Huogu I formula prevents steroid-induced osteonecrosis in rats by down-regulating PPARγ expression and activating Wnt/LRP5/β-catenin signaling

ObjectiveTo investigate the effects of Huogu I formula on regulation of lipid metabolism in steroid-induced osteonecrosis of the femoral head (SONFH) rats and verify our hypothesis that Huogu I formula regulates lipid metabolism by down-regulating peroxisome proliferator-activated receptor gamma (PPARγ) expression and activating Wnt signaling pathways.MethodsEighty-five rats were divided into four groups: control, model, Huogu 15 g/kg and Huogu 30 g/kg. Six weeks later, animals were anaesthetized, femora were dissected for histopathological examination of the osteonecrotic changes and repair processes, micro computed tomography (Micro-CT)-based micro-angiography was performed to assess vascularization. Serum lipid levels were detected by haematological examination. The expressions of PPARγ, Wnt3a, low density lipoprotein receptor-related protein 5 (LRP5) and β-catenin were evaluated by immunohistochemistry, Western blot and quantitative real-time polymerase chain reaction analyses.ResultsThe incidence of osteonecrosis, ratio of empty lacuna, adipose tissue area and adipocyte perimeter in the bone marrow were dramatically lower in the Huogu I formula treatment groups. By micro-CT quantification, Huogu I formula treatment dose-dependently increased vessel volume, vessel surface, percentage of vessel volume and vessel thickness of the femoral heads of SONFH rats. Levels of serum lipid in Huogu 15 g/kg and Huogu 30 g/kg groups reduced significantly. Huogu I formula treatment could suppress the expression of PPARγ and increase the expressions of Wnt3a, LRP5 and β-catenin at both protein and mRNA levels.ConclusionThe results of our present study highlight the lipid-lowering potential of Huogu I formula, and provide further evidence of the involvement of the PPARγ inhibition and Wnt/LRP5/β-catenin signaling activation in the effects of Huogu I formula.