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The purpose of the present study was to evaluate the Pearson correlations between hemodynamic parameters obtained with near infrared spectroscopy (NIRS), namely total hemoglobin (tHb) and tissue oxygen index (TOI %), as indicators of blood flow and oxygen extraction, and myoelectric parameters obtained with surface multichannel electromyography (sEMG), namely fractal dimension (FD) and conduction velocity (CV) slopes, as descriptors of central and peripheral fatigue, during sustained high level isometric contractions at 60% maximal voluntary contraction (MVC), in elderly subjects. Ten recreationally healthy elderly subjects (age 67.7 ± 4.6 years), 5 males and 5 females, performed one isometric contraction of the elbow flexors at 120° joint angle at 60% of MVC until exhaustion in two subsequent trials 1 week apart, one for the sEMG and the other one for NIRS recordings from the biceps brachii. A negative strong Pearson’s correlation between TOI % slope in the functional hyperemic phase (HP) of contraction and a positive correlation between the slope of TOI % recorded during the ischemic phase (IP) and the CV slope were found (r = − 0.76, P

A majority of patients with facioscapulohumeral muscular dystrophy (FSHD) report severe fatigue. The aim of this study was to explore whether fatigability during a performance task is related to the main clinical features of the disease in mildly affected patients. A total of 19 individuals with a molecular genetic-based diagnosis of FSHD (median D4Z4 deletion length of 27 kb) performed two isometric flexions of the dominant biceps brachii at 20% of their maximal voluntary contraction (MVC) for 2 min, and then at 60% MVC until exhaustion. Fatigability indices (average rectified value, mean frequency, conduction velocity, and fractal dimension) were extracted from the surface electromyogram (sEMG) signal, and their correlations with age, age at onset, disease duration, D4Z4 contraction length, perceived fatigability, and clinical disability score were analyzed. The conduction velocity during the low level contraction showed a significant negative correlation with the age at onset (p < 0.05). This finding suggest the assessment of conduction velocity at low isometric contraction intensities, as a potential useful tool to highlight differences in muscle involvement in FSHD patients.

In the mild subtype of inherited carnitine palmitoyltransferase II (CPTII) deficiency, muscular mitochondrial fatty acid β-oxidation is impaired. In this condition, interventions involve daily dietary restriction of fats and increase of carbohydrates, whereas physical exercise is commonly contraindicated due to the risk of muscle pain and rhabdomyolysis. We present the case of a 14-year-old female with CPTII deficiency who underwent a 1-h session of unsupervised exercise training for 6 months, 3 days per week, including interval and resistance exercises, after diet assessment and correction. Before and after intervention, the resting metabolic rate (RMR) and respiratory quotient (RQ) were measured by indirect calorimetry, and a cardiopulmonary exercise test (CPET, 10 W/30 s to exhaustion) was performed. Interval training consisted of a 1 min run and a 5 min walk (for 15 min progressively increased to 30 min). During these efforts, the heart rate was maintained over 70% HR max corresponding to respiratory exchange ratio (RER) of 0.98. Resistance training included upper/lower split workouts (3 sets of 8 repetitions each, with 2 min rest between sets). Blood CK was checked before and 36 h after two training sessions chosen randomly without significant difference. After training, RMR increased (+8.1%) and RQ lowered into the physiological range (from 1.0 to 0.85). CPET highlighted an increase of peak power output (+16.7%), aerobic performance (VO2 peak, 8.3%) and anaerobic threshold (+5.7%), oxygen pulse (+4.5%) and a much longer isocapnic buffering duration (+335%). No muscle pain or rhabdomyolysis was reported. Results from our study highlight that training based on short-duration high-intensity exercise improves overall metabolism and aerobic fitness, thus being feasible, at least in a case of CPTII deficiency.

Purpose In facioscapulohumeral muscular dystrophy (FSHD) fatigue is a major complaint. We aimed to investigate whether during isometric sustained elbow flexions, performance fatigability indexes differ in patients with FSHD with respect to healthy controls. Methods Seventeen patients with FSHD and seventeen healthy controls performed two isometric flexions of the dominant biceps brachii at 20% of their maximal voluntary contraction (MVC) for 2 min and then at 60% MVC until exhaustion. Muscle weakness was characterized as a percentage of predicted values. Maximal voluntary strength, endurance time and performance fatigability indices (mean frequency of the power spectrum (MNF), muscle fiber conduction velocity (CV) and fractal dimension (FD)), extracted from the surface electromyogram signal (sEMG) were compared between the two groups. Results In patients with FSHD, maximal voluntary strength was 68.7% of predicted value (p p r = 0.62) and lower levels of performance fatigability, characterized by reduced rate of changes in MNF (p r = 0.56), CV (p p r = 0.51) and increased endurance time (p r = 0.63), during the isometric contraction at 60% MVC. Conclusion A decreased reduction in the slopes of all the considered sEMG parameters during sustained isometric elbow flexions suggests that patients with FSHD experience lower levels of performance fatigability compared to healthy controls.

This study aimed to establish the Dual-Energy X-ray Absorptiometry (DXA)-derived Visceral adipose tissue (VAT) reference values for gender and assess the metabolic outcomes associated to the VAT in a cohort of elderly patients. The sample included 795 elderly patients (226/569: men/women) aged 65&ndash, 100 years (mean age 80.9 &plusmn, 7.5ys). Body composition measures and VAT were assessed by DXA and Core-Scan software. Biochemical analysis and a multidimensional comprehensive geriatric assessment were performed. VAT percentiles at the level of 5, 25, 50, 75, 95 were found in males at the following levels: 246, 832, 1251, 1769, 3048 cm3 and for females at 99, 476, 775, 1178, 2277 cm3. Moreover, this study showed that DXA-VAT was associated to a worsening of lipid, glycemic, hematocrit and kidney profile. Further studies will be needed in order to implement these findings in order to define the (DXA)-derived VAT levels associated to the frailty related risk factors in elderly.

Objective. The aim of this study was to determine the test-retest reliability of muscle fiber conduction velocity (CV) and fractal dimension (FD) obtained from multichannel surface electromyographic (sEMG) recordings. Approach. Forty healthy recreationally active subjects (20 men and 20 women) performed two elbow flexions on two trials with a 1 week interval. The first was a 20% maximal voluntary contraction (MVC) of 120 s, and the second at 60% MVC held until exhaustion. sEMG signals were detected from the biceps brachii, using bi-dimensional arrays. Main results. Initial values and slope of CV and FD were used for the reliability analysis. The intraclass correlation coefficient (ICC) values for the isometric contraction at 20% MVC were (−0.09) and 0.67 for CV and FD respectively; whereas the ICC values at 60% MVC were 0.78 and 0.82 for CV and FD respectively. The Bland Altman plots for the two isometric contractions showed a mean difference close to zero, with no evident outliers between the repeated measurements: at 20% MVC 0.001 53 for FD and −0.0277 for CV, and at 60% MVC 0.006 66 for FD and 0.009 07 for CV. Significance. Overall, our findings suggest that during isometric fatiguing contractions, CV and FD slopes are reliable variables, with potential application in clinical populations.

