在食管癌细胞增殖过程中蛋白酶激活受体-2(PAR-2)对细胞周期蛋白D1(CyclinD1)的调控机制*

目的:探讨在食管癌细胞增殖过程中蛋白酶激活受体-2(PAR-2)影响细胞周期蛋白D1(CyclinD1)的机制。方法:方法:使用食管癌EC109细胞株,实验分为:空白对照组、PAR-2激动组(加入激动剂SLIGKV)、PAR-2反激动组(加入反激动剂VKGILS)、PAR-2 shRNA组(PAR-2shRNA成功转染)和MAPK抑制组(加入阻滞剂PD98059);取对数生长期的细胞,以6×10⁴cells/ml的密度接种于培养瓶中,置于孵育箱中培养24 h后使用PBS清洗3次,更换为无血清的1640培养基培养24 h,之后各实验组按实验设计分别加入所需试剂,每组设置3个复孔,于孵育箱中继续培养24 h,采用RT-PCR法检测PAR-2、ERK1、CyclinD1的mRNA的表达水平;采用Western blot法检测PAR-2、ERK1、p-ERK1、CyclinD1的蛋白表达水平。结果:与空白对照组相比,PAR-2激动组PAR-2mRNA、ERK1 mRNA、和CyclinD1 mRN表达明显升高(P＜0.05),PAR-2、p-ERK1和CyclinD1蛋白表达升高(P＜0.05);PAR-2 shRNA组PAR-2mRNA、ERK1 mRNA和CyclinD1 mRNA表达降低(P＜0.05),PAR-2、p-ERK1和CyclinD1蛋白表达降低(P＜0.05);MAPK抑制组ERK1 mRNA和CyclinD1 mRNA表达明显降低(P＜0.05),p-ERK1和CyclinD1表达降低(P＜0.05)。结论: PAR-2可通过MAPK通路调节CyclinD1的表达从而促进食管癌细胞EC109的增殖。     

HIF-1α/ERK通路活化调控微波长期辐射致大鼠海马神经元线粒体损伤

本文旨在探讨微波辐射致大鼠海马神经元线粒体损伤中HIF-1α和ERK通路分子表达的改变及意义,为深入研究微波辐射损伤机制和防治提供新靶标.2.5,5和10mW/cm2的微波辐射100只雄性Wistar大鼠,辐射时间为6min/次,5次/周,连续辐射1月,于辐射后6h,7d,14d,1周和2月,采用Real-timePCR,Westernblot和免疫组织化学检测海马中hif-1αmRNA,HIF-1α,ERK1/2和p-ERK1/2表达.结果发现,大鼠海马hif-1αmRNA和HIF-1α蛋白分别在2.5和5mW/cm2组于辐射后14d和1月明显增加,10mW/cm2组辐射后14d～2月降低.但海马ERK1/2未见明显改变.假辐射组p-ERK1/2于海马神经元胞浆中呈弱阳性,2.5mW/cm2组p-ERK1/2表达无明显变化,5和10mW/cm2辐射后7d～1月,p-ERK1/2于海马神经元胞浆和胞核中呈阳性或强阳性.2.5,5和10mW/cm2微波长期辐射后大鼠海马HIF-1α和p-ERK1/2表达的改变,表明HIF-1α和ERK通路活化参与微波辐射致海马线粒体损伤的过程,并可能发挥修复线粒体损伤的作用.     

