Association between rhythmic masticatory muscle activity during sleep and masticatory myofascial pain: A polysomnographic study

Aims: To test for an association between rhythmic masticatory muscle activity during sleep, as assessed according to polysomnographic criteria for sleep bruxism (RMMA-SB), and myofascial pain (MFP), as well as the chance of occurrence of MFP in patients with RMMA-SB. Methods: Thirty MFP patients (diagnosed according to the Research Diagnostic Criteria for Temporomandibular Disorders) and 30 age- and gender-matcbed asymptomatic controls underwent a polysomnographic examination. Also, any self-reporting of daytime clenching (DC) was registered in 58 of these subjects. Results: Most MFP patients reported mild or moderate pain (46.67% and 43.33%, respectively), and only 3 (10%) reported severe pain. Pain duration ranged from 2 to 120 months (mean 34.67 +/- 36.96 months). Significant associations were observed between RMMA-SB and MFP as well as between DC and MFP. Conclusions: (1) RMMA-SB is significantly associated with MFP; (2) although RMMA-SB represents a risk factor for MFP, this risk is low; and (3) DC probably constitutes a stronger risk factor for MFP than RMMA-SB.

Akt Expression is Diminished by Physical Inactivity in Early Stages of Development in Soleus Muscle of Rats

Metabolic Syndrome is a group of conditions related to obesity and physical inactivity. Little is known about the role of physical inactivity, in early stages of development, in the susceptibility to insulin resistant phenotype induced by high fat diet. Akt plays a key role in protein synthesis and glucose transport in skeletal muscle and has been regulated by muscle activity. The objective of present study was to determine the effect of early physical inactivity on muscle growth and susceptibility to acquire a diabetic phenotype and to assess its relationship with Akt expression. Forty Wistar male rats were distributed in two groups (standard group, Std) and movement restriction (RM). Between days 23 and 70 after birth, RM group was kept in small cages that did not allow them to perform relevant motor activity. From day 71 to 102 after birth, 10 rats of each group were fed with hyperlipidic diet (groups Std-DAG and RM-DAG). No differences were observed in total body weight although DAG increased epididymal fat pad weight. RM decreased significantly the soleus weight. Insulin-mediated glucose uptake was lower in RM-DAG group. Akt protein levels were lower in RM groups. Real time RT-PCR analysis showed that movement restriction decreased mRNA levels of AKT1 in soleus muscle, regardless of supplied diet. These findings suggest that early physical inactivity limits muscle`s growth and contributes to instauration of insulin resistant phenotype, which can be partly explained by dysregulation of Akt expression.

Participation of peripheral tachykinin NK(1) receptors in the carrageenan-induced inflammation of the rat temporomandibular joint

Temporomandibular disorders represent one of the major challenges in dentistry therapeutics. This study was undertaken to evaluate the time course of carrageenan-induced inflammation in the rat temporomandibular joint (TMJ) and to investigate the role of tachykinin NK(1) receptors. Inflammation was induced by a single intra-articular (i.art.) injection of carrageenan into the left TMJ (control group received sterile saline). Inflammatory parameters such as plasma extravasation, leukocyte influx and mechanical allodynia (measured as the head-withdrawal force threshold) and TNF alpha and IL-1 beta concentrations were measured in the TMJ lavages at selected time-points. The carrageenan-induced responses were also evaluated after treatment with the NK(1) receptor antagonist SR140333. The i.art. injection of carrageenan into the TMJ caused a time-dependent plasma extravasation associated with mechanical allodynia, and a marked neutrophil accumulation between 4 and 24 h. Treatment with SR140333 substantially inhibited the increase in plasma extravasation and leukocyte influx at 4 and 24 h, as well as the production of TNF alpha and IL-1 beta into the joint cavity, but failed to affect changes in head-withdrawal threshold. The results obtained from the present TMJ-arthritis model provide, for the first time, information regarding the time course of this experimental inflammatory process. In addition, our data show that peripheral NK(1) receptors mediate the production of both TNF alpha and IL-1 beta in the TMJ as well as some of the inflammatory signs, such as plasma extravasation and leukocyte influx, but not the nociceptive component. 2008 European Federation of Chapters of the International Association for the Study of Pain. Published by Elsevier Ltd. All rights reserved.

