CST3 and diabetes mellitus: Several biomarkers can be used to evaluate renal function in patients with diabetes, such as creatinine, urea, glomerular filtration rate (GFR), UAE and cystatin C. Creatinine is derived from metabolism of creatine and phosphocreatine of muscle cells, while urea is the major nitrogenous metabolite derived from the degradation of proteins (4,5).