摘要:

AbstractIn 1982, we proposed a large‐scale randomized prospective trial to test the hypothesis that decreasing dietary fat intake from 38% to 20% of total calories would increase the disease‐free interval and/or five‐year survival rate for postmenopausal breast cancer patients. We now review new evidence from epidemiological studies, laboratory animal model studies, and preliminary feasibility trials that has accumulated over the past decade, in support of such a trial, and suggest that a more appropriate dietary goal is a reduction in fat intake to 15% of total calories.

ISSN:0163-5581    

DOI:10.1080/01635589309514231

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

AbstractLarge differences exist between human populations in the frequency of colonic cancer. Epidemiological evidence indicates that these differences are strongly influenced by country of residence, and a negative correlation has been found between the fiber content of the diet and frequency of colonic cancer. This has prompted the hypothesis that high‐fiber diets are in some way protective. However, reanalysis of the dietary data provides equally strong support for the hypothesis that the protective element may be phytic acid (inositol hexaphosphate). This heat‐and acid‐stable substance is present in high concentration in many food items, including cereal grains, nuts, and seeds. Phytic acid forms chelates with various metals and suppresses damaging iron‐catalyzed redox reactions. Inasmuch as colonic bacteria have been shown to produce oxygen radicals in appreciable amounts, dietary phytic acid might suppress oxidant damage to intestinal epithelium and neighboring cells. Indeed, rapidly accumulating data from animal models indicate that dietary supplementation with phytic acid may provide substantial protection against experimentally induced colonic cancer. Should further investigations yield additional support for this hypothesis, purposeful amplification of dietary phytic acid content would represent a simple method for reducing the risk of colonic carcinogenesis.

ISSN:0163-5581    

DOI:10.1080/01635589309514232

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

AbstractAmount and type of fat and energy density of diets may influence tumor incidences. The purpose of this report is to summarize the influence of com oil gavage and different nonpurified diets on spontaneous tumor incidences in 64 diet and 59 com oil gavage control groups in two‐year studies involving approximately 6,100 control Fischer 344 rats of each sex. The maximum mean body weight attained during the course of the study, survival at 106 weeks of age, and spontaneous tumor incidences of groups fed different nonpurified diets with or without corn oil gavage were summarized and evaluated for differences. Male rats fed NIH‐07 open‐formula diet with or without corn oil gavage had significantly higher body weight, lower survival, and higher incidence of pancreatic acinar cell tumors than rats fed commercial proprietary diets with or without corn oil gavage. Female rats fed NIH‐07 diet with or without corn oil gavage had significantly higher body weights and pancreatic tumor incidences than groups fed commercial diets. Time‐related trends could account for other apparent differences in tumor incidences between the groups fed commercial and NIH‐07 diets. Corn oil gavage significantly increased the body weight and pancreatic tumor incidences but decreased the incidence of leukemia, a lethal tumor, which resulted in higher survival in male rats. Corn oil gavage significantly lowered the body weight and anterior pituitary tumor incidence in female rats. The pancreatic acinar cell tumor incidence appears to be due to a combination of fat intake and body weight.

ISSN:0163-5581    

DOI:10.1080/01635589309514233

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

AbstractAlthough a growing number of epidemiological studies indicate that dietaryβ‐carotene has anticarcinogenic activity, the mechanism(s) ofβ‐carotene protection remains to be definitively established. In this context,in vitrostudies ofβ‐carotene have been, and continue to be, valuable. We examined the following critical features in designing anin vitrosystem for studying the protective action ofβ‐carotene: 1) form ofβ‐carotene used for cellular uptake, 2) cellular metabolism ofβ‐carotene, and 3) subcellular distribution ofβ‐carotene. It was determined thatβ‐carotene added to medium in a water‐dispersible formulation is readily taken up by BALB/c 3T3 cells and is located predominantly in cellular membranes. Cellular uptake ofβ‐carotene added to medium in an organic solvent is greatly reduced. It was also found that intracellular retinol increased significantly after a three‐day exposure of BALB/c 3T3 cells to media containingβ‐carotene. This result suggests that the ability to metabolizeβ‐carotene to retinoids is not limited to cells of intestinal origin. The results and methodology described here will be useful in the rational design ofin vitroassays for elucidating the mechanism(s) ofβ‐carotene protective effects at the cellular level.

