Kinetics of iron absorption by in situ ligated small intestinal loops of broilers involved in iron transporters

Two experiments were conducted with 28-d-old commercial male broilers to study the kinetics of iron (Fe) absorption and the effect of Fe treatment on divalent metal transporter 1 (DMT1) and ferroportin 1 (FPN1) mRNA levels in in situ ligated segments from different small intestinal regions of broilers. In Exp. 1, we compared Fe absorption in 3 small intestinal segments at different post-perfusion time points after perfusion with 0.45 m of Fe as Fe sulfate (FeSO ∙ 7HO), and found that the Fe absorption in the duodenum at 30, 45, and 60 min was greater ( < 0.006) than that in the jejunum, and at 60 min, the Fe absorption in the duodenum was greater ( = 0.034) than that in the ileum. In addition, the Fe absorption at 30 min was more than 85.0% of the maximum absorption in each segment. In Exp. 2, a kinetic study of Fe absorption was performed with the duodenal, jejunal, and ileal loops perfused with solutions containing 0 (control), 0.11, 0.22, 0.45, 0.80, 1.79, or 3.58 m of Fe as FeSO 7HO. The Fe concentrations in perfusates were measured at 30 min after perfusion, and in the control group and the group treated with 0.45 m Fe as FeSO 7HO, the DMT1 and FPN1 mRNA levels in the ligated duodenum, jejunum, and ileum were analyzed. The kinetic curves of Fe absorption showed that Fe absorption in the duodenum and jejunum depended on a saturated carrier-mediated process. The maximum absorption rate in the duodenal segment was greater ( < 0.0001) than that in the jejunum (42.75 vs. 8.16 nmol × cm × min), and the Michaelis-Menten constant value was higher ( < 0.0001) in the duodenum than in the jejunum (6.16 vs. 1.31 m). In the ileum, however, the Fe absorption was a non-saturated diffusion process, and the diffusive constant was 3.54 × 10 cm × min. The DMT1 and FPN1 mRNA levels in the duodenum were greater ( < 0.0001) than those in the jejunum and ileum, and greater ( < 0.009) in the jejunum than in the ileum. No differences ( > 0.25) were detected in the DMT1 and FPN1 mRNA levels of the duodenum or jejunum and the DMT1 mRNA level of the ileum between the control and the 0.45 m Fe group, but Fe perfusion increased ( < 0.03) FPN1 mRNA level in the ileum. The above results indicate that the duodenum is the main site of Fe absorption in the small intestine of broilers, and Fe absorption in the duodenum and jejunum is a saturated carrier-mediated process, but a non-saturated diffusion process in the ileum.

HIV and malnutrition: effects on immune system

HIV or human immunodeficiency virus infection has assumed worldwide proportions and importance in just a span of 25 years. Continuous research is being done in many parts of the world regarding its treatment and vaccine development, and a lot of money has flown into this. However, fully understanding the mechanisms of immune depletion has still not been possible. The focus has also been on improving the quality of life of people living with HIV/AIDS through education, counselling, and nutritional support. Malnutrition further reduces the capacity of the body to fight this infection by compromising various immune parameters. Knowledge of essential components of nutrition and incorporating them in the management goes a long way in improving quality of life and better survival in HIV-infected patients.

Pterins as sensors of response to the application of Fe3+ -dextran in piglets

The aim of the presented study was to assess the effect of a single administration of Fe(3+)-dextran on immune cell counts and pterin biomolecule production as novel sensors of the piglets' immune system activation, and to determine concentrations of cortisol, a traditional hormonal biosensor of the stress response. Pterins (neopterin and biopterin) in the piglets' blood serum were analyzed by separation using reversed-phase HPLC. A single dose of Fe(3+)-dextran produced a special stress situation in the piglets' organism which manifested itself by an increased production of neopterin (p < 0.05) and biopterin (p < 0.01) in the experimental piglets. Changes in cortisol concentrations and leukocyte counts were influenced by handling stress and were not specifically correlated to iron dextran application. Iron concentrations in the internal environment of the experimental piglets' group were higher by an order of magnitude compared with the controls, and the highest serum concentrations of iron (p < 0.01) were reached 24 h following Fe(3+)-dextran administration. The data presented offer a new perspective on the evaluation of stress situations in the animal organism and, not least importantly, extends the rather modest current list of references on the role of pterins in livestock animals.

