Human skeletal muscle CD90+ fibro-adipogenic progenitors are associated with muscle degeneration in type 2 diabetic patients.

Type 2 diabetes mellitus (T2DM) is associated with impaired skeletal muscle function and degeneration of the skeletal muscles. However, the mechanisms underlying the degeneration are not well described in human skeletal muscle. Here we show that skeletal muscle of T2DM patients exhibit degenerative remodeling of the extracellular matrix that is associated with a selective increase of a subpopulation of fibro-adipogenic progenitors (FAPs) marked by expression of THY1 (CD90)-the FAPCD90+. We identify platelet-derived growth factor (PDGF) as a key FAP regulator, as it promotes proliferation and collagen production at the expense of adipogenesis. FAPsCD90+ display a PDGF-mimetic phenotype, with high proliferative activity, clonogenicity, and production of extracellular matrix. FAPCD90+ proliferation was reduced by in vitro treatment with metformin. Furthermore, metformin treatment reduced FAP content in T2DM patients. These data identify a PDGF-driven conversion of a subpopulation of FAPs as a key event in the fibrosis development in T2DM muscle.

Acute and sustained effects of a periodized carbohydrate intake using the sleep-low model in endurance-trained males.

Repeated periodization of carbohydrate (CHO) intake using a diet-exercise strategy called the sleep-low model can potentially induce mitochondrial biogenesis and improve endurance performance in endurance-trained individuals. However, more studies are needed to confirm the performance-related effects and to investigate the sustained effects on maximal fat oxidation (MFO) rate and proteins involved in intramuscular lipid metabolism. Thirteen endurance-trained males (age 23-44 years; V ˙ O2 -max, 63.9 ± 4.6 mL·kg-1 ·min-1 ) were randomized into two groups: sleep-low (LOW-CHO) or high CHO availability (HIGH-CHO) in three weekly training blocks over 4 weeks. The acute metabolic response was investigated during 60 minutes of exercise within the last 3 weeks of the intervention. Pre- and post-intervention, 30-minute time-trial performance was investigated after a 90-minute pre-load, which as a novel approach included nine intense intervals (and estimation of MFO). Additionally, muscle biopsies (v. lateralis) were obtained to investigate expression of proteins involved in intramuscular lipid metabolism using Western blotting. During acute exercise, average fat oxidation rate was ~36% higher in LOW-CHO compared to HIGH-CHO (P = .03). This did not translate into sustained effects on MFO. Time-trial performance increased equally in both groups (overall time effect: P = .005). We observed no effect on intramuscular proteins involved in lipolysis (ATGL, G0S2, CGI-58, HSL) or fatty acid transport and ß-oxidation (CD-36 and HAD, respectively). In conclusion, the sleep-low model did not induce sustained effects on MFO, endurance performance, or proteins involved in intramuscular lipid metabolism when compared to HIGH-CHO. Our study therefore questions the transferability of acute effects of the sleep-low model to superior sustained adaptations.

Influence of Oral Contraceptive Use on Adaptations to Resistance Training.

Introduction: The majority of young women use oral contraceptives (OCs). Use of OCs has been associated with lower myofibrillar protein and tendon collagen synthesis rates, but it is unknown whether OCs will limit the adaptive response of myotendinous tissue to resistance training. Design and Methods: Fourteen healthy untrained young regular OC users (24 ± 1 years, fat% 32 ± 1, 35 ± 2 ml⋅min-1⋅kg-1) and 14 NOC users (non-OC, controls) (24 ± 1 years, fat% 32 ± 2, 34 ± 2 ml⋅min-1⋅kg-1) performed a 10-week supervised lower extremity progressive resistance training program. Before and after the intervention biopsies from the vastus lateralis muscle and the patellar tendon were obtained. Muscle (quadriceps) and tendon cross-sectional area (CSA) was determined by magnetic resonance imaging (MRI) scans, and muscle fiber CSA was determined by histochemistry. Maximal isometric knee extension strength was assessed by dynamometry while 1 repetition maximum (RM) was determined during knee extension. Results: Training enhanced CSA in both muscle (p < 0.001) and tendon (p < 0.01). A trend toward a greater increase in muscle CSA was observed for OC (11%) compared to NOC (8%) (interaction p = 0.06). Analysis of mean muscle fiber type CSA showed a trend toward an increase in type II muscle fiber area in both groups (p = 0.11, interaction p = 0.98), whereas type I muscle fiber CSA increased in the OC group (n = 9, 3821 ± 197 to 4490 ± 313 mm2, p < 0.05), but not in NOC (n = 7, 4020 ± 348 to 3777 ± 354 mm2, p = 0.40) (interaction p < 0.05). Post hoc analyses indicated that the effect of OCs on muscle mass increase was induced by the OC-users (n = 7), who used OCs containing 30 µg ethinyl estradiol (EE), whereas the response in users taking OCs with 20 µg EE (n = 7) did not differ from NOC. Both the OC and NOC group experienced an increase in maximal knee strength (p < 0.001) and 1RM leg extension (p < 0.001) after the training period with no difference between groups. Conclusion: Use of OCs during a 10-week supervised progressive resistance training program was associated with a trend toward a greater increase in muscle mass and a significantly greater increase in type I muscle fiber area compared to controls. Yet, use of OCs did not influence the overall increase in muscle strength related to training.

