| 摘要: | 抗胰島激素、第一型內皮素、SOCS-3被發現和脂肪細胞的活性以及胰島素的阻抗性有關。一些研究指出抗胰島激素會藉由活化SOCS-3而去抑制胰島素作用。然而不論是抗胰島激素還是第一型內皮素他們所影響SOCS-3的訊號機制並不完全清楚。於是本論文想要探討抗胰島激素和第一型內皮素它們是利用什麼途徑來調控3T3-L1脂肪細胞內SOCS-3基因的表現，我們利用RT-PCR 和real time-PCR方法來偵測SOCS-3基因的表現。我們發現處理30 ng/ml的抗胰島激素2小時以及50和100 nM的第一型內皮素4小時都會增加SOCS-3 mRNA的表現。而當我們先加了抑制物比如AG490 (a JAK inhibitor)，U0126(an ERK inhibitor)，SB203580(a p38 MAPK inhibitor)，SP60015 (a JNK inhibitor)，Wortmannin (a PI3K inhibitor)，LY294002 (a PI3K inhibitor)，以及epigallocatechin gallate (EGCG; an ERK inhibitor)都會抑制不論是抗胰島激素或是第一型內皮素所刺激的SOCS-3 mRNA的表現。且這些抑制物單獨處理時並不會影響 SOCS-3 mRNA 表現,但U0126 單獨處理時會增加SOCS-3 mRNA 表現。這些結果表示了抗胰島激素和第一型內皮素會經由JAK2，ERK，p38 MAPK，JNK，和PI3K的途徑來刺激SOCS-3 mRNA的表現。更進一步我們也發現BQ610 (an ETA receptor inhibitor)但不是BQ788 (an ETB receptor inhibitor)會去抑制第一型內皮素增加的SOCS-3 mRNA表現, 然而在單獨處理這些抑制劑時並不會影響SOCS-3的基因表現。這代表了第一型內皮素增加的SOCS-3 mRNA表現是藉由ETAR而不是ETBR。有趣的是，當我們先處理抗胰島激素再處理第一型內皮素時，抗胰島激素會減弱第一型內皮素所增加的SOCS-3 mRNA表現。而當我們先處理第一型內皮素再處理抗胰島激素時，發現第一型內皮素會更進一步增加抗胰島激素所增加的SOCS-3 mRNA表現。這表示在脂肪細胞抗胰島激素和第一型內皮素他們會調控彼此互相拮抗而影響SOCS-3基因表現。它們影響SOCS-3基因表現的途徑能可是藉由相似的kinase 途徑。 Resistin, endothelin-1 (ET-1), and suppressor of cytokine signaling protein-3 (SOCS-3) have been reported to regulate fat cell activity and insulin resistance, respectively. Previous reports showed that resistin could inhibit insulin action through activation of SOCS-3 protein. However, little are known about the signaling mechanisms of either resistin or ET-1 action on expression of adipocyte SOCS-3 gene. This study investigated the pathways involved in resistin and ET-1 modulation of SOCS-3 gene expression in 3T3-L1 adipocytes using the methods of both RT-PCR and real time-PCR. We found that resistin at 30 ng/ml for 2 h and ET-1 at 50 and 100 nM for 4 h induced increases in SOCS-3 mRNA levels, respectively. In addition, pretreatment with the inhibitors, including AG490 (a JAK inhibitor), an Uo126 (ERK inhibitor), SB203580 (a p38 MAPK inhibitor), SP60015 (a JNK inhibitor), Wortmannin (a PI3K inhibitor), LY294002 (a PI3K inhibitor), and epigallocatechin gallate (EGCG; an ERK inhibitor) inhibited either resistin or ET-1 stimulation of SOCS-3 mRNA levels. Treatment with each inhibitor alone did not significantly alter SOCS-3 mRNA expression, but U0126 alone significantly increased SOCS-3 levels. These data suggest that resistin and ET-1 stimulate SOCS-3 gene expression via the JAK-, ERK-, p38 MAPK-, JNK-, and PI3K-dependent pathways. Moreover, BQ610 (an ETA receptor inhibitor), but not BQ788 (an ETB receptor inhibitor), blocked ET-1-increased SOCS-3 mRNA levels, while treatment with each inhibitor alone did not alter SOCS-3 levels. This suggests the ETAR-dependent and ETBR-independent effect of ET-1. Interestingly, pretreatment with resistin reduced ET-1-increased SOCS-3 mRNA levels, pretreatment with ET-1 increased further resistin-induced increases in SOCS-3 levels. These data suggest that resistin and ET-1 can antagonistically interact to mediate expression of adipocyte SOCS-3 gene and their interactive effects likely depend on a common kinase pathway. |
