Early intraoperative iron-binding proteins are associated with acute kidney injury after cardiac surgery
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Iron regulation is an important modifier of renal ischemia-reperfusion injury, but the role of iron-binding proteins during cardiopulmonary bypass remains unclear. The goal was to characterize iron-binding proteins throughout ischemia-reperfusion injury to determine their association with acute kidney injury development.A prospective observational cohort of adult patients who underwent cardiac surgery (n = 301) was obtained, and acute kidney injury was defined by Kidney Disease Improving Global Outcomes. Serum ferritin, transferrin saturation, and urine hepcidin-25 were measured.Intraoperative serum ferritin was lower at the start of cardiopulmonary bypass (P = .005) and 1-hour cardiopulmonary bypass (P = .001) in patients with acute kidney injury versus patients without acute kidney injury. Lower serum ferritin and higher transferrin saturation at 1-hour cardiopulmonary bypass were independent predictors of acute kidney injury (serum ferritin odds ratio, 0.66; 95% confidence interval [CI], 0.48-0.91; transferrin saturation odds ratio, 1.26; 95% CI, 1.02-1.55) and improved model discrimination (area under the curve [AUC], 0.76; 95% CI, 0.67-0.85) compared with clinical prediction alone (AUC, 0.72; 95% CI, 0.62-0.81; ΔAUC and net reclassification index, P = .01). Lower ferritin, higher transferrin saturation at 1-hour cardiopulmonary bypass, and lower urine hepcidin-25 at postoperative day 1 were also independent predictors for acute kidney injury development, and this model demonstrated an AUC of 0.80 (0.72-0.87), which was superior to clinical prediction (ΔAUC P = .002, integrated discrimination improvement and net reclassification index P = .003).Our findings suggest that lower levels of intraoperative iron-binding proteins may reflect an impaired capacity to rapidly handle catalytic iron released during cardiopulmonary bypass, leading to kidney injury. These data highlight the importance of iron homeostasis in human ischemia-reperfusion injury and suggest it is a potentially modifiable risk during cardiac surgery. Intraoperative detection of incipient acute kidney injury may be feasible and could be used as an enrichment strategy for clinical trials.Keywords:
Transferrin saturation
Abstract Aim Iron overload is frequently reported in haemodialysis (HD) patients particularly those with chronic hepatitis C virus (HCV) infection. Soluble haemojuvelin (sHJV) has recently emerged as one of the significant regulators of iron homeostasis and hepcidin expression. The aim of the present study was to evaluate the potential associations of sHJV and hepcidin with inflammation, iron parameters and erythropoietin requirement in prevalent HD patients with HCV. Methods Serum sHJV and hepcidin were measured in 60 prevalent HD patients with [group I ( n = 30)] and without [group II ( n = 30)] HCV, and controls ( n = 30) by enzyme‐linked immunosorbent assay. Parameters related to anaemia, iron metabolism, inflammation, sHJV and hepcidin were measured. Results Serum hepcidin in HCV positive versus negative groups was 89.40 ± 46.08 ng/mL and 224.1 ± 72.36 ng/mL, P = 0.000, respectively, while sHJV was 245 ± 1.338 ng/mL and 254 ± 0.762 ng/mL, P = 0.147, respectively in positive versus negative patients. In group I, hepcidin correlated with serum ferritin ( r = −0.512 P = 0.005) and transferrin saturation (TSAT%) ( r = 0.572, P = 0.000) and sHJV correlated with ferritin ( r = 0.40, P 0.000), TSAT% ( r = 0.450, P = 0.002) and a significant correlation also existed between sHJV and hepcidin ( r = −0.259, P = 0.045). In the regression analysis, ferritin and TSAT% were able to predict sHJV; (standardized β = 0.52, P 0.001) and (standardized β = 0.48, P 0.010). Ferritin and sHJV were also able to predict hepcidin (standardized β = 0.627, P = 0.006) and (standardized β = 0.300, P = 0.007) in group I. Conclusion Soluble haemojuvelin levels seem to be associated with iron overload parameters and hepcidin levels in HCV positive HD patients.
