Magnetic stimulation of muscle evokes cerebral potentials in assessment of paraspinal muscle spasm.

Objectlve: To assess the muscle spasm by magnetic stimulation of muscle evokes cerebral potentials (MMSEP). Methods: Paraspinal MMSEP and function assessment was recorded in detail before and after treat-     

Inflammatory muscle disease – An update

Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of inflammatory myopathies whose common feature is immune-mediated muscle injury. There are distinct subgroups including dermatomyositis (DM), polymyositis (PM), inclusion body myositis, and immune-mediated necrotizing myopathy. Antisynthetase syndrome is also emerging as a distinct subgroup with its unique muscle histopathological characteristic of perifascicular necrosis. While the newly updated EULAR/ACR Classification Criteria for IIM have brought advancements in diagnosis and the exclusion of mimickers, the use of only one autoantibody in the derivation of the schema limits its use. Similarly, while the advent of multiple novel therapeutics in the treatment of myositis has been exciting, it has also highlighted the scarcity of validated outcome measures. The purpose of our review is to highlight the updated classification criteria of myositis, newly reported clinical phenotypes associated with myositis autoantibodies, the measurement of outcomes, and emerging treatments in the field.     

Does muscle inflammation influence recovery of muscle strength and function in patients undergoing total hip replacement?

BackgroundGenetic markers of muscle inflammation (eg, tumour necrosis factor α [TNFα] and interleukin [IL] 6 are downregulated following repeated transient increases after bouts of exercise. Total hip replacement (THR) typically resolves preoperative pain, although strength deficits of 10–21% persist in the affected hip at 1 year postoperatively. This study assessed whether mRNA expression of TNFα and IL6 in the vastus lateralis (VL) of the operated leg was related to changes in the strength of the operated leg quadriceps in patients following THR.MethodsTen patients were recruited prospectively after ethical approval. Distal VL (5 cm proximal to lateral suprapatellar pouch) biopsy samples were obtained intraoperatively and at 6 weeks postoperatively, with maximal voluntary contraction of the operated leg quadriceps (MVCOLQ) in Newtons (N), assessed preoperatively and at 6 weeks postoperatively. RT-PCR was used to assess mRNA expression in the biopsy samples and associations evaluated with Spearman's correlation coefficient.FindingsMean mRNA relative quotient (RQ) for comparison of 6 week intraoperative VL samples was 6·23 [SD 12·85] for TNFα and 17·10 [47·46] for IL6. Preoperatively, mean MVCOLQ was 188·90 N [76·84] and at 6 weeks it was 217·00 N [53·91]. There was no significant relation between TNFα or IL-6 RQ and absolute MVCOLQ at 6 weeks (r=0·115 [p=0·376] and ?0·491 [p=0·075], respectively). No statistically significant relation existed between TNFα mRNA RQ and the improvement in MVCOLQ at 6 weeks (r=–0·498, p=0·071) nor with IL6 and the same measure (r=0·091, p=0·401).InterpretationThere is a trend to correlation that exists for improvement in MVCOLQ with a reduction in TNFα mRNA expression, as well as between absolute MVCOLQ and reduction in IL-6 mRNA expression at 6 weeks postoperatively. Improvement in muscle strength may be mediated by reduced muscle inflammation and the associated reduction in pain in patients with severe osteoarthritis.FundingWales Deanery and Betsi Cadwaladr University Health Board Small Grants Scheme.     

Is the vitamin d receptor found in muscle?

The active form of vitamin D, 1α,25-dihydroxyvitamin D(3), is critical for the regulation of serum calcium and phosphorus levels that in turn support bone mineralization and neuromuscular activity. It is well known that vitamin D deficiency causes rachitic/osteomalacic myopathy and cardiac disorder and the provision of vitamin D can reverse the symptoms. However, the underlying mechanisms remain unclear. The question of whether the vitamin D receptor is found in muscle has been debated but not settled. We recently studied all available antibodies against the vitamin D receptor and found that most antibodies used detect proteins other than the vitamin D receptor, and therefore, the utility of these antibodies may generate the false-positive results. Using antibodies that do not detect proteins in tissues from vitamin D receptor null mice, we have developed a specific and sensitive immunohistochemical assay. The results from this investigation show that the vitamin D receptor is undetectable in skeletal, cardiac, and smooth muscle, suggesting that the function of vitamin D on muscle is either of an indirect nature or does not involve the known receptor.     

