Abstract
Purpose:
Accumulation of advanced glycation endproducts (AGE) due to non-enzymatic glycation of proteins has been implicated in several pathophysiologies associated with diabetic ocular complications. Earlier we have identified a few dietary sources such as cinnamon that have the potential to inhibit AGE formation. In this study, we have isolated and identified procyanidin-B2 as the antiglycating agent from cinnamon bark (Cinnamomum zeylanicum) and investigated its potential to prevent diabetic cataract and retinopathy in rat model.
Methods:
Using bioassay-guided fractionation, procyanidin-B2 was identified as an antiglycating agent from cinnamon and demonstrated its antiglycating potential and mechanism of action of using in vitro and ex vivo protein glycation systems. Further the effect of procyanidin-B2 and its dietary source (cinnamon) to prevent diabetic cataract and retinopathy was investigated using streptozotocin-induced diabetic rat model.
Results:
Under in vitro conditions, procyanidin-B2 inhibited the protein glycation as assessed by AGE-fluorescence, SDS-PAGE and immunodetection of specific AGE. Further, we provided insight into the mechanism of inhibition of protein glycation that it scavenges free radicals directly and trapping of dicarbonyls. In addition, procyanidin-B2 inhibited the glycosylated hemoglobin formation in human RBC under ex vivo conditions. We also demonstrated that feeding of proycanidin-B2 to diabetic rats in the diet was effective against development of cataract and retinopathy in streptozotocin mainly through its antiglycating potential. Procyanidin-B2 decreased levels of glial fibrillary acidic protein expression and vascular endothelial growth factor and enhanced nerve growth factor expression in diabetic retina.
Conclusions:
Thus, the active principle procyanidin-B2 isolated from dietary cinnamon might be useful for the treatment and/ or prevention of diabetic ocular complications.
Keywords: 499 diabetic retinopathy •
445 cataract •
657 protein modifications-post translational