Short‐term feeding of fermentable dietary fibres influences the gut microbiota composition and metabolic activity in rats

This study investigated the effects of dietary fibres on gut bacterial abundance and metabolic activity in rats fed short‐term. Faecal samples from rats fed for 7 days showed differences in the effects of dietary fibres on gut bacterial populations. Broccoli fibre, inulin, potato fibre and potato resistant starch significantly increased the faecal Bacteroides‐Prevotella‐Porphyromonas group compared with cellulose. Growth of pathogenic bacteria such as Clostridium perfringens, Escherichia coli and Enterococcus spp. was decreased significantly in rats fed barley β‐glucan, citrus pectin, inulin and broccoli fibre diets. An increase in Bifidobacterium spp. and butyric acid levels, the so‐called bifidogenic and butyrogenic effects, was observed in rats fed inulin and potato fibre diets. Organic acid concentrations and polysaccharide contents in the rat faeces confirm the fermentability of dietary fibres in the gut. This study demonstrates the positive effects of plant‐sourced dietary fibres on gut microbiota composition and metabolic activity.     

Effects of kiwifruit and mixed dietary fibre on faecal properties and microbiota in rats: a dose–response analysis

In this study, a rat model was used to explore the interaction of kiwifruit with co‐consumed mixed dietary fibre. Rats were used in three consecutive trials in which faecal properties and composition, and bacterial populations were examined. In trial 1 diets, content of a dietary fibre mixture (DFM; Raftiline–citrus fibre–wheat fibre) was increased from 0% to 20%. In trial 2, dried kiwifruit pulp (KFP) content was increased from 0% to 20%. In trial 3, KFP was increased from 0% to 20% in a diet containing a 20% basal content of the DFM. The KFP caused a small dose‐dependent increase in faecal bulk and water‐holding capacity and had much less effect than the DFM. Faecal bacterial populations examined were stable across all diets and intakes of DFM and KFP. The disappearance of fermentable fibre during hind gut passage was not reduced with increasing KFP. Therefore, kiwifruit may not only have the beneficial effect of extending fermentation distally in the colon through gut activation, but may do so without disrupting the bacterial ecosystem and its functions.     

Effects of dietary broccoli fibre and corn oil on serum lipids, faecal bile acid excretion and hepatic gene expression in rats

To determine the effects of broccoli fibre and corn oil on lipid metabolism, male Sprague-Dawley rats were fed diets containing high (30%) or low (5%) corn oil, in combination with either 7.5% broccoli fibre or cellulose, for 4 months. High corn oil groups had significantly lower serum cholesterol and triglycerides than had low corn oil groups (p < 0.001). Broccoli fibre also lowered serum cholesterol and triglyceride levels compared to cellulose fibre. Faecal bile acid concentrations were higher in high corn oil-fed rats than in low corn oil-fed rats, with broccoli fibre inclusion in high corn oil diets resulting in higher faecal bile acid concentrations. Regardless of corn oil level, broccoli fibre supplementation in the diet resulted in an increase (p = 0.018) in hepatic cytochrome P450, family 7A1 (CYP7A1) expression. High corn oil feeding resulted in reduced expression of fatty acid synthase (FAS) and increased expression of carnitine palmitoyl transferase 1a (CPT1a) and 3-hydroxy-3-methyl-coenzyme A reductase (HMGCR) (p < 0.05). Our findings suggest that high dietary corn oil and broccoli fibre have beneficial effects on lipid metabolism. Corn oil lipid-lowering effects may be due to alteration of hepatic expression of genes involved in lipid synthesis and increased rate of cholesterol catabolism to bile acids. Broccoli fibre may also act via its physical properties to reduce enterohepatic bile acid recycling and intestinal lipid absorption, and increase luminal binding of bile acids, resulting in increased faecal bile acid excretion.     

Proanthocyanidin metabolites associated with dietary fibre from in vitro colonic fermentation and proanthocyanidin metabolites in human plasma

Proanthocyanidins (PAs) or condensed tannins, a major group of dietary polyphenols, are oligomers and polymers of flavan‐3‐ol and flavan‐3, 4‐diols widely distributed in plant foods. Most literature data on PAs' metabolic fate deal with PAs that can be extracted from the food matrix by aqueous‐organic solvents ( extractable proanthocyanidins). However, there are no data on colonic fermentation of non‐extractable proanthocyanidins (NEPAs), which arrive almost intact to the colon, mostly associated to dietary fibre (DF). The aim of the present work was to examine colonic fermentation of NEPAs associated with DF, using a model of in vitro small intestine digestion and colonic fermentation. Two NEPA‐rich materials obtained from carob pod (Ceratonia siliqua L. proanthocyanidin) and red grapes (grape antioxidant dietary fibre) were used as test samples. The colonic fermentation of these two products released hydroxyphenylacetic acid, hydroxyphenylvaleric acid and two isomers of hydroxyphenylpropionic acid, detected by HPLC‐ESI‐MS/MS. Differences between the two products indicate that DF may enhance the yield of metabolites. In addition, the main NEPA metabolite in human plasma was 3,4‐dihydroxyphenyl acetic acid. The presence in human plasma of the same metabolites as were detected after in vitro colonic fermentation of NEPAs suggests that dietary NEPAs would undergo colonic fermentation releasing absorbable metabolites with potential healthy effects.     

