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Armed conflict and forced migration (ACFM) represent a set of extreme environments that are increasingly common for children and adolescents to experience. Adolescence may constitute a sensitive period (puberty and psychoneurological maturation) through which ACFM adversity leaves a lasting mark. Adolescence has become a focal point for analysis and intervention as it relates to the effects of early life adversity on puberty, linear growth, and mental health. Research in public health and psychological science suggests early life adversity (ELA) may accelerate puberty, heightening risks for mental health disorders. However, it is not well substantiated whether ACFM-derived adversities accelerate or delay relative pubertal timing. Secondly, ACFM provides salient context through which to probe the relationships between nutritional, psychosocial, and demographic changes and their respective impact on puberty and mental health. We conducted a narrative review which 1) examined constructions of early life adversity and their proposed influence on puberty 2) reviewed empirical findings (n = 29 studies, n = 36 samples) concerning effects of ACFM ELA on age at menarche and 3) discussed proposed relationships between early life adversity, puberty, and mental ill-health. Contrary to prior research, we found war-derived early life adversity was more consistently associated with pubertal delay than acceleration and may exert counterintuitive effects on mental health. We show that ELA cannot be operationalized in the same way across contexts and populations, especially in the presence of extreme forms of human stress and resilience. We further discuss the ethics of puberty research among conflict-affected youth., Competing Interests: Declaration of Competing Interest None., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Pubertal research has primarily focused on hypothalamic-pituitary-gonadal axis (HPG) regulation of puberty, though the hypothalamic-pituitary-adrenal axis (HPA) is increasingly considered critical. Heightened HPA function proxied by increasing cortisol levels may play a role in accelerated pubertal timing. However, the extent to which cortisol varies across ages and its relation to pubertal changes in linear growth are less well substantiated. We explored relationships between age, linear growth, adiposity, C-peptide (proxy for insulin), and cortisol across puberty, and we tested whether higher cortisol levels are associated with earlier ages at menarche and peak height velocity. We utilize longitudinal data (n = 777 urine samples) from Qom females ages 7-14 (n = 46) and test our pre-registered analysis using Bayesian longitudinal mixed effects models and joint modeling techniques. We find limited evidence supporting the overarching hypothesis that HPA upregulation is associated with pubertal maturation or timing. We find some evidence that HPA upregulation, as proxied by cortisol, may be more clearly related to differences in relative linear growth at early-mid puberty, as measured by height-for-age z-scores. Transdisciplinary perspectives on puberty, including the assumption that stressors acting via cortisol accelerate pubertal development, are discussed., (© 2024 Wiley Periodicals LLC.)

The Ser/Thr protein phosphatase 2 A (PP2A) regulates the dephosphorylation of many phosphoproteins. Substrate recognition are mediated by B regulatory subunits. Here, we report the identification of a substrate conserved motif [RK]-V-x-x-[VI]-R in FAM122A, an inhibitor of B55α/PP2A. This motif is necessary for FAM122A binding to B55α, and computational structure prediction suggests the motif, which is helical, blocks substrate docking to the same site. In this model, FAM122A also spatially constrains substrate access by occluding the catalytic subunit. Consistently, FAM122A functions as a competitive inhibitor as it prevents substrate binding and dephosphorylation of CDK substrates by B55α/PP2A in cell lysates. FAM122A deficiency in human cell lines reduces the proliferation rate, cell cycle progression, and hinders G1/S and intra-S phase cell cycle checkpoints. FAM122A-KO in HEK293 cells attenuates CHK1 and CHK2 activation in response to replication stress. Overall, these data strongly suggest that FAM122A is a short helical motif (SHeM)-dependent, substrate-competitive inhibitor of B55α/PP2A that suppresses multiple functions of B55α in the DNA damage response and in timely progression through the cell cycle interphase., (© 2024. The Author(s).)

Liver zonation characterizes the separation of metabolic pathways along the lobules and is required for optimal hepatic function. Wnt signaling is a master regulator of spatial liver zonation. A perivenous-periportal Wnt activity gradient orchestrates metabolic zonation by activating gene expression in perivenous hepatocytes, while suppressing gene expression in their periportal counterparts. However, the understanding as to the liver gene zonation and zonation regulators in diseases is limited. Non-alcoholic steatohepatitis (NASH) is a chronic liver disease characterized by fat accumulation, inflammation, and fibrosis. Here, we investigated the perturbation of liver gene zonation in a mouse NASH model by combining spatial transcriptomics, bulk RNAseq and in situ hybridization. Wnt-target genes represented a major subset of genes showing altered spatial expression in the NASH liver. The altered Wnt-target gene expression levels and zonation spatial patterns were in line with the up regulation of Wnt regulators and the augmentation of Wnt signaling. Particularly, we found that the Wnt activator Rspo3 expression was restricted to the perivenous zone in control liver but expanded to the periportal zone in NASH liver. AAV8-mediated RSPO3 overexpression in controls resulted in zonation changes, and further amplified the disturbed zonation of Wnt-target genes in NASH, similarly Rspo3 knockdown in Rspo3 +/- mice resulted in zonation changes of Wnt-target genes in both chow and HFD mouse. Interestingly, there were no impacts on steatosis, inflammation, or fibrosis NASH pathology from RSPO3 overexpression nor Rspo3 knockdown. In summary, our study demonstrated the alteration of Wnt signaling in a mouse NASH model, leading to perturbed liver zonation., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: All authors are or were employees and shareholders of Regeneron Pharmaceuticals. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Brca1 mouse models were first reported in the mid-1990's shortly after cloning the human gene. Since then, many mouse models with a range of mutations have been generated, some mimic patient mutations, others are designed to probe specific protein domains and functions. In this review, we discuss early and recent studies using engineered Brca1 mouse alleles, and their implications for understanding Brca1 protein function in the context of DNA repair, tumorigenesis, and anti-cancer therapeutics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Homologous recombination (HR)-deficiency induces a dependency on DNA polymerase theta (Polθ/Polq)-mediated end joining, and Polθ inhibitors (Polθi) are in development for cancer therapy. BRCA1 and BRCA2 deficient cells are thought to be synthetic lethal with Polθ, but whether distinct HR gene mutations give rise to equivalent Polθ-dependence, and the events that drive lethality, are unclear. In this study, we utilized mouse models with separate Brca1 functional defects to mechanistically define Brca1-Polθ synthetic lethality. Surprisingly, homozygous Brca1 mutant, Polq -/- cells were viable, but grew slowly and had chromosomal instability. Brca1 mutant cells proficient in DNA end resection were significantly more dependent on Polθ for viability; here, treatment with Polθi elevated RPA foci, which persisted through mitosis. In an isogenic system, BRCA1 null cells were defective, but PALB2 and BRCA2 mutant cells exhibited active resection, and consequently stronger sensitivity to Polθi. Thus, DNA end resection is a critical determinant of Polθi sensitivity in HR-deficient cells, and should be considered when selecting patients for clinical studies., (© 2023. The Author(s).)

