Haematological Indicators of Response to Erythropoietin Therapy in Chronic Renal Failure Patients on Haemodialysis: Impact of Angiotensin-Converting Enzyme rs4343 Gene Polymorphism

PURPOSE

This is the first cross-sectional study studying the changes in haematological indicators of the response to recombinant human erythropoietin (rHuEPO) therapy in chronic renal failure (CRF) patients on haemodialysis (HD) stratified according to ACE G2350A (rs4343) gene polymorphism.

DESIGN

An observational cross-sectional study.

SETTING

Nephrology department and Biochemistry and molecular biology department, faculty of medicine, Cairo University.

PATIENTS

A total of 256 CRF patients on HD for at least six months (162 male and 103 female) and 160 healthy subjects (122 male and 38 female) were recruited in the current study after signing a consent form. ACE G2350A (rs4343) Insertion/Deletion (I/D) was tested, the association between ACE G2350A (RS4343) gene polymorphisms and patients response to rHuEpo was evaluated.

RESULTS

ACE G2350A (rs4343) I/D was the most prevalent genotype, while I/I genotype was the lowest prevalent among patient or control subjects included in the study. D allele is the most prevalent allele, either among patients or the control group. Hemoglobin (Hb) level in patients with I/I and Deletion/Deletion (D/D) genotype was significantly higher compared to those with I/D genotype (P = 0.012 and P = 0.005, respectively). Serum iron in the I/D genotype was significantly higher than those with either I/I or D/D genotype (P = 0.045 and P = 0.018, respectively). Angiotensin-converting enzyme (ACE) content, total leukocytic count (TLC), and soluble erythropoietin receptor (sEpoR) were independent predictors of Hb level. The ACE gene, TLC, and serum iron were the independent factors that may affect the Haematocrit (Hct) level. ACE G2350A (rs4343) gene polymorphisms may affect the HD patient's responses to rHuEPOs.

CONCLUSION

In HD patients, screening for ACE G2350A (rs4343) gene polymorphisms before rHuEpo administration may help predict patient response.

The Effect of Proinflammatory Cytokine Gene and Angiotensin-Converting Enzyme Polymorphisms on Erythropoietin Requirements in Patients on Continuous Ambulatory Peritoneal Dialysis

Background

The correction of anemia by recombinant human erythropoietin (rHuEPO) improves quality of life and prolongs life in end-stage renal failure. rHuEPO requirements for an individual are determined by a range of factors, including iron deficiency and inflammation. Single nucleotide polymorphisms in the promoter sequence of several proinflammatory cytokines have been shown, in different fields of medicine, to influence the cytokine response to different stimuli, with effects on clinical outcome.

Methods

The angiotensin-converting enzyme (ACE) insertion/deletion polymorphism and polymorphisms in the promoter regions of the genes for tumor necrosis factor alpha (-308 A/G), interleukin-6 (-174 G/C), and interferon gamma were examined for their association with rHuEPO requirements in 112 patients on continuous ambulatory peritoneal dialysis (CAPD). Genomic DNA was extracted from peripheral blood leukocytes and genotyping performed with ARMS-PCR methodology, with sequence-specific primers. We examined rHuEPO requirements and C-reactive protein at baseline and during a 6-month study period.

Results

We found no significant effect of proinflammatory cytokine polymorphisms on rHuEPO responsiveness. However, throughout the study, we observed that there was a significantly higher rHuEPO requirement in the II and ID ACE genotypes compared with the DD group, which remained an independent association following multivariate analysis.

Conclusions

ACE insertion/deletion polymorphism may determine rHuEPO responsiveness in CAPD patients and should be considered in relative rHuEPO resistance.

Effect of angiotensin-converting enzyme gene insertion/deletion polymorphism and angiotensin-converting enzyme inhibition on erythropoiesis in patients on haemodialysis

BACKGROUND

Angiotensin-converting enzyme inhibitors (ACEis) improve survival; however, their effect on erythropoiesis remains a matter of debate in this population. Since insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene largely influences serum ACE activity, its effect on erythropoiesis is also anticipated.

