肌肉~（31）P-MRS的临床研究进展

磁共振波谱分析（magnetic resonance spectroscopy MRS）是目前唯一无创性定量研究人体组织细胞代谢、生理生化改变的方法。磁共振磷谱（31P-MRS）可对无机磷（Pi）、磷酸肌酸（PCr）、三磷酸腺苷（ATP）等含磷高能化合物进行定量分析,是在体研究骨骼肌能量代谢的有力工具。动态磷谱技术可测量肌肉在静息状态、收缩过程和恢复过程中细胞内高能磷酸化合物的变化,评价骨骼肌做功时的能量的转换效率,实现对线粒体功能的无创性评价。本文将对肌肉磷谱的研究进展做综述,尤其侧重于动态磷谱的应用,为以后利用磷谱客观研究肌肉相关疾病奠定良好的基础。     

低温对大鼠骨骼肌能量代谢的影响——Ⅰ.高能磷酸化合物含量的变化

本实验选择对低温比较敏感的骨骼肌组织作为实验对象。将19只大鼠随机分成3组,其右后肢经冷冻处理使组织温度分别达 5℃、0℃及-5℃,于复温后不同时间测定骨骼肌中四种高能磷酸化合物AMP,ADP、ATP及CP的含量。结果表明,大鼠骨骼肌组织中高能磷酸化合物含量随冷冻时组织最低温度的下降而不同程度的减少,并且具有明显的时相过程。复温后即刻至4小时下降迅速,4～12小时三组值较为接近,其后随时间延长而明显分离。 5℃组恢复得早而且明显,0℃组恢复程度次于 5℃组,-5℃组含量下降最明显而且几乎不恢复。提示:低温使骨骼肌组织能量的产生和贮存过程受到影响。     

剧烈运动中的能量供应

剧烈运动是指持续时间短、运动强度大,以无氧供能为主的运动,但是机体的能量供应又是一个连续的统一整体。剧烈运动时能量供应主要有以下两种形式: 1.高能磷化物(ATP、CP)供能 ATP是高能化合物中最重要的一种,在提供能量中起重要作用。肌肉活动时,肌肉中的ATP在ATP酶的催化下,分解为ADP和无机磷酸,同时放出能量。每克分子ATP分解为ADP可释放7-12千卡的热能,这是肌肉收缩时唯一的直接能源。 ATP在释放能量转变为ADP后,ADP再接受能量又生成ATP。ADP虽也有一个高     

第五章 新陈代谢的概念和糖代谢(提要)

从这章开始,我们将介绍组成生物体的主要物质在生物体内是如何变化的,如何相互转化的,变化过程中的能量又是如何转化的,即物质代谢。首先要学习新陈代谢的有关概念,再学习具体的代谢途径。学习“新陈代谢的概念”这一节,要注意准确地掌握基本概念。如什么是新陈代谢?什么是合成代谢?什么是分解代谢?以及了解新陈代谢的特点。随着学习具体的代谢途径,对新陈代谢的认识会逐步具体、深入。在这一节中要简要介绍有关高能化合物的知识。要求掌握什么是高能化合物,并了解腺苷三磷酸(ATP)、磷酸烯醇式丙酮酸、甘油酸-1.3-二磷酸、乙酰CoA等是生物体内常见的高能化合物。对于ATP的结构应熟悉。1摩尔ATP水解成ADP时可释放出7.3千卡(30.5KJ)的能量。     

简述肌肉收缩时的化学变化

肌肉收缩为身体的各种活动提供基本动力,例如行走、写字、说话、呼吸、心跳等。肌肉收缩时,肌肉内部的化学变化和能量变化可概括成三个部分: 一、三磷酸腺苷(ATP)分解所提供的能量是肌肉收缩的直接能源. 当运动神经纤维上的神经冲动到达肌纤维时,肌纤维内一系列微观的兴奋性变化,激发了ATP酶活性,引起ATP分解成二磷酸腺苷(ADP)及磷酸根(P)高能磷酸键的断开可释放较多的能量(E)。     

