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PubMed2001

Comparative effects of dietary fat types on hepatic enzyme activities related to the synthesis and oxidation of fatty acid and to lipogenesis in rats.

The effects of different types of dietary fat on the activities of hepatic enzymes related to fatty acid synthesis [glucose-6-phosphate dehydrogenase (G6PDH) and acetyl-CoA carboxylase (ACC)], oxidation [acyl-CoA synthetase (AST), carnitine palmitoyl transferase (CPT), and peroxisomal beta-oxidation (PbetaOX)], and lipogenesis [phosphatidate phosphohydrolase (PAP), diacylglycerol acyltransferase (DGAT), and phosphocholine diacylglycerol transferase (PCDGT)], and plasma and liver lipid levels were investigated in male Wistar rats. The animals were 6 weeks old and about 120 g of body weight, and were fed on test diets containing 20% of a mixture of tripalmitin, tristearin and corn oil (SFA), olive oil (OLI), sunflower oil (SUN), linseed oil (LIS), and sardine oil (SAR) for 2 weeks. The concentrations of plasma total cholesterol (T-CHOL), high-density lipoprotein-cholesterol (HDL-CHOL), triacylglycerol (TG) and phospholipid (PL) were generally higher in the rats fed on SFA and OLI than in those given SUN, LIS and SAR. The rats fed on OLI had a higher level of liver T-CHOL than those fed on the other fats. The liver TG content was nearly higher from the intake of SFA and OLI than from SUN, LIS and SAR, although the liver PL level was not affected by the type of dietary fat. The SFA and OLI groups had the highest activities of hepatic G6PDH and ACC, and the SAR group, the lowest activities. The activities of AST and CPT, and peroxisomal PbetaOX in the liver were higher in the rats fed on the LIS and SAR diets than in those given the other diets. The hepatic PAP activity was higher from the intake of OLI and SUN, and tended to be higher from SFA than from LIS and SAR. The activity of liver DGAT was higher from SFA and inclined to be higher from OLI, SUN, and LIS than from SAR, while the PCDGT activity in the liver was not effected by the type of dietary fat. The concentrations of plasma and liver TG were generally positively correlated with the activities of liver enzymes related to the synthesis of fatty acids and lipids, and negatively with those involved in fatty acid oxidation. Based on these results, it is suggested that the levels of plasma and liver TG were controlled by different types of dietary fat through changes in the hepatic enzyme activities related to fatty acid synthesis, lipogenesis, and fatty acid oxidation.

Animals↗
PubMedDate not supplied

The relative effect of dietary fats and carbohydrates on lipid metabolism in the albino rat.

This study is concerned with the effect of two carbohydrates, cane-sugar and corn starch, at four different levels in the presence of two dietary fats, on the serum and the tissue lipids (cholesterol, phospholipid and fatty acid patterns). Keeping the dietary fats (coconut safflower seed oil) at 20% level, diets containing (a) startch (54%) + cane sugar (0%), (b) starch (44%) + cane sugar 10%), (c) starch (10%) + cane sugar (44%) and (d) only cane sugar (54%) were administered to rats for 8 weeks. The lipid levels were determined at the end of the feeding period. The beneficial effect of the unsaturated fat in lowering the serum cholesterol level is nullified by an excess of cane sugar in the diet. In liver, there is an increase of 40-50% of cholesterol, as the cane sugar level in the diet is raised, irrespective of the type of dietary fat. The fatty acid pattern of the serum and tissue lipids is influenced by dietary fats as well as carbohydrates.

Animals↗
PubMed2004

Problems with the assessment of dietary fat in prostate cancer studies.

The authors conducted a detailed review of studies on the association between prostate cancer and total dietary fat along with specific fatty acids. Overall, the 29 studies reporting actual dietary fat levels in grams of fat were heterogeneous, suggesting that pooling of the relative risks may be inappropriate. Heterogeneity was also seen by study design. More specifically, although the pooled estimate for prostate cancer and an increase of 45 g in total fat consumption per day was small (relative risk = 1.2), heterogeneity between studies was large, and the association was not supported by specific fatty acids. The strongest association was found among the five extremely inconsistent studies of alpha-linolenic fatty acid. The associations with advanced prostate cancer were more homogeneous and suggest a relation with total and saturated fat but none with specific fatty acids. This review highlights the inconsistent way in which total dietary fat and specific fatty acids have been measured and reported across epidemiologic studies of prostate cancer. The heterogeneity between studies was large, possibly because of the variation in the dietary instruments used and the corresponding databases (nondifferential misclassification), recall bias, differing case definitions, residual confounding, or potential selection bias in different studies.

