Exercise is essential in regulating energy metabolism and whole-body insulin sensitivity. To explore the exercise signaling network, we undertook a global analysis of protein phosphorylation in human ...skeletal muscle biopsies from untrained healthy males before and after a single high-intensity exercise bout, revealing 1,004 unique exercise-regulated phosphosites on 562 proteins. These included substrates of known exercise-regulated kinases (AMPK, PKA, CaMK, MAPK, mTOR), yet the majority of kinases and substrate phosphosites have not previously been implicated in exercise signaling. Given the importance of AMPK in exercise-regulated metabolism, we performed a targeted in vitro AMPK screen and employed machine learning to predict exercise-regulated AMPK substrates. We validated eight predicted AMPK substrates, including AKAP1, using targeted phosphoproteomics. Functional characterization revealed an undescribed role for AMPK-dependent phosphorylation of AKAP1 in mitochondrial respiration. These data expose the unexplored complexity of acute exercise signaling and provide insights into the role of AMPK in mitochondrial biochemistry.
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•Identification of the human muscle acute exercise signaling repertoire•Integrated AMPK substrate prediction in human muscle and cells•Targeted validation of exercise-regulated AMPK substrates•AKAP1 phosphorylation by AMPK that regulates mitochondrial respiration
Combining phosphoproteomics, biochemical, and bioinformatics approaches, Hoffman et al. perform a global analysis of exercise signaling in human skeletal muscle and reveal an interconnected network of kinases and AMPK substrates in response to exercise. Among these, AKAP1 is shown to regulate mitochondrial respiration via AMPK-dependent phosphorylation.
Isolating soil organic carbon (SOC) from soil inorganic carbon (SIC) is necessary to quantify SOC stocks and understanding SOC dynamics. Inorganic acids are commonly used to remove SIC and several ...methods have been developed to minimize the impacts these acid treatments have on the residual SOC. Negative impacts on the SOC pool, such as underestimating SOC stocks, are caused in part due to differences in the amount and composition of the organic matter pool. The effects of SIC removal on SOC are often ignored within experimental studies based on the assumption that soils from the same site do not differ enough to impact results. However, some experimental treatments, such as elevated atmospheric CO
2
, change SOC pools in both concentration and composition. Therefore, SIC removal can introduce different biases in control and treatment soils that may differ by method. In this work, we compare two commonly used methods of SIC removal on a set of soil samples from the same elevated CO
2
experiment. We use soils from the Nevada Desert Free Air Carbon dioxide Enrichment Facility to quantify how SIC removal with either acid washing or acid fumigation affect SOC in control and elevated CO
2
plots. We then use the difference in SOC (%C and δ
13
C) between methods to infer changes in the SOC pool driven by the elevated CO
2
treatment. Our results show that acid washing underestimates SOC relative to fumigation and that this difference is larger in soils from control CO
2
plots than elevated CO
2
plots. This may suggest that stabilization mechanisms sensitive to acidification, such as calcium bridging, are disrupted under elevated CO
2
treatment and therefore are less susceptible to SOC loss during acid washing. Our results present future research avenues for exploring the effects of acidic organic compounds, such as root exudates, on SOC stability in alkaline soils.
The increasing concentration of CO2 in the atmosphere is perturbing the global carbon (C) cycle, altering stocks of organic C, including soil organic matter (SOM). The effect of this disturbance on ...soils in arid ecosystems may differ from other ecosystems due to water limitation. In this study, we conducted a density fractionation on soils previously harvested from the Nevada Desert FACE Facility (NDFF) to understand how elevated atmospheric CO2 (eCO2) affects SOM stability. Soils from beneath the perennial shrub, Larrea tridentata, and from unvegetated interspace were subjected to a sodium polytungstate density fractionation to separate light, particulate organic matter (POM, <1.85 g/cm3) from heavier, mineral associated organic matter (MAOM, >1.85 g/cm3). These fractions were analyzed for organic C, total N, δ13C and δ15N, to understand the mechanisms behind changes. The heavy fraction was further analyzed by pyrolysis GC/MS to assess changes in organic compound composition. Elevated CO2 decreased POM‐C and MAOM‐C in soils beneath L. tridentata while interspace soils exhibited only a small increase in MAOM‐N. Analysis of δ13C revealed incorporation of new C into both POM and MAOM pools indicating eCO2 stimulated rapid turnover of both POM and MAOM. The largest losses of POM‐C and MAOM‐C observed under eCO2 occurred in soils 20–40 cm in depth, highlighting that belowground C inputs may be a significant driver of SOM decomposition in this ecosystem. Pyrolysis GC/MS analysis revealed a decrease in organic compound diversity in the MAOM fraction of L. tridentata soils, becoming more similar to interspace soils under eCO2. These results provide further evidence that MAOM stability may be compromised under disturbance and that SOC stocks in arid ecosystems are vulnerable under continued climate change.
