铁皮石斛“厚肠胃”改善高糖高脂饮食诱导胰岛素抵抗大鼠IETM的作用及机制研究

Recent studies have suggested that systemic, low level elevations of gut derived endotoxin (lipopolysaccharide, LPS) may play an important role in metabolic perturbations. As a triggering factor, LPS initiates a well-characterized signaling cascade that elicits many pro- and anti-inflammatory pathways when bound to its receptor, Toll-Like Receptor 4 (TLR4). Intestinal endotoxemia (IETM) and this stateis associated with a heightened pro-inflammatory and insulin resistance(IR). Dendrobium officinale as a traditional herb medicine mainly used for diabetes showed obvious protective effect in various metabolic diseases. Our previous studies have shown that it has obvious effect on the hyperglycemia ,hyperlipidemia, and can alleviate inflammation and insulin resistance in the rats with metabolic syndrome induced by a high sucrose and high fat diet(HSHF).Meanwhile it has obvious enterogastric function, such as modulating of enteric dysbacteriosis, improving gut barrier, promoting digestion, regulating intestinal immune, etc. We speculate that Dendrobium officinale improve HSHF diet induced metabolic disturbances and insulin resistance mainly depend on the regulation of intestinal homeostasis, improving or blocking the IETM mediated inflammatory reaction. In this regard, we first investigated whether Dendrobium officinale suppresses IETM, inflammation in HSHF diet induced metabolic syndrome model rats and analyze its correlation with markers of IR by dynamic observation of intestinal permeability, serum LPS concentration, pro- inflammatory factor and HOMA-IR. Furthermore, underlying mechanisms by which Dendrobium officinale may recover them will be further confirmed by Caco-2 cell models in vitro. This study aim to indicate that Dendrobium officinale prevents a high sucrose and high fat diet-induced insulin resistance and inflammation in rats through inhibition of IETM and its underlying mechanism. Our research will promote its application in the prevention and treatment of metabolic diseases especially induced by improper diet composition and it’s a new enrichment of enterogastric function.

新近研究表明，饮食不节导致的肠源性内毒素血症（IETM），可上调TLR4介导的炎症通路，引发慢性低度炎症和胰岛素抵抗(IR)，促发多种代谢疾病。铁皮石斛是传统治疗“消渴症”要药，对糖尿病等多种代谢相关疾病均有良好的防治作用，机制与改善IR有关。前期研究证明，铁皮石斛能明显改善长期饮食不节模型大鼠呈现的糖脂紊乱、低度炎症，降低HOMA-IR。结合其“厚肠胃”功效及调节菌群、保护黏膜等作用，我们认为铁皮石斛改善饮食不节所致IR可能与调节肠道稳态，改善或阻断IETM介导的炎症反应有关。拟采用高糖高脂致胰岛素抵抗大鼠模型和Caco-2细胞模型，运用现代药理学方法及分子生物学技术，考察铁皮石斛对IETM、LPS/TLR4信号途径的影响，分析与IR相关性；并从IETM形成的三个关键环节阐明其作用机制。本研究可为铁皮石斛改善慢性代谢性疾病的机制研究提供新的切入点，并丰富石斛“厚肠胃”的现代科学内涵。

铁皮石斛是传统中医治“消渴症”要药，对糖尿病等多种代谢相关疾病具有防治作用，机制与改善胰岛素抵抗有关。其“益胃”功效确切，是中医常用的“肠胃药”，铁皮石斛改善饮食不节所致胰岛素抵抗可能与其改善肠源性内毒素血症（IETM），阻断不合理膳食引发的过多内毒素（LPS）入血、并抑制TLR4 通路激活有关。为此，课题组模拟人类饮食不节，采用高糖高脂喂养6w建立胰岛素抵抗大鼠模型，灌胃给予铁皮石斛4 W，期间观察铁皮石斛对模型糖、脂及胰岛素水平的影响，明确了铁皮石斛能改善长期高糖高脂喂养所致胰岛素抵抗及伴随的代谢紊乱；并从内毒素（LPS）的产生、移位、消除3个肠源性内毒素血症（IETM）形成的关键环节及LPS 介导下游炎症信号通路入手，探讨了铁皮石斛改善IETM 的作用和机制。结果显示，铁皮石斛能减少肠源性LPS入血，抑制肠及肝脏组织LPS/TLR4信号通路的激活，降低炎症因子水平和炎性细胞浸润，改善IETM。机制可能与其①调节肠道菌群紊乱，降低F/B比值，减少LPS的生成有关；②调整肠道菌群代谢产物短链脂肪酸SCFAs组成及含量，增加紧密连接蛋白ZO-1、occludin及claudin-1的表达，提高肠屏障功能，降低肠道渗透性，减少LPS位移有关；实验进一步采用LPS致小鼠肠屏障损伤模型明确了铁皮石斛对LPS所致肠粘膜屏障损伤的改善作用。经双变量相关性分析和逐步回归分析进一步确证，铁皮石斛降低LPS，改善IETM与其改善胰岛素抵抗密切相关。本课题为铁皮石斛防治代谢性疾病的机制研究提供新的切入点，丰富和发展石斛“厚肠胃”的中医药理论和科学内涵。本课题完成了全部研究内容并达到预期目标，发表论文8篇，申报专利3项，培养毕业硕士2名，在培硕士1名。