Benzbromarone, Quercetin, and Folic Acid Inhibit Amylin Aggregation

Pharmacoinformatics approach for type 2 diabetes mellitus therapeutics using phytocompounds from Costus genus: an in-silico investigation

Type 2 Diabetes Mellitus (T2DM), as a significant health concern globally, particularly in India, underscoring the vital need for effective therapeutics. Current drug therapies for T2DM may have limitations, leading researchers to explore natural products as alternatives. In this study. We have investigated the anti-diabetic compounds from the Costus genus, known as the insulin plant, which is abundant in southern India. The bioinformatics tools and software used for in-silico analysis to identify potential therapeutic compounds and hub genes associated with T2DM in the Indian population that could cut short the in-vitro and in-vivo experimental approaches in near future. The systematic review and combinatorial in-silico analysis revealed IGF2BP2, INS and TCF as the key targets that are associated with T2DM. The compounds stigmasterol, cycloartenol, and diosgenone were explored to be potent among all the 38 phytocompounds from genus Costus with binding energies -8.48, -10.07, and -10.31 kcal/mol against IGF2BP2, INS and TCF. The molecular dynamics (MD) simulation studies of these complexes demonstrated stable and consistent dynamic behavior, particularly in the INS-cycloartenol, IGF2BP2-stigmasterol and TCF7L2-diosgenone complexes. The identified compounds and associated targets represent potential candidates for T2DM therapeutics in the Indian population. The pharmacoinformatics approach presented in the study could streamline the drug discovery process by prioritizing compounds for further experimental validation.Communicated by Ramaswamy H. Sarma.

Pomegranate peel, chokeberry leaves and Ironwort extract as novel natural inhibitors of amylin aggregation and cellular toxicity in pancreatic β cells

Impeding or reducing human amylin aggregation and/or its toxicity can be key to preventing pancreatic islet amyloidosis and β-cell loss in patients with Type 2 Diabetes Mellitus (T2DM). Here, Punica granatum (pomegranate) peel, Sideritis raeseri (ironwort) and Aronia melanocarpa (chokeberry) leaf extracts, were tested for their novel anti-aggregative and antitoxic properties in human amylin (hIAPP) treated rat pancreatic insulinoma (INS) cells. The protein aggregation (Th-T) assay revealed an inhibitory trend of all three plant extracts against amylin aggregates. In agreement with this finding, pomegranate peel and ironwort extracts effectively prevented the transition of hIAPP from disordered, random coil structures into aggregation prone β-sheet enriched molecular assemblies, revealed by CD spectroscopy. Consistent with their anti-aggregative action, all three extracts prevented, to various degrees, reactive oxygen species (ROS) accumulation, mitochondrial stress, and, ultimately, apoptosis of INS cells. Collectively, the results from this study demonstrate effectiveness of natural products to halt hIAPP aggregation, redox stress, and toxicity, which could be exploited as novel therapeutics against amylin-derived islet amyloidosis and β-cell stress in T2DM.

Big versus small: The impact of aggregate size in disease

Protein aggregation results in an array of different size soluble oligomers and larger insoluble fibrils. Insoluble fibrils were originally thought to cause neuronal cell deaths in neurodegenerative diseases due to their prevalence in tissue samples and disease models. Despite recent studies demonstrating the toxicity associated with soluble oligomers, many therapeutic strategies still focus on fibrils or consider all types of aggregates as one group. Oligomers and fibrils require different modeling and therapeutic strategies, targeting the toxic species is crucial for successful study and therapeutic development. Here, we review the role of different-size aggregates in disease, and how factors contributing to aggregation (mutations, metals, post-translational modifications, and lipid interactions) may promote oligomers opposed to fibrils. We review two different computational modeling strategies (molecular dynamics and kinetic modeling) and how they are used to model both oligomers and fibrils. Finally, we outline the current therapeutic strategies targeting aggregating proteins and their strengths and weaknesses for targeting oligomers versus fibrils. Altogether, we aim to highlight the importance of distinguishing the difference between oligomers and fibrils and determining which species is toxic when modeling and creating therapeutics for protein aggregation in disease.

