Circulating cytokines in pulmonary tuberculosis according to HIV status and dietary iron content.

OBJECTIVE: To evaluate human immunodeficiency virus (HIV) serology, dietary iron and serum concentrations of markers of T-helper type (Th) 1 and Th-2 immune pathways in the setting of tuberculosis (TB). METHODS: A total of 49 patients with pulmonary TB in rural Zimbabwe, 32 of whom were HIV-positive, were evaluated at presentation and over 10 weeks of anti-tuberculosis treatment. RESULTS: Interleukin (IL) 12 and neopterin, Th-1 markers, were both elevated at presentation in 92% of the subjects. In contrast, only 23% had elevation of the Th-2 marker, IL-4. Neopterin and IL-6 concentrations decreased over 10 weeks of treatment (P

Ferritin and increased vs upper reference interval tibc saturation to identify increased iron stores in African Americans.

BACKGROUND: Increased serum ferritin (SF) in combination with increased total iron binding capacity saturation (TS) in the upper reference internal was evaluated to identify African Americans with increased iron stores. METHODS: Among 16,856 primary care-based African Americans screened at Howard University Field Center of the Hereditary Hemochromatosis and Iron Overload Screening (HEIRS) Study, 142 with SF >500 microg/l women or >700 microg/l men and increased TS (>45% women or >50% men; main study) and 146 with similar ferritin increases and upper reference interval TS (30-45% women or 35-50% men; ancillary study) were offered clinical evaluation to confirm increased SF and identify the cause. RESULTS: Repeat SF remained increased in 83% of 92 participants with increased TS initially (main study) vs 58% of 64 with upper reference interval TS initially (ancillary study) (P=0.0002). These persistent SF increases were associated with blood transfusions (treatment for sickle cell disease) in 20% of 76 main study and 11% of 37 ancillary study participants (P=0.4). Ninety percent of participants with persistent non-transfusional increased SF in the main study and 85% in the ancillary study had alanine-aminotransferase, aspartate-aminotransferase, C-reactive protein and/or hemoglobin values outside of the reference interval. Increased iron stores were documented by phlebotomy or liver biopsy in 4 of 7 main study and 2 of 2 ancillary study participants with persistent non-transfusional increase in SF. CONCLUSION: Increased iron stores occur in African Americans with increased SF in combination with either increased or upper reference interval TS. Limiting clinical evaluation to only those individuals with both increased SF and increased TS will miss individuals with increased iron stores.

A genome-wide linkage scan for iron phenotype quantitative trait loci: the HEIRS Family Study.

Iron overload phenotypes in persons with and without hemochromatosis are variable. To investigate this further, probands with hemochromatosis or evidence of elevated iron stores and their family members were recruited for a genome-wide linkage scan to identify potential quantitative trait loci (QTL) that contribute to variation in transferrin saturation (TS), unsaturated iron-binding capacity (UIBC), and serum ferritin (SF). Genotyping utilized 402 microsatellite markers with average spacing of 9 cM. A total of 943 individuals, 64% Caucasian, were evaluated from 174 families. After adjusting for age, gender, and race/ethnicity, there was evidence for linkage of UIBC to chromosome 4q logarithm of the odds (LOD) = 2.08, p = 0.001) and of UIBC (LOD = 9.52), TS (LOD = 4.78), and SF (LOD = 2.75) to the chromosome 6p region containing HFE (each p < 0.0001). After adjustments for HFE genotype and other covariates, there was evidence of linkage of SF to chromosome 16p (LOD = 2.63, p = 0.0007) and of UIBC to chromosome 5q (LOD = 2.12, p = 0.002) and to chromosome 17q (LOD = 2.19, p = 0.002). We conclude that these regions should be considered for fine mapping studies to identify QTL that contribute to variation in SF and UIBC.

Initial screening transferrin saturation values, serum ferritin concentrations, and HFE genotypes in Native Americans and whites in the Hemochromatosis and Iron Overload Screening Study.

