Fig 2: Chronic anti-diabetic effect of BR103354 in ob/ob mice. Male ob/ob mice were treated with vehicle or BR103354 (20 and 50 mg/kg) for 4 weeks (n = 13/group). (a) Nonfasting blood glucose levels in ob/ob mice. (b) Plasma FAP activity was measured by fluorometric assay using AMC substrate at week 4. (c) Serum mouse FGF21 levels at week 4 (d) OGTT and AUC in ob/ob mice. (e) Fasting body weight, liver weight and epididymal fat weight from ob/ob mice. (f) Fasting blood glucose, insulin concentrations and HOMA-IR in ob/ob mice. (g) The plasma levels of ALT (GPT), AST (GOT), TG, total cholesterol and NEFA in ob/ob mice. (h) Oil red O staining of the liver from ob/ob mice (Scale bar = 50 µm). (i) Relative expression of genes related to intrahepatic lipogenic gene (GCK), fatty acid and TG synthesis genes (FASN, SREBP and APOC3, LIPIN1), β-oxidation genes (CPT1α, MCAD and PPARα) and FGF21 related genes (ATF4, CHOP, FGF21 and β-klotho) in liver and FGF21 related genes (AdipoQ and β-klotho) in white adipose tissue of ob/ob mice. (j) Immunoblots of p-ERK/ERK of epididymal white adipose tissue lysates from ob/ob mice. The graph shows densitometric quantification of western blot bands. All data are the means ± S.D. *P < 0.05, **P < 0.01 and ***P < 0.001 vs. vehicle group.

Fig 3: Modulation of Nprc expression by rosiglitazone and PPARγ.A, mRNA levels of Nprc and Fabp4 in 3T3-L1 adipocytes after treatment with 1 μM rosiglitazone (Rosi) or vehicle (Veh) for 6 h. B, mRNA levels of Nprc, Fabp4, and Pparγ1/2 mRNA in 3T3-L1 adipocytes after siRNA knockdown of Pparγ (siPparγ). C, protein levels of PPARγ1/2, NPRC, FABP4, and ADIPOQ in 3T3-L1 adipocytes after siPparγ. D, mRNA levels of Nprc and Fabp4 in NIH-3T3 cells (NIH) and NIH-3T3 cells stably expressing PPARγ (NIH-PPARγ) after treatment with 1 μM rosiglitazone (Rosi) or vehicle (Veh) for 6 h. Quantitative PCR data were normalized with 36B4. Student's t test, ∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001, and ∗∗∗∗p < 0.0001. Fabp4, fatty acid–binding protein 4; NIH, National Institutes of Health; Nprc, NP receptor C; ns, not significant; PPARγ, peroxisome proliferator–activated receptor gamma.

Fig 4: The effect of SPATA4 on ERK signaling and adipocyte differentiation in adipose tissue. (a) The phosphorylation of ERK1/2 and C/EBPβ was measured in subcutaneous white adipose tissue (sWAT) and epidydimal white adipose tissue (eWAT). Representative blots are shown. N = 4, **p < 0.01. qPCR was used to determine the expression of Adipoq, Fabp4 and Fasn in sWAT and eWAT from male (b) and female (c) mice. N = 4–6, *p < 0.05, **p < 0.01, ***p < 0.001

Fig 5: Nprc mRNA expression during 3T3-L1 adipocyte differentiation.A–C, mRNA levels of Nprc (A), Fabp4 (B), and Pparγ1/2 (C) during 3T3-L1 adipocyte differentiation. Data were normalized with 36B4. D, protein levels of NPRC, FABP4, PPARγ1/2, and ADIPOQ during 3T3-L1 adipocyte differentiation (Day 0, 2, 4, and 6). FABP4, fatty acid–binding protein 4; Nprc, NP receptor C; PPARγ1/2, peroxisome proliferator–activated receptor gamma1/2.