Influence of diet and age on fecal bacterial enzymes

Integrating Microbiome Analysis, Metabolomics, Bioinformatics, and Histopathology to Elucidate the Protective Effects of Pomegranate Juice against Benzo-alpha-pyrene-Induced Colon Pathologies

Polycyclic aromatic hydrocarbons, e.g., benzo[a]pyrene (BaP), are common dietary pollutants with potential carcinogenic activity, while polyphenols are potential chemopreventive antioxidants. Although several health benefits are attributed to polyphenol-rich pomegranate, little is known about its interaction with BaP. This study integrates histochemical, microbiomic, and metabolomic approaches to investigate the protective effects of pomegranate juice from BaP-induced pathologies. To this end, 48 Sprague-Dawley rats received, for four weeks, either pomegranate, BaP, both, or neither (n = 12 rats per group). Whereas histochemical examination of the colon indicated tissue damage marked by mucin depletion in BaP-fed animals, which was partially restored by administration of pomegranate juice, the fecal microbiome and metabolome retained their resilience, except for key changes related to pomegranate and BaP biotransformation. Meanwhile, dramatic microbiome restructuring and metabolome shift were observed as a consequence of the elapsed time (age factor). Additionally, the analysis allowed a thorough examination of fecal microbiome-metabolome associations, which delineated six microbiome clusters (marked by a differential abundance of Lactobacillaceae and Prevotellaceae, Rumincococcaceae, and Erysipelotrichaceae) and two major metabolome clusters (a sugar- and amino-acids-dominated metabotype vs. a cluster of fatty acids and hydrocarbons), with sugar alcohols maintaining a unique signature. In conclusion, using paired comparisons to minimize inter-individual animal variations allowed the dissection of temporal vs. treatment-derived variations. Microbiome-metabolome association clusters may be further exploited for metabotype prediction and gut-health biomarker discovery.

Discovery and characterization of the flavonoids in Cortex Mori Radicis as naturally occurring inhibitors against intestinal nitroreductases

Gut bacterial nitroreductases are found to be heavily related with the intestinal toxicity of nitroaromatic compounds in food or medicine, which can be converted into mutagenic and enterotoxic nitroso or N-hydroxyl intermediates. Thus, inhibiting the gut microbe-encoded nitroreductases has become an attractive method to reduce the mutagen metabolites in colon and prevent intestinal diseases. In this study, the inhibitory effects of sixteen constituents in Cortex Mori Radicis on two kinds of gut bacterial nitroreductases (EcNfsA and EcNfsB) were evaluated with nitrofurazone (NFZ) as substrate and NADPH as electron donor. The results clearly demonstrated that four flavonoids including kuwanon G, kuwanon A, sanggenol A and kuwanon C showed dual inhibition on both EcNfsA and EcNfsB mediated NFZ reduction; morusin, morin, and sanggenone C were strong inhibitors towards EcNfsA; kuwanon H and kuwanon E exhibited effective inhibition on EcNfsB. Further inhibition kinetic analysis and molecular docking simulations displayed that all inhibitors above suppressed both EcNfsA and EcNfsB activities in competitive manners, except non-competitive inhibition of morin on EcNfsA and non-competitive inhibition of kuwanon C on EcNfsB, respectively. Taking together, these findings revealed that most flavonoids in Cortex Mori Radicis presented effective inhibition on gut microbial nitroreductases, suggesting that Cortex Mori Radicis might be a promising candidate for ameliorating nitroreductases mediated intestinal mutagenicity.