Background: As a result of aging, skeletal muscle undergoes atrophy and a decrease in function. This age-related skeletal muscle weakness is known as "sarcopenia". Sarcopenia is part of the frailty observed in humans. In order to discover treatments for sarcopenia, it is necessary to determine appropriate preclinical models and the genes and signaling pathways that change with age in these models., Methods and Results: To understand the changes in gene expression that occur as a result of aging in skeletal muscles, we generated a multi-time-point gene expression signature throughout the lifespan of mice and rats, as these are the most commonly used species in preclinical research and intervention testing. Gastrocnemius, tibialis anterior, soleus, and diaphragm muscles from male and female C57Bl/6J mice and male Sprague Dawley rats were analyzed at ages 6, 12, 18, 21, 24, and 27 months, plus an additional 9-month group was used for rats. More age-related genes were identified in rat skeletal muscles compared with mice; this was consistent with the finding that rat muscles undergo more robust age-related decline in mass. In both species, pathways associated with innate immunity and inflammation linearly increased with age. Pathways linked with extracellular matrix remodeling were also universally downregulated. Interestingly, late downregulated pathways were exclusively found in the rat limb muscles and these were linked to metabolism and mitochondrial respiration; this was not seen in the mouse., Conclusions: This extensive, side-by-side transcriptomic profiling shows that the skeletal muscle in rats is impacted more by aging compared with mice, and the pattern of decline in the rat may be more representative of the human. The observed changes point to potential therapeutic interventions to avoid age-related decline in skeletal muscle function., (© 2023. The Author(s).)

Objectives: Complement activation has been implicated in COVID-19 pathogenesis. This study aimed to assess the levels of complement activation products and full-length proteins in hospitalized patients with COVID-19, and evaluated whether complement pathway markers are associated with outcomes., Methods: Longitudinal measurements of complement biomarkers from 89 hospitalized adult patients, grouped by baseline disease severity, enrolled in an adaptive, phase 2/3, randomized, double-blind, placebo-controlled trial and treated with intravenous sarilumab (200 mg or 400 mg) or placebo (NCT04315298), were performed. These measurements were then correlated with clinical and laboratory parameters., Results: All complement pathways were activated in hospitalized patients with COVID-19. Alternative pathway activation was predominant earlier in the disease course. Complement biomarkers correlated with multiple variables of multi-organ dysfunction and inflammatory injury. High plasma sC5b-9, C3a, factor Bb levels, and low mannan-binding lectin levels were associated with increased mortality. Sarilumab treatment showed a modest inhibitory effect on complement activation. Moreover, sera from patients spontaneously deposited C5b-9 complex on the endothelial surface ex vivo, suggesting a microvascular thrombotic potential., Conclusion: These results advance our understanding of COVID-19 disease pathophysiology and demonstrate the importance of specific complement pathway components as prognostic biomarkers in COVID-19., Competing Interests: Declaration of competing interest All the authors are employees of Regeneron Pharmaceuticals, Inc. and own stock or stock options., (Copyright © 2023 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

Objective: People living in war may experience deteriorating health via weathering (wear and tear) from long-term exposures to psychosocial and environmental stressors. Weathering embodied in somatic health complaints may illuminate the effects of war on health., Methods: We investigate whether wartime stress exposures occurring during adolescence and early adulthood affect weathering in late adulthood via linear regression with data from the Vietnamese Health and Aging Study (VHAS). VHAS is a cross-sectional study wherein investigators surveyed 2447 adults aged 60+ in four districts of northern and central Vietnam in 2018. These same individuals ranged in age from seven to 52 in 1965, with most having been in adolescence or early adulthood at the peak of the American war in Vietnam (1965-1975). The sample used for this study (n = 2254) were participants in the first VHAS wave in 2018., Results: We find older Vietnamese adults exposed to higher-intensity provincial bombing suffer more numerous somatic health complaints (unstandardized β = 0.005, SE = 0.001, p = 0.001). Additionally, greater health complaints emerge among older adults whose most intense bombing exposures were at younger ages of adolescence (< age 15) as compared to those whose peak exposures were in older ages (19-25) (unstandardized β = 0.62 95%, SE = 0.19, p = 0.01)., Conclusion: Our findings suggest that age of exposure to armed conflict is a critical determinant of weathering across the life course., Competing Interests: Declaration of Competing Interest The authors have no competing interests to report., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Background: Sarcopenia is defined as age-related low muscle mass and function, and can also describe the loss of muscle mass in certain medical conditions, such as sarcopenic obesity. Sarcopenic obesity describes loss of muscle and function in obese individuals; however, as sarcopenia is an age-related condition and obesity can occur in any age group, a more accurate term is obesity with low lean muscle mass (OLLMM). Given limited data on OLLMM (particularly in those aged < 65 years), the purpose of this study was to estimate the prevalence of OLLMM in adults aged ≥ 20 years in the USA., Methods: Data from the National Health and Nutrition Examination Survey (NHANES) 2017-2018 and 1999-2006 were used. OLLMM was defined as an appendicular lean mass, adjusted for body mass index (BMI), cut-off point < 0.789 for males and < 0.512 for females, measured by dual-energy X-ray absorptiometry (DXA). DXA was only measured in individuals 20-59 years old in NHANES 2017-2018; we therefore utilized logistic regression models to predict OLLMM from NHANES 1999-2006 for those aged ≥ 60 years. The prevalence of OLLMM was estimated overall, and by sex, age, race/ethnicity, and clinical subgroup (high BMI, prediabetes, type 2 diabetes mellitus [T2DM], non-alcoholic fatty liver disease [NAFLD] with fibrosis, or post-bariatric surgery). Prevalence estimates were extrapolated to the USA population using NHANES sampling weights., Results: We estimated that, during 2017-2018, 28.7 million or 15.9% of the USA population had OLLMM. The prevalence of OLLMM was greater in older individuals (8.1%, aged 20-59 years vs 28.3%, aged ≥ 60 years), highest (66.6%) in Mexican-American females aged ≥ 60 years, and lowest (2.6%) in non-Hispanic Black males aged 20-59 years. There was a higher prevalence of OLLMM in adults with prediabetes (19.7%), T2DM (34.5%), NAFLD with fibrosis (25.4%), or post-bariatric surgery (21.8%), compared with those without each condition., Conclusions: Overall, the burden of OLLMM in the USA is substantial, affecting almost 30 million adults. The prevalence of OLLMM increased with age, and among those with prediabetes, T2DM, NAFLD with fibrosis, or post-bariatric surgery. A unified definition of OLLMM will aid diagnosis and treatment strategies., (© 2022. The Author(s).)