METHOD

In this multicentre, cross-sectional study of 660 patients on maintenance haemodialysis, we analysed the effect of ACEi use and ACE gene I/D polymorphism on haemoglobin levels and erythropoietin resistance. Patients were allocated in groups based on genotype and ACEi therapy. We identified 128 matched pairs with I/I and D/D genotypes.

RESULT

There was no difference in haemoglobin levels between genotype groups. Haemoglobin levels were lower in patients on ACEi therapy in the entire cohort (95.5±12.1 g/l vs 97.4±13.4 g/l, p=0.02) and patients with I/D (95.2±11 g/l vs 98.2±11.9 g/l, p=0.04) and D/D (93.3±13.2 g/l vs 97.4±14.2 g/l, p=0.02) genotypes. In patient pairs treated with ACEi therapy, subjects with D/D genotype had lower Haemoglobin level (93.0±12.8 g/l vs 98.2±11.9 g/l, p=0.006) and higher erythropoietin resistance index (ERI) (199.1 vs 175.0, p=0.046) than individuals with I/I genotype.

CONCLUSION

These results indicate that ACEi therapy may increase erythropoietin resistance and worsen erythropoiesis in haemodialysis patients with the D allele.

Relationship between angiotensin-converting enzyme gene polymorphism and body composition, functional performance, and blood biomarkers in advanced cancer patients

PURPOSE

Nutritional and functional outcome measures have been shown to vary in patients with chronic diseases according to the polymorphic alleles of angiotensin-converting enzyme (ACE), but little is known about the associations between ACE gene polymorphism (ACEGP) and the components of body composition, strength, and selected blood markers in advanced cancer patients (ACP).

EXPERIMENTAL DESIGN

Data were collected from an inception cohort of 172 newly diagnosed ACP with gastrointestinal and non-small cell lung cancer. ACEGP status was defined by the presence of one of the following three combinations of alleles: insertion/insertion, insertion/deletion, and deletion/deletion. Body composition measurements using Dual-energy X-ray Absorptiometry comprised of the following: total fat mass, percent body fat, lean body mass, and appendicular lean mass. Body mass index; handgrip force by Jamar dynamometry; subjective recording of nutrition and performance status as per patient-generated subjective global assessment; cell blood count and differential, serum albumin, ACE, and C-reactive protein were also recorded.

RESULTS

Multiple regression analysis, controlling for gender, age, diagnosis, treatments (radio/chemo), survival, and medication use (ACE inhibitors, anti-inflammatories, statins) revealed the following significant (P </= 0.05) relationships in the insertion/deletion compared with insertion/insertion group: higher hemoglobin (Hb; beta, 6.39 g/dl; 95% confidence interval, 0.01-12.78), lower total fat mass (-5.78 kg; -11.62 to 0.07), percent body fat (-6.04%; -12.20 to 0.12), and lean body mass (-3.26 kg; -6.78 to 0.26). When comparing the DD to the II group, higher serum ACE (9.10; 1.96-16.25), Hb (6.25 g/dl; -0.63 to 13.12), and handgrip force by Jamar (6.85 lbs; 0.78-12.93) were found.

CONCLUSION

Of the variables studied, ACEGP seems to be primarily associated with differences in body composition, Hb, and muscle strength in ACP. Further data are needed to determine the clinical effect of ACEGP in cancer cachexia.

Analyses of age, gender and other risk factors of erythropoietin resistance in pediatric and adult dialysis cohorts

