Differing roles of body mass and the renin-angiotensin system in mediating the 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 function. This investigation has examined a possible role for the renin-angiotensin system as well as body mass and insulin values in mediating these cardiovascular and renal aspects of the hypertension syndrome.


METHODS
This was a cross-sectional study of 142 patients identified by community screening. Mean (+/-SE) age was 46 +/- 1 years and patients had stage I-II hypertension (blood pressure: 145 +/- 1/98 +/- 0.5 mm Hg). For analysis, patients were divided into 2 groups: those with body mass index (BMI) <27 kg/m(2) (lean, 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 multivariate regression, only PRA (p < 0.01) and BMI (p < 0.04) remained in the model as independent predictors of LVM. For LVM in overweight patients, only BMI (p < 0.02) remained in the model. For total arterial compliance (stroke volume/pulse pressure) only fasting plasma insulin (in the overweight group) was significantly related (p < 0.01). For urinary protein excretion, the only predictor in lean patients was PRA (p < 0.02), whereas in overweight patients it was BMI (p < 0.03). For creatinine clearance, BMI (p < 0.01 in overweight patients) remained in the model, though by univariate regression PRA 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 > or =55 years.


CONCLUSIONS
These findings suggest that in overweight patients cardiovascular and renal values depend chiefly on body weight and insulin, but that in normal weight hypertensives the renin-angiotensin system may play the major role.
Weber
M A
MA
The Brookdale University Hospital, SUNY Health Science Center, Brooklyn, NY 11212, USA. michaelwebermd@cs.com
Smith
D H
DH
Neutel
J M
JM
D000328:Adult; D000368:Aged; D000450:Aldosterone / Q000097:blood; D015992:Body Mass Index; D003404:Creatinine / Q000652:urine; D003430:Cross-Sectional Studies; D015150:Echocardiography, Doppler; D005260:Female; D006801:Humans; D006973:Hypertension / Q000097:blood*; D017379:Hypertrophy, Left Ventricular / Q000097:blood* / Q000000981:diagnostic imaging; D007328:Insulin / Q000097:blood; D008297:Male; D008875:Middle Aged; D009391:Nephelometry and Turbidimetry; D009765:Obesity / Q000097:blood; D011507:Proteinuria; D011863:Radioimmunoassay; D012044:Regression Analysis; D012083:Renin / Q000097:blood*; D012084:Renin-Angiotensin System / Q000502:physiology*
D007328:Insulin; D000450:Aldosterone; D003404:Creatinine; D012083:Renin