Palmitate increases superoxide production through mitochondrial electron transport chain and NADPH oxidase activity in skeletal muscle cells

The effect of unbound palmitic acid (PA) at plasma physiological concentration range on reactive oxygen species (ROS) production by cultured rat skeletal muscle cells was investigated. The participation of the main sites of ROS production was also examined. Production of ROS was evaluated by cytochrome c reduction and dihydroethidium oxidation assays. PA increased ROS production after 1 h incubation. A xanthine oxidase inhibitor did not change PA-induced ROS production. However, the treatment with a mitochondrial uncoupler and mitochondrial complex III inhibitor decreased superoxide production induced by PA. The importance of mitochondria was also evaluated in 1 h incubated rat soleus and extensor digitorum longus (EDL) muscles. Soleus muscle, which has a greater number of mitochondria than EDL, showed a higher superoxide production induced by PA. These results indicate that mitochondrial electron transport chain is an important contributor for superoxide formation induced by PA in skeletal muscle. Results obtained with etomoxir and bromopalmitate treatment indicate that PA has to be oxidized to raise ROS production. A partial inhibition of superoxide formation induced by PA was observed by treatment with diphenylene iodonium, an inhibitor of NADPH oxidase. The participation of this enzyme complex was confirmed through an increase of p47(phox) phosphorylation after treatment with PA.

Effect of short-term creatine supplementation on markers of skeletal muscle damage after strenuous contractile activity

The protective effect of short-term creatine supplementation (CrS) upon markers of strenuous contractile activity-induced damage in human and rat skeletal muscles was investigated. Eight Ironman triathletes were randomized into the placebo (Pl; n = 4) and creatine-supplemented (CrS; n = 4) groups. Five days prior to the Ironman competition, the CrS group received creatine monohydrate (20 g day(-1)) plus maltodextrin (50 g) divided in two equal doses. The Pl group received maltodextrin (50 g day(-1)) only. The effect of CrS (5 g day(-1)/kg body weight for 5 days) was also evaluated in a protocol of strenuous contractile activity induced by electrical stimulation in rats. Blood samples were collected before and 36 and 60 h after the competition and were used to determine plasma activities of creatine kinase (CK), lactate dehydrogenase (LDH), aldolase (ALD), glutamic oxaloacetic acid transaminase (GOT), glutamic pyruvic acid transaminase (GPT), and C-reactive protein (CRP) level. In rats, plasma activities of CK and LDH, muscle vascular permeability (MVP) using Evans blue dye, muscle force and fatigue were evaluated. Activities of CK, ALD, LDH, GOT, GTP, and levels of CRP were increased in the Pl group after the competition as compared to basal values. CrS decreased plasma activities of CK, LDH, and ALD, and prevented the rise of GOT and GPT plasma activities. In rats, CrS delayed the fatigue, preserved the force, and prevented the rise of LDH and CK plasma activities and MVP in the gastrocnemius muscle. CrS presented a protective effect on muscle injury induced by strenuous contractile activities.

Effects of supplementation with free glutamine and the dipeptide alanyl-glutamine on parameters of muscle damage and inflammation in rats submitted to prolonged exercise

In this study, we investigated the effect of the supplementation with the dipeptide L-alanyl-L-glutamine (DIP) and a solution containing L-glutamine and L-alanine on plasma levels markers of muscle damage and levels of pro-inflammatory cytokines and glutamine metabolism in rats submitted to prolonged exercise. Rats were submitted to sessions of swim training for 6 weeks. Twenty-one days prior to euthanasia, the animals were supplemented with DIP (n = 8) (1.5 g.kg(-1)), a solution of free L-glutamine (1 g.kg(-1)) and free L-alanine (0.61 g.kg(-1)) (G&A, n = 8) or water (control (CON), n = 8). Animals were killed at rest before (R), after prolonged exercise (PE-2 h of exercise). Plasma concentrations of glutamine, glutamate, tumour necrosis factor-alpha (TNF-alpha), prostaglandin E2 (PGE2) and activity of creatine kinase (CK), lactate dehydrogenase (LDH) and muscle concentrations Of glutamine and glutamate were measured. The concentrations of plasma TNF-alpha, PGE2 and the activity of CK were lower in the G&A-R and DIP-R groups, compared to the CON-R. Glutamine in plasma (p < 0.04) and soleus muscle (p < 0.001) was higher in the DIP-R and G&A-R groups relative to the CON-R group. G&A-PE and DIP-PE groups exhibited lower concentrations of plasma PGE2 (p < 0.05) and TNF-alpha (p < 0.05), and higher concert I rations of glutamine and glutamate in soleus (p < 0.001) and gastrocnemius muscles (p < 0.05) relative to the CON-PE group. We concluded that supplementation with free L-glutamine and the dipeptide LL-alanyl-LL-glutamine represents an effective source of glutamine, which may attenuate inflammation biomarkers after periods of training and plasma levels of CK and the inflammatory response induced by prolonged exercise. Copyright (C) 2009 John Wiley & Sons, Ltd.

