胆固醇影响大鼠脂肪代谢的机制研究

目的:研究胆固醇影响大鼠脂肪代谢的机制。方法:以添加1%胆固醇的AIN76合成饲料喂食Wistar大鼠4w,对照组不添加胆固醇。分别测血清甘油三酯(TG)、总胆固醇(TC)、磷脂(PL)、高密度脂蛋白(HDL-C)、血糖、游离脂肪酸(NEFA)浓度;测肝脏TG、TC、PL浓度以及苹果酸酶(ME)、葡萄糖6磷酸脱氢酶(G6PDH)、脂肪酸合成酶(FAS)、磷脂酸磷酸酶(PAP)和肉毒碱棕榈酰转移酶(CPT)活性、酰基辅酶A-胆固醇酰基转移酶(ACAT)、胆固醇7a-羟化酶(CYP7A)和羟甲基戊二酸单酰辅酶A还原酶(HMG-CoA reductase)mRNA。结果:胆固醇显著增加大鼠血液TC和非HDL-C浓度、降低HDL-C和TG浓度,使肝脏TC和TG浓度分别提高了20和4倍。胆固醇组大鼠肝脏ME活性降低40%、G6PDH活性降低70%、FAS活性降低50%,PAP活性降低15%,CPT的活性降低25%,肝脏FAS的mRNA量降低35%,CPT1和CPT2的mRNA量分别降低30%和50%。HMG-CoA还原酶mRNA量降低25%,而CYP7A和ACAT mRNA量分别增加了6.5和1.6倍。结论:高胆固醇饮食引起肝脏TG蓄积,但并不增加肝脏TG合成相关酶的活性和基因表达。     

孕期高蛋白饲料对子代大鼠脂肪酸合成酶和磷酸烯醇丙酮酸羧激酶的影响

目的探讨孕期膳食对子代肥胖和肥胖相关基因脂肪酸合成酶(FAS)和磷酸烯醇丙酮酸羧激酶(PEPCK)表达的影响。方法将Wistar孕鼠随机分为2组,分别食用标准饲料和高蛋白质饲料。所产雄性子代分为对照组和高蛋白质组。交叉哺乳,断乳后用标准饲料喂养至成年时,从对照组中随机抽取一部分大鼠(高脂对照组)与高蛋白质组的大鼠均喂饲高脂饲料,高脂诱导肥胖至实验结束。分期处死大鼠取材,应用荧光定量PCR法检测褐色脂肪中FAS及PEPCK mRNA的表达丰度。结果孕期高蛋白质饲料可降低子代断乳及高脂诱导肥胖后的体重及肥胖率(P<0.05);高蛋白质组褐色脂肪组织中PEPCK mRNA的表达持续低于对照值和高脂对照组,而FAS mRNA在诱导肥胖前、后分别低于对照组和高脂对照组。结论孕期适当增加蛋白质摄入,可通过程序性降低子代FAS和PEPCK基因的表达,预防子代成年高脂诱导肥胖的发生。     

半饥饿状态下高脂喂养对大鼠肉毒碱及脂类代谢的影响

目的探讨高脂饲料喂养半饥饿状态下大鼠肉碱及脂肪代谢的变化.方法用限食的方法造成半饥饿大鼠模型,观察给予普通饲料的半饥饿对照组与给予高脂饲料的实验组血浆肉碱浓度、附睾脂肪垫重量,肝游离氨基酸和脂肪含量,血中甘油三酯、游离脂肪酸以及游离氨基酸浓度等指标的变化.结果给予高脂饲料的实验组动物血浆游离肉碱浓度显著低于正常组和实验前水平(P＜0.05);肝脂肪含量、血游离脂肪酸浓度均显著高于半饥饿对照组(P＜0.05);两组半饥饿动物血和肝脏中大部分游离氨基酸浓度显著低于正常组,半饥饿对照组其浓度降低更显著,同时合成肉碱的赖氨酸和蛋氨酸浓度也显著降低.结论高脂饲料喂养半饥饿状态下,游离肉碱浓度降低,脂类代谢负担加重,提示在高脂半饥饿状态下需补充外源性肉碱.     

