Ascorbic acid inhibits human insulin aggregation and protects against amyloid induced cytotoxicity

Elucidating the Inhibitory Potential of Designed Peptides Against Amyloid Fibrillation and Amyloid Associated Cytotoxicity

“…Far-UV CD is a widely used technique for the determination of alterations in the secondary structure of a protein (Li et al, 2015 ; Alam P. et al, 2016 ). In agreement with previous reports (Ahmad et al, 2004 ; Alam et al, 2017 ), the far-UV CD spectrum of insulin alone exhibited two negative minima at 222 nm and 208 nm, characteristic of α-helical proteins (Figure 6 ). The changes in protein secondary structure upon incubation of insulin with peptides (P4 and P5) at 25°C were rather insignificant as it follows from little changes in the intensity and shape of the CD spectra.…”

“…These results suggest that peptides retard the amyloid formation even at physiological conditions. However, it requires 240 h (Alam et al, 2017 ) (longer than 72 h at acidic pH) to form amyloids. Overall, the above results demonstrate that our peptides may act as a general inhibitor for the protein aggregation.…”

“…These results suggested that peptides probably altered insulin structure masking the available hydrophobic patches. This ability to interact with such patches is likely to be related to their inhibitory potential against insulin fibrillation (Alam et al, 2017 ). Control experiments performed in the absence of insulin showed negligible ANS fluorescence in the presence of P4 and P5 peptides, under the same experimental conditions (Supplementary Figure S3 ).…”

“…This behavior was similar to the nanobody, which inhibited amyloid fibril formation. They reported the effects of two camelid antibody fragments, generally called nanobodies (De Genst et al, 2013 ; Gong et al, 2014 ; Alam et al, 2017 ). Figures 10C,F show the amino acid residues involved in the interaction of insulin with P4 and P5 and that appear to play an important role in inhibiting the insulin amyloid fibril formation.…”

“…Figures 10C,F show the amino acid residues involved in the interaction of insulin with P4 and P5 and that appear to play an important role in inhibiting the insulin amyloid fibril formation. These results suggested that instead of blocking the aggregation prone region, peptides (P4 and P5) inhibited the amyloid formation by restricting the participation of these key residues in the intermolecular interactions during the course of amyloidogenesis (De Genst et al, 2013 ; Alam et al, 2017 ).…”