ROLE OF CIRCADIAN RHYTHM AND INTERMITTENT DOSING IN MUSCLE TRIGLYCERIDE LIPASE INDUCTION BY GLUCOCORTICOIDS

项目摘要 糖皮质激素（GC）类固醇是我们体内能量代谢昼夜节律调节的原始信号。的 昼夜节律不仅调节内源性GCs，而且调节外源性合成GCs的作用。 三酰甘油代谢与肌肉生物学的昼夜节律调节特别相关，如肌细胞内代谢。 三酰基甘油（IMTG）是健康年轻男性中因昼夜节律失调而升高的最丰富的脂质。 然而，GC调节对IMTG代谢的昼夜节律特异性影响仍然未知。引人注目的是，在 与每日一次GCs的代谢异常作用相反，间歇性每周一次GCs促进肌肉 营养不良小鼠的代谢和力的产生，与GC中代谢应激的缓解相关， 治疗营养不良的病人。在美国，慢性GC摄入的患病率> 250万人。因此有 对区分GC治疗的有益机制与有害机制的未满足的需求。在WT小鼠中，我们 研究发现，在饮食诱导的肥胖症的情况下，光相特异性间歇性泼尼松降低了IMTG 和老化，而暗相特异性GC给药消除了这些促代谢作用。治疗驱动 IMTG降低与肌肉质量、AKT磷酸化和力产生的增加相关。 经处理的老化肌肉的转录组学分析显示脂肪三酰甘油脂肪酶（ATGL）的上调。 GC激活脂肪组织中的ATGL，但ATGL在肌肉对GC反应中的作用仍不清楚。此外，委员会认为， GC对IMTG的影响和相关的肌肉重塑所需的肌肉ATGL的程度是 仍然未知。我们现在已经产生了具有肌肉特异性诱导型ATGL消融（imATGL-KO）的小鼠。在 与组成型KO相反，这些小鼠将在没有发育或出生后的情况下揭示肌肉ATGL效应， 补偿。在这里，我们将使用这个新的模型来测试假设，肌肉ATGL是必要的， 间歇性GC对肌肉IMTG的影响取决于GC摄入的昼夜节律时间和间歇频率。 我们还将测试肌肉ATGL在多大程度上介导了光相GC对肌肉重塑的影响 和葡萄糖摄取。在目标1中，我们将确定肌肉ATGL在GC昼夜节律特异性效应中的作用 对IMTG代谢的影响我们推测，肌肉特异性ATGL是外源性GC对 IMTG取决于光相位限制暴露，即与内源性GC节律相反。我们将测试这个 在我们的imATGL-KO小鼠中，测量IMTG对外源性和内源性的昼夜节律调节的响应， GC。在目标2中，我们将阐明肌肉ATGL在GC对肌肉的频率特异性效应中的作用 新陈代谢.我们假设肌肉ATGL将IMTG分解与有利和不利的 肌肉程序诱导的间歇性与每日剂量的轻相特异性GC。我们将在我们的 imATGL-KO小鼠，测量间歇性与每日泼尼松后的IMTG和肌肉葡萄糖摄取。我们 一项研究确定了将GC从代谢毒性药物再转化为肌肉中代谢激动剂的机制。 我们还将测试肌肉ATGL作为昼夜节律激素信号（如GC）效应器的新概念。

PROJECT SUMMARY Glucocorticoid (GC) steroids are a primal signal for circadian regulation of energy metabolism in our body. The circadian rhythm regulates not only the endogenous GCs, but also the effects of exogenous synthetic GCs. Triacylglycerol metabolism is particularly relevant for circadian regulation of muscle biology, as intramyocellular triacylglycerols (IMTGs) are the most abundant lipid elevated by circadian misalignment in healthy young men. However, the circadian-specific effects of GC modulation on IMTG metabolism are still unknown. Strikingly, in contrast to the dysmetabolic effects of once-daily GCs, intermittent once-weekly GCs promoted muscle metabolism and force production in dystrophic mice, correlating with a mitigation of metabolic stress in GC- treated dystrophic patients. Chronic GC intake has a prevalence of >2.5M people in the US. Therefore, there is an unmet need to discriminate the beneficial versus deleterious mechanisms of GC treatments. In WT mice, we found that light-phase-specific intermittent prednisone decreased IMTGs in conditions of diet-induced obesity and aging, whereas dark-phase-specific GC dosing abrogated these pro-metabolic effects. The treatment-driven IMTG decrease correlated with increases in muscle mass, AKT phosphorylation and force production. Transcriptomic profiling of treated aging muscle showed upregulation of adipose triacylglycerol lipase (ATGL). GCs activate ATGL in fat tissue but the role of ATGL in the muscle response to GCs is still unknown. Moreover, the extent to which muscle ATGL is required for GC effects on IMTGs and the associated muscle remodeling is still unknown. We have now generated mice with muscle-specific inducible ATGL ablation (imATGL-KO). In contrast to constitutive KO, these mice will unveil muscle ATGL effects without developmental or postnatal compensations. Here we will use this new model to test the hypothesis that muscle ATGL is required for the intermittent GC effects on muscle IMTGs depending on circadian time and intermittent frequency of GC intake. We will also test the extent to which muscle ATGL mediates the light-phase GC effects on muscle remodeling and glucose uptake. In Aim 1 we will determine the role of muscle ATGL in the circadian-specific effects of GCs on IMTG metabolism. We hypothesize that muscle-specific ATGL is required for the exogenous GC effects on IMTGs depending on light-phase-restricted exposure, i.e. opposite to endogenous GC rhythm. We will test this in our imATGL-KO mice, measuring IMTGs in response to circadian modulation of exogenous and endogenous GCs. In Aim 2 we will elucidate the role of muscle ATGL in the frequency-specific effects of GCs on muscle metabolism. We hypothesize that muscle ATGL links IMTG breakdown to the favorable versus unfavorable muscle programs induced by intermittent versus daily dosing of light-phase-specific GCs. We will test this in our imATGL-KO mice, measuring IMTGs and muscle glucose uptake after intermittent versus daily prednisone. Our study identifies mechanisms to reconvert GCs from metabolically toxic drugs to metabolic agonists in muscle. We will also test the novel concept of muscle ATGL as effector of circadian hormonal signals like GCs.