Effects of sodium nitrite reduction, removal or replacement on cured and cooked meat for microbiological growth, food safety, colon ecosystem, and colorectal carcinogenesis in Fischer 344 rats

Epidemiological and experimental evidence indicated that processed meat consumption is associated with colorectal cancer risks. Several studies suggest the involvement of nitrite or nitrate additives via N-nitroso-compound formation (NOCs). Compared to the reference level (120 mg/kg of ham), sodium nitrite removal and reduction (90 mg/kg) similarly decreased preneoplastic lesions in F344 rats, but only reduction had an inhibitory effect on Listeria monocytogenes growth comparable to that obtained using the reference nitrite level and an effective lipid peroxidation control. Among the three nitrite salt alternatives tested, none of them led to a significant gain when compared to the reference level: vegetable stock, due to nitrate presence, was very similar to this reference nitrite level, yeast extract induced a strong luminal peroxidation and no decrease in preneoplastic lesions in rats despite the absence of NOCs, and polyphenol rich extract induced the clearest downward trend on preneoplastic lesions in rats but the concomitant presence of nitrosyl iron in feces. Except the vegetable stock, other alternatives were less efficient than sodium nitrite in reducing L. monocytogenes growth

Are condition factors powerful proxies of energy content in wild tropical tunas?

The "condition" is used as an indicator of fish health and is generally equated with the quantity of energy reserves. Biometric condition factors have been widely used and preferred over costly and time-consuming biochemical condition. Here, we investigated the relevance of four common condition factors based on biometric measurements (Le Cren's index, girth -length index, gonado-somatic index and hepato-somatic index) and of size- and weight -based empirical models to describe the physiological condition of tropical tunas. Biometric condition factors of bigeye (Thunnus obesus), skipjack (Katsuwonus pelamis) and yellowfin (Thunnus albacares) tunas sampled throughout 2013 in the western Indian Ocean region were assessed against benchmark biochemical indices (lipid content, protein content, triacylglycerol:sterol ratio and energy density) estimated in tissues with different physiological functions, i.e. red muscle, white muscle, liver, and gonads. Our findings suggest that tropical tunas do not store lipids in white muscle and that protein content is less variable than lipid content, which largely varies with ontogeny and the seasons according to tissue and species. This variability induced inconsistency between biometric factors, including the empirically adjusted ones, and biochemical indices, with the exception of the gonado-somatic index that fitted well to the composition of the gonads in the three species, and especially in females. (C) 2016 Elsevier Ltd. All rights reserved

Biological and environmental influence on tissue fatty acid compositions in wild tropical tunas

International audienceThis study examined the fatty acid composition of three sympatric tropical tuna species (bigeye Thunnus obesus, yellowfin T. albacares and skipjack tuna Kastuwonus pelamis) sampled in the Western Indian Ocean in 2013. The fatty acid compositions of neutral and polar lipids, respectively involved in energy storage and cell membrane structure, were explored and compared in four tissues (red and white muscles, liver and gonads), according to biological (size, sex and maturity) and environmental (season and area) factors. The liver and the red muscle were the fattest tissues (i.e., higher levels of storage lipids) in all species and polar lipids were the lowest in the white muscle. Species and tissue types explained most differences in fatty acid compositions, while environmental factors had limited effects, except in the hepatic cell membrane where fatty acid composition varied with monsoons. Docosahexaenoic acid (22:6n-3) was the major fatty acid in both polar and neutral lipid fractions, especially in muscles. Eicosapentaenoic acid (20:5n-3) and oleic acid (18:1n-9) were in higher proportion in neutral than in polar lipids. Arachidonic acid (20:4n-6) and 22:6n-3, together with docosapentaenoic acid (22:5n-6) and stearic acid (18:0), showed preferential accumulation in polar lipids. 20:4n-6 was particularly involved in cell membranes of ovary and white muscle. Overall, an important inter-individual variability in fatty acid compositions of structural lipids was found within tissue types despite considering biological factors that are most likely to influence this type of lipids. It suggests that fatty acid profiles are influenced by individual-specific behaviors

A dual model of normal vs isogenic Nrf2-depleted murine epithelial cells to explore oxidative stress involvement

Abstract Cancer-derived cell lines are useful tools for studying cellular metabolism and xenobiotic toxicity, but they are not suitable for modeling the biological effects of food contaminants or natural biomolecules on healthy colonic epithelial cells in a normal genetic context. The toxicological properties of such compounds may rely on their oxidative properties. Therefore, it appears to be necessary to develop a dual-cell model in a normal genetic context that allows to define the importance of oxidative stress in the observed toxicity. Given that the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) is considered to be the master regulator of antioxidant defenses, our aim was to develop a cellular model comparing normal and Nrf2-depleted isogenic cells to qualify oxidative stress–related toxicity. We generated these cells by using the CRISPR/Cas9 technique. Whole-genome sequencing enabled us to confirm that our cell lines were free of cancer-related mutations. We used 4-hydroxy-2-nonenal (HNE), a lipid peroxidation product closely related to oxidative stress, as a model molecule. Here we report significant differences between the two cell lines in glutathione levels, gene regulation, and cell viability after HNE treatment. The results support the ability of our dual-cell model to study the role of oxidative stress in xenobiotic toxicity

