Xanthine oxidase activity is influenced by environmental factors in Ethiopians

Objectives. To investigate xanthine oxidase (XO) polymorphism in Ethiopians and influence of environmental factors, smoking habit and gender-related differences on enzyme activity among Ethiopians living in Ethiopia or Sweden. Methods. One hundred healthy unrelated Ethiopians living in Ethiopia and 73 living in Sweden participated in the study. Subjects received a 100-mg oral dose of caffeine before bedtime. All urine voided in the following 8 h was collected and the concentrations of 1-methyluracil (1U) and 1-methylxanthine (1X) (mumol/l) were analyzed by means of high-performance liquid chromatography. The 1U/(1X+1U) metabolic ratio (MR) was calculated and used as an index of XO activity. Results. XO activity was not normally distributed (P<0.0001; Shapiro-Wilk's test). The incidence of putative XO poor metabolizers in Ethiopians was 4%. The effect of differences in country of residence, gender and smoking habit was analyzed using three-way ANOVA/MANOVA. The post-hoc test (P<0.05) and Kruskal-Wallis ANOVA (P<0.004), median test showed a significant difference in XO activity among Ethiopians living in Ethiopia compared with those living in Sweden, the activity being higher in Ethiopians living in Ethiopia. The 95% CI for differences between the two means was (0.012; 0.044). No significant difference was observed in XO MR between men and women or between smokers and non-smokers, the 95% CI for the differences being (-0.059; 0.037) and (-0.010; 0.016) respectively. Conclusion. The XO activity is polymorphic in Ethiopians. Neither gender nor smoking-related differences influenced XO activity but the difference in activity between Ethiopians living in Sweden or in Ethiopia indicates influence of other environmental factors such as dietary habits on XO activity.