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Protein ingestion and exercise stimulate myofibrillar protein synthesis rates. When combined, exercise further increases the postprandial rise in myofibrillar protein synthesis rates. It remains unclear whether protein ingestion with or without exercise also stimulates muscle connective tissue protein synthesis rates. The authors assessed the impact of presleep protein ingestion on overnight muscle connective tissue protein synthesis rates at rest and during recovery from resistance-type exercise in older men. Thirty-six healthy, older men were randomly assigned to ingest 40 g intrinsically L-[1-13C]-phenylalanine and L-[1-13C]-leucine-labeled casein protein (PRO, n = 12) or a nonprotein placebo (PLA, n = 12) before going to sleep. A third group performed a single bout of resistance-type exercise in the evening before ingesting 40 g intrinsically-labeled casein protein prior to sleep (EX+PRO, n = 12). Continuous intravenous infusions of L-[ring-2H5]-phenylalanine and L-[1-13C]-leucine were applied with blood and muscle tissue samples collected throughout overnight sleep. Presleep protein ingestion did not increase muscle connective tissue protein synthesis rates (0.049 ± 0.013 vs. 0.060 ± 0.024%/hr in PLA and PRO, respectively; p = .73). Exercise plus protein ingestion resulted in greater overnight muscle connective tissue protein synthesis rates (0.095 ± 0.022%/hr) when compared with PLA and PRO (p p de novo muscle connective tissue protein synthesis during overnight sleep.

