Effect of raw and heat–moisture‐treated high‐amylose corn starches on the process of digestion in the rat digestive tract

High‐amylose corn starch (HAS) is widely known as a resistant starch foodstuff. We developed heat–moisture‐treated high‐amylose corn starch (HMT‐HAS) that was more resistant to enzymatic hydrolysis. Resistant starch contents of HAS and HMT‐HAS using the enzymatic–gravimetric method were found to be 30% and 65% respectively. Rats were given 10% ordinary corn starch (CS), HAS or HMT‐HAS by meal feeding for 10 days. The caecum contents increased and the caecal pH was lower after their diets were supplemented with HAS and HMT‐HAS. Starch contents increased in the upper and the lower small intestine with HAS and HMT‐HAS. Caecal starch with HAS and HMT‐HAS was more than that with CS. Particularly, caecal starch with HMT‐HAS was seven times more than that with HAS. There were no differences in starch content in the large bowel between CS and HAS, but the content increased with HMT‐HAS. These results suggested that HAS and HMT‐HAS were resistant to digestion and absorption in the small intestine, and any indigestible starches reached the caecum. In the caecum, HAS was hydrolysed almost completely by intestinal bacteria; however, some HMT‐HAS escaped bacterial hydrolysis. This escaped HMT‐HAS reached the large bowel and was excreted in the faeces. © 1999 Society of Chemical Industry     

Effect of pectin on plasma lipids and caecal enzyme activity in rutin‐supplemented mice

BACKGROUND: Few previous reports have considered the effects of dietary fibre on the plasma lipids and caecal enzyme activity of mice fed a rutin‐supplemented diet. This investigation studied the effects of pectin on the plasma lipids and caecal enzyme activities of mice fed a diet supplemented with the quercetin glycoside rutin. RESULTS: Male mice were randomly divided into two groups and fed either a pectin–rutin (PR) diet or a cellulose–rutin (CR) diet for 14 days. Plasma cholesterol and triglyceride concentrations and caecal β‐glucosidase and β‐glucuronidase activities were measured. The plasma cholesterol and triglyceride concentrations were significantly higher in the CR diet group, as were the caecal β‐glucosidase and β‐glucuronidase activities. The caecal β‐glucuronidase/β‐glucosidase activity ratio was significantly higher in the PR diet group, indicating differences in the metabolic activity of the intestinal flora. CONCLUSION: The PR diet greatly affected the caecal enzyme activities. A pectin diet supplemented with the quercetin glycoside rutin might affect the lipid metabolism and metabolic activity of the intestinal flora. The plasma lipid‐lowering effects of the PR diet might have been partially caused by the metabolic actions of the intestinal gut flora. Copyright © 2009 Society of Chemical Industry     

The effect of dietary fibre on bacterial densities in the rat intestine

When non-absorbable food polysaccharides were included in the diet of rats, changes in the distribution of bacteria in intestinal contents were seen. Male Wistar rats were fed a starch-containing fibre-free diet, or a similar diet in which guar gum (40 g kg⁻¹) or cellulose (100 g kg⁻¹) were substituted for an equivalent portion of starch. A fourth group received a commercial pelleted feed. After a 4-week feeding period, the densities (viable count per g contents) of aerobic and anaerobic bacteria in the lumen of the small intestine and caecum were estimated and the concentration of short chain fatty acids (SCFA) in the caecal contents measured.The proximal small intestine from the pellet-fed and the guar-fed rats contained a significantly higher density of anaerobic bacteria than the fibre-free group or the rats fed cellulose. In the caecum, the guar-fed rats had a higher density of anaerobic bacteria than the fibre-free controls, whilst the cellulose-fed group had a lower density. SCFA concentrations in the caecal contents of these three groups were similar. However, although the concentration of SCFA in the caecal contents of the pellet-fed animals was higher than any other group, the density of bacteria was significantly lower than in either the guar-fed or fibre-free animals.It was concluded that dietary fibre influences the distribution of anaerobic bacteria in the small intestine of the rat and alters both the numbers of bacteria and the level of SCFA in the caecum.     

