Central obesity and hypertensive renal disease: association between higher levels of BMI, circulating transforming growth factor beta1 and urinary albumin excretion.

OBJECTIVE: In this study, the relationship between circulating transforming growth factor beta1 (TGFbeta1) and urinary albumin excretion (UAE) has been investigated in non-obese and central obese hypertensive patients. DESIGN AND PATIENTS: Fifty-eight consecutive hypertensive outpatients both lean and with central obesity were enrolled and divided in three groups, according to their body mass index (BMI) values. Group A: 16 lean hypertensives (men with BMI < 25 kg/m2 and women with BMI < 24.7 kg/m2); Group B: 16 overweight hypertensives (men with BMI > or = 25 kg/m2 and < 30 kg/m2 and women with BMI > 24.7 kg/m2 and < 27.3 kg/m2); Group C: 26 obese hypertensives (men with BMI > or = 30 kg/m2 and women with BMI > or = 27.3 kg/m2). MEASURES: In all patients, UAE, by immunonephelometric assay, circulating TGFbeta1 by a solid-phase specific sandwich enzyme-linked immunosorbent assay (ELISA) technique, blood urea nitrogen (BUN) and creatinine, by routine laboratory methods, were determined. In addition, left ventricular telediastolic internal diameter (LVIDd), interventricular septum diastolic (IVSTd), posterior wall thickness (PWT), total and normalized to height2.7 left ventricular mass (LVM, LVM/h2.7), relative wall thickness (RWT) and left ventricular ejection fraction (EF) by M-B Mode echocardiography were calculated.
RESULTS: Overweight and obese hypertensives had significantly (p < 0.05) higher BMI, waist-hip ratio (WHR), UAE and TGFbeta1 than lean hypertensives. Obese hypertensives had significantly (p < 0.05) higher total and indexed LVM values than lean hypertensives. Obese hypertensives had significantly (p < 0.05) higher BMI, UAE and TGFbeta1 than overweight hypertensives. In all subjects, TGFbeta1 correlated directly with BMI (r = 0.52; p < 0.0001), WHR (r = 0.48; p < 0.003), MBP (r = 0.31; p < 0.02) and UAE (r = 0.57; p < 0.0001). Multiple regression analysis indicated that BMI, MBP and UAE were able to explain the 47.9% TGFbeta1 variability (r = 0.69; p < 0.0001), and that TGFbeta1 was the best predictor of UAE changes (r = 0.60; p < 0.0001).
CONCLUSION: Our data suggest that TGFbeta1 levels are positively associated with BMI, MBP and UAE in hypertensive subjects. This also indicates that TGFbeta1 overproduction might be considered a pathophysiology mechanism of progressive renal function impairment in obese hypertensives.