Desautels M, Bhaumick B, Ram J I
Department of Physiology, College of Medicine, University of Saskatchewan, Saskatoon, Canada.
Am J Physiol. 1996 Jun;270(6 Pt 2):R1287-95. doi: 10.1152/ajpregu.1996.270.6.R1287.
The objective of this work was to evaluate whether insulin, like norepinephrine (NE), exerts direct growth effects in brown adipocytes, as assessed by changes in rates of protein labeling with [35S]methionine. Mouse brown adipocytes isolated by tissue collagenase digestion were incubated for up to 24 h with or without NE in Dulbecco's modified Eagle's medium with albumin, calf serum, and antibiotics. There was a 40% cell loss and a 50% decrease in cell content of succinate dehydrogenase (SDH) activity over 24 h. Both cell recovery and SDH content significantly improved in the presence of NE. In addition, NE increased [35S]methionine incorporation into proteins in both cytosolic and mitochondrial compartments. These effects of NE were inhibited by propranolol. Both insulin and insulin-like growth factor-1 (IGF-1) receptors were detected in brown adipocytes, with insulin receptors in much greater concentration. Increased protein labeling was observed when brown adipocytes were incubated for 4 h with 0.2-5 nM insulin in the absence of serum. This effect was small (30% stimulation) compared with the 200-350% increase observed with NE, and 5 nM IGF-1 had no effect. These results indicate direct trophic actions of both NE and insulin in mouse brown adipocytes, with the effects of NE an order of magnitude greater than those of insulin.
本研究的目的是评估胰岛素是否像去甲肾上腺素（NE）一样，对棕色脂肪细胞具有直接的生长作用，这通过用[35S]蛋氨酸标记蛋白质的速率变化来评估。通过组织胶原酶消化分离得到的小鼠棕色脂肪细胞，在含有白蛋白、小牛血清和抗生素的杜尔贝科改良伊格尔培养基中，分别在有或无NE的情况下孵育长达24小时。在24小时内，细胞损失了40%，琥珀酸脱氢酶（SDH）活性的细胞含量下降了50%。在NE存在的情况下，细胞回收率和SDH含量均显著提高。此外，NE增加了[35S]蛋氨酸在胞质和线粒体部分蛋白质中的掺入。NE的这些作用被普萘洛尔抑制。在棕色脂肪细胞中检测到了胰岛素和胰岛素样生长因子-1（IGF-1）受体，其中胰岛素受体的浓度要高得多。在无血清条件下，当棕色脂肪细胞与0.2 - 5 nM胰岛素孵育4小时时，观察到蛋白质标记增加。与NE引起的200 - 350%的增加相比，这种作用较小（30%的刺激），并且5 nM IGF-1没有作用。这些结果表明NE和胰岛素对小鼠棕色脂肪细胞均有直接的营养作用，且NE的作用比胰岛素大一个数量级。