The Role of Gut Microbial β-Glucuronidase in Estrogen Reactivation and Breast Cancer

Over the past decade, the gut microbiota has received considerable attention for its interactions with the host. Microbial β-glucuronidase generated by this community has hence aroused concern for its biotransformation activity to a wide range of exogenous (foreign) and endogenous compounds. Lately, the role of gut microbial β-glucuronidase in the pathogenesis of breast cancer has been proposed for its estrogen reactivation activity. This is plausible considering that estrogen glucuronides are the primary products of estrogens' hepatic phase II metabolism and are subject to β-glucuronidase-catalyzed hydrolysis in the gut via bile excretion. However, research in this field is still at its very preliminary stage. This review outlines the biology of microbial β-glucuronidase in the gastrointestinal tract and elaborates on the clues to the existence of microbial β-glucuronidase-estrogen metabolism-breast cancer axis. The research gaps in this field will be discussed and possible strategies to address these challenges are suggested.

Adaptation of intestinal fermentation over time in the growing pig is influenced by the amount of kiwi fruit consumed

The effect of kiwi fruit at two dietary levels on the adaptation of intestinal fermentation over time in the growing pig was studied. A semi-synthetic fibre-free diet and two semi-synthetic diets containing kiwi fruit as a model fibre source (133 or 266 g/kg (DM basis); 28 or 48 g fibre/kg) were formulated and the diets contained titanium dioxide as an indigestible marker. A total of fourteen ileal cannulated pigs (41 kg body weight) were fed the fibre-free diet for 7 d followed by either the low or high kiwi fruit-containing diets (n 7/diet) for a further 44 d. Ileal digesta and faeces were collected at five times throughout the study. Ileal digesta were fermented (in vitro) with a standard pooled human faecal inoculum, while fresh pig faeces were used as inocula to ferment in vitro a standard purified fibre. Observations were normalised for diet DM intake using the marker. The 16S ribosomal RNA gene copy number of ileal and total faecal bacteria were high for the high-kiwi fruit level diet (P<0·05). The ileal bacteria tended to decrease over time (P<0·1), while the faecal bacteria increased (P<0·05), at the same rate for both diets. The amounts of crude protein and insoluble dietary fibre entering the hindgut changed over time similarly for both diets, whereas for starch it changed only for the low kiwi fruit-containing diet (P<0·05). Changes over time were also observed for the predicted hindgut valeric acid production and butyric acid absorption (P<0·05). In conclusion, adaptational changes over time of some characteristics of intestinal fermentation depended on the dietary level of kiwi fruit.

Developing a metagenomic view of xenobiotic metabolism

The microbes residing in and on the human body influence human physiology in many ways, particularly through their impact on the metabolism of xenobiotic compounds, including therapeutic drugs, antibiotics, and diet-derived bioactive compounds. Despite the importance of these interactions and the many possibilities for intervention, microbial xenobiotic metabolism remains a largely underexplored component of pharmacology. Here, we discuss the emerging evidence for both direct and indirect effects of the human gut microbiota on xenobiotic metabolism, and the initial links that have been made between specific compounds, diverse members of this complex community, and the microbial genes responsible. Furthermore, we highlight the many parallels to the now well-established field of environmental bioremediation, and the vast potential to leverage emerging metagenomic tools to shed new light on these important microbial biotransformations.

Microbial hydrolysis of steviol glycosides

A review of the role of gut microbiota in the metabolism of the steviol glycosides, stevioside and rebaudioside A, indicates that they are not absorbed intact but undergo hydrolysis by the intestinal microflora to steviol. Steviol is not metabolized by the intestinal flora and is absorbed from the intestine. The rate of hydrolysis for stevioside is greater than for rebaudioside A. Recent studies using mass spectrometry have shown that steviol-16,17-epoxide is not a microbial metabolite of steviol glycosides. Bacteroides species are primarily responsible for hydrolysis via their beta-glucosidase activity. Fecal incubation studies with both human and animal mixed flora provide similar results, and this indicates that the rat is an appropriate model for studies on steviol glycosides. Given the similarity in the microbial metabolism of stevioside and rebaudioside A with the formation of steviol as the single hydrolysis product that is absorbed from the intestinal tract, the toxicological data on stevioside are relevant to the risk assessment of rebaudioside A.

