Transferrin receptor on endothelium of brain capillaries

The blood/brain barrier prevents the passive diffusion of proteins and metabolites from cerebral blood vessels into tissue spaces around neuronal and glial cells. To provide nutrients for these cells, transport mechanisms must exist and indeed have been demonstrated for metabolites. We now show that monoclonal antibodies against rat and human transferrin receptors label blood capillaries in the brain but not in other tissues. In the rat this labelling occurs after injection of antibody into the blood, thus the receptors seem to be accessible at the endothelial surface. It is possible that transferrin receptors are expressed on these cells to allow transport of transferrin (and thus iron) into brain tissues.

Prevalence of iron deficiency in the United States

OBJECTIVE

To determine the prevalence of iron deficiency and iron deficiency anemia in the US population.

DESIGN

Nationally representative cross-sectional health examination survey that included venous blood measurements of iron status.

MAIN OUTCOME MEASURES

Iron deficiency, defined as having an abnormal value for at least 2 of 3 laboratory tests of iron status (erythrocyte protoporphyrin, transferrin saturation, or serum ferritin); and iron deficiency anemia, defined as iron deficiency plus low hemoglobin.

PARTICIPANTS

A total of 24,894 persons aged 1 year and older examined in the third National Health and Nutrition Examination Survey (1988-1994).

RESULTS

Nine percent of toddlers aged 1 to 2 years and 9% to 11% of adolescent girls and women of childbearing age were iron deficient; of these, iron deficiency anemia was found in 3% and 2% to 5%, respectively. These prevalences correspond to approximately 700,000 toddlers and 7.8 million women with iron deficiency; of these, approximately 240,000 toddlers and 3.3 million women have iron deficiency anemia. Iron deficiency occurred in no more than 7% of older children or those older than 50 years, and in no more than 1% of teenage boys and young men. Among women of childbearing age, iron deficiency was more likely in those who are minority, low income, and multiparous.

CONCLUSION

Iron deficiency and iron deficiency anemia are still relatively common in toddlers, adolescent girls, and women of childbearing age.

Penetrance of 845G--> A (C282Y) HFE hereditary haemochromatosis mutation in the USA

BACKGROUND

There has been much interest in screening populations for disease-associated mutations. A favoured candidate has been the HFE gene, mutations of which are the most common cause of haemochromatosis in the European population. About five people in 1000 are homozygotes for the 845G-->A mutation, but little is known of how many have mutation-caused clinical manifestations.

METHODS

We screened 41038 individuals attending a health appraisal clinic in the USA for the 845G--> A and 187C-->G HFE mutations, and analysed laboratory data and data on signs and symptoms of haemochromatosis as elicited by questionnaire.

FINDINGS

The most common symptoms of haemochromatosis, including poor general health, diabetes, arthropathies, arrhythmias, impotence, and skin pigmentation were no more prevalent among the 152 identified homozygotes than among the controls. The age distribution of homozygotes and compound heterozygotes did not differ significantly from that of controls: there was no measurable loss of such individuals from the population during ageing. However, there was a significantly increased prevalence of a history of hepatitis or "liver trouble" among homozygotes and in the proportion of homozygotes with increased concentrations of serum aspartate aminotransferase and collagen IV; these changes were not related to iron burden or to age. Only one of the 152 homozygotes had signs and symptoms that would suggest a diagnosis of haemochromatosis.

INTERPRETATION

The normal age distribution of people with the haemochromatosis genotype, and the lack of symptoms in patients of all ages, indicate that the penetrance of hereditary haemochromatosis is much lower than generally thought. The clinical penetrance of a disorder is an essential consideration in screening for genetic disease; disorders with low penetrance are more expensive candidates for screening than disorders with high penetrance. Our best estimate is that less than 1% of homozygotes develop frank clinical haemochromatosis.

