the paraoxonase ( pon ) gene family consists of three members - pon1 , pon2 , and pon3-located adjacent to each other on the long arm of chromosome 7 in humans . these three human pon genes share approximately 60% identity at the amino acid level and approximately 70% identity at the nucleotide level . however among other mammalian species , these three genes share 79 - 90% identity at the amino acid level and 81 - 90% identity at the nucleotide level ( 1 ) . pon1 is synthesized in the liver and secreted in the blood , where it associates with high - density lipoprotein ( hdl ) . changes in hdl size and shape can strongly affect the binding affinity and stability of pon1 and result in reduced antioxidative capacity ( 2 ) . however , pon2 mrna is more widely expressed in nearly every human tissue including the heart , kidney , liver , lung , placenta , small intestine , spleen , stomach , and testis . arterial wall endothelial cells , smooth muscle cells and macrophages of arterial wall are also known to express pon2 ( 3 ) . pon1 might play an important physiological role in lipid metabolism through protecting against the development of atherosclerosis . studies have shown that pon1 inhibits oxidation of hdl and low - density lipoproteins ( ldl ) that preserve hdl function , increases cellular cholesterol efflux from macrophages ameliorates effects of oxidized ldl , and decreases lipid peroxides in atherosclerotic lesions ( 2 ) . the antioxidant and anti - inflammatory properties of pon2 , along with its intracellular localization , ubiquitous expression , and upregulation in times of oxidative stress , suggest an important physiological role for pon2 in host defense against atherosclerosis ( 3 ) . thus , pon2 plays a similar role to that of pon1 in the metabolism of lipids and lipoproteins ( 1 ) . there are two polymorphisms in the pon1 coding region : leucine / methionine at position 55 ( m55l ) and glutamine / arginine at position 192 ( q192r ) . pon2 also has two common polymorphic sites in the coding region : alanine / glycine at position 148 ( g148a ) and cysteine / serine at position 311 ( c311s ) ( 4 ) . these polymorphisms are associated with a number of pathophysiological conditions , such as coronary artery disease , parkinson 's disease , stroke , familial hypercholesterolemia , type 2 diabetes , late - onset alzheimer 's disease , and reduced bone mass in postmenopausal women ( 5 - 11 ) . various population studies have reported inter - ethnic differences in the allele frequencies for pon1 and pon2 polymorphisms . this variability suggests that ethnic differences , gene - gene interactions and susceptibility to environmental factors might modulate the relationship between pon polymorphisms and the above mentioned diseases . considering the important contribution of these polymorphisms to genetic susceptibility in atherosclerosis , and the variability in allele frequencies among different ethnic groups , the aim of this work was to evaluate the distribution of pon polymorphisms and to determine their role association with lipid profiles in a population living in south - western part of korea . the allele distribution of the pon polymorphisms was determined in 988 ( 519 males , 469 females ) unrelated volunteers , all of whom were hospital patients or outpatients for health screening from south - west parts of korea . written informed consent was obtained from each patient . this study protocol was approved by the institutional review board of chonbuk national university hospital . dna samples were quantified using a genequant ii rna / dna calculator ( amersham - pharmacia biotech , uppsala , sweden ) , and 5 - 10 ng of dna form each patient was amplified through a hot start polymerase chain reaction ( pcr ) protocol . the primers applied for pon1 55 pcr and pon1 192 pcr were pon1 - 55f , pon1 - 55r , pon1 - 192f , and pon1 - 192r , determining a 138 bp and a 151 bp pcr amplicon size , respectively . the primers applied for pon2 148 pcr and pon2 311 pcr were pon2 - 148f , pon2 - 148r , pon2 - 311f , and pon2 - 311r , determining a 165 bp and a 225 bp pcr amplicon size , respectively . the detection oligonucleotide sets applied for pon1 55 , pon1 192 , pon2 148 , and