Influence of germ-free status on the excretion of simple phenols of possible significance in tumour promotion

Establishment of orally-administered Lactobacillus gasseri SBT2055SR in the gastrointestinal tract of humans and its influence on intestinal microflora and metabolism

AIMS

To investigate the fate of a streptomycin-rifampicin-resistant variant of Lactobacillus gasseri SBT2055 (LG2055SR) and the influence of its oral administration on the composition and metabolism of the intestinal microflora.

METHODS AND RESULTS

Intestinal passage of LG2055SR was monitored by a combination of selection with antibiotics and identification by a randomly amplified polymorphic DNA (RAPD)-PCR METHOD: Composition of intestinal microflora was analysed by the method developed by Mitsuoka et al. (1965, 1974). Establishment of orally-administered LG2055SR in the human intestine was confirmed in this study. LG2055SR ingestion specifically lowered faecal populations of Staphylococcus and faecal contents of p-cresol.

CONCLUSION

LG2055SR and its parent strain, LG2055, are considered to be appropriate candidates for probiotics.

SIGNIFICANCE AND IMPACT OF THE STUDY

It is clarified that LG2055SR has the ability to establish in the human gastrointestinal tract and alters the composition and metabolism of the intestinal microflora and physical characteristics of faeces.

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.

Pre-neoplastic changes in rat urothelium following portacaval anastomosis

The development of pre-neoplastic and neoplastic changes has been documented in the urinary tract of the rat after portacaval shunting (PCS) and has been attributed variously to circulating carcinogens, the development of bladder stones, or deficiency of vitamin A. Therefore, an investigation of the pathogenesis of bladder tumors after PCS was undertaken in 120 PCS and 120 sham-operated male Sprague Dawley rats. Ten rats from each group were sacrificed at monthly intervals for 1 year after surgery. The incidence of calculus formation in the bladder increased from 20% at 2 months to 80% at 12 months after PCS. Hyperplastic mucosal changes occurred 3 months after surgery. After 5 months, distinct papillomas developed, and after 7 months, increasingly severe papillary changes and squamous metaplasia were evident. Interestingly, these urothelial changes were seen both in animals with and without bladder stones. Significantly decreased serum vitamin A levels were observed at 6 months (54.0 +/- 8.8 IU/dl, n = 10) (P less than .01), and 12 months (41.0 +/- 7.9 IU/dl, n = 10) (P less than .01), compared to those in sham-operated controls of 126.0 +/- 12.5 IU/dl (n = 10) and 122.7 +/- 19.2 IU/dl (n = 10). In addition, PCS resulted in a significantly increased activity of urothelial ornithine decarboxylase (ODC), a marker of neoplastic changes, at 6 months (3.1 +/- 0.4 nmoles CO2 in 60 min/mg protein, n = 5) (P less than .05) and 12 months (8.1 +/- 0.6 nmoles CO2 in 60 min/mg protein, n = 5) (P less than .05), when compared to ODC activity in controls (0.9 +/- 0.2 nmoles CO2 in 60 min/mg protein, n = 5). These data suggest that the development of urinary bladder tumor after PCS in the rat may be due to vitamin A deficiency rather than to bladder calculi or urinary carcinogens.

The urinary excretion of bacterial amino-acid metabolites by rats fed saccharin in the diet

Administration of a diet containing 7.5% saccharin to adult male rats for 40 days caused a three- to four-fold increase in the daily excretion of indican and rho-cresol. Indican is formed from indole which is a microbial metabolite of tryptophan, whilst rho-cresol is formed by the gut flora from tyrosine. The excretion of phenol, which is also a microbial metabolite of tyrosine, was abolished by saccharin administration for 40 days. Analysis of urines collected at 13, 18 and 24 months during a two-generation cancer bioassay showed that these changes occur throughout the life of saccharin-treated rats. These data indicate that saccharin changes the metabolism of amino acids by the gut flora, leading to an increased formation of products known to have promoting or co-carcinogenic properties.

Red wine contains a potent inhibitor of phenolsulphotransferase

Many ethanolic drinks, especially red wine, contain potent inhibitors of phenolsulphotransferase. At a dilution of 1/75 from the original beverage, extracts from six types of red wine inhibited human platelet phenolsulphotransferase P by a mean of 99% and human platelet phenolsulphotransferase M by 12%. Such extracts had no significant effect on rat liver monoamine oxidase A or human platelet monoamine oxidase B. The inhibitors, which have not yet been identified, can be extracted into ethyl acetate at acid or neutral pH. Thus, they are not monoamines. Flavonoid phenols are plausible candidates. As phenolsulphotransferase M and P are involved in the metabolism of many phenols, including drugs, the inhibition of these enzymes could result in the enhancement of pharmacological potency and have important clinical consequences.

Platelet monoamine oxidase and phenolsulphotransferase M and P in cancer

Phenolsulphotransferase and monoamine oxidase inactivate a wide range of dietary and endogenous phenols/monoamines by sulphoconjugation and oxidative deamination respectively. In this study, both enzymes were measured in platelets from cancer patients and controls. Of the two variants of phenolsulphotransferase, activity of the P form was normal in all groups. Activity of the M form was, however, significantly less than control values in patients with cancer of the rectum and bowel but not in other cancer patient groups. If this finding reflects enzyme activity elsewhere in the body and is not merely a manifestation of an abnormal platelet population, the deficit could expose affected subjects to the action of potentially carcinogenic dietary phenols. Platelet monoamine oxidase activity was significantly raised in the cancer group as a whole, and in all sub-types investigated apart from breast cancer. The increase in the cancer group as a whole was independent of sex, age, drugs, radiotherapy, smoking or platelet count. Its mechanism and significance are unknown but there may be links with the patients' psychiatric state.

Nitrous acid mutagenesis of duplex DNA as a three-component system

Purified native Hemophilus influenzae DNA is relatively insusceptible to nitrous acid (NA) mutagenesis in vitro, but is readily mutated following denaturation. NA mutagenicity for duplex DNA is significantly increased in the presence of various alcohols, glycols, phenols or primary amines. Phenol-extracted DNA contains dissociable contaminants of low molecular weight that enhance NA mutagenesis. Enhancement of NA mutagenesis by phenol and by spermine is due to the formation of unstable molecular species. We propose that reactive organic nitroso compounds are formed which then serve as delivery vehicles to promote mutagenicity of native DNA, perhaps via transnitrosation reactions. Similar reactions probably occur in vivo to promote NA-induced base substitution (but not frameshift) mutations in Salmonella typhimurium and in Escherichia coli. The possible significance of these observations to carcinogenesis is discussed.