Undernutrition, infection and immune function

Undernutrition and infection are the major causes of morbidity and mortality in the developing world. These two problems are interrelated. Undernutrition compromises barrier function, allowing easier access by pathogens, and compromises immune function, decreasing the ability of the host to eliminate pathogens once they enter the body. Thus, malnutrition predisposes to infections. Infections can alter nutritional status mediated by changes in dietary intake, absorption and nutrient requirements and losses of endogenous nutrients. Thus, the presence of infections can contribute to the malnourished state. The global burden of malnutrition and infectious disease is immense, especially amongst children. Childhood infections impair growth and development. There is a role for breast-feeding in protection against infections. Key nutrients required for an efficient immune response include vitamin A, Fe, Zn and Cu. There is some evidence that provision of the first three of these nutrients does improve immune function in undernourished children and can reduce the morbidity and mortality of some infectious diseases including measles, diarrhoeal disease and upper and lower respiratory tract infections. Not all studies, however, show benefit of single nutrient supplementation and this might be because the subjects studied have multiple nutrient deficiencies. The situation regarding Fe supplementation is particularly complex. In addition to immunization programmes and improvement of nutrient status, there are important roles for maternal education, improved hygiene and sanitation and increased supply of quality water in the eradication of infectious diseases.

An overview of interactions between micronutrients and of micronutrients with drugs, genes and immune mechanisms

The objective of the present review is to examine critically the consequences of interactions that micronutrients undergo with nutrients and non-nutrients (mainly prescribed medicines) in diets and lifestyle factors (smoking, tea and alcohol consumption). In addition, the review describes recent work on interactions between nutrients and genes, the influence of gene polymorphisms on micronutrients, the impact of immune responses on micronutrients and specific interactions of antioxidant micronutrients in disease processes to minimise potential pro-oxidant damage.

The macrophage cell surface glyceraldehyde-3-phosphate dehydrogenase is a novel transferrin receptor

The reticuloendothelial system plays a major role in iron metabolism. Despite this, the manner in which macrophages handle iron remains poorly understood. Mammalian cells utilize transferrin-dependent mechanisms to acquire iron via transferrin receptors 1 and 2 (TfR1 and TfR2) by receptor-mediated endocytosis. Here, we show for the first time that the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is localized on human and murine macrophage cell surface. The expression of this surface GAPDH is regulated by the availability of iron in the medium. We further demonstrate that this GAPDH interacts with transferrin and the GAPDH-transferrin complex is subsequently internalized into the early endosomes. Our work sheds new light on the mechanisms involved in regulation of iron, vital for controlling numerous diseases and maintaining normal immune function. Thus, we propose an entirely new avenue for investigation with respect to transferrin uptake and regulation mechanisms in macrophages.

Risk factors for low iron intake and poor iron status in a national sample of British young people aged 4-18 years

OBJECTIVE

To examine the prevalence and dietary, sociodemographic and lifestyle risk factors of low iron intake and poor iron status in British young people.

DESIGN

National Diet and Nutrition Survey of young people aged 4-18 years.

SETTING

Great Britain, 1997.

SUBJECTS

In total, 1699 young people provided 7-day weighed dietary records, of which 11% were excluded because the participant reported being unwell with eating habits affected. Blood was obtained from 1193 participants, with iron status indicated by haemoglobin, serum ferritin and transferrin saturation.

RESULTS

Iron intakes were generally adequate in most young people aged 4-18 years. However, low iron intakes (below the Lower Reference Nutrient Intake) occurred in 44% of adolescent girls (11-18 years), being less prevalent with high consumption of breakfast cereals. Low haemoglobin concentration (<115 g l-1, 4-12 years; <120 or <130 g l-1, 13+ years for girls and boys, respectively) was observed in 9% of children aged 4-6 years, pubertal boys (11-14 years) and older girls (15-18 years). Adolescent girls who were non-Caucasians or vegetarians had significantly poorer iron status than Caucasians or meat eaters, independent of other risk factors. The three iron status indices were correlated significantly with haem, but not non-haem, iron intake.

