复合全谷豆粗杂粮对脂代谢紊乱大鼠体内外抗氧化作用的影响

目的阐明复合全谷豆粗杂粮的体外抗氧化能力,及其对大鼠脂代谢紊乱和氧化应激水平的影响。方法制备复合全谷豆粗杂粮和大米、面粉、黑米提取物,用化学比色法测定其总抗氧化能力、羟自由基和超氧阴离子的抑制率。44只SPF级大鼠随机分为阴性对照组、高脂模型组、米面组和复合全谷豆粗杂粮组,分别给予相应饲料,连续喂养8周,实验前后测定各组大鼠体重、血清总胆固醇(TC)、总甘油三酯(TG)、血清高密度脂蛋白胆固醇(HDL-c),以及大鼠血清和肝脏的丙二醛(MDA)、总抗氧化能力(T-AOC)、超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)水平。结果复合全谷豆粗杂粮的体外总抗氧化、清除羟自由基和清除超氧阴离子自由基的能力均显著高于大米和面粉。与高脂模型组和米面组相比,复合全谷豆粗杂粮组血清TC、TG显著下降,HDL-c显著上升,血清和肝脏MDA显著下降,T-AOC、SOD、GSH-Px显著上升;与阴性对照组相比未见显著差异。结论复合全谷豆粗杂粮具有良好抗氧化损伤作用,该作用是其改善脂代谢紊乱的重要功能机制之一。     

全谷豆复合包经SREBP-2、LDLR和Visfatin调控胆固醇代谢机制的探讨

目的探讨全谷豆复合包改善脂代谢紊乱大鼠胆固醇代谢的可能机制。方法 44只雄性SD大鼠随机分为高脂模型组、米面组、全谷豆复合包组和阴性对照组,分别给予对应饲料连续喂养8周。实验前后测定大鼠血清总胆固醇(TC)、甘油三酯(TG)、高密度脂蛋白胆固醇(HDL-C)及低密度脂蛋白胆固醇(LDL-C)含量;实验结束后股动脉取血,分离脏器称重,计算脏体比和脂体比,检测血清中Visfatin浓度、肝脏组织中SREBP-2 mRNA和LDLR mRNA的表达以及脂肪组织中VisfatinmRNA的表达。结果与高脂模型组和米面组相比,全谷豆复合包组大鼠体重、血清TC、TG、LDL-C水平显著下降(P<0.05),血清HDL-C水平显著升高(P<0.05)。全谷豆复合包组大鼠血清Visfatin水平显著低于高脂模型组和米面组(P<0.05);与高脂模型组和米面组比较,全谷豆复合包组大鼠肝脏组织中SREBP-2 mRNA和LDLRmRNA的表达显著升高(P<0.05),脂肪组织中Visfatin mRNA的表达明显降低(P<0.05)。结论全谷豆复合包可以改善高脂膳食诱导的脂代谢紊乱大鼠的血脂和Visfatin水平,可能的机制是全谷豆复合包能增加SREBP-2和LDLR的mRNA表达,降低Visfatin mRNA的表达,经SREBP-2、LDLR和Visfatin途径调控胆固醇的代谢,起到维持TC和LDL-C的正常水平,改善脂代谢紊乱的作用。     

复配式粗杂粮对胰岛素抵抗大鼠LCN-2表达影响

目的探讨全谷豆复配式粗杂粮对高脂膳食诱导胰岛素抵抗大鼠肝脏和脂肪组织中载脂蛋白2(LCN-2)影响。方法 40只雄性SD大鼠随机分为阴性对照组、高脂模型组、米面组和粗杂粮组,以相应饲料连续喂养8周,测定各组大鼠血清空腹血糖(FBG)和胰岛素(FINS)水平,并计算胰岛素抵抗指数(HOMA-IR);Western blotting检测各组大鼠肝脏和脂肪组织中LCN-2和过氧化物酶体增殖体激活受体-γ(PPAR-γ)蛋白表达。结果与阴性对照组比较,高脂模型组和米面组血清FBG和FINS水平明显升高(P<0.05)。高脂模型组和米面组HOMA-IR分别为(10.39±1.63)和(10.34±1.36),明显高于阴性对照组(6.85±1.33);与高脂模型组和米面组比较,粗杂粮组HOMA-IR(6.81±1.37)明显下降,粗杂粮组LCN-2在肝脏和脂肪组织中表达明显低于高脂模型组和米面组,PPAR-γ则相反。结论全谷豆复配式粗杂粮可以激活胰岛素抵抗大鼠PPAR-γ蛋白,进而降低脂肪因子LCN-2表达,改善胰岛素敏感性。     

