduced in the patients (46+/-5 and 48+/-5%). Myocardial glucose uptake correlated with total arterial delivery in the control subjects (r = 0.63, P < 0.01), but not in patients (r = 0.22, P = 0.13). Carbohydrate and lipid oxidation was similar in the two groups at rest, and changes during the clamp were not different in control subjects and patients either at rest, during pacing, or in the recovery period. Patients with syndrome X exhibit myocardial insulin resistance, but cardiac energy metabolism remains unaffected. In patients with syndrome X, insulin-stimulated glucose uptake is independent from myocardial blood flow.
Botker
H E
HE
Department of Cardiology, Skejby Hospital, University Hospital Aarhus, DK-8200 Aarhus N, Denmark.
Moller
N
N
Schmitz
O
O
Bagger
J P
JP
Nielsen
T T
TT
D001786:Blood Glucose / Q000378:metabolism; D006328:Cardiac Catheterization; D004734:Energy Metabolism; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18; D015309:Glucose Clamp Technique; D006019:Glycolysis; D006321:Heart / Q000187:drug effects*; D006439:Hemodynamics; D006801:Humans; D007333:Insulin Resistance; D008297:Male; D017566:Microvascular Angina / Q000175:diagnosis*; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism; D011188:Potassium / Q000097:blood; D014055:Tomography, Emission-Computed
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18; D011188:Potassium