Effect of pectin, wheat bran and cellulose on serum lipids and lipoproteins in rats fed on a low- or high-fat diet

1. Four groups of adult male Sprague-Dawley rats were fed for 6 weeks on a diet with a low-fat content (50 g/kg) and another four groups were given a diet rich in fat (250 g/kg) and cholesterol (12 g/kg). In both cases, the basal diets were either fibre-depleted or supplemented with cellulose (60 g/kg), wheat bran (100 g/kg) or low-methoxyl pectin (100 g/kg). 2. Low-methoxyl pectin displayed the most hypocholesterolaemic effect and decreased the cholesterol content of the very-low-density lipoproteins (VLDL) and low-density lipoproteins (LDL), when the low-fat diet was given. When rats were fed on the high-fat diet, pectin no longer had a hypocholesterolaemic effect but still decreased the VLDL-cholesterol content. Pectin lowered serum triglyceride and VLDL-triglyceride levels only when the low-fat diet was given. 3. Wheat bran exerted no hypocholesterolaemic effect in rats fed on the low- and high-fat diets, but decreased the cholesterol content of VLDL and lowered serum triglycerides and VLDL-triglycerides when the high-fat diet was given. 4. Purified cellulose had no significant effect on plasma lipids. 5. As shown by multivariance analysis, low-methoxyl pectin and wheat bran both beneficially modified the serum triglyceride and cholesterol variables except VLDL-triglycerides. However, the magnitude of the effect of each individual type of fibre was dependent on the fat and cholesterol content of the diet, suggesting the existence of different mechanisms of action.     

Effects of dietary cellulose, pectin and oat bran on the small intestine in the rat

The present study was undertaken to determine if three sources of dietary fiber would alter length, weight, DNA, protein or enzyme activity in the small intestine since various fibers are known to decrease intestinal absorption. Rats were fed semipurified diets that contained either 20% cellulose (C), 20% oat bran, 5% pectin (P) or no fiber source (FF). Leucine aminopeptidase activity were significantly greater in the P and C groups when compared with the FF group. There were no significant differences in sucrase activity. Animals in the P group had heavier and longer small intestine and heavier mucosa than the FF group. There were no significant differences in total mucosal DNA or protein. These results indicate that two sources of dietary fiber, cellulose and pectin, can change leucine aminopeptidase activity in the small intestine.     

Effect of wheat bran on serum lipids: influence of particle size and wheat protein

OBJECTIVE: Wheat fiber appears to protect from cardiovascular disease despite its lack of consistent effect on serum lipids. We therefore wished to determine whether reported inconsistencies in the effect of wheat bran resulted from differences in particle size or its high gluten content. METHODS: Two studies were conducted. In one-month metabolic diets, 24 hyperlipidemic subjects consumed breads providing an additional 19 g/d dietary fiber as medium or ultra-fine wheat bran and extra protein (10% of energy as wheat gluten). In two-week ad libitum diets, 24 predominantly normolipidemic subjects consumed breakfast cereals providing an additional 19 g/d of dietary fiber as coarse or a mixture of ultra-fine and coarse wheat bran with no change in gluten intake. Both studies followed a randomized crossover design with control periods when subjects ate low-fiber breads and cereals respectively with no added gluten. Fasting blood lipids were measured on day zero and at the end of each phase. RESULTS: Wheat bran had no effect on total, LDL or HDL cholesterol irrespective of particle size or level of gluten in the diet. However, consumption of increased gluten in the metabolic study was associated with a 13+/-4% reduction in serum triglycerides (p = 0.005) which was not seen in the normal-gluten ad libitum study. CONCLUSIONS: The protective effect of wheat fiber in cardiovascular disease cannot be explained by an effect of wheat bran in reducing serum cholesterol although in hyperlipidemic subjects displacement of carbohydrate by gluten on the high-fiber phases was associated with lower serum triglycerides.     

Stimulation of intestinal cytokinetics and mucin turnover in rats fed wheat bran or cellulose

Rats were fed defined diets containing no fiber, 10% wheat bran or 10% cellulose, and intestinal morphology and cytokinetics were assessed by light microscopy and autoradiography, respectively. In bran-fed animals, there were no differences in morphological appearance of the jejunum, in the number of cells/villus column or in numbers of goblet cells compared to controls. Autoradiographic analysis, at one and 24 h after [3H]thymidine, however, suggested an increased turnover and villus transit of intestinal cells. There was also a 2.5 fold increase in incorporation of labeled sulfate, and a 2-fold increase in [3H]glucose incorporation into total intestinal glycoproteins and mucins. Similar, albeit less dramatic results were obtained in rats fed diets containing cellulose. These studies provide evidence that diets containing certain fiber derivatives can alter aspects of intestinal cell turnover, and support the earlier morphological observations suggesting increased goblet cell secretory activity in response to feeding these fiber derivatives.     

