ABSTRACT
Several hormones and growth factors, including adipokines, play important roles during muscle development and regeneration. CTRP3, a paralog of adiponectin, is a member of the C1q and tumor necrosis factor-related protein (CTRP) superfamily. CTRP3 is a novel adipokine previously reported to reduce glucose output in hepatocytes and lower glucose levels in mice models. In the present study, we provide the first evidence for a physiological role of the CTRP3 in myogenesis using C2C12 myoblasts. CTRP3 was expressed in developing skeletal muscle tissues, and the expression level of CTRP3 was increased during myogenic differentiation of C2C12 cells. Recombinant CTRP3 (rCTRP3) promoted the proliferation of undifferentiated C2C12 myoblasts and this response required activation of the extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway. In contrary, rCTRP3 inhibited myogenic differentiation and fusion of C2C12 cells by suppressing the expression of myogenic marker genes (myogenin and myosin heavy chain). CTRP3 mRNA expression was increased in C2C12 myoblasts treated with transforming growth factor-ß3 (TGF-ß3), suggesting that TGF-ß3 is one of the extracellular factors regulating CTRP3 expression during myogenesis. These results indicate a novel physiological role for CTRP3 during skeletal myogenesis.
Subject(s)
Adipokines/metabolism , Cell Differentiation/physiology , Muscle Development/physiology , Muscle, Skeletal/embryology , Myoblasts/metabolism , Adipokines/genetics , Animals , Cell Line , Cell Proliferation/physiology , Extracellular Signal-Regulated MAP Kinases/metabolism , Humans , MAP Kinase Signaling System , Mice , Mice, Inbred C57BL , Muscle, Skeletal/metabolism , Myogenin/biosynthesis , Myosin Heavy Chains/biosynthesis , RNA, Messenger/biosynthesis , RNA, Messenger/genetics , Transforming Growth Factor beta3/pharmacologyABSTRACT
Adipose tissue-derived adipokines play important roles as regulators of skeletal growth and development. CTRP1, a paralog of adiponectin, is a member of the C1q and tumor necrosis factor (TNF)-related protein (CTRP) superfamily. It is expressed at high levels in adipose tissue and has recently emerged as a novel adipokine. In the present study, we provide the first evidence for a physiological role of the CTRP1 in chondrocyte proliferation and maturation using a mouse chondrocytic cell line, N1511. The CTRP1 protein was strongly expressed and predominantly distributed in the reserve and proliferative chondrocytes in the fetal growth plate and its mRNA decreased during the maturation of N1511 chondrocytes. Recombinant CTRP1 promoted proliferation of immature proliferating N1511 chondrocytes in a dose-dependent manner, whereas it inhibited maturation of maturing N1511 chondrocytes. The stimulatory effect of CTRP1 on chondrocyte proliferation was associated with activation of the extracellular signal-regulated kinases 1/2 (ERK1/2) signaling pathway. On the other hand, the inhibitory effect of CTRP1 on chondrocyte maturation is associated with suppression of the ERK1/2 pathway. These results suggest a novel physiological role for CTRP1 in endochondral ossification.
Subject(s)
Adipokines/physiology , Cell Proliferation , Chondrocytes/metabolism , MAP Kinase Signaling System , Adipokines/genetics , Adipokines/metabolism , Animals , Cell Line , Chondrocytes/cytology , Growth Plate/cytology , Growth Plate/metabolism , MiceABSTRACT
CTRP3, a paralog of adiponectin, is a member of the C1q and tumor necrosis factor (TNF)-related protein (CTRP) superfamily. It is expressed at high levels in adipose tissue and has recently emerged as a novel adipokine. In the present study, we provide the first evidence for a physiological role of the new adipokine, CTRP3, in the reproductive system. CTRP3 was specifically expressed in interstitial Leydig cells, where testosterone is produced, in the adult mouse testis. CTRP3 increased testosterone production by TM3 mouse Leydig cells in a dose-dependent manner. The increased testosterone production was linked to upregulation of steroidogenic proteins expression, such as steroidogenic acute regulatory (StAR) protein and cholesterol side-chain cleavage cytochrome P450 (P450scc). Moreover, increases in intracellular cyclic AMP (cAMP) concentrations and the phosphorylation of cAMP-response element binding protein (CREB) in CTRP3-stimulated TM3 Leydig cells were observed. Inhibition of this signaling pathway by a specific protein kinase A (PKA) inhibitor, H89, blocked testosterone production in CTRP3-stimulated Leydig cells, suggesting that the stimulatory effect of CTRP3 on testosterone production is associated with activation of the cAMP/PKA signaling pathway. Thus, our results demonstrate a physiological role for CTRP3 in testicular steroidogenesis and provide novel insights in the intracellular mechanisms activated by this protein.
