Plasma Erythropoietin Concentration Research Articles

Renal dysfunction in adults following cardiopulmonary bypass is linked to declines in S-nitroso hemoglobin: a case series.

Impaired kidney function is frequently observed in patients following cardiopulmonary bypass (CPB). Our group has previously linked blood transfusion to acute declines in S-nitroso haemoglobin (SNO-Hb; the main regulator of tissue oxygen delivery), reductions in intraoperative renal blood flow, and postoperative kidney dysfunction. While not all CPB patients receive blood, kidney injury is still common. We hypothesized that the CPB procedure itself may negatively impact SNO-Hb levels leading to renal dysfunction. After obtaining written informed consent, blood samples were procured immediately before and after CPB, and on postoperative day (POD) 1. SNO-Hb levels, renal function (estimated glomerular filtration rate; eGFR), and plasma erythropoietin (EPO) concentrations were quantified. Additional outcome data were extracted from the patients' medical records. Twenty-seven patients were enroled, three withdrew consent, and one was excluded after developing bacteremia. SNO-Hb levels declined after surgery and were directly correlated with declines in eGFR (R=0.48). Conversely, plasma EPO concentrations were elevated and inversely correlated with SNO-Hb (R=-0.53) and eGFR (R=-0.55). Finally, ICU stay negatively correlated with SNO-Hb concentration (R=-0.32). SNO-Hb levels are reduced following CPB in the absence of allogenic blood transfusion and are predictive of decreased renal function and prolonged ICU stay. Thus, therapies directed at maintaining or increasing SNO-Hb levels may improve outcomes in adult patients undergoing cardiac surgery.

Drugs activating hypoxia-inducible factors correct erythropoiesis and hepcidin levels via renal EPO induction in mice.

The erythroid growth factor erythropoietin (EPO) is mainly produced by the kidneys in adult mammals and induces expansion of erythroid cells and iron use for hemoglobin synthesis. The liver also produces EPO at a lower level than the kidneys. Renal and hepatic EPO production is fundamentally regulated by hypoxia-inducible transcription factors (HIFs) in a hypoxia/anemia-inducible manner. Recently, small compounds that activate HIFs and EPO production in the kidneys by inhibiting HIF-prolyl hydroxylases (HIF-PHIs) have been launched to treat EPO-deficiency anemia in patients suffering from kidney disease. However, the roles of the liver in the HIF-PHI-mediated induction of erythropoiesis and iron mobilization remain controversial. Here, to elucidate the liver contributions to the therapeutic effects of HIF-PHIs, genetically modified mouse lines lacking renal EPO-production ability were analyzed. In the mutant mice, HIF-PHI administration marginally increased plasma EPO concentrations and peripheral erythrocytes by inducing hepatic EPO production. The effects of HIF-PHIs on the mobilization of stored iron and on the suppression of hepatic hepcidin, an inhibitory molecule for iron release from iron-storage cells, were not observed in the mutant mice. These findings demonstrate that adequate induction of EPO mainly in the kidney is essential for achieving the full therapeutic effects of HIF-PHIs, which include hepcidin suppression. The data also show that HIF-PHIs directly induce the expression of duodenal genes related to dietary iron intake. Additionally, hepatic EPO induction is considered to partially contribute to the erythropoietic effects of HIF-PHIs but to be insufficient to compensate for the abundant EPO induction by the kidneys.

Possible strategies to reduce altitude-related excessive polycythemia.