Background: Arab Americans' experiences during the COVID-19 pandemic have been largely undocumented. Disparities in vaccine hesitancy between non-Hispanic Whites and minoritized groups have been observed, warranting exploration into the prevalence of COVID-19 vaccine hesitancy among Arab Americans., Methods: Data from the Survey of Arab Health in America (SAHA) (n = 638), collected between May 2020 and September 2020, were analyzed to determine predictors for vaccine intention among Arab Americans. Chi-squared tests and logistic regression models were performed to determine the relationship between sociodemographic, immigration, acculturation, and COVID-19 risk variables and vaccine intention., Results: More than half (56.7%) of respondents reported an intention to be vaccinated with a COVID-19 vaccine, 35.7% reported uncertainty, and 7.5% reported being unlikely to receive a vaccine. Of those unlikely to receive the vaccine, 72.9% were women and 85.4% reported moderate to high religiosity (p < 0.01). Arab American women had higher odds of being uncertain of their vaccine intention (OR = 1.68; 95% CI: 1.10, 2.57) or being unlikely to receive the vaccine (OR = 5.00; 95% CI: 1.95, 12.83) than men in this sample., Discussion: Factors such as high religiosity and gender were positively associated with being unlikely to receive a COVID-19 vaccine. Future studies should qualitatively assess the beliefs that undergird vaccine intention among Arab Americans., (© 2021. W. Montague Cobb-NMA Health Institute.)

Clonal haematopoiesis involves the expansion of certain blood cell lineages and has been associated with ageing and adverse health outcomes 1-5 . Here we use exome sequence data on 628,388 individuals to identify 40,208 carriers of clonal haematopoiesis of indeterminate potential (CHIP). Using genome-wide and exome-wide association analyses, we identify 24 loci (21 of which are novel) where germline genetic variation influences predisposition to CHIP, including missense variants in the lymphocytic antigen coding gene LY75, which are associated with reduced incidence of CHIP. We also identify novel rare variant associations with clonal haematopoiesis and telomere length. Analysis of 5,041 health traits from the UK Biobank (UKB) found relationships between CHIP and severe COVID-19 outcomes, cardiovascular disease, haematologic traits, malignancy, smoking, obesity, infection and all-cause mortality. Longitudinal and Mendelian randomization analyses revealed that CHIP is associated with solid cancers, including non-melanoma skin cancer and lung cancer, and that CHIP linked to DNMT3A is associated with the subsequent development of myeloid but not lymphoid leukaemias. Additionally, contrary to previous findings from the initial 50,000 UKB exomes 6 , our results in the full sample do not support a role for IL-6 inhibition in reducing the risk of cardiovascular disease among CHIP carriers. Our findings demonstrate that CHIP represents a complex set of heterogeneous phenotypes with shared and unique germline genetic causes and varied clinical implications., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

Muscle size is controlled by the PI3K-PKB/Akt-mTORC1-FoxO pathway, which integrates signals from growth factors, energy and amino acids to activate protein synthesis and inhibit protein breakdown. While mTORC1 activity is necessary for PKB/Akt-induced muscle hypertrophy, its constant activation alone induces muscle atrophy. Here we show that this paradox is based on mTORC1 activity promoting protein breakdown through the ubiquitin-proteasome system (UPS) by simultaneously inducing ubiquitin E3 ligase expression via feedback inhibition of PKB/Akt and proteasome biogenesis via Nuclear Factor Erythroid 2-Like 1 (Nrf1). Muscle growth was restored by reactivation of PKB/Akt, but not by Nrf1 knockdown, implicating ubiquitination as the limiting step. However, both PKB/Akt activation and proteasome depletion by Nrf1 knockdown led to an immediate disruption of proteome integrity with rapid accumulation of damaged material. These data highlight the physiological importance of mTORC1-mediated PKB/Akt inhibition and point to juxtaposed roles of the UPS in atrophy and proteome integrity., (© 2022. The Author(s).)

Childhood psychosocial stressors have been proposed to favour fast life history strategies promoting earlier puberty in females. However, studies demonstrating this association often do not elucidate causal mechanisms, nor account for greater childhood energetic availability - also known to promote rapid growth and earlier puberty. To assess the extent to which such confounding has been considered, we conducted a systematized review to identify studies examining measures of both prepubertal growth (e.g. weight, height) and psychosocial stressors (e.g. adversity, father absence) in relation to female pubertal timing. A total of 1069 non-duplicated studies were identified across five databases. Twenty studies met selection criteria for critical review following independent screening of titles, abstracts and manuscripts. Within these studies, measures indicative of rapid childhood growth were more consistently associated with earlier pubertal timing than were measures of psychosocial stress. We discuss future research directions to investigate the impact of psychosocial stress on pubertal timing more robustly, including methodological and mechanistic considerations, and contextualization of findings by socioecological environments., (© The Author(s) 2022.)

A subset of hospitalized COVID-19 patients, particularly the aged and those with comorbidities, develop the most severe form of the disease, characterized by acute respiratory disease syndrome (ARDS), coincident with experiencing a "cytokine storm." Here, we demonstrate that cytokines which activate the NF-κB pathway can induce activin A. Patients with elevated activin A, activin B, and FLRG at hospital admission were associated with the most severe outcomes of COVID-19, including the requirement for mechanical ventilation, and all-cause mortality. A prior study showed that activin A could decrease viral load, which indicated there might be a risk to giving COVID-19 patients an inhibitor of activin. To evaluate this, the role for activin A was examined in a hamster model of SARS-CoV-2 infection, via blockade of activin A signaling. The hamster model demonstrated that use of an anti-activin A antibody did not worsen the disease and there was no evidence for increase in lung viral load and pathology. The study indicates blockade of activin signaling may be beneficial in treating COVID-19 patients experiencing ARDS.

