A capillary zone electrophoresis method to investigate the oligomerization of the human Islet Amyloid Polypeptide involved in Type 2 Diabetes.

Type 2 diabetes is characterized by the aggregation of human Islet Amyloid Polypeptide (hIAPP) from monomer to large and insoluble fibrils. According to several recent studies, small soluble oligomers are now considered as potential toxic species. No monitoring tool has been to date reported to mimic in vitro the oligomerization process of hIAPP over time, although this would allow selecting candidate compounds that slow down or stop this pathological process. Considering the poor stability of those species and the necessity to monitor in real time, a compatible with the monitoring of hIAPP oligomerization CE method coupled to UV detection was developed. Three groups of hIAPP oligomers/monomers formed during this process could be separated. A polybrene coating was used to avoid adsorption of hIAPP onto capillary walls. Peaks identification was performed using a combination of CE-MS, filtrations and SDS-PAGE. They revealed that one peak is composed of monomer with a very small amount of dimer and trimer, whereas the two others are composed of bigger species higher than 100 kDa. We demonstrated that this real time oligomerization process started from the very initial step, with hIAPP principally as a monomer, until the formation of very big oligomers. This method was shown to be repeatable with RSDs on electrophoretic mobilities and relative peak areas less than 1.6 and 5.8% respectively for the monomer peak. Its application to study the anti-aggregation properties of resveratrol showed that this compound saved more than 30% of the monomeric hIAPP form whereas it almost disappeared without. The method opens new perspectives for the screening of potential drugs for type 2 diabetes.