We compared initial screening transferrin saturation (TfSat) and serum ferritin (SF) phenotypes and HFE C282Y and H63D genotypes of 645 Native American and 43,453 white Hemochromatosis and Iron Overload Screening Study participants who did not report a previous diagnosis of hemochromatosis or iron overload. Elevated measurements were defined as TfSat >50% in men and >45% in women and SF >300 ng/ml in men and >200 ng/ml in women. Mean TfSat was 31% in Native American men and 32% in white men (p = 0.0337) and 25% in Native American women and 27% in white women (p < 0.0001). Mean SF was 153 microg/l in Native American and 151 microg/l in white men (p = 0.8256); mean SF was 55 microg/l in Native American women and 63 microg/l in white women (p = 0.0015). The C282Y allele frequency was 0.0340 in Native Americans and 0.0683 in whites (p < 0.0001). The H63D allele frequency was 0.1150 in Native Americans and 0.1532 in whites (p = 0.0001). We conclude that the screening TfSat and SF phenotypes of Native Americans are similar to those of whites. The allele frequencies of HFE C282Y and H63D are significantly lower in Native Americans than in whites.

Benefits and risks of iron therapy for chronic anaemias.

Iron is used widely for the treatment of anaemias with iron-restricted erythropoiesis. This intervention can be both beneficial and detrimental depending on the type of the underlying process. While in iron deficiency anaemia (IDA), the most frequent anaemia in the world, iron is the therapy of choice, this intervention can be harmful in the anaemia of chronic disease or anaemia associated with renal failure, the most common anaemias in hospitalized adult patients in Western countries. Iron is able to negatively affect cell-mediated immune effector mechanisms directed against invading microorganisms and tumour cells while at the same time, as an essential nutrient, it can stimulate the proliferation of these unwanted cells. In addition, iron catalyses the formation of toxic radicals leading to tissue damage or the promotion of cardiovascular events. Thus, it is essential to correctly diagnose the precise cause of anaemia and to consider the benefits and hazards of targeted iron therapy.

Relationship between transferrin saturation and iron stores in the African American and US Caucasian populations: analysis of data from the third National Health and Nutrition Examination Survey.

In previous analyses of transferrin saturation data in African Americans and Caucasians from the second National Health and Nutrition Examination Survey (NHANES II), subpopulations were found consistent with population genetics for common loci that influence iron metabolism. The goal of this new study was to determine if these transferrin saturation subpopulations have different levels of iron stores. Statistical mixture modeling was applied to transferrin saturation data for African Americans and Caucasians from the third National Health and Nutrition Examination Survey (NHANES III), and then the mean serum ferritin concentrations were determined for the transferrin saturation subpopulations that were identified. After adjustment for diurnal variation, 3 subpopulations of transferrin saturation were identified in each racial group. Satisfying Hardy-Weinberg conditions for major locus effects, in both racial groups the sum of the square roots of the proportion with the lowest mean transferrin saturation and the proportion with the highest mean transferrin saturation was approximately 1. When weighted to reflect the US adult population as a whole, these subpopulations of increasing transferrin saturations had progressively increasing mean age-adjusted serum ferritin concentration values in each ethnic grouping as stratified by sex (trend test, P <.002 for all). These results are consistent with the concept that population transferrin saturation subpopulations reflect different levels of storage iron.

An IRP-like protein from Plasmodium falciparum binds to a mammalian iron-responsive element.

This study cloned and sequenced the complementary DNA (cDNA) encoding of a putative malarial iron responsive element-binding protein (PfIRPa) and confirmed its identity to the previously identified iron-regulatory protein (IRP)-like cDNA from Plasmodium falciparum. Sequence alignment showed that the plasmodial sequence has 47% identity with human IRP1. Hemoglobin-free lysates obtained from erythrocyte-stage P falciparum contain a protein that binds a consensus mammalian iron-responsive element (IRE), indicating that a protein(s) with iron-regulatory activity was present in the lysates. IRE-binding activity was found to be iron regulated in the electrophoretic mobility shift assays. Western blot analysis showed a 2-fold increase in the level of PfIRPa in the desferrioxamine-treated cultures versus control or iron-supplemented cells. Malarial IRP was detected by anti-PfIRPa antibody in the IRE-protein complex from P falciparum lysates. Immunofluorescence studies confirmed the presence of PfIRPa in the infected red blood cells. These findings demonstrate that erythrocyte P falciparum contains an iron-regulated IRP that binds a mammalian consensus IRE sequence, raising the possibility that the malaria parasite expresses transcripts that contain IREs and are iron-dependently regulated.

