BACKGROUNDSIRT3 is an important regulator in cell metabolism, and recent studies have shown that it may be involved in the pharmacological effects of metformin. However, the molecular mechanisms underlying this process are unclear.

METHODSThe effects of SIRT3 on the regulation of oxidative stress and insulin resistance in skeletal muscle were evaluated in vitro. Differentiated L6 skeletal muscle cells were treated with 750 µmol/L palmitic acid to induce insulin resistance. SIRT3 was knocked down and overexpressed in L6 cells. SIRT3, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) p65, c-Jun N-terminal kinase 1 (JNK1), and superoxide dismutase 2 (SOD2) were evaluated by Western blotting.

RESULTSOver expression of SIRT3 increased glucose uptake and decreased ROS production in L6-IR cells as well as in L6 cells. Knock-down of SIRT3 induced increased production of ROS while decreased glucose uptake in both L6 and L6-IR cells, and these effects were reversed by N-acetyl-L-cysteine (NAC). Metformin increased the expression of SIRT3 (1.5-fold) and SOD2 (2-fold) while down regulating NF-κB p65 (1.5-fold) and JNK1 (1.5-fold). Knockdown of SIRT3 (P < 0.05) reversed the metformin-induced decreases in NF-κB p65 and JNK1 and the metformin-induced increase in SOD2 (P < 0.05).

CONCLUSIONSUpregulated SIRT3 is involved in the pharmacological mechanism by which metformin promotes glucose uptake. Additionally, SIRT3 may function as an important regulator of oxidative stress and a new alternative approach for targeting insulin resistance-related diseases.

Animals ; Cell Line ; Insulin Resistance ; physiology ; Metformin ; pharmacology ; Muscle Fibers, Skeletal ; drug effects ; metabolism ; Oxidative Stress ; drug effects ; Rats ; Sirtuin 3 ; metabolism ; Transcription Factor RelA ; metabolism

The present study was undertaken to evaluate the influence of the methanolic fruit extract of Momordica cymbalaria (MFMC) on PPARγ (Peroxisome Proliferator Activated Receptor gamma) and GLUT-4 (Glucose transporter-4) with respect to glucose transport. Various concentrations of MFMC ranging from 62.5 to 500 μg·mL(-1) were evaluated for glucose uptake activity in vitro using L6 myotubes, rosiglitazone was used as a reference standard. The MFMC showed significant and dose-dependent increase in glucose uptake at the tested concentrations, further, the glucose uptake activity of MFMC (500 μg·mL(-1)) was comparable with rosigilitazone. Furthermore, MFMC has shown up-regulation of GLUT-4 and PPARγ gene expressions in L6 myotubes. In addition, the MFMC when incubated along with cycloheximide (CHX), which is a protein synthesis inhibitor, has shown complete blockade of glucose uptake. This indicates that new protein synthesis is required for increased GLUT-4 translocation. In conclusion, these findings suggest that MFMC is enhancing the glucose uptake significantly and dose dependently through the enhanced expression of PPARγ and GLUT-4 in vitro.
Biological Transport ; Dose-Response Relationship, Drug ; Fruit ; Gene Expression ; drug effects ; Glucose ; metabolism ; Glucose Transporter Type 4 ; metabolism ; Hypoglycemic Agents ; pharmacology ; In Vitro Techniques ; Insulin ; metabolism ; Momordica ; Muscle Fibers, Skeletal ; drug effects ; PPAR gamma ; metabolism ; Plant Extracts ; pharmacology ; Protein Biosynthesis ; Protein Synthesis Inhibitors ; pharmacology ; Rosiglitazone ; Thiazolidinediones ; pharmacology ; Up-Regulation

PURPOSE: The purpose of this study was to examine the effect of anorexia and neuropathic pain induced by cisplatin on hindlimb muscles of rats. METHODS: Adult male Sprague-Dawley rats were divided into two groups, a cisplatin-treated group (n=10) and a control group (n=10). In the cisplatin-treated group, cisplatin at a dose of 2 mg/kg was injected intraperitoneally two times a week up to a cumulative dose of 20 mg/kg over 5 weeks, and in the control group saline (0.9% NaCl) was injected intraperitoneally at the same dose and duration as the cisplatin-treated group. At 34 days all rats were anesthetized, after which the soleus and plantaris muscles were dissected. Withdrawal threshold, body weight, food intake, activity, muscle weight, Type I and II fiber cross-sectional areas and myofibrillar protein content of the dissected muscles were determined. RESULTS: Compared with the control group, the cisplatin-treated group showed significant decreases (p<.05) in withdrawal threshold, activity, food intake, body weight, Type I and II fiber cross-sectional areas, myofibrillar protein content and weight of the soleus and plantaris muscles. CONCLUSION: Muscular atrophy in hindlimb occurs due to anorexia and neuropathic pain induced by the cisplatin treatment.
Animals ; *Anorexia ; Body Weight ; Cisplatin/*toxicity ; Eating ; Hindlimb ; Injections, Intraperitoneal ; Male ; Motor Activity ; Muscle Fibers, Skeletal/metabolism/pathology ; Muscle Proteins/metabolism ; Muscle, Skeletal/*drug effects/physiology ; Neuralgia/*chemically induced/pathology ; Rats ; Rats, Sprague-Dawley

