Signalling role of skeletal muscle during exercise

Abstract Upon acute exercise skeletal muscle is immediately and heavily recruited, while other organs appear to play only a minor role during exercise. These other organs show significant changes and improvements in function, although they are not directly targeted by exercise. These improvements suggest that skeletal muscle can communicate with other organs. In the past fifteen years it became clear that skeletal muscle produces and secretes a variety of signalling proteins that are able to interact and communicate with other organs. These signalling proteins are called myokines and are likely the link between exercising muscle and the rest of the body. The aim of the research presented this thesis is to study the signalling role of skeletal muscle during exercise and to gain further insight in the local molecular changes in skeletal muscle induced by exercise. In the first part of this thesis the focus was on the local changes induced in skeletal muscle by acute exercise and exercise training. The aim was to gain more insight in the molecular basis of exercise-induced changes in skeletal muscle. First we performed a microarray analysis on human muscle biopsies taken from endurance, resistance and combined exercise training interventions. We showed that despite a substantial overlap between the three exercise training types, each of the exercise training types had an unique gene expression print. The gene expression print found in combined exercise training lacked some specific oxidative and PPAR related components compared to the gene expression print found in endurance exercise training. For acute exercise microarray analysis was performed on muscle biopsies taken before and after an one-legged cycling intervention from resting and exercising skeletal muscle. Results showed that acute exercise induced large gene expression changes in active skeletal muscle. Furthermore, results showed that acute exercise also induced gene expression changes in resting skeletal muscle and that these changes were likely systemically induced via free fatty acids. In the second part of this thesis the focus was on the signalling role of skeletal muscle during exercise. Secretome analysis was performed on the microarrays of the muscle biopsies taken before and after the one-legged cycling intervention. This secretome analysis resulted in a list of putative myokines of which a selection was measured in the plasma. These plasma measurements showed that CCL2 (MCP-1) and CX3CL1 (Fractalkine) increased plasma levels during acute exercise. The findings of the one-legged cycling study furthermore showed that Angptl4 mRNA levels were higher in the resting leg compared to the exercising leg. Follow-up studies using cell culture and mice models revealed that Angptl4 levels were increased in the resting leg via free fatty acids that activated PPARs. In the exercising leg the increased Angptl4 levels were inhibited via AMPK activation. This resulted in an influx of triglyceride derived fatty acids in the exercising, but not in the resting skeletal muscle. In conclusion, we showed that exercise not only elicits molecular changes in active or trained skeletal muscle, but also in non-active organs such as resting skeletal muscle. Furthermore, we were able to identify several myokines produced by skeletal muscle during exercise, of which CCL2, CX3CL1 and Angptl4 were the most promising. CCL2, CX3CL1 and Angptl4 all increased plasma levels during acute exercise. It remains unclear what the systemic role is of these myokines. For Angptl4 we were able to provide more insight in the mechanism and local functioning during exercise. We concluded that Angptl4 is important in the substrate distribution during exercise. From the results presented this thesis we conclude that skeletal muscle has an important signalling role during exercise, but that it remains unclear how important this signalling role is systemically.</p

A portable infrared laser spectrometer for flux measurements of trace gases at the geosphere-atmosphere interface

International audienceA portable infrared laser absorption spectrometer named SPIRIT (SPectrom'etre Infra-Rouge In situ Troposph'erique) has been set up for the simultaneous flux measurements of trace gases at the geosphere-atmosphere interface. It uses a continuous wave distributed feedback room temperature quantum cascade laser and a patented new optical multi-pass cell. The aim of SPIRIT field studies is to get a better understanding of land and water bodies to atmosphere exchange mechanisms of greenhouse gases (GHG). The analytical procedures to derive concentrations and fluxes are described, as well as the performances of the instrument under field conditions. The ability of SPIRIT to assess space and time dependence emissions of two GHG--nitrous oxide (N2O) and methane (CH4)--for different types of ecosystems is demonstrated through in situ measurements on peatland, on fertilized soil, and on water body systems. The objectives of these investigations and preliminary significant results are reported

Reformulation of the strong-field approximation for light-matter interactions

We consider the interaction of hydrogen-like atoms with a strong laser field and show that the strong field approximation and all its variants may be grouped into a set of families of approximation schemes. This is done by introducing an ansatz describing the electron wave packet as the sum of the initial state wave function times a phase factor and a function which is the perturbative solution in the Coulomb potential of an inhomogeneous time-dependent Schr\"odinger equation. It is the phase factor that characterizes a given family. In each of these families, the velocity and length gauge version of the approximation scheme lead to the same results at each order in the Coulomb potential. By contrast, irrespective of the gauge, approximation schemes belonging to different families give different results. Furthermore, this new formulation of the strong field approximations allows us to gain deeper insight into the validity of the strong field approximation schemes. In particular, we address two important questions: the role of the Coulomb potential in the output channel and the convergence of the perturbative series in the Coulomb potential. In all the physical situations we consider here, our results are compared to those obtained by solving numerically the time-dependent Schr\"odinger equation.Comment: 19 pages, 9 figures, submitted for publicatio

Coincidence Angular Correlation in Electron Impact Single or Double Ionisation of Atoms and Molecules

Experimental results obtained with our multi-parameter multi-coincidence spectrometer are presented for the (e,3e) double ionisation of Ar and (e,2e) single ionisation of small molecules. The (e,3e) measurements are discussed in terms of competition between the two double ionisation processes present under the chosen kinematics, and qualitative conclusions are given. The results for the ionisation of H2 and the outer orbital of N2 are compared with the predictions of the most elaborate available theoretical models for description of the molecular ionisation process. Overall reasonable agreement is observed and tentative interpretations for the discrepancies are discussed

Pattern and Outcome of Chest Injuries at Bugando Medical Centre in Northwestern Tanzania.