Sympathetic nerve activity is decreased during device-guided slow breathing

It is known that slow breathing (<10 breaths min(-1)) reduces blood pressure ( BP), but the mechanisms involved in this phenomenon are not completely clear. The aim of this study was to evaluate the acute responses of the muscle sympathetic nerve activity, BP and heart rate (HR), using device-guided slow breathing ( breathe with interactive music (BIM)) or calm music. In all, 27 treated mild hypertensives were enrolled. Muscle sympathetic nerve activity, BP and HR were measured for 5min before the use of the device (n=14) or while subjects listened to calm music (n=13), it was measured again for 15 min while in use and finally, 5min after the interventions. BIM device reduced respiratory rate from 16 +/- 3 beats per minute (b.p.m) to 5.5 +/- 1.8 b.p.m (P<0.05), calm music did not affect this variable. Both interventions reduced systolic (-6 and -4mmHg for both) and diastolic BPs (-4mmHg and -3mmHg, respectively) and did not affect the HR (-1 and -2 b.p.m respectively). Only the BIM device reduced the sympathetic nerve activity of the sample (-8bursts min(-1)). In conclusion, both device-guided slow breathing and listening to calm music have decreased BP but only the device-guided slow breathing was able to reduce the peripheral sympathetic nerve activity. Hypertension Research ( 2010) 33, 708-712; doi: 10.1038/hr.2010.74; published online 3 June 2010

Effect of arginine on the development of the pectoralis muscle and the diameter and the protein:deoxyribonucleic acid rate of its skeletal myofibers in broilers

This work aimed at evaluating the effects of the supplementation of starter diet with Arg on breast muscle development in broilers and the activation of satellite cells and the aggregation of myofibrillar protein. Male Cobb chicks (n = 990) were randomly assigned to 1 of 5 treatments in a complete random design. Measurements of 33 chicks per treatment were made in 6 repetitions. The treatments consisted of a basal diet with 1.390% digestible Arg (without supplementation) and 4 dietary levels of Arg (1.490, 1.590, 1.690, and 1.790%) with Arg:Lys ratios of 1.103, 1.183, 1.262, 1.341, and 1.421, respectively. Arginine supplementation was used only in the starter phase (1 to 21 d). Dietary supplementation with Arg had a positive effect (P < 0.05) on breast and breast fillet weight on d 7 and 21 and on myofiber diameter on d 14 and 21. However, no effect was observed (P > 0.05) on the protein: DNA ratio, which demonstrates that Arg does not interfere with the mitotic activity of the satellite cells. Independently from mechanism, Arg affected muscle growth in the starter phase positively. Dietary supplementation with Arg in the starter phase had no effect (P > 0.05) on the carcass yield of broilers on d 42. Diet supplementation with Arg at levels above the ones recommended for the starter phase may be necessary for improved muscle development in broilers.

