Multimodal cell atlas of the ageing human skeletal muscle.

Muscle atrophy and functional decline (sarcopenia) are common manifestations of frailty and are critical contributors to morbidity and mortality in older people1. Deciphering the molecular mechanisms underlying sarcopenia has major implications for understanding human ageing2. Yet, progress has been slow, partly due to the difficulties of characterizing skeletal muscle niche heterogeneity (whereby myofibres are the most abundant) and obtaining well-characterized human samples3,4. Here we generate a single-cell/single-nucleus transcriptomic and chromatin accessibility map of human limb skeletal muscles encompassing over 387,000 cells/nuclei from individuals aged 15 to 99 years with distinct fitness and frailty levels. We describe how cell populations change during ageing, including the emergence of new populations in older people, and the cell-specific and multicellular network features (at the transcriptomic and epigenetic levels) associated with these changes. On the basis of cross-comparison with genetic data, we also identify key elements of chromatin architecture that mark susceptibility to sarcopenia. Our study provides a basis for identifying targets in the skeletal muscle that are amenable to medical, pharmacological and lifestyle interventions in late life.

Physical Interventions Restore Physical Frailty and the Expression of CXCL-10 and IL-1ß Inflammatory Biomarkers in Old Individuals and Mice.

BACKGROUND: Frailty is a geriatric syndrome associated with negative health outcomes that represents a dynamic condition with a potential of reversibility after physical exercise interventions. Typically, inflammatory and senescence markers are increased in frail individuals. However, the impact that physical exercise exerts on inflammatory and senescence biomarkers remains unknown. We assessed the effect of physical intervention in old individuals and mice and determined the expression of inflammatory and senescence markers. METHODS: Twelve elderly individuals were enrolled from a primary care setting to a 3-month intervention. Frailty was measured by SPPB and the expression of biomarkers by cytokine array and RT-qPCR. In addition, 12 aged C57BL/6 mice completed an intervention, and inflammation and senescence markers were studied. RESULTS: The physical intervention improved the SPPB score, reducing frail and pre-frail individuals. This was correlated with a reduction in several pro-inflammatory biomarkers such as IL-6, CXCL-1, CXCL-10, IL-1ß, IL-7, GM-CSF as well as p16INK4a and p21CIP1 senescence markers. Otherwise, the levels of anti-inflammatory biomarker IL-4 were significantly increased. Moreover, the physical intervention in mice also improved their functional capacity and restored the expression of inflammatory (Il-1ß, Cxcl-10, Il-6, and Cxcl-1) and senescence (p21Cip1) markers. Additionally, PLSDA and ROC curve analysis revealed CXCL-10 and IL-1ß to be the biomarkers of functional improvement in both cohorts. CONCLUSIONS: Our results showed that a physical intervention improves physical frailty, and reverses inflammation and senescence biomarkers comprising CXCL-10 and IL-1ß.

Pharmacological and genetic increases in liver NADPH levels ameliorate NASH progression in female mice.

Non-alcoholic steatohepatitis (NASH) is one of the fastest growing liver diseases worldwide, and oxidative stress is one of NASH main key drivers. Nicotinamide adenine dinucleotide phosphate (NADPH) is the ultimate donor of reductive power to a number of antioxidant defences. Here, we explored the potential of increasing NADPH levels to prevent NASH progression. We used nicotinamide riboside (NR) supplementation or a G6PD-tg mouse line harbouring an additional copy of the human G6PD gene. In a NASH mouse model induced by feeding mice a methionine-choline deficient (MCD) diet for three weeks, both tools increased the hepatic levels of NADPH and ameliorated the NASH phenotype induced by the MCD intervention, but only in female mice. Boosting NADPH levels in females increased the liver expression of the antioxidant genes Gsta3, Sod1 and Txnrd1 in NR-treated mice, or of Gsr for G6PD-tg mice. Both strategies significantly reduced hepatic lipid peroxidation. NR-treated female mice showed a reduction of steatosis accompanied by a drop of the hepatic triglyceride levels, that was not observed in G6PD-tg mice. NR-treated mice tended to reduce their lobular inflammation, showed a reduction of the NK cell population and diminished transcription of the damage marker Lcn2. G6PD-tg female mice exhibited a reduction of their lobular inflammation and hepatocyte ballooning induced by the MCD diet, that was related to a reduction of the monocyte-derived macrophage population and the Tnfa, Ccl2 and Lcn2 gene expression. As conclusion, boosting hepatic NADPH levels attenuated the oxidative lipid damage and the exhausted antioxidant gene expression specifically in female mice in two different models of NASH, preventing the progression of the inflammatory process and hepatic injury.

