In contrast to the situation in the USA, where a wide range of genetically modified (GM) foods is available, in Europe very few GM products have been approved for marketing as foods, and there is widespread public concern about their safety and environmental impact. The marketing of a GM crop for food use in Europe falls under the EC novel foods regulations, and applications require the submission of an extensive dossier of information. The safety evaluation of GM foods presents considerable problems both in the conduct and interpretation of experimental studies, because conventional toxicity tests used in the evaluation of simple chemicals may not be appropriate for whole foods. To rationalise the safety evaluation process and to circumvent the difficulties in toxicological assessment of food materials, the concept of substantial equivalence has been developed. The concept is that if it can be demonstrated that the novel food is essentially similar to its conventional counterpart in terms of critical nutritional or anutritional components, then it is likely to be no more or less toxic than the latter. The possible introduction of unintended effects by the genetic modification process is particularly problematic for the safety evaluation process. The new genomic and post-genomic techniques are potentially valuable in the safety evaluation of GM foods, although they are as yet in their infancy.

Résumé

La génomique de la volaille a bénéficié des avancements technologiques rapides acquis en génomique humaine et sur les organismes modèles. Certains outils et certains approches sont maintenant bien établis chez le poulet, y compris les cartes et marqueurs (génétiques comme physiques), mapping loci pour caractéres quantitatifs, mapping comparative, ressources expressed sequence tag et bacterial artificial chromosome, et mapping physique. De plus, la phase suivante de la découverte génétique, la génomique fonctionnelle, est en cours. Les progre`s dans le mapping de loci pour caracte`res quantitatifs de croissance et d'adiposité seront discutés pour illustrer ces nouvelles technologies et ces nouvelles approches dans l'étude de la génétique et de la physiologie avicole.

Peroxisome proliferator-activated receptor (PPAR) α represents an important member of the nuclear hormone receptor superfamily that can be activated by a variety of natural fatty acids, some of their metabolites and by commonly-used anti-lipidaemic drugs. We recently demonstrated PPARα expression in T lymphocytes, where it controls the initiation of transcription of T-box expressed in T-cells (T-bet) independent of added agonist. T-bet is an activation-inducible transcription factor regulator of interleukin 2 (suppression) and interferon γ (stimulation) synthesis. A suppressed ability to produce interleukin 2 and an enhanced production of interferon γ occurs in activated T-cells from PPARα-/- mice, as well as in T-cells from wild-type aged animals whose lymphocytes express lowered basal levels of PPARα. The dysregulated expression and/or function of cytokines, glucocorticoids or leptin that occurs with advanced age could all be responsible for the reduced expression of PPARα. Dietary supplementation of aged mice with vitamin E, or supplementation with known agonists of PPARα, was associated with elevation of lymphocyte expression of this nuclear hormone receptor, restoration of control over T-bet expression and elimination of the dysregulated production of interleukin 2 and interferon γ following lymphocyte activation. Interleukin 2 and interferon γ play very important roles in the initiation and/or regulation of immune, inflammatory and autoimmune disease states. Thus, the mechanisms that control the timing, magnitude and duration of specific cytokine production by activated T lymphocytes need clarification before appropriate nutritional or therapeutic strategies can be devised to treat disease conditions where cytokine expression and/or activities are deemed to be dysregulated and responsible.

Oxidative damage is present within the brains of patients with Alzheimer's disease (AD), and is observed within every class of biomolecule, including nucleic acids, proteins, lipids and carbohydrates. Oxidative injury may develop secondary to excessive oxidative stress resulting from β-amyloid-induced free radicals, mitochondrial abnormalities, inadequate energy supply, inflammation or altered antioxidant defences. Treatment with antioxidants is a promising approach for slowing disease progression to the extent that oxidative damage may be responsible for the cognitive and functional decline observed in AD. Although not a uniformly consistent observation, a number of epidemiological studies have found a link between antioxidant intake and a reduced incidence of dementia, AD and cognitive decline in elderly populations. In AD clinical trials molecules with antioxidant properties such as vitamin E and Ginkgo biloba extract have shown modest benefit. A clinical trial with vitamin E is currently ongoing to determine if it can delay progression to AD in individuals with mild cognitive impairment. Combinations of antioxidants might be of even greater potential benefit for AD, especially if the agents worked in different cellular compartments or had complementary activity (e.g. vitamins E, C and ubiquinone). Naturally-occurring compounds with antioxidant capacity are available and widely marketed (e.g. vitamin C, ubiquinone, lipoic acid, β-carotene, creatine, melatonin, curcumin) and synthetic compounds are under development by industry. Nevertheless, the clinical value of these agents for AD prevention and treatment is ambiguous, and will remain so until properly designed human trials have been performed.

