Cryptotanshinone promotes commitment to the brown adipocyte lineage and mitochondrial biogenesis in C3H10T1/2 mesenchymal stem cells via AMPK and p38-MAPK signaling

Abstract

Although white adipose tissue (WAT) stores triglycerides and contributes to obesity, brown adipose tissue (BAT) dissipates energy as heat. Therefore, browning of WAT is regarded as an attractive way to counteract obesity. Our previous studies have revealed that treatment with cryptotanshinone (CT) during adipogenesis of 3T3-L1 cells inhibits their differentiation. Here, we found that pretreatment of C3H10T1/2 mesenchymal stem cells with CT before exposure to adipogenic hormonal stimuli promotes the commitment of these mesenchymal stem cells to the adipocyte lineage as confirmed by increased triglyceride accumulation. Furthermore, CT treatment induced the expression of early B-cell factor 2 (Ebf2) and bone morphogenetic protein 7 (Bmp7), which are known to drive differentiation of C3H10T1/2 mesenchymal stem cells toward preadipocytes and to the commitment to brown adipocytes. Consequently, CT treatment yielded brown-adipocyte-like features as evidenced by elevated expression of brown-fat signature genes including Ucp1, Prdm16, Pgc-1 alpha, Cidea, Zic1, and beige-cell-specific genes such as CD137, Hspb7, Cox2, and Tmem26. Additionally, CT treatment induced mitochondrial biogenesis through upregulation of Sirt1, Tfam, Nrf1 and Cox7a and increased mitochondrial mass and DNA content. Our data also showed that cotreatment with CT and BMP4 was more effective at activating brown-adipocyte-specific genes. Mechanistic experiments revealed that treatment with CT activated AMPK alpha and p38-MAPK via their phosphorylation: the two major signaling pathways regulating energy metabolism. Thus, these findings suggest that CT is a candidate therapeutic agent against obesity working via activation of browning and mitochondrial biogenesis in C3H10T1/2 mesenchymal stem cells.