Dates have a low glycemic index and are a source of antioxidants but, nevertheless, contain more than 70% sugar. This study aims to assess the effects of date consumption (three dates daily) on glycemic profile (HbA1c), body mass index (BMI), quality of life, and lipid profile, including total cholesterol, triglyceride, high-density lipoprotein (HDL), and low-density lipoprotein (LDL) in terms of safety for type 2 diabetic mellitus (T2DM) subjects. A randomized controlled trial was conducted with a sample of 100 T2DM subjects (39 male and 61 female) randomly assigned in two groups. The first group received three dates daily for 16 weeks, and the control group avoided date consumption. After a 16-week follow-up period, the study results showed an improvement of lipid profile with a statistically significant decrease in total cholesterol of ∆ = &minus, 0.209 mmol/L (confidence interval (CI) 95% &minus, 0.358, &minus, 0.059, p &lt, 0.05) and in LDL of ∆ = &minus, 0.171 mmol/L (CI 95% &minus, 0.358, 0.016) in the group receiving three dates daily. Intra-group mean differences of BMI were not statistically different in both groups after 16 weeks of date consumption. Even HbA1c did not change, both within and between groups after date consumption (∆ = 0.087%, CI 95% &minus, 0.086, 0.261). Between groups, mean difference changes (intervention minus control) showed a statistically significant improvement of quality of life index of ∆ = &plusmn, 30.66 points (CI 95% 12.45, 48.23) due to the consequent improvement in mental health. Although the definitive effect of dose/intake response of date consumption on Hb1Ac, lipid profile, and BMI in T2DM subjects is still to be established, the study suggests that dates could potentially have a beneficial effect on lipid profile, especially in reducing total cholesterol and elevating HDL, because of its high polyphenolic content. In addition, a low&ndash, moderate consumption of dates did not impact glucose levels because of dates&rsquo, low glycemic index.

To counteract muscle mass, muscle strength and power loss during aging, and to study age-related change of neuromuscular manifestation of fatigue in relation to nutritional supplementation.randomized controlled double-blind study.Twice-daily consumption for 12 weeks of an Essential Amino Acids (EAA)-based multi-ingredient nutritional supplement containing EAA, creatine, vitamin D and Muscle Restore Complex®.38 healthy elderly subjects (8 male, 30 female; age: 68.91±4.60 years; body weight: 69.40±15.58 kg; height: 1.60±0.09 m) were randomized and allocated in supplement (SUPP) or placebo (PLA) group. Mean Measurements: Vitamin D blood level; Appendicular Lean Mass (ALM); Visceral Adipose Tissue (VAT); Maximal Voluntary Contraction (MVC) and Peak Power (PP); myoelectric descriptors of fatigue: Fractal Dimension and Conduction Velocity initial values (FD iv, CV iv), their rates of change (FD slopes, CV slopes) and the Time to perform the Task (TtT). Mean Results: Significant changes were found in SUPP compared to baseline: Vitamin D (+8.73 ng/ml; p0.001); ALM (+0.34 kg; p0.001); VAT (-76.25 g; p0.001); MVC (+0.52 kg; p0.001); PP (+4.82 W; p0.001). Between group analysis (SUPP Vs. PLA) showed improvements: vitamin D blood levels (+11,72 ng/ml; p0.001); Legs FFM (+443.7 g; p0.05); ALM (+0.53 kg; p0.05); MVC (+1.38 kg; p0.05); PP (+9.87 W; p0.05). No statistical changes were found for FD iv, CV iv, FD and CV slopes and TtT, either compared to baseline or between groups. Significant correlations between mean differences in SUPP group were also found.The study demonstrates that in healthy elderly subjects an EAA-based multi-ingredient nutritional supplementation of 12 weeks is not effective to change myoelectric manifestation of fatigue and TtT failure but can positively affect muscle mass, muscle strength, muscle power and VAT, counterbalancing more than one year of age-related loss of muscle mass and strength.

Musculoskeletal disorders in aging and pain are closely connected because of multiple mechanisms leading to loss of mobility and autonomy. Pain is predictive of diability and worsening frailty and the strength of this relationship increases with the severity of pain. This study presents a systematic review of randomized controlled trials, cross sectional studies, and observational studies based on treatment of pain in adults with musculoskeletal disorders using nutritional non-pharmacological (nutrients and antioxidants) interventions. The review found the efficiency of the following topics: (a) accession of the patient to a dietary counselling (e.g., daily recommended amount of protein—equivalent to at least of 1 g of protein per kilogram of body weight); (b) intake of glutamic acid-rich such as soy, egg, and cod and tryptophan-rich foods such as milk and peanuts—or taking quick-acting, free-form supplements; (c) supplementation of vitamin D and magnesium, if lacking; (d) weekly consumption of fish or supplements of omega-3 fatty acids; and (e) availability of botanicals, in particular curcumin and gingerol. These non-pharmacological interventions can help the pain therapist to create a personalized medicine (precision medicine), acting with the maximum efficacy and safety, and also reducing the dosage of analgesic drugs needed.

Duchenne muscular dystrophy (DMD) is one of the most common and severe forms of muscular dystrophy. Oxidative myofibre content, muscle vasculature architecture and exercise tolerance are impaired in DMD. Several studies have demonstrated that nutrient supplements ameliorate dystrophic features, thereby enhancing muscle performance. Here, we report that dietary supplementation with a specific branched-chain amino acid-enriched mixture (BCAAem) increased the abundance of oxidative muscle fibres associated with increased muscle endurance in dystrophic mdx mice. Amelioration of the fatigue index in BCAAem-treated mdx mice was caused by a cascade of events in the muscle tissue, which were promoted by endothelial nitric oxide synthase (eNOS) activation and vascular endothelial growth factor (VEGF) expression. VEGF induction led to recruitment of bone marrow (BM)-derived endothelial progenitors (EPs), which increased the capillary density of dystrophic skeletal muscle. Functionally, BCAAem mitigated the dystrophic phenotype of mdx mice without inducing dystrophin protein expression or replacing the dystrophin-associated glycoprotein (DAG) complex in the membrane, which is typically lost in DMD. BCAAem supplementation could be an effective adjuvant strategy in DMD treatment.

Background: The purpose of this study was to investigate the acute effects of a single oral administration of an essential amino acids enriched mixture (EAA) on myoelectric descriptors of fatigue and maximal force production after a resistance exercise protocol (REP).Methods: Twenty adult males (age: 27 ± 6 years; body mass: 72.7 ± 7.50 kg; height: 1.76 ± 0.06 m) were enrolled in a double-blind crossover placebo-controlled study. Subjects were randomized to receive EAA mix (0.15 g/kg BM) or a placebo (PLA) in two successive trials 7 days apart. In both trials subjects completed a REP 2 h after the ingestion of the EAA mix or PLA. Before ingestion and after REP subjects performed isometric contractions of the dominant upper limb with the elbow joint at 120 degrees: (1) two maximal voluntary contractions (MVCs) for 2–3 s; (2) at 20% MVC for 90 s; (3) at 60% MVC until exhaustion. Mean values of MVC, conduction velocity initial values (CV), fractal dimension initial values (FD), their rates of change (CV slopes, FD slopes) and the Time to perform the Task (TtT) were obtained from a multichannel surface electromyography (sEMG) recording technique. Basal blood lactate (BL) and BL after REP were measured.Results: Following REP a significant decrease of MVC was observed in PLA (P < 0.05), while no statistical differences were found in EAA between pre-REP and post-REP. After REP, although a significant increase in BL was found in both groups (P < 0.0001) a higher BL Δ% was observed in PLA compared to EAA (P < 0.05). After REP, at 60% MVC a significant increase of CV rate of change (P < 0.05) was observed in PLA but not in EAA. At the same force level TtT was longer in EAA compared to PLA, with a significant TtT Δ% between groups (P < 0.001).Conclusion: Acute EAA enriched mix administration may prevent the loss of force-generating capacity during MVC following a REP. During isometric contraction at 60% MVC after REP the EAA mix may maintain CV rate of change values with a delay in the TtT failure.