The XP-D/DinG family of DNA helicases contributes to genomic stability in all three domains of life. Here, we investigate the role of one of these proteins, YoaA, of Escherichia coli. In E. coli, YoaA aids in tolerance to the nucleoside azidothymidine (AZT), a DNA replication inhibitor, and physically interacts with a subunit of the DNA polymerase III holoenzyme, HolC. We map the residues of YoaA required for HolC interaction to its C terminus by yeast two-hybrid analysis. We propose that this interaction competes with HolC's interaction with HolD and the rest of the replisome; YoaA indeed inhibits growth when overexpressed, dependent on this interaction region. By gene fusions, we show that YoaA is repressed by LexA and induced in response to DNA damage as part of the SOS response. Induction of YoaA by AZT is biphasic, with an immediate response after treatment and a slower response that peaks in the late log phase of growth. This growth-phase-dependent induction by AZT is not blocked by lexA3 (Ind - ), which normally negates its self-cleavage, implying another means to induce the DNA damage response that responds to the nutritional state of the cell. We propose that YoaA helicase activity increases access to the 3' nascent strand during replication; consistent with this, YoaA appears to aid in the removal of potential A-to-T transversion mutations in ndk mutants, which are prone to nucleotide misincorporation. We provide evidence that YoaA and its paralog DinG may also initiate template switching that leads to deletions between tandem repeats in DNA. IMPORTANCE Maintaining genomic stability is crucial for all living organisms. Replication of DNA frequently encounters barriers that must be removed to complete genome duplication. Balancing DNA synthesis with its repair is critical and not entirely understood at a mechanistic level. The YoaA protein, studied here, is required for certain types of DNA repair and interacts in an alternative manner with proteins that catalyze DNA replication. YoaA is part of the well-studied LexA-regulated response to DNA damage, the SOS response. We describe an unusual feature of its regulation that promotes induction after DNA damage as the culture begins to experience starvation. Replication fork repair integrates both DNA damage and nutritional signals. We also show that YoaA affects genomic stability.

We conducted a genome-wide association study of 1320 centenarians from the New England Centenarian Study (median age = 104 years) and 2899 unrelated controls using >9 M genetic variants imputed to the HRC panel of ~65,000 haplotypes. The genetic variants with the most significant associations were correlated to 4131 proteins that were profiled in the serum of a subset of 224 study participants using a SOMAscan array. The genetic associations were replicated in a genome-wide association study of 480 centenarians and ~800 controls of Ashkenazi Jewish descent. The proteomic associations were replicated in a proteomic scan of approximately 1000 Ashkenazi Jewish participants from a third cohort. The analysis replicated a protein signature associated with APOE genotypes and confirmed strong overexpression of BIRC2 (p < 5E-16) and under-expression of APOB in carriers of the APOE2 allele (p < 0.05). The analysis also discovered and replicated associations between longevity variants and slower changes of protein biomarkers of aging, including a novel protein signature of rs2184061 (CDKN2A/CDKN2B in chromosome 9) that suggests a genetic regulation of GDF15. The analyses showed that longevity variants correlate with proteome signatures that could be manipulated to discover healthy-aging targets.

Efficient and faithful replication of DNA is essential for all organisms. However, the replication fork frequently encounters barriers that need to be overcome to ensure cell survival and genetic stability. Cells must carefully balance and regulate replication vs. repair reactions. In Escherichia coli, the replisome consists of the DNA polymerase III holoenzyme, including DNA polymerase, proofreading exonuclease, processivity clamp and clamp loader, as well as a fork helicase, DnaB and primase, DnaG. We provide evidence here that one component of the clamp loader complex, HolC (or χ) plays a dual role via its ability to form 2 mutually exclusive complexes: one with HolD (or ψ) that recruits the clamp-loader and hence the DNA polymerase holoenzyme and another with helicase-like YoaA protein, a DNA-damage inducible repair protein. By yeast 2 hybrid analysis, we show that two residues of HolC, F64 and W57, at the interface in the structure with HolD, are required for interaction with HolD and for interaction with YoaA. Mutation of these residues does not interfere with HolC's interaction with single-strand DNA binding protein, SSB. In vivo, these mutations fail to complement the poor growth and sensitivity to azidothymidine, a chain-terminating replication inhibitor. In support of the notion that these are exclusive complexes, co-expression of HolC, HolD and YoaA, followed by pulldown of YoaA, yields a complex with HolC but not HolD. YoaA fails to pulldown HolC-F64A. We hypothesize that HolC, by binding with SSB, can recruit the DNA polymerase III holoenzyme through HolD, or an alternative repair complex with YoaA helicase., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Using samples from the New England Centenarian Study (NECS), we sought to characterize the serum proteome of 77 centenarians, 82 centenarians' offspring, and 65 age-matched controls of the offspring (mean ages: 105, 80, and 79 years). We identified 1312 proteins that significantly differ between centenarians and their offspring and controls (FDR < 1%), and two different protein signatures that predict longer survival in centenarians and in younger people. By comparing the centenarian signature with 2 independent proteomic studies of aging, we replicated the association of 484 proteins of aging and we identified two serum protein signatures that are specific of extreme old age. The data suggest that centenarians acquire similar aging signatures as seen in younger cohorts that have short survival periods, suggesting that they do not escape normal aging markers, but rather acquire them much later than usual. For example, centenarian signatures are significantly enriched for senescence-associated secretory phenotypes, consistent with those seen with younger aged individuals, and from this finding, we provide a new list of serum proteins that can be used to measure cellular senescence. Protein co-expression network analysis suggests that a small number of biological drivers may regulate aging and extreme longevity, and that changes in gene regulation may be important to reach extreme old age. This centenarian study thus provides additional signatures that can be used to measure aging and provides specific circulating biomarkers of healthy aging and longevity, suggesting potential mechanisms that could help prolong health and support longevity., (© 2021 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.)

Covalent linkage between DNA and proteins produces highly toxic lesions and can be caused by commonly used chemotherapeutic agents, by internal and external chemicals and by radiation. In this study, using Escherichia coli, we investigate the consequences of 5-azacytidine (5-azaC), which traps covalent complexes between itself and the Dcm cytosine methyltransferase protein. DNA protein crosslink-dependent effects can be ascertained by effects that arise in wild-type but not in dcmΔ strains. We find that 5-azaC induces the bacterial DNA damage response and stimulates homologous recombination, a component of which is Dcm-dependent. Template-switching at an imperfect inverted repeat ("quasipalindrome", QP) is strongly enhanced by 5-azaC and this enhancement was entirely Dcm-dependent and independent of double-strand break repair. The SOS response helps ameliorate the mutagenic effect of 5-azaC but this is not a result of SOS-induced DNA polymerases since their induction, especially PolIV, seems to stimulate QP-associated mutagenesis. Cell division regulator SulA was also required for recovery of QP mutants induced by 5-azaC. In the absence of Lon protease, Dcm-dependent QP-mutagenesis is strongly elevated, suggesting it may play a role in DPC tolerance. Deletions at short tandem repeats, which occur likewise by a replication template-switch, are elevated, but only modestly, by 5-azaC. We see evidence for Dcm-dependent and-independent killing by 5-azaC in sensitive mutants, such as recA, recB, and lon; homologous recombination and deletion mutations are also stimulated in part by a Dcm-independent effect of 5-azaC. Whether this occurs by a different protein/DNA crosslink or by an alternative form of DNA damage is unknown., (Copyright © 2021. Published by Elsevier B.V.)

