Pathobiology of Aging & Age Related Diseases
Taylor & Francis
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Promoting healthy aging: intervening with diet, drugs, or exercise
Volume: 6, Issue: 1
DOI 10.3402/pba.v6.34153
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Table of Contents

Highlights

Notes

Promoting healthy aging: intervening with diet, drugs, or exercise

Lithium and ThT manipulation of protein aggregation and lifespan in C. elegans

Silvestre Alavez1*, David J. Zucker2, Maithili Vantipalli2 and Gordon J. Lithgow2

1Department of Health Sciences Metropolitan Autonomous University, Mexico City, Mexico

2Buck Institute for Aging Research Novato, CA, USA

*Correspondence to: Silvestre Alavez, Department of Health Sciences, Metropolitan Autonomous University, Mexico City, Mexico, Email: s.alavez@correo.ler.uam.mx

We have shown that exposure to 10 mM LiCl throughout adulthood increases survival (up to 46%) during normal aging in Caenorhabditis elegans. This extension of lifespan may be attained through altered expression of genes encoding nucleosome-associated functions via LSD-1, a histone demethylase. We have also found that adult worms exposed to the amyloid-binding dye thioflavin-T (ThT) resulted in a profoundly extended lifespan. ThT also suppressed pathological features of mutant metastable proteins and human β-amyloid-associated toxicity. In this work, we explored whether lithium treatment would be able to influence proteostasis in two C. elegans models of human proteotoxicity disease; CL4176, which expresses an aggregating Aβ peptide3-42 in muscle tissue, and AM141, which expresses a polyglutamine (polyQ) expansion protein. When raised to 25°C, worms expressing these proteins in muscle accumulate aggregates of these heterologous proteins and become paralyzed. We found that LiCl significantly decreases the proportion of paralyzed worms and prevents paralysis of mutant worms that express metastable worm proteins previously exploited as indicators of the status of the proteostasis network (HE250 and CB1157). This effect is mediated by hsf-1, daf-2, and pha-4. Interestingly, LiCl treatment decreases thermotolerance of the wild-type strain (N2), suggesting that Li+ treatment may compromise the survival during acute stress by employing the protein homeostatic machinery in preventing protein aggregation. Taken together, these results suggest that the modulation of protein homeostasis could play a critical role in the mechanism activated by lithium to increase lifespan and its beneficial effects on several neurodegenerative diseases.

Mitochondrial heteroplasmy changes with reactive oxygen species in nd5 mutation cells

Hongjoo An*

1Department of Cell Systems and Anatomy University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Hongjoo An, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: anh@uthscsa.edu

Human mitochondrial DNA (mtDNA) disorders can disturb multiple tissues, are clinically complicated, and are often destructive. These disorders characterize a large group of diseases with heterogeneous clinical and pathological expressions described by inappropriate functions of, and irreversible damage to, cells. The introduction of an mtDNA mutation produces a diverse population of molecules within the cell, named heteroplasmy. Clinical severity can be subjective by the percentage of pathogenic versus normal mtDNA genomes existing in disturbed cells (heteroplasmy). The cause of changes and shift of heteroplasmy are not fully understood or clear. Here, using various heteroplasmic mutation cell lines treated with hydrogen peroxide (H2O2), we know that optimal ROS level is required to shift heteroplasmy toward wild-type and mutant mtDNA homoplasmy and heteroplasmy. We want to identify how we can alter heteroplasmy pattern, and how we can detect mtDNA and heteroplasmy changes.

Calorie restriction modulates intrinsic and niche factors in the aging murine subventricular zone

Deana M. Apple*, Rene S. Fonseca, Swetha Mahesula, Erzsebet Kokovay

1Department of Cell Systems and Anatomy University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Deana M. Apple, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: appled@uthscsa.edu

The normal aging process in the brain results in increased susceptibility to damage from brain insults like stroke, inflammation, and degeneration. Calorie restriction (CR) can improve physiological markers of health during aging, including extending lifespan and protecting against age-related damage to the brain. The largest source of neural stem cells in the adult brain is the subventricular zone (SVZ). We sought to determine the effect of long-term CR on neurogenesis and the neural stem cell niche in the SVZ of young and aged mice. Here, we show that aged mice fed standard control chow have fewer SVZ-derived neurons in the olfactory bulb, indicating that aging impairs neural stem cell function. Long-term CR preserved neural stem cell function and resulted in a significant increase in neurogenesis in aged mice compared with ad libitum-fed controls. Confocal imaging and fluorescent staining of SVZ whole mounts revealed an increase in both the total number and reactivity of microglia in the aged control mouse, suggesting increased inflammation in the neural stem cell niche during aging. Remarkably, these age-related inflammatory markers were not observed in the long-term CR aged mice, which appeared no different from young controls and young CR mice included in the study. We observed a protective effect of CR on aging-related dysregulation of vascular-associated chemoattractants important for stem cell activity. However, CR did not protect against rarefaction of the SVZ vasculature in the aged brain. Altered proliferation profiles in the aged SVZ have suggested a change in cell fate determination, and CR maintains the expression of lin28a, a modulator of stem cell differentiation that declines in the aged brain. The maintenance of lin28a levels in the aged SVZ by CR suggests a potential mechanism by which CR protects the SVZ neural stem cell population in the aging brain.

Neuronal NF-κB regulates Alzheimer's disease–associated tau protein

Eric Baeuerle*, Miranda E. Orr, Joseph M. Valentine, Hanyu Liang, You Zhou, Nicolas Musi

1Sam and Ann Barshop Institute for Longevity and Aging Studies University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Eric Baeuerle, Sam and Ann Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: baeuerle@livemail.uthscsa.edu

Tau proteins are well known for their role in neurodegenerative diseases such as Alzheimer's disease. The physiological function of tau protein is to regulate and stabilize microtubules within neuronal axons. During pathogenesis, tau hyperphosphorylation leads to disruption of microtubule stabilization and subsequent tau aggregation, which can lead to neurodegeneration and dementia seen in Alzheimer's disease. Although inflammation is known to be a major contributor to Alzheimer's disease progression, the role of tau protein has not been significantly examined. Prior work by our research group has shown that the transcription factor NF-κB, which directly regulates the expression of numerous inflammatory cytokines, also regulates tau protein expression. We have examined the direct effects of NF-κB inhibition on tau expression in a neuronal cell line using an Ad-I?Bα super repressor of NF-κB. We have found that inhibition of NF-κB in neuronal cells increases tau expression. In our ongoing studies, we are examining whether NF-κB regulates Mapt and tau in vivo using stereotaxic delivery of AAV-IκBα and AAV-IKKβ (constitutively active NF-κB) in mouse brains. Furthermore, to confirm whether NF-κB is a direct Mapt transcription factor, we are performing chromatin immunoprecipitation. Previous studies suggest that Mapt has NF-κB binding sites; thus, we hypothesize that NF-κB is a direct regulator of Mapt expression. The results of this work will help elucidate novel mechanisms of tau protein regulation and potentially lead toward a new understanding of the role of inflammation and tau in the pathogenesis of Alzheimer's disease.

Investigating loss of terminal neuronal differentiation in Alzheimer's disease and related tauopathies

Adrian Beckmann1, Wenyan Sun2, Maria Gamez2 and Bess Frost

1Institute of Biotechnology The Barshop Institute for Longevity and Aging, University of Texas Health Science Center at San Antonio, TX, USA

2Department of Cell Systems and Anatomy The Barshop Institute for Longevity and Aging, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Adrian Beckmann, Institute of Biotechnology, The Barshop Institute for Longevity and Aging, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: beckmann@livemail.uthscsa.edu

Tauopathies are progressive neurodegenerative disorders that are defined histologically by deposits of insoluble, hyperphosphorylated tau protein in the brain. Alzheimer's disease is the most common tauopathy, with reported cases approaching nearly 50 million, globally. Current FDA-approved treatments delay the breakdown of acetylcholine with modest, temporary improvements in cognitive function. Alternative strategies target amyloid-beta (Aβ) and neuro-inflammation but have yet to arrest, alter, or reverse the neurodegenerative process. Recently, tau has manifested as a promising avenue for therapeutic intervention for many reasons. First, pathological tau correlates more closely with cognitive dysfunction than Aβ in Alzheimer's disease. Second, deposits of Aβ plaques in an Alzheimer's disease mouse model fail to induce neuronal loss in the absence of tau. Third, multiple mouse models demonstrate that tau acts downstream of Aβ to mediate neurotoxicity. Recently, our laboratory has discovered that pathological tau causes prolonged stabilization of filamentous actin, which disrupts the lamin nucleoskeleton. Nucleoskeletal disruption induces relaxation of heterochromatin, which drives abnormal cell cycle entry and neuronal death. We have also reported that heterochromatin relaxation promotes expression of genes that regulate development and self-renewal (i.e. POU1F1, NOG, and NR5A2). Preliminary data suggest that transcription factors that maintain a terminally differentiated state are downregulated in adult tau transgenic Drosophila. We are currently testing the hypothesis that neurons harboring pathological tau fail to maintain a terminally differentiated state. If our hypothesis is correct, therapeutic strategies aimed at maintaining terminal differentiation in neurons may ameliorate tau-induced neurotoxicity.

