Vitamin D Deficiency Is Associated with an Integrated Inflammatory-Adiposity Network Linked to Cardiovascular Disease: A Community-Based Study

Vitamin D deficiency (VDD) is highly prevalent worldwide and has been associated with chronic inflammatory and cardiovascular diseases (CVD). However, its relationship with coordinated inflammatory and cardiometabolic networks remains unclear. We studied 1075 participants classified as VDD (25(OH)D < 25 nmol/L; n = 304) or in the ≥25 nmol/L group (n = 771) based on circulating 25(OH)D levels. Body composition and plasma levels of IL-17, IL-34, activin A, follistatin, and FSTL1 were assessed; the follistatin/FSTL1 ratio (FOFS) and C-reactive protein–triglyceride–glucose index (CTI) were calculated. Detectable IL-17 and IL-34 concentrations were available for 195 and 247 participants, respectively. VDD participants exhibited higher levels of inflammatory biomarkers and a higher prevalence of hypertension (HTN), hyperlipidemia (HLD), and CVD. Multivariable analysis revealed a particularly strong independent association between IL-17 and VDD (OR = 8.36, 95% CI: 3.72–18.80). Structural equation modeling (SEM) supported an interconnected inflammatory–cardiometabolic association network, characterized by a strong association between VDD and IL-17 (β = 0.689) and significant interrelationships among IL-17, IL-34, FOFS, CTI, and cardiometabolic comorbidities. These findings identify IL-17 as a prominent inflammatory correlate of VDD and suggest that FOFS may represent a link between inflammatory activation and cardiometabolic morbidity associated with VDD.