Combating Osteoporosis and Obesity With Green Tea Polyphenols: Molecular Switching of Osteogenesis Versus Adipogenesis During Early Differentiation of Human Adipose Tissue-Derived Stem Cells

Abstract

Background: Osteoporosis is a metabolic disease affecting the bone mineral density associated with increased adiposity in the aging population with obesity. The nutrients to control osteoblast and adipocyte differentiation from a common precursor, the pluripotent mesenchymal stem cell (MSC), may be a promising therapy for osteoporosis. Previously, we have shown that green tea polyphenols (GTP) exert anti-adipogenic effects on preadipocyte proliferation. In the present study, we investigated regulatory effects of GTP on osteogenesis and adipogenesis during early differentiation of human adipose tissue-derived stem cells (hADSCs). Methods: GTP at concentrations of 1 and 10 µg/ml was incubated with primary hADSCs in presence or absence of pioglitazone (100 µmol) during hADSCs differentiation. Adipogenesis of hADSCs was determined by Oil Red O staining and measurement of the cellular triglyceride synthesis in mature adipocyte. Alkaline phosphatase (ALP) assay and the measurement of intracellular calcium were utilized to determine osteoporosis of hADSCs. Immunofluorescence staining and qRT-PCR were employed to detect PPARγ-CEBPA regulated adipogenic pathway and the RUNX2-BMP2 mediated osteogenic pathway. Results: GTP treatment significantly decreased lipid accumulation and the cellular triglyceride synthesis in mature adipocytes and attenuated pioglitazone-induced adipogenesis in a dose-dependent manner. GTP downregulated protein and mRNA expression of Pparγ and attenuated pioglitazone-stimulated Cebpa expression in mature adipocytes. Concurrently, measurements of calcium content and ALP activity showed that GTP treatment significantly enhanced hADSCs differentiation into osteocytes compared with the control and pioglitazone-treated cells. Meanwhile, GTP upregulated protein and mRNA expression of RunX2 and Bmp2 compared to the control and GTP at 10 µg/mL significantly attenuated the decreased mRNA expression of Runx2 and Bmp2 by pioglitazone. Conclusions: The present study demonstrated that GTP possess a greater ability to facilitate osteogenesis and simultaneously inhibit hADSCs differentiation into the adipogenic lineage through upregulating the RUNX2-BMP2 mediated osteogenic pathway and suppressing PPARγ-induced signaling of adipogenesis. The findings of this study highlight that GTP may be a therapeutic intervention to combat osteoporosis associated obesity.