The role of ATR/atl-1 in modulating lifespan during mitochondrial dysfunction

Megan B. Borror*, Adwitya Kar and Shane L. Rea

1Barshop Institute for Longevity and Aging and Department of Physiology University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Megan B. Borror, Barshop Institute and Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: kingsolver@uthscsa.edu

The Caenorhabditis elegans Mit mutants have reduced mitochondrial electron transport chain (ETC) function, yet have extended lifespan. It is clear that several mechanisms contribute to Mit mutant lifespan extension, and we have evidence that at least one more remains to be identified. A mutation in atl-1, the C. elegans ortholog of ataxia telangiectasia and Rad3-related (ATR) DNA damage response kinase, mitigates the ability of mitochondrial dysfunction to extend lifespan. Our goal is to determine how the atl-1 checkpoint kinase is activated during mitochondrial dysfunction and how its downstream effects mediate longevity. This work encompasses two main goals: 1) determining how atl-1 is activated by mitochondrial dysfunction and 2) identifying the downstream effects that modulate lifespan. To address the activation of atl-1, our studies show that the frequency of DNA mutation, the most common activator of atl-1, is not increased in Mit mutants. Interestingly, nucleotide pools are disrupted in Mit mutants, raising the possibility that transcriptional stalling may activate atl-1. To identify the role of atl-1 in modulating lifespan in the presence of mitochondrial dysfunction, we found that genes coding for ETC complex genes are downregulated in atl-1 mutants. Consistent with previous reports, we confirmed that atl-1 mutants have reduced mitochondrial DNA content compared with the wild-type. However, despite the reduction in mtDNA and ETC gene expression, atl-1 mutants consume oxygen at a rate equal to that of the wild-type worms. Ongoing studies seek to identify the activator of atl-1 and the mechanism through which atl-1 modulates mitochondrial function.

Impact of progeria on mesenchymal stromal stem cells

Regina Brunauer*, Eleanor H. Patterson, Chen-Yu Liao, Emmeline C. Academia, Monique N. O'Leary, Brian K. Kennedy

1Buck Institute for Research on Aging Novato, CA, USA

*Correspondence to: Regina Brunauer, Buck Institute for Research on Aging, Novato, CA, USA, Email: rbrunauer@cvm.tamu.edu

Lamins are a major component of the nuclear lamina, providing a structural network for regulation of gene expression and DNA repair. Mutations of the lamin A gene are the underlying cause of laminopathies such as Hutchinson–Gilford Progeria Syndrome (HGPS). Furthermore, it has been shown that an alternative splicing product of lamin A, progerin, accumulates with aging. Interestingly, predominantly mesenchymal tissues such as bone, fat and muscle are affected in laminopathies. In this project, we hypothesize that mesenchymal stem cells (MSC), the progenitors of mesenchymal tissues, are impacted in their regenerative vigor upon loss of lamin A function and fail to maintain their residing tissue. We isolated mesenchymal stem cells from bone and subcutaneous adipose tissue of progeroid mice and assessed MSC quantity, differentiation potential and proliferation rate as readouts for regenerative capacity. As a next step, we will extend our approach to lifespan-extending interventions. By this means, we hope to unravel strategies to restore stem cell function not only in progeria but also in aging.

Female survival advantage in genetically heterogeneous mice is age- and site-specific

Catherine J. Cheng*, Jonathan A.L. Gelfond, James F. Nelson

1Sam and Ann Barshop Institute for Longevity and Aging Studies University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Catherine J. Cheng, Sam and Ann Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: chengcj@uthscsa.edu

Female survival advantage is one of the most robust characteristics of human longevity. Although the female survival advantage is well-documented, the underlying biological mechanisms are unknown and represent a major knowledge gap in biogerontology. Inbred strains of mice are overwhelmingly used as mammalian models for basic research, but their susceptibility to strain-specific diseases and the lack of a consistent female survival advantage limit their usefulness in studies to model or understand the basis for sex differences in aging. The use of genetically heterogeneous mice overcomes the limitations of strain-specific pathology and countless other traits. Thus, we sought to determine the influence of age and site on the sex differences in mortality of these genetically heterogeneous mice and to compare these survival characteristics with those of humans. We found that female mice showed consistently better survival than males: female mice had a significantly higher median lifespan in every cohort. Further analysis of age-specific mortality showed that this decreased mortality risk is not maintained uniformly at all ages, peaking before 400 days of age and converging until it becomes negligible after midlife. Notably, these patterns of mortality in mice reflect those of human populations, which show a similar peak in relative risk in men compared with women in earlier life, followed by a steady convergence in old age. We found a significant interaction between sex and site on survival across all years. Male but not female survival varied across the three study sites. Together, our results add to the understanding of a model increasingly used for the design and selection of lifespan-extending interventions, with great potential for application to the study of sex differences in aging and treatment response.

The significance of endoplasmic reticulum homeostasis in the long-lived Caenorhabditis elegans proteasomal rpn-10 mutant

Meghna N. Chinchankar1,2* and Alfred L. Fisher1,2,3

1Division of Geriatrics Gerontology, and Palliative Medicine, Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

2Center for Healthy Aging The Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

3GRECC, South Texas VA Healthcare System, San Antonio, TX, USA

*Correspondence to: Meghna N. Chinchankar, Division of Geriatrics, Gerontology, and Palliative Medicine, Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: chinchankar@livemail.uthscsa.edu

The RPN-10 subunit of the 19S regulatory particle of the 26S proteasome is required for the identification and threading of polyubiquitinated substrates into the 20S proteasome core for degradation. We unexpectedly found that the loss-of-function Caenorhabditis elegans rpn-10 (ok1865) mutant exhibits a modest reduction in the ubiquitin–proteasome system (UPS)–mediated protein degradation while bolstering overall organismal fitness. This is established by the rpn-10 mutants being more resistant to proteomic threats, including heat, oxidative stress, the expression of aggregation-prone polyglutamine repeat proteins, or the presence of mutant endogenous metastable proteins. The animals are also long-lived at 25°C. These rpn-10 phenotypes suggest the activation of several compensatory mechanisms by the decline in UPS function. Of significant interest is the endoplasmic reticulum (ER) stress response pathway. We recently determined that rpn-10 mutants demonstrate greater resistance to ER stress compared with the wild-type. Remarkably, though, ER stress reporter assays have shown that both basal as well as activated ER stress response is set at a lower level in rpn-10 mutants. Moreover, while the ER unfolded protein response (UPR) adequately regulates polyglutamine protein aggregation in rpn-10 mutants, it exerts a substantial effect on lifespan. Specifically, certain ER UPR components, including the xbp-1 (XBP1) transcription factor, its target – the ER chaperone hsp-3/-4 (BiP/grp78), as well as ATPase cdc-48.2 (p97/VCP/CDC48) – are critical determinants of rpn-10 longevity. Altogether, our preliminary data indicate that the optimized ER homeostasis is an integral link between graded proteasome function, enhanced proteostasis, and increased lifespan of the rpn-10 mutant.

The intron debranching enzyme (dbr1) in amyotrophic lateral sclerosis

Nathaniel E. Clark*1,2, Adam Katolik3, Stacy A. Hussong2,4, Jordan B. Jahrling2,4, Kenneth M. Roberts1, Alex B. Taylor1, Stephen P. Holloway1, Paul F. Fitzpatrick, Masad J. Damha, Veronica Galvan, P. John Hart

1Department of Biochemistry University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

2The Barshop Institute for Longevity and Aging Studies University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

3Department of Chemistry McGill University, Montreal, Quebec, Canada

4Department of Physiology University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

5Department of Veterans Affairs Geriatric Research, Education, and Clinical Center, South Texas Veterans Health Care System, San Antonio, TX, USA

*Correspondence to: Nathaniel E. Clark, Department of Chemistry, McGill University, Montreal, Quebec, Canada, Email: clarkn@uthscsa.edu

The RNA-debranching enzyme (Dbr1) plays an important role in RNA homeostasis in eukaryotic cells. Splicing of introns generates lariat RNA with an unusual 2’,5’-phosphodiester bond. The only enzyme known to debranch these RNA lariats is Dbr1. Some functional non-coding RNAs derive from intronic RNA, including small nucleolar RNAs that aid in ribosome assembly and approximately one-third of the currently known micro RNAs. It is likely that some roles of these RNA lariats remain undiscovered. A recent article has shown that accumulation of RNA lariats in Δdbr1 cells has a protective effect against TDP-43 toxicity in models of amyotrophic lateral sclerosis (ALS), suggesting that inhibitors of Dbr1 may benefit ALS patients. We have determined the x-ray crystal structure of Dbr1 from Entamoeba histolytica and analyzed the effect of different metal substitutions in the active site as well as the interaction of an inactive Dbr1 variant with a bona fide branched RNA substrate. We have developed a fluorogenic probe of Dbr1 activity and performed a preliminary assessment of the enzymatic properties of Dbr1. Results from these studies call into question the previously reported identity of the metal cofactor(s) required for Dbr1-mediated lariat debranching. To have a clearer understanding of Dbr1's role in biology and human disease, we are examining the expression and processing of Dbr1 in mouse and human tissues, and these results suggest that Dbr1 has a role in neuronal processes. Both Dbr1 and TDP-43 are found in the insoluble fraction of elderly human frontal cortex.

