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  1. Ibitoye MO, Hamzaid NA, Hasnan N, Abdul Wahab AK, Davis GM
    PLoS One, 2016;11(2):e0149024.
    PMID: 26859296 DOI: 10.1371/journal.pone.0149024
    BACKGROUND: Rapid muscle fatigue during functional electrical stimulation (FES)-evoked muscle contractions in individuals with spinal cord injury (SCI) is a significant limitation to attaining health benefits of FES-exercise. Delaying the onset of muscle fatigue is often cited as an important goal linked to FES clinical efficacy. Although the basic concept of fatigue-resistance has a long history, recent advances in biomedical engineering, physiotherapy and clinical exercise science have achieved improved clinical benefits, especially for reducing muscle fatigue during FES-exercise. This review evaluated the methodological quality of strategies underlying muscle fatigue-resistance that have been used to optimize FES therapeutic approaches. The review also sought to synthesize the effectiveness of these strategies for persons with SCI in order to establish their functional impacts and clinical relevance.

    METHODS: Published scientific literature pertaining to the reduction of FES-induced muscle fatigue was identified through searches of the following databases: Science Direct, Medline, IEEE Xplore, SpringerLink, PubMed and Nature, from the earliest returned record until June 2015. Titles and abstracts were screened to obtain 35 studies that met the inclusion criteria for this systematic review.

    RESULTS: Following the evaluation of methodological quality (mean (SD), 50 (6) %) of the reviewed studies using the Downs and Black scale, the largest treatment effects reported to reduce muscle fatigue mainly investigated isometric contractions of limited functional and clinical relevance (n = 28). Some investigations (n = 13) lacked randomisation, while others were characterised by small sample sizes with low statistical power. Nevertheless, the clinical significance of emerging trends to improve fatigue-resistance during FES included (i) optimizing electrode positioning, (ii) fine-tuning of stimulation patterns and other FES parameters, (iii) adjustments to the mode and frequency of exercise training, and (iv) biofeedback-assisted FES-exercise to promote selective recruitment of fatigue-resistant motor units.

    CONCLUSION: Although the need for further in-depth clinical trials (especially RCTs) was clearly warranted to establish external validity of outcomes, current evidence was sufficient to support the validity of certain techniques for rapid fatigue-reduction in order to promote FES therapy as an integral part of SCI rehabilitation. It is anticipated that this information will be valuable to clinicians and other allied health professionals administering FES as a treatment option in rehabilitation and aid the development of effective rehabilitation interventions.

