Relationship between insulin's haemodynamic effects and insulin-mediated glucose uptake

BACKGROUND: Insulin resistance and hyperinsulinaemia are associated with hypertension. The relationship between insulin's metabolic and haemodynamic actions has not been fully elucidated however.METHODS: We investigated, using the euglycaemic clamp technique, the relationship between insulin-mediated glucose uptake and insulin-induced changes in leg blood flow and cardiac index in 13 healthy subjects. As insulin's effects on blood flow are time dependent, studies were performed during a 4-h insulin (50 mU kg-1 h-1) infusion period.RESULTS: Mean arterial pressure during insulin infusion increased (82.9 +/- 6.7 to 89.8 +/- 7.7 mmHg; P < 0.001), whereas heart rate was unaltered. Leg blood flow gradually increased from 1.09 +/- 0.57 to 1.47 +/- 0.67 mL min-1 dL-1 during the second hour, and to 1.65 +/- 0.68 mL min-1 dL-1 during the fourth hour of the clamp (P = 0.01). Stroke volume index increased from 56.5 +/- 13.3 to 63.7 +/- 16.3 mL m-2 (P = 0.004) and cardiac index from 3.42 +/- 1.02 to 3.73 +/- 1.05 L min-1 m-2 (P = 0.04). The insulin-mediated glucose disposal and the increases in leg blood flow were not correlated during the second hour (r = 0.21, P = 0.51) but showed a strong correlation during the fourth hour of the clamp (r = 0.88, P < 0.001). Insulin-mediated glucose disposal was not correlated with the increases in cardiac index.CONCLUSION: Thus, insulin-mediated muscle blood flow may be an important contributor to glucose uptake during sustained exogenous hyperinsulinaemia aiming at physiological insulin levels.