Association of pulmonary tuberculosis with increased dietary iron.

To determine whether increased dietary iron could be a risk factor for active tuberculosis, dietary iron history and human immunodeficiency virus (HIV) status were studied in 98 patients with pulmonary tuberculosis and in 98 control subjects from rural Zimbabwe. Exposure to high levels of dietary iron in the form of traditional beer is associated with increased iron stores in rural Africans. HIV seropositivity was associated with a 17.3-fold increase in the estimated odds of developing active tuberculosis (95% confidence interval [95% CI], 7.4-40.6; P<.001), and increased dietary iron was associated with a 3.5-fold increase (95% CI, 1.4-8.9; P=.009). Among patients treated for tuberculosis, HIV seropositivity was associated with a 3.8-fold increase in the estimated hazard ratio of death (95% CI, 1.0-13.8; P=.046), and increased dietary iron was associated with a 1.3-fold increase (95% CI, 0.4-6.4; P=.2). These findings are consistent with the hypothesis that elevated dietary iron may increase the risk of active pulmonary tuberculosis.

Iron status and the outcome of HIV infection: an overview.

BACKGROUND: Theoretical considerations and experiments in the laboratory suggest that excessive iron stores may have an adverse effect on immunity. If so, high iron stores might be especially a problem in patients with human immunodeficiency virus (HIV) infection. OBJECTIVE AND STUDY DESIGN: Review published clinical studies that provide information regarding the effect of iron status on the outcome of HIV infection. RESULTS: Four clinical observations have provided some perspective on the effect of iron status on the outcome of HIV-1 infection. First, in a retrospective study of HIV-positive thalassemia major patients, the rate of progression of HIV disease was significantly faster in patients with lower doses of desferrioxamine and higher serum ferritin concentrations. Second, the inadvertent simultaneous administration of low doses of oral iron with dapsone for the prophylaxis of Pneumocystis carinii pneumonia in HIV-positive patients may have been associated with excess mortality. Third, a study of haptoglobin polymorphisms in HIV-positive subjects indicated that the haptoglobin 2-2 polymorphism is associated with higher iron stores and shortened survival as compared with the haptoglobin 1-1 or 2-1 phenotypes. Fourth, a retrospective study of bone marrow macrophage iron in HIV-positive patients suggested that survival is shorter with high iron stores. CONCLUSION: These four observations raise the possibility that high iron status may adversely influence the outcome of HIV-1 infection.

Iron and Mycobacterium tuberculosis infection.

BACKGROUND: iron is known to play a role in the susceptibility to and outcome of several infections. In view of the increasing worldwide problem of tuberculosis, it may be important to ascertain whether this is also the case with this infection. OBJECTIVES: (1) to review studies conducted in vitro, in experimental animals, and in humans that provide evidence that iron status may influence the occurrence and outcome of tuberculosis. (2) To perform an in vivo study in mice, examining the effect of iron loading on experimental infection caused by a virulent strain of Mycobacterium tuberculosis. RESULTS: we studied the effect of iron loading on the growth in spleen and lungs of a virulent strain of M. tuberculosis, injected i.v. in female Balb/C mice. At sacrifice on day 42 after the experimental infection, the iron-loaded mice presented a significantly enhanced multiplication of M. tuberculosis in both the spleen and the lungs, when compared to the mice without iron loading. CONCLUSION: Most of the studies, including our experimental study in mice, tend to suggest that an excess of iron may enhance the growth of M. tuberculosis and worsen the outcome of human tuberculosis.

Transferrin polymorphism influences iron status in blacks.

