Human Islet Amyloid Polypeptide (hIAPP) Protofibril-Specific Antibodies for Detection and Treatment of Type 2 Diabetes

Explaining Type 2 Diabetes with Transcriptomic Signatures of Pancreatic β-Cell Dysfunction and Death Induced by Human Islet Amyloid Polypeptide

Amyloid deposits formed by misfolding and aggregation of human islet amyloid polypeptide (hIAPP) are one of the key pathophysiological features of type 2 diabetes mellitus (T2DM) and have been associated with the loss of function and viability of the pancreatic β-cells. The molecular processes by which hIAPP induces cytotoxicity in these cells are not well understood. To the best of our knowledge, this is the first report describing findings from the combined analysis of Affymetrix microarray and high-throughput sequencing (HTS) Gene Expression Omnibus (GEO) datasets of hIAPP-transgenic (Tg) mice islets. In brief, using GEO data, we compared in silico the pancreatic islets obtained from hIAPP-Tg and wild-type mice. Affymetrix microarray datasets (GSE84423, GSE85380, and GSE94672) and HTS datasets (GSE135276 and GSE148809) were chosen. Weighted gene coexpression network analysis was performed using GSE135276 to identify the coexpressed gene networks and establish a correlation pattern between gene modules and hIAPP overexpression under hyperglycemic conditions. Subsequently, we analyzed differential gene expression with the remaining datasets. Network analysis was performed to identify hub genes and the associated pathways using Cytoscape. Key findings from the present study include identification of seven hub genes, namely, Ins2, Agt, Jun, Fos, CD44, Igf1, and Ppar-γ, significantly involved in the process(es) of insulin synthesis and secretion, development of insulin resistance, oxidative stress, inflammation, mitophagy, and apoptosis. In conclusion, we propose that these hub genes can help explain T2DM pathogenesis and can be potentially utilized to develop therapeutic interventions targeting hIAPP for clinical management of T2DM.

Research progress on the correlation between islet amyloid peptides and type 2 diabetes mellitus

Background

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder characterized by insulin resistance and β-cell dysfunction. A hallmark of T2DM pathology is the accumulation of toxic amyloid polypeptides in and around pancreatic islet cells, leading to the progressive loss of β-cell populations. Human islet amyloid polypeptide (hIAPP), also known as amylin, is a 37-amino acid peptide hormone primarily produced by pancreatic β-cells. hIAPP aggregation and amyloid formation are strongly correlated with β-cell death and disease severity in T2DM patients.

Objectives

This article aims to review the current research progress on the correlation between hIAPP and T2DM, focusing on the molecular mechanisms and potential therapeutic strategies.

Methods

We conducted a comprehensive literature review covering recent studies on the molecular structure, physiological function, and pathological mechanisms of hIAPP. Key areas include biosynthesis, monomer structure, and the formation of hIAPP fiber structures. Additionally, we examined the mechanisms of hIAPP-induced β-cell death, including oxidative stress (OS), endoplasmic reticulum stress (ERS), impaired cell membrane and mitochondrial functions, and inflammatory factors.

Results

Our review highlights the critical role of hIAPP in the pathogenesis of T2DM. Specifically, we found that hIAPP biosynthesis and monomer structure contribute to its physiological functions, while hIAPP aggregation forms toxic amyloid fibers, contributing to β-cell dysfunction. OS, ERS, impaired cell membrane and mitochondrial functions, and inflammatory factors play significant roles in hIAPP-induced β-cell death. There is a strong correlation between hIAPP aggregation and the severity of T2DM, and potential therapeutic approaches using small molecule inhibitors to prevent hIAPP aggregation and fibrosis are discussed.

Conclusion

Understanding the molecular mechanisms of hIAPP in T2DM provides insights into potential therapeutic targets and preventive strategies. Future research should focus on developing more effective treatments targeting hIAPP aggregation and its downstream effects.

