GDNF and type 1 diabetes mellitus: For somatic symptoms, five positive associations (CDCP1, FGF-5, MMP-10, TNFRSF9, TRAIL) and one negative association (TNFβ) were observed in people with T1D, while four biomarkers (FGF-19, FGF-21, GDNF, LIF-R) showed positive associations in people with T2D.