Department of Endocrinology, The First Huaian Hospital Affiliated to Nanjing Medical University, Huai'an, 223300 Jiangsu, China.
Nanjing Medical University, School of Public Health, Nanjing, 210000 Jiangsu, China.
J Diabetes Res. 2022 Jan 29;2022:1755563. doi: 10.1155/2022/1755563. eCollection 2022.
As an active form of vitamin D (VD), 1,25-dihydroxyvitamin D (1,25(OH)D) is involved in the development of many metabolic diseases, such as diabetes, autoimmune diseases, and tumours. While prospective epidemiological studies have consistently implicated VD deficiency in the regulation of glucose metabolism and insulin sensitivity, the specific mechanism remains unclear. Here, we generated 1(OH)ase-null mice (targeted ablation of the 25-hydroxyvitamin D 1 hydroxylase enzyme) and found that these mice developed hepatic glucose overproduction, glucose intolerance, and hepatic insulin resistance accompanied by reduced Sirtuin 1 (Sirt1) expression. The chromatin immunoprecipitation (ChIP) and a luciferase reporter assay revealed that 1,25(OH)D-activated VD receptor (VDR) directly interacted with one VD response element (VDRE) in the Sirt1 promoter to upregulate Sirt1 transcription, triggering a cascade of serine/threonine kinase (AKT) phosphorylation at S473 and FOXO1 phosphorylation at S256. This phosphorylation cascade reduced the expression of gluconeogenic genes, eventually attenuating glucose overproduction in the liver. In addition, a signaling pathway was found to modulate gluconeogenesis involving VDR, Sirt1, Rictor (a component of mTOR complex 2 [mTorc2]), AKT, and FOXO1, and Sirt1 and FOXO1 were identified as key modulators of dysregulated gluconeogenesis due to VD deficiency.
作为维生素 D(VD)的一种活性形式,1,25-二羟维生素 D(1,25(OH)D)参与多种代谢疾病的发生,如糖尿病、自身免疫性疾病和肿瘤。虽然前瞻性流行病学研究一致表明 VD 缺乏与葡萄糖代谢和胰岛素敏感性的调节有关,但具体机制尚不清楚。在这里,我们生成了 1(OH)ase 基因敲除小鼠(靶向敲除 25-羟维生素 D 1 羟化酶),发现这些小鼠出现肝葡萄糖过度产生、葡萄糖耐量受损和肝胰岛素抵抗,同时伴有 Sirtuin 1(Sirt1)表达减少。染色质免疫沉淀(ChIP)和荧光素酶报告基因检测显示,1,25(OH)D 激活的 VD 受体(VDR)直接与 Sirt1 启动子中的一个 VD 反应元件(VDRE)相互作用,上调 Sirt1 转录,引发丝氨酸/苏氨酸激酶(AKT)在 S473 位点和 FOXO1 在 S256 位点的磷酸化级联反应。该磷酸化级联反应减少了糖异生基因的表达,最终减弱了肝脏中的葡萄糖过度产生。此外,还发现了一条信号通路可调节涉及 VDR、Sirt1、Rictor(mTOR 复合物 2 [mTorc2] 的一个组成部分)、AKT 和 FOXO1 的糖异生,并且 Sirt1 和 FOXO1 被鉴定为 VD 缺乏导致的糖异生失调的关键调节因子。