Evaluation of muscle mass in obesity,prediabetes and diabetes mellitus by different equations used for the measurement of muscle mass

ObjectiveInsulin resistance is one of risk factors for sarcopenia and there is no specific equation for the measurement of muscle mass. The present study aimed to evaluate muscle mass in the patients with obesity, prediabetes (PDM) and type 2 diabetes mellitus (DM) by different equations for the measurement of muscle mass.MethodsObese patients aged 18–65 years old, who presented between 2013 and 2015 were reviewed and they were separated into three groups as obese, prediabetes (PDM) and diabetes mellitus (DM). Height, body weight, body mass index (BMI), sum of the appendicular lean masses (ALM) were measured in all participants. Body muscle mass ratio was calculated as the total muscle mass divided by the body weight, and skeletal muscle index was calculated as the total muscle mass divided by the square of the height. In addition, ALM/weight, ALM/height² and ALM/BMI ratios were also evaluated.ResultsA total of 1107 participants, of whom 666 (60.2%) were female, were enrolled into the study. Of the participants, 288 (%26.02) had obesity, 524 (%47.33) had PDM and 295 (26.65%) had DM. There was a significant difference in ALM/BMI ratio between the three groups for both genders (p = 0.003 for female and p = 0.003 for male). ALM/weight ratio and body muscle mass ratio were decreased between groups in female, whereas it was no difference in male (p = 0.003, p < 0.001 for females, respectively; p = 0.802, p = 0.840 for males, respectively).ConclusionsALM/BMI may be more accurate for the evaluation of muscle mass in middle-aged obese, PDM and DM subjects.     

The effect of α-actinin-3 deficiency on muscle aging

Deficiency of the fast-twitch muscle protein α-actinin-3 due to homozygosity for a nonsense polymorphism (R577X) in the ACTN3 gene is common in humans. α-Actinin-3 deficiency (XX) is associated with reduced muscle strength/power and enhanced endurance performance in elite athletes and in the general population. The association between R577X and loss in muscle mass and function (sarcopenia) has previously been investigated in a number of studies in elderly humans. The majority of studies report loss of ACTN3 genotype association with muscle traits in the elderly, however, there is some indication that the XX genotype may be associated with faster muscle function decline. To further explore these potential age-related effects and the underlying mechanisms, we examined the effect of α-actinin-3 deficiency in aging male and female Actn3 knockout (KO) mice (2, 6, 12, and 18 months). Our findings support previous reports of a diminished influence of ACTN3 genotype on muscle performance in the elderly: genotype differences in intrinsic exercise performance, fast muscle force generation and male muscle mass were lost in aged mice, but were maintained for other muscle function traits such as grip strength. The loss of genotype difference in exercise performance occurred despite the maintenance of some “slower” muscle characteristics in KO muscles, such as increased oxidative metabolism and greater force recovery after fatigue. Interestingly, muscle mass decline in aged 18 month old male KO mice was greater compared to wild-type controls (WT) (− 12.2% in KO; − 6.5% in WT). These results provide further support that α-actinin-3 deficient individuals may experience faster decline in muscle function with increasing age.     

