Polyunsaturated fatty acids modify expression of TGF-ß in a co-culture model ultilising human colorectal cells and human peripheral blood mononuclear cells exposed to Lactobacillus gasseri, Escherichia coli and Staphylococcus aureus.

Commensal bacteria and polyunsaturated fatty acids (PUFAs) have both been shown independently to modulate immune responses. This study tested the hypothesis that the different colonic immunomodulatory responses to commensal (Lactobacillus gasseri) and pathogenic bacteria (Escherichia coli and Staphylococcus aureus) may be modified by PUFAs. Experiments used a Transwell system combining the colorectal cell line HT29, or its mucous secreting sub-clone HT29-MTX, with peripheral blood mononuclear cells to analyse immunomodulatory signalling in response to bacteria, with and without prior treatment with arachidonic acid, eicosapentaenoic acid or docosahexaenoic acid. L. gasseri increased transforming growth factor ß1 (TGF-ß1) mRNA and protein secretion in colonic cell lines when compared with controls, an effect that was enhanced by pre-treatment with eicosapentaenoic acid. In contrast, the Gram-negative pathogen E. coli LF82 had no significant effect on TGF-ß1 protein. L. gasseri also increased IL-8 mRNA but not protein while E. coli increased both; although differences between PUFA treatments were detected, none were significantly different to controls. Colonic epithelial cells show different immunomodulatory signalling patterns in response to the commensal L. gasseri compared to E. coli and S. aureus and pre-treatment of these cells with PUFAs can modify responses. Practical applications: We have demonstrated an interaction between dietary PUFAs and epithelial cell response to both commensal and pathogenic bacteria found in the gastrointestinal tract by utilising in vitro co-culture models. The data suggest that n-3 PUFAs may provide some protection against the potentially damaging effects of pathogens. Furthermore, the beneficial effects of combining n-3 PUFAs and the commensal bacteria, and potential probiotic, L. gasseri are illustrated by the increased expression of immunoregulatory TGF-ß1.

Influence of dietary blueberry and broccoli on cecal microbiota activity and colon morphology in mdr1a(-/-) mice, a model of inflammatory bowel diseases.

OBJECTIVE: Enteric microbiota has been shown to be associated with various pathological conditions such as inflammatory bowel disease (IBD). This study aimed to determine the anti-inflammatory colonic effects of blueberries and broccoli in mdr1a(-/-) mice (IBD mouse model) through modification of microbiota composition in the gastrointestinal tract. METHODS: The mdr1a(-/-) mice were fed either a control diet or the control diet supplemented with either 10% blueberry or broccoli for 21 wk. We investigated the influence of these diets on cecal microbiota and organic acids, colon morphology, and bacterial translocation to mesenteric lymph nodes. RESULTS: In comparison to mice fed the control diet, blueberry and broccoli supplementation altered cecum microbiota similarly with the exception of Faecalibacterium prausnitzii, which was found to be significantly lower in broccoli-fed mice. High concentrations of butyric acid and low concentrations of succinic acid were observed in the cecum of broccoli-fed mice. Blueberry- and broccoli-supplemented diets increased colon crypt size and the number of goblet cells per crypt. Only the broccoli-supplemented diet significantly lowered colonic inflammation compared to mice fed the control diet. Translocation of total microbes to mesenteric lymph nodes was lower in broccoli-fed mice compared to blueberry and control diet groups. CONCLUSION: Dietary blueberries and/or broccoli altered the composition and metabolism of the cecal microbiota and colon morphology. Overall, these results warrant further investigation through clinical studies to establish whether the consumption of blueberries and/or broccoli is able to alter the composition and metabolism of large intestine microbiota and promote colon health in humans.

Lycopene bioaccessibility and starch digestibility for extruded snacks enriched with tomato derivatives.

To improve the nutritional value of energy-dense extruded snacks, corn grits were replaced with tomato paste and/or tomato skin powder at ratios of 5, 10, and 20% and extruded to make expanded snack foodlike products. Using a model digestion system, lycopene bioaccessibility and uptake from the snacks into Caco-2 cells were determined. The digestibility of the starch, the main nutrient component of the snacks, was also investigated. While extrusion cooking reduced the lycopene content of the snacks, the proportion of bioaccessible lycopene increased. Lycopene uptake by the Caco-2 cells from the extruded snacks exceeded that of the control in which the lycopene was not extruded, by 5% (p < 0.05). The digestibility of starch in the snacks varied depending on the type of tomato derivative and its concentration. Optimization of the extrusion cooking process and the ingredients can yield functional extruded snack products that contain bioavailable lycopene.

A 28-day repeat dose toxicity study of steroidal glycoalkaloids, alpha-solanine and alpha-chaconine in the Syrian Golden hamster.