The effects of high-potency statins on renal function are controversial. To address the impact of statins on renal morpho-functional aspects, normotensive young mice were treated with rosuvastatin (Rvs). Moreover, because statins may impair mitochondrial function, mice received either dietary supplementation with an amino acid mixture enriched in essential amino acids (EAAm), which we previously demonstrated to increase mitochondrial biogenesis in muscle or an unsupplemented control diet for 1 month. Mitochondrial biogenesis and function, apoptosis, and insulin signaling pathway events were studied, primarily in cortical proximal tubules. By electron microscopy analysis, mitochondria were more abundant and more heterogeneous in size, with dense granules in the inner matrix, in Rvs- and Rvs plus EAAm-treated animals. Rvs administration increased protein kinase B and endothelial nitric oxide synthase phosphorylation, but the mammalian target of rapamycin signaling pathway was not affected. Rvs increased the expression of sirtuin 1, peroxisome proliferator-activated receptor γ coactivator-1α, cytochrome oxidase type IV, cytochrome c, and mitochondrial biogenesis markers. Levels of glucose-regulated protein 75 (Grp75), B-cell lymphoma 2, and cyclin-dependent kinase inhibitor 1 were increased in cortical proximal tubules, and expression of the endoplasmic reticulum-mitochondrial chaperone Grp78 was decreased. EAAm supplementation maintained or enhanced these changes. Rvs promotes mitochondrial biogenesis, with a probable anti-apoptotic effect. EAAm boosts these processes and may contribute to the efficient control of cellular energetics and survival in the mouse kidney. This suggests that appropriate nutritional interventions may enhance the beneficial actions of Rvs, and could potentially prevent chronic renal side effects.

A proteomic approach was used to identify proteins differentially expressed in the plasma of mice following alternate day fasting. Male mice (C57Bl6, 9 months old) were randomly assigned to ad libitum (AL, n = 10) and calorie-restricted (IF, n = 10, AL on alternate day basis) groups for 4 weeks. After staining, the gels were imaged and differential protein expression patterns were interrogated using image analysis software. Spots showing a different expression level were identified through a comparison with 2D maps found in databases officially recognized (ExPASy). Master gels of AL and IF mice exhibited slightly different 2-DE patterns as only 14 spots out of 500 appeared differentially expressed: 12 spots were downregulated and identified as apolipoprotein E (APO-E), haptoglobin (HPT), alpha-1-antitrypsin (A1AT), pro- thrombin, and serum amyloid P component (SPA), whereas two spots were unidentified. In conclusion 4 weeks of alternate feeding results in a slight perturbation of the host plasma proteome. Of particular interest is the reduced plasma content in APO-E and acute-phase proteins HPT, A1AT and SPA that confirms a powerful anti-inflammatory effect of this dietary regimen.

The aims were to investigate the plasticity of the myosin heavy chain (MHC) phenotype following neuromuscular electrical stimulation (NMES) and to assess the correlation between MHC isoform distribution and muscle fibre conduction velocity (MFCV).14 men were subjected to 24 sessions of quadriceps NMES. Needle biopsies were taken from the dominant vastus lateralis and neuromuscular tests were performed on the dominant thigh before and after training. NMES significantly increased the quadriceps maximal force by 14.4±19.7% (P=0.02), vastus lateralis thickness by 10.7±8.6% (P=0.01), vastus lateralis MFCV by 11.1±3.5% (P

Aims: Myopathy, characterized by mitochondrial oxidative stress, occurs in ∼10% of statin-treated patients, and a major risk exists with potent statins such as rosuvastatin (Rvs). We sought to determine whether a peculiar branched-chain amino acid-enriched mixture (BCAAem), found to improve mitochondrial function and reduce oxidative stress in muscle of middle-aged mice, was able to prevent Rvs myopathy. Results: Dietary supplementation of BCAAem was able to prevent the structural and functional alterations of muscle induced by Rvs in young mice. Rvs-increased plasma 3-methylhistidine (a marker of muscular protein degradation) was prevented by BCAAem. This was obtained without changes of Rvs ability to reduce cholesterol and triglyceride levels in blood. Rather, BCAAem promotes de novo protein synthesis and reduces proteolysis in cultured myotubes. Morphological alterations of C2C12 cells induced by statin were counteracted by amino acids, as were the Rvs-increased atrogin-1 mRNA and protein levels. Moreover, BCAAem maintained mitochondrial mass and density and citrate synthase activity in skeletal muscle of Rvs-treated mice beside oxygen consumption and ATP levels in C2C12 cells exposed to statin. Notably, BCAAem assisted Rvs to reduce oxidative stress and to increase the anti-reactive oxygen species (ROS) defense system in skeletal muscle. Innovation and Conclusions: The complex interplay between proteostasis and antioxidant properties may underlie the mechanism by which a specific amino acid formula preserves mitochondrial efficiency and muscle health in Rvs-treated mice. Strategies aimed at promoting protein balance and controlling mitochondrial ROS level may be used as therapeutics for the treatment of muscular diseases involving mitochondrial dysfunction, such as statin myopathy. Antioxid. Redox Signal. 25, 595–608.

Introduction: Myopathy is the most common side effect of statins. Because nitric oxide (NO) has a key role in regulating skeletal muscle function, we studied whether the NO-donating atorvastatin NCX 6560 could show a better profile on skeletal muscle function and structure compared with ator- vastatin. Methods: C57BL/6 mice received atorvastatin 40 mg/ kg/day or an equivalent dose of NCX 6560 for 2 months. Mus- cle function assessed by treadmill test, serum creatine kinase (CK) activity, citrate synthase (CS) activity, and muscle histol- ogy were evaluated. Results: Atorvastatin significantly (P < 0.001) reduced muscle endurance, increased serum CK by 6- fold, and induced muscle fiber atrophy. Conversely, NCX 6560 preserved muscle function, prevented CK increase and did not modify muscle structure. Interestingly, atorvastatin reduced CS activity, a marker for mitochondrial function, in gastrocnemius, diaphragm, and heart, whereas NCX 6560 prevented such decrease. Conclusions: These findings suggest that NO may prevent statin-induced myopathy. Muscle Nerve 47: 72-80, 2013

Hypercatabolic syndrome (HS) is a biochemical state characterized by increased circulating catabolic hormones (eg, cortisol, catecholamines) and inflammatory cytokines (eg, tumor necrosis factors, interleukin-1beta), and decreased anabolic insulin effects with consequent insulin resistance. The most important metabolic consequence of HS is the skeletal and cardiac muscle protein breakdown that releases amino acids (AAs), which in turn supports indispensable body energy requirements but also reduces skeletal and cardiac physiologic and metabolic functions. HS occurs in many diseases such as diabetes mellitus, chronic heart failure, chronic obstructive pulmonary disease, renal and liver failure, trauma, sepsis, and senescence. All of these conditions have predominant catabolic molecules with significant muscular wasting and metabolic impairment. Macronutrients such as AA supplements, taken together with conventional therapy, may maintain muscular protein metabolism and cell functions.

