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PubMed1981

Lack of effect of dietary fat on the growth and estrogen sensitivity of the MT-W9B transplantable mammary tumor.

The growth rate and the estrogen responsiveness of the MT-W9B transplantable mammary tumor were examined in female Wistar-Furth rats which were fed diets containing either 0.5% or 20% fat for 50-60 days. Estrogen responsiveness was determined by changes in progesterone receptor concentration in response to estrogen deprivation and replacement. This parameter was also measured in the uterus as a normal tissue control. Progesterone receptor levels in tumor and uterus were reduced by ovariectomy to a similar extent in rats fed either low-or high-fat diets. In addition, estrogen induction of the progesterone receptor in ovariectomized rats was not altered by dietary fat intake. Growth of the MT-W9B tumor was not affected by either diet or endocrine manipulation. Uterine growth, as expected, was dependent on estrogen status, but both the growth and its sensitivity to estrogen manipulation were independent of the fat content of the diet. These data suggest that dietary fat does not influence the sensitivity of normal or neoplastic tissue to estrogen action.

Animals↗

PubMed1987

Association of dietary fat and lung cancer.

An international comparison study of the relationship among dietary predictors, tobacco consumption, income, and truncated age-adjusted lung cancer mortality was conducted with the use of time-lagged data available for 43 countries. A regression analysis weighting each country by the square root of the appropriate population and adjusting for several covariates showed that calories from dietary fat were highly significantly associated (P less than .0001) with lung cancer mortality. This finding was obtained after accounting for disappearance data for tobacco (P less than .0001), the dominant risk factor for lung cancer, and total nonfat calories (P less than .002). Other covariates included per capita gross national product and proportion of calories from fruits, vegetables, roots, tubers, and pulses. Weaknesses of this study, statistical considerations, biologic plausibility, in particular the modulation of tobacco-smoke carcinogens by lipids in the lung, and suggestions for future study are discussed.

Adult↗

PubMed1993

Effects of caloric restriction and dietary fat on epithelial cell proliferation in rat colon.

Epidemiological studies indicate that caloric intake and dietary fat content influence colonic carcinogenesis. In rodents, caloric restriction reduces, and some fats increase, carcinogen-induced colon cancer incidence. The present study was designed to investigate the effects of caloric restriction on colonic cell proliferation (CCP) in carcinogen-treated or control rats fed low- or high-fat diets. F344 rats were treated with azoxymethane (15 mg/kg x2) and then fed an isocaloric AIN 76A diet containing either 5 or 23% corn oil, ad libitum or calorie-restricted to 70 or 80% of the kilocalories consumed by ad libitum rats. Biopsies of the distal colon were taken at 10 and 20 weeks, and rats were sacrificed at 21 or 34 weeks on the experimental diets. Distal CCP was determined by microautoradiography after [3H]thymidine labeling in vitro or presacrifice administration in vivo. The labeling index and number of labeled cells per crypt column were significantly reduced by caloric restriction at all time points (10, 20, 21, 34 weeks). Caloric restriction reduced CCP in high fat- and low fat-fed rats and in azoxymethane-treated and control rats. High fat resulted in decreased CCP in the distal colon compared to low fat at 34 weeks but not earlier. The findings indicate that: (a) caloric restriction is effective in favorably modulating CCP, an intermediate biomarker of colon cancer risk; (b) a high fat ad libitum diet, which increased tumor yield, does not increase distal colon proliferation; (c) dietary fat intake alters proliferation in a manner differing from that induced by changing dietary caloric intake.

Animals↗

PubMed1985

The substitution of sucrose polyester for dietary fat in obese, hypercholesterolemic outpatients.

