Damien Ashby

Plasma hepcidin levels are elevated but responsive to erythropoietin therapy in renal disease

Hepcidin is a critical inhibitor of iron export from macrophages, enterocytes, and hepatocytes. Given that it is filtered and degraded by the kidney, its elevated levels in renal failure have been suggested to play a role in the disordered iron metabolism of uremia, including erythropoietin resistance. Here, we used a novel radioimmunoassay for hepcidin-25, the active form of the hormone, to measure its levels in renal disease. There was a significant diurnal variation of hepcidin and a strong correlation to ferritin levels in normal volunteers. In 44 patients with mild to moderate kidney disease, hepcidin levels were significantly elevated, positively correlated with ferritin but inversely correlated with the estimated glomerular filtration rate. In 94 stable hemodialysis patients, hepcidin levels were also significantly elevated, but this did not correlate with interleukin-6 levels, suggesting that increased hepcidin was not due to a general inflammatory state. Elevated hepcidin was associated with anemia, but, intriguingly, the erythropoietin dose was negatively correlated with hepcidin, suggesting that erythropoietin suppresses hepcidin levels. This was confirmed in 7 patients when hepcidin levels significantly decreased after initiation of erythropoietin treatment. Our results show that hepcidin is elevated in renal disease and suggest that higher hepcidin levels do not predict increased erythropoietin requirements.

Prospective observational single-centre cohort study to evaluate the effectiveness of treating lupus nephritis with rituximab and mycophenolate mofetil but no oral steroids

Objectives Lupus nephritis (LN) is a serious complication of systemic lupus erythematosus (SLE). All current treatment regimens include oral steroids, which are associated with severe adverse events and long-term damage. We have piloted a steroid-avoiding protocol (rituxilup) for the treatment of biopsy-proven active International Society of Nephrology/Renal Pathology Society (ISN/RPS) class III, IV, or class V LN. Methods We report the findings from the first 50 consecutive patients, treated with 2 doses of rituximab (1 g) and methyl prednisolone (500 mg) on days 1 and 15, and maintenance treatment of mycophenolate mofetil. Patients on maintenance steroids or with life-threatening SLE or requiring dialysis were excluded. Renal remission was defined as serum creatinine no greater than 15% above baseline; complete biochemical remission (CR) was defined as urine protein : creatinine ratio (PCR)<50 mg/mmol or partial remission (PR) if PCR>50 mg/mmol but non-nephrotic and >50% reduction. Results A total of 45 (90%) patients achieved CR or PR by a median time of 37 weeks (range 4–200). Overall, 72% (n=36) achieved CR (median time 36 weeks (11–58)) and a further 18% (n=9) achieved persistent PR (median time 32 weeks (19–58)). By 52 weeks, CR and PR had been achieved in 52% (n=26) and 34% (n=17) respectively. In all, 12 relapses occurred in 11 patients, at a median time of 65.1 weeks (20–112) from remission. A total of 6/50 patients had systemic flares. Of the 45 responders, only 2 required >2 weeks of oral steroids. Adverse events were infrequent; 18% were admitted, 10% for an infective episode. Conclusions The rituxilup cohort demonstrates that oral steroids can be safely avoided in the treatment of LN. If findings are confirmed, it could mark a step change in the approach to the treatment of LN.

Erythropoietin administration in humans causes a marked and prolonged reduction in circulating hepcidin

Expression of hepcidin, the key hormone governing iron transport, is reduced by anemia in a manner which appears dependent on increased bone marrow activity. The temporal associations between plasma hepcidin and other iron parameters were examined in healthy humans after erythropoietin administration and venesection. Profound hepcidin suppression appeared abruptly 24 hours after subcutaneous erythropoietin (P=0.003), and was near maximal at onset, with peak (mid-afternoon) levels reduced by 73.2%, gradually recovering over the following two weeks. Minor changes in circulating iron, soluble transferrin receptor and growth differentiation factor-15 were observed after the reduction in hepcidin. Similar but more gradual changes in these parameters were observed after reducing hematocrit by removal of 250 mL blood. These human studies confirm the importance of a rapidly responsive marrow–hepcidin axis in regulating iron supply in vivo, and suggest that this axis is regulated by factors other than circulating iron, soluble transferrin receptor or growth differentiation factor-15.

Iron deficiency and raised hepcidin in idiopathic pulmonary arterial hypertension: clinical prevalence, outcomes, and mechanistic insights.

