具有通过调节肠道菌群改善胰岛素抵抗作用的海参岩藻聚糖硫酸酯作用机理及构效关系研究

Fucoidan from sea cucumber (SC-FUC) was prepared, and its effects on improvement in insulin resistance were investigated using a high calorie diet-induced insulin resistant mouse model. To clarify the molecular mechanisms of SC-FUC-improved insulin resistance through inhibition of chronic inflammation, inflammatory pathways (c-Jun NH2-terminal kinase (JNK) and inhibitor kappa kinase beta (IKKβ) / nuclear factor kappa B (NFκB)) and activation of insulin receptor substrates (IRSs) were analyzed. The mechanism of SC-FUC on improvement in chronic inflammation and insulin resistance was confirmed by detecting gut microbiota and the secondary metabolites in mice. Toll-like receptor 4 (TLR4) / cluster of differentiation 14 (CD14) and adenosine monophosphate activated protein kinase (AMPK) pathways were involved in this study on the mechanism. Furthermore, these effects were further verified using cecal microbiota transplanting experiment. The structure-function relationship of SC-FUC on improvement in insulin resistance was expounded from three aspects including molecular weight, sulfate content, and sulfate ester position. The researches will state firstly that the macromolecular sea cucumber polysaccharide exhibits bioactivities through regulation of gut microbiota in vivo and clarify the structure-function relationship of SC-FUC on improvement in insulin resistance. The results will provide a solid theoretical basis for the exploitation of high-value application of sea cucumber and new marine drugs or functional foods in anti-inflammation / insulin resistance.

制备海参岩藻聚糖硫酸酯（SC-FUC），采用高能饮食饲喂法建立胰岛素抵抗小鼠模型，研究SC-FUC改善胰岛素抵抗的作用。通过研究JNK与IKKβ/NFκB炎症通路、IRSs活化，阐明SC-FUC通过抑制慢性炎症改善胰岛素抵抗的分子机制。通过检测小鼠肠道菌群及其次级代谢产物，以TLR4/CD14和AMPK通路为切入点，确证SC-FUC通过调节肠道菌群改善慢性炎症和胰岛素抵抗的作用机理。在此基础上，通过肠道微生物移植实验，进一步验证SC-FUC通过调节肠道菌群最终改善胰岛素抵抗的作用。以分子量、硫酸根含量和硫酸基团取代位置为切入点，阐述SC-FUC改善胰岛素抵抗的构效关系。通过本项目研究，将初步揭示大分子海参多糖体内通过调节肠道菌群发挥作用的机理，同时阐明SC-FUC改善胰岛素抵抗的构效关系，为海参资源的高值化利用和海洋新型抗炎症/胰岛素抵抗药品或功能食品的开发提供理论依据。

胰岛素抵抗是众多疾病共同的病理生理基础，已严重影响人类的健康，寻找安全有效的缓解胰岛素抵抗的药物和功能食品已成为提高人类身体质量素质的重要研究课题。已证实海参岩藻聚糖硫酸酯（fucoidans form sea cucumber, SC-FUC）具有改善胰岛素抵抗的生物活性，但其作为大分子物质如何在体内发挥作用及构效关系尚不明确。因此，本项目用高脂饮食诱导的胰岛素抵抗小鼠为模型，从SC-FUC对模型小鼠肠道菌群的影响角度，阐述其改善胰岛素抵抗的作用机理；同时以SC-FUC的分子量，硫酸根含量、硫酸基团取代位置为切入点，阐明SC-FUC改善胰岛素抵抗的构效关系。结果显示，SC-FUC能显著地调节模型小鼠的肠道菌群的分布，提高有益菌丰度（如短链脂肪酸产生菌），降低有害菌丰度（如脂多糖产生菌），激活短链脂肪酸代谢相关的AMPK信号通路，抑制脂多糖相关的TLR4/CD14信号通路，改善小鼠胰岛素抵抗。构效关系的研究发现，SC-FUC分子量越小，其生物活性越强；间位硫酸基团取代生物活性强于邻位酸基团取代；4-O-硫酸基团取代生物活性强于2-O-硫酸基团取代。本项目研究结果初步解释了作为大分子物质的SC-FUC在体内通过调节肠道菌群及其次级代谢产物发挥胰岛素抵抗的作用机理，阐明了SC-FUC生物活性与分子量，硫酸基团取代所在的岩藻糖位置及取代C点位有关。本项目研究结果丰富了海洋药物资源研究领域的理论基础，对开发新型抗胰岛素抵抗药品或功能食品具有重要的意义。