Urinary Neutrophil Gelatinase-Associated Lipocalin and Progression of Diabetic Nephropathy in Type 1 Diabetic Patients in a Four-Year Follow-Up Study

Background: Neutrophil gelatinase-associated lipocalin (NGAL), a marker of renal tubular damage, predicts progression in non-diabetic chronic kidney. We evaluated urinary (u)-NGAL as a predictor of progression in diabetic nephropathy in type 1 diabetic (T1D) patients. Methods: As a substudy of a 4-year randomized, intervention study evaluating low-protein diet in T1D patients with diabetic nephropathy, 78 patients were studied with yearly measurements of u-NGAL (ELISA, BioPorto). Outcome: Decline in glomerular filtration rate (GFR) ((51)Cr-EDTA), and end-stage renal disease (ESRD) or death. Results: Mean age 40.7 (8.2) years and 50 men. 13 patients developed ESRD or died. Baseline GFR (mean, SD): 68 (31) ml/min/1.73 m(2). Baseline u-NGAL [geometric mean (95% CI)] and GFR were 15.6 ng/24 h (11.8-20.7) and 68 (31) ml/min/1.73 m(2). During follow-up, an increase in u-NGAL [geometric mean (95% CI)] of 15%/year (4-27) and a decline in GFR of 3.7 (3.0) ml/min/year were observed. Baseline u-NGAL was not associated with the decline in GFR. Elevated u-NGAL at baseline (log-transformed) predicted death and ESRD (HR 3.8, 95% CI 1.04-14.0), however not after adjustment for known progression promoters (HR 2.0, p = 0.6). Conclusion: Elevated u-NGAL was not related to decline in GFR during a 4-year follow-up. Elevated u-NGAL was associated with the development of ESRD and death, but not after adjustment.