High-fat Corn Oil Diet Research Articles

High-Fat Diets Containing Different Amounts of n3 and n6 Polyunsaturated Fatty Acids Modulate Inflammatory Cytokine Production in Mice.

Dysregulation of adipokines is a hallmark of obesity. Polyunsaturated fatty acids in fish oil may exert anti-inflammatory effects on adipose tissue mitigating the dysregulation of adipokines thereby preventing obesity. This study investigated the effects of high-fat diets containing different amounts of n3 polyunsaturated fatty acids (PUFA) on adiposity and adipokine production in mice. Mice were fed a low-fat or a high-fat diet with 16 or 45% of energy from corn oil (low n3 PUFA) in comparison with a high-fat diet containing soybean or high-oleic sunflower oil (adequate n3 PUFA) or flaxseed or fish oil (high n3 PUFA) for 11weeks. High-fat diets, regardless of types of oils, significantly increased body fat mass and body weights compared to the low-fat diet. Adipose fatty acid composition and contents reflected dietary fatty acid profiles. The high-fat fish oil diet significantly increased adiponectin and reduced leptin concentrations in both plasma and adipose tissue; it did not elevate plasma insulin concentration compared to the high-fat corn oil diet. All high-fat diets elevated concentrations of plasminogen activator inhibitor-1 (PAI-1) and monocyte chemoattractant protein-1 (MCP-1) but lowered resistin concentrations in both plasma and adipose tissue. In conclusion, fish oil may be beneficial in improving insulin sensitivity by upregulation of adiponectin and downregulation of leptin production; n3 and n6 PUFA do not play a role at the dietary levels tested in reducing adiposity and production of pro-inflammatory cytokines (leptin, PAI-1, MCP-1 and resistin) and anti-inflammatory cytokine adiponectin.

Effects of Konjac Glucomannan on Putative Risk Factors for Colon Carcinogenesis in Rats Fed a High-Fat Diet

The aim of this study was to determine effects of konjac glucomannan (KGM) in a high fat corn oil diet on risk factors of colon carcinogenesis, that is, fecal β-glucuronidase, mucinase, and bile acids, and on preventive factors, that is, fecal microflora and cecal short-chain fatty acids (SCFAs). Sprague-Dawley rats (n = 8 animals per group) were fed a normal-fat fiber-free (5% corn oil, w/w) or high-fat (25% corn oil, w/w) diet containing no fiber, KGM (5%, w/w), or inulin (5%, w/w, as a prebiotic control) for 4 weeks. Results indicated that the high-fat fiber-free diet significantly elevated the fecal β-glucuronidase and mucinase activities and total bile acid concentration and decreased cecal SCFA contents, as compared with its normal-fat counterpart. The incorporation of KGM, as well as inulin, into the high-fat fiber-free diet beneficially reduced the fecal β-glucuronidase and mucinase activities and lithocholic acid (secondary bile acid) concentration. Although KGM elevated the daily fecal total bile acid excretion, the change was due to the primary, instead of the secondary, bile acids. In addition, KGM beneficially promoted the daily fecal excretion of bifidobacteria and lactobacilli and cecal SCFA contents, as compared with the high-fat fiber-free diet. Therefore, the present study suggests that KGM potentially attenuated the high fat-induced risk in colon carcinogenesis.

An n-3 PUFA-rich microalgal oil diet protects to a similar extent as a fish oil-rich diet against AOM-induced colonic aberrant crypt foci in F344 rats

The chemopreventive effects of high fat microalgal oil diet on azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) were studied in male Fischer 344 rats following 8 weeks of dietary treatment. These effects were compared to the effects of high fat fish oil and high fat corn oil diets to determine whether microalgal oil is a good alternative for fish oil regarding protection against colorectal cancer. Despite the difference in fatty acid composition and total amount of n-3 polyunsaturated fatty acids (PUFAs) between microalgal oil and fish oil, both these oils gave the same 50% reduction of AOM-induced ACF when compared to corn oil. To determine whether oxidative stress could play a role in the chemoprevention of colorectal cancer by n-3 PUFAs, feces and caecal content were examined using the TBA assay. The results showed that lipid peroxidation does occur in the gastrointestinal tract. As several lipid peroxidation products of n-3 PUFAs can induce phase II detoxifying enzymes by an EpRE-mediated pathway, the in vivo results suggest that this route may contribute to n-3 PUFA-mediated chemoprevention. All in all, n-3 PUFA-rich oil from microalgae is as good as fish oil regarding chemoprevention in the colon of the rat.

