Association between serum melatonin level and chronic low-grade inflammation and the mediating role of metabolic indicators

Objective  To explore the association between serum melatonin (MT) level and chronic low-grade inflammation in the general population, as well as the mediating role of metabolic indicators and the impact of disease status.

Methods  This study is a cross-sectional study, with a total of 5, 504 healthy examinees enrolled. The restrictive cubic spline method and linear regression models were used to analyze nonlinear or linear relationships between MT and the scaled low-grade inflammation (sINFLA) score, and mediation analysis and disease stratification analysis were further conducted to identify the influencing factors that regulate the relationship between them.

Results  An inverted U-shaped relationship was found between MT and the sINFLA score. Below the threshold, MT was positive associated with the sINFLA score (β=0.53, 95% CI: 0.24-0.83); above the threshold, it showed a negative association (β=-0.43, 95% CI: -0.85 - -0.01). Fasting blood glucose (FBG) served as a mediator in this association, with a mediation proportion of -9.93%. Hypercholesterolemia significantly modified this association (P-interaction=0.022).

Conclusion  In the general population, an inverted U-shaped association exists between serum MT level and chronic low-grade inflammation, with FBG serving as a mediator, and hypercholesterolemia modifies this relationship.