OBJECTIVES This study sought to understand the prevalence and clinical relevance of iron deficiency in patients with idiopathic pulmonary arterial hypertension (IPAH). BACKGROUND Iron availability influences the pulmonary vascular response to hypoxia in humans and may be significant in the pathogenesis of IPAH. METHODS Iron deficiency, defined by raised levels of soluble transferrin receptor (sTfR), was investigated in 98 patients with IPAH. Hepcidin and erythropoietin (EPO) levels were also measured. The effect of bone morphogenetic protein (BMP) receptor knockdown on BMP-6-stimulated hepcidin production was assessed in human hepatoma HepG2 cells. Relationships between sTfR and exercise capacity, functional class, and all-cause mortality were analyzed. RESULTS Circulating sTfR levels were raised in 63% of IPAH patients, indicating significant iron deficiency. Consistent with this, iron, ferritin, and transferrin saturation levels were reduced and red cell distribution width increased, without overt anemia. Hepcidin correlated inversely with sTfR and positively with increasing ferritin. Hepcidin was inappropriately raised in IPAH independent of the inflammatory marker interleukin-6. EPO levels were also raised and correlated inversely with hepcidin. BMP receptor-type 2 (BMPR2) knockdown in HepG2 cells increased BMP-6-stimulated hepcidin expression. sTfR increased with World Health Organization functional class (p < 0.05), correlated negatively with exercise capacity (p = 0.027), and values >28.1 nmol/l independently predicted survival (p = 0.011). CONCLUSIONS Iron deficiency is common in IPAH patients and associated with disease severity and poor clinical outcome. Inappropriately raised hepcidin levels, which impair iron absorption from the gut, may be a factor.

Sustained appetite improvement in malnourished dialysis patients by daily ghrelin treatment

Malnutrition is a common complication in patients on dialysis and is strongly associated with poor prognosis. Effective therapy could substantially improve morbidity and mortality, but neither enteral nor parenteral supplementation provide long-term benefit because of the strong appetite suppression seen in such patients. We performed a double-blinded randomized crossover study of a week-long treatment with daily subcutaneous ghrelin, a gut hormone that regulates hunger through the hypothalamus, in a group of 12 malnourished dialysis patients. Ghrelin administration increased ghrelin levels in circulation, modestly reduced blood pressure for up to 2 h, and immediately and significantly increased appetite, with an increase in energy intake noted at the first study meal. Persistence of this effect throughout the week was confirmed with food diaries and final study meals. Energy expenditure, measured with free-living pulse and motion monitors, was unchanged by ghrelin. Our study shows that daily treatment with ghrelin achieves a sustained positive change in energy balance in malnourished dialysis patients. Direct manipulation of appetite with ghrelin or its analogs represents an attractive and promising therapeutic strategy for this difficult clinical problem.

Development of a novel immunoassay for the iron regulatory peptide hepcidin.

Abstract To date there have been few published immunoassays for the important iron regulator hepcidin. This study describes a novel competitive radioimmunoassay (RIA) for the bioactive hepcidin peptide. A rabbit anti-hepcidin polyclonal antibody was produced using synthetic hepcidin radiolabelled with 125I to produce a competitive RIA. Normal patient (n=47) samples were collected and assayed for hepcidin to determine a reference range. Other patient groups collected were ulcerative colitis (UC; n=40), iron deficiency anaemia (IDA; n=15), chronic kidney disease not requiring dialysis (CKD; n=45) and chronic kidney disease requiring dialysis (HCKD; n=94). Detection limit of the assay was determined as 0.6 ng/mL. Intra-assay precision was 5 ng/mL (7.2%) and 50 ng/mL (5.8%), inter-assay precision was 5 ng/mL (7.6%) and 50 ng/mL (6.7%). Analytical recovery was 98% (5 ng/mL), 94% (10 ng/mL) and 97% (50 ng/mL). The assay was linear up to 200 ng/mL. No demonstrable cross-reactivity with human insulin, glucagon I, angiotensinogen I, β-defensin 1–4, α-defensin-1 and plectasin was observed. There was significant correlation (r=0.96, P≤0.0001) between the hepcidin RIA and an established hepcidin SELDI-TOF-MS method. Analysis of the normal human samples gave a reference range of 1.1–55 ng/mL for hepcidin. Further statistical evaluation revealed a significant difference between male and female hepcidin levels. There was significant correlation between hepcidin and ferritin in the control group (r=0.6, P≤0.0001). There was also a significant difference between the normal and disease groups (P≤0.0001). Healthy volunteers (n=10) showed a diurnal increase in plasma hepcidin at 4.00 pm compared to 8.00 am. A robust and optimised immunoassay for bioactive hepcidin has been produced and the patient sample results obtained further validates the important role of hepcidin in iron regulation, and will allow further investigation of this important peptide and its role in iron homeostasis.

Bacteremia Associated with Tunneled Hemodialysis Catheters: Outcome after Attempted Salvage

BACKGROUND AND OBJECTIVES Treatment without catheter replacement (catheter salvage) has been described for bacteremia associated with tunneled venous catheters in hemodialysis patients, but few data are available on which to base an estimation of the likelihood of treatment success. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS In a prospective cohort study, all cases of catheter-associated bacteremia that occurred in a large dialysis center were identified during a 12-mo period. Catheter salvage was attempted according to a standard protocol in all cases in which a favorable early response to antibiotic therapy was seen, and patients were followed for at least 6 mo. Bacteremias, catheter changes, and all major clinical events were recorded. RESULTS During a period covering 252,986 catheter days, 208 episodes were identified involving 133 patients, 74% of which were selected for attempted salvage. Salvage was successful in 66.1% of incident bacteremias with a very low complication risk (0.9%). Some bacteremias, however, recurred as late as 6 mo after the initial infection; salvage was less likely to be successful in treating recurrences. CONCLUSIONS Appropriately used catheter salvage can be successful in approximately two thirds of cases; however, recurrences continue to occur up to 6 mo later and are unlikely to be cured without catheter replacement.

