紅龍果透過抑制發炎減緩高脂飲食和葡聚糖硫酸鈉誘導 C57BL/6J 小鼠結腸炎

Abstract

近年來肥胖的流行率不斷上升，並引發了重大關注，有研究顯示肥胖與慢性疾病如發炎性腸道疾病 (IBD) 具有密切的相關性。其中腸道微生物群失調和內臟脂肪組織引起的慢性發炎被認為是 IBD 的機制之一。另外肥胖還會影響腸道屏障功能增加腸道通透性，使更多的促發炎因子進入腸道，同時也會導致腸道免疫調節異常，影響調節性 T 細胞和效應 T 細胞之間的平衡從而促進 IBD 的發展。紅龍果 (Hylocereus polyrhizus) 含有甜菜鹼、多糖、多酚等功能成分，被認為具有抗氧化、抗發炎、降血脂、抗肥胖及治療脂肪肝等與代謝綜合症相關的效果。本研究旨在探討紅龍果果肉和果皮對高脂飲食及 DSS 誘導的小鼠結腸炎中的影響，以及其預防效果和相關分子機制。本實驗使用 C57BL/6J 的小鼠，並將五周齡大的小鼠分為正常飲食組、高脂飲食加 DSS 組及樣品組分別為高低劑量紅龍果果肉及果皮組。在實驗進行的同時給予 50% 高脂飲食並在第 12 週和第 15 週在飲水中添加 2% 的 DSS，DSS 總共介入兩次，並於第 17 週犧牲，收集血液與臟器，進行後續實驗分析。本次結果顯示，在體重方面高低劑量果皮組表現出減緩肥胖作用。DAI 曲線下面積顯示，紅龍果果肉組最低，表明其在給予 DSS 期間可抑制體重減輕、腹瀉和糞便稠度。另外紅龍果果肉和果皮均可降低 HFD 和 DSS 誘導的結腸重量與長度比，此外紅龍果可以減少 HFD 誘導的結腸炎小鼠中促炎細胞因子 IL-6，並從腸道病理判讀結果得知誘導組其單核細胞和中性粒細胞具有嚴重浸潤、輕微的黏膜增生及少量杯狀細胞流失的現象，而此現象在樣品介入有減輕細胞浸潤的現象。在腸道菌相方面，HFD 誘導的結腸炎導致腸道微生物群的改變，誘導組的 Lachnospiraceae 豐度降低，而高劑量的果肉及果皮組均顯著增加，另外高劑量果肉組中 Ruminococcus champanellensis18P13 也有所增加，此外 Muribaculaceae 在誘導組中具有下降趨勢，但在所有樣本組中有顯著增加，然而這些細菌皆與短鏈脂肪酸的生成有關，並與發炎呈負相關，因此進行短鏈脂肪酸的分析，結果顯示丙酸和丁酸有所增加。最後進一步探討相關分子機制，紅龍果可藉由抑制 TLR4/NF-κB 路徑同時增加 GPR43、Foxp-3 與 IL-10 等蛋白來達到抗發炎的效果，接著利用 Tight junction 來觀察腸道的完整性，誘導組的 Occludin 及 Claudin-4 均有下降的現象，介入樣品組則可降低腸道的通透性。綜合上述的結果，紅龍果具有抑制 HFD 誘導的結腸炎的潛力，其中高劑量果肉組表現最為顯著。

In recent years, the increasing prevalence of obesity has raised significant concerns, and research has shown a close association between obesity and chronic diseases such as inflammatory bowel disease (IBD). One of the mechanisms underlying IBD is considered to be chronic inflammation induced by gut microbiota dysbiosis and visceral adipose tissue. Moreover, obesity affects intestinal barrier function, increasing gut permeability and allowing more pro-inflammatory factors to enter the intestines. It also leads to immune dysregulation in the gut, affecting the balance between regulatory T cells and effector T cells, thereby promoting the development of IBD. Red dragon fruit (Hylocereus polyrhizus) contains functional components such as betaine, polysaccharides, and polyphenols, which are believed to have antioxidant, anti-inflammatory, hypolipidemic, anti-obesity, and fatty liver-related metabolic syndrome effects. This study aims to investigate the effects of red dragon fruit pulp and peel on colitis induced by a 50 % high-fat diet and DSS in mice, as well as their preventive effects and related mechanisms. Five-week-old C57BL/6J mice were divided into a normal diet group, a high-fat diet plus DSS group, and sample groups with high and low doses of red dragon fruit pulp and peel. DSS (2%) was added to the drinking water during weeks 12 and 15 of the experiment, administered twice in total, and all mice were sacrificed at week 17 for subsequent analysis. The results showed that both low and high doses of red dragon fruit peel exhibited anti-obesity effects. The area under the DAI curve indicated that the red dragon fruit pulp group showed the most significant reduction, suggesting it could suppress weight loss, diarrhea, and stool consistency. Both the pulp and peel of red dragon fruit reduced the colon weight-to-length ratio in HFD and DSS-induced colitis. Additionally, red dragon fruit could reduce the levels of the pro-inflammatory cytokine IL-6 in HFD induced colitis mice. Based on the pathological interpretation results of intestinal tissue sections,, it was observed that the HFD + DSS group exhibited significant infiltration of mononuclear cells and neutrophils. Additionally, there was a slight increase in mucosal hyperplasia and a loss of goblet cells. However, intervention with the samples effectively alleviated the cellular infiltration. Regarding the gut microbiota, the abundance of Lachnospiraceae decreased in the HFD + DSS group but significantly increased in the high-dose pulp and peel groups. Additionally, Ruminococcus champanellensis18P13 increased in the high-dose pulp group. Muribaculaceae showed a decreasing trend in the HFD + DSS group but significantly increased in all sample groups. These bacteria are associated with the production of short-chain fatty acids and negatively correlated with inflammation. Propionic and butyric acids were also increased in the short-chain fatty acid analysis. Morever the red dragon fruit could exert anti-inflammatory effects by inhibiting the TLR4/NF-κB pathway and increasing the expression of GPR43, Foxp3, and IL-10. Tight junction analysis indicated that the induced group showed a decrease in Occludin and Claudin-4, altering intestinal barrier integrity, while the sample groups reduced intestinal permeability. In summary, red dragon fruit has the potential to inhibit HFD-induced colitis, with the high-dose pulp group showing the most significant effects.