Aging is emerging as a druggable target with growing interest from academia, industry and investors. New technologies such as artificial intelligence and advanced screening techniques, as well as a strong influence from the industry sector may lead to novel discoveries to treat age-related diseases. The present review summarizes presentations from the 7 th Annual Aging Research and Drug Discovery (ARDD) meeting, held online on the 1 st to 4 th of September 2020. The meeting covered topics related to new methodologies to study aging, knowledge about basic mechanisms of longevity, latest interventional strategies to target the aging process as well as discussions about the impact of aging research on society and economy. More than 2000 participants and 65 speakers joined the meeting and we already look forward to an even larger meeting next year. Please mark your calendars for the 8 th ARDD meeting that is scheduled for the 31 st of August to 3 rd of September, 2021, at Columbia University, USA.

PsychTable.org is a new online, mass-collaborative tool for the social sciences that aggregates evidence for and classifies the evolved psychological adaptations (EPAs) that have been proposed to comprise the human mind. This article provides an overview of the need for this reference tool and how it can benefit researchers who incorporate the behavioral sciences into their work. The article walks the reader through a hypothetical use case for PsychTable.org and describes the features of the website. PsychTable.org is intended to help key stakeholders better understand the linkages between EPAs and political behavior, public policy, and ethics.

When replication forks encounter template DNA lesions, the lesion is simply skipped in some cases. The resulting lesion-containing gap must be converted to duplex DNA to permit repair. Some gap filling occurs via template switching, a process that generates recombination-like branched DNA intermediates. The Escherichia coli Uup and RadD proteins function in different pathways to process the branched intermediates. Uup is a UvrA-like ABC family ATPase. RadD is a RecQ-like SF2 family ATPase. Loss of both functions uncovers frequent and RecA-independent deletion events in a plasmid-based assay. Elevated levels of crossing over and repeat expansions accompany these deletion events, indicating that many, if not most, of these events are associated with template switching in postreplication gaps as opposed to simple replication slippage. The deletion data underpin simulations indicating that multiple postreplication gaps may be generated per replication cycle. Both Uup and RadD bind to branched DNAs in vitro. RadD protein suppresses crossovers and Uup prevents nucleoid mis-segregation. Loss of Uup and RadD function increases sensitivity to ciprofloxacin. We present Uup and RadD as genomic guardians. These proteins govern two pathways for resolution of branched DNA intermediates such that potentially deleterious genome rearrangements arising from frequent template switching are averted., (© The Author(s) 2019. Published by Oxford University Press on behalf of Nucleic Acids Research.)

The discovery of treatments to prevent or delay dementia and Alzheimer's disease is a priority. The gene APOE is associated with cognitive change and late-onset Alzheimer's disease, and epidemiological studies have provided strong evidence that the e 2 allele of APOE has a neuroprotective effect, it is associated with increased longevity and an extended healthy lifespan in centenarians. In this study, we correlated APOE genotype data of 222 participants of the New England Centenarian Study, including 75 centenarians, 82 centenarian offspring, and 65 controls, comprising 55 carriers of APOE e 2 , with aptamer-based serum proteomics (SomaLogic technology) of 4,785 human proteins corresponding to 4,137 genes. We discovered a signature of 16 proteins that associated with different APOE genotypes and replicated the signature in three independent studies. We also show that the protein signature tracks with gene expression profiles in brains of late-onset Alzheimer's disease versus healthy controls. Finally, we show that seven of these proteins correlate with cognitive function patterns in longitudinally collected data. This analysis in particular suggests that Baculoviral IAP repeat containing two (BIRC2) is a novel biomarker of neuroprotection that associates with the neuroprotective allele of APOE. Therefore, targeting APOE e 2 molecularly may preserve cognitive function., (© 2019 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.)

HDAC4, a class IIa histone deacetylase, is upregulated in skeletal muscle in response to denervation-induced atrophy. When HDAC4 is deleted postnatally, mice are partially protected from denervation. Despite the name "histone" deacetylase, HDAC4 demonstrably deacetylates cytosolic and non-histone nuclear proteins. We developed potent and selective class IIa HDAC inhibitors. Using these tools and genetic knockdown, we identified three previously unidentified substrates of HDAC4: myosin heavy chain, peroxisome proliferator-activated receptor gamma co-activator 1alpha (PGC-1α), and heat shock cognate 71 kDa protein (Hsc70). HDAC4 inhibition almost completely prevented denervation-induced loss of myosin heavy chain isoforms and blocked the action of their E3 ligase, MuRF1. PGC-1α directly interacts with class IIa HDACs; selective inhibitors increased PGC-1α protein in muscles. Hsc70 deacetylation by HDAC4 affects its chaperone activity. Through these endogenous HDAC4 substrates, we identified several muscle metabolic pathways that are regulated by class IIa HDACs, opening up new therapeutic options to treat skeletal muscle disorders and potentially other disease where these specific pathways are affected., (Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved.)

To understand the changes in gene expression that occur as a result of age, which might create a permissive or causal environment for age-related diseases, we produce a multi-time point age-related gene expression signature (AGES) from liver, kidney, skeletal muscle, and hippocampus of rats, comparing 6-, 9-, 12-, 18-, 21-, 24-, and 27-month-old animals. We focus on genes that changed in one direction throughout the lifespan of the animal, either early in life (early logistic changes), at mid-age (mid-logistic), late in life (late-logistic), or linearly, throughout the lifespan of the animal. The pathways perturbed because of chronological age demonstrate organ-specific and more-global effects of aging and point to mechanisms that could potentially be counter-regulated pharmacologically to treat age-associated diseases. A small number of genes are regulated by aging in the same manner in every tissue, suggesting they may be more-universal markers of aging., (Copyright © 2019 Novartis Institutes for Biomedical Research. Published by Elsevier Inc. All rights reserved.)

There is a lack of pharmacological interventions available for sarcopenia, a progressive age-associated loss of muscle mass, leading to a decline in mobility and quality of life. We found mTORC1 (mammalian target of rapamycin complex 1), a well-established positive modulator of muscle mass, to be surprisingly hyperactivated in sarcopenic muscle. Furthermore, partial inhibition of the mTORC1 pathway counteracted sarcopenia, as determined by observing an increase in muscle mass and fiber type cross-sectional area in select muscle groups, again surprising because mTORC1 signaling has been shown to be required for skeletal muscle mass gains in some models of hypertrophy. Additionally, several genes related to senescence were downregulated and gene expression indicators of neuromuscular junction denervation were diminished using a low dose of a "rapalog" (a pharmacological agent related to rapamycin). Therefore, partial mTORC1 inhibition may delay the progression of sarcopenia by directly and indirectly modulating multiple age-associated pathways, implicating mTORC1 as a therapeutic target to treat sarcopenia., (Copyright © 2019 Joseph et al.)