An investigation into the potential action of polyphenols against human Islet Amyloid Polypeptide aggregation in type 2 diabetes

Type 2 diabetes (T2D), a chronic metabolic disease characterized by hyperglycemia, results in significant disease burden and financial costs globally. Whilst the majority of T2D cases seem to have a genetic basis, non-genetic modifiable and non-modifiable risk factors for T2D include obesity, diet, physical activity and lifestyle, smoking, age, ethnicity, and mental stress. In healthy individuals, insulin secretion from pancreatic islet β-cells is responsible for keeping blood glucose levels within normal ranges. T2D patients suffer from multifactorial onset of β-cell dysfunction and/or loss of β-cell mass owing to reactive oxygen species (ROS) production, mitochondrial dysfunction, autophagy, and endoplasmic reticulum (ER) stress. Most predominantly however, and the focus of this review, it is the aggregation and misfolding of human Islet Amyloid Polypeptide (hIAPP, also known as amylin), which is detrimental to β-cell function and health. Whilst hIAPP is found in healthy individuals, its misfolded version is cytotoxic and able to induce β-cell dysfunction and/or death through various mechanisms including membrane changes in β-cell causing influx of calcium ions, arresting complete granule membrane recovery and ER stress. There are several existing therapeutics for T2D. However, there is a need for alternative or adjunct therapies for T2D with milder adverse effects and greater availability. Foremost among the potential natural therapeutics are polyphenols. Extensive data from studies evaluating the potential of polyphenols to inhibit hIAPP aggregation and disassemble aggregated hIAPP are promising. Moreover, in-vivo, and in-silico studies also highlight the potential effects of polyphenols against hIAPP aggregation and mitigation of larger pathological effects of T2D. Whilst there have been some promising clinical studies on the therapeutic potential of polyphenols, extensive further clinical studies and in-vitro studies evaluating the mechanisms of action and ideal doses for many of these compounds are required. The need for these studies is made more important by the postulated link between Alzheimer's disease (AD) and T2D pathophysiology given the similar aggregation process of their respective amyloid proteins, which evokes thoughts of cross-reactive polyphenols which can be effective for both AD and T2D patients.

Recent Advances in the Discovery of Therapeutics to Curtail Islet Amyloid Polypeptide Aggregation for Type 2 Diabetes Treatment

In humans with type 2 diabetes, at least 70% of patients exhibit islet amyloid plaques formed by misfolding islet amyloid polypeptides (IAPP). The oligomeric conformation and accumulation of the IAPP plaques lead to a panoply of cytotoxic effects on the islet β-cells. Currently, no marketed therapies for the prevention or elimination of these amyloid deposits exist, and therefore significant efforts are required to address this gap. To date, most of the experimental treatments are limited to only in vitro stages of testing. In general, the proposed therapeutics use various targeting strategies, such as binding to the N-terminal region of islet amyloid polypeptide on residues 1-19 or the hydrophobic region of IAPP. Other strategies include targeting the peptide self-assembly through π-stacking. These methods are realized by using several different families of compounds, four of which are highlighted in this review: naturally occurring products, small molecules, organometallic compounds, and nanoparticles. Each of these categories holds immense potential to optimize and develop inhibitor(s) of pancreatic amyloidosis in the near future.

Z-scan optical method complements the Thioflavin T assay for investigation of anti-Alzheimer's impact of polyphenols

Polyphenols are tremendously effective in eliminating the amyloid-beta aggregations, the main hallmark of Alzheimer's disease. In recent years various nano drugs and biomaterials based on polyphenolic compounds have been synthetized to treat or prevent Alzheimer's disease, and the main in-vitro approach to investigate the anti-Alzheimer's properties of materials, is Thioflavin T assay. In spite of being very helpful, it has some drawbacks and cannot guarantee the accuracy of data, specifically in case of polyphenolic compounds; thus, rendering accurate results requires utilizing other assays along with Thioflavin T. In this experiment, we introduced Z-scan technique as a complementary test for Thioflavin T assay. In this study, the anti-Alzheimer's properties of two polyphenols quercetin and fulvic acid were assessed in the presence and absences of silver nanoparticles at various concentrations, both via Z-scan technique and Thioflavin T assay, after which the two tests were aligned with each other. The polyphenols' non-linear refractive indices obtained by the Z-scan technique correlated well with their related fluorescence intensities from the Thioflavin T assay in such a way that, the smaller the magnitude of the non-linear refractive indices, the stronger the anti-amyloidogenic impact. Our work shows that Z-scan could be used along with Thioflavin T for better investigation of polyphenols' anti-Alzheimer's properties.

