Insulin-like growth factor I plays a role in regulating erythropoiesis in patients with end-stage renal disease and erythrocytosis

Lower serum insulin-like growth factor-1 levels are independently associated with anemia in patients undergoing maintenance hemodialysis

The relationship between serum insulin-like growth factor-1 (IGF-1) levels and anemia in patients undergoing maintenance hemodialysis (MHD) remains unclear. This cross-sectional study included patients who underwent MHD treatment for >3 months at our dialysis center in March 2021. Demographic and clinical data were recorded. Blood samples were collected before the hemodialysis sessions, and general serum biochemical parameters, routine blood markers, and serum IGF-1 levels were measured. Patients were divided into a group without anemia (hemoglobin ≥110 g/L) and a group with anemia (hemoglobin <110 g/L), and multivariable linear and binary logistic regression analyses were performed to study the relationship between the levels of serum IGF-1 and anemia. A total of 165 patients (male/female = 99:66) with MHD were enrolled in the study, with a median age of 66.0 (58.0, 75.0) years and a median dialysis vintage of 27.0 (12.0, 55.0) months. The mean hemoglobin level was 96.38 ± 16.72 g/L, and 126 patients had anemia (76.4%). Compared to patients without anemia, patients with anemia had lower serum IGF-1 and triglyceride levels and higher intravenous iron supplementation on dialysis (all p < 0.05). After adjusting for confounding factors in different models, the nine-model multivariate binary logistic regression analyses also confirmed that lower serum IGF-1 levels and serum IGF-1 < 197.03 ng/ml were both independently associated with anemia in patients undergoing MHD. However, further multicenter studies with larger sample sizes are required to confirm these findings.

Post-transplant erythrocytosis after kidney transplantation: A review

Post-transplant erythrocytosis (PTE) is defined as persistently elevated hemoglobin > 17 g/dL or hematocrit levels > 51% following kidney transplantation, independent of duration. It is a relatively common complication within 8 months to 24 months post-transplantation, occurring in 8%-15% of kidney transplant recipients. Established PTE risk factors include male gender, normal hemoglobin/hematocrit pre-transplant (suggestive of robust native kidney erythropoietin production), renal artery stenosis, patients with a well-functioning graft, and dialysis before transplantation. Many factors play a role in the development of PTE, however, underlying endogenous erythropoietin secretion pre-and post-transplant is significant. Other contributory factors include the renin-angiotensin- aldosterone system, insulin-like growth factors, endogenous androgens, and local renal hypoxia. Most patients with PTE experience mild symptoms like malaise, headache, fatigue, and dizziness. While prior investigations showed an increased risk of thromboembolic events, more recent evidence tells a different story-that PTE perhaps has lessened risk of thromboembolic events or negative graft outcomes than previously thought. In the evaluation of PTE, it is important to exclude other causes of erythrocytosis including malignancy before treatment. Angiotensin converting enzyme inhibitors (ACE-I) and angiotensin receptor blockers (ARBs) are the mainstays of treatment. Increased ACE-I/ARB use has likely contributed to the falling incidence of erythrocytosis. In this review article, we summarize the current literature in the field of post-transplant erythrocytosis after kidney transplantation.

Heamanetic Effects of a Dioxidovanadium(V) Complex in STZ-Induced Diabetic Male Sprague Dawley Rats

BACKGROUND

Despite the effective maintenance of glucose homeostasis by insulin in type 1 diabetes mellitus, the drug has been implicated as one of the causes of haematological disturbances, which give rise to cardiovascular complications. As a result, research into alternative therapies for diabetes is needed. In our laboratory, an anti-hyperglycaemic novel vanadium complex has been synthesized using organic heterocyclic ligands. The complex has been shown and improve glycaemic control. The effects of this complex on haematological function, however, have not yet been established. Therefore, this study sought to investigate the haematological effects of dioxidovanadium(V) complex in (STZ)-induced diabetic rats.

METHODS

Diabetic rats received vanadium complex (40 mg kg ^-1 p.o), diabetic untreated (H₂O) and insulin treated (0.175 mg kg^-1 s.c), groups acted as a negative and positive control, respectively. Vanadium complex was administered twice daily, and blood glucose concentration was monitored weekly for 5 weeks. Thereafter, the animals were sacrificed followed by blood and kidneys collection for haematological (full blood count and Annexin V), hormonal (EPO) and oxidative status (SOD and GPx) analysis.

RESULTS

After 5 weeks, untreated diabetic rats presented with hyperglycaemia compared to non-diabetic rats which was attenuated by vanadium complex administration. Furthermore, vanadium treated groups presented with an augmented RBC count, haematocrit, haemoglobin concentration, MCHC, MCV, and (EPO) levels compared to diabetic control. An increase in annexin V expression hence cell survival was observed in vanadium complex treated rats. Lastly, the administration of the complex improved antioxidant status as evidenced by increases in SOD and GPx concentration in plasma and in the kidneys.

CONCLUSION

The administration of the anti-hyperglycaemic dioxidovanadium(V) complex improved haematological parameters, cell survival and the antioxidant status displayed by the diabetic rats. These results give an indication that the complex might be an effective alternative therapeutic drug for the treatment of hyperglycaemia in DM.

A novel germline gain-of-function HIF2A mutation in hepatocellular carcinoma with polycythemia

Hypoxia-inducible factors (HIFs) regulate oxygen sensing and expression of genes involved in angiogenesis and erythropoiesis. Polycythemia has been observed in patients with hepatocellular carcinoma (HCC), but the underlying molecular basis remains unknown. Liver tissues from 302 HCC patients, including 104 with polycythemia, were sequenced for HIF2A mutations. A germline HIF2A mutation was detected in one HCC patient with concurrent polycythemia. Three additional family members carried this mutation, but none exhibited polycythemia or were diagnosed with HCC. The gain-of-function mutation resulted in a HIF-2α protein that was transcribed normally but resistant to degradation. HIF-2α target genes EDN1, EPO, GNA14, and VEGF were significantly upregulated in the tumor bed but not in the surrounding liver tissue. Polycythemia resolved upon total resection of the tumor tissue. This newly described HIF2A mutation may promote HCC oncogenesis.

