Mechanisms mediating the effects of prepubertal (n-3) polyunsaturated fatty acid diet on breast cancer risk in rats

Dietary Recommendations for Glioma: A Mini-Review

PURPOSE OF REVIEW

Glioma is the most common type of brain cancer, associated with a high mortality rate. Diet is one of the most modifiable factors that can influence the risk of various cancers, including glioma. While the relationship between diet and glioma has been explored in recent years, the number of studies in this area remains limited, and the findings are often controversial. Moreover, all existing studies are observational, which means they may be influenced by a range of confounding variables. In this mini-review, we aim to provide a comprehensive and informative overview of the dietary recommendations related to glioma that have been published to date.

RECENT FINDINGS

Research suggests that adherence to healthy dietary patterns-such as the Mediterranean diet, Dietary Approaches to Stop Hypertension (DASH) diet, Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet, Paleolithic diet, high-protein dietary patterns, and vegetarian dietary patterns-may be associated with a reduced risk of glioma. These diets are rich in phytochemicals and antioxidants. Additionally, certain food groups, including fruits, vegetables, legumes, nuts, eggs, fresh fish, tea, and coffee, are emphasized for their protective effects against glioma. Conversely, adherence to unhealthy dietary patterns, such as the Western diet, or diets with high inflammatory potential, glycemic and insulinemic loads, and high consumption of grains (especially refined grains), processed meats, and processed fish, has been linked to an increased risk of glioma. Current studies suggest that following a healthy diet may reduce the odds of developing glioma. However, due to the limited number of studies and the observational nature of the existing research, further investigations with more robust designs, such as randomized controlled trials, are needed to clarify these associations.

Dietary patterns in relation to glioma: a case-control study

Although the association of individual foods and nutrients with glioma have been investigated, studies on the association of major dietary patterns and glioma are scarce. The aim of this study was to examine the association between major dietary patterns and risk of glioma in a group of Iranian adults. In this hospital-based case-control design, we recruited 128 newly diagnosed glioma cases and 256 controls in Tehran from 2009 to 2011. A Willett-format-validated 126-item semi-quantitative Food Frequency Questionnaire (FFQ) was used to assess participants' dietary intake. Factor analysis was used to identify major dietary patterns. We identified 3 major dietary patterns using factor analysis: high protein, vegetarian and western dietary pattern. After several adjustments for potential confounders, adherence to the high protein dietary pattern was inversely associated with risk of glioma (OR: 0.47; 95% CI: 0.23, 0.95). Consumption of vegetarian dietary pattern was also associated with a reduced risk of glioma (OR: 0.16; 95% CI: 0.07, 0.34). Greater adherence to the western dietary pattern was associated with a greater chance of glioma (OR: 3.30; 95% CI: 1.52, 7.17). We found that high protein, vegetarian and western dietary pattern were significantly associated with glioma risk. Further prospective studies are needed to confirm these findings.

Oncogenic signaling of the free-fatty acid receptors FFA1 and FFA4 in human breast carcinoma cells

Globally, breast cancer is the most frequent type of cancer in women, and most breast cancer-associated deaths are due to metastasis and recurrence of the disease. Dietary habits, specifically dietary fat intake is a crucial risk factor involved in breast cancer development and progression. Decades of research has revealed that free-fatty acids (FFA) modulate carcinogenic processes through fatty acid metabolism and lipid peroxidation. The ground-breaking discovery of free-fatty acid receptors, which are members of the G-protein coupled receptor (GPCR) superfamily, has led to the realization that FFA can also act via these receptors to modulate carcinogenic effects. The long-chain free-fatty acid receptors FFA1 (previously termed GPR40) and FFA4 (previously termed GPR120) are activated by mono- and polyunsaturated fatty acids including ω-3, 6, and 9 fatty acids. Initial enthusiasm towards the study of these receptors focused on their insulin secretagogue and sensitization effects, and the downstream associated metabolic regulation. However, recent studies have demonstrated that abnormal expression and/or aberrant FFA1/FFA4 signaling are evident in human breast carcinomas, suggesting that FFA receptors could be a promising target in the treatment of breast cancer. The current review discusses the diverse roles of FFA1 and FFA4 in the regulation of cell proliferation, migration, invasion, and chemotherapy resistance in human breast carcinoma cells and tissue.

Nutritional Regulation of Mammary Gland Development and Milk Synthesis in Animal Models and Dairy Species

In mammals, milk is essential for the growth, development, and health. Milk quantity and quality are dependent on mammary development, strongly influenced by nutrition. This review provides an overview of the data on nutritional regulations of mammary development and gene expression involved in milk component synthesis. Mammary development is described related to rodents, rabbits, and pigs, common models in mammary biology. Molecular mechanisms of the nutritional regulation of milk synthesis are reported in ruminants regarding the importance of ruminant milk in human health. The effects of dietary quantitative and qualitative alterations are described considering the dietary composition and in regard to the periods of nutritional susceptibly. During lactation, the effects of lipid supplementation and feed restriction or deprivation are discussed regarding gene expression involved in milk biosynthesis, in ruminants. Moreover, nutrigenomic studies underline the role of the mammary structure and the potential influence of microRNAs. Knowledge from three lactating and three dairy livestock species contribute to understanding the variety of phenotypes reported in this review and highlight (1) the importance of critical physiological stages, such as puberty gestation and early lactation and (2) the relative importance of the various nutrients besides the total energetic value and their interaction.

