Ultraviolet B radiation enhances glycation of human serum albumin and the formation of CML in vitro

Abstract

Non‐enzymatic glycation of human serum albumin (HSA) is a major contributor to the pathology of diabetes. Exposure to ultraviolet B (UVB) irradiation is known to perturb protein structure and generate reactive oxygen species (ROS) which might accelerate protein glycation. The objective of this study was to evaluate the effect of UVB irradiation on the glycation level of HSA by D‐glucose and the formation of carboxymethyl lysine (CML), an Advanced Glycation Endproducts (AGEs) used as a biomarker of oxidatively damaged tissues. Compared to the untreated HSA, UVB exposed HSA showed a more rapid increase in fluorescence intensity over time, as well as enhanced peak areas of AGEs in the HPLC elution profile. Circular dichroism spectrum revealed a more extended loss in protein secondary structure when glycation had taken place under exposure to UVB. More D‐glucose adducts were found on UVB treated HSA, generating a higher mass shift of protein in MALDI profile. Compared to samples in the dark, reactions exposure to UVB produced about double amount of CML within 60 hours of incubation. In conclusion, UVB radiation accelerates the glycation level of HSA and promotes the formation of AGEs, which may be stimulated by the generation of ROS by UV radiation. This study warrants further investigation as there have been few reports on the correlation between the UV radiation of proteins and their enhanced glycation by a reducing sugar.