Modulation of intestinal gene expression by dietary zinc status: effectiveness of cDNA arrays for expression profiling of a single nutrient deficiency

Effects of Dietary Zinc on Growth, Haematological Indices, Digestive Enzyme Activity, Tissue Mineralization, Antioxidant and Immune Status of Fingerling Heteropneustes fossilis

A 12 week feeding trial was conducted to evaluate the effects of dietary zinc levels on Heteropneustes fossilis. Triplicate groups of fish were fed isoproteic (CP; 400 g/kg) and isocaloric (GE; 17.89 kJ/g) diets increasing levels of zinc (0, 5, 10, 15, 20, 25, 30 mg/kg) achieved by supplementing zinc sulphate heptahydrate to basal diet. Analysed concentrations of zinc in diets were 10.68, 15.83, 21.34, 26.74, 30.61, 34.91 and 41.34 mg/kg. Growth indices increased linearly (P<0.05) up to 26.74 mg/kg Zn. The protein and ash content of whole body also improved significantly up to 26.74 mg/kg Zn. Whole body fat content showed inverse pattern. Haematological parameters also showed an improving trend with the increase in dietary zinc up to 26.74 mg/kg and then levelled off. Activities of antioxidant enzymes were improved with the increase in dietary zinc level up to 26.74 mg/kg followed by no significant change (P>0.05). Serum lysozyme activity also exhibited the similar pattern. Immune response in terms of the activities of lysozyme, alkaline phosphatase and myeloperoxidase was also improved with the increase in dietary zinc levels up to 26.74 mg/kg. Dietary zinc levels affected significantly the whole body as well as vertebrae mineralization. Broken-line regression analysis of weight gain, vertebrae zinc activity, serum superoxide dismutase and protease activity against increasing amounts of dietary zinc revealed that the inclusion of zinc in diet in the range of 26.82-29.84 mg/kg is optimum for growth, haematological indices, antioxidant status, immune response and tissue mineralization in fingerling H. fossilis. The information obtained from present study would be helpful in formulating the zinc-balanced commercial feeds to improve the growth and health status of this important fish, thus contributing to aquaculture production and strengthening the food security.

An alternative modular 'click-SNAr-click' approach to develop subcellular localised fluorescent probes to image mobile Zn2+

Zn2+ is involved in a number of biological processes and its wide-ranging roles at the subcellular level, especially in specific organelles, have not yet been fully established due to a lack of tools to image it effectively. We report a new and efficient modular double 'click' approach towards a range of sub-cellular localised probes for mobile zinc. Through this methodology, endoplasmic reticulum, mitochondria and lysosome localised probes were successfully prepared which show good fluorescence responses to mobile Zn2+in vitro and in cellulo whilst a non-targeting probe was synthesized as a control. The methodology appears to have wide-utility for the generation of sub-cellular localised probes by incorporating specific organelle targeting vectors for mobile Zn2+ imaging.

Genetic and transcriptional analysis of inflammatory bowel disease-associated pathways in patients with GUCY2C-linked familial diarrhea

OBJECTIVE

Activating mutations in the GUCY2C gene, which encodes the epithelial receptor guanylate cyclase C, cause diarrhea due to increased loss of sodium chloride to the intestinal lumen. Patients with familial GUCY2C diarrhea syndrome (FGDS) are predisposed to inflammatory bowel disease (IBD). We investigated whether genes in the guanylate cyclase C pathway are enriched for association with IBD and reversely whether genetic or transcriptional changes associated with IBD are found in FGDS patients.

METHODS

(1) A set of 27 genes from the guanylate cyclase C pathway was tested for enrichment of association with IBD by Gene Set Enrichment Analysis, using genome-wide association summary statistics from 12,882 IBD patients and 21,770 controls. (2) We genotyped 163 known IBD risk loci and sequenced NOD2 in 22 patients with FGDS. Eight of them had concomitant Crohn's disease. (3) Global gene expression analysis was performed in ileal tissue from patients with FGDS, Crohn's disease and healthy individuals.

RESULTS

The guanylate cyclase C gene set showed a significant enrichment of association in IBD genome-wide association data. Risk variants in NOD2 were found in 7/8 FGDS patients with concomitant Crohn's disease and in 2/14 FDGS patients without Crohn's disease. In ileal tissue, downregulation of metallothioneins characterized FGDS patients compared to healthy controls.

CONCLUSIONS

Our results support a role of guanylate cyclase C signaling and disturbed electrolyte homeostasis in development of IBD. Furthermore, downregulation of metallothioneins in the ileal mucosa of FGDS patients may contribute to IBD development, possibly alongside effects from NOD2 risk variants.

Chronic hypoxia changes gene expression profile of primary rat carotid body cells: consequences on the expression of NOS isoforms and ET-1 receptors

Sustained chronic hypoxia (CH) produces morphological and functional changes in the carotid body (CB). Nitric oxide (NO) and endothelin-1 (ET-1) play a major role as modulators of the CB oxygen chemosensory process. To characterize the effects of CH related to normoxia (Nx) on gene expression, particularly on ET-1 and NO pathways, primary cultures of rat CB cells were exposed to 7 days of CH. Total RNA was extracted, and cDNA-32P was synthesized and hybridized with 1,185 genes printed on a nylon membrane Atlas cDNA Expression Array. Out of 324 differentially expressed genes, 184 genes were upregulated, while 140 genes were downregulated. The cluster annotation and protein network analyses showed that both NO and ET-1 signaling pathways were significantly enriched and key elements of each pathway were differentially expressed. Thus, we assessed the effect of CH at the protein level of nitric oxide synthase (NOS) isoforms and ET-1 receptors. CH induced an increase in the expression of endothelial NOS, inducible NOS, and ETB. During CH, the administration of SNAP, a NO donor, upregulated ETB. Treatment with Tezosentan (ET-1 receptor blocker) during CH upregulated all three NOS isoforms, while the NOS blocker L-NAME induced upregulation of iNOS and ETB and downregulated the protein levels of ETA. These results show that CH for 7 days changed the cultured cell CB gene expression profile, the NO and ET-1 signaling pathways were highly enriched, and these two signaling pathways interfered with the protein expression of each other.

The redox biology of redox-inert zinc ions

Zinc(II) ions are redox-inert in biology. Yet, their interaction with sulfur of cysteine in cellular proteins can confer ligand-centered redox activity on zinc coordination sites, control protein functions, and generate signalling zinc ions as potent effectors of many cellular processes. The specificity and relative high affinity of binding sites for zinc allow regulation in redox biology, free radical biology, and the biology of reactive species. Understanding the role of zinc in these areas of biology requires an understanding of how cellular Zn²⁺ is homeostatically controlled and can serve as a regulatory ion in addition to Ca²⁺, albeit at much lower concentrations. A rather complex system of dozens of transporters and metallothioneins buffer the relatively high (hundreds of micromolar) total cellular zinc concentrations in such a way that the available zinc ion concentrations are only picomolar but can fluctuate in signalling. The proteins targeted by Zn²⁺ transients include enzymes controlling phosphorylation and redox signalling pathways. Networks of regulatory functions of zinc integrate gene expression and metabolic and signalling pathways at several hierarchical levels. They affect enzymatic catalysis, protein structure and protein-protein/biomolecular interactions and add to the already impressive number of catalytic and structural functions of zinc in an estimated three thousand human zinc proteins. The effects of zinc on redox biology have adduced evidence that zinc is an antioxidant. Without further qualifications, this notion is misleading and prevents a true understanding of the roles of zinc in biology. Its antioxidant-like effects are indirect and expressed only in certain conditions because a lack of zinc and too much zinc have pro-oxidant effects. Teasing apart these functions based on quantitative considerations of homeostatic control of cellular zinc is critical because opposite consequences are observed depending on the concentrations of zinc: pro- or anti-apoptotic, pro- or anti-inflammatory and cytoprotective or cytotoxic. The article provides a biochemical basis for the links between redox and zinc biology and discusses why zinc has pleiotropic functions. Perturbation of zinc metabolism is a consequence of conditions of redox stress. Zinc deficiency, either nutritional or conditioned, and cellular zinc overload cause oxidative stress. Thus, there is causation in the relationship between zinc metabolism and the many diseases associated with oxidative stress.

