Corn Oil Diet Group Research Articles

The effects of different high-fat (lard, soybean oil, corn oil or olive oil) diets supplemented with fructo-oligosaccharides on colonic alkaline phosphatase activity in rats.

We recently reported that fermentable non-digestible carbohydrates including fructo-oligosaccharides (FOS) commonly elevate colonic alkaline phosphatase (ALP) activity and the expression of IAP-I, an ALP gene, in rats fed a high-fat (HF) diet, and also elevate gut mucins and modulate gut microbiota. This study aims to investigate whether dietary fat types influence the effect of FOS on colonic ALP activity and the luminal environment in HF-fed rats. Male Sprague-Dawley rats were fed a diet containing 30% soybean oil, corn oil, olive oil or lard with or without 4% FOS for 2weeks. Colon ALP activity, gene expression, and gut luminal variables including mucins and microbiota were measured. In the lard diet groups, dietary FOS significantly elevated colonic ALP activity and the expression of IAP-I. The elevating effect of FOS on colonic ALP activity was also observed in the olive oil diet groups, although here the IAP-I expression was not changed. However, the soybean oil and corn oil diet groups did not exhibit the elevating effect of FOS on colon ALP. Fecal ALP and mucins were significantly elevated by dietary FOS regardless of dietary fat types, and the effect of FOS was prominent in the lard diet groups. The number of Lactobacillus spp. observed in fecal matter was significantly increased by dietary FOS in the lard and olive oil diet groups, but not in the soybean oil and corn oil diets groups. This study suggests that dietary fat types may change the effect of FOS on the colonic luminal environment including the ALP activity in rats fed a high-fat diet.

Omega-3 fatty acids and ERPR(-) and HER2/neu(+/-) breast cancer prevention.

TPS1589 Background: The most aggressive breast cancer subtypes tend to be estrogen and progesterone receptor negative (ERPR(-)) and human epidermal growth factor receptor type 2 positive (HER2(+)). Women with these breast cancer subtypes (triple negative, ERPR(-)HER2(+)) tend to experience worse clinical outcomes and have a relatively higher risk of recurrence. Our previous research demonstrated that dietary omega-3 (n-3) fatty acids can significantly inhibit ERPR(-) HER2(+) tumorigenesis in MMTV-HER2/neu transgenic mice fed fish oil vs corn oil-based diets. The fish oil diet group developed 30% fewer breast tumors, had lower Ki67 expression, and experienced less mammary atypia relative to the corn oil diet group. Other studies involving diet, nutrition and breast cancer point to the potentially protective effect of an anti-inflammatory diet on the risk of developing ER(-) and HER2(+) breast cancer, further supporting the evidence that the ERPR(-), HER2(±) subtypes may be highly responsive to this bioactive nutrient. Methods: This is a double-blinded, randomized clinical trial of high dose (~5.4 g EPA+DHA) vs low dose (~0.9 g EPA+DHA in fatty acid mix of the typical American diet) of n-3 fatty acids in breast cancer survivors of ERPR(-), HER2(±) breast cancer. Eligible participants will take 5 capsules/day for 12 months, with cellular samples of breast epithelial and/or adipose tissue obtained by fine needle aspirations of the contralateral breast. The study aims to determine whether n-3 fatty acid supplementation will modify fatty acid metabolite content in breast adipose tissue, modulate cytomorphology and/or cell proliferation in breast epithelial cells, affect DNA methylation patterns, and modulate pro- vs anti-inflammatory gene expression patterns in breast adipose tissue. Correlative aims will evaluate possible associations between factors such as breast adipose tissue, red cell membrane fatty acid profiles, BMI, and reported dietary intake. Sample size of 40 participants per arm was calculated to provide at least 80% power to detect a statistically significant difference for each primary endpoint. This study focuses on women survivors of high risk breast cancer subtypes, specifically triple negative or ERPR(-)HER2(+) disease, who are currently without long term adjuvant options. Eligibility criteria include prior diagnosis of ERPR(-) stage 0 to III breast cancer, ≤5 years from completion of standard therapy.The study was closed to accrual in November 2018; less than 9 months of follow-up remain for active study participants. Clinical trial information: NCT02295059.