The quantitative assessment of body iron

Current initiatives to reduce the high prevalence of nutritional iron deficiency have highlighted the need for reliable epidemiologic methods to assess iron status. The present report describes a method for estimating body iron based on the ratio of the serum transferrin receptor to serum ferritin. Analysis showed a single normal distribution of body iron stores in US men aged 20 to 65 years (mean +/- 1 SD, 9.82 +/- 2.82 mg/kg). A single normal distribution was also observed in pregnant Jamaican women (mean +/- 1 SD, 0.09 +/- 4.48 mg/kg). Distribution analysis in US women aged 20 to 45 years indicated 2 populations; 93% of women had body iron stores averaging 5.5 +/- 3.35 mg/kg (mean +/- 1 SD), whereas the remaining 7% of women had a mean tissue iron deficit of 3.87 +/- 3.23 mg/kg. Calculations of body iron in trials of iron supplementation in Jamaica and iron fortification in Vietnam demonstrated that the method can be used to calculate absorption of the added iron. Quantitative estimates of body iron greatly enhance the evaluation of iron status and the sensitivity of iron intervention trials in populations in which inflammation is uncommon or has been excluded by laboratory screening. The method is useful clinically for monitoring iron status in those who are highly susceptible to iron deficiency.

Hemochromatosis and iron-overload screening in a racially diverse population

BACKGROUND

Iron overload and hemochromatosis are common, treatable conditions. HFE genotypes, levels of serum ferritin, transferrin saturation values, and self-reported medical history were studied in a multiethnic primary care population.

METHODS

Participants were recruited from primary care practices and blood-drawing laboratories. Blood samples were tested for transferrin saturation, serum ferritin, and C282Y and H63D mutations of the HFE gene. Before genetic screening, participants were asked whether they had a history of medical conditions related to iron overload.

RESULTS

Of the 99,711 participants, 299 were homozygous for the C282Y mutation. The estimated prevalence of C282Y homozygotes was higher in non-Hispanic whites (0.44 percent) than in Native Americans (0.11 percent), Hispanics (0.027 percent), blacks (0.014 percent), Pacific Islanders (0.012 percent), or Asians (0.000039 percent). Among participants who were homozygous for the C282Y mutation but in whom iron overload had not been diagnosed (227 participants), serum ferritin levels were greater than 300 mug per liter in 78 of 89 men (88 percent) and greater than 200 microg per liter in 79 of 138 women (57 percent). Pacific Islanders and Asians had the highest geometric mean levels of serum ferritin and mean transferrin saturation despite having the lowest prevalence of C282Y homozygotes. There were 364 participants in whom iron overload had not been diagnosed (29 C282Y homozygotes) who had a serum ferritin level greater than 1000 microg per liter. Among men, C282Y homozygotes and compound heterozygotes were more likely to report a history of liver disease than were participants without HFE mutations.

CONCLUSIONS

The C282Y mutation is most common in whites, and most C282Y homozygotes have elevations in serum ferritin levels and transferrin saturation. The C282Y mutation does not account for high mean serum ferritin levels and transferrin saturation values in nonwhites.

Iron-binding proteins in milk and resistance to Escherichia coli infection in infants

Human milk contains large quantities of iron-binding protein, of which the greater proportion is lactoferrin, though small amounts of transferrin are also present. Three samples of human milk with unsaturated iron-binding capacities of between 56 and 89% had a powerful bacteriostatic effect on Escherichia coli O111/B4. The bacteriostatic properties of milk were abolished if the iron-binding proteins were saturated with iron. Purified human lactoferrin, in combination with specific E. coli antibody, strongly inhibited the growth of E. coli, and this effect was also abolished by saturating the lactoferrin with iron.Guinea-pig milk also contains lactoferrin and transferrin. Newly born guinea-pigs fed on an artificial diet and dosed with E. coli O111 had higher counts of E. coli O111 in the intestine than suckled animals. The apparent suppressive effect of guinea-pig milk on E. coli in the intestine could be reversed by feeding the iron compound haematin. It seems that iron-binding proteins in milk may play an important part in resistance to infantile enteritis caused by E. coli.

A population-based study of the clinical expression of the hemochromatosis gene

BACKGROUND AND METHODS

Hereditary hemochromatosis is associated with homozygosity for the C282Y mutation in the hemochromatosis (HFE) gene on chromosome 6, elevated serum transferrin saturation, and excess iron deposits throughout the body. To assess the prevalence and clinical expression of the HFE gene, we conducted a population-based study in Busselton, Australia. In 1994, we obtained blood samples for the determination of serum transferrin saturation and ferritin levels and the presence or absence of the C282Y mutation and the H63D mutation (which may contribute to increased hepatic iron levels) in 3011 unrelated white adults. We evaluated all subjects who had persistently elevated transferrin-saturation values (45 percent or higher) or were homozygous for the C282Y mutation. We recommended liver biopsy for subjects with serum ferritin levels of 300 ng per milliliter or higher. The subjects were followed for up to four years.