血管紧张素Ⅱ上调自发性高血压大鼠和Wistar-Kyoto大鼠血管平滑肌细胞外信号调节激酶的信号转导

本文研究血管紧张素Ⅱ(angiotensin Ⅱ,Ang Ⅱ)对自发性高血压大鼠(spontaneously hypertensive rat,SHR)和Wistar- Kyoto(WKY)大鼠血管平滑肌细胞(vascular smooth muscle cells．VSMCs)细胞外信号调节激酶(extracellular signal-regulated pro- tein kinases,ERKs)信号途径的影响。体外培养SHR和WKY大鼠的VSMCs,先在培养基中加入终浓度为1×105mmol／L 的缬沙坦或1×105mmol／L的PD98059或不加药物,再给予1×107mmol／L的Ang Ⅱ刺激24 h后收集细胞,以无血清培养基 培养的VSMCs作对照。用免疫沉淀法测定ERK活性;用Western-blot方法检测总ERK(total ERK,t-ERK)、磷酸化ERK (phosphorylated-ERK,p-ERK)及丝裂素活化蛋白激酶磷酸酶-1(mitogen-activated protem kinases phosphatase-1,MKP-1)水 平;用RT-PCR法半定量测定MKP-1 mRNA的含量。结果显示:(1)SHR和WKY大鼠Ang Ⅱ刺激组VSMCs中ERK活 性、p-ERK、MKP-1及MKP-1 mRNA水平均明显高于对照组(P<0．05);SHR和WKY大鼠Ang Ⅱ+缬沙坦组和Ang Ⅱ +PD98059组的上述指标与对照组比较均无显著性差异。(2)SHR大鼠VSMCs中ERK活性、P-ERK、MKP-1及MKP-1 mRNA均显著高于相同干预的WKY大鼠(P<0．01)。(3)SHR和WKY大鼠之间以及对照组、Ang Ⅱ刺激组、Ang Ⅱ+缬沙 坦组和Ang Ⅱ+PD98059组间VSMCs中t-ERK水平均无显著性差异。以上结果表明,Ang Ⅱ可能主要通过其1型(Ang Ⅱ type 1,AT)受体激活SHR和WKY大鼠VSMCs中ERK途径,增加ERK活性和p-ERK蛋白水平,继而引起MKP-1及 MKP-1 mRNA水平升高。     

有氧运动对2型糖尿病大鼠骨骼肌ERK1/2活性的影响

目的：观察有氧运动对2型糖尿病大鼠骨骼肌细胞外信号调节激酶（ERK1/2）活性的影响,探讨有氧运动对2型糖尿病的预防和调控机制。方法：将75只SD大鼠随机分为正常对照组（CON）、糖尿病对照1组（DC1）、糖尿病运动1组（DE1）、糖尿病对照2组（DC2）、糖尿病运动2组（DE2）5组（n=15）。正常对照组用普通饲料喂养,糖尿病组用高脂高糖配方饲料喂养。经过8周高脂高糖喂养后,糖尿病2组大鼠腹腔内注射链脲佐菌素（STZ）,诱发2型糖尿病;糖尿病运动1组游泳的最后1周初和糖尿病对照1组同时注射STZ,注射剂量为35 mg/kg,3 d后尾部取血测血糖≥ 16.7 mmol/L为造模成功。运动干预8周后,测定大鼠血清胰岛素、骨骼肌中ERK1/2蛋白表达等指标。结果：①与正常对照组比较,糖尿病各对照组血液中总胆固醇（TC）、甘油三酯（TG）、低密度脂蛋白（LDL-C）、游离脂肪酸（FFA）显著升高（P<0.05,P<0.01）,空腹血糖（FBG）、胰岛素（FIN）含量和胰岛素抵抗指数（HOMA-IR）显著升高（P<0.01）,ERK1/2磷酸化的蛋白表达显著下降（P<0.05）,糖尿病对照2组ERK1/2蛋白含量显著下降（P<0.05）;②8周游泳运动后,与糖尿病对照组比较,糖尿病运动组血液中TC、TG、FFA、LDL-C显著下降（P<0.05）,FBG、FIN、HOMA-IR显著下降（P<0.05,P<0.01）,ERK1/2磷酸化蛋白表达显著升高（P<0.05）。结论：长时间有氧运动,增加了骨骼肌ERK1/2磷酸化水平,改善了2型糖尿病大鼠胰岛素抵抗的状况,降低血糖。这可能是改善糖代谢紊乱,提高胰岛素敏感性的机制之一。     

