STUDY OF AMYLOID FIBRILLATION OF REGULAR INSULIN: INHIBITION BY AROMATIC COMPOUNDS

The flexible structure of proteins is one important factor in the formation of ordered aggregates (amyloid fibril). This is a major problem for therapeutic proteins such as insulin. Study on the induction and inhibition of insulin fibrillation process with specific compounds such as aromatic derivatives may provide useful information about means of stabilization of protein structures. To induce fibrillation, regular insulin was incubated in phosphate buffer (pH=7.4) during 24 hours. Amyloid formation was investigated by using Congo red absorbance and transmission electron microscopy (TEM). Then nodular amyloidosis was observed in mice upon amyloid fibril injection, after which the excised nodule was studied by Congo red staining and polarized light microscopy. Then, some aromatic compounds effect was investigated on the fibrillation process. Regular insulin form mature amyloid fibrils at pH=7.4, 37°C after 24 hours. Silibinin had the highest inhibitory effect on that process. Furthermore, Amyloid fibril injection in mice caused nodular amyloidosis. Regular insulin has a high potential to undergo amyloid aggregation. Nodular amyloidosis confirms fibril formation by insulin under in vitro condition. Silibinin could be considered as a potential compound capable to increase protein structure stability.