Energy substrate utilization during nightly vocal activity in three species of Scinax (Anura/Hylidae)

Anuran amphibians exhibit different patterns of energy substrate utilization that correlate with the intensity of vocal and locomotor activities. Given the remarkable differences among species in breeding and feeding strategies, and the different ways energy is used in the whole animal, the suggested correlations between calling and locomotor behavior and the level of energy substrates in the muscles responsible for such activities are more complex than previously reported. We explored the relationships between calling and locomotor behavior and energy supply to trunk and hindlimb muscles, respectively, within the ecologically diverse tree-frog genus Scinax. Specifically, we measured the relative amount of carbohydrates and lipids in these two groups of muscles, and in the liver of three species of Scinax that differ in vocal and locomotor performance, and compared our results with those of two other species for which comparable data are available. We also compared the contents of lipids and carbohydrates of conspecific males collected at the beginning and after 4 h of calling activity. The stomach content to potential feeding opportunities across species was also assessed in both groups of males. Scinax hiemalis and S. rizibilis exhibit comparatively low and episodic calling during long periods of activity whereas S. crospedospilus calls at higher rates over shorter periods. Male S. hiemalis had highest levels of trunk muscle glycogen followed by those of S. rizilbilis and S. crospedospilus, respectively. There was no correlation between total lipid content in trunk muscle and calling rate among different species, suggesting that other metabolic aspects may be responsible for the energetic support for vocal activity. The levels of lipids and carbohydrates in trunk and hindlimb muscles and liver of males collected at the beginning and 4 h into the calling period were similar across species, so the extent of energetic reserves does not appear to constrain vocal or locomotor activity. Finally, we found exceptionally high levels of carbohydrates and lipids in the liver of S. rizibilis, a trait perhaps related to a long and demanding breeding period.

Reduction of acethylcolinesterase activity in the brain of mdx mice

Lack of dystrophin in brain structures have been involved with impaired cognitive functions. Acethylcolinesterase (AChE) is implicated in many cognitive functions and probably plays important roles in neurodegenerative disorders. In the present study, we investigated AChE activity in the prefrontal cortex, hippocampus, striatum and cortex of mdx mice. To this aim, brain tissues from male dystrophic mdx and normal control mice were used. We observed that mdx mice display a reduction in AChE activity of 40-60% in all brain structures evaluated. In conclusion, dystrophin deficiency may be affecting AChE activity and contributing negatively, in part, to memory storage and restoring. (C) 2011 Elsevier B.V. All rights reserved.

Sympathetic hyperactivity differentially affects skeletal muscle mass in developing heart failure: role of exercise training

Bacurau AV, Jardim MA, Ferreira JC, Bechara LR, Bueno CR Jr, Alba-Loureiro TC, Negrao CE, Casarini DE, Curi R, Ramires PR, Moriscot AS, Brum PC. Sympathetic hyperactivity differentially affects skeletal muscle mass in developing heart failure: role of exercise training. J Appl Physiol 106: 1631-1640, 2009. First published January 29, 2009; doi:10.1152/japplphysiol.91067.2008.-Sympathetic hyperactivity (SH) is a hallmark of heart failure (HF), and several lines of evidence suggest that SH contributes to HF-induced skeletal myopathy. However, little is known about the influence of SH on skeletal muscle morphology and metabolism in a setting of developing HF, taking into consideration muscles with different fiber compositions. The contribution of SH on exercise tolerance and skeletal muscle morphology and biochemistry was investigated in 3- and 7-mo-old mice lacking both alpha(2A)- and alpha(2C)-adrenergic receptor subtypes (alpha(2A)/alpha(2C)ARKO mice) that present SH with evidence of HF by 7 mo. To verify whether exercise training (ET) would prevent skeletal muscle myopathy in advanced-stage HF, alpha(2A)/alpha(2C)ARKO mice were exercised from 5 to 7 mo of age. At 3 mo, alpha(2A)/alpha(2C)ARKO mice showed no signs of HF and preserved exercise tolerance and muscular norepinephrine with no changes in soleus morphology. In contrast, plantaris muscle of alpha(2A)/alpha(2C)ARKO mice displayed hypertrophy and fiber type shift (IIA -> IIX) paralleled by capillary rarefaction, increased hexokinase activity, and oxidative stress. At 7 mo, alpha(2A)/alpha(2C)ARKO mice displayed exercise intolerance and increased muscular norepinephrine, muscular atrophy, capillary rarefaction, and increased oxidative stress. ET reestablished alpha(2A)/alpha(2C)ARKO mouse exercise tolerance to 7-mo-old wild-type levels and prevented muscular atrophy and capillary rarefaction associated with reduced oxidative stress. Collectively, these data provide direct evidence that SH is a major factor contributing to skeletal muscle morphological changes in a setting of developing HF. ET prevented skeletal muscle myopathy in alpha(2A)/alpha(2C)ARKO mice, which highlights its importance as a therapeutic tool for HF.