抗性淀粉对大鼠肝脏胆固醇代谢相关基因表达的影响

目的:观察抗性淀粉(RS)对大鼠肝脏胆固醇代谢相关基因表达的影响,探讨RS干预胆固醇代谢的作用机制。方法:将18只大鼠随机分为三组,分别饲食正常化学纯合饲料(对照组)、含15%RS纯合饲料(低RS组)和含30%RS纯合饲料(高RS组)6w。采用实时荧光定量PCR技术检测各组大鼠肝组织中胆固醇7a-羟化酶(CYP7A1)、肝清除细胞B1受体(SR-B1)、肝低密度脂蛋白受体(LDLR)mRNA表达水平。检测各组大鼠血胆固醇、盲肠内容物短链脂肪酸(SCFA)含量。结果:大鼠肝组织CYP7A1mRNA、SR-B1mRNA、LDLRmRNA表达水平及盲肠内SCFA含量,高RS组与对照组相比显著增加(P<0.05)。血清胆固醇水平,RS干预组显著低于对照组(P<0.05)。结论:RS通过增强肝组织胆固醇代谢相关基因表达水平,增加盲肠内SCFA含量,发挥降低血胆固醇的作用。     

谷豆复合物、谷豆复合膳食纤维及单一谷物膳食纤维对脂代谢紊乱的影响

目的观察谷豆复合物、谷豆复合膳食纤维和全谷物玉米膳食纤维(DF)对脂代谢紊乱大鼠血脂及肝脏脂肪酸合成酶(FAS)活性,及其对大鼠肝组织固醇调节元件结合蛋白-1c(SREBP-1c)mRNA表达的影响,比较谷豆复合物、谷豆复合DF与单一谷物DF改善脂毒性效果。方法 50只SD大鼠适应性喂养1周后,随机分成阴性对照组、高脂模型组、谷豆复合物组、谷豆复合DF组和玉米DF组;以相应的饲料连续喂养8周后,测定各组大鼠总胆固醇(TC)、甘油三酯(TG)、空腹血糖(FBG)、高密度脂蛋白胆固醇(HDL-C)和FAS等指标,测定各组大鼠肝脏SREBP-1c mRNA的表达。结果与阴性对照组相比,高脂模型组的大鼠血清TC、TG水平显著升高(P0.05);与高脂模型组相比,谷豆复合物组、谷豆复合DF组和玉米DF组大鼠血清TC、TG水平显著降低(P0.05);HDL-C水平显著高于高脂模型组,大鼠肝脏脂肪酸合成酶活性及SREBP-1c的表达显著降低。结论谷豆复合膳食纤维可改善脂代谢紊乱大鼠的血脂水平,降低FAS活性及SREBP-1c的表达水平。     

粗杂粮对大鼠脂代谢紊乱干预作用的机制探讨

目的观察粗杂粮对大鼠脂代谢紊乱及其脂肪组织过氧化物酶体增殖物激活受体γ (PPARγ) mRNA表达水平的影响,探讨粗杂粮改善脂代谢紊乱的作用机制。方法44只SPF级大鼠随机分为阴性对照组(饲常规饲料)和3个实验组(饲高脂饲料6周),造模成功后分别给予高脂粗杂粮、高脂米面和高脂模型饲料共15周。结果粗杂粮高脂组的血清总胆固醇(TC)、总甘油三酯(TG)、白细胞介素-6(IL-6)和C反应蛋白(CRP)显著低于高脂模型组(P<0.05),血清高密度脂蛋白胆固醇(HDL-C)水平显著高于高脂模型和米面高脂组(P<0.05),脂蛋白酯酶(LPL)和肝酯酶(HL)活性及肿瘤坏死因子-α(TNF-α)最接近阴性对照组水平;粗杂粮高脂组白色脂肪组织PPARγ mRNA的表达水平明显高于高脂模型组和米面高脂组(P<0.05)。结论复配式粗杂粮可以激活PPARγ,促进脂肪细胞LPL和HL活性逐步恢复,使血脂水平下降;同时抑制和减少IL-6、TNF-α及CRP的产生,炎症反应减轻,脂代谢紊乱得到改善。     