Purpose The purpose of the present study was to evaluate inter-arm and inter-gender differences in fractal dimension (FD) and conduction velocity (CV) obtained from multichannel surface electromyographic (sEMG) recordings during sustained fatiguing contractions of the biceps brachii. Methods A total of 20 recreationally active males (24±6 years) and 18 recreationally active females (22±9 years) performed two isometric contractions at 120 degrees elbow joint angle: (1) at 20% maximal voluntary contraction (MVC) for 90 s, and (2) at 60% MVC until exhaustion the time to perform the task has been measured. Signals from sEMG were detected from the biceps brachii using bidimensional arrays of 64 electrodes and initial values and rate of change of CV and FD of the sEMG signal were calculated. Results No difference between left and right sides and no statistically significant interaction effect of sides with gender were found for all parameters measured. A significant inter-gender difference was found for MVC (p0.05). During the sustained 60% MVC no statistical correlation was found between MVC and CV or FD initial estimates nor between MVC and CV or FD slopes both in males and females whereas. A significant positive correlation between CV and FD slopes was found in both genders (males: r = 0,61; females: r = 0,55). Conclusions Fatigue determines changes in FD and CV values in biceps brachii during sustained contractions at 60% MVC. In particular males show greater increase in the rate of change of CV and FD than females whereas no difference in percentage change of these sEMG descriptors of fatigue was found. A significant correlation between FD and CV slopes found in both genders highlights that central and peripheral myoelectric components of fatigue may interact during submaximal isometric contractions.

The impact of ageing on force and velocity of human skeletal muscle fibres has been extensively studied. As discrepancies have been reported, it is still unclear whether or not a deterioration of the capacity of muscle fibres to develop force and shortening is involved in determining weakness and decrease in shortening velocity of skeletal muscle of elderly people. We compared myosin heavy chain (MHC) isoform distribution of vastus lateralis muscle, and specific force (Po/CSA) and maximum shortening velocity (Vo) of skeletal muscle fibres among one population of young controls (CTRL) and three populations of elderly (EL) subjects with very variable levels of physical activity: sedentary (EL-SED, n = 3); controls (EL-CTRL, n = 4); endurance trained (EL-END, n = 3). Muscle phenotype was progressively faster in the order EL-END --CTRL --EL-CTRL --EL-SED. Po/CSA and Vo also varied among the different populations of elderly subjects generally showing a decreasing deterioration with increasing activity levels. The results suggest that discrepancies observed so far in age-induced deterioration of contractile properties of muscle fibres could depend on the different activity levels of the populations of elderly subjects enrolled in the studies.

Needle biopsy samples were taken from vastus lateralis muscle (VL) of five male body builders (BB, age 27.4 ± 0.93 years; mean ±s.e.m.), who had being performing hypertrophic heavy resistance exercise (HHRE) for at least 2 years, and from five male active, but untrained control subjects (CTRL, age 29.9 ± 2.01 years). The following determinations were performed: anatomical cross-sectional area and volume of the quadriceps and VL muscles in vivo by magnetic resonance imaging (MRI); myosin heavy chain isoform (MHC) distribution of the whole biopsy samples by SDS-PAGE; cross-sectional area (CSA), force (Po), specific force (Po/CSA) and maximum shortening velocity (Vo) of a large population (n= 524) of single skinned muscle fibres classified on the basis of MHC isoform composition by SDS-PAGE; actin sliding velocity (Vf) on pure myosin isoforms by in vitro motility assays. In BB a preferential hypertrophy of fast and especially type 2X fibres was observed. The very large hypertrophy of VL in vivo could not be fully accounted for by single muscle fibre hypertrophy. CSA of VL in vivo was, in fact, 54% larger in BB than in CTRL, whereas mean fibre area was only 14% larger in BB than in CTRL. MHC isoform distribution was shifted towards 2X fibres in BB. Po/CSA was significantly lower in type 1 fibres from BB than in type 1 fibres from CTRL whereas both type 2A and type 2X fibres were significantly stronger in BB than in CTRL. Vo of type 1 fibres and Vf of myosin 1 were significantly lower in BB than in CTRL, whereas no difference was observed among fast fibres and myosin 2A. The findings indicate that skeletal muscle of BB was markedly adapted to HHRE through extreme hypertrophy, a shift towards the stronger and more powerful fibre types and an increase in specific force of muscle fibres. Such adaptations could not be fully accounted for by well known mechanisms of muscle plasticity, i.e. by the hypertrophy of single muscle fibre (quantitative mechanism) and by a regulation of contractile properties of muscle fibres based on MHC isoform content (qualitative mechanism). Two BB subjects took anabolic steroids and three BB subjects did not. The former BB differed from the latter BB mostly for the size of their muscles and muscle fibres.

The aims of the present study were as follows: (1) to examine the adaptational changes to chronic endurance voluntary exercise and (2) to investigate the effects of amino acid supplementation on the adaptational changes induced by endurance training in hindlimb (gastrocnemius, tibialis, soleus) and respiratory (diaphragm) muscles of mice. Male C57Bl6 mice were divided in four groups: control sedentary, sedentary supplemented with amino acid mixture (BigOne, 1.5 mg g day(-1) in drinking water for 8 weeks), running (free access to running wheels for 8 weeks), and running supplemented with amino acid mixture. Myosin heavy chain (MHC) isoform distribution was determined in all muscles considered. Fiber cross-sectional area (CSA) was measured in the soleus muscle. In all muscles except the tibialis, endurance training was associated with an overall shift towards the expression of slower MHC isoforms. Amino acid supplementation produced a shift towards the expression of faster MHC isoforms in the soleus and diaphragm muscles, and partially antagonized the effects of training. Immunohistochemical analysis of CSA of individual muscle fibers from the soleus muscle suggests that voluntary running produced a decrease in the size of type 1 fibers, and amino acid supplementation during training resulted in an increase in size in both type 1 and type 2A fibers. Collectively, these results suggest that the endurance adaptations induced by voluntary running depend on the muscle type, and that amino acid supplementation is able to modulate both fiber size and MHC isoform composition of skeletal muscles in sedentary and exercised mice.

Data show that uptake of amino acids correlates with myocardial oxygen consumption after aortic cross-clamp in humans; this suggests a direct link between amino acids and myocardial energy metabolism. The aim of this preliminary study was to investigate the anti-ischemic effects of immediate and long-term supplementation of an amino acid mixture. We tested this hypothesis on isolated rats hearts subjected to global ischemia for 30 minutes. Long-term treatment with an amino acid mixture achieved the following: (1) reduced the increase of diastolic pressure (48 +/- 3 mm Hg vs 21 +/- 4 mm Hg; p0.05); (2) maintained the tissue content of adenosine triphosphate during ischemia (2.5 +/- 0.6 micromol/g wet wt [gww] vs 7.0 +/- 1.2 micromol/gww; p0.05); and (3) improved the recovery of developed pressure at the end of postischemic reperfusion (11 +/- 2 mm Hg vs 38 +/- 3 mm Hg; p0.05), reducing the release of creatine kinase (375 +/- 30 microU/min/gww vs 196 +/- 15 microU/min/gww; p0.05) and lactate (15 +/- 1.5 mg/min/gww vs 5 +/- 1 mg/min/gww; p0.05). We conclude that long-term supplementation of an amino acid mixture reduced myocardial ischemic damage.