Previous studies often report lower responses to erythropoietin (EPO) therapy in pediatric patients on chronic dialysis than those of adults. Because of the greater capacity for hematopoiesis in the younger population, these studies may be confounded by poorly identified variables. Thus, we made parallel studies of pediatric and adult cohorts to explore the relationship between age, gender and other risk factors with EPO resistance. Thirty pediatric subjects (aged 8-20 years) and 66 adult subjects (aged 22-85 years) on chronic hemodialysis and EPO were enrolled. After stratification by 50th percentile of EPO response, the best predictive model was identified by backward elimination of the risk factors with the least contribution to the regression. Relationship between age, gender and EPO resistance was examined by analysis of covariance (ANCOVA). The most predictive model of EPO response for the pediatric cohort had, as the major variables, urea clearance x dialysis duration/total body water (Kt/V), urea reduction ratio (URR), intact parathyroid hormone (iPTH), blood loss, normalized protein catabolic rates (nPCR) and indices of malnutrition and inflammation, whereas adults had iron and folate deficiencies as the dominant variables. Although EPO resistance was more common in female subjects than in male subjects, relationship with neither age nor gender was significant. Furthermore, the prescription of a larger (initiating) EPO dose by pediatric physicians compared with adult nephrologists confounded the interaction between age and EPO resistance. In summary EPO resistance in the pediatric dialysis cohort was predicted by nutritional deficits, inflammation, poor dialysis, and hyperparathyroidism, while iron and folate deficits were the major determinants in adults. Although confounded by the pattern of EPO prescription, neither age nor gender was predictive of EPO resistance in the two study groups.

Polymorphisms in two genes, IL-1B and ACE, are associated with erythropoietin resistance in Korean patients on maintenance hemodialysis

Genetic polymorphisms may be linked to inter-individual differences in erythropoietin (EPO) resistance. We investigated the -511C/T polymorphism of the IL-1B gene and the I/D polymorphism of the ACE gene for any association with EPO resistance index (ERI) in maintenance hemodialysis patients (n=167). Because EPO responsiveness is multi-factorial, we also included other possible influences (age, sex, time on dialysis, ACE inhibitor or angiotensin receptor blocker use, ferritin, transferrin saturation, intact PTH, high sensitivity C-reactive protein, albumin, Kt/V, and presence of diabetes mellitus) on ERI in our analyses. Multiple regression analysis showed significant association of the IL-1B-511CC and ACE DD polymorphisms with ERI (P=0.038 and P=0.004 in the recessive model, respectively). The combination (C) of alleles of two loci showed that C1 (I-T) was significantly associated with ERI in the co-dominant and recessive models (P=0.005 and P=0.0001, respectively). Subjects who did not carry C1 showed significantly decreased ERI (10.10+/-5.15 IU/kg weight/g hemoglobin) compared to other study subjects (C1/C1 and C1/-; 12.97+/-4.90 and 15.12+/-7.43 IU/kg weight/g hemoglobin, respectively). Our study indicates that the IL-1B-511C/T and ACE I/D polymorphisms may be useful genetic markers of EPO requirement in hemodialysis patients. These findings might also provide a new perspective on therapeutic approaches to the treatment of end stage renal disease patients with anemia.

Angiotensin-converting enzyme gene polymorphism is associated with anemia in non small-cell lung cancer

The angiotensin-converting enzyme (ACE) plays an important role not only in the regulation of vascular homeostasis but also in stimulation of hematopoiesis. We aimed to evaluate the association between insertion/deletion (I/D) polymorphism of the ACE gene and anemia at the time of the diagnosis. We enrolled 75 patients with non-small-cell lung cancer (NSCLC) and 85 age- and sex-matched healthy control participants. The I/D polymorphism of ACE was identified by using polymerase chain reaction from peripheral blood samples. Statistical analyses were performed with SPSS for Windows. The distributions of the ACE genotypes and alleles are similar in patients and in healthy participants (P=0.29 and P=0.08, respectively). In patients with NSCLC, 34 (45.3%) had anemia; of whom 3 (8.8%) had genotype II, 24 (70.6%) had genotype ID, and 7 (20.6%) had genotype DD (P=0.001). The patients with the II and ID genotypes had more frequent anemia at the time of the diagnosis (odds ratio = 6.02; P=0.001). Our findings suggest that I/D polymorphism of the ACE gene may influence the development of anemia in patients with NSCLC.