Imbalance of dietary nutrients and the associated differentially expressed genes and pathways may play important roles in juvenile Kashin-Beck disease

BACKGROUND

Kashin-Beck disease (KBD) is a childhood-onset endemic osteoarthropathy in China. Nutrients including trace elements may play active roles in the development of KBD.

OBJECTIVE

This study aimed to estimate the nutrient intakes of children in endemic areas and to identify the imbalanced nutrients associated differentially expressed genes in the juvenile patients with KBD.

METHODS

In this cross-sectional study, a consecutive 3 day 24 h semi-quantitative dietary retrospect questionnaire was conducted to estimate the daily nutrient intakes of children using CDGSS 3.0 software. Gene profile analysis was employed to identify differentially expressed genes in peripheral blood mononuclear cells of children with KBD. GOC, CTD, KEGG, and REACTOME databases were used to establish the relationship between nutrients and nutrients-associated differentially expressed genes and pathways. Statistical analyses were accomplished by SPSS 18.0 software.

RESULTS

Daily Se intakes without supplementation of children were significantly lower in Se-supplemented (Se + ) KBD areas (29.3 ∼ 29.6 mg/d) and non-endemic area (27.8 ± 7.9 mg/d) compared to non-Se-supplemented (Se-) KBD area (32.9 ± 7.9 mg/d, c² = 20.24, P < .01). Children in Se+ KBD areas were suffering more serious insufficient intake of multiple nutrients, including vitamins-B₂/-C/-E, Ca, Fe, Zn and I. Gene profile analysis combined with bioinformatics technique identified 34 nutrients associated differentially expressed genes and 10 significant pathways which are related to the pathological changes in juvenile KBD.

CONCLUSIONS

Imbalance of dietary nutrients and nutrients-associated differentially expressed genes and pathways may play important roles in the development of juvenile KBD.

Transcriptomic signature of high dietary organic selenium supplementation in sheep: A nutrigenomic insight using a custom microarray platform and gene set enrichment analysis

The objective of this study was to investigate the effect of a high dietary Se supplementation on the whole transcriptome of sheep. A custom sheep whole-transcriptome microarray, with more than 23,000 unique transcripts, was designed and then used to profile the global gene expression of sheep after feeding a high dietary supplementation of organic Se. Lactating crossbred ewes ( = 10; 3 to 4 yr of age and 55 to 65 kg BW) at late lactation (100 ± 8 d in milk) were acclimated to indoor individual pen feeding of a basal control diet (0.40 mg Se/d, sodium selenite) for 4 wk. Sheep were then kept on a diet with an extra (high) supplementation of organic Se (1.45 mg Se/d as Sel-Plex; Alltech Biotechnology Pty Ltd, Dandenong, Victoria, Australia) for 40 d. Whole blood was collected at 2 time points (last day of the acclimatization period [T0] and after 40 d of the organic Se supplementation [T40]), and then total RNA was isolated and labeled for the subsequent microarray analysis. Significance Analysis of Microarrays, using the -statistic, of the microarray data (T40 versus T0) evidenced the up- and downregulation of 942 and 244 transcripts (false discovery rate < 0.05), respectively. Seven genes showed the same trend of expression (up- or downregulation) when tested by quantitative real-time PCR (qPCR) in a cross-validation step. The microarray showed significant upregulation of the following selenoproteins at T40: selenium binding protein 1 (SELENBP1), selenoprotein W1 (SEPW1), glutathione peroxidase 3 (GPX3), and septin 8 (SEPT8). And the expression trends for SEPW1 and SEPT8 were validated using qPCR. Functional annotation of the differentially expressed genes showed the enrichment of several immune system-related biological processes (lymphocyte activation, cytokine binding, leukocyte activation, T cell differentiation, and B cell activation) and pathways (cytokine and interleukin signaling). Moreover, Gene Set Enrichment Analysis evidenced the enrichment of B and T cell receptors signaling pathways, with an enrichment score of 0.63 and 0.59, respectively. Overall, from a global gene expression (whole-transcriptome) point of view, short-term supplementation of a high dietary organic Se to Se-nondeficient sheep results in a transcriptomic signature that mainly reflects an induced immune system and a modulation of transcription effect. Also, the present study provides a custom whole-transcriptome microarray platform that can be used in further global gene expression studies in the ovine species.

Dietary Zinc Regulates Apoptosis through the Phosphorylated Eukaryotic Initiation Factor 2α/Activating Transcription Factor-4/C/EBP-Homologous Protein Pathway during Pharmacologically Induced Endoplasmic Reticulum Stress in Livers of Mice

BACKGROUND

Several in vitro studies have shown that zinc deficiency could induce endoplasmic reticulum (ER) stress, resulting in activation of the unfolded protein response.

OBJECTIVE

We aimed to determine whether consumption of a zinc-deficient diet (ZnD) triggers ER stress and to understand the impact of dietary zinc intake on ER stress-induced apoptosis using a mouse model.

METHODS

Young adult (8-16 wk of age) male mice of strain C57BL/6 were fed either a ZnD (<1 mg/kg diet), or a zinc-adequate diet (ZnA; 30 mg/kg diet). After 2 wk, liver, pancreas, and serum samples were collected and analyzed for indexes of ER stress. In another experiment, mice were fed either a ZnD, a ZnA, or a zinc-supplementation diet (ZnS; 180 mg/kg diet). After 2 wk, vehicle or tunicamycin (TM; 2 mg/kg body weight) was administered to mice to model ER stress. Liver and serum were analyzed for indexes of ER stress to evaluate the effects of zinc status.

RESULTS

Mice fed a ZnD did not activate the apoptotic and ER stress markers in the liver or pancreas. During the TM challenge, mice fed a ZnD showed greater C/EBP-homologous protein expression in the liver (3.8-fold, P < 0.01) than did ZnA-fed mice. TM-treated mice fed a ZnD also had greater terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling-positive cells in the liver (2.2-fold, P < 0.05), greater hepatic triglyceride accumulation (1.5-fold, P < 0.05), greater serum alanine aminotransferase activity (1.6-fold, P < 0.05), and greater protein-tyrosine phosphatase 1B activity (1.5-fold, P < 0.05), respectively, than did those fed a ZnA. No significant differences were observed in these parameters between mice fed ZnAs and ZnSs.

CONCLUSIONS

Consumption of a ZnD per se is not a critical factor for induction of ER stress in mice; however, once ER stress is triggered, adequate dietary zinc intake is required for suppressing apoptotic cell death and further insults in the liver of mice.

