Abstract: Objective To investigate the difference of serum bilirubin between non-diabetic retinopathy(NDR) in long-standing type-2 diabetes mellitus and proliferative diabetic retinopathy(PDR). Methods Type-2 diabetic patients who were out-patient or who attended the department of endocrinology at Capital Medical University affiliated Tongren Hospital between March 2010 and December 2011 were recruited. Of all the patients, 253 had diabetic duration longer than 10 years and non-diabetic retinopathy(NDR)(male female ratio: 136/117), and 218 had proliferative diabetic retinopathy(PDR) and diabetic duration was not restricted(male female ratio: 98/120). Comparing the level of serum bilibubin between the two groups and the significant parameters were taken to the logistic regression formula. Results Both total bilirubin and indirect bilirubin were not significantly different between the two groups(P>0.05), however, patients with NDR had higher direct bilirubin than those with PDR(P<0.05). Concerning sex, male patients in NDR group had higher direct bilirubin than those with PDR. But in female patients, no significant diffenence was found. In the logistic regression analysis about diabetic retinopathy risk factors, age and direct bilirubin were protective factors; and systolic blood pressure, HbA1c were risk factors. Conclusion The level of direct bilirubin between the NDR group with diabetic duration longer than 10 years and PDR was different. Bilirubin is a natural anti-oxidant, and can play a protective role in the onset and development of diabetic retinopathy.

Key words: type 2 diabetes mellitus, diabetic retinopathy, serum bilirubin, oxidative stress