Study of the effects of dietary polyunsaturated fatty acids: Molecular mechanisms involved in intestinal inflammation

The use of “omics” techniques in combination with model systems and molecular tools allows to understand how foods and food components act on metabolic pathways to regulate transcriptional processes. Polyunsaturated fatty acids have distinctive nutritional and metabolic effects because they give rise to lipid mediated products and affect the expression of various genes involved in intestinal inflammation. The present review focuses on the molecular effects of dietary polyunsaturated fatty acids on intestinal inflammatio

Peroxisome Proliferator-Activated Receptor Alpha Target Genes

The peroxisome proliferator-activated receptor alpha (PPARα) is a ligand-activated transcription factor involved in the regulation of a variety of processes, ranging from inflammation and immunity to nutrient metabolism and energy homeostasis. PPARα serves as a molecular target for hypolipidemic fibrates drugs which bind the receptor with high affinity. Furthermore, PPARα binds and is activated by numerous fatty acids and fatty acid-derived compounds. PPARα governs biological processes by altering the expression of a large number of target genes. Accordingly, the specific role of PPARα is directly related to the biological function of its target genes. Here, we present an overview of the involvement of PPARα in lipid metabolism and other pathways through a detailed analysis of the different known or putative PPARα target genes. The emphasis is on gene regulation by PPARα in liver although many of the results likely apply to other organs and tissues as well

Estudio del efecto de los ácidos grasos poliinsaturados de la dieta: Mecanismos moleculares involucrados en la inflamación intestinal

The use of “omics” techniques in combination with model systems and molecular tools allows to understand how foods and food components act on metabolic pathways to regulate transcriptional processes. Polyunsaturated fatty acids have distinctive nutritional and metabolic effects because they give rise to lipid mediated products and affect the expression of various genes involved in intestinal inflammation. The present review focuses on the molecular effects of dietary polyunsaturated fatty acids on intestinal inflammation.El uso de técnicas «omic» en combinación con sistemas modelo y herramientas moleculares nos permiten entender como los alimentos y sus componentes actúan en las rutas metabólicas que regulan los procesos transcripcionales. Los ácidos grasos poliinsaturados tienen efectos nutricionales y metabólicos diferenciadores porque producen una elevación de los productos regulados por lípidos y afectan a la expresión de varios genes involucrados en la inflamación intestinal. La presente revisión se enfoca en los efectos moleculares de los ácidos grasos poliinsaturados de la dieta en la inflamación intestinal

Molecular Characterization of the Onset and Progression of Colitis in Inoculated Interleukin-10 Gene-Deficient Mice: A Role for PPARα

The interleukin-10 gene-deficient (Il10−/−) mouse is a model of human inflammatory bowel disease and Ppara has been identified as one of the key genes involved in regulation of colitis in the bacterially inoculated Il10−/− model. The aims were to (1) characterize colitis onset and progression using a histopathological, transcriptomic, and proteomic approach and (2) investigate links between PPARα and IL10 using gene network analysis. Bacterial inoculation resulted in severe colitis in Il10−/− mice from 10 to 12 weeks of age. Innate and adaptive immune responses showed differences in gene expression relating to colitis severity. Actin cytoskeleton dynamics, innate immunity, and apoptosis-linked gene and protein expression data suggested a delayed remodeling process in 12-week-old Il10−/− mice. Gene expression changes in 12-week-old Il10−/− mice were related to PPARα signaling likely to control colitis, but how PPARα activation might regulate intestinal IL10 production remains to be determined

The effects of dietary eicosapentaenoic acid and arachidonic acid on gene expression changes in a mouse model of human inflammatory bowel diseases : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Nutritional Science at Massey University, Palmerston North, New Zealand

Nutrigenomics studies the genome-wide influence of nutrients to understand the association between nutrition and human health. Studies in animal models and humans have demonstrated that dietary n-3 polyunsaturated fatty acids (PUFA) from fish oil may be beneficial in inflammatory bowel diseases (IBD). This thesis aimed to test the hypothesis that dietary n-3 PUFA eicosapentaenoic acid (EPA) reduced and n-6 PUFA arachidonic acid (AA) increased colitis in the interleukin- 10 gene-deficient (Il10–/–) mouse model of IBD, and that these PUFA altered the intestinal bacteria community during colitis development using genome-wide expression and bacterial profiling. Using a combined transcriptomic and proteomic approach, the time-course study defined the onset and progression of colitis in Il10–/– mice. Histopathology, transcript and protein changes before and after colitis onset involved in innate and adaptive immune responses suggested delayed remodelling processes in colitic Il10–/– mice and 11 weeks of age as suitable time point to study the effects of dietary PUFA on colitis development. Comparing the transcriptome and proteome profiles associated with colon inflammation of mice fed with the AIN-76A or oleic acid (OA) diet showed that OA was an appropriate control for unsaturated fatty acids in multi-omic studies. The PUFA intervention study indicated that dietary EPA-induced lipid oxidation might have a potential anti-inflammatory effect on inflamed colon tissue partially mediated through activation of peroxisome proliferator-activated receptor alpha (PPARα). Unexpectedly, dietary AA decreased the expression of inflammatory and stress colonic genes in Il10–/– mice. Altered intestinal bacteria community observed in Il10–/– mice before and after colitis onset was associated with the lack of IL10 protein led to changes in intestinal metabolic and signalling processes. Interestingly, dietary EPA and AA seemed to change intestinal bacteria profiles during colitis development. The role of PPARα in the colon was further examined in a concluding study which identified vanin1 as a likely new PPARα-target gene which may also be involved in lipid metabolism. These findings using a state-of-the-art approach combining transcriptomics, proteomics and physiology provide a basis for future research on molecular mechanisms underlying the effects of dietary PUFA, and might contribute to the development of fortified foods that improve intestinal health and wellness

