Aim
The aim of this study was to investigate the effects of 4 consecutive simulated night shifts on glucose homeostasis, mitochondrial function and central and peripheral rhythmicities compared with ...a simulated day shift schedule.
Methods
Seventeen healthy adults (8M:9F) matched for sleep, physical activity and dietary/fat intake participated in this study (night shift work n = 9; day shift work n = 8). Glucose tolerance and insulin sensitivity before and after 4 nights of shift work were measured by an intravenous glucose tolerance test and a hyperinsulinaemic euglycaemic clamp respectively. Muscles biopsies were obtained to determine insulin signalling and mitochondrial function. Central and peripheral rhythmicities were assessed by measuring salivary melatonin and expression of circadian genes from hair samples respectively.
Results
Fasting plasma glucose increased (4.4 ± 0.1 vs. 4.6 ± 0.1 mmol L−1; P = .001) and insulin sensitivity decreased (25 ± 7%, P < .05) following the night shift, with no changes following the day shift. Night shift work had no effect on skeletal muscle protein expression (PGC1α, UCP3, TFAM and mitochondria Complex II‐V) or insulin‐stimulated pAkt Ser473, pTBC1D4Ser318 and pTBC1D4Thr642. Importantly, the metabolic changes after simulated night shifts occurred despite no changes in the timing of melatonin rhythmicity or hair follicle cell clock gene expression across the wake period (Per3, Per1, Nr1d1 and Nr1d2).
Conclusion
Only 4 days of simulated night shift work in healthy adults is sufficient to reduce insulin sensitivity which would be expected to increase the risk of T2D.
Wind gusts represent one of the main natural hazards due to their increasing socioeconomic and environmental impacts on, for example, human safety, maritime–terrestrial–aviation activities, ...engineering and insurance applications, and energy production. However, the existing scientific studies focused on observed wind gusts are relatively few compared to those on mean wind speed. In Australia, previous studies found a slowdown of near-surface mean wind speed, termed “stilling,” but a lack of knowledge on the multidecadal variability and trends in the magnitude (wind speed maxima) and frequency (exceeding the 90th percentile) of wind gusts exists. A new homogenized daily peak wind gusts (DPWG) dataset containing 548 time series across Australia for 1941–2016 is analyzed to determine long-term trends in wind gusts. Here we show that both the magnitude and frequency of DPWG declined across much of the continent, with a distinct seasonality: negative trends in summer–spring–autumn and weak negative or nontrending (even positive) trends in winter. We demonstrate that ocean–atmosphere oscillations such as the Indian Ocean dipole and the southern annular mode partly modulate decadal-scale variations of DPWG. The long-term declining trend of DPWG is consistent with the “stilling” phenomenon, suggesting that global warming may have reduced Australian wind gusts.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Diabetic cardiomyopathy describes heart disease in patients with diabetes who have no other cardiac conditions but have a higher risk of developing heart failure. Specific therapies to treat the ...diabetic heart are limited. A key mechanism involved in the progression of diabetic cardiomyopathy is dysregulation of cardiac energy metabolism. The aim of this study was to determine if increasing the expression of medium-chain acyl-coenzyme A dehydrogenase (MCAD; encoded by
Acadm
), a key regulator of fatty acid oxidation, could improve the function of the diabetic heart. Male mice were administered streptozotocin to induce diabetes, which led to diastolic dysfunction 8 weeks post-injection. Mice then received cardiac-selective adeno-associated viral vectors encoding MCAD (rAAV6:MCAD) or control AAV and were followed for 8 weeks. In the non-diabetic heart, rAAV6:MCAD increased MCAD expression (mRNA and protein) and increased
Acadl
and
Acadvl
, but an increase in MCAD enzyme activity was not detectable. rAAV6:MCAD delivery in the diabetic heart increased MCAD mRNA expression but did not significantly increase protein, activity, or improve diabetes-induced cardiac pathology or molecular metabolic and lipid markers. The uptake of AAV viral vectors was reduced in the diabetic
versus
non-diabetic heart, which may have implications for the translation of AAV therapies into the clinic.
Key messages
The effects of increasing MCAD in the diabetic heart are unknown.
Delivery of rAAV6:MCAD increased MCAD mRNA and protein, but not enzyme activity, in the non-diabetic heart.
Independent of MCAD enzyme activity, rAAV6:MCAD increased
Acadl
and
Acadvl
in the non-diabetic heart.
Increasing MCAD cardiac gene expression alone was not sufficient to protect against diabetes-induced cardiac pathology.
AAV transduction efficiency was reduced in the diabetic heart, which has clinical implications.
