Changes of biomarkers for erythropoiesis, iron metabolism, and FGF23 by supplementation with roxadustat in patients on hemodialysis.

This study aimed to confirm changes in biomarkers of erythropoiesis and iron metabolism and serum fibroblast growth factor 23 (FGF-23) during darbepoetin-α treatment and then switching to the hypoxia-inducible factor prolyl hydroxylase inhibitor roxadustat. A total of 28 patients on hemodialysis who received weekly doses of darbepoetin-α were switched to roxadustat. Biomarkers for erythropoiesis and iron metabolism and intact and C-terminal FGF-23 were measured in blood samples collected before the HD session on days - 7 (darbepoetin-α injection), - 4, and - 2, and days 0 (switch to roxadustat treatment, three times weekly), 3, 5, 7, 14, 21, and 28. Erythropoietin and erythroferrone levels were elevated on day - 4 by darbepoetin-α injection and decreased to baseline levels at day 0. Levels of erythropoietin were not significantly increased by roxadustat supplementation, but erythroferrone levels were continuously elevated, similar to darbepoetin-α treatment. Hepcidin-25 and total iron binding capacity were significantly decreased or increased in patients treated with roxadustat compared with darbepoetin-α. Changes of intact and C-terminal FGF-23 levels were parallel to changes of phosphate levels during roxadustat treatment. However, the actual and percentage changes of intact FGF-23 and C-terminal FGF-23 in patients with low ferritin levels were greater than those in patients with high ferritin levels. Roxadustat might stimulate erythropoiesis by increasing iron usage through hepcidin-25, which was suppressed by erythroferrone in the physiological erythropoietin condition. Changes of intact FGF-23 and C-terminal FGF-23 levels might be affected by roxadustat in patients on hemodialysis, especially those with a low-iron condition.

Erythropoiesis stimulating agents are associated with serum fibroblast growth factor 23 metabolism in patients on hemodialysis.

BACKGROUND: This study aimed to determine associations among short- and long-acting erythropoiesis stimulating agents (ESAs), changes in serum fibroblast growth factor 23 (FGF23) and biomarkers of iron metabolism. METHODS: Among 108 patients on hemodialysis (HD), 44 received every 2 weeks or monthly doses of continuous erythropoiesis receptor activator (CERA), 31 received weekly doses of darbepoetin-α, 24 received three doses per week of epoetin-ß and 9 were not treated with an ESA. Intact and C-terminal FGF23 and transferrin saturation (TSAT), ferritin, erythroferrone and hepcidin 25 were measured in blood samples collected before the HD session at the end of the dialysis week (baseline, Day 0) and on Days 3, 5, 7 and 14 thereafter. RESULTS: Levels of ferritin, hepcidin 25 and erythroferrone as well as TSAT were significantly decreased or elevated in patients treated with CERA compared with other types of ESAs. Levels of C-terminal FGF23 increased in all groups during the observation period. Levels of intact FGF23 and ratios of intact FGF23 to C-terminal FGF23 gradually decreased between Days 3 and 7 in the CERA but not in the other groups. Multivariate models associated changes in hepcidin 25 and phosphate with those of intact FGF23. CONCLUSION: The long-acting ESA CERA might influence levels of intact FGF23 by increasing FGF23 cleavage in patients on HD in association with prolonged hepcidin 25 suppression.

Differential Impacts of Intravenous Iron Administration and Iron-Containing Phosphate Binders on Serum Intact Fibroblast Growth Factor 23 Levels.

AIMS: This study assessed the impact of iron administration on serum fibroblast growth factor 23 (FGF23) levels. METHODS: Of 123 hemodialysis (HD) patients treated with erythropoiesis-stimulating agents, 22 received once-weekly intravenous iron and 17 received daily oral iron with iron-containing phosphate binders. Intact FGF23 and biomarkers of iron metabolism were measured from blood samples drawn before each HD session, at baseline and on days 3, 5, 7, and 14. RESULTS: Phosphate levels did not differ among the 3 groups during the 14-day period. Ferritin levels were significantly increased in both iron treatment groups compared with the non-iron treatment group, but changes in transferrin saturation levels were similar in the intravenous iron and non-iron groups. However, intact FGF23 levels were continuously higher in the intravenous iron group than those in the other groups. CONCLUSION: Intravenous iron administration may influence intact FGF23 levels in HD patients independently of phosphate and iron metabolism.

Associations among Erythroferrone and Biomarkers of Erythropoiesis and Iron Metabolism, and Treatment with Long-Term Erythropoiesis-Stimulating Agents in Patients on Hemodialysis.