Influence of polyunsaturated fatty acids on intestinal barrier function during colitis

Tight junction proteins are important for intestinal homeostasis. They prevent paracellular transport of large molecules and maintain cell polarity. Impaired tight junction function leads to a more permeable intestinal epithelial barrier and therefore potentially increases disease risk. Limited information is available concerning the effects of food components on the intestinal barrier, particularly paracellular permeability and tight junction proteins. In vitro studies with intestinal epithelial cells and in vivo studies using animal models have demonstrated that dietary n-3 and n-6 polyunsaturated fatty acids (PUFAs), particularly n-3, can reduce intestinal inflammation and permeability. PUFAs can induce transcriptional regulators which may act in combination with their target molecules in defense against oxidative stress, thereby maintaining the intestinal barrier function. More studies that take into account the type and/or amount of individual fatty acids are needed in order to elucidate the molecular mechanisms of PUFAs on intestinal epithelial barrier function

Nutrigenomics applied to an animal model of Inflammatory Bowel Diseases: Transcriptomic analysis of the effects of eicosapentaenoic acid-and arachidonic acid-enriched diets

In vivo models of Inflammatory Bowel Diseases (IBD) elucidate important mechanisms of chronic inflammation. Complex intestinal responses to food components create a unique “fingerprint” discriminating health from disease. Five-week-old IL10−/− and C57BL/6J (C57; control) mice were inoculated orally with complex intestinal microflora (CIF) and/or pure cultures of Enterococcus faecalis and E. faecalis (EF) aiming for more consistent inflammation of the intestinal mucosa. Inoculation treatments were compared to non-inoculated IL10−/− and C57 mice, either kept in specific pathogen free (SPF) or conventional conditions (2×5 factorial design). At 12 weeks of age, mice were sacrificed for intestinal histological (HIS) and transcriptomic analysis using limma and Ingenuity Pathway Analysis Software. Colonic HIS was significantly affected (P \u3c 0.05) in inoculated IL10−/− mice and accounted for approximately 60% of total intestinal HIS. Inoculation showed a strong effect on colonic gene expression, with more than 2000 genes differentially expressed in EF·CIF-inoculated IL10−/− mice. Immune response gene expression was altered (P \u3c 0.05) in these mice. The second study investigated the effect of arachidonic (AA) and eicosapentaenoic acid (EPA) on colonic HIS and gene expression to test whether EPA, contrary to AA, diminished intestinal inflammation in EF·CIF IL10−/− mice (2×4 factorial design). AIN-76A (5% corn oil) and AIN-76A (fat-free) +1% corn oil supplemented with either 3.7% oleic acid (OA), AA or EPA were used. IL10−/− mice fed EPA- and AA-enriched diets had at least 40% lower colonic HIS (P \u3c 0.05) than those fed control diets (AIN-76A and OA diets). The expression of immune response and ‘inflammatory disease’ genes (down-regulated: TNF, IL6, S100A8, FGF7, PTGS2; up-regulated: PPAR, MGLL, MYLK, PPSS23, ABCB4 with EPA and/or AA) was affected in IL10−/−mice fed EPA- and AA-enriched diets, compared to those fed AIN-76A diet

Growth-factor dependent expression of the translationally controlled tumour protein TCTP is regulated through the PI3-K/Akt/mTORC1 signalling pathway

Translationally controlled tumour protein TCTP (gene symbol: TPT1) is a highly-conserved, cyto-protective protein implicated in many physiological and disease processes, in particular cancer, where it is associated with poor patient outcomes. To understand the mechanisms underlying the accumulation of high TCTP levels in cancer cells, we studied the signalling pathways that control translation of TCTP mRNA, which contains a 5?-terminal oligopyrimidine tract (5?-TOP). In HT29 colon cancer cells and in HeLa cells, serum increases the expression of TCTP two- and four-fold, respectively, and this is inhibited by rapamycin or mTOR kinase inhibitors. Polysome profiling and mRNA quantification indicate that these effects occur at the level of mRNA translation. Blocking this pathway upstream of mTOR complex 1 (mTORC1) by inhibiting Akt also prevented increases in TCTP levels in both HeLa and HT29 colon cancer cells, whereas knockout of TSC2, a negative regulator of mTORC1, led to derepression of TCTP synthesis under serum starvation. Overexpression of eIF4E enhanced the polysomal association of the TCTP mRNA, although it did not protect its translation from inhibition by rapamycin. Conversely, expression of a constitutively-active mutant of the eIF4E inhibitor 4E-BP1, which is normally inactivated by mTORC1, inhibited of TCTP mRNA translation in HEK293 cells. Our results demonstrate that TCTP mRNA translation is regulated by signalling through the PI3-K/Akt/mTORC1 pathway. This explains why TCTP levels are frequently increased in cancers, since mTORC1 signalling is hyperactive in ~ 80% of tumours