Genetic association of apolipoprotein E polymorphisms with inflammatory bowel disease

AIM: To study the association of apolipoprotein E (APOE) polymorphisms with the susceptibility of inflammatory bowel disease (IBD) in Saudi patients. METHODS: APOE genotyping was performed to evaluate the allele and genotype frequencies in 378 Saudi subjects including IBD patients with ulcerative colitis (n = 84) or Crohn's disease (n = 94) and matched controls (n = 200) using polymerase chain reaction and reverse-hybridization techniques. RESULTS: The frequencies of the APOE epsilon 2 allele and epsilon 2/epsilon 3 and epsilon 2/epsilon 4 genotypes were significantly higher in IBD patients than in controls (P < 0.05), suggesting that the epsilon 2 allele and its heterozygous genotypes may increase the susceptibility to IBD. On the contrary, the frequencies of the epsilon 3 allele and epsilon 3/epsilon 3 genotype were lower in IBD patients as compared to controls, suggesting a protective effect of APOE epsilon 3 for IBD. The prevalence of the epsilon 4 allele was also higher in the patient group compared to controls, suggesting that the epsilon 4 allele may also increase the risk of IBD. Our results also indicated that the APOE epsilon 4 allele was associated with an early age of IBD onset. No effect of gender or type of IBD (familial or sporadic) on the frequency distribution of APOE alleles and genotypes was noticed in this study. CONCLUSION: APOE polymorphism is associated with risk of developing IBD and early age of onset in Saudi patients, though further studies with a large-size population are warranted.