Longitudinal variation of serum PCSK9 in ulcerative colitis: association with disease activity, T helper 1/2/17 cells, and clinical response of tumor necrosis factor inhibitor.

Aims: Proprotein convertase subtilisin/kexin type 9 (PCSK9) modulates CD4 T cell differentiation and inflammatory response, the latter ones mediate ulcerative colitis (UC) initiation. This study intended to explore the correlation of serum PCSK9 with disease activity, T helper (h)1/Th2/Th17 cells, and clinical response of tumor necrosis factor inhibitor (TNFi) in UC patients.

Methods: In 65 UC patients underwent TNFi treatment, serum PCSK9 was evaluated at baseline (W0), week (W)2, W6, and W12 by enzyme-linked immunosorbent assays; meanwhile, Th1/Th2/Th17 cells were determined at W0 by flow cytometry. Besides, serum PCSK9 was detected in 65 healthy controls (HCs).

Results: Serum PCSK9 was increased in UC patients compared to HCs (P<0.001), which also positively correlated with C-reactive protein (P=0.009), total Mayo score (P=0.018), Mayo-defined disease activity (P=0.020), Th1 (P=0.033), and Th17 (P=0.003) cells, but not Th2 cells (P=0.086) in UC patients. Interestingly, serum PCSK9 was steadily declined from W0 to W12 (P<0.001). W2-W0, W6-W0, and W12-W0 serum PCSK9 change (PCSK9 at W2, W6, or W12 minus PCSK9 at W0, respectively) was gradually becoming greater during TNFi treatment (P<0.001). Furthermore, forty-five (69.2%) patients achieved clinical response at W12, whose serum PCSK9 at W6 (P=0.041) and W12 (P=0.001) was lower, and W6-W0 (P=0.043), W12-W0 (P=0.019) serum PCSK9 change was more obvious compared to patients without clinical response at W12.

Conclusions: Serum PCSK9 is positively related to disease activity, Th1, and Th17 cells in UC patients; further, its decline correlates with TNFi response achievement in these patients.