| 摘要: | 麩醯胺（Glutamine, GLN）為體內含量最多的胺基酸，具有免疫調節功能、抗氧化、輔助腸黏膜再生等生理功能，臨床上補充GLN，可以降低ICU病人的住院天數與預後。目前尚無針對膳食補充GLN對腸炎病程之研究，因此本實驗採用DSS誘導小鼠結腸炎之動物模式，探討短期膳食補充GLN，是否具有緩和炸油惡化小鼠結腸炎病程之功效。採用50隻11週齡C57BL/6品系雌鼠，6隻為正常控制組（B組），其餘分成兩組，每組22隻，包括炸油組 ( 15％炸油，O組 )、炸油加麩醯胺組 ( 15％炸油＋4.17％GLN，OG組)，飼養10天後，O組與OG組於飲水中添加2％（w/v）DSS誘發小鼠結腸炎，連續 5 天後換成蒸餾水2天，每日記錄病情並計算疾病活動指數 ( Disease activity index, DAI），實驗全程飼料、飲水與DSS水均採自由攝取。於第八天隔夜禁食後犧牲，採集小鼠血清、肝臟與大腸，分析脂質過氧化指標、脂質分析、抗氧化分子、抗氧化酵素活性、發炎相關細胞激素及其mRNA 表現。存活率結果顯示，以DSS誘發結腸炎第8天，OG組小鼠存活率為63.6%，O組為27.3%，表示短期GLN餵飼可顯著降低小鼠死亡率。DAI指數方面，急性結腸炎第五天，OG組其血便程度、腹瀉程度與DAI指數均有低於O組的趨勢。血液指標方面，全身性發炎指標Haptoglobin（Hp）之血清濃度，O及OG組顯著高於B組，OG組顯著低於O組，表示DSS會增加發炎狀況，補充GLN具有明顯緩和效應。大腸結果：（1）抗氧化相關指標，TBARS與SOD酵素活性，三組均無統計差異；GSH濃度，O組顯著低於B組，OG組顯著增加為O組的2.1倍，表示添加GLN顯著增加大腸GSH含量，而GPx活性，OG組顯著高於B組；（2）去粒線體上清液細胞激素分析，OG組IL-1β顯著低於O組，IL-6含量則不受GLN添加的影響；（3）mRNA表現，O及OG組iNOS表現均顯著高於B組，O組NOX-1、COX-2、IL-1β、IL-6表現均顯著高於B組，OG組NOX-1、COX-2、IL-1β、IL-6表現均顯著低於O組，可得知DSS會增加促發炎相關基因表現，而補充GLN具有顯著緩和效應。肝臟結果顯示：脂質過氧化指標TBARS 濃度，OG組顯著低於B組。由以上結果得知，短期添加GLN具有緩和炸油惡化結腸炎病程與降低小鼠死亡率之效應，可能透過降低發炎反應與增加GSH含量有關，推測GLN可能為透過降低NF-κB活化而減少大腸促發炎相關激素表現。
Glutamine (GLN) is the most abundant free amino acid in the plasma and tissue pool. Previous studies revealed that GLN-supplemented nutrition had immunomodulatory effects in the body's response to stress and injury. A large clinical data showed that GLN could improve the outcomes of patients in the ICU. To date, no study had definitively described the effects of dietary GLN on DSS-induced colitis. Therefore, we designed this study to investigate the effect of short-term GLN supplementation on the symptoms of DSS-induced colitis in OFO-fed mice.11-wk-old female C57BL/6 mice (n=50) were used in this study. They were acclimatized and housed individually in stainless-steel wire cages in a temperature- and humidity-controlled room supplied with a regular 12-hour light/dark cycle. There were randomized into three dietary groups, including B group (chow diet), O group (15% OFO) and OG group (15% OFO+4.17％ GLN). All mice were allowed free access to powder diets and tap water. After 10 days, mice of O group and OG group were treated by 2% (w/v) DSS administered in drinking water for 5 days, followed by providing DSS-free tap water for 2 days. Clinical symptoms and the disease activity index (DAI) were recorded daily during acute colitis. At day 8 after DSS challenge, mice were sacrificed with carbon dioxide asphyxiation. Blood, liver and colon were collected and assessed for associated parameters, such as inflammatory cytokines, antioxidant defense system, and mRNA expression.The survival 8 days after DSS challenge was 63.6% in the OG group and 27.3% in the O group. The ameliorative effect of short-term GLN feeding on the survival rate was significant. Compared with the O group, the serum haptoglobin (Hp) was significantly lower in the OG group. There was no difference in colonic TABAR content and SOD activity between O and OG group, but the OG group had a higher GSH level than the O group. The OG group had a marked reduction in the colonic IL-1 content. The mRNA abundances of COX2, NOX1, IL-1β and IL-6 were significantly lower in the OG group compared with the O group. Our data demostrated that GLN supplementation caused a significant reduction in the expression of pro-inflammatory genes. Futher study is needed to investigate the role of their transcriptional regulatory factor NF-κB in GLN supplementation. In the results of liver, TBARS were significantly lowered in the OG group compared with the O group. In conclusion, we found for the first time that short-term GLN feeding had a marked ameliorative effect on OFO-worsen DSS-induced colitis in mice. We suggested that the beneficial effect might be partly due to either the GSH increase or a decrease of inflammation. In addition, the lowing effect of GLN on pro-inflammatory cytokines were significant in colon. |
