Guller S, Allen D L, Corin R E, Lockwood C J, Sonenberg M
Department of Obstetrics/Gynecology and Reproductive Science, Mount Sinai Medical Center, New York, New York 10029.
Endocrinology. 1992 May;130(5):2609-16. doi: 10.1210/endo.130.5.1572284.
In the present study we focused on the relationship between GH action and the extracellular matrix in 3T3-F442A preadipose cells. Results from Northern blotting indicated that in serum-free medium, the presence of 2 nM met-human GH down-regulated levels of fibronectin messenger RNA by approximately 40, 60, and 70% as compared with control levels on days 1, 2, and 4, respectively. GH-dependent reduction of levels of collagen alpha 1(I) mRNA expression occurred later and was less pronounced than effects on levels of fibronectin mRNA, suggesting a specificity in the matrix-altering function of GH. Western blot analyses and immunoprecipitation studies revealed that between 2 and 5 days of culture, matrix-associated fibronectin protein was reduced 70 to 90% by GH treatment. Down-regulation of fibronectin protein expression by met-human GH was dose-dependent between 2 and 0.02 nM. The presence of 2 nM insulin or insulin-like growth factor-1 promoted a 30-40% increase in fibronectin levels compared to control cells. The GH-promoted down-regulation of fibronectin expression was eliminated by concomitant addition of insulin. These data demonstrated that GH effects on matrix-associated fibronectin expression were independent of, and in opposition to, effects promoted by insulin and insulin-like growth factor-1. Treatment of culture dishes with fibronectin or collagen inhibited GH-stimulated adipogenesis 50 and 80%, respectively, compared with controls, as judged by levels of glycerol-3-phosphate dehydrogenase activity. Thus, composition of the extracellular matrix was a critical factor in GH-induced adipogenesis of 3T3-F442A fibroblasts. Our results demonstrate that GH action in 3T3 preadipose cells is intimately coupled to the biology of extracellular matrix.
在本研究中，我们聚焦于3T3-F442A前脂肪细胞中生长激素（GH）作用与细胞外基质之间的关系。Northern印迹法的结果表明，在无血清培养基中，与第1、2和4天的对照水平相比，2 nM重组人生长激素（met-human GH）的存在分别使纤连蛋白信使核糖核酸（mRNA）水平下调了约40%、60%和70%。GH依赖性的Ⅰ型胶原α1（collagen alpha 1(I)）mRNA表达水平降低出现得较晚，且不如对纤连蛋白mRNA水平的影响明显，这表明GH在改变基质功能方面具有特异性。蛋白质印迹分析和免疫沉淀研究表明，在培养2至5天期间，经GH处理后，与基质相关的纤连蛋白蛋白减少了70%至90%。在2至0.02 nM之间，重组人生长激素对纤连蛋白蛋白表达的下调呈剂量依赖性。与对照细胞相比，2 nM胰岛素或胰岛素样生长因子-1的存在使纤连蛋白水平提高了30 - 40%。同时添加胰岛素可消除GH促进的纤连蛋白表达下调。这些数据表明，GH对与基质相关的纤连蛋白表达的影响独立于胰岛素和胰岛素样生长因子-1所促进的作用，且与之相反。用纤连蛋白或胶原处理培养皿，与对照相比，分别抑制了GH刺激的脂肪生成50%和80%，这是通过甘油-3-磷酸脱氢酶活性水平来判断的。因此，细胞外基质的组成是GH诱导3T3-F442A成纤维细胞脂肪生成的关键因素。我们的结果表明，3T3前脂肪细胞中的GH作用与细胞外基质生物学密切相关。