Our aim was to determine the effects of the substitution of sucrose polyester (SPE) for dietary fat in a 16-week outpatient study in 36 obese subjects with primary hypercholesterolemia. The subjects were randomized into three groups who followed a 16-week treatment period where all subjects received hypocaloric diets which provided approximately 7 kcal/lb body weight, a polyunsaturated/saturated (P/S) fat ratio of 0.9, and 180 mg cholesterol/day. The percentages of calories as fat in the 3 groups were as follows: a low fat diet group (n = 12) received 27% of dietary calories as fat, a low fat plus SPE group (n = 13) received 25% of calories as fat plus 27 g SPE/day as a bread spread and salad dressing, and a third group (placebo, n = 11) received 37% of calories as fat with a 27 g/day conventional fat placebo (bread spread and salad dressing). Mean weight loss from baseline in the 16 week treatment period was 2.6, 3.9, and 3.4% respectively in the placebo, diet, and SPE groups, p less than .05 for each group, without significant differences between the groups. There was a mean reduction of low density lipoprotein cholesterol (LDL-C) of 16% in the SPE group (p less than .05), more than twice the reductions in the placebo and diet groups, 5% and 6%, respectively. There was a mean 20% reduction in the SPE group in triglyceride and very low density lipoprotein cholesterol (p less than .05), compared to 7 and 10% reductions in the placebo and diet groups respectively. The degree of weight loss was correlated with the degree of reduction in LDL-C in the low fat diet group, and in the low fat diet group plus SPE (r = 0.59 for both groups). Without confounding by different levels of dietary cholesterol or P/S, SPE induced significant reductions in LDL-C in hypercholesterolemic obese subjects beyond the effects of weight loss alone. The effects of SPE were significantly greater than those achieved by the use of a diet which severely limited conventional dietary fat intake (to 40 g/day). SPE in the form of a bread spread and a salad dressing is a practical formulation for outpatient hypocholesterolemic low fat diets and provides the lubricity and organoleptic benefits of authentic foods without the dense caloric content of digestible fats.

Adult↗

PubMed2001

Dietary fat type and regular exercise affect mitochondrial composition and function depending on specific tissue in the rat.

Physical exercise and fatty acids have been studied in relation to mitochondrial composition and function in rat liver, heart, and skeletal muscle. Male rats were divided into two groups according to dietary fat type (virgin olive and sunflower oils). One-half of the animals from each group were subjected to a submaximal exercise for 8 weeks; the other half acted as sedentary controls. Coenzyme Q, cytochromes b, c + c1, a + a3 concentrations, and the activity of cytochrome c oxidase were determined. Regular exercise increased (P < 0.05) the concentration of the above-mentioned elements and the activity of the cytochrome c oxidase by roughly 50% in liver and skeletal muscle. In contrast, physical exercise decreased (P < 0.05) cytochrome c oxidase activity in the heart (in micromol/min/g, from 8.4+/-0.1 to 4.9+/-0.1 in virgin olive oil group and from 9.7+/-0.1 to 6.7+/-0.2 in sunflower oil animals). Dietary fat type raised the levels of coenzyme Q, cytochromes, and cytochrome c oxidase activity in skeletal muscle (P < 0.05) among the rats fed sunflower oil. In conclusion, dietary fat type, regular exercise, and the specific tissue modulate composition and function of rat mitochondria.

Animals↗

PubMed1987

Effect of age and dietary fat (fish, corn and coconut oils) on tocopherol status of C57BL/6Nia mice.

The effect of age and dietary fat type on tocopherol status was investigated using young and old C57BL/6Nia mice fed semipurified diets containing 5% (by weight) fish, corn or coconut oils and supplemented with 30, 100 or 500 ppm dl-alpha-tocopheryl acetate for 6 wk. Tocopherol levels in the diets, plasma, liver, kidney and lung were measured by high performance liquid chromatography following appropriate extractions. The results indicate that mice fed fish oil maintain lower plasma and tissue tocopherol concentrations than those fed corn and coconut oils (fish less than corn oil less than coconut oil). The difference was not due to a loss of tocopherol prior to consumption, but rather appeared to occur during the absorption process. Old mice had lower plasma and liver tocopherol concentrations than young mice. Old mice fed fish oil, however, maintained plasma tocopherol levels better than young mice fed fish oil, presumably due to their larger tocopherol pool. No age effect was detected on kidney and lung tocopherol levels. It is concluded that tocopherol status is affected by age and dietary fat type, especially fish oil.

