A paradoxical negative association between obesity and the plasma B-type natriuretic peptide (BNP) level has been firmly established. An individual's fat mass increases and muscle mass decreases with aging. Because aging is a potent determinant of plasma BNP levels, BNP may be related not only to fat mass but also to muscle mass. However, no studies have evaluated the associations between body composition and plasma levels of BNP. We performed a cross-sectional study to investigate these associations in 1,431 apparently healthy middle-aged to elderly subjects. The abdominal visceral fat area and thigh muscle cross-sectional area (CSA) were quantified by computed tomography. Plasma adiponectin and leptin levels were measured as possible confounding parameters. The brachial-ankle pulse wave velocity was measured as an index of arterial stiffness, and the pulse pressure (PP) of the second peak of the radial systolic blood pressure waveform (PP2) was used as an estimate of the central PP. Plasma BNP levels were significantly and negatively associated with the visceral fat area (r = -0.13, p <0.0001) and thigh muscle CSA (r = -0.25, p <0.0001). Corrections with possible confounding parameters including age, gender, heart rate, mean blood pressure, body weight, body height, adiponectin, leptin, brachial-ankle pulse wave velocity, and PP2 eliminated the association of BNP with visceral fat area but not with thigh muscle CSA (β = -0.27, p <0.0001). These findings indicate that along with adiposity, muscle mass is an independent determinant of plasma BNP.
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