Inhibition of 7,12-dimethylbenz[a]anthracene-induced lipid peroxidation and mammary tumor development in rats by vitamin E in conjunction with selenium

N-Acetyl Cysteine, Selenium, and Ascorbic Acid Rescue Diabetic Cardiac Hypertrophy via Mitochondrial-Associated Redox Regulators

Metabolic disorders often lead to cardiac complications. Metabolic deregulations during diabetic conditions are linked to mitochondrial dysfunctions, which are the key contributing factors in cardiac hypertrophy. However, the underlying mechanisms involved in diabetes-induced cardiac hypertrophy are poorly understood. In the current study, we initially established a diabetic rat model by alloxan-administration, which was validated by peripheral glucose measurement. Diabetic rats displayed myocardial stiffness and fibrosis, changes in heart weight/body weight, heart weight/tibia length ratios, and enhanced size of myocytes, which altogether demonstrated the establishment of diabetic cardiac hypertrophy (DCH). Furthermore, we examined the expression of genes associated with mitochondrial signaling impairment. Our data show that the expression of PGC-1α, cytochrome c, MFN-2, and Drp-1 was deregulated. Mitochondrial-signaling impairment was further validated by redox-system dysregulation, which showed a significant increase in ROS and thiobarbituric acid reactive substances, both in serum and heart tissue, whereas the superoxide dismutase, catalase, and glutathione levels were decreased. Additionally, the expression levels of pro-apoptotic gene PUMA and stress marker GATA-4 genes were elevated, whereas ARC, PPARα, and Bcl-2 expression levels were decreased in the heart tissues of diabetic rats. Importantly, these alloxan-induced impairments were rescued by N-acetyl cysteine, ascorbic acid, and selenium treatment. This was demonstrated by the amelioration of myocardial stiffness, fibrosis, mitochondrial gene expression, lipid profile, restoration of myocyte size, reduced oxidative stress, and the activation of enzymes associated with antioxidant activities. Altogether, these data indicate that the improvement of mitochondrial dysfunction by protective agents such as N-acetyl cysteine, selenium, and ascorbic acid could rescue diabetes-associated cardiac complications, including DCH.

Increased Transglutaminase 2 and GLUT-1 Expression in Breast Tumors not Susceptible to Chemoprevention with Antioxidants

Goals

Expression of GLUT-1 and transglutaminase 2 is increased in aggressive breast cancer, whereas claudin-1, which is expressed in normal tissues, is absent in such tumors. This experimental study was undertaken to establish the aggressiveness and prognosis of DMBA-induced mammary tumors in female Wistar rats based on the assessment of these markers.

Materials and methods

The rats were divided into two groups, a control group (n = 70) and a chemoprevention group (n = 70). Breast tumors were induced in both groups by administration of 7,12-dimethylbenz[a]anthracene (DMBA). The chemoprevention group also received alpha-tocopherol and a solution of micronutrients containing ascorbic acid and selenium. Neoplastic lesions of both groups were randomly selected for immunohistochemical assessment of the expression of GLUT-1, transglutaminase 2 and claudin-1.

Results

A higher proportion of mammary tumors expressed GLUT-1 and transglutaminase 2 in the chemoprevention group. Claudin-1 expression was absent in all tumors of both groups.

Conclusions

These results are suggestive of increased aggressiveness of tumors not susceptible to chemoprevention by the agents used in this study.

Selenium and Breast Cancer Risk: Focus on Cellular and Molecular Mechanisms

Selenium (Se) is a micronutrient with promising breast cancer prevention and treatment potential. There is extensive preclinical evidence of Se mammary carcinogenesis inhibition. Evidence from epidemiological studies is, however, unclear and intervention studies are rare. Here, we examine Se chemoprotection, chemoprevention, and chemotherapy effects in breast cancer, focusing on associated cellular and molecular mechanisms. Se exerts its protective actions through multiple mechanisms that involve antioxidant activities, induction of apoptosis, and inhibition of DNA damage, cell proliferation, angiogenesis, and invasion. New aspects of Se actions in breast cancer have emerged such as the impact of genetic polymorphisms on Se metabolism and response, new functions of selenoproteins, epigenetic modulation of gene expression, and long-term influence of early-life exposure on disease risk. Opportunity exists to design interventional studies with Se for breast cancer prevention and treatment taking into consideration these key aspects.