Low Muscle Mass Is Associated with Poorer Glycemic Control and Higher Oxidative Stress in Older Patients with Type 2 Diabetes.

Body composition changes that occur during aging, such as loss of lean mass, are unfavorable at metabolic level and they can explain, in part, the appearance of certain age-associated diseases such as type 2 diabetes (T2D). Separately, T2D is associated with an increase in oxidative stress (OS) which negatively affects skeletal muscle. Our aim was to study the differences in clinical and nutritional parameters, disease control, and OS in a cohort of older patients with T2D classified according to the amount of lean mass they had. We included 100 adults older than 65 years with T2D. We found that women with low fat-free mass and muscle mass have worse T2D metabolic control. Moreover, the patients with a low percentile of muscle mass present a high value of OS. The study shows that the presence of low lean mass (LM) in the geriatric population diagnosed with T2D is associated with poorer glycemic control and greater OS.

Residual effects of 12 weeks of power-oriented resistance training plus high-intensity interval training on muscle dysfunction, systemic oxidative damage, and antioxidant capacity after 10 months of training cessation in older people with COPD.

OBJECTIVE: This study aimed to assess the residual effects of a 12-week concurrent training program (power training + high-intensity interval training) in older adults with chronic obstructive pulmonary disease (COPD). METHODS: A total of 21 older adults with COPD [intervention (INT), n = 8; control (CON), n = 13; 76.9 ± 6.8 years] were assessed at baseline and 10 months after the completion of the intervention by the short physical performance battery (SPPB), health-related quality of life (EQ-5D-5L), vastus lateralis muscle thickness (MT), peak pulmonary oxygen uptake (peak VO2 ) and peak work rate (Wpeak ), early and late isometric rate of force development (RFD), leg and chest press maximum muscle power (LPmax and CPmax ), and systemic oxidative damage and antioxidant capacity. RESULTS: Compared to baseline, after 10 months of detraining, the INT group presented increased SPPB (∆ = 1.0 point), health-related quality of life (∆ = 0.07 points), early RFD (∆ = 834 N∙s-1 ), LPmax (∆ = 62.2 W), and CPmax (∆ = 16.0 W) (all p < 0.05). In addition, a positive effect was noted in INT compared to CON regarding MT and Wpeak (both p < 0.05). No between-group differences were reported in peak VO2 , late RFD, systemic oxidative damage, and antioxidant capacity from baseline to 10 months after the completion of the intervention (all p > 0.05). CONCLUSIONS: Twelve weeks of concurrent training were enough to ensure improved physical function, health-related quality of life, early RFD and maximum muscle power and to preserve MT and Wpeak but not peak VO2 , late RFD, systemic oxidative damage and antioxidant capacity in the subsequent 10 months of detraining in older adults with COPD.

Peripheral modulation of antidepressant targets MAO-B and GABAAR by harmol induces mitohormesis and delays aging in preclinical models.

Reversible and sub-lethal stresses to the mitochondria elicit a program of compensatory responses that ultimately improve mitochondrial function, a conserved anti-aging mechanism termed mitohormesis. Here, we show that harmol, a member of the beta-carbolines family with anti-depressant properties, improves mitochondrial function and metabolic parameters, and extends healthspan. Treatment with harmol induces a transient mitochondrial depolarization, a strong mitophagy response, and the AMPK compensatory pathway both in cultured C2C12 myotubes and in male mouse liver, brown adipose tissue and muscle, even though harmol crosses poorly the blood-brain barrier. Mechanistically, simultaneous modulation of the targets of harmol monoamine-oxidase B and GABA-A receptor reproduces harmol-induced mitochondrial improvements. Diet-induced pre-diabetic male mice improve their glucose tolerance, liver steatosis and insulin sensitivity after treatment with harmol. Harmol or a combination of monoamine oxidase B and GABA-A receptor modulators extend the lifespan of hermaphrodite Caenorhabditis elegans or female Drosophila melanogaster. Finally, two-year-old male and female mice treated with harmol exhibit delayed frailty onset with improved glycemia, exercise performance and strength. Our results reveal that peripheral targeting of monoamine oxidase B and GABA-A receptor, common antidepressant targets, extends healthspan through mitohormesis.

