URINARY EXCRETION OF N-ACETYL b-D-GLUCOSAMINIDASE AND
RETINOL RINDING PROTEIN AS ALTERNATIVE INDICATORS OF NEPHROPATHY IN TYPE 1
DIABETIC PATIENTS
Mona A.K. Salem*,
Safinaz A. El-Habashy*, Omayma M. Saeid***, Mohamed M.K. El-Tawil* and
Perihan H. Tawfik **
From: Pediatrics* and
Clinical Pathology** Departments, Faculty of Medicine, Ain Shams
University, and National Research Center***, Dokki, Cairo, Egypt
Diabetic
nephropathy is usually characterized by glomerular dysfunction, with
microalbuminuria as an early indicator . In a trial to assess renal tubular
function, urinary excretion of N-acetyl b-glucosaminidase ( b-NAG, by colorimetric assay) and retinol binding protein (RBP by
ELISA) were measured in 59 type 1 diabetic patients (mean age 15±3.2 years) , attending the Diabetes Clinic Children’s Hospital, Ain
Shams University. Of the 59 patients 11 (18.6%) had persistant
microalbuminuria (incipient nephropathy), and the remaining had within
normal range urinary albumin excretion (normoalbuminuria). Diabetic
patients were compared to 40 healthy age and sex matched controls. Results
revealed that diabetics with microalbuminuria had concomitant renal tubular
disorder indicated by elevated urinary b-NAG in all (100%) and RBP in10 (90.9%) of
them. Meanwhile, patients with normoalbuminuria (n=48) had both tubular
markers excreted in urine in significantly higher amounts as compared to
controls, and among them 29 (61%) had raised urinary b-NAG and 39 (82%) had increased loss of RBP in urine. A significant
correlation was found between urinary b-NAG and RBP in normoalbuminuric patients
(r=0.66, P<0.001), as well as between each and HbA1c
(r=0.83,P<0.001). During the regular follow up of diabetic patients, out
of the 48 patients with normoalbuminuria, 2 (4.2%) developed persistent
microalbuminuria, 30 and 36 months after initial evaluation. Both had
elevated HbA and urinary b-NAG.
In conclusion, proximal tubular
dysfunction may occur independent of glomerular alteration whether tubular
markers precede the development of microalbuminuria needs further studies.