Associations between CYP2E1 promoter polymorphisms and plasma 1,3-dimethyluric acid/theophylline ratios.
OBJECTIVE
Theophylline is metabolized to 1,3-dimethyluric acid (1,3-DMU), 3-methylxanthine, and 1-methylxanthine by CYP1A2 and partly by CYP2E1. Because 1,3-DMU is the major metabolite of theophylline, the 1,3-DMU/theophylline ratio is viewed as a good indicator of theophylline metabolic clearance. Here, we investigated the associations between 1,3-DMU/theophylline ratios and genetic polymorphisms of CYP2E1 and CYP1A2.


METHODS
Polymerase chain reaction (PCR) and direct sequencing or PCR-restriction fragment length polymorphism (RFLP) were performed to analyze CYP2E1 and CYP1A2 promoter polymorphisms in 62 Korean asthma patients. Plasma theophylline and 1,3-DMU levels were measured by liquid chromatography-tandem mass spectrometry.


RESULTS
Eleven polymorphisms including Ins(96), -1566 T>A, -1515 T>G, -1414 C>T, -1295 G>C, -1055 C>T, -1027 T>C, -930 A>G, -807 T>C, -352 A>G, and -333 T>A were detected in the 5' flanking region of the CYP2E1 gene (numbering according to GenBank Accession number NT_017795). Of these, five single nucleotide polymorphisms (SNPs) (-1566 T>A, -1295 G>C, -1055 C>T, -1027 T>C, and -807 T>C) were closely linked. Another three polymorphisms (Ins(96,) -930 A>G, and -352 A>G) and two polymorphisms (-1515 T>G and -333 T>A) were also closely linked. The five closely linked polymorphisms were associated with significantly different 1,3-DMU/theophylline ratios between heterozygotes plus homozygotes of a rare allele (n=23, 0.0368+/-0.0171) and common allelic homozygotes (n=39, 0.0533+/-0.0343) (p=0.024 by Mann-Whitney U test). In the CYP1A2 gene, the -2964G>A polymorphisms exhibited a significant difference in 1,3-DMU/theophylline levels between heterozygotes plus homozygotes of a rare allele (n=30, 0.0406+/-0.0272) and homozygotes of a common allele (n=32, 0.0534+/-0.0316) (p=0.032).


CONCLUSIONS
We confirm that hydroxylation at the 8 position of theophylline (1,3-DMU) is significantly affected by genetic polymorphism in CYP2E1 in addition to CYP1A2.
Yoon
Yeomin
Y
Department of Laboratory Medicine, Konkuk University College of Medicine, Seoul, South Korea.
Park
Hyung-Doo
HD
Park
Kyoung Un
KU
Kim
Jin Q
JQ
Chang
Yoon-Seok
YS
Song
Junghan
J
D000483:Alleles; D001249:Asthma / Q000378:metabolism; D019388:Cytochrome P-450 CYP1A2 / Q000235:genetics*; D019392:Cytochrome P-450 CYP2E1 / Q000235:genetics*; D005838:Genotype; D006801:Humans; D010597:Pharmacogenetics; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D012150:Polymorphism, Restriction Fragment Length; D013806:Theophylline / Q000097:blood / Q000378:metabolism*; D014527:Uric Acid / Q000031:analogs & derivatives* / Q000097:blood
D014527:Uric Acid; D013806:Theophylline; C031274:1,3-dimethyluric acid; D019392:Cytochrome P-450 CYP2E1; D019388:Cytochrome P-450 CYP1A2