Objective: To assess the association of blood selenium and polymorphism of glutathione peroxidase-1 (GPx-1) genes in patients with Keshan Disease (KD) and provide genetic evidence for KD susceptibility.
Methods: The levels of whole blood selenium and the activity of GPx-1 were measured with spectrophotometric and enzymatic method among 71 KD patients and 290 controls (including 78 internal controls and 212 external controls). The genotype of GPx-1 at 198 site was analyzed by sequencing and PCR-RFLP. The functions of two GPx-1 variants were studied by rat neonatal cardiomyocytes transfection and expression plasmid.
Results: Blood level of selenium in KD patients was (0.8 ± 0.2) µmol/L, the internal controls' was (0.9 ± 0.2) µmol/L, and the external controls' was (1.2 ± 0.2) µmol/L (F = 4.888, P < 0.001).GPx-1 activity of KD patients was (73.0 ± 12.6) × 10(-10)U/RBC, internal controls' was (80.9 ± 9.2) × 10(-10)U/RBC, and external controls' was (115.8 ± 21.1) × 10(-10)U/RBC (F = 5.324, P < 0.001). Those of KD patients were significantly lower than controls. The polymorphism (Pro198Leu) of GPx-1 were identified; the frequency of Pro198Leu of KD patients was 21.1%, the frequency of controls was 10.7% (χ(2) = 5.588, P = 0.018). The level of blood selenium in variant subgroup (Pro198Leu or Leu198Leu) was (0.9 ± 0.2) µmol/L, and its in non-variant subgroup was (1.1 ± 0.3) µmol/L (t = 3.183, P < 0.01); The GPx-1 activity in variant subgroup was (86.1 ± 23.0) × 10(-10)U/RBC, and its in non-variant subgroup was (101.8 ± 25.9) × 10(-10)U/RBC (t = 5.784, P < 0.01). Further analysis revealed a synergistic-multiplicative interaction between presence of GPx-1 codon198 alleles and low blood selenium level. Over-expression of GPx-1 (198Leu) in rat cardiomyocytes caused 30% lower enzyme activity and less response to increasing concentrations of selenium than with over-expression of GPx-1 (198Pro).
Conclusion: Low blood selenium in carriers with the 198Leu-susceptible genotype of GPx-1 is associated with low GPx-1 activity, synergistic-multiplicative interaction was found between these two factors. And these two factors may increase the risk of KD.