Mechanisms mediating cholinergic antral circular smooth muscle contraction in rats

AIM:To investigate the pathway(s)mediating rat antral circular smooth muscle contractile responses to the cholinomimetic agent,bethanechol and the subtypes of muscarinic receptors mediating the cholinergic contraction. METHODS:Circular smooth muscle strips from the antrum of Sprague-Dawley rats were mounted in muscle baths in Krebs buffer.Isometric tension was recorded.Cumulative concentration-response curves were obtained for( )-cis- dioxolane(cD),a nonspecific muscarinic agonist,at 10~(-8)- 10~(-4)mol/L,in the presence of tetrodotoxin(TTX,10~(-7)mol/L). Results were normalized to cross sectional area.A repeat concentration-response curve was obtained after incubation of the muscle for 90 min with antagonists for M1(pirenzepine), M2(methoctramine)and M3(darifenadn)muscarinic receptor subtypes.The sensitivity to PTX was tested by the ip injection of 100 mg/kg of PTX 5 d before the experiment.The antral circular smooth muscles were removed from PTX-treated and non-treated rats as strips and dispersed smooth muscle cells to identify whether PTX-linked pathway mediated the contractility to bethanechol. RESULTS:A dose-dependent contractile response observed with bethanechol,was not affected by TTx.The pretreatment of rats with pertussis toxin decreased the contraction induced by bethanechol.Lack of calcium as well as the presence of the L-type calcium channel blocker,nifedipine,also inhibited the cholinergic contraction,with a reduction in response from 2.5±0.4 g/mm~2 to 1.2±0.4 g/mm~2(P<0.05).The dose- response curves were shifted to the right by muscarinic antagonists in the following order of affinity:darifenacin (M_3)>methocramine(M_2)>pirenzepine(M_1). CONCLUSION:The muscarinic receptors-dependent contraction of rat antral circular smooth muscles was linked to the signal transduction pathway(s)involving pertussis-toxin sensitive GTP-binding proteins and to extracellular calcium via L-type voltage gated calcium channels.The presence of the residual contractile response after the treatment with nifedipine,suggests that an additional pathway could mediate the cholinergic contraction.The involvement of more than one muscarinic receptor(functionally predominant type 3 over type 2)also suggests more than one pathway mediating the cholinergic contraction in rat antrum.     

Strength training at high versus low external resistance in older adults: Effects on muscle volume,muscle strength,and force–velocity characteristics

Muscle adaptations can be induced by high-resistance exercise. Despite being potentially more suitable for older adults, low-resistance exercise protocols have been less investigated. We compared the effects of high- and low-resistance training on muscle volume, muscle strength, and force–velocity characteristics. Fifty-six older adults were randomly assigned to 12 weeks of leg press and leg extension training at either HIGH (2 × 10–15 repetitions at 80% of one repetition maximum (1RM)), LOW (1 × 80–100 repetitions at 20% of 1RM), or LOW + (1 × 60 repetitions at 20% of 1RM, followed by 1 × 10–20 repetitions at 40% of 1RM). All protocols ended with muscle failure. Leg press and leg extension of 1RM were measured at baseline and post intervention and before the first training session in weeks 5 and 9. At baseline and post intervention, muscle volume (MV) was measured by CT-scan. A Biodex dynamometer evaluated knee extensor static peak torque in different knee angles (PT_stat90°, PT_stat120°, PT_stat150°), dynamic peak torque at different speeds (PT_dyn60°s^− 1, PT_dyn180°s^− 1, PT_dyn240°s^− 1), and speed of movement at 20% (S₂₀), 40% (S₄₀), and 60% (S₆₀) of PT_stat90°. HIGH and LOW + resulted in greater improvements in 1RM strength than LOW (p < 0.05). These differences were already apparent after week 5. Similar gains were found between groups in MV, PT_stat, PT_dyn60°s^− 1, and PT_dyn180°s^− 1. No changes were reported in speed of movement. HIGH tended to improve PT_dyn240°s^− 1 more than LOW or LOW + (p = 0.064). In conclusion, high- and low-resistance exercises ending with muscle failure may be similarly effective for hypertrophy. High-resistance training led to a higher increase in 1RM strength than low-resistance training (20% of 1RM), but this difference disappeared when using a mixed low-resistance protocol in which the resistance was intensified within a single exercise set (40% of 1RM). Our findings support the need for more research on low-resistance programs in older age, in particular long-term training studies and studies focusing on residual effects after training cessation.