TNF—α对哮喘模型大鼠气道平滑肌细胞增殖及ERK1／2活性的影响

目的探讨TNF—α对哮喘大鼠气道平滑肌细胞（ASMCs）增殖及对ASMCs上ERK1／2mRNA、p-ERK1／2表达水平的影响。方法通过对哮喘模型大鼠ASMCs培养,分别以0．2μg／L、1．0μg/L、20μg/L TNF-α干预ASMCs生长。采用流式细胞仪、MTT法检测ASMCs增殖情况,观察不同浓度TNF—α对ASMCs增殖的影响。RT-PCR检测ASMCs上ERK1／2mRNA表达,免疫细胞化学染色法检测磷酸化ERK1／2蛋白的表达及定位。结果哮喘组ASMCsS期比例、A值、ERK1／2mRNA、p-ERK1／2蛋白的表达量分别为（34．45±2．08）％、（0．550±0．010）、（0．995±0．118）、（130．77±4．16）,与对照组（11．17±0．96）％、（0．292±0．008）、（0．576±0．098）、（163．82±1．38）比较均显著增高（均P〈0．01）。各TNF—α干预组ASMCs的S期比例、A值、ERK1／2mRNA和p-ERK1／2蛋白表达量与哮喘组比较均显著降低（均P〈0．01）,0．2μg/L和1．0μg／LTN-α组p-ERK1／2蛋白表达量高于对照组（P〈0．01）,20μg／L TNF-α组p-ERK1／2蛋白表达量与对照组比较无差异（P〉0．05）。结论与正常鼠相比,慢性哮喘大鼠气道平滑肌细胞增殖明显,处于S期的细胞比例明显增高。经TNF—α干预后,慢性哮喘大鼠气道平滑肌细胞处于S期的细胞比例减少,增殖减弱,TNF-α可能抑制慢性哮喘大鼠气道平滑肌细胞增殖。TNF—α可下调慢性哮喘大鼠气道平滑肌细胞上ERK1／2mRNA及p-ERK1／2表达,TNF-α可能通过抑制ERK信号转导通道的活性对气道平滑肌细胞的增殖进行调控。     

大鼠胰岛素抵抗形成中脂联素受体基因表达及运动的影响

目的:检测SD大鼠脂联素受体的分布,观察大鼠胰岛素抵抗(IR)形成中脂联素受体(Adipok)基因表达及运动的影响。方法:46只雄性SD大鼠随机分为4组(n=12),以高脂膳食喂养诱导IR,同时运动组实施10周游泳运动干预。结果:AdipoR1/R2mRNA分别在骨骼肌和肝脏高表达(P<0.05);H组骨骼肌AdipoR1和肝脏AdipoR2mRNA表达显著低于C组(P<0.05)。结论:骨骼肌和肝脏AdipoR1/R2mRNA表达的下调可能是高脂大鼠IR形成的机制之一,未观察到运动干预的显著影响。     

一种环境激素联合冷应激大鼠模型阴茎组织中 Sprouty 2、ERK1/2表达的研究

目的:研究Sprouty 2(Spry 2)和细胞外调节蛋白激酶(ERK1/2)在环境激素联合冷应激大鼠模型阴茎组织中的表达,并观察伊木萨克片对二者表达的影响。方法:选用30只正常的雄性SD大鼠,其中10只为正常对照组(N组),余20只为造模组,采用富含环境雌激素饲料+寒冷环境的干预条件建立复合性应激大鼠模型(20 w),其中10只大鼠采用伊木萨克片干预2 w(Y组),剩余10只为模型组(M组)。采用免疫组化方法检测各组大鼠阴茎组织中Spry 2、ERK1/2的表达。结果:M组大鼠阴茎组织中Spry2表达低于N组(P0.05),Y组大鼠阴茎组织中Spry 2表达明显高于M组(P0.05)。三组大鼠阴茎组织中总ERK1/2(t-ERK1/2)的表达比较差异均无统计学意义(P0.05)。M组大鼠阴茎组织中磷酸化ERK1/2(p-ERK1/2)表达高于N组(P0.05),Y组大鼠阴茎组织中p-ERK1/2表达明显低于M组(P0.05)。结论:Spry 2表达下调和ERK1/2活化可能促进应激反应的发生发展,伊木萨克片可能通过上调Spry 2的表达和减少ERK1/2的活化发挥抗应激作用。     