Effect of a Nutritional Supplement Containing Vitamin E, Selenium, Vitamin C and Coenzyme Q10 on Serum PSA in Patients with Hormonally Untreated Carcinoma of the Prostate: A Randomised Placebo-Controlled Study

OBJECTIVE

To assess the effect of a nutritional supplement containing vitamin E, selenium, vitamin C and coenzyme Q10 on changes in serum levels of PSA in patients with hormonally untreated carcinoma of the prostate and rising serum PSA levels.

METHODS

Eighty patients were randomised to receive a daily supplement with either vitamin E, selenium, vitamin C, coenzyme Q10 (intervention group) or placebo over 21 weeks. Serum levels of PSA were assessed at baseline (-2, -1, 0 weeks) and after 6, 13, 19, 20 and 21 weeks. Mean changes in log serum level of PSA, testosterone, dihydrotestosterone, luteinizing hormone and sex hormone binding globulin over 21 weeks between the verum and the placebo group were compared by analysis of covariance.

RESULTS

Seventy patients completed the study (36 verum; 34 placebo). Compliance was >90% in all patients. In the intervention group, plasma levels of vitamin E, selenium and coenzyme Q10 increased significantly over the 21 weeks study period. No significant differences in serum levels of PSA, testosterone, dihydrotestosterone, luteinizing hormone or sex hormone binding globulin (p>0.2) were observed between the intervention and control group.

CONCLUSION

Our results indicate that supplementation of a combination of vitamin E, selenium, vitamin C and coenzyme-Q10 does not affect serum level of PSA or hormone levels in patients with hormonally untreated carcinoma of the prostate.

Ethanol fraction of Aralia elata Seemann enhances antioxidant activity and lowers serum lipids in rats when administered with benzo(a)pyrene

Aralia elata Seemann is an edible mountain vegetable in Korea containing saponin, alkaloid, palmitic acid, linoleic acid, methyl eicosanoate and hexacosol, and is known to manifest an effect on cardiac infarction, gastric ulcer, colitis, and enervation. This study has examined the effects of Aralia elata Seemann ethanol extract on antioxidant enzyme systems and lipid metabolism in rats along with benzo(a)pyrene (B(a)P) administration. Rats were divided into four groups: control (C), an extract fed group (CE), a B(a)P fed group (CB), and a B(a)P and extract fed group (CBE). The ethanol extracts of Aralia elata Seemann (50 mg/kg body weight) were fed to the rats for 4 weeks by stomach tubing. Extract administration increased the antioxidant activities of glutathione sulfur transferase (GST). Total superoxide dismutase (SOD) and Cu,Zn-SOD activities were stimulated. Catalase activities were increased by 50% with extract feeding. Cu,Zn-SOD was greatly enhanced from 0.10 unit to 0.18 unit and catalase activity also was increased. Serum alpha-tocopherol was markedly increased by the extracts. The ethanol fraction of Aralia elata Seemann decreased total serum cholesterol. However, serum HDL-cholesterol was increased by 35% (p<0.05). The results indicate that Aralia elata Seemann exerts antioxidant and strong hypocholesterolemic and hypolipidemic effects in vivo with the administration of B(a)P.

Vitamin E and breast cancer prevention: current status and future potential

Vitamin E is a collective term used to refer to a number of structurally and functionally different compounds. Although some vitamin E compounds are popular supplements marketed for their potential beneficial antioxidant effects for a number of chronic diseases including various forms of cancer, a recent report by the National Academy of Sciences Food and Nutrition Board concluded that too little is known at present to provide definitive answers regarding whether taking larger doses of dietary antioxidants will help prevent chronic diseases. Recent reviews of epidemiological data suggest that dietary source vitamin E may provide some protection against breast cancer, while vitamin E supplements do not. A majority of studies investigating the protective effects of certain types of vitamin E in animal models of mammary cancer prevention conclude that there is little or no effect. The study of vitamin E is complex, and the vitamin E field faces many scientific challenges.

Does lack of tocopherols and tocotrienols put women at increased risk of breast cancer?

Breast cancer is the leading site of new cancers in women and the second leading cause (after lung cancer) of cancer mortality in women. Observational studies that have collected data for dietary exposure to alpha-tocopherol with or without the other related tocopherols and tocotrienols have suggested that vitamin E from dietary sources may provide women with modest protection from breast cancer. However, there is no evidence that vitamin E supplements confer any protection whatever against breast cancer. Observational studies that have assessed exposure to vitamin E by plasma or adipose tissue concentrations of alpha-tocopherol have failed to provide consistent support for the idea that alpha-tocopherol provides any protection against breast cancer. In addition, evidence from studies in experimental animals suggest that alpha-tocopherol supplementation alone has little effect on mammary tumors. In contrast, studies in breast cancer cells indicate that alpha- gamma-, and delta-tocotrienol, and to a lesser extent delta-tocopherol, have potent antiproliferative and proapoptotic effects that would be expected to reduce risk of breast cancer. Many vegetable sources of alpha-tocopherol also contain other tocopherols or tocotrienols. Thus, it seems plausible that the modest protection from breast cancer associated with dietary vitamin E may be due to the effects of the other tocopherols and the tocotrienols in the diet. Additional studies will be required to determine whether this may be the case, and to identify the most active tocopherol/tocotrienol.