Beta-agonists and glucocorticoids are frequently coprescribed for chronic asthma treatment. In this study the effects of 4 week treatment with beta-agonist clenbuterol (CL) and glucocorticoid dexamethasone (DEX) on respiratory (diaphragm and parasternal) and limb (soleus and tibialis) muscles of the mouse were studied. Myosin heavy chain (MHC) distribution, fibres cross sectional area (CSA), glycolytic (phosphofructokinase, PFK; lactate dehydrogenase, LDH) and oxidative enzyme (citrate synthase, CS; cytochrome oxidase, COX) activities were determined. Muscle samples were obtained from four groups of adult C57/B16 mice: (1) Control (2) Mice receiving CL (CL, 1.5 mg kg(-1) day(-1) in drinking water) (3) Mice receiving DEX (DEX, 5.7 mg kg(-1) day(-1) s.c.) (4) Mice receiving both treatments (DEX + CL). As a general rule, CL and DEX showed opposite effects on CSA, MHC distribution, glycolytic and mitochondrial enzyme activities: CL alone stimulated a slow-to-fast transition of MHCs, an increase of PFK and LDH and an increase of muscle weight and fibre CSA; DEX produced an opposite (fast-to-slow transition) change of MHC distribution, a decrease of muscle weight and fibre CSA and in some case an increase of CS. The response varied from muscle to muscle with mixed muscles, as soleus and diaphragm, being more responsive than fast muscles, as tibialis and parasternal. In combined treatments (DEX + CL), the changes induced by DEX or CL alone were generally minimized: in soleus, however, the effects of CL predominated over those of DEX, whereas in diaphragm DEX prevailed over CL. Taken together the results suggest that CL might counteract the unwanted effects on skeletal muscles of chronic treatment with glucocorticoids.

Biopsy samples were taken from vastus lateralis muscle of seven young (YO, age 30.2 ± 2.2 years), and seven elderly (EL, age 72.7 ± 2.3 years) subjects and two elderly subjects whose right leg had been immobilized for 3.5 months (EL-IMM, ages 70 and 75). The following main parameters were studied: (1) myosin heavy chain (MHC) isoform distribution of the samples, determined by SDS-PAGE; (2) cross-sectional area (CSA), specific force (Po/CSA) and maximum shortening velocity (Vo) of a large population (n = 593) of single skinned muscle fibres, classified on the basis of MHC isoform composition determined by SDS-PAGE; (3) actin sliding velocity (Vf) on pure myosin isoforms determined by in vitro motility assays; (4) myosin concentration in single fibres determined by quantitative SDS-PAGE. MHC isoform distribution was shifted towards fast isoforms in EL and to a larger extent in EL-IMM. In EL and, more consistently, in EL-IMM we observed a higher percentage of hybrid fibres than in YO, and noted the presence of MHC-neonatal and of unusual hybrid fibres containing more than two MHC isoforms. Po/CSA significantly decreased in type 1 and 2A fibres in the order YO → EL → EL-IMM. Vo of type 1 and 2A fibres was significantly lower in EL and higher in EL-IMM than in YO, i.e. immobilization more than counteracted the age-dependent decrease in Vo. The latter phenomenon was not observed for Vf. Vf on myosin 1 was lower in both EL and EL-IMM than in YO. Vf on myosin 2X was lower in EL than in YO, and a similar trend was observed for myosin 2A. Myosin concentration decreased in type 1 and 2A fibres in the order YO → EL → EL-IMM and was linearly related to the Po/CSA values of corresponding fibre types from the same subjects. The experiments suggest that (1) myosin concentration is a major determinant of the lower Po/CSA of single fibres in ageing and especially following immobilization and (2) ageing is associated with lower Vo of single fibres due to changes in the properties of myosin itself, whereas immobilization is associated with higher Vo in the absence of a change in myosin function.

Epidemiological studies pointed out to a strong association between vitamin D deficiency and type 2 diabetes prevalence. However, the role of vitamin D supplementation in the skeletal muscle, a tissue that play a crucial role in the maintenance of glucose homeostasis, has been scarcely investigated so far. On this basis, this study aimed to evaluate the effect of vitamin D supplementation in a murine model of diet-induced insulin resistance with particular attention to the effects evoked on the skeletal muscle. Male C57BL/6J mice (n = 40) were fed with a control or a High Fat-High Sugar (HFHS) diet for 4 months. Subsets of animals were treated for 2 months with vitamin D (7 μg·kg-1, i.p. three times/week). HFHS diet induced body weight increase, hyperglycemia and impaired glucose tolerance. HFHS animals showed an impaired insulin signaling and a marked fat accumulation in the skeletal muscle. Vitamin D reduced body weight and improved systemic glucose tolerance. In addition, vitamin D restored the impaired muscle insulin signaling and reverted myosteatosis evoked by the diet. These effects were associated to decreased activation of NF-κB and lower levels of TNF-alpha. Consistently, a significantly decreased activation of the SCAP/SREBP lipogenic pathway and lower levels of CML protein adducts and RAGE expression were observed in skeletal muscle of animals treated with vitamin D. Collectively, these data indicate that vitamin D-induced selective inhibition of signaling pathways (including NF-κB, SCAP/SREBP and CML/RAGE cascades) within the skeletal muscle significantly contributed to the beneficial effects of vitamin D supplementation against diet-induced metabolic derangements.

Aim of this study was to investigate whether advanced glycation end-products (AGEs) accumulate in skeletal myofibers of two different animal models of diabesity and whether this accumulation could be associated to myosteatosis. Male C57Bl/6j mice and leptin-deficient ob/ob mice were divided into three groups and underwent 15 weeks of dietary manipulation: standard diet-fed C57 group (C57, n = 10), high-fat high-sugar diet-fed C57 group (HFHS, n = 10), and standard diet-fed ob/ob group (OB/OB, n = 8). HFHS mice and OB/OB mice developed glycometabolic abnormalities in association with decreased mass of the gastrocnemius muscle, fast-to-slow transition of muscle fibers, and lipid accumulation (that occurred preferentially in slow compared to fast fibers). Moreover, we found in muscle fibers of HFHS and OB/OB mice accumulation of AGEs that was preferential for the lipid-accumulating cells, increased expression of the lipogenic pathway SCAP/SREBP, and co-localisation between AGEs and SCAP-(hyper)expressing cells (suggestive for SCAP glycosylation). The increased expression of the SCAP/SREBP lipogenic pathway in muscle fibers is a possible mechanism underlying lipid accumulation and linking myosteatosis to muscle fiber atrophy and fast-to-slow transition that occur in response to diabesity.

The effects of the GABAB-selective agonist baclofen were studied on guinea pig nodose ganglion neurones using grease gap and intracellular recording techniques, and on peripheral mechanosensitive endings in the guinea pig oesophagus and stomach with extracellular recordings. GABA dose-dependently reduced the amplitude of the compound action potential of C-type neurones (C spikes, EC50 = 30.9 microM), which was prevented by the GABAA antagonist bicuculline (10 microM). The GABAB agonist baclofen (1-300 microM) did not produce any significant effect on the amplitude of C spikes. In microelectrode studies, baclofen (100 microM) evoked hyperpolarisation (by 2.53 +/- 0.51 mV, n = 6, N = 5) in a subset of nodose neurones (6 out of 26, N = 18). In seven out of eight neurones (N = 8) with a slow after-hyperpolarisation following action potentials, baclofen significantly inhibited its amplitude by 19 +/- 4% (n = 7, p0.05). GABA (100 microM) evoked a depolarisation of 9.3 +/- 2.4 mV (10 nodose neurones, N = 9, p0.05) associated with a decrease in input impedance of 49 +/- 12% (N = 4, p0.05). Baclofen (100-200 microM) did not affect either spontaneous or stretch-evoked firing of distension-sensitive vagal mechanoreceptors of the guinea pig oesophagus and stomach but did inhibit mechanoreceptors in the ferret oesophagus. Antibodies to GABAB receptor 1a splice variants labelled most of the neurones and numerous fibres in the guinea pig nodose ganglion while antibodies to GABAB receptor 1b splice variants stained only nerve cell bodies. There were numerous nerve fibres showing GABAB receptor 1a- and 1b-like immunoreactivity in the myenteric plexus in the guinea pig oesophagus and stomach but not in anterogradely labelled extrinsic vagal nerve fibres. The result indicates that most guinea pig C-type nodose ganglion neurones have GABAB receptors on their cell bodies but their density on distension-sensitive peripheral endings is too low to allow modulation of mechanotransduction. There is a significant species-dependent difference in the expression of GABAB receptors on peripheral vagal mechanosensitive endings.