We sought to determine the effects of three treatments on hemoglobin (Hb) levels in patients with chronic mountain sickness (CMS): 1) descent to lower altitude, 2) nocturnal O2 supply, 3) administration of acetazolamide. Nineteen patients with CMS living at an altitude of 3,940 ± 130 m participated in the study, which consisted of a 3-wk intervention phase and a 4-wk postintervention phase. Six patients spent 3 wk at an altitude of 1,050 m (low altitude group, LAG), six received supplemental oxygen for 12 h overnight (oxygen group, OXG), and seven received 250 mg of acetazolamide daily (acetazolamide group, ACZG). Hemoglobin mass (Hbmass) was determined using an adapted carbon monoxide (CO) rebreathing method before, weekly during, and 4 wk postintervention. Hbmass decreased by 245 ± 116 g (P < 0.01) in the LAG and by 100 ± 38 g in OXG, and 99 ± 64 g in ACZG (P < 0.05, each), respectively. In LAG, hemoglobin concentration ([Hb]) decreased by 2.1 ± 0.8 g/dL and hematocrit by 7.4 ± 2.9% (both P < 0.01), whereas OXG and ACZG only trended toward lower values. Erythropoietin concentration ([EPO]) decreased between 81 ± 12% and 73 ± 21% in LAG at low altitude (P < 0.01) and increased by 161 ± 118% 5 days after return (P < 0.01). In OXG and ACZG, the [EPO] decrease was ∼75% and ∼50%, respectively, during the intervention (P < 0.01). Descent to low altitude (from 3,940 m to 1,050 m) is a fast-acting measure for the treatment of excessive erythrocytosis in patients with CMS, reducing Hbmass by 16% within 3 wk. Nighttime oxygen supplementation and daily acetazolamide administration are also effective, but reduce Hbmass by only 6%.NEW & NOTEWORTHY To our knowledge, this is the first study examining the effect of three different treatments [descending to lower altitude (from 3,900 m to 1,050 m), nocturnal oxygen supply, and administration of acetazolamide] on changes in hemoglobin mass in patients experiencing chronic mountain sickness (CMS). We report that descent to low altitude is a fast-acting measure for the treatment of excessive erythrocytosis in patients with CMS, reducing Hbmass by 16% within 3 wk. Nighttime oxygen supplementation and daily acetazolamide administration are also effective, but reduce Hbmass by only 6%. In all three treatments, the underlying mechanism is a reduction in plasma erythropoietin concentration due to higher oxygen availability.

RESEARCH ON PLASMA ERYTHROPOIETIN CONCENTRATION IN TYPE 2 DIABETIC PATIENTS WITH KIDNEY INJURY

Objectives: To investigate plasma erythropoietin (EPO) concentration and its relationship with some characteristics in type 2 diabetic patients (T2DM) with chronic kidney injury (CKI). Subjects and methods: A cross-sectional descriptive study on 219 subjects, including 129 patients with type 2 diabetes with chronic kidney injury, 51 patients with diabetes without CKI as a disease control group, and 39 healthy people as a normal control group. All subjects had their plasma EPO levels quantified by ELISA. Results: The median EPO concentration of the research group was 35.83 (21.55 - 56.34) UI/L, lower than the disease control group, which was 44.72 (37.25 - 63.90) UI/L, and lower than the normal control group, which was 113.31 (30.55 - 378.42) UI/L, p &lt; 0.001. The rate of EPO reduction in the study group was 41.9%. EPO concentration was positively correlated with GFR, r = 0.242, p &lt; 0.01. Creatinine is an independent factor associated with reduced EPO, p &lt; 0.05. Conclusion: The rate of EPO reduction in the type 2 DM group with CKI was 41.9%. Decreases in EPO levels are common in KI patients with type 2 diabetes and are associated with decreased GFR.

Amyloidogenic amylin deposits on red blood cells of stroke patients

AbstractBackgroundAmylin, a 37‐residue amyloidogenic peptide, is co‐secreted with insulin by pancreatic beta‐cells (Verma et al. 2020). Vascular deposition of amylin has been noted in patients with diabetes and neurocognitive disorders (Ly et al., 2017) Emergent large vessel occlusions (ELVOs) result in severe ischemic strokes without appropriate treatment. Growth factors, including erythropoietin (EPO), are involved in post‐stroke recovery as a potential neuroprotectant target, inhibiting apoptosis and decreasing inflammation (Jerndal et al., 2010). Here, amylin accumulation in plasma, red blood cells (RBCs), and ELVOs (where available) and plasma EPO levels were compared between stroke and control patients. Due to amylin’s amyloidogenic propensity, we hypothesized that there would be an association between amylin uptake and stroke incidence.MethodA prospective registry (Blood and Clot Thrombectomy Registry and Collaboration; BACTRAC) was developed to analyze blood and thrombus directly in patients presenting with an ELVO. Total protein concentration and amylin concentrations of clot lysates, plasma, and RBC lysates were obtained via bicinchoninic acid assay (BCA) and competitive enzyme‐linked immunosorbent assay (ELISA), respectively. Plasma EPO concentrations were obtained via ELISA. An amylin uptake coefficient (the level of amylin in RBC lysates divided by the sum of amylin present in RBC lysates and plasma) was calculated to determine the degree to which circulating amylin is depositing on RBCs.ResultDue to a significant difference between control and stroke RBCs (p = 0.0012, Figure 1) in total protein concentration, all downstream analyses were normalized to respective protein concentrations. A significant difference in amylin uptake by RBCs between stroke and control patients is shown in Figure 2 (p = 0.0073). An uptake coefficient greater than 0.50 indicates uptake of amylin by RBCs. Finally, a significant difference in plasma EPO concentration was observed between stroke and control (p = 0.0017; Figure 3).ConclusionConsistent with our hypotheses, the present data indicates that amylin uptake by RBCs is significantly increased in stroke patients than in control patients. However, both groups show evidence of accumulation, as indicated by uptake coefficients greater than 0.50. Further, levels of erythropoietin are significantly increased in stroke patients. Further investigation into whether amylin may be thrombogenic is warranted.