Effects of branched-chain amino acid supplementation on plasma concentrations of free amino acids, insulin, and energy substrates in young men

The present study was conducted to examine alterations in the concentrations of plasma free amino acids, glucose, insulin, free fatty acids (FFAs), and urea nitrogen induced by branched-chain amino acid (BCAA) supplementation in young men. Overnight-fasted subjects ingested drinks containing 1 or 5 g of a BCAA mixture (weight ratio of 1 : 2.3 : 1.2 for isoleucine : leucine : valine), and blood was intermittently collected for 3 h after ingestion. Ingestion of the BCAA mixture resulted in significant increases in the plasma concentrations of individual BCAAs, corresponding to the amounts of amino acids ingested. On the other hand, plasma concentrations of methionine and aromatic amino acids tended to decrease in the trial with 5 g BCAAs, suggesting that BCAA ingestion affects the metabolism of these amino acids. The ingestion of BCAAs temporarily increased plasma insulin levels and affected plasma concentrations of FFAs, but had almost no effect on glucose or urea nitrogen.     

Soy protein isolate and its hydrolysate reduce body fat of dietary obese rats and genetically obese mice (yellow KK)

This study examined in dietary obese and genetically obese rodents the effects of soy protein isolate (SPI) and its hydrolysate (SPI-H) on the rate of body-fat disappearance. Male Sprague-Dawley rats (4-16 wk old) and yellow KK mice (6-10 wk old) were made obese by feeding high-fat diets containing 30% fat. They were then fed energy-restricted, low-fat (5.0%), and high-protein (35% casein, SPI, or SPI-H) diets for 4 wk at 60% of the level of the energy intake of rodents on laboratory chow. The body-fat contents of rats and mice fed a high-fat diet were 27.3 and 33.6 g/100 g body weight, respectively, at the end of the obese period. For rats, the apparent absorbability of dietary energy and fat was significantly lower in the SPI and SPI-H groups than in the casein group, but vice-versa for nitrogen balance. Body-fat content in mice fed SPI and SPI-H diets was significantly lower than in those fed the casein diet. In rats, plasma total cholesterol level was lower with the SPI-H diet, and plasma glucose level was lower with the SPI and SPI-H diets than with the casein diet. These results indicate that SPI and SPI-H are suitable protein sources in energy-restricted diets for the treatment of obesity.     

Dietary sea cucumber cerebroside alleviates orotic acid-induced excess hepatic adipopexis in rats

ABSTRACT: BACKGROUND: Nonalcoholic fatty liver disease (NAFLD) is a prevalent chronic liver disease in industrialized countries. The present study was undertaken to explore the preventive effect of dietary sea cucumber cerebroside (SCC) extracted from Acaudina molpadioides in fatty liver rats. METHODS: Male Wistar rats were randomly divided into four groups including normal control group, NAFLD model group, and two SCC-treated groups with SCC at 0.006% and 0.03% respectively. The fatty liver model was established by administration of 1% orotic acid (OA) to the rats. After 10d, serum and hepatic lipid levels were detected. And the serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities were also determined. Besides, to gain the potential mechanism, the changes of key enzymes and gene expressions related to the hepatic lipid metabolism were measured. RESULTS: Dietary SCC at the level of 0.006% and 0.03% ameliorated the hepatic lipid accumulation in fatty liver rats. SCC administration elevated the serum triglyceride (TG) level and the ALT, AST activities in OA-fed rats. The activities of hepatic lipogenic enzymes including fatty acid synthase (FAS), malic enzyme (ME) and glucose-6-phosphatedehydrogenase (G6PDH) were inhibited by SCC treatment. And the gene expressions of FAS, ME, G6PDH and sterol-regulatory element binding protein (SREBP-1c) were also reduced in rats fed SCC. However, dietary SCC didn't affect the activity and mRNA expression of carnitine palmitoyltransferase (CPT) in liver. Besides, suppression of microsomal triglyceride transfer protein (MTP) activity was observed in SCC-feeding rats. CONCLUSIONS: These results suggested that dietary SCC could attenuate hepatic steatosis due to its inhibition of hepatic lipogenic gene expression and enzyme activity and the enhancement of TG secretion from liver.     

