[Role of vagosympathetic balance in obesity-induced hypertension]

A sympathetic hyperactivity is a common feature in hypertension, type 2 diabetes (T2D), ageing and obesity-induced hypertension. This increase in sympathetic activity may lead to an elevation of arterial rigidity. By contrast, cardiac parasympathetic impairment is observed in these pathologies. Recently we showed in a model of rats with massive obesity (ventromedial hypothalamic lesions) that an enhanced vagal activity may be protective against hypertension. The aim of the present study was to evaluate the influence of an increase in sympathetic activity and a change in vagal activity on arterial rigidity and hypertension in T2D patients. Fourteen hypertensive T2D patients aged 54 +/- 2 years were compared to 22 elderly normotensive subjects (75 +/- 1 years: 11 controls and 11 T2D) and 34 middle aged normotensive subjects (43 +/- 1 years; 17 controls and 17 T2D). Cardiovascular vagosympathetic activity was investigated by spectral analysis of heart rate (HR) and blood pressure (BP) (Finapres) during 6 min at a controlled breathing rate (12 cycles/min). BP and the low frequencies of systolic BP (LF-SBP) were significantly (p<0.01) higher in hypertensive T2D and elderly patients. Pulse pressure (PP) and the high frequencies of HR (HF-HR) were lower in hypertensive T2D patients. PP was positively correlated to LF-SBP (r=0.58; p=0.03) only in hypertensive T2D patients. Diastolic BP was negatively correlated to HF-HR in elderly control subjects (r=-0.63; p=0.03) but not in hypertensive T2D patients. The present results suggest that: sympathetic nervous system activity is enhanced in subjects over 70 years without any aggravating effect of T2D and in middle-aged hypertensive patients with type 2 diabetes; the increase in pulse pressure, an index of arterial rigidity, in elderly subjects may result from sympathetic override; the decrease in the cardiac sympathovagal balance, mainly due to a high vagal activity, may be protective against the occurrence of hypertension in patients with type 2 diabetes.