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BACKGROUND: In Western societies colonic cancer most frequently develops in the distal colon, largely as a result of the composition of the diet. Modulation of dietary factors is therefore an attractive modality to reduce colorectal cancer risk. This study aims to evaluate the potentially protective effects of calcium in right hemicolectomy patients. MATERIALS AND METHODS: A randomized controlled cross-over intervention trial was performed with 1000 mg of elemental calcium per day for 2 months in 15 right hemicolectomy patients. Primary endpoints were proliferative activity, determined by immunohistochemical detection of BrdU-labeled cells (LI) in rectal biopsies, and cytotoxicity and alkaline phosphatase activity of faecal water. Secondary endpoints were bile acid composition in faeces. RESULTS: Calcium-reduced LI in the superficial one-third of the crypt (from 0.84 +/- 0.27% to 0.37 +/- 0.08%, P = 0.04) and a trend towards a lower total LI and LI in the mid one-third of the crypt was observed. Alkaline phosphatase activity was reduced from 6.2 +/- 2.6 U mL-1 in the placebo period to 4.6 +/- 2.2 in the calcium period (P = 0.02), and a trend toward a lower cytotoxicity of faecal water was observed. No effect on total bile acids in faeces was observed, but calcium increased the percentage of deoxycholic acid (from 49.6 +/- 7.0% to 56.5 +/- 6.2%, P = 0.03) and decreased the percentages of cholic acid (from 10.3 +/- 4.7% to 5.8 +/- 2.7%, P = 0.05) and lithocholic acid (from 26.7 +/- 3.4% to 23.9 +/- 2.9%, P = 0.04). CONCLUSION: Calcium may have a protective effect against colorectal cancer risk in right hemicolectomy patients.

Ursodeoxycholic acid (UDCA) has been shown to affect membrane-damaging effects of bile acids in vitro and fecal bile acid composition in rats. This study evaluates the effect of UDCA on fecal bile acid composition and on cytolytic activity of fecal water in man to clarify the potential chemopreventive role of UDCA for colorectal cancer.In this placebo-controlled crossover intervention trial, the effect of 900 mg/day UDCA orally in 15 healthy volunteers was studied. At the end of each 4-week period, 72 h feces were collected. Total and individual bile acids in feces were determined by gas chromatography and soluble bile acids were analyzed by high-performance liquid chromatography. Cytolytic activity of fecal water was measured using an erythrocyte lysis assay.In feces, the percentages of primary bile acids-cholic acid (CA) and chenodeoxycholic acid (CDCA)-and of secondary bile acid-deoxycholic acid (DCA) - decreased after supplementation with UDCA, whereas those of UDCA and LCA increased from 2.7 +/- 0.4% to 23.7 +/- 2.6%, P0.0001 and from 26.2 +/- 1.2% to 49.4 +/- 1.8%, P0.0001 respectively. The concentrations of these two bile acids in fecal water also increased after UDCA administration from 7.8 +/- 1.9 micromol/l to 47.0 +/- 6.7 micromol/l (UDCA), P0.0001 and from 2.5 +/- 0.6 micromol/l to 18.3 +/- 4.1 micromol/l (LCA), P0.002, respectively. Cytolytic activity of fecal water was not affected by UDCA.These results do not support a protective effect of UDCA supplementation against colorectal cancer in man.

BACKGROUND & AIMS: Dietary calcium decreases the cytotoxicity of intestinal contents and intestinal epitheliolysis by precipitating cytotoxic surfactants such as bile acids. A decreased luminal cytotoxicity might not only strengthen the barrier function of the gut mucosa but also reinforce the protective, endogenous microflora. We hypothesized, therefore, that dietary calcium increases the resistance to intestinal infections. METHODS: Rats on a low-, medium-, or high- calcium purified diet were orally infected with a single dose of Salmonella enteritidis. The kinetics of fecal Salmonella excretion was studied to determine the colonization resistance. Intestinal bacterial translocation was quantitated by measuring urinary oxidation products of nitric oxide (NOx) excretion and culturing bacteria from tissues. RESULTS: Compared with the low-calcium group, the medium- and high- calcium diet-fed rats had a substantially improved colonization resistance. Calcium supplementation also reduced translocation of Salmonella, considering the diminished urinary NOx excretion and viable Salmonella counts in the Ileal Peyer's patches and spleen. Dietary calcium decreased the bile acid concentration and cytotoxicity of fecal water. Several indicators of fecal bacterial mass were significantly increased by supplemental calcium. CONCLUSIONS: Dietary calcium improves the colonization resistance and reduces the severity of gut- derived systemic infections, which is probably attributable to its luminal cytoprotective effects. (Gastroenterology 1997 Aug;113(2):550-7)