Aging↗

PubMed2003

Effect of iron overload and dietary fat on indices of oxidative stress and hepatic fibrogenesis in rats.

BACKGROUND/AIMS: Oxidative stress is presumed to play an important role in hepatic fibrogenesis. Diets high in polyunsaturated fatty acids (PUFA) enhance fibrosis and have been associated with increased oxidative damage in some models of liver injury. The aim of this study was to determine the effects of dietary fat of varying PUFA content on iron-induced oxidative stress and fibrosis. METHODS: Rats were given parenteral iron and diets supplemented with coconut oil, safflower oil or menhaden oil. RESULTS: Hepatic iron overload was associated with induction of heme oxygenase-1, a sensitive indicator of oxidative stress, and with modest increases in hydroxyproline and procollagen I mRNA levels without histologically evident fibrosis, all of which were unaffected by dietary fat. In addition, iron loading was associated with increases in cysteine, gamma-glutamylcysteine and glutathione. Dietary fat brought about the expected alterations in peroxidizability, but did not alter indices of oxidative damage. CONCLUSION: These data highlight the distinction between oxidative stress and oxidative damage and suggest that the former is not sufficient to elicit overt fibrosis. Furthermore, while hepatic iron overload leads to oxidative stress, there is an associated upregulation of antioxidant defenses involving thiol metabolism that may be a critical factor limiting the accumulation of oxidative damage.

Animals↗

PubMed2000

Lymphatic transport in rats of several dietary fats differing in fatty acid profile and triacylglycerol structure.

We examined in rats the intestinal absorption of nine very different dietary fats (two rapeseed oils, corn, olive, palm and menhaden oil, butter, cocoa butter and lard) to investigate the influence of fatty acid profile and triacylglycerol structure on absorption. Absorption was followed for 24 h after administration of similar amounts of fats, and the accumulated lymphatic transport and amount of triacylglycerols found in lymph in response to the administered fats were calculated, revealing major differences. The transport of olive and low alpha-linolenic rapeseed oil was significantly higher than that of the other fats (P < 0.05), except corn oil. The lymphatic transport of the other fats followed a slower course, with cocoa butter and menhaden oil having the lowest amounts transported. The amount of triacylglycerols found in lymph in response to the administered fats at 8 h ranged from 27.5% of the administered dose for cocoa butter to 72.1% for olive oil. The value for cocoa butter was significantly lower than that for most other fats. At 24 h, the values ranged from 66.5% for cocoa butter to 121.2% for olive oil. The high value for olive oil suggested transport of endogenous as well as exogenous fatty acids. The low value observed after cocoa butter resulted from decreased lipolysis and possibly also low absorption of triacylglycerols with high levels of long-chain saturated fatty acids in the sn-1/3 position. Furthermore, a low value was observed after menhaden oil administration, suggesting decreased absorption of fats containing (n-3) long-chain polyunsaturated fatty acids. Overall, these results demonstrate the influence of the fatty acid composition and triacylglycerol structure on the lymphatic absorption of dietary fat.

Analysis of Variance↗

PubMed1997

Dietary fat type related changes in tissue cholesterol and fatty acid synthesis are influenced by energy intake level in rats.

