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: BackgroundTransforming growth factor-β1 (TGF-β1) has been demonstrated to be overexpressed in hypertension. Leptin, an adipocyte product, has been shown to play a role in obesity-related hypertension and in vitro studies demonstrated a biologic interaction between leptin and TGF-β1. Thus, we evaluate a possible in vivo association between TGF-β1, body mass index (BMI), and leptin circulating levels in hypertensive subjects.: MethodsBlood samples for fasting leptin and TGF-β1, were evaluated in 29 overweight, 46 obese, and 29 nonobese hypertensive patients before and after a 12-week calorie-restricted diet. Monocyte cultures were used for in vitro experiments.: ResultsTransforming growth factor-β1 was significantly elevated in hypertensive obese patients (n = 46) as compared with TGF-β1 levels of hypertensive patients with normal BMI (n = 29) (8. 9 ± 3 ng/mL v 4.4 ± 2; P < .001). The circulating levels of TGF-β1 were associated with BMI and leptin levels in an univariate analysis (r = 0.59, P < .0001; r = 0.62, P < .0001, respectively) and these associations were still present after stepwise multivariate analysis. Weight loss of 10% produced a parallel decrease in TGF-β1 (from 8.9 ± 3 ng/mL to 5.3 ± 2.8 ng/mL; P < .01) and leptin levels (from 30 ± 24 ng/mL to 17 ± 14; P < .05). In vitro experiments showed that leptin is able to induce a dose-dependent increase in TGF-β1 production and mRNA expression in human monocyte cultures.: ConclusionsOur data indicate that TGF-β1 levels are positively associated with BMI and leptin levels in hypertensive patients and suggest that adipose tissue may be an important determinant of TGF-β1 levels possibly by a leptin-dependent pathway. [Copyright &y& Elsevier]