Mechanisms Underlying the Antidiabetic Activities of Polyphenolic Compounds: A Review

Polyphenolic compounds are thought to show considerable promise for the treatment of various metabolic disorders, including type 2 diabetes mellitus (T2DM). This review addresses evidence from in vitro, in vivo, and clinical studies for the antidiabetic effects of certain polyphenolic compounds. We focus on the role of cytotoxic human amylin (hA) aggregates in the pathogenesis of T2DM, and how polyphenols can ameliorate this process by suppressing or modifying their formation. Small, soluble amylin oligomers elicit cytotoxicity in pancreatic islet β-cells and may thus cause β-cell disruption in T2DM. Amylin oligomers may also contribute to oxidative stress and inflammation that lead to the triggering of β-cell apoptosis. Polyphenols may exert antidiabetic effects via their ability to inhibit hA aggregation, and to modulate oxidative stress, inflammation, and other pathways that are β-cell-protective or insulin-sensitizing. There is evidence that their ability to inhibit and destabilize self-assembly by hA requires aromatic molecular structures that bind to misfolding monomers or oligomers, coupled with adjacent hydroxyl groups present on single phenyl rings. Thus, these multifunctional compounds have the potential to be effective against the pleiotropic mechanisms of T2DM. However, substantial further research will be required before it can be determined whether a polyphenol-based molecular entity can be used as a therapeutic for type 2 diabetes.

Islet amyloid toxicity: From genesis to counteracting mechanisms

Islet amyloid polypeptide (IAPP or amylin) is a hormone co-secreted with insulin by pancreatic β-cells and is the major component of islet amyloid. Islet amyloid is found in the pancreas of patients with type 2 diabetes (T2D) and may be involved in β-cell dysfunction and death, observed in this disease. Thus, investigating the aspects related to amyloid formation is relevant to the development of strategies towards β-cell protection. In this sense, IAPP misprocessing, IAPP overproduction, and disturbances in intra- and extracellular environments seem to be decisive for IAPP to form islet amyloid. Islet amyloid toxicity in β-cells may be triggered in intra- and/or extracellular sites by membrane damage, endoplasmic reticulum stress, autophagy disruption, mitochondrial dysfunction, inflammation, and apoptosis. Importantly, different approaches have been suggested to prevent islet amyloid cytotoxicity, from inhibition of IAPP aggregation to attenuation of cell death mechanisms. Such approaches have improved β-cell function and prevented the development of hyperglycemia in animals. Therefore, counteracting islet amyloid may be a promising therapy for T2D treatment.

The Therapeutic Effects and Mechanisms of Quercetin on Metabolic Diseases: Pharmacological Data and Clinical Evidence

Metabolic diseases have become major public health issues worldwide. Searching for effective drugs for treating metabolic diseases from natural compounds has attracted increasing attention. Quercetin, an important natural flavonoid, is extensively present in fruits, vegetables, and medicinal plants. Due to its potentially beneficial effects on human health, quercetin has become the focus of medicinal attention. In this review, we provide a timely and comprehensive summary of the pharmacological advances and clinical data of quercetin in the treatment of three metabolic diseases, including diabetes, hyperlipidemia, and nonalcoholic fatty liver disease (NAFLD). Accumulating evidences obtained from animal experiments prove that quercetin has beneficial effects on these three diseases. It can promote insulin secretion, improve insulin resistance, lower blood lipid levels, inhibit inflammation and oxidative stress, alleviate hepatic lipid accumulation, and regulate gut microbiota disorders in animal models. However, human clinical studies on the effects of quercetin in diabetes, hyperlipidemia, and NAFLD remain scarce. More clinical trials with larger sample sizes and longer trial durations are needed to verify its true effectiveness in human subjects. Moreover, another important issue that needs to be resolved in future research is to improve the bioavailability of quercetin. This review may provide valuable information for the basic research, drug development, and clinical application of quercetin in the treatment of metabolic diseases.

Repurposing a Cardiovascular Disease Drug of Cloridarol as hIAPP Inhibitor

Accumulating evidence have shown a strong pathological correlation between cardiovascular disease (CVD) and Type II diabetes (T2D), both of which share many common risk factors (e.g., hyperglycemia, hypertension, hypercoagulability, and dyslipidemia) and mutually contribute to each other. Driven by such strong CVD-T2D correlation and marginal benefits from drug development for T2D, here we proposed to repurpose a CVD drug of cloridarol as human islet amyloid peptide (hIAPP) inhibitor against its abnormal misfolding and aggregation, which is considered as a common and critical pathological event in T2D. To this end, we investigated the inhibition activity of cloridarol on the aggregation and toxicity of hIAPP_1-37 using combined experimental and computational approaches. Collective experimental data from ThT, AFM, and CD demonstrated the inhibition ability of cloridarol to prevent hIAPP aggregation from its monomeric and oligomeric states, leading to the overall reduction of hIAPP fibrils up to 57% at optimal conditions. MTT and LDH cell assays also showed that cloridarol can also effectively increase cell viability by 15% and decrease cell apoptosis by 28%, confirming its protection of islet β-cells from hIAPP-induced cell toxicity. Furthermore, comparative molecular dynamics simulations revealed that cloridarol was preferentially bound to the C-terminal β-sheet region of hIAPP oligomers through a combination of hydrophobic interactions, π-π stacking, and hydrogen bonding. Such multiple site bindings allowed cloridarol to disturb hIAPP structures, reduce β-sheet content, and block the lateral association pathway of hIAPP aggregates, thus explaining experimental findings. Different from other single-target hIAPP inhibitors, cloridarol is unique in that it works as both a CVD drug and hIAPP inhibitor, which can be used as a viable structural template (especially for benzofuran) for the further development of cloridarol-based or benzofuran-based inhibitors of amyloid proteins.