OBJECTIVE: To investigate the interaction of dietary fat source and energy intake level on tissue cholesterol and triacylglycerol fatty acid (TG-FA) synthesis. METHODS: Ninety-six rats were randomly divided into 12 groups and fed diets containing fish oil, safflower oil, olive oil or beef tallow, each consumed ad libitum and at 85% and 68% of ad libitum intake for 10 weeks. Cholesterol and TG-FA fractional and absolute synthesis rates in the liver and fractional synthesis rates in the small intestine were determined using deuterium (D) incorporation 2 hours after injecting D2O. RESULTS: Olive oil feeding was associated with higher (p < 0.05) cholesterol and TG-FA synthesis rates in the liver and small intestine compared with other fats. Modifications in cholesterol synthesis by fat type depended on energy intake level. With ad libitum feeding, synthesis rates were lower (p < 0.01) following the safflower oil vs. the olive oil treatment. This effect was not observed in 68% energy restricted animals. However, in the intestine, differences (p < 0.01) in cholesterol synthesis rates between groups fed fish oil and beef tallow ad libitum were not observed with energy restriction. Energy restriction increased (p < 0.05) TG-FA synthesis rates in intestine of fish and safflower oil-fed groups, but not in that of olive oil- and beef tallow-fed animals. CONCLUSIONS: These results demonstrate the possible importance of dietary fat selection to control against hyperlipidemia during consumption of weight-reduction diets.

Animals↗

PubMed1990

Effects of different levels of dietary fat on methyl-nitrosourea-induced mammary carcinogenesis in correlation with parameters of fat metabolism in female Sprague-Dawley rats.

The aim of this study was to elucidate the effects of different levels of dietary fat on methyl-nitrosourea-induced rat mammary carcinogenesis in correlation with parameters of the fat metabolism. 90 female Sprague-Dawley rats were initiated i.v. with 25 mg MNU/kg on day 50 of life. For a period of 6 months, beginning after the day of initiation, the animals received either a control diet (12% of total energy as fat, Group I) or one of the fat-enriched semisynthetic diets (25 en% of fat, Group II, or 45 en%, Group III, respectively) at an isocaloric level of 50 kcal/rat/day. The principal observations of this experiment were: (1) The fat content of diet did not significantly influence mammary carcinogenesis. (2) The values of plasma total lipids, cholesterol and triglycerides and their density separated VLDL and LDL-fractions showed a significant time-dependent increase. (3) HDL-values of cholesterol and triglycerides showed no changes in dependence to time and fat content of the diet. (4) The liver lipid concentrations of groups increased significantly with dietary fat content.

Animals↗

PubMed1986

The effects of dietary fat and selenium on the development of preneoplastic lesions in rat liver.

In this study, the effects of dietary fat and selenium on the development of putative preneoplastic foci induced by aflatoxin B1 were examined. Rat hepatic gamma-glutamyl transpeptidase (GGT) activity, selenium-dependent glutathione peroxidase activity, glutathione, and total lipid were analyzed 3 and 13 weeks after the start of dietary and carcinogen treatment. Results indicate that high dietary fat has an enhancing effect on the development of preneoplastic foci. A high-fat, selenium-deficient diet resulted in an increase in foci development, but the increase was not significant. An interaction between aflatoxin and the two nutrients was also observed in liver glutathione content and GGT activity at Week 3.

Aflatoxin B1↗

PubMed1998

Variations in dietary fat and cholesterol intakes modify antioxidant status of SHR and WKY rats.

