Differential Protein Expression in Serum of Abdominal Aortic Aneurysm Patients – A Proteomic Approach

Objective: The aim of the study is to investigate the differential expression of proteins in serum of abdominal aortic aneurysm (AAA) patients in relation to aneurysm size (Dmax) and progression. Methods: Two-dimensional differential in-gel electrophoresis (2D-DIGE) together with tandem mass spectrometry (MS/MS) was used to analyse the serum proteome from patients with small (Dmax 30e54 mm) AAA, either stable (increase Dmax < 5m m year � 1 ; n Z 8) or progressive (increase Dmax �5 mm year � 1 ; n Z 8), and large (Dmax �55 mm; n Z 8) AAA. The identified proteins were quantitatively validated in a larger population (n Z 80). Results: Several proteins were differentially expressed in serum of small stable, small progres- sive and large AAA. Three validated proteins (immunoglobulin G (IgG), a1-antitrypsin (a1-AT) and Factor XII activity) showed strong correlation with Dmax. Size combined with either Factor XII activity or a1-antitrypsin had minimal effect on the prognostic value in predicting aneurysm progression compared with size alone (area under the curve (AUC), 0.85; 95% confidence interval (CI), 0.73e0.97; p < 0.001 and AUC, 0.85; 95% CI, 0.72e0.98; p < 0.001 vs. AUC, 0.83; 95% CI, 0.71e0.96; p < 0.001, respectively). Conclusion: The present study indicates that both Factor XII and a1-antitrypsin are found in increased amounts in the serum of patients with expanding AAA. However, combination of either Factor XII or a1-antitrypsin with aneurysm diameter had little effect on prediction of aneurysm progression versus diameter alone.