Allopurinol blocks aortic aneurysm in a mouse model of Marfan syndrome via reducing aortic oxidative stress.

BACKGROUND: Increasing evidence indicates that redox stress participates in MFS aortopathy, though its mechanistic contribution is little known. We reported elevated reactive oxygen species (ROS) formation and NADPH oxidase NOX4 upregulation in MFS patients and mouse aortae. Here we address the contribution of xanthine oxidoreductase (XOR), which catabolizes purines into uric acid and ROS in MFS aortopathy. METHODS AND RESULTS: In aortic samples from MFS patients, XOR protein expression, revealed by immunohistochemistry, increased in both the tunicae intima and media of the dilated zone. In MFS mice (Fbn1C1041G/+), aortic XOR mRNA transcripts and enzymatic activity of the oxidase form (XO) were augmented in the aorta of 3-month-old mice but not in older animals. The administration of the XOR inhibitor allopurinol (ALO) halted the progression of aortic root aneurysm in MFS mice. ALO administrated before the onset of the aneurysm prevented its subsequent development. ALO also inhibited MFS-associated endothelial dysfunction as well as elastic fiber fragmentation, nuclear translocation of pNRF2 and increased 3'-nitrotyrosine levels, and collagen maturation remodeling, all occurring in the tunica media. ALO reduced the MFS-associated large aortic production of H2O2, and NOX4 and MMP2 transcriptional overexpression. CONCLUSIONS: Allopurinol interferes in aortic aneurysm progression acting as a potent antioxidant. This study strengthens the concept that redox stress is an important determinant of aortic aneurysm formation and progression in MFS and warrants the evaluation of ALO therapy in MFS patients.

Glucose 6-P Dehydrogenase-An Antioxidant Enzyme with Regulatory Functions in Skeletal Muscle during Exercise.

Hypomorphic Glucose 6-P dehydrogenase (G6PD) alleles, which cause G6PD deficiency, affect around one in twenty people worldwide. The high incidence of G6PD deficiency may reflect an evolutionary adaptation to the widespread prevalence of malaria, as G6PD-deficient red blood cells (RBCs) are hostile to the malaria parasites that infect humans. Although medical interest in this enzyme deficiency has been mainly focused on RBCs, more recent evidence suggests that there are broader implications for G6PD deficiency in health, including in skeletal muscle diseases. G6PD catalyzes the rate-limiting step in the pentose phosphate pathway (PPP), which provides the precursors of nucleotide synthesis for DNA replication as well as reduced nicotinamide adenine dinucleotide phosphate (NADPH). NADPH is involved in the detoxification of cellular reactive oxygen species (ROS) and de novo lipid synthesis. An association between increased PPP activity and the stimulation of cell growth has been reported in different tissues including the skeletal muscle, liver, and kidney. PPP activity is increased in skeletal muscle during embryogenesis, denervation, ischemia, mechanical overload, the injection of myonecrotic agents, and physical exercise. In fact, the highest relative increase in the activity of skeletal muscle enzymes after one bout of exhaustive exercise is that of G6PD, suggesting that the activation of the PPP occurs in skeletal muscle to provide substrates for muscle repair. The age-associated loss in muscle mass and strength leads to a decrease in G6PD activity and protein content in skeletal muscle. G6PD overexpression in Drosophila Melanogaster and mice protects against metabolic stress, oxidative damage, and age-associated functional decline, and results in an extended median lifespan. This review discusses whether the well-known positive effects of exercise training in skeletal muscle are mediated through an increase in G6PD.

Age-dependent impact of two exercise training regimens on genomic and metabolic remodeling in skeletal muscle and liver of male mice.