Protein hydrolysate vs free amino acid-based diets on the nutritional recovery of the starved rat

Summary Background and Aims To test the hypothesis that a peptide-based enteral product was equivalent to a low-fat, free amino acid-based formula in the nutritional and functional recovery of the starved rat. Methods Sixteen male Wistar rats were starved for 3 days. Then, rats were randomised to a whey protein hydrolysate-based diet or a free amino acid-based diet and refed for 3 days. The experiment was designed to provide the same energy intake in both groups. The parameters studied included body weight gain, nitrogen retention, plasma free amino acid concentrations, muscle glutamine concentrations and glutathione levels in gut mucosa and liver. Results Weight gain was statistically higher on the peptide-based diet than on the elemental diet after rhe refeeding period. This difference in weight gain was associated with a statistically higher nitrogen retention. Plasma and muscle free glutamine concentrations were higher in rats fed the whey protein hydrolysate-based diet than those in rat refed the free amino acid-based diet, even though the glutamine intake was higher in the latter group. Glutathione concentrations in liver and gut mucosa were similar in the groups. Conclusion We conclude that enteral diets containing peptides were more effective than a diet containing free amino acids in the nutritional recovery of the starved rat. Received: 17 May 2000, Accepted: 1 September 2000     

Comparative effects of protein, protein hydrolysate and amino acid diets on nitrogen metabolism of normal, protein-deficient, gastrectomized or hepatectomized rats

The effects of diets containing protein, protein hydrolysate or an amino acid mixture on nitrogen metabolism of normal and severely protein-deficient rats and on rats after gastrectomy and hepatectomy were compared. In experiment 1, rats weighing about 80 g were fed one of three experimental diets containing casein, protein hydrolysate or an amino acid mixture for 28 d. In experiment 2, rats weighing about 270 g were fed a protein-free diet for 40 d, and then one of the above three experimental diets for 14 d. In experiment 3, rats weighing about 220 g were totally gastrectomized and fed one of the three experimental diets for 21 d. In experiment 4, rats weighing about 210 g had about 70% of the liver resected, and then were fed one of the three experimental diets for 15 d. In all four experiments, daily food intake, daily body weight gain, nitrogen balance, urinary nitrogen compounds, body composition and hematologic values were measured. In normal, protein-deficient and hepatectomized rats, most results were similar for the groups fed protein, protein hydrolysate or amino acid diets, except that urinary ammonia was higher in the group fed the amino acid diet than in the other two groups. For about 10 d after total gastrectomy, food intake and growth of the animals fed the protein diet were lower than in the other two groups.     

Intact protein versus free amino acids in the nutritional support of thermally injured animals

This study compared the nutritional effects of intact protein with that of constituent amino acids as the sole source of nitrogen in a burn guinea pig model. Forty-five guinea pigs bearing a gastrostomy feeding tube were given 30% total body surface area, full thickness flame burn and were randomized into four groups. Group I (n = 12) and group III (n = 15) received a diet containing whey protein, while group II (n = 9) and group IV (n = 9) received an otherwise identical diet containing free amino acids in a whey protein pattern. Full strength continuous intragastric feeding was initiated immediately postburn in groups I and II, but a 72-hr adaptive period was provided in groups III and IV. Resting metabolic expenditure was measured by indirect calorimetry on postburn days 2, 6,9, and 13. After 14 days of enteral feeding, the animals were killed. Immediate enteral feeding of intact protein or free amino acids reduced postburn hypermetabolic response (p less than 0.01). However, the intact protein was found to maintain body weight and provide nitrogen retention better than the amino acid mixture (p less than 0.05). The animals on the intact protein diet also showed statistically significant benefits in carcass, liver, and gastrocnemius muscle weights and in serum albumin, transferrin and C3 levels. It is concluded that intact protein is superior to free amino acids for nutritional support following burn injury.     

