Age- and activity-related differences in the abundance of Myosin essential and regulatory light chains in human muscle

Traditional methods for phenotyping skeletal muscle (e.g., immunohistochemistry) are labor-intensive and ill-suited to multixplex analysis, i.e., assays must be performed in a series. Addressing these concerns represents a largely unmet research need but more comprehensive parallel analysis of myofibrillar proteins could advance knowledge regarding age- and activity-dependent changes in human muscle. We report a label-free, semi-automated and time efficient LC-MS proteomic workflow for phenotyping the myofibrillar proteome. Application of this workflow in old and young as well as trained and untrained human skeletal muscle yielded several novel observations that were subsequently verified by multiple reaction monitoring (MRM).We report novel data demonstrating that human ageing is associated with lesser myosin light chain 1 content and greater myosin light chain 3 content, consistent with an age-related reduction in type II muscle fibers. We also disambiguate conflicting data regarding myosin regulatory light chain, revealing that age-related changes in this protein more closely reflect physical activity status than ageing per se. This finding reinforces the need to control for physical activity levels when investigating the natural process of ageing. Taken together, our data confirm and extend knowledge regarding age- and activity-related phenotypes. In addition, the MRM transitions described here provide a methodological platform that can be fine-tuned to suite multiple research needs and thus advance myofibrillar phenotyping

The basic chemistry of exercise-induced DNA oxidation:oxidative damage, redox signalling and their interplay

Acute exercise increases reactive oxygen and nitrogen species generation. This phenomenon is associated with two major outcomes: (1) redox signalling and (2) macromolecule damage. Mechanistic knowledge of how exercise-induced redox signalling and macromolecule damage are interlinked is limited. This review focuses on the interplay between exercise-induced redox signalling and DNA damage, using hydroxyl radical (·OH) and hydrogen peroxide (H2O2) as exemplars. It is postulated that the biological fate of H2O2 links the two processes and thus represents a bifurcation point between redox signalling and damage. Indeed, H2O2 can participate in two electron signalling reactions but its diffusion and chemical properties permit DNA oxidation following reaction with transition metals and ·OH generation. It is also considered that the sensing of DNA oxidation by repair proteins constitutes a non-canonical redox signalling mechanism. Further layers of interaction are provided by the redox regulation of DNA repair proteins and their capacity to modulate intracellular H2O2 levels. Overall, exercise-induced redox signalling and DNA damage may be interlinked to a greater extent than was previously thought but this requires further investigation

Influence of vitamin C and vitamin E on redox signalling:implications for exercise adaptations

The exogenous antioxidants vitamin C (ascorbate) and vitamin E (α-tocopherol) often blunt favourable cell signalling responses to exercise, suggesting that redox signalling contributes to exercise adaptations. Current theories posit that this antioxidant paradigm interferes with redox signalling by attenuating exercise-induced reactive oxygen species (ROS) and reactive nitrogen species (RNS) generation. The well-documented in vitro antioxidant actions of ascorbate and α-tocopherol and characterisation of the type and source of the ROS/RNS produced during exercise theoretically enables identification of the redox-dependent mechanism responsible for the blunting of favourable cell signalling responses to exercise. This review aimed to apply this reasoning to determine how the aforementioned antioxidants might attenuate exercise-induced ROS/RNS production. The principal outcomes of this analysis are (1) neither antioxidant is likely to attenuate nitric oxide signalling either directly (reaction with nitric oxide) or indirectly (reaction with derivatives, e.g. peroxynitrite) (2) neither antioxidant reacts appreciably with hydrogen peroxide, a key effector of redox signalling (3) ascorbate but not α-tocopherol has the capacity to attenuate exercise-induced superoxide generation and (4) alternate mechanisms, namely pro-oxidant side reactions and/or reduction of bioactive oxidised macromolecule adducts, are unlikely to interfere with exercise-induced redox signalling. Out of all the possibilities considered, ascorbate mediated suppression of superoxide generation with attendant implications for hydrogen peroxide signalling is arguably the most cogent explanation for blunting of favourable cell signalling responses to exercise. However, this mechanism is dependent on ascorbate accumulating at sites rich in NADPH oxidases, principal contributors to contraction mediated superoxide generation, and outcompeting nitric oxide and superoxide dismutase isoforms. The major conclusions of this review are: (1) direct evidence for interference of ascorbate and α-tocopherol with exercise-induced ROS/RNS production is lacking (2) theoretical analysis reveals that both antioxidants are unlikely to have a major impact on exercise-induced redox signalling and (3) it is worth considering alternate redox-independent mechanisms

