The role of N-acetyltransferase 2 polymorphism in the etiopathogenesis of inflammatory bowel disease

BACKGROUND AND PURPOSE

Inflammatory bowel disease (IBD) consists of ulcerative colitis (UC) and Crohn's disease (CD), which are complex genetic disorders resulting from the interplay between several genetic and environmental risk factors. The arylamine N-acetyltransferase 2 (NAT2) enzyme detoxifies a wide spectrum of naturally occurring xenobiotics including carcinogens and drugs. Acetylation catalyzed by NAT2 is an important process in metabolic activation of arylamines to electrophilic intermediates that initiate carcinogenesis. The aim of our study was to determine whether there is any association between the susceptibility to inflammatory bowel disease among the variations of NAT2 genotypes.

METHODS

This study was carried out in 80 patients with IBD. The control group consisted of 100 healthy volunteers. The most common mutations found in the Caucasian population are at the positions 481T, 803G, 590A and 857A on the NAT2 gene. This was determined using the polymerase chain reaction-restriction fragment length polymorphism method with DNA extracted from peripheral blood.

RESULTS

Risk of IBD development was 3.86 for the carriers of the NAT2*5/NAT2*7 genotype and 2.53 for the carriers with NAT2*6/NAT2*7, but it was not statistically significant. A statistically significant correlation between the NAT2*7 allele prevalence and the risk for developing IBD was found (OR = 5.8; P = 0.005).

CONCLUSIONS

Higher prevalence of the NAT2*7 allele in patients with IBD and the obtained OR values could suggest that this mutation has the effect of increasing IBD development. Future studies are needed to confirm our assumptions on larger group of patients.

Genetic polymorphisms of CYP2D6 oxidation in patients with inflammatory bowel disease

Inflammatory bowel disease (IBD) consists of ulcerative colitis and Crohn's disease, both of which are associated with increased colorectal cancer risk. The relationship between genetically determined polymorphic metabolism of exogenous substances by oxidation catalyzed by CYP2D6 isoenzyme and susceptibility to cancer has aroused great interest. We determined whether there was an association between susceptibility to inflammatory bowel disease and particularly to CYP2D6 genotypes. The study was carried out in 39 patients with IBD. The control group consisted of 129 healthy volunteers. The CYP2D6 genotypes were analyzed by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) method with DNA extracted from peripheral blood. Among 39 patients with inflammatory bowel disease, extensive metabolizer (EM) genotype constituted 97.4%. One patient (2.6%) was poor metabolizer with CYP2D6*4/CYP2D6*4 genotype. Results obtained in the inflammatory bowel disease group did not differ significantly from those of the control group. Although the odds ratio for EM metabolizers was about 3.8-fold greater in the group of patients with inflammatory bowel disease, this association was not statistically significant. This data also showed no overall statistically significant association between alleles and incidence risk of inflammatory bowel disease [odds ratio (OR) of 1.36 for CYP2D6*1 allele, 0.83 for CYP2D6*3 allele, and 0.74 for CYP2D6*4 allele]. The present results suggest that EM genotype may be the risk factor of inflammatory bowel disease. Future studies are needed to confirm our assumptions on larger group of patients.

Lack of association between arylamine N-acetyltransferase 2 (NAT2) polymorphism and systemic sclerosis

OBJECTIVES

It has been shown that exposure to some environmental toxins may induce scleroderma-like illness in predisposed individuals, but the etiopathogenesis of the idiopathic form of systemic sclerosis (SSc) remains obscure. The genetic background of this illness has been confirmed in multiple studies. We investigated whether patients with SSc differ from healthy subjects with regard to the enzymatic activity of polymorphic N-acetyltransferase 2 (NAT2).

METHODS

The study was carried out in 39 patients with SSc; 15 fulfilled the criteria of diffuse SSc (dSSc) and 24 of limited SSc (lSSc); an ethnically matched control group consisted of 100 healthy volunteers. Acetylation phenotype was estimated using the isoniazid as a model drug. The most common mutations in the Caucasian population at positions 481T, 803G, 590A and 857A on the NAT2 gene were determined using the polymerase chain reaction-restriction fragment length polymorphism method with deoxyribonucleic acid (DNA) extracted from peripheral blood.

RESULTS

In the group of patients with SSc, the frequency of fast acetylator genotypes was 38.5% (95% CI 23.4-55.4), while that for the genotypes coding slow acetylator status was 51.3% (95% CI 34.8-67.6). There was a strong correlation between NAT2 phenotype and NAT2 genotype with a concordance of 97%. We did not observe a preponderance of slow acetylators among patients with SSc and in two subsets of SSc. With the sample size analyzed in the present study, there is a 90% probability of detecting significant differences in distribution of slow, fast, and intermediate phenotypes between patients with SSc and controls, there is a difference of at least 30.3, 28.7 and 21.9% in the distribution of these phenotypes in the general population, respectively.

CONCLUSION

Acetylator status does not seem to be the significant factor in the development of SSc in patients with both subsets of this autoimmune disease, but further studies are required to confirm this conclusion.