The effects of varying dietary fat saturation [butter (B), beef tallow (BT)] or polyunsaturation [(n-6) soybean oil (SBO), (n-3) menhaden oil (MO)] and cholesterol content (0.05 and 0.5 g/100 g) on systolic blood pressure (SBP), plasma lipids and tissue antioxidant status were investigated in 14-wk-old spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto (WKY) rats. Varying dietary fat composition for 9 wk had no influence on SBP in either SHR or WKY rats. Rats fed MO diets exhibited smaller (P < 0.05) body weight gains, lower (P < 0.05) feed efficiency ratios and lower (P < 0.05) plasma cholesterol concentrations than those fed the B, BT and SBO diets. Significant (P < 0.05) interactions for animal strain x cholesterol intake and animal strain x fat source were noted for serum cholesterol concentrations. SHR exhibited higher (P < 0.05) RBC and liver catalase (CAT), and heart and liver superoxide dismutase (SOD) activities similar to those of WKY rats. The lower (P <0.01) RBC, heart and liver glutathione peroxidase (GSH-Px) activities observed in SHR coincided with higher (P <0.01) glutathione reductase (GSSG-Red), compared with WKY rats. Dietary cholesterol intake had no effect on RBC, heart and liver total sulfhydryl concentration or GSH-Px activities, but increased (P <0. 001) liver GSSG-Red. Feeding MO resulted in lower (P <0.001) RBC and heart GSH-Px activities. In contrast, feeding B and BT resulted in lower GSH-Px in liver. The significant (P < 0.01) animal strain x fat source interaction obtained for liver GSH-Px activity indicated that SHR responded differently to polyunsaturated fatty acid feeding than their WKY counterparts. Diet-induced changes in tissue antioxidant status were tissue specific and did not affect the development of hypertension in SHR.

Analysis of Variance↗

PubMed1992

Effects of dietary fat on cholesterol movement between tissues in CBA/J and C57BR/cdJ mice.

Differences in dietary fats cause differences in cholesterol metabolism in mice. CBA/J mice are resistant to diet-induced hypercholesterolemia and atherosclerosis; they adjust hepatic hydroxymethyl-glutaryl-CoA reductase activity (HMGR) to maintain homeostasis; C57BR/cdJ mice are susceptible, but young animals are thought to maintain homeostasis by changing fecal excretion of sterols. Compartmental modelling of movement of [4-14C]cholesterol was used to analyze movement of cholesterol between serum and liver, heart, and carcass in mice fed 40 en% fat, polyunsaturated to saturated fatty acid ratio (P/S) = 0.24 (US74) or 30 en% fat, P/S = 1 (MOD). Dietary effects were quite pronounced, while strain effects were more subdued. The C57/cdJ animals appear to regulate the overall cholesterol balance by reducing synthesis, as do the CBA/J animals, even though synthesis is not reduced to the same degree as in the CBA/J animals. Both diet and strain influence the whole-animal turnover rate, with slower turnover occurring for C57BR/cdJ animals and animals fed the US74 diet.

Animals↗

PubMed1993

[The role of dietary fats in health].

The current knowledge shows that the quality and quantity of dietary fat have a meaningful role in the etiology and pathogenesis of atherosclerosis. The risk of coronary heart disease is positively related to the cholesterol level in the low-density lipoprotein (LDL) fraction. Cholesterol-lowering diet is recommended for everyone. The recommended diet is low in total fat, saturated fatty acids, dietary cholesterol and salt and high in fiber.

Arteriosclerosis↗

PubMed1995

Formation of an oxidative DNA damage, 8-hydroxydeoxyguanosine, in mouse lung DNA after intratracheal instillation of diesel exhaust particles and effects of high dietary fat and beta-carotene on this process.

Diesel exhaust particles (DEP) cause tumors in the respiratory tracts of experimental animals. It was previously shown that DEP produced superoxide and hydroxyl radical. To examine whether oxygen radicals are involved in mouse lung tumorigenesis induced by DEP, formation of an oxidative DNA damage, 8-hydroxydeoxyguanosine (oh8dG), by DEP was investigated. Furthermore, the role of high dietary fat and beta-carotene on this process was studied. After intratracheal instillation of DEP, a significant increase of oh8dG in mouse lung DNA was observed. High dietary fat enhanced the formation of oh8dG in lung DNA. Intake of beta-carotene suppressed the formation of oh8dG in lung DNA, but the protective effect of beta-carotene against this process was not statistically significant. These results suggest that formation of oh8dG in lung DNA was induced by oxygen free radicals produced by DEP. Thus, it is possible that oh8dG is a promutagenic lesion in DEP-induced lung tumorigenesis in mice and high dietary fat enhances this process through the generation of oh8dG in mouse lung DNA.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2001

Validation of decisional balance and situational temptations measures for dietary fat reduction in a large school-based population of adolescents.