Activity profile of glutathione-dependent enzymes and respiratory chain complexes in rats supplemented with antioxidants and treated with carcinogens

Appropriate dietary interventions may reduce the potentially damaging effects of free radicals generated during metabolism and various physiological conditions. We have investigated the effects of dietary vitamins C, E, beta-carotene, or selenium (Se) on the activity of endogenous antioxidant enzymes and respiratory chain complexes in rats exposed to 7,12-dimethylbenz[a]anthracene (DMBA), a mammary carcinogen and bleomycin (BLM), an antineoplastic drug. These agents are known to generate DNA-reactive species during their metabolism, which may enhance oxidative stress in cells. Female Fischer 344 rats aged 4 months were given antioxidant supplements singly or as a mixture 2 weeks prior to mutagen treatments; antioxidant supplementation continued for an additional 4 weeks. In rats treated with mutagens, the antioxidant intake lowered the activity of Se-dependent glutathione peroxidase (Se-GPx) in liver cytosolic and mitochondrial fractions, compared to activity in rats treated with mutagens alone. However, the vitamins, but not Se supplement, persistently increased Se-GPx activity in untreated control animals. Treatment of animals with mutagen raised K(m) value of Se-GPx and this correlated with an increase in V(max). However, Se intake, either singly or mixture, significantly reduced K(m) value in mutagen-treated and untreated rats in both fractions. Se intake increased glutathione S-transferases (GST) activity (P < 0.05) in both liver fractions of mutagen-treated and untreated animals. Similar response was seen in Se-independent GPx. Since GST-alpha possesses Se-independent GPx activity, the enhanced effect observed in GST activity may be due, in part, to increased activity in Se-independent GPx. Also, selenium or the antioxidant vitamin supplementation increased the activity of all four respiratory chain complexes in untreated rats. Although BLM treatment significantly increased the activity of electron transport complexes III and IV, selenium or the vitamin supplements modulated the responses. These results indicate that the intake of dietary vitamins or Se enhances antioxidant capacity in chemically exposed animals compared to animals receiving antioxidants alone. Furthermore, in addition to being an enhancer of the catalytic function of glutathione peroxidase, selenium may directly play a role as an antioxidant.

The role of complementary medicine in the treatment of prostate cancer

Complementary and alternative medicine (CAM) has recently attracted national attention in the United States because of its widespread use and associated cost. CAM covers a broad spectrum of healing philosophies and approaches. Despite its widespread use, little is known about its safety, efficacy, cost effectiveness, and mechanism of action. The role of CAM in the management of prostate cancer is becoming more apparent with its rise in use among patients who are suffering from prostate cancer. This trend is patient-driven and reflects the change in values perceived by patients toward conventional medical treatment. In this review, several complementary therapies that can be used for prevention and treatment of prostate cancer are discussed. These therapies were selected because they are supported by scientific evidence. The popularity of CAM continues to grow and CAM is here to stay. Health care professionals can no longer afford to ignore or to treat CAM as an entity outside of conventional science. To acknowledge and to monitor its use among our patients may in the future help evaluate the safety and efficacy of CAM. Our current challenge is to move the field of CAM forward scientifically and systematically with wisdom and reasoning.

