Plasma brain natriuretic peptide (BNP) level is known to reflect left ventricular wall stress (LVWS). Recent studies have shown that obese individuals have lower BNP levels. However, the usefulness of BNP level as a marker of LVWS in obese individuals remains unclear. This study examined whether BNP reflects LVWS even in obese individuals.
This study enrolled 136 hospital inpatients who had suffered chronic heart failure (NYHA class I or II), or who had undergone a thorough examination for angina pectoris. On the basis of body mass index (BMI), we divided the inpatients into nonobese (< 25) and obese (≥ 25) groups. All BNP measurements, cardiac catheterizations, and echocardiographic examinations were carried out within 24 hours.
Although no significant differences were found between the two groups in the hemodynamic parameters examined, including end-diastolic LVWS (LV-EDWS) and end-systolic LVWS (LV-ESWS), BNP levels were significantly lower in the obese group compared to the nonobese group. In the nonobese group, a definite correlation between LV-EDWS or LV-ESWS and BNP (r = 0.43, r = 0.46, respectively) was observed, whereas no correlation was found between LV-EDWS or LV-ESWS and BNP in the obese group (r = -0.09, r = 0.06, respectively). To explore the mechanism for suppressed BNP levels in obese individuals, the correlation of BNP with biochemical markers was analyzed. Statistical significance was found only between adiponectin and BNP (r = 0.44), implying that BNP or adiponectin might influence the plasma levels of the other.
In conclusion, BNP levels cannot be used as a marker of LVWS in obese individuals.