Hemoglobin Mass and Blood Volume in Patients With Altitude-Related Polycythemia.

Patients with chronic mountain sickness (CMS) have a high hemoglobin concentration [Hb] due to increased hemoglobin mass (Hbmass) and possibly reduced plasma volume (PV). The values of Hbmass, PV and blood volume (BV) have been described differently, and the relationships between [Hb] and Hbmass or PV are poorly understood. This study obtained representative Hbmass, PV and BV data from healthy, high-altitude residents and CMS patients and quantified the dependency of [Hb] on Hbmass and PV. Methods: Eighty-seven subjects born at high altitude (∼3,900 m) were enrolled. Thirty-four had CMS (CMS), 11 had polycythemia without CMS (intermediate, IM), 20 were healthy highlanders (HH), and 22 living near sea level (SL, 420 m) served as the sea level (SL) control group. Hbmass, PV and BV were determined using a CO-rebreathing method modified for assessing polycythemia patients. Furthermore, [Hb], hematocrit (Hct), plasma erythropoietin concentration [EPO] and blood gas and acid–base status were determined. Results: In the HH group, Hbmass was 27% higher (940 ± 105 g) than in the SL group (740 ± 112 g) and 72% (1,617 ± 265 g) lower than in the CMS group. The PV in the HH group was similar to that in the SL group (−6%) and 15% higher than that in the CMS group (p < 0.001). In the HH group, the BV (5,936 ± 673 ml) did not differ from that in the SL group and was 28% lower than in the CMS group (7,606 ± 1075 ml, p < 0.001). Log [EPO] was slightly increased in the CMS group relative to the HH group (p < 0.01). All values in the IM group were between those in the HH and CMS groups. Hbmass and BV were positively correlated, and PV was negatively correlated with peripheral O2 saturation. Increased Hbmass and decreased PV contributed approximately 65 and 35%, respectively, to the difference in [Hb] between the HH (17.1 ± 0.8 g/dl) and CMS (22.1 ± 1.0 g/dl) groups. Conclusions: In CMS patients, the decrease in PV only partially compensated for the substantial increase in Hbmass, but it did not prevent an increase in BV; the decrease in PV contributed to an excessively high [Hb].

Hematological and Ventilatory Responses to a 3900 M Altitude Sojourn in an Elite Wheelchair-marathoner

This case study aimed to report blood markers and resting respiratory rate (RR) oscillations at sea level, during a 5-wk 3900 m altitude sojourn, and after returning to sea level in a 36-year-old professional wheelchair marathoner. Outcome measures plasma erythropoietin (EPO) concentration, hemoglobin, reticulocytes count, erythrocytes and hematocrit as well as RR were measured upon wakening 7-weeks pre-altitude, 7-days pre-altitude, 35 hours after arrival to altitude, on days 8, 15, 21, 28 and 35 at altitude, 6 and 16 days after returning to sea level. EPO increased up to 259 % (31.6 U l-1) 35 hours upon arrival at altitude and decreased below pre-altitude level (12.2 U l-1) on the 21st day of the camp (8.7 U l-1), reaching the lowest values 16 days after returning from altitude (1.9 U l-1). All blood parameters, except for reticulocytes, increased (range: +17.9 to +23.8%) after 35 days of altitude exposure. Compared to pre-altitude, RR increased during the first week of exposure to hypoxic conditions and remained elevated throughout the camp until the fifth week (5.1±0.4 vs. 9.1±1.6 and 6.6±0.8 breaths min-1; Cohen´s d = +3.4 and +2.4, respectively). A 5-wk high-altitude sojourn triggered polycythemia and elevations in RR (as indicators of effective hypoxic acclimatization) in a professional wheelchair-marathoner.

Effects of 100-km ultramarathon on erythropoietin variation in runners with hepatitis B virus carrier.