下丘脑腹内侧核损伤性肥胖大鼠急性期脂肪代谢相关酶活性研究

目的 :　观察下丘脑腹内侧核损伤性肥胖大鼠在自由进食状态下脂肪合成与分解代谢的变化。方法 :　雌性 SD大鼠分为下丘脑腹内侧核损伤肥胖组 (VMH)和下丘脑腹内侧核非损伤对照组 (假手术 ) ,于下丘脑腹内侧核手术 1 w后 ,留取血样、肝脏、皮下脂肪、子宫外周和肠系膜脂肪组织以及腓肠肌分别测定生化指标、脂肪合成酶和分解酶活性。结果 :　在自由进食状态下VMH血清胰岛素水平显著高于对照组 ,而血浆游离脂肪酸显著低于对照组。大鼠肝脏微粒体甘油三酯转运蛋白 (MTP)、肝脏磷脂酰磷酸水解酶 (PAP)、苹果酸酶 (ME)、葡萄糖 - 6-磷酸脱氢酶(G6PDH)以及子宫外周脂肪组织 ME和肠系膜脂肪组织 ME、G6PDH的活性均高于对照组。与对照组相比 ,VMH组子宫外周、肠系膜脂肪组织和腓肠肌激素敏感脂酶 (HSL)活性没有变化 ,皮下脂肪组织的 HSL活性升高。在 VMH组 ,皮下脂肪组织、子宫外周脂肪组织、肠系膜脂肪组织以及腓肠肌中的脂蛋白脂酶活性均显著升高。结论 :　下丘脑腹内侧核损伤性肥胖大鼠自由进食状态下肝脏合成和转运甘油三酯能力增强 ,脂肪组织如子宫外周和肠系膜脂肪组织的脂质合成和储存增多 ;而外周组织如肌肉组织和皮下脂肪组织的脂肪分解和动员也增加     

不同肥胖易感性大鼠体内的氧化应激反应

目的观察不同肥胖易感性大鼠的氧化应激反应和抗氧化能力的差异。方法 40只雄性Wistar大鼠(200～220g)随机分为高脂饲料组(30只)和正常对照组(10只),高脂饲料组大鼠给予高脂饲料6周后依据体重增加量筛选出肥胖易感(OP)大鼠和肥胖抵抗(OR)大鼠各10只,OP组和OR组大鼠继续喂养高脂饲料,正常对照组大鼠给予基础饲料,13周末处死大鼠,采集样本,测定血清中超氧化物歧化酶(SOD)、丙二醛(MDA)、谷胱甘肽过氧化物酶(GSH-Px)以及空腹血糖(FBG)、胰岛素、甘油三酯(TG)、总胆固醇(TC)、游离脂肪酸(FFA)等指标。结果 OP组大鼠SOD含量显著低于OR组和正常对照组;OP组大鼠GSH-Px水平显著低于OR组;OP组MDA浓度显著高于正常对照组;同时OP组总能量摄入、体脂含量、血糖、血脂、血清胰岛素、胰岛素敏感指数(ISI)和游离脂肪酸水平都与OR组大鼠的差异有显著性,而OR组大鼠与正常对照组相比的差异无显著性。结论与肥胖抵抗大鼠相比,肥胖易感大鼠的氧化应激水平增高,抗氧化能力降低,血糖血脂升高并出现胰岛素抵抗。     

Sulfur-containing amino acid requirements of growing dogs

Three experiments were undertaken to establish the total sulfur-containing amino acid requirement of growing dogs. In experiment 1, six Labradors failed to grow normally when fed a soy isolate diet of 0.28% methionine with 0.18% cystine but grow well when the food was supplemented to either 0.57% or 0.74% methionine. In the next experiment, 12 Labradors and 21 beagles were fed the soy isolate diet containing either 0.39%, 0.57% or 0.74% methionine in the presence of 0.15% cystine for 12 weeks. Dogs fed 0.39% methionine had significantly lower body weights, nitrogen retentions, food intakes and feed efficiencies than their littermates fed the two higher levels. This diet provided 468 kcal metabolizable energy (ME) per 100 g, therefore a level of 116 mg total sulfur-containing amino acids (TSAA)/100 kcal ME was not adequate for growth. The lowest level found to be adequate was 0.57% methionine, or 154 mg TSAA/100 kcal ME, which is similar to the requirement of other young omnivores. A final experiment with a free amino acid diet indicated that a level of 117 mg TSAA/100 kcal ME while inadequate for Labradors, may be sufficient for some beagles, highlighting differences between intact protein and free amino acid diets and suggesting possible breed differences.     

