Autophagy Signaling in Skeletal Muscle of Infarcted Rats

Background

Heart failure (HF)-induced skeletal muscle atrophy is often associated to exercise intolerance and poor prognosis. Better understanding of the molecular mechanisms underlying HF-induced muscle atrophy may contribute to the development of pharmacological strategies to prevent or treat such condition. It has been shown that autophagy-lysosome system is an important mechanism for maintenance of muscle mass. However, its role in HF-induced myopathy has not been addressed yet. Therefore, the aim of the present study was to evaluate autophagy signaling in myocardial infarction (MI)-induced muscle atrophy in rats.

Methods/Principal Findings

Wistar rats underwent MI or Sham surgeries, and after 12 weeks were submitted to echocardiography, exercise tolerance and histology evaluations. Cathepsin L activity and expression of autophagy-related genes and proteins were assessed in soleus and plantaris muscles by fluorimetric assay, qRT-PCR and immunoblotting, respectively. MI rats displayed exercise intolerance, left ventricular dysfunction and dilation, thereby suggesting the presence of HF. The key findings of the present study were: a) upregulation of autophagy-related genes (GABARAPL1, ATG7, BNIP3, CTSL1 and LAMP2) was observed only in plantaris while muscle atrophy was observed in both soleus and plantaris muscles, and b) Cathepsin L activity, Bnip3 and Fis1 protein levels, and levels of lipid hydroperoxides were increased specifically in plantaris muscle of MI rats.

Conclusions

Altogether our results provide evidence for autophagy signaling regulation in HF-induced plantaris atrophy but not soleus atrophy. Therefore, autophagy-lysosome system is differentially regulated in atrophic muscles comprising different fiber-types and metabolic characteristics.     

Increase in the Level of Skeletal Muscle α-Actin mRNA in Rats Fed a Non-protein Diet Supplemented with Cystine and Threonine

Pinguisone accumulated in cultured gametophytes of Aneurapinguis to a significantly high level. A biosynthetic study on the formation of pinguisone was carried out by feeding [2-¹³C]-acetate to the cultured gametophytes. Pinguisone was labeled at an adequate level to determine the labeling positions by a ¹³C-NMR analysis. The labeling pattern indicated two-methyl migration and C-C bond cleavage of the main chain in farnesyl diphosphate in the formation of pinguisone.     

明日叶查尔酮对2型糖尿病大鼠骨骼肌细胞胰岛素抵抗的干预作用

目的:研究明日叶查尔酮对2型糖尿病大鼠骨骼肌胰岛素抵抗的干预作用.方法:将2型糖尿病大鼠随机分成四组,高、中、低剂量组分别每日经口灌胃给予明日叶查尔酮30、10和5mg/(kg·bw),糖尿病对照组给予等量生理盐水.各组均以高脂饲料喂养.四周后采用葡萄糖氧化酶法检测空腹血糖;放射免疫法检测血清胰岛素含量;免疫组化法检测葡萄糖转运体1和葡萄糖转运体4蛋白表达水平.结果:经图像分析,高剂量组骨骼肌细胞中葡萄糖转运体1和葡萄糖转运体4蛋白表达平均光密度值分别为0.054± 0.0064和0.063±0.0139,均较糖尿病对照组显著性升高(P＜0.05).高剂量组空腹血糖和胰岛素水平分别为(12.3± 1.64)mmol/L和(25.65±3.34) (μIU/mL),均较糖尿病对照病显著性降低(P＜0.05).结论:明日叶查尔酮可增加2型糖尿病大鼠骨骼肌葡萄糖转运体l和葡萄糖转运体4蛋白表达水平,降低空腹血糖和胰岛素水平,改善胰岛素抵抗状况.     