The Association of Consumption of Animal Proteins and the Risk of Esophageal Cancer

Aim: Esophageal cancer (EC) is considered one of the most common types of cancer in the world. High intake of dietary proteins is suggested to increase EC. This study examined associations between intake of red meats, processed meat, poultry, and fish and the risk of EC. Methods: This hospital-based Case-Control study included 96 people with EC and 187 people without EC from Bojnurd, Iran. Socio-demographic data was collected from all participants at enrollment using general information questionnaire. Dietary intake was assessed using a validated 168 item semi-quantitative food frequency questionnaire. Results: After adjusting for potential confounders, there was a significant association between the consumption of beef (P = 0.04), processed meats (sausages) (P = 0.01), and chicken with skin (P = 0.001) with the risk of EC. Conclusion: We observed a positive association between red meat, processed meats (sausages), chicken with skin and the risk of EC. The use of lamb meat and fish had no significant association with the risk of EC.

Long-Chain Omega-3 Polyunsaturated Fatty Acids Modulate Mammary Gland Composition and Inflammation

Studies in rodents have shown that dietary modifications as mammary glands (MG) develop, regulates susceptibility to mammary tumor initiation. However, the effects of dietary PUFA composition on MGs in adult life, remains poorly understood. This study investigated morphological alterations and inflammatory microenvironments in the MGs of adult mice fed isocaloric and isolipidic liquid diets with varying compositions of omega (ω)-6 and long-chain (Lc)-ω3FA that were pair-fed. Despite similar consumption levels of the diets, mice fed the ω-3 diet had significantly lower body-weight gains, and abdominal-fat and mammary fat pad (MFP) weights. Fatty acid analysis showed significantly higher levels of Lc-ω-3FAs in the MFPs of mice on the ω-3 diet, while in the MFPs from the ω-6 group, Lc-ω-3FAs were undetectable. Our study revealed that MGs from ω-3 group had a significantly lower ductal end-point density, branching density, an absence of ductal sprouts, a thinner ductal stroma, fewer proliferating epithelial cells and a lower transcription levels of estrogen receptor 1 and amphiregulin. An analysis of the MFP and abdominal-fat showed significantly smaller adipocytes in the ω-3 group, which was accompanied by lower transcription levels of leptin, IGF1, and IGF1R. Further, MFPs from the ω-3 group had significantly decreased numbers and sizes of crown-like-structures (CLS), F4/80+ macrophages and decreased expression of proinflammatory mediators including Ptgs2, IL6, CCL2, TNFα, NFκB, and IFNγ. Together, these results support dietary Lc-ω-3FA regulation of MG structure and density and adipose tissue inflammation with the potential for dietary Lc-ω-3FA to decrease the risk of mammary gland tumor formation.

Poultry and Fish Consumption in Relation to Total Cancer Mortality: A Meta-Analysis of Prospective Studies

Observational studies on the association between fish and poultry intake and the risk of total cancer mortality have been reported with mixed results. Thus, we aimed to assess this association by conducting a meta-analysis of prospective studies. We performed a literature search on PubMed database through February 1, 2017 to identify relative prospective studies. A random-effects model was used to calculate the summary estimates. We identified fourteen prospective studies involving 2,378,204 participants and 96,712 cancer mortality events. Comparing the highest category of consumption with lowest category, pooled relative risk (RR) of total cancer mortality was 0.99 (95% confidence interval [CI], 0.94-1.05) for fish (10 studies) and 0.96 (95% CI, 0.93-1.00) for poultry (8 studies), respectively. However, we failed to identify any dose-response association based on a limited number of eligible studies, with a pooled RR of 0.98 (95% CI, 0.92-1.05) and 0.97 (95% CI, 0.88-1.07) for each 100 g per day increment in fish and poultry consumption, respectively. In summary, this meta-analysis indicates that consumption of either fish or poultry is not substantially associated with lower risk of total cancer mortality. The observed weak inverse association for high poultry consumption needs to be verified in additional large prospective studies.