Perception of carbohydrate availability augments high-intensity intermittent exercise capacity under sleep-low train low conditions

The authors tested the hypothesis that perception of carbohydrate (CHO) availability augments exercise capacity in conditions of reduced CHO availability. Nine males completed a sleep-low train model comprising evening glycogen-depleting cycling followed by an exhaustive cycling protocol the next morning in the fasted state (30 min steady state at 95% lactate threshold followed by 1-min intervals at 80% peak power output until exhaustion). After the evening depletion protocol and prior to sleeping, subjects consumed (a) a known CHO intake of 6 g/kg body mass (TRAIN HIGH) or (b) a perceived comparable CHO intake but 0 g/kg body mass (PERCEPTION) or a known train-low condition of 0 g/kg body mass (TRAIN LOW). The TRAIN HIGH and PERCEPTION trials were conducted double blind. During steady state, average blood glucose and CHO oxidation were significantly higher in TRAIN HIGH (4.01 ± 0.56 mmol/L; 2.17 ± 0.70 g/min) versus both PERCEPTION (3.30 ± 0.57 mmol/L; 1.69 ± 0.64 g/min, p < .05) and TRAIN LOW (3.41 ± 0.74 mmol/L; 1.61 ± 0.59 g/min, p < .05). Exercise capacity was significantly different between all pairwise comparisons (p < .05), where TRAIN LOW (8 ± 8 min) < PERCEPTION (12 ± 6 min) < TRAIN HIGH (22 ± 9 min). Data demonstrate that perception of CHO availability augments high-intensity intermittent exercise capacity under sleep-low, train-low conditions, though this perception does not restore exercise capacity to that of CHO consumption. Such data have methodological implications for future research designs and may also have practical applications for athletes who deliberately practice elements of training in CHO-restricted states

Vitamin D supplementation does not improve human skeletal muscle contractile properties in insufficient young males

Vitamin D may be a regulator of skeletal muscle function, although human trials investigating this hypothesis are limited to predominantly elderly populations. We aimed to assess the effect of oral vitamin D3 in healthy young males upon skeletal muscle function

PGC‑1α alternative promoter (Exon 1b) controls augmentation of total PGC‑1α gene expression in response to cold water immersion and low glycogen availability

This investigation sought to determine whether post-exercise cold water immersion and low glycogen availability, separately and in combination, would preferentially activate either the Exon 1a or Exon 1b Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) promoter. Through a reanalysis of sample design, we identified that the systemic cold-induced augmentation of total PGC-1α gene expression observed previously (Allan et al. in J Appl Physiol 123(2):451–459, 2017) was largely a result of increased expression from the alternative promoter (Exon 1b), rather than canonical promoter (Exon 1a). Low glycogen availability in combination with local cooling of the muscle (Allan et al. in Physiol Rep 7(11):e14082, 2019) demonstrated that PGC-1α alternative promoter (Exon 1b) expression continued to rise at 3 h post-exercise in all conditions; whilst, expression from the canonical promoter (Exon 1a) decreased between the same time points (post-exercise–3 h post-exercise). Importantly, this increase in PGC-1α Exon 1b expression was reduced compared to the response of low glycogen or cold water immersion alone, suggesting that the combination of prior low glycogen and CWI post-exercise impaired the response in gene expression versus these conditions individually. Data herein emphasise the influence of post-exercise cooling and low glycogen availability on Exon-specific contro

Combating pancreatic cancer with PI3K pathway inhibitors in the era of personalised medicine

Pancreatic ductal adenocarcinoma (PDAC) is among the most deadly solid tumours. This is due to a generally late-stage diagnosis of a primarily treatment-refractory disease. Several large-scale sequencing and mass spectrometry approaches have identified key drivers of this disease and in doing so highlighted the vast heterogeneity of lower frequency mutations that make clinical trials of targeted agents in unselected patients increasingly futile. There is a clear need for improved biomarkers to guide effective targeted therapies, with biomarker-driven clinical trials for personalised medicine becoming increasingly common in several cancers. Interestingly, many of the aberrant signalling pathways in PDAC rely on downstream signal transduction through the mitogen-activated protein kinase and phosphoinositide 3-kinase (PI3K) pathways, which has led to the development of several approaches to target these key regulators, primarily as combination therapies. The following review discusses the trend of PDAC therapy towards molecular subtyping for biomarker-driven personalised therapies, highlighting the key pathways under investigation and their relationship to the PI3K pathway

