Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
Am J Clin Nutr. 2010 Mar;91(3):662-71. doi: 10.3945/ajcn.2009.28750. Epub 2010 Jan 27.
Adolescence is a critical period for rising adiposity and falling insulin sensitivity (IS), but the independent relation between adiposity and IS remains understudied.
The objective was to examine which adiposity measures are most strongly associated with IS in nondiabetic adolescents, whether sex-difference exists, and to what degree genetic or environmental factors affect the adiposity-IS relation.
The study included 1613 rural Chinese adolescents (888 males) aged 13-20 y from a population-based twin cohort. We used graphic plots and linear mixed models to examine the relation of anthropometric and dual-energy X-ray absorptiometry-based measures of adiposity with IS [QUantitative Insulin-sensitivity ChecK Index (QUICKI), fasting serum insulin (FSI), homeostasis model assessment of insulin resistance (HOMA-IR)] and structural equation models to estimate genetic/environmental influences on these associations.
In graphic analyses, participants in the highest quintile (quintile 5) of waist circumference (WC) and percentage body fat (%BF) had the lowest QUICKI and the highest FSI and HOMA-IR values for all age-sex groups. In regression models adjusted for age, Tanner stage, zygosity, and physical activity, all adiposity measures showed inverse associations with IS in both sexes, but WC explained the largest fraction of variance in IS measures (10-14%). Of the phenotypic correlations between adiposity measures and IS (-0.28 to -0.38), 74-85% were attributed to shared genetic factors and 15-26% to common unique environmental factors in both sexes.
In these relatively lean Chinese adolescents, WC and %BF (quintile 5) are the adiposity measures most consistently and strongly associated with decreased IS in both sexes. To a large degree, shared genetic factors contribute to this association.
青春期是肥胖率上升和胰岛素敏感性（IS）下降的关键时期，但肥胖与 IS 之间的独立关系仍研究不足。
本研究旨在探讨非糖尿病青少年中哪些肥胖指标与 IS 相关性最强，是否存在性别差异，以及遗传和环境因素在多大程度上影响肥胖与 IS 的关系。
本研究纳入了来自基于人群的双胞胎队列的 1613 名年龄在 13-20 岁的农村中国青少年（男性 888 人）。我们使用图形图和线性混合模型来研究体脂和双能 X 射线吸收法测量的肥胖指标与 IS（QUickI、空腹血清胰岛素（FSI）、稳态模型评估的胰岛素抵抗（HOMA-IR））的关系，并使用结构方程模型来估计遗传/环境因素对这些关联的影响。
在图形分析中，腰围（WC）和体脂百分比（%BF）最高五分位数（五分位 5）的参与者在所有年龄-性别组中 QUICKI 最低，FSI 和 HOMA-IR 值最高。在调整年龄、Tanner 分期、同卵双生子和体力活动的回归模型中，所有肥胖指标在两性中均与 IS 呈负相关，但 WC 对 IS 指标的解释度最大（10-14%）。在肥胖指标与 IS 之间的表型相关性（-0.28 至-0.38）中，74-85%归因于共同的遗传因素，15-26%归因于两性中的共同独特环境因素。
在这些相对较瘦的中国青少年中，WC 和 %BF（五分位 5）是与两性中 IS 下降最一致和最强相关的肥胖指标。在很大程度上，共同的遗传因素促成了这种关联。