Determinants of Peritoneal Solute Transport Rates in Newly Started Nondiabetic Peritoneal Dialysis Patients

Objective

An overrepresentation of a fast peritoneal transport status in new peritoneal dialysis (PD) patients with extensive comorbidity has been reported in some studies. High mass transfer area coefficients (MTACs) of low MW solutes suggest the presence of a large effective peritoneal surface area. The mechanism is unknown. It might include comorbidity, chronic inflammation, or an effect of mesothelial cell mass on peritoneal transport by the production of vasoactive substances. To investigate their relative importance in early PD, peritoneal permeability characteristics in incident PD patients were analyzed for relationships with comorbidity, serum concentrations of inflammatory markers, and products of the mesothelial cells that can be detected in dialysate.

Design

A cross-sectional study.

Setting

A university hospital.

Methods

46 patients who fulfilled the following inclusion criteria were analyzed: a standard peritoneal permeability analysis (SPA) within 6 months after the start of PD, no peritonitis prior to the SPA, older than 18 years, and without diabetes mellitus as a primary renal disease. The patients were divided into tertiles based on the MTAC creatinine: slow, medium, and fast transport groups. The Davies comorbidity score was used to assess comorbidity. Serum and dialysate samples obtained during the SPA were used to determine hyaluronan, interleukin (IL)-6, vascular endothelial growth factor (VEGF), and cancer antigen 125 (CA125). The dialysate concentrations of these substances were expressed as their dialysate appearance rates.

Results

No significant differences were present in the three transport groups for comorbidity, serum concentrations of inflammatory markers, or serum VEGF. Interleukin-6 and VEGF concentration attributed to local VEGF production were not different between the tertiles. Levels of VEGF were higher in the medium transport group compared to the slow transport group ( p = 0.02); CA125 was higher in the fast transport group compared to the medium transport group ( p = 0.01). When analyzed as continuous variables, MTAC creatinine was related to VEGF ( r = 0.33, p < 0.05) and CA125 ( r = 0.41, p = 0.03). In linear regression analysis, VEGF influenced the association between CA125 and MTAC creatinine; IL-6 weakened this association only marginally.

Conclusion

A fast peritoneal transport status in incident nondiabetic PD patients was not related to comorbidity. The relationships found between VEGF, CA125, and MTAC creatinine may suggest a role of VEGF in the regulation of the vascular peritoneal surface area, possibly already before structural abnormalities have developed. Our analyses are consistent with the hypothesis that mesothelial cell mass is an important determinant of the peritoneal transport status in incident nondiabetic PD patients without previous peritonitis. Of the many potential mediators produced by mesothelial cells, VEGF was more important than the inflammation marker IL-6.

Functional erythropoietin-hepcidin axis in recombinant human erythropoietin independent haemodialysis patients

AIM

Relatively few haemodialysis (HD) patients remain independent of recombinant human erythropoietin ('rHU-EPO free patients'). We investigated the role of EPO and hepcidin, two key hormones involved in anaemia.

METHODS

We report a monocentric case-control series. Iron status, EPO and hepcidin levels were analysed in 15 Adult HD (Age > 18 years) with a stable haemoglobin (Hb) level that have not received rHU-EPO for at least 6 months (=rHU-EPO free patients); and in 60 controls with a stable rHU-EPO dose and Hb level.

RESULTS

The rHU-EPO free patients had a higher Hb level compared to controls (12.1 ± 0.99 g/dL vs 11.1 ± 0.73, P = 0.0014), and a lower ferritin level (183 ± 102 vs 312 ± 166 ng/mL, P = 0.001). Hepcidin levels were lower in the rHU-EPO free patients (12.53 ± 10.46 ng/mL) compared to the controls (37.95 ± 34.33 ng/mL), P = 0.0033. Hepcidin levels correlated significantly with ferritin levels; but neither with transferrin saturation, C-reactive protein nor EPO levels. Unsupervised analysis revealed that rHU-EPO free patients had a specific clinical/biological profile (presence of renal cyst, longer dialysis vintage, lower ferritin, and EPO and hepcidin levels compared to the control group). Finally, we showed that a lower ferritin level might be a surrogate marker of a lower hepcidin status in this population.

CONCLUSION

Recombinant human erythropoietin free patients seem to restore the EPO-hepcidin axis that is critical for erythropoiesis. A specific combination of clinical and biological parameters may help to detect future rHU-EPO free patients.

Treatment with insulin analogs, especially Glargine and Lispro, associates with better renal function and higher hemoglobin levels in Type 1 diabetic patients with impaired kidney function

OBJECTIVES

The influence of type of insulin treatment - insulin analogs versus human insulin - on the development of diabetes related vascular complications has been sparsely investigated. We examine here possible differences regarding kidney function and hemoglobin levels.

METHODS

Multiple linear regression was used to investigate the relationship between the following characteristics measured in 509 type 1 diabetic patients who were recruited in an outpatient practice: current clinical status and treatment modalities, type of injected insulin and the routine laboratory parameters hemoglobin, HbA1c, serum creatinine, eGFR, hs CRP and urinary albumin/creatinine ratio.

RESULTS

Compared with human insulin, multiple regression analysis taking into account possible confounders revealed that treatment with insulin analogs was associated with increased eGFR (+7.1 ml/min; P=0.0002), lower urinary albumin/creatinine ratio (ratio logarithm -0.4; P=0.003) and higher hemoglobin concentration (+0.31 g/dl; P=0.04). Stratification by type of insulin showed the best renal status for treatment with insulins Glargine and Lispro. Differences were consistent both for patients with normal (eGFR → 90 ml/min) and with an impaired (eGFR ← 90 ml/min) kidney function.