Recently we showed that supplemental dietary calcium stimulates the intestinal formation of insoluble calcium phosphate and decreases the ratio of dihydroxy to trihydroxy bile acids in human duodenal bile. Because previous in vitro studies indicated that these effects could be due to differential adsorption of bile acids to amorphous calcium phosphate, we characterized the binding of bile acids to calcium phosphate. Freshly formed, amorphous, calcium phosphate bound and thus precipitated glycine-conjugated and unconjugated bile acids, whereas taurine-conjugated bile acids showed little binding. Glycochenodeoxycholic acid hardly adsorbed to other insoluble calcium phosphates, including hydroxyapatite. Adsorption studies using increasing amounts of glycine-conjugated and unconjugated bile acids showed that binding occurred above a bile acid-specific critical minimum concentration, dependent on bile acid hydrophobicity. The simultaneous use of a fluorescent hydrophobic probe indicated that this binding was due to ionic adsorption of monomers of bile acids, followed by their hydrophobic aggregation on the calcium phosphate surface, probably in the form of a bilayer. Finally, using human duodenal bile we found that amorphous calcium phosphate, but not Ca2+, preferentially bound and thus precipitated dihydroxy bile acids. We conclude that freshly formed, amorphous, calcium phosphate is a prerequisite for adsorption of bile acids and that monomers of glycine-conjugated and unconjugated dihydroxy bile acids have a high binding affinity for amorphous calcium phosphate.

It has been hypothesized that bile acids and fatty acids promote colon cancer. A proposed mechanism is a lytic effect of these surfactants on colonic epithelium, resulting in a compensatory proliferation of colonic cells. To investigate the first step of this hypothesis, we studied the lytic activity of fatty acids and physiological mixtures of fatty acids and bile acids. Experiments were performed in both erythrocytes and cultured Caco-2 cells, a model system for intestinal epithelium. Fatty acids with a chain length of 10 C atoms or more were lytic, and the hemolytic activity increased in the order C10:0 less than C18:0 less than C16:0 less than C12:0 less than C14:0 much less than C18:1 approximately C18:2 but was not dependent on their critical micellar concentration. Addition of a sublytic, submicellar concentration of cholate resulted in the formation of highly lytic mixed micelles. Lytic activity of these mixed micelles was closely associated with their micellar aggregation as determined in parallel incubations using a fluorescent micellar probe. With use of identical concentrations of fatty acids and mixed micelles, lysis of erythrocytes was highly correlated (r greater than 0.95) with lysis of Caco-2 cells measured by either release of the apical membrane-marker alkaline phosphatase or the cytosolic marker lactate dehydrogenase. This indicates that the cytolytic activity of these surfactants is not cell-type dependent. Addition of bile acids in concentrations corresponding with the total bile acid concentration in human fecal water resulted in an increased lytic activity of fatty acids.(ABSTRACT TRUNCATED AT 250 WORDS)

Unconjugated secondary bile acids can promote colon cancer by damaging colonic mucosa and consequently increasing epithelial proliferation. It has been proposed that dietary calcium inactivates intestinal bile acids either by a Ca2(+)-dependent precipitation or by binding to insoluble calcium phosphate (CaPi). We studied the molecular mechanisms of these opposing hypotheses by using hemolysis of erythrocytes as a model parameter for cytotoxicity. Washed human erythrocytes were incubated for 15 min with buffered media (pH 7.4) containing increasing amounts of different bile acids. Deconjugation and 7 alpha-dehydroxylation of mixtures of glycine- or taurine-conjugated cholate and chenodeoxycholate drastically increased their cytotoxicity. Parallel measurements, using a fluorescent micellar probe, indicated that micellar aggregation is a prerequisite for this bile acid-induced lysis. Ca2+ concentrations up to 15 mM did not precipitate bile acids but stimulated cytotoxicity of both deoxycholate (DC) and its glycine conjugate (GDC). Cytotoxicity of the taurine conjugate (TDC) was stimulated to a much lesser extent. Increasing amounts of CaPi precipitated micellar DC and GDC, but not TDC, and consequently inhibited only cytotoxicity of the former two. These findings indicate that 1) hydrophobicity and micellar aggregation are important determinants of bile acid-induced cytotoxicity that explain the high cytotoxic potential of secondary bile acids in colon, and 2) cytotoxicity of bile acids is stimulated by free Ca2+ and inhibited by CaPi. This inhibition is due to binding of carboxylic (including secondary) bile acids to CaPi.