Protective role of luteolin in 1,2-dimethylhydrazine induced experimental colon carcinogenesis

The aim of the present study was to unravel the chemopreventive effect of luteolin on bacterial enzymes such as beta-glucuronidase and mucinase in a colon carcinogenesis model induced by 1, 2-dimethyl hydrazine (DMH). Twenty mg/kg body weight of DMH were administered subcutaneously once a week for the first 15 weeks and then discontinued. Luteolin (0.1, 0.2, or 0.3 mg/kg body weight/everyday (p.o.) was administered in a dose dependent manner at the initiation and also at the post-initiation stages of carcinogenesis to DMH treated rats. The animals were sacrificed at the end of 30 weeks. Colon cancer incidence and the activities of bacterial enzymes beta-glucuronidase (in the proximal colon, distal colon, intestines, liver and colon contents) and mucinase (colon and fecal contents) were significantly increased in DMH -treated rats compared to the control rats. On luteolin administration, colon cancer incidence, number of tumors per rat and the activities of beta-glucuronidase and mucinase, were significantly decreased both in the initiation and post-initiation stages of colon carcinogenesis dependent on the three different doses given. The increase in beta-glucuronidase activity may augment the hydrolysis of glucuronide conjugates, liberating toxins, while the increase in the mucinase activity may enhance the hydrolysis of the protective mucins in the colon. Thus our results demonstrate for the first time that luteolin, a dietary flavonoid, exerts chemopreventive and anticarcinogenic effects against DMH induced colon cancer.

Effect of ginger on bacterial enzymes in 1,2-dimethylhydrazine induced experimental colon carcinogenesis

Colon cancer is becoming increasingly common in Asian countries and still remains the second leading cause of cancer death in the United States. Ginger, a natural spice having both antioxidant and antimutagenic property, is known to inhibit chemical carcinogenesis. This study was designed to investigate the chemopreventive efficacy of ginger on the activity of bacterial enzymes in rats induced colon cancer by 1,2-dimethylhydrazine. Twenty milligrams per kilogram body weight of 1,2-dimethylhydrazine was administered subcutaneously once a week for the first 15 weeks and then discontinued. Ginger (50 mg/kg body weight/per day, oral) was given at the initiation and also at the postinitiation stages of carcinogenesis to 1,2-dimethylhydrazine-treated rats. The animals were killed at the end of 30 weeks. The macroscopic findings in the colon and the incidence of tumors were recorded in each group, and the activity of beta-glucuronidase and mucinase was estimated in the tissues and fecal contents of rats. After a total experimental period of 32 weeks (including 2 weeks of acclimatization), tumor incidence was 100% in 1,2-dimethylhydrazine-treated rats. The incidence of cancer as well as the number of tumors in the colon was significantly reduced both in the initiation and postinitiation stages of carcinogenesis on ginger administration. The activities of bacterial enzymes beta-glucuronidase (proximal colon, distal colon, intestines, liver and colon contents) and mucinase (colon and fecal contents) were significantly elevated in 1,2-dimethylhydrazine-treated rats as compared with the control rats. The increase in beta-glucuronidase activity may augment the hydrolysis of glucuronide conjugates, liberating the toxins, while the increase in the mucinase activity may enhance the hydrolysis of the protective mucins in the colon. Ginger administration to 1,2-dimethylhydrazine-treated rats significantly decreased the incidence and number of tumors as well as the activity of beta-glucuronidase and mucinase. Thus, ginger has a chemopreventive and anticarcinogenic effect against 1,2-dimethylhydrazine-induced colon cancer by virtue of its ability to lower the activities of the microbial enzymes beta-glucuronidase and mucinase.

