Paraoxonase 1 polymorphisms and survival

,1,2 1,2 1 L Christiansen* , L Bathum , H Frederiksen and K Christensen

1Epidemiology, Institute of Public Health, University of Southern Denmark, Odense, Denmark; 2Department of Clinical Biochemistry and Clinical Genetics, Odense University Hospital, Denmark

against coronary heart disease (CHD), one of the main causes of death in the Western world. Two coding polymorphisms, 55M/L and 192Q/R, and a promoter variant, (cid:1)107C/T, has been extensively studied with respect to susceptibility to CHD. In this study, we have investigated the impact of these three polymorphisms on mortality using a sample of 1932 Danish individuals aged 47–93 years, previously used

against coronary heart disease (CHD), one of the main causes of death in the Western world. Two coding polymorphisms, 55M/L and 192Q/R, and a promoter variant, (cid:1)107C/T, has been extensively studied with respect to susceptibility to CHD. In this study, we have investigated the impact of these three polymorphisms on mortality using a sample of 1932 Danish individuals aged 47–93 years, previously used in gene-longevity studies. A cross-sectional study comparing the genotype distribution of the three polymorphisms separately as well as the haplotype distribution in different age groups did not reveal any difference. However, a longitudinal follow-up study on survival in the same sample indicated that 192RR homozygotes have a poorer survival compared to QQ homozygotes (hazard rate: 1.38, P ¼ 0.04). We hereafter used an independent sample of 541 Danish individuals from the oldest cohort and confirmed the initial findings (hazard rate: 1.38, P ¼ 0.09). In both samples, the effect was most pronounced in women. Using self-reported data on ischemic heart disease to evaluate the impact of the PON 192Q/R polymorphism on susceptibility to CHD, we found only a nonsignificant trend of 192RR homozygosity in women being a risk factor. Our results thus indicates that PON1 192RR homozygosity is associated with increased mortality in women in the second half of life and that this increased mortality is possibly related to CHD severity and survival after CHD rather than susceptibility to development of CHD. European Journal of Human Genetics (2004) 12, 843–847. doi:10.1038/sj.ejhg.5201235 Published online 7 July 2004

Using self-reported data on ischemic heart disease to evaluate the impact of the PON 192Q/R polymorphism on susceptibility to CHD, we found only a nonsignificant trend of 192RR homozygosity in women being a risk factor. Our results thus indicates that PON1 192RR homozygosity is associated with increased mortality in women in the second half of life and that this increased mortality is possibly related to CHD severity and survival after CHD rather than susceptibility to development of CHD. European Journal of Human Genetics (2004) 12, 843–847. doi:10.1038/sj.ejhg.5201235

Keywords: paraoxonase, polymorphisms; mortality

Introduction

Two polymorphisms, both resulting in amino-acid substitutions, L55M and Q192R, have been described within the coding region of the PON1 gene.5 In addition, Leviev et al6 identified three common polymorphisms in the promoter region of the PON1 gene, and suggested that all three to some extent affected the PON1 level.6 Investigating the influence of the two coding sequence polymorphisms on the efficacy of HDL’s protection of LDL lipid oxidation, Mackness et al7 demonstrated that indivi- duals with the PON1 192QQ/55MM genotype was most effective in protecting LDL against lipid oxidation, whereas PON1 192RR/55LL homozygotes was least effective. An examination of the relevance of the identified PON1 promoter polymorphisms have revealed that promoter- related variations in PON1 concentration and activity was almost exclusively attributable to the C/T polymorphic site at position (cid:1)107, with the (cid:1)107C allele being the high

The antioxidant enzyme paraoxonase 1 (PON1) is found associated with high-density lipoproteins (HDLs) in plasma. Although the physiological substrate remains unknown, one suggested function of PON1 is the elimina- tion of accumulated oxidized lipids in lipoproteins.1 Thus, PON1 has been suggested to be responsible for the ability of HDL to prevent oxidative modification of low-density lipoprotein (LDL), thereby allegedly conferring protection against coronary heart disease (CHD), one of the main causes of death in the Western world.1–4

*Correspondence: Dr L Christiansen, Department of Clinical Biochemistry and Clinical Genetics, Odense University Hospital, Sdr. Boulevard 29, Odense C 5000, Denmark. Tel: þ45 6541 2843; Fax: þ45 6541 1911; E-mail: lchristiansen@health.sdu.dk

expresser allele.8 A recent meta-analysis of 43 studies of the 192Q/R, 55L/M and (cid:1)107C/T polymorphisms involving 11212 CHD cases and 12786 controls suggested that there is no significant association with either 55L/M or (cid:1)107C/T and CHD, and only a weak overall association between 192Q/R and CHD.9

when the diagnosis had been made by a physician was a positive answer accepted as valid.

Genotyping

DNA was isolated from cheek swabs or blood spots using the QIAamp DNA Mini Kit (Qiagen). The three polymorphisms were detected by a Taqman-based allelic discrimination assay using the following primers and probes: (cid:1)107C/T-sense: 50-gcccagctagctgcgga-30; (cid:1)107C/ T-antisense: 50-atcgatgggcgcagaca-30; (cid:1)107C: 50-FAM-cgccc- cgcccctccc-30; 107T: 50-TET-cccgccccacccctcc-30; 55M/L- sense: 50-tttctgttctcttttctggcagaaa-30; 55M/L-antisense: 50-gaaaacactcacagagctaatgaaagc-30; 55M: 50-FAM-ccattagg- cagtatctccatgtcttcagagcc-30; 55L: 50-TET-tccattaggcagtatctc- caagtcttcagagcc-30; 199Q/R-sense: 50-ggacctgagcacttttat- ggca-30; 192Q/R-antisense: 50-gacaacatacgaccacgctaaacc-30; 192Q: 50-FAM-ttcttgacccctacttacaatcctgggagatgt-30; 192R: 50-TET-cttgacccctacttacgatcctgggagatgt-30. All primers and probes were designed using Primer Express software (Applied Biosystems).