Effects of resistant potato starch on cholesterol and bile acid metabolism in the rat

This study examines the effects of two types of resistant starch (RS), raw starch from uncooked potatoes and retrograded starch in the form of cooked and cooled potatoes, on cholesterol and bile acid metabolism in rats. Groups of 8 male Wistar rats were fed a semipurified diet containing 15% cellulose, freeze-dried raw potatoes, or freeze-dried cooked potatoes for four weeks. Serum cholesterol, liver cholesterol, and fecal steroid excretion were determined. Serum cholesterol was significantly higher and liver cholesterol was significantly lower in response to the cooked potato diet compared to the cellulose or raw potato diet. Total steroid excretion was significantly higher in rats fed the cooked potato diet (26.31 mg/d) compared to those fed the cellulose or raw potato diet (14.27 mg/d and 16.81 mg/d, respectively). Daily total bile acid excretion was significantly different among the three groups, with highest excretion seen in rats fed cooked potatoes. High daily excretion of lithocholic acid and hyodeoxycholic acid was observed in rats fed cooked potatoes. These results suggest that changes in the cecal microflora and in the production, pool size, and excretion of chenodeoxycholic acid and its derivatives may be responsible for alterations in cholesterol and bile acid metabolism observed with resistant starch feeding.     

BILE ACID MALABSORPTION IN CYSTIC FIBROSIS

Malabsorption of bile acids occurs in cystic fibrosis but not in celiac disease and is correlated with fecal fat excretion. Bile acid malabsorption may occur secondary to exocrine pancreatic deficiency.     

Effect of ethanol on lipoprotein synthesis and fecal sterol excretion

The effect of variable doses of ethanol on plasma lipoprotein composition, lipoprotein synthesis and fecal sterol excretion was examined in male, atherosclerosis susceptible squirrel monkeys. Primates were divided into three groups: 1) Controls fed isocaloric liquid diet; 2) Low Ethanol monkeys given liquid diet with vodka substituted isocalorically for carbohydrate at 12% of calories; and 3) High Ethanol animals fed diet plus vodka at 24% of calories. Circulating high density lipoprotein (HDL) free cholesterol and phospholipid, very low density-low density lipoprotein (VLDL-LDL) total cholesterol, and total plasma cholesterol and triglyceride were significantly elevated in High Ethanol primates compared to the other treatments. However, the percent distribution of cholesterol among the lipoprotein fractions was identical for the three groups. There were no significant differences in serum glutamate oxalo-acetate transaminase. High Ethanol primates also had significantly greater HDL free cholesterol specific activity following intravenous injection of ³H mevalonolactone compared to the other groups while radioactive VLDL-LDL free cholesterol was elevated in both High and Low Ethanol animals. Although, total fecal bile acid mass was significantly greater in both alcohol treatment groups compared to Controls, fecal neutral sterol specific activity was only higher in monkeys fed the high ethanol diet. This study provides evidence that ethanol at 24% of calories: 1) raises HDL cholesterol levels by enhancing lipoprotein synthesis; 2) increases the fecal output of newly synthesized cholesterol without causing liver dysfunction; and 3) maintains a constant relative distribution of cholesterol among lipoprotein classes.     

Trends in serum total cholesterol and dietary fat intakes in New Zealand between 1989 and 2009

Objective : To describe trends in serum cholesterol and dietary fat intakes for New Zealand adults between 1989 and 2008/09. Methods : Serum total cholesterol concentrations and dietary fat intakes were analysed for 9,346 New Zealanders aged 15–98 years (52% women) who participated in three national surveys in 1989, 1997 and 2008/09. Results : Population mean serum cholesterol decreased from 6.15 mmol/L in 1989 to 5.39 mmol/L in 2008/09. Mean saturated fat intake decreased from 15.9% of energy intake in 1989 to 13.1% in 2008/09. Between 1997 and 2008/09, unsaturated fat intake increased and fat from butter and milk decreased. Older adults had the largest decrease in serum cholesterol (1.35 mmol/L). Conclusions : The decrease in serum cholesterol is substantially larger than reported for many other high‐income countries, and occurred in parallel with changes in dietary fat intakes and, for older adults, increased use of cholesterol‐lowering medications. Implication : Given the demonstrated role of reduced saturated fat intake on lowering serum cholesterol, and as population average serum cholesterol levels and saturated fat intakes exceed recommended levels, initiatives to further encourage reductions in saturated fat are imperative.     

