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"Richter, A."
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Exercise-stimulated glucose uptake — regulation and implications for glycaemic control
Key Points
Exercise-stimulated signal transduction can restore glucose metabolism in insulin-resistant muscle through both acute activation of glucose transport and by improving insulin sensitivity for up to 48 hours after exercise
Glucose is a major fuel source during exercise and glucose uptake by skeletal muscle can increase by up to 50-fold during bouts of exercise
In excess of 1,000 phosphorylation sites in human skeletal muscle are regulated by exercise, which suggests that many regulators of muscle glucose uptake have yet to be discovered
Regulation of exercise-stimulated glucose uptake by skeletal muscle requires three major steps (delivery, transport and intramyocellular metabolism), any of which could be rate-limiting during various exercise conditions
Intensity and duration of exercise are key determinants of glucose uptake by skeletal muscle
Exercise-stimulated glucose transport is regulated by two major pathways that sense either alterations in the intracellular metabolic milieu (probably mediated by AMPK) or mechanical stress (partly mediated by RAC1)
In this Review, Sylow and colleagues discuss the molecular mechanisms and signalling pathways that regulate glucose uptake from the blood into the muscle during exercise, and the roles of both known and candidate molecules in the process.
Skeletal muscle extracts glucose from the blood to maintain demand for carbohydrates as an energy source during exercise. Such uptake involves complex molecular signalling processes that are distinct from those activated by insulin. Exercise-stimulated glucose uptake is preserved in insulin-resistant muscle, emphasizing exercise as a therapeutic cornerstone among patients with metabolic diseases such as diabetes mellitus. Exercise increases uptake of glucose by up to 50-fold through the simultaneous stimulation of three key steps: delivery, transport across the muscle membrane and intracellular flux through metabolic processes (glycolysis and glucose oxidation). The available data suggest that no single signal transduction pathway can fully account for the regulation of any of these key steps, owing to redundancy in the signalling pathways that mediate glucose uptake to ensure maintenance of muscle energy supply during physical activity. Here, we review the molecular mechanisms that regulate the movement of glucose from the capillary bed into the muscle cell and discuss what is known about their integrated regulation during exercise. Novel developments within the field of mass spectrometry-based proteomics indicate that the known regulators of glucose uptake are only the tip of the iceberg. Consequently, many exciting discoveries clearly lie ahead.
Journal Article
Influences of the ocean surface mixed layer and thermohaline stratification on Arctic Sea ice in the central Canada Basin
Variations in the Arctic central Canada Basin mixed layer properties are documented based on a subset of nearly 6500 temperature and salinity profiles acquired by Ice‐Tethered Profilers during the period summer 2004 to summer 2009 and analyzed in conjunction with sea ice observations from ice mass balance buoys and atmosphere‐ocean heat flux estimates. The July–August mean mixed layer depth based on the Ice‐Tethered Profiler data averaged 16 m (an overestimate due to the Ice‐Tethered Profiler sampling characteristics and present analysis procedures), while the average winter mixed layer depth was only 24 m, with individual observations rarely exceeding 40 m. Guidance interpreting the observations is provided by a 1‐D ocean mixed layer model. The analysis focuses attention on the very strong density stratification at the base of the mixed layer in the Canada Basin that greatly impedes surface layer deepening and thus limits the flux of deep ocean heat to the surface that could influence sea ice growth/decay. The observations additionally suggest that efficient lateral mixed layer restratification processes are active in the Arctic, also impeding mixed layer deepening.
Journal Article
مقدمة في الفن الإغريقي
يتناول كتاب (مقدمة في الفن الإغريقي) والذي قام بتأليفه (جيزيلا ريختر) في حوالي (563) صفحة من القطع المتوسط موضوع (الفن الإغريقي) مستعرضا المحتويات التالية : العمارة-النحت-الأحجار الكريمة-المسكوكات المجوهرات-الأعمال الزخرفية المعدنية-الفخار وتلوين المزهريات-الزجاج-الأثاث-المنسوجات التلوين على الجدران والفسيفساء مع 500 صورة.
Book
Cytosolic ROS production by NADPH oxidase 2 regulates muscle glucose uptake during exercise
Reactive oxygen species (ROS) act as intracellular compartmentalized second messengers, mediating metabolic stress-adaptation. In skeletal muscle fibers, ROS have been suggested to stimulate glucose transporter 4 (GLUT4)-dependent glucose transport during artificially evoked contraction ex vivo, but whether myocellular ROS production is stimulated by in vivo exercise to control metabolism is unclear. Here, we combined exercise in humans and mice with fluorescent dyes, genetically-encoded biosensors, and NADPH oxidase 2 (NOX2) loss-of-function models to demonstrate that NOX2 is the main source of cytosolic ROS during moderate-intensity exercise in skeletal muscle. Furthermore, two NOX2 loss-of-function mouse models lacking either p47phox or Rac1 presented striking phenotypic similarities, including greatly reduced exercise-stimulated glucose uptake and GLUT4 translocation. These findings indicate that NOX2 is a major myocellular ROS source, regulating glucose transport capacity during moderate-intensity exercise.
