Risk assessment of substances used in food supplements: the example of the botanical Gymnema sylvestre.

Botanicals and preparations derived from these are among the substances frequently added to foods and food supplements, yet the safety of many botanicals has not been systematically assessed. In the context of the EU-FORA fellowship programme, the fellow performed an assessment on the safety of the botanical Gymnema sylvestre, in accordance with EFSA's guidance on the assessment of safety of botanicals. Although preparations of G. sylvestre are marketed as food supplements, they may appeal to people who are suffering from metabolic syndrome and/or diabetes mellitus. A scientific literature search was carried out using PubMed/MEDLINE and EMBASE electronic databases. Experience was gained by the fellow in systematic data extraction from scientific publications, structuring of the data and evaluating toxicological key parameters, outcomes of clinical significance, pharmacokinetic and pharmacodynamic interactions, uncertainties and methodological shortcomings of studies. Limited evidence from toxicological in vivo studies and human clinical studies suggested lack of relevant adverse effects of this botanical. However, human studies provided some indications that certain Gymnema extracts may enhance the glucose-lowering effects of certain antidiabetic drugs. Considering the uncertainties for the composition of different Gymnema preparations, potential herb-drug interactions and the indications of glucose lowering or hypoglycaemic effects, the use of Gymnema-based food supplements in combination with authorised antidiabetic drugs may be associated with risks. The procedures learned for the safety evaluation of Gymnema may be similarly applied by the fellow for the risk assessment of other substances with nutritional or physiological effect added to foods and food supplements. Furthermore, apart from learning by conducting exercises in risk assessment, the fellow was able to develop other skills (e.g. communication skills), diversify his competencies and expand his network of scientific connections for future collaborations in the field of nutritional risk assessment.

Characterization of aluminum, aluminum oxide and titanium dioxide nanomaterials using a combination of methods for particle surface and size analysis.

The application of appropriate analytical techniques is essential for nanomaterial (NM) characterization. In this study, we compared different analytical techniques for NM analysis. Regarding possible adverse health effects, ionic and particulate NM effects have to be taken into account. As NMs behave quite differently in physiological media, special attention was paid to techniques which are able to determine the biosolubility and complexation behavior of NMs. Representative NMs of similar size were selected: aluminum (Al0) and aluminum oxide (Al2O3), to compare the behavior of metal and metal oxides. In addition, titanium dioxide (TiO2) was investigated. Characterization techniques such as dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA) were evaluated with respect to their suitability for fast characterization of nanoparticle dispersions regarding a particle's hydrodynamic diameter and size distribution. By application of inductively coupled plasma mass spectrometry in the single particle mode (SP-ICP-MS), individual nanoparticles were quantified and characterized regarding their size. SP-ICP-MS measurements were correlated with the information gained using other characterization techniques, i.e. transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). The particle surface as an important descriptor of NMs was analyzed by X-ray diffraction (XRD). NM impurities and their co-localization with biomolecules were determined by ion beam microscopy (IBM) and confocal Raman microscopy (CRM). We conclude advantages and disadvantages of the different techniques applied and suggest options for their complementation. Thus, this paper may serve as a practical guide to particle characterization techniques.

The influence of the SULT1A status - wild-type, knockout or humanized - on the DNA adduct formation by methyleugenol in extrahepatic tissues of mice.

