Abstract 3719: Deletion of Angiotensin II type 2 Receptor Accelerates Adipogenesis in Murine Mesenchymal Stem Cells with Wnt 10b/beta-catenin Signaling: Potential Link to Obesity and Metabolic Syndrome
Recent evidence suggests that the reninangiotensin system (RAS) plays a vital role in adipocyte biology and the pathophysiology of metabolic syndrome. Obesity is a major risk factor and mesenchymal stem cells (MSCs) are suggested to be an important source of new fat cells. Previously we reported that MSCs have all the components of the RAS and that angiotensin II (Ang II) can influence adipocyte differentiation. However, the effect of Ang II type 2 receptor (AT2R) deletion on adipogenesis in mouse model is unknown. Accordingly, we employed AT2R-null mice and examined the role of AT2R in the differentiation of MSCs to adipocytes.
Methods and Results: Murine MSCs were isolated from AT2R-null mice and wildtype littermates (WT). Confluent MSCs were differentiated into adipocytes by the established protocol. Adipogenesis was quantitated by assessing lipid droplet accumulation using 2 different methods. Using the fluorescent dye which binds to lipid droplets (AdipoRed), AT2R-null group showed significantly increased total fluorescence (261.6 ± 49.6 % vs. WT) on day 7. Oil red O staining, followed by extraction of the absorbed dye and measurement of the absorbance on day 14, also exhibited that AT2R-null group showed significantly increased lipid droplet accumulation (202.7 ± 14.1 % vs. WT). We next examined the expression of adipocyte-specific genes by real-time RT-PCR. AT2R-null group exhibited a significantly increased expression of PPARγ, fatty acid synthase, and adiponectin (vs. WT). Since Wnt 10b/beta-catenin signaling is reported to play an important role to inhibit adipogenesis, we further examined it by real-time RT-PCR and immunoblotting. The AT2R-null group exhibited significantly decreased Wnt 10b expression accompanied by a decrease of cellular beta-catenin (vs. WT).
Conclusion: Our results demonstrate that the AT2 receptor has an inhibitory effect on adipogenic differentiation in murine mesenchymal stem cells. Moreover, this inhibitory effect is associated with Wnt 10b/beta-catenin signaling which plays an important role to inhibit adipogenesis. These results provide important insights into the pathophysiology of obesity and obesity related consequences such as metabolic syndrome and may identify potential therapeutic targets.