Brown adipose tissue function is enhanced in the hypopituitary Ames dwarf mouse

Justin Darcy1,2*, Samuel McFadden1, Yimin Fang1, Joshua Huber1, Chi Zhang, Andrzej Bartke1,2

1Department of Internal Medicine Geriatric Research, Southern Illinois University School of Medicine, Springfield, IL, USA

2Department of Medical Microbiology Immunology and Cell Biology, Southern Illinois University School of Medicine, Springfield, IL, USA

*Correspondence to: Justin Darcy, Department of Internal Medicine, Geriatric Research, Southern Illinois University School of Medicine, Springfield, IL, USA, Email: jdarcy@siumed.edu

Growth hormone (GH) has a crucial role in aging. For example, the hypopituitary Ames dwarf mouse is GH-depleted, and it has extended longevity. Along with a dramatic increase in longevity, Ames dwarf mice demonstrate improved glucose homeostasis and energy metabolism. Several studies demonstrated that removal of visceral white adipose tissue (WAT) from mice improves their glucose homeostasis; however, this is not true in Ames dwarf mice, which indicates differences in their visceral WAT function. Further, Ames dwarf mice have improved energy metabolism as measured by respiratory quotient (RQ), oxygen consumption (VO2), and heat production. Given the uniqueness of WAT in Ames dwarf mice, and their improved energy metabolism, we hypothesized that brown adipose tissue (BAT) in Ames dwarf mice might function more efficiently than that of their normal littermates and that surgical removal of BAT will have a greater impact on dwarfs than on normal mice. Here, we find that Ames dwarf mice have more BAT relative to body weight, and that their BAT has an increased expression of thermogenic-specific genes. Further, body temperature in Ames dwarf mice is more drastically decreased by BAT removal than in their normal littermates. Finally, removal of BAT from Ames dwarf mice results in impaired energy metabolism, while normal mice are unaffected. We believe this demonstrates BAT without exposure to GH functions more efficiently. Since energy metabolism may be a mechanism and/or a bio-marker’ for extended longevity, we believe Ames dwarf BAT may play a role in their extended longevity. (Supported by NIA)

β-guanidinopropionic acid alters metabolism and energy substrate utilization in muscle cells

Jonathan Dorigatti* and Adam B. Salmon

1Sam and Ann Barshop Institute for Longevity and Aging Studies University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Jonathan Dorigatti, Sam and Ann Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: dorigatti@livemail.uthscsa.edu

The AMP-activated protein kinase (AMPK) pathway has been shown to play a central role in the regulation of metabolism and longevity. The anti-diabetic and proposed pro-longevity drug metformin targets AMPK signaling; however, metformin is a weak activator of this pathway and is toxic at relatively low concentrations. β-guanidinopropionic acid (β-GPA) is a creatine analogue with little toxicity in mammals and a competitive inhibitor of creatine kinase. By effectively inhibiting the creatine kinase system, β-GPA alters the energy status of the cell, resulting in strong activation of AMPK. β-GPA has been reported to increase lifespan in Drosophila and is currently being tested by the NIH Interventions Testing Program to determine its effect on mouse longevity. In this study, we sought to characterize the direct metabolic effects of β-GPA on the murine muscle–derived C2C12 cell line. We report that administration of β-GPA reduces both basal oxygen consumption and basal glycolysis while increasing maximum reparation and spare respiratory capacity. However, β-GPA administration also drastically reduces maximum glycolytic capacity. Correspondingly, cell cultures treated with β-GPA show a marked reduction in proliferative rate indicating that β-GPA administration reduces cellular metabolism while simultaneously driving activation of AMPK. This pattern is consistent with reported results from dietary restriction studies in mice suggesting β-GPA may act, in some ways, as a mimetic of dietary restriction.

Early and sustained microglia activation contributes to age-associated reductions in neurogenesis

Rene S. Fonseca1*, Swetha Mahesula1, Deana M. Apple1, Allison Dugan1, Astrid Cardona2, Jason O'Connor1 and Erzsebet Kokovay1

1University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

2University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Rene S. Fonseca, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: solanofonsec@livemail.uthscsa.edu

The ventricular-subventricular zone (V-SVZ) is the largest neural stem cell (NSC) reservoir of the mammalian forebrain. However, NSC proliferation and neurogenesis are sharply reduced at mid-age through unknown mechanisms. Our studies establish microglia, the resident immune cells in the brain, as integral V-SVZ niche cells closely associated with NSCs, germinal pinwheels, and the microvasculature. During aging, microglia undergoes substantial positional changes within the niche, losing their close association to the vasculature while becoming increasingly associated with the ependyma and germinal pinwheels. We observed an early and chronic activation of V-SVZ microglia not seen in microglia outside of the niche during aging. This activation was accompanied by increased inflammatory mediators within the NSC compartment. A substantial increase of monocyte infiltration was observed within the aged V-SVZ niche, suggesting the peripheral immune system may also mediate V-SVZ inflammation during aging. Induction of sustained inflammation in young mice results in increased microglia activation accompanied by reduced proliferation in the V-SVZ, and in vitro studies revealed secreted factors from activated microglia reduced proliferation and neuron production compared with secreted factors from resting microglia. Furthermore, minocycline treatment in aged mice reduces microglia activation, niche inflammation, and partially restores proliferation in the aged niche. Interestingly, microglia depletion in the young V-SVZ results in a reduction of proliferation that is restored after microglia numbers are allowed to normalize. Our results suggest that age-associated chronic inflammation contributes to declines in NSC function within the aging neurogenic niche, and microglia may sustain or negatively affect neurogenesis depending on age.

Mechanisms of tau-induced neurological dysfunction: focus on the nucleus

Tyler Jenson1, Grace Wallick1,2, Maria Gamez1,3, Bess Frost1,3*

1The Barshop Institute for Longevity and Aging Studies and Department of Physiology University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

2Boston University Boston, MA, USA

3Department of Cell Systems and Anatomy University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Bess Frost, The Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: bfrost@uthscsa.edu

The filamentous meshwork formed by the lamin nucleoskeleton provides strength and structure to the nucleus and establishes the three-dimensional architecture of the genome. Dysfunction of the lamin nucleoskeleton is strongly implicated in the cellular mechanisms underlying aging because mutations in lamin cause a fatal syndrome involving the appearance of accelerated aging in young children. We have demonstrated that acquired lamin misregulation through aberrant cytoskeletal–nucleoskeletal coupling promotes widespread relaxation of heterochromatin and subsequent neuronal death in a Drosophila model of neurodegenerative tauopathy. We found that lamin dysfunction also causes a significant expansion of the ‘nucleoplasmic reticulum’ in vivo and in postmortem brain tissue from humans with Alzheimer's disease. These lamin- and nuclear pore-lined, cytoplasm-filled invaginations of the nuclear envelope originate at the nuclear periphery and extend deep into the nuclear interior, often traversing the entire nucleus. Such structures have also been observed in laminopathies, various cancers, and physiological brain aging, and are referred to as ‘nucleoplasmic reticulum’. Since the nucleoplasmic reticulum is an extension of the nuclear envelope, we hypothesized that these nuclear envelope invaginations bring functions of the peripheral nuclear envelope into the deep nuclear interior. Indeed, preliminary studies suggest that pathological factors cause a toxic increase in RNA export and a decrease in nuclear calcium signaling. In addition to immediately increasing our mechanistic understanding of tauopathy and physiological brain aging, the results of our studies will be broadly applicable to other physiological brain aging and human disorders involving nucleoplasmic reticulum expansion, and could inform therapeutic approaches.

