A Genotype–Phenotype Analysis of Glutathione Peroxidase 4 in Human Atrial Myocardium and Its Association with Postoperative Atrial Fibrillation

Figure 1. Overall study flow and design. Right atrial appendage samples were collected intra-operatively from patients undergoing non-emergent CABG. Salt ethanol method was used extract DNA from these samples. The genomic region encoding GPX4 was sequenced using Ion AmpliSeq (ThermoFisher) according to methods described in Methods section. GPx4 enzyme content and activity were measured as described in the Methods section. CABG: coronary artery bypass graft.

Figure 2. Relationship between GPx4 enzyme content and activity in human atrial myocardium. GPx4 enzyme activity (μmol·min−1·g−1 total protein) and total GPx4 enzyme (mg) were measured in fresh lysates prepared from samples of human atrial myocardium using protocols described in Methods section. Both enzyme activity and enzyme concentration values shown here are normalized against the total tissue protein (g). Each symbol corresponds to one individual patient (N = 189 patients). Statistical significance was calculated using simple linear regression, with dashed lines showing 95% confidence intervals.

Figure 3. GPX4 variants associated with decreased GPx4 enzyme content but increased activity in human atrial myocardium. Five distinct polymorphisms associated with decreased tissue levels of GPx4 enzyme (A) but increased GPx4 activity (B) are shown in the panels above. Each open circle represents one patient, open bars = Homozygous for the Referent nucleotide, hatched bars = Heterozygous for the variant nucleotide (i.e., one allele), filled bars = Homozygous for the variant nucleotide. **** p < 0.0001, *** p < 0.001, ** p < 0.01, * p < 0.05 for main effect between genotypes indicated.

Figure 4. GPX4 variants associated with increased GPx4 enzyme content but decreased activity in human atrial myocardium. Two distinct polymorphisms associated with increased tissue levels of GPx4 protein (A) but decreased GPx4 activity (B) are shown in the panels above. Each open circle represents one patient, open bars = Homozygous for the Referent nucleotide, hatched bars = Heterozygous for the variant nucleotide (i.e., one allele), filled bars = Homozygous for the variant nucleotide. **** p < 0.0001, *** p < 0.001, ** p < 0.01 for main effect between genotypes indicated.