Novel aspects of erythropoietin response in renal failure patients

CE: Continuing Education Article: MANAGEMENT OF ANAEMIA IN CHRONIC KIDNEY DISEASE

SUMMARY Anaemia is an almost universal issue that develops in the later stages of chronic kidney disease (CKD) primarily due to a lack of erythropoietin (EPO) and the depressed EPO response in bone marrow. This can have a profound effect on the patient's lifestyle and quality of life. Knowledge of both the psychosocial and clinical areas of CKD is imperative for healthcare professionals so that they can be at the forefront of improvements of CKD patient care.

Improved Anemia and Reduced Erythropoietin Need by Medical or Surgical Intervention of Secondary Hyperparathyroidism in Hemodialysis Patients

BACKGROUND

The available literature is still controversial and shows that surgical (parathyroidectomy, PTX) or medical (calcitriol) treatment actually improved or even corrected the rhEPO-resistant anemia of ESRD patients with severe SHP. The aims of this study were to 1) assess the influence of SHP on hematological parameters in ESRD patients, 2) evaluate whether or not calcitriol could improve anemia and reduce the need of erythropoietin in dialysis patients, and 3) investigate the longitudinal effect of a parathyroidectomy for 6 months on regarding any improvements in calcitriol-refractory ESRD patients.

METHODS

37 chronic hemodialysis patients in Chang Gung Memorial Hospital Dialysis Unit were divided into two groups: patients with SHP (iPTH>300 pg/mL) and patients without SHP (ipTH<300 pg/mL) before calcitriol therapy was applied. Sixteen patients remain with a status of hyperparathyroidism and were considered candidates for calcitriol therapy. Furthermore, we divided the patients according to the response of HPT to calcitriol into responding patients and nonresponding patients. Among nonresponder groups, three patients agreed to accept surgical intervention to treat their hyperparathyroidism status.

RESULTS

The phosphate levels and serum alkaline phosphatase levels in patients with SHP were significantly higher when compared with those without SHP (P<0.05). As for the hematological data, hematocrit for patients with SHP was significantly higher than those without SHP (10.5 +/- 0.6 vs. 8.9 +/- 0.8, p<0.05). Other hematological parameters such as transferrin saturation and serum ferritin were not significantly different. We found a significant difference in alkaline phosphate levels in responding and nonresponding patients at 6 months on calcitriol therapy. Concomitantly, the hematocrit level is significantly higher in responding group when compared to those in nonresponding group (10.63 +/- 0.72 vs. 8.96 +/- 1.21, p<0.01). As for the dose of EPO requirement, significant difference between groups was also found after 6-month treatment (3617 +/- 2011 vs. 5416 +/- 1947, p<0.05). As for rhEPO dose requirement, positive effects of PTX were significantly found. The rhEPO doses needed to maintain patients in the hematocrit target range of 30-33% decreased gradually by 29% from 5323 +/- 1326 micro to 3774 +/- 2145 micro per week. The hematocrit level showed a significant increase at 3 months after PTX (p<0.05). This effect lasted until 6 months after PTX. The serum ferritin level was constantly around 350 to 400 pg/mL. While the transferrin saturation decreased 3 months after PTX (p<0.05) and recovered at 6 months.

CONCLUSION

ESRD patients with SHP, usually associated with more severe anemia show resistance to rhEPO. In this case, investigation of SHP is strongly recommended with measurement of serum PTH, phosphate and alkaline phosphatase level. Treatment of calcitriol has a beneficial effect on renal anemia in ESRD patients with SHP. In addition, PTX could also provide another choosing therapy in improving renal anemia when medical treatment fails.

Effect of Intravenous Ascorbic Acid in Hemodialysis Patients With EPO-Hyporesponsive Anemia and Hyperferritinemia

BACKGROUND

Although erythropoietin (EPO)-hyporesponsive anemia in hemodialysis patients most commonly results from iron deficiency, the contributory role of chronic inflammation and oxidative stress in its pathogenesis is poorly understood. We conducted an open-label prospective study to assess the effect of vitamin C, an antioxidant, on EPO-hyporesponsive anemia in hemodialysis patients with unexplained hyperferritinemia.