RESULTS

Sixteen of the subjects (0.5 percent) were homozygous for the C282Y mutation, and 424 (14.1 percent) were heterozygous. The serum transferrin saturation was 45 percent or higher in 15 of the 16 who were homozygous; in 1 subject it was 43 percent. Four of the homozygous subjects had previously been given a diagnosis of hemochromatosis, and 12 had not. Seven of these 12 patients had elevated serum ferritin levels in 1994; 6 of the 7 had further increases in 1998, and 1 had a decrease, although the value remained elevated. The serum ferritin levels in the four other homozygous patients remained in the normal range. Eleven of the 16 homozygous subjects underwent liver biopsy; 3 had hepatic fibrosis, and 1, who had a history of excessive alcohol consumption, had cirrhosis and mild microvesicular steatosis. Eight of the 16 homozygous subjects had clinical findings that were consistent with the presence of hereditary hemochromatosis, such as hepatomegaly, skin pigmentation, and arthritis.

CONCLUSIONS

In a population of white adults of northern European ancestry, 0.5 percent were homozygous for the C282Y mutation in the HFE gene. However, only half of those who were homozygous had clinical features of hemochromatosis, and one quarter had serum ferritin levels that remained normal over a four-year period.

Hepatic transferrin plays a role in systemic iron homeostasis and liver ferroptosis

Although the serum-abundant metal-binding protein transferrin (encoded by the Trf gene) is synthesized primarily in the liver, its function in the liver is largely unknown. Here, we generated hepatocyte-specific Trf knockout mice (Trf-LKO), which are viable and fertile but have impaired erythropoiesis and altered iron metabolism. Moreover, feeding Trf-LKO mice a high-iron diet increased their susceptibility to developing ferroptosis-induced liver fibrosis. Importantly, we found that treating Trf-LKO mice with the ferroptosis inhibitor ferrostatin-1 potently rescued liver fibrosis induced by either high dietary iron or carbon tetrachloride (CCl4) injections. In addition, deleting hepatic Slc39a14 expression in Trf-LKO mice significantly reduced hepatic iron accumulation, thereby reducing ferroptosis-mediated liver fibrosis induced by either a high-iron diet or CCl4 injections. Finally, we found that patients with liver cirrhosis have significantly lower levels of serum transferrin and hepatic transferrin, as well as higher levels of hepatic iron and lipid peroxidation, compared with healthy control subjects. Taken together, these data indicate that hepatic transferrin plays a protective role in maintaining liver function, providing a possible therapeutic target for preventing ferroptosis-induced liver fibrosis.

Effect of alcohol consumption on systemic markers of inflammation

BACKGROUND

Epidemiological studies suggest that light to moderate alcohol intake is associated with lower all-cause mortality than abstention or heavy alcohol intake, primarily through reduced risk of coronary heart disease. The underlying mechanisms are incompletely understood.

METHODS

We investigated the association between alcohol consumption (assessed by a 7-day food record) and concentrations of C-reactive protein (CRP), alpha1-globulins, alpha2-globulins, albumin, and transferrin, and leucocyte count in a sample of 2006 men and women aged 18-88 years participating in a national health survey carried out in former West Germany in 1987-88. Analyses were based on 781 men and 995 women with complete data.

FINDINGS

Among men, alcohol consumption showed a U-shaped association with mean values of CRP (p for linear term 0.65, for quadratic term 0.048), alpha1-globulins (p=0.20, 0.0006), alpha2-globulins (p=0.82, 0.31), and leucocyte count (p=0.51, 0.26) even after adjustment for age, smoking, body-mass index, HDL and LDL cholesterol, history of hypertension, education, and income. There were inverted U-shaped associations between the negative acute-phase reactants albumin (p=0.41, 0.006) and transferrin (p=0.14, 0.28) and alcohol intake. In women, the associations were less strong for CRP (p=0.35, 0.31), leucocyte count (p=0.28, 0.15), and transferrin (p=0.86, 0.83). Concentrations of alpha1-globulins and alpha2-globulins were inversely related to alcohol consumption, and albumin showed a positive association with increasing alcohol intake in women.