OBJECTIVESTo evaluate the expression profile of myoD microRNA-29 (miR-29) family in L6 myoblast differentiated to myotube of L6 myotube treated by glucose and insulin, and to further probe the molecular mechanism of myoD regulating the expression of miR-29 clusters.

METHODSThe expression of myoD and miR-29 family was detected by using real-time PCR and Western blot analysis. The potential promoter and transcription factors binding sites of miR-29 clusters were predicted by Promoter scan and transcriptional factor search. The promoter sequence of miR-29b1-a and miR-29b2-c cluster was cloned into a luciferase reporter plasmid and the regulatory effect of myoD was analyzed by using dual luciferase reporter assay. Electrophoretic mobility shift assay was further conducted to indicate the binding of myoD on specific sequence. Moreover, overexpression of myoD was achieved by a recombinant adenovirus system (Ad-myoD). L6 cells were infected with Ad-myoD and real-time PCR was conducted to analyze the expression of miR-29b and miR-29c.

RESULTSThe expression levels of myoD, miR-29a, miR-29b, and miR-29c were increased in L6 myoblast differentiated to myotube. The expression of myoD, miR-29b, and miR-29c was up-regulated in L6 myotube treated with glucose and insulin, but miR-29a depicted no significant change. Dual luciferase reporter gene assay showed that myoD functioned as a positive regulator of miR-29b2-c expression and myoD could bind to the specific sequence located at the promoter region of miR-29b2-c cluster. Enforced expression of myoD led to a marked increase of miR-29b and miR-29c levels in L6 cells.

CONCLUSIONMyoD might act as a crucial regulator of myogenesis and glucose metabolism in muscle through regulating the expression of miR-29b2-c.

Animals ; Cell Differentiation ; drug effects ; physiology ; Cell Line ; Gene Expression Regulation ; drug effects ; physiology ; Glucose ; pharmacology ; Hypoglycemic Agents ; pharmacology ; Insulin ; pharmacology ; Mice ; MicroRNAs ; biosynthesis ; genetics ; Multigene Family ; physiology ; Muscle Fibers, Skeletal ; cytology ; metabolism ; MyoD Protein ; genetics ; metabolism ; Myoblasts ; cytology ; metabolism ; Sweetening Agents ; pharmacology

PURPOSE: The purpose of this study was to examine effects of nitric oxide synthase (NOS) inhibitor on muscle weight and myofibrillar protein content of affected and unaffected hindlimb muscles in rats with neuropathic pain induced by unilateral peripheral nerve injury. METHODS: Neuropathic pain was induced by ligation and cutting of the left L5 spinal nerve. Adult male Sprague-Dawley rats were randomly assigned to one of two groups: The NOSI group (n=19) had NOS inhibitor (L-NAME) injections daily for 14 days, and the Vehicle group (n=20) had vehicle injections daily for 14 days. Withdrawal threshold, body weight, food intake and activity were measured every day. At 15 days all rats were anesthetized and soleus, plantaris and gastrocnemius muscles were dissected from hindlimbs. Muscle weight and myofibrillar protein content of the dissected muscles were determined. RESULTS: The NOSI group showed significant increases as compared to the Vehicle group for body weight at 15 days, muscle weight and myofibrillar protein content of the unaffected soleus and gastrocnemius. The NOSI group demonstrated a higher pain threshold than the vehicle group. CONCLUSION: NOSI for 14 days attenuates unaffected soleus and gastrocnemius muscle atrophy in neuropathic pain model.
Animals ; Body Weight/drug effects ; Disease Models, Animal ; Eating/drug effects ; Enzyme Inhibitors/*administration & dosage/pharmacology ; *Hindlimb ; Male ; Muscle Fibers, Skeletal/*drug effects/metabolism ; Muscle Proteins/metabolism ; Muscular Atrophy/drug therapy ; NG-Nitroarginine Methyl Ester/*administration & dosage/pharmacology ; Neuralgia/*etiology ; Nitric Oxide Synthase/*antagonists & inhibitors/metabolism ; *Peripheral Nerve Injuries ; Rats ; Rats, Sprague-Dawley