Flavones in pomelo peel resist fibril formation of human islet amyloid polypeptide

Objective

Exploring the formation and aggregation of human islet amyloid polypeptide (hIAPP) (amylin) fibers is significant for promoting the prevention and treatment of type II diabetes mellitus (T2DM). Flavones in pomelo peel have visible biological activity in the anti-diabetes aspect. The present study aimed to investigate the effects of five flavones [naringin (NRG), narirutin (NRR), nobiletin (NOB), sinensetin (SIN), and neohesperidin (NHP)] in pomelo peel on peptide aggregation and explore its possible mechanisms. The cell viability of flavones against peptide aggregation was also evaluated.

Methods

The thioflavin T (ThT) assay and transmission electron microscopy (TEM) were used for evaluating the inhibition and disaggregation of flavones on peptide aggregation. The interaction mechanism was analyzed by endogenous fluorescence, molecular dynamics (MD) simulations, ultraviolet spectroscopy (UV) and isothermal titration calorimetry (ITC) experiments. The 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) and immune assays were performed to characterize the cell viability of flavones against peptide aggregation.

Results

The five flavones showed a decrease in fluorescence intensity, fiber number and size under incubation with different molar ratios of hIAPP. The compounds can bind to the aromatic tyrosine (Tyr) residueTyr 37, resulting in the intrinsic fluorescence quenching of the peptides. Five flavones can form hydrogen bonds with hIAPP, which is likely to be based on their phenolic hydroxyl structure. They showed strong binding affinity with peptides. The reaction system of NRG and NRR observed an exothermic reaction, and the others were endothermic reactions. The absorption peaks of the compounds with hIAPP changed and showed hypochromic effects, indicating that there may be π-π stacking interaction. Flavones noticeably increased the cell viability in the presence of amyloid peptides and reduced the absorption intensity induced by peptide oligomers.

Conclusion

A total of five flavones in pomelo peel have inhibitory and depolymerization effects on amyloid fibrils, and can significantly protect cells from the toxic effect of hIAPP and reduce the production of toxic oligomers.

Anti-Amyloid Aggregation and Anti-Hyperglycemic Activities of Novel Ruthenium Uracil Schiff Base Compounds

The formation and characterization of new diamagnetic ruthenium uracil mono-imine compounds: [(η6-p-cymene)RuII(L)Cl][BF4] (L=H2urpda=5-((pyridin-2-yl)methyleneamino)-6-aminouracil) for 1, urdpy=6-amino-1,3-dimethyl-5-((pyridin-2-ylmethylene)amino)uracil) for 2 or urqda=5-((quinolin-2-yl)methyleneamino)-6-aminouracil) for 3); cis-[Ru(bipy)2(urpy)](BF4)2 (4) (urpy=5-((pyridin-2-yl)methyleneamino)uracil) and cis-[Ru(bipy)2(dapd)] (5) (H2dadp=5,6-diaminouracil) are described. A ruthenium(IV) uracil Schiff base compound, trans-[Ru(urpda)(PPh3)Cl2] (6) was also formed. Various physicochemical techniques were utilized to characterize the novel ruthenium compounds. Similarly, the stabilities of 1-3 and 6 monitored in chloro-containing and the non-coordinating solvent, dichloromethane show that they are kinetically inert, whereas, in a high nucleophilic environment, the chloride co-ligands of these ruthenium complexes were rapidly substituted by DMSO. In contrast, the substitution of the labile co-ligands for these ruthenium complexes by DMSO molecules in a high chloride content was suppressed. Solution chemical reactivities of the different ruthenium complexes were rationalized by density functional theory computations. Furthermore, the binding affinities and strengths between BSA and the respective ruthenium complexes were monitored using fluorescence spectroscopy. In addition, the in vitro anti-diabetic activities of the novel metal complexes were assessed in selected skeletal muscle and liver cell lines.

