Quantitative contribution of factors regulating rat colonic crypt epithelium: role of parenteral and enteral feeding, caloric intake, dietary cellulose level and the colon carcinogen DMH

To elucidate the role and quantitative contribution of several exogenous factors which may regulate colon crypt mitotic activity, proliferative zone height (PZH) and crypt height, groups of rats were subjected to various feeding regimens both with and without treatment with the colon carcinogen, 1,2-dimethylhydrazine (DMH). The rats were divided into two major groups and one group was given eight weekly injections of DMH base at 9.5 mg kg-1 body weight. Throughout this period and for two additional weeks the rats were isocalorically fed either a defined nutritionally complete diet with different levels of dietary cellulose or they were parenterally (i.v.) fed a nutritionally complete liquid formula with different caloric levels. The rats were then injected with colchicine 3 h prior to sacrifice to arrest and to collect dividing cells at metaphase. The results of multiple regression analysis of all data were interpreted to indicate that parenteral feeding caused dramatic suppression of the colon crypt height (CH) and of the number of metaphase figures per crypt (MC). Increased cellulose intake stimulated CH but suppressed MC. The CH was also stimulated by DMH. CH was positively correlated to PZH and MC. The MC was suppressed by cellulose intake and negatively correlated to PZH but was positively correlated to CH. The PZH was positively correlated to CH. These findings were related to the role of luminal food, functional workload, kcal intake and treatment with DMH on the measured colon crypt parameters. A quantitative assessment of factors that regulate the measured colonic crypt parameters was accomplished.     

Aspirin suppresses 1,2-dimethylhydrazine-induced alteration of proliferative parameters in rat colonic crypts

Abstract. Human epidemiological reports and rodent experimental research data indicate a possible chemopreventive effect of regular aspirin use for decreasing risk of colon and rectum cancer incidence and mortality. We have previously demonstrated that aspirin can significantly suppress proliferative parameters in normal rat colonic epithelium when examined 24 h following an acute or chronic course of aspirin administration. To investigate whether aspirin would effectively suppress known carcinogen-induced changes in colonic epithelium, rats were given single s.c. injections of either aspirin (50 mg/kg bw) or saline on days 1–3 and either 1,2-dimethylhydrazine (DMH; 12 mg base/kg bw) or DMH vehicle on day 4 of each week for eight consecutive weeks. Rats were sacrificed 4 days after the last aspirin dose and 3 days after the last DMH or DMH vehicle dose. Using the proliferative biomarkers of proliferating cell nuclear antigen positive cells per midaxial crypt section (SCC), crypt proliferative zone height (PZ), crypt differentiated zone height (DZ), and total crypt height (CH), it was found that aspirin does suppress DMH-induced increases in SCC, PZ and CH. The findings demonstrate that aspirin has a long term (i.e. several days) protective effect against early carcinogen-induced proliferative changes in rat colonic crypts which may help account for aspirin's chemopreventive action against colon cancer.     

Dietary fibre on cell proliferation in large bowel mucosal crypts near or away from lymphoid nodules and on mineral bioavailability

The effect of consumption for 24 weeks of different amounts (0%, 5% or 10% w/w) of fermentable (pectin and guar gum) or nonfermentable (cellulose and lignin) dietary fibres on cell proliferation and other parameters in large bowel mucosal crypts was studied in rats. In all 12 dietary groups, the crypts located over the distal aggregate of lymphoid nodules (ALN) had more colchicine arrested metaphase figures per midaxial crypt section (MC) and a longer crypt column height than crypts located three to four cm away from this ALN. These differences are attributed to the tropic influence of nodular cells in the ALN. Consumption of fermentable fibre decreased pH in the lumen of the caecum, and glucose, Zn and Cu in serum but increased Ca and Mg in serum. The decrease in caecal pH and serum glucose was significantly correlated with a decrease in MC. Increased intake of the nonfermentable fibre types increased faecal bulk but had no significant correlation with the other measured crypt parameters. Multiple regression analyses was used to model the relationships between the mucosal crypt criterion variables and the two measured predictor variables, caecal pH and serum glucose. Relationships between dietary fibre, ALN, MC, bioavailability of dietary minerals and risk of colorectal cancer are discussed.     