복분자씨유의 식용유지 대체가 C57BL/6J Mice의 혈청 지질에 미치는 영향

This study evaluated the effects of Rubus coreanus Miq. oil on the plasma lipid profile of high fat diet (HFD)-induced obese mice. Animals were randomly divided into 4 groups (n=10). After completion of the 5-week experimental period, we measured bodyweight gain, food intake, adipose tissue mass, and plasma lipid profile. We also analyzed the activities of carnitine and superoxide dismutase (SOD) involved in β-oxidation and antioxidation, respectively. Our results show that HFD-induced weight gain in animals in the R. coreanus Miq. oil diet group (RCO) and corn oil diet group (CO) was significantly lower compared to animals in the HFD group; RCO supplementation had a more noticeable effect than CO. Visceral and back fat weights were lower in the RCO and CO groups while plasma HDL cholesterol (HDL-C) and HDL-C per total cholesterol [HDL-C/TC (%)] ratio were significantly higher in the RCO group. The contents of acid-soluble acylcarnitine and total carnitine as well as SOD activation were significantly higher in the RCO group, but no significant difference was observed between the RCO and CO groups. In conclusion, RCO effectively averted elevation of total body weight and fat weight in HFD-induced obese mice and promoted increased HDL-C. Therefore, R. coreanus Miq. oil might play an anti-obesity role in obese people and could be used as an effective oil supplement.

High susceptibility of heterozygous (+/fa) lean Zucker rats to 7,12-dimethylbenz(a)anthracene-induced mammary carcinogenesis

Susceptibility to 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary carcinogenesis was investigated in lean Zucker (+/fa) rats carrying one mutated leptin receptor gene and wild-type controls (+/+). Rats with both genotypes were given a single DMBA administration and divided into two groups, one group was fed on basal diet mixed with 10% corn oil and the other was fed on basal diet alone. The minimum latency period of palpable carcinomas in +/fa rats of both groups was 8 weeks following DMBA treatment, in contrast to the 11-12 weeks in +/+. The incidence and multiplicity of carcinomas increased or showed a tendency for increase in the early stages in +/fa rats of both groups as compared to the +/+ counterparts. The volumes of carcinomas showed a tendency to increase in the corn oil diet groups of both genotypes. The major histopathological phenotype of carcinomas in all groups was well-differentiated without distinct atypia (multiplicity, 0.69-1.09/rat), but moderately/poorly differentiated carcinomas with atypia were also found, predominantly in +/fa rats (0.09-0.21). These latter tumors were characterized by elevated ERK activity but not estrogen receptor expression. Serum leptin concentrations in +/fa rats at 7 weeks of age were higher than those in +/+ and were elevated by the corn oil diet; however, no obvious change was detected in other serum parameters examined. In conclusion, +/fa rats proved more susceptible to DMBA-induced mammary carcinogenesis than +/+ controls, and hyperleptinemia was suggested to contribute to tumor growth as well as to susceptibility to tumorigenesis and more aggressive phenotypes in Zucker lean rats.

母親が摂取したコーン油とシソ油が仔ラットの血漿と脳の脂肪酸組成に及ぼす影響

We investigated the effects of corn oil and perilla oil intake by rats during pregnancy and lactation on the fatty acids composition of plasma and brain of rat pups. Two groups of dams were fed either a corn oil diet (CD) or a perilla oil diet (PD) during their pregnancy and lactation. On days 8, 21 and 33 after birth, two pups each from the litters of all dams were killed and their blood and brain samples were collected. After weaning, the 46 and 60-d-old pups were dissected. On day 8 after birth, although the n-3 fatty acid in the plasma of the PD group was 3 times higher than that of the CD group, no significant difference in the brain was observed between the two groups. On day 1 after birth, no brain n-3 fatty acid composition in the pups from both groups was detected, but they increased with the pup′s growth. The n-6/n-3 in pup′s brain of dams fed the CD and the PD was 1. 88 and 1. 74 on the day 8 after birth, and 1. 26 and 0. 93 on the day 60 after birth, respectively. Therefore, it was suggested that the fatty acid composition of the brain in pups remained constant while the dams were fed different oils during pregnancy and lactation.

