Histomorphometric parameters were measured on the trabecular bone of the metaphysis, on a region of interest consisting of 2 mm width below the growth plate. Measurements were performed find more using an image analysis software (Tablet’measure; GS-9973 in vivo Explora Nova, La Rochelle, France). Histomorphometric parameters were reported in accordance with the ASBMR Committee

nomenclature [28]. Protein extraction and western blot analysis For the isolation of total proteins, right femora from 5-month-old female C57BL/6-129Sv mice were carefully dissected and all their surrounding musculature removed leaving the periosteum intact. We also dissected femora from wild-type C57BL/6 mice that were injected with metformin at 100 mg/kg/daily only for 3 days. The cartilaginous ends of the bones were separated and the remaining femoral shafts were flushed with PBS to remove the marrow. The femoral shafts were then snap-frozen and pulverised under liquid nitrogen using a mortar and pestle, and then lysed in cold denaturing lysis buffer (2 % SDS, 2 M urea, 8 % sucrose, 20 mM sodium glycerophosphate, 1 mM sodium fluoride and 5 mM sodium orthovanadate). Proteins were denatured by boiling for 10 min and concentrations determined by BCA protein assay. Twenty micrograms of proteins was size-fractionated using SDS–PAGE and electrotransferred onto Protran nitrocellulose

membranes (Schliecher and Schuell, GF120918 Dassel, Germany). Membranes were blocked for 1 h in 0.2 % (w/v) I-block (Topix, Bedford, MA, USA) before being incubated with many primary antibodies. The blots were incubated overnight at 4 °C with antibodies against total AMPKα1/2 (tAMPK α1/2, rabbit), phospho-(Thr-172)-AMPKα1/2

(pAMPKα1/2, rabbit) (New England Biolabs, Hitchin, UK) and β-actin (goat) (Dako, Ely, UK), all added at a 1:1,000 dilution. The following secondary antibodies were used, goat anti-rabbit (New England Biolabs) against tAMPK and pAMPK1α1/2 and rabbit anti-goat (Dako) against β-actin antibody, both at 1:2,500 dilution at room temperature for 1 h. Proteins were visualised using the enhanced chemiluminescence detection system (ECL) (GE Healthcare UK Ltd, Little Chalfont, UK). The intensity of the specific bands was quantified by densitometry using Image J software. RNA extraction and quantitative real-time PCR Total RNA was isolated from left whole femora after removal of the bone marrow, as previously described [7]. RNA from three femora in each treatment group was pooled and two separate extractions were performed. Total RNA was reverse-transcribed with Superscript II reverse transcriptase. Real-time QPCR was carried out as described earlier [29] using QuantiTect SYBR green PCR kit and Opticon 2 LightCycler (MJ Research, Waltham, MA, USA). Primer sequences were obtained from Qiagen and are summarised in Table 1. The expression levels for Osterix and Runx2 were normalised to the reference gene 18s rRNA.