Brief, validated, and reliable theory-based measures specifically designed for use in large survey research with adolescent populations are needed to assess attitudes and behaviors about dietary fat consumption. This study validated two transtheoretical model (TTM)-based instruments in 2639 ninth graders from 12 Rhode Island high schools. The Decisional Balance Questionnaire for Adolescent Dietary Fat Reduction (DBQA) measures the importance adolescents assign to the pros and cons of reducing dietary fat consumption, while the Situational Temptations Questionnaire for Adolescents (STQA) measures temptations to eat high-fat foods as both a global construct and across three categories of challenging situations. Four competing models were compared for each instrument. An eight-item, correlated two-factor Pros and Cons model was validated for the decisional balance measure and a nine-item, three-factor hierarchical model was validated for situational temptations. The theoretically predicted relationships between stage of change and the pros and cons, as well as stage and situational temptations were supported. These results demonstrate that both measures have sound psychometric properties and are externally valid.

Journal Article↗

PubMed2005

Dietary fat and risk of breast cancer.

BACKGROUND: Breast cancer is one of the major public health problems among women worldwide. A number of epidemiological studies have been carried out to find the role of dietary fat and the risk of breast cancer. The main objective of the present communication is to summarize the evidence from various case-control and cohort studies on the consumption of fat and its subtypes and their effect on the development of breast cancer. METHODS: A Pubmed search for literature on the consumption of dietary fat and risk of breast cancer published from January 1990 through December 2003 was carried out. RESULTS: Increased consumption of total fat and saturated fat were found to be positively associated with the development of breast cancer. Even though an equivocal association was observed for the consumption of total monounsaturated fatty acids (MUFA) and the risk of breast cancer, there exists an inverse association in the case of oleic acid, the most abundant MUFA. A moderate inverse association between consumption of n-3 fatty acids and breast cancer risk and a moderate positive association between n-6 fatty acids and breast cancer risk were observed. CONCLUSION: Even though all epidemiological studies do not provide a strong positive association between the consumption of certain types of dietary fat and breast cancer risk, at least a moderate association does seem to exist and this has a number of implications in view of the fact that breast cancer is an increasing public health concern.

Journal Article↗

PubMed1989

Effect of the quality of dietary fat on tumor growth and metastasis from a rat mammary adenocarcinoma.

Experiments were performed to investigate whether the type of dietary fat might affect metastasis from the 13,762 mammary tumor. Female Fischer 344 retired breeder rats were placed into one of five dietary groups: 23% (wt/wt) and 5% (wt/wt) corn oil (HFCO, LFCO), 20% (wt/wt) and 5% (wt/wt) olive oil (HFOO and LFOO), or 20% (wt/wt) beef tallow (HFBT). After four weeks on the diets, each rat had a 2-mm3 piece of the tumor subcutaneously implanted. Primary tumor growth and body weight were monitored weekly for 40 days. At necropsy, the average volume of pulmonary metastases in the HFCO animals (n = 30) was significantly greater than in the other four groups. Among the four groups that did not differ significantly from each other, the rank order in average volume of pulmonary metastasis was as follows: HFOO (n = 25), HFBT (n = 26), LFOO (n = 25), and LFCO (n = 18). Growth of the primary tumor did not vary appreciably among the five groups despite the significant difference in pulmonary metastasis volume. The diets varied considerably in fatty acid content; the most salient difference was that the HFCO diet, which stimulated metastasis significantly more than the other diets did, contained about four times more linoleic acid (18:2) than the other diets. The relevance of this difference and other fatty acid differences is discussed. These results suggest that the quality of dietary fat can be an important determinant of pulmonary metastasis from the 13,762 mammary tumor in retired breeder rats.

Adenocarcinoma↗