BACKGROUND: Genetic variants of human transferrin (TF) have been described, but little is known about their functional differences. We studied iron status according to TF phenotype in a healthy Zimbabwean population and in subjects at risk of African iron overload. METHODS: The study population consisted of 483 nondrinkers, 31 drinking spouse pairs, and 5 family pedigrees (n = 88) with index cases of iron overload. TF phenotypes were determined using starch gel electrophoresis. To evaluate iron status, serum iron, total iron-binding capacity (TIBC), ferritin, and soluble TF receptors were measured, and the percentage of saturation and the serum iron:TF ratio were calculated. The binding of the TF variants was studied by equilibrium dialysis. RESULTS: The reference population was characterized by a high TF D allele frequency (0.050) and a complete absence of homozygous TF DD individuals. Similar allele frequencies were observed in subjects at risk of African iron overload. In the reference population, male TF CD heterozygotes had significantly lower (P <0.01) values for serum iron, TIBC, TF saturation, and serum iron:TF ratio than the TF CC homozygotes; in females, only TIBC was significantly different. Overall red blood cell indices did not differ according to TF phenotype. In the population at risk of African iron overload, only serum iron:TF ratio was consistently significantly lower in TF CD phenotypes (P <0.05). After equilibrium dialysis, the amount of iron bound by TF was significantly lower (P <0.01) in TF CD individuals. CONCLUSIONS: The present data demonstrate a functional difference between TF phenotypes in blacks.

African iron overload.

African iron overload has been recognised in sub-Saharan Africa for seventy years. The condition is distinct from the well-characterised HLA-linked haemochromatosis described in Caucasians. Increased dietary iron intake predisposes to the condition. Recent evidence suggest that African iron overload may be caused by an interaction between increased dietary iron and a genetic defect not associated with the HLA-locus. Iron deposition is prominent both in macrophages and in hepatic parenchymal cells. Iron overload is distinct from alcoholic liver disease, although the excess dietary iron is derived from a traditional beverage that contains alcohol. African iron overload has clinical consequences. It is a cause of hepatic fibrosis and cirrhosis, and associations with diabetes mellitus, peritonitis, scurvy and osteoporosis have been described. African iron overload may be a cause of hepatocellular carcinoma. The disorder is associated with a poor outcome in tuberculosis, an infection that is highly prevalent in sub-Saharan Africa.

Measurements of iron status and survival in African iron overload.

INTRODUCTION: Dietary iron overload is common in southern Africa and there is a misconception that the condition is benign. Early descriptions of the condition relied on autopsy studies, and the use of indirect measurements of iron status to diagnose this form of iron overload has not been clarified. METHODS: The study involved 22 black subjects found to have iron overload on liver biopsy. Fourteen subjects presented to hospital with liver disease and were found to have iron overload on percutaneous liver biopsy. Eight subjects, drawn from a family study, underwent liver biopsy because of elevated serum ferritin concentrations suggestive of iron overload. Indirect measurements of iron status (transferrin saturation, serum ferritin) were performed on all subjects. Histological iron grade and hepatic iron concentration were used as direct measures of iron status. RESULTS: There were no significant differences in either direct or indirect measurements of iron status between the two groups. In 75% of these subjects the hepatic iron concentration was greater than 350 micrograms/g dry weight, an extreme elevation associated with a high risk of fibrosis and cirrhosis. Serum ferritin was elevated in all subjects and the transferrin saturation was greater than 60% in 93% of the subjects. Hepatomegaly was present in 20 of the 22 cases and there was only a moderate derangement in liver enzymes except for a tenfold increase in the median gamma-glutamyl transpeptidase concentration. There was a strong correlation between serum ferritin and hepatic iron concentrations (r = 0.71, P = 0.006). After a median follow-up of 19 months, 6 (26%) of the subjects had died. The risk of mortality correlated significantly with both the hepatic iron concentration and the serum ferritin concentration. CONCLUSIONS: Indirect measurements of iron status (serum ferritin concentration and transferrin saturation) are useful in the diagnosis of African dietary iron overload. When dietary iron overload becomes symptomatic it has a high mortality. Measures to prevent and treat this condition are needed.