pon2 311 genotyping consisted of a 3'fluorescein - labeled anchor and either a 5'-lc red 705-labeled ( pon1 192 mutation , pon2 148 mutation ) or a 5'-lc red 640-labeled ( pon1 55 mutation , pon2 311 mutation ) sensor probe . the sequences of primers and probes , as well as the applied fluorophores and nucleotide sets applied for the pon genotyping with melting point analysis , are shown in table 1 . both primers and fluorescently labeled probes were synthesized by tib molbiol ( berlin , germany ) . pcr and melting curve analysis were performed in 20 l volumes in glass capillaries ( hoffmann - la roche , alameda , ca , u.s.a . ) . during pcr , the lightcycler automate ( software version 4.5 ) continuously displays the current fluorescence and fluorescence history of each capillary . analysis of pcr products on agarose gel and sequencing confirmed the presence of the specific pcr products ( data not shown ) . the observed melting point temperature in pon1 55 mm was 63.0 , pon1 55 ll was 58 , pon1 192 qq was 63 , pon1 192 rr was 57 , pon2 148 aa was 64 , pon2 148 gg was 58 , pon2 311 ss was 59 , and pon2 311 cc was 53 ( 5 ) . both melting point temperatures were noted in heterozygotes ( pon1 55 lm , pon1 192qr , pon2 148 ag , pon2 311sc ) . the chi - square test was used both to estimate the hardy - weinberg equilibrium and to compare the genotype and allele frequencies between the sexes . allele frequencies observed in the korean population were compared with those reported in other populations using the mantel - haenszel chi - square test . one - way analysis of variance ( anovar ) was used to compare the mean levels of lipid parameters among the different genotypes . the allele distribution of the pon polymorphisms was determined in 988 ( 519 males , 469 females ) unrelated volunteers , all of whom were hospital patients or outpatients for health screening from south - west parts of korea . written informed consent was obtained from each patient . this study protocol was approved by the institutional review board of chonbuk national university hospital . dna samples were quantified using a genequant ii rna / dna calculator ( amersham - pharmacia biotech , uppsala , sweden ) , and 5 - 10 ng of dna form each patient was amplified through a hot start polymerase chain reaction ( pcr ) protocol . the primers applied for pon1 55 pcr and pon1 192 pcr were pon1 - 55f , pon1 - 55r , pon1 - 192f , and pon1 - 192r , determining a 138 bp and a 151 bp pcr amplicon size , respectively . the primers applied for pon2 148 pcr and pon2 311 pcr were pon2 - 148f , pon2 - 148r , pon2 - 311f , and pon2 - 311r , determining a 165 bp and a 225 bp pcr amplicon size , respectively . the detection oligonucleotide sets applied for pon1 55 , pon1 192 , pon2 148 , and pon2 311 genotyping consisted of a 3'fluorescein - labeled anchor and either a 5'-lc red 705-labeled ( pon1 192 mutation , pon2 148 mutation ) or a 5'-lc red 640-labeled ( pon1 55 mutation , pon2 311 mutation ) sensor probe . the sequences of primers and probes , as well as the applied fluorophores and nucleotide sets applied for the pon genotyping with melting point analysis , are shown in table 1 . both primers and fluorescently labeled probes were synthesized by tib molbiol ( berlin , germany ) . pcr and melting curve analysis were performed in 20 l volumes in glass capillaries ( hoffmann - la roche , alameda , ca , u.s.a . ) . during pcr , the lightcycler automate ( software version 4.5 ) continuously displays the current fluorescence and fluorescence history of each capillary . analysis of pcr products on agarose gel and sequencing confirmed the presence of the specific pcr products ( data not shown ) . the observed melting point temperature in pon1 55 mm was 63.0 , pon1 55 ll was 58 , pon1 192 qq was 63 , pon1 192 rr was 57 , pon2 148 aa was 64 , pon2 148 gg was 58 , pon2 311 ss was 59 , and pon2 311 cc was 53 ( 5 ) . both melting point temperatures were noted in heterozygotes ( pon1 55 lm , pon1 192qr , pon2 148 ag , pon2 311sc ) . differences in demographic characteristics were compared by univariate analysis using student 's t test . allele and genotype frequencies the chi - square test was used both to estimate the hardy - weinberg