Cardiac Survival after Pre-emptive Coronary Angiography in Transplant Patients and Those Awaiting Transplantation

BACKGROUND AND OBJECTIVES Recent interest has focused on wait listing patients without pretreating coronary artery disease to expedite transplantation. Our practice is to offer coronary revascularization before transplantation if indicated. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Between 2006 and 2009, 657 patients (427 men, 230 women; ages, 56.5 ± 9.94 years) underwent pretransplant assessment with coronary angiography. 573 of 657 (87.2%) patients were wait listed; 247 of 573 (43.1%) patients were transplanted during the follow-up period, 30.09 ± 11.67 months. RESULTS Patient survival for those not wait listed was poor, 83.2% and 45.7% at 1 and 3 years, respectively. In wait-listed patients, survival was 98.9% and 95.3% at 1 and 3 years, respectively. 184 of 657 (28.0%) patients were offered revascularization. Survival in patients (n = 16) declining revascularization was poor: 75% survived 1 year and 37.1% survived 3 years. Patients undergoing revascularization followed by transplantation (n = 51) had a 98.0% and 88.4% cardiac event-free survival at 1 and 3 years, respectively. Cardiac event-free survival for patients revascularized and awaiting deceased donor transplantation was similar: 94.0% and 90.0% at 1 and 3 years, respectively. CONCLUSIONS Our data suggest pre-emptive coronary revascularization is not only associated with excellent survival rates in patients subsequently transplanted, but also in those patients waiting on dialysis for a deceased donor transplant.

Translumbar central venous catheters for long-term haemodialysis

BACKGROUND Vascular access for haemodialysis is achieved by tunnelled central venous catheter (CVC) in at least 23% of prevalent patients in the UK, Canada and the USA. Use of CVCs is associated with an increased incidence of venous stenosis that can progressively limit future vascular access routes. Lack of conventional venous access routes mandates the use of alternative strategies such as the translumbar approach. METHODS We retrospectively analysed patients at our centre requiring translumbar inferior vena caval CVCs (TesioCath) for haemodialysis in the period 1999-2008. Written and electronic records capturing dialysis adequacy and complications, hospital admissions and laboratory data were examined. RESULTS Thirty-nine pairs of translumbar CVCs were inserted in 26 patients with 15 864 catheter days follow-up, mean patient age 61.9 +/- 12.1 years, 31% diabetic, 15% with ischaemic heart disease. All insertions were successful. Insertion of one CVC was associated with a self-limiting retroperitoneal haematoma. No patients died of a catheter-related cause or through lack of vascular access. Cumulative assisted primary catheter site patency was 81% at 6 months and 73% at 1 year (median 18.5 months). Good dialysis adequacy was achieved throughout (mean single-pool Kt/V 1.5 +/- 0.4). The incidence of access-related infection was 2.84/1000 catheter days (exit site infection rate 2.02/1000 catheter days; catheter-related bacteraemia rate 0.82/1000 catheter days). Catheter dysfunction (need for thrombolytic infusion or catheter change) led to 0.88 admissions per 1000 catheter days. CONCLUSION Translumbar inferior vena caval CVCs can offer relatively safe and effective long-term haemodialysis access in patients with no other options.

Inadvertent postdialysis anticoagulation due to heparin line locks

Large‐bore dual lumen in‐dwelling venous catheters are used in hemodialysis. These catheters are usually locked with heparin after the treatment. This study addressed the underappreciated postdialysis coagulopathy that can result. Thirty‐six patients were included: 7 dialyzed through arterio‐venous fistulae, 29 through in‐dwelling venous catheters. The latter group was further subdivided according to whether they received heparin or heparin‐free dialysis. To assess the heparin lock, a full‐dose heparin lock as well as a much weaker heparin lock and a citrate lock were used. To assess the coagulopathy, blood was taken 1 hr after dialysis. The activated partial thromboplastin time (APTT) and anti‐Xa level was measured. Additionally, 6 venous catheters were removed and the amount of fluid expelled upon locking with saline was measured. Clotting from the patient group with arterio‐venous fistulae was normal following dialysis. The patients with in‐dwelling venous catheters and heparin locks had significantly deranged clotting; 6 out of 10 patients had abnormal APTT results. All patients with catheters, heparin‐free dialysis, and heparin locks had deranged clotting (7 out of 7). The rate decreased significantly when heparinized saline was used as a lock. A subset of patients had a citrate lock rather than a heparin lock; the clotting results normalized in all but one patient. An in vitro study demonstrated immediate leakage of fluid from the end of the ports upon locking. Significant postdialysis anticoagulation can occur after dialysis, which can be attributed to the heparin line locks. This risk is considerably reduced when a citrate lock is used instead.