Skeletal muscle adapts to different exercise training modalities with age; however, the impact of both variables at the systemic and tissue levels is not fully understood. Here, adult and old C57BL/6 male mice were assigned to one of three groups: sedentary, daily high-intensity intermittent training (HIIT), or moderate intensity continuous training (MICT) for 4 weeks, compatible with the older group's exercise capacity. Improvements in body composition, fasting blood glucose, and muscle strength were mostly observed in the MICT old group, while effects of HIIT training in adult and old animals was less clear. Skeletal muscle exhibited structural and functional adaptations to exercise training, as revealed by electron microscopy, OXPHOS assays, respirometry, and muscle protein biomarkers. Transcriptomics analysis of gastrocnemius muscle combined with liver and serum metabolomics unveiled an age-dependent metabolic remodeling in response to exercise training. These results support a tailored exercise prescription approach aimed at improving health and ameliorating age-associated loss of muscle strength and function in the elderly.

Transcriptomic profile of epileptic children treated with ketogenic therapies.

Background: Ketogenic dietary therapies (KDT) are used as a treatment in childhood epilepsy. However, their mechanism has not yet been established. The main objective of this study was to determine the changes in the transcriptomic profile induced by KDT in children with epilepsy in order to shed light on its possible mechanisms. Methods: Eight children with refractory epilepsy were enrolled in the study. Peripheral blood mononuclear cells were obtained before and after the children were treated with KDT for a minimum of 6 months. RNA was extracted and mRNA and miRNA profiling were performed and analyzed. Results: Our intervention with KDT significantly reduced the seizure number in seven of the eight paediatric patients treated and caused important changes in their gene expression profile. Our study reveals modifications in the transcription of 4630 genes and 230 miRNAs. We found that the genes involved in the protection against epileptic crises were among those mainly changed. These genes collectively encode for ion channels, neurotransmitter receptors, and synapse structural proteins. Conclusions: Together our results explain the possible mechanisms of KDT and reinforce its clinical importance in the treatment of epilepsy.

Glucosamine Supplementation Improves Physical Performance in Trained Mice.

INTRODUCTION: d-Glucosamine (GlcN) is one of the most widely consumed dietary supplements and complementary medicines in the world and has been traditionally used to attenuate osteoarthritis in humans. GlcN extends life span in different animal models. In humans, its supplementation has been strongly associated with decreased total mortality and improved vascular endothelial function. GlcN acts as a suppressor of inflammation, and by inhibiting glycolysis, it can activate the metabolism of stored fat and mitochondrial respiration. METHODS: The conventional human GlcN dose is 1500 mg·d-1, but extensive evidence indicates that much higher doses are well tolerated. GlcN is one of the supplements that has experienced a greater use in the last years in elite athletes mainly because of its potential chondroprotective effects that may promote cartilage health. However, the possibility of it being an ergogenic aid has not been explored. We aimed to study the potential beneficial effects of GlcN on mitochondrial content, physical performance, and oxidative stress in mice that were aerobically trained and supplemented with three different doses of glucosamine (250, 500, and 1000 mg·kg-1) for 6 wk. We measured exercise performance (grip strength, motor coordination, and running capacity) before and after the training period. Proteins involved in mitochondrial biogenesis (AMPK, PGC-1, NRF-1, SIRT-1, cytochrome c, citrate synthase), markers of oxidative stress (GSSG/GSH) or damage (malondialdehyde, carbonylated proteins), antioxidant enzymes (NRF-2, SOD1, SOD2, catalase, and PRDX6), and MAPKs (p38 and ERK1/2 were also determined in skeletal muscle. RESULTS AND CONCLUSIONS: Our results show that GlcN supplementation in aerobically trained mice, at doses equivalent to those conventionally used in humans, increases the protein levels of mitochondrial biogenesis markers, improves motor coordination, and may have a synergistic effect with exercise training on running distance.

Frailty Is Associated with Oxidative Stress in Older Patients with Type 2 Diabetes.

Aging has increased the prevalence of frailty, and type 2 diabetes (T2D) has also increased in prevalence. Diabetes and oxidative stress (OS) have been shown to be related to frailty. However, the exact mechanism by which it occurs is not fully known. Our aim was to analyze body composition in community-dwelling older diabetic people treated in our center and to evaluate the possible relation between OS, frailty, and body composition. We included 100 adults older than 65 years with T2D. We found that 15% were frail and 57% were prefrail. The patients included in the nonrobust group showed increased levels of OS. Our study shows that the presence of T2D in the geriatric population is associated with a high prevalence of frailty and high OS levels, conditions that cause greater morbidity and mortality and that highlight the importance of the diagnosis of frailty in this population.