Immobilization Decreases FOXO3a Phosphorylation and Increases Autophagy-Related Gene and Protein Expression in Human Skeletal Muscle.

Immobilization of the lower limbs promotes a catabolic state that reduces muscle mass, whereas physical training promotes an anabolic state that increases muscle mass. Understanding the molecular mechanisms underlying this is of clinical interest, as loss of muscle mass is a major complication to critical illness in humans. To determine the molecular regulation of protein synthesis and degradation during muscle loss and hypertrophy, we examined skeletal muscle biopsies from healthy human subjects after 2 weeks unilateral immobilization of a lower limb and during 6 weeks of physical rehabilitation. We have previously shown that cross-sectional area of the knee muscle-extensors decreased by ∼10% during immobilization and was completely restored during rehabilitation. Here we provide novel data to suggest that autophagy is an important underlying mechanism involved in regulation of muscle mass. Protein expression of MuRF1 and ATROGIN-1 did not change during the study, indicating that the recruitment of substrates to the proteasomes was unaltered. Phosphorylation of mTORat Ser2448 did not change during the study, and neither did phosphorylation of the mTORC1 substrates 4EBP1 Thr37/46 and p70S6K Thr389, suggesting that this pathway does not suppress protein synthesis during muscle wasting. Protein levels of p62 and ULK1 increased during immobilization and returned to baseline levels during rehabilitation. Same pattern was observed for FOXO3a phosphorylation at Ser318/321, suggesting transcriptional activation during immobilization and inactivation during rehabilitation. To investigate this further, we analyzed mRNA expression of seven autophagy-related genes controlled by FOXO3a. Five of these (p62, LC3B, BECLIN-1, ATG12, and BNIP3) increased during immobilization and returned to baseline during rehabilitation. In conclusion, immobilization of a lower limb increases autophagy-related gene and protein expression in human skeletal muscle in a pattern that mirrors FOXO3a phosphorylation. These findings could imply that FOXO3a dependent transcriptional regulation of autophagy is involved in the regulation of muscle mass in humans. CLINICAL TRIAL REGISTRATION: The study was approved by the Ethics Committee of Copenhagen (j.no. H-1-2010-016).

Molecular and cellular adaptations to exercise training in skeletal muscle from cancer patients treated with chemotherapy.

