Indirubin-3′-oxime, an activator of Wnt/β-catenin signaling, enhances osteogenic commitment of ST2 cells and restores bone loss in high-fat diet-induced obese male mice

•I3O activates Wnt/β-catenin signaling and represses PPAR-γ in ST2 cells.•I3O enhances osteogenic commitment and mineralization of ST2 cells, while suppressing its adipogenic differentiation.•I3O abolishes the reciprocal effect of FA on Wnt/β-catenin and PPAR-γ signaling in ST2 cells.•I3O reverses the suppressive effect of FA on osteogenesis and the promotion of adipogenic differentiation.•I3O reverses bone loss, increases trabecular bone density, and decreases bone marrow adipocytes in HFD-induced obese male mouse.

Obesity is a growing issue of the modern world, and its negative impact on bones in obese male patients has been recently reported. The Wnt/β-catenin pathway has an established role in the regulation of body fat content and bone density. We investigated the effects of indirubin-3′-oxime (I3O), the GSK3β inhibitor that activates Wnt/β-catenin signaling, on trabecular bone in high-fat diet (HFD)-induced obese male mice. I3O reverses the downregulating effect of fatty acid (FA) on Wnt/β-catenin signaling and enhances the osteogenic commitment of the bone marrow-derived stromal cell line ST2. FA induces the adipogenic differentiation of bone marrow stromal cells in vitro. In a male mouse model of HFD-induced obesity, trabecular bone loss was observed in the femora, with a gross increase in abdominal fat; however, the HFD effects were rescued with the activation of Wnt/β-catenin signaling by I3O treatment. I3O administration also reversed the increase in the number of HFD-induced adipocytes in the femur bone marrow in trabecular bone. Overall, our results indicate that I3O could be a potential therapeutic agent for obese male patients through downregulation of abdominal fat and net increment in trabecular bone density.