Consumption of black beans and navy beans (Phaseolus vulgaris) reduced azoxymethane-induced colon cancer in rats.

Beans (Phaseolus vulgaris) are an important food staple in many traditional diets. There is limited evidence to suggest an inverse relationship between bean consumption and colon cancer. The objective of this study was to determine whether consumption of black beans and/or navy beans would reduce colon carcinogenesis in rats. Rats were fed a modified AIN-93G diet (control) or diets containing 75% black beans or 75% navy beans for 4 wk, and then colon cancer was initiated by administration of two injections of azoxymethane 1 wk apart. At 31 wk after the second injection, the incidence of colon adenocarcinomas was significantly lower (P < 0.05) in rats fed the black bean (9%) and navy bean (14%) diets than in rats fed the control diet (36%). Total tumor multiplicity was also significantly lower in rats fed the black bean (1.1) and navy bean (1.0) diets than in rats fed the control diet (2.2). The 44-75% reduction in colon carcinogenesis in rats fed beans was attributed to 1) more controlled appetites, leading to significantly less body fat, and 2) much greater concentrations of butyrate in the distal colon. It was concluded that eating black beans and navy beans significantly lowered colon cancer incidence and multiplicity.

Inhibition of azoxymethane-induced colon cancer by orange juice.

Previous research has shown that hesperidin, a flavanone glycoside in orange juice, inhibits colon carcinogenesis and that feeding double-strength orange juice delays the onset of chemically induced mammary cancer in rats. This study determined whether feeding single-strength, pasteurized orange juice would inhibit azoxymethane (AOM)-induced colon cancer in male Fischer 344 rats. Colon cancer was initiated by injecting AOM (15 mg/kg body wt) at 22 and 29 days of age. One week after the second AOM injection, orange juice replaced drinking water for the experimental group (n = 30). The rats were killed 28 weeks later, and tumors were removed for histological analysis. Feeding orange juice reduced tumor incidence by 22% (p < 0.05). Tumor reduction was associated with a decreased labeling index and proliferation zone in the colonic mucosa. Hesperidin, other flavonoids, limonin 17-beta-D-glucopyranoside, and other limonoid glucosides are potential chemopreventive agents in orange juice that could account for the decreased colon tumorigenesis associated with feeding orange juice.

Prevention of precancerous colonic lesions in rats by soy flakes, soy flour, genistein, and calcium.

The main purpose of this research was to determine whether diets containing soy products would inhibit the early stages of azoxymethane-induced colon cancer in F344 rats. Additional objectives were to determine whether feeding starch instead of sucrose, feeding additional calcium (0.5% compared with 0.1%), or feeding a low-fiber powdered enteral formula would influence early colon carcinogenesis. Colon cancer was initiated with 2 injections of azoxymethane (15 mg/kg body wt) and a 12-wk dietary treatment period was started 1 wk after the second injection. Precancerous colon lesions were assessed as foci with aberrant crypts (FAC). The mean numbers of FAC were 133 [soy concentrate (low concentration of phytochemicals)], 111 (starch substituted for sucrose), 98 [full-fat soy flakes (whole soybeans)], 87 (defatted soy flour), 77 (0.015% genistein), and 70 (0.5% Ca). The soy flour and full-fat soy flake diets contained 0.049% genistein derivatives (primarily glycosides), but were less effective in inhibiting the formation of FAC than the diet containing 0.015% genistein (as the aglycone). Eating soybeans and soy flour may reduce the early stages of colon cancer.

Composition and functional properties of cholesterol reduced egg yolk.

