Ubiquitin-specific protease 2 (USP2) participates in glucose metabolism in peripheral tissues such as the liver and skeletal muscles. However, the glucoregulatory role of USP2 in the CNS is not well known. In this study, we focus on USP2 in the ventromedial hypothalamus (VMH), which has dominant control over systemic glucose homeostasis. ISH, using a Usp2-specific probe, showed that Usp2 mRNA is present in VMH neurons, as well as other glucoregulatory nuclei, in the hypothalamus of male mice. Administration of a USP2-selective inhibitor ML364 (20 ng/head), into the VMH elicited a rapid increase in the circulating glucose level in male mice, suggesting USP2 has a suppressive role on glucose mobilization. ML364 treatment also increased serum norepinephrine concentration, whereas it negligibly affected serum levels of insulin and corticosterone. ML364 perturbated mitochondrial oxidative phosphorylation in neural SH-SY5Y cells and subsequently promoted the phosphorylation of AMP-activated protein kinase (AMPK). Consistent with these findings, hypothalamic ML364 treatment stimulated AMPKα phosphorylation in the VMH. Inhibition of hypothalamic AMPK prevented ML364 from increasing serum norepinephrine and blood glucose. Removal of ROS restored the ML364-evoked mitochondrial dysfunction in SH-SY5Y cells and impeded the ML364-induced hypothalamic AMPKα phosphorylation as well as prevented the elevation of serum norepinephrine and blood glucose levels in male mice. These results indicate hypothalamic USP2 attenuates perturbations in blood glucose levels by modifying the ROS–AMPK–sympathetic nerve axis.

SIGNIFICANCE STATEMENT Under normal conditions (excluding hyperglycemia or hypoglycemia), blood glucose levels are maintained at a constant level. In this study, we used a mouse model to identify a hypothalamic protease controlling blood glucose levels. Pharmacological inhibition of USP2 in the VMH caused a deviation in blood glucose levels under a nonstressed condition, indicating that USP2 determines the set point of the blood glucose level. Modification of sympathetic nervous activity accounts for the USP2-mediated glucoregulation. Mechanistically, USP2 mitigates the accumulation of ROS in the VMH, resulting in attenuation of the phosphorylation of AMPK. Based on these findings, we uncovered a novel glucoregulatory axis consisting of hypothalamic USP2, ROS, AMPK, and the sympathetic nervous system.

泛素特异性蛋白酶 2 (USP2) 参与外周组织如肝脏和骨骼肌中的葡萄糖代谢。然而，USP2 在 CNS 中的血糖调节作用尚不为人所知。在这项研究中，我们专注于腹内侧下丘脑 (VMH) 中的 USP2，它对全身葡萄糖稳态具有显着控制。ISH，使用Usp2特异性探针，表明Usp2mRNA 存在于雄性小鼠下丘脑的 VMH 神经元以及其他葡萄糖调节核中。向 VMH 中施用 USP2 选择性抑制剂 ML364（20 ng/头）引起雄性小鼠循环葡萄糖水平的快速增加，表明 USP2 对葡萄糖动员具有抑制作用。ML364 治疗还增加了血清去甲肾上腺素浓度，而它对血清胰岛素和皮质酮水平的影响可以忽略不计。ML364 扰乱了神经 SH-SY5Y 细胞中的线粒体氧化磷酸化，随后促进了 AMP 活化蛋白激酶 (AMPK) 的磷酸化。与这些发现一致，下丘脑 ML364 治疗刺激了 VMH 中的 AMPKα 磷酸化。抑制下丘脑 AMPK 可防止 ML364 增加血清去甲肾上腺素和血糖。去除 ROS 可恢复 ML364 诱发的 SH-SY5Y 细胞线粒体功能障碍，并阻止 ML364 诱导的下丘脑 AMPKα 磷酸化，并防止雄性小鼠血清去甲肾上腺素和血糖水平升高。这些结果表明下丘脑 USP2 通过改变 ROS-AMPK-交感神经轴来减弱血糖水平的扰动。

意义声明在正常情况下（不包括高血糖或低血糖），血糖水平保持在恒定水平。在这项研究中，我们使用小鼠模型来识别控制血糖水平的下丘脑蛋白酶。VMH 中 USP2 的药理学抑制导致在非应激条件下血糖水平出现偏差，表明 USP2 决定了血糖水平的设定点。交感神经活动的改变解释了 USP2 介导的葡萄糖调节。从机制上讲，USP2 减轻了 VMH 中 ROS 的积累，导致 AMPK 的磷酸化减弱。基于这些发现，我们发现了一个由下丘脑 USP2、ROS、AMPK 和交感神经系统组成的新型血糖调节轴。