Inhibitory mechanism of lithospermic acid on the fibrillation of type 2 diabetes associated islet amyloid polypeptide

The abnormal fibrillation of a 37-residue peptide hormone human islet amyloid polypeptide (hIAPP) is linked with type 2 diabetes (T2D). Pang et al. depicted a prominent role of lithospermic acid (LA) in blocking hIAPP fibrillation and alleviating the hIAPP aggregates-induced cytotoxicity. LA is a polyphenolic compound present in extra virgin olive oil with therapeutic properties. Despite its notable inhibitory effect on hIAPP fibrillation, the inhibition mechanism remains unclear. Here, molecular dynamics (MD) simulations have been utilized to shed light on the putative binding mechanism and inhibitory mechanism of LA against hIAPP fibrillation. The molecular docking predicted favourable binding (-7.1 kcal/mol) of LA with hIAPP. Interestingly, LA increases the helix content in hIAPP and blocks the conformational transition to the aggregation-competent conformations. The conformational clustering and hydrogen bond analyses depicted that LA formed hydrogen bonds with Asn21 of hIAPP, which play an important role in hIAPP aggregation. LA binds favourably to hIAPP (ΔGbinding = -49.62 ± 3.34 kcal/mol) with a major contribution from the van der Waals interactions. The MD simulations highlighted that LA dramatically interfered with the intrapeptide interactions and inhibited sampling of aggregation-competent β-sheet conformations in hIAPP via hydrogen bonds through its hydroxyl groups, van der Waals interactions with hIAPP residues, thus blocking hIAPP aggregation to β-sheet rich cytotoxic fibrillar aggregates. The MD simulations illuminated specific interactions between hIAPP and LA, which will benefit in developing new chemical entities against hIAPP fibrillation.

Research Progress on Hypoglycemic Effects and Molecular Mechanisms of Flavonoids: A Review

As a prevalent metabolic disorder, the increasing incidence of diabetes imposes a significant burden on global healthcare. Flavonoids in natural phytochemical products exhibit notable hypoglycemic properties, making them potential alternatives for diabetes treatment. This article summarizes the hypoglycemic properties of flavonoid subcategories studied in recent years, including flavones, isoflavones, flavonols, flavanols, and others. The relevant targets and signal pathways, such as α-amylase, α-glucosidase, insulin receptor substrate (IRS)/phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT), PKR-like endoplasmic reticulum kinase (PERK)/eukaryotic initiation factor 2α (eIF2α)/activation transcription factor 4 (ATF4)/C/EBP homologous protein (CHOP), etc., are also elaborated. Additionally, flavonoids have also been demonstrated to modulate the gut microbiota and its metabolites. Through the aforementioned mechanisms, flavonoids mainly suppress carbohydrate metabolism and gluconeogenesis; facilitate glucose uptake, glycogenesis, and insulin secretion; and mitigate insulin resistance, oxidative stress, inflammation, etc. Notably, several studies have indicated that certain flavonoids displayed synergistic hypoglycemic effects. In conclusion, this article provides a comprehensive review of the hypoglycemic effects of the flavonoids investigated in recent years, aiming to offer theoretical insights for their further exploration.

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.

Antidiabetic and Antigout Properties of the Ultrasound-Assisted Extraction of Total Biflavonoids from Selaginella doederleinii Revealed by In Vitro and In Silico Studies