Muscle repair after physiological damage relies on nuclear migration for cellular reconstruction.

Regeneration of skeletal muscle is a highly synchronized process that requires muscle stem cells (satellite cells). We found that localized injuries, as experienced through exercise, activate a myofiber self-repair mechanism that is independent of satellite cells in mice and humans. Mouse muscle injury triggers a signaling cascade involving calcium, Cdc42, and phosphokinase C that attracts myonuclei to the damaged site via microtubules and dynein. These nuclear movements accelerate sarcomere repair and locally deliver messenger RNA (mRNA) for cellular reconstruction. Myofiber self-repair is a cell-autonomous protective mechanism and represents an alternative model for understanding the restoration of muscle architecture in health and disease.

Glucose 6-P dehydrogenase delays the onset of frailty by protecting against muscle damage.

BACKGROUND: Frailty is a major age-associated syndrome leading to disability. Oxidative damage plays a significant role in the promotion of frailty. The cellular antioxidant system relies on reduced nicotinamide adenine dinucleotide phosphate (NADPH) that is highly dependent on glucose 6-P dehydrogenase (G6PD). The G6PD-overexpressing mouse (G6PD-Tg) is protected against metabolic stresses. Our aim was to examine whether this protection delays frailty. METHODS: Old wild-type (WT) and G6PD-Tg mice were evaluated longitudinally in terms of frailty. Indirect calorimetry, transcriptomic profile, and different skeletal muscle quality markers and muscle regenerative capacity were also investigated. RESULTS: The percentage of frail mice was significantly lower in the G6PD-Tg than in the WT genotype, especially in 26-month-old mice where 50% of the WT were frail vs. only 13% of the Tg ones (P < 0.001). Skeletal muscle transcriptomic analysis showed an up-regulation of respiratory chain and oxidative phosphorylation (P = 0.009) as well as glutathione metabolism (P = 0.035) pathways in the G6PD-Tg mice. Accordingly, the Tg animals exhibited an increase in reduced glutathione (34.5%, P < 0.01) and a decrease on its oxidized form (-69%, P < 0.05) and in lipid peroxidation (4-HNE: -20.5%, P < 0.05). The G6PD-Tg mice also showed reduced apoptosis (BAX/Bcl2: -25.5%, P < 0.05; and Bcl-xL: -20.5%, P < 0.05), lower levels of the intramuscular adipocyte marker FABP4 (-54.7%, P < 0.05), and increased markers of mitochondrial content (COX IV: 89.7%, P < 0.05; Grp75: 37.8%, P < 0.05) and mitochondrial OXPHOS complexes (CII: 81.25%, P < 0.01; CIII: 52.5%, P < 0.01; and CV: 37.2%, P < 0.05). Energy expenditure (-4.29%, P < 0.001) and the respiratory exchange ratio were lower (-13.4%, P < 0.0001) while the locomotor activity was higher (43.4%, P < 0.0001) in the 20-month-old Tg, indicating a major energetic advantage in these mice. Short-term exercise training in young C57BL76J mice induced a robust activation of G6PD in skeletal muscle (203.4%, P < 0.05), similar to that achieved in the G6PD-Tg mice (142.3%, P < 0.01). CONCLUSIONS: Glucose 6-P dehydrogenase deficiency can be an underestimated risk factor for several human pathologies and even frailty. By overexpressing G6PD, we provide the first molecular model of robustness. Because G6PD is regulated by pharmacological and physiological interventions like exercise, our results provide molecular bases for interventions that by increasing G6PD will delay the onset of frailty.

Activation of the Constitutive Androstane Receptor Inhibits Leukocyte Adhesiveness to Dysfunctional Endothelium.