The Role of Nutraceuticals in Pancreatic Cancer Prevention and Therapy: Targeting Cellular Signaling, MicroRNAs, and Epigenome

Pancreatic cancer is one of the most aggressive malignancies in US adults. Experimental studies have found that antioxidant nutrients could reduce oxidative DNA damage, suggesting that these antioxidants may protect against pancreatic carcinogenesis. Several epidemiologic studies showed that dietary intake of antioxidants was inversely associated with the risk for pancreatic cancer, demonstrating the inhibitory effects of antioxidants on pancreatic carcinogenesis. Moreover, nutraceuticals, the anticancer agents from diet or natural plants, have been found to inhibit the development and progression of pancreatic cancer through the regulation of cellular signaling pathways. Importantly, nutraceuticals also up-regulate the expression of tumor-suppressive microRNAs (miRNAs) and down-regulate the expression of oncogenic miRNAs, leading to the inhibition of pancreatic cancer cell growth and pancreatic cancer stem cell self-renewal through modulation of cellular signaling network. Furthermore, nutraceuticals also regulate epigenetically deregulated DNAs and miRNAs, leading to the normalization of altered cellular signaling in pancreatic cancer cells. Therefore, nutraceuticals could have much broader use in the prevention and/or treatment of pancreatic cancer in combination with conventional chemotherapeutics. However, more in vitro mechanistic experiments, in vivo animal studies, and clinical trials are needed to realize the true value of nutraceuticals in the prevention and/or treatment of pancreatic cancer.

Effects of zinc on epithelial barrier properties and viability in a human and a porcine intestinal cell culture model

Zinc is an essential trace element with a variety of physiological and biochemical functions. Piglets are commonly supplemented, during the weaning period, with doses of zinc above dietary requirements with positive effects on health and performance that might be attributed to anti-secretory and barrier-enhancing effects in the intestine. For a better understanding of these observations increasing zinc sulfate (ZnSO4; 0-200μM) concentrations were used in an in vitro culture model of porcine (IPEC-J2) and human (Caco-2) intestinal epithelial cells and effects on barrier function, viability, and the mRNA expression of one selected heat shock protein (Hsp) were assessed. When treated apically with zinc sulfate, the transepithelial electrical resistance (TEER) did not change significantly. In contrast, cell viability measured by lactate dehydrogenase (LDH) leakage, by ATP and by WST-1 conversion in postconfluent IPEC-J2 monolayers was affected after a 24-h treatment with 200μM ZnSO4. Caco-2 cells were more resistant to Zn. ZnSO4 did not induce any effect on viability, except when it was used at the highest concentration (200μM), and only in preconfluent cells. Furthermore, ZnSO4 induced Hsp70 mRNA expression at 200μM and was more pronounced in preconfluent cells. The observed dose-related effects of zinc are cell-line specific and depended on the differentiation status of the cells. The IPEC-J2 cell line appears to be a suitable in vitro model to characterize specific effects on porcine intestinal cells.

Micronutrient (Zn, Cu, Fe)-gene interactions in ageing and inflammatory age-related diseases: implications for treatments

In ageing, alterations in inflammatory/immune response and antioxidant capacity lead to increased susceptibility to diseases and loss of mobility and agility. Various essential micronutrients in the diet are involved in age-altered biological functions. Micronutrients (zinc, copper, iron) play a pivotal role either in maintaining and reinforcing the immune and antioxidant performances or in affecting the complex network of genes (nutrigenomic approach) involved in encoding proteins for a correct inflammatory/immune response. By the other side, the genetic inter-individual variability may affect the absorption and uptake of the micronutrients (nutrigenetic approach) with subsequent altered effects on inflammatory/immune response and antioxidant activity. Therefore, the individual micronutrient-gene interactions are fundamental to achieve healthy ageing. In this review, we report and discuss the role of micronutrients (Zn, Cu, Fe)-gene interactions in relation to the inflammatory status and the possibility of a supplement in the event of a micronutrient deficiency or chelation in presence of micronutrient overload in relation to specific polymorphisms of inflammatory proteins or proteins related of the delivery of the micronutriemts to various organs and tissues. In this last context, we report the protein-metal speciation analysis in order to have, coupled with micronutrient-gene interactions, a more complete picture of the individual need in micronutrient supplementation or chelation to achieve healthy ageing and longevity.

Marginal zinc deficiency exacerbates experimental colitis induced by dextran sulfate sodium in rats

We investigated the impact of Zn status on the maintenance of mucosal homeostasis. Rats were fed diets containing different amounts of Zn (30, 10, 5, <1 mg Zn/kg diet) for 21 d. Serum Zn concentrations were lower in rats fed marginally Zn-deficient (MZD; 5 mg Zn/kg diet) and severely Zn-deficient (<1 mg/kg) diets but not in those fed the marginally Zn-adequate diet (10 mg/kg) or the Zn-adequate (ZA; 30 mg/kg) group (P < 0.05). However, organ weights, colonic epithelial cell proliferation, and crypt fission did not differ between the MZD and ZA groups. We then evaluated whether MZD modulated dextran sulfate sodium (DSS)-induced colonic inflammation by administering 2% DSS to the MZD and ZA groups for 7 d. Myeloperoxidase activity and TNFα production increased in response to DSS in the MZD group (P < 0.03). Colonic permeability in the 2 groups did not differ after DSS administration. In a culture experiment using isolated mesenteric leukocytes, TNFα production was higher (P < 0.05) and TNF receptor type I (TNFR1) expression was detected in culture medium containing 20 and 30 μmol/L of Zn compared with culture medium lacking Zn supplementation. These results suggest that MZD exacerbated colitis by modulating the immune response through the impairment of TNFα production and TNFR1 expression rather than through the impairment of epithelial barrier function.

The functional effects of nutrients on enterocyte proliferation and intestinal ion transport in early infancy

Nutrition has a key role in the modulation of the developing intestine in early infancy, and nutrients are able to modulate several intestinal functions including nutrient absorption, ion transport, cell growth and differentiation, motility and immunomodulation. Such modulation is exerted in part through a direct interaction between a single nutrient and the enterocyte. Two functions--ion transport and cell growth--are closely connected and appear to be modulated by nutrients. This is supported by the finding that a single nutrient (e.g. zinc) stimulates ion absorption and also promotes enterocyte growth. Interestingly, intracellular signalling for either effect is similar and involves mitogen-activated protein kinase. Other nutrients also modulate enterocyte function and there is evidence that their effect may depend on their side of action (apical or basolateral) and concentration. Knowledge of the interaction between nutrients and enterocytes may be exploited to obtain clinical effects using nutrition as a long-term treatment for intestinal and non-intestinal conditions.

Zinc replenishment reverses overexpression of the proinflammatory mediator S100A8 and esophageal preneoplasia in the rat

BACKGROUND & AIMS

Zinc deficiency is implicated in the pathogenesis of human esophageal cancer. In the rat esophagus, it induces cell proliferation, modulates genetic expression, and enhances carcinogenesis. Zinc-replenishment reverses proliferation and inhibits carcinogenesis. The zinc-deficient rat model allows the identification of biological differences affected by zinc during early esophageal carcinogenesis.

METHODS

We evaluated gene expression profiles of esophageal epithelia from zinc-deficient and replenished rats vs zinc-sufficient rats using microarray analysis. We characterized the role of the top-up-regulated gene S100A8 in esophageal hyperplasia/reversal and in chemically induced esophageal carcinogenesis in zinc-modulated animals by immunohistochemistry and real-time quantitative polymerase chain reaction.

RESULTS

The hyperplastic-deficient esophagus has a distinct expression signature with the proinflammation genes S100 calcium binding protein A8 (S100A8) and A9 (S100A9) up-regulated 57-fold and 5-fold, respectively. Zinc replenishment rapidly restored to control levels the expression of S100A8/A9 and 27 other genes and reversed the hyperplastic phenotype. With its receptor for advanced glycation end products (RAGE), colocalization and overexpression of S100A8 protein occurred in the deficient esophagus that overexpressed nuclear factor kappaBeta p65 and cyclooxygenase-2 (COX-2) protein. Zinc replenishment, but not a COX-2 inhibitor, reduced the overexpression of these 4 proteins. Additionally, esophageal S100A8/A9 messenger RNA levels were associated directly with the diverse tumorigenic outcome in zinc-deficient and zinc-replenished rats.

