Classic coronary heart disease (CHD) risk factors such as smoking, gender, hypertension, and hyperlipidemia fail to explain the large difference in CHD incidence between Northern Ireland and France. For that reason, the Prospective Epidemiological Study of Myocardial Infarction (PRIME), which is a multicentre prospective study of 10,593 healthy middle-aged males, investigated novel risk factors in this population. Troughton et al. investigated whether there was an independent association between paraoxonase (PON) activity, an enzyme that binds to a subfraction of HDL containing apolipoprotein AI, and CHD risk in 299 men who had developed CHD over a 5-year follow-up and in 576 matched controls. They also investigated whether there was an association between PON polymorphism, the PON55 LL genotype, and CHD risk. The authors found that there was no significant difference in PON activity between cases and controls in the France and Northern Ireland populations. Moreover, there was no significant association between genotype and CHD risk and no difference in genotype frequencies between France and Northern Ireland in either cases or controls. Thus, there was no association between PON activity or the PON55 polymorphism and CHD risk in healthy middle-aged men in the PRIME study. These findings do not support the hypothesis that PON enzyme is a novel cardiovascular risk factor in terms of its activity or genotype. However, the authors acknowledged that further studies on the effect of PON activity and concentration are required before the hypothesis that PON is not associated with CHD can be put aside.
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