Effect of corn oil and perilla oil intake by rats during pregnancy and lactation on composition of stomach contents and plasma lipids concentration of pups

We studied the effects of corn oil and perilla oil intake by rats during pregnancy and lactation on the composition of the stomach contents and plasma lipids concentration in their pups. Two groups of dams were fed either a corn oil diet (CD) or a perilla oil diet (PD) during their pregnancy and lactation. On days 8, 21 and 33 after birth, two pups each from the litters of all dams were killed and their blood and stomach were collected. A long chain polyunsaturated fatty acid (LCPUFA; C20-22) not presented in the dams diet was detected in the stomach breast milk of both groups. Although the n-3 fatty acids of LCPUFA in the stomach of the PD group was higher than that of the CD group, no significant difference in the arachidonic acid (AA; 20:4) and docosahexaenoic acid (DHA; 22:6) was observed between the two groups. The plasma lipid concentration in the pups of the PD group was lower than that of the CD group, but there was no significant difference in the two groups after weaning. Therefore, α-lindenic acid (ALA; 18:3) in the PD was synthesized into eicosapentaenoic acid (EPA; 20:5) and DHA in the dam's body and added to the breast milk, which indicated that the plasma lipids concentration in the pups nursed by the dams fed the PD decreased during lactation.

Dietary fish oil inhibits the early stage of recovery of atrophied soleus muscle in rats via Akt–p70s6k signaling and PGF2 α

Skeletal muscle recovery from disuse atrophy requires the recruitment of insulin signaling for muscle growth, which is driven by protein synthesis. Dietary fish oil, which is rich in long-chain n−3 polyunsaturated fatty acids, is known to enhance insulin signaling and protein metabolism. Therefore, this study was performed to evaluate whether dietary fish oil facilitates muscle recovery during remobilization after disuse atrophy. Ten days of immobilization, followed by 3 or 13 days of remobilization, were applied to the hindlimbs of rats fed corn oil [corn oil diet group as control (CO)] or fish oil [fish oil diet group (FO)] as source of dietary fat. The immobilization-induced reductions in soleus muscle weight and myosin heavy-chain content were significantly restored by 3 days of remobilization in CO. However, in FO, these muscle recovery measurements did not significantly change until 13 days of remobilization. At 3 days of remobilization, both groups had significant elevations in p70 ribosomal S6 kinase (p70s6k) activation and at a greater extent in CO than in FO. The activation of Akt was also increased on Day 3, but it was not significant in FO. Throughout the remobilization period, levels of prostaglandin F2 α (PGF2 α) and cyclooxygenase-2 mRNA were significantly augmented. However, FO had a lesser increase in PGF2 α than CO until Day 13. These findings indicate that dietary fish oil inhibits the early stage of soleus muscle recovery after disuse atrophy by suppressing the activation of Akt–p70s6k signaling and PGF2 α synthesis.

Dietary ω‐3 PUFA‐derived NPD1 is renoprotective and augments cytoprotective heme oxygenase‐1 expression in ischemic renal injury