CONCLUSIONS

In vivo zinc regulates S100A8 expression and modulates the link between S100A8-RAGE interaction and downstream nuclear factor kappaBeta/COX-2 signaling. The finding that zinc regulates an inflammatory pathway in esophageal carcinogenesis may lead to prevention and therapy for this cancer.

Intestinal inflammation in rats induces metallothionein in colonic submucosa

The aim of the current study was to determine if induction of metallothionein (MT) via acute or chronic dietary zinc supplementation attenuates intestinal inflammation, and to investigate the relationship with site-specific intestinal MT determined by immunolocalization. Growing rats were assigned to zinc-deficient (ZD), acute zinc-treated (ZT), pair-fed, control or chronic Zn-supplemented (ZS) groups. Half the rats in each dietary group received 5% dextran sulphate sodium (DSS) in their drinking water for 4 days. DSS treatment produced acute intestinal inflammation in the colon only, however, dietary zinc deficiency, acute zinc treatment or chronic zinc supplementation did not alter the severity of ulceration. Serum zinc concentrations were attenuated in the DSS-challenged ZT and ZS groups suggesting that zinc was being utilized in some capacity in response to inflammation. DSS-challenge induced MT immunostaining in the colonic submucosa, however, MT was not associated with histological improvements in the present study. The site-specific MT induction in colonic submucosa during intestinal inflammation requires further clarification as a component of the host defense.

Guar gum and similar soluble fibers in the regulation of cholesterol metabolism: current understandings and future research priorities

The hypocholesterolemic effects associated with soluble fiber consumption are clear from animal model and human clinical investigations. Moreover, the modulation of whole-body cholesterol metabolism in response to dietary fiber consumption, including intestinal cholesterol absorption and fecal sterol and bile acid loss, has been the subject of many published reports. However, our understanding of how dietary fibers regulate molecular events at the gene/protein level and alter cellular cholesterol metabolism is limited. The modern emphasis on molecular nutrition and rapid progress in 'high-dimensional' biological techniques will permit further explorations of the role of genetic polymorphisms in determining the variable interindividual responses to soluble fibers. Furthermore, with traditional molecular biology tools and the application of 'omic' technology, specific insight into how fibers modulate the expression of genes and proteins that regulate intestinal cholesterol absorption and alter hepatic sterol balance will be gained. Detailed knowledge of the molecular mechanisms by which soluble fibers reduce plasma cholesterol concentrations is paramount to developing novel fiber-based "cocktails" that target specific metabolic pathways to gain maximal cholesterol reductions.

Mechanisms of mammalian zinc-regulated gene expression

Mechanisms through which gene expression is regulated by zinc are central to cellular zinc homoeostasis. In this context, evidence for the involvement of zinc dyshomoeostasis in the aetiology of diseases, including Type 2 diabetes, Alzheimer's disease and cancer, highlights the importance of zinc-regulated gene expression. Mechanisms elucidated in bacteria and yeast provide examples of different possible modes of zinc-sensitive gene regulation, involving the zinc-regulated binding of transcriptional activators and repressors to gene promoter regions. A mammalian transcriptional regulatory mechanism that mediates zinc-induced transcriptional up-regulation, involving the transcription factor MTF1 (metal-response element-binding transcription factor 1), has been studied extensively. Gene responses in the opposite direction (reduced mRNA levels in response to increased zinc availability) have been observed in mammalian cells, but a specific transcriptional regulatory process responsible for such a response has yet to be identified. Examples of single zinc-sensitive transcription factors regulating gene expression in opposite directions are emerging. Although zinc-induced transcriptional repression by MTF1 is a possible explanation in some specific instances, such a mechanism cannot account for repression by zinc of all mammalian genes that show this mode of regulation, indicating the existence of as yet uncharacterized mechanisms of zinc-regulated transcription in mammalian cells. In addition, recent findings reveal a role for effects of zinc on mRNA stability in the regulation of specific zinc transporters. Our studies on the regulation of the human gene SLC30A5 (solute carrier 30A5), which codes for the zinc transporter ZnT5, have revealed that this gene provides a model system by which to study both zinc-induced transcriptional down-regulation and zinc-regulated mRNA stabilization.

Transcriptomics and micronutrient research

This review examines the extent to which transcriptomic methods have lived up to their promise in the context of nutrition research, placing particular emphasis on examples from micronutrient research. A case is made that the high quality platform technologies now available, together with established standards and systems for data storage and exchange and powerful new methods of data analysis, mean that microarrays have reached a level of technical maturity at which they can be exploited to their full potential. In the context of nutrition and micronutrient research, transcriptomic methods have already been widely applied, albeit primarily in studies using cell lines and animal models. Using this type of approach, a multitude of genes regulated at the mRNA level by dietary components has been identified and this, in turn, has provided new insights into the biological processes affected by nutritional parameters. Evidence from the very limited number of published transcriptomics-based nutritional studies performed in human volunteers suggests that, with appropriate study design, it is feasible to apply transcriptomic methods successfully in dietary intervention trials. On the other hand, gene expression-based biomarker development still poses a major challenge. Here the use of expression profile 'signatures', rather than single genes, may provide a solution. Approaches designed to identify such 'signatures' are being developed and tested widely, primarily in the context of medical research. The applicability and power of such approaches should also be evaluated in the context of nutrition.

Sequential responses to high-fat and high-calorie feeding in an obese mouse model

OBJECTIVE

Reports on the immediate and long-term responses to high-fat and high-calorie (HFC) feeding are controversial. Therefore, we examined the sequential effects of an HFC diet.

METHODS AND PROCEDURES

C57BL/6J mice were randomly assigned to consume either the control (C) or the HFC diet. Body weights and food intake were measured weekly and other measurements at weeks 2, 4, and 10. Microarrays were used for screening the transcriptional response of the livers at the three time points. Genes, encoding enzymes regulating key steps of lipid metabolism, were then selected from the microarray data for validation by quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR) and their protein expression by western blot assays.

RESULTS

Mice fed with HFC diet for 2 weeks showed no increase in food intake and no difference in weight gain compared to the C mice. At weeks 4 and 10, the HFC mice increased their food intake and gained more weight than their controls (by 1.4 times and 2.5 times, respectively) (P<0.01 at week 10). Genes involved in fatty acid oxidation (FAO) were initially upregulated and then downregulated, whereas the lipogenic genes and genes involved in cholesterol synthesis showed reverse trends. The differential mRNA expression of Cpt1L, Fas, and Hmgcr were confirmed by RT-PCR and their protein expression by western blot assays.

DISCUSSION

Our findings suggested that when mice were fed an HFC diet, they could develop initial compensatory response to resist the increased energy balance; however, a prolonged consumption of an HFC diet appeared to disrupt this adaptation.