INTERPRETATION

Non-drinkers and heavy drinkers had higher CRP concentrations than moderate drinkers. In view of the robust association between markers of inflammation, especially CRP, and risk of coronary heart disease, an anti-inflammatory action of alcohol could contribute to the link between moderate consumption and lower cardiovascular mortality.

Disruption of oxygen homeostasis underlies congenital Chuvash polycythemia

Chuvash polycythemia is an autosomal recessive disorder that is endemic to the mid-Volga River region. We previously mapped the locus associated with Chuvash polycythemia to chromosome 3p25. The gene associated with von Hippel-Lindau syndrome, VHL, maps to this region, and homozygosity with respect to a C-->T missense mutation in VHL, causing an arginine-to-tryptophan change at amino-acid residue 200 (Arg200Trp), was identified in all individuals affected with Chuvash polycythemia. The protein VHL modulates the ubiquitination and subsequent destruction of hypoxia-inducible factor 1, subunit alpha (HIF1alpha). Our data indicate that the Arg200Trp substitution impairs the interaction of VHL with HIF1alpha, reducing the rate of degradation of HIF1alpha and resulting in increased expression of downstream target genes including EPO (encoding erythropoietin), SLC2A1 (also known as GLUT1, encoding solute carrier family 2 (facilitated glucose transporter), member 1), TF (encoding transferrin), TFRC (encoding transferrin receptor (p90, CD71)) and VEGF (encoding vascular endothelial growth factor).

Hepatic proteins and nutrition assessment

Serum hepatic protein (albumin, transferrin, and prealbumin) levels have historically been linked in clinical practice to nutritional status. This paradigm can be traced to two conventional categories of malnutrition: kwashiorkor and marasmus. Explanations for both of these conditions evolved before knowledge of the inflammatory processes of acute and chronic illness were known. Substantial literature on the inflammatory process and its effects on hepatic protein metabolism has replaced previous reports suggesting that nutritional status and protein intake are the significant correlates with serum hepatic protein levels. Compelling evidence suggests that serum hepatic protein levels correlate with morbidity and mortality. Thus, serum hepatic protein levels are useful indicators of severity of illness. They help identify those who are the most likely to develop malnutrition, even if well nourished prior to trauma or the onset of illness. Furthermore, hepatic protein levels do not accurately measure nutritional repletion. Low serum levels indicate that a patient is very ill and probably requires aggressive and closely monitored medical nutrition therapy.

A histochemical study of iron, transferrin, and ferritin in Alzheimer's diseased brains

Immunohistochemical and histochemical staining were performed on Alzheimer's diseased brain tissue obtained at autopsy. The iron-regulatory proteins transferrin and ferritin as well as iron are, in general, found predominantly in oligodendrocytes similar to that previously reported for normal brain tissue. However, in the vicinity of senile plaques, the staining pattern is altered for both proteins and iron. Transferrin is homogenously distributed around the senile plaques and is apparently extracellular. In addition, transferrin is found in astrocytes in the cerebral cortical white matter of the Alzheimer's tissue rather than its normal distribution in oligodendrocytes. A robust ferritin immunoreaction accompanies senile plaques and many blood vessels in the Alzheimer's brain tissue. Although many ferritin-positive oligodendrocytes are present in the Alzheimer's tissue, most of the ferritin-containing cells associated with senile plaques and blood vessels are microglia. Iron can also be demonstrated in the senile plaques. The iron reaction product is observed both diffusely in proximity of the plaques and in cells associated with the plaques. These data strongly suggest a disruption in brain iron homeostasis in Alzheimer's disease as demonstrated by alterations in the normal cellular distribution of iron and the proteins responsible for iron regulation. These data will contribute to understanding both the potential for oxidative damage and the potential for metal neurotoxicity in Alzheimer's disease.

