α-酮戊二酸通过OXGR1调控造血干/前体细胞增殖促进动脉粥样硬化的机制

代谢紊乱导致的骨髓造血干/前体细胞（HSPC）增殖，是促进动脉粥样硬化（AS）的重要原因，但机制不清。我们前期代谢组学分析发现高脂LDLr-/-小鼠骨髓HSPC中α-酮戊二酸（AKG）水平升高；体外细胞培养显示AKG刺激能增加HSPC细胞数量。有报道AKG通过受体OXGR1导致小鼠肌肉肥大。本课题拟在此基础上，利用代谢组学确认正常和高血脂LDLr-/-小鼠HSPC、人CD34+细胞代谢图谱和AKG水平；结合磷酸化芯片、单细胞测序等方法，在OXGR1-/-小鼠给予2%AKG模型探讨AKG/OXGR1调节HSPC增殖的机制；将野生/OXGR1-/-小鼠骨髓细胞移植到LDLr-/-小鼠，明确AKG/OXGR1在AS的作用，以证实我们的假说：脂代谢紊乱时，HSPC糖脂摄取增加促进三羧酸循环，导致α-酮戊二酸水平增加而激活OXGR1受体及其下游通路，促进HSPC增殖，增加AS炎症细胞数量加重AS。

Hematopoietic stem/progenitor cells (HSPC) reside in hypoxic bone marrow niche in which they utilize glycolysis to maintain quiescent status. The homeostasis of quiescence and activation of HSPC is achieved by self-regulation and other cells within the niche. We and others recently found that under hypercholesterolemia conditions, enhanced cholesterol accumulation in HSPC stimulated cell proliferation and differentiation, leading to increased number of inflammatory cells in the peripheral blood and atherosclerotic plaque. When we isolated HSPC from LDLr-/- mice fed on normal or high-fat diet by FACS sorting and performed glycolipid metabonomics, we found that α-ketoglutaric acid was significantly increased in HSPC of hypercholesterolemic LDLr-/- mice compared with those on chow diet. After bone marrow cells were treated with α-ketoglutaric acid for 3-5 days in vitro and harvested for HSPC quantification by FACS, α-ketoglutaric acid induced an increase of HSPC frequency and number in a dose-dependent manner. Recently, Yuan et al demonstrated that α-ketoglutaric acid promoted muscle hypertrophy via its receptor OXGR1. Taken together, we hypothesize that hyperlipidemia enhances tricarboxylic acid cycle in HSPC. Resulting from that, the production of α-ketoglutaric acid is increased that in turn stimulates HSPC proliferation via OXGR1, leading to inflammatory cell production and atherosclerosis (AS) progression. In the project, we will confirm the metabolic feature of HSPC in normo- and hypercholesterolemia mice. Using OXGR1-/- mice, we would clarify whether and how α-ketoglutaric acid activates HSPC proliferation and accelerates atherosclerosis. Ultimately, we hope that the results of this study would shed light on how intermediate metabolites in hyperlipidemia modulate HSPC proliferation in atherosclerosis.