BACKGROUND: A growing body of evidence suggests that exercise training has beneficial effects in cancer patients. The aim of the present study was to investigate the molecular basis underlying these beneficial effects in skeletal muscle from cancer patients. METHODS: We investigated expression of selected proteins involved in cellular processes known to orchestrate adaptation to exercise training by western blot. Skeletal muscle biopsies were sampled from ten cancer patients before and after 4-7 weeks of ongoing chemotherapy, and subsequently after 10 weeks of continued chemotherapy in combination with exercise training. Biopsies from ten healthy matched subjects served as reference. RESULTS: The expression of the insulin-regulated glucose transporter, GLUT4, increased during chemotherapy and continued to increase during exercise training. A similar trend was observed for ACC, a key enzyme in the biosynthesis and oxidation of fatty acids, but we did not observe any changes in other regulators of substrate metabolism (AMPK and PDH) or mitochondrial proteins (Cyt-C, COX-IV, SDHA, and VDAC). Markers of proteasomal proteolysis (MURF1 and ATROGIN-1) decreased during chemotherapy, but did not change further during chemotherapy combined with exercise training. A similar pattern was observed for autophagy-related proteins such as ATG5, p62, and pULK1 Ser757, but not ULK1 and LC3BII/LC3BI. Phosphorylation of FOXO3a at Ser318/321 did not change during chemotherapy, but decreased during exercise training. This could suggest that FOXO3a-mediated transcriptional regulation of MURF1 and ATROGIN-1 serves as a mechanism by which exercise training maintains proteolytic systems in skeletal muscle in cancer patients. Phosphorylation of proteins that regulate protein synthesis (mTOR at Ser2448 and 4EBP1 at Thr37/46) increased during chemotherapy and leveled off during exercise training. Finally, chemotherapy tended to increase the number of satellite cells in type 1 fibers, without any further change during chemotherapy and exercise training. Conversely, the number of satellite cells in type 2 fibers did not change during chemotherapy, but increased during chemotherapy combined with exercise training. CONCLUSIONS: Molecular signaling cascades involved in exercise training are disturbed during cancer and chemotherapy, and exercise training may prevent further disruption of these pathways. TRIAL REGISTRATION: The study was approved by the local Scientific Ethics Committee of the Central Denmark Region (Project ID: M-2014-15-14; date of approval: 01/27/2014) and the Danish Data Protection Agency (case number 2007-58-0010; date of approval: 01/28/2015). The trial was registered at http//www.clinicaltrials.gov (registration number: NCT02192216; date of registration 07/17-2014).

Molecular adaptations in human subcutaneous adipose tissue after ten weeks of endurance exercise training in healthy males.

Endurance exercise training induces adaptations in metabolically active organs, but adaptations in human subcutaneous adipose tissue (scAT) remains incompletely understood. On the basis of animal studies, we hypothesized that endurance exercise training would increase the expression of proteins involved in lipolysis and glucose uptake in scAT. To test these hypotheses, 19 young and healthy males were randomized to either endurance exercise training (TR; age 18-24 yr; BMI 19.0-25.4 kg/m2) or a nonexercising control group (CON; age 21-35 yr; BMI 20.5-28.8 kg/m2). Abdominal subcutaneous fat biopsies and blood were obtained at rest before and after intervention. By using Western blotting and PCR, we determined expression of lipid droplet-associated proteins, various proteins involved in substrate metabolism, and mRNA abundance of cell surface G protein-coupled receptors (GPCRs). Adipose tissue insulin sensitivity was determined from fasting plasma insulin and nonesterified fatty acids (adipose tissue insulin resistance index; Adipo-IR). Adipo-IR improved in TR compared with CON ( P = 0.03). This was accompanied by increased insulin receptor (IR) protein expression in scAT with a 1.54-fold (SD 0.79) change from baseline in TR vs. 0.85 (SD 0.30) in CON ( P = 0.007). Additionally, hexokinase II (HKII) and succinate dehydrogenase complex subunit A (SDHA) protein increased in TR compared with CON ( P = 0.006 and P = 0.04, respectively). We did not observe changes in lipid droplet-associated proteins or mRNA abundance of GPCRs. Collectively, 10 weeks of endurance exercise training improved adipose tissue insulin sensitivity, which was accompanied by increased IR, HKII, and SDHA protein expression in scAT. We suggest that these adaptations contribute to an improved metabolic flexibility. NEW & NOTEWORTHY This study is the first to investigate the molecular adaptations in human subcutaneous adipose tissue (scAT) after endurance exercise training compared with a nonexercising control group. We show that endurance exercise training improves insulin sensitivity in human scAT, and this is accompanied by increased expression of insulin receptor, hexokinase II, and succinate dehydrogenase complex subunit A. Collectively, our data suggest that endurance exercise training induces molecular adaptations in human scAT, which may contribute to an improved metabolic flexibility.

Insulin inhibits autophagy signaling independent of counterregulatory hormone levels but does not affect the effects of exercise.

