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Keywords:

  • TAOS;
  • apolipoprotein E;
  • cardiovascular diseases;
  • diabetes mellitus;
  • gene: environment interaction;
  • smoking

Summary

Data from 1668 men (316 cardiovascular disease events) from the Framingham Offspring Study was reanalysed, specifically examining APOE:smoking interactions. Overall hazard ratio (HR) for smoking was 1.95 (1.52, 2.50) compared to non-smokers. Using ɛ3/3 as a referent group, in non-smokers HRs for ɛ2 carriers (ɛ2+; 1.04 (0.61, 1.76) and ɛ4 carriers (ɛ4+; 1.04 (0.70, 1.54) showed no major risk increase. In smokers, HRs were 1.96 (1.26, 2.78) in ɛ3ɛ3 men, 3.46 (2.14, 5.60; p = 0.09 for interaction) in ɛ2+ and 3.81 (2.49, 5.84; p = 0.01 for interaction), with a significant interaction between daily cigarette consumption and APOE genotype on risk (p = 0.03). The potential mechanism for this APOEɛ4:smoking interaction was examined in a second study of 728 Caucasian patients with diabetes, where markers of reactive oxygen species were available. APOE genotype was not associated with plasma OX-LDL or total antioxidant status (TAOS) in non-smokers. However, in smokers ɛ4+ had 26.7% higher plasma OX-LDL than other genotypes (APOE:smoking interaction p = 0.04), while ɛ2+ had 28.4% higher plasma TAOS than ɛ3ɛ3 and ɛ4+ combined (APOE:smoking interaction p = 0.026). Although direct extrapolation needs to be considered with caution, these results identify that the cardiovascular disease risk-raising effect of ɛ4+ is confined to smokers, and a feasible mechanism is presented by the reduced antioxidant capacity/increased OX-LDL of apoE4.