CONCLUSIONS

Adolescent girls showed the highest prevalence of low iron intake and poor iron status, with the latter independently associated with non-Caucasian ethnicity and vegetarianism. Risk of poor iron status may be reduced by consuming (particularly lean red) meat or enhancers of non-haem iron absorption (e.g. fruit or fruit juice) in vegetarians.

Pathogenesis and treatment of anaemia of chronic disease

Anaemia of chronic disease (ACD), the most frequent anaemia among hospitalized patients, develops under chronic inflammatory disorders such as chronic infections, cancer or autoimmune diseases. A number of different pathways contribute to ACD, such as diversion of iron traffic, a diminished erythropoiesis, a blunted response to erythropoietin, erythrophagocytosis and bone marrow invasion by tumour cells and pathogens. Nevertheless, ACD is a reflection of an activated immune system and possibly results from an innovative defence strategy of the body in order to withdraw the essential growth factor iron from invading pathogens and to increase the efficacy of cell-mediated immunity. Diagnosis of ACD can be assessed by examination of chances in serum iron parameters with low to normal serum iron, transferrin saturation and transferrin concentrations on the one hand and normal to increased ferritin, zinc protoporphyrin IX and cytokine levels on the other side. Therapy of ACD includes the cure of the underlying the disease. Apart from this transfusions for rapid correction of haemoglobin levels, and human recombinant erythropoietin for prolonged therapy are used. However, response rates to recombinant erythropoietin are sometimes low. Iron alone should be strictly avoided due to its growth-promoting effect towards micro-organisms and tumour cells and because of it capacity to inhibit T-cell-mediated immune effector pathways. We urgently need prospective clinical trials to gain knowledge about the effects of anaemia correction and/or the use of erythropoietin towards the course of the underlying disease, to find out if a combination therapy with erythropoietin and iron may be beneficial in ACD and to define therapeutic end-points.

Risk factors for poor iron status in British toddlers: further analysis of data from the National Diet and Nutrition Survey of children aged 1.5-4.5 years

OBJECTIVE

: To examine risk factors for poor iron status in British toddlers.

DESIGN

: National Diet and Nutrition Survey (NDNS) of children aged 1.5-4.5 years.

SETTING

: Mainland Britain, 1992/93.

SUBJECTS

: Of the 1859 children whose parents or guardians were interviewed, a weighed dietary intake was provided for 1675, and a blood sample obtained from 1003.

RESULTS

: Mean haemoglobin (Hb) and ferritin levels were significantly lower in younger (1.5-2.5 years) than in older (3.5-4.5 years) children, with boys having significantly lower ferritin levels than girls. Poor iron status ferritin <10 microg l-1, or low values for both indices) was associated with lower socioeconomic and employment status. Iron status was directly associated with meat and fruit consumption and inversely with that of milk and milk products, after adjustment for age and gender. The latter association remained significant after further adjustment for sociodemographic variables, energy intake and body weight. Children consuming >400 g day-1 of milk and cream were less likely to consume foods in other groups, with those also consuming little meat, fish, fruit and nuts at greatest risk of poor iron status. Few associations were observed between poor iron status and individual nutrient intakes, and iron status was not associated with either iron intake or with consumption of a vegetarian diet.

CONCLUSIONS

: Overdependence on milk, where it displaces iron-rich or iron-enhancing foods, may put toddlers at increased risk of poor iron status. However, this becomes non-significant when moderate-to-high amounts of foods known to enhance iron status (e.g. meat and/or fruit) are also consumed. Milk consumption in this age group should ideally be part of a mixed and balanced diet including all food groups, and particularly lean meat (or other iron-rich or fortified foods) and fruit. This is particularly relevant for households of lower socioeconomic and employment status.

Cellular and molecular aspects of iron and immune function

Fe plays a critical role in the immune system and defence against infection. However, many aspects of the way in which Fe influences these processes at the molecular and cellular level are unclear. The present review summarizes the role of Fe in lymphocyte activation and proliferation, and discusses how Fe is handled by macrophages.