Pancreastatin induces islet amyloid peptide aggregation in the pancreas, liver, and skeletal muscle: An implication for type 2 diabetes

Recent findings suggest that the accumulation of misfolded aggregates of islet amyloid peptide (IAPP) plays an essential role in pancreatic damage and type 2 diabetes (T2D). Pancreastatin (PST), a chromogranin derived peptide, instigates insulin resistance (IR) and promotes T2D. Here, we aimed to investigate whether PST induces IAPP aggregation in the pancreas, liver, and skeletal muscles. Foremost, we unraveled kinetics of fibril formation by ThT kinetic assay, ANS binding, turbidity, and far UV-CD. Subsequently, we checked the microarchitecture of fibril by TEM. Moreover, the PST action on IAPP expression was examined by immunocytochemistry, immunohistochemistry, western blotting, and real-time PCR. The outcome of spectral analysis and TEM demonstrated the fibril formation in the alone IAPP group but not in the alone PST; however, PST with IAPP produced stronger fibril. Moreover, PST was found to stimulate IAPP aggregation and expression more prominently in PANC1 and HepG2 cells, and pancreas and liver tissues than in L6 and skeletal muscle. Subsequently, pancreastatin inhibitor manifested a decline in the extent of the IAPP fibril formation and its expression. To conclude, PST upon combination induces the aggregation of IAPP in the pancreas, liver, and skeletal muscle, which may have the potential to generate IR and cause T2D.

Inhibition of human amylin aggregation by Flavonoid Chrysin: An in-silico and in-vitro approach

Islet amyloid polypeptide (amylin), consecrated by the pancreatic β-cells with insulin, has a significant role to play in maintaining homeostasis of islet cell hormones. Alzheimer's disease is the predominant source of dementia. However, its etiology remains uncertain; it appears that type 2 diabetes mellitus and other prediabetic states of insulin resistance contribute to the intermittent Alzheimer's disease presence. Amylin is abnormally elevated in Type II diabetes patients, accumulated into amylin aggregates, and ultimately causes apoptosis of the β-cells, and till date, its mechanism remains unclear. Several flavonoids have inhibitory effects on amylin amyloidosis, but its inhibition mechanisms are unknown. Screening a collection of traditional compounds revealed the flavone Chrysin, a potential lead compound. Chrysin inhibits amyloid aggregate formation according to Thioflavin T binding, turbidimetry assay. We report results of molecular interaction analysis of Chrysin with amylin which shows potent binding affinity against amylin. Pharmacokinetics and Drug likeness studies of Chrysin also suggest that it is a potential lead compound. Therefore, Chrysin prevented amylin aggregation.

Tyrosine carbon dots inhibit fibrillation and toxicity of the human islet amyloid polypeptide

Misfolding and aggregation of the human islet amyloid polypeptide (hIAPP) are believed to play key roles in the pathophysiology of type-II diabetes. Here, we demonstrate that carbon dots (C-dots) prepared from the amino acid tyrosine inhibit fibrillation of hIAPP, reduce hIAPP-induced cell toxicity and block membrane disruption by the peptide. The pronounced inhibitory effect is traced to the display of ubiquitous aromatic residues upon the C-dots' surface, mimicking the anti-fibril and anti-toxic activity of natural polyphenolic compounds. Notably, spectroscopy and thermodynamics analysis demonstrated different hIAPP interactions and fibril inhibition effects induced by tyrosine-C-dots displaying phenolic residues and C-dots prepared from phenylalanine which exhibited phenyl units on their surface, underscoring the significance of hydrogen bonding mediated by the phenolic hydroxide moieties for the fibril modulation activity. The presented experiments attest to the potential of tyrosine-C-dots as a therapeutic vehicle for protein misfolding diseases, interfering in both π-π interactions as well as hydrogen bonding involving aromatic residues of amyloidogenic peptides.

