Plasma brain natriuretic peptide levels in normotensive noninsulin-dependent diabetic patients with microalbuminuria

Brain natriuretic peptide (BNP), a member of the natriuretic peptide family , is produced and released from cardiac ventricles. BNP regulates the body fluid volume, blood pressure, and vascular tones through the A-type guanyla te cyclase-coupled receptor. The presence of renal dysfunction in patients with diabetes affects the plasma levels of atrial natriuretic peptide (ANP) . In the present study, we investigated the plasma levels of BNP and ANP an d their relationship in normotensive diabetic patients with normoalbuminuri a and microalbuminuria. Forty-seven normotensive lean noninsulin-dependent diabetic patients (31 with normoalbuminuria, 16 with microalbuminuria), wit h normal cardiac function, and 30 age-matched control subjects were enrolle d in this study. The plasma levels of BNP in diabetic patients with microal buminuria were significantly higher than those in diabetic patients with no rmoalbuminuria (16.7 +/- 2.4 vs. 9.6 +/- 1.3 pg/mL, P < 0.01) or normal sub jects (16.7 +/- 2.4 vs. 7.0 +/- 0.6 pg/mL, P < 0.01). There was a significa nt positive correlation between plasma BNP levels and urinary albumin excre tion rate in all diabetic patients (r = 0.58, P < 0.0001). There was also a significantly positive correlation between plasma BNP and ANP levels in di abetic patients (r = 0.62, P < 0.0001). The increased plasma level of BNP i n patients with microalbuminuria and its significant correlation with urina ry albumin excretion rate suggest that the elevated circulating levels of B NP are caused by the presence of diabetic nephropathy. Down-regulation of A -type guanylate cyclase-coupled receptor of renal tubules may explain the i ncreased plasma levels of both BNP and ANP in normotensive diabetic patient s with microalbuminuria.