膳食鐵對大鼠腸道微生物的影響

Abstract

一直以來，腸道微生物與我們有著微妙關係，它不僅在飲食上帶來風味，卻也威脅我們生命。近年微生物的研究技術與知識與日俱進，許多潛在的新效果相繼被提出、調查與應用，像是它們與人類營養狀況的關聯。然而，宿主與微生物的關係既緊密且複雜，本研究乃著手於必需營養素鐵，分析鐵資源的改變如何影響腸道菌的演替 (succession)。 本研究先以缺鐵飼料飼育大鼠 22 天，分組後再以兩種形式鐵 [有機 (市售的檸檬酸亞鐵鈉產品) 或無機 (硫酸亞鐵)] 進行 15 天的補鐵。從缺乏到補充的過程中，透過 real-time qPCR 技術觀察大鼠糞便與盲腸內特定細菌的變化，並用溼式灰化法測量腸內容物鐵含量，最後將兩結果進行相關性分析。 結果顯示，鐵充足的控制組其盲腸鐵濃度顯著高於實驗組，而實驗組間則沒有差異，表示即便宿主 Hb 值 (hemoglobin level) 於補鐵後回復，但盲腸仍處於缺鐵狀態。此外，qPCR 結果指出總細菌量沒有受到膳食鐵的影響；腸桿菌科 (Enterobacteriaceae) 在缺鐵時上升，補鐵後顯著下降；乳桿菌群 (Lactobacillus / Leuconostoc / Pediococcus group) 與雙歧桿菌 (Bifidobacterium) 則因缺鐵而阻止其濃度下降；Roseburia spp. / E. rectale 缺鐵時下降，並在補鐵後回復。有機或無機之鐵型式對腸桿菌科與雙歧桿菌有些微影響。相關性分析指出鐵量與總細菌量為正相關，但與腸桿菌科負相關，與乳酸桿菌群稍微負相關。 從缺鐵到補鐵過程中，本研究觀察到被影響的對象不僅有宿主，還包括一些具鐵處理特性之細菌，然日後仍須更多研究去探討膳食補鐵導致之細菌演替所伴隨的影響。在未來，更多膳食鐵與細菌的研究或許能帶來一些臨床上的意涵。

It's been very long time since the intriguing relationship between intestinal microbiota and human was established. Microbes not only make food tasty but also threaten our life. Recently, due to the advanced technology and knowledge of microbiota, many potential effects was speculated, examined, and applied, such as the nutritional benefits of probiotics. However, the interaction of host and microbiota is pretty complicated and involved in a number of factors. Therefore, the present study was to examine the role of iron in the succession of intestinal microbes. In this study, weanling rats were fed an iron-deficient diet for 22 days and then repleted with iron (either organic form which was a commercial beverage fortified with sodium ferrous citrate or inorganic form which was ferrous sulphate) for 15 days. The alteration of rat fecal and cecal bacterial number was measured by real-time qPCR technique, and the iron content of cecum was measured by wet ashing method. Correlation analyses were also conducted between these two results. First of all, cecal iron in iron sufficient group was significantly higher than the experimental groups; and no significant difference was found in these groups. It showed that exhausted cecal iron was still not yet restored even after the restore of Hb level. Then, qPCR results showed that no sigdifference was observed in the number of total bacteria between control group and experimental groups. Enterobacteriaceae were increased and decreased during the period of iron depletion and repletion respectively. The decrease in Lactobacillus / Leuconostoc / Pediococcus group and Bifidobacterium were slowed down during iron depletion. In contrast, the decreases in Roseburia spp. / E. rectale were restored during iron repletion. Slightly effects of organic or inorganic iron on Enterobacteriaceae and Bifidobacterium were observed. Finally, the results of correlation analyses indicated a positive correlation between iron content and total bacteria but a negative correlation between iron content and Enterobacteriaceae. Slightly negative correlation between iron content and Lactobacillus / Leuconostoc / Pediococcus group was also observed. The impacts of didetary iron on certain bacteria, which possess special capability for iron, were discovered in this study. Therefore, further studies are still needed to examine the consequences caused by these bacteria during this process. In the future, further studying the impacts of dietary iron on human intestinal microbiota should lead to clinical implications.