The rapid globalization of the world economy has increased the need for a knowledge base of reliable socio-cultural differences in perceptions, values and ways of thinking about new food technologies. Awareness of socio-cultural differences is important because collaborative efforts to deal with food hazards presuppose some understanding of where, how and why the viewpoints of various stakeholders may differ. In the present paper factors that influence public perceptions of genetically-modified (GM) food are discussed, with a special focus on the unique circumstances of populations in the USA, Europe and developing countries. It is argued that effective communication and decision making about the risk of GM food depends critically on understanding how socio-cultural groups differ in their values and in the way they deal with the risks and benefits of new technologies. The implications of psychological aspects of perceived risk (including the roles of qualitative dimensions of risk, world views and trust) for public acceptance of new food technologies are highlighted.

Re´sume´Parmi les ge`nes dont les produits jouent un rle critique dans la re´gulation de la re´ponse immune, on trouve les familles de ge`nes de l'antige`ne leucocyte humain (ALH) et de la cytokine. Les ge`nes ALH sont les plus polymorphes du ge´nome humain, et ce polymorphisme entraine des diffe´rences fonctionnelles des mole´cules ALH exprime´es, qui se traduit par des diffe´rences individuelles dans la manie`re dont des peptides antige´niques se pre´sentent aux cellules T. De plus, un nombre conside´rable de polymorphismes des ge`nes associe´s a la cytokine ont e´te´ identifie´s, la plupart d'entre eux se produisent au niveau du promoteur de ces ge`nes, ce que dans de nombreux cas se traduit par l'expression diffe´rentielle in vitro de leurs respectifs produits ge´ne´tiques pro- ou anti-inflammatoire. Des polymorphismes ALH particuliers aboutirent a` des associations bien de´finies avec un grand nombre de maladies immunologiquement medie´es, parmi lesquelles quelques-unes avec des facteurs de risque die´te´tique. Par exemple, des individus de ge´notype HLA-DQA1*0501, DQB1*0201 ont un risque deux cent fois plus grand de de´velopper une intole´rance au gluten alimentaire (maladie ce´liaque), et des facteurs additionnels en relation avec l'ALH peuvent influencer le de´veloppement d'un lymphome maligne dans une maladie ce´liaque existante. De mme, des alle`les HLA-DRB1 qui partage une se´quence motive commune constituent le premier facteur de risque ge´ne´tique de l'arthrite rhumatode. L'influence de polymorphismes associe´s a une expression de cytokine diffe´rentiel sur la susceptibilite´ aux maladies pre´sent dans ce moment un grand inte´rt. La plupart de l'attention a e´tait centre´ les associations avec la susceptibilite´ de maladies medie´es immunologiquement be´nignes, parmi eux un grand nombre de maladies de l'intestin. Toutefois, un travail re´cent dans notre laboratoire indique que les polymorphismes de la cytokine peuvent influencer la susceptibilite´ a` certains cancers (ainsi que son pronostic), entre eux le me´lanome de peau maligne et des tumeurs solides qui peuvent tre affecte´s par l'alimentation, comme le cancer de prostate (collaboration avec le CRC/BPG e´tude familial du cancer de prostate Royaume-Uni). De plus, des travails pre´liminaires sugge`rent que la modulation par l'alimentation des niveaux d'expression de certaines cytokines dans des sujets humains peut tre de´pendent du ge´notype.

