Influence of Insulin Resistance on Contractile Activity-Induced Anabolic Response of Skeletal Muscle

Although the long-term therapeutic benefits of exercise are indisputable, contractile activity may induce divergent adaptations in insulin-resistant vs. insulin-sensitive skeletal muscle. The purpose of this study was to elucidate if the anabolic response following resistance exercise (RE) is altered in myocellular sub-fractions in the face of insulin resistance. Lean (Fa/?) and obese (fa/fa) Zucker rats were assigned to sedentary and RE groups and engaged in either cage rest or four lower-body RE sessions over an 8-d period. Despite obese Zucker rats having significantly smaller hindlimb muscles when compared to age-matched lean rats, basal 24-h fractional synthesis rates (FSR) of mixed protein pools were near normal in distally located muscle groups (gastrocnemius, plantaris, and soleus) and even augmented in those located more proximally (P<0.05; quadriceps). Although 2 x 2 ANOVA indicated a significant main effect of phenotype on mixed FSR in gastrocnemius and soleus (P < 0.05), phenotypic differences were partially accounted for by an exercise effect in the lean phenotype. Interestingly, obese rats exhibited a significant suppression of myofibrillar FSR compared to their lean counterparts (P<0.05; gastrocnemius), while synthesis rates of mitochondrial and cytosolic proteins were normal (gastrocnemius and quadriceps), suggesting a mechanism whereby translation of specific mRNA pools encoding for metabolic enzymes may be favored over other transcripts (e.g., contractile proteins) to cope with nutrient excess in the insulin-resistant state. Immunoblotting of the cytosolic fraction in gastrocnemius muscle indicated an augmented phosporylation of eIF4EBP1 (+ 9%) and p70s6k (+85%) in obese vs. lean rats, but a more potent baseline inhibition of polypeptide-chain elongation as evidenced by an increased phospho/total ratio of eEF2 (+78%) in the obese phenotype. Resistance exercise did not improve synthesis rates of myofibrillar, cytosolic, or mitochondrial proteins to the same extent in obese vs. lean rats, suggesting a desensitization to contractile-induced anabolic stimuli in the insulin-resistant state. We conclude that insulin resistance has diverse effects on protein metabolism, which may vary between muscle groups depending on fiber type distribution, location along the proximodistal body axis, and myocellular sub-fraction, and may blunt the anabolic response to voluntary resistance exercise

Journal Staff

Primary Immunodeficiencies (PID) are genetically inherited disorders characterized by defects of the immune system, leading to increased susceptibility to infection. Due to the variety of clinical symptoms and the complexity of current diagnostic procedures, accurate diagnosis of PID is often difficult in daily clinical practice. Thanks to the advent of "next generation'' sequencing technologies and target enrichment methods, the development of multiplex diagnostic assays is now possible. In this study, we applied a selector-based target enrichment assay to detect disease-causing mutations in 179 known PID genes. The usefulness of this assay for molecular diagnosis of PID was investigated by sequencing DNA from 33 patients, 18 of which had at least one known causal mutation at the onset of the experiment. We were able to identify the disease causing mutations in 60% of the investigated patients, indicating that the majority of PID cases could be resolved using a targeted sequencing approach. Causal mutations identified in the unknown patient samples were located in STAT3, IGLL1, RNF168 and PGM3. Based on our results, we propose a stepwise approach for PID diagnostics, involving targeted resequencing, followed by whole transcriptome and/or whole genome sequencing if causative variants are not found in the targeted exons

Changes in PPARδ Protein Content following Acute Aerobic Exercise in Human Vastus Lateralis Muscle.