Zinc deficiency alters DNA damage response genes in normal human prostate epithelial cells

Zinc is an essential trace element for human health and is a critical component of many proteins and transcription factors involved in DNA damage response and repair. The prostate is known to accumulate high levels of zinc, but levels are markedly decreased with cancer development. We hypothesized that zinc plays a critical role in maintaining DNA integrity in the prostate and zinc deficiency would lead to increased DNA damage and altered DNA damage response mechanisms. To test this hypothesis, the goal of this study was to determine the effects of zinc deficiency on DNA damage and DNA repair mechanisms by examining changes in global gene expression and transcription factor binding abilities in normal prostate epithelial cells (PrEC). Increased single-strand DNA breaks (Comet assay) were observed in PrEC grown in zinc-deficient media compared with cells grown in zinc-adequate media for 7 d. Using Affymetrix HG-U133A gene chips, differential expression of genes involved in cell cycle, apoptosis, transcription, and DNA damage response and repair were identified with low cellular zinc. Among genes involved in DNA damage response and repair, tumor protein p73, MRE11 meiotic recombination 11 homolog A, X-ray repair complementing defective repair in Chinese hamster cells 4, and breast cancer 2, early onset were down-regulated and TP53 was up-regulated. Additionally, western blotting showed increased nuclear p53 protein expression with zinc deficiency. Despite increased p53 gene and nuclear protein expression, there was no significant change in p53 binding activity. Zinc deficiency also induced an increase in binding activity of transcription factors involved in regulating cell proliferation and apoptosis. Thus, zinc deficiency may compromise DNA integrity in the prostate by impairing the function of zinc-containing proteins.

Smart Foods from the pastoral sector - implications for meat and milk producers

Smart Foods, or foods with functions that confer health benefits, are the future of the food and nutrition sectors. Pastoral products such as milk and meat are easily manipulated to improve the health benefits of these products. Therefore, there is the potential for farmers to add value to their current products. Additionally, the identification of key nutrients for health and the prevention of disease using nutrigenomic and nutritional epigenetic approaches may identify new ways to manipulate milk and meat products. However, consumer perceptions of product efficacy and the marketing of foods with health claims will be drivers behind the uptake of Smart Foods in the future.

Sequential effects of a high-fiber diet with psyllium husks on the expression levels of hepatic genes and plasma lipids

OBJECTIVE

We studied the sequential effects of a high-fiber diet using psyllium husks on hepatic gene expression and plasma lipid levels.

METHODS

C57BL/6J mice were randomly assigned to a control diet or a high-fiber diet containing 10% psyllium husks for 3 weeks (PE-3wk) and 10 weeks (PE-10wk). Oligonucleotide microarrays were used to screen the transcriptional response at both time points. Genes encoding enzymes regulating key steps of lipid metabolism were then selected for further validation by quantitative real-time reverse transcription polymerase chain reaction and their protein expression by western blot assays.

RESULTS

Plasma cholesterol and triacylglycerol levels were reduced in both high-fiber groups. Three weeks of high-fiber feeding downregulated genes involved in lipogenesis, whereas those involved in cholesterol and bile acid synthesis were upregulated. With prolonged high-fiber feeding, genes involved in lipogenesis such as fatty acid synthase (Fasn) were then upregulated. Additional genes in cholesterol synthesis such as 3-hydroxy-3-methylglutaryl coenzyme A reductase (Hmgcr) were also upregulated. At week 3, protein expression levels of Fasn were significantly lower in the high-fiber group but increased at week 10. Protein levels of Hmgcr were significantly increased in PE-10wk mice.

CONCLUSION

The high-fiber diet containing psyllium husks reduced plasma total cholesterol and triacylglycerol levels. Cholesterol lowering was most likely mediated by increased bile acid synthesis. The increased transcript levels of genes related to cholesterol synthesis throughout the entire feeding period and the subsequent increased lipogenic gene transcript levels could likely suggest a regulatory mechanism to restore the lowered plasma cholesterol and triacylglycerol levels.

Genomic implications of H(2)O (2) for cell proliferation and growth of Caco-2 cells

Evidence indicates that oxidative stress inhibits cell proliferation in several cell systems. To determine whether the proliferation of Caco-2 cells is inhibited by oxidative stress and to identify any novel key regulatory factors involved in protecting or damaging the intestine from oxidative stress, Caco-2 cells were treated with an oxidizing agent and analyzed by transcriptomic oligonucleotide microarrays. Results indicated that expression of genes involved in cell proliferation and growth, including genes involved in lipid synthesis, cell cycle progression and cell division, angiogenesis, RNA processing and translation, cAMP metabolism, cytoskeleton and cell to cell adhesion, receptor tyrosine kinases, and intracellular and extracellular signaling, were repressed. If an oxidant-induced inhibition in cell proliferation is involved in the pathogenesis of intestinal disease, information gained could help explain the mechanisms contributing to the causes and consequences of intestinal disease and could aid in the elucidation of mechanisms by which intestinal cells protect against oxidative stress.

Splice Variants of the Human Zinc Transporter ZnT5 (SLC30A5) Are Differentially Localized and Regulated by Zinc through Transcription and mRNA Stability

Maintenance of cellular zinc homeostasis includes regulating the expression of cell membrane zinc transporters. Knowledge about the mechanisms underlying changes in mammalian zinc transporter mRNA abundance is poor. We demonstrated that when expressed in Chinese hamster ovary cells as N-terminal fusions to green fluorescent protein, two splice variants of ZnT5 adopt different subcellular locations (either in the Golgi apparatus or throughout the cell, including at the plasma membrane) indicating discrete roles in cellular zinc homeostasis. We demonstrated, using a beta-galactosidase reporter gene, that both splice variants were expressed from a promoter region that was transcriptionally repressed by increased extracellular zinc (150 microM compared with 3 mum; approximately 40%) and by extracellular zinc depletion, using the chelator N,N,N',N'-tetrakis(2-pyridylmethyl) ethylenediamine ( approximately 20%). We mapped the zinc-responsive element to the region -154 to +50, relative to the predicted start of transcription, and showed that a consensus metal response element sequence (-410 to -404) was not responsible for these effects. Changes in ZnT5 mRNA abundance in Caco-2 cells at different zinc concentrations were in parallel to the changes in promoter activity ( approximately 40% reduction at 150 microM zinc) but in the presence of actinomycin D, to prevent transcription, we observed a marked stabilization (1.7-2-fold accumulation over 24 h) of ZnT5 mRNA. We conclude that effects of zinc on ZnT5 transcription and mRNA stability act in opposition to balance mRNA abundance for cellular zinc homeostasis. To our knowledge, this is the first report that zinc affects the stability of a transcript with a direct role in cellular zinc homeostasis.

Discovery of deregulation of zinc homeostasis and its associated genes in esophageal squamous cell carcinoma using cDNA microarray

Esophageal squamous cell carcinoma (ESCC) in the Indian population is associated with poor nutritional status, low socioeconomic conditions, bidi smoking and consumption of smokeless tobacco products, besides alcohol drinking and cigarette smoking. To determine the impact of these risk factors on molecular pathogenesis of ESCC, we determined global gene expression profiles of 7 paired samples of ESCC and histologically confirmed nonmalignant esophageal tissues using 19.1K cDNA microarrays. The most salient finding was identification of 19 differentially expressed genes encoding zinc binding or modulating proteins associated with transcriptional regulation, ubiquitin-protein degradation and maintenance of zinc homeostasis. Validation of differential expression of a subset of genes by real-time quantitative RT-PCR (real-time QRT-PCR) in clinical specimens of ESCC, esophageal dysplasia and histologically nonmalignant esophageal tissues and immunohistochemical analysis using tissue microarrays confirmed the microarray data and demonstrated upregulation of zinc finger proteins, cellular modulator of immune recognition (c-MIR), snail homolog 2 (SLUG), zinc transporter, ZnT7 and downregulation of zinc metabolizing protein, metallothionein MT1G. We also observed upregulation of mitogen activated protein kinase kinase kinase 3 (MAP3K3/MEKK3), a kinase anchor protein 13 (AKAP13) and transglutaminase2 (TG2). Interestingly, we found upregulation of ZnT7 transcripts in ESCC cells (TE13) grown in zinc deficient condition. In conclusion, our data suggest deregulation of genes associated with zinc homeostasis in ESCC.