    Matched MeSH terms: Muscle, Skeletal/physiopathology
  2. Ibitoye MO, Hamzaid NA, Zuniga JM, Hasnan N, Wahab AK
    Sensors (Basel), 2014;14(12):22940-70.
    PMID: 25479326 DOI: 10.3390/s141222940
    The research conducted in the last three decades has collectively demonstrated that the skeletal muscle performance can be alternatively assessed by mechanomyographic signal (MMG) parameters. Indices of muscle performance, not limited to force, power, work, endurance and the related physiological processes underlying muscle activities during contraction have been evaluated in the light of the signal features. As a non-stationary signal that reflects several distinctive patterns of muscle actions, the illustrations obtained from the literature support the reliability of MMG in the analysis of muscles under voluntary and stimulus evoked contractions. An appraisal of the standard practice including the measurement theories of the methods used to extract parameters of the signal is vital to the application of the signal during experimental and clinical practices, especially in areas where electromyograms are contraindicated or have limited application. As we highlight the underpinning technical guidelines and domains where each method is well-suited, the limitations of the methods are also presented to position the state of the art in MMG parameters extraction, thus providing the theoretical framework for improvement on the current practices to widen the opportunity for new insights and discoveries. Since the signal modality has not been widely deployed due partly to the limited information extractable from the signals when compared with other classical techniques used to assess muscle performance, this survey is particularly relevant to the projected future of MMG applications in the realm of musculoskeletal assessments and in the real time detection of muscle activity.
    Matched MeSH terms: Muscle, Skeletal/physiopathology*
  3. Islam A, Sundaraj K, Ahmad RB, Sundaraj S, Ahamed NU, Ali MA
    Muscle Nerve, 2015 Jun;51(6):899-906.
    PMID: 25204740 DOI: 10.1002/mus.24454
    In this study, we analyzed the crosstalk in mechanomyographic (MMG) signals generated by the extensor digitorum (ED), extensor carpi ulnaris (ECU), and flexor carpi ulnaris (FCU) muscles of the forearm during wrist flexion (WF) and extension (WE) and radial (RD) and ulnar (UD) deviations.
    Matched MeSH terms: Muscle, Skeletal/physiopathology*
  4. Ibitoye MO, Estigoni EH, Hamzaid NA, Wahab AK, Davis GM
    Sensors (Basel), 2014;14(7):12598-622.
    PMID: 25025551 DOI: 10.3390/s140712598
    The evoked electromyographic signal (eEMG) potential is the standard index used to monitor both electrical changes within the motor unit during muscular activity and the electrical patterns during evoked contraction. However, technical and physiological limitations often preclude the acquisition and analysis of the signal especially during functional electrical stimulation (FES)-evoked contractions. Hence, an accurate quantification of the relationship between the eEMG potential and FES-evoked muscle response remains elusive and continues to attract the attention of researchers due to its potential application in the fields of biomechanics, muscle physiology, and rehabilitation science. We conducted a systematic review to examine the effectiveness of eEMG potentials to assess muscle force and fatigue, particularly as a biofeedback descriptor of FES-evoked contractions in individuals with spinal cord injury. At the outset, 2867 citations were identified and, finally, fifty-nine trials met the inclusion criteria. Four hypotheses were proposed and evaluated to inform this review. The results showed that eEMG is effective at quantifying muscle force and fatigue during isometric contraction, but may not be effective during dynamic contractions including cycling and stepping. Positive correlation of up to r = 0.90 (p < 0.05) between the decline in the peak-to-peak amplitude of the eEMG and the decline in the force output during fatiguing isometric contractions has been reported. In the available prediction models, the performance index of the eEMG signal to estimate the generated muscle force ranged from 3.8% to 34% for 18 s to 70 s ahead of the actual muscle force generation. The strength and inherent limitations of the eEMG signal to assess muscle force and fatigue were evident from our findings with implications in clinical management of spinal cord injury (SCI) population.
    Matched MeSH terms: Muscle, Skeletal/physiopathology*
  5. Shahrizaila N, Noto Y, Simon NG, Huynh W, Shibuya K, Matamala JM, et al.
    Clin Neurophysiol, 2017 Jan;128(1):227-232.
    PMID: 27940147 DOI: 10.1016/j.clinph.2016.11.010
    OBJECTIVE: The utility of quantitative muscle ultrasound as a marker of disease severity in Charcot-Marie-Tooth (CMT) disease subtypes was investigated.

    METHODS: Muscle ultrasound was prospectively performed on 252 individual muscles from 21 CMT patients (9 CMT1A, 8 CMTX1, 4 CMT2A) and compared to 120 muscles from 10 age and gender-matched controls. Muscle ultrasound recorded echogenicity and thickness in representative muscles including first dorsal interosseus (FDI) and tibialis anterior (TA).

    RESULTS: Muscle volume of FDI and thickness of TA correlated with MRC strength. Muscle echogenicity was significantly increased in FDI (65.05 vs 47.09; p<0.0001) and TA (89.45 vs 66.30; p<0.0001) of CMT patients. In TA, there was significantly higher muscle thickness (23 vs 18 vs 16mm; p<0.0001) and lower muscle echogenicity (80 vs 95 vs 108; p<0.0001) in CMT1A compared to CMTX1 and CMT2A. This corresponded to disease severity based on muscle strength (MRC grading CMT1A vs CMTX1 vs CMT2A: 59 vs 48 vs 44; p=0.002).

    CONCLUSION: In CMT, quantitative muscle ultrasound of FDI and TA is a useful marker of disease severity.

    SIGNIFICANCE: The current findings suggest that quantitative muscle ultrasound has potential as a surrogate marker of disease progression in future interventional trials in CMT.

    Matched MeSH terms: Muscle, Skeletal/physiopathology
  6. Toh TH, Abdul-Aziz NA, Yahya MA, Goh KJ, Loh EC, Capelle DP, et al.
    Clin Neurophysiol, 2021 10;132(10):2722-2728.
    PMID: 34312065 DOI: 10.1016/j.clinph.2021.05.034
    OBJECTIVE: We aimed to develop a model to predict amyotrophic lateral sclerosis (ALS) disease progression based on clinical and neuromuscular ultrasound (NMUS) parameters.