CONCLUSIONS

Present results suggest that treatment of type 1 diabetic patients with normal and impaired renal function with insulin analogs, especially Glargine and Lispro, is associated with better kidney function, lower urinary albumin/creatinine ratio and lower hemoglobin concentration compared to therapy with human insulin. If confirmed by other studies, treatment with insulin analogs may be a further possibility in delaying progression of nephropathy and in preventing early hemoglobin decline.

INSULIN-LIKE GROWTH FACTOR-1 AND ANEMIA IN OLDER SUBJECTS: THE INCHIANTI STUDY

OBJECTIVE

Recent studies indicate a role for the age-related decline of anabolic hormones, especially testosterone, in the onset of "anemia of aging." Some of testosterone's erythropoietic activities are mediated by insulin-like growth factor (IGF)-1, which also seems to have independent erythropoietic effects. However, the associations among IGF-1, anemia, and hemoglobin (Hb) have not been adequately investigated in older populations.

METHODS

We used data from a representative sample of 953 subjects ≥65 years who participated in the InCHIANTI (Invecchiare in Chianti) Study and were not on growth hormone (GH) or erythropoietin therapy and were not diagnosed with hematologic malignancies or other cancers. Anemia was defined according to the World Health Organization (WHO) criteria by Hb level ≤13 g/dL in males and ≤12 g/dL in females. Backward multiple regression analyses including age, IGF binding protein (IGFBP)-3, testosterone, comorbidities, inflammatory markers, and anemia-related measures were used to address the relationship between IGF-1 and Hb and between IGF-1 and anemia in both sexes.

RESULTS

We found that 46/410 (11.2%) males and 71/543 (13.0%) females were defined as anemic. After adjustment for age, anemic males (100 ± 54 vs. 130 ± 56, P<.001) and females (89.1 ± 48 vs. 110 ± 52, P = .001) exhibited lower IGF-1 levels than their nonanemic counterparts. IGF-1 levels were independently and negatively associated with anemia in males (β ± SE = -0.0005 ± 0.0002, P = .04) but not in females (β ± SE = -0.0002 ± 0.0002, P = .40). In both males (β ± SE = 0.002 ± 0.001, P = .03) and females (β ± SE = 0.002 ± 0.0009, P = .03), IGF-1 levels were independently and positively associated with Hb levels.

CONCLUSION

In older males but not in females, IGF-1 levels are negatively associated with anemia. IGF-1 levels are independent and positive determinants of Hb concentration in both sexes.

The Role of the Multiple Hormonal Dysregulation in the Onset of "Anemia of Aging": Focus on Testosterone, IGF-1, and Thyroid Hormones

Anemia is a multifactorial condition whose prevalence increases in both sexes after the fifth decade of life. It is a highly represented phenomenon in older adults and in one-third of cases is "unexplained." Ageing process is also characterized by a "multiple hormonal dysregulation" with disruption in gonadal, adrenal, and somatotropic axes. Experimental studies suggest that anabolic hormones such as testosterone, IGF-1, and thyroid hormones are able to increase erythroid mass, erythropoietin synthesis, and iron bioavailability, underlining a potential role of multiple hormonal changes in the anemia of aging. Epidemiological data more consistently support an association between lower testosterone and anemia in adult-older individuals. Low IGF-1 has been especially associated with anemia in the pediatric population and in a wide range of disorders. There is also evidence of an association between thyroid hormones and abnormalities in hematological parameters under overt thyroid and euthyroid conditions, with limited data on subclinical statuses. Although RCTs have shown beneficial effects, stronger for testosterone and the GH-IGF-1 axis and less evident for thyroid hormones, in improving different hematological parameters, there is no clear evidence for the usefulness of hormonal treatment in improving anemia in older subjects. Thus, more clinical and research efforts are needed to investigate the hormonal contribution to anemia in the older individuals.

Anaemia in chronic obstructive pulmonary disease: an insight into its prevalence and pathophysiology

Chronic obstructive pulmonary disease (COPD) is a major health problem, with increasing morbidity and mortality. There is a growing literature regarding the extra-pulmonary manifestations of COPD, which can have a significant impact on symptom burden and disease progression. Anaemia is one of the more recently identified co-morbidities, with a prevalence that varies between 4.9% and 38% depending on patient characteristics and the diagnostic criteria used. Systemic inflammation seems to be an important factor for its establishment and repeated bursts of inflammatory mediators during COPD exacerbations could further inhibit erythropoiesis. However, renal impairment, malnutrition, low testosterone levels, growth hormone level abnormalities, oxygen supplementation, theophylline treatment, inhibition of angiotensin-converting enzyme and aging itself are additional factors that could be associated with the development of anaemia. The present review evaluates the published literature on the prevalence and significance of anaemia in COPD. Moreover, it attempts to elucidate the reasons for the high variability reported and investigates the complex pathophysiology underlying the development of anaemia in these patients.

Decreased IGF-1 levels potentiate association of inflammation with all-cause and cardiovascular mortality in prevalent hemodialysis patients

OBJECTIVE

Insulin-like growth factor-1 (IGF-1) and inflammation have both been linked to high cardiovascular risk and mortality in the general population, as well as in hemodialysis (HD) patients. We hypothesized that the association of low IGF-1 with chronic inflammation may increase the mortality risk in HD patients.

DESIGN

We investigated the interactions between inflammatory biomarkers (IL-6 and TNF-α) and IGF-1 as predictors of death over a 4 years of follow-up (median--47 months, interquartile range--17.5-75 months) in 96 prevalent HD patients (35% women, mean age of 64.9 ± 11.6 years).