Methyleugenol, present in herbs and spices, has demonstrated carcinogenic activity in the liver and, to a lesser extent, in extrahepatic tissues of rats and mice. It forms DNA adducts after hydroxylation and sulphation. As previously reported, hepatic DNA adduct formation by methyleugenol in mice is strongly affected by their sulphotransferase (SULT) 1A status. Now, we analysed the adduct formation in extrahepatic tissues. The time course of the adduct levels was determined in transgenic (tg) mice, expressing human SULT1A1/2, after oral administration of methyleugenol (50 mg per kg body mass). Nearly maximal adduct levels were observed 6 h after treatment. They followed the order: liver > caecum > kidney > colon > stomach > small intestine > lung > spleen. We then selected liver, caecum, kidney and stomach for the main study, in which four mouse lines [wild-type (wt), Sult1a1-knockout (ko), tg, and humanized (ko-tg)] were treated with methyleugenol at varying dose levels. In the liver, caecum and kidney, adduct formation was nearly completely dependent on the expression of SULT1A enzymes. In the liver, human SULT1A1/2 led to higher adduct levels than mouse Sult1a1, and the effects of both enzymes were approximately additive. In the caecum, human SULT1A1/2 and mouse Sult1a1 were nearly equally effective, again with additive effects in tg mice. In the kidney, only human SULT1A1/2 played a role: no adducts were detected in wt and ko mice even at the highest dose tested and the adduct levels were similar in tg and ko-tg mice. In the stomach, adduct formation was unaffected by the SULT1A status. IN CONCLUSION: (i) the SULT1A enzymes only affected adduct formation in those tissues in which they are highly expressed (mouse Sult1a1 in the liver and caecum, but not in the kidney and stomach; human SULT1A1/2 in the liver, caecum and kidney, not in the stomach of tg mice and humans), indicating a dominating role of local bioactivation; (ii) the additivity of the effects of both enzymes in the liver and caecum implies that the enzyme level was limiting in the adduct formation; (iii) SULT1A forms dominated the activation of methyleugenol in several tissues, but non-Sult1a1 forms or SULT-independent mechanisms were involved in its adduct formation in the stomach.

Application of omics data in regulatory toxicology: report of an international BfR expert workshop.

Advances in omics techniques and molecular toxicology are necessary to provide new perspectives for regulatory toxicology. By the application of modern molecular techniques, more mechanistic information should be gained to support standard toxicity studies and to contribute to a reduction and refinement of animal experiments required for certain regulatory purposes. The relevance and applicability of data obtained by omics methods to regulatory purposes such as grouping of chemicals, mode of action analysis or classification and labelling needs further improvement, defined validation and cautious expert judgment. Based on the results of an international expert workshop organized 2014 by the Federal Institute for Risk Assessment in Berlin, this paper is aimed to provide a critical overview of the regulatory relevance and reliability of omics methods, basic requirements on data quality and validation, as well as regulatory criteria to decide which effects observed by omics methods should be considered adverse or non-adverse. As a way forward, it was concluded that the inclusion of omics data can facilitate a more flexible approach for regulatory risk assessment and may help to reduce or refine animal testing.

Dose dependent molecular effects of acrylamide and glycidamide in human cancer cell lines and human primary hepatocytes.

Recently published studies suggest a weak positive correlation between increased dietary acrylamide intake and the increased risk of endometrial and ovarian cancer. However, risk assessment of acrylamide remains difficult because the carcinogenic mechanisms are still unknown and in particular the molecular effects of low level acrylamide exposure as seen by dietary intake are not well understood. Therefore, we analyzed in ovarian and endometrial cancer cell lines as well as in primary hepatocytes the expression of genes involved in cancer development and xenobiotic metabolism after high and low dose exposure (1-0.001mM) of acrylamide and its metabolite glycidamide. In conclusion our in vitro results demonstrate that exposure to high doses of glycidamide/acrylamide - exceeding the dietary exposure of the general population by far - can induce genes with growth promoting potential like the oncogene cMYC and genes involved in the MAPK pathway. However, low-dose exposure seems to activate primarily genes involved in the elimination of the toxicant.

[Dietary isolated isoflavone supplements for peri- and postmenopausal women: risks and questionable benefits]. / Risiken und fraglicher Nutzen von Nahrungsergänzungsmitteln mit isolierten Isoflavonen für Frauen in und nach der Menopause.