    METHODS: ALS patients were prospectively recruited. Muscle fasciculation (≥2 over 30-seconds, examined in biceps brachii-brachialis (BB), brachioradialis, tibialis anterior and vastus medialis) and nerve cross-sectional area (CSA) (median, ulnar, tibial, fibular nerve) were evaluated through NMUS. Ultrasound parameters were correlated with clinical data, including revised ALS Functional Rating Scale (ALSFRS-R) progression at one year. A predictive model was constructed to differentiate fast progressors (ALSFRS-R decline ≥ 1/month) from non-fast progressors.

    RESULTS: 40 ALS patients were recruited. Three parameters emerged as strong predictors of fast progressors: (i) ALSFRS-R slope at time of NMUS (p = 0.041), (ii) BB fasciculation count (p = 0.027) and (iii) proximal to distal median nerve CSA ratio 

    Matched MeSH terms: Muscle, Skeletal/physiopathology
  7. Hussain J, Sundaraj K, Subramaniam ID
    PLoS One, 2020;15(1):e0228089.
    PMID: 31999750 DOI: 10.1371/journal.pone.0228089
    INTRODUCTION: Cognitive stress (CS) changes the peripheral attributes of a muscle, but its effect on multi-head muscles has not been investigated. The objective of the current research was to investigate the impact of CS on the three heads of the triceps brachii (TB) muscle.

    METHODS: Twenty-five young and healthy university students performed a triceps push-down exercise at 45% one repetition maximum (1RM) with and without CS until task failure, and the rate of fatigue (ROF), endurance time (ET) and number of repetitions (NR) for both exercises were analyzed. In addition, the first and last six repetitions of each exercise were considered non-fatiguing (NF) and fatiguing (Fa), respectively, and the root mean square (RMS), mean power frequency (MPF) and median frequency (MDF) for each exercise repetition were evaluated.

    RESULTS: The lateral and long head showed significant differences (P<0.05) in the ROF between the two exercises, and all the heads showed significant (P<0.05) differences in the RMS between the two exercises under NF conditions. Only the long head showed a significant difference (P<0.05) in the MPF and MDF between the two exercises. CS increases the ET (24.74%) and NR (27%) of the exercise. The three heads showed significant differences (P<0.05) in the RMS, MPF and MDF under all exercise conditions.

    CONCLUSION: A lower ROF was obtained with CS. In addition, the RMS was found to be better approximator of CS, whereas MPF and MDF were more resistant to the effect of CS. The results showed that the three heads worked independently under all conditions, and the non-synergist and synergist head pairs showed similar behavior under Fa conditions. The findings from this study provide additional insights regarding the functioning of each TB head.

    Matched MeSH terms: Muscle, Skeletal/physiopathology*
  8. Singh DK, Bailey M, Lee R
    BMC Musculoskelet Disord, 2013 Jul 22;14:215.
    PMID: 23875830 DOI: 10.1186/1471-2474-14-215
    BACKGROUND: Muscle morphology, age and gender may be determinants of muscle strength in older adults. However, very few research studies have directly examined such correlation in the ageing spine. The aim of the study was to examine the correlation between lumbar extensor muscle strength, its muscle fibre angles, thoracolumbar curvature, age and gender in the older and younger adults.

    METHODS: Muscle fibre angles of lumbar extensor muscles, thoracolumbar curvature and lumbar extensor muscle strength were examined in 26 young (mean age 27.9, SD 5.2) and 26 older (mean age 72.1, SD 5.9) participants. Pearson's correlation was employed to determine the association among lumbar extensor muscle fibre angle, thoracolumbar curvature, age, gender and lumbar extensor muscle strength. Multiple stepwise linear regression analysis was used to identify significant determinants of lumbar extensor muscle strength.

    RESULTS: The results demonstrated a significant correlation between lumbar extensor muscle strength, muscle fibre angle, age and gender. In the step wise regression analysis, both gender and age were identified as the most robust determinant for lumbar extensor muscle strength in older adults. However, gender was the only determinant of muscle strength in the young.

