甘蔗叶多糖成分调节I型糖尿病大鼠血糖及作用机制研究

Sugarcane leaves are worldwide staple crop waste, but there were few reports of its medicinal research. Our preliminary study found that polysaccharides from sugarcane leaves have anti-inflammatory, anti-oxidation, anti-tumor effects, as well as reduce blood glucose in rats with type I diabetic. In this project, rats with streptozotocin-induced type I diabetes were used as model, hypoglycemic activities of all the varieties of the polysaccharides from sugarcane leaves were screened, the components with hypoglycemic effective were clarified, and the purity, composition and chemical structure were analyzed. According to the phenomenon of immune disorders, oxidative stress, and apoptosis of pancreatic β cells in this disease, biochemical, pathological analysis, immunological methods and other means of molecular biology experiments were used. The blood sugar, insulin and glucagon alteration caused by sugarcane leaves polysaccharides were observed. The pancreatic inflammatory cell infiltration, pathological indicators, and apoptosis of pancreatic β cells observed, too. NF-kB and Bcl-2 expression, cell differentiation and the mRNA levels of Th1/Th2/Th17 and were detected. Combined with the detection of expression of NOS, COX-2 and NO, the molecular mechanisms of polysaccharide from sugarcane leaves on regulating blood glucose in type I diabetic rats were clarified. It offered evidence to find natural medicine to treat diabetes, and it was of great significance for the utilization of crop waste.

甘蔗叶是世界性大宗农作物废弃物，但对其药用研究鲜有报道。本课题组前期研究发现甘蔗叶粗多糖具有抗炎、抗氧化、抗肿瘤等作用，可降低I型糖尿病小鼠血糖。本项目建立链脲霉素诱导的Ⅰ型糖尿病大鼠模型，对甘蔗叶不同多糖组分进行降糖活性筛选，明确降糖有效多糖成分并对其纯度、组成和化学结构进行分析。针对免疫失调、氧化应激及胰岛β细胞凋亡等环节，用生化检测、病理分析、免疫学方法、分子生物学实验等多种手段，观察甘蔗叶有效多糖成分引起Ⅰ型糖尿病大鼠血糖、胰岛素、胰高血糖素水平的改变，胰岛炎症细胞浸润、病理学指标以及胰岛β细胞凋亡情况，NF-kB和Bcl-2的蛋白表达水平，Th1/Th2/Th17细胞分化及细胞因子mRNA水平的变化，并结合检测NOS、COX-2、NO的表达，通过整体、细胞和分子水平的药理研究，初步阐明甘蔗叶多糖降低I型糖尿病大鼠血糖的作用及其分子机制。为寻找治疗糖尿病的天然药物提供科学研究依据。

甘蔗叶是世界性大宗农作物废弃物，在广西具有传统应用基础，但对其药用研究鲜有报道。本研究小组前期研究证实甘蔗叶粗多糖具有降糖作用。本项目采用水提醇沉法提取甘蔗叶粗多糖，采用 DEAE 纤维素柱层析、Sephadex 柱层析、QFF 离子交换层析、Sepharcryl S-300 凝胶层析进行分离纯化；采用高效凝胶渗透色谱（HPGPC）法进行分子量测定；采用柱前衍生高效液相色谱法进行单糖组成分析；采用红外光谱（IR）、一维核磁共振波谱（1D-NMR）、二维核磁共振波谱（2D-NMR）、甲基化和气质联用（GC-MS）分析等方法进行结构分析。从甘蔗叶中获得 8 种杂多糖组分，对其中两种纯度较高的多糖组分 SLP0A 和 SLP3A进行了进一步研究，获得了它们的纯度、相对分子量、含量、组成、结构数据。继而采用 STZ 诱导的 SD 大鼠糖尿病模型，对甘蔗叶多糖进行降血糖作用和机制进行研究。采用非肥胖性糖尿病(NOD) 小鼠模型考察甘蔗叶多糖对糖尿病的预防作用及其作用机制。研究证实甘蔗叶多糖对链脲佐菌素所致的 1 型糖尿病大鼠具有降血糖作用，作用机制可能与抑制体内炎症反应、增强机体抗氧化能力有关。甘蔗叶多糖能预防和延缓 NOD 小鼠糖尿病的发生。.本项目还在实施过程中，进一步关注了甘蔗叶多糖对糖尿病心血管并发症的影响。研究表明甘蔗叶多糖能改善心电图，促进血管内皮生长因子（VEGF）表达，能有效的减少心肌细胞凋亡，增加心肌细胞的存活力，其机制可能与增加抑凋亡基因 BCL-2的表达，减少 BAX、Caspase3促凋亡基因的表达，上调 p-AKT/AKT、p-PI3K/PI3K 蛋白的表达有关。