High-Fat Corn Oil Diet Promotes the Development of High Histologic Grade Rat DMBA-Induced Mammary Adenocarcinomas, While High Olive Oil Diet Does Not

Effects of a high corn oil and a high olive oil diet on the histopathologic characteristics of rat dimethylbenz(alpha)anthracene-induced mammary adenocarcinomas were investigated in comparison with those of a control low-fat diet. Two experimental series (A and B) studied the influence of a high corn oil diet on the initiation and the promotion of mammary carcinogenesis, while another one (C) assessed the effects of the two dietary lipids on the promotion. Nine parameters have been analyzed and a new histologic grading method, adapted to rat tumors, has been applied in each carcinoma. High corn oil diets, particularly when acting as promoters, associated with higher-grade carcinomas than control (p < 0.05) and high olive oil groups. Stromal invasion and tumoral necrosis were more prominent and a prevailing cribriform pattern was observed (p < 0.05). High olive oil diet adenocarcinomas exhibited a predominantly low histologic grade and few necrotic and invasive areas, similar to the control, and they presented the highest percentage of papillary areas. Lymphoplasmacytic and mast cell infiltration were also influenced by the dietary lipids. Thus, high corn oil diet adenocarcinomas presented a higher degree of morphological malignancy than control and high olive oil tumors, which is in line with the greater clinical malignancy described in rats from the former group and the non-promoting effect of the high olive oil diet. As far as we are concerned, a similar histopathologic approach of the effects of the dietary lipids on experimental breast cancer has not been carried out up to now.

Modulation of EGFR and neu expression by n-6 and n-9 high-fat diets in experimental mammary adenocarcinomas

In this study we have investigated the influence of dietary mono- and polyunsaturated lipids on 7,12-dimethylbenz(alpha)anthracene (DMBA)-induced mammary tumorigenesis, and the modulation of expression of c-erbB1/EGFR and c-erbB2/neu as a mechanism of this influence. Two series of Sprague-Dawley rats were given a single dose of DMBA. Animals from Series 1 were fed a semi-synthetic low-fat or high-fat corn oil diet, following an initiation-promotion experimental design. Rats from Series 2 were fed low-fat or different high-fat diets (rich in corn oil or rich in olive oil) in the promotion stage of mammary carcinogenesis. High corn oil diet showed clearly a stimulatory effect on experimental breast carcinogenesis, suggesting a role of this kind of lipids on initiation and promotion of mammary tumorigenesis. Moreover, results suggested that olive oil acts as a negative modulator of the experimental breast cancer. On the other hand, two transcripts of EGFR and one neu mRNA were detected by chemiluminescent Northern blot in mammary adenocarcinomas. Analysis of data showed the tendency that high-fat corn oil diet decreases the 2.7 kb mRNA of EGFR, encoding a truncated form of the receptor with no enzimatic activity. High-fat olive oil diet increased EGFR mRNA levels, specially those from 2.7 kb, and decreased the relative abundance of neu mRNA. These data suggest that the modulating effect of dietary lipids on mammary carcinogenesis could result in changes of EGFR and neu mRNA, leading to an increase of EGFR activity by high-fat corn oil diet and a decrease of EGFR and Neu signal transduction pathway by high-fat olive oil diet.