伊木萨克片对异常黏液质证候大鼠阴茎组织中Sprouty 2、ERK1/2表达的影响

目的:研究伊木萨克片对异常黏液质证候大鼠模型阴茎组织中Sprouty 2 (Spry 2)和细胞外调节蛋白激酶(extracellular regulated protein kinases1/2, ERK1/2)表达的影响。方法:选用30只性功能正常的雄性SD大鼠,其中10只为正常对照组(N组),余20只为造模组,采用湿寒饲料+湿寒环境的干预条件建立异常黏液质证候大鼠模型(20 w),其中10只大鼠采用伊木萨克片干预2 w,采用免疫组化方法检测各组大鼠阴茎组织中Spry 2、ERK1/2的表达。结果:B1组大鼠阴茎组织中Spry 2表达低于N组(P0.05),B3组大鼠阴茎组织中Spry 2表达明显高于B1组(P0.05)。三组大鼠阴茎组织中总ERK1/2(t-ERK1/2)的表达比较差异均无统计学意义(P0.05)。B1组大鼠阴茎组织中磷酸化ERK1/2(p-ERK1/2)表达高于N组(P0.05),B3组大鼠阴茎组织中p-ERK1/2表达明显低于B1组(P0.05)。结论:Spry 2表达下调和ERK1/2活化可能促进异常黏液质证候的发生发展,伊木萨克片可能通过上调Spry 2的表达和减少ERK1/2的活化对异常黏液质证候大鼠模型发挥治疗作用。     

大负荷运动诱导大鼠骨骼肌损伤对其自噬超微结构及Beclin1和LC3-Ⅱ/Ⅰ的影响

目的:观察大负荷离心运动对大鼠骨骼肌自噬超微结构及自噬相关蛋白Beclin1和LC3Ⅱ/Ⅰ的影响。方法:48只SD雄性大鼠适应性训练后随机分成对照组(C,n=8)和大负荷离心运动组(E,n=40)。E组于跑台进行90 min下坡跑,运动后0 h、12 h、24 h、48 h和72 h取比目鱼肌,透射电镜观察其自噬体超微结构变化; Western blot检测Beclin1和LC3Ⅱ/Ⅰ蛋白表达;免疫荧光观测LC3的定位及含量变化。结果:E组比目鱼肌自噬体数量在运动后0 h、12 h和24 h均有增加,并伴LC3自噬荧光明显增强(P0.01),同时运动后48 h自噬荧光仍有显著性升高(P0.05); Beclin1和LC3Ⅱ/Ⅰ在大负荷离心干预后表达升高(P0.05),运动后12 h～24 h达到峰值(P0.01),直至运动后72 h完全恢复。结论:大负荷离心运动可诱导骨骼肌自噬超微结构变化,自噬蛋白表达增强,以上可能是运动损伤的骨骼肌功能下降的原因之一。     

阿托伐他汀对甲状旁腺素致心肌肥大的保护作用

目的:观察阿托伐他汀对大鼠甲状旁腺素1-34(rPTH1-34)诱导的新生大鼠心室肌细胞肥大的抑制作用及丝裂素活化蛋白激酶激酶1/细胞外信号调节激酶1/2(MKK1/ERK1/2)表达的变化,分析阿托伐他汀抑制心肌肥大的可能机制。方法:以原代培养的新生Wsitar大鼠心室肌细胞为研究对象,3H-亮氨酸掺入率检测细胞蛋白合成速率,BCA法测定单个细胞蛋白含量,RT-PCR检测心房利钠尿肽mRNA(ANPmRNA)的表达,Western blot方法测定p-MKK1、p-ERK1/2蛋白的表达。结果:1.10-7mmol/LrPTH1-34孵育24h可增加体外培养的心肌细胞蛋白合成速率和ANPmRNA表达,使p-MKK1及p-ERK1/2蛋白表达升高(P<0.05)。2.10-5mmol/L阿托伐他汀能抑制心肌细胞蛋白合成速率及单细胞蛋白含量的增加(P<0.05),且对正常心肌细胞没有影响(P>0.05)。3.10-5mmol/L阿托伐他汀能抑制p-MKK1、p-ERK1/2的表达(P<0.05)。结论:阿托伐他汀能抑制PTH诱导的心肌细胞肥大的发生,可能与抑制MKK1/ERK1/2的活性有关。     