Effects of fat replacement with a mixture of collagen and dietary fibre on small calibre fermented sausages

Effects of fat replacement on physicochemical, microbial and sensory properties of fermented sausages were determined after drying process and 4 weeks of storage. Fermented sausages were formulated with 20% pork back fat (control), and three reduced‐fat treatments were prepared by replacing 25%, 50%, and 75% of fat with a mixture of collagen, dietary fibre and ice (1:1:8). TBARS values of reduced‐fat treatments were significantly lower compared with control after drying (P ≤ 0.05). As fat replacing ratio increased, fat content decreased significantly (P ≤ 0.05), whereas moisture, protein and ash content increased significantly (P ≤ 0.05). There was no marked difference between the treatments in terms of microbial analysis, sensory colour, flavour, off‐flavour or overall acceptability (P > 0.05) during refrigerated storage. Therefore, replacing pork back fat with a mixture of collagen and dietary fibre in fermented sausages may contribute to reduce lipid oxidation and maintain sensory properties during storage.     

Effects of dietary fibre extracts on calcium absorption in the rat

The effects on calcium absorption of several fibre extracts (which differed greatly in their chemical compositions, phytate concentrations, and proportions of soluble and insoluble fibre) and of phytate, as sodium phytate, were investigated in rats. Samples of fibre from apple, orange, pea, sugarbeet, barley and wheat were obtained from Sofalia (France). Calcium absorption (using a ⁴⁷Ca tracer method) in 9-week-old rats from a purified diet, containing fibre at a level of 50 g/kg, was reduced by wheat and wheat-TDF fibre preparations and was unaffected by apple, orange, pea, sugarbeet, barley, pectin and guar gum, compared to the cellulose-containing diet. Calcium absorption was also reduced by increasing phytate concentration in the range 0 to 30 mmol/kg diet. Overall, the results suggest that calcium absorption is not affected by fibre components per se, (i.e. indigestible polysaccharides) and that the reduction in calcium absorption observed with wheat and wheat-TDF fibres is due to their phytate contents.     

Effects of dietary leucine and phenylalanine on pancreas development,enzyme activity,and relative gene expression in milk-fed Holstein dairy calves

This study aimed to investigate the effect of dietary supplementation with leucine and phenylalanine on pancreas development, enzyme activity, and related gene expression in male Holstein calves. Twenty male Holstein calves [1 d of age, 38 ± 3 kg of body weight (BW)] were randomly assigned to 1 of the following 4 treatment groups with 5 calves in each group: control, leucine supplementation (1.435 g/L of milk), phenylalanine supplementation (0.725 g/L of milk), and leucine and phenylalanine (1.435 + 0.725 g/L of milk). The diets were made isonitrogenous with the inclusion of alanine in each respective treatment. The feeding trial lasted for 8 wk, including 1 wk for adaption and 7 wk for the feeding experiment. Leucine tended to increase the concentration of total pancreatic protein (mg/kg of BW). Phenylalanine increased the concentrations of plasma insulin, cholecystokinin, and pancreatic DNA (mg/g) and the expression of trypsin gene but decreased the pancreatic protein:DNA ratio and tended to decrease the pancreas weight (g/kg of BW). No differences were observed in total pancreatic DNA (mg/pancreas and mg/kg of BW), pancreatic protein (mg/pancreas), or activities of α-amylase, trypsin, and lipase. The relative expression levels of the genes encoding α-amylase and lipase did not differ among the 4 groups. The supplementation of both leucine and phenylalanine showed an interaction on the pancreas weight (g and g/kg of BW) and a tendency of an interaction on the pancreatic protein concentration (mg/g of pancreas and mg/kg of BW) and the plasma glucose concentration. Leucine tended to increase the size of the pancreatic cells, whereas phenylalanine tended to increase the number of pancreatic cells. However, neither AA affected the activities of the pancreatic enzymes of the calves. These results indicate that leucine and phenylalanine supplementation in milk-fed Holstein calves differentially affect pancreatic growth and development.     