Age at type 2 diabetes diagnosis and the risk of mortality among US population

To examine the relationship between age at diagnosis of type 2 diabetes (T2DM) with cardiovascular and all-cause mortality in the U.S. population. Data was used from NHANES 1999 ~ 2018, which were screened to include a total of 8,654 participants with a diagnosis of diabetes for the study. We estimated the association between age at diagnosis and cardiovascular and all-cause mortality using weighted multivariate Cox regression analyses. Subgroup analyses and sensitivity analyses were performed to ensure the robustness of the data analysis. The number of participants diagnosed with diabetes at ages < 40, between 40 and 59, and > 60 are 1,492, 3,970, and 3,192, respectively, with median ages of 44.04, 57.59, and 72.24. Among patients diagnosed with T2DM, the relative risk of all-cause mortality increased with younger age at diagnosis: compared to patients with late-onset diabetes (age at type 2 diabetes diagnosis ≥ 60), the hazard ratio for all-cause mortality was 2.72 (95% CI 1.83-4.05) in those with early-onset diabetes (age at type 2 diabetes diagnosis < 40). Similarly, the risk of cardiovascular disease death was observed to be a higher relative risk with younger age at diagnosis. Exposure-effect analysis indicated that younger age at diagnosis is associated with higher risk of all-cause mortality. Subgroup analysis found that the association between age at diagnosis and cardiovascular and all-cause mortality was stronger in the current smokers and hypertensive population. The results of this study suggest that younger age at diagnosis of T2DM is associated with higher risk of death in patients. Younger patients diagnosed with T2DM had a higher risk of cardiovascular and all-cause mortality. These findings strengthen the understanding of the risk of death from T2DM and emphasize the importance of early prevention of diabetes.

Polyphenol-based polymer nanoparticles for inhibiting amyloid protein aggregation: recent advances and perspectives

Polyphenols are a group of naturally occurring compounds that possess a range of biological properties capable of potentially mitigating or preventing the progression of age-related cognitive decline and Alzheimer's disease (AD). AD is a chronic neurodegenerative disease known as one of the fast-growing diseases, especially in the elderly population. Moreover, as the primary etiology of dementia, it poses challenges for both familial and societal structures, while also imposing a significant economic strain. There is currently no pharmacological intervention that has demonstrated efficacy in treating AD. While polyphenols have exhibited potential in inhibiting the pathological hallmarks of AD, their limited bioavailability poses a significant challenge in their therapeutic application. Furthermore, in order to address the therapeutic constraints, several polymer nanoparticles are being explored as improved therapeutic delivery systems to optimize the pharmacokinetic characteristics of polyphenols. Polymer nanoparticles have demonstrated advantageous characteristics in facilitating the delivery of polyphenols across the blood-brain barrier, resulting in their efficient distribution within the brain. This review focuses on amyloid-related diseases and the role of polyphenols in them, in addition to discussing the anti-amyloid effects and applications of polyphenol-based polymer nanoparticles.

A human antibody against pathologic IAPP aggregates protects beta cells in type 2 diabetes models

In patients with type 2 diabetes, pancreatic beta cells progressively degenerate and gradually lose their ability to produce insulin and regulate blood glucose. Beta cell dysfunction and loss is associated with an accumulation of aggregated forms of islet amyloid polypeptide (IAPP) consisting of soluble prefibrillar IAPP oligomers as well as insoluble IAPP fibrils in pancreatic islets. Here, we describe a human monoclonal antibody selectively targeting IAPP oligomers and neutralizing IAPP aggregate toxicity by preventing membrane disruption and apoptosis in vitro. Antibody treatment in male rats and mice transgenic for human IAPP, and human islet-engrafted mouse models of type 2 diabetes triggers clearance of IAPP oligomers resulting in beta cell protection and improved glucose control. These results provide new evidence for the pathological role of IAPP oligomers and suggest that antibody-mediated removal of IAPP oligomers could be a pharmaceutical strategy to support beta cell function in type 2 diabetes.