RESULTS

A significant interaction effect of low IGF-1 (defined as a level less than median) and high IL-6 (defined as a level higher than median) on all-cause and cardiovascular mortality was found: crude Cox hazard ratios (HR) for the product termed IGF-1 × IL-6 were 4.27, with a 95% confidence interval (CI): 2.10 to 8.68 (P<0.001) and 7.49, with a 95% CI: 2.40-24.1 (P=0.001), respectively. Across the four IGF-1-IL-6 categories, the group with low IGF-1 and high IL-6 exhibited the worse outcome in both all-cause and cardiovascular mortality (multivariable adjusted hazard ratios were 4.92, 95% CI 1.86 to 13.03, and 14.34, 95% CI 1.49 to 137.8, respectively). The main clinical characteristics of patients in the low-IGF-1-high IL-6 group didn't differ from other IGF-1-IL-6 categorized groups besides gender that consequently was inserted in all multivariable models together with the other potential confounders.

CONCLUSIONS

An increase in mortality risk was observed in HD patients with low IGF-1 and high IL-6 levels, especially cardiovascular causes.

Increased visfatin in hemodialysis patients is associated with decreased demands for recombinant human erythropoietin

BACKGROUND

Studies detected an association between visfatin and markers of iron metabolism in patients with insulin resistance. In this study, such a relation was evaluated in hemodialysis (HD) patients. Also relations between visfatin and hepcidin, demands for recombinant human erythropoietin (rHuEpo), inflammation, and situations characterized by insulin resistance were evaluated.

METHODS

After a four-week washout period from iron treatment, 33 HD patients and 20 healthy volunteers enrolled in the study. Serum visfatin, hepcidin, and interleukin-6 (IL-6) were assessed by means of enzyme-linked immunosorbent assay. Hemoglobin, serum iron, ferritin, and transferrin saturation (TSAT) were also measured.

RESULTS

Visfatin was markedly increased in HD patients. Visfatin levels did not differ between diabetics and non-diabetics. No relation was detected between visfatin and body mass index or IL-6 in HD patients. From the markers of iron metabolism, the hepcidin included, visfatin was related only to TSAT. A strong positive relation was revealed between visfatin and hemoglobin, whereas visfatin was inversely related to rHuEpo dose. Resistance to rHuEpo index was inversely and independently of TSAT related to visfatin.

CONCLUSION

Visfatin is increased in HD patients and it is associated with decreased demands for rHuEpo.

Anemia and erythrocytosis in patients after kidney transplantation

Anemia is a highly prevalent disorder in recipients of renal allografts. Despite its frequent occurrence, there is still uncertainty with regard to treatment targets and treatment options. This includes questions on appropriate iron management, the choice and dosage of erythropoietin stimulating agents, criteria for the timing of treatment initiation and the targeted hemoglobin values. The review summarizes available data on recent therapeutic strategies for post transplant anemia, as well as for post transplant erythrocytosis, another hematological disorder, that has decreased in recent years.

Mechanisms controlling anaemia in Trypanosoma congolense infected mice

Background

Trypanosoma congolense are extracellular protozoan parasites of the blood stream of artiodactyls and are one of the main constraints on cattle production in Africa. In cattle, anaemia is the key feature of disease and persists after parasitaemia has declined to low or undetectable levels, but treatment to clear the parasites usually resolves the anaemia.

Methodology/Principal Findings

The progress of anaemia after Trypanosoma congolense infection was followed in three mouse strains. Anaemia developed rapidly in all three strains until the peak of the first wave of parasitaemia. This was followed by a second phase, characterized by slower progress to severe anaemia in C57BL/6, by slow recovery in surviving A/J and a rapid recovery in BALB/c. There was no association between parasitaemia and severity of anaemia. Furthermore, functional T lymphocytes are not required for the induction of anaemia, since suppression of T cell activity with Cyclosporin A had neither an effect on the course of infection nor on anaemia. Expression of genes involved in erythropoiesis and iron metabolism was followed in spleen, liver and kidney tissues in the three strains of mice using microarrays. There was no evidence for a response to erythropoietin, consistent with anaemia of chronic disease, which is erythropoietin insensitive. However, the expression of transcription factors and genes involved in erythropoiesis and haemolysis did correlate with the expression of the inflammatory cytokines Il6 and Ifng.

Conclusions/Significance

The innate immune response appears to be the major contributor to the inflammation associated with anaemia since suppression of T cells with CsA had no observable effect. Several transcription factors regulating haematopoiesis, Tal1, Gata1, Zfpm1 and Klf1 were expressed at consistently lower levels in C57BL/6 mice suggesting that these mice have a lower haematopoietic capacity and therefore less ability to recover from haemolysis induced anaemia after infection.

IGF-1 is an independent risk factor for anemia in diabetic pre-dialysis patients

BACKGROUND

We investigated whether the presence of diabetes mellitus (DM) was related to the degree of the anemia in predialytic patients with renal failure and what was the most relevant factor for anemia in patients with chronic kidney disease (CKD) from DM (DM-CKD).

METHODS

Seventy seven patients (47 predialytic patients with long-term type 2 DM (DM-CKD) and 30 predialytic patients whose disease was due to other causes (non DM-CKD)) were enrolled in this study. The blood hemoglobin (Hb) and hematocrit, and the creatinine, ferritin, vitamin B12, folate, iron, LDH, albumin, hs-CRP, intact-PTH, erythropoietin, leptin and Insulin-like growth factor I (IGF-1) levels were measured using standard methods. The estimated GFR was calculated using the abbreviated MDRD equation.

RESULTS

The two groups did not significantly differ as to age, gender, the serum creatinine level and the inflammatory status. The Hb level was significantly lower in the DM-CKD patients than that in the non DM-CKD patients (8.5+/-1.7 g/dL vs 9.6+/-1.6 g/dL, respectively, p=0.01). The Hb level was significantly lower in the DM-CKD patients who were being treated with ACE inhibitors (the DM-ACE patients) than that in the non DM-CKD patients who were being treated with ACE inhibitors (the non DM-ACE patients) (8.5+/-1.5 g/dL vs 10.8+/-1.6 g/dL, respectively, p=0.001). Multiple regression analysis indicated that serum IGF-1 concentration was independently associated with the Hb level (beta=0.425, p=0.02) in the DM-CKD patients.