Mediterranean diet or extended fasting's influence on changing the intestinal microflora, immunoglobulin A secretion and clinical outcome in patients with rheumatoid arthritis and fibromyalgia: an observational study

BACKGROUND

Alterations in the intestinal bacterial flora are believed to be contributing factors to many chronic inflammatory and degenerative diseases including rheumatic diseases. While microbiological fecal culture analysis is now increasingly used, little is known about the relationship of changes in intestinal flora, dietary patterns and clinical outcome in specific diseases. To clarify the role of microbiological culture analysis we aimed to evaluate whether in patients with rheumatoid arthritis (RA) or fibromyalgia (FM) a Mediterranean diet or an 8-day fasting period are associated with changes in fecal flora and whether changes in fecal flora are associated with clinical outcome.

METHODS

During a two-months-period 51 consecutive patients from an Integrative Medicine hospital department with an established diagnosis of RA (n = 16) or FM (n = 35) were included in the study. According to predefined clinical criteria and the subjects' choice the patients received a mostly vegetarian Mediterranean diet (n = 21; mean age 50.9 +/-13.3 y) or participated in an intermittent modified 8-day fasting therapy (n = 30; mean age 53.7 +/- 9.4 y). Quantitative aerob and anaerob bacterial flora, stool pH and concentrations of secretory immunoglobulin A (sIgA) were analysed from stool samples at the beginning, at the end of the 2-week hospital stay and at a 3-months follow-up. Clinical outcome was assessed with the DAS 28 for RA patients and with a disease severity rating scale in FM patients.

RESULTS

We found no significant changes in the fecal bacterial counts following the two dietary interventions within and between groups, nor were significant differences found in the analysis of sIgA and stool ph. Clinical improvement at the end of the hospital stay tended to be greater in fasting vs. non-fasting patients with RA (p = 0.09). Clinical outcome was not related to alterations in the intestinal flora.

CONCLUSION

Neither Mediterranean diet nor fasting treatments affect the microbiologically assessed intestinal flora and sIgA levels in patients with RA and FM. The impact of dietary interventions on the human intestinal flora and the role of the fecal flora in rheumatic diseases have to be clarified with newer molecular analysis techniques. The potential benefit of fasting treatment in RA and FM should be further tested in randomised trials.

Effect of coconut cake on the bacterial enzyme activity in 1,2-dimethyl hydrazine induced colon cancer

BACKGROUND

Colon cancer is one of the most common forms of malignant tumors in humans, and its incidence is increasing. Since the intestinal microflora is directly in contact with the colonic cells, the enzymes of the bacterial microflora may also play a role in colon carcinogenesis. We studied the activity of bacterial enzymes in experimental colon cancer.

METHODS

Twenty milligrams per kilogram body weight of 1,2-dimethyl hydrazine (DMH) was administered subcutaneously once a week for first 15 weeks and then discontinued. Coconut cake (25%) was mixed in the diet and given to 30 rats to study the diet effect throughout the experimental period. After 30 weeks, the macroscopic findings in the colon as well as the incidence of tumors in 30 rats was recorded in each group and the activity of beta-glucuronidase and mucinase was estimated in the tissues, colon and fecal contents of 10 rats per group.

RESULTS

Average number of tumors in the colon as well as the incidence of cancer was significantly increased in DMH-treated rats which was markedly reduced on supplementing coconut cake. DMH injections significantly elevated both the activities of beta-glucuronidase (distal colon, distal intestine, liver and colon contents) and mucinase (colon and fecal contents) as compared to the control rats. The increase in beta-glucuronidase activity may augment the hydrolysis of glucuronide conjugates, liberating the toxins, while the increase in mucinase activity may enhance the hydrolysis of the protective mucins in the colon. Coconut cake supplementation to DMH-treated rats significantly decreased the incidence and number of tumors as well as the activity of beta-glucuronidase and mucinase.

CONCLUSIONS

Coconut cake has a protective effect against DMH induced colon cancer by virtue of its ability to lower the activities of the microbial enzymes beta-glucuronidase and mucinase.

