Department of Internal Medicine, Erasmus Medical Center, Rotterdam, The Netherlands.
Diabetes. 2010 Feb;59(2):505-8. doi: 10.2337/db09-0583.
There is a complex relationship between IGF-I, IGF binding proteins, growth hormone, and insulin. The IGF-I kinase receptor activation assay (KIRA) is a novel method for measuring IGF-I bioactivity in human serum. We speculated that determination of IGF-I bioactivity might broaden our understanding of the IGF-I system in subjects with the metabolic syndrome. The purpose of our study was to investigate whether IGF-I bioactivity was related to insulin sensitivity and the metabolic syndrome.
We conducted a cross-sectional study embedded in a random sample (1,036 elderly subjects) of a prospective population-based cohort study. IGF-I bioactivity was determined by the IGF-I KIRA. Categories of glucose (in)tolerance were defined by the 2003 American Diabetes Association criteria. Insulin sensitivity was assessed by homeostasis model assessment. The Adult Treatment Panel III definition of the metabolic syndrome was used.
In subjects with normal fasting glucose and impaired fasting glucose, IGF-I bioactivity progressively increased with increasing insulin resistance, peaked at fasting glucose levels just below 7.0 mmol/l, and dropped at higher glucose levels. Mean IGF-I bioactivity peaked when three criteria of the metabolic syndrome were present and then declined significantly when five criteria of the metabolic syndrome were present.
We observed that IGF-I bioactivity was related to insulin sensitivity, insulin levels, and the metabolic syndrome. Our study suggests that there exists an inverse U-shaped relationship between IGF-I bioactivity and number of components of the metabolic syndrome. This observation contrasts with previous results reporting an inverse relationship between total IGF-I and components of the metabolic syndrome.
IGF-I、IGF 结合蛋白、生长激素和胰岛素之间存在着复杂的关系。IGF-I 激酶受体激活测定(KIRA)是一种测量人血清中 IGF-I 生物活性的新方法。我们推测,测定 IGF-I 生物活性可能会拓宽我们对代谢综合征患者 IGF-I 系统的理解。本研究旨在探讨 IGF-I 生物活性是否与胰岛素敏感性和代谢综合征有关。
我们进行了一项横断面研究,该研究嵌入了一项前瞻性基于人群的队列研究的随机样本(1036 名老年受试者)中。通过 IGF-I KIRA 测定 IGF-I 生物活性。葡萄糖(耐量)分类根据 2003 年美国糖尿病协会标准定义。胰岛素敏感性通过稳态模型评估进行评估。采用成人治疗小组 III 代谢综合征的定义。
在空腹血糖正常和空腹血糖受损的受试者中,IGF-I 生物活性随着胰岛素抵抗的增加而逐渐增加,在空腹血糖水平略低于 7.0mmol/l 时达到峰值,在更高的血糖水平时下降。当存在代谢综合征的三个标准时,平均 IGF-I 生物活性达到峰值,然后当存在代谢综合征的五个标准时,显著下降。
我们观察到 IGF-I 生物活性与胰岛素敏感性、胰岛素水平和代谢综合征有关。我们的研究表明,IGF-I 生物活性与代谢综合征的组成部分之间存在着反 U 型关系。这一观察结果与先前报告总 IGF-I 与代谢综合征组成部分之间存在反比关系的结果形成对比。