Dose-Dependent Impact of Metformin on Osteoblast-Specific Biomarkers in Cultured Rat Primary Osteoblasts

The objective of this in vitro study was to examine the impact of metformin (MET) at different concentrations (0.1, 1, 10, 50, and 100 mM) on rat primary osteoblasts, as the results obtained so far are inconsistent. Osteoblast apoptosis, viability, alkaline phosphatase (ALPL) activity, production of osteoblast-specific biomarkers, including ALPL, osteocalcin (BGLAP), type I collagen alpha 1 (COL1A1), integrin-binding sialoprotein (IBSP), bone morphogenetic protein 2 (BMP2), runt-related transcription factor 2 (RUNX2), vascular endothelial growth factor (VEGF), tumor necrosis factor ligand superfamily member 11 (TNFSF11 or RANKL), as well as calcium/collagen deposition were assessed. Our results revealed that a dose of 100 mM was cytotoxic to osteoblasts and resulted in a complete loss of their viability. Therefore, this concentration was excluded from further analyses. In general, MET exhibited a dose-dependent impact on multiple osteoblast-specific functional biomarkers, with beneficial effects noted on ALPL activity (at 0.1 and 1 mM) as well as on the levels of ALPL (0.1 and 1 mM), BGLAP (at 0.1-50 mM), IBSP (at 0.1-50 mM), BMP2 (at 0.1, 10 and 50 mM), VEGF (at 0.1 and 1 mM), and RANKL (at 0.1 mM). Calcium/collagen deposition at concentrations of 0.1 and 1 mM reached the same level as control cells, higher doses (10 and 50 mM) dramatically reduced cell viability after 21 days and the aforementioned parameters could not be evaluated. It can be concluded that MET at concentrations up to 1 mM can promote osteoblast viability, osteogenic differentiation, angiogenic signaling, and reduce osteoclastogenesis. Key words Metformin " Osteoblasts " Bone health " In vitro.