Chest injuries constitute a continuing challenge to the trauma or general surgeon practicing in developing countries. This study was conducted to outline the etiological spectrum, injury patterns and short term outcome of these injuries in our setting. This was a prospective study involving chest injury patients admitted to Bugando Medical Centre over a six-month period from November 2009 to April 2010 inclusive. A total of 150 chest injury patients were studied. Males outnumbered females by a ratio of 3.8:1. Their ages ranged from 1 to 80 years (mean = 32.17 years). The majority of patients (72.7%) sustained blunt injuries. Road traffic crush was the most common cause of injuries affecting 50.7% of patients. Chest wall wounds, hemothorax and rib fractures were the most common type of injuries accounting for 30.0%, 21.3% and 20.7% respectively. Associated injuries were noted in 56.0% of patients and head/neck (33.3%) and musculoskeletal regions (26.7%) were commonly affected. The majority of patients (55.3%) were treated successfully with non-operative approach. Underwater seal drainage was performed in 39 patients (19.3%). One patient (0.7%) underwent thoracotomy due to hemopericardium. Thirty nine patients (26.0%) had complications of which wound sepsis (14.7%) and complications of long bone fractures (12.0%) were the most common complications. The mean LOS was 13.17 days and mortality rate was 3.3%. Using multivariate logistic regression analysis, associated injuries, the type of injury, trauma scores (ISS, RTS and PTS) were found to be significant predictors of the LOS (P < 0.001), whereas mortality was significantly associated with pre-morbid illness, associated injuries, trauma scores (ISS, RTS and PTS), the need for ICU admission and the presence of complications (P < 0.001). Chest injuries resulting from RTCs remain a major public health problem in this part of Tanzania. Urgent preventive measures targeting at reducing the occurrence of RTCs is necessary to reduce the incidence of chest injuries in this region

A database of aircraft measurements of carbon monoxide (CO) with high temporal and spatial resolution during 2011–2021

To understand tropospheric air pollution at regional and global scales, the SPIRIT (SPectromètre Infra-Rouge In situ Toute altitude) airborne instrument was developed and used on aircraft to measure volume mixing ratios of carbon monoxide (CO), an important indicator of air pollution, during the last decade. SPIRIT provides high-quality CO measurements with 1σ precision of 0.3 ppbv at a time resolution of 1.6 s thanks to the coupling of a quantum cascade laser to a Robert optical multi-pass cell. It can be operated on different aircraft such as Falcon-20 and ATR-42 from the German Aerospace Agency (DLR) and from SAFIRE (CNRS-CNES-Météo France). With support from various projects, measurements were taken for more than 200 flight hours over three continents (Europe, Asia, and Africa), including two intercontinental transects (Europe–Asia and Europe–Africa). Levels of CO and its spatial distribution are briefly discussed and compared between different regions/continents. CO generally decreases with altitude except in some cases, indicating the important contribution of long-distance transport to CO levels. A 3D trajectory mapped by CO level was plotted for each flight and is presented in this study (which includes a Supplement). The database is archived in the AERIS database (https://doi.org/10.25326/440), the French national center for atmospheric observations (Catoire et al., 2023). In addition, it could help to validate model performance and satellite measurements. For instance, the database covers measurements at high-latitude regions (i.e., Kiruna, Sweden, 68∘ N), where satellite measurements are still challenging, and at low-latitude regions (West Africa and Southeast Asia), where in situ data are scarce and satellites need more validation by airborne measurements.</p

Cytokine responses to repeated, prolonged walking in lean versus overweight/obese individuals.

OBJECTIVES: Obesity is characterized by a pro-inflammatory state, which plays a role in the pathogenesis of metabolic and cardiovascular disease. An exercise bout causes a transient increase in pro-inflammatory cytokines, whilst training has anti-inflammatory effects. No previous study examined whether the exercise-induced increase in pro-inflammatory cytokines is altered with repeated prolonged exercise bouts and whether this response differs between lean and overweight/obese individuals. DESIGN: Lean (n=25, BMI 22.9±1.5kg/m2) and age-/sex-matched overweight/obese (n=25; BMI 27.9±2.4kg/m2) individuals performed walking exercise for 30, 40 or 50km per day on four consecutive days (distances similar between groups). METHODS: Circulating cytokines (IL-6, IL-10, TNF-α, IL-1β and IL-8) were examined at baseline and <30min after the finish of each exercise day. RESULTS: At baseline, no differences in circulating cytokines were present between groups. In response to prolonged exercise, all cytokines increased on day 1 (IL-1β: P=0.02; other cytokines: P<0.001). IL-6 remained significantly elevated during the 4 exercise days, when compared to baseline. IL-10, TNF-α, IL-1β and IL-8 returned to baseline values from exercise day 2 (IL-10, IL-1β, IL-8) or exercise day 3 (TNF-α) onward. No significant differences were found between groups for all cytokines, except IL-8 (Time*Group Interaction P=0.02). CONCLUSIONS: These data suggest the presence of early adaptive mechanisms in response to repeated prolonged walking, demonstrated by attenuated exercise-induced elevations in cytokines on consecutive days that occur similar in lean and overweight/obese individuals

Bounds on the growth of high Sobolev norms of solutions to 2D Hartree Equations

In this paper, we consider Hartree-type equations on the two-dimensional torus and on the plane. We prove polynomial bounds on the growth of high Sobolev norms of solutions to these equations. The proofs of our results are based on the adaptation to two dimensions of the techniques we previously used to study analogous problems on $S^1$, and on $\mathbb{R}$.Comment: 38 page