Gene expression profiles analysis of the growing rat liver in response to different zinc status by cDNA microarray analysis

The effects of zinc on growing rats were characterized using the dietary zinc-deficient (ZD) and Zinc-overdose (ZO) models. Zinc deficiency had negative effects on the host final body weight and liver zinc content, whereas zinc overdose had positive effects. In order to identify the molecular changes in the liver responding to dietary zinc status, cDNA microarrays were used to analyze the expression pattern of 9753 genes in the livers of rats fed ZD and ZO diet for 6 wk, compared with zinc-adequate ZA. The mRNA levels for 62 genes were affected significantly by the ZD diet, whereas 66 gene transcriptions were markedly changed in the ZO diet. Those predominant gene products involved in nitrogen metabolism (glutaminase), carbohydrate metabolism (aldolase), lipid metabolism (stearoyl-CoA desaturase), growth (insulin-like growth factor-binding protein), transcription and translation (zinc-finger protein), immune (natural-killer cell), signal transduction (mitogen- activated protein kinase), and ion transportation (ATPase Na+/K+ transporting peptide) were clustered. In conclusion, a number of mammalian genes related to zinc in the liver were identified. The characterization of the genes and their products will allow a more comprehensive analysis of the role of zinc in metabolism. Furthermore, the mRNA identified could be useful in establishing the mechanisms of zinc in the pleiotropic metabolisms in vivo.

Anti-inflammatory effects of zinc and alterations in zinc transporter mRNA in mouse models of allergic inflammation

There is clinical evidence linking asthma with the trace element, zinc (Zn). Using a mouse model of allergic inflammation, we have previously shown that labile Zn decreases in inflamed airway epithelium (Truong-Tran AQ, Ruffin RE, Foster PS, Koskinen AM, Coyle P, Philcox JC, Rofe AM, Zalewski PD. Am J Respir Cell Mol Biol 27: 286-296, 2002). Moreover, mild nutritional Zn deficiency worsens lung function. Recently, a number of proteins belonging to the Solute Carrier Family 39 (ZIP) and Solute Carrier Family 30 (ZnT) have been identified that bind Zn and regulate Zn homeostasis. Mice were sensitized, and subsequently aerochallenged, with ovalbumin to induce acute and chronic airway inflammation. Mice received 0, 54, or 100 microg of Zn intraperitoneally. Tissues were analyzed for Zn content and histopathology. Inflammatory cells were counted in bronchoalveolar lavage fluid. Cytokine and Zn transporter mRNA levels were determined by cDNA gene array and/or real-time PCR. Zn supplementation decreased bronchoalveolar lavage fluid eosinophils by 40 and 80%, and lymphocytes by 55 and 66%, in the acute and chronic models, respectively. Alterations in Zn transporter expression were observed during acute inflammation, including increases in ZIP1 and ZIP14 and decreases in ZIP4 and ZnT4. Zn supplementation normalized ZIP1 and ZIP14, but it did not affect mRNA levels of cytokines or their receptors. Our results indicate that inflammation-induced alterations in Zn transporter gene expression are directed toward increasing Zn uptake. Increases in Zn uptake may be needed to counteract the local loss of Zn in the airway and to meet an increased demand for Zn-dependent proteins. The reduction of inflammatory cells by Zn in the airways provides support for Zn supplementation trials in human asthmatic individuals.

Cortical Gene Expression in the Vitamin E-Deficient Rat: Possible Mechanisms for the Electrophysiological Abnormalities of Visual and Neural Function

In mammals, severe and chronic deficiency of vitamin E (alpha-tocopherol) is associated with a characteristic neurological syndrome. Previously, we have shown that this syndrome is accompanied by electrophysiological abnormalities of neural and visual function. To investigate the molecular basis of the observed abnormalities, we used microarrays to monitor the expression of approximately 14,000 genes in the cerebral cortex from rats which had received diets containing 0, 1.25 and 5.0 mg/kg diet of all-rac-alpha-tocopheryl acetate for 14 months. Compared to the groups receiving 1.25 and 5.0 mg/kg alpha-tocopheryl acetate, a total of 11 genes were statistically significantly upregulated (> or =1.3-fold) and 34 downregulated (< or =1.3-fold) in the vitamin E-deficient group. Increased expression was observed for the genes encoding the antioxidant enzyme catalase and the axon guidance molecule tenascin-R, while decreased expression was detected for genes encoding protein components of myelin and determinants of neuronal signal propagation. Thus our observations suggest that vitamin E deficiency results in transcriptional alterations in the cerebral cortex of the rat which are consistent with the observed neurological and electrophysiological alterations.

Zinc protection of HepG2 cells from sporidesmin toxicity does not require de novo gene transcription

Sporidesmin is an epidithiodioxopiperazine mycotoxin secreted by the saprophytic fungus Pithomyces chartarum. Ingestion of sporidesmin by ruminants grazing on the saprophyte infested pasture causes severe liver and bile duct damage leading to secondary photosensitisation. Zinc supplementation is used as an effective prophylaxis against sporidesmin toxicity in ruminants, however, the mechanism by which zinc protects is unknown. This study used the human hepatoma cell line, HepG2, as a model to examine the mechanism of zinc protection against sporidesmin toxicity. Treatment of cells with various concentrations of sporidesmin (0-10 microg/ml) resulted in a sigmoidal dose response curve with an LC50 of 5 microg/ml. Cells were protected from sporidesmin toxicity by pre-treatment for 2h or 16 h with zinc sulphate in a concentration dependent manner, with significant protection at 50 microM zinc and maximal protection at 200 microM zinc. To determine whether zinc protection required de novo gene transcription, cells were treated with the transcriptional inhibitor actinomycin D for one hour prior to and throughout the zinc pre-treatment. The presence of actinomycin D did not significantly reduce the zinc protection against sporidesmin cytotoxicity (80% protection without actinomycin D versus 71% protection with actinomycin D). Therefore, de novo gene transcription does not play a major role in the mechanism of zinc protection against sporidesmin toxicity in HepG2 cells.

Modulation of gene expression in precancerous rat esophagus by dietary zinc deficit and replenishment

Zinc deficiency in rats enhances esophageal cell proliferation, causes alteration in gene expression, and promotes esophageal carcinogenesis. Zinc replenishment rapidly induces apoptosis in the esophageal epithelium thereby reversing cell proliferation and carcinogenesis. To identify zinc-responsive genes responsible for these divergent effects, we did oligonucleotide array-based gene expression profiling analyses in the precancerous zinc-deficient esophagus and in zinc-replenished esophagi after treatment with intragastric zinc compared with zinc-sufficient esophagi. Thirty-three genes (21 up-regulated and 12 down-regulated) showed a > or = 2-fold change in expression in the hyperplastic zinc-deficient versus zinc-sufficient esophageal epithelia. Expression of genes involved in cell division, survival, adhesion, and tumorigenesis were markedly changed. The zinc-sensitive gene metallothionein-1 (MT-1 was up-regulated 7-fold, the opposite of results for small intestine and liver under zinc-deficient conditions. Keratin 14 (KRT14, a biomarker in esophageal tumorigenesis), carbonic anhydrase II (CAII, a regulator of acid-base homeostasis), and cyclin B were up-regulated >4-fold. Immunohistochemistry showed that metallothionein and keratin 14 proteins were overexpressed in zinc-deficient esophagus, as well as in lingual and esophageal squamous cell carcinoma from carcinogen-treated rats, emphasizing their roles in carcinogenesis. Calponin 1 (CNN1, an actin cross-linking regulator) was down-regulated 0.2-fold. Within hours after oral zinc treatment, the abnormal expression of 29 of 33 genes returned to near zinc-sufficient levels, accompanied by reversal of the precancerous phenotype. Thus, we have identified new molecular markers in precancerous esophagus and showed their restoration by zinc replenishment, providing insights into the interaction between zinc and gene expression in esophageal cancer development and prevention.