The protective role of selenium on genetic damage and on cancer

Collectively, results from epidemiologic studies, laboratory bioassays, and human clinical intervention trials clearly support a protective role of selenium against cancer development. Several hypotheses have been proposed to explain these observations. Increased genomic instability, either inherent or induced by exogenous agents (mutagens or carcinogens), has been considered as a primary event leading to neoplastic transformation. This report deals specifically with the evidence for a role of selenium in the inhibition of carcinogen-induced covalent DNA adduct formation and retardation of oxidative damage to DNA, lipids and proteins, and for modulating cellular and molecular events that are critical in cell growth inhibition and in the multi-step carcinogenesis process. At present, the bulk of our knowledge on the role of selenium on genetic stability is based primarily on animal data and from studies conducted in in vitro systems. Studies performed in vitro showed that the dose and form of selenium compounds are critical factors with regard to cellular responses. Inorganic (at doses up to 10microM) and organic selenium compounds (at doses equal to or greater than 10microM) elicit distinctly different cellular responses. The recommended daily allowance (RDA) is 50-70 microgramSe per day for healthy adults; with 40 microgramSe as minimum requirement. Less than 11 microgramSe will definitely put people at risk of deficiency that would be expected to cause genetic damage. Daily doses of 100-200 microgramSe inhibited genetic damage and cancer development in humans. About 400 microgramSe per day is considered an upper limit. Clearly, doses above the RDA are needed to inhibit genetic damage and cancer. However, it has been hypothesized that the intake of excessive doses of selenium may cause oxidative damage, leading to genomic instability. The use of a cocktail consisting of selenium, and other vitamins and minerals appears to be a promising approach to inhibit genetic damage and the development of cancer. It is the author's recommendation that development of mechanism-based hypotheses that can be tested in pilot studies in different populations prior to a large-scale clinical trial in humans, is of paramount importance in order to better understand the role of selenium on genetic stability and cancer.

Vanadium chemoprevention of 7,12-dimethylbenz(a)anthracene-induced rat mammary carcinogenesis: probable involvement of representative hepatic phase I and II xenobiotic metabolizing enzymes

Vanadium, a non-platinum group metal and dietary micronutrient, is now proving to act as a promising antitumor agent. The present study was conducted to ascertain its antineoplastic potential against an experimental mammary carcinogenesis. Female Sprague-Dawley rats, at 50 days of age, were treated with 7,12-dimethylbenz(a)anthracene (DMBA) (0.5 mg/100 g body weight) by a single tail vein injection in an oil emulsion. Vanadium (ammonium monovanadate) at the concentration of 0.5 ppm was supplemented in drinking water and given ad libitum to the experimental group immediately after the carcinogen treatment and it continued until the termination of the study (24 weeks for histological and biochemical observations and 35 weeks for morphological findings). It was found that vanadium treatment brought about a substantial protection against DMBA-induced mammary carcinogenesis. This was evident from histological findings that showed no sign of hyperplasia or abnormality after vanadium treatment. There was a significant reduction in incidence (P < 0.05), total number, multiplicity (P < 0.01) and size of palpable mammary tumors and delay in mean latency period of tumor appearance (P < 0.001) following vanadium supplementation compared to DMBA control. From the cumulative results of various hepatic biochemical indices namely, lipid peroxidation, reduced glutathione level, superoxide dismutase activity, cytochrome P450 content and glutathione S-transferase activity, the anticarcinogenic potential of vanadium was well reflected through stabilization of these parameters. Results of the study indicate that the anticarcinogenic activity of vanadium during DMBA-initiated mammary carcinogenesis is mediated through alteration of hepatic antioxidant status as well as modulation of phase I and II drug metabolizing enzymes. On the basis of the observed results, vanadium can be considered as a readily available, promising and novel cancer chemopreventive agent.

Chemoprevention of DMBA-Induced Mammary Tumors in Rats by a Combined Regimen of Alpha-Tocopherol, Selenium, and Ascorbic Acid

This experimental study was designed to evaluate the efficacy of associated naturally occuring antioxidants in the prevention of chemically induced breast cancer using DMBA in virgin female Wistar rats. Rats were randomly allocated to three groups: control group (CG; n = 20), induction group (IG; n = 100), and prevention group (PG; n = 70). A single dose (65 mg/kg) of DMBA was administered in the IG and PG animals at 50 days of age. PG animals also received a single dose of alpha-tocopherol (200 mg/rat) 1 hour after DMBA administration and an association of selenium (p-XSC, 40 ppm/day/rat) and ascorbic acid (540 mg/day/rat) in drinking water, daily, from carcinogenic induction until necropsy. Macroscopic study and pathology revealed a significantly lower development of neoplasms in the PG animals (p < 0.05); the number of rats with mammary tumors, breast cancer incidence, and the number of malignant breast tumors per rat as well as per tumor-bearing rat were significantly decreased in the PG animals. Other types of primary neoplasms existing in the IG animals totally disappeared in the PG animals. Immunostaining to hormone steroid receptors (ER and PR) and cathepsin D was similar in both groups. Overexpression of p53 and metallothioneine was significantly increased in the PG animals (p < 0.05) and immunostaining to bromodeoxiuridin and Ki-67 was also stronger in the remaining tumors in the PG animals. These data thus add to the accumulating evidence that those micronutrients in combination seem to be effective in reducing the incidence of malignant tumors. Nevertheless, remaining tumors seem to present more aggressive behavior and characteristics of drug resistance.

