Insulin action on heart and skeletal muscle glucose uptake in essential hypertension

Abstract

Essential hypertension is characterized by skeletal muscle insulin resistance but it is unknown whether insulin resistance also affects heart glucose uptake. We quantitated whole body (euglycemic insulin clamp) and heart and skeletal muscle (positron emission tomography and 18F-fluoro-2- deoxy-D-glucose) glucose uptake rates in 10 mild essential hypertensive (age 33±1 yr, body mass index 23.7±0.8 kg/m2, blood pressure 146±3/97±3 mmHg, VO(2max) 37±3 ml/kg per min) and 14 normal subjects (29±2 yr, 22.5±0.5 kg/m2, 118±4/69±3 mmHg, 43±2 ml/kg per min). Left ventricular mass was similar in the hypertensive (155±15 g) and the normotensive (164±13 g) subjects. In the hypertensives, both whole body (28±3 vs 44±3 μmol/kg per min, P < 0.01) and femoral (64±11 vs 94±8 μmol/kg muscle per min, P < 0.05) glucose uptake rates were decreased compared to the controls. In contrast, heart glucose uptake was 33% increased in the hypertensives (939±51 vs 707±46 μmol/kg muscle per rain, P < 0.005), and correlated with systolic blood pressure (r = 0.66, P < 0.001) and the minute work index (r = 0.48, P < 0.05). We conclude that insulin-stimulated glucose uptake is decreased in skeletal muscle but increased in proportion to cardiac work in essential hypertension. The increase in heart glucose uptake in mild essential hypertensives with a normal left ventricular mass may reflect increased oxygen consumption and represent an early signal which precedes the development of left ventricular hypertrophy.