Acute exercise increases autophagic signaling through Unc-51 like kinase-1 (ULK1) in human skeletal muscle during both anabolic and catabolic conditions. The aim of the present study was to investigate if changes in ULK1 Ser555 phosphorylation during exercise are reflected by changes in phosphorylation of a newly identified ULK1 substrate (ATG14 Ser29) and to elucidate the involvement of circulatory hormones in the regulation of autophagy in human skeletal muscle. We show that 1 h of cycling exercise increases ATG14 Ser29 phosphorylation during both hyperinsulinemic euglycemic and euinsulinemic euglycemic conditions. This could suggest that counterregulatory hormones stimulate autophagy in skeletal muscle, as circulating concentrations of these hormones are highly elevated during exercise. Furthermore, ATG14 Ser29 correlated positively with ULK1 phosphorylation, suggesting that ULK1 Ser555 (activating site) phosphorylation reflects ULK1 kinase activity. In a separate series of experiments, we show that insulin stimulates ULK1 phosphorylation at Ser757 (inhibitory site) in both hypoglycemic and euglycemic conditions, suggesting that counterregulatory hormones (such as epinephrine, norepinephrine, growth hormone, and glucagon) have limited effects on autophagy signaling in human skeletal muscle. In conclusion, 1 h of cycling exercise increases phosphorylation of ATG14 at Ser29 in a pattern that mirrors ULK1 phosphorylation at Ser555. Moreover, insulin effects on autophagy signaling in human skeletal muscle are independent of hypoglycemic and euglycemic conditions.NEW & NOTEWORTHY Autophagy signaling is regulated in a hierarchical order by exercise, insulin, and counterregulatory hormones. Exercise-induced autophagy signaling is stimulated by local factors in skeletal muscle rather than circulatory hormones. Unc-51 like kinase-1 (ULK1) phosphorylation at Ser555 reflects ULK1 kinase activity.

Altered gene expression and repressed markers of autophagy in skeletal muscle of insulin resistant patients with type 2 diabetes.

This case-control study was designed to investigate the gene expression profile in skeletal muscle from severely insulin resistant patients with long-standing type 2 diabetes (T2D), and to determine associated signaling pathways. Gene expression profiles were examined by whole transcriptome, strand-specific RNA-sequencing and associated signaling was determined by western blot. We identified 117 differentially expressed gene transcripts. Ingenuity Pathway Analysis related these differences to abnormal muscle morphology and mitochondrial dysfunction. Despite a ~5-fold difference in plasma insulin, we did not observe any difference in phosphorylation of AKT or AS160, although other insulin-sensitive cascades, as mTOR/4EBP1, had retained their sensitivity. Autophagy-related gene (ATG14, RB1CC1/FIP200, GABARAPL1, SQSTM1/p62, and WIPI1) and protein (LC3BII, SQSTM1/p62 and ATG5) expression were decreased in skeletal muscle from the patients, and this was associated with a trend to increased phosphorylation of the insulin-sensitive regulatory transcription factor FOXO3a. These data show that gene expression is highly altered and related to mitochondrial dysfunction and abnormal morphology in skeletal muscle from severely insulin resistant patients with T2D, and that this is associated with decreased expression of autophagy-related genes and proteins. We speculate that prolonged treatment with high doses of insulin may suppress autophagy thereby generating a vicious cycle maintaining insulin resistance.

Differential regulation of lipid and protein metabolism in obese vs. lean subjects before and after a 72-h fast.

Increased availability of lipids may conserve muscle protein during catabolic stress. Our study was designed to define 1) intracellular mechanisms leading to increased lipolysis and 2) whether this scenario is associated with decreased amino acid and urea fluxes, and decreased muscle amino acid release in obese subjects under basal and fasting conditions. We therefore studied nine lean and nine obese subjects twice, after 12 and 72 h of fasting, using measurements of mRNA and protein expression and phosphorylation of lipolytic and protein metabolic signaling molecules in fat and muscle together with whole body and forearm tracer techniques. Obese subjects displayed increased whole body lipolysis, decreased urea production rates, and decreased forearm muscle protein breakdown per 100 ml of forearm tissue, differences that persisted after 72 h of fasting. Lipolysis per fat mass unit was reduced in obese subjects and, correspondingly, adipose tissue hormone-sensitive lipase (HSL) phosphorylation and mRNA and protein levels of the adipose triglyceride lipase (ATGL) coactivator CGI58 were decreased. Fasting resulted in higher HSL phosphorylations and lower protein levels of the ATGL inhibitor G0S2. Muscle protein expressions of mammalian target of rapamycin (mTOR) and 4EBP1 were lower in obese subjects, and MuRf1 mRNA was higher with fasting in lean but not obese subjects. Phosphorylation and signaling of mTOR decreased with fasting in both groups, whereas ULK1 protein and mRNA levels increased. In summary, obese subjects exhibit increased lipolysis due to a large fat mass with blunted prolipolytic signaling, together with decreased urea and amino acid fluxes both in the basal and 72-h fasted state; this is compatible with preservation of muscle and whole body protein.

