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

Several studies have well demonstrated that obesity is associated with chan ges in cardiovascular vagosympathetic activity. The aim of the present work was to evaluate this activity in normotensive and in mildly hypertensive o bese 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 hypertensi ve obese patients (group 2), and 21 controls. The high frequency peak of HR variations at a controlled breathing rate (vagal activity) was significant ly reduced in both groups (p<0.001). The mid frequency peak of sBP in the s tanding position (sympathetic activity) was similar in both groups and in t he control group. In groups I and 2, the high frequency peak correlated neg atively with age (p=0.005 and 0.034 respectively). In group 1, the mid freq uency 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 fastin g insulin and insulin resistance index (p=0.006 and 0.007 respectively). This study shows that, in obese patients: 1. cardiac vagal activity is redu ced in normotensive and mildly hypertensive subjects; 2. vascular sympathet ic activity is unchanged in means but may be increased as a consequence of adiposity, hyperinsulinemia and insulin resistance, and this increase is li kely to be involved in the increase of blood pressure.