Mari Eleonora, Vilasi Silvia, Moretti Paolo, Mangione Maria Rosalia, Giorgini Giorgia, Galeazzi Roberta, Ortore Maria Grazia
Department of Life and Environmental Sciences, Marche Polytechnic University, I-60131 Ancona, Italy.
Institute of Biophysics, CNR, I-90146 Palermo, Italy.
Biomolecules. 2024 Dec 31;15(1):40. doi: 10.3390/biom15010040.
The misfolding and amyloid aggregation of proteins have been attracting scientific interest for a few decades, due to their link with several diseases, particularly neurodegenerative diseases. Proteins can assemble and result in insoluble aggregates that, together with intermediate oligomeric species, modify the extracellular environment. Many efforts have been and are devoted to the search for cosolvents and cosolutes able to interfere with amyloid aggregation. In this work, we intensively study the effect of saponins, bioactive compounds, on human insulin aggregation. To monitor the kinetic of amyloid aggregation following secondary structure changes, we perform fluorescence and UV-Visible absorption spectroscopies, using Thioflavin T and Congo Red as amyloid specific probes, and Circular Dichroism. To study the overall structural features and size of aggregates, we perform Synchrotron Small-Angle X-ray Scattering and Dynamic Light Scattering experiments. The morphology of the aggregates was assessed by Atomic Force Microscopy. To deepen the understanding of the saponins interaction with insulin, a Molecular Dynamics investigation is performed, too. The reported data demonstrate that saponins interfere with the amyloid aggregation by inducing a strong inhibition on the formation of insulin fibrils, likely through specific interactions with insulin monomers. A dose-dependent effect is evident, and amyloid inhibition is already clear when saponins are just 0.01% / in solution. We suggest that saponins, which are natural metabolites present in a wide range of foods ranging from grains, pulses, and green leaves to sea stars and cucumbers, can be promising metabolites to inhibit human insulin aggregation. This basic research work can pave the way to further investigations concerning insulin amyloidosis, suggesting the use of saponins as amyloid inhibitors and/or stabilizing agents in solution.
几十年来，蛋白质的错误折叠和淀粉样聚集一直吸引着科学界的关注，因为它们与多种疾病相关，尤其是神经退行性疾病。蛋白质可以组装并形成不溶性聚集体，这些聚集体与中间寡聚体一起改变细胞外环境。人们已经并正在付出许多努力来寻找能够干扰淀粉样聚集的共溶剂和共溶质。在这项工作中，我们深入研究了生物活性化合物皂苷对人胰岛素聚集的影响。为了监测淀粉样聚集动力学随二级结构变化的情况，我们使用硫黄素T和刚果红作为淀粉样特异性探针，通过荧光和紫外可见吸收光谱以及圆二色性进行研究。为了研究聚集体的整体结构特征和大小，我们进行了同步加速器小角X射线散射和动态光散射实验。通过原子力显微镜评估聚集体的形态。为了更深入地了解皂苷与胰岛素的相互作用，还进行了分子动力学研究。报告的数据表明，皂苷可能通过与胰岛素单体的特异性相互作用，对胰岛素纤维的形成产生强烈抑制，从而干扰淀粉样聚集。剂量依赖性效应明显，当皂苷在溶液中的浓度仅为0.01%时，淀粉样抑制作用就已经很明显。我们认为，皂苷作为一种天然代谢产物，存在于从谷物、豆类、绿叶到海星和黄瓜等多种食物中，有望成为抑制人胰岛素聚集的代谢产物。这项基础研究工作可为进一步研究胰岛素淀粉样变性铺平道路，提示可将皂苷用作溶液中的淀粉样抑制剂和/或稳定剂。