Significance of Increasing n-3 PUFA Content in Pork on Human Health

Evidence for the health-promoting effects of food rich in n-3 polyunsaturated fatty acids (n-3 PUFA) is reviewed. Pork is an important meat source for humans. According to a report by the US Department of Agriculture ( http://www.ers.usda.gov/topics ), the pork consumption worldwide in 2011 was about 79.3 million tons, much higher than that of beef (48.2 million tons). Pork also contains high levels of unsaturated fatty acids relative to ruminant meats (Enser, M., Hallett, K., Hewett, B., Fursey, G. A. J. and Wood, J. D. (1996) . Fatty acid content and composition of English beef, lamb, and pork at retail. Meat Sci. 44:443-458). The available literature indicates that the levels of eicosatetraenoic and docosahexaenoic in pork may be increased by fish-derived or linseed products, the extent of which being dependent on the nature of the supplementation. Transgenic pigs and plants show promise with high content of n-3 PUFA and low ratio of n-6/n-3 fatty acids in their tissues. The approaches mentioned for decreasing n-6/n-3 ratios have both advantages and disadvantages. Selected articles are critically reviewed and summarized.

Role of n-3 Polyunsaturated Fatty Acids and Exercise in Breast Cancer Prevention: Identifying Common Targets

Diet and exercise are recognized as important lifestyle factors that significantly influence breast cancer risk. In particular, dietary n-3 polyunsaturated fatty acids (PUFAs) have been shown to play an important role in breast cancer prevention. Growing evidence also demonstrates a role for exercise in cancer and chronic disease prevention. However, the potential synergistic effect of n-3 PUFA intake and exercise is yet to be determined. This review explores targets for breast cancer prevention that are common between n-3 PUFA intake and exercise and that may be important study outcomes for future research investigating the combined effect of n-3 PUFA intake and exercise. These lines of evidence highlight potential new avenues for research and strategies for breast cancer prevention.

Involvement of genetic factors and lifestyle on the occurrence of colorectal and gastric cancer

Gastrointestinal cancers are diseases due to genetic and environmental factors. In this present work we are interested in the influence of environmental factors on the occurrence of gastrointestinal cancers in Tunisian population. We found that the MTHFR C677T polymorphism was associated with colorectal cancer (P<0.04) but not with gastric cancer. In addition, we have shown that alcohol is associated with an increased risk of colorectal cancer, but the consumption of cheese is protective. Furthermore, we studied tymidylate synthase gene involved in folate metabolism. Indeed, we observed that the 5'UTR repeat polymorphism, is associated with risk of colorectal cancer, and the LL genotype (3R/3R) was significantly frequent in patients with colorectal cancer compared to controls (p=0.002; OR=2.7, 95% CI=1.4-5.2). While we found that SL genotype (2R/3R) was associated with risk of gastric cancer (p=0.015; OR=4.46, 95% CI=1.08-19-64). This polymorphism was also shown to be a predictor of response to chemotherapy based 5'-fluorouracil. However, we are interested in studying the GPX -1 gene involved in phase I metabolism of xenobiotics. We therefore evaluated the risk of TT genotype in GPX-1 C599T polymorphism with the onset of gastric cancer (P=0.0001; OR=5.41, 95% CI 1.98 to 15.58) and colorectal cancer (P=0.00008; OR=4.40, 95% CI 1.93 to 10.27). To clarify the possible relationship between environmental factors and the occurrence of the disease, we studied the additive effect of risk genotype and behavior in order to highlight the interaction of gene-environment factors.

Analysis of high fat diet induced genes during mammary gland development: identifying role players in poor prognosis of breast cancer

BACKGROUND

Epidemiological studies have shown that consumption of a high-fat diet (HFD) increases the risk of developing breast cancer (BC). Studies in rodents have shown HFD causes changes in the genetic programming of the maturing mammary gland (MG) increasing the susceptibility of developing the disease. Less is known about how HFD induced genes impact BC development. HFD exposure two weeks before conception to six weeks of age was previously shown to dramatically change MG gene expression in 10 week old mice. Therefore, we investigated these differentially expressed HFD-induced genes for their expression in BC using the NKI 295 breast tumor dataset.

RESULTS

To examine the potential role of HFD induced genes in BC, we first investigated whether these HFD-induced genes in mouse MGs were differentially expressed in different types of human BC. Of the 28 HFD induced genes that were differentially expressed between BC subtypes in the NKI set, 79% were significantly higher in basal-like BC. Next, we analyzed whether HFD induced genes were associated with BC prognosis utilizing gene expression and survival data for each HFD induced gene from the NKI data and constructed Kaplan Meier survival plots. Significantly, 93% of the prognosis associated genes (13/14) were associated with poor prognosis (P = 0.002). Kaplan Meier analysis with 249 non-basal-like BC found that all but one of the genes examined were still significantly associated with poor prognosis. Furthermore, gene set enrichment analysis (GSEA) with HFD microarray data revealed that invasive BC genes where enriched in HFD samples that also had lost expression of luminal genes.

