Fig. 1.

Acute administration of human recombinant GDF15 activates the HPA axis in mice. (A and B) Mouse study 1 (MS1) at standard housing condition: acute effect of human recombinant GDF15 administration on (A) endogenous corticosterone and (B) human GDF15 plasma concentration at 1 h and 4 h post-GDF15 treatment. (C and D) MS2 at thermoneutral housing condition: acute effect of two doses of human recombinant GDF15 on (C) plasma corticosterone and (D) human GDF15 concentrations after 1-h treatment (0.03 and 0.1 mg/kg). (E and F) MS3: (E) Corticosterone serum level in anti-GFRAL- and IgG control-treated mice with or without human recombinant GDF15 administration. (F) Human GDF15 serum concentration in GFRAL blocking antibody (anti-GRFAL) and IgG groups treated with human recombinant GDF15. (G and H) MS4: (G) In situ hybridization analysis of Crh mRNA (red), c-Fos mRNA (blue-green), and hematoxylin counterstain for nuclei at the level of the PVN. Left, representative images of coronal sections of vehicle (Upper Left) and GDF15-treated mice (Lower Left). (Scale bar, 50 μm.) 3V, third ventricle. Middle, higher magnification of the PVN showing coexpression of Crh and c-Fos dots in vehicle (Upper Middle) and GDF15 treated (Lower Middle). (Scale bar, 100 μm.) Right, automated quantification of Crh- and c-Fos-positive cells in vehicle (Upper Right) and GDF15-treated mice (Lower Right) (Scale bar, 100 μm.) Black arrows indicate double-labeled cells. Cell nucleus color in the overlay (Right) represents the cell classification (muted red for Crh-positive cells, bright red for dual-positive cells), while nucleus color intensity correlates with spot counts per cell. Bright blue spots represent c-Fos spot assigned to a Crh-positive cell. (H) Percentage of Crh-positive cells that were also c-Fos positive. Data are expressed as mean ± SEM, n = 6 to 8 per group. *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001, for MS1, -2, and -3, data were analyzed by ANOVA and for MS4, by unpaired Student’s t test.