胚胎发育过程中腺三磷酶作用的研究概况

腺三磷酶(ATPase)是一种能够催化高能磷酸化合物腺三磷(ATP)分解的酶,ATP 分解后产生出大量的储藏能,因此 ATPase-ATP 系统在各种生命活动,包括胚胎发育的能量供给过程中,起着重要的作用。ATP-ase 除了与发育过程中能量的供给有关之外,还关     

酶促合成高比放射性γ-~(32)P-ATP 采用一种简便的管道装置

ATP具有高能磷酸键,在生物体能量的交换中占着中心地位。蛋白质生物合成、肌肉收缩和磷酰基的转移等重要生理过程,都必须有它参加。同位素标记的ATP对研究代谢过程提供了一项有效的方法,对某些可利用它来测     

利用CRISPRi干扰研究MyoG和Myf6基因对牛骨骼肌卫星细胞分化的影响

CRISPR干扰(clustered regularly interspaced short palindromic repeat interference,CRISPRi)技术因高效的基因干扰效率而成为基因功能研究的重要工具。Myo G、Myf6基因是生肌调节因子家族(myogenic regulatory factors,MRFs)的重要成员,是骨骼肌分化所必需的调控因子。该研究以牛骨骼肌卫星细胞为实验材料,探讨Myo G和Myf6基因在骨骼肌卫星细胞分化过程中的相互关系。构建Myo G、Myf6基因CRISPRi载体,分别转染牛骨骼肌卫星细胞,诱导其分化,Real-time PCR检测肌肉分化重要功能基因Myo G、Myf6、MYH2、Myo D的表达情况。结果表明,在牛骨骼肌卫星细胞分化期间,抑制Myo G基因表达将诱导Myf6基因的代偿性升高,但并不能完全弥补Myo G基因的缺少对肌肉分化产生的影响,而抑制Myf6基因表达则不会引起Myo G基因表达升高,这为肌肉分化机制的阐明提供了理论依据。     

六周有氧运动改善动脉粥样硬化小鼠骨骼肌氧化损伤和促进肌肉因子生成

动脉粥样硬化累及外周动脉能引起骨骼肌病变，其中氧化损伤是骨骼肌病变的重要表现，并且动脉粥样硬化也会减少有益肌肉因子的生成分泌。肌肉因子鸢尾素(irisin)、肌肉素(musclin)和BAIBA被认为参与改善动脉粥样硬化。然而，目前尚不明确动脉粥样硬化诱导骨骼肌病变的分子机制，以及有氧运动训练对其骨骼肌氧化损伤和肌肉因子生成的影响。本研究采用高脂饮食(HFD)喂食载脂蛋白E基因敲除(ApoE^-/-)小鼠12周，以建立动脉粥样硬化模型，然后观察动脉粥样硬化小鼠骨骼肌中的氧化损伤、Nrf2抗氧化信号通路以及肌肉因子鸢尾素、musclin和BAIBA生成的变化，并通过6周有氧运动观察对动脉粥样硬化小鼠骨骼肌氧化损伤的改善作用，以及鸢尾素、肌肉素和BAIBA生成的影响。ApoE^-/-小鼠在HFD喂养12周时，采用多普勒超声评估动脉粥样硬化病变，与标准饮食喂养的野生型(WT)小鼠相比，ApoE^-/-小鼠主动脉内-中膜厚度(P<0.01)、峰值血流速度(P<0.05)和阻力指数(P<0.05)显著增加，血浆甘油三酯...     