辣椒总碱对大鼠胆固醇代谢及相关基因表达的影响

目的 探讨辣椒总碱(capasaicinoids,CAP)对不同饲料喂食的SD大鼠胆固醇降低的作用及机制.方法 将32只SD成年大鼠随机分为以下4组:对照组(C,基础饲料+大豆油0.5 ml/100 g bw)、CAP组(基础饲料+大豆油0.5 ml/100g bw+CAP10 mg/kg bw);高脂饲料组(HF,高脂饲料+大豆油0.5 ml/100g bw);HF+CAP组(高脂饲料+大豆油0.5 ml/100 g bw +CAP 10 mg/kg bw).喂养4w后,测定血脂、肝脂、小肠和粪便中总胆汁酸含量变化情况,并用实时荧光定量PCR技术检测肝脏和回肠中与胆固醇代谢相关基因mRNA的表达.结果 CAP能显著降低喂食基础饲料和高脂饲料大鼠的血浆胆固醇浓度、减少脂肪在肝脏中的积累,其中对喂食高脂饲料大鼠胆固醇的降低效果优于基础饲料.同时,CAP能显著降低基础饲料和高脂饲料大鼠肝脏3-羟基-3甲基戊二酰CoA (HMG-CoA)还原酶和胆固醇7α-羟化酶(CYP7A1) mRNA的相对表达量,显著增加法尼酯受体(FXR)、回肠胆汁酸结合蛋白(IBABP)、顶端钠依赖性胆汁酸转运体(ASBT)和辣椒素受体(TRPV1)mRNA的相对表达量;显著降低基础饲料大鼠小肠和粪便中总胆汁酸含量.结论 CAP对基础饲料和高脂饲料大鼠的血脂均有良好的降低作用,其可能作用机制是阻止肝脏内源性胆固醇的合成.     

复合膳食纤维对大鼠生长发育和红细胞膜流动性的影响

目的 :　制备复合膳食纤维 (AFC) ,并分别探讨其与三种单一的膳食纤维 (DF)对高脂血症大鼠生长发育和红细胞膜流动性的影响。方法 :　健康、雌性、断乳 Wistar大鼠 48只 ,按体重随机分为 6组 ,用高脂饲料诱发高脂血症的同时 ,分别添加 1 0 %的 DF:纤维素、果胶、海藻酸钠、(纤维素 -果胶复合膳食纤维 ) AFC1、(纤维素 -海藻酸钠复合膳食纤维 ) AFC2 ,高脂饲料组 (对照组 ) ,观察各种 DF对大鼠的生长发育、粪脂排出量及脂质过氧化、红细胞膜流动性的影响。结果 :1 .添加 1 0 %的各种 DF不影响大鼠的生长发育。 2 .各种 DF可不同程度地增加粪重和粪脂排出量(P<0 .0 5 ,除海藻酸钠组外 ) ,以 AFC为明显。 3 .各种 DF皆可显著升高血清超氧化物歧化酶(SOD) (P<0 .0 1 )、谷胱甘肽过氧化物酶 (GSH-Px)活性 (P<0 .0 1 ) ,降低丙二醛 (MDA)水平 (P<0 .0 5 ,除纤维素、海藻酸钠组外 ) ,提高红细胞膜的流动性 (P<0 .0 5 ) ,以 AFC为明显。结论 :　各种 DF皆可不同程度地增加粪脂排出量、提高红细胞膜的流动性 ,其中可溶性 DF效果优于不可溶性 DF,而 AFC的效果又优于单一的 DF。     

复配式粗杂粮对大鼠胰岛素抵抗及PPAR-γ表达的影响

目的掌握复配式粗杂粮对高脂饮食诱导的大鼠胰岛素抵抗的影响。方法40只SD大鼠随机分为阴性对照组(n=10)和高脂造模组(n=30),分别给予基础饲料和高脂饲料,6周后再将高脂造模组分为高脂模型对照组、米面组、粗杂粮组(n=10),提供相应饲料。继续喂养9周后,测定大鼠血糖和胰岛素水平,RT-PCR法测定脂肪组织中过氧化物酶体增殖物激活受体-γ(PPAR-γ)mRNA表达。结果6周高脂饮食后,高脂造模组胰岛素抵抗指数(HOMA-IR)明显升高,造模成功。粗杂粮组大鼠的体重和HOMA-IR显著低于高脂模型对照组和米面组,粗杂粮组PPAR-γmRNA的表达与其他3组比较明显增加(P0.05)。结论复配式粗杂粮能显著降低高脂饮食引起的胰岛素抵抗大鼠的血糖、胰岛素水平,改善胰岛素敏感性,其机制可能与增加PPAR-γ的表达有关。     