Effect of acute exercise and exercise training on VEGF splice variants in human skeletal muscle

The present study investigated the effect of an acute exercise bout on the mRNA response of vascular endothelial growth factor (VEGF) splice variants in untrained and trained human skeletal muscle. Seven habitually active young men performed one-legged knee-extensor exercise training at an intensity corresponding to approximately 70% of the maximal workload in an incremental test five times/week for 4 wk. Biopsies were obtained from the vastus lateralis muscle of the trained and untrained leg 40 h after the last training session. The subjects then performed 3 h of two-legged knee-extensor exercise, and biopsies were obtained from both legs after 0, 2, 6, and 24 h of recovery. Real-time PCR was used to examine the expression of VEGF mRNA containing exon 1 and 2 (all VEGF isoforms), exon 6 or exon 7, and VEGF(165) mRNA. Acute exercise induced an increase (P < 0.05) in total VEGF mRNA levels as well as VEGF(165) and VEGF splice variants containing exon 7 at 0, 2, and 6 h of recovery. The increase in VEGF mRNA was higher in the untrained than in the trained leg (P < 0.05). The results suggest that in human skeletal muscle, acute exercise increases total VEGF mRNA, an increase that appears to be explained mainly by an increase in VEGF(165) mRNA. Furthermore, 4 wk of training attenuated the exercise-induced response in skeletal muscle VEGF(165) mRNA.     

Effect of endurance and sprint exercise on the sensitivity of glucose metabolism to insulin in the epitrochlearis muscle of sedentary and trained rats

The effects of two types of acute exercise (1 h treadmill running at 20 m.min-1, or 6 x 10-s periods at 43 m.min-1, 0 degree inclination), as well as two training regimes (endurance and sprint) on the sensitivity of epitrochlearis muscle [fast twitch (FT) fibres] to insulin were measured in vitro in rats. The hormone concentration in the incubation medium producing the half maximal stimulation of lactate (la) production and glycogen synthesis was determined and used as an index of the muscle insulin sensitivity. A single period of moderate endurance as well as the sprint-type exercise increased the sensitivity of la production to insulin although the rate of la production enhanced markedly only after sprint exercise at 10 and 100 microU.ml-1 of insulin. These effects persisted for up to 2 h after the termination of exercise. Both types of exercise significantly decreased the muscle glycogen content, causing a moderate enhancement in the insulin-stimulated rates of glycogen synthesis in vitro for up to 2 h after exercise. However, a significant increase in the sensitivity of this process to insulin was found only in the muscle removed 0.25 h after the sprint effort. Training of the sprint and endurance types increased insulin-stimulated rates of glycolysis 24 h after the last period of exercise. The sensitivity of this process to insulin was also increased at this instant. Both types of training increased the basal and maximal rates of glycogen synthesis, as well as the sensitivity of this process to insulin at the 24th h following the last training session.(ABSTRACT TRUNCATED AT 250 WORDS)     

Attenuation of exercise-induced heat shock protein 72 expression blunts improvements in whole-body insulin resistance in rats with type 2 diabetes