Completing an ultramarathon leads to an immediate postrace surge of erythropoietin (EPO). Patients with chronic liver disease may have high plasma EPO concentrations. This study aims to explore whether plasma EPO concentrations vary between hepatitis B virus carrier (HBVc) and non-HBVc runners during long distance running. Blood samples were collected from 8 HBVc and 18 non-HBVc runners at 3 different time points: 1 week before, immediately following, and then 24 h after the 100-km ultramarathon race. Samples were analyzed for plasma EPO levels. EPO concentration had a statistically significant rise immediately after the race (8.7 [7.1-11.9] mU·mL-1 to 23.7 [14.8-37.2] mU·mL-1, P < 0.001) and maintained the high levels 24 h after the race finished (16.7 [11.5-21.0] mU·mL-1, P < 0.001) in all participants. The mean of EPO concentration was 8.9 (5.7-13.2) mU·mL-1 in HBVc runners and was 8.7 (7.7-11.2) mU·mL-1 in non-HBVc runners in the prerace. In HBVc runners, plasma EPO levels were no different at baseline (P = 0.657) and increased in the same fashion in response to ultramarathon compared with non-HBVc runners. Plasma EPO levels between the two groups were not statistically different at any time point. Prolonged endurance exercise led to a significant increase in EPO. A comparable increase in EPO levels was observed in HBVc and non-HBVc runners during and 24 h after 100-km ultramarathon. However, a small sample size might have affected the ability to detect a difference if it does exist.

Evaluation of cobalt as a performance enhancing drug (PED) in racehorses

Cobalt is a required trace element in animals, but administration in excess is considered dangerous and potentially performance enhancing in equine athletes. This study seeks to determine if cobalt may actually act as a performance enhancing drug (PED) by altering biochemical parameters related to red blood cell production as well as markers of aerobic and anaerobic exercise performance. In addition, for adequate regulation of naturally occurring substances, such as cobalt, its distribution among the population must be defined. In order to identify this distribution, plasma Cobalt was determined from 245 Standardbred horses with no cobalt supplementation from farms in New York and New Jersey, including horses at the Rutgers University Equine Science Center. Samples were analysed by Inductively Coupled Plasma Mass Spectrometry. Seven healthy, race fit Standardbreds (4 geldings, 3 mares, age: 5±3 years, ~500 kg) were used for the PED experiment. An incremental graded exercise test (GXT) to measure maximal aerobic capacity (V̇O2max) and markers of performance, measurement of plasma volume and blood volume as well as the measurement of lactate, erythropoietin (EPO), and various blood haematological factors were determined 7 days prior to cobalt administration. Each horse was administered a sterile solution of cobalt salts (50 mg of elemental Co as CoCl2 in 10 ml of saline, IV) at 9 AM on three consecutive days via the jugular vein. Blood samples were obtained from the contralateral jugular vein before and at 1, 2, 4 and 24 h after administration. Plasma and blood volume were measured one day after the last dose of cobalt, and a post administration GXT was performed the next day. Horses were observed for signs of adverse effects of the cobalt administration (agitation, sweating, increased respiration, etc.). Plasma cobalt concentration increased from a pre-administration mean of 1.6±0.6 to 369±28 μg/l following 3 doses of the cobalt solution (P&lt;0.05). This Co concentration was unaccompanied by changes in aerobic or anaerobic performance, plasma EPO concentration, plasma volume, resting blood volume, total blood volume, or estimated red blood cell volume (P&gt;0.05). There were no observed adverse effects.

Failure to confirm a sodium-glucose cotransporter2 inhibitor-induced hematopoietic effect in non-diabetic rats with renal anemia.

Aims/IntroductionClinical studies have shown that treatment with inhibitors of sodium–glucose cotransporter 2 (SGLT2) significantly increases the hematocrit in patients with type 2 diabetes. To investigate whether SGLT2 inhibitors directly promote erythropoietin production independently on blood glucose reduction, the hematopoietic effect of the specific SGLT2 inhibitor, luseogliflozin, was examined in non‐diabetic rats with renal anemia.Materials and MethodsRenal anemia was induced by treatment with adenine (200 or 600 mg/kg/day, orally for 10 days) in non‐diabetic Wistar–Kyoto or Wistar rats, respectively. Luseogliflozin (10 mg/kg bodyweight) or vehicle (0.5% carboxymethyl cellulose) was then administered for 6 weeks. The hematocrit and the hemoglobin (Hb), blood urea nitrogen, plasma creatinine, and plasma erythropoietin levels were monitored.ResultsTreatment with adenine decreased the hematocrit and the Hb level, which were associated with increases in the blood urea nitrogen and plasma creatinine levels. In Wistar–Kyoto rats treated with 200 mg/kg/day adenine, administration of luseogliflozin induced glycosuria, but did not change the blood urea nitrogen, plasma creatinine levels, hematocrit, Hb or plasma erythropoietin levels. Similarly, luseogliflozin treatment failed to change the hematocrit or the Hb levels in Wistar rats with renal anemia induced by 600 mg/kg/day of adenine. Plasma erythropoietin concentrations were also not different between luseogliflozin‐ and vehicle‐treated rats. Similarly, in human erythropoietin‐producing cells derived from pluripotent stem cells, luseogliflozin treatment did not change the erythropoietin level in the medium.ConclusionsThese data suggest that SGLT2 inhibitor fails to exert hematopoietic effects in non‐diabetic conditions.