Colonic bacterial flora: changing understandings in the molecular age

The human intestinal microbiota is a complex bacterial consortium that is critical to normal health. The microflora is present at concentrations of 10(11)-10(12) cells/g of intestinal contents; the number of species present may exceed 500, although exact numbers remain to be defined, due in part to the fact that <30% of microorganisms are culturable with current microbiologic methods. Molecular tools based on 16S rDNA sequence similarities such as fluorescent in-situ hybridization (FISH), denaturing gradient gel electrophoresis (DGGE), quantitative dot blot hybridization, restriction fragment length polymorphism (RFLP) and large scale 16S rDNA sequencing have helped to overcome limitations of conventional microbiological plating methods in studying the fecal microflora composition. However, these tools are just now beginning to be applied to understand the dynamics of this complex community, and its relationship to diet and human health. There is a need to understand both the limitations of the current data and the importance of moving forward with the best possible molecular and epidemiologic techniques as we deal with these critical questions.

Comparison of four microbial enzymes in Clostridia and Bacteroides isolated from human feces

The activities of four microbial enzymes (azoreductase, nitroreductase, beta-glucuronidase, and beta-glucosidase) in major anaerobic members of human fecal microflora were quantified and the influence of the host factors on expression of these microbial enzyme activities was also investigated. Clostridium paraputrificum and C. clostridiiforme showed much higher activities than other fecal anaerobes tested. Nitroreductase activity in C. paraputrificum isolated from fecal specimens of patients with colon cancer was significantly (P < 0.05) higher than that in the clostridia isolated from healthy subjects and the subjects given high beef diets. However, the activities of some microorganisms tested showed marked differences in each strain.

Intestinal transit of an orally administered streptomycin-rifampicin-resistant variant of Bifidobacterium longum SBT2928: its long-term survival and effect on the intestinal microflora and metabolism

AIMS

The objectives of this study are to investigate the fate of a streptomycin-rifampicin-resistant variant of Bifidobacterium longum SBT2928 (BL2928SR) and the influence of its oral administration on the composition and metabolism of the intestinal microflora.

METHODS AND RESULTS

Intestinal passage of BL2928SR was monitored by a combination of selection with antibiotics and identification by a randomly amplified polymorphic DNA (RAPD)-PCR method. Intestinal microflora was analysed by the method developed by Mitsuoka et al. (1965, 1974). Long-term survival of orally administered BL2928SR in the human intestine was confirmed. BL2928SR ingestion specifically lowered faecal populations of Enterobacteriaceae and clostridia, including lecithinase-positive Clostridium spp.

CONCLUSION

BL2928SR and its parent strain, BL2928, are considered to be appropriate candidates for probiotics.

SIGNIFICANCE AND IMPACT OF THE STUDY

It is clarified that BL2928SR has the ability for long-term survival in the human gastrointestinal tract, and alters the composition and metabolism of the intestinal microflora.

Influence of spices on the bacterial (enzyme) activity in experimental colon cancer

In the presence of a known colon carcinogen, 1,2-dimethyl hydrazine (DMH), the activity of beta-glucuronidase was found to be significantly increased in the distal colon, distal intestine, liver and colon contents and the activity of mucinase was increased in both the colon and fecal contents when compared to control rats. Chilli (Capsicum annum L., Solanaceae) administration also showed an increase when compared to control rats, whereas supplementation with cumin (Cuminum cyminum L., Apiaceae) and black pepper (Piper nigrum L., Piperaceae) in the presence of DMH, showed more or less similar values as that of the control rats. The increase in beta-glucuronidase activity may increase the hydrolysis of glucuronide conjugates, liberating the toxins, while the increase in mucinase activity may enhance the hydrolysis of the protective mucins in the colon. Thus cumin and black pepper may protect the colon by decreasing the activity of beta-glucuronidase and mucinase. Histopathological studies also showed lesser infiltration into the submucosa, fewer papillae and lesser changes in the cytoplasm of the cells in the colon in cumin and black pepper groups when compared to the DMH and chilli treated animals.