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Dysmetabolic iron overload syndrome (DIOS) is a frequent condition predisposing to metabolic, cardiovascular and hepatic damage, whose pathogenesis remains poorly defined. Aim of this study was to characterize iron metabolism in DIOS.We evaluated 18 patients with DIOS, compared to 18 with nonalcoholic fatty liver and 23 healthy individuals with normal iron status, and 10 patients with hereditary haemochromatosis by a 24-h oral iron tolerance test with hepcidin measurement and iron metabolism modelling under normal iron stores.Dysmetabolic iron overload syndrome patients had higher peak transferrin saturation and area under the-curve of transferrin saturation than subjects with normal iron status, but lower values than haemochromatosis patients (P < 0.05 for all). Conversely, they had higher peak circulating hepcidin levels and area under the curve of hepcidin than the other groups (P < 0.05 for all). This was independent age, sex, haemoglobin, ferritin, and transferrin saturation levels (P = 0.0002). Hepcidin increase in response to the rise in transferrin saturation (hepcidin release index) was not impaired in DIOS patients. Viceversa, the ability of the hepcidin spike to control the rise in transferrin saturation at the beginning of the test (hepcidin resistance index) was impaired in DIOS (P = 0.0002). In DIOS patients, the hepcidin resistance index was correlated with ferritin levels at diagnosis (P = 0.016).Dysmetabolic iron overload syndrome is associated with a subtle impairment in the ability of the iron hormone hepcidin to restrain iron absorption following an iron challenge, suggesting a hepcidin resistance state. Further studies are required to better characterize the molecular mechanism underpinning this new iron metabolism alteration.
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Hepcidin plays a key role in iron homeostasis. This cross-sectional study measured the serum hepcidin levels of 48 maintenance haemodialysis patients and 20 age-matched healthy control subjects using a competitive enzyme-linked immunosorbent assay (C-ELISA). Serum hepcidin, interleukin (IL)-6 and high-sensitivity C-reactive protein levels were significantly higher in maintenance haemodialysis patients compared with control subjects. In all patients, there was a positive correlation between serum hepcidin levels and ferritin, transferrin saturation and IL-6, and an inverse correlation between serum hepcidin and unsaturated iron-binding capacity, total iron-binding capacity (TIBC) and transferrin. Linear regression analyses showed that ferritin and TIBC were independently associated with serum hepcidin levels. In conclusion, serum hepcidin levels are associated with iron status and microinflammation (defined as hsCRP < 15 mg/l, without clinical manifestation of inflammation) in maintenance haemodialysis patients. The C-ELISA method for measuring serum hepcidin should facilitate the routine measurement of hepcidin in clinical practice.
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HFE hemochromatosis (HFE-H) is the most common and well-defined inherited cause for iron-related morbidity and mortality. Majority of patients with HFE-H are homozygote for C282Y mutation. Recent studies suggest that iron accumulation in most types of hemochromatosis is due to deficiency of hepcidin, a central iron regulator. However, the precise link between hepcidin levels and iron absorption in HFE-H patients has been poorly understood.To measure hepcidin response to oral iron challenge (200 mg ferrous sulphate), in HFE-H (C282Y/C282Y) patients and compare with healthy controls (HCs).Nine patients with C282Y/C282Y HFE-H along with 15 HC were recruited for the study. All HFE-H were iron depleted and studied at a time distant to phlebotomy. Hepcidin was measured using a published immunoassay method after ingestion of 65 mg oral iron challenge. Serum iron, ferritin and transferrin saturation were measured using standard methods. The area under the curve was calculated and compared between the two groups.The basal serum hepcidin levels in patients with HFE-H were significantly low as compared with HC (P=0.0002). Incremental serum hepcidin response seen in HC reached significance at 4 h post iron challenge (P=0.0085) returning to baseline only at 24 h. There was no significant hepcidin response in HFE-H at 4 h (P=0.294). The overall hepcidin response was significantly lower in HFE-H compared with HC (area under the curve: P=0.0127).Failure to mount a rapid hepcidin response to an oral iron challenge is the key mechanisms of iron accumulation despite prevailing excess body iron in patients with HFE-H with C282Y/C282Y mutation.
