Role of interleukin-6 in hypoxic regulation of intestinal iron absorption

Iron and zinc homeostases in female rats with physically active and sedentary lifestyles

To determine the effects of repeated physical activity on iron and zinc homeostases in a living system, we quantified blood and tissue levels of these two metals in sedentary and physically active Long-Evans rats. At post-natal day (PND) 22, female rats were assigned to either a sedentary or an active treatment group (n = 10/group). The physically active rats increased their use of a commercially-constructed stainless steel wire wheel so that, by the end of the study (PND 101), they were running an average of 512.8 ± 31.9 (mean ± standard error) min/night. After euthanization, plasma and aliquots of liver, lung, heart, and gastrocnemius muscle were obtained. Following digestion, non-heme iron and zinc concentrations in plasma and tissues were measured using inductively coupled plasma optical emission spectroscopy. Concentrations of both non-heme iron and zinc in plasma and liver were significantly decreased among the physically active rats relative to the sedentary animals. In the lung, both metals were increased in concentration among the physically active animals but the change in zinc did not reach significance. Similarly, tissue non-heme iron and zinc levels were both increased in heart and muscle from the physically active group. It is concluded that repeated physical activity in an animal model can be associated with a translocation of both iron and zinc from sites of storage (e.g. liver) to tissues with increased metabolism (e.g. the lung, heart, and skeletal muscle).

Comparison of serum erythropoietin levels in smokers and nonsmokers with periodontitis: A biochemical study

Aims:

This study was carried out to compare serum erythropoietin (Epo) levels in smokers and nonsmokers with periodontitis.

Materials and Methods:

Fifty-one subjects of both sexes (age range: 30–65 years) with chronic periodontitis (CP) participated in this study. Seventeen patients with generalized CP, nonsmokers without anemia were included in Group I (control group), 17 patients with generalized CP, nonsmokers with anemia were included in Group II, and 17 patients who were smokers, having generalized CP were included in Group III. Peripheral blood samples were obtained and assessed for the number of erythrocytes (total red blood cell [TRBC]), hemoglobin (Hb), and Epo levels.

Statistical Analysis Used:

One-way analysis of variance and Tukey–Kramer multiple comparisons test to assess the statistical difference between groups.

Results:

Epo levels varied considerably between the 3 groups. Highest values of Epo were seen in Group III with mean Epo value = 42.81 ± 15, followed by Group II Epo value = 35.21 ± 10.9, then Group I Epo value = 22.06 ± 4.19. Smokers in Group III with CP showed more prevalence toward higher values of Hb% (mean Hb = 12.06 ± 0.84) while there was no statistical difference in the values of TRBC values among the 3 groups (Group I TRBC value = 3.87 ± 0.38, Group II TRBC value = 4.01 ± 0.83, and Group III TRBC value = 3.88 ± 0.45).

Conclusion:

Periodontitis patients were seen to have lower Epo values further strengthening the hypothesis that CP may lead to anemia of chronic disease. In smokers, higher Hb values were seen with higher Epo levels. It indicates that periodontitis individually and along with smoking may affect anemic status of smokers. Thus, Epo levels may be better means to assess anemic status of smokers than relying only on Hb values.

Clinical impact of kidney function on presepsin levels

OBJECTIVE

Presepsin is highlighted as a diagnostic and prognostic marker of sepsis. Little information is available regarding the accurate association between presepsin levels and the degree of kidney function. We analyzed presepsin levels in patients with a glomerular filtration rate (GFR) in the categories G1 to G5, evaluated via inulin renal clearance test, and receiving hemodialysis (HD).

METHODS

Patients who were not receiving HD were included if they had undergone inulin renal clearance measurements for the accurate measurement of GFR (measured GFR), and patients who were receiving hemodialysis (HD) were included if they had anuria. Exclusion criteria were infection, cancer, liver disease, autoimmune disorders, or steroid or immunosuppressant use. GFR category was defined as follows; G1: GFR ≥ 90 ml/min/1.73 m2, G2: GFR = 60 to 90 ml/min/1.73 m2, G3: GFR = 30 to 60 ml/min/1.73 m2, G4: GFR = 15 to 30 ml/min/1.73 m2, G5: GFR ≤ 15 ml/min/1.73 m2.