Iron chelators as anti-infectives; malaria as a paradigm.

Malaria is the major life threatening parasitic disease and the cause of a global public health problem. The failure of vector eradication programs and the appearance and spread of drug resistant parasites have posed the urgent challenge of developing effective, safe and affordable anti-malarial drugs. The design of such drugs is largely based on the targeting of agents to the parasite-based machinery for host digestion and to the products of hemoglobin catabolism. Iron chelators, by depriving intracellular parasites from essential iron, lead to selective suppression of parasite growth. However, by acting on parasite-impaired macrophages, chelators can also expedite resumption of phagocytosis and elimination of parasites. In order to be clinically effective, chelators need to be maintained in the blood for extensive time periods. Therapeutic doses can be attained with appropriate drug combinations and formulations or delivery devices and these must be presented in a form well tolerated by the host. The early documentation that chelation therapy has activity against human malaria has paved the road for the design of novel and more efficient remedies based on short-term iron deprivation.

Associations between cellular immune effector function, iron metabolism, and disease activity in patients with chronic hepatitis C virus infection.

We studied the associations of macrophage activity, T-helper cell types 1 and 2 (Th-1/Th-2) responses, and iron status in 55 patients with hepatitis C virus (HCV)-related liver disease and 28 control patients with noninfectious liver disease. Serum concentrations of soluble tumor necrosis factor receptor type II (sTNFrec 75), a macrophage activation marker, were higher in cirrhotic than in noncirrhotic patients (P<.001) regardless of their HCV status, whereas levels of neopterin, interleukin (IL)-4 and IL-10 did not differ significantly. In HCV-positive patients, sTNFrec 75 levels and transferrin saturation (TfS) correlated positively with levels of aspartate transaminase (P<.001 for sTNFrec 75 and P=.028 for TfS) and alanine transaminase (P=.003 for sTNFrec 75 and P=.039 for TfS). Increased TfS correlated significantly with both advanced liver disease and a predominant Th-2 pattern in HCV patients. Our data suggest that an association exists between macrophage activation and hepatic dysfunction, and that iron status may affect the clinical course of HCV infection by modulating Th-1/Th-2 responses in vivo.

A traditional beverage prevents iron deficiency in African women of child bearing age.

OBJECTIVE: To determine if a traditional item in the diet might be useful in preventing iron deficiency in African women of child-bearing age. DESIGN: In a prospective study, the iron status of women who did and did not drink traditional beer high in iron and folic acid, was compared. Iron status was determined by a combination of haemoglobin, serum ferritin and transferrin saturation. SETTING: The study was conducted amongst rural villagers in the Murehwa and Zaka districts of Zimbabwe and in Mpumalanga Province, South Africa. SUBJECTS: 112 women aged between 12 and 50 y from a population of 425 rural people participating in on-going family genetic studies. RESULTS: Women who consumed traditional beer had significantly higher serum ferritin concentrations and transferrin saturations compared to non-drinkers (P = 0.0001 and 0.03 respectively). Iron deficiency anaemia was not present in drinkers but the prevalence in non-drinkers was 13%. Forty seven percent of the non-drinkers and only 14% of the drinkers had evidence of iron deficiency (P = 0.002). Six (21%) of the drinkers and none of the non-drinkers had evidence of iron overload (transferrin saturation > 55% and serum ferritin > 400 ug/l). CONCLUSION: We conclude that the consumption of traditional beer, rich in iron, protects women against iron deficiency. While the use of an alcoholic beverage is not ideal, our findings suggest that indigenous cultural practices might be successfully employed or adapted for promoting iron nutrition.

Chelation of iron within the erythrocytic Plasmodium falciparum parasite by iron chelators.

