Enhanced hepatic production of fibroblast growth factor 21 (FGF21) in ETB-deficient mice fed a high-fat diet. (A) Fibroblast growth factor 21 (FGF21) mRNA expression, normalized to TATA-box binding protein (TBP) in HepG2 cells treated with vehicle control (ctr) or 10 nM 3,3′,5-triiodo-l-thyronine sodium salt (T3) for 24 h (n = 6). (B) Hepatic fibroblast growth factor 21 (Fgf21) mRNA expression (n = 12 per group), normalized to the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (Gapdh) in wild type mice (etb+/+) and etb−/− mice after 12 weeks of feeding a high-fat diet (HFD). (C) Representative original Western blot (left panel) and densitometric analysis (right panel) of hepatic Fgf21 protein abundance, normalized to loading control Gapdh (n = 4–5 per group) from etb+/+ and etb−/− mice fed a HFD for 12 weeks. (D) Serum concentration of FGF21 (n = 16 per group) in etb+/+ and etb−/− mice after feeding a HFD for 12 weeks. All data are expressed as arithmetic means ± SEM. ∗p < 0.05, ∗∗p < 0.01 and ∗∗∗p < 0.001 indicate a significant difference from control-treated cells or wild type mice, respectively. (A: one-sample t test; B: two-tailed unpaired Student's t test with Welch's correction; C: two-tailed unpaired Student's t test; D: Mann–Whitney U test) arbitrary units, a.u.