Nutrition and prostate cancer

Scientific evidence suggests that differences in the diet may, in large part, account for the variability of prostate cancer rates around the world. Epidemiologic studies and animal experiments have yielded compelling results to warrant clinical intervention studies on nutrition from scientists who work on the prevention and treatment of prostate cancer. This article reviews the most recent evidence as to possible mechanisms of action of various dietary constituents, and explores evidence of various nutritional strategies for the prevention of prostate cancer progression.

No inhibition of gamma-glutamyl transpeptidase-positive foci by vitamin E with or without phenobarbital

The effect of vitamin E on gamma-glutamyl transpeptidase-positive foci, with or without phenobarbital, was investigated. Groups of six female Sprague-Dawley rats were initiated with diethylnitrosamine (15 mg/kg) at 24 hours of age. After weaning, they were fed diets with 10% (wt/wt) fish oil; the diets contained 0, 5,000 or 15,000 ppm vitamin E supplementation with or without phenobarbital (500 ppm) for six months. Phenobarbital significantly increased liver weight and liver weight as a percentage of body weight (p < 0.05), suggesting a liver hypertrophic effect of phenobarbital. Phenobarbital significantly decreased hepatic phospholipid arachidonate, eicosapentaenoate, and docosahexaenoate (p < 0.05); this may indicate that phenobarbital stimulates phospholipase A2 activity and results in the increased release of polyunsaturated fatty acids from phospholipids and the decrease of hepatic phospholipid polyunsaturated-to-saturated fat ratio. In rats fed phenobarbital, hepatic vitamin E content was lower than in rats fed no phenobarbital; this suggests that phenobarbital causes oxidative stress or induces enzymes that metabolize the vitamin. Phenobarbital exposure significantly increased hepatic prostaglandin F2 alpha and glutathione S-transferase activity (p < 0.05). Vitamin E did not influence hepatic gamma-glutamyl transpeptidase-positive foci area and number with or without phenobarbital, and phenobarbital showed a strong promoting action on enzyme-altered hepatic foci.

Review of the effects of dietary fat on experimental mammary gland tumorigenesis: role of lipid peroxidation

The purpose of this communication is threefold, that is, (1) to review and critique the studies designed to examine the interrelationship between dietary fat and experimental rodent mammary gland tumorigenesis, (2) to assess the influence of dietary fat on growth of human breast carcinoma transplants in immunodeficient mice, and (3) to examine and discuss the role of products of lipid peroxidation in these tumorigenic processes. It is concluded from this review and critique that the amount and type of dietary fat can significantly influence the development and/or growth of rodent mammary gland tumors and growth of human breast carcinomas in immune deficient mice. Dietary fat can be either stimulatory or inhibitory to these tumorigenic processes, phenomena that could be a function, at least in part, of the generation of products of lipid peroxidation.

High fish oil diet increases oxidative stress potential in mammary gland of spontaneously hypertensive rats

1. The purpose of this study was to determine whether high omega-3 (19% menhaden oil, 1% corn oil) or high omega-6 (20% corn oil) fatty acid diets would decrease expression of hypertension in the female spontaneously hypertensive rat (SHR), promote tumourigenesis in the rat 7,12-dimethylbenz[a]anthracene (DMBA) model of mammary cancer or increase the susceptibility of the mammary gland to lipid peroxidation. A group of rats on a 5% corn oil diet served as the low fat control group. 2. We found that the high omega-3 and high omega-6 fatty acid diets did not significantly decrease mean arterial pressure. Marked differences occurred between the effects of omega-3 and omega-6 high fatty acid diets on baseline oxidation, auto-oxidation and iron-ascorbate catalyzed oxidation. The omega-3 diet showed 675% increase in basal oxidation, a 2624% increase in auto-oxidation and a 4244% increase in iron-ascorbate catalyzed oxidation compared to the omega-6 diet in mammary tissue homogenates. Although all rats were given 5 mg DMBA (i.g.), no mammary tumours were observed in any of the dietary groups. 3. We conclude that: (i) high polyunsaturated fatty acid diets do not decrease blood pressure in the female SHR; (ii) high fish oil diet markedly increases oxidative potential in the mammary gland; and (iii) the female SHR is resistant to DMBA-induced tumourigenesis.