米麩對倉鼠體內脂質代謝及其肝臟相關 mRNA 表現之影響
The effects of rice bran on lipid metabolism and hepatic mRNA
expressions in hamsters
中文摘要 本次研究主要在探討米麩對於倉鼠體內脂質的代謝及肝臟相關mRNA 表現之影 響。稻米為我國主食的來源之ㄧ，米麩則是在稻米精製過程中所產生的副產物， 其內含有豐富的膳食纖維能夠調節體內脂質代謝，然而米麩對於調節血液、肝臟 脂質及膽固醇恆定的相關mRNA 表現之影響仍是未知的。因此，本次的實驗是 選用40 隻 8 週齡大的雄性倉鼠，適應 1 週後以高脂飲食 (含有 modified AIN-93M 配方及額外添加0.2%膽固醇) 餵食 2 週。之後隨機分為五組：控制組 (NC) 餵食modified AIN-93M 及不添加膽固醇的飲食；實驗組則是餵食 modified AIN-93M
及額外添加0.2%膽固醇的飲食之下，以 0% (CC)、5% (R5)、10% (R10)及 15% (R15) 不同劑量的米麩部份取代，每天餵食10 克，餵養 4 週之後，予以犧牲。結果指 出，餵食米麩飲食的組別其血液和肝臟中的三酸甘油酯及膽固醇濃度顯著低於 CC 組，其血液中的 LDL-C 濃度及 LDL-C/HDL-C 比值顯著低於 CC 組 (P < 0.05)，但是血液中的短鏈脂肪酸濃度會顯著高於 CC 組 (P < 0.05)，並且有劑量 反應；除此之外，米麩組別會排出較多的糞便中性固醇及膽酸。餵食倉鼠米麩飲
食4 週之後，其肝臟中的 HMG-CoA reductase mRNA 表現量會顯著低於餵食 CC
組的飲食結果 (P < 0.05)；而當米麩劑量達 15%時，肝臟中的 LDL receptor mRNA 表現量會顯著地增加 (P < 0.05)。在餵食米麩飲食 4 週之後，CYP7A1 mRNA 表 現量會顯著高於餵食CC 組飲食的結果 (P < 0.05)；此外，R5 組相較於 CC 組會 有較高的LPL、SR-B1 及 ACO mRNA 表現量。上述的結果指出，餵食米麩飲食 可以調節倉鼠體內脂質及膽固醇的代謝機制進而去改善高脂血症的情形。 英文摘要
The aim of this study is to investigate the effect of rice bran on lipid metabolism and hepatic mRNA expression in hamsters. Rice bran is a byproduct of the rice milling process. It contains a high level of dietary fiber (25%). Many animal studies indicate that rice bran may contribute to the lowering of plasma levels of various components of the lipid profile. However, how rice bran affects hepatic mRNA related to plasma and hepatic lipid regulation and cholesterol homeostasis is unknown. Forty
8-week-old male hamsters were first fed a high fat diet (modified AIN-93M diet containing 4% soybean oil plus 4% lard) and supplemented with 0.2% cholesterol for 2 weeks and then divided into five groups. The control group was fed modified AIN-93M diet without cholesterol (NC), and the experimental groups were fed modified AIN-93M diet plus 0.2% cholesterol and either 0% (CC), 5% (R5), 10%
(R10), or 15% (R15) rice bran for 4 weeks. The results showed that plasma and hepatic triglyceride and cholesterol concentrations were lower in hamsters fed the rice bran diet than hamsters fed the CC diet. Besides, the plasma LDL-C concentrations and LDL-C/HDL-C ratio were lower and the plasma short chain fatty acid
concentrations, fecal neutral sterol, and bile acid excretion were higher in the rice bran group than the CC group. After 4 weeks, the rice bran diet resulted in lower hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase) mRNA expression. Hepatic HMG-CoA reductase mRNA expression was significantly lower and hepatic LDL receptor mRNA expression was significantly higher in the R15 group than R5 group. Moreover, hepatic cholesterol 7α-hydroxylase (CYP7A1) mRNA expression was higher in the groups fed rice bran than those fed the CC diet. Additionally, the R5 group had higher hepatic lipoprotein lipase, scavenger receptor class B type 1 (SR-B1), and acyl-CoA oxidase (ACO) mRNA expression than the CC group. These findings suggest that the rice bran diet regulates the lipid and cholesterol mechanism in hamsters.
