Glucocorticoid regulation of NAD+ and energy metabolism in skeletal muscle ageing

项目背景和需求糖皮质激素是肌肉能量稳态的调节剂，轻度过量或缺乏会导致代谢性疾病，特别是在肌肉中，导致与年龄相关的虚弱和心血管疾病。NAD+在氧化还原反应中作为代谢辅助因子的作用已被充分理解，NAD+合成受损或消耗增加被认为会导致与年龄相关的功能缺陷，特别是在肌肉中。研究表明，使用NAD+前体增加NAD+代谢组可以改变代谢，并对线粒体功能和炎症产生积极影响。糖皮质激素与肌肉中NAD+代谢组和合成途径相互作用，但这种相互作用对年龄相关代谢失调的性质和影响尚未得到研究。有人提出，对这一新的代谢调节轴的研究将阐明新的肌肉生物学和一系列年龄相关疾病过程的治疗方法。假设糖皮质激素和NAD+的合成和消耗途径相互作用，通过对健康重要的网络的代谢和转录控制来调节老化肌肉的能量代谢。目的和目的：1)明确糖皮质激素和NAD+对肌肉代谢网络动力学和信号通路的响应。2)在NAD和糖皮质激素代谢改变的小鼠模型中研究该网络及其随衰老的调节。3)在年轻人和老年人中检查NAD的动态、敏感性和与糖皮质激素的相互作用。目的：研究糖皮质激素与NAD+通路的相互作用，使用原代小鼠肌管、有无轻度和慢性过量或缺乏的小鼠（如CRH KO）、NAD+合成通路遗传修饰的年轻和老年小鼠模型（NMRK1/2KO、NAMPTKO、NMR2）。Tg过表达)结合最先进的方法[例如NAD+代谢组；NAD+生物合成程序的表达和活性；针对蛋白质组学;高分辨率线粒体呼吸；代谢组学;稳定同位素（C13葡萄糖和棕榈酸酯，N15谷氨酰胺）示踪营养代谢。目的3-为了测试衰老的人是否更容易因糖皮质激素而代谢恶化，并检查NAD在这一过程中的作用，年轻人和老年人将暴露在轻度糖皮质激素过量（使用口服强的松龙）的条件下，同时补充和不补充NR，以评估其对禁食、餐后和运动代谢的影响。这将通过检查肌肉和脂肪活检、脂肪微透析、血液和尿液样本来进行。这一目标将受益于与牛津大学的Jeremy Tomlinson教授的密切合作。Jeremy Tomlinson教授是世界知名的类固醇生物学家和临床医生，在糖皮质激素在健康和疾病中的作用的代谢理解方面具有专业知识。预期结果-糖皮质激素与年轻和老年小鼠和人类肌肉中NAD+代谢网络相互作用的机制和生理学知识。-深入了解营养性NAD+增强肌肉代谢反应和功能在年轻和老年小鼠和人类中的治疗潜力。-学生将在实验室接受最先进的综合生理学的高级培训，并获得良好的指导，促进职业发展和对文献做出有影响力的贡献。

Background and need for the projectGlucocorticoid hormones are regulators of muscle energy homeostasis, and in mild excess or deficiency lead to metabolic disease, particularly in muscle, contributing to age-related frailty and cardiovascular disease. The role of NAD+ as a metabolic cofactor in redox reactions is well understood, and impaired NAD+ synthesis or increased consumption is proposed to drive aspects of age-related functional deficits, particularly in muscle. It has been shown that using NAD+ precursors to augment the NAD+ metabolome can modify metabolism and positively impact on mitochondrial function and inflammation. Glucocorticoids interact with the NAD+ metabolome and synthetic pathways in muscle, but the nature and impact of this interaction on age-related metabolic dysregulation has not been studied. It is proposed that interrogation of this new axis of metabolic regulation will illuminate novel muscle biology and therapies in a range of age-related disease processes.HypothesisGlucocorticoid hormone and NAD+ synthesis and consumption pathways interact to modulate energy metabolism in ageing muscle through metabolic and transcriptional control of networks important to health.Aims and objectives1) Define muscle metabolic network dynamics and pathway signalling in response to glucocorticoid and NAD+.2) Investigate this network and its modulation with ageing in mouse models of altered NAD and glucocorticoid metabolism.3) Examine NAD dynamics, sensitivity and interactions with glucocorticoid in young and aged humans.Brief experimental planAim-1 and 2- To investigate glucocorticoid interaction with NAD+ pathways using primary mouse myotubes, mice with and without mild and chronic excess or deficiency e.g. CRH KO, young and aged mouse models with genetic modifications of NAD+ synthetic pathways (NMRK1/2KO, NAMPTKO, NMR2.Tg overexpression) in combination with state-of-the-art methodologies [e.g. NAD+ metabolome; expression and activity of the NAD+ biosynthetic programme; targeted proteomics; high resolution mitochondrial respiration; metabolomics; stable isotope (C13 glucose and palmitate, N15 glutamine) tracing of nutrient metabolism.Aim 3- To test whether metabolism deteriorates in response to glucocorticoid more readily in ageing humans and examine the role of NAD in this process, young and aged humans will be exposed to conditions of mild glucocorticoid excess (using oral prednisolone) with and without supplementation with NR to assess its effects on fasting, postprandial and exercise metabolism. This will be carried by examining muscle and adipose biopsy, adipose micro-dialysis, blood and urine samples. This aim will benefit from close collaboration with Professor Jeremy Tomlinson at the University of Oxford- a world renowned steroid biologist and clinician with expertise in the metabolic understanding of glucocorticoid hormone action in health and disease.Expected outcome- Mechanistic and physiological knowledge of glucocorticoid interactions with the NAD+ metabolic network in muscle in young and aged mice and humans.- Insight into the therapeutic potential of nutritional NAD+ boosting to augment muscle metabolic responses and function in young and aged mice and humans.- Student to receive advanced training in state-of-the-art integrative physiology in laboratories with reputations for strong mentorship, onward career development and impactful contributions to the literature.