PURPOSE: The purpose of this study was to determine the effect of dehydroepiandrosterone (DHEA) on recovery of muscle atrophy induced by Parkinson's disease. METHODS: The rat model was established by direct injection of 6-hydroxydopamine (6-OHDA, 20 microg) into the left striatum using stereotaxic surgery. Rats were divided into two groups; the Parkinson's disease group with vehicle treatment (Vehicle; n=12) or DHEA treatment group (DHEA; n=22). DHEA or vehicle was administrated intraperitoneally daily at a dose of 0.34 mmol/kg for 21 days. At 22-days after DHEA treatment, soleus, plantaris, and striatum were dissected. RESULTS: The DHEA group showed significant increase (p<.01) in the number of tyrosine hydroxylase (TH) positive neurons in the lesioned side substantia nigra compared to the vehicle group. Weights and Type I fiber cross-sectional areas of the contralateral soleus of the DHEA group were significantly greater than those of the vehicle group (p=.02, p=.00). Moreover, extracellular signal-regulated kinase (ERK) phosphorylation significantly decreased in the lesioned striatum, but was recovered with DHEA and also in the contralateral soleus muscle, Akt and ERK phosphorylation recovered significantly and the expression level of myosin heavy chain also recovered by DHEA treatment. CONCLUSION: Our results suggest that DHEA treatment recovers Parkinson's disease induced contralateral soleus muscle atrophy through Akt and ERK phosphorylation.
Animals ; Corpus Striatum/drug effects/metabolism ; Dehydroepiandrosterone/*pharmacology/therapeutic use ; Extracellular Signal-Regulated MAP Kinases/metabolism ; Male ; Muscle Fibers, Slow-Twitch/drug effects ; Muscle, Skeletal/drug effects/metabolism ; Muscular Atrophy/drug therapy/*etiology/*pathology ; Myosins/metabolism ; Neurons/drug effects/enzymology ; Oxidopamine/toxicity ; Parkinson Disease, Secondary/*chemically induced/*complications ; Phosphorylation ; Proto-Oncogene Proteins c-akt/metabolism ; Rats ; Rats, Sprague-Dawley ; Tyrosine 3-Monooxygenase/metabolism

OBJECTIVETo study the effects of Ligusticum and its two components (Sodium Ferulate and Ligustrazine as main efficacy components in Ligusticum for invigorating blood circulation) on muscle atrophy in a hind limb unloaded rat model.

METHODSThe tail-suspended rats were subjected to a 14-days disuse, immunohistochemistry and hemorheology were used to study the effects of medicines on soleus muscle.

RESULTSCompared with HLU+ W: (1) The CSA of soleus type I fibers in HLU + SfH and HLU+ TmpH increased by 37.3% and 39.4% respectively (P < 0.05). (2) Expression level of MHC II were inhibited in all treatment groups (P < 0.01). (3) Expression of MHC II in nuclear bag 2 fiber were altered from positive to negative. (4) The blood viscosity in low shear rates decreased obviously (P < 0.01), even near to control.

CONCLUSIONLigusticum and its two main efficacy components (Sodium Ferulate and Ligustrazine) can prevent soleus atrophy induced by disuse, and Sodium Ferulate and Ligustrazine in high dose showed most efficacy.

Animals ; Coumaric Acids ; pharmacology ; Drugs, Chinese Herbal ; pharmacology ; Extremities ; Female ; Hemorheology ; Hindlimb Suspension ; Ligusticum ; chemistry ; Muscle Fibers, Skeletal ; drug effects ; Muscular Atrophy ; blood ; etiology ; prevention & control ; Myosin Heavy Chains ; metabolism ; Pyrazines ; pharmacology ; Random Allocation ; Rats ; Rats, Sprague-Dawley

AIMTo study the effect of radix-astragali compound(RC) on muscle atrophy in tail-suspended rats. Muscle weight, fiber type distribution, cross-sectional area (CSA), and activity of myosin adenosine triphosphatase (ATPase) in rat soleus muscle were investigated.

METHODSThe tail-suspended rats were subjected to a 14 days simulated weightlessness, during which period, RC or saltwater was given via intragastric instillation during tail suspension. The changes of soleus muscle weight were scaled by muscle-to-body weight ratio. The activities of myosin ATPase of muscle fibers were detected by method of Ca(2+) -ATPase.

RESULTSAfter a 14 days tail suspension it was found: in rats treated with RC, soleus muscle-to-body weight ratio rose by 33.33% (P < 0.01), both CSA of type I and II fiber drastically enhanced by(143.03%, P < 0.01; 83.25%, P < 0.01), the percentage of type I fiber significantly declined compared to the untreated rats.

CONCLUSIONRC is able to effectively prevent muscle atrophy caused by tail suspension and restrain the increase in the myosin ATPase activities caused by simulated weightlessness.