    CONCLUSION: These results suggest that the decline in the lumbar extensor muscle strength in older adults was more dependent on age when compared to younger adults.

    Matched MeSH terms: Muscle, Skeletal/physiopathology*
  9. Hamid MS, Yusof A, Mohamed Ali MR
    PLoS One, 2014;9(2):e90538.
    PMID: 24587389 DOI: 10.1371/journal.pone.0090538
    INTRODUCTION: Acute muscle injury is one of the commonest injuries that often result in loss of training and competition time. The best management for muscle injury has not been identified. Sports medicine practitioners used several approaches in attempt to accelerate time to recovery from muscle injury. More recently growing interest focussed on autologous blood product injection.
    METHODS: A literature search was conducted systematically using OvidMEDLINE, PubMed, EMBASE, SPORTDiscus and CINAHL databases to retrieve articles published until December 2012. Controlled trials and controlled laboratory studies comparing different strategies to promote early recovery of muscle injury were included. The methodological quality of studies was assessed.
    RESULTS: There are limited studies on the effects of PRP therapy for muscle injury. Three in vivo laboratory studies and one pilot human study were reviewed. The laboratory studies reported histological evidence on significant acceleration of muscle healing in animals treated with autologous conditioned serum (ACS), platelet-rich plasma (PRP) and platelet rich fibrin matrix (PRFM). A pilot human study found athletes treated with repeated ACS injection recovers significantly faster than retrospective controls.
    CONCLUSION: Several in vivo laboratory studies suggest beneficial effects of ACS, PRP and PRFM in accelerating muscle recovery. Evidence to suggest similar effects on humans is however limited, as valuable information from robust human controlled trials is still not available at this moment. Hence, more studies of satisfactory methodological quality with platelet-rich plasma interventions on muscle injury are justified.
    Matched MeSH terms: Muscle, Skeletal/physiopathology
  10. Faridah Y, Abdullah BJ
    Hong Kong Med J, 2003 Apr;9(2):134-6.
    PMID: 12668827
    Magnetic resonance imaging is gaining importance in the diagnosis of nerve and muscular disorders. The ability of magnetic resonance imaging to delineate the different muscles and the nerve in any plane has made the differentiation between the changes of neuropathy, denervation, and nerve entrapment possible. Although findings on magnetic resonance imaging are non-specific, their use, coupled with clinical symptoms and electromyographic findings, allow an accurate diagnosis to be made without resorting to invasive biopsies.
    Matched MeSH terms: Muscle, Skeletal/physiopathology
  11. Jaffar A, Mohd-Sidik S, Nien FC, Fu GQ, Talib NH
    PLoS One, 2020;15(7):e0236140.
    PMID: 32667936 DOI: 10.1371/journal.pone.0236140
    BACKGROUND: Urinary Incontinence (UI) is when a person is unable to hold his/her urine effectively. This is a common problem which can develop and worsen during pregnancy. An effective way to manage UI is to educate patients on the Pelvic Floor Muscle Exercise (PFME) regularly. The present study aimed to ascertain the pregnant women's knowledge, attitudes, and practices (KAP) related to PFME.

    METHODS: This was a cross-sectional study done in a one primary care clinic located in a semi-urban area in Selangor, Malaysia. Simple random sampling was conducted among pregnant women aged 18 years old and above at any gestation. The validated study instruments used consisted of questions on socio-demography, KAP on UI, and also the International Consultation on Incontinence Questionnaire-Urinary Incontinence Short Form to determine UI among the respondents.

    RESULTS: The response rate for this study was 72.1%, where 440 pregnant women consented to take part in the study. The median age of study respondents was 30 years old and majority of the study respondents was from the Malay ethnicity (80.9%). The prevalence of UI was 40.9%. The proportion of pregnant women with good knowledge, attitude and practice scores were 58.0%, 46.6% and 45.2% respectively. There was a significant association between UI and age (p = .03), body mass index (p = .03), ethnicity (p = .04), gravida. (p = .001), knowledge on PFME (p = .007) and attitude towards PFME (p = .006).

