Do vitamin C and zinc support antioxidant defenses, while GSTP1 rs1695 AG increases oxidative stress vulnerability?

Cellular antioxidant defense relies on a coordinated network of dietary cofactors and endogenous enzymes to neutralize reactive oxygen species and prevent systemic damage.

Mechanistic pathways of defense and vulnerability

• Nutrient synergy: Vitamin C acts as a direct, water-soluble scavenger that regenerates vitamin E, while zinc serves as an essential cofactor for copper/zinc-superoxide dismutase (Cu/Zn-SOD) and upregulates glutamate-cysteine ligase to support glutathione (GSH) synthesis.
• Enzymatic alteration: The GSTP1 rs1695 (Ile105Val) polymorphism alters the hydrophobic substrate-binding site of glutathione S-transferase. The Val105 variant is two to three times less thermally stable than the wild-type enzyme.
• Oxidative vulnerability: In individuals with the heterozygous AG genotype, this structural alteration results in an intermediate phenotype with 15% to 20% lower conjugation activity than the AA genotype. This reduces the detoxification of lipid-derived electrophiles, leading to the rapid accumulation of lipid hydroperoxides under oxidative stress.

Clinical and physiological implications

• Biomarker modulation: Supplementation with vitamin C and zinc directly reduces malondialdehyde (MDA)—a key biomarker of lipid peroxidation—while restoring systemic SOD activity.
• Defensive compensation: Because the GSTP1 rs1695 AG variant compromises endogenous glutathione-based detoxification, robust nutrient support is highly relevant to offset genetically elevated oxidative stress vulnerability.

Bottom line

• Bottom line: The GSTP1 rs1695 AG variant reduces glutathione S-transferase conjugation efficiency by 15% to 20%, increasing vulnerability to lipid peroxidation. Supplementation with vitamin C and zinc directly mitigates this risk by reinforcing non-enzymatic scavenging and supporting enzymatic superoxide dismutase defenses.