We evaluated the effects of testosterone overload on mitochondrial superoxide dismutase (MnSOD), cytochrome oxidase (COX) and citrate synthase (CS) activities of the rat superficial gastrocnemius both in non-exercised muscle and following moderate endurance training. Basal (bLPO) and stimulated (sLPO) lipid peroxidation was measured as an index of oxidative tissue damage. Furthermore, to assess the relationship between exercise and testosterone-induced metabolic adaptations and contractile protein expression, the distribution of myosin heavy chain (MHC) isoforms was analysed by SDS-PAGE. Samples were obtained from: controls (C), rats treated with testosterone propionate (Tp) (TP, 5 mg kg(-1) i.m. 6 days/week), trained rats (E, 5 days/week) and rats trained and treated with Tp (ETP). MnSOD significantly increased in E and TP in comparison with C and ETP. Training induced a significant increase in COX activity both in E and ETP whereas a statistical reduction was observed in TP in comparison with the other groups. Moreover, testosterone administration was associated with a significant reduction in CS activity which significantly increased in ETP. A reduction in lipid peroxidation was observed in E and ETP in comparison with controls both in basal and stimulated conditions, whereas TP showed a significant increase of bLPO. In trained rats enzymatic changes were correlated with an increase in the proportion of fast oxidative MHC-2A and MHC-2X with decrease of the proportion of fast MHC-2B. In contrast, Tp treatment induced an increase in the proportion of MHC-2B whereas MHC-2A and MHC-2X disappeared. Finally, ETP showed a reduction in MHC-2B and an increase in MHC-1 and MHC-2X. These data suggest that testosterone supplementation seems not to significantly modify the metabolic adaptation induced by exercise in gastrocnemius muscle. Furthermore, testosterone overload to non-exercised rats seems to reduce the mitochondrial function and increase the lipid peroxidation of the muscle.

Alterations in muscle protein turnover of the unaffected side of stroke patients could contribute to physical disability. We investigated whether hypercatabolic activity occurred in unaffected arm muscle and whether supplemented essential amino acids (EAAs) could limit muscle hypercatabolism (MH). Thirty-eight dysphagic subacute stroke subjects (n= 19; EAA group) or isocaloric placebo (maltodextrin;n= 19, Plac group). Before randomization, all patients had their arterial (A) and venous (V) amino acids measured and muscle (A − V) differences calculated in the unaffected arm. Eight matched and healthy subjects served as controls. When compared to healthy controls, the entire stroke population showed significant muscle release (= negative value A − V) of the amino acid phenylalanine (phenyl-) indicating a prevalence of MH. Moreover, randomized EAA and Plac groups had similar rates of MH. After 38 days from the start of the protocol, the EAA group but not the Plac group had MH converted to balanced protein turnover or anabolic activity. We concluded that muscle protein metabolism of the unaffected arm of dysphagic subacute stroke individuals could be characterized by MH which can be corrected by supplemented EAAs.

Nutrient overload leads to impaired muscle oxidative capacity and insulin sensitivity. However, comparative analyses of the effects of dietary manipulation on skeletal muscles with different fiber composition are lacking. This study aimed to investigate the selective adaptations in the soleus and tibialis anterior muscles evoked by administration of high-fat diet for 12 weeks in 10 mice (HFD mice) compared to 10 animals fed with a normal chow diet (control mice). Mice fed with the HFD diet exhibited hyperlipidemia, hyperinsulinemia, hyperglycemia, and lower exercise capacity in comparison to control mice. In control mice, soleus fibers showed higher lipid content than tibialis anterior fibers. In contrast, the lipid content was similar between the two muscles in HFD mice. Significant differences in markers of muscle mitochondrial production and/or activity as well as of lipid synthesis were detected between HFD mice and control mice, especially in the tibialis anterior. Moreover, translocation of GLUT-4 transporter to the plasma membrane and activation of the insulin signaling pathway were markedly inhibited in the tibialis and slightly reduced in the soleus of HFD mice compared to control mice. Overall, these results show that adaptive responses to dietary manipulation occur in a muscle-specific pattern.

Despite the known risks for health, obesity, which results from a positive energy balance, is a growing epidemic worldwide and its prevalence has doubled over the past 20 years.

Using an in vitro assay we assessed whether the acute exposure of soleus muscle of adult and aged rats to essential amino acid enriched mixture (EAAem) activates mTOR signaling pathway (mTOR and p70S6K) even after prolonged supplementation with the same mixture. A total of 20 adult (9 months of age at the end of treatment) and 20 aged (18 months of age at the end of treatment) male Wistar rats were used. Ten of each group were treated with EAAem (1.5 gr/kg/day in tap water) for 6 months. At the end of treatment the rats were grouped (n = 5 each group) as follows: adult (AD) and aged (AG) untreated controls; adult (AD_EAAem) and aged (AG_EAAem) chronically supplemented with EAAem; adult (AD+EAAem) and aged (AG+EAAem) acutely incubated with EAAem (soleus in 1 percent EAAem for 30 min); AD_EAAem+ and AG_EAAem+ acutely incubated with EAAem. Following treatment the activation level of mTOR and p70S6K was measured by Western blot. The basal level of mTOR and p70S6K activation appeared to be higher in AD compared with AG. In AG+EAAem a significant change in the level of p70S6K activation, unlike mTOR, was observed whereas no change was observed in AD+EAAem. In AD_EAAem muscles the basal level of p70S6K activation, unlike mTOR, was significantly lower than in AD and the acute exposure to EAAem produced a significant reduction of mTOR activation. Contrarily to AG, in AG_EAAem+ the acute exposure to EAAem produced a significant activation of mTOR, unlike p70S6K. Results in the adults indicated a higher basal level of activation and a lower responsiveness of the pathway to acute and chronic exposure to EAA-enriched mixture. On the contrary, in the aged, a lower basal level of activation was associated with a higher responsiveness to EAAem. In particular, although with a different timing, acute exposure to EAAem activated mTOR signaling even following prolonged supplementation.

Muscle injury has been related to resistance exercise and prolonged endurance exercise paradigms both leading to significant local mechanical constraints followed by focal disorders such as sarcolemmal damage and leakage of intracellular proteins, oedema, myofibrillar disorganization and microtrauma-triggered inflammation. These unfavorable events lead to variable soreness, swelling, loss in muscle strength and function with reduced range of motion.

Insulin resistance, the major limiting factor for peripheral glucose disposal in skeletal muscles, has an intricate multifactor origin. In particular, altered insulin signaling and multiple postreceptor defects contribute to decreased glucose transport, phosphorylation, and oxidation.