The essential trace mineral, Se, is of fundamental importance to human health. As a constituent of selenoproteins it plays both structural and enzymic roles, in the latter context being best known as an antioxidant and catalyst for the production of active thyroid hormone. While Se-deficiency diseases have been recognised for some time, evidence is mounting that less-overt deficiency can also cause adverse health effects and furthermore, that supra-nutritional levels of Se may give additional protection from disease. In the context of these effects, low or diminishing Se status in some parts of the world, notably in some European countries such as the UK, is giving cause for concern. While deficiency has an adverse effect on immunocompetence, Se supplementation appears to enhance the immune response. Se appears to be a key nutrient in counteracting certain viral infections; thus, in a Se-deficient host the benign coxsackie virus becomes virulent, causing heart damage, the influenza virus causes more serious lung pathology and HIV infection progresses more rapidly to AIDS. Long recognised as essential for successful animal reproduction, Se is required for human sperm maturation and sperm motility and may reduce the risk of miscarriage. Deficiency has been linked to adverse mood states. Findings have been equivocal in linking Se to cardiovascular disease risk, although other conditions involving oxidative stress and inflammation have shown some association with Se status. There is growing evidence that higher Se intakes are associated with reduced cancer risk. While persuasive evidence already exists to suggest that additional Se would be beneficial in some health conditions, results from intervention trials underway or planned have the potential to reinforce or refute the argument for increasing Se intake.

Dietary fatty acids have numerous effects on cellular function, many of which are achieved by altering the expression of genes. The present paper reviews recent data on the mechanisms by which fatty acids influence DNA transcription, and focus specifically on the importance of three transcription factors: peroxisome proliferator-activated receptor α; liver X receptor α; sterol regulatory element-binding protein 1c. These data indicate that fatty acids induce or inhibit the mRNA expression of a variety of different genes by acting both as agonists and as antagonists for nuclear hormone receptors.

Nutritional epidemiology of cancer has gone through several stages. Initially, the long latency of cancer, the difficulties in undertaking long-term cohort investigations or ascertaining remote diet in case-control studies, and the absence of convenient intermediate biomarkers of disease, such as cholesterol in cardiovascular diseases, discouraged studies on diet and cancer. Subsequently, however, epidemiological successes in the chemical, viral and occupational aetiology of cancer, and the increasing insight into the sources of variation of diet and dietary information, prompted investigators to undertake both case-control and cohort studies. The results have been mixed. On the one hand, vegetables and fruits have been shown to be inversely associated with several forms of cancer. On the other hand, the information concerning specific macro- or micronutrients in relation to particular forms of cancer has been very limited and mostly inconclusive. There are several reasons for the complexity of investigations of the nutritional epidemiology of cancer and these reasons are briefly considered. An overview of our current understanding of the nutritional causes of cancer is also presented. It is noted that, notwithstanding the substantial gaps in our scientific knowledge, preventive nutritional approaches can be envisaged and they are likely to be moderately succeessful.

The skills and knowledge required to carry out food allergen avoidance are becoming increasingly sophisticated. It is not enough to know the names of a handful of dishes which contain a known allergen as an ingredient. Many lifestyles now depend on food prepared away from the home. New product development has introduced a wide range of ingredients and dishes which are labour saving, exciting and innovative. Product traceability now depends on advanced technological support as it struggles to keep up with foods manufactured, prepared and served in ever more complex circumstances. Consumers are now faced with ‘a jungle of choices’. However, those individuals who need to avoid a known allergen, particularly in trace quantities, often find that the food choice deemed suitable is poor, and the information available inadequate or even dangerously misleading. There are two important groups for whom this situation is a major concern. Thousands of families with young children are forced to live with the possibility that everyday foods may be contaminated by a known allergen which could kill in minutes. They live on their nerves, reading every packet and resorting to hyperprotective childcare and vigilance. In addition, the youngest independent consumers, teenagers and those in their twenties, may have little first-hand experience of food preparation. They may be ill-equipped in food-allergen risk assessment. Sadly, those who die from anaphylaxis or allergen-triggered asthma are often in this age-group. Current initiatives to support consumers at risk include a recognised standard for manufacturers seeking to eliminate an allergen from their production, and the integration of food allergy into training for caterers and food standards enforcement professionals.