Isolated isoflavones are frequently offered as dietary supplements for the alleviation of peri- and postmenopausal complaints. These mainly soy-based secondary plant compounds are marketed with the claim of having numerous beneficial effects such as protection against breast cancer, osteoporosis, and cardiovascular diseases. Currently, there is no conclusive evidence for most of these health impacts. In addition, there is a controversial ongoing discussion about the safety of these products. After a long-term intake of high isoflavone doses, adverse effects on the breast tissue, the endometrium, and the thyroid, the last one especially under iodine-deficient conditions, cannot be excluded. Owing to their estrogenic effects, isoflavones may promote the growth of estrogen-sensitive malignant cells. The risk assessment of isoflavones is especially focused on peri- and postmenopausal women because they are the target group for dietary supplements based on isolated isoflavones and have, anyway, a higher risk for breast cancer. Since long-term treatment with isolated isoflavones, especially at high doses, is considered critical, we recommend that patients consume isoflavone-based supplements only after advice and under medical supervision.

Analytical approaches for MCPD esters and glycidyl esters in food and biological samples: a review and future perspectives.

Esters of 2 - and 3-monochloropropane-1,2-diol (MCPD) and glycidol esters are important contaminants of processed edible oils used as foods or food ingredients. This review describes the occurrence and analysis of MCPD esters and glycidol esters in vegetable oils and some other foods. The focus is on the analytical methods based on both direct and indirect methods. Methods of analysis applied to oils and lipid extracts of foods have been based on transesterification to free MCPD and determination by gas chromatography-mass spectrometry (indirect methods) and by high-performance liquid chromatography-mass spectrometry (direct methods). The evolution and performance of the different methods is described and their advantages and disadvantages are discussed. The application of direct and indirect methods to the analysis of foods and to research studies is described. The metabolism and fate of MCPD esters and glycidol esters in biological systems and the methods used to study these in body tissues studies are described. A clear understanding of the chemistry of the methods is important when choosing those suitable for the desired application, and will contribute to the mitigation of these contaminants.

Meeting report: international workshop on endocrine disruptors: exposure and potential impact on consumers health.

The French Agency for Food, Environmental and Occupational Health and Safety (Anses) hosted a two-day workshop on Endocrine Disruptors: Exposure and Potential Impact on Consumers Health, bringing together participants from international organizations, academia, research institutes and from German, Swedish, Danish and French governmental agencies. The main objective of the workshop was to share knowledge and experiences on endocrine disruptors (ED) exposure and potential impact on consumers' health, to identify current risk assessment practices and knowledge gaps and issue recommendations on research needs and future collaboration. The following topics were reviewed: (1) Definition of ED, (2) endpoints to be considered for Risk assessment (RA) of ED, (3) non-monotonic dose response curves, (4) studies to be considered for RA (regulatory versus academic studies), (5) point of departure and uncertainty factors, (6) exposure assessment, (7) regulatory issues related to ED. The opinions expressed during this workshop reflect day-to-day experiences from scientists, regulators, researchers, and others from many different countries in the fields of risk assessment, and were regarded by the attendees as an important basis for further discussions. Accordingly, the participants underlined the need for more exchange in the future to share experiences and improve the methodology related to risk assessment for endocrine disrupters.

Perfluorooctanoic acid affects the activity of the hepatocyte nuclear factor 4 alpha (HNF4α).

Perfluorooctanoic acid (PFOA) is an industrial chemical that is a global contaminant of water, soil and foodstuff. Numerous animal studies have revealed that PFOA has embryotoxic and hepatotoxic effects in rodents. On the molecular level, the adverse effects of PFOA have been correlated with the PFOA-mediated activation of peroxisome proliferator-activated receptor alpha (PPARα), however, the toxicological relevance of this mode of action for humans is under debate. In this study, a proteomic approach was chosen to screen for molecular targets affected by PFOA in human liver cells. Treatment of the human liver cell line HepG2 with 25 µM PFOA resulted in 51 deregulated proteins in a two-dimensional gel experiment, and 36 of these proteins were identified by mass spectrometry. Network analysis revealed that these proteins are primarily involved in lipid metabolism and cancer. The hepatocyte nuclear factor 4α (HNF4α), but not PPARα, was the key regulator of the network. Indeed, subsequent western blot analysis revealed that the amount of HNF4α as well as of its target HNF1α was downregulated in PFOA-treated HepG2 cells. Moreover, PFOA was shown to inhibit HNF4α-dependent gene transcription. Thus, this study provides first experimental evidence that HNF4α is negatively affected by PFOA.