Physical exercise increases autophagic signaling through ULK1 in human skeletal muscle.

Data from transgenic animal models suggest that exercise-induced autophagy is critical for adaptation to physical training, and that Unc-51 like kinase-1 (ULK1) serves as an important regulator of autophagy. Phosphorylation of ULK1 at Ser(555) stimulates autophagy, whereas phosphorylation at Ser(757) is inhibitory. To determine whether exercise regulates ULK1 phosphorylation in humans in vivo in a nutrient-dependent manner, we examined skeletal muscle biopsies from healthy humans after 1-h cycling exercise at 50% maximal O2 uptake on two occasions: 1) during a 36-h fast, and 2) during continuous glucose infusion at 0.2 kg/h. Physical exercise increased ULK1 phosphorylation at Ser(555) and decreased lipidation of light chain 3B. ULK1 phosphorylation at Ser(555) correlated positively with AMP-activated protein kinase-α Thr(172) phosphorylation and negatively with light chain 3B lipidation. ULK1 phosphorylation at Ser(757) was not affected by exercise. Fasting increased ULK1 and p62 protein expression, but did not affect exercise-induced ULK1 phosphorylation. These data demonstrate that autophagy signaling is activated in human skeletal muscle after 60 min of exercise, independently of nutritional status, and suggest that initiation of autophagy constitutes an important physiological response to exercise in humans.

Fasting increases human skeletal muscle net phenylalanine release and this is associated with decreased mTOR signaling.

AIM: Fasting is characterised by profound changes in energy metabolism including progressive loss of body proteins. The underlying mechanisms are however unknown and we therefore determined the effects of a 72-hour-fast on human skeletal muscle protein metabolism and activation of mammalian target of rapamycin (mTOR), a key regulator of cell growth. METHODS: Eight healthy male volunteers were studied twice: in the postabsorptive state and following 72 hours of fasting. Regional muscle amino acid kinetics was measured in the forearm using amino acid tracers. Signaling to protein synthesis and breakdown were assessed in skeletal muscle biopsies obtained during non-insulin and insulin stimulated conditions on both examination days. RESULTS: Fasting significantly increased forearm net phenylalanine release and tended to decrease phenylalanine rate of disappearance. mTOR phosphorylation was decreased by ∼50% following fasting, together with reduced downstream phosphorylation of 4EBP1, ULK1 and rpS6. In addition, the insulin stimulated increase in mTOR and rpS6 phosphorylation was significantly reduced after fasting indicating insulin resistance in this part of the signaling pathway. Autophagy initiation is in part regulated by mTOR through ULK1 and fasting increased expression of the autophagic marker LC3B-II by ∼30%. p62 is degraded during autophagy but was increased by ∼10% during fasting making interpretation of autophagic flux problematic. MAFbx and MURF1 ubiquitin ligases remained unaltered after fasting indicating no change in protesomal protein degradation. CONCLUSIONS: Our results show that during fasting increased net phenylalanine release in skeletal muscle is associated to reduced mTOR activation and concomitant decreased downstream signaling to cell growth.

Effects of divergent resistance exercise contraction mode and dietary supplementation type on anabolic signalling, muscle protein synthesis and muscle hypertrophy.