Change in Flavonoid Composition and Antioxidative Activity during Fermentation of Onion (Allium cepa L.) by Leuconostoc mesenteroides with Different Salt Concentrations

The aim of this study is to investigate the change in flavonoid composition and antioxidative activity during fermentation of onion (Allium cepa L.) by Leuconostoc mesenteroides with different NaCl concentrations. In order to qualify and quantify the flavonoids during fermentation of onion, 7 flavonoids, [quercetin 3,7‐O‐β‐d ‐diglucopyranoside (Q3,7G), quercetin 3,4′‐O‐β‐d ‐diglucopyranoside (Q3,4′G), quercetin 3‐O‐β‐d ‐glucopyranoside (Q3G), quercetin 4′‐O‐β‐d ‐glucopyranoside (Q4′G), isorhamnetin 3‐O‐β‐d ‐glucopyranoside (IR3G), quercetin (Q), and isorhamnetin (IR)], were isolated and identified from onion. During fermentation, the contents of flavonoid glucosides (Q3,7G, Q3,4′G, Q3G, Q4′G, and IR3G) gradually decreased, whereas the contents of flavonoid aglycones (Q, IR) gradually increased. Decline rates of the flavonoid glucosides increased with the addition of L. mesenteroides. Furthermore, the activity of β‐glucosidase, which is produced by L. mesenteroides, is dose‐dependently inhibited with different NaCl concentrations during fermentation. The presence of L. mesenteroides enhanced the antioxidative activity of onion as demonstrated using the 1,1‐diphenyl‐2‐picrylhydrazyl, 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid), and reducing power assays. The enhancement of antioxidative activity was considered because the content of flavonoid aglycones increased during fermentation. However, the addition of NaCl may decrease the antioxidative activity; we surmise that this phenomenon occurs because of the inhibition of β‐glucosidase by NaCl. Therefore, we conclude that the addition of NaCl may be useful for the regulation of antioxidative activity via the control of β‐glucosidase action, during the fermentation of flavonoid glucoside‐rich foods.     

Water‐holding capacity of insoluble fibre decreases free water and elevates digesta viscosity in the rat

BACKGROUND: The relationships between possible physiological properties of insoluble fibre and the viscosity of digesta are poorly understood. The aim of this study was to investigate the effect of insoluble fibres with different water‐holding capacity, swelling, oil‐holding capacity and cation exchange capacity on gastric, small intestinal and caecal contents in rats fed a semi‐purified diet containing either no fibre (control), 50 g kg^?1 tossa jute fibre or 50 g kg^?1 shiitake fibre. RESULTS: The water‐holding capacity, swelling, oil‐holding capacity and cation exchange capacity of insoluble fibres of tossa jute were higher than those of shiitake (P < 0.001). The order of the viscosities of digesta was control group < shiitake fibre group < tossa jute fibre group in gastric, small intestinal and caecal contents (P < 0.05). The digesta viscosity at a shear rate of 40 s^?1 was strongly correlated with the free water content of digesta (r = ? 0.89; P < 0.01). The free water content of digesta depended on the water‐holding capacity of insoluble fibres represented as a linear function with negative slope (P < 0.001). CONCLUSION: The viscosity of digesta depends on the free water content, and this is reduced by fibre that holds water and can swell. Copyright © 2008 Society of Chemical Industry     

Synthesis of Quercetin‐3‐O‐Glucoside from Rutin by Penicillium decumbens Naringinase

