title: Increased mitochondrial DNA deletions and copy number in transfusion-dependent thalassemia.
abstract: BACKGROUND
  Iron overload is the primary cause of morbidity in transfusion-dependent thalassemia. Increase in iron causes mitochondrial dysfunction under experimental conditions, but the occurrence and significance of mitochondrial damage is not understood in patients with thalassemia.
  
  
  METHODS
  Mitochondrial DNA (mtDNA) to nuclear DNA copy number (Mt/N) and frequency of the common 4977-bp mitochondrial deletion (ΔmtDNA4977) were quantified using a quantitative PCR assay on whole blood samples from 38 subjects with thalassemia who were receiving regular transfusions.
  
  
  RESULTS
  Compared with healthy controls, Mt/N and ΔmtDNA4977frequency were elevated in thalassemia (P= 0.038 andP< 0.001, respectively). ΔmtDNA4977was increased in the presence of either liver iron concentration > 15 mg/g dry-weight or splenectomy, with the highest levels observed in subjects who had both risk factors (P= 0.003). Myocardial iron (MRI T2* < 20 ms) was present in 0%, 22%, and 46% of subjects with ΔmtDNA4977frequency < 20, 20-40, and > 40/1 × 107mtDNA, respectively (P= 0.025). Subjects with Mt/N values below the group median had significantly lower Matsuda insulin sensitivity index (5.76 ± 0.53) compared with the high Mt/N group (9.11 ± 0.95,P= 0.008).
  
  
  CONCLUSIONS
  Individuals with transfusion-dependent thalassemia demonstrate age-related increase in mtDNA damage in leukocytes. These changes are markedly amplified by splenectomy and are associated with extrahepatic iron deposition. Elevated mtDNA damage in blood cells may predict the risk of iron-associated organ damage in thalassemia.
authors: Hematology/Oncology, UCSF Benioff Children's Hospital, Oakland, California, USA; Children's Hospital Oakland Research Institute, Oakland, California, USA.
authors: Ashutosh
authors: A
authors: Lal
authors: Hematology/Oncology, UCSF Benioff Children's Hospital, Oakland, California, USA.
authors: Esteban
authors: E
authors: Gomez
authors: Children's Hospital Oakland Research Institute, Oakland, California, USA; Forensic Science Graduate Group, University of California, Davis, California, USA.
authors: Cassandra
authors: C
authors: Calloway