Effects of ACE gene polymorphism on vitamin D therapy according to parathyroid hormone level in patients on hemodialysis

Medical management is still far from optimal in secondary hyperparathyroidism. This may be explained, at least in part, by genetic differences. The aim of this study was to evaluate the association of genetic influences of angiotensinconverting enzyme (ACE) gene polymorphisms with response to vitamin D therapy among patients on hemodialysis (HD). Eighty-two patients (female/male, 34/48; mean age, 47.5+/-15.3 y; HD duration time, 76.6+/-33.2 mo) with endstage renal disease who were on maintenance HD were included in the study. Five-year retrospective demographic, clinical, laboratory, and treatment data (5-y cumulative doses of phosphate-binding drugs and oral and intravenous cumulative doses of active vitamin D) were retrieved from patients' hospital records. ACE gene polymorphisms of patients were documented and were used to group patients as follows: The insertion/deletion polymorphism group (I/D) consisted of (1) group non-DD (n=43), who had the DI or II allele, and (2) group DD (n=39), who had the DD allele. Patients with the DD allele (group DD) of ACE gene polymorphism had (1) significantly elevated mean 5-y intact parathyroid hormone levels when compared with the non-DD group (P=.009), and (2) significantly elevated oral and intravenous 5-y cumulative doses of vitamin D. Oral and intravenous 5-y cumulative doses of vitamin D used in group DD patients were significantly higher than those in group I patients (P=.038 and P=.037, respectively). Knowledge of genetic differences among patients on HD may be useful to the clinician in planning treatment strategy. ACE gene polymorphism may have an effect on hyperparathyroidism, as is seen in patients on HD. Patients from this group who have resistant hyperparathyroidism may be candidates for ACE inhibitor therapy.

Genetics in Dialysis: Gene Polymorphism Association Studies in Dialysis: Anemia and Host Immunity

The typical complications of end-stage renal disease (ESRD) vary in frequency and severity. Whereas anemia of chronic kidney disease might require high doses of exogenous erythropoietin (EPO) in some individuals, others hardly ever need hormone replacement. The same observation can be made for immune defense functions in patients with ESRD. Our understanding of the functional consequences of genetic polymorphisms in a wide array of genes has recently gained momentum. In patients with ESRD, interindividual differences in anemia parameters have been linked in part to genetic polymorphisms. Indeed, although inflammation is an important predictor of the need for EPO, to date a link to cytokine gene polymorphisms has not been established. However, the need for EPO has been linked to polymorphisms in the angiotensin-converting enzyme (ACE) and vitamin D receptor genes. In contrast, in dialysis patients, interindividual variability in host immune responses, including nonspecific (bacterial) and antigen-specific (viral) immune mechanisms has been linked to variations in the interleukin-10 and myeloperoxidase genes as well as variability in human leukocyte antigens (HLAs). In conclusion, the role of genetic polymorphisms in predicting the development and severity of anemia in chronic kidney disease as well as host immune competence is in its infancy and warrants further inquiry.

Role of folate deficiency on erythropoietin resistance in pediatric and adolescent patients on chronic dialysis

Unlike iron therapy, folate use is not a standard of care in hemodialysis (HD) patients. Despite iron repletion, poor response to erythropoietin (EPO) treatment is common. Theoretical evidence for folate deficiency (FD) includes chronic blood loss, inflammation, malnutrition, and nutrient loss during dialysis. Due to poor diagnostic standards, early studies failed to establish a role for FD in EPO resistance. Given that hematological response to therapeutic intervention is the gold standard for FD, its diagnosis was therefore based on composite scoring of RBC and/or folate indices. Fifteen subjects (8-20 years) on chronic HD were enrolled in this study. No folate supplement was given in the first six months. Thereafter, 5-mg folic acid was administered orally after HD sessions over a six-month period. Folate indices before and after treatment were compared using percentage differences and paired t-tests. After folate use, the mean Hb increased by 11.4%, while MCV and RDW were reduced. Similarly, 4 of the 15 subjects each had a > or = 20% rise in Hb and a > or = 5% reduction in MCV, while 46.7% had a > or = 2.5% reduction in RDW. Mean RBC folate increased by 24%, while FD scores reduced from 3.8+/-1.2 to 0.4+/-0.7, and the EPO requirement by 90%. In contrast to previous studies, 26.7% of study subjects met the criteria for FD. Furthermore, the substantial (post-folate) reduction in the EPO requirement validates the need for therapeutic intervention, and therefore the presence of functional FD in the population.