Erythropoietin treatment of anemia associated with multiple myeloma

Anemia is a common complication of multiple myeloma. It resolves early in the disease if chemotherapy induces a complete remission, but persists if the disease progresses, causing disabling symptoms and often requiring blood transfusions. We treated 13 patients with myeloma-associated anemia by administering recombinant human erythropoietin three times a week for six months. Eleven patients (85 percent) had steady increases in hemoglobin levels and eventual correction of the anemia. Their symptoms of anemia subsided, and they reported a heightened sense of well-being. No patient had any adverse side effects, particularly episodes of hypertension. Monitoring of the serum M component showed a predominantly stable tumor load without apparent interaction between the underlying disease and the response to erythropoietin therapy. The number of erythroid burst-forming units in the bone marrow and peripheral blood and the level of erythropoiesis in bone marrow smears increased significantly during therapy. Pretreatment serum levels of erythropoietin were higher in the patients who did not respond and in those who required more than two months of treatment before they responded. Serum iron, ferritin, and transferrin concentrations reflected responses to treatment. We conclude that recombinant human erythropoietin is a promising therapeutic tool for treating myeloma-associated anemia.

Iron deficiency and cognitive achievement among school-aged children and adolescents in the United States

CONTEXT

Iron deficiency anemia in infants can cause developmental problems. However, the relationship between iron status and cognitive achievement in older children is less clear.

OBJECTIVE

To investigate the relationship between iron deficiency and cognitive test scores among a nationally representative sample of school-aged children and adolescents.

DESIGN

The National Health and Nutrition Examination Survey III 1988-1994 provides cross-sectional data for children 6 to 16 years old and contains measures of iron status including transferrin saturation, free erythrocyte protoporphyrin, and serum ferritin. Children were considered iron-deficient if any 2 of these values were abnormal for age and gender, and standard hemoglobin values were used to detect anemia. Scores from standardized tests were compared for children with normal iron status, iron deficiency without anemia, and iron deficiency with anemia. Logistic regression was used to estimate the association of iron status and below average test scores, controlling for confounding factors.

RESULTS

Among the 5398 children in the sample, 3% were iron-deficient. The prevalence of iron deficiency was highest among adolescent girls (8.7%). Average math scores were lower for children with iron deficiency with and without anemia, compared with children with normal iron status (86.4 and 87.4 vs 93.7). By logistic regression, children with iron deficiency had greater than twice the risk of scoring below average in math than did children with normal iron status (odds ratio: 2.3; 95% confidence interval: 1.1-4.4). This elevated risk was present even for iron-deficient children without anemia (odds ratio: 2.4; 95% confidence interval: 1.1-5.2).

CONCLUSIONS

We demonstrated lower standardized math scores among iron-deficient school-aged children and adolescents, including those with iron deficiency without anemia. Screening for iron deficiency without anemia may be warranted for children at risk.

Prospective evaluation of Pringle maneuver in hepatectomy for liver tumors by a randomized study

OBJECTIVE

To evaluate whether vascular inflow occlusion by the Pringle maneuver during hepatectomy can be safe and effective in reducing blood loss.

SUMMARY BACKGROUND DATA

Hepatectomy can be performed with a low mortality rate, but massive hemorrhage during surgery remains a potentially lethal problem. The Pringle maneuver is traditionally used during hepatectomy to reduce blood loss, but there is a potential harmful effect on the metabolic function of hepatocytes. There has been no prospective randomized study to determine whether the Pringle maneuver can decrease blood loss during hepatectomy, improve outcome, or affect the metabolism of hepatocytes.

METHODS

From July 1995 to February 1997, we studied 100 consecutive patients who underwent hepatectomy for liver tumors. The patients were randomly assigned to liver transection under intermittent Pringle maneuver of 20 minutes and a 5-minute clamp-free interval (n = 50), or liver transection without the Pringle maneuver (n = 50). The surface area of liver transection was measured and blood loss during transection per square centimeter of transection area was calculated. Routine liver biochemistry, arterial ketone body ratio (AKBR), and the indocyanine green (ICG) clearance test were done.