Offspring aging is transgenerationally determined by maternal age and diet

Kristin E. Gribble*, Martha J. Bock, George C. Jarvis

1Marine Biological Laboratory Woods Hole, MA, USA

*Correspondence to: Kristin E. Gribble, Marine Biological Laboratory, 7 MBL St., Woods Hole, MA, USA, Email: kgribble@mbl.edu

Anti-aging therapies may increase lifespan not only in an individual but also across generations. Such ‘maternal effects’ occur when the maternal response to the environment causes a change in offspring phenotype without a change in the genome. To better understand the role of maternal effects in aging, we examined the influence of maternal age and diet on offspring lifespan, fecundity, mitochondrial function, response to interventions, and epigenetic modifications in the rotifer, Brachionus manjavacas. Rotifers are microscopic, aquatic invertebrates with many advantages as a new model system for the biology of aging. We found decreased lifespan, fecundity, and oxidative stress resistance in offspring of older mothers compared with offspring of younger mothers. Mitochondrial DNA copy number doubles in offspring of 10-day-old versus 3-day-old mothers, yet mitochondrial gene expression remains unchanged, suggesting an accumulation of damaged mitochondria. Under intermittent fasting, lifespan increases more in offspring of older mothers (50%) than of young mothers (21%). Global H3 methylation increased in offspring of aged mothers; increases in activating marks H3K4me1-3 and H3K27me1 and decreases in repressive H3K9me1 and H3K9me2 suggest transcriptional dysregulation contributes to decreased lifespan. Maternal caloric restriction (CR) increases offspring lifespan and fecundity even when offspring are not directly exposed to CR. Chronic CR and IF result in similar increases in lifespan in mothers and offspring, but chronic CR offspring had larger body size, greater fecundity, and higher mtDNA copy number than IF offspring. We are investigating the genetic and epigenetic mechanisms for the transgenerational determination of lifespan.

Increased antioxidant activity mitigates age-associated dysfunction of thymic stromal cells in aged mice

Sergio Cepeda1, Changchan Xiao1, Thomas Venables2, and Ann Griffith1*

1Department of Microbiology and Immunology School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

2Department of Cancer Biology The Scripps Research Institute, Jupiter, FL, USA

*Correspondence to: Ann Griffith, Department of Microbiology and Immunology, School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: griffitha3@uthscsa.edu

Age-associated thymic atrophy results in diminished production of new T-lymphocytes and a concomitant decrease in responsiveness to new pathogens and vaccines. In addition to loss of thymic size with age, we have shown that critical stromal functions, including tissue-restricted antigen (TRA) expression, are diminished with age. We previously identified deficiency of hydrogen peroxide quenching enzyme catalase (CAT) in thymic stromal cells as the key cause of thymic atrophy during aging, and established that thymic atrophy can be mitigated by genetic or dietary complementation of catalase antioxidant activity. Here, we find that in addition to maintaining thymic mass with age, long-term increases in catalase activity may mitigate age-associated loss of stromal function. Our preliminary studies indicate that life-long overexpression of catalase in mitochondria of transgenic mice (mCAT Tg) results in increased TRA expression, mitigated acquisition of an aged global gene expression signature, and increased maintenance of cortico-medullary organization in aged mCAT Tg mice relative to non-transgenic littermates.

Ferroptosis in forebrain neurons: a novel cell-death mechanism contributing to cognitive impairment

Sealy Hambright1,2*, Lizhen Chen1,3 and Qitao Ran

1Department of Cell Systems and Anatomy University of Texas Health Science Center at San Antonio, TX, USA

2The Barshop Institute for Longevity and Aging Studies University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

3South Texas Veterans Health Care System, San Antonio, TX, USA

*Correspondence to: Sealy Hambright, Department of Cell Systems and Anatomy, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: hambright@uthscsa.edu

Synaptic loss and neuron death are the underlying drivers of neurodegenerative diseases such as Alzheimer's disease (AD); however, the modalities of cell-death remain unclear. Ferroptosis is a newly identified oxidative cell-death pathway regulated by lipid peroxidation that promotes inflammation. Here, we investigated whether the neurons in forebrain regions that are severely afflicted in AD patients (cerebral cortex and hippocampus) might be vulnerable to ferroptosis. To this end, we deleted the ferroptosis regulator Gpx4 exclusively in the forebrain neurons of 3-month-old mice using a novel tamoxifen-inducible knockout model (Gpx4BiKO). At 12 weeks post Gpx4 knockout, the mice exhibited significant deficits in spatial learning and memory versus controls. Hippocampal tissue from Gpx4BiKO mice also showed reduced levels of neural marker proteins, NeuN, Synaptophysin, and SNAP25, indicating the occurrence of neurodegeneration. Interestingly, classical markers of apoptosis such as activation of caspase-3 were absent while several markers associated with ferroptosis were pronounced in Gpx4BiKO mice. These features, which included elevated lipid peroxidation (4-HNE adducts), elevated gliosis (GFAP, Iba1), increased pro-inflammatory cytokine expression, and increased pERK1/2, suggested that neurodegeneration in Gpx4BiKO mice occurred via ferroptosis. Knowing that vitamin-E has anti-ferroptotic properties, we next examined the effects of vitamin-E deficiency (VED) on the rate of neurodegeneration in Gpx4BiKO mice. As expected, Gpx4BiKO-VED exhibited an expedited rate of hippocampal neurodegeneration appearing at 2 weeks post Gpx4 ablation. Taken together, our results indicate that forebrain neurons are indeed susceptible to ferroptosis and that ferroptosis may be an important degenerative mechanism of neurons in AD.

Reprogramming across age and species

Jacob Hemmi*, Anuja Mishra, Peter J. Hornsby

1Sam and Ann Barshop Institute for Longevity and Aging Studies University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Jacob Hemmi, Sam and Ann Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: hemmi@livemail.uthscsa.edu

The ability to generate induced pluripotent stem (iPS) cells on demand from specific patients raises exciting possibilities for the future of regenerative therapy. However, it also raises questions about shortfalls in efficacy and safety that could possibly result from the generation of iPS cells derived from individuals of advanced age. This is significant as the recipients most likely in need of such regenerative treatments will be older individuals, whose cells are known to accumulate age-related change that may or may not be reset by the reprogramming process. In our studies, we aim to develop a model of iPS cell creation followed by directed differentiation and finally autologous or allogenic cell therapy where these questions can be answered. Another focus of our lab is the development of iPS cells from novel species to enable comparative biological studies to be performed between cells derived from species of exceptional biogerontological interest in hopes of better understanding what mechanisms act at the cellular level leading to phenotypes such as extreme longevity, negligible senescence, and cancer resistance.

Here, there, and everywhere: Disconnecting health span from lifespan by knocking down mtorc1 in neurons

Stacy A. Hussong, Raquel Burbank, Jon Halloran, Ai-Ling Lin, Vanessa Y. Soto, Veronica Galvan

1The Barshop Institute for Longevity and Aging Studies University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

2Department of Physiology University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

3Research Imaging Center University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Stacy A. Hussong, The Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: hussong@uthscsa.edu

The mechanistic target of rapamycin (mTOR) is a major regulator of cellular and organismal metabolism. Reduction of TOR signaling by rapamycin alters organismal metabolism and increases lifespan and healthspan. In invertebrate models, selective reduction of function of TOR in the nervous system is sufficient to extend life. We hypothesized that attenuating mTOR signaling in mature mammalian neurons would extend lifespan by altering critical aspects of metabolism non-autonomously. To test this hypothesis, we knocked down the mTOR complex 1 (mTORC1) specific protein, Raptor, in adult neurons in mice. Reduction of mTORC1 complex formation in neurons of mice by 35 or 60% did not affect body weight but increased lean mass while reducing metabolism. This was associated with enhanced exercise endurance and absent post-exercise hypoglycemia, even though glucose and insulin tolerance were unchanged. The 35% knock down animals exhibit increased hepatic glucose production as determined by a pyruvate tolerance test. Wild-type muscle cells treated with serum from 35% knock down mice have reduced glycogen content compared with those treated with WT mouse serum, indicating a change in muscle glycogen production or utilization caused by a circulating factor in the serum. To determine cell-autonomous effects of mTORC1 knockdown in neurons, we measured spatial learning and memory. While 60% mTORC1 knockdown impaired cognitive plasticity, 35% reduction in mTORC1 complex formation resulted in enhanced spatial memory. Consistent with these observations, 60% neuronal mTORC1 knock down reduced brain glucose metabolism and cerebral blood flow, while a 35% decrease enhanced brain glucose uptake with no changes in cerebral blood flow. Taken together, our data suggest that reduction of neuronal mTORC1 may have significant non-cell autonomous effects on basal and exercise metabolism. Furthermore, the relationship between the levels of mTORC1 in neurons and spatial memory is not linear. Rather, spatial memory maybe maximal when neuronal mTORC1 levels are slightly lower than WT but decreases with further reductions in mTORC1.