Enzymatic bioconversion of rutin to quercetin‐3‐O‐glucoside (Q‐3‐G) by Penicillium decumbens naringinase was increased with reaction pH increased approximately to pH 6.0. It resulted in greater than 92% production of Q‐3‐G due to the removal of the terminal rhamnose at the controlled pH 6.0. The enzymatic bioconversion of rutin to Q‐3‐G was repetitively performed, yielding 84% after 5 batches with little quercetin formation. Interestingly, the water solubility of Q‐3‐G was enhanced 69‐ and 328‐fold over those of rutin and quercetin, which may make Q‐3‐G more bioavailable in food. Q‐3‐G was approximately 6‐ and 1.4‐fold more potent than rutin as an inhibitor of human intestinal maltase and human DL‐3‐hydroxy‐3‐methylglutalyl coenzyme A reductase. Q‐3‐G was less potent (16‐ and 1.3‐fold, respectively) than quercetin as an inhibitor of these enzymes. However, the results suggest that Q‐3‐G may be confirmed more effective and bioavailable food component than rutin and even quercetin because of its enhanced solubility and inhibitory properties. Practical Application : Bioconverted intermediate, quercetin‐3‐O‐glucoside (Q‐3‐G), was found and confirmed to be largely more soluble than rutin and quercetin in water solution, which might make it more bioavailable as food ingredient. In addition, Q‐3‐G inhibited mildly the intestinal maltase, which might act as antidiabetic substance by modulating the adsorption of glucose in the intestine.     

Improvement in intestinal function and health by the peel fibre derived from Citrus sinensis L cv Liucheng

The water‐insoluble fibre‐rich fraction (WIFF) was isolated from the peel of Citrus sinensis L cv Liucheng in an economical way. The influences of a WIFF‐containing diet on the intestinal function and health in hamsters were investigated and compared with those of cellulose‐added and fibre‐free diets. Our results showed that the inclusion of WIFF in a fibre‐free diet might result in some significant improvements in serum, intestinal, caecal and faecal parameters, such as elevated serum alkaline phosphatase activity (127%), increased intestinal maltase and sucrase activities (180 and 164% respectively), decreased caecal pH (6.30), reduced caecal and faecal ammonia contents (by 25.4 and 34.1% respectively) and decreased activities of faecal β‐D ‐glucosidase (by 48.1%), β‐D ‐glucuronidase (by 52.9%) and urease (by 81.5%). These results suggested that the incorporation of WIFF in the diet at a level of 50 g kg^?1 might exert a favourable effect on intestinal function and health. Accordingly, WIFF could be exploited as a potential functional ingredient in human diets and also offer industries an opportunity to develop new formulations of fibre‐rich functional foods. Copyright © 2005 Society of Chemical Industry     

A nondigestible saccharide,fructooligosaccharide, increases the promotive effect of a flavonoid, α‐glucosyl‐isoquercitrin,on glucagon‐like peptide 1 (GLP‐1) secretion in rat intestine and enteroendocrine cells

This study conducted in vivo and in situ experiments with rats to investigate the glucagon‐like peptide‐1 (GLP‐1) secretion in response to oral or ileal administration of α‐glucosyl‐isoquercitrin (20–40 mmol in 2 mL; Q3G), fructooligosaccharides (200 mmol in 2 mL; FOS) and Q3G + FOS. Direct effects on GLP‐1‐producing l ‐cells were also examined by an in vitro study using a murine enteroendocrine cell line, GLUTag. To evaluate the plasma GLP‐1 level, blood samples from jugular cannula for in vivo and portal cannula for in situ experiments were obtained before and after administration of Q3G, FOS, or Q3G + FOS. We found tendencies for increases but transient stimulation of GLP‐1 secretion by Q3G in in vivo and in situ experiments. Although FOS alone did not have any effects, Q3G + FOS enhanced and prolonged high plasma GLP‐1 level in both experiments. In addition, application of Q3G on GLUTag cells stimulated GLP‐1 secretion while FOS enhanced the effect of Q3G. Our results suggest that Q3G + FOS possess the potential for the management or prevention of Type 2 diabetes mellitus (T2DM) by enhancing and prolonging the GLP‐1 secretion via direct stimulation of GLP‐1 producing l ‐cell.     

