Differing roles of body mass and the renin-angiotensin system in mediatingthe hypertension syndrome

Background: Hypertension is characterized not only by a metabolic syndrome that includes obesity and insulin resistance, but also by increases in left -ventricular mass (LVM), reduced arterial compliance and altered renal func tion. This investigation has examined a possible role for the renin-angiote nsin system as well as body mass and insulin values in mediating these card iovascular and renal aspects of the hypertension syndrome. Methods: This wa s a cross-sectional study of 142 patients identified by community screening . Mean (+/- SE) age was 46 +/- 1 years and patients had stage I-II hyperten sion (blood pressure: 145 +/- 1/98 +/- 0.5 mm Hg). For analysis, patients w ere divided into 2 groups: those with body mass index (BMI) <27 kg/m(2) (le an, n = 72) or BMI >27 kg/m(2) (overweight, n = 70). Results: By univariate analysis, LVM in lean patients correlated significantly with plasma renin activity (PRA), plasma aldosterone, BMI and systolic BP; but with multivari ate regression, only PRA (p < 0.01) and BMI (p < 0.04) remained in the mode l as independent predictors of LVM. For LVM in overweight patients, only BM I (p < 0.02) remained in the model. For total arterial compliance (stroke v olume/pulse pressure) only fasting plasma insulin (in the overweight group) was significantly related (p < 0.01). For urinary protein excretion, the o nly predictor in lean patients was PRA (p < 0.02), whereas in overweight pa tients it was BMI (p < 0.03). For creatinine clearance, BMI (p < 0.01 in ov erweight patients) remained in the model, though by univariate regression P RA had an age-dependent dichotomous relationship to clearance: r = +0.25 (p < 0.01) in patients <55 years, but r = -0.54 (p < 0.01) in patients 255 ye ars. Conclusion: These findings suggest that in overweight patients cardiov ascular and renal values depend chiefly on body weight and insulin, but tha t in normal weight hypertensives the renin-angiotensin system may play the major role. Copyright (C) 2000 S. Karger AG, Basel.