CYP7B1与ER在胆汁淤积孕鼠胎鼠肝脏中的表达

目的 探讨雌激素受体(ERα、ERβ)与胆固醇7α羟化酶(CYP7B1)mRNA在妊娠期肝内胆汁淤积(ICP)孕鼠、胎鼠肝脏中的表达及其意义.方法 对照组孕鼠30只注射精制植物油;研究组孕鼠30只注射17-α-乙炔雌二醇.两组孕鼠分别于妊娠第13天、17天、21天断尾采母鼠血检测,于妊娠第21天抽取母鼠、胎鼠血并提取肝脏组织.应用酶联免疫吸附试验检测两组孕鼠及胎鼠血清中胆酸水平;应用实时定量PCR技术检测两组胎鼠肝脏ERα、ERβ、CYP7B1 mRNA的表达.结果 ①在妊娠第17天、21天研究组母鼠胆汁酸水平明显高于对照组(55.7±3.2μmol/L vs 23.4±1.2μmol/L,t=2.541,P<0.05;61.4±2.4μmol/L vs 25.5±2.1μmol/L,t=2.621,P<0.05);研究组胎鼠胆汁酸水平明显高于对照组(27.4±2.3μmol/L vs 11.5±2.6μmol/L,t=2.631,P<0.05);②研究组胎鼠肝脏CYP7B1 mRNA水平明显高于对照组(2.15±0.01vs 0.25±0.02,t=2.563,P<0.05);③研究组ERα mRNA水平明显高于对照组(0.81±0.02 vs 0.35±0.01,t=2.534,P<0.01).结论 ICP孕鼠胎鼠肝细胞ERα、CYP7B1的表达升高,胆汁酸的合成与代谢调节机制存在障碍,可能是导致ICP胎儿围生儿死亡发生的原因之一.     

Dietary psyllium increases expression of ileal apical sodium-dependent bile acid transporter mRNA coordinately with dose-responsive changes in bile acid metabolism in rats

Psyllium (PSY), a type of dietary fiber containing mainly soluble components, has been shown to decrease serum cholesterol concentrations in several species; however, mechanisms involved are not clearly defined. Four groups of 10 rats were fed semipurified diets containing 10% dietary fiber from cellulose and/or PSY for 21 d. Increasing levels of PSY were fed (0,3.33, 6.67 and 10% PSY) with the remaining 10% made up with cellulose. Liver cholesterol, cholesterol 7alpha-hydroxylase (CYP7A) activity and mRNA, 3-hydroxy-3-methylglutaryl CoA reductase (HMGR) mRNA, ileal apical sodium-dependent bile acid transporter (ASBT) mRNA, fecal bile acids and total steroids, and intestinal bile acid content were measured. All variables responded in a dose-dependent manner to PSY in the diet. Total liver cholesterol content was significantly reduced in all groups fed PSY compared to cellulose-fed controls [138(a), 105(b), 105(b) and 93(c) micromol (SEM = 4.2) for 0, 3.33, 6.67 and 10% PSY, respectively]. Activity of CYP7A was significantly greater in all groups fed PSY compared to the cellulose-fed controls [6.36(c), 16.92(b), 15.28(b) and 20.37(a) pmol x min(-1) x mg protein(-1) (SEM = 3.19) for 0, 3.33, 6.67 and 10% PSY, respectively]. These differences in CYP7A activity were similar to differences in CYP7A, HMGR and ASBT mRNA levels. Fecal bile acid and total steroid excretion as well as total intestinal bile acids were significantly greater in rats fed PSY-containing diets compared to 0% PSY-fed rats. These results suggest that the reduction in liver cholesterol involves modulating the size and composition of the bile acid pool via regulation of ileal ASBT, CYP7A and HMGR mRNA levels.     