The liver sustains the greatest damage from ethanol (EtOH) abuse. EtOH and its metabolites impair hepatocyte metabolism, causing intracellular accumulation of proteins and lipids and increasing radical oxygen species production. These processes are toxic to the mitochondrial respiratory chain and to mitochondrial DNA. We have recently shown that supplementating the diet of rodents with an essential amino acid-enriched mixture (EAAem) significantly increases mitochondrial mass and number in cardiac and skeletal muscles and improves mitochondrial function in aged animals. Thus, in this study we sought to test whether EAAem supplementation could reduce EtOH-induced liver damage. Groups of adult male Wistar rats were fed a standard diet and water ad libitum (the control group), drinking water with 20% EtOH (the EtOH group), or drinking water with 20% EtOH and EAAem supplementation (1.5 g/kg/day) (the EtOH+EAAem group) for 2 months. The blood EtOH concentration was measured, and markers for fat (Oil-Red-O), mitochondria (Grp75, Cyt-c-ox), endoplasmic reticulum (Grp78), and inflammation (Heme Oxigenase 1, iNOS, and peroxisomes) were analyzed in the liver of animals in the various experimental groups. EAAem supplementation in EtOH-drinking rats ameliorated EtOH-induced changes in liver structure by limiting steatosis, recruiting more mitochondria and peroxisomes mainly to perivenous hepatocytes, stimulating or restoring antioxidant markers, limiting the expression of inflammatory processes, and reducing ER stress. Taken together, these results suggest that EAAem supplementation may represent a promising strategy to prevent and treat EtOH-induced liver damage.

Import JabRef | WosArea Physiology; Sport Sciences; International audience; The aim of the present study was to define the chronic effects of neuromuscular electrical stimulation (NMES) on the neuromuscular properties of human skeletal muscle. Eight young healthy male subjects were subjected to 25 sessions of isometric NMES of the quadriceps muscle over an 8-wk period. Needle biopsies were taken from the vastus lateralis muscle before and after training. The training status, myosin heavy chain (MHC) isoform distribution, and global protein pattern, as assessed by proteomic analysis, widely varied among subjects at baseline and prompted the identification of two subgroups: an "active" (ACT) group, which performed regular exercise and had a slower MHC profile, and a sedentary (SED) group, which did not perform any exercise and had a faster MHC profile. Maximum voluntary force and neural activation significantly increased after NMES in both groups (+similar to 30% and +similar to 10%, respectively). Both type 1 and 2 fibers showed significant muscle hypertrophy. After NMES, both groups showed a significant shift from MHC-2X toward MHC-2A and MHC-1, i.e., a fast-to-slow transition. Proteomic maps showing similar to 500 spots were obtained before and after training in both groups. Differentially expressed proteins were identified and grouped into functional categories. The most relevant changes regarded 1) myofibrillar proteins, whose changes were consistent with a fast-to-slow phenotype shift and with a strengthening of the cytoskeleton; 2) energy production systems, whose changes indicated a glycolytic-to-oxidative shift in the metabolic profile; and 3) antioxidant defense systems, whose changes indicated an enhancement of intracellular defenses against reactive oxygen species. The adaptations in the protein pattern of the ACT and SED groups were different but were, in both groups, typical of both resistance (i.e., strength gains and hypertrophy) and endurance (i.e., a fast-to-slow shift in MHC and metabolic profile) training. These training-induced adaptations can be ascribed

Essential amino acids (EAA) improve basal muscle protein synthesis in the elderly. Nevertheless, in settings of prolonged supplementation, putative signal pathways of EAA are currently unknown. The purpose of this study was to test the effects of prolonged supplementation of EAA enriched mixture (12-L-Amin) on Insulin/Insulin-like Growth Factor-1 (IGF1) pathway by measuring total and phosphorylated Akt (Ser473) and its upstream (IRS1 at Ser636) and downstream (mTOR at Ser2448, p70S6K at Thr389) targets in basal conditions and following acute insulin (0.1 U/L) incubation in vitro. To this aim, soleus muscles were dissected from male Wistar rats divided in three groups of 7 each: adults (AD, 10 mo of age), elderly (EL, 22 mo of age) and elderly supplemented (EL-AA, 12-L-Amin 1.5gr/Kg die in drinking water for 3mo). EL showed reduced basal and post-insulin mTOR and p70S6K activation and reduced post-insulin IRS1 degradation relative to AD. EL-AA showed an increase of post-insulin Akt activation, no change in basal and post-insulin phospho-mTOR, lower reduction of phospho-p70S6K and increased post-insulin IRS1 degradation relative to AD. These results demonstrate that chronic 12-L-Amin administration exerts anti-ageing effects on the activation/inactivation of the Insulin/IGF1/mTOR pathway which is identified as putative target of EAA in the elderly.

Oxidative stress plays an important role in the pathogenesis of diabetic complications. We investigated the effects of a specific oral mixture of amino acid (AA) supplements on the antioxidant defense system, superoxide dismutase (SOD), and heat shock proteins (HSPs: HspB1, similar to Hsp 20 kDa, and HspB7) in the soleus muscle of streptozotocin (STZ)-diabetic mice by bidimensional electrophoresis and mass spectrometry. Four groups of 5 mice were considered: nondiabetic control mice, nondiabetic mice given AA supplements (0.1 g/kg per day for 15 days), diabetic mice (induced with STZ 65 mg/kg), and diabetic mice given AAs. AA supplements in the nondiabetic animals were associated with a statistical increase of SOD and no changes in expression of HSPs. Diabetes mellitus decreased antioxidant SOD and increased cellular stress as demonstrated by the overall upregulated HSPs. Administration of AAs counteracted the effects of diabetes, producing upregulation of SOD and downregulation of HSPs. These data suggest a role for AA supplements in controlling the antioxidant defense system and reducing the oxidative stress in diabetic skeletal muscle.

We investigated the effects of a specific mixture of amino acid (AA) supplements on the adaptation changes induced by aging in the soleus muscle of rats. Male Wistar rats were divided into 3 groups (n = 5 each): young control (YO), 3 months of age; elderly control (EL), 18 months of age; and elderly orally supplemented with an AA mixture (EL-AA), 18 months of age, given as 0.1 g/kg per day in drinking water for 8 weeks. Myosin heavy chain (MHC) composition was analyzed in all muscles. The total fiber number and fiber cross-sectional area of types 1 and 2A fibers were also measured in immunostained sections of the soleus muscle. The ratios between the sarcomere volume (Vsar) and the total volume (Vtot) and single muscle fibers were studied by electron microscopy. The expression of total and phosphorylated serine/threonine protein kinase mammalian target of rapamycin (mTOR), a potent regulator of messenger RNA translation initiation, was also determined in all groups. Aging was associated with an overall shift toward the expression of a slower MHC phenotype, atrophy of fast and slow fibers, a significant decrease in Vtot/Vsar, and no changes in total fiber number. AA supplementation antagonized the effects of aging. A shift toward the expression of faster MHC isoforms was observed. Fiber atrophy appeared to be partly counteracted by the AA supplements; we noted an increase in cross-sectional area fibers and Vtot/Vsar in EL-AAs. Total and phosphorylated mTOR expression appeared to decrease in EL and was restored by the AA supplements. Collectively, these results suggest that aging-induced muscle adaptations can be partly restored by AA supplementation. An mTOR signal pathway may mediate the effects on fiber trophism.

The development of diabetes mellitus is the consequence of defects in the action of insulin in skeletal muscles and adipose tissue other than pancreas and liver defects. Insulin action defects are mostly the results of defects of the insulin intracellular signaling transduction pathway. This review summarizes the main mechanisms involved in insulin signaling and possible intracellular defects that lead to insulin resistance. We also report preliminary experimental data that suggest the existence of intracellular alternatives to insulin metabolic pathways stimulated by nutrients such as amino acids (AAs). Indeed, we found that oral supplements with AAs stimulated both glucose transporter–4 and protein synthesis through independent insulin signals in rat hearts. Evidence suggests that the mammalian target of rapamycin and/or other molecules could be involved in this insulin-independent metabolic pathway. This hypothesis suggests the presence of an ancestral metabolic pathway in eukaryotic cells that is not active when insulin intracellular signaling is efficient but can be activated by alternative stimuli, such as AAs, when insulin signaling is impaired. Our observations provide molecular evidence that supports the use of anabolic nutrients such as AAs, together with standard therapies, to overcome insulin resistance syndrome.