Previous work has demonstrated that, besides its effects on Ca and bone metabolism, the active form of cholecalciferol, 1,25-dihydroxycholecalciferol (1,25(OH)2D3), possesses pronounced immunomodulatory effects. In non-obese diabetic (NOD) mice primary (before disease onset), secondary (after insulitis but before diabetes onset) as well as tertiary (after transplantation of syngeneic islets) prevention of diabetes was demonstrated with 1,25(OH)2D3 and its chemically-manufactured non-hypercalcaemic analogues. 1,25(OH)2D3 exerts its immune effects both at the level of the T lymphocyte (shift in cytokine profile from T-helper (Th)1 to Th2, enhanced sensitivity to apoptosis-inducing signals) as well as at the level of the antigen-presenting cell (reduced antigen presentation, reduced production of Th1-promoting cytokines, reduced expression of co-stimulatory molecules). Also, physiologically, 1,25(OH)2D3 is believed to have a role in the immune system by serving as a negative feedback signal, limiting the mounted immune reaction. To test the clinical applicability of 1,25(OH)2D3 as treatment for type 1 diabetes in genetically-at-risk young children, we tested whether short-term early-life intervention with cholecalciferol or non-hypercalcaemic analogues of 1,25(OH)2D3 could prevent diabetes in NOD mice. Significant protection of pancreatic β cells against autoimmune destruction was observed in analogue-treated and especially in cholecalciferol-treated NOD mice as compared with controls (P < 0.005). This short-term early-life intervention was, however, not able to protect the mice from developing diabetes during their lifetime. Possible solutions are longer or combined treatments with other immunomodulators that have synergistic effects with 1,25(OH)2D3 and its analogues.

Résumé

A la différence des mutations génétiques rares mais séveères qui causent les maladies monogéniques, les facteurs génétiques qui modulent la susceptibilité individuelle aux maladies multifactorielles (maladies cardiovasculaires, cancer, diabeète) sont des formes fréquentes, fonctionnellement différentes, des ge`nes (polymorphismes) qui ont généralement un effet modeste au niveau individuel, mais en raison de leur grande fréquence dans la population, peuvent être associés à un risque attribuable élevé. Les facteurs environnementaux peuvent révéler ou faciliter l'expression phénotypique de ces ge`nes de susceptibilité. En effet, dans le cas des maladies communes, les effets génétiques peuvent etre considérablement amplifiés en présence de facteurs déclenchants. On sait maintenant que la plupart des geènes de susceptibilité aux maladies communes n'ont pas un rôle étiologique primaire dans la prédisposition a` la maladie mais agissent plutot comme des modificateurs dans la réponse a` des facteurs exoge`nes tels que le stress, l'environnement, la maladie, la prise de médicament, le régime alimentaire. Une meilleure caractérisation des interactions entre facteurs génétiques et environnementaux constitue un élément clé dans la compréhension de la pathogéneèse des maladies multifactorielles. Cet article présente trois exemples d'interaction gène-environnement dans le domaine des maladies coronariennes.

Although the clinical benefits of dietary supplementation with n-3 polyunsaturated fatty acids (PUFA) has been recognised for a number of years, the molecular mechanisms by which particular PUFA affect metabolism of cells within the synovial joint tissues are not understood. This study set out to investigate how n-3 PUFA and other classes of fatty acids affect both degradative and inflammatory aspects of metabolism of articular cartilage chondrocytes using an in vitro model of cartilage degradation. Using well-established culture models, cartilage explants from normal bovine and human osteoarthritic cartilage were supplemented with either n-3 or n-6 PUFA, and cultures were subsequently treated with interleukin 1 to initiate catabolic processes that mimic cartilage degradation in arthritis. Results show that supplementation specifically with n-3 PUFA, but not n-6 PUFA, causes a decrease in both degradative and inflammatory aspects of chondrocyte metabolism, whilst having no effect on the normal tissue homeostasis. Collectively, our data provide evidence supporting dietary supplementation of n-3 PUFA, which in turn may have a beneficial effect of slowing and reducing inflammation in the pathogenesis of degenerative joint diseases in man.

