Plasma N-terminal pro-brain natriuretic peptide in Type 1 diabetic patients with and without diabetic nephropathy

Plasma N-terminal pro-brain natriuretic peptide (NT proBNP) is produced and released from cardiac ventricles; it is elevated in patients with heart failure, hypertension and chronic renal failure. This study aimed to examine the plasma levels of NT proBNP and their relationship in Type 1 diabetic patients with and without diabetic nephropathy.

We developed a non-competitive immunoluminometric assay with in-house antibodies to the N- and C-terminal domains of NT proBNP. We compared NT proBNP levels between 47 normoalbuminuric patients (group 1), 12 microalbuminuric patients (group 2) and 12 patients with macroalbuminuria (group 3).

There were significant differences in 24-h systolic and diastolic blood pressure, diabetes duration, serum creatinine, LDL-cholesterol and HbA1c between the three groups; other parameters did not differ significantly. NT proBNP (median and range) levels were 5 (0.75-68), 22 (0.75-82) and 23 (0.75-374) fmol/ml for groups 1-3, respectively. Log-transformed data of NT proBNP were used to compare all three groups (P=0.016). The Pearson correlation between NT proBNP and albuminuria (R=0.27; P=0.02) was positive; HbA1c (R=0.25; P=0.03) and age (R=0.33; P=0.005) correlated significantly as well. On the basis of multiple regression analysis, the adjusted difference remained significant between the three groups.

This is the first demonstration that NT proBNP levels are significantly higher in Type 1 diabetic patients with albuminuria. This may be caused by a down-regulation of A-type guanylate cyclase-coupled natriuretic peptide receptors in renal tubules or by elevated NT proBNP levels leading to higher glomerular hydraulic pressure or higher capillary permeability and possibly increased albumin excretion. Further studies are required to investigate the potential role of NT proBNP in patients with diabetic nephropathy and such other co-morbidities as cardiovascular disease.