大豆蛋白在体外消化实验中对胆汁酸分布的影响

大豆蛋白同酪蛋白相比可在动物包括人体内降低血胆固醇浓度[1～ 3 ] ,但作用机制尚未清楚。可能的机制之一是 :大豆蛋白是一种非磷酸化蛋白 ,在摄入大豆蛋白后 ,肠腔内没有磷肽形成。已形成的钙磷沉淀物不能被磷肽和钙离子复合物所溶解 ,而是同胆汁酸结合 ,从而增加了粪胆汁酸的排出量 [4 ]。由于胆汁酸是胆固醇代谢的终产物 ,故肠道内胆汁酸的损失可导致血胆固醇浓度下降 [5] 。以上机制可称为非磷酸化学说[4 ] 。本研究采用体外消化实验 ,在模拟生理条件下 ,分析大豆蛋白同酪蛋白和脱磷酸酪蛋白相比对胆汁酸在蛋白质消化液的上清和沉淀中…     

Effects of trace components of dietary fat on cholesterol metabolism: phytosterols,oxysterols, and squalene

The effect of dietary fats on serum cholesterol is widely assumed to be due solely to the fatty acids and cholesterol they contain. Phytosterols, sterol oxidation products, and sterol precursors such as squalene, however, are often present in dietary fats. Little is known of the physiology of these substances in natural foods and most published diet studies do not consider them at all. Supplementation of the diet with high-dose phytosterols is now recommended for prevention of heart disease, but both recent and old data strongly suggest that the lower levels of phytosterols naturally present in vegetable fats may also reduce cholesterol absorption and serum cholesterol substantially. Moreover, unmeasured phytosterols may confound otherwise well-controlled diet studies because there is an inverse correlation between phytosterol and saturated fatty acid content of vegetable fats. Sterol oxidation products, many of which are found in foods, are potent regulators of lipoprotein and cholesterol transport pathways in vitro. Squalene is a phytosterol precursor abundant in olive oil that is at least partly absorbed and then quantitatively converted to cholesterol. The effects of dietary triglyceride-derived fatty acids have not been experimentally separated from the effects of trace fat components in most clinical studies. A better understanding of the activity of sterol-related dietary components is needed to reduce variability in diet studies, accurately assess the effects of dietary fatty acids and to maximize the effectiveness of dietary treatment for hypercholesterolemia.     

ASCORBIC ACID AND THE CATABOLISM OF CHOLESTEROL

Guinea pigs with a latent, chronic ascorbic acid deficiency were injected with 26-¹⁴C-cholesterol and the conversion of the labeled chofesterol into bile acids was estimated by following the output of ¹⁴CO₂ for several weeks. Deficient guinea pigs accumulated serum and tissue cholesterol and had a lower output of ¹⁴CO₂ than did the controls. In addition, the turnover time of the labeled cholesterol was less than that of contols. From these, as well as previous results, it was concluded that adequate tissue concentrations of ascorbic acid were necessary for conversion of cholesterol to bile acids.     

中国不同地区膳食脂质摄入量的分析

１９９２年中国总膳食研究在１９９０年的基础上做了适当的改进,将城市和农村的样品分别进行分析。本文报道了该项研究中膳食脂质部分的结果（包括总脂肪、胆固醇、脂肪酸）。除南方二区外,同一地区的城市和农村居民在脂肪、胆固醇的摄入量上有较大的差异。北方二区农村居民的脂肪摄入量明显不足,而北方一区城市居民脂质的摄入量较高,胆固醇摄入量已超过每人每日３００ｍ ｇ 的水平。南方居民膳食脂肪中多不饱和脂肪酸所占比例低而单不饱和脂肪酸所占比例高。基于以上分析,作者认为我国居民膳食脂质摄入情况基本合理,但由于地域差异较大,在进行膳食指导时（如关于补充ＥＰＡ,ＤＨＡ 的问题）应对不同地区的情况进行具体分析,有针对性地提出建议     

Guar gum and similar soluble fibers in the regulation of cholesterol metabolism: Current understandings and future research priorities

The hypocholesterolemic effects associated with soluble fiber consumption are clear from animal model and human clinical investigations. Moreover, the modulation of whole-body cholesterol metabolism in response to dietary fiber consumption, including intestinal cholesterol absorption and fecal sterol and bile acid loss, has been the subject of many published reports. However, our understanding of how dietary fibers regulate molecular events at the gene/protein level and alter cellular cholesterol metabolism is limited. The modern emphasis on molecular nutrition and rapid progress in ‘high-dimensional’ biological techniques will permit further explorations of the role of genetic polymorphisms in determining the variable interindividual responses to soluble fibers. Furthermore, with traditional molecular biology tools and the application of ‘omic’ technology, specific insight into how fibers modulate the expression of genes and proteins that regulate intestinal cholesterol absorption and alter hepatic sterol balance will be gained. Detailed knowledge of the molecular mechanisms by which soluble fibers reduce plasma cholesterol concentrations is paramount to developing novel fiber-based “cocktails” that target specific metabolic pathways to gain maximal cholesterol reductions.     