Zinc-sensitive genes as potential new target genes of the metal transcription factor-1 (MTF-1)

Zinc is an essential trace element that serves as a structural constituent of a large number of transcription factors, which explains its pivotal role in the control of gene expression. Previous studies investigating the effect of zinc deficiency and zinc supplementation on gene expression in the human adenocarcinoma cell line HT-29 led to the identification of a considerable number of genes responding to alterations in cellular zinc status with changes in steady state mRNA levels. For 9 of 20 genes from these previous screenings that were studied in more detail, mRNA steady state levels responded to both high and low media zinc concentrations. As they are primarily zinc-dependent, we assessed whether these genes are controlled by the zinc-finger metal transcription factor MTF-1. To test this hypothesis we generated a doxycyline-inducible Tet-On HT-29 cell line overexpressing MTF-1. Using this conditional expression system, we present evidence that Kruppel-like factor 4 (klf4), hepatitis A virus cellular receptor 1 (hhav), and complement factor B (cfbp) are 3 potential new target genes of MTF-1. To support this, we used in silico analysis to screen for metal-responsive elements (MREs) within promotors of zinc-sensitive genes. We conclude that zinc responsiveness of klf4, hhav, and cfbp in HT-29 cells is mediated at least in part by MTF-1.

Dietary zinc modulation of COX-2 expression and lingual and esophageal carcinogenesis in rats

BACKGROUND

Cancer of the upper aerodigestive tract, including esophageal and tongue carcinomas, is a major cause of cancer deaths worldwide. Esophageal and tongue cancers have both been associated with dietary zinc deficiency (ZD), and cyclooxygenase (COX-2) is often overexpressed in these cancers. Using rat models, we examined whether zinc regulates COX-2 expression in these cancers.

METHOD

Expression of COX-2 protein and mRNA in rat lingual and esophageal epithelia in control (zinc sufficient [ZS]) rats, during ZD, and after intragastric zinc replenishment (ZR) were determined by immunoblotting, immunohistochemistry, and real-time quantitative polymerase chain reaction. COX-2 gene expression, cell proliferation, and apoptosis were analyzed in ZD, ZR, and ZD rats treated with the COX-2 inhibitors celecoxib and indomethacin. Tumor development in ZD rats treated by continuous exposure to the carcinogen 4-nitroquinoline 1 oxide (NQO), which causes tongue tumors in rats, was compared with those in NQO-treated ZS rats. Statistical tests were two-sided.

RESULTS

The esophagus and tongue of ZD rats were hyperplastic and expressed COX-2 protein and mRNA at 8- to 14.7-fold higher levels than control rats. Within hours ZR reduced COX-2 overexpression to threefold that in control rats and reversed the hyperplastic phenotypes. The esophagus of ZD rats treated with celecoxib or indomethacin showed a reduction in cell proliferation and stimulation of apoptosis. NQO treatment resulted in greater incidence of lingual squamous cell carcinomas (74% versus 22%, difference = 52%, 95% confidence interval [CI] = 20% to 80%, P = .015) and greater tumor multiplicity (13.1 versus 4.3, difference = 8.8, 95% CI = 7.0 to 10.6, P = .018) in ZD than ZS rats. Of 23 NQO-treated ZD rats, 39% (9) and 61% (14) harbored esophageal and forestomach tumors, respectively, whereas none of the NQO-treated ZS rats did.

CONCLUSIONS

COX-2 overexpression accompanies hyperplasia in ZD rats. Increased cell proliferation in NQO-treated ZD rats facilitates the development of tumors at multiple sites. The finding that zinc regulates COX-2 expression in vivo in an animal model may lead to prevention or therapeutic possibilities for upper aerodigestive tract cancer.

Differentially expressed genes execute zinc-induced apoptosis in precancerous esophageal epithelium of zinc-deficient rats

Zinc deficiency (ZD) in rats increases esophageal cell proliferation and the incidence of N-nitrosomethylbenzylamine-induced esophageal tumors. Conversely, zinc replenishment (ZR) rapidly induces apoptosis in esophageal epithelia and reverses cancer development. We investigated gene expression changes in ZR versus ZD esophageal epithelia to identify differentially expressed genes associated with the antitumor effect of ZR. Weanling rats were fed a ZD diet for 6 weeks to establish esophageal cell proliferation or a zinc-sufficient (ZS) diet. Then, 10 ZD rats were treated with zinc gluconate intragastrically and switched to ZS diet; the remaining 10 ZD and ZS animals were treated with saline. All animals were killed 26-28 h later. Using cDNA microarrays, real-time polymerase chain reaction amplification and RNA hybridization techniques, we identified novel differentially expressed genes, including a RNA-binding protein with two RNA recognition motifs and a zinc knuckle (ZD7), and a DNA/RNA helicase with a DEAD box (ZD10) with two splice variants, ZD10a and ZD10b. In situ hybridization detected increased mRNA expression of ZD7, ZD10a and ZD10b in ZR esophageal epithelia, which displayed markedly increased occurrence of apoptotic cells, relative to ZD epithelia. Overexpression of ZD7 in human esophageal cancer cells resulted in induction of apoptosis and activation of caspase-3 and -7, activities that were inhibited by caspase-specific inhibitors. In addition, ZD7 mRNA levels and zinc-induced apoptosis in rat squamous carcinoma cells were reduced by specific small interfering ribonucleic acids. Thus, ZR rapidly induces ZD7 and ZD10 expression, which in turn stimulates apoptosis. These results provide the beginnings of a molecular pathway for zinc-induced apoptosis under conditions that reverse esophageal tumor initiation.

Differential gene expression in hippocampus following experimental brain trauma reveals distinct features of moderate and severe injuries

Microarray technology was employed to determine the differential pattern of gene expression within the hippocampus as a result of traumatic brain injury (TBI). The validity of the microarray data was confirmed using real-time RT-PCR. Following either moderate or severe lateral fluid percussion injury, rats were studied 0.5, 4, and 24 h after injury. In general, animals exhibited mRNA up or down regulation of approximately 10% of the genes studied. However, it was clear that the pattern of gene expression was influenced by both the severity of injury and the time after injury at which animals were studied. For example, genes encoding molecules for cellular signaling, synaptic plasticity, metabolism, ion channels and transporters were up regulated following severe injury, but down regulated following moderate injury. Furthermore, moderate injury was associated with an increasing number of responsive genes as a function of time post-injury. However, animals sustaining a severe level of injury exhibited decreasing number of responsive genes during the same post-injury period. The different patterns of gene expression between injury severity and across time after the insult suggests that the pathophysiological cascade induced by TBI is accompanied by a molecular response which, like the other aspects of the cellular response for survival, may indicate a "molecular window" that may offer an opportunity for therapeutic interventions involving gene therapy. Our results also suggest that fundamentally different pathophysiological processes or cascades may be induced by different severities of injury.

