Joanne R. Lupton

We have demonstrated that diets containing fish oil and pectin (FO/P) reduce colon tumor incidence relative to control (corn oil and cellulose [CO/C]) in part by inducing apoptosis of DNA-damaged colon cells. Relative to FO/P, CO/C promotes colonocyte expression of the antiapoptotic modulator, Bcl-2, and Bcl-2 promoter methylation is altered in colon cancer. To determine if FO/P, compared with CO/C, limits Bcl-2 expression by enhancing promoter methylation in colon tumors, we examined Bcl-2 promoter methylation, mRNA levels, colonocyte apoptosis and colon tumor incidence in azoxymethane (AOM)-injected rats. Rats were provided diets containing FO/P or CO/C, and were terminated 16 and 34 weeks after AOM injection. DNA isolated from paraformaldehyde-fixed colon tumors and uninvolved tissue was bisulfite modified and amplified by quantitative reverese transcriptase-polymerase chain reaction to assess DNA methylation in Bcl-2 cytosine-guanosine islands. FO/P increased Bcl-2 promoter methylation (P = 0.009) in tumor tissues and colonocyte apoptosis (P = 0.020) relative to CO/C. An inverse correlation between Bcl-2 DNA methylation and Bcl-2 mRNA levels was observed in the tumors. We conclude that dietary FO/P promotes apoptosis in part by enhancing Bcl-2 promoter methylation. These Bcl-2 promoter methylation responses, measured in vivo, contribute to our understanding of the mechanisms involved in chemoprevention of colon cancer by diets containing FO/P.

We have demonstrated that fish oil- and pectin-containing (FO/P) diets protect against colon cancer compared with corn oil and cellulose (CO/C) by up

Background The effects of dietary polyunsaturated (PUFAs) and monounsaturated fatty acids (MUFAs) on intestinal cytokinetics within the context of colon cancer initiation and progression have been extensively studied. n-3 PUFAs have received the most attention due to their potential protective role. However, further investigation of the epigenetic perturbations caused by fatty acids in the context of colon cancer development is needed. Methods We used DNA microarrays to identify discriminative gene signatures (gene combinations) for the purpose of classifying n-3 PUFA-fed, carcinogen-injected, Sprague–Dawley rats at the initiation and progression stages. Animals were assigned to three dietary treatments differing only in the type of fat (corn oil/n-6 PUFA, fish oil/n-3 PUFA, or olive oil/n-9 monounsaturated fatty acid). Results The effects of diet on colonic mucosal gene expression signatures during tumor initiation and progression were subsequently compared (12 h and 10 weeks after azoxymethane injection). Microarray analysis revealed that the number of differentially expressed (DE) genes in each of the three diet comparisons increased with the progression of colon cancer. Each dietary lipid source exhibited its own unique transcriptional profile, as assessed by linear discriminant analysis. Applying this novel approach, we identified the single genes and the two- to three-gene combinations that best distinguished the dietary treatment groups. For the chemoprotective (fish oil) diet, mediators of stem cell homeostasis, e.g., ephrin B1 and bone morphogenic protein 4, were the top-performing gene classifiers. Conclusions These results suggest that dietary chemoprotective n-3 PUFA impact genes that regulate the colon stem cell niche and tumor evolution.

On November 4, 2008, the 30th session of the Codex Committee on nutrition and foods for special dietary uses (CCNFSDU) was held in South Africa and here a definition of dietary fibre was agreed upon. This was an important major accomplishment, and the result of many individuals, organisations and countries working towards a collaborative effort over a ten year time period. Although many aspects of what can be called ‘dietary fibre’ were resolved, still the application of this definition requires further discussion. This paper notes the major issues that were resolved for the definition of dietary fibre and discusses three issues in need of resolution going forward: (1) the footnote that countries can decide whether or not they accept the degree of polymerisation 3-9 in the definition or not; (2) what will be the process to certify that a fibre added to the food supply rather than intrinsic to foods can be called ‘fibre’? To do this will require both agreed upon endpoints (e.g. increases faecal bulk, lowers blood cholesterol, attenuates glycemic response) and agreed upon standards for the types of studies that will be necessary. (3) What affect does the new definition have on food labels and analytical methods? Although none of these issues is simple, resolution of them will move the entire dietary fibre research agenda forward as it will inform government regulatory agencies, companies with fibre products, academics desiring to do research on dietary fibre, non profit organisations which promote fibre, and consumers who need to know the science behind the recommendations.

