CENTRAL OBESITY AND HYPERTENSION - PATHOPHYSIOLOGIC ROLE OF RENAL HEMODYNAMICS AND FUNCTION

OBJECTIVE: To investigate the role of alterations in renal haemodynami cs and function and in plasma renin activity on obesity-induced hypert ension. DESIGN: Renal haemodynamics and function, salt-regulating horm ones and structural cardiac parameters were evaluated in 20 lean normo tensives and in 64 obese subjects with central or peripheral fat distr ibution, 43 of them were normotensives and 21 of them were hypertensiv es. Obesity and central fat distribution were defined according to sex -specific 85th percentile respectively of Body Mass Index (BMI) and Wa ist to Hip Ratio (WHR). MEASUREMENTS: Serum immunoreactive insulin (IR I), plasma renin activity (PRA), plasma aldosterone (PA), microalbumin uria (UAE) and 24h urinary excretion of sodium (NaU) were evaluated by current methods. Renal haemodynamics was evaluated by radionuclide st udy according to Schlegel's and Gate's methods. By radionuclide study, effective renal plasma flow (ERPF), effective renal blood flow (ERBF) , glomerular filtration rate (GFR), filtration fraction (FF) and renal vascular resistances (RVR) were measured. Left ventricular mass (LVM) and indexed for body height (LVM/H), cardiac output (CO) and total pe ripheral resistances (TPR) by ecocardiography were also calculated. RE SULTS: CO, LVM and LVM/H were significantly (P < 0.05) higher in all t he obese groups than lean controls. In addition, LVM and LVM/H were si gnificantly (P < 0.05) higher in obese hypertensives than obese normot ensives either with central fat distribution. TPR values were signific antly (P < 0.05) higher in central obese hypertensives than peripheral obese hypertensives and than central obese normotensives. Moreover, I RI levels were significantly (P < 0.05) higher in central normotensive and hypertensive obese subjects than lean subjects. ERBF and ERPF wer e significantly (P < 0.05) lower and PRA levels were significantly hig her only in central obese than lean subjects. On the contrary RVR were significantly (P < 0.05) higher in both obese hypertensive groups and in central obese normotensives than lean subjects. Comparisons betwee n peripheral and central obese groups indicated that PRA, RVR and UAE were significantly (P < 0.05) higher and ERBF and ERPF values were sig nificantly (P < 0.05) lower in both central obese groups than comparab le subjects with peripheral obesity. Multiple regression analysis indi cated that RVR increased significantly (P < 0.05) with WHR and PRA but not with CO and IRI. CONCLUSIONS: Our results indicate that obesity w ith body fat distribution of central type, more than obesity of periph eral type, is associated to abnormalities in renal haemodynamics and f unction. These data are consistent with the indication that change in renal haemodynamics take place at an early stage in the obesity-induce d hypertension.