ISSN:0163-5581    

DOI:10.1080/01635589309514234

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

AbstractDietary fiber is believed to decrease the incidence of colorectal cancer, but not all types of fiber are equally protective. Dietary fibers may be divided broadly into insoluble and soluble fibers, and there is evidence from animal experiments that the latter not only fails to protect against colorectal cancer but may enhance its development. Adsorption of carcinogens to insoluble dietary fiber in the intestinal tract is one of the mechanisms by which dietary fiber is believed to protect against colorectal cancer. In previous in vitro experiments, we showed that the hydrophobic carcinogen 1,8‐dinitropyrene (DNP) adsorbs to insoluble plant cell wall components (insoluble dietary fibers). Soluble polysaccharides (pectic polysaccharides) extracted from the walls of parenchyma cells of dicotyledonous plants were found to maintain DNP in aqueous solutions and decrease its adsorption to insoluble wall components. In the present study, we examined a commercial preparation of pectin and seven other soluble‐fiber polysaccharides with diverse structures for their effects on the distribution of DNP. Many of these are used as emulsifiers and stabilizers in the food industry. They all maintained DNP in aqueous solution and decreased its adsorption toα‐cellulose, which we used as an example of an insoluble dietary fiber. Gum arabic was the most effective andκ‐carrageenan the least. The capacity of the polysaccharides to act as emulsifiers and stabilizers may explain their effects on DNP distribution. The monosaccharide glucose and the disaccharide cellobiose had no effect on the distribution of DNP. These results indicate three possible mechanisms by which soluble‐fiber polysaccharides may enhance the development of colorectal cancer. First, because they reduce the ability of insoluble dietary fibers to adsorb hydrophobic carcinogens, more carcinogens may enter the colon maintained in solution than adsorbed onto insoluble fibers. Second, if soluble‐fiber polysaccharides are maintaining hydrophobic carcinogens in solution and these polysaccharides are degraded by bacterial enzymes in the colon, then the carcinogens may come out of solution and be deposited onto the mucosal surface of the colon. Third, soluble‐fiber polysaccharides may cross the intestinal epithelium and carry with them carcinogens maintained in solution. These studies have important consequences for nutrition, because soluble‐fiber polysaccharides represent a common component of foods.

ISSN:0163-5581    

DOI:10.1080/01635589309514235

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

AbstractIn a study of the effects of carotenoids, canthaxanthin (CA),β‐apo‐8'‐carotenal (BA), orβ‐carotene in an extract ofSpirulina‐Dunaliellaalgae (AE) was fed at 0%, 0.1%, or 0.2% in a choline‐deficient (CD) diet. In each of eight groups, 10 adult male Fischer 344 rats were fed diets with designated carotenoid sources and levels or a choline‐sufficient diet for 12 weeks. Carotenoids altered some of the changes induced by the CD diet. Increases in enlargement of fatty livers and low plasma cholesterol levels occurred in rats fed 0.2% BA. Plasma retinal was further reduced 35% by BA or AE. BA and AE increased liver total vitamin A about 80% and 305%, respectively. Liver lipid per oxidation was enhanced and plasmaα‐tocopherol was reduced further by 1.0% AE. AE, BA, and CA (mg/g fat) depressed liverα‐tocopherol about 49%, 67%, and 78%, respectively. The decreased liverα‐tocopherol was concurrent with an increase in carotenoid stores of CA>BA>AE. Histopathological examination of sections of liver tissue by light microscopy showed fatty and cirrhotic changes in all rats fed CD diets. Histochemical evaluation based on a semiquantitative assay revealed a marked increase in peroxisome enzyme activity in the livers of all CD rats. None of the carotenoids appeared to have any effect on the development of morphological changes in the liver. Although carotenoids can function as antioxidants, they did not prevent changes observed in rats fed CD diets.

ISSN:0163-5581    

DOI:10.1080/01635589309514236

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

AbstractThe rates of conversion of 2‐amino‐3‐methyl‐3H‐imidazo[4,5‐f]quinoline (IQ) to its reportedly mutagenic 7‐keto derivative (7‐OHIQ) by intestinal bacteria from humans, mice, and rats were compared. IQ was metabolized faster by cecal contents from rats or mice than by human fecal samples (113 and 87μmol 7‐OHIQ formed/hr/g cecal contents, respectively, vs. 12.3μmol/hr/g feces). Cecal contents from germ‐free rats colonized with human fecal bacteria [human flora‐associated (HFA) rats] converted IQ to 7‐OHIQ at rates generally lower than contents from rats colonized with their native flora. Diet had a marked effect on IQ metabolism by HFA rat cecal contents. The rate of IQ conversion to 7‐OHIQ was increased in rats fed a diet high in beef dripping compared with that in rats fed a low‐fat control diet. A diet high in olive oil, however, did not produce an increase in the IQ conversion rate. Addition of fiber to a purified diet increased the rate of IQ metabolism in the following order: sugar beet fiber>wheat bran>oat bran fiber>fiber‐free diet.In a further study, HFA rats were fed human diets altered independently in their fat, fiber (wheat bran), and beef contents. The high‐fiber diet produced the greatest increase in IQ conversion rate, followed by the high‐fat diet. The diet with a high beef content and the control diet (low levels of all 3 macrocomponents) produced similarly low rates of IQ conversion.Material from incubations of IQ with HFA rat cecal contents, assumed to be 7‐OHIQ on the basis of chromatographic behavior, was confirmed to be directly mutagenic, producing approximately 800 His+revertants per microgram with S. typhimurium TA98.