Greater force produced with eccentric (ECC) compared to concentric (CONC) contractions, may comprise a stronger driver of muscle growth, which may be further augmented by protein supplementation. We investigated the effect of differentiated contraction mode with either whey protein hydrolysate and carbohydrate (WPH + CHO) or isocaloric carbohydrate (CHO) supplementation on regulation of anabolic signalling, muscle protein synthesis (MPS) and muscle hypertrophy. Twenty-four human participants performed unilateral isolated maximal ECC versus CONC contractions during exercise habituation, single-bout exercise and 12 weeks of training combined with WPH + CHO or CHO supplements. In the exercise-habituated state, p-mTOR, p-p70S6K, p-rpS6 increased by approximately 42, 206 and 213 %, respectively, at 1 h post-exercise, with resistance exercise per se; whereas, the phosphorylation was exclusively maintained with ECC at 3 and 5 h post-exercise. This acute anabolic signalling response did not differ between the isocaloric supplement types, neither did protein fractional synthesis rate differ between interventions. Twelve weeks of ECC as well as CONC resistance training augmented hypertrophy with WPH + CHO group compared to the CHO group (7.3 ± 1.0 versus 3.4 ± 0.8 %), independently of exercise contraction type. Training did not produce major changes in basal levels of Akt-mTOR pathway components. In conclusion, maximal ECC contraction mode may constitute a superior driver of acute anabolic signalling that may not be mirrored in the muscle protein synthesis rate. Furthermore, with prolonged high-volume resistance training, contraction mode seems less influential on the magnitude of muscle hypertrophy, whereas protein and carbohydrate supplementation augments muscle hypertrophy as compared to isocaloric carbohydrate supplementation .

Validity and reliability of VO2-max measurements in persons with multiple sclerosis.

BACKGROUND: Direct measurement of whole body maximal oxygen consumption (VO2-max test) is considered the gold standard when assessing cardiorespiratory fitness. Nonetheless, the validity and reliability of the test have not been examined in persons with multiple sclerosis (PwMS). OBJECTIVE: To investigate the validity and reliability of VO2-max measurements in PwMS, and additionally to compare these measures to those of healthy controls. METHODS: Twenty PwMS completed two incremental VO2-max tests on a leg cycling ergometer. Test validity was analyzed based on the first VO2-max test in the total sample and in patient subgroups based on Expanded Disability Status Scale (EDSS) scores (EDSS≤2.5, n=10 and EDSS≥3.0, n=10) by evaluation of the primary VO2 plateau criterion and four common secondary validity criteria. Data from 20 age- and gender-matched healthy controls were used for comparison. The second VO2-max test was used to establish day-to-day reliability. RESULTS: In PwMS 40% were able to achieve the primary validity criterion for VO2-max measurements, while 65-95% were able to achieve the secondary criteria. This corresponded to the age-matched healthy controls. Strong correlations were found between measurements of VO2-max and between the validity criteria from test 1 compared to test 2 in PwMS. MS disability level did not influence criteria attainment. The variability analysis exhibited a 95% prediction interval of -238 to 201 mL·min(-1) (-9.8 to 8.1%) for the difference between the two measurements of VO2-max. CONCLUSION: In mild to moderately impaired PwMS less than half achieve the primary validity criterion when performing a VO2-max test, but the high reliability and the better achievement of the secondary criteria implies that a valid test of VO2-max can be performed, at a level corresponding to that of healthy controls. The day-to-day variation implies that a change of more than 10% in VO2-max is required to be interpreted as a real change.

AMP kinase in exercise adaptation of skeletal muscle.

Regular physical exercise has undisputed health benefits in the prevention and the treatment of many diseases. Understanding the mechanisms that regulate adaptations to exercise training therefore has obvious clinical perspectives. Several lines of evidence suggest that the AMP-activated protein kinase (AMPK) has a central role as a master metabolic regulator in skeletal muscle. Exercise is a potent activator of AMPK, and AMPK signaling can play a key part in regulating protein turnover during and after exercise training.

Resistance exercise, but not endurance exercise, induces IKKß phosphorylation in human skeletal muscle of training-accustomed individuals.

