The effect of Bifidobacterium longum (4 x 10(8) viable cells/g diet) and a derivative of inulin ('Raftiline HP'; 5% w/w in diet) on colonic aberrant crypt foci (ACF) induced by the colon carcinogen azoxymethane (AOM) has been studied. The concentration of ammonia, a putative tumour promoter produced by bacterial degradation of protein and urea, and the activities of certain bacterial enzymes thought to play a role in colon carcinogenesis, beta-glucuronidase and beta-glucosidase were also assayed. Consumption of either B. longum or inulin was associated with a decrease (26 and 41%, respectively) in AOM-induced small ACF (i.e. those comprising 1-3 aberrant crypts per focus). Combined administration of the bifidobacterium and inulin resulted in more potent inhibition of ACF than administration of the two separately, achieving 80% inhibition of small ACF. Furthermore, the combined administration significantly decreased the incidence (by 59%) of large ACF (>4 aberrant crypts per focus), which are considered to be predictive of eventual tumour incidence. Since the dietary treatments were started 1 week after the carcinogen dose, the results suggest that B. longum and inulin may be affecting the early promotion phase of the carcinogenic process. Consumption of diets containing B. longum, inulin or both were also associated with decreases in beta-glucuronidase activity and ammonia concentration in the caecal contents. Both these factors have been associated with carcinogenesis of the colon in experimental animal models. In rats given inulin-containing diets (with or without B. longum) an increase in caecal wt and beta-glucosidase activity and a decrease in caecal pH were observed. The results suggest that consumption of B. longum or inulin was associated with potentially beneficial changes in caecal physiology and bacterial metabolic activity in relation to tumour risk and in the incidence of putative preneoplastic lesions in the colon. The results also indicated that combined treatment with the two agents was more effective in reducing colonic lesions.

The effect of sucrose and resistant starch (‘CrystaLean’– a retrograded, amylose starch) on human gut microflora and associated parameters was studied in human flora‐associated (HFA) rats, colonized with microfloras from UK or Italian subjects, to determine whether such floras were affected differently by dietary carbohydrates. Consumption of the resistant starch diet resulted in significant changes in four of the seven main groups of bacteria enumerated. In both the UK and Italian flora‐associated rats, numbers of lactobacilli and bifidobacteria were increased 10–100‐fold, and there was a concomitant decrease in enterobacteria when compared with sucrose‐fed rats. The induced changes in caecal microflora of both HFA rat groups were reflected in changes in bacterial enzyme activities and caecal ammonia concentration. Although it had little effect on caecal short‐chain fatty acid concentration, CrystaLean markedly increased the proportion of n‐butyric acid in both rat groups and was associated with a significant increase in cell proliferation in the proximal colon of the Italian flora‐associated rats. CrystaLean appeared to play a protective role in the colon environment, lowering caecal ammonia concentration, caecal pH and β‐glucuronidase activity.