In this study, the extraction, purification and metabolic enzyme inhibition potential of Selaginella doederleinii were investigated. In order to extract the total biflavonoids from S. doederleinii (SDTBs), the optimum extraction process was obtained by optimizing the ultrasonic extraction parameters using response-surface methodology. This resulted in a total biflavonoid content of 22.26 ± 0.35 mg/g. Purification of the S. doederleinii extract was carried out using octadecylsilane (ODS), and the transfer rate of the SDTBs was 82.12 ± 3.48% under the optimum purification conditions. We determined the effect of the SDTBs on α-glucosidase (AG), α-amylase and xanthine oxidase (XOD) and found that the SDTBs had an extremely potent inhibitory effect on AG, with an IC50 value of 57.46 μg/mL, which was much lower than that of the positive control. Meanwhile, they also showed significant inhibition of XOD and α-amylase, with IC50 values of 289.67 μg/mL and 50.85 μg/mL, respectively. In addition, molecular docking studies were carried out to understand the nature of the action of the biflavonoids on AG and XOD. The results showed that robustaflavone had the lowest binding energy to AG (-11.33 kcal/mol) and XOD (-10.21 kcal/mol), while, on the other hand, amentoflavone showed a good binding affinity to AG (-10.40 kcal/mol) and XOD (-9.962 kcal/mol). Moreover, molecular dynamics simulations verified the above results.

β-Carboline Alkaloids Resist the Aggregation and Cytotoxicity of Human Islet Amyloid Polypeptide

β-Carboline alkaloids have a variety of pharmacological activities, such as antitumor, antibiosis and antidiabetes. Harmine and harmol are two structurally similar β-carbolines that occur in many medicinal plants. In this work, we chose harmine and harmol to impede the amyloid fibril formation of human islet amyloid polypeptide (hIAPP) associated with type 2 diabetes mellitus (T2DM), by a series of physicochemical and biochemical methods. The results indicate that harmine and harmol effectively prevent peptide fibril formation and alleviate toxic oligomer species. In addition, both small molecules exhibit strong binding affinities with hIAPP mainly through hydrophobic and hydrogen bonding interactions, thus reducing the cytotoxicity induced by hIAPP. Their distinct binding pattern with hIAPP is closely linked to the molecular configuration of the two small molecules, affecting their ability to impede peptide aggregation. The study is of great significance for the application and development of β-carboline alkaloids against T2DM.

Illustrating the Effect of Small Molecules Derived from Natural Resources on Amyloid Peptides

The onset of amyloidogenic diseases is associated with the misfolding and aggregation of proteins. Despite extensive research, no effective therapeutics are yet available to treat these chronic degenerative diseases. Targeting the aggregation of disease-specific proteins is regarded as a promising new approach to treat these diseases. In the past few years, rapid progress in this field has been made in vitro, in vivo, and in silico to generate potential drug candidates, ranging from small molecules to polymers to nanoparticles. Small molecular probes, mostly those derived from natural sources, have been of particular interest among amyloid inhibitors. Here, we summarize some of the most important natural small molecular probes which can inhibit the aggregation of Aβ, hIAPP, and α-syn peptides and discuss how their binding efficacy and preference for the peptides vary with their structure and conformation. This provides a comprehensive idea of the crucial factors which should be incorporated into the future design of novel drug candidates useful for the treatment of amyloid diseases.

Regulation of oxaliplatin and carboplatin on the assembly behavior and cytotoxicity of human islet amyloid polypeptide

Human islet amyloid polypeptide (hIAPP) is associated with the pathology of Type II diabetes (T2DM) due to its misfolding and amyloid deposition. The peptide is widely concerned as a potential drug target, and the prevention of hIAPP fibrillation is a rational therapeutic strategy for T2DM. Platinum complexes are promising anticancer agents with good biocompatibility, they can resist the aggregation of amyloid peptides, while the effects of oxaliplatin and carboplatin on hIAPP fibrillation are unknown. In the present work, we selected the two platinum drugs to reveal their inhibition and disaggregation against hIAPP fibrillation by various biophysical methods. The two complexes impeded hIAPP fibril formation and dispersed the aggregates into small oligomers and most monomers. They also reduced peptides oligomerization and promoted rat insulinoma β-cells viability. They bound to hIAPP mainly through metal coordination and hydrophobic interactions. Moreover, oxaliplatin showed better inhibition and regulation on peptides aggregation and cytotoxicity than carboplatin. This work is of important biomedical values for clinical platinum drugs against T2DM and other amyloidosis related diseases.