PPARδ is a transcription factor which functions in the regulation of lipid and glucose metabolism, and may be implicated as a therapeutic target for several metabolic diseases. Exercise training has previously been shown to increase PPARδ protein content, but the response of PPARδ to acute exercise is not yet understood. PURPOSE: To explore changes in PPARδ protein content following an acute bout of aerobic exercise in untrained obese adults. METHODS: 8 men and 4 women participated in the study. Subjects’ mean age, weight, VO2MAX (Bruce treadmill GXT), and body composition (DEXA) were 44 yr, 93.2 kg, 28.2 mL/kg/min, and 40.5% body fat, respectively. Subjects were asked to refrain from exercise for 1 week prior to the experiment and to maintain normal dietary habits during the study. Muscle biopsies were obtained from the vastus lateralis 3 days prior to acute exercise and again 24 hours after exercise. Subjects were exercised on a motorized treadmill at 70% VO2MAX for a target duration of 400kcal energy expenditure during the exercise session. PPARδ protein content in biopsied tissue was determined by Western blot analysis. Data were analyzed by repeated measures ANOVA and expressed as means ± standard error. RESULTS: PPARδ content was enhanced 24 hours following acute exercise in previously untrained, obese adults (unexercised 1.54±0.38 vs. exercised 2.30±0.39 arbitrary units, P\u3c0.05). Gel mobility shift indicated no difference in activity of PPARδ (phosphorylated: total) following exercise (unexercised 0.36±0.03 vs. exercised 0.34±0.04). CONCLUSION: Our study shows that PPARδ expression is enhanced in untrained, obese adults following a single bout of aerobic exercise with no relative change in phosphorylation of PPARδ. These data indicate that acute exercise plays a role in the expression of PPARδ. Funding for this research was provided by HydroWorx International, Inc., the Sydney & J.L. Huffines Institute for Sports Medicine and Human Performance at Texas A&M University and The Texas Chapter of The American College of Sports Medicin

DEPTOR Expression Correlates with Muscle Protein Synthesis

Mammalian target of rapamycin (mTOR) has long been declared a focal point of muscle protein synthesis. mTORC1 (an mTOR complex consisting of mTOR, raptor, PRAS40, and mLST8) has been associated with regulation of protein translation in muscle, altering expression and activity levels of key downstream targets S6K1 and eIF-4E-BP1. mTORC1 has been shown to be affected by various stimuli, including nutritional status, growth factors, and mechanical loading. But in past incidents we have found disconnects in muscle protein synthesis and mTOR signaling, stimulating discussions that mTOR content and activation alone may not be able to fully account for muscle protein synthesis. Gaining popularity as a target for anti-cancer therapies, we became interested in DEPTOR, an endogenous inhibitor of mTORC1. Pharmacological inhibition of DEPTOR in cell culture and mouse studies has displayed increases of anabolic signaling in response to atrophic circumstances. We present two unique catabolic conditions in which we explore DEPTOR expression and muscle protein synthesis and demonstrate the first known data proposing that DEPTOR expression is not only influenced by physiological stimuli, including mechanical loading and insulin sensitivity, but that DEPTOR expression strongly correlates with 24-hr cumulative muscle protein synthesis rates. In one study, male Sprague Dawley rats were subjected to various conditions of musculoskeletal unloading, reloading, and overload, in which hindlimb unloading (HU) was utilized to mimic chronic disuse atrophy (28-d), followed by ambulatory reloading (56-d post HU) with and without the addition of resistance exercise prescribed to assist in recovery (3 sessions/wk for 7-wks; progressive increases in added resistance up to ~60% BW). DEPTOR expression was assessed via Immunoblotting. 24-hr cumulative muscle protein synthesis (FSR) was measured via stable isotope labeling and quantified by gas chromatogram/mass spectrometry. DEPTOR demonstrated a strong negative correlation with FSR in the gastrocnemius (r = - 0.93261; p \u3c0.01). In our second study, male obese Zucker rats were divided into their lean and obese phenotypes, as well as placed into sedentary and resistance exercised groups. DEPTOR and FSR were assessed as described above following operant conditioning and four progressive exercise sessions over 9-d. Gastrocnemius DEPTOR/FSR was again significant (r = - 0.75723; p\u3c0.01). Collectively, these results are the first to associate physiologic changes in DEPTOR expression with alterations of FSR, which may have important implications towards the design of therapeutic targets for the control of muscle mass or in evaluating muscle anabolism

Rapid Identification of Bio-Molecules Applied for Detection of Biosecurity Agents Using Rolling Circle Amplification