Animals ; Drugs, Chinese Herbal ; pharmacology ; Hindlimb Suspension ; Male ; Muscle Fibers, Skeletal ; enzymology ; Muscle, Skeletal ; drug effects ; enzymology ; Muscular Atrophy ; prevention & control ; Myosins ; metabolism ; Rats ; Rats, Sprague-Dawley ; Weightlessness Simulation ; methods

trans-Resveratrol (t-RVT), a naturally occurring polyphenol found in Polygonum cuspidatum, grape, and red wine, has been reported to have anti- inflammatory, cardioprotective, and cancer chemopreventive properties. However antidiabetic effect of t-RVT has not yet been reported. In this study, we show that t-RVT increases glucose uptake in C2C12 myotubes by activating AMP-activated protein kinase (AMPK), uncovering an antidiabetic potential of t-RVT for the first time. AMPK plays a central role in the regulation of glucose and lipid metabolism, and hence it is considered a novel therapeutic target for metabolic syndrome such as type 2 diabetes. t-RVT significantly induced glucose uptake in C2C12 cells, via AMPK activation, but not a phosphatidylinositol-3 kinase (PI-3 kinase) signal pathway. The induced glucose uptake was attenuated by pretreatment with a pharmacological inhibitor for AMPK, indicating that the effect of t-RVT primarily depends on AMPK activation. However, in the presence of insulin, t-RVT also potentiated the effect of insulin on glucose uptake via AMPK activation, which led to further activation of PI-3 kinase/Akt signal pathway.
1-Phosphatidylinositol 3-Kinase/metabolism ; AMP-Activated Protein Kinases ; Animals ; Biological Transport/drug effects ; Cell Line ; Enzyme Activation/drug effects ; Glucose/*metabolism ; Insulin/metabolism ; Mice ; Models, Biological ; Multienzyme Complexes/*metabolism ; Muscle Fibers, Skeletal/*drug effects/enzymology/metabolism ; Protein-Serine-Threonine Kinases/*metabolism ; Proto-Oncogene Proteins c-akt/metabolism ; Stilbenes/*pharmacology

OBJECTIVETo study the effects of insulin on the proteolysis of cultured rabbit skeletal muscular myotubes in vitro, and their possible mechanisms.

METHODSMuscles of lower limbs of juvenile rabbits were isolated for tissue-block culture. After passage, myoblasts were formed and fused into myotubes. Then the protein in myotubes was radiolabelled with L-[ 3,5-3H] tyrosine. The myotubes were cultured in DMEM medium containing 100 nmol/L insulin (n = 24, group B) , 100 nmol/L dexamethasone (n = 24, group C) , 100 nmol/L insulin and 100 nmol/L dexamethasone (n = 24, group D) , no insulin or dexamethasone (n =24, group A), respectively. Twenty-four hours after culture, the L-[3,5-3H] tyrosine content in culture medium and cells were determined, and the degradation rates of protein were calculated. The mRNA expressions of ubiquitin and protease C2 subunit were determined by Northern blot.

RESULTSThe degradation rates of myotube protein in group A(0. 38+/-0.04) was obviously lower than that in group C (0.50+/-0.03, P <0.01), but it was obviously higher than that in group B(0. 35+/-0.03, P <0.05). Though the degradation rates of myotube protein in group D (0.41+/-0. 03) was evidently lower than that in group C ( P < 0.01) , it was still higher than that in group A( P < 0.05 ). The mRNA expressions of ubiquitin and protease C2 subunit in group A ( the scale: 2. 4 kb ubiquitin was 0. 82+/-0. 15, 1. 2 kb ubiquitin was 0. 60+/-0. 10, C2 subunit was 0. 75+/-0. 16) was obviously lower than that in group C ( the scale: 2.4 kb ubiquitin was 2. 15+/-0. 23, 1.2 kb ubiquitin was 1.50+/-0. 14,C2 subunit was 1.50+/-0. 13 , P <0. 01) , but it in group D was lower than that in group C (the scale: 2. 4 kb ubiquitin was 1. 25+/-0. 17, 1. 2 kb ubiquitin was 0. 85+/-0. 09, C2 subunit was 0. 90+/-0. 15, P <0. 01) , and it was similar to that in group B (the scale: 2.4 kb ubiquitin was 0. 85+/-0.07, 1.2 kb ubiquitin was 0. 65+/- 0. 12, C2 subunit was 0. 76 +/-0. 09, P > 0. 05).

CONCLUSIONThe effects of insulin on the activity of ubiquitin-proteasome pathway and the proteolytic rate in normal myotubes were relatively weak. However, insulin can significantly inhibit the effects of dexamethasone on the gene expressions of ubiquitin system and the proteolytic rate in myotubes, but the mechanism needs further research.

Animals ; Cells, Cultured ; In Vitro Techniques ; Insulin ; pharmacology ; Male ; Muscle Fibers, Skeletal ; drug effects ; metabolism ; Muscle Proteins ; metabolism ; Rabbits ; Ubiquitin ; metabolism