Peripheral GDF15 as an early biomarker for brain disorders: A large prospective cohort study.
BACKGROUND Growth differentiation factor 15 (GDF15) is a stress-responsive cytokine involved in metabolic and inflammatory pathways. We examined the associations of plasma GDF15 with incident brain disorders and explored potential mediating pathways and causality. METHODS UK Biobank participants were followed for a median of 14 years. Plasma GDF15 was measured at baseline. Cox proportional hazards models assessed associations with incident brain disorders, including all-cause dementia (ACD), Alzheimer's disease (AD), Parkinson's disease (PD), anxiety, depression, sleep disorders, stroke, and epilepsy. Mediation analyses evaluated biochemical and hematological pathways, and one-sample Mendelian randomization (MR) was used to assess potential causal effects. RESULTS Higher GDF15 levels were associated with increased risks of overall brain disorders and all examined subtypes. In continuous analyses (per 1-unit increase in log2-transformed GDF15), hazard ratios (95% CIs) were 1.54 (1.48-1.60) for overall brain disorders, 1.98 (1.80-2.17) for ACD, 1.84 (1.60-2.10) for AD, 1.37 (1.18-1.59) for PD, 1.26 (1.16-1.37) for anxiety, 1.38 (1.29-1.49) for depression, 1.40 (1.26-1.55) for sleep disorders, 1.92 (1.81-2.05) for stroke, and 1.71 (1.46-2.01) for epilepsy (all P < 0.001). Lipid- and inflammation-related markers appeared to partially mediate these associations. High-density lipoprotein cholesterol (HDL-C) accounted for an estimated 7.51% of the association with depression and 11.47% with sleep disorders, while neutrophil count showed relatively larger mediation estimates across multiple outcomes. MR analyses did not support a direct causal effect of GDF15. CONCLUSION Plasma GDF15 is associated with a broad range of incident brain disorders and may act partly through lipid- and inflammation-related pathways, particularly HDL-C and neutrophil count.