    CONCLUSIONS: Findings from this study fill a gap in the prevalence and KAP concerning PFME at the primary care level. The foundation areas for future education and health promotion on UI should address the importance of correct PFME. This education can be delivered through a pragmatic way to ensure its effectiveness and sustainability of the health promotion program.

    Matched MeSH terms: Muscle, Skeletal/physiopathology*
  12. Chan YC, Punzalan-Sotelo AM, Kannan TA, Shahrizaila N, Umapathi T, Goh EJH, et al.
    Muscle Nerve, 2017 Nov;56(5):919-924.
    PMID: 28093784 DOI: 10.1002/mus.25577
    INTRODUCTION: In this study we propose electrodiagnostic criteria for early reversible conduction failure (ERCF) in axonal Guillain-Barré syndrome (GBS) and apply them to a cohort of GBS patients.

    METHODS: Serial nerve conduction studies (NCS) were retrospectively analyzed in 82 GBS patients from 3 centers. The criteria for the presence of ERCF in a nerve were: (i) a 50% increase in amplitude of distal compound muscle action potentials or sensory nerve action potentials; or (ii) resolution of proximal motor conduction block with an accompanying decrease in distal latencies or compound muscle action potential duration or increase in conduction velocities.

    RESULTS: Of 82 patients from 3 centers, 37 (45%) had ERCF, 21 (26%) had a contrasting evolution pattern, and 8 (10%) had both. Sixteen patients did not show an amplitude increase of at least 50%.

    CONCLUSION: Our proposed criteria identified a group of patients with a characteristic evolution of NCS abnormality that is consistent with ERCF. Muscle Nerve 56: 919-924, 2017.

    Matched MeSH terms: Muscle, Skeletal/physiopathology
  13. Muhamad Effendi F, Nam Y, Shin CH, Cho TJ, Yoo WJ, Cheon JE, et al.
    J Pediatr Orthop B, 2018 Sep;27(5):407-411.
    PMID: 28704300 DOI: 10.1097/BPB.0000000000000477
    Heterotopic ossification in soft tissue or muscle is rare in the pediatric and adolescent age group. Most cases are associated with musculoskeletal injury and trauma to the central nervous system. Here, we describe an adolescent patient without a history of trauma or lesions in the central nervous system who presented with a painful limp with limited motion of the left hip. Investigations indicated unusually large heterotopic ossification extending from the inner aspect of the ilium down to the anterior part of the hip, highly likely to have developed after an unrecognized periacetabular pyomyositis primarily involving the iliacus muscle. Surgical excision was performed successfully without perioperative complications. No recurrence was detected at the final follow-up.
    Matched MeSH terms: Muscle, Skeletal/physiopathology*
  14. Mohamad Shariff HA, Ashril Y, Mohamed Razif MA
    Singapore Med J, 2013 Oct;54(10):587-91.
    PMID: 24154585
    INTRODUCTION: The purpose of this study was to investigate the pattern of muscle injuries and the factors that predict the return-to-play duration among Malaysian athletes.

    METHODS: This is a retrospective review of the case notes of athletes who attended the National Sports Institute Clinic in Malaysia. The medical records of athletes with muscle injury, diagnosed on clinical assessment and confirmed by diagnostic ultrasonography, were included for final analysis.

    RESULTS: From June 2006 to December 2009, 397 cases of muscle injury were diagnosed among 360 athletes. The median age of the athletes with muscle injuries was 20.0 years. Muscle injuries were mostly diagnosed among national-level athletes and frequently involved the lower limb, specifically the hamstring muscle group. Nearly all of the athletes (99.2%) were treated conservatively. The median return-to-play duration was 7.4 weeks. Athletes who waited more than one week before seeking medical attention, those with recurrent muscle injuries and female athletes were significantly more likely (p < 0.05) to take more than six weeks before returning to the sport.