Dietary Fats↗
PubMed1994

Interaction of dietary fat saturation and cholesterol level on cholesterol synthesis measured using deuterium incorporation.

To examine interactive effects of dietary fat saturation and cholesterol level on serum lipids and de novo cholesterogenesis, moderately hypercholesterolemic subjects were fed solid-foods diets containing 30% fat (80 mg C.1000 Kcal-1) in which 2/3 fat was either corn oil or beef tallow, with and without 120 mg C.1000 Kcal-1, for 5 wk. At the end of each diet period, subjects were given deuterium (D) oxide orally and de novo cholesterol synthesis was measured over 24 h from D incorporation into cholesterol as fractional synthesis rates (FSR) and absolute synthetic rate (ASR) into the rapid exchangeable cholesterol pool. Plasma total and low density lipoprotein levels were elevated (P < 0.01) with both beef tallow and cholesterol feeding. High density lipoprotein (HDL) levels were not influenced by fat saturation or cholesterol level; however, HDL was higher with addition of cholesterol to corn oil versus beef tallow (P < 0.02). Plasma triglycerides were higher (P < 0.02) with beef tallow feeding but were not influenced by cholesterol level. FSR was increased (P < 0.02) by feeding corn oil, versus beef fat, but not by dietary cholesterol level. Calculated cholesterol pools sizes did not differ across groups; however, ASR was also elevated with corn oil versus beef tallow feeding (P < 0.02). Results indicate that corn oil feeding lowers circulating cholesterol by mechanisms other than reduced synthesis, and that cholesterol at the level of supplementation used is not associated with feedback inhibition of cholesterogenesis. However, with the exception of HDL levels, dietary fat saturation and cholesterol levels do not interactively influence circulating lipoprotein cholesterol levels and cholesterol synthesis.

Aged↗
PubMed1981

Effect of intestinal microflora and dietary fat on 3,2'-dimethyl-4-aminobiphenyl-induced colon carcinogenesis in F344 rats.

The effect of dietary fat and intestinal microflora on colon and small intestinal carcinogenesis was studied in weanling male F344 germfree and conventional rats fed semipurified diets containing low and high fat. At 7 weeks of age, all animals, except vehicle-treated groups, received weekly s.c. injections of 50 mg 3,2'-dimethyl-4-aminobiphenyl (DMAB) per kg body weight for 20 weeks. The DMAB- and vehicle-treated germfree and conventional rats fed high- and low-fat diets were autopsied 20 weeks after the last injection of DMAB. The incidence of colon, small intestinal, ear duct, and skin tumors was lower in germfree rats than in the conventional animals. The incidence and multiplicity of DMAB-induced colon tumors were higher in conventional rats fed the high-fat diet than in the conventional animals fed the low-fat diet; however, the tumor incidence did not differ significantly between the high- and low-fat-fed germfree animals. Dietary fat had no effect on the incidence of small intestinal tumors in both germfree and conventional rats.

Aminobiphenyl Compounds↗
PubMed1981

Dietary fat and its relationship to large bowel cancer.

Epidemiological data have provided clues to the etiological factors involved in large bowel cancer development. High intake of dietary fat tends to promote colon carcinogenesis. Studies in metabolic epidemiology have shown that the high dietary fat affects the metabolic activity of gut bacteria as well as the levels of secondary bile acids that may act as tumor promoters for the colon. Animal model studies indicate that total dietary fat, rather than type of fat, exerts a promoting role in colon carcinogenesis.

Adenocarcinoma↗
PubMedDate not supplied

The effects of different percentages of dietary fat intake, exercise, and calorie restriction on body composition and body weight in obese females.

