Serum Bilirubin Levels Can be Used as a Potential Biomarker in the Progression of Diabetic Nephropathy in Rats

Abstract
Background: Diabetes mellitus is a widespread syndrome and a major cause of morbidity and mortality all over the world. Diabetic nephropathy is a progressive and irreversible renal affection that may end by renal failure in sever conditions. Bilirubin is the end product of heme catabolism. It has been recognized as a strong antioxidant. Many studies relate bilirubin to diabetes.
Aim of Study: The present investigation aimed to study the changes in serum billirubin level in diabetic nephropathy and to know whether there is a correlation between its level and the stages of nephropathy in diabetic rats.
Material and Methods: Sixty male albino rats were used and divided into the following groups; non-diabetic control group, diabetic nephropathy group and insulin-treated diabetic nephropathy group. By the end of the experimental period, 24 hours urine samples were collected to measure urine volume & urinary creatinine concentration and calculation of creatinine clearance. Then systolic blood pressure (SBP) was measured using rat tail sphygmomanometer technique. Fasting blood samples were collected for estimation of glycemic state, liver function tests and renal function tests. Finally both kidneys were fixed in 10% formalin solution for histopathology by using H&E & periodic acid schiffe (PAS).
Results: Our data showed that streptozotocin injection significantly elevated glycemic state, aspartate transaminase (AST), alanine transaminase (ALT), serum urea, serum creat-inin, SBP and significantly decreased seum albumin, creatinin clearance, total and direct bilirubin. Alkaline phosphatase (ALP) and serum albumin showed insignificant change. Histopathological examination of the same group showed slight thickening of the basement membrane, arterioles, few inflammatory cells and hydropic changes in renal tubules. Insulin treatment significantly decreased glycemic state, AST, ALT, serum urea, serum creatinin, SBP and significantly elevated seum albumin, creatinin clearance, total and direct bilirubin. Histopathological examination of the same group showed some healthy glomeruli but still hydropic changes in renal tubules.
Conclusion: Regular monitoring of bilirubin in diabetic patients is essential marker for progression and prognosis of diabetic nephropathy and effect of treatment.