Leukocyte cell recruitment into the vascular subendothelium constitutes an early event in the atherogenic process. As the effect of the constitutive androstane receptor (CAR) on leukocyte recruitment and endothelial dysfunction is poorly understood, this study investigated whether the role of CAR activation can affect this response and the underlying mechanisms involved. Under physiological flow conditions, TNFα-induced endothelial adhesion of human leukocyte cells was concentration-dependently inhibited by preincubation of human umbilical arterial endothelial cells with the selective human CAR ligand CITCO. CAR agonism also prevented TNFα induced VCAM-1 expression, as well as MCP-1/CCL-2 and RANTES/CCL-5 release in endothelial cells. Suppression of CAR expression with a small interfering RNA abrogated the inhibitory effects of CITCO on these responses. Furthermore, CITCO increased interaction of CAR with Retinoid X Receptor (RXR) and reduced TNFα-induced p38-MAPK/NF-κB activation. In vivo, using intravital microscopy in the mouse cremasteric microcirculation treatment with the selective mouse CAR ligand TCPOBOP inhibited TNFα-induced leukocyte rolling flux, adhesion, and emigration and decreased VCAM-1 in endothelium. These results reveal that CAR agonists can inhibit the initial inflammatory response that precedes the atherogenic process by targeting different steps in the leukocyte recruitment cascade. Therefore, CAR agonists may constitute a new therapeutic tool in controlling cardiovascular disease-associated inflammatory processes.

Exploring Potential Benefits of Accumulated Multicomponent-Training in Non-Active Older Adults: From Physical Fitness to Mental Health.

The present study aimed to analyze the impact of a multicomponent training (MCT) program in a group of non-active older adults, comparing two different dose distributions. Twenty-four individuals, assigned to two groups, completed 15 weeks of MCT (2 days/week). The continuous group (CMCT; n = 14, 9 females; 71.07 ± 5.09 years) trained for 60 min/session in the morning. The accumulated group (AMCT; n = 10, 5 females; 72.70 ± 3.59 years) performed the same exercises, volume, and intensity, but the training was distributed twice per day (30 min in the morning; 30 more in the afternoon). Bonferroni post hoc comparisons revealed significant (p < 0.001) and similar large improvements in both groups in lower limb strength (five times sit-to-stand test: CMCT, 12.55 ± 2.83 vs. 9.44 ± 1.72 s; AMCT, 10.37 ± 2.35 vs. 7.46 ± 1.75 s). In addition, there were large gains in preferred walking speed and instrumental daily life activities, which were higher for CMCT and AMCT, respectively (in this order: 1.00 ± 0.18 vs. 1.44 ± 0.26 m/s and 1.09 ± 0.80 vs. 1.58 ± 0.18 m/s; 33.07 ± 2.88 vs. 36.57 ± 1.65 points and 32.80 ± 1.93 vs. 36.80 ± 0.92 points); improvements in cardiorespiratory fitness, now moderate for CMCT (474.14 ± 93.60 vs. 529.64 ± 82.76 m) and large for AMCT (515.10 ± 20.24 vs. 589.60 ± 40.38 m); and medium and similar enhancements in agility in both groups (TUG test: CMCT: 7.49 ± 1.11 vs. 6.77 ± 1.16 s; AMCT: 6.84 ± 1.01 vs. 6.18 ± 0.62 s). None of the protocols had an impact on the executive function, whereas health-related quality of life showed a trend to significance in the whole sample only (EQindex overall sample, p = 0.062; d = 0.48 CMCT; d = 0.34 AMCT). Regardless of the type of dose distribution, starting multicomponent training improves physical function in non-active older adults, but does not improve cognitive function at mid-term. Because both forms of MCT showed similar compliance, slightly positive differences in accumulated strategies may indicate some benefits related to breaking afternoon sedentary behaviors, which deserves further research in longer and larger interventions. The mixed nature of MCT suggests accumulative group interventions may be a promising approach to address sedentary aging.

Redox-related biomarkers in physical exercise.

Research in redox biology of exercise has made considerable advances in the last 70 years. Since the seminal study of George Pake's group calculating the content of free radicals in skeletal muscle in resting conditions in 1954, many discoveries have been made in the field. The first section of this review is devoted to highlight the main research findings and fundamental changes in the exercise redox biology discipline. It includes: i) the first steps in free radical research, ii) the relation between exercise and oxidative damage, iii) the redox regulation of muscle fatigue, iv) the sources of free radicals during muscle contractions, and v) the role of reactive oxygen species as regulators of gene transcription and adaptations in skeletal muscle. In the second section of the manuscript, we review the available biomarkers for assessing health, performance, recovery during exercise training and overtraining in the sport population. Among the set of biomarkers that could be determined in exercise studies we deepen on the four categories of redox biomarkers: i) oxidants, ii) antioxidants, iii) oxidation products (markers of oxidative damage), and iv) measurements of the redox balance (markers of oxidative stress). The main drawbacks, strengths, weaknesses, and methodological considerations of every biomarker are also discussed.