equilibrium and to compare the genotype and allele frequencies between the sexes . allele frequencies observed in the korean population were compared with those reported in other populations using the mantel - haenszel chi - square test . one - way analysis of variance ( anovar ) was used to compare the mean levels of lipid parameters among the different genotypes . the mean age was 66.1812.2 yr , with no age difference between the sexes ( male , n=519 , 64.1312.2 yr ; female , n=469 , 6712.4 yr ; p=0.561 ) . with respect to vascular disease risk factors , a large proportion of individuals had hypertension . genotype and allele frequencies for the pon1m55l , pon1q192r , pon2a148 g , and pon2s311c polymorphisms are summarized in table 3 . observed and expected frequencies for the polymorphisms were at hardy - weinberg equilibrium . in the case of the pon1 55 polymorphism , the most frequent allele was l ( 94.3% ) , and the most common genotype was the homozygote ll ( 88.6% ) . the most frequent pon1 192 allele was q ( 70.3% ) and the most common genotype was heterozygote qr ( 59.4% ) . in the case of the pon2 148 polymorphism , the most frequent allele was a ( 79.2% ) , and the most common genotype was the homozygote aa ( 61.9% ) . the most frequent pon2 311 allele was s ( 79.2% ) , and the most common genotype was homozygote ss ( 61.9% ) . there was no significant difference between the sexes in terms of genotype or allele frequency . the alle frequencies of pon1m55l , pon1q192r , pon2a148 g , and pon2s311c were compared in the korean population to those previously described in other asian ( 12 - 18 ) , american ( 19 - 23 ) and european ( 7 , 8 , 24 - 31 ) groups ( table 4 ) . the pon1 55 l allele frequencies in asian populations were higher than in other ethnic groups ( p<0.05 ) , and the allele frequency in koreans was higher than those seen in thai , iranian , and pakistani populations ( p<0.05 ) . the korean population showed a pon1 192q allele frequency similar to that seen in other ethnic groups , except for those of china , taiwan , mexico and latin america ( p<0.05 ) . the pon2 148 a allele frequency in the korean population was similar to that seen in other populations , except for those of pakistan and brazil ( p<0.005 ) . the pon2 311s allele frequency in the korean population was different compared to that of populations in pakistan and the u.s.a . ( p<0.05 ) . to determine the of pon gene polymorphisms on the lipid profile , the lipid profile was classified as high , normal or low according to the previously defined normal ranges ( cholesterol , 0 - 200 mg / dl ; triglyceride , 0 - 200 mg / dl ; hdl cholesterol , 48.9 - 73.5 mg / dl ; ldl cholesterol , 0 - 140 mg / dl ; apoai , 1.08 - 2.24 g / l , apob 0.60 - 1.17 g / l ; lipoprotein a , 0 - 30 mg / dl ; total homocysteine 5 - 20 m / l ) . there was no difference in lipid profile among pon 1 polymorphisms , but the pon2 a148 g and pon2s311c polymorphisms showed significant differences in ldl and apob concentrations ( p=0.023 , p<0.001 ) ( table 5 ) . homozygotes for pon2 148 g and pon2 311 c showed higher concentrations of ldl cholesterol and higher apob levels ( table 6 ) . numerous studies have been conducted on the relation between pon polymorphisms and genetic susceptibility to coronary heart disease ( chd ) . the pon1 192r allele is positively associated with chd while the q allele is protective against atherosclerosis ( 1 ) . on meta - analysis of pon q192r polymorphisms and chd , a highly significant positive association was confirmed in the population with type 2 diabetes ( 32 ) . fewer studies have been conducted on the pon1 l55 m , pon2 a148 g , and pon2 s311c polymorphisms in chd , but the results have proved conflicting ( 2 , 33 ) . the major factor contributing of these differences is a completely different distribution of pon polymorphisms among different ethnic populations . in the present study , the allele and genotype frequencies of pon polymorphisms were described in a south - western korean population . we found no significant difference between the sexes with respect to pon genotype distribution or allele frequency . frequency distribution showed that the korean population had a similar distribution