To the Editor: Quadriceps weakness and atrophy is present in approximately 30% of patients with chronic obstructive pulmonary disease (COPD) in secondary care (1, 2). The quadriceps also displays a shift in fiber type so that there are fewer type I (oxidative) fibers and more type II (glycolytic) fibers (3). Pulmonary rehabilitation only partially addresses this fiber shift (4). Muscle mass (5) and strength (6) are both associated with increased mortality, but the prognostic significance of fiber shift is unknown. In a retrospective multicenter analysis of 392 patients from four sites (see Tables E1–E4 in the online supplement), mortality data were collated, as part of audit procedures, on outpatients with stable COPD who had undergone a vastus lateralis biopsy between 1995 and 2013. Data from these subjects have been previously published (e.g., References 2, 4, 5). Fiber proportion, reported as the percentage of type II fibers (type II fiber %), was established by immunohistochemistry. Fiber shift, evaluated as a dichotomous variable, was considered to have occurred when the proportion of type II fibers was greater than 68% (men) or greater than 65% (women) based on normal ranges established from an age-matched healthy population published by Natanek and colleagues (3). Body mass index (BMI), fat-free mass index (FFMI), dominant leg isometric quadriceps maximum voluntary contraction (QMVC and QMVC/BMI), mid-thigh cross-sectional area determined by computed tomography scan (MTCSA), residual volume normalized to total lung capacity (RV/TLC), and percent predicted value for the carbon monoxide transfer factor corrected for hemoglobin (TLCOc), when available, were included in subanalyses. Data were analyzed for the whole dataset and also after splitting the group into those with an FEV1 less than 50% predicted and those with an FEV1 greater than or equal to 50% predicted. Further details on the methodology and statistical analyses are presented in the online supplement. Some of the results of this study have been previously reported in abstract form (7). Patients were followed up for a median of 1,699 days (127–6,601 d); 102 of 392 (26.7%) patients died during follow-up (Table E6). Cohort characteristics are presented in Tables 1 and ​and22 and Tables E1–E5. One hundred fifty-one patients had Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage I/II disease and 241 had GOLD stage III/IV disease. Those who died were older and had a lower FEV1 % predicted, and there was a greater male preponderance (Table E6A). One hundred seventy-seven (45.1%) of the patients had fiber shift. The patients who died had a higher percentage of type II fibers (69.5% [62.2, 76.3%] vs. 66.0% [54.0, 74.2%]; P = 0.002) and a higher proportion of them exhibited fiber shift (58% vs. 41%, P = 0.004). BMI, FFMI, QMVC, MTCSA, and TLCOc were all lower, and RV/TLC higher, in those who died (Table E6B). Table 1. Core Characteristics of the Cohort (n = 392) in Addition to Univariate and Multivariate Analyses Including Type II Fiber Proportion Dichotomized into the Occurrence of Fiber Shift Table 2. Core Characteristics of the Cohort (n = 392) in Addition to Univariate and Multivariate Analyses Including Type II Fiber Proportion as a Continuous Measure In the cohort considered as a whole, both type II fiber % and the presence of fiber shift were univariate predictors of mortality, as were age and FEV1 % predicted (Tables 1 and ​and2).2). In a multivariate analysis including fiber shift as a dichotomous variable, fiber shift was retained, as were age and FEV1 % predicted, Table 1. When age, FEV1 % predicted, and type II fiber % were entered into a multivariate analysis, age and FEV1 % predicted were retained as independent predictors, but the association between fiber type and mortality just missed statistical significance (Table 2). The relationship between FEV1 and fiber proportion is shown in Figure 1A, and survival as a function of fiber shift, adjusted for age and FEV1, is shown in Figure 1B. Additional data regarding other lung function and muscle parameters are presented in Tables E7–E10. FEV1 expressed in liters and TLCOc were also univariate predictors of mortality; however, RV/TLC was not. When including TLCOc in the analysis (n = 209), fiber shift, age, FEV1 % predicted, and TLCOc were all independent predictors of mortality. In other subanalyses, BMI, FFMI, QMVC, QMVC/BMI, and MTCSA were not univariate predictors of mortality. Figure 1. (A) The relationship between type II fiber percentage and FEV1 % predicted (dashed lines demonstrate the 95% confidence interval), and (B) survival curves for those with fiber shift (n = 177) and those without fiber shift (n = 215) after adjusting for ... When limiting the analysis to those with an FEV1 greater than or equal to 50% predicted, age was the only predictor of mortality (hazard ratio [HR], 1.16; 95% CI, 1.07, 1.25; P < 0.0001; Table E11). In a multivariate analysis confined to those with an FEV1 less than 50%, fiber shift was retained as an independent predictor (HR, 1.71; 95% CI, 1.08, 2.71; P = 0.02), as were age (HR, 1.06; 95% CI, 1.03, 1.09; P < 0.0001), and FEV1 % predicted (HR, 0.96; 95% CI, 0.94, 0.99; P = 0.002; Table E12A). In a separate analysis confined to those with an FEV1 less than 50%, type II fiber % was not retained as an independent predictor (HR, 1.014; 95% CI, 0.996, 1.032; P = 0.13), whereas age and FEV1 % predicted were (Table E12B). Fiber shift in the vastus lateralis of patients with COPD was associated with increased mortality, although this association was weaker when lung function and age were included in the analysis. This finding was pronounced in patients with GOLD stage III/IV disease but undetectable in those with GOLD stage I/II disease. The relationship between skeletal muscle atrophy (5) and weakness (6) with mortality has been previously noted in COPD. However, we believe the present analysis is timely because we (3) and others (8) have recently shown that the nature of skeletal muscle involvement in COPD is heterogeneous rather than uniform. No prior study has related quadriceps biopsy appearances to long-term outcome in COPD. Given the known relationship between exercise capacity and survival (9), these data are consistent with our prior studies, which demonstrated a relationship between fiber shift (although not fiber atrophy) and impaired exercise capacity (3) and functional performance (10). Nevertheless, it remains unclear whether fiber shift causes poor exercise tolerance or is a manifestation of exercise intolerance and reduced physical activity, which are both associated with increased mortality in COPD (9, 11). Both concepts can be supported by in vivo models that demonstrate that muscle disuse results in type I to type II fiber shift (12) and that fiber shift toward a type I fiber predominance increases exercise performance (13). Due to the retrospective nature of the current analysis, exercise performance and physical activity data were not available for inclusion in this report, so a causative role for fiber shift in mortality cannot be demonstrated from this study. A prospective study would have been preferable and could also have considered other factors of relevance, including pulmonary rehabilitation over the intervening period. Despite the limitations of the current study, it is doubtful that a prospective study of comparable size and duration will ever be done. Interest in pharmacological management of skeletal muscle dysfunction is growing (14), and addressing fiber shift may eventually become a therapeutic possibility. Further studies to address whether the reversal of fiber shift is of benefit are of value.

