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Superoxide produced by mitochondria has been implicated in numerous physiologies and pathologies. Eleven different mitochondrial sites that can produce superoxide and/or hydrogen peroxide (O2.-/H2O2) have been identified in vitro, but little is known about their contributions in vivo. We introduce novel variants of S1QELs and S3QELs (small molecules that suppress O2.-/H2O2 production specifically from mitochondrial sites IQ and IIIQo, respectively, without compromising bioenergetics), that are suitable for use in vivo. When administered by intraperitoneal injection, they achieve total tissue concentrations exceeding those that are effective in vitro. We use them to study the engagement of sites IQ and IIIQo in mice lacking functional manganese-superoxide dismutase (SOD2). Lack of SOD2 is expected to elevate superoxide levels in the mitochondrial matrix, and leads to severe pathologies and death about 8 days after birth. Compared to littermate wild-type mice, 6-day-old Sod2-/- mice had significantly lower body weight, lower heart succinate dehydrogenase activity, and greater hepatic lipid accumulation. These pathologies were ameliorated by treatment with a SOD/catalase mimetic, EUK189, confirming previous observations. A 3-day treatment with S1QEL352 decreased the inactivation of cardiac succinate dehydrogenase and hepatic steatosis in Sod2-/- mice. S1QEL712, which has a distinct chemical structure, also decreased hepatic steatosis, confirming that O2.- derived specifically from mitochondrial site IQ is a significant driver of hepatic steatosis in Sod2-/- mice. These findings also demonstrate the ability of these new S1QELs to suppress O2.- production in the mitochondrial matrix in vivo. In contrast, suppressing site IIIQo using S3QEL941 did not protect, suggesting that site IIIQo does not contribute significantly to mitochondrial O2.- production in the hearts or livers of Sod2-/- mice. We conclude that the novel S1QELs are effective in vivo, and that site IQ runs in vivo and is a significant driver of pathology in Sod2-/- mice.

Many vital processes in the eye are under circadian regulation, and circadian dysfunction has emerged as a potential driver of eye aging. Dietary restriction is one of the most robust lifespan-extending therapies and amplifies circadian rhythms with age. Herein, we demonstrate that dietary restriction extends lifespan in D. melanogaster by promoting circadian homeostatic processes that protect the visual system from age- and light-associated damage. Disrupting circadian rhythms in the eye by inhibiting the transcription factor, Clock (CLK), or CLK-output genes, accelerated visual senescence, induced a systemic immune response, and shortened lifespan. Flies subjected to dietary restriction were protected from the lifespan-shortening effects of photoreceptor activation. Inversely, photoreceptor inactivation, achieved via mutating rhodopsin or housing flies in constant darkness, primarily extended lifespan in flies reared on a high-nutrient diet. Our findings establish the eye as a diet-sensitive modulator of lifespan and indicate that vision is an antagonistically pleiotropic process that contributes to organismal aging.

Skeletal muscle mass and function can decline with aging, resulting in a syndrome known as sarcopenia. This decline is linked to functional alterations in critical cell types within mature muscle, including fibro-adipogenic progenitors (FAPs) and satellite cells (SCs), driven in part by cellular senescence. We utilized single-cell RNA sequencing and isolated FAPs and SCs to identify novel targets responsible for senescent cell killing - senolysis. We identified the small alpha-crystalline heat shock protein CRYAB as a novel senolytic target. Using chemical inhibitor screening of CRYAB, we identified 25-hydroxycholesterol (25HC), an endogenous metabolite of cholesterol biosynthesis, as a potent senolytic capable of killing senescent cells. We validated 25HC as a senolytic in mouse and human cells in culture and in vivo in mouse skeletal muscle. Thus, 25HC represents a potential new class of senolytics, which may be useful in combating diseases or physiologies in which cellular senescence is a key driver.

Aging is accompanied by a loss of muscle mass and function, termed sarcopenia, which causes numerous morbidities and economic burdens in human populations. Mechanisms implicated in age-related sarcopenia include inflammation, muscle stem cell depletion, mitochondrial dysfunction and loss of motor neurons, but whether there are key drivers of sarcopenia is not yet known. To gain deeper insights into age-related sarcopenia, we performed transcriptome profiling on lower limb muscle biopsies from 72 young, old and sarcopenic subjects using bulk RNA-seq (N = 72) and single-nuclei RNA-seq (N = 17). This combined approach revealed novel changes in gene expression that occur with age and sarcopenia in multiple cell types comprising mature skeletal muscle. Notably, we found increased expression of the genes MYH8 and PDK4, and decreased expression of the gene IGFN1, in old muscle. We validated key genes in fixed human muscle tissue using digital spatial profiling. We also identified a small population of nuclei that express CDKN1A, present only in aged samples, consistent with p21-driven senescence in this subpopulation. Overall, our findings identify unique cellular subpopulations in aged and sarcopenic skeletal muscle, which will facilitate the development of new therapeutic strategies to combat age-related sarcopenia.

Summary Senescent cells play important roles in both physiological and pathological processes, including cancer and aging. In all cases, however, senescent cells comprise only a small fraction of tissues. Senescent phenotypes have been studied largely in relatively homogeneous populations of cultured cells. In vivo, senescent cells are generally identified by a small number of markers, but whether and how these markers vary among individual cells is unknown. We therefore utilized a combination of single‐cell isolation and a nanofluidic PCR platform to determine the contributions of individual cells to the overall gene expression profile of senescent human fibroblast populations. Individual senescent cells were surprisingly heterogeneous in their gene expression signatures. This cell‐to‐cell variability resulted in a loss of correlation among the expression of several senescence‐associated genes. Many genes encoding senescence‐associated secretory phenotype (SASP) factors, a major contributor to the effects of senescent cells in vivo, showed marked variability with a subset of highly induced genes accounting for the increases observed at the population level. Inflammatory genes in clustered genomic loci showed a greater correlation with senescence compared to nonclustered loci, suggesting that these genes are coregulated by genomic location. Together, these data offer new insights into how genes are regulated in senescent cells and suggest that single markers are inadequate to identify senescent cells in vivo.

Cellular senescence suppresses cancer by irreversibly arresting cell proliferation. Senescent cells acquire a proinflammatory senescence-associated secretory phenotype. Many genotoxic chemotherapies target proliferating cells nonspecifically, often with adverse reactions. In accord with prior work, we show that several chemotherapeutic drugs induce senescence of primary murine and human cells. Using a transgenic mouse that permits tracking and eliminating senescent cells, we show that therapy-induced senescent (TIS) cells persist and contribute to local and systemic inflammation. Eliminating TIS cells reduced several short- and long-term effects of the drugs, including bone marrow suppression, cardiac dysfunction, cancer recurrence, and physical activity and strength. Consistent with our findings in mice, the risk of chemotherapy-induced fatigue was significantly greater in humans with increased expression of a senescence marker in T cells prior to chemotherapy. These findings suggest that senescent cells can cause certain chemotherapy side effects, providing a new target to reduce the toxicity of anticancer treatments. Significance: Many genotoxic chemotherapies have debilitating side effects and also induce cellular senescence in normal tissues. The senescent cells remain chronically present where they can promote local and systemic inflammation that causes or exacerbates many side effects of the chemotherapy. Cancer Discov; 7(2); 165–76. ©2016 AACR. This article is highlighted in the In This Issue feature, p. 115

Summary: Most ribosomal proteins (RP) are regarded as essential, static components that contribute only to ribosome biogenesis and protein synthesis. However, emerging evidence suggests that RNA-binding RP are dynamic and can influence cellular processes by performing “extraribosomal,” regulatory functions involving binding to select critical target mRNAs. We report here that the RP, Rpl22, and its highly homologous paralog Rpl22-Like1 (Rpl22l1 or Like1) play critical, extraribosomal roles in embryogenesis. Indeed, they antagonistically control morphogenesis through developmentally regulated localization to the nucleus, where they modulate splicing of the pre-mRNA encoding smad2, an essential transcriptional effector of Nodal/TGF-β signaling. During gastrulation, Rpl22 binds to intronic sequences of smad2 pre-mRNA and induces exon 9 skipping in cooperation with hnRNP-A1. This action is opposed by its paralog, Like1, which promotes exon 9 inclusion in the mature transcript. The nuclear roles of these RP in controlling morphogenesis represent a fundamentally different and paradigm-shifting mode of action for RP. : Zhang et al. reveal that ribosomal proteins can perform regulatory functions of fundamental importance while separated from the ribosome. They demonstrate that ribosomal proteins Rpl22 and Rpl22-Like1 (Like1) are retained in the nucleus during gastrulation, where they control morphogenesis by modulating the splicing of Smad2 pre-mRNA in cooperation with HNRNP-A1. Keywords: ribosomal protein, paralog, morphogenesis, gastrulation, extraribosomal function, Rpl22, Rpl22l1, pre-mRNA splicing, Smad2, hnRNP-A1

Summary: Vitamin D has multiple roles, including the regulation of bone and calcium homeostasis. Deficiency of 25-hydroxyvitamin D, the major circulating form of vitamin D, is associated with an increased risk of age-related chronic diseases, including Alzheimer’s disease, Parkinson’s disease, cognitive impairment, and cancer. In this study, we utilized Caenorhabditis elegans to examine the mechanism by which vitamin D influences aging. We found that vitamin-D3-induced lifespan extension requires the stress response pathway genes skn-1, ire-1, and xbp-1. Vitamin D3 (D3) induced expression of SKN-1 target genes but not canonical targets of XBP-1. D3 suppressed an important molecular pathology of aging, that of widespread protein insolubility, and prevented toxicity caused by human β-amyloid. Our observation that D3 improves protein homeostasis and slows aging highlights the importance of maintaining appropriate vitamin D serum levels and may explain why such a wide variety of human age-related diseases are associated with vitamin D deficiency. : Maintenance of protein homeostasis is crucial to cellular health and contributes significantly to the lifespan of organisms. Mark et al. demonstrate that vitamin D supplementation promotes protein homeostasis and slows aging in the nematode, C. elegans. These findings identify a mechanism by which vitamin D influences aging. Keywords: Ceanorhabditis elegans, vitamin D, lifespan. aging, insoluble protein, SKN-1, XBP-1, IRE-1, proteostasis, protein aggregation, Alzheimer’s disease

© 2017 Elsevier Ltd Cellular senescence is a state of irreversibly arrested proliferation, often induced by genotoxic stress [1]. Senescent cells participate in a variety of physiological and pathological conditions, including tumor suppression [2], embryonic development [3, 4], tissue repair [5–8], and organismal aging [9]. The senescence program is variably characterized by several non-exclusive markers, including constitutive DNA damage response (DDR) signaling, senescence-associated β-galactosidase (SA-βgal) activity, increased expression of the cyclin-dependent kinase (CDK) inhibitors p16INK4A (CDKN2A) and p21CIP1 (CDKN1A), increased secretion of many bio-active factors (the senescence-associated secretory phenotype, or SASP), and reduced expression of the nuclear lamina protein LaminB1 (LMNB1) [1]. Many senescence-associated markers result from altered transcription, but the senescent phenotype is variable, and methods for clearly identifying senescent cells are lacking [10]. Here, we characterize the heterogeneity of the senescence program using numerous whole-transcriptome datasets generated by us or publicly available. We identify transcriptome signatures associated with specific senescence-inducing stresses or senescent cell types and identify and validate genes that are commonly differentially regulated. We also show that the senescent phenotype is dynamic, changing at varying intervals after senescence induction. Identifying novel transcriptome signatures to detect any type of senescent cell or to discriminate among diverse senescence programs is an attractive strategy for determining the diverse biological roles of senescent cells and developing specific drug targets.