Modified soybean affects cholesterol metabolism in rats similarly to a commercial cultivar

The consumption of soy protein lowers blood cholesterol in humans and animals. Breeding may alter the physiological effects of soybeans, such as its cholesterol-lowering property. Our hypothesis is that breeding affects the hypocholesterolemic effect of soy by modulating the expression of key hepatic enzymes related to cholesterol and bile acid biosynthesis, as well as altering fecal neutral and acidic steroid excretion. Therefore the aim of this study was to evaluate the effect of a new Brazilian soybean cultivar (UFV-116), lacking lipoxygenases 2 and 3, compared with a commercial cultivar (OCEPAR-19), on 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR) and cholesterol 7α-hydroxylase (CYP7A) mRNA expression and fecal steroid output in rats. Thirty-six male rats were fed UFV-116, OCEPAR-19, or casein as the protein source, with or without addition of dietary cholesterol (0.25%). Blood and liver cholesterol, HMGR and CYP7A mRNA abundance, and fecal excretion of steroids were measured. Blood and liver cholesterol levels were lowered by both soybean cultivars, with and without cholesterol, but UFV-116 was more effective when included in the cholesterol-free diet. Both soy diets promoted lower levels of HMGR mRNA, higher levels of CYP7A mRNA, and higher excretion of fecal secondary bile acids. There was higher fecal neutral steroid output when cholesterol was added to all diets. These data show that both soybean cultivars acted similarly in lowering serum and hepatic cholesterol; therefore, breeding did not affect the hypocholesterolemic effect of the new cultivar.     

Effects of saponins on bile acids and plasma lipids in the rat.

1. The effects of feeding isolated saponins on plasma lipid concentrations and on concentrations of biliary and faecal bile acids and neutral sterols were studied in the rat. 2. The animals were given one of four diets, i.e. a standard low-cholesterol synthetic diet, the diet + 10 g saponins/kg, the diet + 10 g cholesterol/kg, the diet + 10 g cholesterol + 10 g saponins/kg. 3. Saponins partially reversed the hypercholesterolaemia caused by the high-cholesterol diet and increased both the rate of bile acid secretion and the faecal excretion of bile acids and neutral sterols. The proportionate contribution of the primary bile acids (particularly chenodeoxycholic) to faecal excretion was also increased by saponins. 4. The results are discussed in relation to the hypothesis that saponins act by inducing the adsorption of bile acids by dietary fibre.     

Adzuki resistant starch lowered serum cholesterol and hepatic 3-hydroxy-3-methylglutaryl-CoA mRNA levels and increased hepatic LDL-receptor and cholesterol 7alpha-hydroxylase mRNA levels in rats fed a cholesterol diet

We examined the effects of adzuki bean resistant starch on serum cholesterol and hepatic mRNA in rats fed a cholesterol diet. The mRNA coded for key regulatory proteins of cholesterol metabolism. The control rats were fed 15 % cornstarch (basal diet, BD). The experimental rats were fed BD plus a 0.5 % cholesterol diet (CD), or a 15 % adzuki resistant starch plus 0.5 % cholesterol diet (ACD) for 4 weeks. The serum total cholesterol and VLDL + intermediate density lipoprotein + LDL-cholesterol levels in the ACD group were significantly lower than those in the CD group throughout the feeding period. The total hepatic cholesterol concentrations in the CD and ACD groups were not significantly different. The faecal total bile acid concentration in the ACD group was significantly higher than that in the BD and CD groups. Total SCFA and acetic acid concentrations in the ACD group were significantly higher than those in the CD group but there were no significant differences in the concentrations between the ACD and BD groups. The hepatic LDL-receptor mRNA and cholesterol 7alpha-hydroxylase mRNA levels in the ACD group were significantly higher than those in the CD group and the hepatic 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase mRNA level in the ACD group was significantly lower than in the CD group. The results suggest that adzuki resistant starch has a serum cholesterol-lowering function via enhancement of the hepatic LDL-receptor mRNA and cholesterol 7alpha-hydroxylase mRNA levels and faecal bile acid excretion, and a decrease in the hepatic HMG-CoA reductase mRNA level, when it is added to a cholesterol diet.     