We separated soils from a long‐term elevated atmospheric CO2 experiment into less‐stable and more‐stable pools of organic matter. We found a decrease in organic carbon from both pools in soils beneath the dominant perennial shrubs, Larrea tridentata, indicating that elevated CO2 stimulated decomposition. Using stable isotope analysis, we also show that new organic carbon is incorporated into the more‐stable pool of organic matter. These results demonstrate that elevated CO2 disrupts and possibly accelerates soil carbon cycling in arid ecosystems, leading to a loss of stable organic carbon in soils under some perennial vegetation cover types.
The increasing concentration of CO
in the atmosphere is perturbing the global carbon (C) cycle, altering stocks of organic C, including soil organic matter (SOM). The effect of this disturbance on ...soils in arid ecosystems may differ from other ecosystems due to water limitation. In this study, we conducted a density fractionation on soils previously harvested from the Nevada Desert FACE Facility (NDFF) to understand how elevated atmospheric CO
(eCO
) affects SOM stability. Soils from beneath the perennial shrub, Larrea tridentata, and from unvegetated interspace were subjected to a sodium polytungstate density fractionation to separate light, particulate organic matter (POM, <1.85 g/cm
) from heavier, mineral associated organic matter (MAOM, >1.85 g/cm
). These fractions were analyzed for organic C, total N, δ
C and δ
N, to understand the mechanisms behind changes. The heavy fraction was further analyzed by pyrolysis GC/MS to assess changes in organic compound composition. Elevated CO
decreased POM-C and MAOM-C in soils beneath L. tridentata while interspace soils exhibited only a small increase in MAOM-N. Analysis of δ
C revealed incorporation of new C into both POM and MAOM pools indicating eCO
stimulated rapid turnover of both POM and MAOM. The largest losses of POM-C and MAOM-C observed under eCO
occurred in soils 20-40 cm in depth, highlighting that belowground C inputs may be a significant driver of SOM decomposition in this ecosystem. Pyrolysis GC/MS analysis revealed a decrease in organic compound diversity in the MAOM fraction of L. tridentata soils, becoming more similar to interspace soils under eCO
. These results provide further evidence that MAOM stability may be compromised under disturbance and that SOC stocks in arid ecosystems are vulnerable under continued climate change.
Adrenergic receptors (ARs) are G protein-coupled receptors that are stimulated by catecholamines to induce a wide array of physiological effects across tissue types. Both α1- and β-ARs are found on ...cardiomyocytes and regulate cardiac contractility and hypertrophy through diverse molecular pathways. Acute activation of cardiomyocyte β-ARs increases heart rate and contractility as an adaptive stress response. However, chronic β-AR stimulation contributes to the pathobiology of heart failure. By contrast, mounting evidence suggests that α1-ARs serve protective functions that may mitigate the deleterious effects of chronic β-AR activation. Here, we will review recent studies demonstrating that α1- and β-ARs differentially regulate mitochondrial biogenesis and dynamics, mitochondrial calcium handling, and oxidative phosphorylation in cardiomyocytes. We will identify potential mechanisms of these actions and focus on the implications of these findings for the modulation of contractile function in the uninjured and failing heart. Collectively, we hope to elucidate important physiological processes through which these well-studied and clinically relevant receptors stimulate and fuel cardiac contraction to contribute to myocardial health and disease.
Aims
Tropical forests are increasingly threatened by edge effects as forest degradation and deforestation continues, compromising soil integrity, seedling regeneration capacity, and ecosystem ...services. Ninety-three percent of the last remaining forests of northern Ethiopia, which number 1022 in the South Gondar region of our study, are <16 ha and are protected because they have a Tewahido Orthodox Christian church at their center. The aim of this study was to determine the effects of human disturbance, forest size, distance from population center and other factors on the soil properties and nutrient status of sacred church forests. We also compared forest soil physical and chemical properties across land cover types in these forests.
Methods
We assessed the soil physical (water content and bulk density) and chemical (total carbon and nitrogen, available phosphorus, ammonium) properties of 40 sacred church forests across three spatial scales: within individual forests; among forests; and across land cover type (forest, forest edge-exterior,
Eucalyptus
plantation). We used distance from the edge within each forest to examine edge effects on soil nutrients.
