Evaluation of Serum Obestatin Level in Rat Model of Diabetic Nephropathy

Abstract
Background: Diabetic nephropathy is characterized by excessive protienuria and progressive irreversible renal dam-age. Various mechanisms were suspected to the development of diabetic nephropathy. However, a few studies have reported associations between obestatin and diabetic complications.
Aim of the Work: To evaluate serum OBST in type II diabetic nephropathy rat model and the possible association with the different biochemical and renal parameters.
Material and Methods: Twenty male albino rats were included in the study and divided into two groups: Group (I): Control group, group (II) type II diabetic group rats were fed High Fat Diet (HFD) for 5wks, then the HFD was replaced with normal rodent diet and animals received single intraperi-toneal injection of low dose of Streptozotocin (STZ) (35mg/kg). However, rats had been followed up for two weeks (group IIa), four weeks (group IIb) and for eight weeks (group IIc) after induction of diabetes, the following parameters were examined BMI, mean arterial blood pressure, serum OBST, insulin, glucose and calculated insulin resistance, lipids profile, tumor necrosis factor-alpha, angiotensin II levels, urea, cre-atinine and uric acid. Proteinuria, glomerular filtration rate and renal malondialdhyde level, glutathione peroxidase and superoxide dismutase activities. Histopathological examina-tions for kidney tissues were also done at the end of experiment.
Results: There were a significant progressive increase in serum levels of OBST, TNF-a and MAP in group II (a, b, c levels) and progressive increase in serum urea, creatinen, UA, ANG II and proteinuria in group IIb and c levels while, group IIa showed insignificant changes. In addition, there were a significant increase in serum glucose, HOMA-IR, total cho-lesterol, TG, LDL, VLDL and renal MDA, with a significant decrease in serum insulin, HDL, GFR and renal GSH-Px, SOD activities in group IIc level. Moreover, there was a progressive significant decrease in BMI in group II (b and c levels). Furthermore, obestatin levels were positively correlated with all the previously affected parameters in group II at all levels, except with insulin, HDL and GFR which showed a significant negative correlation. While no significant correlation had been found with GSH-Px, SOD activities.
Conclusion: Serum OBST levels were significantly ele-vated in experimentally induced diabetic nephropathy in rats and positively correlated with most of the measured biochem-ical and renal parameters except for insulin, HDL-C and GFR was negatively correlated. These findings simplify that OBST can be used as a novel biomarker for diabetes induced com-plications. As its increase may play a compensatory role in this metabolic disturbance.