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.