Type 2 Diabetic Rats on Diet Supplemented With Chromium Malate Show Improved Glycometabolism,Glycometabolism-Related Enzyme Levels and Lipid Metabolism

Our previous study showed that chromium malate improved the regulation of blood glucose in mice with alloxan-induced diabetes. The present study was designed to evaluate the effect of chromium malate on glycometabolism, glycometabolism-related enzymes and lipid metabolism in type 2 diabetic rats. Our results showed that fasting blood glucose, serum insulin level, insulin resistance index and C-peptide level in the high dose group had a significant downward trend when compared with the model group, chromium picolinate group and chromium trichloride group. The hepatic glycogen, glucose-6-phosphate dehydrogenase, glucokinase, Glut4, phosphor-AMPKβ1 and Akt levels in the high dose group were significantly higher than those of the model, chromium picolinate and chromium trichloride groups. Chromium malate in a high dose group can significantly increase high density lipoprotein cholesterol level while decreasing the total cholesterol, low density lipoprotein cholesterol and triglyceride levels when compared with chromium picolinate and chromium trichloride. The serum chromium content in chromium malate and chromium picolinate group is significantly higher than that of the chromium trichloride group. The results indicated that the curative effects of chromium malate on glycometabolism, glycometabolism-related enzymes and lipid metabolism changes are better than those of chromium picolinate and chromium trichloride. Chromium malate contributes to glucose uptake and transport in order to improved glycometabolism and glycometabolism-related enzymes.     

An Atherogenic Paigen-Diet Aggravates Nephropathy in Type 2 Diabetic OLETF Rats

Diabetic nephropathy develops in association with hyperglycemia, is aggravated by atherogenic factors such as dyslipidemia, and is sometimes initiated before obvious hyperglycemia is seen. However, the precise mechanisms of progression are still unclear. In this study, we investigated the influence of an atherogenic Paigen diet (PD) on the progression of nephropathy in spontaneous type 2 diabetic OLETF rats. Feeding PD to male OLETF rats for 12 weeks caused an extensive increase in excretion of urinary albumin and markers of tubular injury such as KIM-1 and L-FABP, accompanied by mesangial expansion and tubular atrophy. PD significantly increased plasma total cholesterol concentration, which correlates well with increases in urine albumin excretion and mesangial expansion. Conversely, PD did not change plasma glucose and free fatty acid concentrations. PD enhanced renal levels of mRNA for inflammatory molecules such as KIM-1, MCP-1, TLR4 and TNF-α and promoted macrophage infiltration and lipid accumulation in the tubulointerstitium and glomeruli in OLETF rats. Intriguingly, PD had little effect on urine albumin excretion and renal morphology in normal control LETO rats. This model may be useful in studying the complex mechanisms that aggravate diabetic nephropathy in an atherogenic environment.     

Effect of Combined Excess Iodine and Low-Protein Diet on Thyroid Hormones and Ultrastructure in Wistar Rats

The aim of the present study was to illustrate the combined effect of excess iodine and low-protein diet on the thyroid, and the potential molecular mechanism of this effect. One hundred ninety-two Wistar rats were randomly divided into the following groups: normal; 10- (10HI), 50- (50HI), or 100-fold excess iodine (100HI); low-protein; and low-protein combined with 10- (L10HI), 50- (L50HI), or 100-fold excess iodine (L100HI). At the end of 2, 4, or 6 months, the rats were sacrificed for iodine concentration and thyroid hormone analyses. The histological appearance of the thyroid gland was observed at the end of 6 months. At the end of 6 months, the serum total thyroxine (TT₄), free thyroxine (FT₄), total triiodothyronine (TT₃), and free triiodothyronine (FT₃) levels in the 100HI, L10HI, L50HI, and L100HI groups were significantly lower than the control group (P?<?0.05 or P?<?0.01). Serum TT₄, FT₄, TT₃, and FT₃ levels in the low-protein excess iodine groups were significantly lower than the groups with an equal amount of excess iodine alone (P?<?0.05 or P?<?0.01). Light and electron microscopy showed that excess iodine caused damage to the ultrastructure of thyroid and apoptosis of follicular epithelial cells. In the 100HI, L50HI, and L100HI groups, thyroid follicular epithelial cells became flattened, and follicles became distended with colloid. The damage was more serious in low-protein groups. The present findings demonstrated that the low-protein diet aggravated the damage to the thyroid caused by excess iodine alone.     