Recently, we used several assays of expression and function to quantify adrenergic receptors (ARs) in isolated, individual adult mouse ventricular myocytes. We found that the β1 and α1B were present on all cells. The α1A was expressed and functional in a 60% subset, with 20% having high receptor levels, and the β2 and β3 were mostly absent on myocytes, but abundant on nonmyocytes.1 Balligand and Michel raise concerns that we could have missed β3-ARs on myocytes with our assays, instead proposing an important role for the β3-AR in cardiac myocytes (in the letter by Balligand and Michel). We thank our colleagues for calling attention to our article. However, we disagree with their concerns. First, Balligand and Michel note that our mRNA arrays and RT-qPCR might not have detected the C-terminal b isoform of the mouse β3-AR.2 On the contrary, the β3-mRNA probes in our arrays, which detected only 4 of 50 cells positive for the β3 (Figure 6 in the study by Myagmar et al1), targeted the exon common to both the a and b isoforms. Our RT-qPCR, which used intron-spanning primers, focused on the a isoform because the β3 b isoform is an extremely tiny fraction of a low total β3-mRNA in mouse heart,2 and its presence or absence would not alter the conclusions. Our RT-qPCR found no β3 in ventricular myocytes but abundant β3 in nonmyocytes, including endothelial cells (Online Figure V in the study by Myagmar et al1). Second, Balligand and Michel raise concerns that our radioligand …

Rationale: It is unknown whether every ventricular myocyte expresses all 5 of the cardiac adrenergic receptors (ARs), β1, β2, β3, α1A, and α1B. The β1 and β2 are thought to be the dominant myocyte ARs. Objective: Quantify the 5 cardiac ARs in individual ventricular myocytes. Methods and Results: We studied ventricular myocytes from wild-type mice, mice with α1A and α1B knockin reporters, and β1 and β2 knockout mice. Using individual isolated cells, we measured knockin reporters, mRNAs, signaling (phosphorylation of extracellular signal–regulated kinase and phospholamban), and contraction. We found that the β1 and α1B were present in all myocytes. The α1A was present in 60%, with high levels in 20%. The β2 and β3 were detected in only ≈5% of myocytes, mostly in different cells. In intact heart, 30% of total β-ARs were β2 and 20% were β3, both mainly in nonmyocytes. Conclusion: The dominant ventricular myocyte ARs present in all cells are the β1 and α1B. The β2 and β3 are mostly absent in myocytes but are abundant in nonmyocytes. The α1A is in just over half of cells, but only 20% have high levels. Four distinct myocyte AR phenotypes are defined: 30% of cells with β1 and α1B only; 60% that also have the α1A; and 5% each that also have the β2 or β3. The results raise cautions in experimental design, such as receptor overexpression in myocytes that do not express the AR normally. The data suggest new paradigms in cardiac adrenergic signaling mechanisms.

Summary Aging causes cardiac dysfunction, often leading to heart failure and death. The molecular basis of age‐associated changes in cardiac structure and function is largely unknown. The fruit fly, Drosophila melanogaster, is well‐suited to investigate the genetics of cardiac aging. Flies age rapidly over the course of weeks, benefit from many tools to easily manipulate their genome, and their heart has significant genetic and phenotypic similarities to the human heart. Here, we performed a cardiac‐specific gene expression study on aging Drosophila and carried out a comparative meta‐analysis with published rodent data. Pathway level transcriptome comparisons suggest that age‐related, extra‐cellular matrix remodeling and alterations in mitochondrial metabolism, protein handling, and contractile functions are conserved between Drosophila and rodent hearts. However, expression of only a few individual genes similarly changed over time between and even within species. We also examined gene expression in single fly hearts and found significant variability as has been reported in rodents. We propose that individuals may arrive at similar cardiac aging phenotypes via dissimilar transcriptional changes, including those in transcription factors and micro‐RNAs. Finally, our data suggest the transcription factor Odd‐skipped, which is essential for normal heart development, is also a crucial regulator of cardiac aging.