Interactive Effects of Indigestible Carbohydrates,Protein Type,and Protein Level on Biomarkers of Large Intestine Health in Rats

The effects of indigestible carbohydrates, protein type, and protein level on large intestine health were examined in rats. For 21 days, 12 groups of six 12-week-old male Wistar rats were fed diets with casein (CAS), or potato protein concentrate (PPC), providing 14% (lower protein level; LP), or 20% (higher protein level; HP) protein, and containing cellulose, resistant potato starch, or pectin. Fermentation end-products, pH, and β-glucuronidase levels in cecal digesta, and ammonia levels in colonic digesta were determined. Cecal digesta, tissue weights, cecal and colon morphology, and colonocyte DNA damage were also analyzed. Digesta pH was lower, whereas relative mass of cecal tissue and digesta were higher in rats fed pectin diets than in those fed cellulose. Cecal parameters were greater in rats fed PPC and HP diets than in those fed CAS and LP diets, respectively. Short-chain fatty acid (SCFA) concentrations were unaffected by protein or carbohydrate type. Total SCFA, acetic acid, and propionic acid concentrations were greater in rats fed LP diets than in those fed HP. Cecal pool of isobutyric and isovaleric acids was greater in rats fed PPC than in those fed CAS diets. PPC diets decreased phenol concentration and increased ammonia concentration in cecal and colonic digesta, respectively. Cecal crypt depth was greater in rats fed PPC and HP diets, and was unaffected by carbohydrates; whereas colonic crypt depth was greater in rats fed cellulose. Myenteron thickness in the cecum was unaffected by nutrition, but was greater in the colon of rats fed cellulose. Colonocyte DNA damage was greater in rats fed LP diets than in those fed HP diets, and was unaffected by carbohydrate or protein type. It was found that nutritional factors decreasing cecal digesta weight contribute to greater phenol production, increased DNA damage, and reduced ammonia concentration in the colon.     

Effects of low copper intake on dimethylhydrazine-induced colon cancer in rats.

Rats fed low copper show a high incidence of dimethylhydrazine (DMH)-induced colon tumors compared with rats fed very high Cu. The difference could be due to Cu deficiency in the low group or to Cu toxicity in the high group. In the present study, rats fed low Cu (0.2 ppm) showed greater DMH-stimulated colon tumorigenesis than rats fed adequate Cu (8 ppm). Differences were seen in the number of rats developing tumors (5 of 11 vs 1 of 10), total tumors (7 vs 2), and average tumor mass (1.02 g vs 0.29 g). Low Cu intake did not cause any general DMH toxicity as assessed by body weight gain. To prevent Cu deficiency-induced mortality, low Cu feeding was begun in postweanling rats (weight, about 80 g) housed in groups of five to six, rather than individually. This limited the effects of low Cu feeding to only a moderate Cu deficiency based on several parameters, including three Cu antioxidant enzyme activities. Group-housed rats fed marginal Cu levels (2.5 ppm) showed normal Cu status, and DMH produced only one tumor in 10 rats. In conclusion, high DMH-induced colon tumorigenesis can be found in rats with low activities of Cu antioxidant enzymes.     

Dietary copper and dimethylhydrazine affect protein kinase C isozyme protein and mRNA expression and the formation of aberrant crypts in colon of rats.

