Dietary fat, calories, and mammary gland tumorigenesis

Effect of Dietary Fish Oil on Mammary Gland Development and Milk Production of Holstein Cow

The aim of this study was to evaluate the effect of feeding oil supplement on mammary gland development and milk production responses in Holstein cows. Ten multiparous Holstein cows (42.2±9.2 d before calving, 3.25±0.25 body condition score, and 620±35 kg body weight) were randomly assigned to treatments. Treatments were a diet with oil added as palm oil (PO; n=5), or fish oil (FO; n=5) given to cows until 63 d in milk. Milk yield was recorded daily, milk composition (fat, protein, lactose, total solid and somatic cell count) was measured weekly and fatty acid profiles of milk fat were determined at first and last week of the experiment. Samples of mammary tissue were obtained at 7 and 63 d in milk by biopsy gun. Tissue slides were analyzed by Image J software. Results showed that fish oil supplemented diet compared to the palm oil supplemented diet increased milk production after 6 weeks of lactation (P<0.05), content of polyunsaturated fatty acids milk fat (P<0.05) and docosahexaenoic acid (P<0.01). Moreover, n-6:n-3 ratio was decreased by fish oil supplement (P<0.05). Histological studies showed that FO increased the relative percentage of tissue area occupied by epithelial cells as well as a number of total alveoli in each microscopic field (P<0.05). Data suggested that feeding fish oil during the dry period and early lactation could improve development and function of the mammary gland in the dairy cow.

Diet composition as a source of variation in experimental animal models of cancer cachexia

BACKGROUND

A variety of experimental animal models are used extensively to study mechanisms underlying cancer cachexia, and to identify potential treatments. The important potential confounding effect of dietary composition and intake used in many preclinical studies of cancer cachexia is frequently overlooked. Dietary designs applied in experimental studies should maximize the applicability to human cancer cachexia, meeting the essential requirements of the species used in the study, matched between treatment and control groups as well as also being generally similar to human consumption.

METHODS

A literature review of scientific studies using animal models of cancer and cancer cachexia with dietary interventions was performed. Studies that investigated interventions using lipid sources were selected as the focus of discussion.

RESULTS

The search revealed a number of nutrient intervention studies (n = 44), with the majority including n-3 fatty acids (n = 16), mainly eicosapentaenoic acid and/or docosahexaenoic acid. A review of the literature revealed that the majority of studies do not provide information about dietary design; food intake or pair-feeding is rarely reported. Further, there is a lack of standardization in dietary design, content, source, and overall composition in animal models of cancer cachexia. A model is proposed with the intent of guiding dietary design in preclinical studies to enable comparisons of dietary treatments within the same study, translation across different study designs, as well as application to human nutrient intakes.

CONCLUSION

The potential for experimental endpoints to be affected by variations in food intake, macronutrient content, and diet composition is likely. Diet content and composition should be reported, and food intake assessed. Minimum standards for diet definition in cachexia studies would improve reproducibility of pre-clinical studies and aid the interpretation and translation of results to humans with cancer.

Diet modulation is an effective complementary agent in preventing and treating breast cancer lung metastasis

A significant percentage of breast cancer victims will suffer from metastases indicating that new approaches to preventing breast cancer metastasis are thus needed. Dietary stearate (ST) and chemotherapy have been shown to reduce breast cancer metastasis. We tested the complementary use of dietary ST with a taxol-based chemotherapy which work through separate mechanisms to reduce breast cancer metastasis. We therefore carried out a prevention study in which diets were initiated prior to human MDA-MB-435 cancer cells being injected into the host and a treatment study in which diets were combined with paclitaxel (PTX). Using an orthotopic athymic nude mouse model and three diets [corn oil (CO) control diet, low fat (LF) or ST] the prevention study demonstrated that the ST diet decreased the incidence of lung metastasis by 50 % compared to both the LF and CO diets. The ST diet also reduced the number and size of metastatic lung nodules compared to the LF diet. Results of the treatment study indicated that both the CO and ST diets decreased the number of mice with lung metastasis compared to the LF diet. Both CO and ST also decreased the number of lung metastases per mouse compared to the LF diet however only the ST diet cohort was significant. Histomorphometric analysis of the lung tumor tissue indicated that the ST diet plus PTX decreased angiogenesis compared to the LF diet plus PTX. In conclusion these results support combining diet with chemotherapy in both treatment and prevention settings.