Supplementation has many potential advantages over fortification and dietary approaches for improving micronutrient intake. Pregnant and lactating women and infants are most likely to benefit from supplementation. Recent experience with vitamin A supplementation in young children has proved to be remarkably successful. Demonstrated efficacy of vitamin A supplements for improved child survival in many settings and a technical consensus on how to implement interventions were major factors in achieving this success. Bilateral and UN agencies worked together so that in 1999 80 % of children under 5 years of age in the least-developed countries received a vitamin A capsule in the last 6 months. At least one million child lives saved were associated with the increase in coverage in the last 2 years of the 1990s. Experience with Fe-folate supplements has not been as successful. Whilst a technical consensus has been reached on how to implement programmes to control Fe deficiency, the lack of convincing evidence of efficacy of Fe-folate supplements in terms of maternal and child survival outcomes has undoubtedly contributed to the limited pursuit of effective action. A new multiple micronutrient supplement for se amongst women of reproductive age in developing countries has been formulated. UNICEF is employing the supplement in programmes aimed at helping to prevent low birth weight. The new supplement is likely to be more efficacious than Fe-folate supplements for both maternal and child survival and development outcomes. Successful completion of rigorous efficacy trials will be critical for creating the political support needed to achieve universal coverage.

Experimental evidence indicates that the primary maternal environmental factor that regulates feto–placental growth is substrate delivery to the placental site, which is the product of maternal substrate levels and the rate of placental-bed blood flow. Thus, maternal factors which change either substrate level or flow alter feto–placental growth rate. The best-studied substrate in human pregnancy is glucose, and there is a direct relationship between maternal blood glucose levels and size at birth. Altering the type of carbohydrate eaten (high- v. low-glycaemic sources) changes postprandial glucose and insulin responses in both pregnant and non-pregnant women, and a consistent change in the type of carbohydrate eaten during pregnancy influences both the rate of feto–placental growth and maternal weight gain. Eating primarily high-glycaemic carbohydrate results in feto–placental overgrowth and excessive maternal weight gain, while intake of low-glycaemic carbohydrate produces infants with birth weights between the 25th and the 50th percentile and normal maternal weight gain. The calculated difference in energy retention with similar total energy intakes is of the order of 80 000 kJ. Preliminary information from subsequent metabolic studies indicates that the mechanisms involved include changes in: daily digestible energy requirements (i.e. metabolic efficiency), substrate utilization (glucose oxidation v. lipid oxidation), and insulin resistance and sensitivity. Thus, altering the source of maternal dietary carbohydrate may prove to be a valuable tool in the management of pregnancies at risk for anomalous feto–placental growth and for the prevention and/or treatment of obesity and insulin resistance in the non-pregnant state.

The ultimate goal of an organism is to maximise its inclusive fitness, and an important sub-goal must be the optimisation of the lifetime pattern of food intake, in order to meet the nutrient demands of survival, growth and reproduction. The conventional assumption that fitness is maximised by maximising daily food intake, subject to physical and physiological constraints, has been challenged recently. Instead, it can be argued that fitness is maximised by balancing benefits and costs over the organism's lifetime. The fitness benefits of food intake are a function of its contribution to survival, growth (including necessary body reserves) and reproduction. Against these benefits must be set costs. These costs include not only extrinsic foraging costs and risks, such as those due to predation, but also intrinsic costs associated with food intake, such as obesity and oxidative metabolism that may reduce vitality and lifespan. We argue that the aggregate of benefits and costs form the fitness function of food intake and present examples of such an approach to predicting optimal food intake.

It is widely believed that body fatness (and hence total body mass) is regulated by a lipostatic feedback system. This system is suggested to involve at least one peripheral signalling compound, which signals to the brain the current size of body fat stores. In the brain the level of the signal is compared with a desirable target level, and food intake and energy expenditure are then regulated to effect changes in the size of body fat stores. There is considerable support for this theory at several different levels of investigation. Patterns of body-mass change in subjects forced into energy imbalance seem to demonstrate homeostasis, and long-term changes in body mass are minor compared with the potential changes that might result from energy imbalance. Molecular studies of signalling compounds have suggested a putative lipostatic signal (leptin) and a complex network of downstream processing events in the brain, polymorphisms of which lead to disruption of body-mass regulation. This network of neuropeptides provides a rich seam of potential pharmaceutical targets for the control of obesity. Despite this consistent explanation for the observed phenomena at several different levels of enquiry, there are alternative explanations. In the present paper we explore the possibility that the existence of lipostatic regulation of body fatness is an illusion generated by the links between body mass and energy expenditure and responses to energy imbalance that are independent of body mass. Using computer-based models of temporal patterns in energy balance we show that common patterns of change in body mass following perturbation can be adequately explained by this ‘non-lipostatic’ model. This model has some important implications for the interpretations that we place on the molecular events in the brain, and ultimately in the search for pharmaceutical agents for alleviation of obesity.