The composition and functional properties of cholesterol reduced egg yolk (CREY) were compared to those of control egg yolk (EY). The CREY was prepared by absorbing cholesterol with beta-cyclodextrin after dilution and dissociation of granules at pH 10.5. The CREY contained less lipid and protein and more carbohydrate and ash than EY. Egg lipids were fractionated into triglycerides, cholesterol esters, free cholesterol, phosphatidyl choline, and phosphatidyl ethanolamine. Free and esterified cholesterol in CREY were reduced by 91.6 and 94.4%, respectively. Triglycerides were the major lipid class in CREY. The CREY contained more oleic acid and less linoleic acid than the control. Protein solubility in 0.1 and 0.6 M NaCl and sponge cake volume did not differ. The composition of proteins soluble in 0.6 M NaCl in both egg preparations were similar as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The electrophoretic profiles of proteins soluble in 0.1 M NaCl were similar, except that lipovitellin form EY was insoluble under these conditions. The CREY was less yellow than EY, as indicated by beta-carotene concentrations and Hunter b values. These results suggest that beta-cyclodextrin can be used to produce a low cholesterol egg product with compositional and functional properties similar to EY.

The absorption and effect of dietary supplementation with omega-3 fatty acids on serum leukotriene B4 in patients with cystic fibrosis.

The substitution of omega-3 (n-3) fatty acids for omega-6 (n-6) fatty acids generates eicosanoids with diminished inflammatory effects. As the lungs of patients with cystic fibrosis (CF) are in a state of chronic inflammation in which increased amounts of eicosanoids are found, n-3 supplementation may reduce this level of inflammation and result in clinical improvement. The absorption and clinical effects of n-3 vs. n-6 fatty acids in CF were measured in a prospective, randomized, double-blind, crossover study in which 14 patients with CF (age: 6-16 years, mean 10.5 years; baseline Shwachman-Brasfield scores: 41-88, mean 76.7) received 6 weeks of n-3 ethyl ester concentrate from menhaden oil (100-131 mg/kg/day, mean 112.8) or n-6 fatty acids from safflower oil (102-132 mg/kg/day, mean 113.3), followed by a washout period of 6 weeks, and then 6 weeks of the other supplement. Analysis by gas chromatography showed that n-3 supplementation resulted in increased eicosapentaenoic acid (20:5n-3) in platelet phospholipids, from 0.14 to 2.16%, P < 0.05 and in increased docosahexaenoic acid (22:6n-3), from 1.33 to 3.72%, P < 0.05. Clinical effects were evaluated at weeks 0, 6, 12, and 18, and analyzed for differences among the n-3, n-6, and washout periods. No adverse effects were reported or observed. No statistically significant differences were found (ANOVA, P > 0.05) in Shwachman-Brasfield scores, sweat test, weight change, or forced expiratory volume and flow (FEV1, FEF25-75%, and FVC) percentiles. Tumor necrosis factor was not measurable in any serum sample. Serum leukotriene B4 (LTB4) levels were significantly reduced by n-3 fatty acids, mean reduction (-177 pg/mL) compared to n-6 fatty acids (+63 pg/mL) P < 0.05. These results show that both n-3 fatty acids are absorbed and incorporated into platelet phospholipids in patients with CF and reduced serum LTB4. No significant clinical differences or adverse effects were found.

The stimulatory effect of insulin on diacylglycerol generation in adipocyte membranes from ob/ob mice is impaired by growth hormone.

Physiologically, the action of insulin on carbohydrate and lipid metabolism is opposed by several hormones, including glucocorticoids, glucagon, catecholamines, and pituitary GH. Perhaps least is known about the mechanism(s) involved in the antiinsulin action of GH. Since the generation of diacylglycerol (DAG) appears to be an early event in the insulin-signaling cascade, it was of interest to determine whether GH would interfere with this effect of insulin. Experiments were conducted to determine whether insulin would stimulate the generation of DAG in adipocytes of the obese (ob/ob) mouse, and whether this response could be blocked by the diabetogenic GH derivative S-carboxymethylated human GH (RCM-hGH). Isolated adipocytes of the ob/ob mouse were used for these studies, because unlike normal rodents, the ob/ob mouse responds predictably to the antiinsulin action of GH. Insulin produced a rapid biphasic increase in the amount of DAG in a crude membrane fraction of the adipocytes. The first peak in DAG mass occurred within 5 min of exposure of the cells to insulin, and the second peak occurred after 30 min. The first peak in DAG mass did not occur in adipocytes that had been incubated with pertussis toxin before exposure to insulin. Also, adipocytes isolated from ob/ob mice that had been treated with RCM-hGH failed to respond to insulin with an increase in DAG mass. RCM-hGH blocked both the first and second insulin-induced peaks in DAG mass within 6 h of its administration. This is the time at which ob/ob mouse adipocytes exhibit increased insulin resistance in response to RCM-hGH. Neither exposure to insulin nor treatment with RCM-hGH had any appreciable effect on the fatty acid composition of the DAG present in the adipocyte membranes. These findings are compatible with the idea that GH produces some defect in the insulin-signaling cascade that is proximal to the events that result in the generation of DAG in the adipocyte.