This study identifies metabolic and protein phenotypic alterations in gastrocnemius, tibialis anterior and diaphragm muscles of Col6a1(-/-) mice, a model of human collagen VI myopathies. All three muscles of Col6a1(-/-) mice show some common changes in proteins involved in metabolism, resulting in decreased glycolysis and in changes of the TCA cycle fluxes. These changes lead to a different fate of α-ketoglutarate, with production of anabolic substrates in gastrocnemius and tibialis anterior, and with lipotoxicity in diaphragm. The metabolic changes are associated with changes of proteins involved in mechanotransduction at the myotendineous junction/costameric/sarcomeric level (TN-C, FAK, ROCK1, troponin I fast) and in energy metabolism (aldolase, enolase 3, triose phosphate isomerase, creatine kinase, adenylate kinase 1, parvalbumin, IDH1 and FASN). Together, these change may explain Ca(2+) deregulation, impaired force development, increased muscle-relaxation-time and fiber damage found in the mouse model as well as in patients. The severity of these changes differs in the three muscles (gastrocnemius

International audience; Background: Dietary interventions are critical in the prevention of metabolic diseases. Yet, the effects of fatty fish consumption on type 2 diabetes remain unclear. The aim of this study was to investigate whether a diet containing farmed salmon prevents or contributes to insulin resistance in mice. Methodology/Principal Findings: Adult male C57BL/6J mice were fed control diet (C), a very high-fat diet without or with farmed Atlantic salmon fillet (VHF and VHF/S, respectively), and Western diet without or with farmed Atlantic salmon fillet (WD and WD/S, respectively). Other mice were fed VHF containing farmed salmon fillet with reduced concentrations of persistent organic pollutants (VHF/S(-POPs)). We assessed body weight gain, fat mass, insulin sensitivity, glucose tolerance, ex vivo muscle glucose uptake, performed histology and immunohistochemistry analysis, and investigated gene and protein expression. In comparison with animals fed VHF and WD, consumption of both VHF/S and WD/S exaggerated insulin resistance, visceral obesity, and glucose intolerance. In addition, the ability of insulin to stimulate Akt phosphorylation and muscle glucose uptake was impaired in mice fed farmed salmon. Relative to VHF/S-fed mice, animals fed VHF/S(-POPs) had less body burdens of POPs, accumulated less visceral fat, and had reduced mRNA levels of TNF alpha as well as macrophage infiltration in adipose tissue. VHF/S(-POPs)-fed mice further exhibited better insulin sensitivity and glucose tolerance than mice fed VHF/S. Conclusions/Significance: Our data indicate that intake of farmed salmon fillet contributes to several metabolic disorders linked to type 2 diabetes and obesity, and suggest a role of POPs in these deleterious effects. Overall, these findings may participate to improve nutritional strategies for the prevention and therapy of insulin resistance.

International audience; Myostatin (MSTN), a member of the TGF-beta superfamily, is a negative regulator of skeletal muscle mass. We have previously shown that the cell survival/apoptosis pathway is a downstream target of MSTN loss-of-function in mice through the regulation of the expression or abundance of many survival and apoptotic factors. In this study, we used western-blot and quantitative PCR (qPCR) analyses to validate these novel downstream targets of MSTN in double-muscled (DM) cattle v. their controls including 260-day-old foetuses and adult cows from the INRA95 strain. MSTN loss-of-function in DM foetuses and DM cows resulted in a glycolytic shift of the muscles (e. g. upregulation of H-MyBP, PGM1 and SNTA1 and downregulation of H-FABP), activation of cell survival pathway through regulation of some components of the PI3K/Akt pathway (e. g. upregulation of DJ-1 and Gsk-3 beta ser9/Gsk-3 beta total ratio and downregulation of PTEN) and upregulation of cell survival factors translationally controlled tumour protein (14-3-3E, Pink1). We also found a lower abundance of pro-apoptotic transcripts and/or proteins (Caspase-3, caspase-8, caspase-9, BID, ID2 and Daxx) and a higher expression of anti-apoptotic transcripts (Traf2 and Bcl2l2) in DM muscles. All together, these results are in favour of activation of the cell survival pathway and loss of apoptosis pathway within the muscles of DM animals. Alteration of both pathways may increase myonuclear or satellite cell survival, which is crucial for protein synthesis. This could contribute to muscle hypertrophy in DM foetuses and DM cows.