Redefining the impact of nutrition on breast cancer incidence: is epigenetics involved?

Breast cancer incidence is rising worldwide with an increase in aggressive neoplasias in young women. Possible factors involved include lifestyle changes, notably diet that is known to make an impact on gene transcription. However, among dietary factors, there is sufficient support for only greater body weight and alcohol consumption whereas numerous studies revealing an impact of specific diets and nutrients on breast cancer risk show conflicting results. Also, little information is available from middle- and low-income countries. The diversity of gene expression profiles found in breast cancers indicates that transcription control is critical for the outcome of the disease. This suggests the need for studies on nutrients that affect epigenetic mechanisms of transcription, such as DNA methylation and post-translational modifications of histones. In the present review, a new examination of the relationship between diet and breast cancer based on transcription control is proposed in light of epidemiological, animal and clinical studies. The mechanisms underlying the impact of diets on breast cancer development and factors that impede reaching clear conclusions are discussed. Understanding the interaction between nutrition and epigenetics (gene expression control via chromatin structure) is critical in light of the influence of diet during early stages of mammary gland development on breast cancer risk, suggesting a persistent effect on gene expression as shown by the influence of certain nutrients on DNA methylation. Successful development of breast cancer prevention strategies will require appropriate models, identification of biological markers for rapid assessment of preventive interventions, and coordinated worldwide research to discern the effects of diet.

Distinct effects of calorie restriction and exercise on mammary gland gene expression in C57BL/6 mice

Energy balance, including diet, weight, adiposity, and physical activity, is associated with carcinogenesis. Epidemiologic studies indicate that obesity and sedentary and/or active behavior are risk factors for breast cancer in postmenopausal women and survival in both premenopausal and postmenopausal breast cancer patients. Thus, understanding the influence of energy balance modulation on changes in gene expression patterns in the normal mammary gland is important for understanding mechanisms linking energy balance and breast cancer. In a 6-week-long study, female C57BL/6 mice (9-week-old) were randomized into four groups: (a) food consumed ad libitum (AL), (b) AL with access to running wheels (AL+EX), (c) 30% calorie restricted (CR), and (d) 30% CR with access to running wheels (CR+EX). CR mice received 70% of calories but 100% of all other nutrients compared with AL mice. Diet and exercise treatments, individually and combined, had significant effects on body composition and physical activity. Affymetrix oligomicroarrays were used to explore changes in gene expression patterns in total RNA samples from excised whole mammary glands. Contrasting AL versus CR resulted in 425 statistically significant expression changes, whereas AL versus AL+EX resulted in 45 changes, with only 3 changes included among the same genes, indicating that CR and EX differentially influence expression patterns in noncancerous mammary tissue. Differential expression was observed in genes related to breast cancer stem cells, the epithelial-mesenchymal transition, and the growth and survival of breast cancer cells. Thus, CR and EX seem to exert their effects on mammary carcinogenesis through distinct pathways.

Role of nuclear receptors in the regulation of gene expression by dietary fatty acids (review)

Long chain fatty acids, derived either from endogenous metabolism or by nutritional sources play significant roles in important biological processes of membrane structure, production of biologically active compounds, and participation in cellular signaling processes. Recently, the structure of dietary fatty acids has become an important issue in human health because ingestion of saturated fats (containing triglycerides composed of saturated fatty acids) is considered harmful, while unsaturated fats are viewed as beneficial. It is important to note that the molecular reason for this dichotomy still remains elusive. Since fatty acids are important players in development of pathology of cardiovascular and endocrine system, understanding the key molecular targets of fatty acids, in particular those that discriminate between saturated and unsaturated fats, is much needed. Recently, insights have been gained on several fatty acid-activated nuclear receptors involved in gene expression. In other words, we can now envision long chain fatty acids as regulators of signal transduction processes and gene regulation, which in turn will dictate their roles in health and disease. In this review, we will discuss fatty acid-mediated regulation of nuclear receptors. We will focus on peroxisome proliferators-activated receptors (PPARs), liver X receptors (LXR), retinoid X receptors (RXRs), and Hepatocyte Nuclear Factor alpha (HNF-4alpha), all of which play pivotal roles in dietary fatty acid-mediated effects. Also, the regulation of gene expression by Conjugated Linoleic Acids (CLA), a family of dienoic fatty acids with a variety of beneficial effects, will be discussed.