Attenuation of mTOR with rapamycin restores blood–brain barrier integrity and function in aging disease models

Jordan B. Jahrling, Naomi Sayre, Angela Olson, Veronica Galvan

1Department of Physiology and The Barshop Institute for Longevity and Aging Studies University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

2Department of Neurosurgery University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Jordan B. Jahrling, Department of Physiology and The Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: jahrling@uthscsa.edu

Background: Cerebrovascular changes are a ubiquitous attribute with age, both in the disease state and in healthy patients. Prominent features of such changes include cerebral hypo-perfusion and blood–brain barrier (BBB) dysfunction, each of which contribute to overall cognitive impairment. Recent evidence suggests a critical link between vascular function and susceptibility to neurodegenerative disease – in particular, Alzheimer's disease and vascular dementia. Our laboratory recently showed that attenuating activity of the mechanistic target of rapamycin (mTOR) restores brain vascular integrity and cognitive function in a mouse model of Alzheimer's disease. Here, we investigate the mechanisms by which rapamycin-induced mTOR attenuation decreases BBB permeability and vascular leakage.

Materials and methods: We utilized the bEnd3 immortalized mouse brain endothelial cell line to create an in vitro BBB model. We also used J20 Alzheimer's mice and low-density lipoprotein receptor knockout mice for in vivo experiments.

Results: Our findings indicate that acute rapamycin treatment is sufficient to decrease BBB permeability by facilitating expression of tight junction proteins and subsequently improving barrier function by a mechanism likely involving the reduction of MMP9 activity. We also show that chronic rapamycin treatment decreases brain vascular leakage in both the low-density lipoprotein receptor knockout mouse model and also in the J20 Alzheimer's mouse model, and this treatment is protective against Aβ-mediated insult in our in vitro BBB model.

Conclusions: Rapamycin treatment to restore proper vascular function may represent an early-stage intervention in the treatment of neurodegenerative processes associated with aging.

Acknowledgements: JBJ is funded by NIH 2T32AG021890-11. Two-photon images were generated in the Core Optical Imaging Facility, which is supported by University of Texas Health Science Center at San Antonio, NIH-NCI P30 CA54174 (CTRC at UTHSCSA), and NIH-NIA P01AG19316.

The effect of acarbose on mouse health span

Alex Kramer, Vanessa Martinez, Elizabeth Fernandez, Randy Strong

1The Barshop Institute for Longevity and Aging Studies University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

2Department of Physiology University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

3MD/PhD Program University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

4Geriatric Research Education and Clinical Center, South Texas Veterans Health Care System, San Antonio, TX, USA

5Research Service, South Texas Veterans Health Care System, San Antonio, TX, USA

6Department of Pharmacology University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Alex Kramer, The Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: kramerd@livemail.uthscsa.edu

Acarbose, an FDA-approved drug for the treatment of diabetes, decreases postprandial blood glucose excursions by inhibiting intestinal enzymes that liberate glucose from starch oligosaccharides. In patients with impaired glucose tolerance, acarbose improves measures of glucose homeostasis and reduces the risk of cardiovascular disease, hypertension, and rheumatoid arthritis. Acarbose has recently been shown to extend lifespan in genetically heterogeneous mice, but the drug's effect on healthspan remains unclear. To address this question, we fed acarbose to genetically heterogeneous mice starting at 8 months of age until they reached 22 months of age, at which point measures of age-related change were collected and compared with those of 22- and 4-month-old untreated control cohorts. In addition, beginning at 8 months of age mouse body weight and composition were recorded at 4-month intervals until study completion. In spite of the treatment and control groups having nearly identical food intake and activity levels, acarbose-treated mice featured significant reductions in body weight and fat percentage relative to untreated age-matched controls, suggesting that acarbose attenuates age-related metabolic changes independent of caloric intake and activity-dependent energy expenditure. In addition, a test of grip strength and duration revealed that acarbose abrogates age-related declines in muscle endurance and fatigability in males, but not in females. Altogether, these data show that acarbose delays or attenuates age-related changes in mouse body composition and muscle fatigability and also suggest that the drug may have potential in serving as a treatment for aging and age-related disease in humans.

Hydrogen sulfide effect on aging-induced changes in the kidney and the brain

Hak Joo Lee, Jordan Jahrling, Vanessa Martinez, Vivian Diaz, Sae Byeol Oh, Denis Feliers, Christopher G. Kevil, Jeffrey L. Barnes, Goutam Ghosh Choudhury, James Nelson, Elizabeth Fernandez, Randy Strong, Veronica Galvan, Balakuntalam S. Kasinath

1Department of Medicine University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

2The Barshop Institute for Longevity and Aging Studies University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

3Department of Physiology University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

4Pharmacology University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

5Louisiana State Health Science Center, Shreveport, LA, USA

*Correspondence to: Hak Joo Lee, Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: leehj@uthscsa.edu

Background: Aging is associated with reduced H2S content and expression of H2S synthesizing enzymes in the kidney and the brain accompanied by mTORC1 activation. Our goal was to test if age-related changes could be ameliorated by H2S.

Methods: We randomized 18- to 19-month-old C57BL6 male mice (from NIA) to receive water (n=14 mice) or 30 µmol/L of sodium hydrosulfide (NaHS), a source of H2S for 5 months (n=20 mice).

Results: NaHS did not affect body weight, blood glucose level, and food and water consumption but ameliorated systolic and diastolic hypertension. NaHS decreased urinary albumin excretion and serum cystatin C level, suggesting improved renal function. Preliminary data show that NaHS reduced renal matrix protein increment and inhibited mTORC1 activity in the kidney. NaHS did not affect measures of cognitive (fear conditioning and novel object recognition) or non-cognitive (tail suspension test) function or of frailty or spontaneous activity, but impaired some neuromotor outcomes (performance in the grip test but not in rotarod).

Conclusion: Aging-related kidney injury can be ameliorated by H2S administration and this may involve mTORC1 inhibition. However, H2S did not affect frailty, or measures of nervous and neuromotor system function for which decreases are expected during aging.

Elevated biogenic aldehydes exacerbate motor behavior deficits in mice overexpressing human wild-type alpha-synuclein

Paul Anthony Martinez, Vanessa Martinez, Elizabeth Fernandez, Randy Strong

1The Barshop Institute for Longevity and Aging Studies University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

2Department of Pharmacology University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

3Center for Biomedical Neuroscience University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

4Geriatric Research Education and Clinical Center, South Texas Veterans Health Care Network, San Antonio, TX, USA

*Correspondence to: Paul Anthony Martinez, The Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: martinezp3@uthscsa.edu

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease. The progressive degeneration of nigrostriatal dopaminergic neurons results in reduced striatal dopamine, ultimately leading to the dysregulation of motor movement. Deficits in striatal dopamine release lead to several clinical features including resting tremor, bradykinesia, and muscular rigidity. Cytoplasmic protein inclusions known as Lewy bodies have been identified in surviving dopamine neurons. Lewy bodies are primarily composed of alpha-synuclein (αSyn), a pre-synaptic protein believed to have a central role in neurotransmitter release. This natively unfolded and monomeric protein is capable of forming toxic oligomers, particularly under conditions of oxidative stress. Evidence from in vitro studies suggests that two biogenic aldehydes, the lipid peroxidation end-product (4-hydroxynonenal – 4HNE), and the first aldehyde product of dopamine metabolism by MAO (3,4-dihydroxyphenylacetaldehyde – DOPAL) promote and stabilize the formation of toxic αSyn oligomers. To determine whether aldehydes promote enhanced αSyn toxicity in vivo, we crossed mice having a double homozygous null mutation in the only two aldehyde dehydrogenases (Aldh1a1 and Aldh2), known to exist in midbrain dopamine neurons with mice overexpressing human wild-type (WT) α-synuclein (Thy1) to create TTG mice. We then tested their performance on a series of tests of locomotor function. The groups consisted of WT mice, mice null for Aldh1a1 and Aldh2 (DKO), Thy1, and TTG mice. We found that TTG mice performed significantly worse on tests of locomotor function than mice in the other three groups. This result is consistent with the hypothesis that elevated biogenic aldehydes promote the formation of toxic oligomers of αSyn in vivo. In future studies, we will measure brain levels of aldehyde – adducted αSyn – and determine whether it is associated with neurochemical deficits in the nigrostriatal pathway.

