Proteome Dynamics Reveals Pro-inflammatory Remodeling of Plasma Proteome in a Mouse Model of NAFLD

Nonalcoholic fatty liver disease (NAFLD) is associated with an increased risk of cardiovascular disease (CVD). Liver is the major source of the circulatory proteins and alterations in plasma proteome have been implicated in atherosclerosis. We used a recently developed 2H2O-metabolic labeling method in combination with the label-free quantification to evaluate the effect of a Western diet (WD) on the dynamics of plasma proteins in LDL receptor-deficient (LDLR-/-) mice, a model of NAFLD and atherosclerosis. There were no significant changes in the expression level of total proteins due to the WD with a bulk protein mean half-life of 18.0±15.1 hours in control and 16.7±11.1 hours in WD groups. WD led to pro-inflammatory distribution of circulatory proteins analyzed in apoB-depleted plasma attributed to their increased production. The fractional catabolic rates of fast-turnover proteins with stress-response, lipid metabolism and transport functions were significantly increased with WD (P<0.05). The pathway analyses revealed that alterations in plasma proteome dynamics were related to the suppression of hepatic PPARα, which was confirmed based on reduced gene and protein expression of PPARα on WD. These changes were associated with ~4 fold increase (P<0.0001) in pro-inflammatory property of apoB-depleted plasma. In conclusion, the proteome dynamics method reveals pro-inflammatory remodeling of plasma proteome relevant to liver disease. As in vivo metrics of liver function, this approach can be used to test therapies in NAFLD and other diseases非酒精性脂肪性肝病（NAFLD）与心血管疾病（CVD）发病风险升高显著相关。肝脏是循环蛋白的主要合成器官，血浆蛋白质组的异常改变已被证实与动脉粥样硬化的发生发展密切相关。本研究采用新近开发的重水代谢标记法（2H2O-metabolic labeling method）结合无标记定量（label-free quantification）技术，评估了西方饮食（WD）对低密度脂蛋白受体缺陷（LDL receptor-deficient, LDLR-/-）小鼠血浆蛋白动态变化的影响；该小鼠模型同时可作为非酒精性脂肪性肝病与动脉粥样硬化的研究模型。 结果显示，两组小鼠的总蛋白表达水平未出现显著差异；对照组总蛋白的平均半衰期为18.0±15.1小时，西方饮食组为16.7±11.1小时。西方饮食可使载脂蛋白B缺失血浆（apoB-depleted plasma）中检测到的循环蛋白呈现促炎分布特征，该现象与这些蛋白的合成水平升高有关。对于具备应激反应、脂质代谢及转运功能的快速更新蛋白，西方饮食可显著提升其分解代谢分数速率（fractional catabolic rates, P<0.05）。通路分析结果表明，血浆蛋白质组的动态变化与肝脏过氧化物酶体增殖物激活受体α（PPARα）的表达抑制相关，这一结论通过西方饮食组小鼠肝脏PPARα的基因与蛋白表达水平降低得到了验证。上述变化与载脂蛋白B缺失血浆的促炎特性提升约4倍显著相关（P<0.0001）。 综上，蛋白质组动态分析方法可揭示与肝脏疾病相关的血浆蛋白质组促炎性重塑。作为反映肝脏功能的体内检测指标，该方法可用于非酒精性脂肪性肝病及其他疾病的治疗方案评估。