Fig. 5. METRNL alleviates inflammation and insulin resistance through a PPARδ-mediated pathway.

a Western blot analysis of PPARδ expression in differentiated C2C12 cells treated with METRNL (0–200 ng/mL) for 24 h. b Confirmation of PPARδ siRNA efficiency in differentiated C2C12 cells. Western blot analysis of palmitate (200 μM)-induced inflammation markers in PPARα siRNA (20 nM)-transfected differentiated C2C12 cells treated with METRNL (0–200 ng/mL) for 24 h. c Western blot analysis of the palmitate-induced impairment of IRS-1 and Akt phosphorylation in PPARδ siRNA-transfected differentiated C2C12 cells treated with METRNL (0–200 ng/mL) for 24 h. Human insulin (10 nM) was used to stimulate insulin signaling for 3 min. d Western blot analysis of PPARδ expression in soleus muscle of mice treated with HFD and METRNL (5 animals/treatment group). e Western blot analysis of METRNL (200 ng/mL)-induced PGC1α expression in PPARδ siRNA (20 nM)-transfected differentiated C2C12 cells for 24 h. Western blot analysis of f AMPK phosphorylation in PPARδ siRNA or g PPARδ expression in AMPK siRNA-transfected differentiated C2C12 cells treated with METRNL (200 ng/mL) for 24 h. Confirmation of PPARδ siRNA efficiency in skeletal muscle of mice. Western blot analysis of IRS-1 and Akt phosphorylation (h), and inflammatory markers (i) in PPARδ siRNA-transfected skeletal muscle of experimental mice. j Western blot analysis of PPARδ expression in AMPK siRNA-transfected skeletal muscle of experimental mice. k Western blot analysis of AMPK phosphorylation in PPARδ siRNA-transfected skeletal muscle of experimental mice. Means ± SEM were obtained from three separate experiments or five animals. ^***P < 0.001 and ^**P < 0.01 compared to control or ND treatment. ^!!!P < 0.001, ^!!P < 0.01, and ^!P < 0.05 compared to palmitate, HFD or METRNL treatment. ^###P < 0.001, ^##P < 0.01, and ^#P < 0.05 compared to palmitate plus METRNL treatment