Barley beta-glucan lowers serum cholesterol based on the up-regulation of cholesterol 7alpha-hydroxylase activity and mRNA abundance in cholesterol-fed rats

Barley, which is high in soluble dietary fiber (particularly beta-glucan), is thought to have hypocholesterolemic effects. The present study was performed to further elucidate the hypocholesterolemic actions of waxy barley, and the extent to which they can be attributed to beta-glucan. Male Sprague-Dawley rats (n=21) were fed control (fiber-free) diets, diets with the addition of 2.5%, refined beta-glucan or 30% waxy barley that provides approximately 2.5% beta-glucan in the diet for 2 wk. Body weight gain and food efficiency of rats were unaffected by diet. beta-glucan or waxy barley decreased serum levels of total cholesterol (p < 0.05) by 13.5% or 18.9%, and also decreased LDL-cholesterol 19.4% or 24.3%, respectively. Addition of refined beta-glucan or waxy barley to the diet resulted in greater bile acid excretions (p < 0.05) compared to the control group. The waxy barley diet up-regulated by 2. 3 times and the beta-glucan diet by 1.5 times the activity of cholesterol 7a-hydroxylase (CYP7A1). Hepatic CYP7A1 mRNA level paralleled the increases in enzyme activity. The results of this study suggest that the hypocholesterolemic effects of both beta-glucan and a waxy barley diet may be due to the enhancement of CYP7A1 expression resulting from increased fecal excretion of bile acids.     

Potato pulps lowered the serum cholesterol and triglyceride levels in rats

In our previous study, we demonstrated that retrograded starch, a kind of resistant starch, of beans reduced serum lipid levels in rats. In this study, we examined whether retrograded starch in potato pulps could reduce serum lipid concentrations. Rats were given diets containing 15 g of retrograded starch in potato pulps from the Benimaru potato (BM) or Hokkaikogane potato (HK) in a 100 g diet for 4 wk. At the 4th week, the total cholesterol level in the serum in the BM group and serum triglyceride (TG) level in the HK group were significantly lower than those in the control group. In the BM group, the contents of fecal bile acids were significantly higher than those in the control group. On the other hand, in the HK group, the hepatic mRNA level of fatty acid synthase (FAS) was significantly lower than that in the control group. The FAS mRNA level correlated with the mRNA level of sterol regulatory element-binding protein-1c (SREBP-1c), a regulator of expression of FAS, positively. These results suggested that BM pulp promoted the excretion of bile acids, which resulted in a low concentration of serum cholesterol. On the other hand, HK pulp inhibited the synthesis of fatty acids at the mRNA levels of FAS and SREBP-1c, which might lead to a reduction of the serum TG level.     

Corn fiber oil lowers plasma cholesterol by altering hepatic cholesterol metabolism and up-regulating LDL receptors in guinea pigs

To evaluate some of the mechanisms involved in the hypocholesterolemic effects of corn fiber oil (CFO), male Hartley guinea pigs were fed diets containing increasing doses of CFO [0 (control), 5, 10 or 15 g/100 g]. Total fat was adjusted to 15 g/100 g in all diets with regular corn oil. Diets contained 0.25 g/100 g cholesterol. A positive control group (LC) with low dietary cholesterol (0.04 g/100 g) was also included. Plasma LDL cholesterol concentrations were 32, 55 and 57% (P < 0.0005) lower with increasing doses of CFO. Compared with controls, intake of CFO resulted in 27-32% lower hepatic microsomal cholesterol (P < 0.0001), the regulatory pool of LDL receptor (LDL-R) expression. CFO intake resulted in favorable plasma and hepatic cholesterol concentrations, similar to those in guinea pigs fed the LC diet. Hepatic cholesterol 7alpha-hydroxylase (CYP7) activity was approximately 88% higher in guinea pigs fed the two higher dosages of CFO (P < 0.05). In parallel, CYP7 mRNA abundance was approximately 88% higher in guinea pigs fed all three CFO diets. CFO treatment also induced hepatic LDLR mRNA by 66-150% with significant differences at the highest CFO dose. These results suggest that CFO, as a result of decreased bile acid absorption, increased mRNA abundance and activity of CYP7. Because hepatic cholesterol is the substrate for CYP7, a lowering of cholesterol concentrations in the total and microsomal pools was observed. As a response to the depleted microsomal free cholesterol pool, the LDL receptor was up-regulated, drawing more cholesterol from plasma, thus leading to the observed decrease in plasma LDL cholesterol concentrations.     

