Fig. 3: Circulating GP73 traffics to the liver to stimulate gluconeogenesis.
From: GP73 is a glucogenic hormone contributing to SARS-CoV-2-induced hyperglycemia
a, In vivo imaging of various organs from two mice 30 min after rmGP73-Cy7 or free Cy7 injection. Two representative images from four mice are shown. b, The level of biotin on the hepatocyte surface upon incubation of HepG2 cells with increasing concentrations of rhGP73-biotin. Specific binding (shown in red) was calculated as the difference between the two curves. c, Glucose production in PMHs treated with rmGP73 at the indicated concentrations for 2 h. P < 0.0001 for 4 nM versus 0 nM, 8 nM versus 0 nM, 16 nM versus 0 nM, 32 nM versus 0 nM and 64 nM versus 0 nM by one-way ANOVA followed by Bonferroni’s post hoc test. d, Glucose production in PMHs treated with 32 nM rmGP73 or glucagon in the presence of cAMPS-Rp (20 μM), H89 (20 μM), LY2409021 (2.5 μM), or insulin (10 μM) for 2 h. P = 0.0070 for rmGP73 + insulin versus rmGP73, P = 0.0062 for rmGP73 + LY2409021 versus rmGP73, P = 0.0004 for glucagon + insulin versus glucagon, P < 0.0001 for rmGP73 + H89 versus rmGP73, rmGP73 + cAMPS-Rp versus rmGP73, glucagon + insulin versus glucagon, glucagon + LY2409021 versus glucagon, glucagon + H89 versus glucagon and glucagon + cAMPS-Rp versus glucagon by one-way ANOVA followed by Bonferroni’s post hoc test. e, Gluconeogenesis gene expression in PMHs treated with 32 nM rmGP73 for 2 h. P = 0.0051 for rmGP73 versus PBS (Pcx), P < 0.0001 for rmGP73 versus PBS (Pck1 and G6pc) by two-tailed Student’s t-tests. f, Immunoblotting analysis of phosphorylated PKA-C subunit (PKA-C-α-p) levels and substrate (phosphoRRXT*T*-PKA substrate, RRXpS/T) levels in HepG2 cells treated with 32 nM rmGP73 or 10 μM IBMX for the indicated times. DMSO, dimethylsulfoxide. g, Glucose production in PMHs isolated from WT or KO mice treated with or without rmGP73 (32 nM) for 4 h. P = 0.0090 for KO versus WT, P < 0.0001 for KO + rmGP73 versus KO by one-way ANOVA followed by Bonferroni’s post hoc test. h–j, Basal and clamp HGP (h), glucose disposal rate (GDR) (i) and insulin levels (j) in GP73 KO mice infused with GFP or recombinant GP73 during the clamp study. P = 0.0194 for rmGP73 versus GFP (basal), P = 0.0026 for rmGP73 versus GFP (clamp) (h), P = 0.0047 for rmGP73 versus GFP (i) and P = 0.8818 for rmGP73 versus GFP (j) by two-tailed Student’s t-tests. Animal and cell-based studies were performed independently at least three biological replicates with comparable results. Data are mean ± s.e.m. NS, not significant; *P < 0.05; **P < 0.01; ***P < 0.001.