Low dietary copper has been shown to decrease the expression of various protein kinase C (PKC) isozymes and increase the risk of colon cancer development in experimental animals. The purpose of this study was to investigate the relationship between dietary copper and carcinogen administration on PKC isozyme accumulation and aberrant crypt foci (ACF) formation in rats fed 0.9 and 7.7 microg Cu/g diet. After 24 and 31 d on the diets, the rats were injected with either dimethylhydrazine (DMH) (25 mg/kg i.p.) or saline and killed at two time points (2 wk and 8 wk after DMH). Rats fed low dietary copper had significantly lower (p<0.0001) hematocrits, hemoglobin, ceruloplasmin activity and plasma and liver copper concentrations than rats fed adequate dietary copper. Ingestion of low dietary copper significantly (p<0.005) increased the formation of DMH-induced ACF (116.8 vs 59.6). Low dietary copper significantly (p<0.05) decreased the concentration of PKC alpha, delta, and zeta in the colon at 2 wk but not at 8 wk. Thus, changes in PKC isoform protein concentration may be related to increased susceptibility of copper-deficient animals to colon cancer.     

DNA damage and aberrant crypt foci as putative biomarkers to evaluate the chemopreventive effect of annatto (Bixa orellana L.) in rat colon carcinogenesis

Chemoprevention opens new perspectives in the prevention of cancer and other degenerative diseases. Use of target-organ biological models at the histological and genetic levels can markedly facilitate the identification of such potential chemopreventive agents. Colon cancer is one of the highest incidence rates throughout the world and some evidences have indicated carotenoids as possible agents that decrease the risk of colorectal cancer. In the present study, we evaluate the activity of annatto (Bixa orellana L.), a natural food colorant rich in carotenoid, on the formation of aberrant crypt foci (ACF) induced by dimethylhydrazine (DMH) in rat colon. Further, we investigate, the effect of annatto on DMH-induced DNA damage, by the comet assay. Male Wistar rats were given s.c. injections of DMH (40 mg/kg body wt.) twice a week for 2 weeks to induce ACF. They also received experimental diets containing annatto at 20, 200 or 1000 ppm for five 5 weeks before (pre-treatment), or 10 weeks after (post-treatment) DMH treatment. In both protocols the rats were sacrificed on week 15th. For the comet assay, the animals were fed with the same experimental diets for 2 weeks. Four hours before the sacrifice, the animals received an s.c. injection of DMH (40 mg/kg body wt.). Under such conditions, dietary administration of 1000 ppm annatto neither induce DNA damage in blood and colon cells nor aberrant crypt foci in rat distal colon. Conversely, annatto was successful in inhibiting the number of crypts/colon (animal), but not in the incidence of DMH-induced ACF, mainly when administered after DMH. However, no antigenotoxic effect was observed in colon cells. These findings suggest possible chemopreventive effects of annatto through their modulation of the cryptal cell proliferation but not at the initiation stage of colon carcinogenesis.     

Vanadium inhibits placental glutathione S-transferase (GST-P) positive foci in 1,2-dimethyl hydrazine induced rat colon carcinogenesis

Vanadium (V) has recently been found to possess potent anti-neoplastic activity in rat colon carcinogenesis. In the present study attempts have been made to investigate the expression of the number and area of aberrant crypt foci positive for placental glutathione S-transferase (GST-P) during 1,2-dimethyl hydrazine (DMH)-induced rat colon carcinogenesis. Male Sprague Dawley rats were randomly divided into four groups. Rats in group A were designed as normal controls. Group B animals received DMH once a week (20 mg/kg body wt.) intraperitoneally for 16 weeks. Group C rats received the same treatment of DMH as in group B, along with 0.5-ppm vanadium as ammonium monovanadate ad libitum in drinking water throughout the experiment. Vanadium alone was given to Group D rats without any DMH injection. The expression of the number and the area of aberrant crypt foci (ACF) positive for GST-P was maximum in DMH-treated group. Vanadium-treated rats significantly reduced (P < 0.001) the expression of GST-P positive ACF cells (by 71.13%) for the entire period of the study. Moreover the histopathological examination also showed that vanadium action could minimize the aberrant crypt foci (P < 0.001). Furthermore, vanadium supplementation also elevated SOD activities in both liver and colon (P < 0.01, P < 0.02 and P < 0.01, P < 0.02 respectively) when compared to their carcinogen counterparts. Our results confirm that vanadium is particularly effective in limiting the action of the carcinogen, thereby establishing its anticarcinogenicity in chemically induced rat colon carcinogenesis.     