CONCLUSIONS

HFD exposed mouse MGs maintain differential expression of genes that are found highly expressed in basal-like breast cancer. These HFD-induced genes associate with poor survival in numerous BC subtypes, making them more likely to directly impact prognosis. Furthermore, HFD exposure leads to a loss in the expression of luminal genes and a gain in expression of mesenchymal and BC invasion genes in MGs. Collectively, our study suggests that HFD exposure during development induces genes associated with poor prognosis, thus identifying how HFD diet may regulate BC development.

Lifelong exposure to n-3 PUFA affects pubertal mammary gland development

There is growing evidence that early developmental periods may importantly influence future breast cancer risk. Also, there is great interest in the role of dietary fat in breast cancer risk, but the role of dietary fat during pubertal mammary gland development remains poorly understood. This study investigated the effect of n-3 polyunsaturated fatty acids (PUFA) using complementary dietary and genetic approaches to examine the effect of lifelong exposure of n-3 PUFA or n-6 PUFA (control) on mammary gland development and fatty acid composition. n-3 PUFA from both diet and genetics were enriched in mammary glands as early as 3 weeks of age. Parameters related to mammary gland development, including number of terminal end buds (TEB), percent coverage of ductal tree, and infiltration of TEB, were influenced by n-3 PUFA at 3 and 4 weeks of age. Overall, findings suggest that n-3 PUFA incorporation into the mammary gland early in life plays a role in the morphological development of the mammary gland during puberty.

The association between fish consumption and risk of renal cancer: a meta-analysis of observational studies

Background

Several case-control studies and cohort studies have investigated the association between fish intake and renal cancer risk, however, they yielded conflicting results. To our knowledge, a comprehensive assessment of the association between fish consumption and risk of renal cancer has not been reported. Hence, we conducted a systematic literature search and meta-analysis to quantify the association between fish consumption and renal cancer.

Methods

A systematic search was performed using the PubMed, Embase, and Cochrane Library Central database for case-control and cohort studies that assessed fish intake and risk of renal cancer. Two authors independently assessed eligibility and extracted data. Fixed-effect and random-effect models were used to estimate summary relative risks (RR) and the corresponding 95% confidence intervals (CIs). Subgroup analyses, sensitivity analysis and cumulative meta-analysis were also performed.

Results

A total of 12 case-control studies and three cohort studies published between 1990 and 2011 were included in the meta-analysis, involving 9,324 renal cancer cases and 608,753 participants. Meta-analysis showed that fish consumption did not significantly affect the risk of renal cancer (RR=0.99, 95% CI [0.92,1.07]). In our subgroup analyses, the results were not substantially affected by study design, region, gender, and confounder adjustments. Furthermore, sensitivity analysis confirmed the stability of results.

Conclusions

The present meta-analysis suggested that there was no significant association between fish consumption and risk of renal cancer. More in-depth studies are warranted to report more detailed results, including stratified results by fish type, preparation method, and gender.

Poultry and fish intake and risk of esophageal cancer: A meta-analysis of observational studies

AIM

Mixed results regarding the association between white meat (including poultry and fish) intake and the risk of esophageal cancer (EC) have been reported. We performed a meta-analysis to provide a quantitative assessment of this association.

METHOD(S)

Relevant studies were identified in MEDLINE until December 31, 2012. Summary relative risks (SRRs) with 95% confidence intervals (CIs) were pooled with a random-effects model.

RESULTS

A total of 20 articles, including 3990 cases with EC, were included in this meta-analysis. Compared to individuals with the lowest level of fish intake, individuals with the highest fish intake were found to have reduced risk of EC (SRRs = 0.69; 95% CIs: 0.57-0.85), while poultry intake was not associated with EC (SRRs = 0.83; 95% CIs: 0.62-1.12). Total fish consumption is associated with reduced esophageal squamous cell carcinoma (ESCC) risk, while poultry consumption was not associated with ESCC risk. Additionally, neither poultry nor fish consumption was associated with esophageal adenocarcinoma risk.

CONCLUSION(S)

Our results suggest that fish consumption may have a potential role in EC prevention, while poultry intake has no effect. However, because the majority of data was from case-control studies, further well-designed prospective studies are warranted.

Fish consumption and risk of esophageal cancer and its subtypes: a systematic review and meta-analysis of observational studies

BACKGROUND/OBJECTIVES

Inconsistent results regarding the association between fish intake and risk of subtypes of esophageal cancer (EC), esophageal squamous cell carcinoma (ESCC) and esophageal adenocarcinoma (EAC), have been reported. To provide a quantitative assessment of this association, we summarized the evidence from observational studies.

SUBJECTS/METHODS

Relevant studies were identified in MEDLINE and EMBASE until 31 May, 2012. Summary relative risks (SRRs) with 95% confidence intervals (CIs) were pooled with a random-effects model. Between-study heterogeneity was assessed using the Cochran's Q and I(2) statistics.

