The Role of Treatment for Anemia as a Therapeutic Target in the Management of Chronic Heart Failure: Insights After RED-HF

Ancestry-specific associations identified in genome-wide combined-phenotype study of red blood cell traits emphasize benefits of diversity in genomics

BACKGROUND

Quantitative red blood cell (RBC) traits are highly polygenic clinically relevant traits, with approximately 500 reported GWAS loci. The majority of RBC trait GWAS have been performed in European- or East Asian-ancestry populations, despite evidence that rare or ancestry-specific variation contributes substantially to RBC trait heritability. Recently developed combined-phenotype methods which leverage genetic trait correlation to improve statistical power have not yet been applied to these traits. Here we leveraged correlation of seven quantitative RBC traits in performing a combined-phenotype analysis in a multi-ethnic study population.

RESULTS

We used the adaptive sum of powered scores (aSPU) test to assess combined-phenotype associations between ~ 21 million SNPs and seven RBC traits in a multi-ethnic population (maximum n = 67,885 participants; 24% African American, 30% Hispanic/Latino, and 43% European American; 76% female). Thirty-nine loci in our multi-ethnic population contained at least one significant association signal (p < 5E-9), with lead SNPs at nine loci significantly associated with three or more RBC traits. A majority of the lead SNPs were common (MAF > 5%) across all ancestral populations. Nineteen additional independent association signals were identified at seven known loci (HFE, KIT, HBS1L/MYB, CITED2/FILNC1, ABO, HBA1/2, and PLIN4/5). For example, the HBA1/2 locus contained 14 conditionally independent association signals, 11 of which were previously unreported and are specific to African and Amerindian ancestries. One variant in this region was common in all ancestries, but exhibited a narrower LD block in African Americans than European Americans or Hispanics/Latinos. GTEx eQTL analysis of all independent lead SNPs yielded 31 significant associations in relevant tissues, over half of which were not at the gene immediately proximal to the lead SNP.

CONCLUSION

This work identified seven loci containing multiple independent association signals for RBC traits using a combined-phenotype approach, which may improve discovery in genetically correlated traits. Highly complex genetic architecture at the HBA1/2 locus was only revealed by the inclusion of African Americans and Hispanics/Latinos, underscoring the continued importance of expanding large GWAS to include ancestrally diverse populations.

Prevalence and Severity of Anemia in Children Hospitalized with Acute Heart Failure

OBJECTIVE

Anemia is common among adult heart failure patients and is associated with adverse outcomes, but data are lacking in children with heart failure. The purpose of this study was to determine the prevalence of anemia in children hospitalized with acute heart failure and to evaluate the association between anemia and adverse outcomes.

DESIGN

Review of the medical records of 172 hospitalizations for acute heart failure.

SETTING

Single, tertiary children's hospital.

PATIENTS

All acute heart failure admissions to our institution from 2007 to 2012.

INTERVENTIONS

None.

OUTCOME MEASURES

Composite endpoint of death, mechanical circulatory support deployment, or cardiac transplantation.

RESULTS

Patients ages ranged in age from 4 months to 23 years, with a median of 7.5 years, IQR 1.2, 15.9. Etiologies of heart failure included: dilated cardiomyopathy (n = 125), restrictive cardiomyopathy (n = 16), transplant coronary artery disease (n = 18), ischemic cardiomyopathy (n = 7), and heart failure after history of congenital heart disease (n = 6). Mean hemoglobin concentration at admission was 11.8 g/dL (±2.0 mg/dL). Mean lowest hemoglobin prior to outcome was 10.8 g/dL (±2.2 g/dL). Anemia (hemoglobin <10 g/dL) was present in 18% of hospitalizations at admission and in 38% before outcome. Anemia was associated with increased risk of death, transplant, or mechanical circulatory support deployment (adjusted odds ratio 1.79, 95% confidence interval = 1.12-2.88, P = .011). For every 1 g/dL increase in the patients' lowest hemoglobin during admission, the odds of death, transplant, or mechanical circulatory support deployment decreased by 18% (adjusted odds ratio = 0.82, 95% confidence interval = 0.74-0.93, P = 0.002).

CONCLUSIONS

Anemia occurs commonly in children hospitalized for acute heart failure and is associated with increased risk of transplant, mechanical circulatory support, and inhospital mortality.

Iron, oxidative stress, and redox signaling in the cardiovascular system

The redox state of the cell is predominantly dependent on an iron redox couple and is maintained within strict physiological limits. Iron is an essential metal for hemoglobin synthesis in erythrocytes, for oxidation-reduction reactions, and for cellular proliferation. The maintenance of stable iron concentrations requires the coordinated regulation of iron transport into plasma from dietary sources in the duodenum, from recycled senescent red cells in macrophages, and from storage in hepatocytes. The absorption of dietary iron, which is present in heme or nonheme form, is carried out by mature villus enterocytes of the duodenum and proximal jejunum. Multiple physiological processes are involved in maintaining iron homeostasis. These include its storage at the intracellular and extracellular level. Control of iron balance in the whole organism requires communication between sites of uptake, utilization, and storage. Key protein transporters and the molecules that regulate their activities have been identified. In this field, ferritins and hepcidin are the major regulator proteins. A variety of transcription factors may be activated depending on the level of oxidative stress, leading to the expression of different genes. Major preclinical and clinical trials have shown advances in iron-chelation therapy for the treatment of iron-overload disease as well as cardiovascular and chronic inflammatory diseases.