Depressor Effect by Exercise Training Is Associated with Amelioration of Hyperinsulinemia and Sympathetic Overactivity

Abstract

Objective In hypertensive subjects, exercise training is a therapeutic modality that not only lowers blood pressure but also corrects metabolic abnormality, such as hyperinsulinemia. Insulin causes sympatho-excitation via the modification of baroreflex, norepinephrine release, or central sympathetic outflow. However, the link between neural and metabolic changes by exercise training in hypertensive patients remains unknown. The aim of this study was to examine whether or not the blood pressure lowering effect of exercise training is associated with the improvement of insulin sensitivity in conjunction with the inhibition of sympathetic tone in hypertensive patients.
Methods We evaluated plasma insulin levels, arterial baroreflex function and humoral parameters before and after exercise training. Twenty-nine patients with essential hypertension under hospitalization participated in the study. Before and after three weeks of exercise training (75% max VO₂, 6 min, q.i.d.), 24-hour blood pressure recordings, arterial baroreflex function testing and 75 g glucose tolerance tests were conducted. Area under the curve of insulin (∑ insulin) to glucose load was calculated as an index of hyperinsulinemia.
Results Three weeks of exercise training decreased the 24-hour mean arterial pressure, heart rate and ∑ insulin, and improved baroreflex function. There was a significant correlation between the reduction of arterial pressure and the change in ∑ insulin. Furthermore, the reduction of ∑ insulin was correlated with the improvement of baroreflex function and with the decrease in heart rate.
Conclusions Exercise training lowered the arterial pressure, with parallel changes in heart rate, baroreflex function and insulin resistance. The correction of sympathetic overactivity was closely associated with the amelioration of hyperinsulinemia. Our results suggest that the improvement of neuro-metabolic factors may be involved in the depressor effect caused by exercise training.
(Internal Medicine 39: 1013-1019, 2000)