Results
We found that nutrients and carbon decreased significantly from the interior to the outer edge of these forests and with forest size. Further, the soil of
Eucalyptus
plantations and areas outside of the forest were largely indistinguishable; both had significantly lower nutrient concentrations than sacred church forest soil.
Conclusion
Our research highlights the insidious impacts of edge effects and human disturbance on forest soils and the need for an integrated soil management program in the region that balances local needs with forest conservation. The conservation of these sacred church forests is important for maintaining regional soil nutrient status relative to agricultural lands and
Eucalyptus
plantations.
The sympathetic nervous system regulates numerous critical aspects of mitochondrial function in the heart through activation of adrenergic receptors (ARs) on cardiomyocytes. Mounting evidence ...suggests that α1-ARs, particularly the α1A subtype, are cardioprotective and may mitigate the deleterious effects of chronic β-AR activation by shared ligands. The mechanisms underlying these adaptive effects remain unclear. Here, we tested the hypothesis that α1A-ARs adaptively regulate cardiomyocyte oxidative metabolism in both the uninjured and infarcted heart.
We used high resolution respirometry, fatty acid oxidation (FAO) enzyme assays, substrate-specific electron transport chain (ETC) enzyme assays, transmission electron microscopy (TEM) and proteomics to characterize mitochondrial function comprehensively in the uninjured hearts of wild type and α1A-AR knockout mice and defined the effects of chronic β-AR activation and myocardial infarction on selected mitochondrial functions.
We found that isolated cardiac mitochondria from α1A-KO mice had deficits in fatty acid-dependent respiration, FAO, and ETC enzyme activity. TEM revealed abnormalities of mitochondrial morphology characteristic of these functional deficits. The selective α1A-AR agonist A61603 enhanced fatty-acid dependent respiration, fatty acid oxidation, and ETC enzyme activity in isolated cardiac mitochondria. The β-AR agonist isoproterenol enhanced oxidative stress in vitro and this adverse effect was mitigated by A61603. A61603 enhanced ETC Complex I activity and protected contractile function following myocardial infarction.
Collectively, these novel findings position α1A-ARs as critical regulators of cardiomyocyte metabolism in the basal state and suggest that metabolic mechanisms may underlie the protective effects of α1A-AR activation in the failing heart.
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•Cardiac mitochondria from α 1A-AR knockout mice had deficits in basal oxidative metabolism.•A selective α 1A-AR agonist improved basal oxidative metabolism in the heart.•A selective α 1A-AR agonist mitigated metabolic injury due to isoproterenol.•A selective α 1A-AR agonist protected against myocardial infarction.
Soil sampling at the landscape scale is increasingly in demand for assessing C sequestration projects in agroecosystems. Efforts to decrease sampling costs across large areas have thus far largely ...ignored improved soil harvesting tools as a means of decreasing sampling time and effort. Rigorous analysis of trade‐offs in speed and accuracy among soil harvesting methods is needed. Here, we compare two different methods of soil sampling soil, a standard push probe and a novel drill‐auger system, which were used to collect soils for analysis of total C by dry combustion. We designed sampling plots to compare soil C concentrations at increasing spatial scales to understand the difference in soil C concentrations between methods relative to spatial heterogeneity. We sampled two farms in Upstate New York, one conventional and one organically managed, to assess the impact of these methods across relevant farm practices. We found that probe and auger methods provide indistinguishable soil carbon estimates at both farms. The difference between paired probe and auger samples taken less than 0.15 m apart was 0.22%, an amount equivalent to the difference in C concentrations at points 2 m apart and less than the difference at points 10 m apart. Using the soil auger was up to three times faster than using the push probe—a saving of 7 h of sampling time to inventory the two farms studied. Lowering inventory cost is a critical step in demonstrating the feasibility of soil carbon sequestration as a component of climate smart agriculture. The results presented indicate that the drill‐auger system is preferable to the push probe method for farm‐scale soil carbon inventory.
Core Ideas
One component of lowering soil sampling cost is to increase the efficiency of in‐field sample collection.
Comparison of a soil probe to a drill‐auger demonstrates that C estimates are indistinguishable at the farm scale.
The difference between methods at <0.15 m is less than the spatial heterogeneity in %C at a distance of 2 or 10 m.
The drill‐auger is 1.75–3x faster than the probe that translates to an approximate savings of $1.18 per acre.
Considering the trade‐offs of sampling methods can save significant time and resources in large‐scale projects.
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