Acyl-CoA:lysocardiolipin acyltransferase regulates cellular bioenergetics and lysosomal function: implications for aging and age-related diseases

Kennedy Mdaki, Jun Zhang, Youhua Wang, Yuguang Shi

1The Barshop Institute for Longevity and Aging Studies University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Kennedy Mdaki, The Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: mdaki@uthscsa.edu

The molecular mechanism underlying a causative role of aging in the pathogenic conditions remains poorly understood. We recently reported a novel pathway controlled by acyl-CoA:lysocardiolipin acyltransferase-1 (ACLAT1), an acyltransferase that catalyzes the remodeling of mitochondrial cardiolipin with fatty acyl chains that are highly sensitive to oxidative damage. Here, we investigated the mechanisms by which cellular bioenergetics and lysosomal function may be regulated by ALCAT1 using a previously described mouse model of ALCAT1 knockout and Tafazzin (TAZ) knockdown. Primary cardiomyocytes (CM), aortic smooth muscle cells, and mouse embryonic fibroblasts (MEFs) were used for the studies. Cellular bioenergetics were assessed using a seahorse XF24. Lysosomal function was assessed by monitoring changes in lysosomal size, pH, and degradation capacity during starvation and refeeding. ALCAT1 knockout increased mitochondrial coupling efficiency and maximum oxygen consumption in CMs. Moreover, glycolysis stress test revealed an increase in glycolytic capacity in ALCAT1 knockout ASMC. Lysosomal size, pH, and degradation capacity were improved by ALCAT1 knockout in TAZ knockdown MEFs. We found that ALCAT1 knockout improves cellular bioenergetics and lysosomal function. This improvement may partially be due to a reduction in acyl chains that are sensitive to oxidative damage, which may increase coupling of mitochondrial membrane potential to oxidative phosphorylation. In addition, optimal lysosomal function is essential for regulation of autophagy in response to metabolic or oxidative stress. As ALCAT1 is mainly expressed in the heart, ALCAT1 suppression presents a potential therapeutic target against aging and aging-related diseases.

Acyl-CoA:lysocardiolipin acyltransferase-1 (ACLAT1) function in islet during aging and aging-related diseases

Jia Nie, Yuguang Shi, Nicolas Musi

1The Barshop Institute for Longevity and Aging Studies University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Jia Nie, The Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: niej@uthscsa.edu

Acyl-CoA:lysocardiolipin acyltransferase-1 (ACLAT1) promotes cardiolipin peroxidation by catalyzing pathological remodeling of cardiolipin with aberrant fatty acyl chains commonly found in aging, leading to increased cellular reactive oxygen species. Islet β-cells are particularly sensitive to oxidative stress and mitochondrial dysfunction associated with aging, since redox signaling plays a pivotal role in glucose-stimulated insulin secretion (GSIS). Thioredoxin-interacting protein (TXNIP), an oxidative stress mediator by inhibiting thioredoxin activity, plays a key role in islet β-cell function, since TXNIP depletion promotes endogenous islet β-cell survival and prevents streptozotocin- and obesity-induced diabetes. Our previous work showed that targeted deletion of ALCAT1 in mice ameliorates the onset of age-related metabolic diseases, including obesity, type 2 diabetes, and cardiovascular diseases. However, ALCAT1 function in the islet β-cell, which plays a major role in obesity, diabetes, and aging, remains elusive. In this study, we will test our hypothesis that ALCAT1 causes islet β-cell dysfunction during aging in part by upregulating TXNIP expression, which is supported by our preliminary data that TXNIP expression is downregulated in islets isolated from ALCAT1 knockout mice compared with wild-type control mice. The hypothesis will be further tested by analyzing the gain and loss of ALCAT1 function on different aged islet β-cells, including GSIS, islet β-apoptosis/regeneration, oxidative stress, and ATP production, which is a driving force for GSIS.

The effect of rapamycin on LRP1 transcytosis of Aβ

Angela Olson, Jordan Jarhling, Stacy Hussong, Veronica Galvan

1Department of Physiology University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Angela Olson, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: olsona@livemail.uthscsa.edu

Advanced age is the greatest known risk factor for the development of Alzheimer's disease (AD). Yet, despite decades of ongoing research, little has been discovered regarding the biological mechanisms involved in the regulation of aging that initiate the detrimental neurodegenerative processes observed in AD. A characteristic phenotype of AD is the accumulation of amyloid beta (Aβ) in the brain, which aggregates to form plaques and fibrils. The vast majority of Aβ is cleared from brain into blood across the blood–brain barrier (BBB). Low-density lipoprotein receptor-related protein 1 (LRP1) is the main transporter of Aβ at the BBB. Expression of LRP1 in brain vascular endothelial cells is dramatically decreased in AD, and this is associated with an increase in Aβ brain levels and Aβ plaque deposition. Furthermore, it has recently been suggested that the remaining LRP1 receptors at BBB may have decreased affinity for Aβ due to oxidative modifications of the receptor itself, which render it dysfunctional. We have recently demonstrated that rapamycin, a potent inhibitor of the mechanistic target of rapamycin (mTOR), reduced Aβ accumulation, decreased cerebral amyloid angiopathy, and halted the progression and even restored established AD-like memory deficits in several different AD mouse models. In this study, we tested the hypothesis that mTOR may contribute to increased Aβ brain levels by reducing LRP1-mediated transport across BBB. To test this hypothesis, we measured the expression of LRP1 protein and mRNA in endothelial cell culture, in a model of BBB, and in brain vasculature of AD mice. We found that mTOR attenuation resulted in increased LRP1 expression in cell culture systems and in vivo, and that the increase in LRP1 was linked to an increase in Aβ clearance across the BBB. Mass spectrometry studies showed specific differences in oxidative modifications of LRP1 between brain vasculature from AD mice treated with rapamycin and controls, suggesting that mTOR attenuation may increase the abundance and functionality of LRP1, the main Aβ receptor at BBB. Taken together, our data suggest that mTOR contributes to the pathogenesis of AD by downregulating and possibly by promoting oxidative modifications of LRP1 and, thus, may reveal novel mechanisms by which attenuation of mTOR may significantly delay or stop the progression of AD.

Alzheimer's disease–associated tau pathology induces cellular senescence in brain

Miranda E. Orr, George A. Carlson, Nicolas Musi

1The Barshop Institute for Longevity and Aging Studies University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

2McLaughlin Research Institute for Biomedical Sciences Great Falls, MT, USA

*Correspondence to: Miranda E. Orr, The Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: orrm3@uthscsa.edu

In brain, intraneuronal inclusions of tau protein are the most common pathology associated with neurodegeneration. These diseases encompass over 15 distinct disorders, including Alzheimer's disease (AD). Large insoluble tau-containing aggregates, neurofibrillary tangles (NFTs), are the closest histopathological correlates with neuron loss and cognitive decline in AD. However, because NFT-containing neurons do not die, their role in neurodegeneration remains unclear. We suggest that NFTs may evoke toxicity through secondary, non-cell autonomous mechanisms. Specifically, we propose that NFT-containing cells may contribute to tissue destruction by secreting toxic soluble factors in a mechanism similar to cellular senescence. Cellular senescence is generally characterized by a permanent cell-cycle arrest and alterations in gene expression, metabolic state, morphology, and cytokine secretion. While there is no single unifying marker that defines the complex stress response, robust phenotypes include elevated gene expression of tumor suppressor p16INK4a (p16) and inflammatory cytokines. Recently, we found that transgenic mice with NFTs have a significant elevation in senescence markers in the brain, including p16. The increase in p16 was associated with an elevation in brain cytokines, TNF-α and IL-1β. Only mice with NFTs, but not age-matched controls with high levels of soluble tau, expressed senescence-associated factors. Collectively, these data suggest that pathogenic tau and cellular senescence are interconnected. Ongoing studies with transgenic mice will focus on molecular mediators of cellular senescence in the brain, specific cell types involved, and the mechanistic interplay among cellular senescence, tau pathology, neurodegeneration, and cognitive decline.

The effects of rapamycin on activity and behavior in marmoset monkeys

Molly Mireles, Adam Salmon, Suzette Tardif, Corinna Ross

1Texas Biomedical Research Institute, Texas A&M University, San Antonio, TX, USA

2University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

3Southwest National Primate Research Center San Antonio, TX, USA

*Correspondence to: Corinna Ross, Texas Biomedical Research Institute, Texas A&M University, San Antonio, TX, USA, Email: rossc4@uthscsa.edu

Rapamycin has been shown to extend lifespan in rodent models, but the effects of rapamycin on broader aspects of healthspan are still being evaluated. Prior to rapamycin being used as a treatment to extend either lifespan or healthspan in the human population, it is vital to assess the effects of the treatment on healthspan in animal model systems, including a closely related non-human primate model. In this lifespan study with marmosets, we began treatment in March 2016 of the first cohort consisting of 12 rapamycin-dosed animals and 9 eudragit control animals. Two aspects of locomotor behavior are being examined for each of the individuals. To examine the daily activity, Actiwatch units are worn in backpacks for 96 hours and daily movement counts are tallied. The first examination of this activity in September revealed no differences between rapamycin and control animals. To evaluate social behavior and movement within the cage, 10-minute behavior observations noting leaping, hanging, movement, and placement in the cage were collected from June through September. While geriatric animals are significantly more likely to be near their partner than younger animals (p=0.035), there are no significant differences between rapamycin and control animals to date. We are continuing to add behavioral measures of activity and evaluations of cognitive change in this longitudinal lifespan study. The marmosets offer an interesting alternative animal model for future intervention testing and translational modeling.