A pancreatic player in dementia: pathological role for islet amyloid polypeptide accumulation in the brain

Type 2 diabetes mellitus patients have a markedly higher risk of developing dementia. While multiple factors contribute to this predisposition, one of these involves the increased secretion of amylin, or islet amyloid polypeptide, that accompanies the pathophysiology of type 2 diabetes mellitus. Islet amyloid polypeptide accumulation has undoubtedly been implicated in various forms of dementia, including Alzheimer's disease and vascular dementia, but the exact mechanisms underlying islet amyloid polypeptide's causative role in dementia are unclear. In this review, we have summarized the literature supporting the various mechanisms by which islet amyloid polypeptide accumulation may cause neuronal damage, ultimately leading to the clinical symptoms of dementia. We discuss the evidence for islet amyloid polypeptide deposition in the brain, islet amyloid polypeptide interaction with other amyloids implicated in neurodegeneration, neuroinflammation caused by islet amyloid polypeptide deposition, vascular damage induced by islet amyloid polypeptide accumulation, and islet amyloid polypeptide-induced cytotoxicity. There are very few therapies approved for the treatment of dementia, and of these, clinical responses have been controversial at best. Therefore, investigating new, targetable pathways is vital for identifying novel therapeutic strategies for treating dementia. As such, we conclude this review by discussing islet amyloid polypeptide accumulation as a potential therapeutic target not only in treating type 2 diabetes mellitus but as a future target in treating or even preventing dementia associated with type 2 diabetes mellitus.

The potential role of human islet amyloid polypeptide in type 2 diabetes mellitus and Alzheimer's diseases

Human Islet amyloid polypeptide (hIAPP) from pancreatic β cells in the islet of Langerhans has different physiological functions including inhibiting the release of insulin and glucagon. Type 2 diabetes mellitus (T2DM) is an endocrine disorder due to relative insulin insufficiency and insulin resistance (IR) is associated with increased circulating hIAPP. Remarkably, hIAPP has structural similarity with amyloid beta (Aβ) and can engage in the pathogenesis of T2DM and Alzheimer's disease (AD). Therefore, the present review aimed to elucidate how hIAPP acts as a link between T2DM and AD. IR, aging and low β cell mass increase expression of hIAPP which binds cell membrane leading to the aberrant release of Ca2+ and activation of the proteolytic enzymes leading to a series of events causing loss of β cells. Peripheral hIAPP plays a major role in the pathogenesis of AD, and high circulating hIAPP level increase AD risk in T2DM patients. However, there is no hard evidence for the role of brain-derived hIAPP in the pathogenesis of AD. Nevertheless, oxidative stress, mitochondrial dysfunction, chaperon-mediated autophagy, heparan sulfate proteoglycan (HSPG), immune response, and zinc homeostasis in T2DM could be the possible mechanisms for the induction of the aggregation of hIAPP which increase AD risk. In conclusion, increasing hIAPP circulating levels in T2DM patients predispose them to the development and progression of AD. Dipeptidyl peptidase 4 (DPP4) inhibitors and glucagon-like peptide-1 (GLP-1) agonists attenuate AD in T2DM by inhibiting expression and deposition of hIAP.

Molecular Dynamics-Assisted Interaction of Vanadium Complex-AMPK: From Force Field Development to Biological Application for Alzheimer's Treatment

A large part of the world's population is affected by Alzheimer's disease (AD) and diabetes mellitus type 2, which cause both social and economic impacts. These two conditions are associated with one protein, AMPK. Studies have shown that vanadium complexes, such as bis(N',N'-dimethylbiguanidato)-oxovanadium(IV), VO(metf)₂·H₂O, are potential agents against AD. A crucial step in drug design studies is obtaining information about the structure and interaction of these complexes with the biological targets involved in the process through molecular dynamics (MD) simulations. However, MD simulations depend on the choice of a good force field that could present reliable results. Moreover, general force fields are not efficient for describing the properties of metal complexes, and a VO(metf)₂·H₂O-specific force field does not yet exist; thus, the proper development of a parameter set is necessary. Furthermore, this investigation is essential and relevant given the importance for both the scientific community and the population that is affected by this neurodegenerative disease. Therefore, the present work aims to develop and validate the AMBER force field parameters for VO(metf)₂·H₂O since the literature lacks such information on metal complexes and investigate through classical molecular dynamics the interactions made by the complex with the protein. The proposed force field proved to be effective for describing the vanadium complex (VC), supported by different analyses and validations. Moreover, it had a great performance when compared to the general AMBER force field. Beyond that, MD findings provided an in-depth perspective of vanadium complex-protein interactions that should be taken into consideration in future studies.