Aging is associated with progressive structural disorganization of muscular and cardiac fibers, decreasing functional capacity, and increased rates of disease and death. Aging is also characterized by disturbances in protein synthesis with impaired cellular organelle functions, particularly in the mitochondria. The availability of amino acids is a key factor for the overall metabolism of mammals and exogenous supplements of amino acid mixtures (AAm) could be a valid therapeutic strategy to improve quality of life, avoiding malnutrition and muscle wasting in the elderly. We investigated the morphoquantitative effects of long-term AAm supplementation on the mitochondria and sarcomeres (by electron microscope) and on collagen matrix deposition (by histologic techniques) in both skeletal and cardiac muscles of young and aged mice. Our data showed that old animals have fewer mitochondria and massive fibrosis in both muscles. Long-term AAm supplementation increased the number and volume of mitochondria and sarcomeres and decreased fibrosis in both skeletal muscle and hearts in old rats. These findings indicate that AAm restored muscular morphologic parameters and probably improved the mechanical performance of these organs.

We aimed to assess whether a specific mixture of amino acid (AA) supplements counteracts the metabolic and functional changes in the streptozotocin (STZ)-induced diabetic rat heart model. Adult male Wistar rats were divided into 6 groups (n = 10 each) and treated for 43 days: nondiabetic controls, nondiabetic rats given an AA mixture (0.1 g/kg per day), diabetic rats (induced with 65 mg/kg STZ given intraperitoneally), diabetic rats given AAs, diabetic rats given insulin (5 IU/day given subcutaneously), and diabetic rats given insulin plus AAs. During treatment, glycemia and insulinemia levels were measured in all groups. Changes in enzyme (reduced nicotinamide adenine dinucleotide-dehydrogenase, cytochrome c oxidase) activities and myosin heavy chain (MHC) composition were measured in the left ventricle. In 5 rats contractile function was assessed by measuring maximal shortening velocity of skinned ventricular trabeculae and the expression of translational regulator mammalian target of rapamycin (mTOR) was also found. STZ-induced diabetes was associated with reduced myocardial contractility, overall loss of oxidative capacity, a shift toward a slower MHC phenotype, and decreased mTOR tissue content. All of these changes appeared to be reversible with insulin. AA supplements partially restored the myocardial and oxidative dysfunction and also increased mTOR tissue content. The combination of insulin and AAs did not have a synergistic effect on either enzymatic or functional profiles. We conclude that AA supplements may contribute to restoring the oxidative and contractile dysfunction of diabetic rat hearts, probably through an mTOR-insulin independent mechanism.

Four elderly women (78 +/- 4.3 years) were resistance trained (RT) for one year and needle biopsies of the vastus lateralis muscle were taken pre- and post-RT. A training intensity of 60% one-repetition maximum (1RM) was adopted for the entire duration of the study. Following RT, significant gain in isometric force of the quadriceps muscles was observed and MHC isoform distribution of vastus lateralis muscle showed a very significant shift from MHC-1 and MHC-2X towards MHC-2A, i.e. a bi-directional shift. A large population (n = 310) of individual skinned muscle fibres were dissected from biopsy samples and used for determination of cross-sectional area (CSA), specific force (Po/CSA) and unloaded shortening velocity (Vo) at 12 degrees C and maximum activation. Fibres were classified on the basis of their MHC isoform content determined by SDS-PAGE in three pure fibre types (1, 2A and 2X) and two hybrid fibre types (1-2A and 2AX). Whereas the CSA of individual muscle fibres did not change, Po/CSA was significantly higher in both type 1 and type 2A fibres post training. Vo of type 1 fibres was significantly higher post-training, whereas no change in Vo was observed in type 2A fibres. The number of pure type 2X fibres was very low especially post-training and did not enable a statistically significant comparison. The data suggest that in elderly women moderate and prolonged RT: (1) can determine similar adaptations in MHC distribution of skeletal muscle to those expected in young subjects; (2) can improve function of muscle fibres.

Skeletal muscles are composed of fibres of different types, each type being identified by the isoform of myosin heavy chain which is expressed as slow 1, fast 2A, fast 2X, and fast 2B. Slow fibres are resistant to fatigue due to their highly oxidative metabolism whereas 2X and 2B fibres are easily fatiguable and fast 2A fibres exhibit intermediate fatigue resistance. Slow fibres and fast fibres are present in equal proportions in the adult human diaphragm while intercostal muscles contain a higher proportion of fast fibres. A small fibre size, abundance of capillaries, and a high aerobic oxidative enzyme activity are typical features of diaphragm fibres and give them the resistance to fatigue required by their continuous activity. Because of their fibre composition, intercostal muscles are less resistant to fatigue. The structural and functional characteristics of respiratory muscle fibres are not fixed, however, and can be modified in response to several physiological and pathological conditions such as training (adaptation to changes in respiratory load), adaptation to hypoxia, age related changes, and changes associated with respiratory diseases. The properties of respiratory muscle fibres can also be modified by pharmacological agents such as beta2 agonists and corticosteroids used for the treatment of respiratory diseases.

Steroid myopathy is a non-inflammatory toxic myopathy that occurs as side effect of exogenous and endogenous glucocorticoid excess. The purpose of this review is to examine issues that limit our understanding of this myopathy with respect to nosology, etiopathogenesis, conditioning factors, and muscle fiber selectivity. We suggest that if more data were available on these issues, the understanding of steroid myopathy would be enhanced substantially, thus allowing an early detection of its occurrence (before the appearance of clinical or laboratory signs) and a proper treatment of the patients.

Chronic kidney diseases are a social and economic problem, and diet has long been recognized as a fundamental modulator of kidney health in human and experimental models. Age-dependent alterations in mitochondrial function play a crucial role in the development of diseases of aging, and mitochondrial disorders have been observed in experimental models of kidney failure. Recently, the beneficial dietary effect of a specific mixture of essential amino acids (EAA) has been studied in elderly subjects, but no data were collected from the kidney. The aim of this study was to assess whether daily supplementation of the diet with EAA at the beginning of senescence could preserve renal health. We used middle-aged (18-month-old) male Wistar rats fed a standard diet and water ad libitum (M-aged group) or a diet with added EAA (1.5 g/kg per day) dissolved in drinking water for 3 months (M-aged+EAA group). Young (2-month-old) rats fed a standard diet for 3 months were used as controls. Mitochondrial morphology and markers for collagen, cyt-c-oxidase, HSP60, GRP75, eNOS, iNOS, Bax, Bcl2 and VEGF were analyzed in glomeruli and tubules. EAA supplementation limited fibrosis and increased the capillary tuft area in the glomeruli of M-aged rats. VEGF and eNOS were enhanced in glomeruli and the peritubular space with the EAA-supplemented diet. Mitochondrial cyt-c oxidase, Bcl2, and chaperones increased in the distal tubules of the EAA group to levels similar to those observed in the young group. Mitochondrial area and density after EAA intake did not differ from young groups. The results suggest that prolonged EAA intake could represent a strategy for maintaining the healthy status of the kidney in M-aged animals.