CONCLUSIONS

The Hb concentration was significantly lower in the DM-CKD patients than that in the non DM-CKD patients. It was independently associated with the serum IGF-1 concentration in the DM-CKD patients.

Correction of Hemodialysis Anemia is Associated with Significant Increase in Serum Concentration of IGF-I in Patients Treated with Erythropoietin: A Randomized Controlled Study

BACKGROUND

The effect of erythropoietin (EPO) therapy on the serum level of IGF-I among hemodialysis patients is debated. The aim of this study is to study the effect of EPO on the erythropoiesis and the change of serum level of IGF-I among adequately hemodialyzed patients.

PATIENTS AND METHODS

Forty patients (25 males and 15 females) who had an adequate level of both hemodialysis and nutrition were randomly allocated into two equal groups. Besides parenteral iron, the first group of patients received a conventional EPO dose regimen of 2000 U subcutaneously (SC) thrice weekly, the second group of patients remained on parenteral iron and ranked as a control group. The patients were subjected to thorough laboratory investigations. IGF-I concentration was measured before and at the end of the study.

RESULTS

Both groups were comparable in their demographic, laboratory, dialysis level, and nutritional status. There was no statistical differences in hemoglobin, hematocrit %, iron store indices and serum level of IGF-I at the study entry. We found a significant rise of both hemoglobin and hematocrit as well as IGF-I serum level in the EPO group at the end of the study in comparison to their values at the starting points in comparison to the control group (P< 0.001).

CONCLUSION

Erythropoietin therapy enhances erythropoiesis and modulates the serum concentration of IGF-I.

Childhood polycythemias/erythrocytoses: classification, diagnosis, clinical presentation, and treatment

Polycythemias or erythrocytoses in childhood and adolescence are very rare. Systematic data on the clinical presentation and laboratory evaluations as well as on treatment regimens are sparse. The diagnostic program in absolute erythrocytosis includes extensive clinical, hematological, biochemical, and molecular biological examinations which should be applied following a stepwise algorithm. Absolute erythrocytoses are usually subdivided into primary and secondary forms. Primary erythrocytosis is a condition in which the erythropoietic compartment is expanding independently of extrinsic influences or by responding inadequately to them. Primary erythrocytoses include primary familial and congenital polycythemia (PFCP) due to mutations of the erythropoietin (Epo) receptor gene and the myeloproliferative disorder polycythemia vera. Secondary erythrocytoses are driven by hormonal factors (predominantly by Epo) extrinsic to the erythroid compartment. The increased Epo secretion may represent either a physiologic response to tissue hypoxia, an abnormal autonomous Epo production, or a dysregulation of the oxygen-dependent Epo synthesis. Congenital secondary erythrocytoses are caused, e.g., by hemoglobin variants with increased oxygen affinity, by 2,3-bisphosphoglycerate deficiency, or by mutations in the von Hippel-Lindau gene associated with a disturbed oxygen-dependent regulation of Epo synthesis.

Angiotensin II receptor type 1 expression in erythroid progenitors: implications for the pathogenesis of postrenal transplant erythrocytosis

Under normal physiological conditions red blood cell production is controlled primarily by erythropoietin, although multiple additional stimulatory factors are likely to be involved. One of these factors, angiotensin II, can modulate erythropoiesis directly via its type 1 receptor, as well as indirectly through multiple secondary mediators. We propose that angiotensin II exerts its stimulatory effect during the early stages of erythropoiesis, and that this effect serves as an important compensatory mechanism if erythropoietin production is chronically inadequate. We speculate that if this compensatory stimulation continues to be abnormally high after restoration of erythropoietin production following renal transplantation, erythrocytosis ensues.

Expression of SSAT, a novel biomarker of tubular cell damage, increases in kidney ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) is the major cause of acute renal failure in native and allograft kidneys. Identifying the molecules and pathways involved in the pathophysiology of renal IRI will yield valuable new diagnostic and therapeutic information. To identify differentially regulated genes in renal IRI, RNA from rat kidneys subjected to an established renal IRI protocol (bilateral occlusion of renal pedicles for 30 min followed by reperfusion) and time-matched kidneys from sham-operated animals was subjected to suppression subtractive hybridization. The level of spermidine/spermine N(1)-acetyltransferase (SSAT) mRNA, an essential enzyme for the catabolism of polyamines, increased in renal IRI. SSAT expression was found throughout normal kidney tubules, as detected by nephron segment RT-PCR. Northern blots demonstrated that the mRNA levels of SSAT are increased by greater than threefold in the renal cortex and by fivefold in the renal medulla at 12 h and returned to baseline at 48 h after ischemia. The increase in SSAT mRNA was paralleled by an increase in SSAT protein levels as determined by Western blot analysis. The concentration of putrescine in the kidney increased by approximately 4- and approximately 7.5-fold at 12 and 24 h of reperfusion, respectively, consistent with increased functional activity of SSAT. To assess the specificity of SSAT for tubular injury, a model of acute renal failure from Na(+) depletion (without tubular injury) was studied; SSAT mRNA levels remained unchanged in rats subjected to Na(+) depletion. To distinguish SSAT increases from the effects of tubular injury vs. uremic toxins, SSAT was increased in cis-platinum-treated animals before the onset of renal failure. The expression of SSAT mRNA and protein increased by approximately 3.5- and >10-fold, respectively, in renal tubule epithelial cells subjected to ATP depletion and metabolic poisoning (an in vitro model of kidney IRI). Our results suggest that SSAT is likely a new marker of tubular cell injury that distinguishes acute prerenal from intrarenal failure.

