Role of sex and time of blood sampling in SOD1 and SOD2 expression variability

Objectives: This study investigates how some of human physiological parameters, in particular sex and daytime, can contribute to the normal variation in blood gene expression. Design and methods: The expressions of two genes: SOD1 (Cu/Zn) and SOD2 (Mn) in white blood cells of 19 healthy individuals (10 men and 9 women) were examined by qPCR at 09.00, 12.00, and 15.00 h over three consecutive weeks at 7-day intervals. SOD1 and SOD2 expressions differ between sexes, higher expression being exhibited in males (P < 0.005). In the male group both genes had lower expression (P < 0.005) with smaller variation at 09.00 h. In females, both inter- and intra-subject, variability in SOD1 expression was increased at ovulation. Intra-individually, the expressions of genes positively correlated in males, but less in females. Conclusions: SOD1 and SOD2 expressions demonstrate how sex and daytime, merit being controlled when human gene expression analyses are evaluated, particularly within the framework of clinical trials or cohort studies. © 2008 The Canadian Society of Clinical Chemists.