Viandes rouges, charcuteries et cancer du côlon : vers une prévention par modification des modes de production et d’élevage

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Study of the colonic epithelial-mesenchymal dialogue through establishment of two activated or not mesenchymal cell lines: Activated and resting ones differentially modulate colonocytes in co-culture

International audienceContinuous and rapid renewal of the colonic epithelium is crucial to resist the plethora of luminal deleterious agents. Subepithelial fibroblasts contribute to this turnover by regulating epithelial proliferation and differentiation. However, when intestinal homeostasis is disturbed, fibroblasts can acquire an activated phenotype and play a major role in the progression of intestinal pathologies. To evaluate the involvement of fibroblasts in the regulation of colonocytes under homeostatic or pathological conditions, we established resting and activated conditionally immortalized fibroblast cell lines (nF and mF) from mouse colonic mucosa. We then studied the epithelial-mesenchymal interactions between activated or resting fibroblasts and the normal mouse colonocytes (Co) using a co-culture model. Both fibroblastic cell lines were characterized by RT-qPCR, western blot and immunofluorescence assay. Our results showed that nF and mF cells were positive for fibroblastic markers such as vimentin and collagen 1, and negative for cytokeratin 18 and E-cadherin, attesting to their fibroblastic type. They also expressed proteins characteristic of the epithelial stem cell niche such as Grem1, CD90 or Wnt5a. Only rare nF fibroblasts were positive for α-SMA, whereas all mF fibroblasts strongly expressed this marker, supporting that mF cells were activated fibroblasts/myofibroblasts. In coculture, nF fibroblasts and Co cells strongly interacted via paracrine exchanges resulting in BMP4 production in nF fibroblasts, activation of BMP signaling in Co colonocytes, and decreased growth of colonocytes. Activated-type mF fibroblasts did not exert the same effects on Co cells, allowing colonocytes free to proliferate. In conclusion, these two colonic fibroblast lines, associated with Co cells in coculture, should allow to better understand the role of mesenchymal cells in the preservation of homeostasis and the development of intestinal pathologies

NMR-based metabolic profiling and discrimination of wild tropical tunas by species, size category, geographic origin, and on-board storage condition

International audienceTunas are among the most traded and valued fish species, and good traceability of tuna products in the world market is needed to protect both consumers and tuna stocks. To that purpose, high-resolution proton nuclear magnetic resonance (1H NMR) spectroscopy combined with multivariate data analysis was used to investigate the molecular components of the aqueous extract of white and red muscles in three species of wild tropical tuna species, namely yellowfin tuna (Thunnus albacares), skipjack tuna (Katsuwonus pelamis) and bigeye tuna (T. obesus). Principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) applied to the processed 1H NMR spectra showed significant separation according to the species and size category (i.e., small tunas 80 cm fork length), the storage conditions on-board the purse-seine vessels (i.e., brine- vs deep-freezing), and the geographical origin (i.e., where the tuna was caught: Mozambique Channel vs western-central Indian Ocean). The major groups of metabolites responsible for differentiation in PLS-DA score plots were the dipeptides (anserine, carnosine) and organic acids (lactate, creatine/phosphocreatine) in the white muscle, and the free amino acids, essential nutrients (choline and its derivatives, phosphatidylethanolamine), dipeptides and organic acids in the red muscle. Our results showed that NMR-based metabolomics is a powerful tool to efficiently discriminate specific profiles among wild tuna species, raw muscle tissues, fish storage conditions and tuna geographical origin

Hepatic Fasting-Induced PPARα Activity Does Not Depend on Essential Fatty Acids

The liver plays a central role in the regulation of fatty acid metabolism, which is highly sensitive to transcriptional responses to nutrients and hormones. Transcription factors involved in this process include nuclear hormone receptors. One such receptor, PPARα, which is highly expressed in the liver and activated by a variety of fatty acids, is a critical regulator of hepatic fatty acid catabolism during fasting. The present study compared the influence of dietary fatty acids and fasting on hepatic PPARα-dependent responses. Pparα−/− male mice and their wild-type controls were fed diets containing different fatty acids for 10 weeks prior to being subjected to fasting or normal feeding. In line with the role of PPARα in sensing dietary fatty acids, changes in chronic dietary fat consumption influenced liver damage during fasting. The changes were particularly marked in mice fed diets lacking essential fatty acids. However, fasting, rather than specific dietary fatty acids, induced acute PPARα activity in the liver. Taken together, the data imply that the potent signalling involved in triggering PPARα activity during fasting does not rely on essential fatty acid-derived ligand