Figure 3.

Effects of methylglyoxal on the early steps of insulin aggregation. Insulin (3 mg.ml^-1) was incubated in the absence of methylglyoxal and in the presence of 5 mM of the glycation agent with stirring. Samples were collected at specific incubation times and immediately analysed by size exclusion chromatography (A) and PAGE (B). Sample buffer in PAGE did not contain SDS and β-mercaptoethanol in order to preserve the insulin oligomerization. To investigate the nature of insulin aggregates, the monomeric form of glycated insulin collected at incubation time 0 h (M) and the tetrameric form of glycated insulin collected at time 18 h (T) were analysed by a standard SDS-PAGE (C).