of pom1 55 polymorphisms compared to the asian population , with the exception of an increased frequency of the l allele in the korean population . the korean population had important differences in pon1 distribution when compared to american and european population ( p<0.05 ) . with respect to the pon1 192 polymorphism , the korean population showed a frequency pattern similar to that of other ethnic groups , with increased frequency of the q allele . the genotype distribution of pon2 polymorphism was narrower than that seen in the pon1 polymorphism . pon2 a148 g and pon2 s311c polymorphisms seen in the korean population exhibited a pattern similar to those seen in other ethnic groups , with increased frequencies of a and s alleles . however , there were significant distribution differences compared with populations from pakistan , brazil , and the u.s.a . pon serum concentration and activity are considered more important than pon polymorphisms in the risk of atherosclerotic disease , and gene - gene and gene - environmental interaction may increase or decrease susceptibility to the disease . therefore , these ethnic variations in pon polymorphisms could help us to understand the role of pon as a marker for the interpretation of data correlated with a specific disease . in order to determine the role of pon polymorphism in the lipid profile of this study population , the lipid levels were determined and the association of the pon polymorphisms and lipid profiles was evaluated . in this analysis , no association was found between pon1 genotypes and lipid concentration ( data not shown ) . homozygotes for pon2 148 g and pon2 311 c showed higher concentrations of ldl cholesterol and higher apob levels ( p=0.017 , 0.014 , respectively ) . homozygotes for pon2 148a and pon2 311s had significantly higher plasma total cholesterol and ldl cholesterol and higher apob levels than homozygotes for pon2 148 g and pon2 311c and heterozygotes for pon2 a148 g and pon2 s311c ( 4 ) . another report found that homozygotes for pon2 148 g had the highest plasma concentrations of total cholesterol , hdl cholesterol , and apoai ( 34 ) . homozygotes of for pon2 311c was reported to have the highest concentration of total cholesterol and ldl cholesterol ( 24 ) . these discrepancies suggest that polymorphisms in the pon gene are associated with significant variations in intermediate traits in plasma lipoprotein metabolism , through an unknown mechanism . additional studies using large population based cohorts will be needed to determine the general applicability of the present results for korean population . in this study , the pon polymorphisms and allele frequencies were described in a korean population , and compared with other ethnic groups . these ethnic variations are considered important factors in the interpretation of diseases associated with pon polymorphism .
paraoxonase ( pon ) has anti - atherogenic activity . considering the important role of polymorphism in the genetic susceptibility to cardiovascular disease and the variability of its allele frequencies in different ethnic groups , 
 the distribution of genotypes and allele frequencies of pon1m55l , pon1q192r , pon2a148 g , and pon2s311c polymorphisms was analyzed in a total 988 south - western koreans and determined their effects on lipid parameters . 
 the genotype distribution of pon1 at position 55 was ll=0.886 , lm=0.114 ; and at position 192 was qq=0.406 , qr=0.594 . 
 the frequencies of the pon1 55l allele and the pon1 192r allele were similar to those seen in chinese populations and western populations , respectively . 
 the genetic distribution of pon2 at position 148 was aa=0.619 , ag=0.345 , gg=0.035 ; and at position 311 was cc=0.035 , sc=0.345 , ss=0.619 . 
 the frequencies of the pon2 148 g and 311s alleles were similar to those seen in chinese populations . 
 the concentrations of ldl and apob were significantly different between the pon2a148 g ( p<0.05 ) and pon2 s311c polymorphisms ( p<0.01 ) . 
 pon polymorphisms and allele frequencies were described in koreans living south - western part of korea . 
 these ethnic variations are considered important in the interpretation of diseases associated with pon polymorphisms .