Effect of dietary copper on intestinal mucosa enzyme activity, morphology, and turnover rates in weanling pigs.

Twenty-four pigs from four litters weaned at 21 d of age (6.6 kg of BW) were used to evaluate the influence of 250 ppm of dietary Cu on intestinal mucosa glucose-6-phosphatase (GP), alkaline phosphatase (AP), and adenosine triphosphatase (ATPase) activity; mucosal morphology; and the turnover rate of the intestinal mucosa throughout the gastrointestinal tract. Pigs were allotted into four pens of six pigs each based on sex, litter, and weight. Pens were then assigned to one of two treatments: 1) corn-soybean meal-whey diet with no antimicrobials (CO), or 2) CO + 250 ppm of Cu. Pigs were fed twice daily an amount approximately equal to ad libitum intake for 14 d. On d 14, pigs were injected i.p. with [3H]thymidine (50 microCi/kg of BW) 10 h after the morning meal. One pig from each pen was euthanatized at 1, 6, 12, 20, 32, and 44 h postinjection, and intestinal tissue was collected from the duodenum, two jejunum sites (upper and lower), ileum, cecum, and colon. The activity of GP and AP in the lower jejunum tended to decrease in pigs fed Cu (P less than .11, P less than .08, respectively). The ATPase activity was not affected by treatment (P greater than .10). Crypt death, villus height, or epithelial cell size (P greater than .10) were not affected by feeding Cu. Migration rate of epithelial cells up the villus was also not affected by treatment (P greater than .10).(ABSTRACT TRUNCATED AT 250 WORDS)

Incorporation of n-3 fatty acids into WB-F344 cell phospholipids inhibits gap junctional intercellular communication.

In this investigation, we demonstrate that rat liver epithelial (WB-F344) cells grown in medium supplemented with n-3 fatty acids (FA) results in the inhibition of gap junctional intercellular communication (GJIC). Cells incubated for 48 hr in medium containing 50 microM alpha-linolenate (18:3n-3) resulted in a 60% inhibition of GJIC, compared to control cells, while treatment with gamma-linolenate (18:3n-6) had no effect. Supplementation with octadecatetraenoate (18:4n-3), eicosapentaenoate (20:5n-3), and docosahexaenoate (22:6n-3), inhibited GJIC by 42%, 28%, and 18%, respectively. Incubation with each of the n-3 FA markedly increased the total n-3 FA content of cellular phospholipids (PL). Growing cells in medium containing 50 microM arachidonate (20:4n-6) plus 50 microM 18:3n-3 partially attenuated the inhibition of GJIC induced by 18:3n-3. The mechanism by which n-3 FA inhibit GJIC remains to be determined.

Inhibition of gap junction-mediated intercellular communication by alpha-linolenate.

The purpose of this investigation was to assess whether alterations in the fatty acid composition of rat liver epithelial (WB-F344) cell phospholipids would modulate gap junction-mediated intercellular communication (GJIC). WB-F344 cells were grown to confluency in culture medium supplemented with one of seven different fatty acids at a concentration of 50 microM for 48 h. Only alpha-linoleate (18:3 n-3) significantly inhibited GJIC. Saturated fatty acids (12:0, 16:0, and 18:0), a monounsaturated fatty acid (18:1 n-9), and n-6 polyunsaturated fatty acids (18:2 and 20:4) did not affect GJIC. The alpha-linolenate-induced inhibition of GJIC was not due to the activation of protein kinase C or intracellular hydroperoxide production, two lipid-dependent parameters previously shown to inhibit GJIC. In addition, alpha-linolenate did not alter membrane fluidity. Although the mechanism by which alpha-linolenate inhibits GJIC is unclear, changes in the fatty acid composition of cell phospholipids may be of critical importance. Subsequent to supplementation with alpha-linolenate, WB-F344 cell phospholipids had reduced 20:4 n-6 and elevated n-3 fatty acids. The results of this investigation emphasize the importance of current research into the influence of lipids on cell function and identify a new mechanism by which gap junctions can be modulated.