Mechanisms by which energy restriction inhibits carcinogenesis

Cancer that occurs at numerous organ sites, including the colon and breast, is inhibited by energy restriction, and the inhibition is proportional to the degree of restriction imposed. In an effort to identify the mechanism(s) by which energy restriction exerts this effect, a short term model system of experimentally induced mammary carcinogenesis was used. Given that carcinogenesis is known to involve a dysregulation to tissue size homeostasis in which cell proliferation and cell death are in dysequilibrium, we hypothesized that energy restriction exerts its effect by altering one or more aspects of cell cycle regulation. It was observed that energy restriction inhibited cell proliferation and increased cell death due to apoptosis. Thus attention was next focused on aspects of cell cycle regulation that might be affected by energy restriction. It was observed that the amount of p27 protein, one member of the Cip/Kip family of genes that are involved in cell cycle arrest, was increased dose dependently by energy restriction. Based on this and related observations, the hypothesis is advanced that energy restriction inhibits carcinogenesis, at least in part, by delaying cell cycle progression via shifting cell populations into a G(0)/G(1)state. Ongoing work indicates that corticosteroids, which are produced in increased amounts in response to energy restriction, may be involved in mediating this effect.

Effects of physical activity and exercise on experimentally-induced mammary carcinogenesis

Physical activity is defined as skeletal muscle contraction resulting in a quantifiable expenditure of energy, whereas exercise is a specific type of physical activity in which planned, structured, and repetitive bodily movement is done to improve or maintain one or more components of physical fitness. The focus of laboratory studies of the physical activity-breast cancer hypothesis has been on evaluating how various types of physical activity including exercise affect the process of mammary carcinogenesis. A key objective has been the evaluation of the characteristics of physical activity, i.e. intensity, duration, and frequency, required to confer protection against experimentally-induced breast cancer. The results of those studies indicate that exercise rather than physical activity can exert a greater inhibitory effect against experimentally-induced breast cancer, and that the duration of exercise may not be as important as its intensity. This finding differs from evidence that other health benefits attributed to physical activity are proportional to the total amount of activity rather than the manner in which it is obtained. In this review criteria are defined for categorizing laboratory studies into those that investigated the effects of physical activity versus exercise on experimentally-induced mammary carcinogenesis, and the literature is reinterpreted in this context.

Chronic dietary restriction influences tumor metastasis in the rat: parametric considerations

Chronic dietary restriction is a well-documented means of inhibiting tumor growth. This study examines the effects of chronic dietary restriction on tumor metastasis in the rat. We investigate the effect of 1) the degree of food restriction, 2) the effect of preexposure to food restriction, and 3) the duration of food restriction after tumor inoculation on tumor metastasis. We also compare two methods of dietary restriction: 1) the time that food is available and 2) the amount of food available. Our findings demonstrate that rats restricted to 50% of ad libitum diet for one week before inoculation with MADB106 tumor cells and for three weeks after inoculation exhibit a significant (p < 0.001) reduction in lung colonization compared with animals fed ad libitum. Animals restricted to access to food for 4 hrs/day (60% of ad libitum) for the same period of time exhibit significantly (p < 0.005) greater lung tumor colonization than animals fed ad libitum. Preadaptation to the feeding regimen for one week before tumor inoculation proved to be critical in inhibiting tumor metastasis. The tumor-inhibitory effect was not significantly influenced by the duration of restriction after inoculation or by the manner in which food restriction was implemented. Finally, we demonstrate that inhibition of tumor colonization may be mediated by enhanced natural killer cell activity in the early postinoculation period.

