The deposition of insoluble amyloid fibrils resulting from the aggregation of the human islet amyloid polypeptide (hIAPP) within the islet of Langerhans is a pathological feature of type 2 diabetes mellitus (T2DM). Increasing evidence indicates that biological membranes play a key role in amyloid aggregation, modulating among others the kinetics of amyloid formation, and being the target of toxic species generated during amyloid formation. In T2DM patients, elevated levels of cholesterol, an important determinant of the physical state of biological membranes, are observed in β-cells and are thought to directly impair β-cell function and insulin secretion. However, it is not known whether cholesterol enhances membrane-interaction or membrane-insertion of hIAPP. In this study, we investigated the effect of cholesterol incorporated in zwitterionic and anionic membranes. Our circular dichroism and liquid state NMR data reveal that 10–30% of cholesterol slightly affects the aggregational and conformational behaviour of hIAPP. Additional fluorescence results indicate that 10 and 20% of cholesterol slightly slow down the kinetics of oligomer and fibril formation while anionic lipids accelerate this kinetics. This behavior might be caused by differences in membrane insertion and therefore in membrane binding of hIAPP. The membrane binding affinity was evaluated using ¹H NMR experiments and our results show that the affinity of hIAPP for membranes containing cholesterol is significantly smaller than that for membranes containing anionic lipids. Furthermore, we found that hIAPP-induced membrane damage is synchronized to fibril formation in the absence and in the presence of cholesterol.

人类胰岛淀粉样多肽（hIAPP）在朗格汉斯胰岛内聚集所导致的不溶性淀粉样原纤维沉积是2型糖尿病（T2DM）的病理特征。越来越多的证据表明，生物膜在淀粉样蛋白聚集，调节淀粉样蛋白形成动力学等过程中起着关键作用，并且是淀粉样蛋白形成过程中产生的有毒物质的目标。在T2DM患者中，在β细胞中观察到胆固醇水平升高（胆固醇是生物膜物理状态的重要决定因素），并被认为直接损害β细胞功能和胰岛素分泌。但是，尚不清楚胆固醇是否会增强hIAPP的膜相互作用或膜插入。在这项研究中，我们研究了两性离子和阴离子膜中胆固醇的作用。我们的圆二色性和液态NMR数据表明，胆固醇的10–30％会轻微影响hIAPP的聚集和构象行为。附加的荧光结果表明，胆固醇的10％和20％会稍微减慢低聚物和原纤维形成的动力学，而阴离子脂质会加速这一动力学。此行为可能是由于hIAPP的膜插入差异以及膜结合差异引起的。使用以下方法评估膜结合亲和力 附加的荧光结果表明，胆固醇的10％和20％会稍微减慢低聚物和原纤维形成的动力学，而阴离子脂质会加速这一动力学。此行为可能是由于hIAPP的膜插入差异以及膜结合差异引起的。使用以下方法评估膜结合亲和力 附加的荧光结果表明，胆固醇的10％和20％会稍微减慢低聚物和原纤维形成的动力学，而阴离子脂质会加速这一动力学。此行为可能是由于hIAPP的膜插入差异以及膜结合差异引起的。使用以下方法评估膜结合亲和力¹ H NMR实验和我们的结果表明，hIAPP对含有胆固醇的膜的亲和力明显小于对含有阴离子脂质的膜的亲和力。此外，我们发现在没有胆固醇存在的情况下，hIAPP诱导的膜损伤与原纤维形成同步。