Phosphorus-31 magnetic resonance spectroscopy of forearm flexor muscles in student rowers using an exercise protocol adjusted for differences in cross-sectional muscle area

To assess exercise energy metabolism of forearm flexor muscles in rowers, six male student rowers and six control subjects matched for age and sex were studied using phosphorus-31 magnetic resonance spectroscopy (31P-MRS). Firstly, to adjust for the effect of differences in cross-sectional muscle area, the maximal cross-sectional area (CSAmax) of the forearm flexor muscles was estimated in each individual using magnetic resonance imaging. Multistage exercise was then carried out with an initial energy production of 1 J.cm-2 CSAmax for 1 min and an increment of 1 J.cm-2 CSAmax every minute to the point of muscle exhaustion. A series of measurements of 31P-MRS were performed every minute. The CSAmax was significantly greater in the student rowers than in the control subjects [19.8 (SD 2.2) vs 17.1 (SD 1.2) cm2, P less than 0.05]. The absolute maximal exercise intensity (J.min-1) was greater in the rowers than in the control subjects. However, the maximal exercise intensity per unit of muscle cross sectional area (J.min-1.cm-2) was not significantly different between the two groups. During mild to moderate exercise intensities, a decrease in phosphocreatine and an increase in inorganic phosphate before the onset of acidosis were significantly less in the rowers, indicating a requirement of less adenosine 5'-diphosphate to drive adenosine 5'-triphosphate production. The onset of acidosis was also significantly delayed in the rowers. No difference was observed in forearm blood flow between the two groups at the same exercise intensity (J.min-1.cm-2).(ABSTRACT TRUNCATED AT 250 WORDS)     

Work-Related Pain in Extrinsic Finger Extensor Musculature of Instrumentalists Is Associated with Intracellular pH Compartmentation during Exercise

Background

Although non-specific pain in the upper limb muscles of workers engaged in mild repetitive tasks is a common occupational health problem, much is unknown about the associated structural and biochemical changes. In this study, we compared the muscle energy metabolism of the extrinsic finger extensor musculature in instrumentalists suffering from work-related pain with that of healthy control instrumentalists using non-invasive phosphorus magnetic resonance spectroscopy (³¹P-MRS). We hypothesize that the affected muscles will show alterations related with an impaired energy metabolism.

Methodology/Principal Findings

We studied 19 volunteer instrumentalists (11 subjects with work-related pain affecting the extrinsic finger extensor musculature and 8 healthy controls). We used ³¹P-MRS to find deviations from the expected metabolic response to exercise in phosphocreatine (PCr), inorganic phosphate (Pi), Pi/PCr ratio and intracellular pH kinetics. We observed a reduced finger extensor exercise tolerance in instrumentalists with myalgia, an intracellular pH compartmentation in the form of neutral and acid compartments, as detected by Pi peak splitting in ³¹P-MRS spectra, predominantly in myalgic muscles, and a strong association of this pattern with the condition.

Conclusions/Significance

Work-related pain in the finger extrinsic extensor muscles is associated with intracellular pH compartmentation during exercise, non-invasively detectable by ³¹P-MRS and consistent with the simultaneous energy production by oxidative metabolism and glycolysis. We speculate that a deficit in energy production by oxidative pathways may exist in the affected muscles. Two possible explanations for this would be the partial and/or local reduction of blood supply and the reduction of the muscle oxidative capacity itself.     

Exercise-induced splitting of the inorganic phosphate peak: investigation by time-resolved 31P-nuclear magnetic resonance spectroscopy

To investigate the splitting of the inorganic phosphate (Pi) peak during exercise and recovery, a time-resolved ³¹phosphorus nuclear magnetic resonance spectroscopy (³¹P-MRS) technique was used. Seven healthy young sedentary male subjects performed knee flexion exercise in the prone position inside a 2.1-T magnet, with the surface coil for ³¹P-MRS being placed on the biceps femoris muscle. After a 1-min warm-up without loading, the exercise intensity was increased by 0.41 W at 15-s intervals until exhaustion, followed by a 5-min recovery period. The ³¹P-MRS were recorded every 5 s during the rest-exercise-recovery sequence. Computer-aided contour analysis and pixel imaging of the Pi and phosphocreatine peaks were performed. Five of the seven subjects showed two distinct Pi peaks during exercise, suggesting two different pH distributions in exercising muscle (high pH and low pH region). In these five subjects, the high-pH increased rapidly just after the onset of exercise, while the low-pH peak increased gradually approximately 60 s after the onset of exercise. During recovery, the disappearance of the high-pH peak was more rapid than that of the low-pH peak. These findings suggest that our method ³¹P-MRS provides a simple approach for studying the kinetics of the Pi peak and intramuscular pH during exercise and recovery.     

