Nonenzymatic glycation of human fibrinogen and myelin basic protein

摘要

The nonenzymatic glycation and formation of advanced glycation endproducts (AGE) of human fibrinogen and myelin basic protein (MBP) were studied, with the major focus on the comparison of fructose and glucose glycation and AGE formation. Fibrinogen fructose glycation rapidly forms a AGE related high molecular weight product which is designated as fibrinogen glycation oligomer. The formation of this glycation oligomer corresponds with the formation of a new UV/visible absorption peak and a new fluorescence peak characteristic of AGE. In the glycation of MBP, while no high molecular weight oligomer could be detected, the AGE related new absorption and fluorescence peaks formed. EDTA enhances the glycation and AGE formation while Ca(II) ion inhibits. Glucose also initiates the above reaction but at a lower rate than fructose. Glycation also appears to protect these proteins from proteolysis. Aminoguanidine and pyridoxal 5$spprime$-phosphate, two glycation inhibitors, also inhibit the formation of fibrinogen glycation oligomer and AGE of MBP. Antioxidants, thiourea and dimethyl sulfoxide, have little effect on the fibrinogen oligomerization. AGE of MBP are altered by the presence of Cu(II) ion, suggesting oxidation may contribute to the AGE formation with MBP. The fibrinogen glycation oligomer also displays decreased coaguability when compared with native fibrinogen, but its immunoactivity appeared to be almost unaffected. The results of this study demonstrate the formation of AGE of fibrinogen and MBP which may have some roles in the pathophysiology of diabetes and aging.