Lactic acid bacteria (LAB) are proposed to have several beneficial effects, including the inactivation of carcinogens. We have studied the potential of Lactobacillus acidophilus (from a commercially available yogurt), Lactobacillus gasseri (P79), Lactobacillus confusus (DSM20196), Streptococcus thermophilus (NCIM 50083), Bifidobacterium breve and Bifidobacterium longum (from human infant stool) to prevent the induction of DNA damage by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG, 7.5 mg/kg body wt) in colon cells of the rat. Using the new technique of single cell microgel electrophoresis, all investigated strains were antigenotoxic toward MNNG after a single dose of 10(10) viable cells/kg body wt p.o. eight hours before the carcinogen. One-half and one-tenth of this initial dose resulted in a loss of protective activity. High doses of heat-treated L. acidophilus strains were also not antigenotoxic. One mechanism of the preventive effect could be that bacterial metabolites or components are responsible. Accordingly, selected examples were investigated in vitro in colon cells of the rat. Metabolically active L. acidophilus cells, as well as an acetone extract of the culture, prevented MNNG-induced DNA damage. Different cell fractions from L. acidophilus (cytoplasm, cell wall skeleton, cell wall) were devoid of antigenotoxic activity, whereas the peptidoglycan fraction and whole freeze-dried cells were antigenotoxic. As a second carcinogen, 1,2-dimethylhydrazine (DMH) was used. A dose- and time-response study was first performed to assess the effects of DMH in several segments of the gastrointestinal (GI) tract. Exposure for 16 hours to 15 or 25 mg DMH/kg body wt p.o. induced DNA damage in cells of the distal colon of rats, whereas no cytotoxicity was seen. Pretreatment orally with LAB on four consecutive mornings before DMH gavage (8 hours after the last LAB application) revealed that L. acidophilus, L. confusus, L. gasseri, B. longum, and B. breve inhibited the genotoxic effect of DMH. One of four S. thermophilus and one of three Lactobacillus delbrueckeii ssp. bulgaricus strains were also protective. Heat-treated L. acidophilus did not inhibit DMH-induced genotoxicity. A few aliquots of the colon cells were processed immunohistochemically for the presence of the "proliferation cell nuclear antigen" (PCNA). DMH treatment did not increase PCNA, nor was there any modulation by LAB. The effect of L. acidophilus on foreign compound-metabolizing enzymes (Phase I and Phase II) in liver and colon cells of rats revealed only one parameter to be modulated, namely, a two- to three-fold increase in the levels of NADPH-cytochrome P-450 reductase. The meaning of this finding, in terms of possible chemoprevention by LAB, remains unclear. In conclusion, our studies show that most, but not all, LAB tested could strongly inhibit genotoxicity in the GI tract of the rat and that viable LAB organisms are required for the protective effect in vivo. The comet assay technique is a powerful tool to elucidate such in vivo antigenotoxic act...

The effect on various caecal bacteria and their metabolic activities of feeding diet containing transgalactosylated oligosaccharides (TOS) with or without Bifidobacterium breve (administered in the drinking water) was investigated in rats colonized with a human faecal microflora. TOS (5% w/w in diet) or TOS plus B. breve, given for 4 weeks, induced increases in caecal concentration of total anaerobic bacteria, lactobacilli and bifidobacteria, and decreases in numbers of enterobacteria. Caecal pH was significantly reduced by feeding TOS, as were the activities of beta-glucuronidase and nitrate reductase. In contrast, beta-glucosidase activity was increased in TOS-fed rats. Dietary TOS was also associated with decreased conversion, by caecal contents, of the dietary carcinogen 2-amino-3-methyl-3H-imidazo[4,5-f] quinoline (IQ) to its genotoxic 7-hydroxy derivative.

No abstract

Objective: To investigate the dose -response effects of a novel fat emulsion (Olibra TM ) on energy and macronutrient intakes up to 36 h post-consumption in non-overweight subjects. Design: A single-blind, placebo-controlled, within-subject cross-over design was used. Setting: Metabolic suite of the University of Ulster, Coleraine. Subjects: Fifty subjects (30 female, 20 male) from the student and staff population of the University of Ulster, Coleraine. Interventions: Subjects were given in random order, 7 days apart, a 200 g portion of yoghurt containing a total of 15 g of fat, which varied in quantity of Olibra TM fat (0, 2, 4, 6 g) at 09:00 h. At 13:00 h subjects were given ad libitum access to a range of foods. Amounts of food consumed were measured by covert pre-and post-consumption weighing of individual serving dishes. For the remainder of the day and the following 24 h, subjects weighed and recorded all food intakes. 39.3, 38.2, 39.6% energy), intakes were progressively reduced with increasing doses of Olibra TM fat in the total group (P < 0.001). A similar response was observed in the female group up to 4 g (P < 0.001) and in the male group after 2 and 6 g (P < 0.05). Energy and macronutrient intakes for the remainder of each study day and over the following 24 h were significantly lower after all dose levels compared to the control (P < 0.001). Conclusion:The results suggest that Olibra TM fat reduced the effect of overeating during an ad libitum lunch meal and subsequent food intake up to 36 h post-consumption.