Copper deficiency suppresses effector activities of differentiated U937 cells

Dietary copper (Cu) deficiency impairs both innate and acquired branches of immunity. Specific roles of Cu in the activation and effector activities of host-defense cells remain largely unknown. The effects of Cu status on effector activities of a monocytic cell line were investigated as an initial step in the elucidation of specific functions of Cu in phagocytic cells. Exposure of differentiating U937 human promonocytic cells to 5 micromol/L 2,3, 2-tetraamine (tet), a high affinity Cu chelator, for 4 d decreased cellular Cu by 62% without altering cellular Cu,Zn-superoxide dismutase (SOD) activity, Zn content, mitochondrial activity and protein synthesis. In contrast, Cu deficiency suppressed the respiratory burst activity and markedly compromised the ability of U937 cells to kill Salmonella. Similarly, treatment of RAW264.7 murine macrophages with 5 micromol/L tet decreased cell Cu by 78% and Cu,Zn-SOD activity by 15% and increased bacterial survival by 180%. The tet-induced impairment of respiratory burst and bactericidal activities was blocked in cultures supplemented with Cu, but not Zn or Fe. In addition, lipopolysaccharide (LPS)-induced secretion of the inflammatory mediators, tumor necrosis factor-alpha, interleukin (IL)-1beta, IL-6 and prostaglandin E(2) (PGE(2)), was decreased by 30-60% in tet-treated U937 cells. Flow cytometric analysis of the surface antigens CD11b and CD71 showed that the suppressed activities of Cu-deficient cells were not due to an attenuation in the degree of differentiation or secondary iron deficiency. These data demonstrate that U937 cells provide a useful model for examining the biochemical roles of Cu in monocyte activity.

Ferritin-associated iron induces neutrophil dysfunction in hemosiderosis

Neutrophils (PMNs) from patients with secondary iron overload have an increased iron and ferritin content as well as a phagocytosis defect. Several serum components might be incriminated in the cellular iron accumulation. We therefore compared the effects on the PMN phagocytosis of total serum as well as the ferritin and transferrin fractions of serum derived from patients with thalassemia major and healthy control subjects. An incubation system of PMNs was developed. PMN phagocytosis was measured before and after incubation. Total serum from patients with thalassemia induced a defect that was prevented by co-incubation with deferoxamine (DFO). Gel-filtration chromatography was performed to separate the serum fraction containing transferrin and albumin from that containing ferritin. The transferrin-albumin fraction had no effect on PMN phagocytosis. On the contrary, the ferritin fraction of normal serum was deleterious to PMN phagocytosis, and the same fraction from thalassemic serum decreased PMN phagocytosis even more. Co-incubation with DFO or catalase improved this defect. Moreover, a cellular increase in the L-type subunit of ferritin was observed after the incubation of PMNs with the ferritin-containing fraction from thalassemic serum. In conclusion, serum from patients with thalassemia is toxic to PMNs, and this toxicity is due to ferritin-associated iron.

Nutrition and the immune system of the gut

Studies suggest that the development and expression of the regional immune system in the gastrointestinal (GI) tract is relatively independent of systemic immunity. This is reflected in significant differences in functional response of T cells and B cells and affects cytokine patterns and activation pathways when regional immunity is compared to systemic immunity. Nutrients have fundamental and regulatory influences on the immune response of the GI tract and, therefore, on host defense. In addition to the effect of nutrition during development, the local impact of different dietary and antigenic elements on the regional immune system contributes to potential diversion of the two systems throughout life. The route of exposure during antigenic contact is known to affect host immune response, whether it be a normal process, happening in the context of normal environmental encounter with nonpathogenic microbes or planned immunization, or occurring as a result of resolution of a potentially pathologic process i.e., an infectious encounter. Interactions at the local level profoundly influence systemic immune response, in part because of intrinsic differences in these systems, and also because of different requirements for optimal function. Although inflammatory processes are central to host defense in the periphery, the protective blocking action of the secretory immunoglobulin A immune response is crucial to local host defense, and, therefore, to the integrity of GI tract immune function. For these reasons, interaction with normal bacteria of the GI tract may be seen as the model of how the system has evolved and provide clues to the restoration of balance in the immunocompromised host. Reduction of normal commensal bacteria in the context of infection or after antibiotic treatment may interfere with nutrient availability and impair beneficial stimulation of GI immune response. This impairment may be associated with continued colonization with opportunistic microbes and inflammatory immune response that could lead to malabsorption and malnutrition. Study of the impact of nutrient imbalance on the function of the GI tract has profound implications for clinical medicine and may in the future lead to the rational design of preventive approaches to support immune response and host defense.