Nutrient insults in early pregnancy, such as nutrient deprivation during famines, are often associated with an unfavourable outcome. Suboptimal nutrition in the early stage of gestation has been linked to a number of adverse effects on fetal growth and development. Historically, nausea and vomiting in pregnancy (NVP) was an important contributor to pregnancy-related mortality; indeed, Charlotte Bronte died from starvation and dehydration after suffering very severe NVP 4 months into her first pregnancy (Gaskell, 1858). Although NVP seldom now progresses to be life-threatening, it affects the majority of pregnant women, and potentially presents a challenge to nutrient intake in the most vulnerable period of development. Symptoms range from mild (nausea only) to severe (a level of vomiting that restricts nutrient intake and ultimately threatens metabolic and electrolyte balance). Although NVP has been documented for thousands of years, its cause has not yet been satisfactorily elucidated, but seems to be related to endocrinological changes. Pregnant women also frequently report dietary cravings and aversions during pregnancy which can be linked to both the incidence and severity of NVP. Paradoxically, NVP appears to be positively associated with a favourable outcome of pregnancy, including increased birth weight and gestational age. The mechanisms by which NVP favours the outcome of pregnancy are not known. They may be related to women increasing their nutrient intake to alleviate symptoms, improving the quality of their diet or reducing energy expenditure. Alternatively, adaptation to a reduced nutrient intake might stimulate the expression of growth factors and affect placentation or metabolism, thus favouring fetal growth when NVP resolves.

Food fortification is likely to have played an important role in the current nutritional health and well-being of populations in industrialized countries. Starting in the early part of the 20th century, fortification was used to target specific health conditions: goitre with iodized salt; rickets with vitamin D-fortified milk; beriberi, pellagra and anaemia with B-vitamins and Fe-enriched cereals; more recently, in the USA, risk of pregnancy affected by neural-tube defects with folic acid-fortified cereals. A relative lack of appropriate centrally-processed food vehicles, less-developed commercial markets and relatively low consumer awareness and demand, means it has taken about another 50 years for fortification to be seen as a viable option for the less-developed countries. The present paper reviews selected fortification initiatives in developing countries to identify different factors that contributed to their successful implementation, as well as the challenges that continually threaten the future of the se programmes. Ultimately, the long-term sustainability of fortification programmes is ensured when consumers are willing and able to bear the additional cost of fortified foods. There has been an enormous increase in fortification programmes over the last couple of decades in developing countries. Considerable progress has been made in reducing vitamin A and I deficiencies, although less so with Fe, even as Zn and folic acid deficiencies are emerging as important public health problems. Food fortification based on sound principles and supported by clear policies and regulations can play an increasingly large role in this progress towards prevention and control of micronutrient malnutrition.

The aim of the present paper is to briefly review the literature relating to clinical studies of the use of polyunsaturated long-chain fatty acids in the treatment of inflammatory bowel diseases ( IBD) such as ulcerative colitis and Crohn's disease. The reasons for the discrepancies in the findings could be related to the different study designs, different treatments, overlapping of treatment effects, as well as the variety of treatment formulations and doses used, which have led to results that are, in certain instances, very difficult to explain. Emphasis on a treatment formulation which reduces the incidence of side effects, together with careful selection of patients and experimental design, seems to be associated with benefits, and these studies point to the therapeutic potential for these lipids in the therapy of IBD. It is possible that these fatty acids act by reducing low-grade active inflammation rather than by preventing reinitiation of the inflammatory process from a truly quiescent state. Whether this treatment is applicable to all IBD patients has not been fully elucidated. Nevertheless, taken together, all these studies suggest the effectiveness of these new therapeutic approaches, not only when conventional treatment fails or when it is not possible to treat chronically, but also, in some instances, as first choice.