PURPOSE: The goal of this study was to determine the effect of varying the amount of dietary fat, while holding calories at 1,200 kcals/day, on body weight and percent body fat in 35 obese women. DESIGN: A pretest, midtest, posttest experimental design was employed, and subjects were randomly divided into one of four dietary fat groups, with 10%, 20%, 30%, or 40% of caloric intake as dietary fat. INTERVENTION: Subjects consumed 1,200 kcals/day and a specified percentage of total energy as fat, depending on their dietary group. Protein was held constant at 20%. All subjects engaged in a five day/week walking program. SETTING: Participants were recruited from the general community using newspaper advertisements. SUBJECTS: Thirty-five obese women 25 to 45 years of age (means=38 +/- 4.97) served as subjects. All were at least 20% above ideal weight and 30% to 52% body fat. MEASURES: Percent body fat, body weight, and anthropomorphic measurements were taken at baseline, six and 12 weeks. Dietary intake was recorded daily by each subject, and exercise walking logs were maintained by each participant. RESULTS: All subjects lost body weight and body fat; however, there were no significant differences in the rate or amount of body weight or percent body fat lost across the four groups during the intervention. CONCLUSIONS: It appears that during calorie restriction and exercise for 12 weeks, percent of calories derived from dietary fats does not influence loss of body weight or percent body fat in adult obese women.

Adult↗
PubMed1994

Mechanisms in multiple risk factor interventions: smoking, physical activity, and dietary fat intake among manufacturing workers. Working Well Research Group.

BACKGROUND: Individuals who have multiple poor health behaviors account for a disproportionately large percentage of the preventable U.S. health care cost burden. Understanding the relationships between multiple risk factors is important for the design of both individual and public health interventions. There have been few efforts to examine the co-occurrence of psychosocial and motivational mechanisms that mediate smoking, dietary fat intake, and physical activity in a defined population of blue collar workers. METHODS: The sample comprised 1,559 manufacturing workers who participated in a self-help physical activity intervention and who completed a computerized assessment battery about their smoking, dietary fat intake, physical activity, and demographic characteristics. RESULTS: Twenty-six percent of the sample were smokers, 51% did not exercise regularly, and 35% consumed more than an estimated 40% of calories per day from fat. Almost half of the sample was in the later stages of readiness for physical activity and dietary fat intake, compared with only 3% for smoking. Only 12% of the smokers had smoking as their only risk factor. Smokers were significantly more likely to engage in poor dietary and physical activity behaviors, compared with nonsmokers. The relationship among smoking status and the other risk factors was apparent both in terms of dietary fat and physical activity behaviors, as well as mediators such as motivation for change. Lower dietary fat intake was associated with an absence of the other two risk factors. CONCLUSIONS: The results suggest that there are important mediating mechanisms both within and among workers with one or more risk factors. Smokers are a particularly important target for health promotion interventions, and it may be possible to make initial contact with them through other health programs at the worksite. The role of other lifestyle changes as a gateway to smoking cessation has not yet been explored, but may have potential for reaching smokers who are very low in their motivational readiness to change. The implications of these findings for research and the design of multiple risk factor interventions are discussed.

Adult↗
PubMed2001

Manganese absorption and retention in rats is affected by the type of dietary fat.

There is evidence that manganese (Mn) metabolism may be altered by the form and amount of dietary fat. Also, iron (Fe) absorption is greater with saturated fats, as compared to polyunsaturated fatty acids (PUFAs). The absorption of Fe and Mn are interrelated in many aspects; therefore, the form of dietary fat may indirectly alter Mn absorption. The reported studies were conducted to determine whether saturated fat, as compared to unsaturated fat, affected Mn absorption, retention, and metabolism. In experiment I, adult rats were fed diets containing either 0.7 or 100.4 microg/g Mn with the fat source as high-linoleic safflower oil or stearic acid. After 2 wk of equilibration, the animals were fed a test meal of 54Mn followed by whole-body counting for 10 d. Manganese absorption was significantly (p < 0.05) lower in the stearic acid group (0.9-4.8%) than in the safflower oil group (20-33.8%); however, the biological half-life was shorter in the safflower oil group. Retention of 54Mn and total Mn was always significantly (p < 0.05) greater in the safflower oil group when dietary Mn was low, but it was the same when dietary Mn was high. In experiment II, weanling rats were fed 1.3, 39.3, or 174.6 microg Mn/g and either stearate, high-oleic safflower oil or high-linoleic safflower oil for 8 wk. Long-term feeding of the stearate and low Mn-containing diet resulted in a significant (p < 0.0001) reduction in heart superoxide dismutase activity and kidney and liver Mn concentrations compared to the other diets. These data show that stearic acid inhibitits Mn absorption, but it may not inhibit Mn retention when dietary Mn is high.