Hyperphagia and obesity in OLETF rats lacking CCK-1 receptors

The brain-gut peptide cholecystokinin (CCK) inhibits food intake following peripheral or site directed central administration. Peripheral exogenous CCK inhibits food intake by reducing the size and duration of a meal. Antagonist studies have demonstrated that the actions of the exogenous peptide mimic those of endogenous CCK. Antagonist administration results in increased meal size and meal duration. The feeding inhibitory actions of CCK are mediated through interactions with CCK-1 receptors. The recent identification of the Otsuka-Long-Evans-Tokushima Fatty (OLETF) rat as a spontaneous CCK-1 receptor knockout model has allowed a more comprehensive evaluation of the feeding actions of CCK. OLETF rats become obese and develop non-insulin dependent diabetes mellitus (NIDDM). Consistent with the absence of CCK-1 receptors, OLETF rats do not respond to exogenous CCK. OLETF rats are hyperphagic and their increased food intake is characterized by a large increase in meal size with a decrease in meal frequency that is not sufficient to compensate for the meal size increase. Deficits in meal size control are evident in OLETF rats as young as 2 days of age. OLETF obesity is secondary to the increased food intake. Pair feeding to amounts consumed by intact control rats normalizes body weight, body fat and elevated insulin and glucose levels. Hypothalamic arcuate nucleus peptide mRNA expression in OLETF rats is appropriate to their obesity and is normalized by pair feeding. In contrast, pair fed and young pre-obese OLETF rats have greatly elevated dorsomedial hypothalamic (DMH) neuropeptide Y (NPY) mRNA expression. Elevated DMH NPY in OLETF rats appears to be a consequence of the absence of CCK-1 receptors. In intact rats NPY and CCK-1 receptors colocalize to neurons within the compact subregion of the DMH and local CCK administration reduces food intake and decreases DMH NPY mRNA expression. We have proposed that the absence of DMH CCK-1 receptors significantly contributes to the OLETF's inability to compensate for their meal size control deficit leading to their overall hyperphagia. Access to a running wheel and the resulting exercise normalizes food intake and body weight in OLETF rats. When given access to running wheels for 6 weeks shortly after weaning, OLETF rats do not gain weight to the same degree as sedentary OLETF rats and do not develop NIDDM. Exercise also prevents elevated levels of DMH NPY mRNA expression, suggesting that exercise exerts an alternative, non-CCK mediated, control on DMH NPY. The OLETF rat is a valuable model for characterizing actions of CCK in energy balance and has provided novel insights into interactions between exercise and food intake.     

Effect of quality and quantity of dietary fat and dimethylhydrazine in colon carcinogenesis in rats.

The effect, quality, and quantity of dietary fat on colon tumor induction by DMH were studied in rats exposed to a given regimen for two generations prior to treatment with DMH. Animals fed a 20% corn oil or 20% lard and treated with DMH had a higher incidence of colonic tumors than did rats fed a 5% corn oil, 5% lard or Purina lab chow and treated similarly. The quality of fat had no major difference on the incidence of colonic tumors.     

Leptin, cell proliferation and crypt fission in the gastrointestinal tract of intravenously fed rats