Physiology of erythropoietin during mammalian development

Growth is a fundamental process of mammalian development. Several observations regarding regulation of erythropoiesis during growth are not easily explained by the hypoxia-erythropoietin (Epo) concept. This review focuses primarily on this aspect of the physiology of Epo. The question is raised of whether this regulation during growth is based on the hypoxia-Epo mechanism alone, or whether Epo acts in concert with general growth-promoting factors, particularly growth hormone (GH) and the insulin-like growth factors (IGF-I and -II). Supporting the latter hypothesis is the observation that the Epo and GH/IGF systems are activated by hypoxia and share similar receptors and pathways. Recent studies indicate that human fetal and infant growth is stimulated by GH, IGF-I and IGF-II. Epo, GH and IGFs are expressed early in fetal life. Although the rate of erythropoiesis in the fetus is high, serum Epo levels are low. The Epo response to hypoxia in the fetus and neonate is reduced compared with adults. Following delivery the Epo levels vary between species, probably related to the oxygen transport capacity of the hemoglobin (Hb) mass. IGF-I levels are low in the fetus and increase slowly following birth, except in preterm infants in whom the levels decline. In all mammals Hb declines following birth, giving rise to "early anemia". Except in the human, Epo levels increase proportionally with the fall in Hb, but there is a discrepancy between the curves for serum immunoreactive Epo (siEpo) and for erythropoiesis stimulating factors (ESF): the latter include other stimulatory factors in addition to Epo. Hypertransfusion of mice in the period of "early anemia" suppresses siEpo, but not ESF and erythropoiesis, as it does in adult mice. GH and IGF-I have direct effects on erythropoiesis in vitro and act particularly at the later stages of red cell differentiation. IGF-I acts synergistically with Epo, and its effects are most marked when Epo levels are low. Human recombinant (rhu) IGF-I stimulates erythropoiesis in neonatal rats, but not in newborn mice and lambs. In adult mice, in hypophysectomized rats and in mice with end-stage renal failure, however, a stimulatory effect of this growth factor was found on red cell production. RhuGH stimulates erythropoiesis in GH-deficient short children.

CONCLUSION

Fetal and early postnatal erythropoiesis are dependent on factors in addition to Epo. The likely candidates are GH and IGF-I. The in vitro stimulating effects of these factors on erythropoiesis are convincing, but more data are needed on the in vivo effects.

Perturbation of autocrine/paracrine loops of burst-forming units of erythroid-derived cells in rHuEPO-hyporesponsive hemodialysis patients

BACKGROUND

Quantitative or qualitative abnormalities of erythroid progenitors in patients with chronic renal failure (CRF) could be the major factor for recombinant human erythropoietin (rHuEPO) hyporesponsiveness and severe anemia in hemodialysis (HD) patients receiving rHuEPO therapy.

METHODS

Purified 1 x 10(4) circulating CD34+ cells isolated from rHuEPO-hyporesponsive HD patients (EPO-H; n = 10), rHuEPO-responsive non-HD patients with CRF (EPO-R; n = 8), nonanemic HD patients without rHuEPO therapy (EPO-W/O; n = 10), and healthy volunteer controls (CON; n = 10) were subjected to a methylcellulose culture system supplemented with rHuEPO, recombinant human interleukin-3 (IL-3), recombinant human stem cell factor (SCF), and recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) for 14 days.

RESULTS

The average number of burst-forming units of erythroids (BFU-Es) was significantly less in the EPO-H group compared with the CON and EPO-W/O groups. Furthermore, colony size also was significantly smaller in the EPO-H group. Total RNAs were extracted from approximately 100 colonies/patient and subjected to complementary DNA expression array studies of 268 growth factors, cytokines, chemokines, and their receptors. A characteristic cluster upregulated in the EPO-R and EPO-W/O groups and downregulated in the EPO-H group was identified that contained various cytokines and growth factors, including IL-6, GM-CSF, vascular endothelial growth factor B, IL-9, IL-3, leukemia inhibitory factor, and interferon alpha-2, and such receptors as thrombopoietin receptor, IL-9 receptor, and colony-stimulating factor 1 receptor.

CONCLUSION

These data suggest that the cross-talk network or autocrine/paracrine regulatory loop is critically impaired in BFU-E-derived cells in EPO-H patients, and investigation of these cluster genes would facilitate the development of novel therapeutic strategies for such patients.

Disruption of oxygen homeostasis underlies congenital Chuvash polycythemia

Chuvash polycythemia is an autosomal recessive disorder that is endemic to the mid-Volga River region. We previously mapped the locus associated with Chuvash polycythemia to chromosome 3p25. The gene associated with von Hippel-Lindau syndrome, VHL, maps to this region, and homozygosity with respect to a C-->T missense mutation in VHL, causing an arginine-to-tryptophan change at amino-acid residue 200 (Arg200Trp), was identified in all individuals affected with Chuvash polycythemia. The protein VHL modulates the ubiquitination and subsequent destruction of hypoxia-inducible factor 1, subunit alpha (HIF1alpha). Our data indicate that the Arg200Trp substitution impairs the interaction of VHL with HIF1alpha, reducing the rate of degradation of HIF1alpha and resulting in increased expression of downstream target genes including EPO (encoding erythropoietin), SLC2A1 (also known as GLUT1, encoding solute carrier family 2 (facilitated glucose transporter), member 1), TF (encoding transferrin), TFRC (encoding transferrin receptor (p90, CD71)) and VEGF (encoding vascular endothelial growth factor).