Perspectives on integrating experimental and epidemiologic research on diet, anthropometry and breast cancer

Three perspectives on the integration of experimental and epidemiologic research on diet, anthropometry and breast cancer are presented. 1) Although body weight and height have been linked to breast cancer risk by epidemiologic research, their roles have not been directly explored with animal models. However, basic, clinical and epidemiologic research on obesity and associated metabolic alterations may be pertinent. Individual differences in the timing and magnitude of weight gain and loss during adult life need to be considered in epidemiologic studies of adiposity and breast cancer, along with individual differences in the pattern of body fat deposition, the hormonal and metabolic changes that accompany the adiposity, and family history of obesity-related chronic diseases. Animal models with genetic predispositions to obesity, diabetes and breast cancer merit further exploration, as well as models that can evaluate exposures occurring after puberty. 2) The synergy between experimental and epidemiologic studies on fat and energy intake and breast carcinogenesis has been productive because each discipline has had to incorporate recent findings of the other. Dietary studies utilizing animals with different genetic profiles are promising, but require identification of the critical genes in human carcinogenesis. 3) Controlled dietary intervention studies with human participants using intermediate endpoints can bridge the gap between animal and epidemiologic studies, but generally accepted intermediate endpoints for breast cancer need to be developed. Such studies would permit better control of diet than large clinical trials and the opportunity to explore mechanisms.

Intervention of transplantable human mammary carcinoma MX-1 chemotherapy with dietary menhaden oil in athymic mice: increased therapeutic effects and decreased toxicity of cyclophosphamide

We investigated the effects of dietary menhaden oil on cyclophosphamide (CP) antineoplastic activity and its protective effect against CP toxicity. We found that dietary menhaden oil (HMO, 20% menhaden oil + 5% corn oil) enhanced the CP antitumor effect at the lowest dose tested (50 mg/kg) compared with the control group (LCO, 5% corn oil). Dietary HMO and CP treatment had a significant effect on the activities of tumor and liver microsomal cytochrome P-450 (CYP) over the controls. Activity of one of the key CP activating enzymes, CYP2B1 (which is similar to human CYP2B6), was significantly enhanced in the liver and tumor by the HMO diet, which could result in the formation of more pharmacologically active CP metabolites and, therefore, increased CP antitumor response. Moreover, the HMO diet exhibited a very significant protective effect against CP acute toxicity. The activity of the CP detoxifying enzyme aldehyde dehydrogenase (ADH) was significantly increased in the liver after HMO feeding; thus the observed protective effect of HMO feeding against CP toxicity may be partially the result of induction of ADH activity in the liver. In summary, our findings suggested that dietary menhaden oil can modulate ADH and CYP activities in a manner that may alter the metabolism of CP and, therefore, improve its therapeutic index by increasing its therapeutic effect and decreasing its toxicity.

Nutrition, hormones, and breast cancer: is insulin the missing link?

Breast cancer incidence rates are high in societies with a Western lifestyle characterized by low levels of physical activity, and by an energy-dense diet rich in total and saturated fat and refined carbohydrates. Epidemiologic studies, so far mostly on postmenopausal women, have shown that breast cancer risk is increased in hyperandrogenic women, with decreased levels of plasma sex-hormone binding globulin, and with increased levels of testosterone and of free estrogens. This paper describes the role of hyperinsulinemia as a physiologic link between nutritional lifestyle factors, obesity, and the development of a hyperandrogenic endocrine profile, and reviews evidence that may or may not support the theory that chronic hyperinsulinemia is an underlying cause of breast cancer. An hypothesis is presented, stipulating that breast cancer risk is increased not only in hyperandrogenic postmenopausal women, but also in premenopausal women with mild hyperandrogenism and normal (ovulatory) menstrual cycles. The author suggests further investigation as to whether there is a positive association between risk of breast cancer before menopause and subclinical forms of the polycystic ovary syndrome (PCOS), and to what extent diet and physical activity during childhood, by modulating the degree of insulin resistance during adolescence, may or may not be determinants of a PCO-like hyperandrogenic endocrine profile persisting into adulthood.