Anticarcinogenic, hypocholesterolemic, and antagonistic activities of Lactobacillus acidophilus

Lactobacillus acidophilus is considered to possess health-promoting attributes. These include anticarcinogenic and hypocholesterolemic properties and antagonistic action against intestinal and food-born pathogens. L. acidophilus can also survive the hostile environment and establish in the complex ecosystem of the gastrointestinal tract. Therefore, the beneficial effects of ingesting L. acidophilus accrue over a longer period than those organisms that cannot colonize the gut. However, the exact mechanisms of these attributes are not known. Presumably, the anticarcinogenic activity may be attributed to production of compounds and/or conditions that inhibit the proliferation of tumor cells, suppression of microorganisms that convert procarcinogens to carcinogens, and degradation of carcinogens formed. They hypocholesterolemic effect is probably exerted by inhibition of 3-hydroxy-3-methylglutaryl CoA reductase, which is a rate-limiting enzyme in endogenous cholesterol biosynthesis in the body and by promoting the excretion of dietary cholesterol in feces as a result of coprecipitation in the presence of deconjugated bile acids in the intestine and/or adsorption by the organisms. The antagonistic effect against pathogens and other organisms is possibly mediated by competition for nutrients and adhesion sites, formation of metabolites such as organic acids, hydrogen peroxide, and production of antibiotic-like compounds and bacteriocins.

Development changes to gut microflora metabolism in mice

Developmental changes in the activities of bacterial nitrate reductase, nitroreductase and beta-glucuronidase and their response to fermentable dietary fibre, were investigated in caecal contents from suckling mice (2-week-old) and in mice aged 4-24 weeks fed either a purified fibre-free diet or that diet supplemented with 5% (w/w) pectin. There was no apparent age-related trend common to the three enzymes studied. Nitrate reductase activity in the mice fed the fibre-free diet did not markedly alter with age. Pectin administration, however, was associated with a significant increase in nitrate reductase activity, particularly in 4-week-old mice. Nitroreductase activity exhibited an overall upward trend in mice from 2 to 12 weeks and thereafter decreased. Caecal beta-glucuronidase activity in mice increased sharply between 2 weeks and 4 weeks of age, thereafter not changing significantly until the 24th week. Pectin feeding had no consistent effect on activities either of nitroreductase or beta-glucuronidase. The changes in enzyme activities with age were not related to the concentration of bacteria in the caecum, which was highest in the 2-week-old mice. We conclude that the weaning is a period in which marked changes in caecal bacterial enzyme activities can occur.

Plantago ovata seeds as dietary fibre supplement: physiological and metabolic effects in rats

In rats, the effects of a 4-week supplementation of a fibre-free elemental diet with 100 or 200 g Plantago ovata seeds/kg was compared with that of the husks and wheat bran. The seeds increased faecal fresh weight up to 100%, faecal dry weight up to 50% and faecal water content up to 50%. The husks, at the high concentration only, were more effective and wheat bran less effective. Length and weight of the small intestine were not greatly affected by the seeds, but both variables increased significantly in the large intestine. The husks had more pronounced effects, especially in the small intestine, and wheat bran almost no effect. Faecal bacterial mass as estimated from the 2,6-diaminopimelic acid output was increased to the greatest extent by the seed-containing diet and by the high concentration of husks, but to a lesser extent by wheat bran. Faecal and caecal protein content was enhanced by the seeds and wheat bran, but to a lesser extent by the husks. Total acetate in caecal contents or faeces was highest on the seeds and husks diet and not elevated by wheat bran. Total faecal bile acid excretion was stimulated and beta-glucuronidase (EC 3.2.1.31) activity reduced by both Plantago ovata preparations, but not by wheat bran. Mucosal digestive enzyme activities were inhibited to different degrees by all dietary fibres in the jejunum, and sometimes activated in the ileum. These results suggest that Plantago ovata seeds are a partly-fermentable dietary fibre supplement which increases stool bulk; metabolic and mucosa-protective effects are also probable.