Effects of high fat fish oil and high fat corn oil diets on initiation of AOM-induced colonic aberrant crypt foci in male F344 rats

Modulating effects of high fat fish oil (HFFO) and high fat corn oil (HFCO) diets on azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) were studied in male F344 rats following 8 weeks of dietary treatment. The incidence of AOM-induced ACF was significantly lower in the proximal colon of rats fed the HFFO diets compared with rats fed the HFCO diets. No differential effects were found on enzyme activities that are involved in metabolic activation and detoxification of AOM. Activities of hepatic P450 IAI and P450 IIBI and hepatic and feacal levels of lipid peroxidation were increased by feeding the HFFO diet. Hepatic GST activity and plasma levels of PGE 2 were significantly lower in rats fed the HFFO diets compared with those fed the HFCO diets. These observations demonstrate that HFFO diets with high levels of n-3 PUFAs are also protective against preneoplastic lesions in the early stages of chemically induced colon carcinogenesis. It seems unlikely from our results that the inhibitory effect of a HFFO diet can be attributed to an altered metabolic activation and detoxification of AOM. Other mechanisms such as oxidative stress or reduction of PGE 2 levels may play an important role in the anticarcinogenic effects of n-3 PUFAs.

The stimulating effect of a high-fat n-6 polyunsaturated diet on rat DMBA-induced mammary tumors is not related to changes in c-Ha-ras1 mRNA tumor expression

The aim of this study was to investigate if the modulation of the tumor c-Ha-ras1 mRNA expression may be one of the mechanisms implicated in the effect of the dietary n-6 polyunsaturated lipids on experimental mammary carcinogenesis. Sprague-Dawley rats were treated with dimethylbenz(α)anthracene and fed a low-fat or high-fat corn oil diet following an initiation-promotion experimental design. Results showed a shorter latency and significantly higher incidence of affected animals, total tumor yield and total tumor volume in groups of rats fed the high-fat diet than in the control low-fat diet group. This stimulating effect on mammary carcinogenesis, which was produced above all on the promotion stage, did not result in a modification of the tumor c-Ha-ras1 mRNA levels. Moreover, c-Ha-ras1 was not amplified in these experimental mammary tumors. These results do not discard the possible implication of this gene, and suggest that dietary fat may act on c-Ha-ras1 at a different level, maybe on protein function.

Maternal High n-6 Polyunsaturated Fatty Acid Intake during Pregnancy Increases Voluntary Alcohol Intake and Hypothalamic Estrogen Receptor Alpha and Beta Levels among Female Offspring

Identification of nongenetic biological factors that predispose to alcohol abuse is central to attempts to prevent alcoholism. Since an exposure to estradiol in utero increases voluntary alcohol intake in adulthood, we investigated whether an increase in pregnancy estradiol levels, caused by feeding pregnant mice a high-fat corn oil diet, also influences voluntary alcohol intake among female offspring. In addition, the effect on estrogen receptor α (ER-α) and ER-β protein levels in the brain using Western blot assay, was determined. Pregnant CD-1 mice were kept on a high n-6 polyunsaturated fatty acid (PUFA; 43% calories from corn oil) or low n-6 PUFA diet (16% calories from corn oil) throughout gestation, and switched to a Purina laboratory chow after the pups were born. When 4 months of age, the female offspring were given a choice between 5% alcohol and tap water. The offspring of high n-6 PUFA mothers voluntarily consumed more alcohol than the offspring of low n-6 PUFA mothers. ER-α and ER-β protein levels in the hypothalamus were 1.5- and 2-fold higher, respectively, in the female offspring of high n-6 PUFA mothers than in the low n-6 PUFA offspring. No significant changes in the protein levels of ER-α and ER-β were seen in the frontal brain. Our findings indicate that a maternal exposure to a high n-6 PUFA diet during pregnancy increases alcohol intake among female offspring. This behavioral change, together with previously observed increase in aggressiveness and reduction in depressive-like behavior in these offspring, may be linked to an increase in the hypothalamic ER-α and ER-β levels.

The effect of treadmill exercise on azoxymethane-induced intestinal neoplasia in the male Fischer rat on two different high-fat diets.

