Supplementary Material for: Metabonomic Profiling Reveals Difference in Altered Metabolic Pathways Between Chronic Kidney Disease and High-Fat-Induced Insulin Resistance in Rats

<b><i>Background/Aims:</i></b> Chronic kidney disease (CKD) is closely correlated with the development of insulin resistance (IR). Until now, the underlying molecular mechanisms remain to be elucidated. This study aimed to identify metabolites and molecular pathways unique to CKD-induced IR. <b><i>Methods:</i></b> Ultra-performance liquid chromatography-tandem mass spectrometer (UPLC-MS) analysis coupled with orthogonal partial least square discriminant analysis (OPLS-DA) were performed to profile metabolites in the serum, liver, and muscle tissues and to analyze molecular pathways in relation to CKD- and high fat diet (HFD)-induced IR in the rats. <b><i>Results:</i></b> At 18 weeks after the 5/6 Nx operation, CKD induction was demonstrated by renal histology and biochemical tests. Furthermore, both CKD-induced IR and HFD-induced IR rats showed significantly greater levels of fasting insulin and homeostasis model assessment of insulin resistance (HOMA-IR). In the UPLC-MS in combination with OPLS-DA analysis, we identified 101, 59, and 41 differential metabolites in the serum, liver, and muscle, which were associated with the CKD-induced IR, while 58, 38, and 17 differential metabolites in the serum, liver, and muscle were revealed in the HFD-induced rats compared to controls. Moreover, compared to HFD-induced IR rats, those with CKD-induced IR exhibited abnormal pathways primarily in the tryptophan metabolism, arginine metabolism, and trimethylamine oxide metabolite. Interestingly, altered metabolites in the CKD-induced IR and HFD-induced IR displayed an opposite direction. <b><i>Conclusion:</i></b> Alterations in metabolites and relevant pathways were significantly different between the CKD- and HFD-induced IR rats. These findings may offer important information regarding the pathogenesis specific to IR caused by the decline in the renal function.

<b><i>背景与目的:</i></b> 慢性肾脏病（Chronic kidney disease, CKD）与胰岛素抵抗（insulin resistance, IR）的发生发展密切相关。截至目前，其潜在分子机制仍有待阐明。本研究旨在鉴定慢性肾脏病诱导的胰岛素抵抗所特有的代谢物及分子通路。<b><i>方法:</i></b> 采用超高效液相色谱-串联质谱（Ultra-performance liquid chromatography-tandem mass spectrometer, UPLC-MS）分析结合正交偏最小二乘判别分析（orthogonal partial least square discriminant analysis, OPLS-DA），对大鼠血清、肝脏及肌肉组织中的代谢谱进行分析，并探究与慢性肾脏病和高脂饮食（high fat diet, HFD）诱导的胰岛素抵抗相关的分子通路。<b><i>结果:</i></b> 在5/6肾切除术（5/6 Nephrectomy, 5/6 Nx）术后18周，通过肾脏组织病理学检测与生化指标分析证实慢性肾脏病造模成功。此外，慢性肾脏病诱导的胰岛素抵抗大鼠与高脂饮食诱导的胰岛素抵抗大鼠，其空腹胰岛素水平及胰岛素抵抗稳态模型评估指数（homeostasis model assessment of insulin resistance, HOMA-IR）均显著升高。通过超高效液相色谱-串联质谱结合正交偏最小二乘判别分析，我们在慢性肾脏病诱导的胰岛素抵抗大鼠的血清、肝脏及肌肉组织中分别鉴定出101、59及41种差异代谢物；而与对照组相比，高脂饮食诱导的胰岛素抵抗大鼠的血清、肝脏及肌肉组织中分别发现58、38及17种差异代谢物。进一步对比发现，相较于高脂饮食诱导的胰岛素抵抗大鼠，慢性肾脏病诱导的胰岛素抵抗大鼠主要表现出色氨酸代谢、精氨酸代谢及氧化三甲胺代谢通路的异常。值得注意的是，慢性肾脏病诱导的胰岛素抵抗与高脂饮食诱导的胰岛素抵抗大鼠体内的差异代谢物呈现相反的变化趋势。<b><i>结论:</i></b> 慢性肾脏病诱导的胰岛素抵抗大鼠与高脂饮食诱导的胰岛素抵抗大鼠，其代谢物及相关通路的改变存在显著差异。本研究结果可为肾功能下降所致胰岛素抵抗的特异性发病机制提供重要参考依据。