Evaluation of neutrophil gelatinase-associated lipocalin and cystatin C as early markers of diabetic nephropathy

Diabetes mellitus (DM) is a major cause of concern because of its increasing prevalence rate and related microvascular as well as macrovascular complications, including kidney disease. Microalbuminuria has been accepted as the earliest marker for diabetic nephropathy; however, a large proportion of renal impairment occurs in nonalbuminuric state. We planned to investigate the serum and urinary levels of the tubular damage markers (neutrophil gelatinase-associated lipocalin [NGAL] and cystatin C [Cys C]) in patients of type 2 diabetes to detect early kidney injury. This cross-sectional hospital-based study included 180 patients with type 2 DM according to the American Diabetes Association criteria. Serum NGAL (S.NGAL) and urine NGAL (U.NGAL) and Cys C were measured in all study participants and investigated for correlation with microalbuminuria. Our results showed that U.NGAL and S.NGAL levels were significantly high in patients with microalbuminuria as compared to normoalbuminuric controls. Serum Cys C was also higher in microalbuminuric patients than who had normoalbuminuria. A positive correlation of urinary albumin excretion with S.NGAL and U.NGAL was noted. U.NGAL also showed positive correlation with duration of diabetes, glycated hemoglobin, and dyslipidemia. Receiver operating characteristic curve analysis showed that the area under the curve for U.NGAL and S.NGAL were 1 and 0.8, respectively, which indicates that they are sensitive markers for early renal damage. Urinary biomarkers were significantly elevated in normoalbuminuric type 2 diabetic patients compared with nondiabetic controls and could be used as markers of nephropathy at a very early stage even before the development of microalbuminuria, the current gold standard for early diagnosis. Despite the promise of these new biomarkers, further large, multicenter prospective studies are still needed.