Leucopenia, Neutropenia, Lymphopenia and Monocytopenia in a 15 year Old Girl with Iron Deficiency Anemia Responding to Iron Therapy: A Case Report

Despite the high prevalence of iron deficiency anemia (IDA) in children, extensive information about its impact on growth and cognitive functions, less is known about how it affects the non-erythrocytes cell lines and its implications. High erythropoietin levels in severe iron deficiency anemia may down regulate the production of non- erythroid precursors resulting in various cytopenia, however, the mechanism of this is not fully understood. Reports depicting the association of iron deficiency anemia with cytopenia is quite scarce in pediatric population. We report a case of a 15 year old girl presented with severe iron deficiency anemia and leucopenia, lymphopenia, neutropenia and monocytopenia who has no other evidence of bone marrow dysfunction. The patient responded to iron therapy with prompt reversal of all cell counts. It is therefore recommended to include iron study and plasma erythropoietin concentration in the evaluation of otherwise healthy children presenting with cytopenia. Likewise, to consider iron deficiency in the causative list of non-erythroid cytopenia such as neutropenia.

JTZ-951 (enarodustat), a hypoxia-inducibe factor prolyl hydroxylase inhibitor, stabilizes HIF-α protein and induces erythropoiesis without effects on the function of vascular endothelial growth factor

JTZ-951 (enarodustat) is an oral hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitor. JTZ-951 has inhibitory activities on human HIF-prolyl hydroxylase 1–3, but not on various receptors or enzymes. In Hep3B cells, JTZ-951 increased HIF-1α and HIF-2α protein levels, erythropoietin (EPO) mRNA levels, and EPO production. In normal rats, after a single oral dose of JTZ-951, the hepatic and renal EPO mRNA levels and plasma EPO concentrations were also increased. In 5/6-nephrectomized rats, repeated oral doses of JTZ-951 once daily or intermittent dosing showed the erythropoiesis stimulating effect. The administration of JTZ-951 at a high dose increased plasma vascular endothelial growth factor (VEGF) levels; however, retinal VEGF mRNA levels and the retinal vascular permeability were not changed. Finally, we evaluated the effect of JTZ-951 in a colorectal cancer cell-inoculated mouse model. Although JTZ-951 at a high dose increased the plasma VEGF, it had no effect on tumor growth.In summary, JTZ-951 induces erythropoiesis without affecting VEGF function. Therefore, it is expected that JTZ-951 will be a new oral candidate that increases and maintains hemoglobin concentrations in renal anemia patients.

Placental erythropoietin expression is upregulated in growth-restricted fetuses with abnormal umbilical artery Doppler findings: a case\u2013control study of monochorionic twins

BackgroundWe previously reported that fetal plasma erythropoietin (EPO) concentrations are significantly increased in growth-restricted fetuses with abnormal umbilical artery (UA) Doppler. During hypoxia in an ovine model, the primary site of fetal EPO synthesis was switched from the kidneys to the placenta. Therefore, we designed this study to evaluate human placental EPO gene expression and the correlation to fetal serum EPO concentration in growth-restricted fetuses in a monochorionic (MC) twin model.MethodsIn MC twin pairs, selective intrauterine growth restriction (sIUGR) was defined as the presence of (i) birth weight discordance of > 20% and (ii) a smaller twin with a birth weight less than the 10th percentile. Fetal UA and middle cerebral artery (MCA) Doppler were checked within 1 week before delivery. An abnormal UA Doppler was defined as persistently absent or reverse end-diastolic flow. Cerebroplacental ratio (CPR) was defined as MCA-pulsatility index (PI)/UA-PI. Fetal plasma EPO concentrations were measured in cord blood, and EPO gene expression was assayed in each twin’s placental territory. The intertwin plasma EPO ratio was calculated as the cord plasma EPO level of the smaller (or sIUGR) twin divided by the EPO concentration of the larger (or appropriate-for-gestational-age (AGA)) twin, and the intertwin placental EPO gene expression ratio was calculated similarly.ResultsTwenty-six MC twins were analyzed, including normal twins (Group 1, n = 9), twins with sIUGR without UA Doppler abnormalities (Group 2, n = 9), and twins with sIUGR and UA Doppler abnormalities (Group 3, n = 8). The CPRs of smaller (sIUGR) fetuses were significantly decreased in Group 3 MC twins (p < 0.001), but not significantly different between Group 1 and Group 2. The highest fetal plasma EPO ratio and placental EPO gene expression ratio were identified in Group 3 MC twins (p < 0.001). The placental EPO gene expression ratios were significantly correlated with the fetal plasma EPO ratios (Pearson’s correlation test, p = 0.004).ConclusionThis study provides evidence of increased placental EPO expression in MC twin fetuses with sIUGR and abnormal UA Doppler. Future studies are needed to confirm the similar role of placental EPO in severe IUGR singletons.