Antibiofilm activity of flavonoids on staphylococcal biofilms through targeting BAP amyloids

The opportunistic pathogen Staphylococcus aureus is responsible for causing infections related to indwelling medical devices, where this pathogen is able to attach and form biofilms. The intrinsic properties given by the self-produced extracellular biofilm matrix confer high resistance to antibiotics, triggering infections difficult to treat. Therefore, novel antibiofilm strategies targeting matrix components are urgently needed. The Biofilm Associated Protein, Bap, expressed by staphylococcal species adopts functional amyloid-like structures as scaffolds of the biofilm matrix. In this work we have focused on identifying agents targeting Bap-related amyloid-like aggregates as a strategy to combat S. aureus biofilm-related infections. We identified that the flavonoids, quercetin, myricetin and scutellarein specifically inhibited Bap-mediated biofilm formation of S. aureus and other staphylococcal species. By using in vitro aggregation assays and the cell-based methodology for generation of amyloid aggregates based on the Curli-Dependent Amyloid Generator system (C-DAG), we demonstrated that these polyphenols prevented the assembly of Bap-related amyloid-like structures. Finally, using an in vivo catheter infection model, we showed that quercetin and myricetin significantly reduced catheter colonization by S. aureus. These results support the use of polyphenols as anti-amyloids molecules that can be used to treat biofilm-related infections.

Repurposing Benzbromarone for Familial Amyloid Polyneuropathy: A New Transthyretin Tetramer Stabilizer

Transthyretin (TTR) is a homotetrameric protein involved in human amyloidosis, including familial amyloid polyneuropathy (FAP). Discovering small-molecule stabilizers of the TTR tetramer is a therapeutic strategy for these diseases. Tafamidis, the only approved drug for FAP treatment, is not effective for all patients. Herein, we discovered that benzbromarone (BBM), a uricosuric drug, is an effective TTR stabilizer and inhibitor against TTR amyloid fibril formation. BBM rendered TTR more resistant to urea denaturation, similarly to iododiflunisal (IDIF), a very potent TTR stabilizer. BBM competes with thyroxine for binding in the TTR central channel, with an IC50 similar to IDIF and tafamidis. Results obtained by isothermal titration calorimetry (ITC) demonstrated that BBM binds TTR with an affinity similar to IDIF, tolcapone and tafamidis, confirming BBM as a potent binder of TTR. The crystal structure of the BBM-TTR complex shows two molecules binding deeply in the thyroxine binding channel, forming strong intermonomer hydrogen bonds and increasing the stability of the TTR tetramer. Finally, kinetic analysis of the ability of BBM to inhibit TTR fibrillogenesis at acidic pH and comparison with other stabilizers revealed that benzbromarone is a potent inhibitor of TTR amyloidogenesis, adding a new interesting scaffold for drug design of TTR stabilizers.

Natural Polyphenols as Modulators of the Fibrillization of Islet Amyloid Polypeptide

Diabetes mellitus type 2 (type-2 diabetes) is a metabolic disorder characterized by the increased blood glucose concentration and insulin resistance in peripheral tissues (e.g., muscles and adipose tissue). The initiation of the pathological cascade of events that lead to type-2 diabetes has been subject of debate; however, it has been commonly accepted that the oversecretion of human islet amyloid polypeptide (hIAPP, a hormone co-secreted with insulin) by the pancreatic 𝛽-cells is the main trigger of type-2 diabetes. In fact, 90% of the type-2 diabetes patients present hIAPP deposits in the extracellular space of the 𝛽-cells. These hIAPP supramolecular arrangements (both fibrillar and oligomeric) have been reported to be the origin of cytotoxicity, which leads to 𝛽-cell dysfunction through a series of different mechanisms, including the interaction of hIAPP oligomers with the cell membrane that leads to the influx of Ca²⁺ and increase in the cellular oxidative stress, among others. This overview shows the importance of developing type-2 diabetes treatment strategies able to (1) remodel of the secondary structure of cytotoxic hIAPP oligomers entrapping them into off-pathway nontoxic species and (2) reestablish physiological levels of oxidative stress. Natural polyphenols are a class of antioxidant compounds that are able to perform both functions. Herein we review the published literature of the most studied polyphenols, in particular for their ability to remodel the hIAPP aggregation pathway, to rescue the in vitro pancreatic 𝛽-cell viability and function, as well as to perform under a complex biological environment, i.e., in vivo animal models and clinical trials. Overall, natural polyphenols are able to control the cytotoxic hIAPP aggregation and minimize hIAPP-mediated cellular dysfunction and can be considered as important lead compounds for the treatment of type-2 diabetes.

