Impact of hyperglycemia and treatment with metformin on ligature-induced bone loss, bone repair and expression of bone metabolism transcription factors.

This study evaluated the influence of type 2 diabetes mellitus on bone loss, bone repair and cytokine production in hyperglycemic rats, treated or not with metformin. The animals were distributed as follow: Non-Hyperglycemic (NH), Non Hyperglycemic with Ligature (NH-L), Treated Non Hyperglycemic (TNH), Treated Non Hyperglycemic with Ligature Treated (TNH-L), Hyperglycemic (H), Treated Hyperglycemic (TH), Hyperglycemic with Ligature (H-L), Treated Hyperglycemic with Ligature (TH-L). At 40th day after induction of hyperglycemia, the groups NH-L, TNH-L, H-L, TH-L received a ligature to induce periodontitis. On the 69th, the TNH, TNH-L, TH, TH-L groups received metformin until the end of the study. Bone repair was evaluated at histometric and the expression levels of Sox9, RunX2 and Osterix. Analysis of the ex-vivo expression of TNF-α, IFN-γ, IL-12, IL-4, TGF-ß, IL-10, IL-6 and IL-17 were also evaluated. Metformin partially reverse induced bone loss in NH and H animals. Lower OPG/RANKL, increased OCN and TRAP expression were observed in hyperglycemic animals, and treatment with metformin partially reversed hyperglycemia on the OPG/RANKL, OPN and TRAP expression in the periodontitis. The expression of SOX9 and RunX2 were also decreased by hyperglycemia and metformin treatment. Increased ex vivo levels of TNF-α, IL-6, IL-4, IL-10 and IL-17 was observed. Hyperglycemia promoted increased IL-10 levels compared to non-hyperglycemic ones. Treatment of NH with metformin was able to mediate increased levels of TNF-α, IL-10 and IL-17, whereas for H an increase of TNF-α and IL-17 was detected in the 24- or 48-hour after stimulation with LPS. Ligature was able to induce increased levels of TNF-α and IL-17 in both NH and H. This study revealed the negative impact of hyperglycemia and/or treatment with metformin in the bone repair via inhibition of transcription factors associated with osteoblastic differentiation.

Lithium chloride improves bone filling around implants placed in estrogen-deficient rats.

OBJECTIVE: This study evaluated the ability of lithium chloride (LiCl) to increase bone filling (BF) around threaded titanium implants inserted in estrogen-deficient rats and, thein-vitro effects of this drug on osteoblast-like cell viability, proliferation, mineralization and expression of bone-related markers. DESIGN: In vivo: Rats received sham surgery plus water (Estrogen-sufficient group), ovariectomy plus water (Estrogen-deficient group) or ovariectomy plus LiCl (150 mg/kg/every other day) (LiCl/estrogen-deficient group). On the 21st day after ovariectomy/sham surgeries, a threaded titanium implant was inserted in the rat tibia. BF and the number of TRAP + cells were assessed at 10, 20 and 30 days after implant placement. In vitro: Osteosarcoma SAOS-2 cells were exposed to 0, 0.01, 0.05, and 0.1 mM of LiCl; cell proliferation, viability, mineralization (alizarin red staining) and gene expressions of RUNX-2, OCN, OPN, BSP and ALP (Real Time PCR) were estimated in the cultures. RESULTS: In vivo: The estrogen-sufficient and LiCl/estrogen-deficient groups demonstrated higher percentages of BF, within the limits of implant threads, than the estrogen-deficient group at 20 and 30 days (p < 0.05). The number of TRAP + cells was lower in LiCl/estrogen-deficient than in the estrogen-deficient group at all experimental times (p < 0.05). In vitro: Cell cultures exposed to LiCl (0.01 or 0.05 mM) exhibited larger areas of mineralized matrix than the non-exposed cultures (p < 0.05) and demonstrated the highest expressions of the genes investigated. CONCLUSION: LiCl treatment improved BF around threaded titanium implants inserted in estrogen-deficient rats and stimulated matrix mineralization and overexpression of bone-formation markers in osteoblastic cells in culture.