Serum Bilirubin and Ferritin Levels Link Heme Oxygenase-1 Gene Promoter Polymorphism and Susceptibility to Coronary Artery Disease in Diabetic Patients

  1. Ying-Hwa Chen, MD, PHD1,2,
  2. Lee-Young Chau, PHD3,
  3. Jaw-Wen Chen, MD2,4 and
  4. Shing-Jong Lin, MD, PHD1,2,4
  1. 1Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan, Republic of China
  2. 2Division of Cardiology, Department of Internal Medicine, Taipei Veterans General Hospital, Taipei, Taiwan, Republic of China
  3. 3Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan, Republic of China
  4. 4Cardiovascular Research Center, National Yang-Ming University, Taipei, Taiwan, Republic of China
  1. Corresponding author: Shing-Jong Lin, sjlin{at}vghtpe.gov.tw

Abstract

OBJECTIVE—Heme oxygenase (HO) leads to the generation of free iron, carbon monoxide, and bilirubin. A length polymorphism of GT repeats in the promoter of human HO-1 gene has been shown to modulate gene transcription. The aim of this study was to assess the association of the length of (GT)n repeats in the HO-1 gene promoter with serum bilirubin, markers of iron status, and the development of coronary artery disease (CAD).

RESEARCH DESIGN AND METHODS—We screened the allelic frequencies of (GT)n repeats in the HO-1 gene promoter in 986 unrelated individuals who underwent coronary angiography. Serum bilirubin and markers of iron status were evaluated.

RESULTS—The distribution of numbers of (GT)n repeats was divided into two subclasses: class S included shorter (<27) repeats, and class L included longer (≥27) repeats. Among those with diabetes, subjects with the L/L genotype had significantly lower bilirubin levels than those with S/S and S/L genotypes (0.70 ± 0.22 vs. 0.81 ± 0.24 mg/dl, P = 0.001) and higher serum ferritin values (4.76 ± 0.72 vs. 4.28 ± 1.05 μg/l for log ferritin, P = 0.001). Compared with those carrying the S allele, diabetic subjects with the L/L genotype had an almost threefold increase in CAD risk after controlling for conventional risk factors (odds ratio 2.81, [95% CI 1.22–6.47], P = 0.015). With adjustment for both serum bilirubin and ferritin, the effect of HO-1 promoter polymorphism on susceptibility to CAD disappeared.

CONCLUSIONS—Length polymorphism in the HO-1 gene promoter is correlated with susceptibility to CAD in diabetic patients, and this effect might be conveyed through its influence on serum bilirubin and ferritin.

Footnotes

  • Published ahead of print at http://care.diabetesjournals.org on 28 April 2008.

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    • Received November 21, 2007.
    • Accepted April 20, 2008.
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  1. Diabetes Care vol. 31 no. 8 1615-1620
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