The hormone αKlotho regulates lifespan in mice, as knockouts die early of what appears to be accelerated aging due to hyperphosphatemia and soft tissue calcification. In contrast, the overexpression of αKlotho increases lifespan. Given the severe mouse phenotype, we generated zebrafish mutants for αklotho as well as its binding partner fibroblast growth factor-23 (fgf23). Both mutations cause shortened lifespan in zebrafish, with abrupt onset of behavioral and degenerative physical changes at around 5 months of age. There is a calcification of vessels throughout the body, most dramatically in the outflow tract of the heart, the bulbus arteriosus (BA). This calcification is associated with an ectopic activation of osteoclast differentiation pathways. These findings suggest that the gradual loss of αKlotho found in normal aging might give rise to ectopic calcification., (Copyright © 2019 Novartis Institutes for Biomedical Research. Published by Elsevier Inc. All rights reserved.)

Dopamine transporter (SLC6A3) deficiency causes infantile Parkinson disease, for which there is no effective therapy. We have explored the effects of genetically deleting SLC6A3 in zebrafish. Unlike the wild-type, slc6a3-/- fish hover near the tank bottom, with a repetitive digging-like behavior. slc6a3-/- fish manifest pruning and cellular loss of particular tyrosine hydroxylase-immunoreactive neurons in the midbrain. Clozapine, an effective therapeutic for treatment-resistant schizophrenia, rescues the abnormal behavior of slc6a3-/- fish. Clozapine also reverses the abnormalities in the A8 region of the mutant midbrain. By RNA sequencing analysis, clozapine increases the expression of erythropoietin pathway genes. Transgenic over-expression of erythropoietin in neurons of slc6a3-/- fish partially rescues the mutant behavior, suggesting a potential mechanistic basis for clozapine's efficacy., (Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved.)

Loss of innervation of skeletal muscle is a determinant event in several muscle diseases. Although several effectors have been identified, the pathways controlling the integrated muscle response to denervation remain largely unknown. Here, we demonstrate that PKB/Akt and mTORC1 play important roles in regulating muscle homeostasis and maintaining neuromuscular endplates after nerve injury. To allow dynamic changes in autophagy, mTORC1 activation must be tightly balanced following denervation. Acutely activating or inhibiting mTORC1 impairs autophagy regulation and alters homeostasis in denervated muscle. Importantly, PKB/Akt inhibition, conferred by sustained mTORC1 activation, abrogates denervation-induced synaptic remodeling and causes neuromuscular endplate degeneration. We establish that PKB/Akt activation promotes the nuclear import of HDAC4 and is thereby required for epigenetic changes and synaptic gene up-regulation upon denervation. Hence, our study unveils yet-unknown functions of PKB/Akt-mTORC1 signaling in the muscle response to nerve injury, with important implications for neuromuscular integrity in various pathological conditions.

Microgravity exposure is associated with loss of muscle mass and strength. The E3 ubiquitin ligase MuRF1 plays an integral role in degrading the contractile apparatus of skeletal muscle; MuRF1 null (KO) mice have shown protection in ground-based models of muscle atrophy. In contrast, MuRF1 KO mice subjected to 21 days of microgravity on the International Space Station (ISS) were not protected from muscle atrophy. In a time course experiment microgravity-induced muscle loss on the ISS showed MuRF1 gene expression was not upregulated. A comparison of the soleus transcriptome profiles between spaceflight and a publicly available data set for hindlimb suspension, a claimed surrogate model of microgravity, showed only marginal commonalities between the models. These findings demonstrate spaceflight induced atrophy is unique, and that understanding of effects of space requires study situated beyond the Earth's mesosphere.

The anabolic effects of β 2 -adrenoceptor ( β 2 -AR) agonists on skeletal muscle have been demonstrated in various species. However, the clinical use of β 2 -AR agonists for skeletal muscle wasting conditions has been limited by their undesired cardiovascular effects. Here, we describe the preclinical pharmacological profile of a novel 5-hydroxybenzothiazolone (5-HOB) derived β 2 -AR agonist in comparison with formoterol as a representative β 2 -AR agonist that have been well characterized. In vitro, 5-HOB has nanomolar affinity for the human β 2 -AR and selectivity over the β 1 -AR and β 3 -AR. 5-HOB also shows potent agonistic activity at the β 2 -AR in primary skeletal muscle myotubes and induces hypertrophy of skeletal muscle myotubes. Compared with formoterol, 5-HOB demonstrates comparable full-agonist activity on cAMP production in skeletal muscle cells and skeletal muscle tissue-derived membranes. In contrast, a greatly reduced intrinsic activity was determined in cardiomyocytes and cell membranes prepared from the rat heart. In addition, 5-HOB shows weak effects on chronotropy, inotropy, and vascular relaxation compared with formoterol. In vivo, 5-HOB significantly increases hind limb muscle weight in rats with attenuated effects on heart weight and ejection fraction, unlike formoterol. Furthermore, changes in cardiovascular parameters after bolus subcutaneous treatment in rats and rhesus monkeys are significantly lower with 5-HOB compared with formoterol. In conclusion, the pharmacological profile of 5-HOB indicates superior tissue selectivity compared with the conventional β 2 -AR agonist formoterol in preclinical studies and supports the notion that such tissue-selective agonists should be investigated for the safe treatment of muscle-wasting conditions without cardiovascular limiting effects., (Copyright © 2019 by The Author(s).)

GDF11 is a secreted factor in the TGFß family of cytokines. Its nearest neighbor evolutionarily is myostatin, a factor discovered as being a negative regulator of skeletal muscle growth. High profile studies several years ago suggested that GDF11 declines with age, and that restoration of systemic GDF11 to 'youthful' levels is beneficial for several age-related conditions. Particularly surprising was a report that supplementation of GDF11 aided skeletal muscle regeneration, as its homolog, myostatin, has the opposite role. Given this apparent contradiction in functionality, multiple independent labs sought to discern differences between the two factors and better elucidate age-related changes in circulating GDF11, with most failing to reproduce the initial finding of declining GDF11 levels, and, importantly, all subsequent studies examining the effects of GDF11 on skeletal muscle described an inhibitory effect on regeneration - and that higher doses induce skeletal muscle atrophy and cachexia. There have also been several studies examining the effect of GDF11 and/or the downstream ActRII pathway on cardiac function, along with several interesting reports on bone. A review of the GDF11 literature, as it relates in particular to aging and skeletal muscle, cardiac and bone biology, is presented.

