Significance of the Hardy-Weinberg equilibrium in genetic association studies

Susceptibility to Ulcerative Colitis and Genetic Polymorphisms of A251G SOD1 and C-262T CAT

BACKGROUND

Reactive oxygen species can attack and damage almost every molecule found in living cells, including proteins, carbohydrates, lipids, and DNA. For this reason, their production is normally tightly controlled. Among the most important defenses against these radicals are the superoxide dismutase (SOD) enzymes and catalase (CAT). Increasing attention has been given to the role of reactive oxygen metabolites in the pathogenesis of ulcerative colitis (UC), which is defined as an idiopathic and chronic intestinal inflammation. Accordingly, we hypothesized a relation between genetic polymorphisms in the two antioxidant enzymes SOD1 A251G (rs2070424) and CAT C-262T (rs1001179) and the risk of UC.

METHODS

The present case-control study included 109 UC patients (46 males and 50 females) and 186 (67 males and 119 females) gender-matched healthy controls. Genotyping was done by the PCR-RFLP method.

RESULTS

After adjusting for age and gender, a significant association was observed between the AG+GG genotypes of SOD1 A251G polymorphism (vs. AA genotype) and risk of UC (OR=0.29, 95% CI: 0.10-0.86, P= 0.025) after adjusting for age and gender. Our statistical analysis revealed that the CAT C-262T polymorphism did not associate with the risk of UC before and/or after adjusting for age and gender.

CONCLUSIONS

Based on the present statistical analysis, the G allele of the SOD1 A251G polymorphism decreases the risk of UC, thus it might be assumed that the G allele has a protective role.

p53 Arg72Pro polymorphism confers the susceptibility to endometriosis among Asian and Caucasian populations

PURPOSE

Findings from studies on the association between the p53 Arg72Pro polymorphism and endometriosis susceptibility have so far been inconsistent. Therefore, we undertook a meta-analysis to clarify the association of p53 Arg72Pro polymorphism with the risk of endometriosis.

METHODS

Relevant studies were chosen by searching PubMed, Embase, the Cochrane Library databases, CNKI, Wanfang database, and CBM for articles published before and up to April 30, 2015. Two independent reviewers performed the eligibility evaluation and data extraction. The odds ratios (ORs) and 95 % confidence intervals (CIs) were calculated for the overall risk estimate.

RESULTS

Eleven case-control studies involving 1834 endometriosis cases and 2331 controls were included. Pooled data analysis suggested that the p53 72Pro variant is a significant endometriosis risk factors in comparison to the 72Arg variant (Pro vs. Arg: OR = 1.298, 95 % CI 1.082-1.558; Pro/Pro vs. Arg/Arg: OR = 1.751, 95 % CI 1.130-2.711; Pro/Arg vs. Arg/Arg: OR = 1.530, 95 % CI 1.174-1.994), which was strengthened in the dominant model (Pro/Pro + Arg/Pro vs. Arg/Arg: OR = 1.570, 95 % CI = 1.181-2.087). In the stratified analysis by ethnicity and Hardy-Weinberg equilibrium (HWE) in the controls, we found strong associations in Asians and in studies that were consistent with HWE. However, the analyses of the revised American Fertility Society (rAFS) stage and the menopausal status subgroup did not reveal any significant associations.

CONCLUSION

In conclusion, the p53 Arg72Pro polymorphism was closely related to the risk of endometriosis, especially in Asian populations.