Heat shock proteins (HSPs) play an important role in insulin resistance and improve the cellular stress response via HSP induction by exercise to treat type 2 diabetes. In this study, the effects of exercise-induced HSP72 expression levels on whole-body insulin resistance in type 2 diabetic rats were investigated. Male 25-week-old Otsuka Long-Evans Tokushima Fatty rats were divided into three groups: sedentary (Sed), trained in a thermal-neutral environment (NTr: 25 °C), and trained in a cold environment (CTr: 4 °C). Exercise training was conducted 5 days/week for 10 weeks. Rectal temperature was measured following each bout of exercise. An intraperitoneal glucose tolerance test (IPGTT) was performed after the training sessions. The serum, gastrocnemius muscle, and liver were sampled 48 h after the final exercise session. HSP72 and heat shock cognate protein 73 expression levels were analyzed by Western blot, and serum total cholesterol, triglyceride (TG), and free fatty acid (FFA) levels were measured. NTr animals exhibited significantly higher body temperatures following exercise, whereas, CTr animals did not. Exercise training increased HSP72 levels in the gastrocnemius muscle and liver, whereas, HSP72 expression was significantly lower in the CTr group than that in the NTr group (p < 0.05). Glucose tolerance improved equally in both trained animals; however, insulin levels during the IPGTT were higher in CTr animals than those in NTr animals (p < 0.05). In addition, the TG and FFA levels decreased significantly only in NTr animals compared with those in Sed animals. These results suggest that attenuation of exercise-induced HSP72 expression partially blunts improvement in whole-body insulin resistance and lipid metabolism in type 2 diabetic rats.     

Exercise training improves muscle insulin resistance but not insulin receptor signaling in obese Zucker rats.

Exercise training improves skeletal muscle insulin sensitivity in the obese Zucker rat. The purpose of this study was to investigate whether the improvement in insulin action in response to exercise training is associated with enhanced insulin receptor signaling. Obese Zucker rats were trained for 7 wk and studied by using the hindlimb-perfusion technique 24 h, 96 h, or 7 days after their last exercise training bout. Insulin-stimulated glucose uptake (traced with 2-deoxyglucose) was significantly reduced in untrained obese Zucker rats compared with lean controls (2.2 +/- 0.17 vs. 5.4 +/- 0.46 micromol x g(-1) x h(-1)). Glucose uptake was normalized 24 h after the last exercise bout (4.9 +/- 0.41 micromol x g(-1) x h(-1)) and remained significantly elevated above the untrained obese Zucker rats for 7 days. However, exercise training did not increase insulin receptor or insulin receptor substrate-1 (IRS-1) tyrosine phosphorylation, phosphatidylinositol 3-kinase (PI3-kinase) activity associated with IRS-1 or tyrosine phosphorylated immunoprecipitates, or Akt serine phosphorylation. These results are consistent with the hypothesis that, in obese Zucker rats, adaptations occur during training that lead to improved insulin-stimulated muscle glucose uptake without affecting insulin receptor signaling through the PI3-kinase pathway.     

Increased atypical PKC activity in endurance-trained human skeletal muscle

Exercise training may modulate protein content and enzyme activities in skeletal muscle. However, it is not known whether atypical protein kinase C (aPKC) is affected by training. Thus, we investigated aPKC, extracellular-regulated protein kinase 1/2 (ERK 1/2), and P38 mitogen-activated protein kinase (P38 MAPK) activities and expression in skeletal muscle from untrained and endurance-trained subjects at rest and after 20min of cycle exercise (80% of VO(2peak)). Activities of aPKC (P<0.05) and ERK 1/2 (P=0.06), but not phosphorylation of P38 MAPK, were higher in trained than in sedentary subjects at rest. Exercise increased the activities of ERK 1/2 (P<0.01) and aPKC (P<0.05) and the phosphorylation (Thr180/Tyr182) of P38 MAPK (P<0.01) similarly in muscle from trained and sedentary subjects. Protein expression of the kinases was similar in trained and sedentary muscle. The increased aPKC activity in exercise-trained subjects could be important in explaining the enhanced insulin action in these individuals.     