Factors contributing to higher hematocrit levels in hemodialysis patients not receiving recombinant human erythropoietin

Recombinant human erythropoietin (rHuEPO) is used to correct anemia in the majority of hemodialysis patients, but a few patients can maintain greater hematocrits without the use of rHuEPO. We aim to investigate which factors stimulate erythropoiesis, other than rHuEPO, in hemodialysis patients. One hundred fifty-eight patients undergoing regular hemodialysis treatment participated in a cross-sectional study. To keep the target hematocrit of 30%, 133 patients (84%) were administered rHuEPO, but 25 patients (16%) did not need rHuEPO. Mean hematocrits were 33.4% +/- 4.6% in patients who did not need rHuEPO and 30.9% +/- 4.0% in those administered rHuEPO. In the analysis of factors contributing to the lack of requirement of rHuEPO with multivariate logistic regression analysis, years on dialysis therapy and body mass index (BMI) were determined to be independent factors with odds ratios of 1.12 (95% confidence interval [CI], 1.02 to 1.23; P = 0.02) and 1.36 (95% CI, 1.13 to 1.63; P = 0.001), respectively. Neither serum erythropoietin level, albumin concentration, nor normalized protein catabolic rate contributed to the lack of requirement of rHuEPO. BMI correlated closely with log serum leptin level (r = 0.55; P < 0.0001), and log serum leptin level correlated inversely with rHuEPO dose (r = -0.18; P = 0.03). These results indicate that 16% of hemodialysis patients could maintain greater hematocrits without the administration of rHuEPO, and independently contributing factors were greater BMI and more years on hemodialysis therapy. Regarding nutritional parameters, a relatively greater BMI, possibly through effects of greater leptin levels, may stimulate erythropoiesis in uremic patients even in the absence of sufficient erythropoietin production.

Randomized prospective comparison between erythropoietin and androgens in CAPD patients

BACKGROUND

Anemia and malnutrition are significant complications in peritoneal dialysis (PD) patients. Previous studies in hemodialysis have shown that androgens are effective as therapy for anemia; however, this has not been tested in a randomized prospective trial in PD patients. Furthermore, the anabolic properties of androgens may exert additional benefits on the nutritional status in this population.

METHODS

Twenty-seven stable male patients over 50 years who were under maintenance continuous ambulatory peritoneal dialysis (CAPD) therapy were randomized to receive recombinant human erythropoietin (rHuEPO; N = 14) or nandrolone decanoate (ND; 200 mg/week IM; N = 13) as therapy for anemia. The evolution of hematologic parameters and the impact on both nutritional anthropometric and biochemical variables were evaluated after six months of treatment.

RESULTS

Hemoglobin and hematocrit experienced similar increases in both groups: from 8.5 +/- 0.9 g/dL and 25.8 +/- 2.7% to 11.7 +/- 0.6 g/dL and 34.7 +/- 1.6% (P < 0.001) in patients receiving rHuEPO, and from 8.9 +/- 0.8 and 27 +/- 2.2% to 11.8 +/- 0.4 g/dL and 35.1 +/- 1.5% (P < 0.001) in subjects treated with ND. At the end of the study, out of the diverse nutritional variables included in this investigation, only weight and body mass index significantly increased in the rHuEPO group. Conversely, both anthropometric [weight, body mass index, triceps skinfold, mid-arm circumference (MAC) and mid-arm muscle circumference (MAMC)] and biochemical parameters (serum total proteins, albumin, prealbumin and transferrin) were significantly increased in patients treated with ND. In this group, serum urea nitrogen, urea net excretion and protein equivalent of nitrogen appearance significantly decreased. These facts, together with an increase in serum creatinine and no changes in dietary intake during the study, suggest a rise in muscle mass related to an anabolic effect of nandrolone decanoate. Interestingly, serum levels of insulin-like growth factor type 1 (IGF-1) increased in patients on the androgen group compared to subjects treated with rHuEPO. Moreover, there was a positive and significant correlation between the rise in IGF-1 concentrations and the increase in hemoglobin, hematocrit, MAC and MAMC.

CONCLUSIONS

Androgens therapy improved the anemia in elderly male CAPD patients in a similar manner to that observed with rHuEPO. Furthermore, compared with rHuEPO, androgen administration was associated with beneficial effects on nutritional status. The mechanism of action of androgens on hematologic and nutritional parameters might be mediated, at least in part, by IGF-1.

Effects of losartan or enalapril on hemoglobin, circulating erythropoietin, and insulin-like growth factor-1 in patients with and without posttransplant erythrocytosis

Both angiotensin-converting enzyme inhibitors and angiotensin II receptor antagonists reduce hemoglobin (Hb) levels in patients with posttransplantation erythrocytosis (PTE). However, their effects in transplant recipients without PTE are not certain, and the mechanism by which they reduce Hb levels in patients with PTE remains unclear. This study evaluated the effects of losartan and enalapril on Hb levels in relation to serum erythropoietin (EPO) and insulin-like growth factor-1 (IGF-1) levels in 8 patients with PTE and 10 patients without PTE. All 18 patients were treated sequentially with 24 weeks of losartan therapy, followed by 24 weeks of enalapril therapy; the two treatment phases were separated by a washout period. Patients with PTE showed significantly greater baseline Hb and IGF-1 concentrations compared with patients without PTE before both losartan and enalapril treatments. Baseline serum EPO levels were similar for patients with and without PTE. Baseline Hb level correlated significantly with IGF-1 level (r = 0.517; P = 0.002), but not with EPO level. Treatment with enalapril, 5 mg, reduced Hb levels more markedly than treatment with losartan, 50 mg, in patients with PTE. In patients without PTE, enalapril, 5 mg, mildly reduced Hb levels, whereas losartan, 50 mg, had no significant Hb-lowering effect. The reduction in Hb levels with enalapril therapy in patients with PTE was associated with a significant reduction in circulating IGF-1 levels, but not EPO levels, whereas losartan reduced Hb levels with no significant change in circulating IGF-1 and EPO levels. In patients without PTE, no significant change was noted in serum EPO and IGF-1 levels with either treatment. The differential Hb-lowering effect with losartan and enalapril treatment in patients with and without PTE suggests that the pathogenesis for PTE is complex and heterogeneous. Different erythropoietic mechanisms may be involved in patients with and without PTE. Further large-scale study is needed to determine the exact interaction between the renin-angiotensin system and regulation of IGF-1 and EPO synthesis and define the exact mechanism by which losartan and enalapril reduce Hb levels.