Evaluation of muscle oxidative potential by 31P-MRS during incremental exercise in old and young humans

The purpose of this study was to compare muscle oxidative capacity between moderately active young and old humans by measuring intracellular threshold (IT) during exercise with ³¹P-magnetic resonance spectroscopy (³¹P-MRS). Changes in phosphocreatine, inorganic phosphate, and intracellular pH were measured by ³¹P-MRS during a progressive unilateral ankle plantar flexion exercise protocol in groups of moderately active old (n=12, mean age 66.7 years) and young (n=13, mean age 26.2 years) individuals. From muscle biopsy samples of the lateral gastrocnemius, citrate synthase (CS) activity was determined in six subjects from each group, and fibre type composition was determined in nine old and ten young subjects. The old group had a lower IT for pH, as a percentage of peak work rate (P<0.05), despite a similar CS activity compared to the young. IT was significantly correlated with CS activity (R=0.59; P<0.05), but not with fibre type composition. It was concluded that metabolic responses to exercise are affected by ageing, as indicated by a lower IT in old compared to young individuals. Accepted: 7 May 1998     

In vivo 31P-NMR studies on energy metabolism in and catecholamine effect on rat liver during hypovolemic shock

In vivo 31P-NMR spectroscopy (31P-MRS) was used to study the metabolism of phosphate compounds in rat liver under various conditions. The changes in hepatic concentrations of ATP and inorganic phosphate (Pi) or intracellular pH (pHi) were monitored during hypovolemic shock with or without the infusion of catecholamines. Rapid decreases in the ATP level and pHi with a concomitant increase of Pi were observed upon induction of the hypovolemic shock. Dopamine infusion markedly improved the liver ATP concentration and intracellular acidosis, but epinephrine or norepinephrine were without effects. The present results suggest that dopamine increases abdominal blood flow and improves the energy metabolism in the liver during hypovolemic shock.     

Correlations between 31P-NMR spectroscopy and tissue O2 tension measurements in a murine fibrosarcoma

Size-dependent changes in therapeutically relevant and interrelated metabolic parameters of a murine fibrosarcoma (FSaII) were investigated in vivo using conscious (unanesthetized) animals and tumor sizes less than or equal to 2% of body weight. Tumor pH and bioenergetics were evaluated by 31P nuclear magnetic resonance spectroscopy (31P-MRS), and tumor tissue oxygen tension (pO2) distribution was examined using O2-sensitive needle electrodes. During growth FSaII tumors showed a progressive loss of phosphocreatine (PCr) and nucleoside triphosphate (NTP) with increasing inorganic phosphate (Pi) and phosphomonoester (PME) signals. Ratios for PCr/Pi, PME/Pi, NTP/Pi, and phosphodiester/inorganic phosphate (PDE/Pi) as well as pH determined by 31P-NMR (pHNMR) and the mean tissue pO2 progressively declined as the tumors increased in size. The only relevant ratio increasing with tumor growth was PME/NTP. When the mean tissue pO2 value was plotted against pHNMR, NTP/Pi, PCr/Pi, PME/Pi, and PDE/Pi for tumor groups of similar mean volumes, a highly significant positive correlation was observed. There was a negative correlation between mean tumor tissue pO2 values and PME/NTP. From these results we concluded that 31P-MRS can detect changes in tumor bioenergetics brought about by changes in tumor oxygenation. Furthermore, the close correlation between oxygenation and energy status suggests that the microcirculation in FSaII tumors yields an O2-limited energy metabolism. Finally, a correlation between the proportion of pO2 readings between 0 and 2.5 mmHg and the radiobiologically hypoxic cell fraction in FSaII tumors was observed. The latter finding might be of particular importance for radiation therapy.     