Tartary buckwheat sprout powder lowers plasma cholesterol level in rats

We examined the effects of different types of buckwheat sprouts on the plasma cholesterol concentration, fecal steroid excretion and hepatic mRNA expression related to cholesterol metabolism in rats. Rats were fed a cholesterol-free diet with 5 g of Kitawasesoba common buckwheat sprout powder (KS)/100 g, 5 g of Hokkai T no. 8 tartary buckwheat sprout powder (HS-8)/100 g or 5 g of Hokkai T no. 9 tartary buckwheat sprout powder (HS-9)/100 g of diet for 4 wk. Control rats were fed a diet with alpha-cornstarch instead of sprout powder for 4 wk. There were no significant differences in food intake, body weight, liver weight or cecal contents among the groups. Plasma total cholesterol concentrations in the HS-8 and HS-9 groups were significantly lower than in the control group, whereas there was no significant difference between the KS and control groups. Fecal bile acid excretion and cecal short-chain fatty acid concentrations in the KS, HS-8 and HS-9 groups were significantly greater than in the control group. Furthermore, fecal matter excretion in the KS, HS-8 and HS-9 groups tended to be increased compared to the control group, with that in the HS-8 group being significantly higher than in the control group. Hepatic cholesterol 7alpha-hydroxylase mRNA expression in the KS, HS-8 and HS-9 groups and hepatic HMG-CoA reductase mRNA expression in the HS-9 group were significantly higher than in the control group. The results suggest that tartary buckwheat sprout powder has a serum cholesterol-lowering function by enhancing fecal bile acid excretion through increased fecal matter excretion or the upregulation of hepatic cholesterol 7alpha-hydroxylase mRNA expression in rats.     

Raw Chinese yam (Dioscorea opposita) promotes cecal fermentation and reduces plasma non-HDL cholesterol concentration in rats

We examined the effects of raw Chinese yam (Dioscorea opposita), containing resistant starch (RS), on lipid metabolism and cecal fermentation in rats. Raw yam (RY) and boiled yam (BY) contained 33.9% and 6.9% RS, respectively. Male Sprague-Dawley rats were fed a cholesterol-free, control (C) diet supplemented with or without 15 and 30 g of RY or BY/100 g for 3 wk. Plasma total cholesterol concentrations in the tail vein of rats fed the 30% RY diet were significantly lower than in the C group throughout the feeding period. Compared with the C group, non-HDL concentrations in arterial plasma in the 30% RY group was significantly reduced. Liver cholesterol concentration in rats fed the 30% RY diet was significantly higher compared with those fed the C diet. Hepatic cholesterol 7α-hydroxylase mRNA and fecal bile acid excretion were significantly higher in the BY, but not the RY group, compared with the C group. Fecal cholesterol excretion in the 30% RY group was greater compared with the C group. Hepatic microsomal triacylglycerol transfer protein mRNA was significantly lower in the 30% RY group compared with the C group. Cecal pools of acetate, propionate and butyrate were 113-257%, 181-476% and 410-789% greater in the RY group compared with the C group. These results suggest raw yam is effective as a source of RS and facilitates production of short chain fatty acid (SCFA), especially butyrate, in the rat cecum. In addition, RY has a plasma-cholesterol lowering effect, possibly due to the inhibited release of VLDL.     

Brewer's spent grain, serum lipids and fecal sterol excretion in human subjects with ileostomies

A crossover design studying lipid and apoprotein levels in serum and excretion of sterol, nitrogen and fat in ileostomy effluent was performed in 10 subjects fed diets with or without supplementation with brewer's spent grain, which is the residue of barley after the brewing of beer. More cholesterol, nitrogen, fat and energy were excreted in the ileostomy effluents when the subjects consumed a brewer's spent grain supplemented, high fiber diet than when they consumed a low fiber diet. No significant change was found in the daily net sterol excretion. The six subjects with low daily excretion of bile acids (less than 1000 mg/24 h) had increased cholesterol and net cholesterol and decreased bile acid excretion per day, and lowered serum LDL-cholesterol and apoprotein B levels after supplementation with brewer's spent grain. We propose that subjects with low daily bile acid excretion are suitable models for studying the effect of dietary changes on sterol excretion and serum lipid levels. Increased fecal cholesterol excretion is suggested to be the primary mechanism for the serum LDL-cholesterol lowering effect of brewer's spent grain.