Preventive Effect of Pyridoxal 5’–Phosphate on the Diabetic Retinopathy of Streptozotocin–Induced Diabetic Rat

Abstract

Abstract: : Purpose: Preventive effect of pyridoxal 5’–phosphate (PLP) on diabetic retinopathy was investigated in streptozotocin–induced diabetic rat model. Methods: Streptozotocin (70 mg/kg) was injected intraperitoneally to induce diabetes in 18 Sprague–Dawley male rats at the age of 7 weeks. Blood glucose level and the body weight were monitored as the indicator of the diabetic status of the rats. After one week of the streptozotocin injection, induced diabetes mellitus was certified by the blood glucose level. PLP is one of the active coenzyme in vitamin B6 family. On the basis of the proportion of body weight compared to human (1.5 mg / 60 kg), recommended therapeutic dose of PLP was calculated as 5 µg / 200 gm . PLP was injected intraperitoneally every two days after two weeks of streptozotocin injection, by 5 µg in normal dose group and by 50 µg in mega–dose group. In control group, normal saline was injected intraperitoneally. As a risk factor of vascular disease in diabetic state, blood homocysteine levels were measured after 3 weeks of PLP injections. Retinal vascular integrity was checked by fluorophotometer and the retinal ischemia was postulated by the expression of vascular endothelial growth factor (VEGF) in the retina. Results: Normal and mega–dose PLP group showed lower blood homocysteine level than that of the control group. Fluorophotometry showed less leakage of the fluorescein from the retinal vessels in normal and mega–dose group. VEGF was increased much more in the retina of control group than in the normal and mega–dose group. There were no differences between the normal and mega–dose group in all evaluation. There was no difference of the blood glucose level between the treatment group and control group. Conclusions: PLP seems to have inhibitory effect on the progression of early diabetic retinopathy without lowering blood glucose level.

Keywords: diabetic retinopathy