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Inhibition of insulin fibrillation by osmolytes: Mechanistic insights.

Choudhary S, Kishore N, Hosur RV - Sci Rep (2015)

Bottom Line: We have studied here using a number of biophysical tools the effects of osmolytes, betaine, citrulline, proline and sorbitol which differ significantly in terms of their physical characteristics such as, charge distribution, polarity, H-bonding abilities etc, on the fibrillation of insulin.Among these, betaine, citrulline, and proline are very effective in decreasing the extent of fibrillation.Proline also causes a substantial delay in the onset of fibrillation in the concentration range (50-250 mM) whereas such an effect is seen for citrulline only at 250 mM, and in case of betaine this effect is not seen at all in the whole concentration range.

View Article: PubMed Central - PubMed

Affiliation: UM-DAE Centre for Excellence in Basic Sciences, Mumbai University Campus, Mumbai 400098, India.

ABSTRACT
We have studied here using a number of biophysical tools the effects of osmolytes, betaine, citrulline, proline and sorbitol which differ significantly in terms of their physical characteristics such as, charge distribution, polarity, H-bonding abilities etc, on the fibrillation of insulin. Among these, betaine, citrulline, and proline are very effective in decreasing the extent of fibrillation. Proline also causes a substantial delay in the onset of fibrillation in the concentration range (50-250 mM) whereas such an effect is seen for citrulline only at 250 mM, and in case of betaine this effect is not seen at all in the whole concentration range. The enthalpies of interaction at various stages of fibrillation process have suggested that the preferential exclusion of the osmolyte and its polar interaction with the protein are important in inhibition. The results indicate that the osmolytes are most effective when added prior to the elongation stage of fibrillation. These observations have significant biological implications, since insulin fibrillation is known to cause injection amyloidosis and our data may help in designing lead drug molecules and development of potential therapeutic strategies.

No MeSH data available.


Related in: MedlinePlus

Transmission electron microscopic images of insulin after 600 min of incubation in presence of 250 mM (A) betaine, (B) citruine, (C) proline and (D) sorbitol.
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f5: Transmission electron microscopic images of insulin after 600 min of incubation in presence of 250 mM (A) betaine, (B) citruine, (C) proline and (D) sorbitol.

Mentions: Figure 5 (A–D) shows transmission electron microscopic images of insulin taken after 600 min when incubated at 37 °C under stirring condition at 250 rpm, in the presence of 250 mM betaine, citrulline, proline and sorbitol, respectively. It is clear from the that small amorphous aggregates of insulin are formed in the presence of betaine, citrulline and proline (Fig. 5A–C respectively), whereas the presence of sorbitol leads to formation of fibrils having bundle like morphology (Fig. 5D). The TEM images support the results obtained from ThT fluorescence assay that in the presence of betaine, citrulline and proline the fibril formation is inhibited. A slight decrease in the ThT fuorescence intensity in the presence of sorbitol (Fig. 3D) is associated with reduction in the effective area for ThT binding upon bundle formation of fibrils.


Inhibition of insulin fibrillation by osmolytes: Mechanistic insights.

Choudhary S, Kishore N, Hosur RV - Sci Rep (2015)

Transmission electron microscopic images of insulin after 600 min of incubation in presence of 250 mM (A) betaine, (B) citruine, (C) proline and (D) sorbitol.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4663473&req=5

f5: Transmission electron microscopic images of insulin after 600 min of incubation in presence of 250 mM (A) betaine, (B) citruine, (C) proline and (D) sorbitol.
Mentions: Figure 5 (A–D) shows transmission electron microscopic images of insulin taken after 600 min when incubated at 37 °C under stirring condition at 250 rpm, in the presence of 250 mM betaine, citrulline, proline and sorbitol, respectively. It is clear from the that small amorphous aggregates of insulin are formed in the presence of betaine, citrulline and proline (Fig. 5A–C respectively), whereas the presence of sorbitol leads to formation of fibrils having bundle like morphology (Fig. 5D). The TEM images support the results obtained from ThT fluorescence assay that in the presence of betaine, citrulline and proline the fibril formation is inhibited. A slight decrease in the ThT fuorescence intensity in the presence of sorbitol (Fig. 3D) is associated with reduction in the effective area for ThT binding upon bundle formation of fibrils.

Bottom Line: We have studied here using a number of biophysical tools the effects of osmolytes, betaine, citrulline, proline and sorbitol which differ significantly in terms of their physical characteristics such as, charge distribution, polarity, H-bonding abilities etc, on the fibrillation of insulin.Among these, betaine, citrulline, and proline are very effective in decreasing the extent of fibrillation.Proline also causes a substantial delay in the onset of fibrillation in the concentration range (50-250 mM) whereas such an effect is seen for citrulline only at 250 mM, and in case of betaine this effect is not seen at all in the whole concentration range.

View Article: PubMed Central - PubMed

Affiliation: UM-DAE Centre for Excellence in Basic Sciences, Mumbai University Campus, Mumbai 400098, India.

ABSTRACT
We have studied here using a number of biophysical tools the effects of osmolytes, betaine, citrulline, proline and sorbitol which differ significantly in terms of their physical characteristics such as, charge distribution, polarity, H-bonding abilities etc, on the fibrillation of insulin. Among these, betaine, citrulline, and proline are very effective in decreasing the extent of fibrillation. Proline also causes a substantial delay in the onset of fibrillation in the concentration range (50-250 mM) whereas such an effect is seen for citrulline only at 250 mM, and in case of betaine this effect is not seen at all in the whole concentration range. The enthalpies of interaction at various stages of fibrillation process have suggested that the preferential exclusion of the osmolyte and its polar interaction with the protein are important in inhibition. The results indicate that the osmolytes are most effective when added prior to the elongation stage of fibrillation. These observations have significant biological implications, since insulin fibrillation is known to cause injection amyloidosis and our data may help in designing lead drug molecules and development of potential therapeutic strategies.

No MeSH data available.


Related in: MedlinePlus