TPA-induced inhibition of gap junctional intercellular communication is not mediated through free radicals.

The present investigation was designed to determine whether the inhibition of gap junction-mediated intercellular communication (GJIC) induced by TPA (12-O-tetradecanoylphorbol-13-acetate) in rat liver epithelial (WB-F344) cells in vitro is mediated through free radical production. As assessed by fluorescence redistribution after photobleaching (FRAP) analysis, GJIC was significantly inhibited in cells treated for 1 hr with either 10 ng/ml TPA or 500 microM hydrogen peroxide (H2O2). Addition of 1000 U/ml catalase or 25 microM N',N'-diphenyl-p-phenylenediamine (DPPD) to TPA-treated cells did not alleviate the TPA-induced inhibition of GJIC. However, the concurrent addition of 1000 U/ml catalase to the culture medium prevented the H2O2 inhibition of GJIC. 2'-7'-dichlorofluorescein-mediated fluorescence, a measure of free radical production utilizing the Meridian ACAS 470 interactive laser cytometer, was not significantly increased in WB-F344 cells treated with 10 and 100 ng/ml TPA when compared to control cells. However, polymorphonuclear leukocytes (PMNs) treated for 10 min with 100 ng/ml TPA showed a substantial oxidative burst, as did WB-F344 cells treated for 1 hr with 500 microM H2O2. The concurrent addition of 1000 U/ml catalase to the culture medium attenuated H2O2-mediated free radical production in both PMNs and WB-F344 cells. Data from this study do not support a role for free radicals in the TPA-induced inhibition of GJIC in WB-F344 cells.

Influence of diet or intrarectal bile acid injections on colon epithelial cell proliferation in rats previously injected with 1,2-dimethylhydrazine.

The effects of varying colon bile acid concentrations on rat colon epithelial cell proliferation were studied. Bile acid concentrations were altered by intrarectally injecting either deoxycholic or lithocholic acid for 4 weeks or by increasing the dietary fat or fiber (wheat bran, agar, or carrageenan) intake for 4 weeks. 1,2-Dimethylhydrazine (DMH) was s.c. injected into half of the rats 1 week before treatments began. Colon epithelial cell proliferation was measured by [3H]thymidine autoradiography of colon crypts. Rats injected with DMH had more DNA-synthesizing cells per crypt. Neither bile acid injection nor any of the diets altered the number of DNA-synthesizing cells per crypt. DMH injections, deoxycholic and lithocholic acid intrarectal injections, and dietary agar and wheat bran all increased the total number of cells per crypt. High fat diets and dietary carrageenan did not affect cell number. All diets containing fiber lowered total fecal bile acid concentrations, but increasing the fat content of the diet did not affect them. These results indicate that the bile acid injections and dietary agar and wheat bran induce a slight hyperplasia in the colon.

Metabolism of 1,2-dimethylhydrazine by cultured rat colon epithelial cells.

The colon carcinogen 1,2-dimethylhydrazine (DMH) was cultured with rat colon epithelial cells to determine if these cells have the ability to metabolize DMH. Colon epithelial cells isolated from conventional and germfree Sprague-Dawley rats were incubated in CMRL 1066 supplemented medium containing 14C-DMH. Cells from both groups of rats metabolized DMH to gaseous metabolites, to metabolites in the medium that were putatively identified as azoxymethane and methylazoxymethanol, and to products that bound to DNA. Cells from germfree rats metabolized DMH at an equal or greater rate than cells from conventional rats for the criteria examined. This report demonstrates that rat colon epithelial cells can metabolize DMH without previous metabolism by other tissues or colon bacteria.