Effect of Konjac mannan on intestinal microbial metabolism in mice bearing human flora and in conventional F344 rats

The effects of dietary Konjac mannan (KM), a frequent ingredient of traditional Japanese foods, on intestinal microbial metabolism and microflora composition were investigated using two laboratory animal models, namely, conventional F344 rats and C3H/He male mice bearing human flora. Dietary KM led to a significant reduction in faecal beta-glucuronidase, nitroreductase and azoreductase activities, and in the production of phenol and indole in the faeces of conventional F344 rats. In the C3H/He male mice bearing human flora, faecal beta-glucuronidase and nitroreductase activities were significantly reduced by KM ingestion, as were the amounts of the putrefactive products, p-cresol and indole, in the faeces. Slight differences in intestinal microflora composition between control and KM diet groups were noted. The results indicate that, in C3H/He male mice bearing human flora, dietary KM may modify microbial metabolism without causing significant alterations in intestinal microflora composition.

The human intestinal microflora

The major host defense mechanisms against bacterial overgrowth in the small bowel are the normal propulsive activity of the bowel itself and gastric acid secretion. Microbial interactions are a major factor in regulating the indigenous bacterial flora. Studies of the bacterial enzymes of the gut suggest that changes in diet may lead to marked changes in the colonic flora. Antibiotics affect the composition of the colonic microflora. The microflora also influence the degradation of mucin, the conversion of urobilin to urobilinogen, of cholesterol to coprostanol, and the production of short chain fatty acids. Current interests are focused on the bacterial flora of tropical sprue, the role of bacteria in colorectal cancer, and the involvement of intestinal microflora in the enterohepatic circulation of sex steroid hormones.

Diet and faecal flora in three dietary groups in rural northern Nigeria

Quantitative bacterial counts, concentrations of bile acids and bacterial enzyme profiles were measured in faecal samples from three tribal groups with distinctive dietary patterns in a rural area of northern Nigeria. Samples were obtained from Maguzawa (with a predominantly cereal diet), Hausa (cereal with regular meat consumption) and Fulani (cereal with frequent consumption of cows' milk). Numbers of bacteroides, clostridia and concentrations of bile acids were lower in the Maguzawa than the other dietary groups but these differences were not statistically significant. Bacterial enzyme profiles in each group were similar. The results are discussed with respect to possible influences of diet on the human intestinal microflora.

Cellulose and pectin alter intestinal beta-glucuronidase (EC 3.2.1.31) in the rat

Groups of rats were given a fibre-free diet containing none or one of the three fibre components: pectin, cellulose or galactomannan. After feeding for 16 weeks, total protein level and beta-glucuronidase (EC 3.2.1.31) activity in the contents and mucosa of jejunum and ileum, and in the contents only of the caecum, were determined. The pectin supplement reduced protein concentration in jejunal contents while cellulose reduced protein concentration in the ileal and caecal contents. beta-Glucuronidase activity of caecal contents was significantly reduced in both the pectin- and cellulose-fed groups. Cellulose affected the beta-glucuronidase activity of both the ileal contents while pectin reduced the beta-glucuronidase of the ileal but not the jejunal contents. Dietary fibre components did not significantly affect jejunal or ileal mucosal beta-glucuronidase activity.

The National Large Bowel Cancer Project: a progress report

The progress report from the National Large Bowel Cancer Project updates the state of the art of investigations concerning causes, role of animal models, early diagnosis of disease including potential biochemical markers, genetic and pharmacological consideration, proventive measures, and new approaches to the treatment of large bowel cancer. It points out the many interrelations in the multidisciplinary approaches to understanding the mechanisms of disease, means of prevention, methods of earlier diagnosis, and development of rational approaches in the control of large bowel cancer.