TRB3基因敲除减轻糖尿病小鼠中骨骼肌萎缩和纤维化的研究

摘要 目的：探讨TRB3基因敲除对糖尿病小鼠中骨骼肌萎缩和纤维化的影响。方法：选择30只TRB3敲除（TRB3-/-）小鼠和30只C57/BL6J小鼠,随机分为4组,包括TRB3基因敲除糖尿病模型组（A组）、TRB3基因敲除正常对照组（B组）、普通对照组（C组）和糖尿病模型组（D组）。正常对照组小鼠喂养标准大鼠饲料,糖尿病模型小鼠使用腹腔注射小剂量链脲佐菌素的方法建立糖尿病小鼠模型。进行前肢握力测试、悬栅试验、肌肉功能试验,同时测定骨微结构各指标水平、抗I型胶原蛋白和抗III型胶原蛋白水平、萎缩基因MuRF1和Atrogin-1水平。结果：A组、B组、D组小鼠前肢握力显著低于C组,其中D组小鼠前肢握力最低（P<0.05）;A组、B组、D组小鼠悬栅试验倒挂时间显著低于C组,其中D组小鼠悬栅试验倒挂时间最短（P<0.05）;A组、B组、D组小鼠肌肉功能CSA值显著低于C组,其中D组小鼠肌肉功能CSA值最低（P<0.05）;A组、B组、D组小鼠骨微结构指标BMD、BV/TV、Tb.N、Tb.Th值显著小于C组,其中D组数值最低（P<0.05）;而Tb.Sp和SMI值显著大于C组,其中D组数值最高（P<0.05）;A组、B组、D组小鼠抗I型胶原蛋白和抗III型胶原蛋白水平显著高于C组,其中D组抗I型胶原蛋白和抗III型胶原蛋白水平最高（P<0.05）;A组、B组、D组小鼠萎缩基因MuRF1和Atrogin-1水平显著高于C组,其中D组萎缩基因MuRF1和Atrogin-1水平最高（P<0.05）。结论：TRB3基因敲除可显著减轻糖尿病小鼠中骨骼肌萎缩和纤维化,增加骨强度。     

左旋氨氯地平联合氯沙坦治疗2 型糖尿病肾病合并高血压的疗效及对血 压和肾功能的影响*

目的:探讨左旋氨氯地平联合氯沙坦治疗2型糖尿病肾病(T2DN)合并高血压的疗效及对血压和肾功能的影响。方法:采用随机数字表法将2010年1月至2013年1月本院门诊及住院部收治的260例T2DN合并高血压患者分为实验组和对照组,每组患者130例,实验组给予左旋氨氯地平和氯沙坦口服联合治疗,对照组仅给予左旋氨氯地平口服治疗,对比两组疗效,并观察两组治疗前后的收缩压(SBP)和舒张压(DBP)、血肌酐(Scr)水平、尿微量白蛋白(UMALB)/尿肌酐(Ucr)水平和24 h UMALB水平。结果:实验组的总有效率90.77%显著高于对照组的78.46%(P0.05);治疗后两组SBP、DBP、脉压差、SCr、UMALB/Ucr及24h UMALB水平均有显著下降(P0.05),且实验组均显著低于对照组(P0.05)。结论:左旋氨氯地平联合氯沙坦不仅可有效降低T2DN合并高血压患者血压,还可有效减少尿液中蛋白的排放,保护患者的肾脏功能,疗效显著,值得推广。     

Intracerebroventricular Injection of Alarin Increased Glucose Uptake in Skeletal Muscle of Diabetic Rats

In order to investigate the central effect of alarin on glucose uptake, we administered alarin and/ or its inhibitor, ala6-25Cys into the cerebral ventricles of the type 2 diabetic rats. Then the relative parameters about glucose uptake in skeletal muscles were measured. We found that central treatment with alarin significantly increased the food intake, body weight and glucose infusion rates in hyperinsulinemic euglycemic clamp tests of the animals. Besides, the treatment also enhanced 2-deoxy-[³H]-D-glucose uptake, vesicle-associated membrane protein 2 contents, glucose transporter 4 protein and mRNA expression, as well as pAkt^Thr308, pAkt^Ser473 and total Akt levels in muscle cells, but reduced plasma glucose and insulin levels of the rats. All of the alarin-inducing events may be antagonised by central injection of ala6-25Cys. These results suggest that central administration of alarin stimulates glucose uptake mediated by activation of Akt signal pathway in type 2 diabetic animals.     