A novel mechanism for the promotion of quercetin glycoside absorption by megalo α-1,6-glucosaccharide in the rat small intestine

The presence of an α-1,6-glucosaccharide enhances absorption of water-soluble quercetin glycosides, a mixture of quercetin-3-O-β-d-glucoside (Q3G, 31.8%), mono (23.3%), di (20.3%) and more d-glucose adducts with α-1,4-linkage to a d-glucose moiety of Q3G, in a ligated small intestinal loop of anesthetized rats. We prepared α-1,6-glucosaccharides with different degrees of polymerization (DP) enzymatically and separated them into a megalo-isomaltosaccharide-containing fraction (M-IM, average DP = 11.0) and an oligo-isomaltosaccharide-containing fraction (O-IM, average DP = 3.6). Luminal injection of either saccharide fraction promoted the absorption of total quercetin-derivatives from the small intestinal segment and this effect was greater for M-IM than O-IM addition. M-IM also increased Q3G, but not the quercetin aglycone, concentration in the water-phase of the luminal contents more strongly than O-IM. The enhancement of Q3G solubilization in the luminal contents may be responsible for the increases in the quercetin glucoside absorption promoted by α-1,6-glucosaccharides, especially that by M-IM. These results suggest that the ingestion of α-1,6-glucosaccharides promotes Q3G bioavailability.     

Effects of dietary inclusion of xylooligo‐ saccharides,arabinoxylooligosaccha‐ rides and soluble arabinoxylan on the microbial composition of caecal contents of chickens

BACKGROUND: Arabinoxylan (AX)‐derived preparations have raised particular interest by the suggestion that they exert prebiotic properties. Therefore an in vivo experiment was conducted to study the effects of xylooligosaccharides (XOS), arabinoxylooligosaccharides (AXOS) and soluble AX (S‐AX) on several groups of gut bacteria of chickens. Chickens were fed a control diet or the same diet supplemented with 2.5 g kg^?1 of XOS (average degree of polymerisation (avDP) of 3, average degree of arabinose substitution (avDS) of 0.09), wheat bran‐derived AXOS (avDP 9, avDS 0.34) or wheat endosperm alkali‐solubilised AX (S‐AX, avDP > 6000, avDS 0.5). RESULTS: All treatment groups showed an increase in the number of caecal bifidobacteria after 2 weeks of feeding (P < 0.05), while the treatments did not impact numbers of Enterobacteriaceae and aerobic lactobacilli in the caeca relative to the control. XOS led to a tremendous increase in caecal bifidobacteria counts (10⁸ g^?1 for the XOS treatment versus 10³ g^?1 for the control treatment) after only 1 week of supplementation, while AXOS and S‐AX led to similar strong increases in bifidobacteria counts after 2 weeks of supplementation. Addition of S‐AX to the diet, but not of AXOS or XOS, led to a significantly decreased (P < 0.05) body weight gain after 2 weeks of feeding relative to animals on the control diet, consistent with its known viscosity‐related antinutritive effects in chickens. CONCLUSION: Similar to XOS, AXOS selectively stimulate the presence of bifidobacteria in the caeca of chickens, establishing their bifidogenic effect as a first indicator for prebiotic potential. Copyright © 2008 Society of Chemical Industry     

Effect of flavonol glycoside in mulberry (Morus alba L.) leaf on glucose metabolism and oxidative stress in liver in diet‐induced obese mice

BACKGROUND: Mulberry therapies on type 2 diabetic patients or streptozotocin‐induced diabetic rats have been reported to improve fasting blood glucose levels. We investigated the effects of dietary consumption of mulberry‐leaf powder and purified quercetin 3‐(6‐malonylglucoside), the quantitatively major flavonol glycoside in mulberry leaves, on glucose and lipid metabolism in high‐fat diet‐induced obese mice. Male C57BL/6J mice aged 8 weeks were assigned to three groups (control, mulberry leaf powder (MLP), and quercetin 3‐(6‐malonylglucoside) (Q3MG)) and treated with their respective diets for 8 weeks. RESULTS: We found that dietary supplementation of 10 g MLP kg^?1 or 1 g Q3MG kg^?1 in high‐fat diet effectively suppressed blood glucose levels. We also noted increased expression of glycolysis‐related genes and suppression of thiobarbituric acid reactive substances concentrations in the liver of Q3MG group compared to control mice. CONCLUSION: Dietary consumption of Q3MG, the quantitatively major flavonol glycoside in mulberry leaves, improved hyperglycemia in obese mice and reduced oxidative stress in the liver. Copyright © 2010 Society of Chemical Industry     

