McCaleb M L, Izzo M S, Lockwood D H
J Clin Invest. 1985 Feb;75(2):391-6. doi: 10.1172/JCI111712.
We have previously shown that the incubation of normal rat adipose tissue with sera from nondialyzed, nondiabetic uremic patients reduces the transport and metabolism of glucose, in the absence and presence of insulin. In this study insulin-stimulated glucose metabolism by normal rat adipocytes was used as a bioassay to identify the resistance activity, assess the effect of chemical modification on it, and the clinical states associated with its production. The resistance activity was trypsin-labile and had an apparent isoelectric point between 6 and 7, but was not retained by either protein A or concanavalin A columns. The insulin resistance activity was decreased by coincubation with the protein synthesis inhibitor, cycloheximide. Purification to greater than 200,000-fold was attained by heating (100 degrees C) uremic serum, subjecting the supernatant to Sephadex G-25 chromatography and subsequent adsorption to DEAE at pH 7.8 and elution at pH 6.5. The partially purified resistance activity was retained within dialysis tubing of 1,000-mol wt cutoff but not within 2,000-mol wt cutoff. Hemodialysis of patients over 1 wk to 18 mo reduced significantly the amount of resistance activity in their sera. The resistance activity, present in most uremic patients, was not found in the sera of individuals with normal renal function but who were either obese, fasted, elderly or had type II diabetes mellitus. Thus, a circulating small molecular weight peptide, unique to uremia, induced insulin resistance by a protein synthesis-dependent mechanism.
我们之前已经表明，将正常大鼠脂肪组织与未透析的非糖尿病尿毒症患者的血清一起孵育，无论有无胰岛素，都会降低葡萄糖的转运和代谢。在本研究中，正常大鼠脂肪细胞的胰岛素刺激葡萄糖代谢被用作生物测定法，以鉴定抵抗活性，评估化学修饰对其的影响以及与其产生相关的临床状态。该抵抗活性对胰蛋白酶敏感，表观等电点在6至7之间，但既不被蛋白A柱也不被伴刀豆球蛋白A柱保留。与蛋白质合成抑制剂环己酰亚胺共同孵育可降低胰岛素抵抗活性。通过加热（100℃）尿毒症血清、将上清液进行葡聚糖凝胶G-25层析，随后在pH 7.8吸附到DEAE并在pH 6.5洗脱，可实现纯化至超过200,000倍。部分纯化的抵抗活性保留在截留分子量为1000的透析袋内，但不保留在截留分子量为2000的透析袋内。患者进行1周至18个月的血液透析可显著降低其血清中抵抗活性的量。大多数尿毒症患者血清中存在的抵抗活性，在肾功能正常但肥胖、禁食、年老或患有II型糖尿病的个体血清中未发现。因此，一种尿毒症特有的循环小分子肽通过蛋白质合成依赖性机制诱导胰岛素抵抗。
