The Cardiotonic Steroid Marinobufagenin Is a Predictor of Increased Left Ventricular Mass in Obesity: The African-PREDICT Study

The endogenous Na(+)/K(+)-ATPase inhibitor, marinobufagenin (MBG), strongly associates with salt intake and a greater left ventricular mass index (LVMi) in humans and was shown to promote cardiac fibrosis and hypertrophy in animals. The adverse effects of MBG on cardiac remodeling may be exacerbated with obesity, due to an increased sensitivity of Na(+)/K(+)-ATPase to MBG. This study determined whether MBG is related to the change in LVMi over time in adults with a body mass index (BMI) ≥30 kg/m(2) (obese) and <30 kg/m(2) (non-obese). The study followed 275 healthy participants (aged 20–30 years) from the African-Prospective study on the Early Detection and Identification of Cardiovascular disease and Hypertension (African-PREDICT) study over 4.5 years. At baseline, we measured 24 h urine MBG excretion. MBG levels were positively associated with salt intake. LVMi was determined by two-dimensional echocardiography at baseline and after >4.5 years. With multivariate adjusted analyses in obese adults (N = 56), we found a positive association of follow-up LVMi (Adjusted (Adj.) R(2) = 0.35; Std. β = 0.311; p = 0.007) and percentage change in LVMi (Adj. R(2) = 0.40; Std. β = 0.336; p = 0.003) with baseline MBG excretion. No association of LVMi (Adj. R(2) = 0.37; p = 0.85) or percentage change in LVMi (Adj. R(2) = 0.19; p = 0.68) with MBG excretion was evident in normal weight adults (N = 123). These findings suggest that obese adults may be more sensitive to the adverse cardiac effects of MBG and provide new insight into the potential role of dietary salt, by way of MBG, in the pathogenesis of cardiac remodeling in obese individuals.