RESULTS

Seventy-one patients were included. The median (IQR) presepsin values of patients in each GFR category were as follows: G1 + G2: 69.8 (60.8-85.9) pg/ml; G3: 107.0 (68.7-150.0) pg/ml; G4: 171.0 (117.0-200.0) pg/ml; G5: 251.0 (213.0-297.5) pg/ml; and HD: 1160.0 (1070.0-1400.0) pg/ml. The log-transformed presepsin values, excluding patients receiving HD, inversely correlated with the measured GFR (Pearson's correlation coefficient = -0.687, P < 0.001). The multivariate analysis revealed that measured GFR and hemoglobin levels significantly correlated with elevated presepsin levels.

CONCLUSION

Presepsin levels were markedly high in patients receiving HD, similar to values seen in patients with severe sepsis or septic shock. In patients who were not receiving HD, presepsin levels increased as GFR decreased. Thus, the evaluation of presepsin levels in patients with chronic kidney disease requires further consideration, and a different cutoff value is needed for diagnosing sepsis in such patients.

Characterization of the inflammatory and metabolic profile of adipose tissue in a mouse model of chronic hypoxia

In both obesity and chronic obstructive pulmonary disease (COPD), altered oxygen tension in adipose tissue (AT) has been suggested to evoke AT dysfunction, subsequently contributing to metabolic complications. Studying the effects of chronic hypoxia on AT function will add to our understanding of the complex pathophysiology of alterations in AT inflammation, metabolism, and mass observed in both obesity and COPD. This study investigated the inflammatory and metabolic profile of AT after chronic hypoxia. Fifty-two-week-old C57Bl/6J mice were exposed to chronic hypoxia (8% O2) or normoxia for 21 days, after which AT and plasma were collected. Adipocyte size, AT gene expression of inflammatory and metabolic genes, AT macrophage density, and circulating adipokine concentrations were measured. Food intake and body weight decreased upon initiation of hypoxia. However, whereas food intake normalized after 10 days, lower body weight persisted. Chronic hypoxia markedly reduced AT mass and adipocyte size. AT macrophage density and expression of Emr1, Ccl2, Lep, and Tnf were decreased, whereas Serpine1 and Adipoq expression levels were increased after chronic hypoxia. Concomitantly, chronic hypoxia increased AT expression of regulators of oxidative metabolism and markers of mitochondrial function and lipolysis. Circulating IL-6 and PAI-1 concentrations were increased, and leptin concentration was decreased after chronic hypoxia. Chronic hypoxia is associated with decreased rather than increased AT inflammation, and markedly decreased fat mass and adipocyte size. Furthermore, our data indicate that chronic hypoxia is accompanied by significant alterations in AT metabolic gene expression, pointing toward an enhanced AT metabolic rate.

Determinants of red cell distribution width (RDW) in cardiorenal patients: RDW is not related to erythropoietin resistance

BACKGROUND

Studies have shown that red cell distribution width (RDW) is related to outcome in chronic heart failure (CHF). The pathophysiological process is unknown. We studied the relationship between RDW and erythropoietin (EPO) resistance, and related factors such as erythropoietic activity, functional iron availability and hepcidin.

METHODS AND RESULTS

In the Mechanisms of Erythropoietin Action in the Cardiorenal Syndrome (EPOCARES) study, which investigates the role of EPO in 54 iron-supplemented anemic patients with CHF and chronic kidney disease (CKD) (n = 35 treated with 50 IU/kg/wk Epopoetin beta, n = 19 control), RDW was not associated with EPO resistance. We defined EPO resistance by EPO levels (r = 0.12, P = .42), the observed/predicted log EPO ratio (r = 0.12, P = .42), the increase in reticulocytes after 2 weeks of EPO treatment (r = -0.18, P = .31), and the increase of hemoglobin after 6 months of EPO treatment (r = 0.26, P = .35). However, RDW was negatively correlated with functional iron availability (reticulocyte hemoglobin content, r = -0.48, P < .001, and transferrin saturation, r = -0.39, P = .005) and positively with erythropoietic activity (soluble transferrin receptor, r = 0.48, P < .001, immature reticulocyte fraction, r = 0.36, P = .01) and positively with interleukin-6 (r = 0.48, P < .001). No correlation existed between hepcidin-25 and RDW.

CONCLUSIONS

EPO resistance was not associated with RDW. RDW was associated with functional iron availability, erythropoietic activity, and interleukin-6 in anemic patients with CHF and CKD.