Detection and identification of pathogens in environmental samples for biosecurity applications are challenging due to the strict requirements on specificity, sensitivity and time. We have developed a concept for quick, specific and sensitive pathogen identification in environmental samples. Target identification is realized by padlock- and proximity probing, and reacted probes are amplified by RCA (rolling-circle amplification). The individual RCA products are labeled by fluorescence and enumerated by an instrument, developed for sensitive and rapid digital analysis. The concept is demonstrated by identification of simili biowarfare agents for bacteria (Escherichia coli and Pantoea agglomerans) and spores (Bacillus atrophaeus) released in field

A case report of vibration-induced hand comorbidities in a postwoman

<p>Abstract</p> <p>Background</p> <p>Prolonged exposure to hand-transmitted vibration is associated with an increased occurrence of symptoms and signs of disorders in the vascular, neurological and osteoarticular systems of the upper limbs. However, the available epidemiological evidence is derived from studies on high vibration levels caused by vibratory tools, whereas little is known about possible upper limb disorders caused by chronic exposure to low vibration levels emitted by fixed sources.</p> <p>Case presentation</p> <p>We present the case of a postwoman who delivered mail for 15 years using a low-powered motorcycle. The woman was in good health until 2002, when she was diagnosed with bilateral Raynaud's phenomenon. In March 2003 a bilateral carpal tunnel syndrome was electromyographically diagnosed; surgical treatment was ineffective. Further examinations in 2005 highlighted the presence of chronic tendonitis (right middle finger flexor).</p> <p>Risk assessment</p> <p>From 1987, for 15 years, our patient rode her motorcycle for 4 h/day, carrying a load of 20-30 kg. For about a quarter of the time she drove over country roads. Using the information collected about the tasks carried out every day by the postwoman and some measurements performed on both handles of the motorcycle, as well as on both iron parts of the handlebars, we reconstructed the woman's previous exposure to hand-arm vibration. 8-hour energy-equivalent frequency weighted acceleration was about 2.4 m/s². The lifetime dose was 1.5 × 10⁹(m²/s⁴)hd.</p> <p>Conclusions</p> <p>The particular set of comorbidities presented by our patient suggests a common pathophysiological basis for all the diseases. Considering the level of exposure to vibrations and the lack of specific knowledge on the effects of vibration in women, we hypothesize an association between the work exposure and the onset of the diseases.</p

Warming response of peatland CO2 sink is sensitive to seasonality in warming trends

Peatlands have acted as net CO2 sinks over millennia, exerting a global climate cooling effect. Rapid warming at northern latitudes, where peatlands are abundant, can disturb their CO2 sink function. Here we show that sensitivity of peatland net CO2 exchange to warming changes in sign and magnitude across seasons, resulting in complex net CO2 sink responses. We use multiannual net CO2 exchange observations from 20 northern peatlands to show that warmer early summers are linked to increased net CO2 uptake, while warmer late summers lead to decreased net CO2 uptake. Thus, net CO2 sinks of peatlands in regions experiencing early summer warming, such as central Siberia, are more likely to persist under warmer climate conditions than are those in other regions. Our results will be useful to improve the design of future warming experiments and to better interpret large-scale trends in peatland net CO2 uptake over the coming few decades.Peatlands have historically acted as a carbon sink, but it is unclear how climate warming will affect this. The response of peatland carbon uptake to warming depends on the timing of summer warming; early warming leads to increased CO2 uptake and later warming to decreased uptake

Dual TNFα-induced effects on NRF2 mediated antioxidant defence in astrocyte-rich cultures: role of protein kinase activation