Effect of fermented soybean product (Cheonggukjang) intake on metabolic parameters in mice fed a high‐fat diet

As a nontargeted metabolomics approach, we investigated changes in the plasma metabolite levels in a mouse model of obesity induced by a high‐fat diet and fermented soybean product diet. We analyzed the plasma samples by using ultra‐performance liquid chromatography coupled with quadrupole time‐of‐flight mass spectrometry (UPLC‐Q‐TOF‐MS). In the present study, the animals were divided into four groups according to the diet type; normal fat diet control group (ND), high‐fat diet control group (HD), high‐fat diet plus 30% cooked soybean power (HD + S), and high‐fat diet plus 30% 72‐h fermented Cheonggukjang powder (HD + CGJ). To examine the changes in plasma metabolite levels because of high‐fat diet feeding, total cholesterol and triglyceride levels were measured. Total cholesterol and triglyceride levels were lower in the HD + S and HD + CGJ groups than in the ND group. According to partial least‐squares discriminant analysis (PLS‐DA), major metabolites contributing to the discrimination between each group were assigned as lipid metabolites in plasma, e.g., lyso‐phosphatidylcholines and phosphatidylcholines. Therefore, diets containing soy‐based food products, which are rich sources of isoflavonoids, might be helpful for controlling the lipid metabolism under high‐fat diet conditions.     

Dill seed extract improves abnormalities in lipid metabolism through peroxisome proliferator‐activated receptor‐α (PPAR‐α) activation in diabetic obese mice

Dill, a small annual herb, is widely used as a flavoring agent in dishes including salads. It has been demonstrated that dill extract and its essential oil show hypolipidemic effects in rats. However, the mechanism of these effects has not been elucidated yet. We found that dill seed extract (DSE) activated peroxisome proliferator‐activated receptor‐α (PPAR‐α), an indispensable regulator for hepatic lipid metabolism, by luciferase assay. Thus, we performed DSE feeding experiments using diabetic obese model KK‐Ay mice to examine the effects of DSE on PPAR‐α activation in vivo. A 4‐week feeding of DSE contained in a high‐fat diet decreased plasma triacylglyceride and glucose levels and increased the mRNA expression levels of fatty acid oxidation‐related genes in the liver. In addition, the DSE feeding as well as bezafibrate (a PPAR‐α potent agonist) feeding increased oxygen consumption rate and rectal temperature. These results indicate that DSE suppresses high‐fat diet‐induced hyperlipidemia through hepatic PPAR‐α activation.     

Anti‐inflammatory Potential of Quercetin‐3‐O‐β‐D‐(“2”‐galloyl)‐glucopyranoside and Quercetin Isolated from Diospyros kaki calyx via Suppression of MAP Signaling Molecules in LPS‐induced RAW 264.7 Macrophages