METHODS

Forty-six of 262 patients in an inner-city hemodialysis center met the inclusion criteria (administration of intravenous iron and EPO for > or = 6 months at a dose > or = 450 U/kg/wk, average 3-month hemoglobin [Hb] level < or = 11.0 g/dL [< or = 110 g/L], ferritin level > or = 500 ng/mL (microg/L), and transferrin saturation [TSAT] < or = 50%). Patients were excluded if they had a clear explanation for the EPO hyporesponsiveness. Four patients refused to participate. The remaining patients were randomly assigned; 20 patients to receive standard care and 300 mg of intravenous vitamin C with each dialysis session (group 1) and 22 patients to receive standard care only (group 2). Study duration was 6 months. During the study, 1 patient from group 1 was removed (upper gastrointestinal bleeding) from final analysis. Monthly assessment included Hb level, mean corpuscular volume, iron level, iron-binding capacity, ferritin level, TSAT, and Hb content in reticulocytes. In addition, biointact parathyroid hormone, aluminum, C-reactive protein (CRP), and liver enzymes were measured every 3 months.

RESULTS

Age, sex, race, and time on dialysis therapy were similar in both groups. At 6 months, Hb levels significantly increased from 9.3 to 10.5 g/dL (93.0 to 105.0 g/L) in group 1, but not group 2 (9.3 to 9.6 g/dL [93.0 to 96.0 g/L]; P = 0.0001). Similarly, TSAT increased from 28.9% to 37.3% in group 1, but not group 2 (28.7% to 29.3%; P = 0.0001). EPO dose (477 to 429 versus 474 to 447 U/kg/wk), iron-binding capacity (216 to 194 versus 218 to 257 microg/dL [38.7 to 34.7 versus 39 to 46 micromol/L]), and CRP level (2.8 to 0.9 versus 2.8 to 2.2 mg/dL) decreased significantly in group 1, but not in controls. Changes in Hb content in reticulocytes and ferritin level also were statistically significant in group 1. There was no change in biointact parathyroid hormone levels. Although serum iron levels and intravenous iron doses changed within each group, changes were equal between the 2 groups.

CONCLUSION

In hemodialysis patients with refractory anemia and hyperferritinemia, vitamin C improved responsiveness to EPO, either by augmenting iron mobilization from its tissue stores or through antioxidant effects.

Efficacy and immunogenicity of novel erythropoietic agents and conventional rhEPO in rats with renal insufficiency

Recombinant human erythropoietin (rhEPO) is used to treat anemia in chronic renal insufficiency. Erythropoietin (EPO) immunogenicity can lead to EPO-resistant anemia. Conjugating proteins with polyethylene glycol (PEG) can prolong elimination half-life and diminish protein immunogenicity. We investigated the efficacy of new erythropoietic agents, synthesized by single (Ro 50-3821) and multiple (MIX) integrations of PEG and succinimidyl butanoic acid with rhEPO, in rats with chronic renal insufficiency. Sprague-Dawley rats with surgically induced renal insufficiency received Ro 50-3821 or MIX subcutaneously (s.c.) over 4-12 weeks compared to rhEPO and NaCl. Hemoglobin and antibody levels served as primary efficacy and safety variables. Dosing intervals and dose-response characteristics were investigated. Ro 50-3821 (2.5 microg/kg once weekly) increased hemoglobin levels by 7 g/dl after 4 weeks compared to 1 g/dl in NaCl controls (P<0.05). MIX (2.5 microg/kg once weekly) and rhEPO (0.25 microg/kg three times weekly) increased hemoglobin levels by 3 g/dl. Ro 50-3821 administered for 12 weeks (0.75 microg/kg once weekly) increased hemoglobin levels (from 13 to 19 g/dl) more effectively than rhEPO (0.75 microg/kg once weekly, decline from 13 to 11 g/dl, P<0.05). No antibodies against Ro 50-3821 were detected after 12 weeks of treatment. Antibodies against rhEPO were seen in 69% of animals (P<0.00001). Ro 50-3821 increased hemoglobin levels with once weekly s.c. dosing. Multiple pegylated EPO is less effective. In rats, rhEPO failed to increase hemoglobin levels with once weekly long-term dosing. Antibody formation following rhEPO may explain this finding. Therefore, Ro 50-3821 may provide important clinical advantages compared to unpegylated EPO. It can be administered in longer dosing intervals and has a lower risk of unfavorable immunological responses.