RESULTS

A total of 24 studies (21 case-control and 3 cohort studies) were included in this systematic review and meta-analysis. The SRRs of ESCC were 0.81 (95% CI: 0.66-0.99) for those in the highest fish consumption category compared with those in the lowest consumption category, with significant heterogeneity among studies (P(heterogeneity)=0.007, I(2)=51.9%). Subgroup analysis suggested that a weak association between fish consumption and ESCC risk was shown in hospital-based case-control studies, but not in population-based case-control or cohort studies. According to high vs low analysis, fish consumption had no relationship with EAC risk (SRR=0.86, 95% CI: 0.61-1.22).

CONCLUSIONS

Our results suggest that fish consumption is not appreciably related to risk of both ESCC and EAC.

PUFAs in serum cholesterol ester and oxidative DNA damage in Japanese men and women

BACKGROUND

PUFAs are susceptible to lipid peroxidation and play a role in inflammation, both of which can induce oxidative stress. However, the relation of PUFA to oxidative DNA damage in humans is elusive.

OBJECTIVE

We examined the association between concentrations of circulatory PUFAs and urinary 8-oxo-7,8-dihydroguanine (8-oxoGua) in Japanese men and women.

DESIGN

The subjects were 495 participants (290 men and 205 women) in a cross-sectional study in 2 municipal offices in Japan. Serum cholesterol ester (CE) and phospholipid fatty acid composition were measured by gas-liquid chromatography. Urinary 8-oxoGua concentrations were measured by HPLC, and 8-oxoGua values for each tertile of PUFA after adjustment for covariates were calculated by multiple regression.

RESULTS

Urinary 8-oxoGua concentrations increased with increasing concentrations of n-3 (omega-3) PUFAs, EPA, and DHA in serum CE (P-trend = 0.001, 0.01, and 0.009, respectively), whereas they decreased with increasing concentrations of n-6 PUFAs and linoleic acid (P-trend = 0.02 and 0.051, respectively).

CONCLUSION

Oxidative DNA damage may be greater with higher concentrations of long-chain n-3 PUFAs but lower with higher concentrations of n-6 (omega-6) PUFAs.

Combined supplementation of vanadium and fish oil suppresses tumor growth, cell proliferation and induces apoptosis in DMBA-induced rat mammary carcinogenesis

The anti-cancer activity of vanadium and fish oil has been shown in a large number of studies. This study was undertaken to analyze the combined effect of vanadium and fish oil on 7,12-dimethylbenz(α)anthracene (DMBA)-induced mammary carcinogenesis in female Sprague-Dawley rats. The whole experiment was divided into three parts: (1) DNA strand breaks study, (2) morphological analysis, and (3) histological and immunohistochemical study. Rats were treated with DMBA (0.5 mg/0.2 ml corn oil/100 g body weight) by a tail vein injection. Rats received vanadium (w/v) as ammonium monovanadate at a concentration of 0.5 ppm (4.27 µmol/L) in the drinking water and given ad libitum and/or fish oil (0.5 ml/day/rat) by oral gavage. Histology, morphology, DNA strand breaks, cell proliferation, and apoptosis of the mammary tissue were assessed in this study. Treatment with vanadium or fish oil alone significantly reduced the DNA strand breaks, palpable mammary tumors, tumor multiplicity, and cell proliferation but the maximum protection effect was found in the group that received both vanadium and fish oil and the combination treatment offered an additive effect (P < 0.05). Furthermore, vanadium and fish oil significantly increased the TUNEL-positive apoptotic cells (P < 0.05) but the increase was maximal with combination treatment and had an additive effect. These results affirm the benefits of administration of vanadium and fish oil in the prevention of rat mammary carcinogenesis which was associated with reduced DNA strand breaks, palpable mammary tumors and cell proliferation and increased TUNEL-positive apoptotic cells.

Differential mammary gland development in FVB and C57Bl/6 mice: implications for breast cancer research

A growing body of research suggests a linkage between pubertal mammary gland development and environmental factors such as diet as modifiers of long term breast cancer risk. Much of this research is dependent upon mouse models, which may vary between studies. However, effects may be strain dependent and further modified by diet, which has not been previously examined. Therefore, the objective of the present study was to determine whether mammary gland development differs between FVB and C57Bl/6 strains on diets containing either n-6 or n-3 polyunsaturated fats. Developmental measures related to onset of puberty and mammary gland development differed between strains. Mice fed the n-3 polyunsaturated fatty acids (PUFA) diet were shown to have lower numbers of terminal end buds, a marker of mammary gland development. This study helps to further clarify differences in development and dietary response between FVB and C57Bl/6 mice in order to more appropriately relate mammary gland research to human populations.

