Relationship between vagosympathetic activity and insulin resistance in normotensive and mildly hypertensive obese patients

Several studies have well demonstrated that obesity is associated with changes in cardiovascular vagosympathetic activity. The aim of the present work was to evaluate this activity in normotensive and in mildly hypertensive obese patients, and to correlate this activity with clinical and biological indexes of insulin resistance. Heart rate (HR) and systolic blood pressure (sBP) were examined by spectral analysis in 70 normotensive obese patients (group 1), 32 mildly hypertensive obese patients (group 2), and 21 controls. The high frequency peak of HR variations at a controlled breathing rate (vagal activity) was significantly reduced in both groups (p<0.001). The mid frequency peak of sBP in the standing position (sympathetic activity) was similar in both groups and in the control group. In groups I and 2, the high frequency peak correlated negatively with age (p=0.005 and 0.034 respectively). In group 1, the mid frequency peak correlated positively with fat mass, fasting plasma insulin and triglyceride levels, and insulin resistance index (p<less than or equal to>0.03). In group 2, the mid frequency peak correlated positively with fasting insulin and insulin resistance index (p=0.006 and 0.007 respectively). This study shows that, in obese patients: 1. cardiac vagal activity is reduced in normotensive and mildly hypertensive subjects; 2. vascular sympathetic activity is unchanged in means but may be increased as a consequence of adiposity, hyperinsulinemia and insulin resistance, and this increase is likely to be involved in the increase of blood pressure.