Ischemic acute renal failure (ARF) is a clinical problem associated with high morbidity and mortality, and inflammation is a key feature of its pathophysiology. Fish oil contains the essential ω-3 polyunsaturated fatty acid (PUFA) docosahexaenoic (DHA) acid which has anti-inflammatory effects and can ameliorate ARF in animal models. The molecular mechanisms of action for the protective effects of DHA have been attributed to the formation of DHA-derived lipid mediators (LM), namely neuroprotectin D1 (NPD1) and 17-HDHA. We set out to investigate if the protective actions of dietary DHA in ischemic renal injury are mediated by DHA-derived LM. Ischemic injury was induced by clamping the renal pedicle and inflammatory markers and renal function were measured in mice placed on a standard, DHA-enriched fish oil, or a corn oil diet. Endogenous formation of DHA-derived LM was analyzed by LC/MS/MS and impact of systemic NPD1 was investigated. 30 min of ischemia elevated serum creatinine in the corn oil diet group by 156%, in contrast, renal function remained normal in the fish oil diet group. Severe ischemic injury (45 min) caused 100% mortality in corn oil fed mice in sharp contrast to 0% in fish oil fed mice. Fish oil diet suppressed PMN influx by 62%, PGE2 by 57%, and also attenuated levels of MIP-2, KC, IL-1β, IL-6, and TNF-α, which correlated with endogenous formation of NPD1 and 17-HDHA in the kidney. Systemic treatment with NPD1 reduced PMN levels in the kidney by 64% and, more importantly, amplified renoprotective heme oxygenase-1 (HO-1) protein and mRNA expression in the kidney and in cultured mesangial cells. Taken together, these findings demonstrate that NPD1 mediates, in part, the beneficial effects of dietary DHA in ischemic renal injury and identify amplification of cytoprotective HO-1 as a potential mechanism.

Identification of novel differentially expressed genes by the effect of a high‐fat n‐6 diet in experimental breast cancer

In previous studies, we demonstrated that high corn oil diets promote the development of 7,12-dimethylbenz(alpha)anthracene (DMBA)-induced mammary tumors. In this study, we have investigated whether modulation of gene expression is one of the mechanisms by which this high-fat diet exerts such effects. Female Sprague-Dawley rats were induced with DMBA and fed normolipidic (3% corn oil) or high-fat (20% corn oil) diet. Screening of genes differentially expressed in adenocarcinomas from the high corn oil diet group compared to the control diet group was performed with cDNA microarrays. The resulting six upregulated and nine downregulated genes were validated by Northern blot and/or reverse transcription (RT)-polymerase chain reaction (PCR). Further investigation in a higher number of adenocarcinomas showed that in the high-fat n-6 diet group, where the tumor phenotype was verified to be more aggressive, the expression of submaxillary gland alpha-2u globulin, vitamin D(3)-upregulated protein 1 (VDUP1), H19, and the unknown function gene that codifies the expressed sequence tag (EST)-Rn.32385 was significantly decreased in comparison with the control group (C). These results, together with the fact that VDUP1, H19, and this globulin have been associated with cell proliferation and differentiation, open a new line of research about how the underexpression of these genes contributes to the stimulating effect of a high corn oil diet on experimental mammary carcinogenesis.

Dietary Oils and Phospholipids Containing n-3 Highly Unsaturated Fatty Acids Suppress 2, 4-Dinitro-1-fluorobenzene-induced Contact Dermatitis in Mice

Dietary perilla oil, tuna oil and salmon roe phospholipids (fish roe PL) containing n-3 polyunsaturated fatty acids were compared with n-6 fatty acid-rich corn oil for their anti-inflammatory activities in the contact hypersensitivity reaction in the ears of mice sensitized with 2, 4-dinitro-1-fluorobenzene (DNFB). Suppression of ear swelling was most active with fish roe PL followed by tuna oil and Saibokuto, a traditional Chinese medicine, when compared with the corn oil diet group; perilla oil enriched with α-linolenic acid (n-3) tended to suppress the ear swelling, but the effect was not statistically significant. Infiltration of inflammatory CD4-positive T lymphocytes into the ears was suppressed by fish roe PL. Fish roe PL diet suppressed the expression of mRNAs for IFN-γ, IL-6 and IL-1β in the ears. These results suggest that tuna oil and fish roe PL may be effective in suppressing delayed-type hypersensitivity.

