Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, FitzGerald Building, 150 College St, Toronto, ON, Canada.
Diabetologia. 2011 Dec;54(12):3047-54. doi: 10.1007/s00125-011-2322-2. Epub 2011 Sep 30.
Associations of proinsulin-to-insulin ratios with incident type 2 diabetes have been inconsistent. The use of C-peptide as the denominator in the ratio may allow for better prediction because C-peptide concentration is not affected by hepatic insulin clearance. The objective of this paper was to compare fasting intact and split proinsulin-to-insulin ratios (PI/I, SPI/I) with intact and split proinsulin-to-C-peptide ratios (PI/C-pep, SPI/C-pep) in the prediction of type 2 diabetes.
Prospective data on 818 multi-ethnic adults without diabetes at baseline from the Insulin Resistance Atherosclerosis Study (IRAS) were used. Insulin sensitivity (S(I)) and acute insulin response (AIR) were determined from frequently sampled intravenous glucose tolerance tests, and fasting intact and split proinsulin were measured using specific two-site monoclonal antibody-based immunoradiometric assays. Associations of proinsulin ratios with type 2 diabetes were determined using logistic regression and differences in prediction were assessed by comparing areas under the receiver operating characteristic curve (AROCs).
In logistic regression analyses, PI/C-pep and SPI/C-pep were more strongly associated with incident type 2 diabetes (n = 128) than PI/I and SPI/I, and were significantly better predictors of diabetes in AROC analyses (PI/C-pep = 0.662 vs PI/I = 0.603, p = 0.02; SPI/C-pep = 0.690 vs SPI/I = 0.631, p = 0.01). Both PI/C-pep and SPI/C-pep were associated with type 2 diabetes after adjustment for age, sex, ethnicity, waist circumference, impaired glucose tolerance, lipids and S(I). Both PI/C-pep and SPI/C-pep were significantly associated with incident type 2 diabetes in models that included AIR.
Proinsulin-to-C-peptide ratios were stronger predictors of diabetes in comparison with proinsulin-to-insulin ratios. These findings support the use of C-peptide as the denominator for proinsulin ratios, to more accurately reflect the degree of disproportional hyperproinsulinaemia.
胰岛素原与胰岛素比值与 2 型糖尿病发病的相关性尚不一致。在比值中使用 C 肽作为分母可能会更好地进行预测，因为 C 肽浓度不受肝胰岛素清除率的影响。本文的目的是比较空腹完整和分裂胰岛素原与胰岛素比值（PI/I、SPI/I）与完整和分裂胰岛素原与 C 肽比值（PI/C-pep、SPI/C-pep）在预测 2 型糖尿病中的作用。
使用基线时无糖尿病的胰岛素抵抗动脉粥样硬化研究（IRAS）中 818 名多民族成年人的前瞻性数据。通过频繁采样的静脉葡萄糖耐量试验确定胰岛素敏感性（S(I)）和急性胰岛素反应（AIR），并使用特异性双位点单克隆抗体免疫放射测定法测量空腹完整和分裂胰岛素原。使用逻辑回归分析胰岛素原比值与 2 型糖尿病的相关性，并通过比较接受者操作特征曲线下面积（AROCs）来评估预测差异。
在逻辑回归分析中，PI/C-pep 和 SPI/C-pep 与 2 型糖尿病的发病更密切相关（n=128），并且在 AROC 分析中是糖尿病的更好预测指标（PI/C-pep=0.662 比 PI/I=0.603，p=0.02；SPI/C-pep=0.690 比 SPI/I=0.631，p=0.01）。在调整年龄、性别、种族、腰围、糖耐量受损、血脂和 S(I)后，PI/C-pep 和 SPI/C-pep 均与 2 型糖尿病相关。在包括 AIR 的模型中，PI/C-pep 和 SPI/C-pep 均与 2 型糖尿病的发生显著相关。
与胰岛素原与胰岛素比值相比，胰岛素原与 C 肽比值是糖尿病更好的预测指标。这些发现支持使用 C 肽作为胰岛素原比值的分母，以更准确地反映出不成比例的高胰岛素原血症的程度。