Lean body mass, consisting mostly of skeletal muscle, is important for healthy aging. We performed a genome-wide association study for whole body (20 cohorts of European ancestry with n = 38,292) and appendicular (arms and legs) lean body mass (n = 28,330) measured using dual energy X-ray absorptiometry or bioelectrical impedance analysis, adjusted for sex, age, height, and fat mass. Twenty-one single-nucleotide polymorphisms were significantly associated with lean body mass either genome wide (p, We acknowledge the essential role of the Cohorts for Heart and Aging Research in Genome Epidemiology (CHARGE) Consortium in development and support of this manuscript. CHARGE members include the Netherland’s Rotterdam Study (RS), Framingham Heart Study (FHS), Cardiovascular Health Study (CHS), the NHLBI’s Atherosclerosis Risk in Communities (ARIC) Study, and Iceland’s Age, Gene/Environment Susceptibility (AGES) Reykjavik Study. Age, Gene/Environment Susceptibility Reykjavik Study (AGES-Reykjavik): has been funded by NIH contract N01-AG-12100, the NIA Intramural Research Program, Hjartavernd (the Icelandic Heart Association), and the Althingi (the Icelandic Parliament). The study is approved by the Icelandic National Bioethics Committee, (VSN: 00-063) and the Data Protection Authority. The researchers are indebted to the participants for their willingness to participate in the study. Old Order Amish (OOA): this work was supported by NIH research grants U01 HL72515, U01 GM074518, R01 HL088119, R01 AR046838, and U01 HL084756. Partial funding was also provided by the Mid-Atlantic Nutrition and Obesity Research Center of Maryland (P30 DK072488).). L.M.Y.-A. was supported by F32AR059469 from NIH/NIAMS. M.F. was supported by American Heart Association grant 10SDG2690004. Cardiovascular Health Study (CHS): This CHS research was supported by NHLBI contracts N01-HC- 85079, N01-HC-85080, N01-HC-85081, N01-HC-85082, N01-HC-85083, N01-HC-85084, N01-HC-85085, N01-HC-85086; N01-HC-35129, N01 HC-15103, N01 HC-55222, N01-HC-75150, N01-HC-45133, N01-HC-85239, and by HHSN268201200036C and NHLBI grants HL080295, HL087652, HL105756, HL103612, HL120393, and HL130114 with additional contribution from NINDS. Additional support was provided through AG-023629, AG-15928, AG-20098, and AG-027058 from the NIA. See also http://www.chs-nhlbi.org/pi.htm. DNA handling and genotyping at Cedars-Sinai Medical Center was supported in part by the National Center for Research Resources, grant UL1RR033176, and is now at the National Center for Advancing Translational Sciences, CTSI grant UL1TR000124; in addition to the National Institute of Diabetes and Digestive and Kidney Disease grant DK063491 to the Southern California Diabetes Endocrinology Research Center. CoLaus: The CoLaus study received financial contributions from GlaxoSmithKline, the Faculty of Biology and Medicine of Lausanne, and the Swiss National Science Foundation (grants 33CSCO-122661, 33CS30-139468, and 33CS30-148401). We thank Vincent Mooser and Gérard Waeber, Co-PIs of the CoLaus study. Special thanks to Yolande Barreau, Mathieu Firmann, Vladimir Mayor, Anne-Lise Bastian, Binasa Ramic, Martine Moranville, Martine Baumer, Marcy Sagette, Jeanne Ecoffey, and Sylvie Mermoud for data collection. Data analysis was supervised by Sven Bergmann and Jacques S. Beckmann. The computations for this paper were performed in part at the Vital-IT Center for high-performance computing of the Swiss Institute of Bioinformatics. deCODE Study: The study was funded by deCODE Genetics, ehf. We thank all the participants of this study, the staff of deCODE Genetics core facilities and recruitment center and the densitometry clinic at the University Hospital for their important contributions to this work. The EPIC Study: The EPIC Obesity study is funded by Cancer Research United Kingdom and the Medical Research Council. I.B. acknowledges support from EU FP6 funding (contract no. LSHM-CT-2003-503041) and by the Wellcome Trust (WT098051). Erasmus Rucphen Family (ERF) Study: The study was supported by grants from The Netherlands Organisation for Scientific Research (NWO), Erasmus MC, the Centre for Medical Systems Biology (CMSB), and the European Community’s Seventh Framework Programme (FP7/2007-2013), ENGAGE Consortium, grant agreement HEALTH-F4-2007-201413. We are grateful to all general practitioners for their contributions, to Petra Veraart for her help in genealogy, Jeannette Vergeer for the supervision of the laboratory work and Peter Snijders for his help in data collection. Fenland: The Fenland Study is funded by the Wellcome Trust and the Medical Research Council, as well as by the Support for Science Funding programme and CamStrad. We are grateful to all the volunteers for their time and help, and to the General Practitioners and practice staff for help with recruitment. We thank the Fenland Study co-ordination team and the Field Epidemiology team of the MRC Epidemiology Unit for recruitment and clinical testing. Tuomas O. Kilpeläinen was supported by the Danish Council for Independent Research (DFF—1333-00124 and Sapere Aude program grant DFF—1331-00730B). Framingham Osteoporosis Study (FOS)/Framingham Heart Study (FHS): The study was funded by grants from the US National Institute for Arthritis, Musculoskeletal and Skin Diseases and National Institute on Aging (R01 AR 41398 and U24AG051129; D.P.K. and R01AR057118; D.K. D.K. was also supported by FP7-PEOPLE-2012-Marie Curie Career Integration Grants (CIG)). The Framingham Heart Study of the National Heart, Lung, and Blood Institute of the National Institutes of Health and Boston University School of Medicine were supported by the National Heart, Lung, and Blood Institute’s Framingham Heart Study (N01-HC-25195) and its contract with Affymetrix, Inc. for genotyping services (N02-HL-6-4278). Analyses reflect intellectual input and resource development from the Framingham Heart Study investigators participating in the SNP Health Association Resource (SHARe) project. A portion of this research was conducted using the Linux Cluster for Genetic Analysis (LinGA-II) funded by the Robert Dawson Evans Endowment of the Department of Medicine at Boston University School of Medicine and Boston Medical Center. eQTL HOb Study: The study was supported by Genome Quebec, Genome Canada and the Canadian Institutes of Health Research (CIHR). Gothenburg Osteoporosis and Obesity Determinants Study (GOOD): The study was funded by the Swedish Research Council, the Swedish Foundation for Strategic Research, The ALF/LUA research grant in Gothenburg, the Lundberg Foundation, the Emil and Vera Cornell Foundation, the Torsten and Ragnar Söderberg’s Foundation, Petrus and Augusta Hedlunds Foundation, the Västra Götaland Foundation, and the Göteborg Medical Society. We would like to thank Dr Tobias A. Knoch, Luc V. de Zeeuw, Anis Abuseiris, and Rob de Graaf as well as their institutions the Erasmus Computing Grid, Rotterdam, The Netherlands, and especially the national German MediGRID and Services@MediGRID part of the German D-Grid, both funded by the German Bundesministerium fuer Forschung und Technology under grants #01 AK 803 A-H and # 01 IG 07015G for access to their grid resources. We also thank Karol Estrada, Department of Internal Medicine, Erasmus MC, Rotterdam, the Netherlands for advice regarding the grid resources. Health Aging and Body Composition Study (Health ABC): This study was funded by the National Institutes of Aging. This research was supported by NIA contracts N01AG62101, N01AG62103, and N01AG62106. The genome-wide association study was funded by NIA grant 1R01AG032098-01A1 to Wake Forest University Health Sciences and genotyping services were provided by the Center for Inherited Disease Research (CIDR). CIDR is fully funded through a federal contract from the National Institutes of Health to The Johns Hopkins University, contract number HHSN268200782096C. Indiana: We thank the individuals who participated in this study, as well as the study coordinators, without whom this work would not have been possible. This work was supported by National Institutes of Health grants R01 AG 041517 and M01 RR-00750. Genotyping services were provided by CIDR. CIDR is fully funded through a federal contract from the National Institutes of Health to The Johns Hopkins University, contract number HHSN268200782096C. This research was supported in part by the Intramural Research Program of the NIH, National Library of Medicine. Kora (KORA F3 and KORA F4): The KORA research platform was initiated and financed by the Helmholtz Center Munich, German Research Center for Environmental Health, which is funded by the German Federal Ministry of Education and Research (BMBF) and by the State of Bavaria. Part of this work was financed by the German National Genome Research Network (NGFN-2 and NGFNPlus: 01GS0823). Our research was supported within the Munich Center of Health Sciences (MC Health) as part of LMUinnovativ. The London Life Sciences Population (LOLIPOP): The study was funded by the British Heart Foundation, Wellcome Trust, the Medical Research Council, and Kidney Research UK. The study also receives support from a National Institute for Health Research (NIHR) programme grant. Rotterdam Study (RSI, RSII & RSIII): The generation and management of GWAS genotype data for the Rotterdam Study (RS I, RS II, RS III) was executed by the Human Genotyping Facility of the Genetic Laboratory of the Department of Internal Medicine, Erasmus MC, Rotterdam, The Netherlands. The GWAS datasets are supported by the Netherlands Organisation of Scientific Research NWO Investments (no. 175.010.2005.011, 911-03-012), the Genetic Laboratory of the Department of Internal Medicine, Erasmus MC, the Research Institute for Diseases in the Elderly (014-93-015; RIDE2), the Netherlands Genomics Initiative (NGI)/Netherlands Organisation for Scientific Research (NWO) Netherlands Consortium for Healthy Aging (NCHA), project no. 050-060-810. We thank Pascal Arp, Mila Jhamai, Marijn Verkerk, Lizbeth Herrera, Marjolein Peters, MSc, and Carolina Medina-Gomez, MSc, for their help in creating the GWAS database, and Karol Estrada, PhD, Yurii Aulchenko, PhD, and Carolina Medina-Gomez, PhD, for the creation and analysis of imputed data. The Rotterdam Study is funded by Erasmus Medical Center and Erasmus University, Rotterdam, Netherlands Organization for the Health Research and Development (ZonMw), the Research Institute for Diseases in the Elderly (RIDE), the Ministry of Education, Culture and Science, the Ministry for Health, Welfare and Sports, the European Commission (DG XII), and the Municipality of Rotterdam. We are grateful to the study participants, the staff from the Rotterdam Study and the participating general practitioners and pharmacists. We thank Dr Karol Estrada, Dr Fernando Rivadeneira, Dr Tobias A. Knoch, Anis Abuseiris, and Rob de Graaf (Erasmus MC Rotterdam, The Netherlands) for their help in creating GRIMP, and we thank BigGRID, MediGRID, and Services@MediGRID/D-Grid (funded by the German Bundesministerium fuer Forschung und Technology; grants 01 AK 803 A-H, 01 IG 07015G) for access to their grid computing resources. Rush Memory and Aging Project (MAP): The Memory and Aging Project was supported by National Institute on Aging grants R01AG17917, R01AG15819, and R01AG24480, the Illinois Department of Public Health, the Rush Clinical Translational Science Consortium, and a gift from Ms Marsha Dowd. TwinsUK (TUK): The study was funded by the Wellcome Trust, Arthritis Research UK, and the Chronic Disease Research Foundation. The study also received support from a National Institute for Health Research (NIHR) comprehensive Biomedical Research Centre award to Guy’s & St Thomas’ NHS Foundation Trust in partnership with King’s College London. We thank the staff and volunteers of the TwinsUK study. The study was also supported by Israel Science Foundation, grant number 994/10. Age, Gene/Environment Susceptibility Reykjavik Study (AGES-Reykjavik) has been funded by NIH contract N01-AG-12100, the NIA Intramural Research Program, Hjartavernd (the Icelandic Heart Association), and the Althingi (the Icelandic Parliament). The study is approved by the Icelandic National Bioethics Committee (VSN: 00-063) and the Data Protection Authority. The researchers are indebted to the participants for their willingness to participate in the study. Berlin Aging Study II (BASE-II) was supported by the German Federal Ministry of Education and Research (BMBF (grants #16SV5536K, #16SV5537, #16SV5538, and #16SV5837; previously #01UW0808)). Additional contributions (e.g., financial, equipment, logistics, personnel) are made from each of the other