ensinogen, periostin, and monocyte chemoattractant protein-1 (MCP-1) reflect tubular injury. In this article, we focused on the potential applications of these biomarkers in diabetic nephropathy as shown in [Table 1](#tab1){ref-type="table"}.

4.1. Cystatin-C {#sec4.1}
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Cystatin-C is produced from nucleated cells in the body. It has a molecular weight of 13 kDa, is easily filtered by the glomeruli, and is reabsorbed and catabolized by the proximal tubule. From a prospective observational study, urine cystatin C predicted the progression of T2DM with nephropathy \[[@B15]\]. T2DM with rapid renal progression had significantly increased levels of urine cystatin C when compared with the nonrapid renal progression group \[[@B16]\]. Urine cystatin C was an independent predictor of CKD progression in T2DM.

4.2. Neutrophil Gelatinase-Associated Lipocalin (NGAL) {#sec4.2}
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NGAL is a 24 kDa secreted glycoprotein. NGAL is expressed in the renal tubular epithelium, and a rise in urinary concentrations may provide an indication of acute renal injury that can be detected before the rise in serum creatinine concentration \[[@B17]\]. Models of acute kidney injury- (AKI-) to-chronic kidney disease (CKD) transition have implicated its role as a potential biomarker of a chronically injured kidney. In patients with CKD, overexpression of NGAL occurs in renal tubular cells, compared with its expression among non-CKD patients \[[@B18]\], and both serum and urinary NGAL represent a novel, independent renal predictor of the severity of renal disease and CKD progression \[[@B19]\]. In a related study carried out among patients with diabetic nephropathy, elevated urine NGAL level was reported to be associated with the progressive course of the disease leading to ESRD \[[@B20]\]. Similarly, in observational follow-up and our cohort study among patients with T2DM, high urine NGAL levels at baseline correlated with rapid decline of estimated GFR levels and increased 