BACKGROUND: We aimed to identify associations between erythroferrone (ERFE), a regulator of hepcidin 25, and biomarkers of erythropoiesis and iron metabolism. We also aimed to determine the effects of erythropoiesis-stimulating agents (ESA), continuous erythropoietin receptor activator (CERA) and darbepoetin-α (DA) on ERFE production in patients on hemodialysis (HD). METHODS: Blood samples were obtained from 59 patients before HD sessions on day 0 (baseline). Twenty patients who were injected with either CERA (N = 10) or DA (N = 10) at the end of the dialysis week (day 0), who had ferritin ≥ 100 ng/mL and/or transferrin saturation ≥ 20%, and hemoglobin > 9 g/dL were selected from among the 59 patients. Blood was sampled serially before HD sessions on days 3, 5, 7 from patients on DA and on the same days plus day 14 from those on CERA. RESULTS: Levels of ERFE correlated inversely with those of hepcidin 25 and ferritin, and positively with those of soluble transferrin receptor. The hepcidin 25: ERFE ratio and hepcidin 25 levels positively correlated with ferritin levels. Levels of ERFE significantly increased from day 3 of treatment with DA and CERA and decreased by days 7 and 14, respectively. Erythropoiesis-stimulating agents concomitantly decreased levels of hepcidin 25 as those of ERFE increased. CONCLUSION: We identified a novel association between ESA and ERFE in patients on HD. Both DA and CERA increased levels of ERFE that regulated hepcidin 25 and led to iron mobilization from body stores during erythropoiesis.

Effects of Long-Term Erythropoiesis-Stimulating Agents on Iron Metabolism in Patients on Hemodialysis.

Continuous erythropoietin receptor activator (CERA) and darbepoetin-α (DA) might differently affect iron metabolism and erythropoiesis in patients on hemodialysis (HD). This prospective study examined a cohort of patients on HD who had received either intravenous CERA every 2 or 4 weeks (N = 25) or DA once each week (N = 47). Blood was sampled before HD sessions on days 0, 2, 4, 7 and 14, and on days 0, 3, 5, 7 and 14 from patients who were injected with ESA at the beginning and end of the dialysis week, respectively. Changes in factors indicating erythropoiesis and biomarkers of iron metabolism were examined. Hemoglobin levels were maintained in the target range between 10.0 and 11.0 g/dL and ferritin levels at baseline and during the study period were similar between the DA and CERA groups. Levels of hepcidin 25 decreased from days 2-3 to day 5 and returned to the baseline at day 7 in the DA group, whereas those and transferrin saturation were serially suppressed from days 2-3 to day 14 in the CERA group. Levels of soluble transferrin receptor and reticulocyte counts were significantly elevated from days 4-5 to day 14 by CERA. Both DA and CERA stabilized erythropoiesis, but CERA might mobilize iron from body stores more effectively than DA in patients on HD.

CD36 single nucleotide polymorphism is associated with variation in low-density lipoprotein-cholesterol in young Japanese men.

Macrophages uptake oxidized low-density lipoprotein (LDL) via a scavenger receptor such as CD36 from plasma, and then become foam cells. We examined the association of CD36 gene single nucleotide polymorphisms (SNPs) with certain metabolic characteristics in a young male Japanese population (n = 494). The G allele in a SNP located at +30215 on the 3'-untranslated region (UTR) was significantly correlated with the plasma LDL-cholesterol concentrations (r = 0.13, p <0.01). The difference in LDL-cholesterol concentrations was 10 mg dl(-1) between GG- and AA-genotype carriers (p <0.05). The CD36 gene SNP is a novel maker of the variation in the LDL-cholesterol levels in young Japanese men.

Possible association of tumor necrosis factor receptor 2 gene polymorphism with severe hypertension using the extreme discordant phenotype design.