Diospyros kaki (DK) contains an abundance of flavonoids and has been used in folk medicine in Korea for centuries. Here, we report for the first time the anti‐inflammatory activities of Quercetin (QCT) and Quercetin 3‐O‐β‐(“2”‐galloyl)‐glucopyranoside (Q32G) isolated from DK. We have determine the no cytotoxicity of Q32G and QCT against RAW 264.7 cells up to concentration of 50 μM. QCT and Q32G demonstrated potent anti‐inflammatory activities by reducing expression of nitric oxide (NO), tumor necrosis factor (TNF)‐α, interleukin (IL)‐1β, IL‐6 inducible NO synthase (iNOS), cyclooxygenase (COX)‐2, and mitogen‐activated protein kinase (MAPKs) in mouse RAW 264.7 macrophages activated with lipopolysaccharide (LPS). Both QCT or Q32G could decrease cellular protein levels of COX‐2 and iNOS as well as secreted protein levels of NO, PGE₂, and cytokines (TNF‐α, IL‐1β, and IL‐6) in culture medium of LPS‐stimulated RAW 264.7 macrophages. Immunoblot analysis showed that QCT and Q32G suppressed LPS‐induced MAP kinase pathway proteins p‐p38, ERK, and JNK. This study revealed that QCT and Q32G have anti‐inflammatory potential, however Q32G possess comparable activity as that of QCT and could be use as adjuvant to treat inflammatory diseases.     

Review on the Use of Cell Cultures to Study Metabolism,Transport, and Accumulation of Flavonoids: From Mono‐Cultures to Co‐Culture Systems

The aim of this review is to provide a comprehensive discussion on the various human/animal cell‐based models used to study the absorption, transport, and metabolism of flavonoids. Flavonoids are plant‐based bioactive compounds that have been extensively investigated for their active role in health alleviation and disease prevention. For this purpose, cell lines isolated from various human and animal tissues have been routinely used as an in vitro model to assess the bioavailability and bioactivity of these compounds. This paper reviews for the first time various transporters (SLCT, SGLT, bilitranslocase, and ABC transporters), metabolic routes (deglycosylation, glucuronidation, sulfation, and deconjugation), and accumulation of flavonoids in different cell lines commonly used in flavonoid research. Also, the use of co‐culture systems to study flavonoid bioactivity will be discussed. To date, no definite mono‐culture or co‐culture formulation has been generally accepted to be the most accurate representation of the in vivo situation. Therefore, further investigation and improvement of cell‐based in vitro models for flavonoid research merit further investigation.     

Reverse Effect of Opuntia ficus‐indica L. Juice and Seeds Aqueous Extract on Gastric Emptying and Small‐Bowel Motility in Rat

This study was conducted to compare the effects of juice and seeds on gastric emptying, small‐bowel motility and intestinal ion transport. Separate groups of rats were randomized to receive NaCl, increasing doses of juice (5, 10, and 20 mL/kg, b.w.) or seeds aqueous extract (100, 200, and 400 mg/kg, b.w.). Simultaneously, two other groups were received, the reference drugs; clonidine (1 mg/kg) and yohimbine (2 mg/kg). The charcoal meal was used as a suspension for gastrointestinal motility test. The purgative action of juice was confirmed using the loperamide (5 mg/kg, p.o.) induced constipation. To evaluate the antisecretory effect, we were used as a hypersecretion agent, the castor oil at the dose of 5 mL/kg. Compared to the control and standard groups, we were showed that the prickly pear has an opposite effect on small‐bowel motility and gastric emptying. Indeed, the juice at various doses has a laxative effect of gastrointestinal transit in healthy and constipated‐rats. However, the aqueous extract of the seeds leads to a reduction of motility in normal rats which gives it a remarkable antidiarrhoeal activity, a notable intestinal fluid accumulation decline and electrolyte concentrations reestablishment. Moreover, orally juice administered at different doses accelerated the stomach emptying time in contrast to the seeds aqueous extract. More importantly, a significant variation in the phytochemical constituents levels between juice and seeds was found. These findings confirm the reverse therapeutic effects of this fruit in the treatment of digestive disturbances such as difficulty stool evacuation and massive intestinal secretion, likewise, the gastric emptying process perturbation.     

