Compromised respiratory adaptation and thermoregulation in aging and age-related diseases

Antioxidant properties of lactic acid bacteria isolated from traditional fermented yak milk and their probiotic effects on the oxidative senescence of Caenorhabditis elegans

The objectives of the current study were to screen antioxidant lactic acid bacteria (LAB) strains isolated from traditionally fermented Tibetan yak milk, and to evaluate their probiotic effects on the oxidative senescence of Caenorhabditis elegans (C. elegans). A total of 10 LAB isolates were assessed for their antioxidant activity by in vitro assays, and three strains with high activity were selected for an investigation of their probiotic functions in C. elegans. The results indicated that Lactobacillus plantarum As21 showed high anti-oxidant capacity and had a high survival rate (64%) in a simulated gastrointestinal tract. The lifespan of C. elegans treated with As21 was increased by 34.5% compared to the control group. Strain As21 also showed improved motility and enhanced resistance to heat stress and H₂O₂ stimulation in C. elegans. Moreover, treatment with As21 reduced the production of age-related reactive oxygen species (ROS) and malondialdehyde (MDA) damage and promoted the production of the antioxidants superoxide dismutase (SOD), catalase (CAT) and glutathione GSH. These results suggest that Lactobacillus plantarum strain As21 could be a potential probiotic strain for retarding ageing and could be used in functional foods.

Local hyperthermia therapy induces browning of white fat and treats obesity

Beige fat plays key roles in the regulation of systemic energy homeostasis; however, detailed mechanisms and safe strategy for its activation remain elusive. In this study, we discovered that local hyperthermia therapy (LHT) targeting beige fat promoted its activation in humans and mice. LHT achieved using a hydrogel-based photothermal therapy activated beige fat, preventing and treating obesity in mice without adverse effects. HSF1 is required for the effects since HSF1 deficiency blunted the metabolic benefits of LHT. HSF1 regulates Hnrnpa2b1 (A2b1) transcription, leading to increased mRNA stability of key metabolic genes. Importantly, analysis of human association studies followed by functional analysis revealed that the HSF1 gain-of-function variant p.P365T is associated with improved metabolic performance in humans and increased A2b1 transcription in mice and cells. Overall, we demonstrate that LHT offers a promising strategy against obesity by inducing beige fat activation via HSF1-A2B1 transcriptional axis.

Mito-nuclear interactions modify Drosophila exercise performance

Endurance exercise has received increasing attention as a broadly preventative measure against age-related disease and dysfunction. Improvement of mitochondrial quality by enhancement of mitochondrial turnover is thought to be among the important molecular mechanisms underpinning the benefits of exercise. Interactions between the mitochondrial and nuclear genomes are important components of the genetic basis for variation in longevity, fitness and the incidence of disease. Here, we examine the effects of replacing the mitochondrial genome (mtDNA) of several Drosophila strains with mtDNA from other strains, or from closely related species, on exercise performance. We find that mitochondria from flies selected for longevity increase the performance of flies from a parental strain. We also find evidence that mitochondria from other strains or species alter exercise performance, with examples of both beneficial and deleterious effects. These findings suggest that both the mitochondrial and nuclear genomes, as well as interactions between the two, contribute significantly to exercise capacity.

Spatiotemporal and demographic variation in the association between temperature variability and hospitalizations in Brazil during 2000-2015: A nationwide time-series study

BACKGROUND

Extreme temperature events are known to be adversely associated with a range of health outcomes, but little is known about the effect of less extreme, but more frequent fluctuation in temperature. We examined the spatiotemporal and demographic variation in the effect of temperature variability (TV) on nationwide hospitalizations in Brazil during 2000-2015.

METHODS

Data on daily hospitalizations and weather variables were collected from 1814 cities, comprising 78.4% of Brazilian population. TV was defined as the standard deviation of daily minimum and maximum temperatures during exposure days. City-specific TV effect was estimated using a quasi-Poisson regression model, and then pooled at the national and regional level using meta-analysis. Stratified analyses were performed by sex, 10 age-groups, and 11 cause categories. Meta-regression was applied to city-year-specific estimates to examine the temporal change.