Chronic supplementation of beta-hydroxy-beta methylbutyrate (HM beta) increases the activity of the GH/IGF-I axis and induces hyperinsulinemia in rats

Objective: Beta-hydroxy-beta-methylbutyrate (HM beta) is a metabolite of leucine widely used for improving sports performance. Although limp is recognized to promote anabolic or anti-catabolic effects on protein metabolism, the impact of its long-term use on skeletal muscle and/or genes that control the skeletal protein balance is not fully known. This study aimed to investigate whether chronic HM beta treatment affects the activity of GH/IGF-I axis and skeletal muscle IGF-I and myostatin mRNA expression. Design: Rats were treated with HK beta (320 mg/kg BW) or vehicle, by gavage, for 4 weeks, and killed by decapitation. Blood was collected for evaluation of serum insulin, glucose and IGF-I concentrations. Samples of pituitary, liver, extensor digitorum longus (EDL) and soleus muscles were collected for total RNA or protein extraction to evaluate the expression of pituitary growth hormone (GH) gene (mRNA and protein), hepatic insulin-like growth factor I (IGF-I) mRNA, skeletal muscle IGF-I and myostatin mRNA by Northern blotting/real time-PCR, or Western blotting. Results: Chronic HM beta treatment increased the content of pituitary GH mRNA and GH, hepatic IGF-I mRNA and serum IGF-I concentration. No changes were detected on skeletal muscle IGF-I and myostatin mRNA expression. However, the HIM-treated rats although normoglycemic, exhibited hyperinsulinemia. Conclusions: The data presented herein extend the body of evidence on the potential role of HM beta-treatment in stimulating GH/IGF-I axis activity. In spite of this effect, HM beta supplementation also induces an apparent insulin resistance state which might limit the beneficial aspects of the former results, at least in rats under normal nutritional status and health conditions. (C) 2010 Growth Hormone Research Society. Published by Elsevier Ltd. All rights reserved.

Prolonged exposure to palmitate impairs fatty acid oxidation despite activation of AMP-activated protein kinase in skeletal muscle cells

The aim of this study was to investigate the chronic effects of palmitate on fatty acid (FA) oxidation, AMPK/ACC phosphorylation/activation, intracellular lipid accumulation, and the molecular Mechanisms involved in these processes in skeletal muscle cells. Exposure of L6 myotubes for 8 h to 200, 400, 600, and 800 mu M of palmitate did rot affect cel viability but significantly reduced FA oxidation by similar to 26.5%, similar to 43.5%, similar to 50%, and similar to 47%, respectively. Interestingly, this occurred despite significant increases in AMPK (similar to 2.5-fold) and ACC (similar to 3-fold) phosphorylation and in malonyl-CoA decarboxylase activity (similar to 38-60%). Low concentrations of palmitate (50-100 mu M) caused an increase (similar to 30%) in CPT-I activity. However, as the concentration of palmitate increased, CPT-I activity decreased by similar to 32% after exposure for 8 h to 800 mu M of palmitate. Although FA uptake was reduced (similar to 35%) in cells exposed to increasing, palmitate concentrations, intracellular lipid accumulation increased in a dose-dependent manner, reaching values similar to 2.3-, similar to 3-, and 4-fold higher than control in muscle cells exposed to 400, 600, and 800 mu M palmitate, respectively. Interestingly, myotubes exposed to 400 mu M of palmitate for 1h increased basal glucose uptake and glycogen synthesis by similar to 40%. However, as time of incubation in the presence of palmitate progressed from 1 to 8h, these increases were abolished and a time-dependent inhibition of insulin-stimulated glucose uptake (similar to 65%) and glycogen synthesis (30%) was observed in myotubes. These findings may help explain the dysfunctional adaptations that occur in glucose and FA Metabolism in skeletal muscle under conditions of chronically elevated circulating levels of non-esterified FAs. Such as in obesity and Type 2 Diabetes.

