Insulin Induces an Increase in Cytosolic Glucose Levels in 3T3-L1 Cells with Inhibited Glycogen Synthase Activation

Glucose is an important source of energy for mammalian cells and enters the cytosol via glucose transporters. It has been thought for a long time that glucose entering the cytosol is swiftly phosphorylated in most cell types; hence the levels of free glucose are very low, beyond the detection level. However, the introduction of new fluorescence resonance energy transfer-based glucose nanosensors has made it possible to measure intracellular glucose more accurately. Here, we used the fluorescent indicator protein (FLIPglu-600µ) to monitor cytosolic glucose dynamics in mouse 3T3-L1 cells in which glucose utilization for glycogen synthesis was inhibited. The results show that cells exhibit a low resting cytosolic glucose concentration. However, in cells with inhibited glycogen synthase activation, insulin induced a robust increase in cytosolic free glucose. The insulin-induced increase in cytosolic glucose in these cells is due to an imbalance between the glucose transported into the cytosol and the use of glucose in the cytosol. In untreated cells with sensitive glycogen synthase activation, insulin stimulation did not result in a change in the cytosolic glucose level. This is the first report of dynamic measurements of cytosolic glucose levels in cells devoid of the glycogen synthesis pathway.     

Autophagosomal glycogen‐degrading activity and its relationship to the general autophagic activity in newborn rat hepatocytes: The effects of parenteral glucose administration

The effects of the administration of parenteral glucose on the postnatal glycogen autophagic activity and its relationship to the general autophagic activity, were studied in newborn rat liver using electron microscopy and biochemical methods. Glucose abolished the normal postnatal hypoglycemia and preserved the hepatocytic hyaloplasmic glycogen to the levels of birth. It also inhibited the normal postnatal increase in the number and volume of autophagic vacuoles. Glucose especially decreased the rate of postnatal development of the glycogen‐containing autophagic vacuoles. This decrease was greater than that of the autophagic vacuoles in general. In the control animals at the age of 6 h, the total volume of the glycogen‐containing autophagic vacuoles accounted for 87% of the autophagic vacuoles in general, whereas in the glucose‐treated animals of the same age, for only 62%. The results of this and previous studies support the view that the general autophagic activity that develops in the immediate postnatal period in rat hepatocytes is mainly expressed as glycogen autophagic activity selectively inhibited by glucose. Microsc. Res. Tech., 2010. © 2009 Wiley‐Liss, Inc.     

天然酵素运动饮料的抗疲劳性研究

目的研究天然酵素运动饮料对小鼠的抗疲劳作用。方法将健康雄性小鼠随机分为4组,低、中、高剂量组和对照组,灌胃剂量分别为10、20、60和0 mL/(kg·bw),即对照组按同体积纯净水灌胃,喂养30 d,末次给药30min后,测定负重游泳时间、尿素氮、血乳酸、肌乳酸和肝糖原含量。结果与对照组相比,实验组小鼠的负重游泳时间和肝糖原含量明显增加(P0.05),血清尿素氮、血乳酸和肌乳酸含量明显降低(P0.05),且存在着一定的浓度依赖性。结论此天然酵素运动饮料对小鼠增强运动耐力和消除疲劳具有一定的作用。     

Glycogen--a covalently linked component of the cell wall in Saccharomyces cerevisiae.

Glycogen in Saccharomyces cerevisiae is present in two pools, one soluble and intracellular, the other present in the cell wall and rendered water-insoluble owing to its covalent linkage to cell wall beta-glucan. The insoluble glycogen fraction was solubilized using beta-1,3-glucanase. The alpha beta-glucan complex obtained showed intense red staining with iodine and was isolated from free beta-glucans by affinity chromatography using concanavalin A sepharose 4B. Further use of molecular sieving has confirmed that glycogen is linked to beta-glucan as the non-retained fraction on Biogel P2 split into two peaks on treatment with amyloglucosidase. Partial acid hydrolysis and subsequent paper chromatography of the alpha beta-glucan complex isolated revealed the presence of gentiobiose and other higher oligosaccharides, indicating that glycogen is linked to beta-1,3-glucan through a beta-1,6 branch. The insoluble glycogen can be extracted in a soluble form by acetic acid treatment and is known as acid-soluble glycogen. The presence of glycogen in the cell wall is confirmed by controlled enzymatic release of alpha beta-glucan complex using lyticase from Arthobacter luteus without disruption of the plasma membrane, as can be visualized using electron microscopy.     