Activin type II receptor (ActRII) ligands have been implicated in muscle wasting in aging and disease. However, the role of these ligands and ActRII signaling in the heart remains unclear. Here, we investigated this catabolic pathway in human aging and heart failure (HF) using circulating follistatin-like 3 (FSTL3) as a potential indicator of systemic ActRII activity. FSTL3 is a downstream regulator of ActRII signaling, whose expression is up-regulated by the major ActRII ligands, activin A, circulating growth differentiation factor-8 (GDF8), and GDF11. In humans, we found that circulating FSTL3 increased with aging, frailty, and HF severity, correlating with an increase in circulating activins. In mice, increasing circulating activin A increased cardiac ActRII signaling and FSTL3 expression, as well as impaired cardiac function. Conversely, ActRII blockade with either clinical-stage inhibitors or genetic ablation reduced cardiac ActRII signaling while restoring or preserving cardiac function in multiple models of HF induced by aging, sarcomere mutation, or pressure overload. Using unbiased RNA sequencing, we show that activin A, GDF8, and GDF11 all induce a similar pathologic profile associated with up-regulation of the proteasome pathway in mammalian cardiomyocytes. The E3 ubiquitin ligase, Smurf1, was identified as a key downstream effector of activin-mediated ActRII signaling, which increased proteasome-dependent degradation of sarcoplasmic reticulum Ca 2+ ATPase (SERCA2a), a critical determinant of cardiomyocyte function. Together, our findings suggest that increased activin/ActRII signaling links aging and HF pathobiology and that targeted inhibition of this catabolic pathway holds promise as a therapeutic strategy for multiple forms of HF., (Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Background: Spinal and bulbar muscular atrophy is an X-linked neuromuscular disease caused by CAG repeat expansion in the androgen receptor gene. Patients with this disease have low concentrations of insulin-like growth factor-1 (IGF-1), and studies of overexpression and administration of IGF-1 showed benefit in a transgenic model; thus the IGF-1 pathway presents as a potential treatment target. We assessed safety, tolerability, and preliminary efficacy of BVS857, an IGF-1 mimetic, in patients with spinal and bulbar muscular atrophy., Methods: In this randomised, double-blind, placebo-controlled trial, we recruited patients from neuromuscular centres in Denmark (Copenhagen), Germany (Ulm), Italy (Padova), and three sites within the USA (Bethesda, MD; Irvine, CA; and Columbus, OH). Eligible patients were 18 years or older with a confirmed genetic diagnosis of spinal and bulbar muscular atrophy, were ambulatory, had symptomatic weakness, and had serum IGF-1 concentrations of 170 ng/mL or lower. Patients were randomly assigned (2:1) to study drug or placebo by a number scheme. Patients, investigators, and study personnel were masked to treatment assignment. After a safety and tolerability assessment with eight patients, BVS857 was administered once a week (0·06 mg/kg intravenously) for 12 weeks. Primary outcome measures were safety, tolerability, and the effects of BVS857 on thigh muscle volume (TMV) measured by MRI. The ratio of TMV at day 85 to baseline was analysed with ANCOVA per protocol. Secondary outcomes of muscle strength and function were measured with the Adult Myopathy Assessment Tool, lean body mass through dual energy x-ray absorptiometry, and BVS857 pharmacokinetics. This trial was registered with ClinicalTrials.gov, NCT02024932., Findings: 31 patients were assessed for eligibility, 27 of whom were randomly assigned to either BVS857 treatment (n=18) or placebo (n=9), and 24 were included in the preliminary efficacy analysis (BVS857 group, n=15; placebo group, n=9). BVS857 was generally safe with no serious adverse events. No significant differences were found in adverse events between the BVS857 and placebo groups. Immunogenicity was detected in 13 (72%) of 18 patients in the BVS857 group, including crossreacting antibodies with neutralising capacity to endogenous IGF-1 in five patients. TMV decreased from baseline to day 85 in the placebo group (-3·4% [-110 cm 3 ]) but not in the BVS857 group (0% [2 cm 3 ]). A significant difference in change in TMV was observed in the BVS857 group versus the placebo group (geometric-mean ratio 1·04 [90% CI 1·01-1·07]; p=0·02). There were no differences between groups in measures of muscle strength and function., Interpretation: TMV remained stable in patients with spinal and bulbar muscular atrophy after being given BVS857 for 12 weeks. The intervention was associated with high incidence of immunogenicity and did not improve muscle strength or function. Additional studies might be needed to assess the efficacy of activating the IGF-1 pathway in this disease., Funding: Novartis Pharmaceuticals and the US National Institutes of Health., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Facioscapulohumeral muscular dystrophy (FSHD) is among the most prevalent of the adult-onset muscular dystrophies. FSHD causes a loss of muscle mass and function, resulting in severe debilitation and reduction in quality of life. Currently, only the symptoms of FSHD can be treated, and such treatments have minimal benefit. The available options are not curative, and none of the treatments address the underlying cause of FSHD. The genetic, epigenetic, and molecular mechanisms triggering FSHD are now quite well-understood, and it has been shown that expression of the transcriptional regulator double homeobox 4 ( DUX4 ) is necessary for disease onset and is largely thought to be the causative factor in FSHD. Therefore, we sought to identify compounds suppressing DUX4 expression in a phenotypic screen using FSHD patient-derived muscle cells, a zinc finger and SCAN domain-containing 4 (ZSCAN4)-based reporter gene assay for measuring DUX4 activity, and ∼3,000 small molecules. This effort identified molecules that reduce DUX4 gene expression and hence DUX4 activity. Among those, β 2 -adrenergic receptor agonists and phosphodiesterase inhibitors, both leading to increased cellular cAMP, effectively decreased DUX4 expression by >75% in cells from individuals with FSHD. Of note, we found that cAMP production reduces DUX4 expression through a protein kinase A-dependent mode of action in FSHD patient myotubes. These findings increase our understanding of how DUX4 expression is regulated in FSHD and point to potential areas of therapeutic intervention., Competing Interests: The authors declare that they have no conflicts of interest with the contents of this article., (© 2018 Cruz et al.)