Targeting mTOR inhibition to extend non-human primate longevity

Aubrey Sills, Bryan DeRosa, Yuhong Liu, Corinna Ross, Suzette Tardif, Adam Salmon

1Geriatric Research Education and Clinical Center, South Texas Veterans Health Care System, San Antonio, TX, USA

2Sam and Ann Barshop Institute for Longevity and Aging Studies and Department of Molecular Medicine University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Adam Salmon, Sam and Ann Barshop Institute for Longevity and Aging Studies and Department of Molecular Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: salmona@uthscsa.edu

The inhibition of mechanistic target of rapamycin (mTOR) has emerged as a viable means to lengthen lifespan and healthspan in mice, though it is still unclear whether these benefits will translate to human benefit. Testing whether the inhibition of mTOR extends longevity and improves healthspan in a non-human primate model is a major step towards the development of translational approaches to delay or reduce the incidence and severity of age-related diseases in humans through manipulation of this pathway. We have approached this question by utilizing the shortest-lived anthropoid primate, the common marmoset (Callithrix jacchus). In our previous studies, we have developed an effective treatment protocol for daily administration of encapsulated rapamycin that results in clinical concentrations of rapamycin in the blood, inhibition of mTOR in vivo, and evidence for enhanced proteostasis in liver and skeletal muscle of treated animals. Here, we outline the design and initial reports of our established study to test whether aging is altered by rapamycin treatment in this non-human primate. A cohort of middle-aged male and female marmosets have begun daily treatment with rapamycin with an ultimate goal of testing whether longevity is extended over the next 5 to 6-year period. In addition, we will measure longitudinal outcomes of functional assays targeted to five general physiological systems shown to be affected by rapamycin in rodent models: muscle function, cognition and memory, metabolism, immune and inflammation, and cardiovascular risk. In our initial assessments of this cohort, our rapamycin administration protocol reduces mTORC1 (though not mTORC2) signaling and has limited to no adverse side-effects. Importantly, in contrast to rodent studies, glucose metabolism is not significantly altered in this non-human primate orally treated with once-daily encapsulated rapamycin. Moreover, there is little evidence for dramatic changes in body weight or composition despite dramatic reduction in mTOR signaling in vivo. When complete, this study will describe for the first time the potential for pharmaceutical intervention to extend longevity of a primate species with the ultimate goal of significant translational impact to human aging.

The metabolic benefits of methionine restriction require methionine oxidation repair

Yuhong Liu, Adam Salmon

1Geriatric Research Education and Clinical Center, South Texas Veterans Health Care System, San Antonio, TX, USA

2Sam and Ann Barshop Institute for Longevity and Aging Studies and Department of Molecular Medicine University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Adam Salmon, Sam and Ann Barshop Institute for Longevity and Aging Studies and Department of Molecular Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: salmona@uthscsa.edu

The pro-longevity effects of dietary restriction have been largely attributed simply to the reduction in caloric intake, though there is growing evidence that restriction of protein alone may recapitulate many of the same phenotypes. In particular, dietary restriction of the essential acid methionine has been shown to extend longevity, improve metabolic health, and alter mitochondrial utilization of energetic resources in rodent models. The underlying mechanisms behind the effects of methionine restriction are still not clear; although limiting the available methionine pool seems to require enhanced maintenance of the existing pool, this amino acid cannot be made by the body. Of the small group of known endogenous protein repair mechanisms, the methionine sulfoxide reductases (Msr) can uniquely repair oxidation of free and protein-bound methionine residues through enzymatic reduction. Msr exist in two isoforms in eukaryotes, with the MsrA isoform ubiquitously expressed among mammalian tissues and found in both cytosolic and mitochondrial sub-cellular localizations. In this study, we addressed whether the effects of methionine restriction require the presence of MsrA in mice. Adult female C57/BL6 mice fed a methionine-restricted diet (0.15% methionine in restricted vs. 0.43% methionine in replete diet), lost weight, and their body composition was altered to a similar degree regardless of the presence of MsrA in vivo. In wild-type mice, methionine restriction promoted a robust improvement in glucose metabolism within a few weeks after restriction regime was begun. In contrast, mice lacking MsrA (MsrA-/-) experience no metabolic benefit from methionine restriction as glucose tolerance measurements are indistinguishable between restricted and replete methionine diets. What role changes in the oxidation status of the methionine pool plays with age, or healthy aging, are not known but these requirements are likely to change during the aging process and under dietary restriction. Moreover, these findings suggest that functional expression of MsrA may be a requirement for the longevity benefits of methionine restriction.

Loss of tmem127 improves insulin signaling and protects against insulin resistance due to aging, high fat diet, and rapamycin treatment

Subramanya Srikantan, Yilun Deng, Anqi Luo, Yuejuan Qin, Ziming Cheng, Qing Gao, Myrna Garcia, Zhi Li, Adam Salmon, Lily Dong, Robert Reddick, Luke Norton, Muhammad Abdul-Ghani, Patricia L.M. Dahia

1Department of Medicine University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

2Department of Cellular & Structural Biology University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

3Department of Molecular Medicine University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

4Department of Pathology University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Subramanya Srikantan, Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: subramanyasr@uthscsa.edu

mTORC1 and mTORC2 complexes control anabolic and catabolic processes and have been implicated in metabolic disorders and cancer. Inhibition of mTORC1 by rapamycin increases lifespan in mammals, and mTORC1 inhibitors are clinically used in cancers. However, rapamycin treatment leads to glucose intolerance and insulin resistance by inhibiting mTORC2, potentially limiting its use as an anti-aging or anti-cancer agent. TMEM127 is a lysosomal protein that impinges on mTORC1 through mechanisms involving mTORC1 recruitment to its activation site at the lysosome. We investigated the effects of TMEM127 loss by targeted deletion of the Tmem127 gene in mice (KO). Chow diet-fed KO mice have reduced body weight and fat mass, and show resistance to age-dependent glucose and insulin intolerance (Table 1). When challenged with insulin, KO liver, fat, and muscle displayed higher Akt activation, consistent with increased insulin sensitivity. Thus, we investigated the response to other insulin resistance-inducing stresses. After a high-fat diet (HFD), KO mice remained insulin-sensitive and were faster to normalize body weight and insulin levels when switched to chow. Similarly, KO mice were protected from glucose and insulin intolerance after rapamycin exposure, suggesting a broader effect of Tmem127 deficiency against insulin resistance induced by distinct stimuli. Mechanistically, liver from HFD- and rapamycin-treated KO mice retained mTORC2 activity. We propose that the favorable insulin metabolism of Tmem127 KO mice may be due to heightened mTORC2 stability. The primary tissue target of TMEM127 is under investigation with tissue-specific deletion models; however, our data suggest that TMEM127 inhibition might enhance effectiveness of interventions aiming to selectively inhibit mTORC1.

Table 1. Insulin tolerance test, area under the curve (mean±standard error)
ConditionWTKOp
Young (<6 months)2334±113 (n=18)2019±206 (n=13)0.18
Old (9–19 months)3221±340 (n=17)2338±143.9 (n=16)<0.05
HFD (60% calories, 16 weeks)5566±187 (n=8)4557±239 (n=9)<0.01
HFD-recovery (HFD, 16 weeks followed by chow, 10 weeks)5165±466 (n=3)3317±310 (n=4)<0.05
Rapamycin (2 mg/kg, IP, 2 weeks)2938±160 (n=14)2504±108 (n=9)<0.05

Analysis of the PERK juxtamembrane domain reveals a strategy for visualizing ER stress in situ

Brian J. Stoveken, James D. Lechleiter

1Department of Cell Systems and Anatomy University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

2The Barshop Institute for Aging and Longevity Studies University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Brian J. Stoveken, Department of Cell Systems and Anatomy, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: Stoveken@livemail.uthscsa.edu

The PKR-like endoplasmic reticulum kinase (PERK) is an ER transmembrane kinase that regulates proteostasis through phosphorylation of the translation initiation factor eIF2α. Proper regulation of PERK activity is essential to human health, and dysregulated PERK signaling is observed in neurodegenerative disorders including Alzheimer's disease. Unfortunately, the mechanisms that govern PERK activation are poorly understood, limiting targeted interventions to kinase inhibitors with marked in vivo toxicity. We found that the 45-amino acid cytosolic juxtamembrane domain (JMD) of PERK is necessary for catalytic activity, as PERK (ΔJMD) mutants did not rescue eIF2α phosphorylation in PERK-deficient fibroblasts exposed to chemical ER stress. Notably, this effect was independent of the JMD sequence as a 45-amino acid glycine–serine linker could functionally substitute for the native JMD. PERK truncation mutants in which the PERK kinase domain was replaced with the monomeric fluorescent protein, mEos3.2, formed numerous intracellular foci upon overexpression, suggestive of oligomerization from weak homotypic fluorescent protein interactions. In live cell imaging experiments, we observed an increase in mutant foci upon ER stress. These structures were abolished by deletion of the JMD, leading us to conclude that both kinase domain trans-autophosphorylation and weak mEos3.2 interactions are promoted by the optimal ER membrane proximity and conformational freedom afforded by the PERK JMD. Curiously, deletion of PERK's ER luminal domain significantly reduced foci formation, suggesting that the luminal domain promotes productive interaction JMD-tethered cytosolic elements. Full-length PERK:mEos3.2 did not spontaneously form discrete foci upon overexpression. Therefore, we posit that mEos3.2 stabilizes luminal-domain initiated interactions in PERK:mEos3.2 truncation mutants to a greater extent than the native PERK kinase domain does in full-length PERK, despite equivalent JMD tether distances. Hence, the PERK:mEos3.2 truncation mutants used in this study may be useful fluorescent reporters that integrate ER stress sensed by PERK into visual fluorescent signals.