Disorders of iron metabolism. Part 1: molecular basis of iron homoeostasis

IRON FUNCTIONS: Iron is an essential micronutrient, as it is required for satisfactory erythropoietic function, oxidative metabolism and cellular immune response. IRON PHYSIOLOGY: Absorption of dietary iron (1-2 mg/day) is tightly regulated and just balanced against iron loss because there are no active iron excretory mechanisms. Dietary iron is found in haem (10%) and non-haem (ionic, 90%) forms, and their absorption occurs at the apical surface of duodenal enterocytes via different mechanisms. Iron is exported by ferroportin 1 (the only putative iron exporter) across the basolateral membrane of the enterocyte into the circulation (absorbed iron), where it binds to transferrin and is transported to sites of use and storage. Transferrin-bound iron enters target cells-mainly erythroid cells, but also immune and hepatic cells-via receptor-mediated endocytosis. Senescent erythrocytes are phagocytosed by reticuloendothelial system macrophages, haem is metabolised by haem oxygenase, and the released iron is stored as ferritin. Iron will be later exported from macrophages to transferrin. This internal turnover of iron is essential to meet the requirements of erythropoiesis (20-30 mg/day). As transferrin becomes saturated in iron-overload states, excess iron is transported to the liver, the other main storage organ for iron, carrying the risk of free radical formation and tissue damage. REGULATION OF IRON HOMOEOSTASIS: Hepcidin, synthesised by hepatocytes in response to iron concentrations, inflammation, hypoxia and erythropoiesis, is the main iron-regulatory hormone. It binds ferroportin on enterocytes, macrophages and hepatocytes triggering its internalisation and lysosomal degradation. Inappropriate hepcidin secretion may lead to either iron deficiency or iron overload.

Anemia of chronic disease and chronic periodontitis: does periodontal therapy have an effect on anemic status?

BACKGROUND

As the periodontal tissues mount an immune inflammatory response to bacteria and their products, the systemic challenge with these agents also induces a major vascular response. Certain inflammatory cytokines produced during periodontal inflammation can depress erythropoietin production leading to the development of anemia. The aim of this study is to investigate whether patients with chronic periodontitis have an anemic status, and subsequently, to analyze the effect of non-surgical periodontal therapy on the anemic status of subjects over a 6-month period.

METHODS

A total of 187 patients with chronic periodontitis participated in the study. After red blood cell analyses, 60 patients with hemoglobin concentrations below reference ranges entered into the second part of the study in which patients were treated with non-surgical periodontal therapy. Clinical parameters and red blood cell analyses were repeated at 3 and 6 months.

RESULTS

In the first part of the study, 33.6% of patients had hemoglobin concentrations below normal reference ranges. In the second part of the study, all red blood cell parameters and clinical parameters showed statistical improvements over a 6-month period.

CONCLUSION

The present study strengthens the hypothesis that chronic periodontitis may lead to anemia and provides evidence that non-surgical periodontal therapy can improve the anemic status of patients with chronic periodontitis with greater improvement in females.

Iron restriction improves type 2 diabetes mellitus in Otsuka Long-Evans Tokushima fatty rats

Accumulating evidence suggests that alcohol, hepatitis C virus infection, steatosis with obesity, and insulin resistance are accompanied by iron overload states. Phlebotomy and oral iron chelators are effective treatments for these conditions and for hemochromatosis. However, the mechanisms by which iron depletion improves clinical factors remain unclear. We examined the effect of iron depletion in a model of type 2 diabetes, Otsuka Long-Evans Tokushima Fatty (OLETF) rats. Age-matched Long-Evans Tokushima Otsuka (LETO) rats were used as controls for all experiments. Iron restriction was performed by eliminating iron in the diet from 15 wk of age or by phlebotomy. Phlebotomy was commenced at 29 wk of age by removing 4 and 3 ml of blood from the tail vein every week in OLETF and LETO rats, respectively. Rats were euthanized at 43 wk of age, and detailed analyses were performed. The plasma ferritin concentration was markedly higher in OLETF rats and decreased in iron-deficient (ID) diet and phlebotomy rats. Hemoglobin A(1c) (Hb A(1c)) was decreased significantly in OLETF rats fed the ID diet and in the phlebotomy group. Increased levels of triglycerides, glucose, free fatty acids, and total cholesterol were found in ID OLETF rats. Plasma, liver, and pancreas lipid peroxidation and hepatic superoxide production decreased in both groups. Pancreatic fibrosis and insulin levels improved in both groups of OLETF rats. Pancreatic levels of peroxisome proliferator-activated receptor-beta/delta (PPARbeta/delta) ligands and hypoxia-inducible factor (HIF)-1alpha were decreased significantly in OLETF rats. These factors were normalized in both rats fed ID and phlebotomy groups of OLETF rats. In conclusion, iron depletion improved diabetic complications by inhibition of oxidative stress and TGFbeta signal pathways and the maintenance of pancreatic PPARbeta/delta and HIF-1alpha pathways.