Altered Neurotrophin mRNA Levels in Peripheral Nerve and Skeletal Muscle of Experimentally Diabetic Rats

Abstract: The levels of neurotrophin mRNA in sensory ganglia, sciatic nerve, and skeletal muscle were measured in the streptozotocin-diabetic rat using northern blotting. Periods of diabetes of 4, 6, and 12 weeks significantly elevated brain-derived neurotrophic factor (BDNF) mRNA levels in soleus muscle compared with age-matched controls, the increase being highest at 6 weeks. At all time periods studied, the levels of nerve growth factor (NGF) mRNA in soleus muscle were decreased by 21–47%. Following 12 weeks of diabetes, BDNF mRNA levels were increased approximately two-to threefold in L4 and L5 dorsal root ganglia (DRG), and in sciatic nerve, NGF mRNA levels were raised 1.65-fold. Intensive insulin treatment of diabetic rats for the final 4 weeks of the 12-week period of diabetes reversed the up-regulation of BDNF mRNA in DRG and muscle and NGF mRNA in sciatic nerve. All diabetes-induced changes in neurotrophin mRNA were not paralleled by similar alterations in the levels of β-actin mRNA in muscle and nerve, or of GAP-43 mRNA in DRG and nerve. It is proposed that the up-regulation of neurotrophin mRNA is an endogenous protective and/or repair mechanism induced by insult and, as such, appears as an early marker of peripheral nerve and muscle damage in experimental diabetes.     

金樱子对糖尿病大鼠肾MCP-1表达的影响

目的:研究金樱子对糖尿病大鼠单核细胞趋化因子-1(MCP-1)表达的影响.方法:用STZ腹腔注射诱导建立SD大鼠糖尿病模型后,随机分为糖尿病模型组和金樱子干预组,同时另设正常对照组和金樱子对照组.测定大鼠血糖、血肌酐(Scr)、血尿素氮(BUN)、胆固醇(TC)、甘油三酯(TG)、24小时尿蛋白.HE染色观察肾组织病理改变、免疫组织化学、Western blot检测各组肾组织MCP-1表达情况.结果:金樱子能明显改善肾功能,降低实验性糖尿病大鼠血糖、血肌酐、血尿素氮、胆固醇、甘油三酯、24小时尿蛋白定量.形态学观察,糖尿病大鼠在金樱子干预后,肾小球硬化指数与肾小管损伤指数明显减小.免疫组织化学和Western bolt分析显示,MCP-1蛋白表达在糖尿病模型组中显著增强,而在金樱子干预组的表达显著减弱(P＜0.05),但仍较正常对照组蛋白表达升高.结论:金樱子对糖尿病肾病具有防治作用,其机制可能与降低MCP-1表达有关.     

The Vagotomy Alleviates the Anorectic Effect of an Excess Amount of Dietary Leucine on Rats Fed a Low-Protein Diet

It is well known that large dose of leucine reduces the food intake and causes growth retardation in experimental animals when leucine is given with a low-protein diet. However, the mechanism for the anorectic effect of leucine has not yet been clarified. We demonstrate here that the anorectic effect of leucine was significantly reduced in a vagotomized rat.     

Glutamine Supplementation Stimulates Protein-Synthetic and Inhibits Protein-Degradative Signaling Pathways in Skeletal Muscle of Diabetic Rats

