- 學位論文
薑黃素及其類似物改善腸道屏障功能與腸道菌相組成以緩解葡聚醣硫酸鈉誘導慢性腸炎之功效
Effects of curcumin and its analogs on ameliorating dextran sodium sulfate-induced chronic colitis by improving intestinal barrier function and gut microbiota
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摘要
發炎性腸道疾病 (inflammatory bowel disease, IBD) 為一種慢性、復發性的腸胃道失衡情形，由於工業化發展與飲食及生活模式西化等環境因子，使其在全球的盛行率大幅提升。而腸道屏障功能受損發生早於疾病症狀的出現，腸道通透性的增加造成大量食物抗原、微生物及其毒性產物滲漏，可能進一步引起黏膜免疫系統失衡，最終導致慢性發炎及併發症的發生。雖目前已有多種藥物可改善疾病臨床表徵，但長期使用可能出現許多副作用，因此尋求具保護腸道屏障功能及改善菌群失調的植化素已成為當今預防 IBD 的重要目標。薑黃素 (curcumin, CUR) 為天然存在於薑黃中的多酚色素，已被證實具抗氧化、抗發炎及抗癌等多種藥理活性。然而較低的生體可利用率可能限制其化學預防功效，故其代謝物或結構類似物亦開始廣泛被研究，然而 CUR 及其衍生物的生理活性比較仍有待釐清。因此本實驗旨在探討 CUR 和其代謝物四氫薑黃素 (tetrahydrocurcumin, THC) 與氨化類似物，包含氨化薑黃素 (aminated-curcumin, AC) 及氨化四氫薑黃素 (aminated-tetrahydrocurcumin, ATHC) 之屏障保護及發炎減緩潛力，並進一步了解不同劑量 AC 產生抗發炎活性差異之原因。首先利用 LPS 誘導 RAW 264.7 細胞發炎的模式初步比較樣品抗發炎的能力，再透過 dextran sulfate sodium (DSS) 誘導 ICR 小鼠慢性腸炎模式以評估樣品對腸道屏障功能、發炎反應、腸道菌相組成的影響及相關調節機制。細胞實驗結果顯示，AC 可最顯著降低一氧化氮生成，展現調節免疫潛力。而在動物實驗結果發現，相同劑量條件下，THC 及 CUR 可能透過改善自噬受損來促進黏液分泌，並顯著恢復緊密結合蛋白表現及排列失調，從而維持較佳的屏障完整性，更可抑制 TLR4/p38 MAPK/AP-1 路徑來減緩發炎情形，而 AC 的給予在較低劑量條件下亦展現相似於 THC 及 CUR 的抗發炎效果。由腸道菌相結果分析可知所有樣品皆具有改變菌群組成的能力，可增加 Duncaniella、Muribaculum 及 Kineothrix 相對豐度。此外，相較於較高劑量的 AC 組別，低劑量的 AC 可顯著增加 Akkermansia muciniphila、Eubacterium ventriosum 及 Dorea longicatena 等有益菌，藉此增加短鏈脂肪酸 (short chain fatty acid, SCFA) 生成來發揮屏障保護及腸道發炎減緩之功效。綜合上述，THC、CUR 及低劑量 AC 皆具預防腸炎進程之潛力。
並列摘要
Inflammatory bowel disease (IBD), which is defined as a chronic relapsing gastrointestinal disorder, is on the rise globally due to industrialization and changes in environmental factors such as westernized lifestyle. The impairment of the intestinal barrier function precedes the onset of the symptoms of IBD. Increased intestinal permeability allows the leakage of food antigens, microorganisms, and their toxic products, potentially leading to mucosal immune system imbalance and eventually causing chronic inflammation and several complications. Although many synthetic drugs could improve the clinical signs of the disease, long-term use of these drugs may result in numerous side effects. Therefore, exploring phytochemicals that can protect the intestinal barrier function and avoid dysbiosis has become an important goal in preventing IBD today. Curcumin (CUR), a naturally occurring polyphenol pigment in Turmeric, has been shown to possess several pharmacological activities, including antioxidant, anti-inflammatory, and anti-cancer. However, the shortcomings of curcumin, such as poor bioavailability, may curtail its chemopreventive effects on diseases, and thus, its metabolites or structural analogs have also begun to be widely studied. Nevertheless, comparing the physiological activities of CUR and its derivatives remains unclear. Therefore, this study aims to investigate the barrier protection and anti-inflammatory potential of CUR and its metabolite tetrahydrocurcumin (THC) as well as aminated analogs, including aminated-curcumin (AC) and aminated-tetrahydrocurcumin (ATHC), and to further understand the reasons for the differences in anti-inflammatory activity produced by different doses of AC. First, the anti-inflammatory ability of the samples was preliminarily compared using an LPS-induced inflammation model in RAW 264.7 cells, and then a chronic colitis model induced by dextran sulfate sodium (DSS) in ICR mice was used to evaluate the effects of the samples on intestinal barrier function, inflammatory response, gut microbiota composition, and related regulatory mechanisms. The results of the cell experiments showed that AC could most significantly reduce nitric oxide production, demonstrating immunomodulatory potential. In the animal experiment results, it was found that under the same dosage conditions, THC and CUR might promote mucus secretion by improving autophagy impairment and significantly restoring the expression and arrangement of tight junction proteins, thereby maintaining better barrier integrity. They can also inhibit the TLR4/p38 MAPK/AP-1 pathway to reduce inflammation, and the administration of AC at a lower dosage also showed anti-inflammatory effects similar to those of THC and CUR. Analysis of gut microbiota results showed that all samples could change the composition of the microbiota, increasing the relative abundance of Duncaniella, Muribaculum, and Kineothrix. Additionally, compared to the high-dose AC group, the low-dose AC group could significantly increase beneficial bacteria such as Akkermansia muciniphila, Eubacterium ventriosum, and Dorea longicatena, thereby increasing the production of short-chain fatty acids (SCFAs) to exert barrier protection and alleviate intestinal inflammation. In summary, THC, CUR, and low-dose AC all have the potential to prevent the progression of colitis.
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