Abstract 365: Potential Relationship Between Nitric Oxide Bioactivity And Kidney Function Following Cardio-pulmonary Bypass

Background: Impaired kidney function is frequently observed in heart surgery patients following cardio-pulmonary bypass. Previous studies by our group have linked acute reductions in nitric oxide bioactivity, specifically declines in the main regulator of tissue blood flow S-nitrosohemoglobin (SNO-Hb), to reductions in kidney oxygenation and blood flow and subsequent renal impairment. For the current study, we hypothesized that components of the bypass procedure (viz. transfusion and red blood cell trauma) would reduce circulating SNO-Hb levels with the magnitude of this reduction correlating with markers of kidney function and patient outcome. Methods: After obtaining written informed consent, blood samples were obtained before and during bypass and on post-operative day (POD) 1. In addition to quantifying SNO-Hb samples were analyzed for change in kidney function (estimated glomerular filtration rate; eGFR), and plasma erythropoietin (EPO) concentration. Status and outcome data were secured from the patients’ medical record. Results: In the patients studied to date (n=30), there was a significant decline in SNO-Hb concentration by POD 1, the level of which inversely correlated with ICU stay (R=-0.32). In addition, there was a direct correlation between SNO-Hb and eGFR on PODs 1 &amp; 2 (R=0.48 and 0.30, respectively), i.e. lower SNO-Hb tracked with reductions in kidney function. Consistent with a presumed reduction in kidney oxygenation, we observed a significant rise in plasma EPO levels when coming off pump that were sustained into POD 1. Furthermore, the rise in EPO was inversely correlated with both SNO-Hb (R=-0.53) and eGFR (R=-0.55). Conclusion: CPB decreases SNO-Hb and is associated with kidney dysfunction and worse patient outcome (e.g. increased ICU stay). While the mechanism for this decline remains to be determined, the results suggest that therapies directed at maintaining or increasing NO bioactivity could improve outcome in adult cardiac surgery patients.

Robust increases in erythropoietin production by the hypoxic fetus is a response to protect the brain and other vital organs.

Fetal erythropoietin (EPO), in addition to regulating erythropoiesis, has also tissue-protective properties based on its anti-inflammatory, anti-apoptotic, antioxidant, and neurotrophic effects. Notably, EPO concentrations needed for tissue protection are 100-1000 times higher than concentrations needed for regulating erythropoiesis. This dual effect of EPO is based on EPO-receptor (EPO-R) isoforms, which differ structurally and functionally. We hypothesize in this Integrated Mechanism Review that during severe fetal hypoxia the observed, but poorly understood, marked increases of fetal plasma EPO concentrations occur to protect the brain, heart, and other vital fetal organs. We further hypothesize that the concurrent marked increases of EPO in the amniotic fluid during fetal hypoxia, occur to protect newborn infants from necrotizing enterocolitis. This review presents experimental and clinical evidence in support of these hypotheses and points out unknown or poorly understood functions of EPO in the fetus. If these novel hypotheses are correct, the importance of fetal EPO as an antenatal hypoxia biomarker will become apparent. It will also likely point the way to important diagnostic and therapeutic fetal and neonatal interventions.

The effect of zinc deficiency and diet restriction on gene expression of hypoxia‐inducible factors in rat's kidney

