Dataset Information

Inhibition of insulin fibrillation by osmolytes: Mechanistic insights.

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.

SUBMITTER: Choudhary S

PROVIDER: S-EPMC4663473 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Inhibition of insulin fibrillation by osmolytes: Mechanistic insights.

Choudhary Sinjan S Kishore Nand N Hosur Ramakrishna V RV

Scientific reports 20151130

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 (50-2 ...[more]

PMID: 26616401

Similar Datasets

Project description:Bovine serum albumin (BSA) is an important transport protein of the blood and its aggregation/fibrillation would adversely affect its transport ability leading to metabolic disorder. Therefore, understanding the mechanism of fibrillation/aggregation of BSA and design of suitable inhibitor molecules for stabilizing its native conformation, are of utmost importance. The qualitative and quantitative aspects of the effect of osmolytes (proline, hydroxyproline, glycine betaine, sarcosine and sorbitol) on heat induced aggregation/fibrillation of BSA at physiological pH (pH 7.4) have been studied employing a combination of fluorescence spectroscopy, Rayleigh scattering, isothermal titration calorimetry (ITC), dynamic light scattering (DLS) and transmission electron microscopy (TEM). Formation of fibrils by BSA under the given conditions was confirmed from increase in fluorescence emission intensities of Thioflavin T over a time period of 600 minutes and TEM images. Absence of change in fluorescence emission intensities of 8-Anilinonaphthalene-1-sulfonic acid (ANS) in presence of native and aggregated BSA signify the absence of any amorphous aggregates. ITC results have provided important insights on the energetics of interaction of these osmolytes with different stages of the fibrillar aggregates of BSA, thereby suggesting the possible modes/mechanism of inhibition of BSA fibrillation by these osmolytes. The heats of interaction of the osmolytes with different stages of fibrillation of BSA do not follow a trend, suggesting that the interactions of stages of BSA aggregates are osmolyte specific. Among the osmolytes used here, we found glycine betaine to be supporting and promoting the aggregation process while hydroxyproline to be maximally efficient in suppressing the fibrillation process of BSA, followed by sorbitol, sarcosine and proline in the following order of their decreasing potency: Hydroxyproline> Sorbitol> Sarcosine> Proline> Glycine betaine.

Project description:Background & aimsThe sodium taurocholate co-transporting polypeptide (NTCP) is the entry receptor for the hepatitis B and delta virus (HBV/HDV) and the main hepatic uptake transporter of conjugated bile acids. Myrcludex B, a synthetic peptide mimicking the NTCP-binding domain of HBV, blocks HBV/HDV infection and inhibits NTCP-mediated bile acid uptake. In humans this increases systemic bile acid levels, which remain elevated for hours even after Myrcludex B is cleared from the circulation. Here, we investigated the dynamics of Myrcludex B-induced NTCP-mediated bile acid transport inhibition in mice and if/how the duration of this effect relates to NTCP protein turnover.MethodsPlasma bile acids were determined in Myrcludex B-treated OATP1a/1b-deficient mice. In vitro, plasma membrane-resident NTCP was labeled with biotin or fluorescein isothiocyanate (FITC)-labeled Myrcludex B and traced in time using hNTCP-overexpressing U2OS cells. Förster resonance energy transfer by fluorescent lifetime imaging microscopy was used to investigate whether Myrcludex B can transfer to newly synthesized NTCP.ResultsConjugated bile salt levels in plasma peaked 4 h after subcutaneous Myrcludex B administration. After 24 h, plasma bile salt levels were completely normalized, in line with restored NTCP-mediated bile acid transport in vitro. Biotin-labeled NTCP disappeared faster than Myrcludex B-FITC, with almost 40% of FITC signal remaining after 24 h. FITC fluorescence lifetime was strongly decreased upon expression of DY547-labeled acyl carrier protein-tagged NTCP, demonstrating transfer of pre-bound Myrcludex B-FITC to newly formed NTCP.ConclusionsThe dynamics of NTCP protein turnover and Myrcludex B-induced plasma bile salt elevations are similar, suggesting that the Myrcludex B:NTCP interaction is very long-lived. Nevertheless, Myrcludex B is not completely degraded together with NTCP and can transfer to newly synthesized NTCP.Lay summaryThe experimental drug Myrcludex B binds the sodium taurocholate co-transporting polypeptide (NTCP), the viral entry receptor for the hepatitis B and D virus (HBV/HDV), and thereby prevents infection, but also inhibits hepatic bile salt uptake leading to transiently elevated bile salt levels. This study describes that while the normalization of plasma bile salt levels likely depends on the protein turnover rate of NTCP, Myrcludex B partly escapes co-degradation with NTCP by transferring from one NTCP molecule to another. This is of importance to the HBV/HDV research field as it provides a potential explanation for the distinct kinetics and dose-dependence of Myrcludex B's effects on viral infection versus bile salt transport.

Dataset Information

Inhibition of insulin fibrillation by osmolytes: Mechanistic insights.

Publications

Inhibition of insulin fibrillation by osmolytes: Mechanistic insights.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure