Fernández-Veledo S, Nieto-Vazquez I, Rondinone C M, Lorenzo M
Department of Biochemistry and Molecular Biology II, Faculty of Pharmacy, Complutense University, Madrid, Spain.
Diabetologia. 2006 Dec;49(12):3038-48. doi: 10.1007/s00125-006-0472-4. Epub 2006 Oct 27.
AIMS/HYPOTHESIS: The nuclear receptors, including nuclear receptor subfamily 1, group H, member 3 (NR1HR, also known as liver X receptor [LXR]), are sensors of cholesterol metabolism and lipid biosynthesis that have recently been proposed as insulin sensitisers. TNFalpha has been described as a link between obesity and the development of insulin resistance, an important contributor to the pathogenesis of type 2 diabetes. Therefore, we decided to investigate the ability of NR1HR agonists to ameliorate TNFalpha-induced insulin resistance in brown adipocytes.
Primary brown adipocytes from rat fetuses, and from wild-type neonate mice and neonate mice deficient in the gene encoding protein tyrosine phosphatase-1B (Ptpn1, also known as Ptp1b) were cultured in the absence or presence of TNFalpha and different nuclear receptor agonists. Among them, the unrelated NR1HR ligands T0901317, GW3965 and (22R)-hydroxycholesterol were tested. After insulin stimulation, glucose uptake and solute carrier family 2 (facilitated glucose transporter), member 4 (SLC2A4, formerly known as GLUT4) translocation were measured. Next the insulin signalling cascade was determined by submitting cells to lysis, immunoprecipitation and immunoblotting.
NR1HR agonists ameliorate TNFalpha-induced insulin resistance restoring completely insulin-stimulated glucose uptake and SLC2A4 translocation to plasma membrane. This effect is parallel to the recovery of the insulin cascade insulin receptor/IRS-2/phosphatidylinositol 3-kinase/protein kinase B, and could be due to the fact that T0901317 prevents the increase of PTPN1 production and phosphatase activity produced by TNFalpha. In this regard, Ptpn1-deficient brown adipocytes showed protection against insulin resistance by TNFalpha. Moreover, we observed that T0901317 produced in itself a significant increase over basal glucose uptake consistent with an increase of SLC2A4 protein content in plasma membrane, attributable to the activation of protein kinase zeta and/or the increase of Slc2a4 expression.
CONCLUSIONS/INTERPRETATION: Nuclear receptors NR1HR are interesting potential targets for drug treatment of insulin resistance.
目的/假设：核受体，包括核受体亚家族1、H组、成员3（NR1HR，也称为肝脏X受体[LXR]），是胆固醇代谢和脂质生物合成的传感器，最近被认为是胰岛素增敏剂。肿瘤坏死因子α（TNFα）被描述为肥胖与胰岛素抵抗发展之间的联系，胰岛素抵抗是2型糖尿病发病机制的重要促成因素。因此，我们决定研究NR1HR激动剂改善棕色脂肪细胞中TNFα诱导的胰岛素抵抗的能力。
将来自大鼠胎儿、野生型新生小鼠以及缺乏编码蛋白酪氨酸磷酸酶-1B（Ptpn1，也称为Ptp1b）基因的新生小鼠的原代棕色脂肪细胞，在有无TNFα和不同核受体激动剂的情况下进行培养。其中，测试了无关的NR1HR配体T0901317、GW3965和（22R）-羟基胆固醇。胰岛素刺激后，测量葡萄糖摄取和溶质载体家族2（促进性葡萄糖转运蛋白）成员4（SLC2A4，以前称为GLUT4）的转位。接下来，通过细胞裂解、免疫沉淀和免疫印迹来确定胰岛素信号级联反应。
NR1HR激动剂改善TNFα诱导的胰岛素抵抗，完全恢复胰岛素刺激的葡萄糖摄取和SLC2A4向质膜的转位。这种作用与胰岛素级联反应胰岛素受体/胰岛素受体底物-2/磷脂酰肌醇3激酶/蛋白激酶B的恢复平行，可能是因为T0901317阻止了TNFα引起的PTPN1产生增加和磷酸酶活性增加。在这方面，缺乏Ptpn1的棕色脂肪细胞对TNFα诱导的胰岛素抵抗具有保护作用。此外，我们观察到T0901317本身使基础葡萄糖摄取显著增加，这与质膜中SLC2A4蛋白含量增加一致，这归因于蛋白激酶ζ的激活和/或Slc2a4表达的增加。
结论/解读：核受体NR1HR是胰岛素抵抗药物治疗中有趣的潜在靶点。