Implementing Precision Medicine in Human Frailty through Epigenetic Biomarkers.

The main epigenetic features in aging are: reduced bulk levels of core histones, altered pattern of histone post-translational modifications, changes in the pattern of DNA methylation, replacement of canonical histones with histone variants, and altered expression of non-coding RNA. The identification of epigenetic mechanisms may contribute to the early detection of age-associated subclinical changes or deficits at the molecular and/or cellular level, to predict the development of frailty, or even more interestingly, to improve health trajectories in older adults. Frailty reflects a state of increased vulnerability to stressors as a result of decreased physiologic reserves, and even dysregulation of multiple physiologic systems leading to adverse health outcomes for individuals of the same chronological age. A key approach to overcome the challenges of frailty is the development of biomarkers to improve early diagnostic accuracy and to predict trajectories in older individuals. The identification of epigenetic biomarkers of frailty could provide important support for the clinical diagnosis of frailty, or more specifically, to the evaluation of its associated risks. Interventional studies aimed at delaying the onset of frailty and the functional alterations associated with it, would also undoubtedly benefit from the identification of frailty biomarkers. Specific to the article yet reasonably common within the subject discipline.

Impact of COVID-19 Confinement on Physical Activity and Sedentary Behaviour in Spanish University Students: Role of Gender.

During the COVID-19 pandemic, entire populations were instructed to live in home-confinement to prevent the expansion of the disease. Spain was one of the countries with the strictest conditions, as outdoor physical activity was banned for nearly two months. This study aimed to analyse the changes in physical activity and sedentary behaviours in Spanish university students before and during the confinement by COVID-19 with special focus on gender. We also analysed enjoyment, the tools used and motivation and impediments for doing physical activity. An online questionnaire, which included the International Physical Activity Questionnaire Short Form and certain "ad hoc" questions, was designed. Students were recruited by distributing an invitation through the administrative channels of 16 universities and a total of 13,754 valid surveys were collected. Overall, university students reduced moderate (-29.5%) and vigorous (-18.3%) physical activity during the confinement and increased sedentary time (+52.7%). However, they spent more time on high intensity interval training (HIIT) (+18.2%) and mind-body activities (e.g., yoga) (+80.0%). Adaptation to the confinement, in terms of physical activity, was handled better by women than by men. These results will help design strategies for each gender to promote physical activity and reduce sedentary behaviour during confinement periods.

Overexpression of glucose 6 phosphate dehydrogenase preserves mouse pancreatic beta cells function until late in life.

NAD(P)H donates electrons for reductive biosynthesis and antioxidant defense across all forms of life. Glucose-6-phosphate dehydrogenase (G6PD) is a critical enzyme to provide NADPH. G6PD deficiency is present in more than 400 million people worldwide. This enzymopathy provides protection against malaria but sensitizes cells to oxidative stressors. Oxidative stress has been involved in the pathogenesis of the diabetic complications and several studies have provided evidences of a link between G6PD deficiency and type 2 diabetes (T2D). We hypothesized that a moderate overexpression of G6PD (G6PD-Tg) could protect ß-cells from age-associated oxidative stress thus reducing the risk of developing T2D. Here we report, that G6PD-Tg mice show an improved glucose tolerance and insulin sensitivity when compared to old age-matched Wild Type (WT) ones. This is accompanied by a decrease in oxidative damage and stress markers in the pancreas of the old Tg animals (20-24month-old). Pancreatic ß-cells progress physiologically towards a state of reduced responsiveness to glucose. In pancreatic islets isolated from G6PD-Tg and WT animals at different ages, and using electrophysiological techniques, we demonstrate a wider range of response to glucose in the G6PD-Tg cells that may explain the improvements in glucose tolerance and insulin sensitivity. Together, our results show that overexpression of G6PD maintains pancreatic ß-cells from old mice in a "juvenile-like" state and points to the G6PD dependent generation of NADPH as an important factor to improve the natural history of diabetes.