In vitro - in vivo correlation of gene expression alterations induced by liver carcinogens.

Although cultivated hepatocytes are widely used in the studies of drug metabolism, their application in toxicogenomics is considered as problematic, because previous studies have reported only little overlap between chemically induced gene expression alterations in liver in vivo and in cultivated hepatocytes. Here, we identified 22 genes that were altered in livers of rats after oral administration of the liver carcinogens aflatoxin B1 (AB1), 2-nitrofluorene (2-NF), methapyrilene (MP) or piperonyl-butoxide (PBO). The functions of the 22 genes have been classified into two groups. Genes related to stress response, DNA repair or metabolism and genes associated with cell proliferation, respectively. Next, rat hepatocyte sandwich cultures were exposed to AB1, 2-NF, MP or PBO for 24h and expression of the above mentioned genes was determined by RT-qPCR. Significant correlations between the degree of gene expression alterations in vivo and in vitro were obtained for the stress, DNA repair and metabolism associated genes at concentrations covering a range from cytotoxic concentrations to non-toxic/in vivo relevant concentrations. In contrast to the stress associated genes, no significant in vivo/in vitro correlation was obtained for the genes associated with cell proliferation. To understand the reason of this discrepancy, we compared replacement proliferation in vivo and in vitro. While hepatocytes in vivo, killed after administration of hepatotoxic compounds, are rapidly replaced by proliferating surviving cells, in vitro no replacement proliferation as evidenced by BrdU incorporation was observed after washing out hepatotoxic concentrations of MP. In conclusion, there is a good correlation between gene expression alterations induced by liver carcinogens in vivo and in cultivated hepatocytes. However, it should be considered that cultivated primary hepatocytes do not show replacement proliferation explaining the in vivo/in vitro discrepancy concerning proliferation associated genes.

[Current aspects in risk assessment of allergen traces in foodstuffs]. / Aktuelle Aspekte zur Risikobewertung von Allergenspuren in Lebensmitteln.

In contrast to usual ingredients in processed packaged foodstuffs, there are no suitable and binding regulations for the labeling of unintentional allergen traces in these foods as yet. This situation is unsatisfactory in regard to the fact that even traces of undeclared "hidden" allergens can constitute a considerable health risk for food allergic consumers. Furthermore, the unintentional cross-contact (cross-contamination) of allergens is also an issue in regard to food manufacturer product liability and due diligence. Therefore, stakeholders consider imperative need for the scientific determination of maximum tolerable levels of allergen traces in order to establish thresholds for legally binding food labeling. In addition to conventional toxicological risk assessments, the risk assessment of allergen traces that would be necessary in this context nowadays also incorporates modern approaches such as benchmark procedures and probabilistic modeling and methods. The scientific debate concerning the establishment of safe threshold levels continues, and a consensus must still be reached.

[Assessment of allergenicity of genetically modified food crops]. / Allergenitätsbewertung von Lebensmitteln aus gentechnisch veränderten Pflanzen.

The placing on the European Union's market of genetically modified crops requires authorization by the European Commission which is based on the proof that the derived foods are as safe as their conventional counterparts. The assessment of potential allergenicity is part of the necessary investigations recommended in the updated Guidance Document of the Scientific Panel on Genetically Modified Organisms (GMO) of the European Food Safety Authority (EFSA), which is based on internationally agreed recommendations. All genetically modified crops which so far have been authorized in the European Union were evaluated by the EFSA GMO Panel which considered it unlikely that their overall allergenicity has been altered.

Immunological detection of osteocalcin in meat and bone meal: a novel heat stable marker for the investigation of illegal feed adulteration.