The effect of wheat bran and pectin on paracetamol absorption in the rat.

1. The absorption of an oral dose of paracetamol was measured in rats given either a basal fibre-free diet, or the basal diet with either pectin or bran added. 2. Urinary excretion of the oral dose was significantly greater during the first 8 h in the pectin-fed rats compared with those on basal diet, though cumulative excretion after 72 h was the same. 3. Free paracetamol levels in the plasma were significantly higher in the pectin-fed rats compared with those on basal diet at 30, 60, 90 and 120 min after the oral dose. 4. The plasma half-life of intravenously-injected paracetamol was shorter in the pectin-fed rats than in those on basal diet alone, but the antipyrine half-lives were not significantly different. 5. Pectin feeding had no effect on either the apparent volume of distribution of paracetamol and antipyrine, or on the rate of gastric empyting. 6. Perfusion of the whole length of the small bowel showed a significantly greater capacity for paracetamol absorption in the pectin-fed rats. 7. Bran had no effect on paracetamol absorption. 8. It was concluded that dietary fibre intake affects drug absorption and that the effect varies with the type of fibre. Unexpectedly pectin accelerates rather than retards absorption of paracetamol, though the mechansim of this effect is unknown.     

Effect of bran and cellulose on lipid metabolism in obese female Zucker rats

The effects on lipid metabolism of bran and cellulose added to a low-cholesterol purified diet were studied in female obese Zucker rats. The obese Zucker rat was chosen for the experiment because of its sensitivity to dietary changes with regard to lipid metabolism. Cellulos, as well as bran, had an effect on lipid metabolism, which is expressed as an increase in the excretion of fecal bile acid and cholesterol and, in the case of bran feeding, as a decrease in liver cholesterol level and an increase of fecal fat excretion. The increased excretion rate of cholesterol and bile acids did not result in a reduction of the plasma cholesterol levels, which suggests a compensatory mechanism in the form of either an increase of hepatic cholesterol synthesis and/or changes within the body cholesterol pools. The increased excretion of fecal fat that occurred when bran was added to the diet, is not likely to influence cholesterol metabolism, since fecal fat excretion only appeared to form a small percentage of the total fat intake. Bran as well as cellulose caused a significant increase in fecal wet weight and a decrease in transit time. Though both cellulose and bran are capable of binding bile acid, cholesterol and/or fat, the intestinal transit time and the fecal bulk might also be a cause of increased steroid excretion. The fact that our results are inconsistent with those of some investigations described in the literature but in agreement with the findings of other workers, again stresses the primary need for a better chemical characterization of the various fiber sources.     

The influence of diets based on whole wheat, wheat flour and wheat bran on exocrine pancreatic secretion in pigs

Six pigs, initially 40 kg live weight, were prepared with a duodenal pouch for collection of pancreatic juice to assess the influence of the type and amount of dietary fiber on exocrine pancreatic secretion. Four isonitrogenous diets were fed to each pig: W (whole wheat); WBS (whole wheat, wheat bran, wheat starch); WFS (whole wheat, wheat flour, wheat starch); and FC (wheat flour, wood cellulose). Wheat and wheat fractions came from the same batch of wheat. Crude fiber and dietary fiber (nonstarch polysaccharide) contents of diets W, WBS, WFS and FC (g/kg), respectively, were 40.8, 101.8; 63.7, 201.2; 20.5, 50.3; and 39.0, 60.7. Mean volumes of pancreatic juice (mL/24 h) for diets W, WBS, WFS and FC, respectively, were 4108, 4560, 2556 and 1757. Total enzymic and electrolyte concentrations were not significantly affected by diet changes, but mean protein and amylase outputs were lower for diet FC than for the others. It was concluded that the principal effect of increasing the dietary fiber content of the diets was to increase the volume of pancreatic juice and that this may have been due to noncellulosic components of the dietary fiber.     

Effect of a standardized wheat bran preparation on serum lipids in young healthy males.

Feeding of a chemically standardized coarse wheat bran product in a dose of 0.5 g/kg body weight per day over a period of 4 weeks in young healthy male volunteers did cause a significant reduction in total serum cholesterol as well as in total serum triglycerides of 10 and 24%, respectively. Very low density lipoprotein-, high density lipoprotein-, and low density lipoprotein-cholesterol levels tended to diminish during bran feeding. The most marked reduction was observed in the high density lipoprotein- cholesterol fraction. Although the duration of this study was relatively short, it is concluded, that these results could have therapeutic consequences for the dietary management of hyperlipidemia. However, the lowering of high density lipoprotein-cholesterol could also be interpreted as unfavorable since an inverse relationship between high density lipoprotien-cholesterol levels and the occurrence of coronary heart disease has been established.     