Effect of Processed Onions on the Plasma Concentration of Quercetin in Rats and Humans

Onion is a major dietary source of the bioactive flavonoid, quercetin. Quercetin aglycone (QA) is exclusively distributed in the onion peel, although quercetin‐4′‐β‐O‐glucoside (Q4′G) is present in both the peel and the bulb, and quercetin‐3,4′‐β‐O‐diglucoside (Q3,4′diG) is present only the bulb. The bioavailability of flavonoids from fruits and vegetables is frequently affected by the manufacturing process and related conditions. The present study aimed to estimate the effect of food processing on the bioavailability of onion QA and its glucosides, Q4′G and Q3,4′diG, provided through the consumption of onion products. Rats were fed onion peel and onion bulb products‐mixed meal or pure QA/Q4′G+Q3,4′diG‐mixed meal at 5 mg QA equivalent/kg body weight. A comparison of the blood plasma concentrations strongly suggested that quercetin glucosides (Q4′G and Q3,4′diG) are superior or at least equal to QA in their bioavailability, when each purified compound is mixed with the meal. The intake of a peel powder‐containing meal provided a significantly higher increase of plasma quercetin concentration than the peel extract, bulb powder, bulb extract, and bulb sauté containing meals at each period tested. A human ingestion study confirmed the superiority of onion peel powder to onion peel extract. The difference of log P for QA between peel powder and peel extract indicated that a food matrix improves the bioavailability of QA in onion peel products. These results demonstrated that the bioavailability of quercetin provided by not the onion bulb but the onion peel is significantly affected by food processing.     

Effects of ingestion of a green seaweed,Ulva lactuca,upon caecal and colonic mucosas in the germ‐free rat and in the heteroxenic rat harbouring a human bacterial flora

Effect of ingestion of green seaweed, Ulva lactuca, (70 g kg⁻¹) during a 6‐week period on caecal and colonic mucosas was studied in germ‐free (GF) rats and in heteroxenic (HE) rats harbouring a human bacterial flora (GF rats associated with a human flora). The pH and sulphide concentration of the caecal contents, crypt morphometry, mitotic index and mucin types in the caecal and distal colonic mucosas were determined. In the GF caecum, Ulva strongly increased crypt depth and mucin‐containing cells irrespective of the mucin type studied (neutral, acidic or sulphated) compared to the control diet but had no significant effect on mitotic index. The crypt depth and mucin‐containing cells in the caecum were higher in HE than in GF control rats. They were slightly but significantly increased by Ulva. In the distal colon mucosa of GF rats, Ulva decreased crypt depth and cell number as well as sulphomucin‐containing cells. Conversely, in the HE rats, it increased crypt depth and reduced the number of neutral mucin‐containing cells. These results show that Ulva lactuca exerts an intrinsic effect on mucosal morphometry and on mucin biosynthesis in GF rats. No pathological alteration was observed in the mucosas and no significant modification of the mitotic index or sulphide production was observed in HE rats. © 1999 Society of Chemical Industry     

The fermentation of lactulose in rats inoculated with Clostridium paraputrificum influences the activities of liver and intestinal xenobiotic‐metabolising enzymes

One of the most recent hypotheses concerning the protective effect of some dietary fibres against colon cancer implicates butyrate. Very few publications have addressed its possible influence on the phase II enzymes and on the bacterial enzymes involved in the enterohepatic recirculation of toxic compounds. We used an original model of monoxenic rats oriented towards the preferential production of butyrate. Fischer male germ‐free rats were mono‐associated with a strain of Clostridium paraputrificum. They were fed either a control diet or a lactulose‐enriched diet for 6 weeks. In the caeco‐colon the specific activities (SAs) of the microsomal enzymes (glutathione‐S‐transferase and UDP‐glucuronosyl‐transferase) were 1.7‐fold those of the control rats. In the intestine and liver the SAs of the phase II enzymes were not altered, nor was the hepatic cytochrome P450. In the caecum of the lactulose‐fed rats the SA of β‐glucuronidase decreased by 27% and that of β‐glucosidase doubled. The chronic consumption of lactulose doubled the total caecal short‐chain fatty acids, and the production of butyrate was enhanced. Since the germ‐free rats behaved differently when fed the same diets, we concluded that the fermentation products of lactulose (and not the lactulose itself) were involved in the effects we describe. The involvement of butyrate in this phenomenon is discussed. © 2001 Society of Chemical Industry