participating sites, i.e., the Max Planck Institute for Human Development (MPIB), Max Planck Institute for Molecular Genetics (MPIMG), Charite University Medicine, German Institute for Economic Research (DIW), all located in Berlin, Germany, and University of Lübeck in Lübeck, Germany. B-vitamins in the prevention of osteoporotic fractures (B-PROOF): B-PROOF is supported and funded by The Netherlands Organization for Health Research and Development (ZonMw, grant 6130.0031), the Hague; unrestricted grant from NZO (Dutch Dairy Association), Zoetermeer; Orthica, Almere; NCHA (Netherlands Consortium Healthy Ageing) Leiden/Rotterdam; Ministry of Economic Affairs, Agriculture and Innovation (project KB-15-004-003), the Hague; Wageningen University, Wageningen; VU University Medical Center, Amsterdam; Erasmus Medical Center, Rotterdam. All organizations are based in the Netherlands. We thank Dr Tobias A. Knoch, Anis Abuseiris, Karol Estrada, and Rob de Graaf as well as their institutions the Erasmus Grid Office, Erasmus MC Rotterdam, The Netherlands, and especially the national German MediGRID and Services@MediGRID part of the German D-Grid, both funded by the German Bundesministerium fuer Forschung und Technology (grants #01 AK 803 A-H and #01 IG 07015G) for access to their gird resources. Further, we gratefully thank all participants. Calcium Intake Fracture Outcome Study (CAIFOS): This study was funded by Healthway Health Promotion Foundation of Western Australia, Australasian Menopause Society and the Australian National Health and Medical Research Council Project Grants (254627, 303169, and 572604). We are grateful to the participants of the CAIFOS Study. The salary of Dr Lewis is supported by a National Health and Medical Research Council of Australia Career Development Fellowship. Danish Osteoporosis Study (DOPS): The study was supported by Karen Elise Jensen foundation. Family Heart Study (FamHS): The study was supported by NIH grants R01-HL-117078, R01-HL-087700, and R01-HL-088215 from NHLBI; and R01-DK-089256 and R01-DK-075681 from NIDDK. GenMets (Health 2000): S.R. was supported by the Academy of Finland Center of Excellence in Complex Disease Genetics (213506 and 129680), Academy of Finland (251217), the Finnish foundation for Cardiovascular Research and the Sigrid Juselius Foundation. S.M. was supported by grants #136895 and #141005, V.S. by grants #139635 and 129494, and M.P. by grant #269517 from the Academy of Finland and a grant from the Finnish Foundation for Cardiovascular Research. M.P. was supported by the Yrjö Jahnsson Foundation. Helsinki Birth Cohort Study (HBCS): We thank all study participants as well as everybody involved in the HBCS. HBCS has been supported by grants from the Academy of Finland, the Finnish Diabetes Research Society, Samfundet Folkhälsann, Novo Nordisk Foundation, Liv och Hälsa, Finska Läkaresällskapet, Signe and Ane Gyllenberg Foundation, University of Helsinki, European Science Foundation (EUROSTRESS), Ministry of Education, Ahokas Foundation, Emil Aaltonen Foundation, Juho Vainio Foundation, and Wellcome Trust (grant number WT089062). Johnston County Study: The Johnston County Osteoarthritis Project is supported in part by cooperative agreements S043, S1734, and S3486 from the Centers for Disease Control and Prevention/Association of Schools of Public Health; the NIAMS Multipurpose Arthritis and Musculoskeletal Disease Center grant 5-P60-AR30701; and the NIAMS Multidisciplinary Clinical Research Center grant 5 P60 AR49465-03. Genotyping services were provided by Algynomics company. Korean Genome Epidemiology Study (KoGES): Korean Genome Epidemiology Study (KoGES): This work was supported by the Research Program funded by the Korea Centers for Disease Control and Prevention (found 2001-347-6111-221, 2002-347-6111-221, 2009-E71007-00, 2010-E71004-00). Kora F3 and Kora F4: The KORA research platform was initiated and financed by the Helmholtz Center Munich, German Research Center for Environmental Health, which is funded by the German Federal Ministry of Education and Research (BMBF) and by the State of Bavaria. Part of this work was financed by the German National Genome Research Network (NGFN-2 and NGFNPlus: 01GS0823). Our research was supported within the Munich Center of Health Sciences (MC Health) as part of LMUinnovativ. LOLIP-REP-IA610: The study was supported by the Wellcome Trust. We thank the participants and research teams involved in LOLIPOP. LOLIP-REP-IA_I: The study was supported by the British Heart Foundation Grant SP/04/002. LOLIP-REP-IA_P: The study was supported by the British Heart Foundation Grant SP/04/002. METSIM: The study was supported by the Academy of Finland, the Finnish Diabetes Research Foundation, the Finnish Cardiovascular Research Foundation, the Strategic Research Funding from the University of Eastern Finland, Kuopio, and the EVO grant 5263 from the Kuopio University Hospital. MrOS Sweden: Financial support was received from the Swedish Research Council (2006-3832), the Swedish Foundation for Strategic Research, the ALF/LUA research grant in Gothenburg, the Lundberg Foundation, the Torsten and Ragnar Söderberg’s Foundation, Petrus and Augusta Hedlunds Foundation, the Västra Götaland Foundation, the Göteborg Medical Society, and the Novo Nordisk foundation. Greta and Johan Kock Foundation, A. Påhlsson Foundation, A. Osterlund Foundation, Malmö University Hospital Research Foundation, Research and Development Council of Region Skåne, Sweden, the Swedish Medical Society. MrOS US: The Osteoporotic Fractures in Men (MrOS) Study is supported by National Institutes of Health funding. The following institutes provide support: the National Institute on Aging (NIA), the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), the National Center for Advancing Translational Sciences (NCATS), and NIH Roadmap for Medical Research under the following grant numbers: U01 AG027810, U01 AG042124, U01 AG042139, U01 AG042140, U01 AG042143, U01 AG042145, U01 AG042168, U01 AR066160, and UL1 TR000128. The National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) provided funding for the MrOS ancillary study “GWAS in MrOS and SOF” under the grant number RC2ARO58973. Osteoporosis Prospective Risk Assessment study (OPRA): This work was supported by grants from the Swedish Research Council (K2009-53X-14691-07-3, K2010-77PK-21362-01-2), FAS (grant 2007-2125), Greta and Johan Kock Foundation, A. Påhlsson Foundation, A. Osterlund Foundation, Malmö University Hospital Research Foundation, Research and Development Council of Region Skåne, Sweden, the Swedish Medical Society. We are thankful to all the women who kindly participated in the study and to the staff at the Clinical and Molecular Osteoporosis Research Unit for helping in recruitment of study individuals. Orkney Complex Disease Study (ORCADES): ORCADES was supported by the Chief Scientist Office of the Scottish Government (CZB/4/276, CZB/4/710), the Royal Society, the MRC Human Genetics Unit, Arthritis Research UK (17539) and the European Union framework program 6 EUROSPAN project (contract no. LSHG-CT-2006-018947). DNA extractions were performed at the Wellcome Trust Clinical Research Facility in Edinburgh. We acknowledge the invaluable contributions of Lorraine Anderson and the research nurses in Orkney, the administrative team in Edinburgh and the people of Orkney. PEAK 25: This work was supported by grants from the Swedish Research Council (K2009-53X-14691-07-3, K2010-77PK-21362-01-2), FAS (grant 2007-2125), Greta and Johan Kock Foundation, A. Påhlsson Foundation, A. Osterlund Foundation, Malmö University Hospital Research Foundation, Research and Development Council of Region Skåne, Sweden, the Swedish Medical Society. We are thankful to all the women who kindly participated in the study and to the staff at the Clinical and Molecular Osteoporosis Research Unit for helping in recruitment of study individuals. Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS): The study was supported by grants from the Swedish research council (projects 2008-2202 and 2005-8214) and ALF/LUA research grants from Uppsala university hospital, Uppsala, Sweden. Relationship between Insulin Sensitivity and Cardiovascular Disease (RISC): The RISC study is supported by European Union Grant QLG1-CT-2001-01252 and AstraZeneca. We thank Merck Research Labs for conducting DNA genotyping on RISC samples.Rotterdam III: Rotterdam Study (RS): See discovery. SHIP and SHIP TREND: This work was supported by SHIP, which is part of the Community Medicine Research Network of the University of Greifswald, Germany, by the Federal Ministry of Education and Research (01ZZ9603, 01ZZ0103, and 01ZZ0403), the Ministry of Cultural Affairs as well as the Social Ministry of the Federal State of Mecklenburg-West Pomerania and the network “Greifswald Approach to Individualized Medicine (GANI_MED)” funded by the Federal Ministry of Education and Research (03IS2061A). Genome-wide data have been supported by the Federal Ministry of Education and Research (03ZIK012) and a joint grant from Siemens Healthcare, Erlangen, Germany, and the Federal State of Mecklenburg-West Pomerania. The University of Greifswald is a member of the “Center of Knowledge Interchange” program of the Siemens. A.G. and the Cache´ Campus program of the InterSystems GmbH. The SHIP authors are grateful to the contribution of Florian Ernst, Anja Wiechert, and Astrid Petersmann in generating the SNP data and to Mario Stanke for the opportunity to use his Server Cluster for SNP Imputation. Data analyses were further supported by the German Research Foundation (DFG Vo 955/10-1) and the Federal Ministry of Nutrition, Agriculture and Consumer’s Safety. SOF: The Study of Osteoporotic Fractures (SOF) is supported by National Institutes of Health funding. The National Institute on Aging (NIA) provides support under the following grant numbers: R01 AG005407, R01 AR35582, R01 AR35583, R01 AR35584, R01 AG005394, R01 AG027574, and R01 AG027576. The National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) provided funding for the SOF ancillary study “GWAS in MrOS and SOF” under the grant number RC2ARO58973. Uppsala Longitudinal Study of Adult Men (ULSAM): The study was funded by grants from the Swedish research council (projects 2008-2202 and 2005-8214), the Wallenberg foundation, and ALF/LUA research grants from Uppsala university hospital, Uppsala, Sweden. Andrew P. Morris is a Wellcome Trust Senior Fellow in Basic Biomedical Science, grant number WT098017. CROATIA-VIS (VIS): The CROATIA-Vis study was funded by grants from the Medical Research Council (UK) and Republic of Croatia Ministry of Science, Education and Sports research grants to I.R. (108-1080315-0302). We acknowledge the staff of several institutions in Croatia that supported the field work, including but not limited to The University of Split and Zagreb Medical Schools, the Institute for Anthropological Research in Zagreb and Croatian Institute for Public Health. The SNP genotyping for the CROATIA-Vis cohort was performed in the core genotyping laboratory of the Wellcome Trust Clinical Research Facility at the Western General Hospital, Edinburgh, Scotland. Women’s Health Initiative (WHI): The WHI program is funded by the National Heart, Lung, and Blood Institute, National Institutes of Health, US Department of Health and Human Services through contracts N01WH22110, 24152, 32100–2, 32105–6, 32108–9, 32111–13, 32115, 32118–32119, 32122, 42107–26, 42129–32, and 44221. We thank the WHI investigators and staff for their dedication, and the study participants for making the program possible. A listing of WHI investigators can be found at https://www.whi.org/researchers/Documents%20%20Write%20a%20Paper/WHI%20Investigator%20Short%20List.pdf. FUSION: This research was supported in part by US National Institutes of Health grants 1-ZIA-HG000024 (to F.S.C.), U01DK062370 (to M.B.), R00DK099240 (to S.C.J.P.), the American Diabetes Association Pathway to Stop Diabetes Grant 1-14-INI-07 (to S.C.J.P.), and Academy of Finland Grants 271961 and 272741 (to M.L.) and 258753 (to H.A.K.). We thank all the subjects for participation and the study personnel for excellent technical assistance. The Pima Indian Study: This study was supported by the Intramural Research Program of the National Institute of Diabetes and Digestive and Kidney Diseases, NIH, USA. Studies of a Targeted Risk Reduction Intervention with Defined Exercise (STRRIDE): This study was supported by the National Heart Lung and Blood Institute of the National Institutes of Health, HL57453 (WEK). Gene expression in old and young muscle biopsies: S.M. and T.G. were supported in part by NIH U24AG051129.

