Association of haptoglobin genotype and common cardiovascular risk factors with the amount of iron in atherosclerotic carotid plaques.

INTRODUCTION: The aim of this study was to evaluate the iron burden of carotid atherosclerotic plaques removed from patients treated for carotid disease and find any relation with haptoglobin genotype and other common cardiovascular risk factors.

METHODS: Consecutive patients undergoing carotid endarterectomy were included in the study. All patients had high-grade carotid stenosis (>70%). The clinical characteristics and serum parameters of the study population were recorded and the haptoglobin genotype was determined. The presence of hemosiderin deposits in the plaques was identified using Perl's stain on adjacent serial sections.

RESULTS: 70 specimens were processed for histologic examination: 27 plaques from diabetic patients (16 with the Hp 1-1 or 2-1 genotype and 11 with the Hp 2-2 genotype) and 43 plaques from non diabetic patients (20 with the Hp 1-1 or 2-1 genotype and 23 with the Hp 2-2 genotype). In plaques from diabetic patients the density of Perl's iron stain was significantly higher in the Hp 2-2 group compared with that in the Hp 1-1 or 2-1 group (p = 0.008). The correlation and regression analysis of all possible clinical and laboratory predictors of intraplaque iron deposition showed that four factors were independently associated with intraplaque iron deposition: male gender, serum homocysteine, Hp 2-2 genotype and diabetes mellitus treatment.

CONCLUSIONS: Male diabetic patients with increased plasma levels of homocysteine and the Hp 2-2 genotype had higher carotid plaque iron deposition. Current evidence and pathophysiological considerations suggest that the increased intraplaque iron deposition may be associated with increased oxidative stress, affecting the stability of the carotid plaque.