Comparative Study of Novel Biomarkers of Kidney Injury; Kidney Injury Molecule and Liver Type Fatty Acid Binding Protein in Experimentally Induced Diabetic Nephropathy in Rats, and their Correlation with Renal Histopathological Changes

Abstract
Background: Diabetic nephropathy is a serious microvas-cular complication of type 2 diabetes mellitus that can progress slowly to end-stage renal disease that can be fatal. It is characterized by highly specific, slowly progressing histopatho-logical changes. As the standard biomarkers lack the adequate sensitivity, novel biomarkers are needed for the early detection and risk stratification of diabetic nephropathy.
Aim of Study: To investigate the histopathological changes occurring in diabetic nephropathy, to study the associated changes of two novel biomarkers; Liver Fatty Acid Binding Protein (L-FABP) and Kidney Injury Molecule (KIM), to correlate their gene expression with the degree of histopatho-logical changes and to compare their sensitivity and degree of correlation against the standard biomarkers, notably blood urea and serum creatinine.
Material and Methods: 24 experimental male rats were divided into two groups, a control group, and a diabetic nephropathy group. Type 2 diabetes mellitus was induced by High Fat Diet (HFD) followed by Streptozotocin (STZ) intraperitoneal injection. The presence of diabetes was con-firmed by fasting plasma glucose & insulin levels, and the induction of diabetic nephropathy was confirmed by the presence of albuminuria.
Histological examination was performed for all experi-mental rats using hematoxylin and eosin stain (H & E) staining as well as Periodic Acid Schiff (PAS) stain. These results were expressed as the mean optical density of the PAS-positive reaction.
The gene expression for L-FABP and KIM were measured by Polymerase Chain Reaction (PCR) reverse transcriptase method and the levels of blood urea and serum creatinine, as standard biomarkers were measured. Statistical correlation analysis was performed by Pearson's correlation method to investigate the correlation of their gene expression and the histopathological changes.
Results: Significant histopathological changes occurred in diabetic nephropathy manifested by several changes in the H & E staining as well as PAS-positive reactions. All biomar-kers are elevated in the diabetic nephropathy group compared to the control group. However, no statistically significant correlation was found between the standard renal biomarkers (blood urea and serum creatinine) and gene expression of KIM. Only statistically significant correlation was found between the gene expression of L-FABP and the degree of histopathological changes.
Conclusion: The standard biomarkers (blood urea & serum creatinine) are lacking the adequate sensitivity for correlation with the histopathological changes in diabetic nephropathy. L-FABP is a promising future biomarker that can potentially be used for early detection as well as the follow-up of cases of diabetic nephropathy.