Many peptides, hormones and growth factors have been implicated in the control of cell renewal in the gastrointestinal epithelium. Leptin is present in the stomach and salivary glands and leptin receptors are seen throughout the gut. Leptin can stimulate mitogen-activated protein kinase activity in vitro and short-term infusion has been reported to have a proliferative action on the colon in vivo, suggesting a biological link between obesity, physical activity and colon cancer. Food intake is one of the most important determinants of intestinal mucosal cell renewal, thus any direct effects of leptin on the gut may be hidden. This problem has been avoided experimentally by maintaining animals on total parenteral nutrition (TPN). Male Wistar rats were anaesthetized and cannulae were inserted into the jugular vein to deliver the TPN diet to which had been added 0, 0.5, 2.5, or 10 mg/kg of recombinant murine leptin. Orally fed rats were also studied. After 6 days of treatment, all animals were injected with vincristine and killed 2 h later. Tissue weight was recorded and crypt cell proliferation (arrested metaphases) and crypt fission were scored in 'microdissected' crypts. Leptin infusion led to a small decrease in body weight and in the weight of the caecum. Intestinal cell proliferation was significantly reduced by TPN when compared to the orally fed rats, but the addition of leptin had no effect on the small intestine or colon. Crypt fission was also significantly lowered in the TPN group. Fission was slightly but significantly increased in the proximal and mid-colon of the leptin-treated rats, but was decreased in the distal colon. Although leptin did not significantly alter cell proliferation, it had significant effects on the process of crypt fission in the colon, which varied according to the exact locality.     

Dietary arsenic affects dimethylhydrazine-induced aberrant crypt formation and hepatic global DNA methylation and DNA methyltransferase activity in rats

Cell culture studies have suggested that arsenic exposure results in decreased S-adenosylmethionine (SAM), causing DNA hypomethylation. Previously, we have shown that hepatic SAM is decreased and/or S-adenosylhomocysteine increased in arsenic-deprived rats; these rats tended to have hypomethylated DNA. To determine, the effect of dietary arsenic on dimethylhydrazine (DMH)-induced aberrant crypt formation in the colon, Fisher 344 weanling male rats were fed diets containing 0,05, or 50 μg As (as NaAsO₂)/g. After 12 wk, dietary arsenic affected the number of aberrant crypts (p<0.02) and aberrant crypt foci (p<0.007) in the colon and the amount of global DNA methylation (p<0.04) and activity of DNA methyltransferase (DNMT) (p<0.003) in the liver. In each case, there were more aberrant crypts and aberrant crypt foci, a relative DNA hypomethylation, and increased activity of DNMT in the rats fed 50 μg As/g compared to those fed 0.5 μg As/g. The same phenomenon, an increased number of aberrant crypts and aberrant crypt foci, DNA hypomethylation, and increased DNMT tended to hold when comparing rats fed the diet containing no supplemental arsenic compared to rats fed 0.5 μg As/g. The data suggest that there is a threshold for As toxicity and that possibly too little dietary As could also be detrimental. The U.S. Department of Agriculture, Agricultural Research Service. Northern Plains Area is an equal opportunity/affirmative action employer and all agency services are available without discrimination.     

Effects of sodium butyrate and salinomycin upon intestinal microbiota,mucosal morphology and performance of broiler chickens

The effect of dietary sodium butyrate (SB) or salinomycin (SAL) or both additives on performance, small intestinal morphology and microbial ecology of broiler chickens was studied. A growth trial was conducted with 96 Ross 308 female broilers from 1 to 30 days of age. Four treatment groups were fed with a non-supplemented control diet or three experimental diets supplemented with i) 300 mg SB (Adimix 30 coated) per kg, ii) 60 mg SAL (Sacox) per kg or iii) both additives in combination. Feed intake and body-weight gain decreased and gain-to-feed ratio increased due to SAL supplementation, while addition of SB did not affect performance in comparison with the control diet but positively affected feed intake and body-weight gain in comparison with birds fed the SAL-supplemented diet. Villus height in jejunum decreased, while crypt depth increased due to SAL supplementation. Addition of SB increased crypt depth in jejunum. No significant effect of either additive was observed in ileum morphology. Total short-chain organic acids concentration in ileal digesta decreased with SAL supplementation, mainly due to lower lactic acid concentration, but no effects were observed in the caeca. The SAL supplementation was accompanied by a pH increase in ileum and a pH decrease in caecum. No significant effect of SB addition was observed for these parameters. Total bacterial numbers and Lactobacillus [lactic acid bacteria (LAB)] counts in ileal and caecal contents were lower in birds fed with SAL-supplemented diet in comparison with birds fed with control or SB diet. DNA fingerprints revealed SAL supplementation to affect the microbial population by suppressing dominating LAB, potentially L. aviarius. The presented results show that dietary SAL, supplemented alone or in combination with SB, suppressed the microbial activity and altered the microbial community structure mainly in ileum. SAL alone negatively affected feed intake and body-weight gain; however, the effect was ameliorated by SB supplementation.     