Retinal and brain accretion of long-chain polyunsaturated fatty acids in developing felines: the effects of corn oil-based maternal diets

A study was carried out in domestic felines to determine whether corn oil-based maternal diets are an adequate source of essential fatty acids to support normal accumulation of long-chain polyunsaturated fatty acids in the brains and retinas of offspring and whether these diets have any subsequent effect on visual function. Female domestic felines were acclimated to one of six different defined diets 1 mo before mating and maintained on the diets throughout pregnancy and lactation. Four diets contained only corn and hydrogenated coconut oils as their source of fat in ratios of 1:9, 3:7, 6:4, and 9:1, respectively. Two reference diets also contained the long-chain polyunsaturated fatty acids arachidonate (20:4n-6) and docosahexaenoate (22:6n-3). When the offspring were 8 wk old, electroretinograms were obtained and the a- and b-wave implicit times were determined. The results showed that animals raised in litters in which the maternal diets were devoid of 20:4n-6 and 22:6n-3 had an increase in a- and b-wave implicit times compared with the controls. In the rod outer segments and brains of these animals, there were lower amounts of 22:6n-3 and higher amounts of long-chain n-6 polyunsaturated fatty acids compared with control animals. These findings showed that although corn oil-based diets were capable of maintaining 20:4n-6 concentrations in the developing brain and retina, only those diets containing 22:6n-3 could support a high accumulation of docosahexaenoic acid in these tissues. Moreover, low amounts of 22:5n-6 in the brains of animals in all of the corn oil-diet groups suggested that young felines have a low biosynthetic capacity to produce this fatty acid or 22:6n-3. These findings suggest that in juvenile felines, maintenance of 22:6n-3 status in the nervous system is important for optimal retinal function.

Is Dietary Arachidonic Acid Necessary for Feline Reproduction?

A study was carried out to determine whether corn oil-based diets devoid of arachidonic acid, 20:4(n-6), are capable of supporting feline reproduction. One group of four adult female felines were acclinmated to a 10 weight% (wt%) fat diet consisting of 1 wt% corn oil and 9 wt% hydrogenated coconut oil for 1 mo before mating. One female produced two live offspring, and the other three females delivered either stillborn fetuses or offspring that were severely deformed and died shortly after birth. Two of these females were subsequently placed on a 1 wt% corn oil diet that was supplemented with 20:4(n-6) (200 mg/kg of diet), and after 2 mo they were mated. Offspring resulting from the second mating were healthy. A third group of females that were maintained on a 10 wt% fat diet consisting of 3 wt% corn oil were also mated. The offspring from these matings appeared healthy at birth. Neonates from each diet group were killed, and the fatty acyl composition of the livers, plasma and brains was analyzed. In the offspring livers and plasma, the level of 20:4(n-6) from both the 1 wt% or 3 wt% corn oil diet groups was about half that of offspring from those receiving 20:4(n-6) in the diet. There were no differences in the level of 20:4(n-6) in the neonate brains among any of the groups. This study suggests that nutritional factors unrelated to the tissue accumulation of arachidonic acid in the offspring may be responsible for the high percentage of stillbirths and deformities associated with maternal diets containing low amounts of essential fatty acids but that diets that contain a higher percentage of corn oil can support feline reproduction.

Animal and Plant Fats Selectively Modulate Oxidizability of Rabbit LDL and LDL-Mediated Disruption of Endothelial Barrier function1