Defective antifungal immunity in patients with COVID-19

The COVID-19 pandemic has placed a huge strain on global healthcare and been a significant cause of increased morbidity and mortality, particularly in atrisk populations. This disease attacks the respiratory systems and causes significant immune dysregulation in affected patients creating a perfect opportunity for the development of invasive fungal disease (IFD). COVID-19 infection can instill a significant, poorly regulated pro-inflammatory response. Clinically induced immunosuppression or pro-inflammatory damage to mucosa facilitate the development of IFD and Aspergillus, Mucorales, and Candida infections have been regularly reported throughout the COVID-19 pandemic. Corticosteroids and immune modulators are used in the treatment of COVID-19. Corticosteroid use is also a risk factor for IFD, but not the only reason for IFD in COVID -19 patients. Specific dysregulation of the immune system through functional exhaustion of Natural killer (NK) cells and T cells has been observed in COVID-19 through the expression of the exhaustion markers NK-G2A and PD-1. Reduced fungicidal activity of neutrophils from COVID-19 patients indicates that immune dysfunction/imbalance are important risk factors for IFD. The COVID-19 pandemic has significantly increased the at risk population for IFD. Even if the incidence of IFD is relatively low, the size of this new at-risk population will result in a substantial increase in the overall, annual number of IFD cases. It is important to understand how and why certain patients with COVID-19 developed increased susceptibility to IFD, as this will improve our understanding of risk of IFD in the face of future pandemics but also in a clinical era of increased clinical immuno-suppression/modulation

Parkinson's disease brain mitochondria have impaired respirasome assembly, age-related increases in distribution of oxidative damage to mtDNA and no differences in heteroplasmic mtDNA mutation abundance

Abstract Background Sporadic Parkinson's disease (sPD) is a nervous system-wide disease that presents with a bradykinetic movement disorder and is frequently complicated by depression and cognitive impairment. sPD likely has multiple interacting causes that include increased oxidative stress damage to mitochondrial components and reduced mitochondrial bioenergetic capacity. We analyzed mitochondria from postmortem sPD and CTL brains for evidence of oxidative damage to mitochondrial DNA (mtDNA), heteroplasmic mtDNA point mutations and levels of electron transport chain proteins. We sought to determine if sPD brains possess any mtDNA genotype-respiratory phenotype relationships. Results Treatment of sPD brain mtDNA with the mitochondrial base-excision repair enzyme 8-oxyguanosine glycosylase-1 (hOGG1) inhibited, in an age-dependent manner, qPCR amplification of overlapping ~2 kbase products; amplification of CTL brain mtDNA showed moderate sensitivity to hOGG1 not dependent on donor age. hOGG1 mRNA expression was not different between sPD and CTL brains. Heteroplasmy analysis of brain mtDNA using Surveyor nuclease® showed asymmetric distributions and levels of heteroplasmic mutations across mtDNA but no patterns that statistically distinguished sPD from CTL. sPD brain mitochondria displayed reductions of nine respirasome proteins (respiratory complexes I-V). Reduced levels of sPD brain mitochondrial complex II, III and V, but not complex I or IV proteins, correlated closely with rates of NADH-driven electron flow. mtDNA levels and PGC-1α expression did not differ between sPD and CTL brains. Conclusion PD brain mitochondria have reduced mitochondrial respiratory protein levels in complexes I-V, implying a generalized defect in respirasome assembly. These deficiencies do not appear to arise from altered point mutational burden in mtDNA or reduction of nuclear signaling for mitochondrial biogenesis, implying downstream etiologies. The origin of age-related increases in distribution of oxidative mtDNA damage in sPD but not CTL brains is not clear, tracks with but does not determine the sPD phenotype, and may indicate a unique consequence of aging present in sPD that could contribute to mtDNA deletion generation in addition to mtDNA replication, transcription and sequencing errors. sPD frontal cortex experiences a generalized bioenergetic deficiency above and beyond aging that could contribute to mood disorders and cognitive impairments.</p