We reported that plasma erythropoietin (EPO) concentration, kidney EPO concentration and kidney EPO mRNA level were changed by moderate zinc deficiency or diet restriction. It is not established how moderate zinc deficiency or diet restriction induces these alterations. We investigated whether moderate zinc deficiency or diet restriction affects renal hypoxia‐inducible factor genes expression in rats.Thirty 3‐week‐old male Sprague‐Dawley rats were assigned into 3 dietary groups (n=10 each) and fed on dietary regimens for 4 weeks: control group (AIN‐93G; Control), moderate zinc‐deficient group (4.5 mg Zn/kg) and pair‐fed group (AIN‐93G; diet restriction). Kidney was separated into cortex and medulla for RNA isolation. Quantitative real time‐PCR using TaqMan proves was performed for mRNA measurement of hypoxia‐inducible factor (Hif) genes (Hif‐1a, Hif‐1an and Hif‐3a). Statistical analysis was performed by ANOVA and PLSD with separate variance approach (when normality was satisfied) or the Kruskal‐Wallis and Conover‐Iman tests (when normality was not satisfied). P value less than 0.05 was considered significant. Kidney medulla mRNA expressions per organ weight of Hif‐1a and Hif‐1an were significantly decreased by zinc deficiency or diet restriction compared with Control. Kidney medulla Hif‐3a and cortex Hif‐1a, Hif‐1an and Hif‐3a mRNA expressions per organ weight were not significantly different among all groups.These results suggest that kidney hypoxia‐inducible factor gene expressions are decreased by zinc deficiency and diet restriction.Support or Funding InformationThis work was supported by KAKENHI grant‐in‐aid for Young Scientists (B) (23700928) and (15K16216).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Erythropoietin Production Systems by the Kidneys and Liver

Background: Erythropoietin has been thought to be secreted to plasma soon after the production because of the difficulty of Western blot analysis and immunohistochemistry. Methods: We established the new methods of Western blot analysis and immunohistochemistry. Using the new methods, we investigated the effects of fludrocortisone, an analogue of aldosterone, and severe hypoxia on erythropoietin production by the kidneys and liver. Findings: Western blot analysis showed a recombinant erythropoietin at 34-45 kDa and kidney erythropoietin at 36-40 and 42 kDa, both of which shifted to 22 kDa by deglycosylation. Erythropoietin protein expression was observed in the nephrons but not in the interstitial cells in control condition. Fludrocortisone stimulated erythropoietin mRNA and protein expressions in the distal nephrons, particularly in the intercalated cells of the collecting ducts. Life-threatening severe hypoxia (7% O2) induced an increase in erythropoietin mRNA and protein expression in interstitial fibroblasts, no increase in the nephrons, decreased erythropoietin protein expression in the liver, and a large increase of plasma erythropoietin concentration, suggesting that a large amount of erythropoietin was released from the liver to the plasma. Interpretation: These data show that erythropoietin is produced by the nephrons in control condition by the regulation of renin-angiotensinaldosterone system and by the renal interstitial cells in response to hypoxia. Liver also produces erythropoietin in response to hypoxia and releases stored erythropoietin in life-threatening severe hypoxia. Funding Statement: This study was supported by a Grant-in Aid for Scientific Research from the Ministry of Education, Culture, Sports, Sciences and Technology of Japan (24591244, 26461259, 26893202, 16K19493, 16K08505, 16K096549, and 17K16578) and by the Science Research Promotion Fund from the Promotion and Mutual Aid Corporation for Private Schools of Japan. Declaration of Interests: The authors have no financial conflicts to declare. Ethics Approval Statement: Animal experiments were conducted in accordance with the Kitasato University Guide for the Care and Use of Laboratory Animals and were approved by the Institutional Animal Care and Use Committee (Approval No. 2016-033, 25-2).

Erythropoiesis with endurance training: dynamics and mechanisms.

The purpose of the present study was to characterize the progression of red blood cell volume (RBCV) expansion and potential volumetric and endocrine regulators of erythropoiesis during endurance training (ET). Nine healthy, untrained volunteers (age = 27 ± 4 yr) underwent supervised ET consisting of 3-4 × 60 min cycle ergometry sessions per week for 8 wk. Plasma volume (PV), RBCV, and overnight fasting hematological markers were determined before and at weeks 2, 4, and 8 of ET. In addition, plasma erythropoietin (EPO), cortisol, copeptin, and proatrial natriuretic peptide concentrations were measured during a 3-h morning period at baseline and postexercise at weeks 1 and 8 PV increased from baseline (2,405 ± 335 ml) at weeks 2, 4, and 8 (+374 ± 194, +505 ± 156, and +341 ± 160 ml, respectively, P < 0.001). Increases in RBCV from baseline (1,737 ± 442 ml) were manifested at week 4 (+109 ± 114 ml, P = 0.030) and week 8 (+205 ± 109 ml, P = 0.001). Overnight fasting plasma EPO concentration increased from baseline (11.3 ± 4.8 mIU/ml) at week 2 (+2.5 ± 2.8 mIU·ml-1, P = 0.027) and returned to baseline concentration at weeks 4 and 8 Higher 3-h-postexercise EPO concentration was observed at week 1 (11.6 mIU/ml) compared with week 8 (8.4 ± 3.9 mIU/ml, P = 0.009) and baseline (9.0 ± 4.2 mIU/ml, P = 0.019). Linear relationships between EPO concentration and hematocrit (β = -56.2, P < 0.001) and cortisol (β = 0.037, P < 0.001) were detected throughout the ET intervention. In conclusion, ET leads to mild, transient increases in circulating EPO concentration, concurring with early PV expansion and lowered hematocrit, preceding gradual RBCV enhancement.