Enrichment of lipoproteins with fatty acids derived from animal and/or plant fats may modify the oxidizability of lipoproteins and their effects on endothelial barrier function. To test this hypothesis, rabbits were fed for 30 days diets containing 2 g corn oil/100 g diet (low fat diet) or low fat supplemented with 16 g/100 g diet of corn oil, corn oil with added cholesterol, milk fat, chicken fat, beef tallow or lard. Compared with those fed the low fat, serum and LDL cholesterol concentrations were significantly lower in rabbits fed corn oil and greater in animals fed corn oil with added cholesterol or chicken fat. In contrast to the cholesterol data, lipid hydroperoxide levels were highest in oxidized LDL derived from rabbits fed corn oil or lard. LDL vitamin E levels were highest in rabbits fed corn oil with added cholesterol. The significant elevations in linoleic acid [18:2(n-6)] in serum and LDL may partially explain the high oxidizability of LDL in rabbits fed corn oil. LDL isolated from animals fed corn oil, lard or milk fat had significantly greater albumin transfer across cultured endothelial monolayers compared with those of the low fat diet group. Their oxidative modification further contributed to endothelial barrier dysfunction. Dietary cholesterol supplementation to the corn oil diet decreased the oxidizability of LDL and partially protected the oxidized LDL-mediated endothelial cell dysfunction as compared with the corn oil diet group. These data suggest that beef tallow and chicken fat are the least atherogenic fats if oxidative modification of LDL is a critical issue in atherosclerosis.

Effect of dietary calcium on the absorption of triglycerides esterified at 1,2 and 1,3 positions of glycerol with long chain saturated fatty acids in rats

We investigated the effect of dietary Ca on the absorption of 1,3-dipalmitoyl-2-oleoyl glycerol (POP), 1(3),2-dipalmitoyl-3-oleoyl glycerol (PPO), cocoa butter (CB) which contained 1-palmitoyl-2-oleoyl-3-stearoyl glycerol (POS) as major triglycerides, chocolate (Choco) made from cocoa butter and corn oil. Rats were fed the diets containing 10% of one of the above lipids for 7 days. The apparent absorption efficiency of nutrients, especially fat, were lower in rats fed CB+Ca or POP+Ca diet than those fed CB or PPO+Ca diet. The low apparent absorption efficiency of fat was due to the low absorption efficiency of palmitic and stearic acids. Absorbed fat energy was 10% lower in CB+Ca diet group than in CB diet group, and was 18% lower in Choco+Ca diet group than in corn oil diet group. Although the apparent absorption efficiency of energy was lower in Choco diet group than in corn oil diet group, the apparent absorption efficiency of palmitic and stearic acids in Choco were larger than those in cocoa butter even when Ca was fortified. The apparent absorption efficiency of Ca were lower in rats fed Ca-fortified diets than in Ca-non-fortified groups, however absolute amounts of absorbed Ca were not different among all the groups. The present results suggest that Ca-fortification decreased the apparent absorption efficiency of fat with long chain saturated fatty acids, particularly at 1,3 positions of glyceride, and the apparent absorption efficiency of saturated fatty acids in foodstuff such as chocolate were also decreased by Ca-fortification.

Polyunsaturated fatty acid-mediated suppression of insulin-dependent gene expression of lipogenic enzymes in rat liver.

The effects of dietary polyunsaturated fat on insulin-dependent gene expression of lipogenic enzymes and a possible mechanism for PUFA-mediated suppression of the gene expression have been investigated in rat livers. When diabetic rats were injected with insulin, the insulin dose-dependent induction of lipogenic enzyme mRNAs were markedly reduced with increasing dietary corn oil. On the other hand, the PUFA-mediated suppression of the mRNA concentrations was partially restored by treatment with pioglitazone, a candidate for increasing insulin receptor phosphorylation. Moreover, insulin binding to receptors of liver, receptor autophosphorylation, and kinase activity toward exogenous substrate were lower in the corn oil diet group than in the hydrogenated fat group. The PUFA-mediated suppression of insulin binding was somewhat restored by pioglitazone, and the suppression of insulin receptor phosphorylation was significantly restored. It is suggested that the PUFA-mediated suppression of insulin-dependent gene expression of lipogenic enzymes can be ascribed to a decrease in insulin receptor binding primarily and also to receptor phosphorylation. Thus, PUFA appears to suppress the lipogenic enzyme gene expression stimulated by insulin.