Nutrition modulation of gastrointestinal toxicity related to cancer chemotherapy: from preclinical findings to clinical strategy

Chemotherapy-induced gut toxicity is a major dose-limiting toxicity for many anticancer drugs. Gastrointestinal (GI) complications compromise the efficacy of chemotherapy, promote overall malnutrition, aggravate cancer cachexia, and may contribute to worsened prognosis. The GI tract is an attractive target for nutrition modulation, owing to its direct exposure to the diet, participation in uptake and metabolism of nutrients, high rate of cell turnover, and plasticity to nutrition stimuli. Glutamine, ω-3 polyunsaturated fatty acids, and probiotics/prebiotics are therapeutic factors that potentially modulate GI toxicity related to cancer treatments. Preclinical and clinical evidence are reviewed to critically define plausible benefits of these factors and their potential development into adjuncts to cancer chemotherapy. Mechanisms underlying the action of these nutrients are being unraveled in the laboratory. Optimal strategies to translate these findings into clinical care still remain to be elucidated. Key questions that remain to be answered include the following: which nutrient or combination of nutrients is selected for which patient and chemotherapy regimen? What mechanisms are responsible for modulation, and how are nutrient(s) administered in a clinically optimal manner? Research exploring interactions between different nutrients in GI protection is ongoing and demands further understanding. How nutrition preparations given to chemotherapy-treated patients are formulated in terms of component selection and dose optimization should be carefully studied and justified.

Fish consumption and the risk of gastric cancer: systematic review and meta-analysis

BACKGROUND

Gastric cancer is the fourth most frequently occurring malignancy after lung, breast, and colorectal cancer, and the second most common cause of death from cancer worldwide. Epidemiologic studies have examined the possible association between fish consumption and gastric cancer, but the results were inconclusive. We conducted a systematic review and meta-analysis to examine the association between fish intake and the risk of gastric cancer.

METHODS

PubMed was searched for studies published in English-language journals from 1991 through 2009. We identified 17 epidemiologic studies (15 case-control and 2 cohort studies) that included relative risks (RRs) or odds ratios (ORs) estimates with 95% confidence intervals (CIs) of the relationship between gastric cancer and fish consumption. Data were extracted using standardized data forms. Summary RRs or ORs for the highest versus non/lowest fish consumption levels were calculated using random-effects model. Heterogeneity among studies was examined using Q and I2 statistics.

RESULTS

In this study, 5,323 cases of gastric cancer and over 130,000 non-cases were included. The combined results from all studies indicated that the association between high fish consumption and reduced gastric cancer risk was not statistically insignificant (RR = 0.87, 95% CI = 0.71-1.07).

CONCLUSIONS

Current evidence indicated that the association between fish consumption and risk of gastric cancer remains unclear.

Fish oil regulates cell proliferation, protect DNA damages and decrease HER-2/neu and c-Myc protein expression in rat mammary carcinogenesis

BACKGROUND & AIMS

The aim of this study is to assess the effect of dietary fish oil (MaxEPA) on DNA-strand breaks, cell proliferation and anti-apoptotic protein expressions in rat mammary carcinogenesis.

METHODS

Eighty-one female Sprague-Dawley rats were divided into two parts, one for DNA-strand breaks study and the other for immunohistochemical study. Female Sprague-Dawley rats were treated with 7,12-dimethylbenz(alpha)anthracene (DMBA) (0.5 mg/0.2 ml corn oil/100 g body weight) by a tail vein injection. Rats were fed either fish oil or corn oil (0.5 ml/day/rat) by oral gavage.

RESULTS

Fish oil-treated group showed significant protection against generation of single-strand breaks (SSBs) (56.1%, P < 0.05) but increased effect (72.3%, P < 0.05) was found in the corn oil-treated group when compared to DMBA control group. Furthermore, fish oil-treated group exhibited substantial decrease in Ki-67 (P < 0.05), HER-2/neu (P < 0.05) and c-Myc (P < 0.05) immunolabelling indices when compared to carcinogen counterpart. However, corn oil treatment resulted in significant increase in the above parameters.

CONCLUSIONS

The above data support the role of n-3 PUFA as a preventive agent for DNA damages and a potential to inhibit mammary carcinogenesis.

Role of dietary fatty acids in mammary gland development and breast cancer

Breast cancer is the most common cancer among women worldwide. Estimates suggest up to 35% of cases may be preventable through diet and lifestyle modification. Growing research on the role of fats in human health suggests that early exposure in life to specific fatty acids, when tissues are particularly sensitive to their environment, can have long-term health impacts. The present review examines the role of dietary fat in mammary gland development and breast cancer throughout the lifecycle. Overall, n-3 polyunsaturated fatty acids have promising cancer-preventive effects when introduced early in life, and warrant further research to elucidate the mechanisms of action.

