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

Abstract

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.