Effect of coarse wheat bran fiber and exercise on plasma lipids and lipoproteins in moderately overweight men

The effects of the American Association of Cereal Chemists coarse wheat bran fiber and exercise were evaluated in 20 males, aged 24 to 35 yr, and at least 10% above ideal weight. Thirteen of the subjects participated in a 4 mile walk-jog run program 3 times weekly. In a cross-over design with diets switched midway through the experiment, both the exercising and sedentary groups consumed isocaloric amounts of either white bread or white bread containing wheat bran (0.5 g/kg body weight). Plasma total and lipoprotein cholesterol and triglycerides, body weights, and percentage body fats were determined at 0, 6, and 12 wk. No consistent effects were observed as a result of the wheat bran feeding on any of the parameters measured. Exercise training tended to decrease body weights and percentage body fats, and was associated with significantly increased (p less than 0.05) plasma high-density lipoprotein cholesterol levels and high-density lipoprotein cholesterol to low-density lipoprotein cholesterol ratios. After a rise in triglycerides at wk 6, a significant decline (p less than 0.05) back to base-line values was observed at wk 12 for the exercised subjects.     

果胶对大鼠血脂及抗氧化功能的影响

目的 研究不同剂量的果胶对高脂血症大鼠的血脂及抗氧化功能的影响。方法 根据血清总胆固醇和体重将Wistar大鼠随机分为5组，以正常饲料和高脂饲料为对照组，低、中、高剂量组分别喂饲不同水平(5％，10％，20％)的果胶，测定血脂和抗氧化功能指标。结果 各剂量水平果胶均可显著降低大鼠的摄食；同高脂对照组相比。中剂量和高剂量组大鼠血清总胆固醇(TC)、甘油三脂(TG)水平显著降低。且中剂量组血清高密度脂蛋白胆固醇(HDL-C)水平提高，各剂量组血清丙二醛(MDA)水平均降低，低剂量组和中剂量组的血清超氧化物歧化酶(SOD)和谷胱甘肽过氧化物酶(GSH-Px)水平无显著性变化。结论 果胶对高脂血症大鼠的血脂有调节作用，并且降低其体内的脂质过氧化水平；高剂量果胶对大鼠机体产生副作用。     

Dietary wheat bran lowers colonic pH in rats

The effect of chronic dietary wheat bran supplementation on the pH of gastrointestinal contents was examined in thirty-one Sprague-Dawley rats. Ten control rats received a fiber-free diet while twenty-one rats were fed the same diet plus a 20% wheat bran supplement. The fiber-fed rats developed a greater acidity of intestinal contents: cecal pH was 6.30 +/- 0.33 in the controls (P less than 0.01). These changes in gastrointestinal pH may be of relevance to the nutrient modulation of gastric and colonic tumor development.     

The effect of wheat bran on the absorption and accumulation of cadmium in rats

1. The major purpose of the present study was to determine whether the addition of wheat bran to endosperm crisp bread in a composite diet given to rats for 6 weeks causes an increase in the accumulation of cadmium in the rats due to the Cd content in the bran, or whether binding factors in the bran, such as dietary fibre and phytic acid, reduce or prevent the accumulation of this Cd. A second purpose was to determine whether the accumulation of Cd can be estimated by measuring the absorption of 109Cd given in a single meal of the diet. 2. Three groups of eight rats were fed on one of three diets. Half of each diet consisted of a basal mixture of starch, protein, oil, minerals and vitamins. The remainder consisted of crisp breads based on refined wheat flour (endosperm group), wheat flour + bran in equal amounts (bran group) and wheat flour + Cd to give a Cd content similar to that of the bran group (endosperm + Cd group). After 41 d on the diets, the rats were deprived of food but not water for 12 h and then given a 5 g test meal of their respective diets with 109Cd added. After 3 h the remaining 109Cd-labelled diets were replaced with the unlabelled diets for 3 h before the rats were killed. 3. The total Cd contents in the wall of the proximal small intestine, including mucus, and in the liver and kidneys were highest in the endosperm + Cd group and lowest in the endosperm group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of oat bran, rice bran, wheat fiber, and wheat germ on postprandial lipemia in healthy adults.

Six normolipidemic males ingested on separate days a low-fiber test meal [2.8 g dietary fiber (TDF)] containing 70 g fat and 756 mg cholesterol, enriched or not with 10 g TDF as oat bran, rice bran, or wheat fiber or 4.2 g TDF as wheat germ. Fasting and postmeal blood samples were obtained for 7 h and chylomicrons were isolated. Adding fibers to the test meal induced no change in serum glucose or insulin responses. The serum triglyceride response was lower (P less than or equal to 0.05) in the presence of oat bran, wheat fiber, or wheat germ and chylomicron triglycerides were reduced with wheat fiber. All fiber sources reduced chylomicron cholesterol. Cholesterolemia decreased postprandially for 6 h and was further lowered in the presence of oat bran. Serum apolipoprotein (apo) A-1 and apo B concentrations were not affected. Thus, dietary fibers from cereals may reduce postprandial lipemia in humans to a variable extent.     