Expression of cardiac troponin I (TnIcardiac) and slow skeletal troponin I (TnIslow) genes was analyzed at the mRNA and protein level in the developing rat heart. TnIslow mRNA was detectable by in situ hybridization in the embryonic cardiac tube as early as the 13-somite stage (Embryonic Day 10). In contrast, TnIcardiac transcripts were first detected in the primordial atrium and ventricle of 11-day-old embryos, but were absent in the outflow tract region. TnIslow mRNA levels decreased after birth in atria and later in ventricles but persisted even in adult life in myocytes of the conduction system. TnIslow protein was detected by specific antibodies in atrial myocytes beginning from Embryonic Day 11; in contrast, ventricular myocytes were unreactive until Embryonic Day 18. Western blot analysis of 16-day-old fetal hearts confirmed the expression of TnIcardiac in atrial but not in ventricular myocardium. Slot blot analysis showed that at this stage equivalent amounts of TnIslow and TnIcardiac mRNAs are expressed in atria and ventricles. Similar differences in the expression of TnIslow and TnIcardiac mRNAs and proteins were observed in cultures of embryonic atrial and ventricular myocytes. The results suggest serial rather than simultaneous activation of TnIslow and TnIcardiac genes and they show that different regions of the developing heart differ in their patterns of TnIcardiac expression due to the operation of distinct mechanisms that separately affect the accumulation of TnIcardiac mRNA and protein.

Background\ud \ud Fibrillins 1 (FBN1) and 2 (FBN2) are components of microfibrils, microfilaments that are present in many connective tissues, either alone or in association with elastin. Marfan's syndrome and congenital contractural arachnodactyly (CCA) result from dominant mutations in the genes FBN1 and FBN2 respectively. Patients with both conditions often present with specific muscle atrophy or weakness, yet this has not been reported in the mouse models. In the case of Fbn1, this is due to perinatal lethality of the homozygous null mice making measurements of strength difficult. In the case of Fbn2, four different mutant alleles have been described in the mouse and in all cases syndactyly was reported as the defining phenotypic feature of homozygotes.\ud \ud Methodology/Principal Findings\ud \ud As part of a large-scale N-ethyl-N-nitrosourea (ENU) mutagenesis screen, we identified a mouse mutant, Mariusz, which exhibited muscle weakness along with hindlimb syndactyly. We identified an amber nonsense mutation in Fbn2 in this mouse mutant. Examination of a previously characterised Fbn2-null mutant, Fbn2fp, identified a similar muscle weakness phenotype. The two Fbn2 mutant alleles complement each other confirming that the weakness is the result of a lack of Fbn2 activity. Skeletal muscle from mutants proved to be abnormal with higher than average numbers of fibres with centrally placed nuclei, an indicator that there are some regenerating muscle fibres. Physiological tests indicated that the mutant muscle produces significantly less maximal force, possibly as a result of the muscles being relatively smaller in Mariusz mice.\ud \ud Conclusions\ud \ud These findings indicate that Fbn2 is involved in integrity of structures required for strength in limb movement. As human patients with mutations in the fibrillin genes FBN1 and FBN2 often present with muscle weakness and atrophy as a symptom, Fbn2-null mice will be a useful model for examining this aspect of the disease process further.