Modulation of the levels of cytochromes P450 in rat liver and lung by dietary lipid

This study was undertaken to investigate the effect of dietary lipid on the regulation of several constitutive P450 isozymes. Male Sprague-Dawley rats with body weights of 130–140 g were fed either a 20% corn oil (CO) diet or a fat-free (FF) diet for 4 days following 2 days of fasting. Using liver microsomes, the catalytic activities and immunochemically detectable protein levels of P450s 1A1 and 2, 2A1, 2B1 and 2, 2C11, 2E1, and 3A were determined. The microsomes from rats fed the 20% CO diet exhibited 2-fold higher levels in N-nitrosodimethylamine demethylase activity and P450 2E1 protein than those from rats fed the FF diet. the CO group also showed 2.5-fold higher levels in 6β-hydroxylation of testosterone and P450 3A protein than the FF group. In contrast, the CO diet did not affect the immunodetectable level of P450 2C11 protein and its catalytic activities such as benzphetamine demethylase activity and 2α-hydroxylation of testosterone. P450 1A1 was not detectable in either group, but 1A2 was 2.5-fold higher in the CO group than in the FF group. In the liver, the P450 2B1 level was very low in both groups as measured by pentoxyresorufin dealkylase activity and the protein level, whereas 2B2 was 2.5-fold higher in the CO diet group. In lung microsomes from rats fed different amounts of CO, an inverse relationship was observed between the P450 2B1 level and the dietary CO level. the results suggest that the constitutive levels of P450 isozymes are modulateted by dietary lipid in a selective manner; the levels of hepatic P450s 1A2, 2B2, 2E1, and 3A were regulated positively but the level of pulmonary P450 2B1 was suppressed by dietary lipid.

Effect of Different Levels of Dietary <italic>Trans</italic> Fat or Corn Oil on Azoxymethane-Induced Colon Carcinogenesis in F344 Rats<xref ref-type="fn" rid="FN1">2</xref><xref ref-type="fn" rid="FN2">3</xref>

The effect of various levels of dietary corn oil or trans fat on azoxymethane (AOM; CAS: 25843-45-2)-induced carcinogenesis was investigated in female F344 rats fed the AIN-76 semipurified diets. Starting at 5 weeks of age, groups of rats were fed the low-fat diet containing 5% corn oil (designated as low-fat control diet). At 7 weeks of age, all animals except the vehicle-treated controls, were given sc injections of AOM (15 mg/kg body wt, once weekly) for 3 weeks. After 1 week, groups of animals were transferred to semipurified diets containing 13.6% corn oil and 23.5% corn oil or high-fat diets containing 5.9% corn oil plus 5.9% trans fat plus 11.8% Oleinate (low trans fat), 5.9% corn oil plus 11.8% trans fat plus 5.9% Oleinate (intermediate trans fat), and 5.9% corn oil plus 17.6% trans fat (high trans fat). Fecal bile acids were measured in vehicle-treated rats. All animals were necropsied 34 weeks after the last AOM injection. The animals fed the 23.5% corn oil diet had a higher incidence of colon tumors than did those in the groups fed the 5 and 13.6% corn oil diets. There was no difference in colon tumor incidence between the 5 and 13.6% corn oil diet groups. The animals fed the high-fat diets containing low trans fat, intermediate trans fat, and high trans fat developed significantly fewer liver and colon tumors and more small intestinal tumors than did the rats fed 23.5% corn oil diet. The excretion of fecal deoxycholic acid, lithocholic acid, and 12-ketolithocholic acid was higher in animals fed the 23.5% corn oil diet compared to the excretion in animals fed the other diets.

Mechanism of growth enhancement of 7,12-dimethylbenz[a]-anthracene-induced mammary tumors in rats given high polyunsaturated fat diet.

