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

背景和项目需要糖皮质激素是肌肉能量平衡的调节器，轻度过量或不足会导致代谢性疾病，特别是在肌肉中，导致与年龄相关的虚弱和心血管疾病。NAD+作为代谢辅助因子在氧化还原反应中的作用是众所周知的，NAD+合成受损或消耗增加被认为是年龄相关功能缺陷的驱动因素，特别是在肌肉中。已有研究表明，使用NAD+前体增强NAD+代谢组可以调节代谢，对线粒体功能和炎症有积极影响。糖皮质激素与肌肉中的NAD+代谢体和合成途径相互作用，但这种相互作用的性质和对年龄相关代谢失调的影响尚未被研究。假设糖皮质激素和NAD+合成和消耗途径相互作用，通过对对健康至关重要的网络的代谢和转录控制，调节衰老肌肉的能量代谢。目的和目的1)定义肌肉代谢网络动力学和对糖皮质激素和NAD+反应的通路信号。2)在NAD和糖皮质激素代谢改变的小鼠模型中，研究该网络及其与衰老的调节。3)研究NAD的动力学、敏感性以及与糖皮质激素的相互作用有或没有轻度和慢性过剩或缺乏的小鼠，例如CRH KO，结合最先进的方法[例如NAD+代谢体]，具有NAD+合成途径(NMRK1/2KO，NAMPTKO，NMR2.Tg过表达)基因修饰的年轻和老年小鼠模型；NAD+生物合成程序的表达和活性；靶向蛋白质组学；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，N15谷氨酰胺)对营养代谢的追踪。AIM 3-为了测试老年人是否更容易对糖皮质激素做出反应而导致代谢恶化，并研究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的条件下(使用口服强的松龙)，并补充和不补充NR，以评估其对空腹、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。这一目标将得益于与牛津大学杰里米·汤姆林森教授的密切合作。杰里米·汤姆林森教授是世界著名的类固醇生物学家和临床医生，在了解糖皮质激素在健康和疾病中的代谢作用方面具有专业知识。预期结果-糖皮质激素与年轻和老年小鼠和人类肌肉中的NAD+代谢网络相互作用的机制和生理学知识。-洞察营养NAD+增强的治疗潜力，以增强年轻和老年小鼠和人类的肌肉代谢反应和功能。-学生在实验室接受最先进的综合生理学高级培训，以强大的导师、未来的职业发展和对文献的影响而闻名。

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.