Patiag D, Gray S, Idris I, Donnelly R
School of Medical and Surgical Sciences, Division of Vascular Medicine, University of Nottingham, UK.
Clin Sci (Lond). 2000 Oct;99(4):303-7. doi: 10.1042/cs0990303.
Clinical and experimental studies have implicated high circulating levels of the cytokine tumour necrosis factor-alpha (TNF-alpha) in the pathogenesis of insulin resistance, not only in obesity and diabetes, but also in clinical conditions associated with cachexia and sepsis. TNF-alpha impairs insulin-mediated glucose uptake in adipocytes, but because of lipolytic effects the interpretation of clinical studies and the extent to which TNF-alpha affects muscle insulin sensitivity are unclear. In addition, protein kinase C (PKC) has recently been implicated in the mechanism of TNF-alpha-induced insulin resistance. The present study investigated the effects of TNF-alpha and a PKC inhibitor (RO-318220) on basal and insulin-stimulated 2-[(3)H]deoxyglucose uptake in cultured L6 myoblasts. Reverse transcriptase-PCR analysis confirmed that L6 myoblasts express TNF-alpha receptors I and II (p60 and p80). Dose-response curves for glucose uptake were fitted to a quadratic function to derive C(I-150) values (concentration of insulin required to increase glucose uptake by 50%). Incubation with TNF-alpha at 1 or 10 ng/ml for 24 h had no significant effect on basal glucose uptake, insulin sensitivity or maximal insulin responsiveness. C(I-150) values (means+/-S.E.M.) were as follows: basal, 91.2+/-13 nM; 1 ng/ml TNF-alpha, 102+/-12 nM; and basal, 70.8+/-13 nM; 10 ng/ml TNF-alpha, 43.7+/-40 nM. PKC inhibition markedly attenuated glucose uptake, but there was no difference in insulin sensitivity with RO-318220 alone compared with RO-318220+TNF-alpha. In conclusion, although increased TNF-alpha expression and plasma concentrations have been implicated in the pathogenesis of insulin resistance in various clinical states, there is no evidence that TNF-alpha impairs insulin-stimulated glucose uptake in a skeletal-muscle-derived cell line.
临床和实验研究表明，细胞因子肿瘤坏死因子-α（TNF-α）的高循环水平与胰岛素抵抗的发病机制有关，不仅在肥胖症和糖尿病中如此，在与恶病质和脓毒症相关的临床病症中也是如此。TNF-α会损害脂肪细胞中胰岛素介导的葡萄糖摄取，但由于其脂解作用，临床研究的解释以及TNF-α对肌肉胰岛素敏感性的影响程度尚不清楚。此外，蛋白激酶C（PKC）最近也被认为参与了TNF-α诱导的胰岛素抵抗机制。本研究调查了TNF-α和一种PKC抑制剂（RO-318220）对培养的L6成肌细胞基础状态及胰岛素刺激下的2-[(3)H]脱氧葡萄糖摄取的影响。逆转录酶-PCR分析证实L6成肌细胞表达TNF-α受体I和II（p60和p80）。葡萄糖摄取的剂量反应曲线拟合为二次函数以得出C(I-150)值（使葡萄糖摄取增加50%所需的胰岛素浓度）。用1或10 ng/ml的TNF-α孵育24小时对基础葡萄糖摄取、胰岛素敏感性或最大胰岛素反应性均无显著影响。C(I-150)值（均值±标准误）如下：基础状态下为91.2±13 nM；1 ng/ml TNF-α时为102±12 nM；基础状态下为70.8±13 nM；10 ng/ml TNF-α时为43.7±40 nM。PKC抑制显著减弱了葡萄糖摄取，但单独使用RO-318220与RO-318220+TNF-α相比，胰岛素敏感性并无差异。总之，尽管在各种临床状态下，TNF-α表达增加和血浆浓度升高与胰岛素抵抗的发病机制有关，但没有证据表明TNF-α会损害骨骼肌来源细胞系中胰岛素刺激的葡萄糖摄取。