The insulin-like growth factor system in hematopoietic cells

The insulin-like growth factor (IGF) system regulates proliferation and differentiation of hematopoietic cells. IGFs exert their effects through specific receptors on growing and differentiating blood cells as they emerge from their small pool of ancestral stem cells. The IGF system is complex as both stimulating and inhibiting effects occur by interaction of IGFs and IGF-binding proteins (IGFBPs). IGFs stimulate erythrocytes and lymphocytes but also promote leukemic hematopoietic cell proliferation. IGF-I appears to be correlated with hemoglobin levels in anemia and could also be of benefit for patients with bone marrow aplasia after transplantation. Hypersensitivity to IGF-I has been implicated as an underlying cause of polycythemia vera. Loss of imprinting of IGF-II is found in acute myeloid leukemia and myelodysplastic syndrome. Apoptosis of hematopoietic cells is significantly reduced by IGF-I involving an intriguing signal transduction pathway. IGFs could therefore, although not classical hematopoietic growth factors, be of benefit for patients with diverse hematopoietic disorders.

Endemic polycythemia in Russia: mutation in the VHL gene

Chuvash polycythemia (CP) is an autosomal recessive condition that is endemic in the Russian mid-Volga River region of Chuvashia. We previously found that CP patients may have increased serum erythropoietin (EPO) levels, ruled out linkage to both the EPO and EPO receptor (EPOR) gene loci, and hypothesized that the defect may lie in the oxygen homeostasis pathway. We now report a study of five multiplex Chuvash families which confirms that CP is associated with significant elevations of serum EPO levels and rules out a location for the CP gene on chromosome 11 as had been reported by other investigators or a mutation of the HIF-1 alpha gene. Using a genome-wide screen, we localized a region on chromosome 3 with a LOD score >2. After sequencing three candidate genes, we identified a C to T transition at nucleotide 598 (an R200W mutation) in the von Hippel-Lindau (VHL) gene. The VHL protein (pVHL) downregulates the alpha subunit of hypoxia-inducible factor 1 (HIF-1 alpha), the main regulator of hypoxia adaptation, by targeting the protein for degradation. In the simplest scenario, disruption of pVHL function causes a failure to degrade HIF-1 alpha resulting in accumulation of HIF-1 alpha, upregulation of downstream target genes such as EPO, and the clinical manifestation of polycythemia. These findings strongly suggest that CP is a congenital disorder of oxygen homeostasis.

Relative erythrocytosis of patients with end stage renal failure undergoing CAPD

BACKGROUND AND AIM

Although the majority of patients with end stage renal failure have anemia, some have relative erythrocytosis. Patients treated with continuous ambulatory peritoneal dialysis (CAPD) having relative erythrocytosis were studied in order to determine the factors that would be responsible.

METHODS

Nine out of 89 CAPD patients (10%) were identified as having relative erythrocytosis. Age-, sex- and duration of disease-matched eight patients undergoing CAPD were taken as control. Beside factors of etiologies of renal failure, smoking, renal cysts, viral hepatitides, residual renal function, the adequacy of CAPD, nutritional status, hypertension, serum levels of erythropoietin, IL-1, IL-6, TNF-, and IGF-1 levels were also investigated.

RESULTS

Relative erythrocytosis occurred most often in diabetic and amyloidosis patients. None of the parameters studied were found to be significantly different between groups. During 2-year follow-up, although statistically non-significant, patients having relative erythrocytosis seemed to have higher mortality rate due to vascular complications.

CONCLUSION

No single factor seemed to explain erythrocytosis in patients undergoing CAPD. Being diabetic or with amyloidosis may increase the risk.

Advanced glycosylation end products (AGEs), insulin-like growth factor-1 (IGF-1) and IGF-binding protein-3 (IGFBP-3) in patients with type 2 diabetes mellitus

BACKGROUND

Advanced glycosylation end product (AGE) formation is a major mechanism for the development of complications in diabetes, and the possible roles of insulin-like growth factor 1 (IGF-1) and IGF binding protein 3 (IGFBP-3) are not clearly established.

METHODS

We examined the associations of AGEs, free IGF-I and IGFBP-3 in Type 2 diabetes mellitus (DM) patients under diverse conditions. In a cross-sectional design we studied 110 subjects (67 women and 43 men): non-diabetic controls in group 1, (n = 15) and diabetes patients as follows: group 2, without complications (n = 25); group 3, with chronic complications (n = 25); group 4, with acute or chronic infections (n = 24); group 5, hospitalized for reasons unrelated to diabetes (n = 9); group 6, with end-stage renal disease (ESRD) (n = 12). AGEs were determined by a spectrofluorometric method (HPLC). Insulin and IGFBP-3 were measured by RIA and free IGF-1 with an IRMA method.

RESULTS

AGEs were 13-fold higher in patients with ESRD (p<0.001), and lower in healthy individuals. Free IGF-1 was lower in the patients with complications (p = 0.017), with infections (p = 0.006) and hospitalized (p = 0.04). IGFBP-3 was higher in hospitalized patients (p=0.017). AGEs were associated with free IGF-1 (r = 0.41, p = 0.04) in the group with complications, and with HbA(1c) (r = -0.90, p = 0.002) in hospitalized patients. In the total group, free IGF-1 (r = -0.25, p = 0.008), and IGFBP-3 (r = -0.22, p = 0.021) were associated with HbA(1c).

CONCLUSION

We concluded that AGEs were markedly increased in diabetic patients with ESRD, IGF-1 was decreased in patients with infections and hospitalized, and was negatively associated with HbA(1c). IGFBP-3 was increased in hospitalized patients, with higher levels in patients with long bone fractures. A complex interaction of humoral factors may participate in the acceleration of complications of diabetes.