Effect of dietary methionine and arginine on uric acid excretion of cocks fed a protein-free diet.

Cocks were fed a protein-free diet supplemented with methionine plus arginine or glutamic acid for 25 days to investigate the effect of these amino acids on fecal and urinary nitrogen excretion. Addition of either methionine plus arginine or glutamic acid did not change the fecal nitrogen excretion. Methionine plus arginine supplementation reduced the urniary nitrogen excretion compared to the protein-free diet, whereas glutamic acid supplementation increased it. The reduced urinary nitrogen excretion resulting from supplementation with methionine plus arginine was mostly accounted for by a reduction in uric acid excretion. In the methionine plus arginine group, free amino acid analysis showed that free glutamine and glutamic acid content significantly decreased in liver while no differences were found in plasma. Since glutamine may play an important role in the formation of uric acid for chickens, the reduced amount of free glutamine and glutamic acid in the liver of cocks fed the diet suplemented with methionine plus arginine might account for the reduced excretion of uric acid, and therefore for the nitrogen sparing action of methionine plus arginine in chickens fed a protein-free diet.     

The role of dietary protein in hepatic lipogenesis in the young rat

1. The effect of varying dietary levels of casein (40-140 g/kg) on hepatic lipogenesis and the levels of hepatic fatty acid synthetase (FAS), glucose-6-phosphate dehydrogenase (EC 1.1.1.49; G6PD), malic enzyme (EC 1.1.1.40; ME), citrate cleavage enzyme (EC 4.1.3.8; CCE), acetyl CoA carboxylase (EC 6.4.1.2; AcCx), glucokinase (EC 2.7.1.2; GK), and pyruvate dehydrogenase (PDH) was examined in young, growing rats. 2. The activities of AcCx, FAS, G6PD and in vivo fatty acid synthesis were generally found to increase with increased dietary protein. 3. The levels of GK and PDH were not related to dietary protein. 4. ME decreased with increasing dietary protein. 5. The results demonstrate a dissociation between hepatic fatty acid synthesis and ME and suggest that when rats consume low-protein diets the NADPH needed for fatty acid synthesis is generated primarily by ME but that as the level of dietary protein is increased the contribution of ME is reduced while that of the phosphogluconate pathway becomes more important.     

元宝枫叶提取物的减肥作用研究

目的研究元宝枫叶提取物对营养性肥胖大鼠的减肥作用及机制。方法利用营养饲料制备大鼠肥胖模型,分别给予不同组别大鼠元宝枫叶提取物10、30和100mg/kg BW。于实验结束测定体重、体脂、食物消耗量、脂/体比及肝脏脂肪酸合酶活性指标。实验持续31天。结果与模型对照组比较,30mg/kg与100mg/kg组3周后体重和实验终体重均显著降低(P<0.01),能降低肥胖模型大鼠体脂重量和脂/体比(P<0.05),可抑制脂肪酸合酶活性(P<0.05)。结论元宝枫叶提取物具有减肥功能。     

断乳后不同饲料构成对高脂膳食大鼠肥胖发生的影响

目的研究断乳后不同饲料构成对高脂膳食大鼠肥胖发生的影响。方法雄性Wistar大鼠出生后24天断乳,按体重随机分为A、B、C三组,分别给予高碳水化合物供能的基础饲料、高蛋白质供能饲料和高不饱和脂肪供能饲料。3周后均转为基础饲料。2周后再按体重将A组分为A1、A2两组,A1组继续基础饲料,A2、B、C组则转为以猪油为主的高脂膳食,6周后结束实验。分别在不同处理期末每组随机处死8只动物,称重、留取脂肪组织,计算脂体比,采血检测血糖、血脂和激素指标。结果断乳后喂饲高不饱和脂肪饲料可以显著降低高脂膳食大鼠的体重、体脂肪含量和脂体比(P<0.05),显著降低胰岛素水平、提高胰岛素敏感性(P<0.05),显著增加胰高血糖素、甲状腺激素等促脂解激素的水平(P<0.05),增加瘦素敏感性(P<0.05),改善高脂膳食大鼠的瘦素抵抗。早期喂饲高蛋白质饲料也有一定的降低体重、体脂肪含量和促脂解作用趋势,但是该组的血糖值高于A2组。结论断乳后给予高不饱和脂肪饲料可以显著抑制高脂膳食大鼠的肥胖发生。     