A sandwich ELISA was developed for the detection of bovine meat and bone meal (BMBM) in feed, based on polyclonal rabbit antibodies raised against the synthetic N-terminal amino acid sequence 1-9 (YLDHWLGAP) of bovine osteocalcin. To set up a sandwich ELISA pair, a commercial mouse monoclonal capture antibody binding to a highly conserved epitope in the mid-fragment of the peptide was employed. It is shown that the bone marker osteocalcin is immunologically well detectable in BMBM extracts obtained by a simple EDTA-based procedure even in a sample heated up to 145°C. Furthermore, a genus-specific restriction of the major specificity to cattle and horse was possible. The observed bi-specificity is consistent with theoretical predictions. The assay sensitivity with bovine osteocalcin of 1 ng was sufficient to enable the detection of 0.1% BMBM in compound plant feed or fish meal, for which no cross reaction was observed. In general the quantification of osteocalcin in extracts is possible using a standard curve procedure with pure bovine osteocalcin.

Glutathione S-transferase expression and isoenzyme composition during cell differentiation of Caco-2 cells.

The human colon adenocarcinoma cell line Caco-2 is frequently used to study human intestinal metabolism and transport of xenobiotica. Previous studies have shown that both Caco-2 cells and human colon cells constitutively express the multigene family of detoxifying enzymes glutathione S-transferases (GSTs), particularly GST alpha and GST pi. GSTs may play a fundamental role in the molecular interplay between phase I, II enzymes and ABC-transporters. The gut fermentation product, butyrate, can modulate the potential for detoxification. The aim of this study was to investigate the basal expression of further cytosolic GSTs in Caco-2 cells during cell differentiation. In addition, a comparison was made with expression levels in MCF-7 and HepG2, two other cell types with barrier functions. Finally, the butyrate-mediated modulation of gene and protein expression was determined by real time PCR and western blot analysis. In Caco-2, gene and protein expression levels of GST alpha increased during cell differentiation. High levels of GSTO1 and GSTP1 were constantly expressed. No expression of GSTM5 and GSTT1 was detected. HepG2 expressed GSTO1 and MCF-7 GSTZ1 most intensively. No expression of GSTA5, GSTM5, or GSTP1 was detected in either cell. Incubation of Caco-2 cells with butyrate (5 mM) significantly induced GSTA1 and GSTM2 in proliferating Caco-2 cells. In differentiated cells, butyrate tended to increase GSTO1 and GSTP1. The results of this study show that a differentiation-dependent expression of GSTs in Caco-2 cells may reflect the in vivo situation and indicate the potential of butyrate to modify intestinal metabolism. GSTA1-A4 have been identified as good markers for cell differentiation. The Caco-2 cell line is a useful model for assessing the potential of food-related substances to modulate the GST expression pattern.

Effect-based and chemical analysis of polycyclic aromatic hydrocarbons in smoked meat: a practical food-monitoring approach.

Polycyclic aromatic hydrocarbons (PAHs), which are generated by heat treatment and smoke curing of meat, pose a risk to human health. At present, the determination of these unwanted contaminants requires costly, time-consuming chemical analysis of smoked meat. An alternative is effect-directed high-throughput bioassays, which could also be used as a pre-screening method. The authors recently adapted the in vitro chemical-activated luciferase gene expression (CALUX) assay as a rapid, sensitive, and inexpensive screening technique for compounds such as dioxins, polychlorinated biphenyls, and PAHs. The aim of the present study was to apply a practical approach under realistic conditions. Custom-made meat samples produced under defined conditions with different PAH levels were analysed using this bioassay and gas chromatography-mass spectrometry (GC/MS) to determine the influence of different smoking conditions (temperature and duration) on PAH levels. It was found that cold smoking for up to 6 h did not result in strong PAH contamination, whereas hot (65 degrees C) and longer smoking times caused a considerable increase in both the bioassay response and the levels of 31 individually determined PAHs. The response in the effect-based bioassay was in good agreement with the values of chemical analysis. The bioassay made it possible to determine accurately the degree of contamination. The results show that this assay is suitable for high-throughput screening for unknown levels of toxicologically relevant PAHs in meat samples and is sensitive enough to differentiate between different PAH levels generated under various smoking conditions. Effect-based screening techniques, therefore, provide a new instrument for official food monitoring.

Detection of estrogenically active substances in diets for sows by an in vitro bioassay supported by HPLC analysis.