Cell proliferation in the small intestine and colon of intravenously fed rats: effects of urogastrone-epidermal growth factor

Abstract. There is marked intestinal hypoplasia in the intestine of intravenously fed (TPN) rats. Recombinant urogastrone-epidermal growth factor (URO-EGF) reversed these changes by significantly increasing the length of the intestinal crypts. Crypt diameter, however, was not affected to the same extent. Few differences in labelling indices were seen between the orally fed and TPN groups, however, this was the consequence of the concomitant changes in crypt population.
The number of mitoses and labelled cells per crypt, and thus the crypt cell production rates, were significantly decreased in the TPN group when compared to the orally fed. URO-EGF significantly increased both proliferative indices and the number of dividing cells per crypt. Crypt cell production in the small intestine was restored to those levels seen in the orally fed rats, moreover, labelling per crypt in the colon was increased to more than twice that of orally fed rats. The location of the mean labelling position and the half maximum labelling position followed the changes in crypt length in the small intestine, but to a lesser extent; thus the growth fraction was significantly increased in the TPN rats in comparison with the orally fed and the URO-EGF treated groups. Similar changes in these positions were seen in the colon, but the growth fraction was much reduced in the URO-EGF treated rats, as a consequence of the large increase in crypt length without a concomitant alteration in label distribution.     

The effects of diet on the esterification of glycerol phosphate, dihydroxyacetone phosphate and 2-hexadecylglycerol by homogenates of rat adipose tissue.

1. Male rats were fed for 5 weeks after weaning on a diet containing (by weight) 59% of starch or on diets that contained 39% of starch and 20% of either sucrose, beef tallow or corn oil. 2. The rats fed on the beef tallow consumed more energy than did the rats fed on the starch and sucrose diets. The rats fed on the corn oil drank less water than did the other groups of rats. 3. There were no significant differences between the four groups in terms of body-weight gain, epididymal-fat-pad weight and in the size, number and triacylglycerol content of the adipocytes in the fat-pads. 4. There was a significant correlation (P less than 0.001) between the activities of glycerol phosphate acyltransferase and monoacylglycerol acyltransferase in individual rats. Both of these activities were highest in the group fed on the high-starch diet and both correlated with the consumption of glucose by individual rats in the four groups. 5. The percentage of glycerol phosphate converted into diacylglycerol and triacylglycerol was positively correlated with the mean diameters, surface area and triacylglycerol content of the adipocytes for individual rats and was greates in the sucrose-fed rats. 6. The specific activity of dihydroxyacetone phosphate acyltransferase was highest in the rats fed on beef tallow. This activity was positively correlated with the energy intake for all dietary groups over the 5-week feeding period. 7. The results are discussed in terms of the functions of the three routes of glycerolipid synthesis in adipose tissue.     

Mitogenic effects of both amidated and glycine-extended gastrin-releasing peptide in defunctioned and azoxymethane-treated rat colon in vivo