    CONCLUSION: Grade 2 lower limb muscle injury was commonly diagnosed among national-level athletes in this study. The frequency of weekly physiotherapy sessions did not affect the return-to-play duration. Factors such as initial consultation at more than one week post injury, recurrent muscle injuries and female gender were significant predictors of return-to-play duration among Malaysian athletes. These predictive factors should be kept in mind during clinical assessment so as to aid in prognosticating recovery after muscle injury.
    Matched MeSH terms: Muscle, Skeletal/physiopathology
  15. Chen LK, Liu LK, Woo J, Assantachai P, Auyeung TW, Bahyah KS, et al.
    J Am Med Dir Assoc, 2014 Feb;15(2):95-101.
    PMID: 24461239 DOI: 10.1016/j.jamda.2013.11.025
    Sarcopenia, a newly recognized geriatric syndrome, is characterized by age-related decline of skeletal muscle plus low muscle strength and/or physical performance. Previous studies have confirmed the association of sarcopenia and adverse health outcomes, such as falls, disability, hospital admission, long term care placement, poorer quality of life, and mortality, which denotes the importance of sarcopenia in the health care for older people. Despite the clinical significance of sarcopenia, the operational definition of sarcopenia and standardized intervention programs are still lacking. It is generally agreed by the different working groups for sarcopenia in the world that sarcopenia should be defined through a combined approach of muscle mass and muscle quality, however, selecting appropriate diagnostic cutoff values for all the measurements in Asian populations is challenging. Asia is a rapidly aging region with a huge population, so the impact of sarcopenia to this region is estimated to be huge as well. Asian Working Group for Sarcopenia (AWGS) aimed to promote sarcopenia research in Asia, and we collected the best available evidences of sarcopenia researches from Asian countries to establish the consensus for sarcopenia diagnosis. AWGS has agreed with the previous reports that sarcopenia should be described as low muscle mass plus low muscle strength and/or low physical performance, and we also recommend outcome indicators for further researches, as well as the conditions that sarcopenia should be assessed. In addition to sarcopenia screening for community-dwelling older people, AWGS recommends sarcopenia assessment in certain clinical conditions and healthcare settings to facilitate implementing sarcopenia in clinical practice. Moreover, we also recommend cutoff values for muscle mass measurements (7.0 kg/m(2) for men and 5.4 kg/m(2) for women by using dual X-ray absorptiometry, and 7.0 kg/m(2) for men and 5.7 kg/m(2) for women by using bioimpedance analysis), handgrip strength (<26 kg for men and <18 kg for women), and usual gait speed (<0.8 m/s). However, a number of challenges remained to be solved in the future. Asia is made up of a great number of ethnicities. The majority of currently available studies have been published from eastern Asia, therefore, more studies of sarcopenia in south, southeastern, and western Asia should be promoted. On the other hand, most Asian studies have been conducted in a cross-sectional design and few longitudinal studies have not necessarily collected the commonly used outcome indicators as other reports from Western countries. Nevertheless, the AWGS consensus report is believed to promote more Asian sarcopenia research, and most important of all, to focus on sarcopenia intervention studies and the implementation of sarcopenia in clinical practice to improve health care outcomes of older people in the communities and the healthcare settings in Asia.
    Matched MeSH terms: Muscle, Skeletal/physiopathology
  16. A Hamid MS, Mohamed Ali MR, Yusof A, George J
    BMC Musculoskelet Disord, 2012 Aug 06;13:138.
    PMID: 22866670 DOI: 10.1186/1471-2474-13-138
    BACKGROUND: Muscle injuries are one of the commonest injuries affecting athletes. It often leads to significant pain and disability causing loss of training and competition time. With current treatment, the duration to return-to-play ranges form six weeks to never, depending on injury severity. Recent researches have suggested that autologous platelet-rich plasma (PRP) injection into the injured site may hasten soft tissues healing. To-date, there has been no randomised clinical trials to evaluate the effects of PRP on muscle healing. The aim of this study is to examine the effects of autologous PRP on duration to return-to-play after muscle injury.

    METHODS AND DESIGN: A randomised, single blind controlled trial will be conducted. Twenty-eight patients aged 18 years and above with a recent grade-2 hamstring injury will be invited to take part. Participants will be randomised to receive either autologous PRP injection with rehabilitation programme, or rehabilitation programme only. Participants will be followed up at day three of study and then weekly for 16 weeks. At each follow up visit, participants will be assessed on readiness to return-to-play using a set of criteria. The primary end-point is when participants have fulfilled the return-to-play criteria or end of 16 weeks.The main outcome measure of this study is the duration to return-to-play after injury.

    CONCLUSION: This study protocol proposes a rigorous and potential significant evaluation of PRP use for grade-2 hamstring injury. If proven effective such findings could be of great benefit for patients with similar injuries.