RESULTS

The estimate of TV effect peaked on 0-1 days' exposure, contributing to 3.5% [95% confidence interval (CI): 3.1-3.8%] of hospitalizations nationwide, equalling 221 (95%CI: 200-242) cases per 100,000 population annually. The effect estimate varied across 11 cause categories, which was strongest for respiratory admissions. Males, particular those 10-49 year old were more affected than females but there was no sex difference for the attributable hospitalization rate. The attributable rate for the under-fives was twice as high as for the elderly, and five times higher than in adults. The majority of the most affected cities were located in the central west and the inland of northeast. The risk of hospitalization related to TV showed a significant increase over the 16-year period at the national level.

CONCLUSIONS

In Brazil, the effect of TV on hospitalization is acute, and varies by spatial, sex, age, and cause category. Given there is no evidence regarding TV adaptation, hospitalization burden associated with TV is likely to further increase and warrants consideration when developing future public health policies in the context of climate change.

Study of respiratory chain dysfunction in heart disease

The relentlessly beating heart has the greatest oxygen consumption of any organ in the body at rest reflecting its huge metabolic turnover and energetic demands. The vast majority of its energy is produced and cycled in form of ATP which stems mainly from oxidative phosphorylation occurring at the respiratory chain in the mitochondria. A part from energy production, the respiratory chain is also the main source of reactive oxygen species and plays a pivotal role in the regulation of oxidative stress. Dysfunction of the respiratory chain is therefore found in most common heart conditions. The pathophysiology of mitochondrial respiratory chain dysfunction in hereditary cardiac mitochondrial disease, the aging heart, in LV hypertrophy and heart failure, and in ischaemia-reperfusion injury is reviewed. We introduce the practicing clinician to the complex physiology of the respiratory chain, highlight its impact on common cardiac disorders and review translational pharmacological and non-pharmacological treatment strategies.

Perspectives on mitochondrial uncoupling proteins-mediated neuroprotection

The integrity of mitochondrial function is essential to cell life. It follows that disturbances of mitochondrial function will lead to disruption of cell function, expressed as disease or even death. Considering that neuronal uncoupling proteins (UCPs) decrease reactive oxygen species (ROS) production at the expense of energy production, it is important to understand the underlying mechanisms by which UCPs control the balance between the production of adenosine triphosphate (ATP) and ROS in the context of normal physiological activity and in pathological conditions. Here we review the current understanding of neuronal UCPs-mediated respiratory uncoupling process by performing a survey in their physiology and regulation. The latest findings regarding neuronal UCPs physiological roles and their involvement and interest as potential targets for therapeutic intervention in brain diseases will also be exploited.

The breathing heart - mitochondrial respiratory chain dysfunction in cardiac disease

The relentlessly beating heart has the greatest oxygen consumption of any organ in the body at rest reflecting its huge metabolic turnover and energetic demands. The vast majority of its energy is produced and cycled in form of ATP which stems mainly from oxidative phosphorylation occurring at the respiratory chain in the mitochondria. Apart from energy production, the respiratory chain is also the main source of reactive oxygen species and plays a pivotal role in the regulation of oxidative stress. Dysfunction of the respiratory chain is therefore found in most common heart conditions. The pathophysiology of mitochondrial respiratory chain dysfunction in hereditary cardiac mitochondrial disease, the ageing heart, in LV hypertrophy and heart failure, and in ischaemia-reperfusion injury is reviewed. We introduce the practising clinician to the complex physiology of the respiratory chain, highlight its impact on common cardiac disorders and review translational pharmacological and non-pharmacological treatment strategies.