Anaemia after renal transplantation

Anaemia is a frequent complication among long-term renal transplant recipients. A prevalence of approximately 40% has been reported in several studies. If renal function declines to stage 5 kidney disease, the prevalence of anaemia in kidney transplants is even higher. A positive correlation between haemoglobin concentration and creatinine clearance has been reported, which is a function of endogenous erythropoietin production by the functioning graft. Inflammation related to a retained kidney graft may cause hypo-responsiveness to erythropoietic agents once kidney transplant recipients return to dialysis. Furthermore, the use of azathioprine, mycophenolate mofetil and sirolimus may be associated with post-transplant anaemia. Along with erythropoietin deficiency, depletion of iron stores is one of the major reasons for anaemia in the kidney transplant population. The proportion of hypochromic red blood cells appears to be a useful parameter to measure iron supply and utilization as well as to estimate mortality risks in kidney transplant recipients. While anaemia is an important cardiovascular risk-factor after transplantation, our data suggest that anaemia is not associated with mortality and graft loss. Nevertheless, inadequate attention is paid so far to the management of anaemia after renal transplantation. A promising future aspect for risk reduction of cardiovascular disease includes the effect of erythropoietic agents on endothelial progenitor cells.

Effects of Intravenous Polymaltose Iron on Oxidant Stress and Non-Transferrin-Bound Iron in Hemodialysis Patients

BACKGROUND

The use of intravenous iron to correct anemia in end-stage renal diseases (ESRD) has been suspected of catalyzing the production of activated oxygen species and promoting oxidative damage. We investigated the pro-oxidative potential of injected iron in hemodialysis patients.

METHODS

In study A, 65 patients with ESRD were studied. 20 patients received weekly infusions of iron polymaltose (maltofer), whereas 45 patients had been off iron therapy for more than 2 months. In study B, 12 patients were investigated during two consecutive hemodialysis sessions, one session without and one session with infusion of 100 mg of maltofer over 4 h. Serum iron status, non-transferrin-bound iron (NTBI) and markers of oxidative stress were studied in blood samples from these patients.

RESULTS

In study A, NTBI was detected in 41% of the patients and the proportion of NTBI-positive patients was the same whether or not they received iron therapy. In study B, the serum iron and transferrin saturation index increased during iron infusion and NTBI transiently appeared in some patients but markers of oxidative stress were not significantly affected.

CONCLUSION

Although ESRD patients have a high prevalence of NTBI in their serum, no correlation could be established between the presence of NTBI and an increased oxidative stress. The slow infusion of maltofer does not promote a significant increase in the plasma concentration of oxidative stress markers. It may therefore be considered as a safe complement to erythropoietin therapy.

Risk factors and risk for mortality of mild hypoparathyroidism in hemodialysis patients

Relative hypoparathyroidism (parathyroid hormone [PTH] < or = 200 pg/mL) is prevalent in hemodialysis (HD) patients, with unknown pathogenesis and prognosis. Thus, to clarify risk factors and prognosis of time-dependent relative hypoparathyroidism in HD patients, a retrospective cohort study was performed for 126 HD patients with four or more PTH determinations and no previous total or subtotal parathyroidectomy. Values for intact PTH, ionized calcium, phosphate, magnesium, albumin, creatinine, urea reduction ratio (URR), glucose, hemoglobin A1c (HbA1c), aluminum, and 1,25(OH)2D were obtained at enrollment and at some time during follow-up. The prevalence of relative hypoparathyroidism at entry was 76 of 126 patients (60.3%). Univariate analysis showed that patients with hypoparathyroidism were older, more likely to have diabetes, and had greater ionized calcium levels and lower phosphate, albumin, blood urea nitrogen (BUN), and creatinine levels. Patients with diabetes were older and had a shorter duration of dialysis therapy and lower PTH, phosphate, albumin, BUN, and creatinine levels and URRs. Conversely, multivariate analysis showed that PTH levels at entry were associated directly with creatinine levels and inversely with age and ionized calcium levels (but not diabetes). During follow-up, PTH levels fluctuated concomitantly with ionized calcium and phosphate levels over time in all patients. Time-dependent PTH levels were associated directly with duration of dialysis therapy and use of vitamin D and phosphate and albumin levels, but inversely with age and ionized calcium and magnesium levels (but not glucose or HbA1c levels). Interestingly, time-dependent PTH levels were independently associated with survival after adjusting for traditional risk factors (diabetes, age, albumin and creatinine levels, and URR) and duration of dialysis therapy. We conclude that in HD patients, relative hypoparathyroidism was not associated with diabetes per se. Time-dependent PTH levels were associated with age, duration of dialysis, and levels of ionized calcium, phosphate, albumin, and magnesium. Moreover, relative hypoparathyroidism at entry and lower time-dependent PTH levels predict mortality.