|摘要: ||近年來慢性腎臟疾病 (chronic kidney disease, CKD) 的罹患率逐年攀升，不健康的生活作息、飲食型態或疾病均可能造成腎臟損傷。膳食油脂品質與含量是否會影響腎臟功能，導致慢性腎病的發生，仍屬未知。 因此，本研究目的為炸油是否改變腎臟抗氧化狀況、發炎與細胞凋亡相關分子表現，並利用 DSS 誘發小鼠結腸炎模式，初探炸油對腸炎病程發展與腸外組織肝、腎之影響。
本研究分為三個實驗，皆採用 5 週齡 C57BL/6J 品系雌鼠，實驗 A 探討餵食高、低炸油 (15% 與 7%) 與限食對小鼠腎臟抗氧化狀況之影響，前人研究發現餵食炸油會導致小鼠攝食量降低，為了確認炸油效應與限食效應的異同而設計了高、低炸油對飼育組，飼養四週後犧牲。結果得知，攝食量降低對腎臟抗氧化作用影響較小或無顯著影響，因此實驗 B 探討高、低炸油對小鼠腎臟抗氧化相關酵素與分子表現之影響，飼養 6 週後犧牲， 結果顯示油脂品質對腎臟抗氧化狀況影響較顯著，則實驗 C 採用 7% 油脂 (新鮮油與炸油) 進行實驗，並採用 DSS (Dextran Sulfate Sodium) 誘發結腸炎之實驗動物模式，目的在於觀察炸油餵食是否會惡化 DDS 誘發結腸炎病程發展，並探討組織抗氧化相關分子與酵素表現，於飲用水中添加 2% DSS（w/v），誘發腸道發炎，連續5天後換成ㄧ般飲水，並計算疾病活動指數 (disease activity index, DAI)，飼養97天後犧牲。
結果顯示炸油餵食顯著增加小鼠腎臟 GSH 與維生素 C 濃度，增加 CAT 酵素活性及蛋白質含量，降低腎臟 -生育醇濃度。長時間餵食炸油對腎臟、肝臟及結腸抗氧化狀況類似。
炸油餵食顯著增加小鼠對 DSS 感受性，出現嚴重血便、腹瀉及體重流失，並延緩復原速度。餵食 DSS 小鼠血清中急性期蛋白濃度 (Hp) 顯著增加，而單純炸油餵食亦使 Hp 顯著上升，因此推測餵食炸油小鼠處於有發炎傾向的 pre-illness 狀態。炸油顯著增加腎臟 NQO1 mRNA 表現，但降低 Nrf2 mRNA 表現。低炸油餵食有活化腎臟 caspase 3 的趨勢，不過高炸油活化 caspase 3 就越顯著。
綜合本實驗之結果，我們首次發現膳食炸油會惡化 DSS 誘發結腸炎病程發展，負調控腎臟 Nrf2，可能會降低細胞保護能力。炸油餵食也顯著增加結腸、肝臟脂質過氧化，改變組織抗氧化分子與抗氧化酵素間的平衡，雖然小鼠腎臟受到炸油餵食影響抗氧化狀況平衡，但未觀察到有組織損傷情況產生。
Unhealthy lifestyle, dietary patterns or disease may increase risk of chronic kidney disease (CKD). The mechanism is still poorly understood whether dietary fat quantity and quality affect renal function, resulting in the occurrence of CKD. Therefore, the purpose of this study was to determine the effect of oxidized frying oil (OFO) on antioxidative status, inflammation and apoptosis-related molecules expression of kidney.
This study was divided into three experiments which used five-week-old female C57BL/6 mice. The experiment A was to study the kidney antioxidative status in mice fed high and low OFO (15% and 7%) and food restriction (OFO-pair fed group) for 4 weeks. Results showed the specific effects of OFO on kidney antioxidative change were not due to reducing food intake. The experiment B was to study the kidney antioxidant enzymes nad molecules expression in mice fed high and low OFO for 6 weeks. Result showed that the fat quality was the major dietary factor influencing significantly antioxidative status in kidney. The experiment C was used by 7% fat (fresh and oil) to carry out experiments. It was to observe DSS (dextran sulfate sodium)-induced colitis course and antioxidant-related molecules and enzymes expression in mice fed OFO. After 2 months feeding, a half mice of each group were exposed to 2% DSS (w/v) in drinking water for 5 days and killed at day 40. Clinical symptoms and the disease activity index (DAI) were recorded daily during acute and chronic colitis.
In OFO-fed mice, the GSH and vitamin C contents were significantly increased and vitamin E concentration were lowered in kidney. The activity and protein abundance of catalase in liver and kidney were significantly increased by dietary OFO feeding. According to the results of experiment C, we showed that OFO-fed mice had severe clinical manifestation, marked significantly by weight loss, diarrhea score, visible fecal blood and increasing disease activity index (DAI) from day 2. The serum haptoglobin (Hp) was significantly increased in DSS- and OFO-fed mice. The spleen weight was significantly increased, whereas hemoglobin, serum albumin and colon length were all decreased by DSS treatment (p<0.05). In OFO-fed mice, NQO1 (NAD(P)H : quinone oxidoreductase 1) mRNA expression was significant increased, but Nrf2 (Nuclear factor-erythroid 2-related factor 2) mRNA expression was lowered. The procaspase 3 protein abundance was significant decreased by dietary OFO.
In summary, we show for the first time that OFO-fed mice are more susceptible to DSS-induced colitis, significantly deteriorate the progression course of this disease. Dietary OFO decreased the expression of Nrf2, which may led to reduce the renal cytoprotection against inflammation. We suggested OFO-fed mice had a tendency to inflammation of the pre-illness state. Although OFO-fed mice were influenced oxidant-antioxidant balance, but no any obvious renal injuries had been observed.