IGF2 and Huntington disease: IDO1 levels were significantly decreased (Fig. 1C, MD = 0.285, 95% CI: 0.036–0.533, *P = 0.020), whereas IGF2 (Fig. 1D, MD = −0.274, 95% CI: −0.497 to −0.050, *P = 0.012), IGHG1 (Fig. 1E, MD = −0.344, 95% CI: −0.592 to −0.097, **P = 0.004) and NEFL (Fig. 1F, MD = −0.848, 95% CI: −1.368 to −0.327, **P = 0.002) were significantly increased in late HD compared with control individuals.