Adipose tissue interleukin-18 mRNA and plasma interleukin-18: effect of obesity and exercise

Objectives: Obesity and a physically inactive lifestyle are associated with increased risk of developing insulin resistance. The hypothesis that obesity is associated with increased adipose tissue (AT) interleukin (IL)‐18 mRNA expression and that AT IL‐18 mRNA expression is related to insulin resistance was tested. Furthermore, we speculated that acute exercise and exercise training would regulate AT IL‐18 mRNA expression. Research Methods and Procedures: Non‐obese subjects with BMI < 30 kg/m² (women: n = 18; men; n = 11) and obese subjects with BMI >30 kg/m² (women: n = 6; men: n = 7) participated in the study. Blood samples and abdominal subcutaneous AT biopsies were obtained at rest, immediately after an acute exercise bout, and at 2 hours or 10 hours of recovery. After 8 weeks of exercise training of the obese group, sampling was repeated 48 hours after the last training session. Results: AT IL‐18 mRNA content and plasma IL‐18 concentration were higher (p < 0.05) in the obese group than in the non‐obese group. AT IL‐18 mRNA content and plasma IL‐18 concentration was positively correlated (p < 0.05) with insulin resistance. While acute exercise did not affect IL‐18 mRNA expression at the studied time‐points, exercise training reduced AT IL‐18 mRNA content by 20% in both sexes. Discussion: Because obesity and insulin resistance were associated with elevated AT IL‐18 mRNA and plasma IL‐18 levels, the training‐induced lowering of AT IL‐18 mRNA content may contribute to the beneficial effects of regular physical activity with improved insulin sensitivity.     

Metabolic and hormonal response to short term fasting after endurance training in the rat

The metabolic and hormonal response to short term fasting was studied after endurance exercise training. Rats were kept running on a motor driven rodent treadmill 5 days/wk for periods up to 1 h/day for 6 wk. Trained and untrained rats were then fasted for 24 h and 48 h. Liver and muscle glycogen, blood glucose, lactate, beta OH butyrate, glycerol, plasma insulin, testosterone and corticosterone were measured in fed and fasted trained and untrained rats. 48 h fasted trained rats show a lower level of blood lactate (1.08 +/- 0.05 vs 1.33 +/- 0.08 mmol/l-1 of blood glycerol (1 +/- 0.11 vs 0.84 +/- 0.08 mmol/l-1), and of muscle glycogen. There is a significant increase in plasma corticosterone in 48 h fasted trained rats from fed values. Plasma testosterone decreases during fasting, the values are higher in trained rats. Plasma insulin decreases during fasting without any difference between the two groups. These results show higher lipolysis, and decreased glycogenolysis in trained animals during 48 h fasting. The difference between the groups in steroid hormone response could reduce neoglucogenesis and muscle proteolysis in trained animals.     

Bdnf expression in rat skeletal muscle after acute or repeated exercise

Brain derived growth factor (BDNF) gene of rat has a complex structure: at least four 5' untranslated exons regulated by different promoters and one 3' exon containing the encoding region. BDNF is expressed by skeletal muscles in an activity-dependent manner. In this study, BDNF mRNA was analysed by RT-PCR in the soleus muscle following a single (acute) session of running or a training of five days of running (repetitive exercise). Moreover, the expression of the exons was quantitatively analysed by real time RT-PCR. Finally, muscle BDNF protein level was evaluated by western blotting. BDNF mRNA was found to increase over the second day after acute exercise; on the other hand, two peaks (2 and 24 hours after the last session, respectively) in BDNF mRNA level were found after repetitive exercise, but it was similar to that of controls 6 hours after the last session. BDNF protein level progressively increased also after the mRNA went back to the basal level, so suggesting that it cumulates within the cell after acute exercise, whereas it followed the mRNA level time course after repetitive exercise. These results point to the following conclusions: BDNF mRNA is up-regulated by activity, but this response is delayed to the second day after acute exercise; repetitive exercise transiently depresses the expression of BDNF mRNA, so that the over-expression due to the previous day's exercise completely disappears 6 hours after the last exercise session.