Tumor necrosis factor-α (TNFα) is a pleiotropic molecule that can have both protective and detrimental effects in neurodegeneration. Here we have investigated the temporal effects of TNFα on the inducible Nrf2 system in astrocyte-rich cultures by determination of glutathione (GSH) levels, γglutamylcysteine ligase (γGCL) activity, the protein levels of Nrf2, Keap1, the catalytic and modulatory subunit of γGCL (γGCL-C and γGCL-M respectively). Astrocyte-rich cultures were exposed for 24 or 72 h to different concentrations of TNFα. Acute exposure (24 h) of astrocyte-rich cultures to 10 ng/mL of TNFα increased GSH, γGCL activity, the protein levels of γGCL-M, γGCL-C and Nrf2 in parallel with decreased levels of Keap1. Antioxidant responsive element (ARE)-mediated transcription was blocked by inhibitors of ERK1/2, JNK and Akt whereas inactivation of p38 and GSK3β further enhanced transcription. In contrast treatment with TNFα for 72 h decreased components of the Nrf2 system in parallel with an increase of Keap1. Stimulation of the Nrf2 system by tBHQ was intact after 24 h but blocked after 72 h treatment with TNFα. This down-regulation after 72 h correlated with activation of p38 MAPK and GSK3β, since inhibition of these signalling pathways reversed this effect. The upregulation of the Nrf2 system by TNFα (24 h treatment) protected the cells from oxidative stress through elevated γGCL activity whereas the down-regulation (72 h treatment) caused pronounced oxidative toxicity. One of the important implications of the results is that in a situation where Nrf2 is decreased, such as in Alzheimer’s disease, the effect of TNFα is detrimental.Fil: Correa, Fernando Gabriel. University Goteborg; Suecia. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mallard, Carina. University Goteborg; SueciaFil: Nilsson, Michael. University Goteborg; SueciaFil: Sandberg, Mats. University Goteborg; Sueci

The influence of hydrological regimes on sex ratios and spatial segregation of the sexes in two dioecious riparian shrub species in northern Sweden

River management practices have altered the hydrological regimes of many rivers and also altered the availability of regeneration niches for riparian species. We investigated the impact of changed hydrological regimes on the sex ratios and the Spatial Segregation of the Sexes (SSS) in the dioecious species Salix myrsinifolia Salisb.–phylicifolia L. and S. lapponum L. by studying the free-flowing Vindel River and the regulated Ume River in northern Sweden. We surveyed sex ratios of these species in 12 river reaches on the Vindel River and in 17 reaches on the Ume River. In addition, we surveyed the sex and location above mean river stage of 1,002 individuals across both river systems to investigate the SSS of both species. Cuttings were collected from male and female individuals of S. myrsinifolia–phylicifolia from both rivers and subjected to four different water table regimes in a greenhouse experiment to investigate growth response between the sexes. We found an M/F sex ratio in both river systems similar to the regional norm of 0.62 for S. myrsinifolia–phylicifolia and of 0.42 for S. lapponum. We found no evidence of SSS in either the free-flowing Vindel River or the regulated Ume River. In the greenhouse experiment, hydrological regime had a significant effect on shoot and root dry weight and on root length. Significantly higher shoot dry weights were found in females than in males and significantly different shoot and root dry weights were found between cuttings taken from the two rivers. We concluded that changed hydrological regimes are likely to alter dimensions of the regeneration niche and therefore to influence sex ratios and SSS at an early successional stage, making it difficult to find clear spatial patterns once these species reach maturity and can be sexed

A Novel DBL-Domain of the P. falciparum 332 Molecule Possibly Involved in Erythrocyte Adhesion

Plasmodium falciparum malaria is brought about by the asexual stages of the parasite residing in human red blood cells (RBC). Contact between the erythrocyte surface and the merozoite is the first step for successful invasion and proliferation of the parasite. A number of different pathways utilised by the parasite to adhere and invade the host RBC have been characterized, but the complete biology of this process remains elusive. We here report the identification of an open reading frame (ORF) representing a hitherto unknown second exon of the Pf332 gene that encodes a cysteine-rich polypeptide with a high degree of similarity to the Duffy-binding-like (DBL) domain of the erythrocyte-binding-ligand (EBL) family. The sequence of this DBL-domain is conserved and expressed in all parasite clones/strains investigated. In addition, the expression level of Pf332 correlates with proliferation efficiency of the parasites in vitro. Antibodies raised against the DBL-domain are able to reduce the invasion efficiency of different parasite clones/strains. Analysis of the DBL-domain revealed its ability to bind to uninfected human RBC, and moreover demonstrated association with the iRBC surface. Thus, Pf332 is a molecule with a potential role to support merozoite invasion. Due to the high level of conservation in sequence, the novel DBL-domain of Pf332 is of possible importance for development of novel anti-malaria drugs and vaccines