The tumor necrosis factor (TNF)-alpha pathway has a key role in regulating insulin resistance. TNF receptor 2 (TNFR2) is an emerging candidate gene for insulin resistance in essential hypertension. We examined the association of insulin resistance and enhanced TNF pathway with severe hypertension and the association of a microsatellite polymorphism of the TNFR2 gene with severe hypertension. Male severe essential hypertensive patients (HT) with the onset before 60 years of age and with genetic predispositions to hypertension were consecutively enrolled at our outpatient department (N=92). Normotensive men (NT) over 50 years of age were randomly registered from the participants in the annual health check program (N=78). Patients were selected as HT and NT who met stringent criteria for systolic/diastolic blood pressure (SBP/DBP) levels >or=180 and/or 110 mm Hg and <120/80 mm Hg, respectively. HT revealed significantly higher plasma insulin levels, C-reactive protein (CRP) and soluble fraction of TNFR2 concentrations (sTNFR2) than NT. A microsatellite polymorphism of the CA repeat in intron 4 of the TNFR2 gene was analyzed. The allele frequency of CA16 in HT differed significantly from that in NT (66/184 vs. 36/156, P=0.01 by chi(2) analysis). In HT, the CA16 carriers showed significantly higher SBP and plasma insulin levels and a higher tendency of sTNFR2 than did those without this allele. In NT, CA16 carriers revealed significantly higher sTNFR2 and CRP levels than did the CA16 non-carriers. These results suggest that the TNFR2 gene locus has a potential effect on developing severe hypertension through the augmented TNF pathway and insulin resistance.

Congenic substitution mapping for intracellular Ca2+ in spontaneously hypertensive rats.

BACKGROUND: Intracellular Ca(2+) ([Ca(2+)](i)) may be a factor of importance to hypertension in spontaneously hypertensive rats (SHR). Platelet hyperactivity caused by increased [Ca(2+)](i) may contribute to atherothrombotic cardiovascular events. In a genome scan, we have recently demonstrated that a candidate quantitative trait locus (QTL) for [Ca(2+)](i) in platelets is located near the sarco(endo)plasmic reticulum Ca(2+)-dependent ATPase (Serca) II gene locus on chromosome 12 in backcrossed rats derived from SHR and normotensive Fischer 344 rats (F344). METHODS: Congenic substitution mapping was performed for the chromosomal region including the Serca II gene locus. The segment including the Serca II gene locus was transferred from F344 onto the genetic background of the progenitor SHR. Systolic blood pressure (SBP), platelet aggregation, and ratio of heart weight to body weight (HW/BW) as well as [Ca(2+)](i) responses in platelets were compared between SHR and the congenic strain. RESULTS: Among the parental strains, thrombin-stimulated and thapsigargin-induced peak values of [Ca(2+)](i) in platelets, platelet aggregation, SBP, and HW/BW were significantly greater in SHR than in F344 and F(1) rats. The heterozygous congenic rats for the Serca II gene segment had significantly attenuated [Ca(2+)](i) responses and platelet aggregation compared with SHR. Furthermore, they demonstrated significantly lower SBP and HW/BW. CONCLUSION: Congenic substitution mapping clarified that a chromosomal segment including the Serca II gene locus was responsible for attenuated [Ca(2+)](i) responses and platelet aggregation in the heterozygous congenic rats. Therefore, this chromosomal region may contribute to the development of hypertension and cardiac hypertrophy by augmenting Ca(2+) signaling in SHR.

Cellular insulin resistance in Epstein-Barr virus-transformed lymphoblasts from young insulin-resistant Japanese men.

The metabolic syndrome is characterized by a blunted insulin-mediated glucose uptake in various cell types. We compared the glucose uptake characteristics of Epstein-Barr virus (EBV)-transformed lymphoblasts obtained from young men with vs without metabolic and cardiovascular evidence of metabolic syndrome. From a population of 218 men, 20- to 25-year-old, 10 men with a systolic blood pressure (BP) > or =130 mm Hg and family history of hypertension were assigned to a high BP (HBP) group, and 10 with a BP < or =110 mm Hg, and no family history of hypertension was assigned to a low BP (LBP) group. Multiple clinical and metabolic characteristics were examined in both groups and compared. Peripheral lymphocytes from HBP and LBP subjects were EBV-transformed, and the glucose transporter (Glut)-mediated glucose uptake from each group was compared in lymphoblasts. Body mass index, fasting glucose, immunoreactive insulin, insulin resistance index based on a homeostasis model assessment (HOMA-R), and total and low-density lipoprotein cholesterol were significantly higher in the HBP than the LBP subgroup (whole-body insulin resistance). Baseline Glut-mediated and Glut-mediated insulin-stimulated glucose uptake by lymphoblasts from the HBP group were significantly lower than by lymphoblasts from the LBP group (cellular insulin resistance). The net increment in Glut-mediated glucose uptake by insulin was inversely correlated with HOMA-R. In conclusion, cellular insulin resistance in EBV-transformed lymphoblasts is associated with young Japanese subjects with HBP. The net increment in Glut-mediated glucose uptake by insulin in lymphoblasts may be a useful intermediate phenotype to study genetic aspects of the metabolic syndrome.