Islet Amyloid Polypeptide: A Partner in Crime With Aβ in the Pathology of Alzheimer's Disease

Diabetes affects hundreds of millions of patients worldwide. Despite the advances in understanding the disease and therapeutic options, it remains a leading cause of death and of comorbidities globally. Islet amyloid polypeptide (IAPP), or amylin, is a hormone produced by pancreatic β-cells. It contributes to the maintenance of glucose physiological levels namely by inhibiting insulin and glucagon secretion as well as controlling adiposity and satiation. IAPP is a highly amyloidogenic polypeptide forming intracellular aggregates and amyloid structures that are associated with β-cell death. Data also suggest the relevance of unprocessed IAPP forms as seeding for amyloid buildup. Besides the known consequences of hyperamylinemia in the pancreas, evidence has also pointed out that IAPP has a pathological role in cognitive function. More specifically, IAPP was shown to impair the blood–brain barrier; it was also seen to interact and co-deposit with amyloid beta peptide (Aß), and possibly with Tau, within the brain of Alzheimer's disease (AD) patients, thereby contributing to diabetes-associated dementia. In fact, it has been suggested that AD results from a metabolic dysfunction in the brain, leading to its proposed designation as type 3 diabetes. Here, we have first provided a brief perspective on the IAPP amyloidogenic process and its role in diabetes and AD. We have then discussed the potential interventions for modulating IAPP proteotoxicity that can be explored for therapeutics. Finally, we have proposed the concept of a “diabetes brain phenotype” hypothesis in AD, which may help design future IAPP-centered drug developmentstrategies against AD.

Revealing the Mechanism of EGCG, Genistein, Rutin, Quercetin, and Silibinin Against hIAPP Aggregation via Computational Simulations

To inhibit hIAPP aggregation and reduce toxicity of its oligomers are one of the potential strategies for the treatment of Type 2 diabetes (T2D). It has been reported that there is an effective inhibitory effect on hIAPP aggregation by five natural flavonoids, including Genistein, Rutin, Quercetin, Epigallocatechin gallate (EGCG), and Silibinin, which are widely found in our daily food. However, the detailed mechanisms to inhibit hIAPP aggregation remain unclear. Here, we explore the mechanisms of the five flavonoids against hIAPP aggregation by molecular docking and molecular dynamics simulations. We show that these flavonoids can disaggregate Chain A and Chain B of hIAPP to reduce the extended conformation by binding with two regions of hIAPP, Leu₁₂-Ala₁₃-Asn₁₄ and Asn₃₁-Val₃₂-Gly₃₃-Ser₃₄-Asn₃₅, with the inhibitory ability of Genistein > Rutin > Quercetin > EGCG > Silibinin. These five compounds exhibit a common mechanism for disaggregation of the hIAPP pentamer; that is, they loosen the two nearest peptide chains to potentially destroy the hIAPP oligomer. Mutations of eight key residues remarkably affected by the flavonoids indicate that the secondary structures of the hIAPP pentamer change from β-sheet to be random coil, thereby to destroy its structural stability; moreover, the 28th (Ser), 12th (Leu) and 32nd (Val) amino acids exhibit significant effects on structural stability of the hIAPP pentamer, providing an important hint that these amino acids can be considered as potential targets for design of new candidate inhibitors against hIAPP oligomers. This work is beneficial to understanding of mechanism of these inhibits against hIAPP aggregation and will facilitate screening, modification, and design of new inhibitors.

A computational approach to get insights into multiple faces of additives in modulation of protein aggregation pathways

An enormous population worldwide is presently confronted with debilitating neurodegenerative diseases. The etiology of the disease is connected to protein aggregation and the events involved therein. Thus, a complete understanding of an inhibitor at different stages in the process is imperative for the formulation of a drug molecule. This review presents a detailed summary of the current status of different cosolvents. It further develops how the complex aggregation pathway can be simplified into three steps common to all proteins and the way computer simulations can be exploited to gain insights into the ways by which known inhibitors can affect all these stages. Computation of theoretical parameters in this regard and their correlation with experimental techniques is accentuated. In addition to providing an outline of the scope of different additives, this review showcases the way by which the problem of analyzing an effect of an additive can be addressed effectively via MD simulations.

Spontaneous Fluctuations Can Guide Drug Design Strategies for Structurally Disordered Proteins

Structure-based "rational" drug design strategies fail for diseases associated with intrinsically disordered proteins (IDPs). However, structural disorder allows large-amplitude spontaneous intramolecular dynamics in a protein. We demonstrate a method that exploits this dynamics to provide quantitative information about the degree of interaction of an IDP with other molecules. A candidate ligand molecule may not bind strongly, but even momentary interactions can be expected to perturb the fluctuations. We measure the amplitude and frequency of the equilibrium fluctuations of fluorescently labeled small oligomers of hIAPP (an IDP associated with type II diabetes) in a physiological solution, using nanosecond fluorescence cross-correlation spectroscopy. We show that the interterminal distance fluctuates at a characteristic time scale of 134 ± 10 ns, and 6.4 ± 0.2% of the population is in the "closed" (quenched) state at equilibrium. These fluctuations are affected in a dose-dependent manner by a series of small molecules known to reduce the toxicity of various amyloid peptides. The degree of interaction increases in the following order: resveratrol < epicatechin ∼ quercetin < Congo red < epigallocatechin 3-gallate. Such ordering can provide a direction for exploring the chemical space for finding stronger-binding ligands. We test the biological relevance of these measurements by measuring the effect of these molecules on the affinity of hIAPP for lipid vesicles and cell membranes. We find that the ability of a molecule to modulate intramolecular fluctuations correlates well with its ability to lower membrane affinity. We conclude that structural disorder may provide new avenues for rational drug design for IDPs.