A total of 120 eight-week-old male rats were exposed to azoxymethane (15 mg/kg body wt in saline s.c.) on Days 1, 4, and 8. Two days after the last injection of carcinogen, the rats were randomized into four experimental groups: two groups were given a chow high in corn oil (23% corn oil) and two groups a chow high in coconut oil (21% coconut oil and 2% corn oil). One group on each chow was kept sedentary, and one group was exposed to moderate exercise, running 2 km/day on weekdays for 38 weeks. At the end of the experiment, the exercising and sedentary rats fed coconut oil were significantly heavier than those fed corn oil. Among the rats fed the high-fat corn oil diet, exercise reduced the number of animals developing carcinomas in the colon (sedentary, 10; exercise, 0) and in the small intestine (sedentary, 5; exercise, 0). The same tendency was observed in the rats fed the coconut oil diet: colon (sedentary, 6; exercise, 3) and small intestine (sedentary, 3; exercise, 2). In the sedentary rats fed the high corn oil diet, 16 intestinal carcinomas were recorded; none were found in the exercised group. In the rats fed the high coconut oil diet, nine carcinomas were recorded in the sedentary groups as opposed to five in the exercised rats. Rats fed the high-fat coconut oil developed significantly fewer neoplasms than the rats fed the equally high-fat corn oil diet.

Effect of n-3 fatty acids on spontaneous and experimental metastasis of rat mammary tumour 13762

Dietary fish oils rich in n-3 fatty acids have been shown to inhibit the development of carcinogen-induced and transplanted mammary tumours (Karmali et al., 1984, 1987). Kort et al. (1987) have shown that fish oil inhibits the growth of mammary adenocarcinoma BN472 in BN/Bi female rats. A mechanism proposed for the anti-tumour effects of n-3 fatty acids is inhibition of arachidonic acid metabolism. Since previous studies suggested that prostaglandin E2 (Rolland et al., 1980) and thromboxane B2 (Karmali et al., 1983) were elevated in certain types of metastasis, the present studies were undertaken to determine if dietary fish oil would inhibit the metastasis of 13762NF (spontaneous model) and 13762MAT:B (experimental model) in Fischer 344 rats. Weanling Fischer 344 female rats (Charles River Breeding Laboratory, Kingston, NJ, USA) were maintained in a temperature and humidity controlled facility with a 12-h light/dark cycle. Fifteen rats were used for each treatment group. The composition of low-fat and high-fat diets and fatty acid profiles of corn oil (CO) and fish oil (FO) (MaxEPA) have been described previously (Cohen et al., 1986; Karmali et al., 1987). Rats were placed on one of four diets: (1) 23.52% corn oil, (2) 8% corn oil + 15.52% fish oil; (3) 3% corn oil + 20.52% fish oil, or (4) 5% corn oil. Diets were mixed fresh weekly and fed fresh daily to prevent autooxidation of unsaturated fatty acids (Karmali et al., 1987). Since rats were housed five per cage, only a rough estimate for daily feed intake per rat could be made. Diets were fed for 8 weeks before tumour injections and continued until killing (5 weeks spontaneous model; 3 weeks experimental model). The spontaneous metastasis studies were carried out with the 13762NF mammary adenocarcinoma subline (Mason Research Institute, Worcester, MA, USA). A pool of tumours from four rats was minced, filtered through 20 im Nytex nylon mesh, and 105 cells in 0.05 ml saline were injected i.m. in the thigh. Tumour size was measured weekly, and tumour volume was estimated using the formula +(4i/3)(length/2)(width/2)(height) (Rockwell et al., 1972). The 13762MAT:B subline was chosen for the experimental metastasis studies. A pool of ascites tumour cells from four rats was washed in phosphate buffered saline, and 105 cells in 0.2 ml saline were injected i.v. via the lateral tail vein. At the time of killing under anaesthesia in both model systems, the lungs were fixed in situ and processed by a lung clearing technique that allows the enumeration and sizing of subsurface as well as surface tumour foci in the right superior lobe (Yuhas & Walker, 1973). Metastatic tumour volumes were calculated by the formula V = 4/3nr3 in both metastatic models. All data were analysed by Dunnett's multiple comparison test. In both experiments, the animals on the low-fat corn oil diet consumed the largest number of grams of food per day (14.1), followed by those on fish oil diets (12.6 and 12.3) and the high-fat corn oil diet (11.6).