Animals↗
PubMed1987

Dietary fat modulation of murine mammary tumor metabolism studied by in vivo 31P-nuclear magnetic resonance spectroscopy.

The effect of dietary fat concentration and saturation on high energy phosphate metabolites and phospholipid turnover in transplanted line 168 murine mammary tumors was studied using surface coil 31P-nuclear magnetic resonance spectroscopy. Female BALB/c mice were fed one of five diets each containing at least the minimum of essential fatty acids (EFA). Four diets contained additional safflower or palm oil for a total fat concentration of 5 or 20% by weight. The growth rate of tumors from mice fed the high safflower oil diet was significantly greater than the growth rate of tumors for mice fed all other diets including the one which contained the minimal EFA. 31P-nuclear magnetic resonance-observable phosphate metabolite ratios. ATP/Pi, ATP/phosphomonoester (ATP/PME), and PME/Pi, and tumor pH of line 168 tumors decreased with increasing tumor volume, indicating a shift from active to inactive tumor metabolism. The rates of those decreases with progressive tumor growth differed significantly among tumors of mice fed the different diets. Decreases in ATP/Pi, ATP/PME, and pH were the most rapid in the tumors of mice fed the high safflower oil diet and significantly faster than tumors of mice fed the diet containing minimum EFA. In addition, the decrease in the PME/Pi ratio of tumors was significantly greater in mice fed the high fat (high palm oil and high safflower oil) diets than mice fed the diet containing the minimum of EFA. The rate of decline of ATP/Pi and ATP/PME with progressive tumor growth was directly correlated with levels of linoleic acid as well as total unsaturated fat. High levels of a polyunsaturated fat had a significant effect on mammary tumor metabolism particularly during early stages of tumor growth. Differences in high energy phosphate metabolite dynamics relative to dietary fat were present in tumors of equal volume. Thus, dietary fat influences on mammary tumorigenesis may be related to high energy phosphate metabolites.

Adenosine Triphosphate↗
PubMed2005

Influence of dietary fats on weight gain in albino rats.

Carbon-chain length and degree of saturation of dietary fat may influence weight gain. To examine this hypothesis we randomly allotted 100 male, 30-day old, albino rats to each of four groups. Each group was fed, ad libitum, a diet containing, as the only source of fat, either lard (L) or safflower oil (SO) (representing saturated and polyunsaturated fat respectively) or groundnut oil (GO) or coconut oil (CO) (representing long-chain and medium-chain triglycerides respectively). At the end of 90 days it was found that rats fed SO consumed more food than those fed L enriched diet (P < 0.001) but the weight gain was similar in the two groups. Similarly rats fed GO-containing diet ate more than those fed diet containing CO (P < 0.001), yet weight gain was similar. Thus it appears that carbon-chain length and degree of saturation of dietary fat does not influence weight gain in rats fed an ad libitum diet.

Animals↗
PubMed1985

Effects of dietary fat on the growth of normal, preneoplastic and neoplastic mammary epithelial cells in vivo and in vitro.