The mammalian target of rapamycin complex 1 (mTORC1) is considered an important role in the muscular adaptations to exercise. It has been proposed that exercise-induced signaling to mTORC1 do not require classic growth factor PI3K/Akt signaling. Activation of IKKß and the mitogen-activated protein kinases (MAPKs) Erk1/2 and p38 has been suggested to link inflammation and cellular stress to activation of mTORC1 through the tuberous sclerosis 1 (TSC1)/tuberous sclerosis 2 (TSC2) complex. Consequently, activation of these proteins constitutes potential alternative mechanisms of mTORC1 activation following exercise. Previously, we demonstrated that mTOR is preferentially activated in response to resistance exercise compared to endurance exercise in trained individuals without concomitant activation of Akt. In the present study, we extended this investigation by examining IκB kinase complex (IKK), TSC1, MAPK, and upstream Akt activators, along with gene expression of selected cytokines, in skeletal muscles from these subjects. Biopsies were sampled prior to, immediately after, and in the recovery period following resistance exercise, endurance exercise, and control interventions. The major finding was that IKKß phosphorylation increased exclusively after resistance exercise. No changes in TSC1, Erk1/2, insulin receptor, or insulin receptor substrate 1 phosphorylation were observed in any of the groups, while p38 phosphorylation was higher in the resistance exercise group compared to both other groups immediately after the intervention. Resistance and endurance exercise increased IL6, IL8, and TNFα gene expression immediately after exercise. The non-exercise control group demonstrated that cytokine gene expression is also sensitive to repeated biopsy sampling, whereas no effect of repeated biopsy sampling on protein expression and phosphorylation was observed. In conclusion, resistance exercise, but not endurance exercise, increases IKKß phosphorylation in trained human subjects, which support the idea that IKKß can influence the activation of mTORC1 in human skeletal muscle.

Regulation of urea synthesis during the acute-phase response in rats.

The acute-phase response is a catabolic event involving increased waste of amino-nitrogen (N) via hepatic urea synthesis, despite an increased need for amino-N incorporation into acute-phase proteins. This study aimed to clarify the regulation of N elimination via urea during different phases of the tumor necrosis factor-α (TNF-α)-induced acute-phase response in rats. We used four methods to study the regulation of urea synthesis: We examined urea cycle enzyme mRNA levels in liver tissue, the hepatocyte urea cycle enzyme proteins, the in vivo capacity of urea-N synthesis (CUNS), and known humoral regulators of CUNS at 1, 3, 24, and 72 h after TNF-α injection (25 µg/kg iv rrTNF-α) in rats. Serum acute-phase proteins and their liver mRNA levels were also measured. The urea cycle enzyme mRNA levels acutely decreased and then gradually normalized, whereas the urea cycle enzyme proteins remained essentially unchanged over time. The CUNS rose after 3 h and then normalized. The acute-phase response was fully activated at 24 h with markedly increased serum levels of the acute-phase proteins. TNF-α acutely upregulated the CUNS. Later, despite the fully established 24-h acute-phase response and the decreased activity of the urea cycle enzyme genes, there was no change in the urea cycle enzyme proteins or the CUNS. Thus in no phase after the initiation of the acute-phase response was in vivo urea synthesis orchestrated in combination with acute-phase protein synthesis so as to limit N waste.

Validity and variability of the 5-repetition sit-to-stand test in patients with multiple sclerosis.

PURPOSE: To investigate; (i) the relationship between the 5STS-test and lower extremity muscle strength and balance, and (ii) the variability of the 5STS-test in multiple sclerosis (MS) patients. METHOD: 22 MS patients were divided into two groups (Group A and Group B) who completed one 5STS familiarization test session and two testing sessions. In Group A, session 1 also included assessment of lower extremity muscle strength. Session 2 and 3 involved completion of two 5STS-tests and assessment of balance. In Group B, session 2 and 3 involved completion of two rounds of two 5STS-tests separated by a 30 min break. RESULTS: Significant correlations were found between the 5STS-test and isometric and isokinetic knee flexor and extensor muscle strength of the most affected leg (R = -0.60 to -0.77), and between the 5STS-test and balance performance (R = 0.69). Intra-assessor day-to-day variability, intra-assessor test-retest variability and intra-assessor variability within test were 25.5, 22.3, and 23.1%, respectively. Inter-assessor variability within test and inter-assessor variability were 23.4 and 5.9%, respectively. CONCLUSIONS: The 5STS-test is related to lower extremity muscle strength and to balance performance in MS patients. For interventional purposes, a change of >25% can be regarded as a real change.