RESULTS

The two groups were comparable in terms of preoperative liver function and in the proportion of patients having major hepatectomy. The Pringle maneuver resulted in less blood loss per square centimeter of transection area (12 mL/cm2 vs. 22 mL/cm2, p = 0.0001), a shorter transection time per square centimeter of transection area (2 min/cm2 vs. 2.8 min/cm2, p = 0.016), a significantly higher AKBR in the first 2 hours after hepatectomy, lower serum bilirubin levels in the early postoperative period, and, in cirrhotic patients, higher serum transferrin levels on postoperative days 1 and 8. The complication rate, the hospital mortality rate, and the ICG retention at 15 minutes on postoperative day 8 were equal for the two groups.

CONCLUSION

Performing the Pringle maneuver during liver transection resulted in less blood loss and better preservation of liver function in the early postoperative period. This is probably because there was less hemodynamic disturbance induced by the bleeding.

Malnutrition in surgical patients. An unrecognised problem

Indices of nutritional state were measured in 105 surgical patients. The indices were chosen to give information on protein-calorie malnutrition, anaemia, vitamin deficiency. Abnormal values for the various indices were common in the group as a whole and most frequent (50%) in patients who were still in hospital more than a week after major surgery. These patients had a high frequency of anaemia, vitamin deficiency, weight-loss, loss of arm-muscle bulk, and low plasma levels of transferrin and albumin. These abnormalities had gone almost entirely unrecognised, even in patients with sepsis after major surgery, who would benefit from improvement in nutritional state.

Intravenous Iron in Patients Undergoing Maintenance Hemodialysis

BACKGROUND

Intravenous iron is a standard treatment for patients undergoing hemodialysis, but comparative data regarding clinically effective regimens are limited.

METHODS

In a multicenter, open-label trial with blinded end-point evaluation, we randomly assigned adults undergoing maintenance hemodialysis to receive either high-dose iron sucrose, administered intravenously in a proactive fashion (400 mg monthly, unless the ferritin concentration was >700 μg per liter or the transferrin saturation was ≥40%), or low-dose iron sucrose, administered intravenously in a reactive fashion (0 to 400 mg monthly, with a ferritin concentration of <200 μg per liter or a transferrin saturation of <20% being a trigger for iron administration). The primary end point was the composite of nonfatal myocardial infarction, nonfatal stroke, hospitalization for heart failure, or death, assessed in a time-to-first-event analysis. These end points were also analyzed as recurrent events. Other secondary end points included death, infection rate, and dose of an erythropoiesis-stimulating agent. Noninferiority of the high-dose group to the low-dose group would be established if the upper boundary of the 95% confidence interval for the hazard ratio for the primary end point did not cross 1.25.

RESULTS

A total of 2141 patients underwent randomization (1093 patients to the high-dose group and 1048 to the low-dose group). The median follow-up was 2.1 years. Patients in the high-dose group received a median monthly iron dose of 264 mg (interquartile range [25th to 75th percentile], 200 to 336), as compared with 145 mg (interquartile range, 100 to 190) in the low-dose group. The median monthly dose of an erythropoiesis-stimulating agent was 29,757 IU in the high-dose group and 38,805 IU in the low-dose group (median difference, -7539 IU; 95% confidence interval [CI], -9485 to -5582). A total of 320 patients (29.3%) in the high-dose group had a primary end-point event, as compared with 338 (32.3%) in the low-dose group (hazard ratio, 0.85; 95% CI, 0.73 to 1.00; P<0.001 for noninferiority; P=0.04 for superiority). In an analysis that used a recurrent-events approach, there were 429 events in the high-dose group and 507 in the low-dose group (rate ratio, 0.77; 95% CI, 0.66 to 0.92). The infection rate was the same in the two groups.

CONCLUSIONS

Among patients undergoing hemodialysis, a high-dose intravenous iron regimen administered proactively was superior to a low-dose regimen administered reactively and resulted in lower doses of erythropoiesis-stimulating agent being administered. (Funded by Kidney Research UK; PIVOTAL EudraCT number, 2013-002267-25 .).

A mutation in SLC11A3 is associated with autosomal dominant hemochromatosis

Hereditary hemochromatosis (HH) is a very common disorder characterized by iron overload and multi-organ damage. Several genes involved in iron metabolism have been implicated in the pathology of HH (refs. 1-4). We report that a mutation in the gene encoding Solute Carrier family 11, member A3 (SLC11A3), also known as ferroportin, is associated with autosomal dominant hemochromatosis.