Although there is abundant evidence that gastrin-releasing peptide acts as a mitogen in various carcinoma cell lines, the effect of administration of gastrin-releasing peptide on the colorectal mucosa in vivo has not been reported. The aims of this study were to determine whether continuous infusion of gastrin-releasing peptide stimulated proliferation or accelerated carcinogenesis in the rat gastrointestinal tract and other organs. The possible requirement for C-terminal amidation for mitogenic activity in vivo was also investigated. Proliferation was measured in the colon by metaphase index and by immunostaining for the proliferation marker Ki-67, and in other tissues by immunostaining alone. Acceleration of colorectal carcinogenesis was assessed by counting aberrant crypt foci after treatment with the carcinogen azoxymethane. Defunctioning of the rectum reduced both the proliferative index and the crypt height of the rectal mucosa of untreated rats. Treatment with amidated or glycine-extended gastrin-releasing peptide for 4 weeks using implanted mini-osmotic pumps resulted in a two- to three-fold increase in proliferation, and an increase in crypt height, in the defunctioned rectal mucosa (p<0.001), with smaller but significant increases in the caecum and distal colon. No changes in proliferation were detected in lung, pancreas or gastric mucosa. The numbers of aberrant crypt foci in the mid-colon, distal colon and rectum following treatment with azoxymethane were also significantly increased by infusion with amidated or glycine-extended gastrin-releasing peptide. We conclude that administration of gastrin-releasing peptide to mature rats stimulates proliferation and accelerates carcinogenesis in the colorectal mucosa, and that C-terminal amidation is not essential for either effect. Gastrin-releasing peptides could thus potentially act as promoters of colorectal carcinogenesis.     

Effects of sodium butyrate and salinomycin upon intestinal microbiota, mucosal morphology and performance of broiler chickens

The effect of dietary sodium butyrate (SB) or salinomycin (SAL) or both additives on performance, small intestinal morphology and microbial ecology of broiler chickens was studied. A growth trial was conducted with 96 Ross 308 female broilers from 1 to 30 days of age. Four treatment groups were fed with a non-supplemented control diet or three experimental diets supplemented with i) 300 mg SB (Adimix 30 coated) per kg, ii) 60 mg SAL (Sacox) per kg or iii) both additives in combination. Feed intake and body-weight gain decreased and gain-to-feed ratio increased due to SAL supplementation, while addition of SB did not affect performance in comparison with the control diet but positively affected feed intake and body-weight gain in comparison with birds fed the SAL-supplemented diet. Villus height in jejunum decreased, while crypt depth increased due to SAL supplementation. Addition of SB increased crypt depth in jejunum. No significant effect of either additive was observed in ileum morphology. Total short-chain organic acids concentration in ileal digesta decreased with SAL supplementation, mainly due to lower lactic acid concentration, but no effects were observed in the caeca. The SAL supplementation was accompanied by a pH increase in ileum and a pH decrease in caecum. No significant effect of SB addition was observed for these parameters. Total bacterial numbers and Lactobacillus [lactic acid bacteria (LAB)] counts in ileal and caecal contents were lower in birds fed with SAL-supplemented diet in comparison with birds fed with control or SB diet. DNA fingerprints revealed SAL supplementation to affect the microbial population by suppressing dominating LAB, potentially L. aviarius. The presented results show that dietary SAL, supplemented alone or in combination with SB, suppressed the microbial activity and altered the microbial community structure mainly in ileum. SAL alone negatively affected feed intake and body-weight gain; however, the effect was ameliorated by SB supplementation.     

The modulatory influence of p-methoxycinnamic acid, an active rice bran phenolic acid, against 1,2-dimethylhydrazine-induced lipid peroxidation, antioxidant status and aberrant crypt foci in rat colon carcinogenesis

We investigated the chemopreventive effect of p-methoxycinnamic acid (p-MCA), an active phenolic acid of rice bran, turmeric, and Kaemperfia galanga against 1,2-dimethylhydrazine-induced rat colon carcinogenesis. Male albino Wistar rats were randomly divided into six groups. Group 1 consisted of control rats that received a modified pellet diet and 0.1% carboxymethyl cellulose. The rats in Group 2 received a modified pellet diet supplemented with p-MCA [80 mg/kg body weight (b.wt.) post-orally (p.o.)] everyday. The rats in Groups 3-6 received 1,2-dimethylhydrazine (DMH) (20 mg/kg b.wt.) via subcutaneous injections once a week for the first 4 weeks; additionally, the rats in Groups 4, 5 and 6 received p-MCA at doses of 20, 40 and 80 mg/kg b.wt./day p.o., respectively, everyday for 16 weeks. The rats were sacrificed at the end of the experimental period of 16 weeks. The DMH-treated rats exhibited an increased incidence of aberrant crypt foci (ACF) development; an increased crypt multiplicity; decreased concentrations of tissue lipid peroxidation markers such as thiobarbituric acid reactive substances (TBARS), conjugated dienes (CD) and lipid hydroperoxides (LOOH); decreased levels of tissue enzymic antioxidants such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR); and decreased levels of non-enzymic antioxidants such as reduced glutathione (GSH) and vitamins C, E and A in the colon. Supplementation with p-MCA significantly reversed these changes and significantly inhibited the formation of ACF and its multiplicity. Thus, our findings demonstrate that p-MCA exerts a strong chemopreventive activity against 1,2-dimethylhydrazine-induced colon carcinogenesis by virtue of its ability to prevent the alterations in DMH-induced circulatory and tissue oxidative stress and preneoplastic changes. p-MCA was more effective when administered at a dose of 40 mg/kg b.wt. than at the other two doses tested.     