Gene polymorphism association studies in dialysis: cardiovascular disease

Cardiovascular disease (CVD) is the most important cause of morbidity and mortality in dialysis patients. The high prevalence of CVD is due to the cumulative effects of multiple risk factors from the early stages of chronic kidney disease (CKD). Familial predispositions to CVD, CKD, and their respective risk factors are well known, and it is likely that genetic factors determine the interindividual variability in risks for disease. Advances in genomic technology have facilitated the study of genetic variation--most commonly single nucleotide polymorphisms (SNPs) in candidate genes--and their associations with disease. This review examines CVD in dialysis patients as a model of a complex disease, discusses the approach to gene polymorphism association studies, including the roles of gene-environment and gene-gene interactions and provides an overview of available studies.

Levels of Hematopoiesis InhibitorN-Acetyl-Seryl-Aspartyl-Lysyl-Proline Partially Explain the Occurrence of Anemia in Heart Failure

BACKGROUND

Anemia is common in patients with chronic heart failure (CHF) and is associated with a poor prognosis. However, only a minority of patients with CHF have impaired renal function or underlying hematinic deficiencies. It has been shown that inhibition of the renin-angiotensin system is associated with the development of anemia. The aim of the present study was to determine possible mechanisms linking anemia to renin-angiotensin system activity in CHF patients.

METHODS AND RESULTS

We initially evaluated 98 patients with advanced stable CHF who were treated with ACE inhibitors (left ventricular ejection fraction, 28+/-1%; age, 69+/-1 years; 80% male), 10 of whom had an unexplained anemia (normal hematinics and no renal failure). These 10 anemic patients were matched with 10 nonanemic patients in terms of age and left ventricular ejection fraction. Serum ACE activity was 73% lower in anemic CHF patients compared with nonanemic CHF patients (P=0.018). Moreover, serum of these patients inhibited in vitro the proliferation of bone marrow-derived erythropoietic progenitor cells of healthy donors by 17% (P=0.003). Levels of the hematopoiesis inhibitor N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP), which is almost exclusively degraded by ACE, were significantly higher in anemic CHF patients and were clearly correlated to erythroid progenitor cell proliferation (r=-0.64, P=0.001).

CONCLUSIONS

Serum ACE activity is markedly lower in anemic CHF patients, and serum of these patients inhibits hematopoiesis. The clear correlation between Ac-SDKP and proliferation of erythroid progenitor cells suggests an inhibitory role of Ac-SDKP on hematopoiesis in CHF patients, which may explain the observed anemia in patients treated with ACE inhibitors.

Model for gene-environment interaction: the case for dialysis

Organ complications in end-stage renal disease (ESRD) such as cardiovascular disease, anemia, bone disease, malnutrition, inflammation, and infections occur in many organ systems and are caused by a multitude of underlying disease-, uremia-, and therapy-related factors, and with a wide range of manifestations and severity. Interindividual variability in the pathophysiologic response of the uremic host to environmental factors, including renal replacement therapy, may be governed to a significant degree by genetic susceptibility factors. Specific genes regulate the pathophysiologic responses of organ systems affected by ESRD and can serve as candidate genes for the host-environment interaction. This review summarizes emerging clinical and translational research work in the field of genetic polymorphism of candidate genes and their effects on the development of organ complications in ESRD. Methodologic limitations of the existing published data, the need for large prospective cohort studies, and potential future risks for the use of genomic information in resource allocation are also highlighted.

From pharmacogenetics to personalized medicine: a vital need for educating health professionals and the community

The field of pharmacogenetics will soon celebrate its 50th anniversary. Although science has delivered an impressive amount of information in these 50 years, pharmacogenetics has suffered from lack of integration into clinical practice. There are several reasons for this, including the unmet need for education at medical schools and the lack of awareness about the impact of genetic medicine on healthcare in the community. Recently, the FDA announced that it considers pharmacogenomics one of three major opportunities on the critical path to new medical products. This notion by the FDA is filling the regulatory void that existed between drug developers and drug users. However, in order to bring pharmacogenetic testing to the prescription pad successfully, healthcare professionals and policy makers, as well as patients, need to have the necessary background knowledge for making educated treatment decisions. To effectively move pharmacogenetics into everyday medicine, it is therefore imperative for scientists and teachers in the field to take on the challenge of disseminating pharmacogenetic insights to a broader audience.