Insights into diabetic nephropathy biomarkers with focus on existing indices and potential future developments

Diabetic nephropathy (DN) is a diabetes microvascular disorder that is characterized by increased deposition of mesangial matrix, glomerulosclerosis, tubulointerstitial fibrosis, and impairment (thickening) of tubular and glomerular basement structures as well as excessive excretion of albumin in urine due to poor glycemic control. Identification of very sensitive, precise, and distinct markers of kidney injury will pave the way for early diagnosis and management of DN. An ideal biomarker reveals the structural injury, molecular and biochemical alterations of the kidney in diabetes. Among these biomarkers, albumin is an initial marker for kidney injury, especially the glomerular region of the kidney and it can be identified in both urine and serum of diabetic patients. Biomarkers for diagnosing glomerular injury include transferrin, extracellular matrix protein, nephrin, podocalyxin, Wilms’ tumor-1, and cystatin C. However, biomarkers for detecting defective renal tubules in DN are α1-microglobulin, retinol-binding protein 4, neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, N-acetyl-β-D-glucosidase, and heart-type fatty acid binding protein. Other than the mentioned markers, indices such as long non-coding RNA, microRNA, micro-particles, and urinary exosomes are also vital in hyperglycemia-linked kidney injury. Moreover, the field of omics (transcriptomics, proteomics and metabolomics) are gaining more attention as they serve as avenue for the discovery of new, specific, sensitive, and precise biological markers for diagnosing the onset and progression DN. However, adequate information on their use as diagnosing biomarkers is still required. Therefore, the review presents information on these DN biomarkers and their future perspectives.