Long-term feeding of various fat diets modulates azoxymethane-induced colon carcinogenesis through Wnt/beta-catenin signaling in rats

The Wnt signaling pathway plays an essential role in carcinogenesis, and the amount of fat intake and composition of dietary fatty acids are crucial factors for colon carcinogenesis. We investigated whether various dietary fats affected the Wnt signaling pathway of colon tumorigenesis in azoxymethane (AOM)-treated rats. Male Sprague-Dawley rats were given intraperitoneal injections of AOM and supplemented with 10% corn, olive, beef, and fish oil for 44 wk. Aberrant crypt foci (ACF) and tumors were examined at 12 and 44 wk. Normal appearing colon mucosal proliferation and apoptosis were evaluated by 5-bromo-2'-deoxyuridine (BrdU) incorporation and percentages of fragmented DNA, respectively. Expressions of beta-catenin, cyclin D(1), Wnt2, Wnt3, and Wnt5a of normal appearing colon mucosa were analyzed by Western blot analysis. Long-term dietary corn oil and beef tallow increased ACF, tumor incidence, and tumor numbers in AOM-treated rats. In contrast, both olive and fish oil inhibited them. Dietary corn oil and beef tallow increased BrdU incorporation and the expression of cytosolic beta-catenin and cyclin D(1) and decreased apoptosis in the colon mucosa. Expressions of Wnt2 and Wnt3 in rats fed with beef tallow and Wnt5a in rats fed with corn oil increased with or without AOM-treatment. BrdU-incorporated cells were often observed at the tops of crypts in rats fed with beef tallow, whereas this was not observed in rats fed with the other diet. Long-term high intake of corn oil and beef tallow enhanced cell proliferation through Wnt signaling and modulated the distribution of proliferating cells, which might contribute to promoting effects in colon tumorigenesis.     

Enriched protein diet-modified ghrelin expression and secretion in rats

Gastrointestinal (GI) integrity and function are regulated by nutrition and growth factors. The discovery of ghrelin, a natural growth hormone (GH) secretagogue produced by the gastrointestinal (GI) tract, is a potential link between diet and growth signals. The aim of this study was to evaluate macronutrient effect on ghrelin expression and secretion in addition to some possible function in intestinal trophic status. Wistar rats were fed a high-carbohydrate, high-protein (HP), high-fat or standard (St) diet. Animals received the same daily food volume and caloric intake. After 7 days, animals were fasted for 24 h and blood and tissue samples were obtained just before feeding or at 2 or 6 h after feeding. Fasting high-protein-fed rats had higher ghrelin plasma levels than with rats fed the high-carbohydrate, high-fat or standard diets. Two-hours after refeeding, ghrelin plasma levels had decreased in all groups with a slight recovery at 6 h after refeeding, except in the high-protein group. Ghrelin plasma levels in rats fed with the high-protein diet correlated negatively with their GH and insulin-like growth factor 1 (IGF-1) plasma concentrations which were also the lowest among the study groups. In conclusion, ghrelin secretion was nutritionally manipulated because a protein-enriched diet increased its levels.