Reactive oxygen species (ROS) stimulate GLUT4-mediated glucose transport following contraction of isolated muscle, but it is not clear if this occurs in vivo. Here, the authors show in human volunteers that exercise induces ROS increase in muscle and, using loss of-function animal models, they demonstrate that NOX2 is a major ROS source required to stimulate glucose uptake during exercise.
Journal Article
مقدمة في الفن الإغريقي
يتناول الكتاب جذور الفن الاغريقي - العمارة مواد البناء وطرقها العصر(الارخي) حوالي 630-480 ق.م العصر الكلاسيكي 480-450 ق.م النصف الثاني من القرن الخامس قبل الميلاد القرن الرابع المذابح، الخزائن، تامباني الدائرية، البوابات المذابح الخزائن المباني الدائرية البوابات المسارح حلبات السباق أماكن الإجتماعات الأروقة ليسخاي مجالس البلديات البريتانيا البنيكس التيليستيرون بيوت الينابيع الجمنازيوم ومدارس الرياضة النصب الجنائزية والنذرية المنائر المنازل والفنادق والتحصينات ومخططات المدن.
BOOK
Long-term changes of tropospheric NO2 over megacities derived from multiple satellite instruments
Tropospheric NO2 , a key pollutant in particular in cities, has been measured from space since the mid-1990s by the GOME, SCIAMACHY, OMI, and GOME-2 instruments. These data provide a unique global long-term dataset of tropospheric pollution. However, the observations differ in spatial resolution, local time of measurement, viewing geometry, and other details. All these factors can severely impact the retrieved NO2 columns. In this study, we present three ways to account for instrumental differences in trend analyses of the NO2 columns derived from satellite measurements, while preserving the individual instruments' spatial resolutions. For combining measurements from GOME and SCIAMACHY into one consistent time series, we develop a method to explicitly account for the instruments' difference in ground pixel size (40 × 320 km2 vs. 30 × 60 km2 ). This is especially important when analysing NO2 changes over small, localised sources like, e.g. megacities. The method is based on spatial averaging of the measured earthshine spectra and extraction of a spatial pattern of the resolution effect. Furthermore, two empirical corrections, which summarise all instrumental differences by including instrument-dependent offsets in a fitted trend function, are developed. These methods are applied to data from GOME and SCIAMACHY separately, to the combined time series, and to an extended dataset comprising also GOME-2 and OMI measurements. All approaches show consistent trends of tropospheric NO2 for a selection of areas on both regional and city scales, for the first time allowing consistent trend analysis of the full time series at high spatial resolution. Compared to previous studies, the longer study period leads to significantly reduced uncertainties. We show that measured tropospheric NO2 columns have been strongly increasing over China, the Middle East, and India, with values over east-central China tripling from 1996 to 2011. All parts of the developed world, including Western Europe, the United States, and Japan, show significantly decreasing NO2 amounts in the same time period. On a megacity level, individual trends can be as large as +27.2 ± 3.9% yr-1 and +20.7 ± 1.9% yr-1 in Dhaka and Baghdad, respectively, while Los Angeles shows a very strong decrease of -6.00 ± 0.72% yr-1 . Most megacities in China, India, and the Middle East show increasing NO2 columns of +5 to 10% yr-1 , leading to a doubling to tripling within the study period.
Journal Article
Global patterns of phosphatase activity in natural soils
Soil phosphatase levels strongly control the biotic pathways of phosphorus (P), an essential element for life, which is often limiting in terrestrial ecosystems. We investigated the influence of climatic and soil traits on phosphatase activity in terrestrial systems using metadata analysis from published studies. This is the first analysis of global measurements of phosphatase in natural soils. Our results suggest that organic P (P
org
), rather than available P, is the most important P fraction in predicting phosphatase activity. Structural equation modeling using soil total nitrogen (TN), mean annual precipitation, mean annual temperature, thermal amplitude and total soil carbon as most available predictor variables explained up to 50% of the spatial variance in phosphatase activity. In this analysis, P
org
could not be tested and among the rest of available variables, TN was the most important factor explaining the observed spatial gradients in phosphatase activity. On the other hand, phosphatase activity was also found to be associated with climatic conditions and soil type across different biomes worldwide. The close association among different predictors like P
org
, TN and precipitation suggest that P recycling is driven by a broad scale pattern of ecosystem productivity capacity.
Journal Article