There is considerable evidence that exogenous estrogenic compounds can have adverse effects on fertility. The main reason cited in literature for hyperestrogenism in pigs is contamination of feedstuffs by the mycotoxin zearalenone (Boehm, 2000), but further estrogenically active substances might also be involved in cases of impaired fertility with symptoms like enlarged, red-coloured vulvae in piglets, irregular estrus cycles and anestrus of sows (Bennetts et al., 1946; Drane et al., 1981). It is well known that soy used in diets for pigs as a main protein source contains phytoestrogens. Amongst them, isoflavones like genistein and daidzein are of particular interest. Aim of this study was to optimize and use an established bioassay (Kluczka, 2003) to determine estrogenic activity in feedstuffs for pigs related to isoflavones and further substances with estrogenic potential. This bioassay is a reporter gene assay based on stably transfected human embryonal kidney cells (HEK 293) that contains either alpha or beta estrogen receptor (alpha- or beta-HEK). The estrogenic activity measured in the luciferase assay was expressed in estradiol-equivalents (EEQ) and the results were compared with the isoflavone content (genistein, daidzein) obtained by chemical analysis using high performance liquid chromatography-Ultraviolet (HPLC-UV). Mean estrogenic activity in diets fed to sows in herds with altered fertility was 275.8 microg EEQ/kg feed in alpha-HEK cells and 295.0 microg EEQ/kg feed in beta-HEK cells. Feedstuffs from herds without any altered fertility showed an average estrogenic activity of 204.9 microg EEQ/kg feed in alpha-HEK and 213.3 microg EEQ/kg feed in beta-HEK. The estrogenic activity was strongly related to the concentration of the isoflavones (alpha-HEK, r(2)=0.9488; beta-HEK, r(2)=0.9427). Clinically relevant zearalenone concentrations (>50-150 microg/kg feed) displayed estrogenic effects in the bioassay that did not differ significantly from those caused by high isoflavone concentration because of the use of soy as protein source.

Molecular and cellular effects of cis-9, trans-11-conjugated linoleic acid in enterocytes: effects on proliferation, differentiation, and gene expression.

It has been hypothesized that dietary conjugated linoleic acids (CLA) may inhibit colon tumorigenesis. The aim of our study was to investigate the cellular and molecular effects of cis-9 (9Z), trans-11 (11E)-CLA on the proliferation, differentiation, interaction with peroxisome proliferator-activated receptors (PPARs), and expression of genes relevant in the APC-beta-catenin-TCF4 signalling pathway in human HT-29 and Caco-2 colon cells. We found that 9Z,11E-CLA inhibited the proliferation of HT-29 and Caco-2 cells. Trans-vaccenic acid (VA) showed no antiproliferative effects at all. We determined that 9Z,11E-CLA induced cell differentiation as measured by intestinal alkaline phosphatase (IAP) enzyme activity in Caco-2 cells, mRNA expression of IAP, and activation of a 5' flanking region of IAP. The 9Z,11E-CLA activated human PPARdelta as measured in a reporter gene assay. Treatment of HT29 cells in the poliferation phase with 9Z,11E-CLA repressed mRNA-expression of proliferation genes such as c-myc, cyclin D1 and c-jun in a concentration dependent manner. The promoter activities of c-myc and AP1 were also inhibited after incubation with 9Z,11E-CLA. beta-Catenin mRNA and protein expression was also repressed by the treatment with 9Z,11E-CLA. In addition, the mRNA expression of PPARdelta was repressed by treatment of the HT-29 cells with 9Z,11E-CLA. We conclude that 9Z,11E-CLA has an antiproliferative effect at the cellular and molecular levels in human colon cells. The results indicate that the preventive effects of CLA in the development of colon cancer may be due to their downregulation of some target genes of the APC-beta-catenin-TCF-4- and PPARdelta signalling pathway.

Induction of gene expression of xenobiotic metabolism enzymes and ABC-transport proteins by PAH and a reconstituted PAH mixture in human Caco-2 cells.