ISSN:0163-5581    

DOI:10.1080/01635589309514237

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

AbstractBioassay‐directed fractionation of celery seed oil from the plantApium graveolens(Umbel‐liferae) led to the isolation of five natural products, including d‐limonene,p‐mentha‐2,8‐dien‐1‐ol, p‐mentka‐8(9)‐en‐1,2‐diol, 3‐n‐butyl phthalide, and sedanolide. Of these compounds p‐mentha‐2,8‐dien‐1‐ol, 3‐n‐butyl phthalide, and sedanolide exhibited high activities to induce the detoxifying enzyme glutathione S‐transferase (GST) in the target tissues of female A/J mice. 3‐n‐Butyl phthalide and sedanolide (20 mg/dose every two days for a total of 3 doses) increased GST activity 4.5–5.9 and 3.2–5.2 times over the controls in the mouse liver and small intestinal mucosa, respectively. At the same dose, p‐mentha‐2,8‐dien‐1‐ol induced GST activity about 3.7‐fold above that of the controls. Thus, these compounds were further tested for their ability to inhibit benzo[a]pyrene‐(BP) induced tumorigenesis in mice. After treatment with 3‐n‐butyl phthalide and sedanolide, the tumor incidence was reduced from 68% to 30% and 11%, respectively. About 67% and 83% reduction in tumor multiplicity was also observed with 3‐n‐butyl phthalide and sedanolide.p‐Mentha‐2,8‐dien‐1‐ol produced only a small or no significant reduction of forestomach tumor formation. The data indicating that 3‐n‐butyl phthalide and sedanolide were both active in tumor inhibition and GST assays suggested a correlation between the inhibitory activity and the GST‐inducing ability. The phthalides are known to determine the characteristic odor of celery. The results suggest that phthalides, as a class of bioactive natural products occurring in edible umbelliferous plants, may be effective chemopreventive agents.

ISSN:0163-5581    

DOI:10.1080/01635589309514238

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

AbstractRates of lipogenesis and lipoprotein lipase (LPL) activity were measured in liver, adipose tissue, heart, and tumor at several stages during 10 days of palpable growth of a transplantable Leydig cell tumor in rats. This model showed the same characteristics as human cancer cachexia, including anorexia, weight loss, and muscle wasting. Comparison with pair‐fed controls showed that the rate of loss of body fat was greater than could be explained by anorexia alone.The rate of lipogenesis tended to decrease during the later stages of tumor growth, particularly in the liver, where there was a statistically significant reduction on Days 5 and 10. This may be largely attributable to decreased availability of substrates caused by decreasing food intake and increasing glucose uptake by the tumor. There was a significant decrease in plasma glucose concentration by Day 10. In contrast, LPL activity in adipose tissue was depressed from the earliest stage of tumor growth, and this is likely to be a major cause of lipid depletion in cancer. There was no difference in adipose tissue LPL activity between the fed and postabsorptive states in the tumor‐bearing rats, indicating that the normal response to nutrient intake was impaired. Thus, treatment of cancer cachexia should concentrate on normalizing the metabolic response to nutrient ingestion.

ISSN:0163-5581    

DOI:10.1080/01635589309514239

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor

摘要:

AbstractIn a 2.5‐year carcinogenicity study, two groups, both including male and female Wistar rats, were fed two different diets with 4% and 16% fat. In addition to 4% soybean oil, the high‐fat diet contained 12% mono‐and diglycerides, of which 85% was stearic acid and 13% palmitic acid. There was no difference in food consumption, body weight, weight gain, and longevity between the two groups.A statistically significant increase in the incidence of tumors in the high‐fat group was seen in fibroadenoma of the mammae (female, p = 0.05). No statistically significant difference was seen when the incidence of benign mammary tumors (adenomas and fibroadenomas) was combined, just as the overall incidence of mammary tumors (adenomas, fibroadenomas, and adenocarci‐nomas) was not significantly different between the groups.A statistically significant decrease in the incidence of tumors in the high‐fat group was seen in adenoma of the parathyroid gland (male, p = 0.04) and medullary carcinoma of the adrenal gland (male, p = 0.04). Combining the incidences of benign and malignant tumors of the adrenal medulla led to a further increase in the level of significance (p = 0.02).The present study showed that a high‐fat diet influenced the tumor incidence in certain organs of rats. However, the overall differences in tumor incidence between rats fed the low‐and the high‐fat diet are considered marginal. Therefore we were not able to confirm or deny the hypothesis that a high‐fat diet promotes the development of cancer. It should be noted that, in our study, fat accounted for about 30% of the total energy in the high‐fat diet. This is much below the amount of fat normally found in the western diet but corresponds well to the level recommended for human intake.In addition, the rats fed the high‐fat diet did not gain more weight, even though no difference was recorded in food consumption (g/kg body wt) between the groups.

ISSN:0163-5581    

DOI:10.1080/01635589309514240

出版商:Taylor&Francis Group    

年代:1993

数据来源: Taylor