Association between serum bilirubin and albuminuria in type 2 diabetes mellitus and diabetic nephropathy

Introduction: Diabetic nephropathy develops due to oxidative stress and inflammation resulting from chronic hyperglycemia. Bilirubin, a product of heme catabolism is found to have antioxidant and anti-inflammatory properties. Though previous studies have examined the relationship between total bilirubin and diabetic nephropathy, very few studies have focused on indirect and direct bilirubin levels. Hence, the present study aimed to compare serum bilirubin (total, indirect and direct) levels between non-diabetics, type 2 diabetics and diabetic nephropathy subjects and also to correlate albuminuria with serum bilirubin in type 2 diabetics and diabetic nephropathy subjects. Materials and Methods: 50 non-diabetics, 50 type 2 diabetics and 50 diabetic nephropathy subjects were included in the study. Fasting blood glucose, HbA1C, serum bilirubin (total, indirect and direct), serum creatinine, urine microalbumin and urine creatinine were measured. Estimated glomerular filtration rate (eGFR) and urine albumin creatinine ratio (ACR) was calculated. Results: Total bilirubin, direct and indirect bilirubin were significantly decreased in type 2 diabetics and diabetic nephropathy subjects compared to non-diabetics. Total bilirubin and indirect bilirubin were also significantly decreased in diabetic nephropathy subjects compared to type 2 diabetics. Total bilirubin, direct and indirect bilirubin showed significant negative correlation with albuminuria (Urine ACR) in type 2 diabetics and diabetic nephropathy subjects. Conclusion: Our study suggests that low bilirubin levels might be a risk factor for the development of type 2 diabetes and diabetic nephropathy. Bilirubin can be used as a marker to predict the risk of developing type 2 diabetes among general population and diabetic nephropathy among type 2 diabetes patients.