Effects of alfalfa protein concentrate on spatial learning and memory in weaned rats

Alfalfa has been used as animal feedstuff and nowadays as a human dietary supplement in undernourished populations. Therefore, we considered whether a 65 °C prepared unfractionated alfalfa protein concentrate (UAPC) could be capable of supporting the normal body growth of weaned rats as well as their spatial learning, memory and astroglial organization. Rats were fed isocaloric (1.8 kJ g^?1) and isoproteic (100 g kg^?1) diets for 28 days containing UAPC or casein as their protein source. Thereafter, animals were submitted to a Morris water maze test (MWM) followed by an evaluation of memory retention. At the end of the spatial learning tests, the cerebral cortex, hippocampus and hypothalamus astrocyte population was morphologically and immunohistochemically analyzed. UAPC had two limiting essential amino acids that seem to have retarded rates of growth and caused temporary learning and memory alterations. The UAPC diet induced a transitory memory loss as well as a recoverable memory retention delay after returning to a commercial ration. The astrocyte cell number was decreased in the parietal cortex and arcuate nucleus but not in the hippocampus; however, the latter showed a minor reduction in their cell density. UAPC did not adequately support the development of weaned rats, and decreased the number of astrocytes in the cerebral cortex and hypothalamus. Copyright © 2005 Society of Chemical Industry     

柚皮膳食纤维对去势雌性大鼠肠道发酵的影响

研究柚皮中提取的膳食纤维对去势雌性大鼠肠道发酵的影响。将40只SD成年雌鼠随机分为5组,4组大鼠做双侧卵巢切除手术,一周后分为空白组、柚皮原料组、柚皮可溶性膳食纤维组和柚皮不溶性膳食纤维组;用伪切除同龄大鼠作对照(Sham组)。喂养4周后解剖,测定各组体重、盲肠组织重量、盲肠内容物中游离氨、短链脂肪酸以及微生物的数量等指标。结果显示,饲料中添加柚皮原料、柚皮可溶性膳食纤维和柚皮不溶性膳食纤维均能显著增加去势雌性大鼠短链脂肪酸含量和盲肠面积(p<0.05)、降低盲肠内容物pH和游离氨的含量以及增加肠道内有益菌的数量并抑制有害菌生长。柚皮膳食纤维能够明显促进去势雌性大鼠肠道发酵作用,改善肠道环境。      

Effects of dietary fat level on the xenobiotic metabolism enzymes activity and antioxidant enzymes in rats

Male Wistar rats received fat-free diet or diets containing 5, 10 and 30% of fat (sunflower oil + lard, 1:1) for 4 weeks. The direct relationship between dietary fat level and ethoxyresorufin O-dealkylase activity of CYP1A1, methoxyresorufin O-dealkylase activity of CYP1A2, pentoxyresorufin O-dealkylase activity of CYP2B1 and testosterone 6beta-hydroxylase activity of CYP3A was found. Activities of key enzymes of phase II xenobiotic metabolism (total activity of glutathione transferase, activity of UDP-glucuronosyle transferase) and antioxidant enzymes (catalase, glutathione peroxidase, glutathione reductase, paraoxonase-1 and heme oxygenase-1) also increased with higher dietary fat level.     

Effect of the insoluble dietary fibre from oil palm fat-free flour on digestibility in rats

This work shows the results of comparing the effects of the insoluble dietary fibre from oil palm fat-free flour and cellulose on the growth, weight, humidity and composition of faeces in adult rats (Sprague–Dawley). Five groups of rats were fed for 4 weeks. The control group was fed with a diet free of fibre, and the remaining four groups with diets containing 50 or 100 g of either oil palm fat-free flour or cellulose, respectively. The adaptation period was 4 days. The evolution of growth and food intake did not vary significantly p<0.05 regardless of the type of diet. On the other hand, faeces excretion increased by 3.3–4.7 g/day in the groups of rats fed with oil palm fat-free flour, while it increased by only 3.1–4 g/day in diets based on cellulose. A higher content of water was observed in the faeces of rats fed with insoluble dietetic fibre from oil palm fat-free flour. The apparent digestibility of the insoluble dietary fibre of oil palm fat-free flour was low (35%), showing resistance to fermentation. The digestibility of the protein tended to decrease more with the insoluble dietary fibre of oil palm than with the cellulose, which may be related. ©     

Mexican lime peel: Comparative study on contents of dietary fibre and associated antioxidant activity