The effect of zinc deficiency and diet restriction on GATA family gene expression in rat's kidney

We reported that plasma erythropoietin (EPO) concentration, kidney EPO concentration and kidney EPO mRNA level were changed by moderate zinc deficiency or diet restriction. It is not established how moderate zinc deficiency or diet restriction induces these alterations. We propose a hypothesis that moderate zinc deficiency or diet restriction affects renal GATA family genes expression. Thirty 3‐week‐old male Sprague‐Dawley rats were assigned into 3 dietary groups (n=10 each) and fed on dietary regimens for 4 weeks: control group (AIN‐93G; Control), moderate zinc‐deficient group (4.5 mg Zn/kg; zinc deficiency) and pair‐fed group (AIN‐93G; diet restriction). Kidney was separated into cortex and medulla for RNA isolation. Quantitative real time‐PCR using TaqMan proves was performed for mRNA of GATA family gene (GATA1, GATA2, GATA3, GATA4, GATA5, GATA6, Gatad1, Gatad2a and Gatad2b). Statistical analysis was performed by ANOVA and the multiple comparison test of Tukey‐Kramer. P value less than 0.05 was considered significant. Kidney medulla mRNA expression per tissue weight of GATA4 and GATA5 were significantly decreased by zinc deficiency compared with Control. GATA2, GATA3, Gatad1, Gatad2a and Gatad2b were significantly decreased by zinc deficiency and diet restriction compared with Control. Kidney cortex mRNA expression per tissue weight were not significantly different among the groups for all genes. Cortex and medulla GATA1 and GATA6 mRNA expression per tissue weight were not changed. These results suggest that kidney GATA family gene mRNA expression were decreased by zinc deficiency and diet restriction, especially in medulla.Support or Funding InformationThis work was supported by KAKENHI grant‐in‐aid for Research Activity Start‐up (21800073) and Young Scientists (B) (23700928) and (15K16216).

Renal Handling of Ketones in Response to Sodium-Glucose Cotransporter 2 Inhibition in Patients With Type 2 Diabetes.

Pharmacologically induced glycosuria elicits adaptive responses in glucose homeostasis and hormone release, including decrements in plasma glucose and insulin levels, increments in glucagon release, enhanced lipolysis, and stimulation of ketogenesis, resulting in an increase in ketonemia. We aimed at assessing the renal response to these changes. We measured fasting and postmeal urinary excretion of glucose, β-hydroxybutyrate (β-HB), lactate, and sodium in 66 previously reported patients with type 2 diabetes and preserved renal function (estimated glomerular filtration rate ≥60 mL · min-1 · 1.73 m-2) and in control subjects without diabetes at baseline and following empagliflozin treatment. With chronic (4 weeks) sodium-glucose cotransporter 2 inhibition, baseline fractional glucose excretion (<2%) rose to 38 ± 12% and 46 ± 11% (fasting vs. postmeal, respectively; P < 0.0001) over a range of BMIs (range 23-41 kg/m2) and creatinine clearance (65-168 mL · min-1 · m-2). Excretion of β-HB (median [interquartile range]: 0.08 [0.10] to 0.31 [0.43] µmol · min-1), lactate (0.06 [0.06] to 0.28 [0.25] µmol · min-1), and sodium (0.27 [0.22] to 0.36 [0.16] mEq · min-1) all increased (P ≤ 0.001 for all) and were each positively related to glycosuria (P ≤ 0.001). These parameters changed in the same direction in subjects without diabetes, but changes were smaller than in the patients with diabetes. Although plasma N-terminal pro-B-type natriuretic peptide levels were unaltered, plasma erythropoietin concentrations increased by 31 (64)% (P = 0.0078). We conclude that the sodium-glucose cotransporter 2 inhibitor-induced increase in β-HB is not because of reduced renal clearance but because of overproduction. The increased lactate excretion contributes to lower plasma lactate levels, whereas the increased natriuresis may help in normalizing the exchangeable sodium pool. Taken together, glucose loss through joint inhibition of glucose and sodium reabsorption in the proximal tubule induces multiple changes in renal metabolism.