Ferric gluconate is highly efficacious in anemic hemodialysis patients with high serum ferritin and low transferrin saturation: results of the Dialysis Patients' Response to IV Iron with Elevated Ferritin (DRIVE) Study

Few data exist to guide treatment of anemic hemodialysis patients with high ferritin and low transferrin saturation (TSAT). The Dialysis Patients' Response to IV Iron with Elevated Ferritin (DRIVE) trial was designed to evaluate the efficacy of intravenous ferric gluconate in such patients. Inclusion criteria were hemoglobin <or=11 g/dl, ferritin 500 to 1200 ng/ml, TSAT <or=25%, and epoetin dosage >or=225 IU/kg per wk or >or=22,500 IU/wk. Patients with known infections or recent significant blood loss were excluded. Participants (n=134) were randomly assigned to no iron (control) or to ferric gluconate 125 mg intravenously with eight consecutive hemodialysis sessions (intravenous iron). At randomization, epoetin was increased 25% in both groups; further dosage changes were prohibited. At 6 wk, hemoglobin increased significantly more (P=0.028) in the intravenous iron group (1.6 +/- 1.3 g/dl) than in the control group (1.1 +/- 1.4 g/dl). Hemoglobin response occurred faster (P=0.035) and more patients responded after intravenous iron than in the control group (P=0.041). Ferritin <or=800 or >800 ng/ml had no relationship to the magnitude or likelihood of responsiveness to intravenous iron relative to the control group. Similarly, the superiority of intravenous iron compared with no iron was similar whether baseline TSAT was above or below the study median of 19%. Ferritin decreased in control subjects (-174 +/- 225 ng/ml) and increased after intravenous iron (173 +/- 272 ng/ml; P<0.001). Intravenous iron resulted in a greater increase in TSAT than in control subjects (7.5 +/- 7.4 versus 1.8 +/- 5.2%; P<0.001). Reticulocyte hemoglobin content fell only in control subjects, suggesting worsening iron deficiency. Administration of ferric gluconate (125 mg for eight treatments) is superior to no iron therapy in anemic dialysis patients receiving adequate epoetin dosages and have a ferritin 500 to 1200 ng/ml and TSAT <or=25%.

The coated pit and macropinocytic pathways serve distinct endosome populations

Clathrin-coated vesicle endocytosis and macropinocytosis are distinct endocytic pathways demonstrable in several cell types including human epidermoid A431 cells (West, M.A., M.S. Bretscher, and C. Watts. 1989. J. Cell Biol. 109:2731-2739). Here we analyze the extent of mixing of macropinocytic endosome (macropinosome) content with that of conventional endosomes served by coated vesicle endocytosis. Using laser scanning confocal fluorescence microscopy we detected very little delivery of macropinosome content to either early or late endosomes-lysosomes as defined by labeling with transferrin or with LDL. Mixing of the contents of the macropinosomes and conventional endosomes was not induced by the addition of brefeldin A. Moreover, the morphology of macropinosomes was not grossly altered in the presence of brefeldin A, whilst in the same cells there were dramatic tubulation effects on conventional endosomes as reported by others. Although refractory to fusion with conventional endosomes, macropinosomes were nonetheless dynamic structures which sometimes exhibited vesiculo-tubular morphology in living cells and were capable of fusing with each other. We suggest that different endocytic mechanisms can give rise to distinct endosome populations.

The prevalence of anemia in patients with chronic kidney disease

OBJECTIVE

Anemia is a complication of chronic kidney disease and may contribute to adverse clinical outcomes. Early identification and treatment of anemia may improve cardiovascular morbidity and mortality. No large-scale population data are available specifically for patients with chronic kidney disease regarding prevalence of anemia, subpopulations at risk, and relationships between anemia and kidney function. This study was undertaken to address these questions in patients with chronic kidney disease, and investigate the relationship between anemia and glomerular filtration rate.

RESEARCH DESIGN AND METHODS

Large-scale, cross-sectional, US multicenter survey; 5222 patients (mean age, 68.2 years; 46.6% male); 237 physician practices. Eligible patients: > or = 18 years of age; serum creatinine: 1.5 mg/dL-6.0 mg/dL (females), 2.0 mg/dL-6.0 mg/dL (males).