In Western societies colonic cancer most frequently develops in the distal colon, largely as a result of the composition of the diet. Modulation of dietary factors is therefore an attractive modality to reduce colorectal cancer risk. This study aims to evaluate the potentially protective effects of calcium in right hemicolectomy patients.A randomized controlled cross-over intervention trial was performed with 1000 mg of elemental calcium per day for 2 months in 15 right hemicolectomy patients. Primary endpoints were proliferative activity, determined by immunohistochemical detection of BrdU-labeled cells (LI) in rectal biopsies, and cytotoxicity and alkaline phosphatase activity of faecal water. Secondary endpoints were bile acid composition in faeces.Calcium-reduced LI in the superficial one-third of the crypt (from 0.84 +/- 0.27% to 0.37 +/- 0.08%, P = 0.04) and a trend towards a lower total LI and LI in the mid one-third of the crypt was observed. Alkaline phosphatase activity was reduced from 6.2 +/- 2.6 U mL-1 in the placebo period to 4.6 +/- 2.2 in the calcium period (P = 0.02), and a trend toward a lower cytotoxicity of faecal water was observed. No effect on total bile acids in faeces was observed, but calcium increased the percentage of deoxycholic acid (from 49.6 +/- 7.0% to 56.5 +/- 6.2%, P = 0.03) and decreased the percentages of cholic acid (from 10.3 +/- 4.7% to 5.8 +/- 2.7%, P = 0.05) and lithocholic acid (from 26.7 +/- 3.4% to 23.9 +/- 2.9%, P = 0.04).Calcium may have a protective effect against colorectal cancer risk in right hemicolectomy patients.

Item does not contain fulltext High intake of red meat is associated with increased colon cancer risk. We have shown earlier that this may be due to the high haem content of red meat, because dietary haem increased cytolytic activity of faecal water and colonic epithelial proliferation. Dietary calcium inhibits diet-induced epithelial hyperproliferation. Furthermore, it has been shown that supplemental calcium inhibited the recurrence of colorectal adenomas. Therefore, we studied whether dietary calcium phosphate can exert its protective effects by inhibiting the deleterious effects of haem. In vitro, calcium phosphate precipitated haem and inhibited the haem-induced cytotoxicity. Subsequently, rats were fed diets, differing in haem (0 or 1.3 micromol/g) and calcium phosphate content only (20 or 180 micromol/g). Faeces were collected for biochemical analyses. Cytolytic activity of faecal water was determined from the degree of lysis of erythrocytes by faecal water. Colonic epithelial proliferation was measured in vivo using [(3)H]thymidine incorporation. In rats fed low calcium diets, dietary haem increased cytolytic activity of faecal water (98 +/- 1 versus 1 +/- 1%, P < 0.001) and the concentration of cations in faeces (964 +/- 31 versus 254 +/- 20 micromol/g), when compared with controls. This indicates that dietary haem increased colonic mucosal exposure to luminal irritants. Colonic epithelial proliferation was increased compared with controls (70 +/- 4 versus 48 +/- 8 d.p.m./microg DNA, P < 0.001). This was accompanied by metabolism of the ingested haem and solubilization of haem compounds in the faecal water. A high calcium diet largely prevented this metabolism and solubilization. It also inhibited the haem-induced cytolytic activity of faecal water and increase in faecal cation concentration. In accordance, the haem-induced colonic epithelial hyperproliferation was prevented. We therefore suggest that dietary calcium phosphate acts as a chemopreventive agent in colon carcinogenesis by inhibiting the cytolytic and hyperproliferative effects of dietary haem.

