Inhibition of protein glycation and advanced glycation end products by ascorbic acid
Advanced glycation end products (AGEs) formation is increased in diabetes mellitus, leading to microvascular and macrovascular complications. Recently, much attention has been focused on natural and synthetic inhibitors to delay the onset or progression of diabetes and its comorbidities. Ascorbic acid (AA) can react with proteins, including hemoglobin and possibly interfere with protein glycation process. An in vitro glycation model containing plasma from type 2 diabetic and non-diabetic healthy volunteers together with glucose as glycating agent was used to study antiglycation activity of AA. Samples with different concentrations of glucose and AA were incubated for five weeks at 37°C. Nonenzymatic glycation (NEG) was quantitated by thiobarbituric acid calorimetry and AGEs were measured by enzyme linked immuno-sorbent assay (ELISA). The NEG and AGEs levels were reduced by AA. Increasing the AA concentrations greatly diminished protein glycations, indicating dose-dependent effects of AA. Plasma NEG and AGEs were decreased with an average of 20 to 26% (p < 0.05) and 26 to 28% (p < 0.05). A significant correlation was found between the glycation inhibition and the inhibition of AGE formation (p < 0.05). The antiglycation role of AA is evident in the present study and it also indicates the possibility of inexpensive, relatively non-toxic vitamin therapy for the prevention and treatment of diabetic complications. It is plausible that AGEs inhibition by AA may also form the basis for future intervention strategies in both diabetic and non-diabetic individuals.
Keywords: Diabetes mellitus, glycation, advanced glycation end products, hyperglycemia, ascorbic acid