Polyunsaturated fatty acids, DNA repair single nucleotide polymorphisms and colorectal cancer in the Singapore Chinese Health Study

Animal and in vitrostudies support a role for polyunsaturated fatty acids (PUFAs) in colon carcinogenesis; however, the epidemiological evidence is inconclusive. Recently, we investigated their role within the Singapore Chinese Health Study, a population-based cohort of Singapore Chinese men and women. We reported that a high intake of marine n-3 PUFAs was associated with an increased risk of colorectal cancer (CRC). Oxidation of PUFAs incorporated into cell membranes generates lipid hydroperoxides, which can be mutagenic. In this report, we investigated whether single nucleotide polymorphisms (SNPs) in DNA repair genes modified the effect of PUFAs on CRC risk using a nested case-control study within the Singapore Chinese Health Study. We genotyped 1,181 controls and 311 cases (180 colon and 131 rectal cancer) for SNPs in the XRCC1 (Arg194Trp, Arg399Gln), OGG1 (Ser326Cys), PARP (Val762Ala, Lys940Arg), and XPD (Asp312Asn, Lys751Gln) genes. We observed that the PARP Val762Ala SNP modified the association between marine n-3 PUFA and rectal cancer risk, with no evidence of interaction among colon cancer (heterogeneity test p=0.003). Our results suggest a positive association between high intake of marine n-3 PUFA and rectal cancer risk among carriers of at least one PARP codon 762 Ala allele (odds ratio=1.7, 95% confidence interval=1.1-2.7).

Lifestyle-induced metabolic inflexibility and accelerated ageing syndrome: insulin resistance, friend or foe?

The metabolic syndrome may have its origins in thriftiness, insulin resistance and one of the most ancient of all signalling systems, redox. Thriftiness results from an evolutionarily-driven propensity to minimise energy expenditure. This has to be balanced with the need to resist the oxidative stress from cellular signalling and pathogen resistance, giving rise to something we call 'redox-thriftiness'. This is based on the notion that mitochondria may be able to both amplify membrane-derived redox growth signals as well as negatively regulate them, resulting in an increased ATP/ROS ratio. We suggest that 'redox-thriftiness' leads to insulin resistance, which has the effect of both protecting the individual cell from excessive growth/inflammatory stress, while ensuring energy is channelled to the brain, the immune system, and for storage. We also suggest that fine tuning of redox-thriftiness is achieved by hormetic (mild stress) signals that stimulate mitochondrial biogenesis and resistance to oxidative stress, which improves metabolic flexibility. However, in a non-hormetic environment with excessive calories, the protective nature of this system may lead to escalating insulin resistance and rising oxidative stress due to metabolic inflexibility and mitochondrial overload. Thus, the mitochondrially-associated resistance to oxidative stress (and metabolic flexibility) may determine insulin resistance. Genetically and environmentally determined mitochondrial function may define a 'tipping point' where protective insulin resistance tips over to inflammatory insulin resistance. Many hormetic factors may induce mild mitochondrial stress and biogenesis, including exercise, fasting, temperature extremes, unsaturated fats, polyphenols, alcohol, and even metformin and statins. Without hormesis, a proposed redox-thriftiness tipping point might lead to a feed forward insulin resistance cycle in the presence of excess calories. We therefore suggest that as oxidative stress determines functional longevity, a rather more descriptive term for the metabolic syndrome is the 'lifestyle-induced metabolic inflexibility and accelerated ageing syndrome'. Ultimately, thriftiness is good for us as long as we have hormetic stimuli; unfortunately, mankind is attempting to remove all hormetic (stressful) stimuli from his environment.

Involvement of PPARα in the growth inhibitory effect of arachidonic acid on breast cancer cells

Epidemiological studies suggest that dietary PUFA may influence breast cancer progression.n-3 PUFA are generally known to exert antitumour effects, whereas reports relative ton-6 PUFA anti-carcinogen effects are controversial. Arachidonic acid (AA; 20 : 4n − 6) and its metabolites have been shown to inhibit the growth of human breast cancer cell lines, even if the downstream mechanisms by which AA may influence carcinogenesis remain unresolved. We explored the molecular basis for AA influence on proliferation, signal transduction and apoptosis in two human breast cancer cell lines, MCF-7 and MDA-MB-231. In both cell lines AA inhibited cell growth in a dose-dependent manner, even if MDA-MB-231 was somewhat more growth-inhibited than MCF-7. AA decreased extracellular signal-regulated protein kinase 1/2 phosphorylation level, and positively modulated PPARγ and PPARα expression, with only a slight effect against PPARβ/δ. In addition, AA increased Bak (an apoptosis-regulating protein) expression and reduced procaspase-3 and -9 levels only in MDA-MB-231 cells, thus indicating that the growth inhibitory effect can be correlated with apoptosis induction. In both cell lines the use of a specific antagonist made it possible to establish a relationship between AA growth inhibitory effect and PPARα involvement. AA decreases cell proliferation most likely by inducing apoptosis in MDA-MB-231 cells, while in the MCF-7 cell line the growth inhibitory activity can be attributed to the inhibition of the signal transduction pathway involved in cell proliferation. In both cases, the results here presented suggest PPARα as a possible contributor to the growth inhibitory effect of AA.