Inhibition of the mechanistic target of rapamycin (mTOR) protein kinase extends life span and ameliorates aging-related pathologies including declining immune function in model organisms. The objective of this phase 2a randomized, placebo-controlled clinical trial was to determine whether low-dose mTOR inhibitor therapy enhanced immune function and decreased infection rates in 264 elderly subjects given the study drugs for 6 weeks. A low-dose combination of a catalytic (BEZ235) plus an allosteric (RAD001) mTOR inhibitor that selectively inhibits target of rapamycin complex 1 (TORC1) downstream of mTOR was safe and was associated with a significant ( P = 0.001) decrease in the rate of infections reported by elderly subjects for a year after study drug initiation. In addition, we observed an up-regulation of antiviral gene expression and an improvement in the response to influenza vaccination in this treatment group. Thus, selective TORC1 inhibition has the potential to improve immune function and reduce infections in the elderly., (Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Rapalogs, inhibitors of mTORC1 (mammalian target of rapamycin complex 1), increase life span and delay age-related phenotypes in many species. However, the molecular mechanisms have not been fully elucidated. We determined gene expression changes comparing 6- and 24-month-old rats in the kidney, liver, and skeletal muscle, and asked which of these changes were counter-regulated by a clinically-translatable (short-term and low-concentration) treatment, with a rapalog (RAD001). Surprisingly, RAD001 had a more pronounced effect on the kidney under this regimen in comparison to the liver or skeletal muscle. Histologic evaluation of kidneys revealed that the severity of chronic progressive nephropathy lesions was lower in kidneys from 24-month-old rats treated with RAD001 compared with vehicle. In addition to other gene expression changes, c-Myc, which has been shown to regulate aging, was induced by aging in the kidney and counter-regulated by RAD001. RAD001 caused a decrease in c-Myc protein, which could be rescued by a proteasome inhibitor. These findings point to settings for use of mTORC1 inhibitors to treat age-related disorders, and highlight c-Myc regulation as one of the potential mechanisms by which mTORC1 inhibition is perturbing age-related phenotypes.

Background: Sarcopenia is defined as the age-related loss of skeletal muscle mass and function. While all humans lose muscle with age, 2-5% of elderly adults develop functional consequences (disabilities). The aim of this study was to investigate muscle myogenesis in healthy elderly adults, with or without sarcopenia, compared with middle-aged controls using both in vivo and in vitro approaches to explore potential biomarker or causative molecular pathways associated with sarcopenic versus non-sarcopenic skeletal muscle phenotypes during ageing., Methods: Biomarkers of multiple molecular pathways associated with muscle regeneration were analysed using quantitative polymerase chain reaction in quadriceps muscle samples obtained from healthy elderly sarcopenic (HSE, n = 7) or non-sarcopenic (HENS, n = 21) and healthy middle-aged control (HMC, n = 22) groups. An in vitro system of myogenesis (using myoblasts from human donors aged 17-83 years) was used to mimic the environmental challenges of muscle regeneration over time., Results: The muscle biopsies showed evidence of satellite cell activation in HENS (Pax3, P < 0.01, Pax7, P < 0.0001) compared with HMC. Early myogenesis markers Myogenic Differentiation 1 (MyoD1) and Myogenic factor 5 (Myf5) (P < 0.0001) and the late myogenesis marker myogenin (MyoG) (P < 0.01) were increased in HENS. In addition, there was a 30-fold upregulation of TNF-α in HENS compared with HMC (P < 0.0001). The in vitro system demonstrated age-related upregulation of pro-inflammatory cytokines (2-fold upregulation of interleukin (IL)-6, IL-8 mRNA, increased secretion of tumor necrosis factor-α (TNF-α) and IL-6, all P < 0.05) associated with impaired kinetics of myotube differentiation. The HSE biopsy samples showed satellite cell activation (Pax7, P < 0.05) compared with HMC. However, no significant upregulation of the early myogenesis (MyoD and Myf5) markers was evident; only the late myogenesis marker myogenin was upregulated (P < 0.05). Higher activation of the oxidative stress pathway was found in HENS compared with the HSE group. In contrast, there was 10-fold higher upregulation of HSPA1A a stress-induced chaperone acting upon misfolded proteins in HSE compared with the HENS group., Conclusions: Both pathological and adaptive processes are active in skeletal muscle during healthy ageing. Muscle regeneration pathways are activated during healthy ageing, but there is evidence of dysregulation in sarcopenia. In addition, increased cellular stress, with an impaired oxidative-stress and mis-folded protein response (HSPA1A), may be associated with the development of sarcopenia. The in vitro system of young and old myoblasts replicated some of the differences between young and old muscle., (© 2017 The Authors. Journal of Cachexia, Sarcopenia and Muscle published by John Wiley & Sons Ltd on behalf of the Society on Sarcopenia, Cachexia and Wasting Disorders.)

ATP citrate lyase (ACL) plays a key role in regulating mitochondrial function, as well as glucose and lipid metabolism in skeletal muscle. We report here that ACL silencing impairs myoblast and satellite cell (SC) differentiation, and it is accompanied by a decrease in fast myosin heavy chain isoforms and MYOD. Conversely, overexpression of ACL enhances MYOD levels and promotes myogenesis. Myogenesis is dependent on transcriptional but also other mechanisms. We show that ACL regulates the net amount of acetyl groups available, leading to alterations in acetylation of H3(K9/14) and H3(K27) at the MYOD locus, thus increasing MYOD expression. ACL overexpression in murine skeletal muscle leads to improved regeneration after cardiotoxin-mediated damage. Thus, our findings suggest a mechanism for regulating SC differentiation and enhancing regeneration, which might be exploited for devising therapeutic approaches for treating skeletal muscle disease., (Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.)

The TGF-β family ligands myostatin, GDF11, and activins are negative regulators of skeletal muscle mass, which have been reported to primarily signal via the ActRIIB receptor on skeletal muscle and thereby induce muscle wasting described as cachexia. Use of a soluble ActRIIB-Fc "trap," to block myostatin pathway signaling in normal or cachectic mice leads to hypertrophy or prevention of muscle loss, perhaps suggesting that the ActRIIB receptor is primarily responsible for muscle growth regulation. Genetic evidence demonstrates however that both ActRIIB- and ActRIIA-deficient mice display a hypertrophic phenotype. Here, we describe the mode of action of bimagrumab (BYM338), as a human dual-specific anti-ActRIIA/ActRIIB antibody, at the molecular and cellular levels. As shown by X-ray analysis, bimagrumab binds to both ActRIIA and ActRIIB ligand binding domains in a competitive manner at the critical myostatin/activin binding site, hence preventing signal transduction through either ActRII. Myostatin and the activins are capable of binding to both ActRIIA and ActRIIB, with different affinities. However, blockade of either single receptor through the use of specific anti-ActRIIA or anti-ActRIIB antibodies achieves only a partial signaling blockade upon myostatin or activin A stimulation, and this leads to only a small increase in muscle mass. Complete neutralization and maximal anabolic response are achieved only by simultaneous blockade of both receptors. These findings demonstrate the importance of ActRIIA in addition to ActRIIB in mediating myostatin and activin signaling and highlight the need for blocking both receptors to achieve a strong functional benefit., Competing Interests: Conflict of interest statement: All authors but F.W. are employees of Novartis Pharma AG (F.M., C.Z., C.S., J.-M.R., C.J., A.S., P.B., V.R., G.T., M.K., X.L., S.L., E.K., G.M., C.K., S.G., D.J.G., E.L.-T.), and some are also shareholders of Novartis. F.W. was an employee of MorphoSys AG at the time of contribution., (Copyright © 2017 the Author(s). Published by PNAS.)