A decline in skeletal muscle mass and function with aging is well recognized, but remains poorly characterized at the molecular level. Here, we report for the first time a genome-wide study of DNA methylation dynamics in skeletal muscle of healthy male individuals during normal human aging. We predominantly observed hypermethylation throughout the genome within the aged group as compared to the young subjects. Differentially methylated CpG (dmCpG) nucleotides tend to arise intragenically and are underrepresented in promoters and are overrepresented in the middle and 3′ end of genes. The intragenic methylation changes are overrepresented in genes that guide the formation of the junction of the motor neuron and myofibers. We report a low level of correlation of gene expression from previous studies of aged muscle with our current analysis of DNA methylation status. For those genes that had both changes in methylation and gene expression with age, we observed a reverse correlation, with the exception of intragenic hypermethylated genes that were correlated with an increased gene expression. We suggest that a minimal number of dmCpG sites or select sites are required to be altered in order to correlate with gene expression changes. Finally, we identified 500 dmCpG sites that perform well in discriminating young from old samples. Our findings highlight epigenetic links between aging postmitotic skeletal muscle and DNA methylation.

In tissues with complex architectures such as bone, it is often difficult to purify and characterize specific cell types via molecular profiling. Single cell gene expression profiling is an emerging technology useful for characterizing transcriptional profiles of individual cells isolated from heterogeneous populations. In this study we describe a novel procedure for the isolation and characterization of gene expression profiles of single osteoblast lineage cells derived from cortical bone. Mixed populations of different cell types were isolated from adult long bones of C57BL/6J mice by enzymatic digestion, and subsequently subjected to FACS to purify and characterize osteoblast lineage cells via a selection strategy using antibodies against CD31, CD45, and alkaline phosphatase (AP), specific for mature osteoblasts. The purified individual osteoblast lineage cells were then profiled at the single cell level via nanofluidic PCR. This method permits robust gene expression profiling on single osteoblast lineage cells derived from mature bone, potentially from anatomically distinct sites. In conjunction with this technique, we have also shown that it is possible to carry out single cell profiling on cells purified from fixed and frozen bone samples without compromising the gene expression signal. The latter finding means the technique can be extended to biopsies of bone from diseased individuals. Our approach for single cell expression profiling provides a new dimension to the transcriptional profile of the primary osteoblast lineage population in vivo, and has the capacity to greatly expand our understanding of how these cells may function in vivo under normal and diseased states.

The majority of cellular superoxide is generated in the mitochondria as a by-product of normal oxidative metabolism. In the mitochondria, superoxide is detoxified by manganese superoxide dismutase (SOD2). Mice lacking SOD2 demonstrate a multifaceted neonatal lethal phenotype, including a spongiform encephalopathy that is preventable through antioxidant treatment. The molecular events behind the observed pathology in the cortex of these mice are unknown. We hypothesized that the lack of SOD2 would result in significant changes in cortical gene expression and that therapeutically beneficial antioxidant treatment would normalize the expression of some genes, providing insight into the mechanism by which mitochondrial oxidative stress results in neurodegeneration. We report the identification of gene expression profiles associated with this paradigm, which characterize the degree of response to the pharmacologic intervention. We have identified specific pathways targeted by endogenous oxidative stress, including glutathione metabolism, iron metabolism, and cell-survival pathways centering on the kinase AKT. The normalization of expression of some of these pathways by antioxidant treatment suggests approaches to treating disease in which endogenous oxidative stress plays a role.

Salen Mn complexes, including EUK-134, EUK-189 and a cyclized analog EUK-207, are synthetic superoxide dismutase (SOD) and catalase mimetics that are beneficial in many models of oxidative stress. Though not designed to target the mitochondria, salen Mn complexes show "mito-protective" activity, that is, an ability to attenuate mitochondrial injury, in various experimental systems. Treatment with EUK-134 prevents respiratory chain abnormalities induced by ionizing radiation in rat astrocyte cultures. Treatment with salen Mn complexes also prolongs survival, protects mitochon- drial enzymes and prevents oxidative pathologies in Sod2-/- mice, which lack the mitochondrial form of superoxide dis- mutase. Recently, EUK-207 was shown to attenuate ischemia reperfusion injury, including mitochondrial dysfunction, in hearts from ABC-me-/+ mice, which are deficient in a mitochondrial transporter and more vulnerable to oxidative stress. Since mitochondrial dysfunction has been implicated in many forms of injury and degeneration, this "mito-protective" property may explain some of the cytoprotective effects of salen Mn complexes in vivo, and may also enhance their poten- tial therapeutic value.

SummaryChanges in fat content have been associated with dietary restriction (DR), but whether they play a causal role in mediating various responses to DR remains unknown. We demonstrate that upon DR, Drosophila melanogaster shift their metabolism toward increasing fatty-acid synthesis and breakdown, which is required for various responses to DR. Inhibition of fatty-acid synthesis or oxidation genes specifically in the muscle tissue inhibited life-span extension upon DR. Furthermore, DR enhances spontaneous activity of flies, which was found to be dependent on the enhanced fatty-acid metabolism. This increase in activity was found to be at least partially required for the life-span extension upon DR. Overexpression of adipokinetic hormone (dAKH), the functional ortholog of glucagon, enhances fat metabolism, spontaneous activity, and life span. Together, these results suggest that enhanced fat metabolism in the muscle and physical activity play a key role in the protective effects of DR.

The C. elegans germline and somatic gonad are actively developing until the animal reaches adulthood, and then continue to undergo striking changes as the animal ages. Reported changes include a depletion of available sperm, a decrease in oocyte quality up till mid-life, a reduction in germline nuclei, a decrease in fertility, and an accumulation of DNA in the midbody of aging C. elegans. Here, we have focused on the aging gonad in old animals, and show in detail that the aging gonad undergoes a massive uterine growth composed of endoreduplicating oocytes, yolk, and expanses of chromatin. We use a novel series of imaging techniques in combination with histological methodology for reconstructing aged worms in 3-dimensions, and show in old animals growing masses swelling inside the uterus to occupy most of the diameter of the worm. We link this accelerated growth to the cep-1/p53 tumor suppressor. Because cep-1 is required for DNA damage induced apoptosis, and daf-2 limits longevity, these results suggest a role for age-related DNA damage in dysplastic uterine growths, which in some respects resemble premalignant changes that can occur in aging mammals.

Cellular senescence arrests the proliferation of mammalian cells at risk for neoplastic transformation, and is also associated with aging. However, the factors that cause cellular senescence during aging are unclear. Excessive reactive oxygen species (ROS) have been shown to cause cellular senescence in culture, and accumulated molecular damage due to mitochondrial ROS has long been thought to drive aging phenotypes in vivo. Here, we test the hypothesis that mitochondrial oxidative stress can promote cellular senescence in vivo and contribute to aging phenotypes in vivo, specifically in the skin. We show that the number of senescent cells, as well as impaired mitochondrial (complex II) activity increase in naturally aged mouse skin. Using a mouse model of genetic Sod2 deficiency, we show that failure to express this important mitochondrial anti-oxidant enzyme also impairs mitochondrial complex II activity, causes nuclear DNA damage, and induces cellular senescence but not apoptosis in the epidermis. Sod2 deficiency also reduced the number of cells and thickness of the epidermis, while increasing terminal differentiation. Our results support the idea that mitochondrial oxidative stress and cellular senescence contribute to aging skin phenotypes in vivo.

Summary We utilized induced pluripotent stem cells (iPSCs) derived from Huntington’s disease (HD) patients as a human model of HD and determined that the disease phenotypes only manifest in the differentiated neural stem cell (NSC) stage, not in iPSCs. To understand the molecular basis for the CAG repeat expansion-dependent disease phenotypes in NSCs, we performed transcriptomic analysis of HD iPSCs and HD NSCs compared to isogenic controls. Differential gene expression and pathway analysis pointed to transforming growth factor β (TGF-β) and netrin-1 as the top dysregulated pathways. Using data-driven gene coexpression network analysis, we identified seven distinct coexpression modules and focused on two that were correlated with changes in gene expression due to the CAG expansion. Our HD NSC model revealed the dysregulation of genes involved in neuronal development and the formation of the dorsal striatum. The striatal and neuronal networks disrupted could be modulated to correct HD phenotypes and provide therapeutic targets., Graphical Abstract, Highlights • HD stem cell models have phenotypes in the differentiated NSC and not the IPSC state • Bioinformatic analysis of RNA-seq data identifies TGF-β and netrin-1 in HD phenotypes • WGCNA analysis in the HD-NSC linked module to development of the dorsal striatum • Modulation of TGF-β and netrin-1 in HD-NSCs is neuroprotective, Ellerby and colleagues use expression profiling and bioinformatic analysis to identify critical pathways mediating Huntington’s disease (HD) phenotypes in neural stem cells. They identify and show modulation of TFG-β and netrin-1 signaling is relevant to HD phenotypes found in neural stem cells and not iPSCs. Further, HD phenotypes are linked to genes in the dorsal striatum.

SummaryReducing protein synthesis slows growth and development but can increase adult life span. We demonstrate that knockdown of eukaryotic translation initiation factor 4G (eIF4G), which is downregulated during starvation and dauer state, results in differential translation of genes important for growth and longevity in C. elegans. Genome-wide mRNA translation state analysis showed that inhibition of IFG-1, the C. elegans ortholog of eIF4G, results in a relative increase in ribosomal loading and translation of stress response genes. Some of these genes are required for life span extension when IFG-1 is inhibited. Furthermore, enhanced ribosomal loading of certain mRNAs upon IFG-1 inhibition was correlated with increased mRNA length. This association was supported by changes in the proteome assayed via quantitative mass spectrometry. Our results suggest that IFG-1 mediates the antagonistic effects on growth and somatic maintenance by regulating mRNA translation of particular mRNAs based, in part, on transcript length.

Medicinal benefits of Allium vegetables, such as garlic, have been noted throughout recorded history, including protection against cancer and cardiovascular disease. We now demonstrate that garlic constituent diallyl trisulfide (DATS) increases longevity of Caenorhabditis elegans by affecting the skn-1 pathway. Treatment of worms with 5-10 μM DATS increased worm mean lifespan even when treatment is started during young adulthood. To explore the mechanisms involved in the DATS-mediated increase in longevity, we treated daf-2, daf-16, and eat-2 mutants and found that DATS increased the lifespan of daf-2 and daf-16 mutants, but not the eat-2 mutants. Microarray experiments demonstrated that a number of genes regulated by oxidative stress and the skn-1 transcription factor were also changed by DATS treatment. Consistently, DATS treatment leads to the induction of the skn-1 target gene gst-4, and this induction was dependent on skn-1. We also found that the effects of DATS on worm lifespan depend on skn-1 activity in both in the intestine and ASI neurons. Together our data suggest that DATS is able to increase worm lifespan by enhancing the function of the pro-longevity transcription factor skn-1.