The goal of the Smart Choices Program (SCP) is to provide a simple front-of-the-package icon system to direct consumers to smarter food choices in the supermarket, which will eventually lead to more balanced diets and to more beneficial foods as food manufacturers renovate products to meet the nutrition criteria for carrying the icon. The SCP was developed by a coalition of scientists and nutrition educators, experts with experience with dietary guidelines, public health organizations, and food manufacturers in response to consumer confusion over multiple front-of-the-package systems based on different criteria. Representatives from different government organizations acted as observers. The process of developing the program was facilitated by the nonprofit Keystone Center, an organization that develops consensus solutions to complex health and social policy changes. The nutrition criteria for receiving the SCP icon are specific for product category by indicating “smarter” products within that category. A calorie indicator noting calories per serving and servings per package accompanies the SCP icon to remind consumers that calories do count, even for smarter food choices. For a product to qualify, it first has to be below the threshold for “nutrients to limit” and then (in most cases) it must be above the threshold for one or more nutrients or food groups to encourage. The criteria are based on the 2005 Dietary Guidelines and other consensus science and are transparent and available on the SCP website. This article describes the nutrition criteria and rationales for their selection.

Background: Developing and evaluating new technology that enables researchers to recover gene-expression levels of colonic cells from fecal samples could be key to a non-invasive screening tool for early detection of colon cancer. The current study, to the best of our knowledge, is the first to investigate and report the reproducibility of fecal microarray data. Using the intraclass correlation coefficient (ICC) as a measure of reproducibility and the preliminary analysis of fecal and mucosal data, we assessed the reliability of mixture density estimation and the reproducibility of fecal microarray data. Using Monte Carlo-based methods, we explored whether ICC values should be modeled as a beta-mixture or transformed first and fitted with a normal-mixture. We used outcomes from bootstrapped goodness-of-fit tests to determine which approach is less sensitive toward potential violation of distributional assumptions.Results: The graphical examination of both the distributions of ICC and probit-transformed ICC (PT-ICC) clearly shows that there are two components in the distributions. For ICC measurements, which are between 0 and 1, the practice in literature has been to assume that the data points are from a beta-mixture distribution. Nevertheless, in our study we show that the use of a normal-mixture modeling approach on PT-ICC could provide superior performance.Conclusions: When modeling ICC values of gene expression levels, using mixture of normals in the probit-transformed (PT) scale is less sensitive toward model mis-specification than using mixture of betas. We show that a biased conclusion could be made if we follow the traditional approach and model the two sets of ICC values using the mixture of betas directly. The problematic estimation arises from the sensitivity of beta-mixtures toward model mis-specification, particularly when there are observations in the neighborhood of the the boundary points, 0 or 1. Since beta-mixture modeling is commonly used in approximating the distribution of measurements between 0 and 1, our findings have important implications beyond the findings of the current study. By using the normal-mixture approach on PT-ICC, we observed the quality of reproducible genes in fecal array data to be comparable to those in mucosal arrays.

There has been significant public debate about the susceptibility of research to biases of various kinds. The dialogue has extended to the peer-reviewed literature, scientific conferences, the mass media, government advisory bodies, and beyond. Although biases can come from myriad sources, the overwhelming focus of the discussion, to date, has been on industry-funded science. Given the critical role that the industry has played and will continue to play in the research process, the International Life Sciences Institute North America Working Group on Guiding Principles has, in this article, set out proposed conflict-of-interest guidelines regarding industry funding for protecting the integrity and credibility of the scientific record, particularly with respect to health, nutrition, and food-safety science. Eight principles are enumerated, specifying ground rules for industry-sponsored research. The article, which issues a challenge to the broader scientific community to address all bias issues, is only a first step; the document is intended to be dynamic, prompting ongoing discussion and refinement