In-vitro investigation of non-enzymatic glycation of human serum albumin by three-carbon reducing sugars
Advanced glycation end products (AGEs) are a heterogeneous group of compounds formed from the nonenzymatic reaction of reducing sugars with free amino groups of proteins, lipids, and nucleic acids. The initial product of this reaction is called a Schiff base, which spontaneously rearranges itself into an Amadori product. A line of subsequent reactions including dehydrations, oxidation-reduction reactions, and arrangements leads to the formation of AGEs. The initial stages of reaction are reversible depending on the concentration of the reactants and formation of AGEs from Amadori products is irreversible. Accumulation of AGEs in tissues and plasma causes progressive disease conditions such as debate complications, Alzheimer's and atherosclerosis. The formation of AGEs occurs at a higher rate initiates complications of hyperglycemia, and oxidative stress in tissues and plasma. Modified Proteins stimulate dysfunctional mitocondria and increase the production of reactive oxygen species. Elevated concentrations of reactive oxygen species cause the activation of pathways related to the pathogenesis. Human serum albumin (HSA), the most abundant plasma protein, can bind to numerous metabolites and can adopt various conformations depending on the ligand bound to the protein. HSA has a half-life time of 21 days, which is fairly long compared to other plasma proteins and present in high concentration in plasma, so that, this protein is highly susceptible to glycation. Compared to large cyclic forms of reducing sugars, small three member reducing sugars induce glycation process with albumin at higher rate because of small sugars contain a greater percentage of acyclic form. The current in vitro studies show that D/L glyceraldehydes and methyl glyoxal, glycolitc byproducts, non-enzymatically glycate HSA in the presence of Zn(II) and gold nano particles at a relatively reduced reaction rate than normal. Furthermore, Dihydroxyacetone phosphate (DHAP), another intermediate of the glycolitic pathway, is an analogue of Dihydroxyacetone (DHA). In addtion to physiological generation of DHA, it is widely used as an artificial skin-browning agent in tanning procedures. This study shows that HSA readily formed Maillard reaction products with DHA and DHAP and its browning reaction is accelerated with increasing pH and temperatures. This study also envisions that high concentrations of DHA, and DHAP increased the rate of formation of advanced glycation end products. The rates of formation AGE products were evaluated by comparing UV and fluorescence absorbance, high-pressure liquid chromatography elution profiles, SDS PAGE gel electrophoresis profiles of incubated reaction mixtures with their respective controls. Circular Dichroism and FTIR spectral methods were also provided reliable analysis of the secondary structure changes in modified HSA.
Padmanie Champika Seneviratne,
"In-vitro investigation of non-enzymatic glycation of human serum albumin by three-carbon reducing sugars"
Dissertations and Master's Theses (Campus Access).