Influence of a low carbohydrate diet on performance of pregnant and lactating dogs.

Beagle bitches, obtained 3 weeks post-conception, were fed one of two diets; diet 1 contained 44% of metabolizable energy from carbohydrate and diet 2 contained 0% of metabolizable energy from carbohydrate. Bitches consumed similar amounts of energy from the two diets. Plasma glucose levels were similar in bitches fed the two diets, except in the week before whelping. At this time, plasma glucose levels as low as 15--20 mg/dl were observed in several bitches fed diet 2. None of the bitches fed diet 1 exhibited hypoglycemia. Bitches fed diet 2 also had depressed plasma levels of alanine and lactate and elevated levels of free fatty acids and B-hydroxybutyrate near the end of gestation. Total number of pups whelped by the bitches was unaffected by diet, but fewer pups from bitches fed diet 2 were alive at birth (63%) than from bitches fed diet 1 (96%). Only 35% of the pups whelped by bitches fed diet 2 were alive at 3 days of age. Milk from bitches fed diet 2 had a lower percentage of energy from lactose and a higher percentage of energy from fat than did milk of bitches fed diet 1. Growth of pups, however, was unaffected by composition of diet fed to the bitches. We concluded that pregnant bitches require dietary carbohydrate for optimal reproductive performance.

Effect of deoxycholic acid on 7,12-dimethylbenz(a)anthracene-induced, two-stage mouse skin carcinogenesis.

The effect of deoxycholic acid on 7,12-dimethylbenz(a)anthracenecroton oil carcinogenesis in mouse skin was tested. Painting deoxycholic acid in addition to croton oil during promotion resulted in the earlier appearance of tumors, a greater tumor incidence, and a larger number of tumors per animal. DMBA initiation followed by either deoxycholic acid or solvents during the promotion period produced no tumors. Animals receiving deoxycholic acid or solvents alone developed no tumors.

Relationship of level and type of dietary fat to fetal and maternal rat lipogenesis and lipid deposition.

Pregnant rats were pair-fed isoenergetic diets with varying fat content and varying fatty acid compositions to determine if manipulation of the maternal diet would affect fetal lipid metabolism. A mixture of tallow and lard replaced cornstarch on an equal-energy basis so that fat supplied 5 to 65% of the metabolizable energy. Fat content of the maternal diet did not affect fetal weight or fetal body composition. No differences in fetal liver fatty acid synthetase (FAS), glucose-6-phosphate dehydrogenase (G6PD) activities or rate of in vivo fatty acid synthesis were noted. In vivo fatty acid synthesis was greater in fetal liver than maternal liver. Dietary manipulation did not affect in vivo fatty acid synthesis in either fetal or maternal liver. Maternal liver FAS and G6PD activities were generally greater than fetal liver FAS and G6PD activities. These enzyme activities were decreased in maternal livers when the high-fat diet was fed. A sudden decrease in food consumption 24 hours before killing may explain the apparent inconsistencies in enzyme activities and fatty acid synthesis rates. The results of this study indicate that the level of fat in the maternal diet has no effect on the amount of lipid accumulated in fetal tissues or fetal lipogenesis.

Ionic milieu of bovine and ovine rumen as affected by diet.

Postprandial changes in osmolality, mineral, and volatile fatty acid concentrations in rumen fluid were examined in three cattle fed six widely differing diets. Mineral concentrations varied with diet and postprandial time. However, net changes in postprandial mineral concentrations did not contribute significantly to changes in osmotic pressure. There was an effect of diet and time after feeding on concentrations of volatile fatty acids. Postprandial changes in osmotic pressure were primarily due to changes in concentrations of volatile fatty acids. Magnesium oxide and sodium bicarbonate were fed to sheep to increase the osmotic pressure in rumen fluid. The salt supplement decreased acetate, propionate, heat, and methane production. However, rumen water flux was unaffected by the salt supplementation. Diets which produce hypertonic rumen fluid due to high mineral and/or concentrations of volatile fatty acids may reduce fermentation in rumen.