-Reactive oxygen species (ROS) produced in skeletal muscle may play a role in potentiating the beneficial responses to exercise; however, the effects of exercise-induced ROS on insulin action and ...protein signaling in humans has not been fully elucidated. Seven healthy, recreationally active participants volunteered for this double-blind, randomized, repeated-measures crossover study. Exercise was undertaken with infusion of saline (CON) or the antioxidant N-acetylcysteine (NAC) to attenuate ROS. Participants performed two 1-h cycling exercise sessions 7-14 days apart, 55 min at 65% V̇o2peak plus 5 min at 85%V̇o2peak, followed 3 h later by a 2-h hyperinsulinemic euglycemic clamp (40 mIU·min(-1)·m(2)) to determine insulin sensitivity. Four muscle biopsies were taken on each trial day, at baseline before NAC infusion (BASE), after exercise (EX), after 3-h recovery (REC), and post-insulin clamp (PI). Exercise, ROS, and insulin action on protein phosphorylation were evaluated with immunoblotting. NAC tended to decrease postexercise markers of the ROS/protein carbonylation ratio by -13.5% (P = 0.08) and increase the GSH/GSSG ratio twofold vs. CON (P < 0.05). Insulin sensitivity was reduced (-5.9%, P < 0.05) by NAC compared with CON without decreased phosphorylation of Akt or AS160. Whereas p-mTOR was not significantly decreased by NAC after EX or REC, phosphorylation of the downstream protein synthesis target kinase p70S6K was blunted by 48% at PI with NAC compared with CON (P < 0.05). We conclude that NAC infusion attenuated muscle ROS and postexercise insulin sensitivity independent of Akt signaling. ROS also played a role in normal p70S6K phosphorylation in response to insulin stimulation in human skeletal muscle.
Fuel cells offer great promise for portable electricity generation, but their use is currently limited by their low durability, excessive operating temperatures, and expensive precious metal ...electrodes. It is therefore essential to develop fuel cell systems that can perform effectively using more robust electrolyte materials, at reasonable temperatures, with lower‐cost electrodes. Recently, proton exchange membrane fuel cells have attracted attention due to their generally favorable chemical stability and quick start‐up times. However, in most membrane materials, water is required for proton conduction, severely limiting operational temperatures. Here, for the first time it is demonstrated that when acidified, PAF‐1 can conduct protons at high temperatures, via a unique framework diffusion mechanism. It shows that this acidified PAF‐1 material can be pressed into pellets with high proton conduction properties even at high temperatures and pellet thickness, highlighting the processibility, and ease of use of this material. Furthermore, a fuel cell is shown with high power density output is possible using a non‐precious metal copper electrode. Acid‐doped PAF‐1 therefore represents a significant step forward in the potential for a broad‐purpose fuel cell due to it being cheap, robust, efficient, and easily processible.
In this work, an acidified porous aromatic framework, acid@PAF‐1, exhibits excellent proton conductivity at high temperatures is demonstrated. Moreover, the H3PO4@PAF‐1 can be used as an electrolyte coupled with a non‐precious metal copper electrode in a fuel cell that demonstrates excellent performance at high temperatures.
Continental lacustrine laminites deposited in low latitudes have been examined from the Devonian and Torridonian (Mesoproterozoic) strata of northern Scotland to investigate the consistency of ...sunspot periodicity through geological time. The thicknesses of 2448 annual laminae were measured from the Middle Devonian (c. 388 Ma) Achanarras Limestone Member, Lower Caithness Flagstone Group, and of 2821 laminae from the Mesoproterozoic (1.2 Ga) Poll a'Mhuilt Member of the Stoer Group. Time-series analysis resolved periodicities of 13.8 and 13.9 years in the complete Devonian and Mesoproterozoic datasets respectively. When sedimentological variance was considered and the data were examined as evolutive spectra those sections consisting of the most robust data consistently yielded periodicities between 8.6 and 13.7 years for the Devonian section and 9.2 and 10.6 years for the Mesoproterozoic section. These correspond well to Schwabe cycles. Evidence for the presence of the longer Hale cycles (20 years) was also recognized in the Devonian time series. The sunspot periodicities identified within the Devonian and Mesoproterozoic show little variance from published examples from the Quaternary and Eocene and therefore provide evidence for the consistency of solar processes and solar-atmospheric interactions for the past 1.2 Ga.
