IL-6 as an integrative biomarker of residual inflammation and visceral adiposity in psoriasis: a VAI threshold-dependent model.

Introduction: Psoriasis patients are frequently exposed to residual inflammation and visceral obesity, two factors that synergistically increase cardiometabolic risk. Methods: We evaluated IL-6 as a potential integrative biomarker linking these pathways in a cross-sectional study including 80 patients with well-controlled skin disease and 20 matched healthy controls. Serum IL-6 was measured by ELISA, and visceral adiposity estimated using the Visceral Adiposity Index (VAI). Results: Psoriasis patients displayed significantly higher IL-6 than controls (38.1 pg/mL [35.5-41.3] vs. 21.4 pg/mL [19.5-33.4]; p<0.001). A distinct VAI threshold of 1.3 was identified, above which IL-6 levels rose steeply until VAI 2.2 and then plateaued. Patients with VAI ≥1.3 had markedly higher IL-6 and pro-inflammatory cytokines than those below this cutoff. Random forest regression confirmed IFN-γ, IL-1β, IL-12p70, and IL-17 as dominant predictors of IL-6, while HbA1c, FIB-4, and treatment contributed minimally. Discussion: These findings suggest that IL-6 elevation in psoriasis primarily reflects cytokine-driven residual inflammation, with non-linear amplification once visceral adiposity exceeds a critical threshold. The threshold-dependent IL-6 dynamic highlights a clinically meaningful inflection point, integrating residual inflammation and visceral fat dysfunction, and may guide early cardiometabolic risk stratification and intervention. Prospective validation is warranted.