The roundworm C. elegans is widely used as an aging model, with hundreds of genes identified that modulate aging (Kaeberlein et al., 2002. Mech. Ageing Dev.123, 1115-1119). The development and bodyplan of the 959 cells comprising the adult have been well described and established for more than 25 years (Sulston & Horvitz, 1977. Dev. Biol.56, 110-156; Sulston et al., 1983. Dev. Biol.100, 64-119.). However, morphological changes with age in this optically transparent animal are less well understood, with only a handful of studies investigating the pathobiology of aging. Age-related changes in muscle (Herndon et al., 2002. Nature419, 808-814), neurons (Herndon et al., 2002), intestine and yolk granules (Garigan et al., 2002. Genetics161, 1101-1112; Herndon et al., 2002), nuclear architecture (Haithcock et al., 2005. Proc. Natl Acad. Sci. USA102, 16690-16695), tail nuclei (Golden et al., 2007. Aging Cell6, 179-188), and the germline (Golden et al., 2007) have been observed via a variety of traditional relatively low-throughput methods. We report here a number of novel approaches to study the pathobiology of aging C. elegans. We combined histological staining of serial-sectioned tissues, transmission electron microscopy, and confocal microscopy with 3D volumetric reconstructions and characterized age-related morphological changes in multiple wild-type individuals at different ages. This enabled us to identify several novel pathologies with age in the C. elegans intestine, including the loss of critical nuclei, the degradation of intestinal microvilli, changes in the size, shape, and cytoplasmic contents of the intestine, and altered morphologies caused by ingested bacteria. The three-dimensional models we have created of tissues and cellular components from multiple individuals of different ages represent a unique resource to demonstrate global heterogeneity of a multicellular organism.

A causal role for mitochondrial DNA (mtDNA) mutagenesis in mammalian aging is supported by recent studies demonstrating that the mtDNA mutator mouse, harboring a defect in the proofreading-exonuclease activity of mitochondrial polymerase gamma, exhibits accelerated aging phenotypes characteristic of human aging, systemic mitochondrial dysfunction, multisystem pathology, and reduced lifespan. Epidemiologic studies in humans have demonstrated that endurance training reduces the risk of chronic diseases and extends life expectancy. Whether endurance exercise can attenuate the cumulative systemic decline observed in aging remains elusive. Here we show that 5 mo of endurance exercise induced systemic mitochondrial biogenesis, prevented mtDNA depletion and mutations, increased mitochondrial oxidative capacity and respiratory chain assembly, restored mitochondrial morphology, and blunted pathological levels of apoptosis in multiple tissues of mtDNA mutator mice. These adaptations conferred complete phenotypic protection, reduced multisystem pathology, and prevented premature mortality in these mice. The systemic mitochondrial rejuvenation through endurance exercise promises to be an effective therapeutic approach to mitigating mitochondrial dysfunction in aging and related comorbidities.

The balance between self-renewal and differentiation ensures long-term maintenance of stem cell (SC) pools in regenerating epithelial tissues. This balance is challenged during periods of high regenerative pressure and is often compromised in aged animals. Here, we show that target of rapamycin (TOR) signaling is a key regulator of SC loss during repeated regenerative episodes. In response to regenerative stimuli, SCs in the intestinal epithelium of the fly and in the tracheal epithelium of mice exhibit transient activation of TOR signaling. Although this activation is required for SCs to rapidly proliferate in response to damage, repeated rounds of damage lead to SC loss. Consistently, age-related SC loss in the mouse trachea and in muscle can be prevented by pharmacologic or genetic inhibition, respectively, of mammalian target of rapamycin complex 1 (mTORC1) signaling. These findings highlight an evolutionarily conserved role of TOR signaling in SC function and identify repeated rounds of mTORC1 activation as a driver of age-related SC decline.

Lymphomas adapt to their environment by undergoing a complex series of biochemical changes that are currently not well understood. To better define these changes, we examined the gene expression and gene ontology profiles of thymic lymphomas from a commonly used model of carcinogenesis, the p53(-/-) mouse. These tumors show a highly significant upregulation of mitochondrial biogenesis, mitochondrial protein translation, mtDNA copy number, reactive oxygen species, antioxidant defenses, proton transport, ATP synthesis, hypoxia response, and glycolysis, indicating a fundamental change in the bioenergetic profile of the transformed T cell. Our results suggest that T cell tumorigenesis involves a simultaneous upregulation of mitochondrial biogenesis, mitochondrial respiration, and glycolytic activity. These processes would allow cells to adapt to the stressful tumor environment by facilitating energy production and thereby promote tumor growth. Understanding these adaptations is likely to result in improved therapeutic strategies for this tumor type.

The nematode Caenorhabditis elegans has become one of the most widely used model systems for the study of aging, yet very little is known about how C. elegans age. The development of the worm, from egg to young adult has been completely mapped at the cellular level, but such detailed studies have not been extended throughout the adult lifespan. Numerous single gene mutations, drug treatments and environmental manipulations have been found to extend worm lifespan. To interpret the mechanism of action of such aging interventions, studies to characterize normal worm aging, similar to those used to study worm development are necessary. We have used 4′,6′-diamidino-2-phenylindole hydrochloride staining and quantitative polymerase chain reaction to investigate the integrity of nuclei and quantify the nuclear genome copy number of C. elegans with age. We report both systematic loss of nuclei or nuclear DNA, as well as dramatic age-related changes in nuclear genome copy number. These changes are delayed or attenuated in long-lived daf-2 mutants. We propose that these changes are important pathobiological characteristics of aging nematodes.

Tissue homeostasis declines with age partly because stem/progenitor cells fail to self-renew or differentiate. Because mitochondrial damage can accelerate aging, we tested the hypothesis that mitochondrial dysfunction impairs stem cell renewal or function. We developed a mouse model, Tg(KRT14-cre/Esr1) (20Efu/J) × Sod2 (tm1Smel) , that generates mitochondrial oxidative stress in keratin 14-expressing epidermal stem/progenitor cells in a temporally controlled manner owing to deletion of Sod2, a nuclear gene that encodes the mitochondrial antioxidant enzyme superoxide dismutase 2 (Sod2). Epidermal Sod2 loss induced cellular senescence, which irreversibly arrested proliferation in a fraction of keratinocytes. Surprisingly, in young mice, Sod2 deficiency accelerated wound closure, increasing epidermal differentiation and reepithelialization, despite the reduced proliferation. In contrast, at older ages, Sod2 deficiency delayed wound closure and reduced epidermal thickness, accompanied by epidermal stem cell exhaustion. In young mice, Sod2 deficiency accelerated epidermal thinning in response to the tumor promoter 12-O-tetradecanoylphorbol-13-acetate, phenocopying the reduced regeneration of older Sod2-deficient skin. Our results show a surprising beneficial effect of mitochondrial dysfunction at young ages, provide a potential mechanism for the decline in epidermal regeneration at older ages, and identify a previously unidentified age-dependent role for mitochondria in skin quality and wound closure.

Mice that lack the mitochondrial form of superoxide dismutase (SOD2) incur severe pathologies and mitochondrial deficiencies, including major depletion of complex II, as a consequence of buildup of endogenous reactive oxygen species (Melov, S., Coskun, P., Patel, M., Tuinstra, R., Cottrell, B., Jun, A. S., Zastawny, T. H., Dizdaroglu, M., Goodman, S. I., Huang, T. T., Miziorko, H., Epstein, C. J., and Wallace, D. C. (1999) Proc. Natl. Acad. Sci. U. S. A. 96, 846–851 and Li, Y., Huang, T. T., Carlson, E. J., Melov, S., Ursell, P. C., Olson, J. L., Noble, L. J., Yoshimura, M. P., Berger, C., Chan, P. H., Wallace, D. C., and Epstein, C. J. (1995) Nat. Genet. 11, 376–381). These problems can be greatly attenuated or rescued by synthetic antioxidant treatment, such as with the catalytic antioxidant EUK189 (Hinerfeld, D., Traini, M. D., Weinberger, R. P., Cochran, B., Doctrow, S. R., Harry, J., and Melov, S. (2004) J. Neurochem. 88, 657–667). We have used heart mitochondria from sod2 null mice to better understand mitochondrial reactive oxygen species production both in the absence of SOD2 and following in vivo antioxidant treatment. Isolated heart mitochondria from 5-day-old sod2 null animals respiring on the complex II substrate succinate exhibited statistically significant higher levels of mitochondrial (157%, p < 0.01) but significantly less H2O2 (33%, p < 0.001) than wild type littermates. Treatment of sod2 nullizygous mice with EUK189 proportionately increased the levels of complex II and H2O2. Increased production of resulting from complex II normalization had no effect on steady state levels due to the rapid conversion to H2O2, a process presumably aided by the presence of the EUK189, an SOD mimetic.

During the last 10 years, the theory known as the "free radical theory of aging" has achieved prominence as one of the most compelling explanations for many of the degenerative changes associated with aging. Although its appeal derives from a long-standing body of supporting correlative data, the theory was only recently more rigorously tested. Ongoing researches in the study of free radical biochemistry and the genetics of aging have been at the forefront of this work. First, transgenic approaches in invertebrate models with candidate genes such as superoxide dismutase (SOD) involved in the detoxification of reactive oxygen species (ROS) have shown that the endogenous production of ROS due to normal physiologic processes is a major limiter of life span. Genes involved in ROS detoxification are highly conserved among eukaryotes; hence, the physiologic processes that limit life span in invertebrates are likely to be similar in higher eukaryotes. Secondly, transgenic mice deficient in the antioxidant enzyme mitochondrial superoxide dismutase (SOD2) die within their first week of life, demonstrating the importance of limiting endogenous mitochondrial free radicals in mammals. Together, data from studies using transgenic invertebrates and those using sod2 mutant mice demonstrate that modulation of metabolic ROS can have a profound effect on life span. We show here that the effects of mitochondrial ROS can be modulated through appropriate catalytic antioxidant intervention. These catalytic antioxidants are discussed in the context of mitochondrial oxidative stress and their potential role in intervening in mitochondrial oxidative stress and aging.