D-核糖对高脂喂饲小鼠胰岛素抵抗的影响

目的观察D-核糖对高脂喂饲的C57BL/6小鼠血糖、血脂及胰岛素等的影响,探讨D-核糖对改善高脂膳食引起的糖耐量异常和胰岛素抵抗的可能性。方法 8 w龄C57BL/6雄性小鼠36只,随机分成正常对照、高脂对照、低剂量的D-核糖+高脂组(高脂+2.5%核糖)和高剂量的D-核糖+高脂组(高脂+5%核糖),喂饲12 w,记录摄食量和体重变化。11w进行葡萄糖耐量试验(OGTT),并计算葡萄糖曲线下面积(AUC)。干预12w处死,进行血生化指标及胰岛素检测。结果高脂+5%核糖组小鼠的血糖水平低于高脂对照组(P<0.05);高脂+2.5%核糖和高脂+5%核糖组糖耐量曲线下面积(P<0.01)、血清胰岛素水平(P<0.05)及胰岛素抵抗指数HOMA-IR(P<0.01)均显著低于高脂对照组。血清胆固醇(CHO)、高密度脂蛋白胆固醇(HDL-C)在核糖干预后的变化并不明显(P>0.05);高脂+5%核糖组血清低密度脂蛋白胆固醇(LDL-C)、血清甘油三酯(TG)及游离脂肪酸(FFA)低于高脂对照组(P<0.05)。结论 D-核糖可以改善高脂饲料喂饲小鼠的糖耐量异常和胰岛素抵抗。[营养学报,2013,35(2):142-145]     

孕期高蛋白膳食对子代大鼠解偶联蛋白和肉毒碱棕榈酰基转移酶的影响

目的探讨孕期膳食对子代肥胖和肥胖相关基因解偶联蛋白（UCP）和肉毒碱棕榈酰基转移酶1（CPT1）表达的影响,寻找肥胖预防和治疗的靶标,寻求合理的孕期膳食。方法将Wistar孕鼠按随机数字表法分为两组,孕期全程分别食用标准膳食（SD）和高蛋白质膳食（HPD）。所产雄性子鼠分别为对照组（CON）和高蛋白质组（HP）,均由CON组的母亲喂养,24d断乳,用SD喂养至成年后,将CON组大鼠按随机数字表法分为两组：一组继续食用SD（CON）;另一组食用高脂膳食（HFD）,为高脂对照组（HFCON）。同时HP组也食用HFD,HFCON和HP组高脂诱导肥胖至实验结束。分期处死大鼠,检测血清甘油三酯（TG）和褐色脂肪中UCP2、UCP3及CPT1mRNA的表达丰度。结果孕期HPD可降低子代断乳前后的体重和高脂诱导肥胖后的体重及肥胖率;断乳时和高脂诱导肥胖后HP组的血清TG分别低于CON和HFCON组;HP组UCP3和CPT1的表达持续高于CON和HFCON组,UCP2的表达在断乳后也持续高于CON和HFCON组;动态观察发现断乳时和高脂诱导肥胖后CPT1的表达均明显升高,高脂诱导肥胖后UCP2、UCP3的表达也明显升高;但在食用SD至成年时CPT1的表达较断乳时略有下降,UCP3的表达与断乳时基本一致。结论孕期适当增加蛋白质摄人可降低子代成年高脂诱导肥胖发生的风险;程序性升高子代UCP2、UCP3和CPT1基因的表达;UCP2、UCP3和CPT1可通过参与脂肪酸氧化调节肥胖的发生。