In this study, we investigated the effect of glutamine (Gln) supplementation on the signaling pathways regulating protein synthesis and protein degradation in the skeletal muscle of rats with streptozotocin (STZ)-induced diabetes. The expression levels of key regulatory proteins in the synthetic pathways (Akt, mTOR, GSK3 and 4E-BP1) and the degradation pathways (MuRF-1 and MAFbx) were determined using real-time PCR and Western blotting in four groups of male Wistar rats; 1) control, non-supplemented with glutamine; 2) control, supplemented with glutamine; 3) diabetic, non-supplemented with glutamine; and 4) diabetic, supplemented with glutamine. Diabetes was induced by the intravenous injection of 65 mg/kg bw STZ in citrate buffer (pH 4.2); the non-diabetic controls received only citrate buffer. After 48 hours, diabetes was confirmed in the STZ-treated animals by the determination of blood glucose levels above 200 mg/dL. Starting on that day, a solution of 1 g/kg bw Gln in phosphate buffered saline (PBS) was administered daily via gavage for 15 days to groups 2 and 4. Groups 1 and 3 received only PBS for the same duration. The rats were euthanized, and the soleus muscles were removed and homogenized in extraction buffer for the subsequent measurement of protein and mRNA levels. The results demonstrated a significant decrease in the muscle Gln content in the diabetic rats, and this level increased toward the control value in the diabetic rats receiving Gln. In addition, the diabetic rats exhibited a reduced mRNA expression of regulatory proteins in the protein synthesis pathway and increased expression of those associated with protein degradation. A reduction in the skeletal muscle mass in the diabetic rats was observed and was alleviated partially with Gln supplementation. The data suggest that glutamine supplementation is potentially useful for slowing the progression of muscle atrophy in patients with diabetes.     

低聚原花青素对过度训练大鼠骨骼肌损伤的保护作用机制

为研究低聚原花青素对过度训练大鼠骨骼肌损伤的保护作用机制,将大鼠随机分为安静对照组(C)、过度训练组(OM)、低聚原花青素干预组(OOM).C组无运动干预,其他组采用42 d递增负荷跑台训练.训练期间,OOM组每天灌胃低聚原花青素1次(150 mg/kg,5 mL/kg),其他组给予等体积蒸馏水.末次训练后即刻取材,经...     

失神经骨骼肌萎缩的研究现状及进展

当今骨科领域,周围神经损伤一直影响着患者疗效。肌萎缩的发生,细胞凋亡导致骨骼肌萎缩,神经-肌肉接头处营养因子的代谢发生障碍,肌卫星细胞的减少,生长因子以及线粒体和各种酶的变化都是失神经骨骼肌萎缩的机制。电刺激法,保护神经元,生长因子,神经植入提高神经再生速度以及被动活动可以有效治疗患者。失神经骨骼肌萎缩的研究进展也趋于完善。     

Effects of Maternal Diet and Exercise during Pregnancy on Glucose Metabolism in Skeletal Muscle and Fat of Weanling Rats

Obesity during pregnancy contributes to the development of metabolic disorders in offspring. Maternal exercise may limit gestational weight gain and ameliorate these programming effects. We previously showed benefits of post-weaning voluntary exercise in offspring from obese dams. Here we examined whether voluntary exercise during pregnancy influences lipid and glucose homeostasis in muscle and fat in offspring of both lean and obese dams. Female Sprague-Dawley rats were fed chow (C) or high fat (F) diet for 6 weeks before mating. Half underwent voluntary exercise (CE/FE) with a running wheel introduced 10 days prior to mating and available until the dams delivered; others remained sedentary (CS/FS). Male and female pups were killed at postnatal day (PND)19 and retroperitoneal fat and gastrocnemius muscle were collected for gene expression. Lean and obese dams achieved similar modest levels of exercise. At PND1, both male and female pups from exercised lean dams were significantly lighter (CE versus CS), with no effect in those from obese dams. At PND19, maternal obesity significantly increased offspring body weight and adiposity, with no effect of maternal exercise. Exercise significantly reduced insulin concentrations in males (CE/FE versus CS/FS), with reduced glucose in male FE pups. In males, maternal obesity significantly decreased muscle myogenic differentiation 1 (MYOD1) and glucose transporter type 4 (GLUT4) mRNA expressions (FS vs CS); these were normalized by exercise. Maternal exercise upregulated adipose GLUT4, interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and peroxisome proliferator activated receptor gamma coactivator 1 alpha (PGC1α) mRNA expression in offspring of dams consuming chow. Modest voluntary exercise during pregnancy was associated with lower birth weight in pups from lean dams. Maternal exercise appeared to decrease the metabolic risk induced by maternal obesity, improving insulin/glucose metabolism, with greater effects in male than female offspring.