Clinic Center of Human Gene Research, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
Hubei Key Laboratory of Metabolic Abnormalities and Vascular Aging, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
Clin Transl Med. 2022 May;12(5):e854. doi: 10.1002/ctm2.854.
Iron is essential for all mammalian life, and either a deficiency or excess of iron can cause diseases. AMP-activated protein kinase (AMPK) is a critical regulator of metabolic homeostasis; however, it has not been established whether AMPK regulates iron metabolism.
Iron, hepcidin and ferroportin levels were examined in mice with global and hepatocyte-specific knockout of AMPKα1 and AMPKα2. Primary AMPKα1 or AMPKα2 deleted hepatocytes were isolated and cultured in hypoxia condition to explore PHD2, HIF and hydroxylated HIF1α levels. We performed immunoprecipitation, in vitro AMPK kinase assay and site-direct mutant assay to detect phosphorylation sites of PHD2. We also obtained liver tissues from patients with anaemia of chronic disease undergoing surgery, AMPKα1 and hydroxylated HIF1α levels were measured by immunohistochemical analysis.
We found that mice with global deficiency of AMPKα1, but not AMPKα2, exhibited hypoferraemia as well as iron sequestration in the spleen and liver. Hepatocyte-specific, but not myeloid-specific, ablation of AMPKα1 also reduced serum iron levels in association with increased hepcidin and decreased ferroportin protein levels. Mechanistically, AMPKα1 directly phosphorylated prolyl hydroxylase domain-containing (PHD)2 at serines 61 and 136, which suppressed PHD2-dependent hydroxylation of hypoxia-inducible factor (HIF)1α and subsequent regulation of hepatic hepcidin-related iron signalling. Inhibition of PHD2 hydroxylation ameliorated abnormal iron metabolism in hepatic AMPKα1-deficient mice. Furthermore, we found hepatic AMPKα/PHD2/HIFα/ hepcidin axes were highly clinically relevant to anaemia of chronic disease.
In conclusion, these observations suggest that hepatic AMPKα1 has an essential role in maintaining iron homeostasis by PHD2-dependent regulation of hepcidin, thus providing a potentially promising approach for the treatment of iron disturbances in chronic diseases.
铁是所有哺乳动物生命所必需的，无论是铁的缺乏还是过量都会导致疾病。AMP 激活的蛋白激酶（AMPK）是代谢稳态的关键调节剂；然而，AMPK 是否调节铁代谢尚不清楚。
检查了 AMPKα1 和 AMPKα2 基因敲除的全身性和肝细胞特异性敲除的小鼠的铁、hepcidin 和 ferroportin 水平。分离并在低氧条件下培养原发性 AMPKα1 或 AMPKα2 缺失的肝细胞，以研究 PHD2、HIF 和羟化的 HIF1α 水平。我们进行免疫沉淀、体外 AMPK 激酶测定和定点突变测定，以检测 PHD2 的磷酸化位点。我们还从接受手术的慢性病贫血患者获得肝组织，通过免疫组化分析测量 AMPKα1 和羟化的 HIF1α 水平。
我们发现，AMPKα1 基因全身性敲除的小鼠，而不是 AMPKα2 基因敲除的小鼠，表现出低铁血症以及脾脏和肝脏中铁的蓄积。肝细胞特异性而非髓系特异性的 AMPKα1 缺失也降低了血清铁水平，同时增加了 hepcidin 并降低了 ferroportin 蛋白水平。机制上，AMPKα1 直接在丝氨酸 61 和 136 处磷酸化脯氨酰羟化酶结构域（PHD）2，抑制 PHD2 依赖性羟化缺氧诱导因子（HIF）1α，从而抑制肝脏 hepcidin 相关铁信号转导。抑制 PHD2 羟化可改善肝细胞 AMPKα1 缺陷小鼠异常的铁代谢。此外，我们发现肝脏 AMPKα/PHD2/HIFα/hepcidin 轴与慢性病贫血高度相关。
总之，这些观察结果表明，肝 AMPKα1 通过 PHD2 依赖性调节 hepcidin 在维持铁稳态方面发挥重要作用，从而为治疗慢性病中的铁紊乱提供了一种有潜力的方法。
