Abstract 11511: Insulin Resistance is an Independent Predictor for Impaired Exercise Tolerance in Hypertensive Patients Without Type 2 Diabetes Mellitus

Abstract

Background Increase of insulin resistance is well known to cause the autonomic imbalance and decreased muscle strength, resulting in the impaired exercise tolerance in patients with type 2 diabetes mellitus (DM). However, it is still unclear whether the insulin resistance deceases exercise tolerance independent of the autonomic imbalance and decreased muscle strength. The aim of this study was to investigate the influence of insulin resistance on exercise tolerance in patients with hypertension (HT).

Methods We recruited 48 HT patients who had no DM nor coronary heart disease. We measured exercise duration time and heart rate recovery as parameters of exercise tolerance and parasympathetic activity, respectively, in the exercise test using a treadmill. Plasma noradrenaline was measured before and after 19-minute exercise at a moderate intensity using bicycle ergometer as a parameter of sympathetic activity. We assessed the homeostasis model assessment ratio(HOMA-R)and isometric muscle strength of quadriceps as parameters of insulin resistance and muscle strength, respectively. Patients were divided into low HOMA-R and high HOMA-R groups according to 2.50 of HOMA-R. We compared parameters on clinical characteristics, autonomic activity, muscle strength and exercise tolerance between the two groups and determined the correlation between HOMA-R and exercise tolerance. Stepwise multiple regression analysis was used to identify independent factors against exercise tolerance using clinical characteristics, HOMA-R, autonomic activity and muscle strength.

Results There were no significant differences in clinical characteristics, autonomic activity and muscle strength between the two groups. The exercise tolerance was significantly lower in the high HOMA-R group than in the low HOMA-R group (P<0.05), and negatively correlated with HOMA-R (r=-0.366, P<0.05). The HOMA-R and muscle strength were found to be significant independent predictors against the exercise tolerance by multiple regression analysis (R²=0.327, P<0.001).

Conclusion The increase of insulin resistance was an independent predictor for impaired exercise tolerance in HT patients without DM regardless the autonomic imbalance and decreased muscle strength.