Relationships between single nucleotide polymorphisms of antioxidant enzymes and disease.

The presence and progression of numerous diseases have been linked to deficiencies in antioxidant systems. The relationships between single nucleotide polymorphisms (SNPs) arising from specific antioxidant enzymes and diseases associated with elevated oxidative stress have been studied with the rationale that they may be useful in screening for diseases. The purpose of this narrative review is to analyse evidence from these studies. The antioxidant enzyme SNPs selected for analysis are based on those most frequently investigated in relation to diseases in humans: superoxide dismutase (SOD2) Ala16Val (80 studies), glutathione peroxidise (GPx1) Pro197Leu (24 studies) and catalase C-262T (22 studies). Although the majority of evidence supports associations between the SOD2 Ala16Val SNP and diseases such as breast, prostate and lung cancers, diabetes and cardiovascular disease, the presence of the SOD2 Ala16Val SNP confers only a small, clinically insignificant reduction (if any) in the risk of these diseases. Other diseases such as bladder cancer, liver disease, nervous system pathologies and asthma have not been consistently related to this SOD SNP genotype. The GPx1 Pro197Leu and catalase C-262T SNP genotypes have been associated with breast cancer, but only in a small number of studies. Thus, currently available evidence suggests antioxidant enzyme SNP genotypes are not useful for screening for diseases in humans.