Acid production and conversion of konjac glucomannan during in vitro colonic fermentation affected by exogenous microorganisms and tea polyphenols

Impacts of exogenous microorganisms and tea polyphenols on acid production and conversion during in vitro colonic fermentation of konjac glucomannan (KGM) were assessed in this study. Colonic fermentation of KGM by the fecal extract of healthy adults resulted in a propionate-rich profile, as acetic, propionic, butyric and lactic acids production were 16.1, 13.0, 3.3 and 20.2?mmol/L, respectively. Inoculation of one of ten exogenous microorganisms in the fermentative systems increased acetic, propionic and butyric acids production by 50?230%, 9?190% and 110?350%, respectively, and also accelerated lactic acid conversion by 14?40%. Tea polyphenols in the fermentative systems showed clear inhibition on both acid production and conversion; however, this inhibition could be partially or mostly antagonised by the inoculated exogenous microorganisms, resulting in improved acid production and conversion. In total, Lactobacillus brevis and Sterptococcus thermophilus were more able to increase acid production, and the propionate-rich profile was not changed in all cases.     

Dietary Fats and Blood Pressure: A Critical Review of the Evidence

Comparisons of blood pressure patterns among populations suggest that low-fat diets or consumption of unsaturated fatty acids decrease blood pressure. However, in most single populations dietary fatty acids and total fat, as determined by diet history, are not significantly correlated with blood pressure. Dietary fatty acids, quantitated by levels in adipose tissue or plasma lipoproteins, had no consistent association with blood pressure. Dietary fatty acids and total fat were not predictive of the development of hypertension over four years in a large cohort of nurses in the United States. Although several dietary trials lacking randomized controls suggested effects of dietary fats on blood pressure, 11 of 12 controlled trials showed no significant effects. All seven double-blind trials, and the two trials of longest duration (one and five years), showed no effect of either varying the content of total fat or of exchanging polyunsaturated for saturated fatty acids. In summary, there is little convincing evidence that the amount or type of dietary fat, varied within customary dietary patterns, affects blood pressure levels in persons with normal or mildly elevated blood pressure.     

CHOLESTEROL FEEDING AFFECTS MICROSOMAL METABOLISM OF STEROIDS

Feeding cholesterol and bile acids to conventional and germ-free rats affects microsomal enzyme activities involved with the metabolism of such steroids. The most consistent effects, particularly on hydroxylases, were found with cholesterol, which may be a regulator of microsomal enzyme activities.     

Lyophilized carrot ingestion lowers lipemia and beneficially affects cholesterol metabolism in cholesterol–fed C57BL/6J mice

Summary Background Several lines of evidence indicate that diet rich in fruit and vegetable can protect against cardiovascular diseases by acting on cholesterol metabolism and on oxidative stress. Aim of the study The aim of this study was to assess whether daily carrot consumption (provided as lyophilized powder) could differentially influence the consequences of cholesterol supplementation on lipid metabolism and oxidative stress in C57BL/6J mice. Methods Fourteen mice were randomized in four groups. Mice were fed either control diets (without or with 0.25% cholesterol added) or lyophilized carrot enriched diets (20% wt/wt without or with 0.25 % cholesterol added) for 4 weeks. Cholesterol and triglycerides in plasma and in liver were measured at the end of the experimental period. Fecal excretion of sterols was evaluated. Vitamin E and carotenoid concentrations were also determined. Several biomarkers relative to oxidative stress such as FRAP (Ferric Reducing Ability of Plasma) and isoprostanes were investigated. Results Feeding the carrot diet resulted in a decrease of cholesterol (–41%) and triglycerides (–49 %) in plasma and in the liver (–41% and –39%, respectively) in animals fed cholesterol–supplemented diets. Carrot diet induced an increase of total neutral sterols fecal excretion, which inhibits digestive cholesterol absorption. Carrot diet increased antioxidant status in cholesterolfed mice as related by the 16% higher FRAP values. Although vitamin E was not affected by carrot diet, vitamin E/TG ratio was significantly higher in animals fed carrot diets. The carrot diet induced an increase of vitamin E in the heart in both cholesterol–free and cholesterol–supplemented mice suggesting a higher protection of this tissue. Conclusion This study shows that carrot ingestion decreases lipemia and improves antioxidant status in mice. Such results suggest that carrot intake may exert a protective impact against CVD linked to atherosclerosis. It is likely that these effects could be due to the synergistic effect of fiber and associated antioxidants.     