Inhibition of Human Amylin Aggregation and Cellular Toxicity by Lipoic Acid and Ascorbic Acid

More than 30 human degenerative diseases result from protein aggregation such as Alzheimer's disease (AD) and type 2 diabetes mellitus (T2DM). Islet amyloid deposits, a hallmark in T2DM, are found in pancreatic islets of more than 90% of T2DM patients. An association between amylin aggregation and reduction in β-cell mass was also established by post-mortem studies. A strategy in preventing protein aggregation-related disorders is to inhibit the protein aggregation and associated toxicity. In this study, we demonstrated that two inhibitors, lipoic acid and ascorbic acid, significantly inhibited amylin aggregation. Compared to amylin (15 μM) as 100%, lipoic acid and ascorbic acid reduced amylin fibril formation to 42.1 ± 17.2% and 42.9 ± 12.8%, respectively, which is confirmed by fluorescence and TEM images. In cell viability tests, both inhibitors protected RIN-m5f β-cells from the toxicity of amylin aggregates. At 10:1 molar ratio of lipoic acid to amylin, lipoic acid with amylin increased the cell viability to 70.3%, whereas only 42.8% RIN-m5f β-cells survived in amylin aggregates. For ascorbic acid, an equimolar ratio achieved the highest cell viability of 63.3% as compared to 42.8% with amylin aggregates only. Docking results showed that lipoic acid and ascorbic acid physically interact with amylin amyloidogenic region (residues Ser20-Ser29) via hydrophobic interactions; hence reducing aggregation levels. Therefore, lipoic acid and ascorbic acid prevented amylin aggregation via hydrophobic interactions, which resulted in the prevention of cell toxicity in vitro.

A Rationally Designed Hsp70 Variant Rescues the Aggregation-Associated Toxicity of Human IAPP in Cultured Pancreatic Islet β-Cells

Molecular chaperones are key components of the protein homeostasis system against protein misfolding and aggregation. It has been recently shown that these molecules can be rationally modified to have an enhanced activity against specific amyloidogenic substrates. The resulting molecular chaperone variants can be effective inhibitors of protein aggregation in vitro, thus suggesting that they may provide novel opportunities in biomedical and biotechnological applications. Before such opportunities can be exploited, however, their effects on cell viability should be better characterised. Here, we employ a rational design method to specifically enhance the activity of the 70-kDa heat shock protein (Hsp70) against the aggregation of the human islet amyloid polypeptide (hIAPP, also known as amylin). We then show that the Hsp70 variant that we designed (grafted heat shock protein 70 kDa-human islet amyloid polypeptide, GHsp70-hIAPP) is significantly more effective than the wild type in recovering the viability of cultured pancreatic islet β-cells RIN-m5F upon hIAPP aggregation. These results indicate that a full recovery of the toxic effects of hIAPP aggregates on cultured pancreatic cells can be achieved by increasing the specificity and activity of Hsp70 towards hIAPP, thus providing evidence that the strategy presented here provides a possible route for rationally tailoring molecular chaperones for enhancing their effects in a target-dependent manner.

Advances in liquid biopsy on-chip for cancer management: Technologies, biomarkers, and clinical analysis

Liquid biopsy, as a minimally invasive method of gleaning insight into the dynamics of diseases through a patient fluid sample, has been growing in popularity for cancer diagnosis, prognosis, and monitoring. While many technologies have been developed and validated in research laboratories, there has also been a push to expand these technologies into other clinical settings and as point of care devices. In this article, we discuss and evaluate microchip-based technologies for circulating tumor cell (CTC), exosome, and circulating tumor nucleic acid (ctNA) capture, detection, and analysis. Such integrated systems streamline otherwise multiple-step, manual operations to get a sample-to-answer quantitation. In addition, analysis of disease biomarkers is suited to point of care settings because of ease of use, low consumption of sample and reagents, and high throughput. We also cover the basics of biomarkers and their detection in biological fluid samples suitable for liquid biopsy on-chip. We focus on emerging technologies that process a small patient sample with high spatial-temporal resolution and derive clinically meaningful results through on-chip biomarker sensing and downstream molecular analysis in a simple workflow. This critical review is meant as a resource for those interested in developing technologies for capture, detection, and analysis platforms for liquid biopsy in a variety of settings.

