Soluble interleukin‐6 receptor in young adults and its relationship with body composition and autonomic nervous system

BACKGROUND: The immune system generates inflammatory responses through cytokines like Interleukin 6 (IL‐6) and the Tumor Necrosis Factor alpha (TNF α); these cytokines mediate cellular responses aided by the presence of soluble receptors such as: Soluble Interleukin 6 Receptor (sIL6R) and Soluble Tumor Necrosis Factor Receptors Type 1 and 2 (sTNFR1, sTNFR2); the literature is limited about the relationship between this cytokines and the role of its soluble receptors. OBJECTIVES: This study is to determine a possible relationship between specific inflammatory markers and their soluble receptors with the autonomic nervous system's activity and body composition. METHODS: 27 subjects (13 men of 19.3 ± 1.6 years old and 14 women of 19.1 ± 1.7 years old) were evaluated. Body composition, autonomic nervous system activity and plasma concentration of inflammatory markers IL‐6, TNF α, sIL6R, sTNFR1 and sTNFR2 were measured using bio‐impedance, heart rate variability and ELISA respectively. RESULTS: A positive association between body‐fat percentage and the sIL6R (0.47, p = .013) as well as inverse relationship between muscular mass and the sIL6R (−0.45, p = .019) were found. The sIL6R was also positively correlated with sympathetic activity markers: Relation LF/HF (0.52, p = .006), cardiac sympathetic index (0.45, p = .008), and cardiac vagal index (−0.44, p = .022). CONCLUSION: This study suggested that the IL‐6 trans‐signaling involving both the soluble receptor, sIL6R, and gp130 membrane co‐receptor could produce inflammatory responses that generate an impact on the autonomic nervous system, possibly due to its direct action on the hypothalamus, the solitary tract nucleus, or the heart.