    TRIAL REGISTRATION: Current Controlled Trials ISCRTN66528592.

    Matched MeSH terms: Muscle, Skeletal/physiopathology
  17. Hong YH, Betik AC, Premilovac D, Dwyer RM, Keske MA, Rattigan S, et al.
    Am J Physiol Regul Integr Comp Physiol, 2015 May 15;308(10):R862-71.
    PMID: 25786487 DOI: 10.1152/ajpregu.00412.2014
    Nitric oxide (NO) has been shown to be involved in skeletal muscle glucose uptake during contraction/exercise, especially in individuals with Type 2 diabetes (T2D). To examine the potential mechanisms, we examined the effect of local NO synthase (NOS) inhibition on muscle glucose uptake and muscle capillary blood flow during contraction in healthy and T2D rats. T2D was induced in Sprague-Dawley rats using a combined high-fat diet (23% fat wt/wt for 4 wk) and low-dose streptozotocin injections (35 mg/kg). Anesthetized animals had one hindlimb stimulated to contract in situ for 30 min (2 Hz, 0.1 ms, 35 V) with the contralateral hindlimb rested. After 10 min, the NOS inhibitor, N(G)-nitro-l-arginine methyl ester (l-NAME; 5 μM) or saline was continuously infused into the femoral artery of the contracting hindlimb until the end of contraction. Surprisingly, there was no increase in skeletal muscle NOS activity during contraction in either group. Local NOS inhibition had no effect on systemic blood pressure or muscle contraction force, but it did cause a significant attenuation of the increase in femoral artery blood flow in control and T2D rats. However, NOS inhibition did not attenuate the increase in muscle capillary recruitment during contraction in these rats. Muscle glucose uptake during contraction was significantly higher in T2D rats compared with controls but, unlike our previous findings in hooded Wistar rats, NOS inhibition had no effect on glucose uptake during contraction. In conclusion, NOS inhibition did not affect muscle glucose uptake during contraction in control or T2D Sprague-Dawley rats, and this may have been because there was no increase in NOS activity during contraction.
    Matched MeSH terms: Muscle, Skeletal/physiopathology
  18. Abu Bakar MH, Shariff KA, Tan JS, Lee LK
    Eur J Pharmacol, 2020 Sep 15;883:173371.
    PMID: 32712089 DOI: 10.1016/j.ejphar.2020.173371
    Accumulating evidence indicates that adipose tissue inflammation and mitochondrial dysfunction in skeletal muscle are inextricably linked to obesity and insulin resistance. Celastrol, a bioactive compound derived from the root of Tripterygium wilfordii exhibits a number of attributive properties to attenuate metabolic dysfunction in various cellular and animal disease models. However, the underlying therapeutic mechanisms of celastrol in the obesogenic environment in vivo remain elusive. Therefore, the current study investigated the metabolic effects of celastrol on insulin sensitivity, inflammatory response in adipose tissue and mitochondrial functions in skeletal muscle of the high fat diet (HFD)-induced obese rats. Our study revealed that celastrol supplementation at 3 mg/kg/day for 8 weeks significantly reduced the final body weight and enhanced insulin sensitivity of the HFD-fed rats. Celastrol noticeably improved insulin-stimulated glucose uptake activity and increased expression of plasma membrane GLUT4 protein in skeletal muscle. Moreover, celastrol-treated HFD-fed rats showed attenuated inflammatory responses via decreased NF-κB activity and diminished mRNA expression responsible for classically activated macrophage (M1) polarization in adipose tissues. Significant improvement of muscle mitochondrial functions and enhanced antioxidant defense machinery via restoration of mitochondrial complexes I + III linked activity were effectively exhibited by celastrol treatment. Mechanistically, celastrol stimulated mitochondrial biogenesis attributed by upregulation of the adenosine monophosphate-activated protein kinase (AMPK) and sirtuin 1 (SIRT1) signaling pathways. Together, these results further demonstrate heretofore the conceivable therapeutic mechanisms of celastrol in vivo against HFD-induced obesity mediated through attenuation of inflammatory response in adipose tissue and enhanced mitochondrial functions in skeletal muscle.
    Matched MeSH terms: Muscle, Skeletal/physiopathology
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