High intake of red meat is associated with an increased risk of colon cancer. It has been suggested that fat from red meat is responsible, because high fat intake increases the concentration of cytotoxic lipids in the colon. Experimental studies have not unequivocally supported such a role for fat, however. Recently, we showed that dietary haem, which is abundant in red meat, increased colonic cytotoxicity and epithelial proliferation. In this study, we wanted to clarify whether dietary fat affects colon cancer risk by itself or by modulating the detrimental effects of haem on the colonic epithelium. Rats were fed control or haem-supplemented diets with 10%, 25% or 40% of the energy derived from fat for 14 days. Faeces were collected for biochemical analyses. Colonic cytotoxicity was determined from the degree of lysis of erythrocytes by faecal water. Colonic epithelial proliferation was measured in vivo using [(3)H]thymidine incorporation. Increasing the fat content of the control diets stimulated faecal disposal of both fatty acids and bile acids. It also increased the concentration of fatty acids, but not that of bile acids, in faecal water in control rats. The cytolytic activity of faecal water and colonic epithelial proliferation were unaffected. Dietary haem increased faecal cation content and cytolytic activity of faecal water at all fat levels, suggesting that the colonic mucosa was exposed to high amounts of luminal irritants. This effect was smaller in rats on the low-fat diet. Dietary haem also increased colonic epithelial proliferation at all fat levels. The haem-induced effects were independent of fatty acids or bile acids in the faecal water. In western societies, 30-40% of ingested energy is supplied by dietary fat, so our results suggest that the association between consumption of red meat and risk of colon cancer is mainly due to its haem content, and is largely independent of dietary fat content.

BACKGROUND AND AIMS: Lactulose fermentation by the intestinal microflora acidifies the gut contents, resulting in an increased resistance to colonisation by acid sensitive pathogens. The extent of fermentation should be controlled to prevent acid induced epithelial cell damage. Considering the buffering capacity of calcium phosphate and its intestinal cytoprotective effects, whether supplemental calcium phosphate adds to the increased resistance to intestinal infections by lactulose fermentations was studied. METHODS: In a strictly controlled experiment, rats were fed a purified low calcium control diet, a low calcium/lactulose diet, or a high calcium/lactulose diet, and subsequently infected orally with Salmonella enteritidis. RESULTS: Lactulose fermentation lowered the pH and increased the lactic acid concentration of the intestinal contents, which significantly reduced excretion of this pathogen in faeces; thus it improved the resistance to colonisation. This agreed with the high sensitivity of S enteritidis to lactic acid (main metabolite of lactulose fermentation) in vitro. Calcium phosphate decreased translocation of S enteritidis to the systemic circulation, an effect independent of lactulose. The unfavourable increased cytotoxicity of faecal water caused by lactulose fermentation was more than counteracted by supplemental calcium phosphate. Moreover, calcium phosphate stimulated lactulose fermentation, as judged by the reduced lactulose excretion in faeces and increased lactic acid, ammonia, and faecal nitrogen excretion. CONCLUSION: Extra calcium phosphate added to a lactulose diet improves the resistance to colonisation and translocation of S enteritidis. This is probably mediated by a calcium induced stimulation of lactulose fermentation by the intestinal microflora and reversion of the lactulose mediated increased luminal cytotoxicity, which reduces damage inflicted on the intestinal mucosa.

Calcium in milk products stimulates gastric acid secretion and inhibits the cytolytic activity of intestinal contents. Based on these effects, it was hypothesised that calcium might lessen the severity of food borne intestinal infections. The possible differential effects of a low calcium milk and normal milk products (milk, acidified milk, and pasteurised yoghurt) on the resistance of rats to a salmonella infection was therefore studied. Rats were infected orally with Salmonella enteritidis just after food consumption. The first day after infection, faecal salmonella counts of the yoghurt fed rats were significantly lower than those of the other groups. Thereafter, faecal salmonella excretion declined rapidly in all high calcium groups, whereas rats fed the low calcium milk continued to excrete high numbers of salmonella. The reduced colonisation resistance to salmonella of rats fed low calcium milk might be caused by the high cytolytic activity of faecal water or a high iron concentration in faecal water, already present before infection, or both. The reduced resistance of these rats corresponded with a large infection induced increase in the cytolytic activity of faecal water, an appreciable reduction in apparent iron absorption, and a large increase in faecal mucin and alkaline phosphatase excretion. In yoghurt fed rats, only minor infection induced changes in luminal parameters were noticed. The rats fed milk and acidified milk always showed intermediate reactions. In conclusion, in addition to fermentation by yoghurt bacteria, calcium in milk products strongly enhanced the resistance to salmonella infection by lowering luminal cytolytic activity or diminishing the availability of iron for pathogen growth, or both.

Calcium has been proposed to prevent colon cancer in subjects at risk for this tumour. This effect is supposed to be due at least in part to binding the bile acids to calcium, making them insoluble and harmless. To evaluate the effects of oral calcium supplementation on intestinal bile acids, 19 patients with adenomatous colonic polyps were supplemented with 35.5 mmol Ca2+ daily for 12 weeks. Duodenal bile, 24-h feces and 24-h urine were collected before and at the end of the 12-week period. In duodenal bile proportional concentration of cholic acid increased (38 +/- 4 vs. 51 +/- 3%, P