OBJECTIVE:To investigate the effects of a yoghurt containing a novel fat emulsion on energy and macronutrient intakes up to 8 h post-consumption in non-overweight, overweight and obese subjects, and to assess energy compensation over the following 24 h. DESIGN: A double-blind, placebo-controlled, within-subject crossover design was used. Twenty (10 female, 10 male) nonoverweight (body mass index (BMI) 20 -24.9 kg=m 2 ), 20 (10 female, 10 male) overweight (BMI 25 -29.9 kg=m 2 ) and 20 (13 female, 7 male) obese (BMI > 30 kg=m 2 ) subjects participated in the study. Subjects were given in random order, 7 days apart, either a 200 g portion of a test (5 g of a novel fat emulsion þ 1 g milk fat) or control (6 g milk fat) yoghurt at 09:00 h. At 4 and 8 h post-consumption subjects were given ad libitum access to a range of foods. Amounts of food consumed were determined by pre and post-covert weighing of individual serving dishes. Over the following 24 h subjects weighed and recorded all food intakes. RESULTS: Mean energy intakes were significantly lower after the test yoghurt compared with the control yoghurt in nonoverweight (3.79 vs 5.43 MJ; P < 0.01) and overweight (4.43 vs 6.12 MJ; P < 0.001) subjects 4 h post-consumption and in nonoverweight (3.82 vs 5.38 MJ; P < 0.001), overweight (3.94 vs 5.80 MJ; P < 0.001) and obese (4.91 vs 6.26 MJ; P < 0.01) subjects 8 h post-consumption. The corresponding macronutrient intakes were also significantly reduced in non-overweight and overweight subjects (P < 0.01) at 4 h post-consumption and in all subjects 8 h post-consumption (P < 0.01). In the total group, energy intakes over the following 24 h were also significantly reduced (6.35 vs 7.70 MJ; P < 0.01) after the test yoghurt relative to the control yoghurt. CONCLUSIONS: These results suggest that the effects of this novel fat emulsion are maintained at least up to 8 h and are evident in non-overweight, overweight and obese subjects.

BACKGROUND: The satiating properties of fat remain poorly understood, particularly with reference to its physicochemical characteristics. OBJECTIVE: To investigate the short-term effects of consumption of yoghurt containing either a novel fat emulsion or normal milk fat, on the energy and macronutrient intakes of non-obese subjects. DESIGN: Two double-blind, placebo-controlled, within-subject crossover studies were conducted three months apart. Twenty-nine (15 F, 14 M) and thirty (16 F, 14 M) subjects participated in Study 1 and Study 2 respectively. In each study, subjects were given in random order, 7 days apart, either a 200 g portion of a test (5 g of a novel fat emulsion 1 g milk fat) or control (6 g milk fat) yoghurt at 1300 h. At 4 h post-consumption subjects were given ad libitum access to a range of foods. Amounts of food consumed by individuals were determined by pre-and post-covert weighing of individual serving dishes. RESULTS: Mean energy intakes were signi®cantly lower after the test yoghurt compared with the control yoghurt in Study 1 (6.4 vs 7.6 MJ; P`0.001), Study 2 (6.9 vs 7.9 MJ; P`0.001), and for both studies combined (6.7 vs 7.7 MJ; P`0.001). The corresponding fat intakes in Study 1, Study 2 and in the combined studies were all signi®cantly reduced (P`0.001). Protein and carbohydrate intakes were also signi®cantly reduced in Study 1 (P`0.05), Study 2 (P`0.01), and for the combined studies (P`0.001). CONCLUSIONS: These results suggest that the physicochemical characteristics of small amounts of dietary fat affect short-term satiety.