Inhibition of Protein Aggregation by Several Antioxidants

Amyloid fibril formation is a shared property of all proteins; therefore, model proteins can be used to study this process. We measured protein aggregation of the model amyloid-forming protein stefin B in the presence and absence of several antioxidants. Amyloid fibril formation by stefin B was routinely induced at pH 5 and 10% TFE, at room temperature. The effects of antioxidants NAC, vitamin C, vitamin E, and the three polyphenols resveratrol, quercetin, and curcumin on the kinetics of fibril formation were followed using ThT fluorescence. Concomitantly, the morphology and amount of the aggregates and fibrils were checked by transmission electron microscopy (TEM). The concentration of the antioxidants was varied, and it was observed that different modes of action apply at low or high concentrations relative to the binding constant. In order to obtain more insight into the possible mode of binding, docking of NAC, vitamin C, and all three polyphenols was done to the monomeric form of stefin B.

A Novel Multi-Epitope Vaccine Based on Urate Transporter 1 Alleviates Streptozotocin-Induced Diabetes by Producing Anti-URAT1 Antibody and an Immunomodulatory Effect in C57BL/6J Mice

Hyperuricemia (HUA) is related to diabetes. Uric acid-induced inflammation and oxidative stress are risk factors for diabetes and its complications. Human urate transporter 1 (URAT1) regulates the renal tubular reabsorption of uric acid. IA-2(5)-P2-1, a potent immunogenic carrier designed by our laboratory, can induce high-titer specific antibodies when it carries a B cell epitope, such as B cell epitopes of DPP4 (Dipeptidyl peptidase-4), xanthine oxidase. In this report, we describe a novel multi-epitope vaccine composing a peptide of URAT1, an anti-diabetic B epitope of insulinoma antigen-2(IA-2) and a Th2 epitope (P2:IPALDSLTPANED) of P277 peptide in human heat shock protein 60 (HSP60). Immunization with the multi-epitope vaccine in streptozotocin-induced diabetes C57BL/6J mice successfully induced specific anti-URAT1 antibody, which inhibited URAT1 action and uric acid reabsorption, and increased pancreatic insulin level with a lower insulitis incidence. Vaccination with U-IA-2(5)-P2-1 (UIP-1) significantly reduced blood glucose and uric acid level, increased Th2 cytokines interleukin (IL)-10 and IL-4, and regulated immune reactions through a balanced Th1/Th2 ratio. These results demonstrate that the URAT1-based multi-epitope peptide vaccine may be a suitable therapeutic approach for diabetes and its complications.

Unfolding Novel Mechanisms of Polyphenol Flavonoids for Better Glycaemic Control: Targeting Pancreatic Islet Amyloid Polypeptide (IAPP)

Type 2 diabetes (T2D) is characterised by hyperglycaemia resulting from defective insulin secretion, insulin resistance, or both. The impact of over-nutrition and reduced physical activity, evidenced by the exponential rise in obesity and the prevalence of T2D, strongly supports the implementation of lifestyle modification programs. Accordingly, an increased consumption of fruits and plant-derived foods has been advocated, as their intake is inversely correlated with T2D prevalence; this has been attributed, in part, to their contained polyphenolic compounds. Over the last decade, a body of work has focussed on establishing the mechanisms by which polyphenolic compounds exert beneficial effects to limit carbohydrate digestion, enhance insulin-mediated glucose uptake, down-regulate hepatic gluconeogenesis and decrease oxidative stress; the latter anti-oxidative property being the most documented. Novel effects on the inhibition of glucocorticoid action and the suppression of amylin misfolding and aggregation have been identified more recently. Amyloid fibrils form from spontaneously misfolded amylin, depositing in islet cells to elicit apoptosis, beta cell degeneration and decrease insulin secretion, with amyloidosis affecting up to 80% of pancreatic islet cells in T2D. Therefore, intervening with polyphenolic compounds offers a novel approach to suppressing risk or progression to T2D. This review gives an update on the emerging mechanisms related to dietary polyphenol intake for the maintenance of glycaemic control and the prevention of T2D.

Brazilin inhibits fibrillogenesis of human islet amyloid polypeptide, disassembles mature fibrils, and alleviates cytotoxicity

Inhibitory effect of brazilin on the fibrillogenesis of hIAPP was explored using biochemical, biophysical, cytobiological and molecular simulation experiments. Brazilin was a potential compound for therapeutic treatment of type II diabetes mellitus.