Regulation of intestinal iron absorption: the mucosa takes control?

Two studies (Shah et al., 2009; Mastrogiannaki et al., 2009) show that the hypoxia inducible factor HIF-2alpha is a major player in regulating iron absorption by directly controlling the transcription of iron transporters in the intestine in response to changes in mucosal iron or oxygen levels. The HIF-2alpha mechanism has major effects on iron metabolism which can override the well-known hepcidin-ferroportin regulatory axis.

Restless legs syndrome in patients with irritable bowel syndrome: response to small intestinal bacterial overgrowth therapy

BACKGROUND

Small intestinal bacterial overgrowth (SIBO) occurs in irritable bowel syndrome (IBS) and fibromyalgia. Since restless legs syndrome (RLS) occurs with fibromyalgia, a link between IBS, SIBO, and RLS was studied.

METHODS

BS patients with abnormal lactulose breath tests received rifaximin 1,200 mg day(-1) for 10 days, followed by tegaserod 3 mg, long-term, and 1 month of zinc 220 mg day(-1) and once-daily probiotic (N = 11) or rifaximin monotherapy (N = 2). IBS symptom improvement was assessed after rifaximin. RLS symptoms, IBS symptoms, and overall IBS global improvement were assessed at last posttreatment visit: 8/10 patients were followed long-term (mean, 139 days; range, 54-450 days).

RESULTS

Ten of 13 patients exhibited > or =80% improvement from baseline in RLS symptoms. Five maintained complete resolution of RLS symptoms. Global gastrointestinal symptom improvement was great (n = 6), moderate (n = 5), or mild (n = 2).

CONCLUSION

This study suggests that SIBO associated with IBS may be a factor in some RLS patients and SIBO therapy provides long-term RLS improvement.

Pathophysiology of anemia and erythrocytosis

An increasing understanding of the process of erythropoiesis raises some interesting questions about the pathophysiology, diagnosis and treatment of anemia and erythrocytosis. The mechanisms underlying the development of many of the erythrocytoses, previously characterised as idiopathic, have been elucidated leading to an increased understanding of oxygen homeostasis. Characterisation of anemia and erythrocytosis in relation to serum erythropoietin levels can be a useful addition to clinical diagnostic criteria and provide a rationale for treatment with erythropoiesis stimulating agents (ESAs). Recombinant human erythropoietin as well as other ESAs are now widely used to treat anemias associated with a range of conditions, including chronic kidney disease, chronic inflammatory disorders and cancer. There is also heightened awareness of the potential abuse of ESAs to boost athletic performance in competitive sport. The discovery of erythropoietin receptors outside of the erythropoietic compartment may herald future applications for ESAs in the management of neurological and cardiac diseases. The current controversy concerning optimal hemoglobin levels in chronic kidney disease patients treated with ESAs and the potential negative clinical outcomes of ESA treatment in cancer reinforces the need for cautious evaluation of the pleiotropic effects of ESAs in non-erythroid tissues.

Animal models with enhanced erythropoiesis and iron absorption

The regulation of iron absorption is of considerable interest in mammals since excretion is minimal. Recent advances in iron metabolism have expounded the molecular mechanisms by which iron absorption is attuned to the physiological demands of the body. The pinnacle was the discovery and identification of hepcidin, a hepatic antimicrobial peptide that regulates absorption to maintain iron homeostasis. While the intricacies of its expression and regulation by HFE, transferrin receptor 2 and hemojuvelin are still speculative, hepcidin responsiveness has correlated negatively with iron absorption in different models and disorders of iron metabolism. Consequently, hepcidin expression is repressed to enhance iron absorption during stimulated erythropoiesis even in situations of elevated iron stores. Animal models have been crucial to the advances in understanding iron metabolism and the present review focuses on phenylhydrazine treated and hypotransferrinaemic rodents. These, respectively, experimental and genetic models of enhanced erythropoiesis highlight the shifting focus of iron absorption regulation from the marrow to the liver.