A novel semisynthetic molecule icaritin stimulates osteogenic differentiation and inhibits adipogenesis of mesenchymal stem cells.

BACKGROUND: We previously reported that the constitutional flavonoid glycosides derived from herb Epimedium (EF, composed of seven flavonoid compounds with common nuclear stem) exerted beneficial effects on the bone, including promoting bone formation and inhibiting bone marrow fat deposition. Recent in vivo study showed that Icaritin was a common metabolite of these constitutional flavonoid glycosides, indicating that Icaritin is a bioactive compound. The present study was designed to investigate whether Icaritin could promote osteogenic differentiation and suppress adipogenic differentiation of marrow mesenchymal stem cells (MSCs). METHODS: Primary MSCs were harvested from adult mice and exposed to Icaritin to evaluate whether it could promote osteogenesis and suppress adipogenesis using the following assays: determination of alkaline phosphatase (ALP) activity and mineralization; mRNA expression of osteogenic differentiation marker Runx2; osteocalcin and bone sialoprotein (BSP) by RT-PCR; quantification of adipocyte-like cells by Oil Red O staining assay and mRNA expression for adipogenic differentiation markers peroxisome proliferator-activated receptor gamma (PPARγ); adipocyte fatty acid binding protein (aP2) and lipoprotein lipase (LPL) by RT-PCR. For the underlying mechanism, glycogen synthase kinase-3beta (GSK3ß) and ß-catenin were also explored by western blotting. RESULTS: Icaritin promoted osteogenic differentiation and maturation of MSCs as indicated by increased mRNA expression for Runx2, osteocalcin and BSP, and enhanced ALP activity and mineralization; Icaritin inhibited adipogenic differentiation, as indicated by decreased mRNA expression for PPARγ, LPL, aP2, and suppressed formation of adipocyte-like cells; Icaritin inactivated GSK3ß and suppressed PPARγ expression when promoting osteogenesis and suppressing adipogenesis of MSCs. CONCLUSION: This was the first study demonstrating that the novel semisynthetic molecule Icaritin could stimulate osteogenic differentiation and inhibit adipogenesis of MSCs, which was associated with the suppression of GSK3ß and PPARγ.

The skeletal effects of thiazolidinedione and metformin on insulin-resistant mice.

To explore the skeletal effects and the potential underlying mechanisms of treatment with two thiazolidinediones (rosiglitazone and pioglitazone) or metformin in insulin-resistant mice, 24 female, 12-week-old C57BL6J ob/ob mice were evaluated according to the following treatment groups for 6 weeks: placebo group, pioglitazone group (Pio), rosiglitazone group (Rosi), and metformin group (Met). Bone mineral density (BMD), bone microarchitecture, bone histomorphometry, and expression of three phenotype-specific gene markers, including bone morphogenetic protein 2 (Bmp2), runt-related transcription factor 2 (Runx2), and fatty acid-binding protein 4 (Fabp4), were compared across the four groups. At the femur, the Met group had the highest BMD (0.084 ± 0.001 g/cm(2)) and trabecular bone volume/total volume (0.644 ± 0.018 %) and the lowest trabecular spacing (Tb.Sp.) (0.143 ± 0.008 µm), whereas the Rosi group had lower BMD (0.076 ± 0.003 g/cm(2)) and a relatively higher degree of Tb.Sp. (0.173 ± 0.024 µm). A histomorphometric analysis revealed that in the Rosi group the number of adipocytes was fourfold higher than in the placebo group and fivefold higher than in the Met group, whereas the highest osteoid width and mineral apposition rate were found in the Met group (49.88 ± 48.53 µm and 4.46 ± 1.72 µm/day). Furthermore, the Rosi group displayed the highest level of Fabp4 gene expression, which was accompanied by normal expression levels of Bmp2 and Runx2. Seemingly, metformin is a bone-friendly antidiabetic drug. Rosiglitazone had adverse effects on the skeleton at the trabecular bone even in insulin-resistant mice, whereas no evidence of adverse effects was found for pioglitazone.

Low bone mineral density in chinese adults with nonalcoholic Fatty liver disease.

Aim. To investigate bone metabolic characteristics in Chinese adults with nonalcoholic fatty liver disease (NAFLD). Methods. A total of 224 patients (99 males and 125 postmenopausal females) were recruited and divided into 4 groups: males without NAFLD, males with NAFLD, females without NAFLD, and females with NAFLD. Bone mineral density (BMD) was evaluated according to body mass index (BMI), waist circumference (WC), and serum biomarkers. ß cell function was evaluated by HOMA2%B, HOMA2%S, and HOMA2IR. Results. Males in the NAFLD group had lower BMD of the right hip and the femoral neck (0.852 ± 0.117 versus 0.930 ± 0.123, P = 0.002; 0.736 ± 0.119 versus 0.812 ± 0.132, P = 0.004), and females had lower BMD of the right hip (0.725 ± 0.141 versus 0.805 ± 0.145, P = 0.002) even after adjusted for weight, BMI, waist, HDL, and ALT. There was no significant difference in bone metabolic markers between patients with and without NAFLD. NAFLD was an important factor that affected the bone; moreover, the effect attenuated when HOMA2IR entered into the model (R (2) = 0.160, ß = -0.172, and P = 0.008). Conclusions. NAFLD exerts a detrimental effect on BMD in both males and females. Insulin resistance may play an important role in this pathophysiological process.

Pathomorphological changes of bone marrow adipocytes in process of steroid-associated osteonecrosis.

OBJECTIVE: The role of extravascular fat deposition in pathogenesis of steroid-associated osteonecrosis (ON) still remains unclear. This study aimed to explore the pathomorphological changes of bone marrow adipocytes over time in a rabbit ON model. METHODS: Thirty-two adult rabbits were divided into control group (n=16) and steroid group (n=16). Rabbits in the steroid group were injected with venous lipopolysaccharide once and intramuscular methylprednisolone trice to induce ON. Rabbits in the control group were treated with normal saline of equal volume. 2 weeks (early stage; n=8) and 4 weeks (late stage; n=8) after the last steroid injection, animals were sacrificed, and bilateral femora were harvested. The density, diameter and area of bone marrow adipocytes were determined by histomorphometry, and ON was evaluated histopathologically. RESULTS: The adipocyte density in steroid group increased by 67.1% and 54.4% at week 2 and week 4, respectively, when compared with control group, but there was no significant difference between week 2 and week 4. The adipocyte diameter in the steroid group at week 4 was significantly larger than that in the control group, but the adipocyte diameter in the steroid group at week 2 was slightly smaller than that in the control group. The adipocyte area in the steroid group increased by 44% and 83.4% at week 2 and week 4, respectively, when compared with the control group, and the adipocyte area in the steroid group at week 4 was markedly larger than that at week 2. In the control group, there were a largest number of adipocytes with 40-50 µm in diameter. When compared with the control group, most of increased adipocytes in the steroid group at week 2 were 30-40 µm in diameter, and those at week 4 were 50-60 µm in diameter. In the steroid group, histopathological examination showed ON was found in 25% (2/8) of rabbits at week 2 and 87.5% (7/8) of rabbits at week 4. CONCLUSION: In the process of ON, extravascular fat deposition is characterized by increased small adipocytes at the early stage and hypertrophy of adipocytes at the late stage.