Evidence that a higher ATP cost of muscular contraction contributes to the lower mechanical efficiency associated with COPD: preliminary findings

Impaired metabolism in peripheral skeletal muscles potentially contributes to exercise intolerance in chronic obstructive pulmonary disease (COPD). We used (31)P-magnetic resonance spectroscopy ((31)P-MRS) to examine the energy cost and skeletal muscle energetics in six patients with COPD during dynamic plantar flexion exercise compared with six well-matched healthy control subjects. Patients with COPD displayed a higher energy cost of muscle contraction compared with the controls (control: 6.1 ± 3.1% of rest·min(-1)·W(-1), COPD: 13.6 ± 8.3% of rest·min(-1)·W(-1), P = 0.01). Although, the initial phosphocreatine resynthesis rate was also significantly attenuated in patients with COPD compared with controls (control: 74 ± 17% of rest/min, COPD: 52 ± 13% of rest/min, P = 0.04), when scaled to power output, oxidative ATP synthesis was similar between groups (6.5 ± 2.3% of rest·min(-1)·W(-1) in control and 7.8 ± 3.9% of rest·min(-1)·W(-1) in COPD, P = 0.52). Therefore, our results reveal, for the first time that in a small subset of patients with COPD a higher ATP cost of muscle contraction may substantially contribute to the lower mechanical efficiency previously reported in this population. In addition, it appears that some patients with COPD have preserved mitochondrial function and normal energy supply in lower limb skeletal muscle.     

The rate of phosphocreatine hydrolysis and resynthesis in exercising muscle in humans using 31P-MRS

Time-resolved 31-phosphorus nuclear magnetic resonance spectroscopy (31P-MRS) of the biceps femoris muscles was performed during exercise and recovery in six healthy sedentary male subjects (maximal oxygen uptake; 46.6 +/- 1.7 (SEM) ml.kg-1.min-1), 5 male sprinters (56.2 +/- 2.5), and 5 male long-distance runners (73.6 +/- 2.2). Each performed 4 min of knee flexion exercises at absolute values of 1.63 W and 4.90 W, followed by 5 min of recovery in a prone position in a 2.1 T superconducting magnet with a 67 cm bore. 31P-MRS spectra were recorded every 12.8 s during the rest-exercise-recovery sequence. Computer-aided contour analysis and pixel imaging of phosphocreatine peaks (PCr) and inorganic phosphate (Pi) were performed. The work loads in the present study were selected as mild exercise (1.63 W) and heavy exercise (4.90 W), corresponding to 18-23% and 54-70% of maximal exercise intensity. Long-distance runners showed a significantly smaller decrement in PCr and less acidification at a given exercise intensity compared to those shown by sedentary subjects. The transient responses of PCr and Pi during recovery were characterized by first-order kinetics. After exercise, the recovery rates of PCr and Pi were significantly faster in long-distance runners than in sedentary subjects (P < 0.05). Since it is postulated that PCr resynthesis is controlled by aerobic metabolism and mitochondrial creatine kinase, it is suggested that the faster PCr and Pi recovery rates and decreased acidification seen in long-distance runners during and after exercise might be attributed to their greater capacity for aerobic metabolism.     

Combined study of 1H-magnetic resonance imaging and depth-selected, EKG-gated 31P-magnetic resonance spectroscopy of the heart in vivo

NMR is useful for both 1H-magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS). We undertook to combine these two merits of NMR for in vivo characterization of living rat heart in wide bore (9 cm) superconducting magnet under high magnetic field (6.4 Tesla). Spatial resolution of 1H-MRI attained 0.1 mm by spin warp method. Then, depth-selected, EKG-gated 31P-MRS was performed, adjusting the detection area to cover the heart that was identified by the preceding 1H-MRI. Three evidences that 31P-SMR signal chiefly originated from the heart without cross talk of adjacent organs indicated that combination of 1H-MRI and in vivo 31P-MRS under high magnetic field in whole animal is promising for more accurate evaluation of cardiac muscle metabolism.