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Iron disorder and abnormal expression of hepcidin play important roles in many diseases, but it is still unclear in type 2 diabetes mellitus (T2DM). We aimed to assess iron, ferritin and hepcidin levels in plasma of with or without T2DM and evaluated increased body iron stores as risk factor for developing T2DM. Plasma samples were collected from 88 participants, who were categorized into 2 groups based on the presence or absence of T2DM. Demographics and general health parameters were recorded. Chemiluminescence microparticle immunoassay and enzyme-linked immunosorbent assay were used to detect iron, ferritin and hepcidin concentrations. The geometric mean±SD of the plasma level of hepcidin, ferritin, iron and insulin among T2DM comparing with that of healthy controls were evaluated. Plasma ferritin and hepcidin levels in T2DM group were higher than in the control group (P < 0.05). The geometric mean ± SD of hepcidin and ferritin for T2DM were 41.1±23.3 μg/L and 227.2±156.1 ŋg/L respectively; higher than the 15.2±2.3 μg/L and 114.4±60.4 ŋg/L of controls respectively. There was a significant associated between high level of plasma hepcidin (OR=2.75) and ferritin (OR=2.24); with T2 DM. In conclusion: the regulation of body iron, an essential but also toxic element is strictly controlled by a small peptide hormone hepcidin. The present data demonstrated that the higher hepcidin level in diabetic patients may be due to that higher ferritin, the elevated hepcidin might have adaptive value through down-regulated iron absorb and play an important role in pathogenesis of T2 DM.
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Erythropoiesis-stimulating agents used to treat anaemia in patients with chronic kidney disease (CKD) have been associated with cardiovascular adverse events. Hepcidin production, controlled by bone morphogenic protein 6 (BMP6), regulates iron homeostasis via interactions with the iron transporter, ferroportin. High hepcidin levels are thought to contribute to increased iron sequestration and subsequent anaemia in CKD patients. To investigate alternative therapies to erythropoiesis-stimulating agents for CKD patients, monoclonal antibodies, LY3113593 and LY2928057, targeting BMP6 and ferroportin respectively, were tested in CKD patients.Preclinical in vitro/vivo data and clinical data in healthy subjects and CKD patients were used to illustrate the translation of pharmacological properties of LY3113593 and LY2928057, highlighting the novelty of targeting these nodes within the hepcidin-ferroportin pathway.LY2928057 bound ferroportin and blocked interactions with hepcidin, allowing iron efflux, leading to increased serum iron and transferrin saturation levels and increased hepcidin in monkeys and humans. In CKD patients, LY2928057 led to slower haemoglobin decline and reduction in ferritin (compared to placebo). Serum iron increase was (mean [90% confidence interval]) 1.98 [1.46-2.68] and 1.36 [1.22-1.51] fold-relative to baseline following LY2928057 600 mg and LY311593 150 mg respectively in CKD patients. LY3113593 specifically blocked BMP6 binding to its receptor and produced increases in iron and transferrin saturation and decreases in hepcidin preclinically and clinically. In CKD patients, LY3113593 produced an increase in haemoglobin and reduction in ferritin (compared to placebo).LY3113593 and LY2928057 pharmacological effects (serum iron and ferritin) were translated from preclinical-to-clinical development. Such interventions may lead to new CKD anaemia treatments.
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Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder caused by the loss of motor neurons. Its etiology remains unknown, but several hypothesis have been raised to explain motor neuron death, including oxidative stress. Dysregulation of cellular iron metabolism can lead to increased oxidative stress, and existing data argue for a role of iron metabolism in ALS pathophysiology.We performed a retrospective analysis of iron metabolism (IM) variables (serum levels of iron, transferrin, ferritin, and TSC for Transferrin Saturation Coefficient) in a cohort of 694 ALS patients and 297 healthy controls.Serum ferritin levels and TSC were higher, whereas serum transferrin levels were lower in ALS patients than controls. In addition, patients with a high level serum ferritin had a shorter survival time compared to those with low level serum ferritin (618 days versus 921 days for men subgroup; p = .007). Site of onset and ALS-FRS score were not associated with IM variables.This study suggests that ALS patients may have increased iron storage, as measured by increased serum ferritin and TSC. Elevated serum ferritin may also have a deleterious impact on survival in ALS.
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