Fig. 4

AMPK activation is involved in the protective effect of metformin against IL-1β-driven catabolism in chondrocytes. Mice articular chondrocytes (n = 3) were cultured in the absence of IL-1β, with or without 10 mM metformin, dorsomorphin, or dimethyl sulfoxide (DMSO), vehicle of dorsomorphin. Protein levels of pAMPKα and AMPKα1 (a) were detected by western blot. The transcription of mmp13 (b) was determined by qRT-PCR. Protein levels of MMP13 (c) and type II collagen (e) were detected by western blot. The quantitation of protein expression of MMP13 (d) and type II collagen (f) was done by densitometry analysis of the protein bands. Values were normalized against tubulin or GAPDH. Data were expressed as the mean ± 95% confidence intervals. *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001; statistical significance was calculated using one-way ANOVA with Tukey’s post hoc test. pAMPKα, phosphorylated alpha subunit of adenosine monophosphate-activated protein kinase; AMPKα1, alpha1 subunit of adenosine monophosphate-activated protein kinase; MMP13, matrix metalloproteinase 13; dimethylsulfoxide; GAPDH, glyceraldehyde-phosphate dehydrogenase