It was shown recently that in epithelial Caco-2 cells the food contaminant benzo[a]pyrene (B[a]P) is metabolized and B[a]P-sulfate metabolites were transported out of the cells. The aim of this study was to investigate whether B[a]P and other polycyclic aromatic hydrocarbons (PAH) such as chrysene, phenanthrene, benzo[k]fluoranthene (B[k]F), dibenzo[a,l]pyrene (DB[a,l]P), and pyrene alone or in a mixture in a ratio as they occur in tobacco smoke have effects on gene expression of intestinal cytochrome P450 enzymes (CYP), Phase II enzymes and ATP-binding cassette (ABC)-transport proteins in the human Caco-2 cells. B[a]P induced its own metabolism. Treatment of the Caco-2 cells with B[a]P, chrysene, B[k]F, or DB[a,l]P induced mRNA expression of CYP1A1 and CYP1B1 specifically as measured by RT-PCR. In contrast, the mRNA expression of the microsomal epoxide hydrolase (mEH) was not affected by PAH. The gene expression of the Phase II enzymes UDP-glucuronosyltransferase 1A6 (UGT1A6) and UGT1A7 was also induced by these PAH but treatment with them had no effect on gene expression of sulfotransferases (SULT) at all. Of the ABC-transport proteins, MDR1 mRNA expression was induced by treatment with carcinogenic PAH, whereas MRP2 mRNA expression was not changed. The mixture of PAH also induced CYP1A1, CYP1B1, UGT1A6, and UGT1A7 mRNA expression. We conclude that B[a]P, chrysene, B[k]F, and DB[a,l]P have specific effects on intestinal CYP1A1, CYP1B1, UGT1A6, and UDP1A7 mRNA expression but no effects on the expression of SULT.

[Food safety in the future: genes, molecular mechanisms and test systems]. / Lebensmittelsicherheit in der Zukunft: Gene, molekulare Mechanismen und Testsysteme.

The idenfication of the human genome makes it possible to investigate complex biological issues with new molecular techniques. Platformtechnologies such as DNA-Arrays or 2-D gelelectrophoresis combined with mass spectrometry will make it possible to have a faster look from gene to the protein and to find new target genes of compounds as well as new molecular mechanisms involved. The knowledge about complex molecular signalling pathways will give a real impact to new diagnostics in food analytics. As an example reporter gene assays as screening methods in the diagnostic of food contaminants will be discussed. Additionally, another example, the Novel Food will be discussed because the molecular techniques will improve diagnostics and the risk assessment of novel foods.

Phytanic acid and docosahexaenoic acid increase the metabolism of all-trans-retinoic acid and CYP26 gene expression in intestinal cells.

Retinoids are essential for growth and cell differentiation of epithelial tissues. The effects of the food compounds phytol, the phytol metabolite phytanic acid, and the fatty acid docosahexaenoic acid (DHA) on the retinoid signaling pathway in intestinal cells were studied. Phytol inhibited the formation of all-trans-retinoic acid (RA) from dietary retinol in intestinal cells. Phytanic acid, a known retinoic X receptor (RXRalpha) and peroxisome proliferator activating receptor (PPARalpha) activator, also activated PPARdelta, and to a lesser degree PPARgamma, in a transactivation assay. Phytanic acid had no effect on intestinal RA hydroxylase CYP26 (also named P450RAI) gene expression and metabolism of all-trans-RA in intestinal Caco-2 cells. However, in combination with retinoic acid receptor (RAR)-ligands (all-trans-RA or synthetic Am580) phytanic acid enhanced the induction of CYP26 and RA-metabolism in comparison to treatments with all-trans-RA or Am580 alone. Also treatment with DHA did not affect CYP26 gene expression and RA-metabolism but cotreatment of the cells with DHA and all-trans-RA or Am580 enhanced the induction of CYP26, in comparison to the induction caused by all-trans-RA or Am580 alone. This study indicates that food compounds such as phytanic acid and DHA that are RXR-agonists and have an impact on intestinal CYP26 gene expression and metabolism of all-trans-RA in intestinal cells.