Effect of zinc deficiency on the mRNA expression pattern in liver and jejunum of adult rats: monitoring gene expression using cDNA microarrays combined with real-time RT-PCR

In the study presented here, the effect of zinc deficiency on mRNA expression levels in liver and jejunum of adult rats was analyzed. Feed intake was restricted to 8 g/day. The semi-synthetic diet was fortified with pure phytate and contained either 2 microg Zn/g (Zn deficiency, n = 6) or 58 microg Zn/g (control, n = 7). After 29 days of Zn depletion feeding, entire jejunum and liver were retrieved and total RNA was extracted. Tissue specific expression pattern were screened and quantified by microarray analysis and verified individually via real-time RT-PCR. A relative quantification was performed with the newly developed Relative Expression Software Tool Copyright on numerous candidate genes which showed a differential expression. This study provides the first comparative view of gene expression regulation and fully quantitative expression analysis of 35 candidate genes in a non-growing Zn deficient adult rat model. The expression results indicate the existence of individual expression pattern in liver and jejunum and their tissue specific regulation under Zn deficiency. In addition, in jejunum a number of B-cell related genes could be demonstrated to be suppressed at Zn deficiency. In liver, metallothionein subtype 1 and 2 (MT-1 and MT-2) genes could be shown to be dramatically repressed and therefore represent putative markers for Zn deficiency. Expression results imply that some genes are expressed constitutively, whereas others are highly regulated in tissues responsible for Zn homeostasis.

Identification of hepatic molecular mechanisms of action of alpha-tocopherol using global gene expression profile analysis in rats

The recent discovery that vitamin E (VE) regulates gene activity at the transcriptional level indicates that VE may exert part of its biological effects by mechanisms which may be independent of its well-recognised antioxidant function. The objective of this study was the identification of hepatic vitamin E-sensitive genes and examination of the effects of VE on their corresponding biological endpoints. Two groups of male rats were randomly assigned to either a VE-sufficient diet or to a control diet deficient in VE for 290 days. High-density oligonucleotide microarrays comprising over 7000 genes were used to assess the transcriptional response of the liver. Differential gene expression was monitored over a period of 9 months, at four different time-points, and rats were individually profiled. This experimental strategy identified several VE-sensitive genes, which were chronically altered by dietary VE. VE supplementation down-regulated scavenger receptor CD36, coagulation factor IX and 5-alpha-steroid reductase type 1 mRNA levels while hepatic gamma glutamyl-cysteinyl synthetase was significantly up-regulated. Measurement of the corresponding biological endpoints such as activated partial thromboplastin time, plasma dihydrotestosterone and hepatic glutathione substantiated the gene chip data which indicated that dietary VE plays an important role in a range of metabolic processes within the liver.

Human nutrition and food research: opportunities and challenges in the post-genomic era

Sequencing of the human genome has opened the door to the most exciting new era for nutritional science. It is now possible to study the underlying mechanisms for diet-health relationships, and in the near future dietary advice (and possibly tailored food products) for promoting optimal health could be provided on an individual basis, in relation to genotype and lifestyle. The role of food in human evolution is briefly reviewed, from palaeolithic times to modern-day hunter-gatherer societies. The aetiology of 'diseases of modern civilization', such as diabetes, heart disease and cancer, and the effect of changes in dietary patterns are discussed. The risk of disease is often associated with common single nucleotide polymorphisms, but the effect is dependent on dietary intake and nutritional status, and is often more apparent in intervention studies employing a metabolic challenge. To understand the link between diet and health, nutritional research must cover a broad range of areas, from molecular to whole body studies, and is an excellent example of integrative biology, requiring a systems biology approach. The annual cost to the National Health Service of diet-related diseases is estimated to be in excess of 15 billion, and although diet is a key component of any preventative strategy, it is not given the prominence it deserves. For example, less than 1% of the pound 1.6 billion budget for coronary heart disease is spent on prevention. The polygenic and multifactorial nature of chronic diseases requires substantial resources but the potential rewards, in terms of quality of life and economics, are enormous. It is timely therefore to consider investing in a long-term coordinated national programme for nutrition research, combining nutritional genomics with established approaches, to improve the health of individuals and of the nation.

Nutrient-gene interactions: a single nutrient and hundreds of target genes

Based on the effects of a selective experimental zinc deficiency in a rodent model we explore the use of transcriptome profiling for assessing nutrient-gene interactions in the liver at the molecular and cellular levels. Zinc deficiency caused pleiotropic alterations in mRNA/protein levels of hundreds of genes. In the context of observed metabolic alterations in hepatic metabolism, possible mechanisms are discussed for how a low zinc status may be sensed and transmitted into changes in various metabolic pathways. However, it also becomes obvious that analysis of such complex nutrient-gene interactions beyond the descriptional level is a real challenge for systems biology.

Identification of genes responsive to intracellular zinc depletion in the human colon adenocarcinoma cell line HT-29

Zinc is essential for the structural and functional integrity of cells and plays a pivotal role in the control of gene expression. To identify genes with altered mRNA expression level after zinc depletion, we employed oligonucleotide arrays with approximately 10,000 targets and used the human colon adenocarcinoma epithelial cell line HT-29 as a model. A low intracellular zinc concentration caused alterations in the steady-state mRNA levels of 309 genes at a threshold factor of 2.0. Northern blot analysis and/or real-time RT-PCR confirmed the array results for 12 of 14 selected targets. Genes identified as regulated based on microarray data encode mainly proteins involved in central pathways of intermediary metabolism (79 genes) including protein metabolism (21). We also identified five groups of genes important for basic cellular functions such as signaling (30), cell cycle control and growth (15), vesicular trafficking (15), cell-cell interaction (13), cytoskeleton (10) and transcription control (19). The latter group comprises several zinc finger-containing transcription factors of which the Kruppel-like factor 4 showed the most pronounced changes. Western blot analysis confirmed the increased expression level of this protein in cells grown under low zinc conditions. Our findings in a homogeneous cell population demonstrate that the molecular mechanisms by which cellular functions are altered at a low zinc status, occur via pleiotropic effects on gene expression. In conclusion, the pattern of zinc-affected genes may represent a reference for further studies to define the zinc regulon in mammalian cells.

Nutritional genomics: implications for companion animals

This is an exciting time for biological scientists as the "omics" era continues to evolve and shape the way science is understood and conducted. As genome sequencing of the human comes to a close, other mammals are in line to be sequenced. Along with pigs and cows, dogs are now on the high priority list for sequencing, and cats may soon follow suit. Until sequence data are available, genetic maps may be used to reveal important physical characteristics of a genome. Genome mapping is important in identifying gene placement, but gives little information regarding function. Therefore, functional genomics, including the global analysis of RNA and protein expression, protein localization and protein-protein interactions will emerge as important areas of study. The major use of the dog and cat genome maps hitherto has been for the study of human and veterinary medicine. These powerful resources also can be applied to the field of nutritional genomics and proteomics, enhancing our understanding of metabolism and optimizing companion animal nutritional and health status. Genomics has begun to be applied to nutritional research, but issues specifically relevant to companion animals have not been elucidated thus far. The study of genomics and proteomics will be crucial in areas such as nutrient requirement determination, disease prevention and treatment, functional ingredient testing and others. Nutritional genomics and proteomics will definitely play a vital role in the future of pet foods.

Trophic and cytoprotective nutrition for intestinal adaptation, mucosal repair, and barrier function

Intestinal epithelial cell turnover (proliferation, migration, differentiation, and apoptosis) and gut barrier functions are dynamic processes that are markedly affected by nutritional status, the route of feeding, and the adequacy of specific nutrients in the diet. Emerging studies are defining potential therapeutic roles for specific nutrients and diet-derived compounds (including arginine, glutamate, glutamine, glutathione, glycine, vitamin A, zinc, and specific lipids) in gut mucosal turnover, repair, adaptation after massive bowel resection, and barrier function. The role and regulation of endogenous bowel flora in generating short-chain fatty acids from diet-derived fiber and other diet-derived compounds and the effects of these agents on gut function are increasingly being elucidated. Results of these investigations should define new nutritional methods for trophic and cytoprotective effects on the intestine in conditions such as inflammatory bowel disease, malnutrition, and short bowel syndrome.