FIGURE 4.

CTRP3 acts directly on liver cells, independent of insulin, to suppress gluconeogenic gene expression and glucose production. Gluconeogenesis was reduced in rat H4IIE hepatoma cells treated with recombinant CTRP3 (n = 6) for 16 h (A); this effect was independent of insulin concentration (n = 6) (B). Recombinant CTRP3 suppressed the expression of gluconeogenic genes PEPCK and G6Pase in hepatoma cells (n = 6) (C). Additionally, CTRP3 treatment increased Akt (D) and GSK3-β (E) phosphorylation but not AMPKα (F) in hepatoma cells. Treatment with recombinant CTRP3 in the absence or presence of insulin (10 nm) resulted in no change in glucose uptake in 3T3-L1 adipocytes (G) and rat L6 myotubes (H). In all experiments, cells were treated with 5 μg/ml recombinant CTRP3. All in vitro signaling experiments have been repeated at least twice, and comparable results were obtained. Each bar represents the mean ± S.E. (error bars). *, p < 0.05.