High dietary fibre (DF) powders from Persian and Mexican lime peels were prepared and their dietary fibre composition and antioxidant capacities determined. The total dietary fibre (TDF) contents of both varieties were high; 70.4% and 66.7%, respectively. Both lime peel varieties had an appropriate ratio of soluble/insoluble fractions. The water-holding capacities (WHC) of DF concentrates are high (6.96–12.8 g/g). The WHC was related to the soluble dietary fibre (SDF) which was higher in the DF concentrate of Mexican lime. As part of this analysis, the antioxidant activity (AA) of total extractable polyphenols (TEP) was studied, using three methods: azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) ABTS radical-scavenging activity, α,α-diphenyl–picrylhydrazyl (DPPH) and β-carotene-linoleic acid antioxidant assay. DF concentrates of Persian lime peel had greater polyphenol contents than those of Mexican lime peel. The polyphenols associated with the DF in both lime peel varieties showed a good AA. From a nutritional standpoint, DF lime concentrates may be suitable as food additives.     

Effects of dietary fiber on some indices of the activity of the gastrointestinal tract in rats]

Now nobody doubts of necessity and importance of inclusion of vegetative food fibres (as the separately isolated biopolymers--lignin, cellulose, gemicellulose, pectine substances; in composition of a food fibres complex or introduction last in traditional products of nutrition) in a daily human diet. Is proved by experimental researches, that the investigated kinds of food fibres are non-toxic, do not influence on internal structure, are well perceived by animals and can be recommended as the additive in a human diet.     

Changes in dietary fibre, phenolic acids and activity of endogenous enzymes during rye bread-making

The content and composition of dietary fibre (DF), phenolic acids and ferulic acid dehydrodimers as well as the activity of endogenous enzymes were measured in freeze-dried samples of rye wholemeal, dough and bread during the rye bread-making process. Activities of !-amylase, #-xylosidase, !-arabinofuranosidase, and cinnamoyl esterase(s) were found in extracts of wholemeal and in dough after mixing and proofing, whereas activity of endo-xylanase was only found in the wholemeal. As a result of dough mixing, the content of total DF decreased by 21%, which was caused by a decrease in the amount of water-unextractable (WUE) DF. The content of water-extractable (WE) DF was unchanged during the bread-making process, but the relative content of WE DF increased. The content of total ester-bound phenolic acids and ferulic acid dehydrodimers decreased from 1575 µg/g in the wholemeal to 1472 µg/g in rye bread. The most pronounced effect occurred in an imitated sour dough (acidified with lactic and acetic acid instead of by lactic acid bacteria). The observed changes in content and solubility of DF in the dough could be explained by the activity of endogenous enzymes and mechanical disaggregation, whereas the changes observed in the imitated sour dough indicated that some acid hydrolysis might also have taken place.     

Effect of raw and cooked onion dietary fibre on the antioxidant activity of ascorbic acid and quercetin

The effect of cell walls (dietary fibre) from raw and cooked onions (Allium cepa L. red skinned variety) on two dietary antioxidants, l-ascorbic acid (AA) and quercetin, was investigated. Cell walls isolated from onion parenchyma tissues were incubated with AA or quercetin in HEPES buffer at pH 6.5 and 37 °C for 2 h. The resulting supernatants were analysed by the ferric reducing antioxidant power (FRAP) assay and cyclic voltammetry (CV). Results show that onion cell walls effectively reduced AA degradation, but provided no protective effect against quercetin degradation, and may increase the degradation. This suggests some type of favourable interaction of the cell wall components with AA but not with quercetin. Cooking facilitates the extraction of cell wall polysaccharides and hence influences the extent of interaction of cell wall components and antioxidants. The redox behaviour of the antioxidants, the polysaccharide components of cell walls, and their relative extractabilities all appear to have important influences on the interactions.     

Effects of dietary fibre and soybean oil on the digestion of extruded and roller-dried maize starch

The effects of soybean dietary fibre (SDF), microcrystalline cellulose (MCC), konjac glucomannan (KGM), soluble soybean polysaccharide (SSPS) and soybean oil (SO) on in vitro digestion of extruded maize starch (EMS) and roller-dried maize starch (RDMS) samples were investigated. Adding MCC, particularly in high doses, induced slow digestion in EMS and RDMS samples, but not after adding SDF. KGM and SSPS addition reduced starch hydrolysis of RDMS but did not have a significant effect on EMS, whereas SO addition reduced starch hydrolysis of EMS but had no effect on RDMS. Principal component analysis demonstrated that the addition of MCC, SO, KGM (0.51%), and SSPS (0.51%) to EMS and KGM (0.51%) to RDMS were the best choices to slow the hydrolysis of starch, compared with that of other additives. These findings provide useful information on the selection of exogenous additives in the development of low glycaemic index products for maize starch.