To examine the site of action of antimalarial iron chelators, iron ligands were added to control erythrocytes and to erythrocytes parasitized with Plasmodium falciparum, and the concentration of intracellular labile iron was monitored with the fluorescent probe, calcein. The fluorescence of calcein quenches upon binding iron and increases upon releasing iron. The chelators included desferrioxamine B, 2',2'-bipyridyl, and aminophenol II, a compound that is being newly reported as having anti-plasmodial properties. Calcein-loaded parasitized cells displayed fluorescence predominantly within the cytosol of both rings and trophozoites. The addition of chelators to both control and parasitized erythrocytes led to significant increases of fluorescence (P < 0.001). Fluorescence was observed to increase within the parasite itself after addition of iron chelators, indicating that these agents bound labile iron within the plasmodium. The relative increases of fluorescence after addition of chelators were greater in control than parasitized erythrocytes (P < 0.05) as were the estimated labile iron concentrations (P < or = 0.001). These results suggest that (i) the anti-malarial action of iron chelators might result from the ability to reach the infected cell's parasite compartment and bind iron within the parasite cytosol, and (ii) the labile iron pool of the host red cell may be either utilized or stored during plasmodial growth.

Iron overload in urban Africans in the 1990s.

BACKGROUND: In a previously described model, heterozygotes for an African iron loading locus develop iron overload only when dietary iron is high, but homozygotes may do so with normal dietary iron. If an iron loading gene is common, then homozygotes with iron overload will be found even in an urban population where traditional beer, the source of iron, is uncommon. AIMS: To determine whether iron overload and the C282Y mutation characteristic of hereditary haemochromatosis are readily identifiable in an urban African population. METHODS: Histological assessment, hepatocellular iron grading, and dry weight non-haem iron concentration were determined in post mortem tissue from liver, spleen, heart, lungs, and skin. DNA of subjects with elevated hepatic iron indexes was analysed for the C282Y mutation. Iron concentrations in other tissues were compared. RESULTS: A moderate increase (>30 micromol/g) in hepatic iron concentrations was found in 31 subjects (23%; 95% confidence interval 15.9 to 30.1%), and they were considerably elevated (>180 micromol/g) in seven subjects (5.2%; 95% confidence interval 1.5 to 8.9%). Appreciably elevated hepatic iron concentrations were associated with heavy iron deposition in both hepatocytes and macrophages, and either portal fibrosis or cirrhosis. All were negative for the C282Y mutation. Very high concentrations were uncommon in subjects dying in hospital. Concentrations of iron in spleen, heart, lung, and skin were significantly higher in subjects with elevated hepatic iron. CONCLUSIONS: Iron overload is readily identified among urban Africans and is associated with hepatic damage and iron loading of several tissues. The condition is unrelated to the genetic mutation found in hereditary haemochromatosis.

Bone marrow macrophage iron grade and survival of HIV-seropositive patients.

OBJECTIVE: Increased iron stores predispose to certain microbial infections. This association might be especially important in patients whose immune system is impaired by HIV. This study examined the relationship between iron stores and the survival times of patients with HIV infection. DESIGN: Retrospective analysis of iron stores, as determined directly in bone marrow aspirates, and of hospital records. SETTING: The George Washington University Hospital, an urban academic tertiary care institution. PATIENTS: Three hundred and forty-eight HIV-seropositive adults who had diagnostic bone marrow aspirates between January 1985 and June 1996. MEASUREMENTS: Bone marrow macrophage iron stores were graded on a scale of 0 to 5. For analysis of the influence of iron stores on survival, we compared patients with grades 4-5 iron stores (markedly or massively increased; n = 188) to those with grades 0-2 iron stores (normal or decreased; n = 130). RESULTS: Infections caused by Candida spp., Pneumocystis carinii, and Mycobacterium spp. were more common in patients with high macrophage iron grades than in patients with low or normal iron grades (P < or = 0.006). The adjusted estimated rate of death (hazards ratio) was higher in patients with high iron stores compared with patients with low or normal iron stores, both from the time of the bone marrow study (ratio of 2.1; 95% confidence interval 1.3-3.5; P = 0.003) and the determination of HIV-seropositivity (ratio of 2.8; 95% confidence interval 1.4-4.9; P = 0.001). CONCLUSION: High iron stores, as determined by bone marrow macrophage iron grade, may be associated with shorter survival times in patients with HIV infection.