Non-enzymatic glycation of human fibrillin-1

Non-enzymatic glycation of proteins is one of the key mechanisms in the pathogenesis of diabetic complications and may be significant in the age-related changes of tissues. We isolated and investigated the in vitro glycation of human aortic fibrillin-1. Fibrillin-1 was prepared from thoracic aortas of 9 accident victims distributed in three age groups. The purity of isolated fibrillin-1 was proved. It was glycated by incubating with different glucose concentrations in 0.2 M phosphate buffer, pH 7.4, for 30 days, at 37 degrees C. The degree of early products of glycation was measured by two colorimetric methods, i.e. nitroblue tetrazolium and 2-thiobarbituric acid. Advanced glycation end products (AGEs) were determined by fluorescence measurement. The highest level of early products of glycation was found on day 2 after the beginning of incubation for the fibrillin-1 isolated from the youngest group. Fluorescence in the age groups, as an index of advanced glycation, consistently increased between days 6 and 24. The fibrillin-1 isolated from the youngest group had the highest capacity to form fructosamine and AGEs under glycation in vitro. The capacity of glycation of the 'oldest' fibrillin did not increase significantly during the incubation. Investigation of the properties of glycated fibrillin-1 will help to understand the importance of this long-lived protein to age-related changes in tissues and for diabetic complications.