Iron Metabolism and Oxidative Status in Patients with Hb H Disease

Disease burden, management strategies, and unmet needs in α-thalassemia due to hemoglobin H disease

Alpha-thalassemia is an inherited blood disorder caused by impaired α-globin chain production, leading to anemia and other complications. Hemoglobin H (HbH) disease is caused by a combination of mutations generally affecting the expression of three of four α-globin alleles; disease severity is highly heterogeneous, largely driven by genotype. Notably, non-deletional mutations cause a greater degree of ineffective erythropoiesis and hemolysis, higher transfusion burden, and increased complication risks versus deletional mutations. There are limited treatment options for HbH disease, and effective therapies are needed. This review discusses the pathophysiology of HbH disease, current management strategies, unmet needs, and emerging treatment options.

Pyruvate kinase activators: targeting red cell metabolism in thalassemia

Thalassemia is an inherited red blood cell disorder whereby the qualitative and/or quantitative imbalance in α- to β-globin ratio results in hemolysis and ineffective erythropoiesis. Oxidative stress, from the precipitated excess globin and free iron, is a major factor that drives hemolysis and ineffective erythropoiesis. Pyruvate kinase activity and adenosine triphosphate availability are reduced due to the overwhelmed cellular antioxidant system from the excessive oxidative stress. Mitapivat, a pyruvate kinase activator in development as a treatment for thalassemia, was shown to increase hemoglobin and reduce hemolysis in a small phase 2 single-arm trial of patients with α- and β-thalassemia. The ongoing phase 3 studies with mitapivat and the phase 2 study with etavopivat will examine the role of pyruvate kinase activators as disease modifying agents in thalassemia.

Amniotic fluid metabolomic and lipidomic alterations associated with hemoglobin Bart's diseases

INTRODUCTION

α-Thalassemia is the most common inherited disease in southern China. The severest form is hemoglobin (Hb) Bart's disease, in which the affected fetuses almost always die in utero or shortly after birth, and the mothers are at high risk for severe morbidity.

OBJECTIVE

To investigate the changes in all metabolites in fetuses with Hb Bart's disease and to characterize the metabolomic and lipidomic biomarkers in the development of Hb Bart's fetuses.

METHODS

Amniotic fluid (AF) specimens were selected from 34 pregnant women who underwent interventional prenatal diagnosis from June 2017 to June 2018. Gap-PCR analysis was used to diagnose Hb Bart's disease, and untargeted metabolomic and lipidomic analyses were performed.

RESULTS

By analyzing AF samples, 935 differential metabolites were selected between Hb Bart's and control fetuses. The metabolites with significant changes mainly involved D-glutamine and D-glutamate metabolism, histidine metabolism, arginine metabolism, beta-alanine metabolism and alanine, aspartate and glutamate metabolism. Further lipidomics analysis revealed 132 differential lipids, mainly involved phosphatidylcholine and triglyceride metabolism. Through the characterized metabolites in AF, a schematic model of Hb Bart's disease was established.

CONCLUSION

Glutamate and glutathione metabolism, aspartate metabolism, urea metabolism and triglyceride metabolism were significantly changed in the Hb Bart's group compared to the control group. The characterized biomarkers were mainly involved in oxidative stress reaction, iron overload and liver dysfunction. This finding may help improve the treatment options for α-thalassemia as well as diagnosing phenotype of patients.