State of the climate in 2011 BLUNDEN, J; ARNDT, D.S
Bulletin of the American Meteorological Society,
07/2012, Letnik:
93, Številka:
7
Journal Article
Recenzirano
Odprti dostop
The following ECVs, included in this edition, are considered "fully monitored", such that they are observed and analyzed across much of the world, with a sufficiently long-term dataset that has ...peer-reviewed documentation: * Atmospheric Surface: air temperature, precipitation, air pressure, water vapor. * Atmospheric Upper Air: earth radiation budget, temperature, water vapor, cloud properties. * Atmospheric Composition: carbon dioxide, methane, ozone, nitrous oxide, chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, sulfur hexafluorides, perflurocarbons, aerosols. * Ocean Surface: temperature, salinity, sea level, sea ice, current, ocean color. * Ocean Subsurface: temperature, salinity. * Terrestrial: snow and ice cover, albedo. ...we have often commented that the State of the Climate series not only offers annual snapshots of the climate's state, but also of our capacity to monitor it.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Antioxidant supplements are commonly consumed by endurance athletes to minimize exercise-induced oxidative stress, with the intention of enhancing recovery and improving performance. There are ...numerous commercially available nutritional supplements that are targeted to athletes and health enthusiasts that allegedly possess antioxidant properties. However, most of these compounds are poorly investigated with respect to their in vivo redox activity and efficacy in humans. Therefore, this review will firstly provide a background to endurance exercise-related redox signalling and the subsequent adaptations in skeletal muscle and vascular function. The review will then discuss commonly available compounds with purported antioxidant effects for use by athletes. N-acetyl cysteine may be of benefit over the days prior to an endurance event; while chronic intake of combined 1000 mg vitamin C + vitamin E is not recommended during periods of heavy training associated with adaptations in skeletal muscle. Melatonin, vitamin E and α-lipoic acid appear effective at decreasing markers of exercise-induced oxidative stress. However, evidence on their effects on endurance performance are either lacking or not supportive. Catechins, anthocyanins, coenzyme Q10 and vitamin C may improve vascular function, however, evidence is either limited to specific sub-populations and/or does not translate to improved performance. Finally, additional research should clarify the potential benefits of curcumin in improving muscle recovery post intensive exercise; and the potential hampering effects of astaxanthin, selenium and vitamin A on skeletal muscle adaptations to endurance training. Overall, we highlight the lack of supportive evidence for most antioxidant compounds to recommend to athletes.
Exercise is a robust stimulus for mitochondrial adaptations in skeletal muscle which consequently plays a central role in enhancing metabolic health. Despite this, the precise molecular events that ...underpin these beneficial effects remain elusive. In this review, we discuss molecular signals generated during exercise leading to altered mitochondrial morphology and dynamics. In particular, we focus on the interdependence between reactive oxygen species (ROS) and redox homeostasis, the sensing of cellular bioenergetic status via 5' adenosine monophosphate (AMP)-activated protein kinase (AMPK), and the regulation of mitochondrial fission and fusion. Precisely how exercise regulates the network of these responses and their effects on mitochondrial dynamics is not fully understood at present. We highlight the limitations that exist with the techniques currently available, and discuss novel molecular tools to potentially advance the fields of redox biology and mitochondrial bioenergetics. Ultimately, a greater understanding of these processes may lead to novel mitochondria-targeted therapeutic strategies to augment or mimic exercise in order to attenuate or reverse pathophysiology.
Mitochondrial respiration results in an electrochemical proton gradient, or protonmotive force (pmf), across the mitochondrial inner membrane. The pmf is a form of potential energy consisting of ...charge (∆ψm) and chemical (∆pH) components, that together drive ATP production. In a process called uncoupling, proton leak into the mitochondrial matrix independent of ATP production dissipates the pmf and energy is lost as heat. Other events can directly dissipate the pmf independent of ATP production as well, such as chemical exposure or mechanisms involving regulated mitochondrial membrane electrolyte transport. Uncoupling has defined roles in metabolic plasticity and can be linked through signal transduction to physiologic events. In the latter case, the pmf impacts mitochondrial reactive oxygen species (ROS) production. Although capable of molecular damage, ROS also have signaling properties that depend on the timing, location, and quantity of their production. In this review, we provide a general overview of mitochondrial ROS production, mechanisms of uncoupling, and how these work in tandem to affect physiology and pathologies, including obesity, cardiovascular disease, and immunity. Overall, we highlight that isolated bioenergetic models—mitochondria and cells—only partially recapitulate the complex link between the pmf and ROS signaling that occurs in vivo.
Display omitted
•Mitochondria use a protonmotive force (pmf) for energy transduction.•The pmf and reactive oxygen species (ROS) production are linked.•Dissipating the pmf, or uncoupling, can decrease ROS production.•Uncoupling can affect ROS signaling and diverse physiologic outputs.
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