Impact of Fecal Microbiota Transplantation on Gut Bacterial Bile Acid Metabolism in Humans

Fecal microbiota transplantation (FMT) is a promising therapeutic modality for the treatment and prevention of metabolic disease. We previously conducted a double-blind, randomized, placebo-controlled pilot trial of FMT in obese metabolically healthy patients in which we found that FMT enhanced gut bacterial bile acid metabolism and delayed the development of impaired glucose tolerance relative to the placebo control group. Therefore, we conducted a secondary analysis of fecal samples collected from these patients to assess the potential gut microbial species contributing to the effect of FMT to improve metabolic health and increase gut bacterial bile acid metabolism. Fecal samples collected at baseline and after 4 weeks of FMT or placebo treatment underwent shotgun metagenomic analysis. Ultra-high-performance liquid chromatography-mass spectrometry was used to profile fecal bile acids. FMT-enriched bacteria that have been implicated in gut bile acid metabolism included Desulfovibrio fairfieldensis and Clostridium hylemonae. To identify candidate bacteria involved in gut microbial bile acid metabolism, we assessed correlations between bacterial species abundance and bile acid profile, with a focus on bile acid products of gut bacterial metabolism. Bacteroides ovatus and Phocaeicola dorei were positively correlated with unconjugated bile acids. Bifidobacterium adolescentis, Collinsella aerofaciens, and Faecalibacterium prausnitzii were positively correlated with secondary bile acids. Together, these data identify several candidate bacteria that may contribute to the metabolic benefits of FMT and gut bacterial bile acid metabolism that requires further functional validation.     

Further studies on the cholesterol-lowering effect of apple in human. Biochemical mechanims involved

Thirty volunteers participated in a metabolic study to measure the response of plasma cholesterol to apple consumption. On average, a reduction exceeding 10% was observed. However, the cholesterol-lowering effect of apple depended on the subjects. In 15 subjects the reduction was 11.7% to 29.2%, in the others the cholesterol decline was less than 10% or absent. Moreover, apples tended to increase the α:β ratio of the circulating lipoproteins. The biochemical mechanisms involved in the effects of apple are discussed with regard to the marked changes induced by apple consumption in laboratory animals. Apple could enhance the fecal excretion of bile acids, thereby stimulating the hepatic degradation of cholesterol. This process could also be facilitated both by a strong parallel diminution of the esterification of the newly synthesized sterol and by beneficial modifications in plasma lipoprotein cholesterol transport. These hypotheses, drawn from an extensive study in animals, warrant further investigations in humans under controlled metabolic conditions.     

我国居民膳食脂类摄入量的研究

目的:研究我国居民膳食脂肪、胆固醇和脂肪酸摄入量状况,为进行合理的膳食指导提供基础资料。 方法: 在我国北方和南方各选两个区,每个区包括3个省、市或自治区。 在每个省、市、自治区内选出3个具有代表性的调查点。 采用三日称重和记帐法进行膳食调查,记录烹调方法。以调查点为单位计算每个标准人(体重63 kg成年男子) 每日的食物消费量。将食物聚为12类,各类食物均为烹调后制成的混合样品。其中8类样品测定脂肪、脂肪酸含量,4类样品测定胆固醇含量。 计算出各个地区每人每日脂肪、胆固醇、脂肪酸的摄入量。 结果: 北方一区、北方二区、南方一区、南方二区居民每人每日脂肪摄入量分别为70.5 g, 46.5 g, 58.7 g, 71.0 g, 胆固醇摄入量分别为 329.6 mg, 128.5 mg, 400.9mg, 306.0 mg。 膳食脂肪的主要来源是肉类和蔬菜类食物。三个地区胆固醇的主要来源是蛋类食物,南方二区肉类食物提供的膳食胆固醇量与蛋类食物非常接近。四个地区约90%的膳食饱和脂肪酸是棕榈酸和硬脂酸, 90%的单不饱和脂肪酸是油酸。亚油酸是最主要的n-6系列多不饱和脂肪酸,α-亚麻酸是最主要的n-3系列多不饱和脂肪酸。 S∶M∶P的比例分别是, 北方一区1∶1.1∶1.1, 北方二区 1∶1.6∶1.3, 南方一区1∶1.6∶1.3, 南方二区 1∶1.5∶1。     

大豆蛋白降低大鼠血浆胆固醇机理的初步探讨

目的 初步探讨大豆蛋白在大鼠体内降低血胆固醇的可能机理.方法 Wistar雌性大鼠,经14天诱发高血胆固醇模型后,以2×2析因设计,分别喂饲含有20%酪蛋白或大豆分离蛋白和正常钙(0.59%)或高钙浓度(1.12%)的纯合成高脂饲料21天.实验结束前,测血浆总胆固醇浓度,收集3天粪便,测定脂肪、钙、磷、镁的消化率及粪胆汁酸排出量.结果 同酪蛋白组相比,其它各组动物的血浆胆固醇浓度及钙和磷的消化率显着下降(P<0.05).大豆蛋白组动物的脂肪消化率低于其它各组动物,而大豆蛋白高钙组动物的粪胆汁酸排出量高于其它各组动物.结论 本实验结果提示大豆蛋白在大鼠体内降血胆固醇机理可能与大豆蛋白本身的非磷酸化状态有关.