Glycogen resynthesis in liver and muscle after exercise: measurement of the rate of resynthesis by13C magnetic resonance spectroscopy

We have used natural abundance¹³C magnetic resonance spectroscopy (MRS) to measure glycogen content of muscle and liver before and after heavy exercise, and after consumption of different carbohydrate-based drinks. After an overnight fast, five healthy men (mean±SEM age 23±1 years) exercised to exhaustion at 75% of VO_2max on two occasions (mean work rate 165±8 W for 78±14 min) and then, in a single blind random order, consumed either of two drinks containing the same carbohydrate load (177 g). Spectra were recorded over Vastus Lateralis muscle and the liver before and after exercise, and hourly for 5 h after the carbohydrate load. In muscle, glycogen content after exercise was 37% and 31% of basal (preexercise) concentration before consuming the drinks. After carbohydrate loading, glycogen concentration had increased significantly (p<0.05) to 70% and 64% of basal concentration respectively after 5 h. Hepatic glycogen concentration did not change significantly throughout. The study demonstrates the feasibility of sequential MRS measurement of muscle and liver glycogen before and after exercise and after carbohydrate loading.     

强化生物除磷污泥糖原的近红外光谱分析

采用蒽酮法测定强化生物除磷(EBPR)反应器污泥中糖原物质的含量,运用间隔偏最小二乘法(iPLS)对近红外光谱进行建模,将光谱划分为20个子区间,选出最佳波数区间为4775-4389cm-1,并用这个模型预测未知样品中糖原含量。结果表明:所建模型对糖原校正时的相关系数(rc)为0.9583,校正均方根误差(RMSECV)为0.3554;预测时的相关系数(rp)=0.9769,预测均方根误差(RMSEP)为0.4243。所建的模型对糖原含量的预测效果较好,模型预测精度高,为污泥中糖原的测定提供了一种快速可行的分析技术。     

扇贝糖原酶法提取及其硫酸化修饰条件

以新鲜扇贝闭壳肌为原料,酶法提取扇贝糖原,其得率为13.78%,其中糖质量分数为91.62%,蛋白质质量分数为1.4%。采用氯磺酸-吡啶法对所提取扇贝糖原进行硫酸酯化修饰,以硫酸取代度(DS)为指标,对硫酸酯化试剂体积、反应温度以及反应时间进行优化。实验结果显示,最佳修饰条件为酯化试剂中氯磺酸与吡啶的体积比为1∶5,反应温度为60℃,反应时间为3h。经红外光谱分析表明,硫酸基与扇贝糖原形成硫酸酯化合物。     

麦胚抗疲劳作用研究

研究用不同剂量麦胚饲喂小鼠 ,观察麦胚对小鼠血乳酸 (LAC)、尿素氮 (BUN)、糖原含量和血乳酸脱氢酶 (LDH)活力及运动耐力的影响。结果表明 ,麦胚能明显促进实验小鼠体重的增长 (P <0 .0 5 )、降低运动一段时间后的血乳酸 (P <0 .0 5 )和尿素氮含量 (P <0 .0 1)、提高血乳酸脱氢酶的活力 (P <0 .0 5 )、明显增加肌、肝糖原的储备量 (P <0 .0 1)、提高小鼠的运动耐力。提示 ,麦胚具有提高体能、抗疲劳的作用。     

可口革囊星虫抗疲劳作用的研究

目的:研究可口革囊星虫对小鼠的抗疲劳效果。方法:将可口革囊星虫进行组织匀浆、冷冻干燥处理后过80目筛,加蒸馏水制备得到干粉悬浊液。然后小鼠灌胃给药,通过游泳实验,分别测定小鼠运动后肝糖元和肌糖元、血清尿素氮及血乳酸含量水平。结果:可口革囊星虫干粉悬浊液能明显延长小鼠负重游泳时间,力竭最长游泳时间从584s可延长到1015s;增加肝糖元和肌糖元含量;降低血清尿素氮含量和血乳酸含量,高剂量组降低率分别达到9.69%、38.22%。结论:可口革囊星虫对小鼠具有明显的抗疲劳作用。