The mechanism of growth enhancement of 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumors by high fat diet was investigated in 169 female Sprague-Dawley rats fed a semisynthetic diet containing 0, 8 or 40% corn oil by weight. The animals, most of which were intubated with 10 mg of DMBA twice during the 8th week of age, were fed an unsupplemented or fat-supplemented diet for 2 months from the 12th to the 21st week of age and finally killed during the 21st week of age. Compared to the rats fed a fat-free diet, a significantly increased yield of mammary adenocarcinoma with a shorter latency was observed in the rats fed a 40% corn oil diet. DNA synthesis of the biopsied mammary tumors more than 1 month after diet switch-over was estimated in terms of the rate of [3H]thymidine incorporation into the tissue. Significantly higher DNA synthesis of the mammary tumors biopsied from proestrous hosts was found, as compared with the tumors in similar hosts at other stages of the estrous cycle. The greatest enhancement of DNA synthesis in small and rapidly growing tumors was observed in the 40% corn oil diet group. Feeding with 40% corn oil diet always resulted in elevation of the weight percentage of linoleic acid in both simple lipids and phospholipids of the mammary tumors. These data indicate that the effects of dietary fat on mammary tumor growth might be mediated by the enhancement of tumor response to certain hormones, and that the enhanced responsiveness of tumors was associated with increased linoleic acid in tumor lipids.

食餌コーン油含量の乳癌発育に及ぼす効果

To ascertain the effect of fat-content in diet on the development of breast cancer, the semisynthetic diets containing corn oil (polyunsaturated fatty acids; more than 80%) in the weight percentages of 0,8 or 40 were prepared and 141 young adult Sprague-Dawley females were used for the following experimental designs. In the first group, the uptake and clearance of labeled DMBA within the mammary fatty pads of 20 rats administered by fat-free and 40%corn oil diets, respectively, at the ages of 45-87 days were observed in 3 days after the intravenous injection of carcinogen. In the second group,90 rats (a-subgroup) were intubated by 10mg of DMBA twice on the ages of 56 and 59 days, and 31 rats (b-subgroup) never received DMBA. The animals of b-subgroup were fed on fat-free,8% corn oil and 40% corn oil diets, respectively, at the ages of 70-100 or -115 days, and they were finally sacrificed either for the determination of serum prolactin and estrogens or for the analysis of fatty acid compositions within the mammary fatty pads. The effective number of rats in a-subgroup were fed on 3kinds of the above-mentioned semisynthetic diets, respectively, at the ages of 90-150 days, and they were applied to the observations on the developments of mammary cancers, endocrinologic states of these cancer-bearers and fatty acid compositions of these mammary tumor phospholipids.In group II a, the averages of caloric intake were 52.4,52.2 and 50.3 Cal/rat/day, respectively, in the fat-free,8% corn oil and 40% corn oil diet groups, and the curves of average body weight were not different from each other diet group. However, both the average number of cancer per a rat (3.2±2.2,6.5±2.5) and average weight of cancer per a rat (654.0±498.7mg,690.5±477.3mg) were much higher in the 8% and 40% corn oil diet groups, wit h compared from the fat-free diet group (1.6±0.9,331.6±226.5mg). These figures were statistically different from each other diet group (p<0.01). The endocrinologic states (serum prolactin, serum estrogens, prolactin/estrogens at the same sexual cycle and weight of the endocrine organs) of the hosts were similar in each diet groups. In the mammary tumor phospholipids, linoleic acid increased and arachidonic acid decreased in the 40% corn oil diet group, in comparison of the fat-free diet group. These deviations were statistically significant (p<0.01). In group 11b, the hormonal balances of animals seemed to be not disturbed by these semisynthetic diets, and linoleic acid within the mammary fatty pads decreased profoundly in the fat-free diet group, where any disorders from essential fatty acid deficiency could not be detected yet. In group II, the uptake and clearance of tritiated DMBA within the mammary fatty pads of the 40% corn oil diet group were not significantly different from those of the other diet groups.In conclusion, the extremely high corn oil diet enhanced prominently the devel opment of DMBA-induced mammary cancers, especially number of cancer per an animal, without any endocrinologic and caloric alterations in these cancer-bearers. Such an enhancement might be introduced by the increased amounts of polyunsaturated fatty acids within the mammary fatty pads of the hosts and by some alterations of fatty acid composition of the tumor phospholipids.