Glycoalkaloids alpha-solanine and alpha-chaconine are naturally present toxicants in the potato plant (Solanumtuberosum). Human intake of high doses of glycoalkaloids has led to acute intoxication, in severe cases coma and death. Previous studies have indicated that the ratio of alpha-solanine to alpha-chaconine may determine the degree and nature of the glycoalkaloid toxicity in potatoes, as the toxicity of the two alkaloids act synergistically. The aim of the present study was to investigate whether an altered ratio of alpha-solanine and alpha-chaconine would reduce the toxicity of the glycoalkaloids. The Syrian Golden hamster was given daily doses of alpha-solanine and alpha-chaconine by gavage for 28 days. Doses of up to 33.3 mg total glycoalkaloids/kg body weight were applied in ratios of 1:3.7 and 1:70 (alpha-solanine:alpha-chaconine). Administration of the highest doses of both ratios resulted in distended and fluid filled small intestines and stomach. Animals receiving the ratio with the reduced content of alpha-solanine were less affected compared to those receiving the other ratio. Gene expression profiling experiments were conducted using RNA from epithelial scrapings from the small intestines of the hamsters administered the highest doses of the glycoalkaloid treatments. In general, more differential gene expression was observed in the epithelial scrapings of the hamsters fed the ratio of 1:3.7. Mostly, pathways involved in lipid and energy metabolism were affected by the ratio of 1:3.7.

PI3K/AKT, JNK, and ERK pathways are not crucial for the induction of cholesterol biosynthesis gene transcription in intestinal epithelial cells following treatment with the potato glycoalkaloid alpha-chaconine.

We previously reported that exposure of the intestinal epithelial Caco-2 cell line to noncytotoxic concentrations of potato glycoalkaloids resulted in increased expression of cholesterol biosynthesis genes. Genes involved in mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K)/v-akt murine thymoma viral oncogene homologue (AKT) pathways and their downstream effectors such as Jun, c-Myc, and Fos also were induced. MAPK and PI3K/AKT pathways have been described to regulate the activity of sterol regulatory element binding transcription factors (SREBPs) and consequently the expression of cholesterol biosynthesis genes. In this study, to understand the mechanism of induction of cholesterol biosynthesis upon alpha-chaconine treatment, its effect on SREBP-2 protein levels was investigated. We also examined whether MAPK and PI3K/AKT pathways are required for the observed induction of these genes following exposure of cells to alpha-chaconine. Differentiated Caco-2 cells were pretreated with LY294002 (PI3K inhibitor), PD98059 (MEK1 inhibitor), or SP600125 (JNK inhibitor) or a combination of all inhibitors for 24 h prior to coincubation with 10 microM alpha-chaconine for 6 h. Significant increases in precursor and mature protein levels of SREBP-2 were observed after alpha-chaconine exposure. We also observed that alpha-chaconine treatment resulted in significant phosphorylation of AKT, extracellular signal related protein kinase (ERK), and c-jun N terminal protein kinase (JNK) but not that of p38. In general, the kinase inhibitor experiments revealed that phosphorylation of kinases of PI3K/AKT, ERK, and JNK pathways was not crucial for the induction of expression of cholesterol biosynthesis genes, with the exception of SC5DL. The transcription of this later gene was reduced when all three pathways were inhibited. On the basis of these results, it can be postulated that other mechanisms, which may be independent of the MAPK and PI3K/AKT pathways, including possibly post-translational activation of SREBP-2, may be more pivotal for the induction of cholesterol biosynthesis genes following exposure of intestinal cells to alpha-chaconine.

Differential gene expression in intestinal epithelial cells induced by single and mixtures of potato glycoalkaloids.

Alpha-chaconine and alpha-solanine are naturally occurring toxins. They account for 95% of the total glycoalkaloids in potatoes ( Solanum tuberosum L.). At high levels, these glycoalkaloids may be toxic to humans, mainly by disrupting cell membranes of the gastrointestinal tract. Gene-profiling experiments were performed, whereby Caco-2 cells were exposed to equivalent concentrations (10 microM) of pure alpha-chaconine or alpha-solanine or glycoalkaloid mixtures of varying alpha-chaconine/alpha-solanine ratios for 6 h. In addition, lactate dehydrogenase, cell cycle, and apoptosis analyses experiments were also conducted to further elucidate the effects of glycoalkaloids. The main aims of the study were to determine the transcriptional effects of these glycoalkaloid treatments on Caco-2 cells and to investigate DNA microarray utility in conjunction with conventional toxicology in screening for potential toxicities and their severity. Gene expression and pathway analyses identified changes related to cholesterol biosynthesis, growth signaling, lipid and amino acid metabolism, mitogen-activated protein kinase (MAPK) and NF-kappaB cascades, cell cycle, and cell death/apoptosis. To varying extents, DNA microarrays discriminated the severity of the effect among the different glycoalkaloid treatments.

Induction of the cholesterol biosynthesis pathway in differentiated Caco-2 cells by the potato glycoalkaloid alpha-chaconine.

Glycoalkaloids are naturally occurring toxins in potatoes, which at high levels may induce toxic effects in humans, mainly on the gastrointestinal tract by cell membrane disruption. In order to better understand the molecular mechanisms underlying glycoalkaloid toxicity, we examined the effects of alpha-chaconine on gene expression in the Caco-2 intestinal epithelial cell line using DNA microarrays. Caco-2 cells were exposed for 6h to 10 microM alpha-chaconine in three independent experiments (randomized block design). The most prominent finding from our gene expression and pathway analyses was the upregulation of expression of several genes involved in cholesterol biosynthesis. This to some extent is in line with the literature-described mechanism of cell membrane disruption by glycoalkaloids. In addition, various growth factor signaling pathways were found to be significantly upregulated. This study is useful in understanding the mechanism(s) of alpha-chaconine toxicity, which may be extended to other potato glycoalkaloids more generally.