MAIN OUTCOME MEASURES

Primary study end point: prevalence and severity of anemia (hemoglobin < or = 12 g/dL). Data further stratified by hemoglobin (< or = 12 g/dL, < or = 10 g/dL).

RESULTS

Primary etiologies of chronic kidney disease (5222 evaluable patients): diabetes (49.5%); hypertension (33.0%). Glomerular filtration rate: < 60 mL/min/1.73 m2 for 97.7% of evaluable patients. Mean +/- SD serum creatinine level: 2.2 mg/dL +/- 0.9 mg/dL; 2.5 mg/dL +/- 1.0 mg/dL for males, 2.0 mg/dL +/- 0.8 mg/dL for females. Mean +/- SD hemoglobin: 12.2 g/dL +/- 1.6 g/dL (47.7% had hemoglobin < or = 12 g/dL; 8.9% had hemoglobin < or = 10 g/dL). Prevalence of anemia was strongly associated with declining glomerular filtration rate. Percentage of patients with hemoglobin < or = 12 g/dL increased from 26.7% to 75.5% when glomerular filtration rate decreased from > or = 60 mL/min/1.73 m2 to < 15 mL/min/1.73 m2. Prevalence of hemoglobin < or = 10 g/dL increased substantially from 5.2% to 27.2% when glomerular filtration rate diminished from > or = 60 mL/min/1.73 m2 to < 15 mL/min/1.73 m2. After controlling for other patient characteristics associated with increased prevalence of anemia, the prevalence odds ratio for hemoglobin < or = 10 g/dL was 0.54 (0.49-0.60) and for hemoglobin < or = 12 g/dL was 0.68 (0.65-0.72), with each 10-mL/min/1.73 m2 increase in glomerular filtration rate. Predictors of anemia: diabetes, female sex, and race/ethnicity.

CONCLUSIONS

Anemia was present in 47.7% of 5222 predialysis patients with chronic kidney disease. Prevalence of anemia increased as kidney function decreased. Certain subgroups are at increased risk for anemia.

Liver iron concentrations and urinary hepcidin in beta-thalassemia

BACKGROUND AND OBJECTIVES

Patients with beta-thalassemia, like those with genetic hemochromatosis, develop iron overload due to increased iron absorption, and their iron burden is further exacerbated by transfusion therapy. Hepcidin, a hepatic hormone, regulates systemic iron homeostasis by inhibiting the absorption of iron from the diet and the recycling of iron by macrophages. In turn, hepcidin release is increased by iron loading and inhibited by erythropoietic activity. Hepcidin deficiency is the cause of iron overload in most forms of hereditary hemochromatosis. We sought to determine hepcidin's role in the pathogenesis of iron overload in b-thalassemia.

DESIGN AND METHODS

We assessed the degree of iron overload in thalassemia intermedia and major patients by measuring hepatic iron concentration in liver biopsy samples and serum ferritin, estimated erythropoietic drive by assaying soluble transferrin receptor and serum erythropoietin levels and correlated these with urinary hepcidin measurements.

RESULTS

Urinary hepcidin levels in beta-thalassemia demonstrate severe hepcidin deficiency in thalassemia intermedia. There was a strong inverse relationship between urinary hepcidin levels and both erythropoietin and soluble transferrin receptor, markers of erythropoietic activity. In contrast, hepcidin levels were elevated in thalassemia major, presumably due to transfusions that reduce erythropoietic drive and deliver a large iron load. Despite similar liver iron concentrations in the two conditions, serum ferritin was much lower in thalassemia intermedia.

INTERPRETATION AND CONCLUSIONS

In thalassemia intermedia, high erythropoietic drive causes severe hepcidin deficiency. The lack of hepcidin results in hyperabsorption of dietary iron, but also in iron depletion of macrophages, lowering their secretion of ferritin and, consequently, serum ferritin levels. In contrast, in thalassemia major, transfusions decrease erythropoietic drive and increase the iron load, resulting in relatively higher hepcidin levels. In the presence of higher hepcidin levels, dietary iron absorption is moderated and macrophages retain iron, contributing to higher serum ferritin. In the future, hepcidin measurements may allow a more accurate assessment of the degree of iron overload and the maldistribution of iron in thalassemia.