In order to determine: (1) whether there is a growth-regulating interaction between the mammary fat pad and mammary epithelium; (2) whether this interaction could be modified by dietary fats; and (3) whether these effects could be demonstrated in vitro, the following experiments were performed. Virgin Balb/c mice had the left inguinal mammary fat pad cleared of epithelium and were then maintained on one of four fully defined diets. These diets contained the following proportions of fat by weight: 5% or 10% mixed fats; 20% saturated fat plus cholesterol; or 20% polyunsaturated fat. To test for effects in vivo, animals received subcutaneous injections into the cleared fat pad of tumorigenic mammary cells (WAZ-2T(+SA) or WAZ-2T(-SA)) or preneoplastic mammary cells (CL-S1). Dietary fat had little effect on the latent period of tumour formation, but a low-fat diet increased the invasive/metastatic potential of both tumorigenic cell lines. A high-saturated-fat diet inhibited the growth of normal and preneoplastic epithelium in vivo. To test for effects in vitro, CL-S1 cells were co-cultured with explants of cleared mammary fat pad embedded within collagen gels. CL-S1 cells co-cultured with adipose explants obtained from mice fed on a diet containing 20% polyunsaturated fat showed a threefold increase in incorporation of [3H]thymidine into trichloroacetic acid-precipitable material. These results imply that dietary fats may affect the growth of mammary epithelium in two ways: the inhibition of growth caused by the high-saturated-fat diet may be due to systemic effects as it was not apparent in vitro; the increase in growth seen in vitro and caused by a high-polyunsaturated-fat diet is due to a direct interaction between the mammary fat pad and mammary epithelial cells. This interaction may be masked by systemic effects in vivo.

Adipose Tissue↗
PubMed1986

Hepatic mitochondrial and peroxisomal oxidative capacity in riboflavin deficiency: effect of age, dietary fat and starvation in rats.

The effects of riboflavin deficiency on mitochondrial and peroxisomal substrate oxidation were examined in young (treatment begun at weaning) and adult Sprague-Dawley rats that were fed diets low and high in fat. State 3 respiration rates (ADP-stimulated) were used as an estimate of mitochondrial oxidation rates. The oxidation of palmitoyl-CoA and palmitoylcarnitine, and to a lesser extent, glutamate, pyruvate and succinate, by hepatic mitochondria isolated from the young rats was depressed with riboflavin deficiency. There was no effect of dietary fat level on mitochondrial substrate oxidation. Carnitine palmitoyltransferase-A (CPT-A) Vmax was increased with riboflavin deficiency and with increasing dietary fat. Cyanide-insensitive palmitoyl-CoA oxidation was used to estimate peroxisomal palmitate oxidation. Expressed as total hepatic capacity, peroxisomal palmitate oxidation was depressed with riboflavin deficiency. This effect was the result of the reduced feed intake rather than riboflavin deficiency per se. Increasing dietary fat resulted in increased peroxisomal palmitate oxidation. Starvation of young rats did not change mitochondrial oxidation rates, although riboflavin-deficient starved rats exhibited increased rates of palmitoyl-CoA oxidation as well as increased CPT-A Vmax. In adult rats, after 5 wk of deficiency, only palmitoyl-CoA and palmitoylcarnitine oxidation rates were depressed. Dietary fat level did not interact with riboflavin deficiency. However, CPT-A Vmax was increased with riboflavin deficiency and with increased dietary fat level. Further, depressed hepatic fatty acid oxidation can occur in adult rats as a sequel to the feeding of riboflavin-deficient diets.

Aging↗
PubMedDate not supplied

[Effects of dietary fat composition on food anaphylaxis and formaldehyde sensitization in guinea pigs].

Adult guinea pigs were fed for 10-14 days with synthetic diets, fat constituting 11% of its total energy. Dietary fat was composed of coconut, corn, dairy and soybean oils mixtures with ratio of polyunsaturated fatty acids (PUFA) omega-6 to PUFA omega-3 equal to 24.2 (K1) or 5.53 (K2). The animals were sensitized orally by pasteurized cow milk (PCM) or epicutaneously by formaldehyde (F) during these diets feeding. The degree of the sensitization was assessed in the reaction of active anaphylactic shock (AAS) in PCM-sensitized animals and in the reaction of leukocytes specific lysis (LSL) in F-sensitized guinea pigs. In the latter pigs the concentration of serum antibodies (Ab) against dietary soya protein was measured by ELISA. Animals fed by K1 and K2 were also tested for histamine mean lethal dose resistance. The lowest lethality in AAS, number of convulsions, of positive LSL cases and Ab level were found in animals fed by K1 compared to both K2 and to animals fed by common animal chew. Resistance to histamine was similar in K1 and K2 groups, but was significantly higher compared to control (chew) group. In convulsion, the changes in PUFA omega-6/PUFA omega-3 ratio have marked effect on different indices of allergic sensitivity.

Anaphylaxis↗