Biomarkers for classification and class prediction of stress in a murine model of chronic subordination stress

Selye defined stress as the nonspecific response of the body to any demand and thus an inherent element of all diseases. He reported that rats show adrenal hypertrophy, thymicolymphatic atrophy, and gastrointestinal ulceration, referred to as the stress triad, upon repeated exposure to nocuous agents. However, Selye’s stress triad as well as its extended version including reduced body weight gain, increased plasma glucocorticoid (GC) concentrations, and GC resistance of target cells do not represent reliable discriminatory biomarkers for chronic stress. To address this, we collected multivariate biological data from male mice exposed either to the preclinically validated chronic subordinate colony housing (CSC) paradigm or to single-housed control (SHC) condition. We then used principal component analysis (PCA), top scoring pairs (tsp) and support vector machines (SVM) analyses to identify markers that discriminate between chronically stressed and non-stressed mice. PCA segregated stressed and non-stressed mice, with high loading for some of Selye’s stress triad parameters. The tsp analysis, a simple and highly interpretable statistical approach, identified left adrenal weight and relative thymus weight as the pair with the highest discrimination score and prediction accuracy validated by a blinded dataset (92% p-value塞利将应激定义为机体对任何需求所产生的非特异性应答，因此是所有疾病的固有组成部分。他报告称，大鼠在反复暴露于有害因子后会出现肾上腺肥大、胸腺淋巴组织萎缩以及胃肠道溃疡，上述三种变化被称为应激三联征。不过，塞利的应激三联征及其扩展版本（包括体重增长减少、血浆糖皮质激素（glucocorticoid, GC）浓度升高以及靶细胞的糖皮质激素抵抗）并不能作为慢性应激的可靠鉴别生物标志物。为解决这一问题，我们从暴露于经临床前验证的慢性从属群居（chronic subordinate colony housing, CSC）造模模型或单笼饲养对照（single-housed control, SHC）条件的雄性小鼠中收集了多变量生物学数据。随后我们采用主成分分析（principal component analysis, PCA）、最高得分对（top scoring pairs, tsp）以及支持向量机（support vector machines, SVM）分析，以识别可区分慢性应激与非应激小鼠的标志物。主成分分析可将应激与非应激小鼠区分开来，其中部分塞利应激三联征参数具有较高的载荷值。最高得分对分析作为一种简单且极具可解释性的统计学方法，筛选出左侧肾上腺重量与胸腺相对重量这一对指标，其区分评分与预测准确度经盲法数据集验证可达92%（p值）。