Tyrosine hydroxylase immunoreactivity as indicator of sympathetic activity: simultaneous evaluation in different tissues of hypertensive rats

Burgi K, Cavalleri MT, Alves AS, Britto LRG, Antunes VR, Michelini LC. Tyrosine hydroxylase immunoreactivity as indicator of sympathetic activity: simultaneous evaluation in different tissues of hypertensive rats. Am J Physiol Regul Integr Comp Physiol 300: R264-R271, 2011. First published December 9, 2010; doi: 10.1152/ajpregu.00687.2009.-Vasomotor control by the sympathetic nervous system presents substantial heterogeneity within different tissues, providing appropriate homeostatic responses to maintain basal/stimulated cardiovascular function both at normal and pathological conditions. The availability of a reproducible technique for simultaneous measurement of sympathetic drive to different tissues is of great interest to uncover regional patterns of sympathetic nerve activity (SNA). We propose the association of tyrosine hydroxylase immunoreactivity (THir) with image analysis to quantify norepinephrine (NE) content within nerve terminals in arteries/arterioles as a good index for regional sympathetic outflow. THir was measured in fixed arterioles of kidney, heart, and skeletal muscle of WistarKyoto rats (WKY) and spontaneously hypertensive rats (SHR) (123 +/- 2 and 181 +/- 4 mmHg, 300 +/- 8 and 352 +/- 8 beats/min, respectively). There was a differential THir distribution in both groups: higher THir was observed in the kidney and skeletal muscle (similar to 3-4-fold vs. heart arterioles) of WKY; in SHR, THir was increased in the kidney and heart (2.4- and 5.3-fold vs. WKY, respectively) with no change in the skeletal muscle arterioles. Observed THir changes were confirmed by either: 1) determination of NE content (high-performance liquid chromatography) in fresh tissues (SHR vs. WKY): +34% and +17% in kidney and heart, respectively, with no change in the skeletal muscle; 2) direct recording of renal (RSNA) and lumbar SNA (LSNA) in anesthetized rats, showing increased RSNA but unchanged LSNA in SHR vs. WKY. THir in skeletal muscle arterioles, NE content in femoral artery, and LSNA were simultaneously reduced by exercise training in the WKY group. Results indicate that THir is a valuable technique to simultaneously evaluate regional patterns of sympathetic activity.

Regulation of glycolysis and expression of glucose metabolism-related genes by reactive oxygen species in contracting skeletal muscle cells

Contractile activity induces a marked increase in glycolytic activity and gene expression of enzymes and transporters involved in glucose metabolism in skeletal muscle. Muscle contraction also increases the production of reactive oxygen species (ROS). In this study, the effects of treatment with N-acetylcysteine (NAC), a potent antioxidant compound, on contraction-stimulated glycolysis were investigated in electrically stimulated primary rat skeletal muscle cells. The following parameters were measured: 2-[(3)H]deoxyglucose (2-DG) uptake; activities of hexokinase, phosphofructokinase (PFK), and glucose-6-phosphate dehydrogenase (G6PDH); lactate production; and expression of the glucose transporter 4 (GLUT4), hexokinase II (HKII), and PFK genes after one bout of electrical stimulation in primary rat myotubes. NAC treatment decreased ROS signal by 49% in resting muscle cells and abolished the muscle contraction-induced increase in ROS levels. In resting cells, NAC decreased mRNA and protein contents of GLUT4, mRNA content and activity of PFK, and lactate production. NAC treatment suppressed the contraction-mediated increase in 2-DG uptake; lactate production; hexokinase, PFK, and G6PDH activities; and gene expression of GLUT4. HKII, and PFK. Similar to muscle contraction, exogenous H(2)O(2) (500 nM) administration increased 2-DG uptake; lactate production; hexokinase, PFK, and G6PDH activities; and gene expression of GLUT4. HKII, and PFK. These findings support the proposition that ROS endogenously produced play an important role in the changes in glycolytic activity and gene expression of GLUT4, HKII, and PFK induced by contraction in skeletal muscle cells. (C) 2010 Elsevier Inc. All rights reserved.