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.     

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.     

Haptoglobin polymorphism and mortality in patients with tuberculosis.

SETTING: A rural Zimbabwean hospital and the surrounding community. OBJECTIVES: To determine whether a particular haptoglobin phenotype is associated with increased susceptibility to clinical pulmonary tuberculosis, and to determine the outcome of treatment for pulmonary tuberculosis according to haptoglobin phenotype. DESIGN: A case-control study, and a prospective cohort study. RESULTS: We studied 98 consecutive patients with sputum-positive pulmonary tuberculosis and 98 sex- and age-matched controls. The haptoglobin (Hp) phenotype distributions did not differ significantly between the tuberculosis patients and controls (P = 0.5). During the 18-month follow-up period after the start of tuberculosis treatment, 6/18 (33%) cases with Hp 2-2 phenotype died compared to 9/47 (19%) with Hp 2-1 and 3/31 (10%) with Hp 1-1. In a logistic regression model, the odds of dying were 6.1-fold greater with Hp 2-2 than with Hp 1-1 (95%CI 1.04-35.1, P = 0.04). CONCLUSION: Our results suggest that there is equal susceptibility to clinical pulmonary tuberculosis disease amongst different haptoglobin phenotypes. Nonetheless, tuberculosis patients with Hp 2-2 phenotype had a higher risk of mortality.     

短期的脱氢表雄酮治疗增加中年男性受试者的血小板cGMP产生

目的临床和人群研究提示,脱氢表雄酮和它的硫酸盐在抗动脉粥样硬化和冠心病中起保护作用。然而,这种作用的机制仍不清楚。最近报道,硫酸脱氢表雄酮通过增加一氧化氮的生成来延缓动脉粥样硬化的形成。方法24岁的男性受试者(年龄65.4±0.7岁;范围58.2~67.6岁)经盲法安慰剂对照研究,使用脱氢表雄酮(每天50 mg睡前口服)或安慰剂2个月。2个月前和2个月后评价血小板环一磷酸鸟苷(cGMP)浓度(作为一氧化氮产生的标记)和血清中硫酸脱氢表雄酮钠、脱氢表雄酮、胰岛素样生长因子1、胰岛素、葡萄糖、雌二醇、睾酮、纤溶酶原激活物抑制剂1抗原、高半胱…     

Carbonyl iron therapy for iron deficiency anemia

To determine if elemental carbonyl iron powder is safe and effective therapy for iron deficiency anemia, 20 nonanemic and 32 anemic volunteers were studied. Single doses of 1,000 to 10,000 mg of carbonyl iron (15 to 150 times the 65 mg of iron in the usual dose of ferrous sulfate) were tolerated by nonanemic volunteers with no evidence of toxicity and only minor gastrointestinal side effects. Anemic volunteers (menstruating women who had previously donated blood) were treated with several regimens providing 1,000 to 3,000 mg of carbonyl iron daily in one to three doses for 8 to 28 days. After 12 weeks anemia was corrected in 29 of 32 patients, and serum ferritin was greater than 12 micrograms/L in 14. Hemoglobin regeneration proceeded at a rate similar to that described for therapy with oral iron salts and parenteral iron dextran. There was no evidence of hematologic, hepatic, or renal toxicity, but mild gastrointestinal side effects occurred in a majority of anemic volunteers. Carbonyl iron is an effective, inexpensive treatment for iron deficiency anemia, is accompanied by tolerable side effects and may have an advantage over therapy with iron salts by substantially reducing or eliminating the risk of iron poisoning in children.     

Hemochromatosis and Iron Overload Screening (HEIRS) study design for an evaluation of 100,000 primary care-based adults

BACKGROUND: The HEIRS Study will evaluate the prevalence, genetic and environmental determinants, and potential clinical, personal, and societal impact of hemochromatosis and iron overload in a multiethnic, primary care-based sample of 100,000 adults over a 5-year period. Participants are recruited from 5 Field Centers. Laboratory testing and data management and analysis are performed in a Central Laboratory and Coordinating Center, respectively. METHODS: Participants undergo testing for serum iron measures and common mutations of the hemochromatosis gene ( ) on chromosome 6p and answer questions on demographics, health, and genetic testing attitudes. Participants with elevated values of transferrin saturation and serum ferritin and/or C282Y homozygosity are invited to undergo a comprehensive clinical examination (CCE), as are frequency-matched control subjects. These examinations provide data on personal and family medical history, lifestyle characteristics, physical examination, genetic counseling, and assessment of ethical, legal, and social implications. Primary and secondary causes of iron overload will be distinguished by clinical criteria. Iron overload will be confirmed by quantification of iron stores. Recruiting family members of cases will permit DNA analysis for additional genetic factors that affect iron overload. RESULTS: Of the first 50,520 screened, 51% are white, 24% are African American, 11% are Asian, 11% are Hispanic, and 3% are of other, mixed, or unidentified race; 63% are female and 37% are male. CONCLUSIONS: Information from the HEIRS Study will inform policy regarding the feasibility, optimal approach, and potential individual and public health benefits and risks of primary care-based screening for iron overload and hemochromatosis.     

Conjunctival and pulmonary hemodynamic properties in sickle cell disease subjects with and without pulmonary hypertension

Conjunctival microvascular hemodynamic alterations were reported for the first time in sickle cell subjects with and without pulmonary hypertension. Assessment of the conjunctival microcirculation using noninvasive imaging may improve understanding of microvascular hemodynamic alterations that occur due to pulmonary hypertension in sickle cell disease.     

Iron chelation with desferrioxamine B in adults with asymptomatic Plasmodium falciparum parasitemia.

To determine if iron chelation therapy has activity against human malaria, we administered desferrioxamine B in amounts of 100 mg/kg per day by continuous 72-hour subcutaneous infusions to 28 volunteers with asymptomatic Plasmodium falciparum infection in a randomized, double-blind, placebo-controlled crossover trial. Peripheral blood concentrations of P falciparum ring forms were determined at 12-hour intervals in all subjects and serum concentrations of desferrioxamine B + ferrioxamine (the iron complex of desferrioxamine B) were measured in 26 subjects. Geometric mean concentrations of asexual intraerythrocytic parasites decreased with both chelator and placebo treatment, but the decrement with desferrioxamine B was significantly greater than that with placebo (P less than .006) during both the initial and crossover periods. Compared with placebo, desferrioxamine B treatment was associated with an almost 10-fold enhancement of the rate of parasite clearance during both phases of the trial (P less than .007). Mean +/- SEM steady state concentrations of desferrioxamine B + ferrioxamine were 6.90 +/- 0.60 mumol/L at 36 hours and 7.72 +/- 0.68 mumol/L at 72 hours; in vitro, the ID50 has been reported to be approximately 4 to 20 mumol/L. No drug toxicity was detected. Parasitemia recurred in 19 of 24 participants followed-up over 1 to 6 months. We conclude that desferrioxamine B enhances the clearance of P falciparum parasitemia and that iron chelation may provide a new strategy to be developed for the treatment of malaria.