- 學位論文
米糠粉對高脂飲食小鼠腸道菌相及腸道免疫的影響
Effects of rice bran consumption in high-fat diet fed mice oncommensal microbiota and gut immune responses
摘要
研究指出飲食所導致的腸道菌相失衡可能會引起肥胖，且過多的壞菌增殖使內毒素進入全身性循環，可能導致全身性低度發炎。米糠雖富含高度營養價值，但以往多作為飼料，近年來以全食品觀念逐漸被食用。因其所含的可溶性纖維能被腸道共生菌利用，產生短鏈脂肪酸，可能具有免疫調節和抑制發炎的作用。在此，本實驗欲探討米糠是否能改善高脂飲食對小鼠腸道菌群及腸道免疫的影響。首先，實驗一為初步探討在開放性動物飼養環境下，米糠對高脂飲食小鼠的腸道菌群是否有影響，將9~10週齡大的9隻Balb/c公鼠分為高油 (HF) 及高油添加米糠 (HF-RB) 兩組餵飼10週，收集糞便，以PCR增幅16S rDNA序列分析選定的指標菌種。結果顯示HF-RB組的腸道菌群有較低的厚壁菌門、腸桿菌科，較高的擬桿菌門及擬桿菌屬。實驗二進一步探討米糠粉對腸道免疫的影響，為避免腸道菌群差異性過大，以自行交配的方式取得C57BL/6J小鼠，於5週大時分為正常油脂 (NF) 組、高油 (HF) 組、高油添加米糠 (HF-RB) 組、以及高油添加益生菌 (HF-PRO) 組四組，餵飼8週後，確認高脂飲食會減少糞便的比菲德氏菌屬、擬桿菌門及增加腸桿菌科，且HF-RB組及HF-PRO組皆可回復糞便的比菲德氏菌屬及腸桿菌科。與實驗一結果相同，HF-RB組與HF組相比，有顯著較低的厚壁菌門，較高的擬桿菌門及擬桿菌屬。HF-RB組的糞便短鏈脂肪酸顯著高於HF組和HF-PRO組，且血清和糞便葉酸皆顯著高於HF組。免疫相關指標的結果，HF組影響MLN細胞分泌IL-2及TGF-β的能力，而HF-RB組及HF-PRO組皆能回復此現象。綜合以上結果，米糠粉能減低高脂飲食對腸道指標菌群、腸道共生菌代謝物及腸道免疫的影響。
並列摘要
Research demonstrated that diet-induced dysbiosis might play an important role in obesity, overgrowth of pathobionts are involved in obesity-related inflammation due to its cell wall component lipopolysaccharide. Rice bran is rich in valuable nutrients, mostly used as animal feed in the past, become popular nowadays due to prevalence of whole-food consumption concept. Dietary fiber of rice bran can be utilized by gut microbiota to produce SCFAs that have immuno-modulatory and anti-inflammatory effects. Thus, this research aims to investigate whether rice bran can reverse the effects of high-fat diet on gut microbiota and immune responses. Experiment 1 was to explore the effects of rice bran on gut microbiota in the conventional animal facility. Nine to ten-week-old Balb/c mice were fed with either high-fat (HF) diet or HF-diet supplemented with rice bran (HF-RB) for ten weeks, feces were collected and measured by 16S rDNA sequence analysis to amplify target microbiota gene. Results showed that the HF-RB group had lower Firmicutes, Enterobacteriaceae, higher Bactroidetes and Bacteroides compare with the HF group, suggesting the ability of rice bran to modulate gut microbiota., Further experiment 2, C57BL/6J mice were mated in our animal facility to avoid variations of gut microbiota in newborns due to maternal microbial transmission. Five-week-old mice were divided into four groups: normal fat (NF), HF, HF-RB, and HF supplemented with probiotics (HF-PRO) for 8 weeks’ feeding. First, we confirmed that HF-diet reduced fecal Bifidobacteria, Bacteoridetes, and increased Enterobacteriaceae. Both the HF-RB and the HF-PRO groups restored fecal Bifidobacterium and Enterobacteriaceae to the level of the NF group. In consistent with experiment 1, the HF-RB group had lower Firmicutes, and higher Bacteroidetes, Bacteroides compared with the HF group. Fecal SCFAs are significantly higher in the HF-RB group than those in the HF and the HF-PRO groups. Serum and fecal folate are also significantly higher in the HF-RB group. Cytokine secretion ability (IL-2, TGF-β) of isolated MLN cells in the HF-RB group was similar to the NF group. In conclusion, rice bran can lessen the effects of HF-diet on target gut microbiota, gut microbiota metabolites and gut immune responses.