UCP2 and ANT differently modulate proton-leak in brain mitochondria of long-term hyperglycemic and recurrent hypoglycemic rats

A growing body of evidence suggests that mitochondrial proton-leak functions as a regulator of reactive oxygen species production and its modulation may limit oxidative injury to tissues. The main purpose of this work was to characterize the proton-leak of brain cortical mitochondria from long-term hyperglycemic and insulin-induced recurrent hypoglycemic rats through the modulation of the uncoupling protein 2 (UCP2) and adenine nucleotide translocator (ANT). Streptozotocin-induced diabetic rats were treated subcutaneously with twice-daily insulin injections during 2 weeks to induce the hypoglycemic episodes. No differences in the basal proton-leak, UCP2 and ANT protein levels were observed between the experimental groups. Mitochondria from recurrent hypoglycemic rats presented a decrease in proton-leak in the presence of GDP, a specific UCP2 inhibitor, while an increase in proton-leak was observed in the presence of linoleic acid, a proton-leak activator, this effect being reverted by the simultaneous addition of GDP. Mitochondria from long-term hyperglycemic rats showed an enhanced susceptibility to ANT modulation as demonstrated by the complete inhibition of basal and linoleic acid-induced proton-leak caused by the ANT specific inhibitor carboxyatractyloside. Our results show that recurrent-hypoglycemia renders mitochondria more susceptible to UCPs modulation while the proton-leak of long-term hyperglycemic rats is mainly modulated by ANT, which suggest that brain cortical mitochondria have distinct adaptation mechanisms in face of different metabolic insults.

Synthesis of deuterium-labeled analogs of the lipid hydroperoxide-derived bifunctional electrophile 4-oxo-2(E)-nonenal

Lipid hydroperoxides undergo homolytic decomposition into the bifunctional 4-hydroxy-2(E)-nonenal and 4-oxo-2(E)-nonenal (ONE). These bifunctional electrophiles are highly reactive and can readily modify intracellular molecules including glutathione (GSH), deoxyribonucleic acid (DNA) and proteins. Lipid hydroperoxide-derived bifunctional electrophiles are thought to contribute to the pathogenesis of a number of diseases. ONE is an α,β-unsaturated aldehyde that can react in multiple ways and with glutathione, proteins and DNA. Heavy isotope-labeled analogs of ONE are not readily available for conducting mechanistic studies or for use as internal standards in mass spectrometry (MS)-based assays. An efficient onestep cost-effective method has been developed for the preparation of C-9 deuterium-labeled ONE. In addition, a method for specific deuterium labeling of ONE at C-2, C-3 or both C-2 and C-3 has been developed. This latter method involved the selective reduction of an intermediate alkyne either by lithium aluminum hydride or lithium aluminum deuteride and quenching with water or deuterium oxide. The availability of these heavy isotope analogs will be useful as internal standards for quantitative studies employing MS and for conducting mechanistic studies of complex interactions between ONE and DNA bases as well as between ONE and proximal amino acid residues in peptides and proteins.

cAMP/PKA signaling balances respiratory activity with mitochondria dependent apoptosis via transcriptional regulation

Background

Appropriate control of mitochondrial function, morphology and biogenesis are crucial determinants of the general health of eukaryotic cells. It is therefore imperative that we understand the mechanisms that co-ordinate mitochondrial function with environmental signaling systems. The regulation of yeast mitochondrial function in response to nutritional change can be modulated by PKA activity. Unregulated PKA activity can lead to the production of mitochondria that are prone to the production of ROS, and an apoptotic form of cell death.

Results

We present evidence that mitochondria are sensitive to the level of cAMP/PKA signaling and can respond by modulating levels of respiratory activity or committing to self execution. The inappropriate activation of one of the yeast PKA catalytic subunits, Tpk3p, is sufficient to commit cells to an apoptotic death through transcriptional changes that promote the production of dysfunctional, ROS producing mitochondria. Our data implies that cAMP/PKA regulation of mitochondrial function that promotes apoptosis engages the function of multiple transcription factors, including HAP4, SOK2 and SCO1.

Conclusions

We propose that in yeast, as is the case in mammalian cells, mitochondrial function and biogenesis are controlled in response to environmental change by the concerted regulation of multiple transcription factors. The visualization of cAMP/TPK3 induced cell death within yeast colonies supports a model that PKA regulation plays a physiological role in coordinating respiratory function and cell death with nutritional status in budding yeast.