The abnormal accumulation of amyloid beta-peptide (Abeta) in the form of senile (or amyloid) plaques is one of the main characteristics of Alzheimer disease (AD). Both cholesterol and Cu2+ have been implicated in AD pathogenesis and plaque formation. Abeta binds Cu2+ with very high affinity, forming a redox-active complex that catalyzes H2O2 production from O2 and cholesterol. Here we show that Abeta:Cu2+ complexes oxidize cholesterol selectively at the C-3 hydroxyl group, catalytically producing 4-cholesten-3-one and therefore mimicking the activity of cholesterol oxidase, which is implicated in cardiovascular disease. Abeta toxicity in neuronal cultures correlated with this activity, which was inhibited by Cu2+ chelators including clioquinol. Cell death induced by staurosporine or H2O2 did not elevate 4-cholesten-3-one levels. Brain tissue from AD subjects had 98% more 4-cholesten-3-one than tissue from age-matched control subjects. We observed a similar increase in the brains of Tg2576 transgenic mice compared with nontransgenic littermates; the increase was inhibited by in vivo treatment with clioquinol, which suggests that brain Abeta accumulation elevates 4-cholesten-3-one levels in AD. Cu2+-mediated oxidation of cholesterol may be a pathogenic mechanism common to atherosclerosis and AD.

Alzheimer disease is characterized by cerebral Abeta deposition, which we have recently discovered occurs also in the lens as cataracts in Alzheimer disease patients. Here we report the presence of significantly increased cataracts in the lenses of an Abeta-transgenic mouse model for Alzheimer disease and their amelioration upon treatment with EUK-189, a synthetic SOD/catalase mimetic. These data support an oxidative etiology for AD-associated lens cataracts and their potential to be treated preventatively with antioxidants.

Mitochondria and aging are fast becoming two of the most paired terms in biology. As a crucial nexus for the cell, mitochondria are involved in numerous essential aspects of cell function, from energy production via the respiratory chain to steroid biosynthesis, heme assembly, pyrimidine biosynthesis, the tricarboxylic acid cycle, and apoptosis. Mitochondria are also the main producers of reactive oxygen species within the cell. Theories about aging have revolved around mitochondria for decades, but it is only in the past few years that animal models have started to give significant insights into mitochondria-mediated pathophysiology that might be intimately associated with aging. This review will highlight several new animal models of mitochondrial dysfunction in the context of aging.

Oxidative stress and mitochondrial dysfunction have been linked to neurodegenerative disorders such as Parkinson's and Alzheimer's disease. However, it is not yet understood how endogenous mitochondrial oxidative stress may result in mitochondrial dysfunction. Most prior studies have tested oxidative stress paradigms in mitochondria through either chemical inhibition of specific components of the respiratory chain, or adding an exogenous insult such as hydrogen peroxide or paraquat to directly damage mitochondria. In contrast, mice that lack mitochondrial superoxide dismutase (SOD2 null mice) represent a model of endogenous oxidative stress. SOD2 null mice develop a severe neurological phenotype that includes behavioral defects, a severe spongiform encephalopathy, and a decrease in mitochondrial aconitase activity. We tested the hypothesis that specific components of the respiratory chain in the brain were differentially sensitive to mitochondrial oxidative stress, and whether such sensitivity would lead to neuronal cell death. We carried out proteomic differential display and examined the activities of respiratory chain complexes I, II, III, IV, V, and the tricarboxylic acid cycle enzymes alpha-ketoglutarate dehydrogenase and citrate synthase in SOD2 null mice in conjunction with efficacious antioxidant treatment and observed differential sensitivities of mitochondrial proteins to oxidative stress. In addition, we observed a striking pattern of neuronal cell death as a result of mitochondrial oxidative stress, and were able to significantly reduce the loss of neurons via antioxidant treatment.

Summary Reactive oxygen species are an inevitable by-product of mitochondrial respiration. It has been estimated that between 0.4 and 4% of molecular oxygen is converted to the radical superoxide () and this level is significantly influenced by the functional status of the mitochondria. It is well established that exogenous oxidative stress and high doses of mitochondrial poisons such as paraquat and carbonyl cyanide 4 (trifluoromethoxy) phenylhydrazone (FCCP) can lead to genomic instability. In this report we show for the first time that endogenous mitochondrial oxidative stress in standard cell culture conditions results in nuclear genomic instability in primary mouse embryonic fibroblasts (MEFs). We show that lack of mitochondrial superoxide dismutase in MEFs leads to a severe increase of double strand breaks, end-to-end fusions, chromosomal translocations, and loss of cell viability and proliferative capacity. Our results predict that endogenous mitochondrial oxidative stress can induce genomic instability, and therefore may have a profound effect in cancer and aging.

The advent of microarrays in studying gene expression in aging has created tremendous excitement due to its potential for uncovering molecular mechanisms of aging and age-related disease. However, the appropriate implementation of this technology in the science of aging requires serious attention to methodological detail and statistical rigor. This report highlights discussions from the microarray workshop on aging held at the First Conference on Functional Genomics of Aging in Seville, Spain. The topics discussed by the participants included technical issues relating to the printing of arrays, RNA isolation, cDNA labeling and hybridization, optimal design of microarray experiments, and statistical analysis of these data. Microarray analysis of complex tissues through the use of laser capture microdissection was also discussed.

The Longevity Genomics Research Project is designed to create a publicly-available research resource available through its website (www.longevitygenomics.org) to enable scientists to develop translational strategies to promote human longevity and healthy aging. Our resource will consist of software tools as R packages, curated datasets, and project results. We will identify Longevity-Associated Genes (LAGs) from Longevity-Associated Variants (LAVs), gene expression studies of aging, and evidence from model organisms. Mendelian Randomization using cohort studies with genetic data and longitudinal measures of aging-related traits will be used to evaluate the potential impact of modulating LAG’s on longevity. Candidate Longevity-Associated Drugs (LADs) that target LAG activity are then identified. Using sets of genes whose expression changes with age, we will report associations between genetically predicted expression of these genes and human survival, followed by connectivity map analysis to identify compounds that could target the expression of these genes.

SUMMARY Inhibition of DAF-2 (insulin-like growth factor 1 [IGF-1] receptor) or RSKS-1 (S6K), key molecules in the insulin/IGF-1 signaling (IIS) and target of rapamycin (TOR) pathways, respectively, extend lifespan in Caenorhabditis elegans. However, it has not been clear how and in which tissues they interact with each other to modulate longevity. Here, we demonstrate that a combination of mutations in daf-2 and rsks-1 produces a nearly 5-fold increase in longevity that is much greater than the sum of single mutations. This synergistic lifespan extension requires positive feedback regulation of DAF-16 (FOXO) via the AMP-activated protein kinase (AMPK) complex. Furthermore, we identify germline as the key tissue for this synergistic longevity. Moreover, germlinespecific inhibition of rsks-1 activates DAF-16 in the intestine. Together, our findings highlight the importance of the germline in the significantly increased longevity produced by daf-2 rsks-1, which has important implications for interactions between the two major conserved longevity pathways in more complex organisms.

It has been hypothesized that a major factor in the progression of mitochondrial disease resulting from defects in oxidative phosphorylation (OXPHOS) is the stimulation of the mitochondrial production of reactive oxygen species (ROS) and the resulting damage to the mtDNA. To test this hypothesis, we examined the mitochondria from mice lacking the heart/muscle isoform of the adenine nucleotide translocator ( Ant1 ), designated Ant1 tm2Mgr (−/−) mice. The absence of Ant1 blocks the exchange of ADP and ATP across the mitochondrial inner membrane, thus inhibiting OXPHOS. Consistent with Ant1 expression, mitochondria isolated from skeletal muscle, heart, and brain of the Ant1 -deficient mice produced markedly increased amounts of the ROS hydrogen peroxide, whereas liver mitochondria, which express a different Ant isoform, produced normally low levels of hydrogen peroxide. The increased production of ROS by the skeletal muscle and heart was associated with a dramatic increase in the ROS detoxification enzyme manganese superoxide dismutase (Sod2, also known as MnSod) in muscle tissue and muscle mitochondria, a modest increase in Sod2 in heart tissue, and no increase in heart mitochondria. The level of glutathione peroxidase-1 (Gpx1), a second ROS detoxifying enzyme, was increased moderately in the mitochondria of both tissues. Consistent with the lower antioxidant defenses in heart, the heart mtDNAs of the Ant1 -deficient mice showed a striking increase in the accumulation of mtDNA rearrangements, whereas skeletal muscle, with higher antioxidant defenses, had fewer mtDNA rearrangements. Hence, inhibition of OXPHOS does increase mitochondrial ROS production, eliciting antioxidant defenses. If the antioxidant defenses are insufficient to detoxify the ROS, then an increased mtDNA mutation rate can result.

Mitochondrial DNA (mtDNA) rearrangements have been shown to accumulate with age in the post-mitotic tissues of a variety of animals and have been hypothesized to result in the age-related decline of mitochondrial bioenergetics leading to tissue and organ failure. Caloric restriction in rodents has been shown to extend life span supporting an association between bioenergetics and senescence. In the present study, we use full length mtDNA amplification by long-extension polymerase chain reaction (LX-PCR) to demonstrate that mice accumulate a wide variety of mtDNA rearrangements with age in post mitotic tissues. Similarly, using an alternative PCR strategy, we have found that 2-4 kb minicircles containing the origin of heavy-strand replication accumulate with age in heart but not brain. Analysis of mtDNA structure and conformation by Southern blots of unrestricted DNA resolved by field inversion gel electrophoresis have revealed that the brain mtDNAs of young animals contain the traditional linear, nicked, and supercoiled mtDNAs while old animals accumulate substantial levels of a slower migrating species we designate age-specific mtDNAs. In old caloric restricted animals, a wide variety of rearranged mtDNAs can be detected by LX-PCR in post mitotic tissues, but Southern blots of unrestricted DNA reveals a marked reduction in the levels of the age- specific mtDNA species. These observations confirm that mtDNA mutations accumulate with age in mice and suggest that caloric restriction impedes this progress.

