Abstract: Objective: Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a serine protease that regulates cholesterol metabolism and has been linked to cardiovascular (CV) risk. The purpose of the present study was to examine whether PCSK9 levels are related to abnormalities in the lipid profile and the development of atherosclerosis that occurs in patients with axial SpA (axSpA). Methods: We performed a cross-sectional study that encompassed 545 individuals; 299 patients with axSpA and 246 statin use-matched controls. PCSK9 and standard lipid profiles were analysed in patients and controls. Carotid intima-media thickness (cIMT) and carotid plaques were assessed in patients. A multivariable analysis, adjusted for standard CV risk factors, was performed to evaluate the influence of PCSK9 on axSpA-related dyslipidaemia and subclinical carotid atherosclerosis. Results: Total cholesterol, high-density lipoprotein and low density lipoprotein cholesterol, lipoprotein (a) and apolipoprotein A1 were significantly lower in axSpA patients than controls. PCSK9 serum levels [? coefficient -44 ng/dl (95% CI -60, -27), P = 0.000] were also downregulated in axSpA patients after fully multivariable adjustment. ASDAS-CRP was found to be independently and significantly related to PCSK9 [? coefficient 10 ng/dl (95% CI 1, 18), P = 0.023] after analysing fully adjusted models that took age, sex and the rest of the lipid profile molecules into account. Whereas patients taking prednisone showed higher serum levels of PCSK9 [55 ng/ml (95% CI 24, 8), P = 0.001], those under anti-TNF-? therapies exhibited lower levels [? coefficient -26 ng/ml (95% CI -43, -9], P = 0.003]. Conclusion: PCSK9 is downregulated in patients with axSpA. Disease activity is positive and significantly related to PSCK9. Anti-TNF-therapy yields a reduction in PCSK9 serum levels.

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