Involvement of PPAR gamma and E-cadherin/beta-catenin pathway in the antiproliferative effect of conjugated linoleic acid in MCF-7 cells

Conjugated linoleic acid (CLA) is a naturally occurring fatty acid, which has been shown to exert beneficial effects against breast carcinogenesis. It has been reported that CLA could modulate cellular proliferation and differentiation through the activation of peroxisome proliferator-activated receptors (PPARs). Among different PPAR isotypes, PPAR gamma is involved in growth inhibition of transformed cells. Ligands of PPAR gamma are considered as potential anticancer drugs, so CLA was tested for its ability to induce PPAR gamma expression in MCF-7 breast cancer cells. The effects of CLA and of a specific synthetic PPAR gamma antagonist were evaluated on cell growth as well as on parameters responsible for cell growth regulation. We demonstrated here that CLA stimulated the expression of PPAR gamma to levels up to control and caused PPAR gamma translocation into the nucleus. Furthermore, the overexpression of PPAR gamma positively correlates with the inhibition of cell proliferation and with the modulation of ERK signaling induced by CLA; in all cases the administration of the antagonist reverted CLA effects. The PPAR-signaling pathway is connected with the beta-catenin/E-cadherin pathway, thus we evaluated CLA effects on the expression and cellular distribution of these proteins, which are involved in cell adhesion and responsible for invasive behavior. The treatment with CLA determined the up-regulation and the redistribution of beta-catenin and E-cadherin and the antagonist reverted only the effect on beta-catenin. These studies indicate that CLA regulates PPAR gamma expression by selectively acting as an agonist and may influence cell-cell adhesion and invasiveness of MCF-7 cells.

Timing of Dietary Estrogenic Exposures and Breast Cancer Risk

The same dietary component, such as fat or phytochemicals in plant foods, can have an opposite effect on breast cancer risk if exposed in utero through a pregnant mother or at puberty. Dietary exposures during pregnancy often have similar effects on breast cancer risk among mothers and their female offspring. High fat intake and obesity are illustrative examples: excessive pregnancy weight gain that increases high birth weight is associated with increased breast cancer risk among mothers and daughters. High body weight during childhood is inversely linked to later breast cancer risk. The main reason why the age when dietary exposures occur determines their effect on breast cancer risk likely reflects the extensive programming of the mammary gland during fetal life and subsequent reprogramming at puberty and pregnancy. Programming is a series of epigenetic/transcriptional modifications in gene expression that can be influenced by changes in the hormonal environment induced, for example, by diet. Because epigenetic modifications are inherited by daughter cells, they can persist throughout life if they occur in mammary stem cells or uncommitted mammary myoepithelial or luminal progenitor cells. Our results indicate that the estrogen receptor (ER), mitogen-activated protein kinase (MAPK), and the tumor suppressors BRCA1, p53, and caveolin-1 are among the genes affected by diet-induced alterations in programming/reprogramming. Consequently, mammary gland morphology may be altered in a manner that increases or reduces susceptibility to malignant transformation, including an increase/reduction in cell proliferation, differentiation, and survival, or in the number of terminal end buds (TEBs) or pregnancy-induced mammary epithelial cells (PI-MECs) that are the sites where breast cancer is initiated. Thus, dietary exposures during pregnancy and puberty may play an important role in determining later risk by inducing epigenetic changes that modify vulnerability to breast cancer.

Differential effects of omega-3 and omega-6 Fatty acids on gene expression in breast cancer cells

Essential fatty acids have long been identified as possible oncogenic factors. Existing reports suggest omega-6 (omega-6) essential fatty acids (EFA) as pro-oncogenic and omega-3 (omega-3) EFA as anti-oncogenic factors. The omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), inhibit the growth of human breast cancer cells while the omega-6 fatty acids induces growth of these cells in animal models and cell lines. In order to explore likely mechanisms for the modulation of breast cancer cell growth by omega-3 and omega-6 fatty acids, we examined the effects of arachidonic acid (AA), linoleic acid (LA), EPA and DHA on human breast cancer cell lines using cDNA microarrays and quantitative polymerase chain reaction. MDA-MB-231, MDA-MB-435s, MCF-7 and HCC2218 cell lines were treated with the selected fatty acids for 6 and 24 h. Microarray analysis of gene expression profiles in the breast cancer cells treated with both classes of fatty acids discerned essential differences among the two classes at the earlier time point. The differential effects of omega-3 and omega-6 fatty acids on the breast cancer cells were lessened at the late time point. Data mining and statistical analyses identified genes that were differentially expressed between breast cancer cells treated with omega-3 and omega-6 fatty acids. Ontological investigations have associated those genes to a broad spectrum of biological functions, including cellular nutrition, cell division, cell proliferation, metastasis and transcription factors etc., and thus presented an important pool of biomarkers for the differential effect of omega-3 and omega-6EFAs.