Wheat bran and wheat germ: effect on digestion and intestinal absorption of dietary lipids in the rat

We investigated the effects of fiber-rich wheat bran and wheat germ on dietary fat and cholesterol assimilation. Rats were given a test meal containing [14C]triolein and [3H]cholesterol. After various digestion periods, addition of the wheat fractions (10% of meal solids) did not modify the lipid gastric emptying rate. Gastric and intestinal triglyceride lipolysis was significantly reduced when wheat fractions were present. The mucosal uptakes of [14C]lipids and [3H]cholesterol were significantly modified by the wheat fractions after 1 and 2.5 h. No shift in the site of intestinal absorption and no change in the distribution of labeled lipid in the intestinal mucosa was observed. Plasma [14C]lipids and [3H]cholesterol were significantly decreased by both wheat fractions whereas these increased cecal accumulation of dietary lipids and cholesterol. Thus wheat bran and wheat germ alter fat and cholesterol processing in rats. A mechanism of action accounting for the data observed in proposed.     

Effect of reduced phytate wheat bran on zinc absorption

The rise in plasma zinc after the ingestion of 765 mumol (50 mg) elemental zinc was measured over 6 h in three groups of healthy subjects who, in a second test, also consumed a standard wheat bran, a reduced phytate, high fibre processed bran or rice-based, low phytate, low fibre breakfast cereal (Rice Krispies). Standard bran, reduced phytate bran and Rice Krispies all significantly decreased the area under the plasma zinc time curve (AUC) compared to the zinc alone test. The AUC obtained with standard bran was significantly lower than that after reduced phytate bran (mean +/- s.e.: -5.9 +/- 2.7 vs 18.5 +/- 4.2 mumol.h/l, P less than 0.001). The percentage reductions in AUC produced by the test meals were: standard bran 106.4 +/- 2.4, reduced phytate bran 75.9 +/- 4.8, Rice Krispies 46.3 +/- 10.4 per cent, P less than 0.01). Histidine, taken with standard bran in a small subgroup of subjects, tended to improve zinc absorption but the difference was not statistically significant.     

Effect of microparticulated wheat bran on the physical properties of bread

Wheat bran and flour mixtures were used in a bread formulation to improve its quality characteristics. Wheat bran was microparticulated using a jet mill, and this microparticulated wheat bran (MWB) was substituted for a portion of wheat flour. As the MWB content increased, water-holding capacity, hardness and springiness increased while the swelling property decreased slightly. The hardness of bread containing MWB was lower than that made with commercial whole wheat flour (WWF). Bread containing 7% MWB had a higher specific volume (8.3%) than that of WWF bread. Enthalpy of dough decreased with increasing MWB content, and peak viscosity and breakdown decreased with increasing setback. Inner crust structures of bread containing MWB showed a slight reduction in gelatinization and gluten development in comparison with wheat bread. These results indicate that MWB could be used as a diet-enriching bread ingredient while maintaining bread quality.     

Effects of dietary fiber from wheat, corn, and soy hull bran on excretion of fecal bile acids in humans

Effects of dietary fiber on bile acid excretion and fecal bile acid concentration have been studied for seven subjects fed 26 g of either soft white wheat bran, corn bran, soybean hulls, or hard red spring wheat bran. Results indicate that even in a controlled study using a metabolic word, individual subject variation has a major impact on fecal bile acid excretion. This observation has not been fully appreciated in previous human studies. No significant change in the composition of fecal bile acids could be associated with the decrease in serum lipid levels previously reported. A method for the isolation and quantitation of fecal bile acids is described which does not require purification by thin-layer chromatography. A preliminary study of lyophilized fecal samples stored at -10 to -30 degrees C showed very little or no change in bile acid content. Samples stored at room temperatures for 11 months showed a substantial reduction in bile acid content.     

Response to dietary wheat bran in the exocrine pancreas and intestine of rats

Rats were fed a fiber-free (FF) mixture or the same diet with a supplement of 20% wheat bran (WB). After 2 weeks, the pancreas contained higher levels of amylase and trypsin in rats fed WB. In response to a meal, the intestine contained more lipase activity in the WB group. The dry weight of material and protein level in the intestinal contents were also elevated in the WB group. The size of the intestinal villi had not changed, but it did contain more goblet cells. The results indicate that consumption of wheat bran can lead to changes in the exocrine pancreas, perhaps associated with shifts in gut hormones, and may effect absorption by increasing the bulk of material as well as enhancing mucus production in the intestine.