In an article published in the EMBO reports Special Issue on Time and Ageing, Aubrey D.N.J. de Grey criticizes biogerontologists for what he sees as their generally pessimistic view of the possibilities for intervening in the ageing process (de Grey, 2005). In his view, “resistance [of biogerontologists] to debate on how to postpone ageing is delaying progress and costing lives.” de Grey believes he has formulated a research plan that, in his words, will “stop people from getting frailer and more prone to life‐threatening diseases as they get older, and moreover [will] restore the already frail to youthful vitality”. Similar to vintage cars maintained by careful mechanics, individuals will then retain this happy state “indefinitely … even at ages many times what we reach today”. In de Grey's opinion, “the failure of most biogerontologists to maintain an open mind concerning the scientific options … [has] the result that much longer healthy lives are being denied those who will die before ’real anti‐aging medicine' arrives.” In the words of the great American journalist H.L. Mencken, “for every complex problem, there is a simple solution, and it is wrong.” de Grey's research programme, which he terms ’strategies for engineered negligible senescence' (SENS), involves a combination of preventative and therapeutic interventions (de Grey, 2003). To solve the problem of apoptosis in senescent cells, one simply uses “senescence marker‐tagged toxins”. To cure cancer, one just calls on “total telomerase deletion plus cell therapy”. To prop up the failing immune system, one can turn on “IL‐7 mediated thymopoiesis”. To reverse mitochondrial mutations, one need only use “allotopic [mitochondrial]‐coded proteins” of the type favoured by algae. Cell replacement can be accomplished by “stem cell therapy and growth factors”, whereas retooling the endocrine system relies on “genetically engineered muscle”. Cleavage of glycosylation crosslinks will involve periodic exposure …

The brain is a highly metabolically active tissue that critically relies on oxidative phosphorylation as a means for maintaining energy. One result of this process is the production of potentially damaging radicals such as the superoxide anion (O2(-)). Superoxide has the capacity to damage components of the electron transport chain and other cellular constituents. Eukaryotic systems have evolved defenses against such damaging moieties, the chief member of which is superoxide dismutase (SOD2), an enzyme that efficiently converts superoxide to the less reactive hydrogen peroxide (H2O2), which can freely diffuse across the mitochondrial membrane. Loss of SOD2 activity can result in numerous pathological phenotypes in metabolically active tissues, particularly within the central nervous system. We review SOD2's potential involvement in the progression of neurodegenerative diseases such as stroke and Alzheimer and Parkinson diseases, as well as its potential role in "normal" age-related cognitive decline. We also examine in vivo models of endogenous oxidative damage based upon the loss of SOD2 and associated neurological phenotypes in relation to human neurodegenerative disorders.

Rapamycin has been shown to extend lifespan in numerous model organisms including mice, with the most dramatic longevity effects reported in females. However, little is known about the functional ramifications of this longevity-enhancing paradigm in mammalian tissues. We treated 24-month-old female C57BL/6J mice with rapamycin for 3 months and determined health outcomes via a variety of noninvasive measures of cardiovascular, skeletal, and metabolic health for individual mice. We determined that while rapamycin has mild transient metabolic effects, there are significant benefits to late-life cardiovascular function with a reversal or attenuation of age-related changes in the heart. RNA-seq analysis of cardiac tissue after treatment indicated inflammatory, metabolic, and antihypertrophic expression changes in cardiac tissue as potential mechanisms mediating the functional improvement. Rapamycin treatment also resulted in beneficial behavioral, skeletal, and motor changes in these mice compared with those fed a control diet. From these findings, we propose that late-life rapamycin therapy not only extends the lifespan of mammals, but also confers functional benefits to a number of tissues and mechanistically implicates an improvement in contractile function and antihypertrophic signaling in the aged heart with a reduction in age-related inflammation.

We have discovered that three longevity mutants of the nematode Caenorhabditis elegans also exhibit increased intrinsic thermotolerance (Itt) as young adults. Mutation of the age-1 gene causes not only 65% longer life expectancy but also Itt. The Itt phenotype cosegregates with age-1. Long-lived spe-26 and daf-2 mutants also exhibit Itt. We investigated the relationship between increased thermotolerance and increased life-span by developing conditions for environmental induction of thermotolerance. Such pretreatments at sublethal temperatures induce significant increases in thermotolerance and small but statistically highly significant increases in life expectancy, consistent with a causal connection between these two traits. Thus, when an animal's resistance to stress is increased, by either genetic or environmental manipulation, we also observe an increase in life expectancy. These results suggest that ability to respond to stress limits the life expectancy of C. elegans and might do so in other metazoa as well.

For decades, researchers in the biology of aging have focused on defining mechanisms that modulate aging by primarily studying a single metric, sometimes described as the “gold standard” lifespan. Increasingly, geroscience research is turning towards defining functional domains of aging such as the cardiovascular system, skeletal integrity, and metabolic health as being a more direct route to understand why tissues decline in function with age. Each model used in aging research has strengths and weaknesses, yet we know surprisingly little about how critical tissues decline in health with increasing age. Here I discuss popular model systems used in geroscience research and their utility as possible tools in preclinical studies in aging.

Several reports have shown that individual mitochondrial DNA (mtDNA) deletions accumulate with age. However, the overall extent of somatic mtDNA damage with age remains unclear. We have utilized full-length PCR to concurrently screen for multiple mtDNA rearrangements in total DNA extracted from skeletal muscle derived from physiologically normal individuals (n = 35). This revealed that both the number and variety of mtDNA rearrangements increases dramatically between young and old individuals (P < 0.0001). We further examined the mtDNA from both the younger and older subjects by Southern blot analysis and observed an age-related increase in mtDNA(s) comparable in size to mtDNA products unique to patients with known mtDNA deletions. These data imply that a wide spectrum of mtDNA rearrangements accumulate in old individuals, which correlates with the marked age related decrease in OXPHOS capacity observed in post-mitotic tissues.

Background Despite the success of highly active antiretroviral therapy (HAART), HIV infected individuals remain at increased risk for frailty and declines in physical function that are more often observed in older uninfected individuals. This may reflect premature or accelerated muscle aging. Methods Skeletal muscle gene expression profiles were evaluated in three uninfected independent microarray datasets including young (19 to 29 years old), middle aged (40 to 45 years old) and older (65 to 85 years old) subjects, and a muscle dataset from HIV infected subjects (36 to 51 years old). Using Bayesian analysis, a ten gene muscle aging signature was identified that distinguished young from old uninfected muscle and included the senescence and cell cycle arrest gene p21/Cip1 (CDKN1A). This ten gene signature was then evaluated in muscle specimens from a cohort of middle aged (30 to 55 years old) HIV infected individuals. Expression of p21/Cip1 and related pathways were validated and further analyzed in a rodent model for HIV infection. Results We identify and replicate the expression of a set of muscle aging genes that were prematurely expressed in HIV infected, but not uninfected, middle aged subjects. We validated select genes in a rodent model of chronic HIV infection. Because the signature included p21/Cip1, a cell cycle arrest gene previously associated with muscle aging and fibrosis, we explored pathways related to senescence and fibrosis. In addition to p21/Cip1, we observed HIV associated upregulation of the senescence factor p16INK4a (CDKN2A) and fibrosis associated TGFβ1, CTGF, COL1A1 and COL1A2. Fibrosis in muscle tissue was quantified based on collagen deposition and confirmed to be elevated in association with infection status. Fiber type composition was also measured and displayed a significant increase in slow twitch fibers associated with infection. Conclusions The expression of genes associated with a muscle aging signature is prematurely upregulated in HIV infection, with a prominent role for fibrotic pathways. Based on these data, therapeutic interventions that promote muscle function and attenuate pro-fibrotic gene expression should be considered in future studies.

Alpha-synuclein has been reported to be present in the nucleus and levels enhanced by oxidative stress. Herein, we sought to investigate the mechanistic role of nuclear alpha-synuclein. We found that alpha-synuclein nuclear localization coincided with enhanced chromatin binding both in an in vitro and a corresponding in vivo brain oxidative stress model previously characterized by our laboratory as well as in PD brain tissues. Genome-wide chromatin immunoprecipitation (ChIP)-on-chip analysis of alpha-synuclein:promoter binding in response to oxidative stress in vitro revealed that binding occurs at several promoters belonging to a range of functional categories including transcriptional regulation. Interestingly, given the important role of mitochondrial dysfunction in PD, this included binding to the promoter for the master mitochondrial transcription activator, PGC1alpha in vitro , in vivo , and in human brain tissue with age and PD. To test the possible mechanistic impact of alpha-synuclein PGC1alpha promotor binding, we assessed PGC1alpha promoter activity, mRNA, and protein levels and expression of candidate PGC1alpha target genes in our in vitro model. All were found to be reduced in conjunction with increased levels of aberrant mitochondrial morphology and impaired mitochondrial function. Exogenous PGC1alpha expression was found to attenuate alpha-synuclein-mediated mitochondrial dysfunction and subsequent neurotoxicity in vitro. Our data suggest that nuclear alpha-synuclein localization under conditions of oxidative stress may impact on mitochondrial function in part via the protein’s capacity to act as a transcriptional modulator of PGC1alpha. This represents a novel role for alpha-synuclein as it relates to mitochondrial dysfunction in PD.

Massage therapy is commonly used during physical rehabilitation of skeletal muscle to ameliorate pain and promote recovery from injury. Although there is evidence that massage may relieve pain in injured muscle, how massage affects cellular function remains unknown. To assess the effects of massage, we administered either massage therapy or no treatment to separate quadriceps of 11 young male participants after exercise-induced muscle damage. Muscle biopsies were acquired from the quadriceps (vastus lateralis) at baseline, immediately after 10 min of massage treatment, and after a 2.5-hour period of recovery. We found that massage activated the mechanotransduction signaling pathways focal adhesion kinase (FAK) and extracellular signal-regulated kinase 1/2 (ERK1/2), potentiated mitochondrial biogenesis signaling [nuclear peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α)], and mitigated the rise in nuclear factor κB (NFκB) (p65) nuclear accumulation caused by exercise-induced muscle trauma. Moreover, despite having no effect on muscle metabolites (glycogen, lactate), massage attenuated the production of the inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) and reduced heat shock protein 27 (HSP27) phosphorylation, thereby mitigating cellular stress resulting from myofiber injury. In summary, when administered to skeletal muscle that has been acutely damaged through exercise, massage therapy appears to be clinically beneficial by reducing inflammation and promoting mitochondrial biogenesis.