Recently we have shown that surplus dietary tryptophan (TRP) reduced the plasma concentrations of cortisol and noradrenaline in pigs. Stress hormones are known to affect insulin sensitivity and metabolism. We now investigated the long-term effects of surplus dietary TRP on 1) plasma and urinary stress hormone kinetics, 2) insulin sensitivity for glucose and amino acid clearance, and 3) whole body nitrogen balance. Pigs were fed for 3 weeks a high (13.2%) vs normal (3.4%) TRP to large neutral amino acids (LNAA) diet, leading to reduced fasting (14 h) plasma cortisol (17.1 ± 3.0 vs 28.9 ± 4.3 ng/mL, p

Newly hatched precocial chicks of arctic shorebirds are able to walk and regulate their body temperatures to a limited extent. Yet, they must also grow rapidly to achieve independence before the end of the short arctic growing season. A rapid growth rate may conflict with development of mature function, and because of the allometric scaling of thermal relationships, this trade-off might be resolved differently in large and small species. We assessed growth (mass) and functional maturity (catabolic enzyme activity) in leg and pectoral muscles of chicks aged 1-16 d and adults of two scolopacid shorebirds, the smaller dunlin (Calidris alpina: neonate mass 8 g, adult mass 50 g) and larger whimbrel (Numenius phaeopus; neonate mass 34 g, adult mass 380 g). Enzyme activity indicates maximum catabolic capacity, which is one aspect of the development of functional maturity of muscle. The growth rate-maturity hypothesis predicts that the development of catabolic capacity should be delayed in faster-growing muscle masses. Leg muscles of both species were a larger proportion of adult size at hatching and grew faster than pectoral muscles. Pectoral muscles grew more rapidly in the dunlin than in the whimbrel, whereas leg muscles grew more rapidly in the whimbrel. In both species and in both leg and pectoral muscles, enzyme activities generally increased with age, suggesting increasing functional maturity. Levels of citrate synthase activity were similar to those reported for other species, but L-3-hydroxyacyl-CoA-dehydrogenase and pyruvate kinase (PK) activities were comparatively high. Catabolic capacities of leg muscles were initially high compared to those of pectoral muscles, but with the exception of glycolytic (PK) capacities, these subsequently increased only modestly or even decreased as chicks grew. The earlier functional maturity of the more rapidly growing leg muscles, as well as the generally higher functional maturity in muscles of the more rapidly growing dunlin chicks, contradicts the growth rate-maturity function trade-off and suggests that birds have considerable latitude to modify this relationship. Whimbrel chicks, apparently, can rely on allometric scaling of power requirements for locomotion and the thermal inertia of their larger mass to reduce demands on their muscles, whereas dunlin chicks require muscles with higher metabolic capacity from an earlier age. Thus, larger and smaller species may adopt different strategies of growth and tissue maturation.

Myocardial contusion is an infrequent, but sometimes serious complication in patients who experienced deceleration (blunt) trauma. We investigated the assessment of the new cardiac markers troponin I (cTnI) and troponin T (cTnT) in relation to the conventional CKMB-activity, the CKMB-activity/CK-total ratio, CKMB-mass and the CKMB-mass/CK-total ratio for the detection of myocardial contusion in 89 patients with blunt trauma (38 patients with thoracic injuries and 51 patients without thoracic injuries). All parameters were analysed at admission (t(1)) and 24 h after admission (t(2)). For the patients with thoracic injuries, at t(1) cTnI was elevated in three, and cTnT in four patients; at t(2) both cTnI and cTnT were elevated in nine patients. At t(1), eighteen to thirty patients had increased levels of the conventional parameters; at t(2) this was true for six to thirty-five patients. For the patients without thoracic injuries all cTnT and cTnT levels were within the reference ranges at t(1). At t(2) one patient, who experienced an acute myocardial infarction, had elevated cTnI and cTnT levels. At t(1), five to thirty-five patients had increased levels of the conventional parameters; at t(2) this was true for four to forty-two patients. From this study we conclude that the conventional parameters are not useful for the detection of myocardial contusion in patients experiencing blunt trauma. The parameters cTnT and cTnT are equally accurate and more reliable for the selection of patients who require intensive cardiac monitoring. If at admission the cTnI or the cTnT levels are within the reference ranges, a second analysis after admission is necessary to reach a reliable conclusion concerning myocardial contusion as a result of trauma on basis of the troponin levels. (C) 1998 Published by Elsevier Science B.V. All rights reserved.