Acknowledgment: This work was supported by a pre-doctoral fellowship to BJS from the Glenn Foundation for Medical Research and NIH/NIA T32 Institutional Aging Training Grant AG021890.

Investigating dysregulation of transposable elements and piRNAs as a driver of neurodegeneration in Alzheimer's disease and related tauopathies

Wenyan Sun, Adrian Paul Beckmann, Bess Frost

1Sam and Ann Barshop Institute for Longevity and Aging Studies University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

2Department of Cell Systems and Anatomy University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Wenyan Sun, Sam and Ann Barshop Institute for Longevity and Aging Studies, Department of Cell Systems and Anatomy, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: sunw@uthscsa.edu

Tauopathies, including Alzheimer's disease, are age-related progressive neurodegenerative disorders that are pathologically defined by aggregates of tau protein in the brain. Our previous data suggest that tau-induced relaxation of heterochromatic DNA promotes neuronal death in tauopathies. In tauopathy, heterochromatin relaxation allows transcription of genes that are normally silenced by heterochromatin, including Ago3, a gene whose protein product is involved in the biogenesis of PIWI-interacting RNAs (piRNAs). We hypothesize that dysregulation of piRNAs, small RNAs that target transposable element transcripts for destruction, promotes neurodegeneration in tauopathy, and that tau-induced heterochromatin relaxation facilitates the transcription of non-coding DNA, including transposable elements. In support of this hypothesis, we found that genetic manipulation of piRNA biogenesis machinery modifies tau-induced neurotoxicity. Based on targeted transcriptomics, we detect a significant increase in Idefix, a retrotransposon, in tau transgenic Drosophila. We are currently utilizing a fluorescence-based reporter of transposable element mobilization to determine if transposable elements are capable of mobilizing in tauopathy and are comprehensively surveying piRNA and transposable element expression in tau transgenic Drosophila using RNA sequencing. Future studies will employ super-resolution microscopy to identify the subcellular localization of piRNAs in Drosophila and human brain, and will detect components of the piRNA biogenesis complex and RNA targets of piRNAs that are significantly increased in tauopathy by in situ hybridization. A deeper understanding of the relationship between piRNAs and transposable elements in tauopathy may lead to the development of predictive biomarkers and will guide therapeutic strategies.

A mouse model to examine the role of the Sirt1 gene in aging bone

Ramkumar Thiyagarajan, Kenneth L. Seldeen, Merced Leiker, Bruce R. Troen

1Division of Geriatrics and Palliative Medicine Department of Medicine, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, USA

2VA Western New York Healthcare System, Buffalo, NY, USA

*Correspondence to: Ramkumar Thiyagarajan, Biomedical Sciences, University at Buffalo, Buffalo, NY, USA; VA Western New York Healthcare System, Buffalo, NY, USA, Email: rthiyaga@buffalo.edu

Half of Americans over age 50 are at risk for osteoporosis. Age-associated increases in reactive oxygen species (ROS) and mitochondrial dysfunction lead to poor bone remodeling. Sirtuin 1 (Sirt1) expression declines with aging and appears to play a role in mitochondrial function and bone metabolism. We hypothesize that Sirt1 ablation will reduce bone mineral density (BMD) by altering bone remodeling via reduction of mitochondrial efficiency and increased aberrant ROS signaling. BMD in old (24 months) C57BL/6J mice was lower than in young (3 months) mice (g/cm2: 0.05 ± 0.004 vs. 0.048 ± 0.002, p = 0.03). The bone marrow of old mice yielded more osteoclasts (OCs) than the bone marrow from young mice (32 ± 8 vs. 64 ± 12, p = 0.036). Similar to aged mice, young OC-specific constitutive Sirt1 knockout (KO) mice exhibited lower BMD and generated more OCs as compared with age-matched controls. We now demonstrate effective ablation of Sirt1 expression for at least 6 months in an inducible knockout model (UBC-Cre-ERT2×Sirt1flox-exon4). In addition, pursuant to understanding the impact of Sirt1 on bone marrow cell metabolism, we have begun to assess mitochondrial oxygen consumption using the XFe24 Seahorse flux analyzer. In conclusion, young Sirt1KO mice exhibit declines in bone health similar to aged mice, including lower BMD and greater OC formation. Our future experiments will elucidate the impact of Sirt1 on cellular energetics of bone cells, as well as enhance our understanding of the longitudinal and age-related impacts of Sirt1 upon skeletal health in vivo.

Physical activity reverts miRNA signatures in aged human muscle

Joseph M. Valentine, Sangeeta Ghosh, Yousin Suh, Nicolas Musi

1Sam and Ann Barshop Institute for Longevity and Aging Studies and Department of Medicine University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

2Department of Genetics Albert Einstein College of Medicine, New York, NY, USA

*Correspondence to: Joseph M. Valentine, Sam and Ann Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: valentinej@livemail.uthscsa.edu

A strong negative correlation exists between the age of an organism (invertebrates, rodents, non-human primates and humans) and skeletal muscle function, such that muscle function declines with advancing age. Physical activity can mitigate and even reverse some of these large-scale changes in skeletal muscle structure and function. One potential mechanism capable of regulating global alterations to a particular tissue is modification to the microRNA (miR) system. To elucidate the role that miRs play in the global changes observed in skeletal muscle with aging and in response to exercise, we conducted transcriptional profiling of vastus lateralis muscle obtained from healthy, younger (n=14, age = 27±0.89 years) and older (n=14, age = 71±1.39 years) human subjects of both genders before and after a 4-month training program. Gene set enrichment analyses of RNAseq data revealed upregulation of genes involved in mitochondrial respiration, protein translation, and tricarboxylic acid cycle after training. Analysis of microRNAseq data revealed unique signatures for men and women who were altered with both aging and physical activity. For instance, miR-486, miR-21, and Let-7, which are known to play a role in skeletal muscle protein synthesis and mitochondrial function, were significantly altered with aging and were reverted back to youthful levels with training. In addition, we identified novel miRNAs that were deferentially expressed with aging and reverted back to youthful levels after exercise training, including miR-7, miR-421, and miR-181a. These findings suggest that aging is associated with specific microRNA expression patterns that may be linked to aging-related declines in muscle function. The relationship between these transcriptomic patterns and the metabolic alterations of aging merits further investigation.

TOR drives cerebral amyloid angiopathy in a mouse model of Alzheimer's disease

Candice E. Van Skike, Jordan B. Jahrling, Nick DeRosa, Veronica Galvan

1The Barshop Institute for Longevity and Aging Studies University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

2Department of Physiology University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

*Correspondence to: Candice E. Van Skike, The Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: vanskike@uthscsa.edu

Cerebral amyloid angiopathy (CAA), the accumulation of fibrillar amyloid β (Aβ) within the neurovasculature, is present in up to 90% of patients with Alzheimer's disease (AD). We have previously shown that chronic treatment with rapamycin, an inhibitor of mechanistic target of rapamycin (mTOR), ameliorates memory deficits and reduces parenchymal Aβ accumulation in mice modeling AD. However, the role of TOR in CAA-induced pathology remains unknown.

To determine the role of mTOR in the pathogenesis of CAA and associated neurovascular dysfunction in AD, we used intravital two-photon microscopy through a thinned skull to measure amyloid accumulation and vascular function in a living mouse. Male and female Tg2576 mice were fed chow containing either eudragit vehicle or rapamycin beginning at 4 months of age and were between 18 and 19 months old at the time of imaging. Chronic mTOR attenuation reduced both the quantity and density of cerebrovascular Aβ lesions, preserved BBB integrity and brain vascular reactivity, especially in vasculature affected by high Aβ load, and restored contextual memory impairments in old Tg2576 mice. These data indicate that chronic mTOR attenuation restores brain vascular integrity and function in a model of advanced AD with CAA, possibly by reducing vascular Aβ lesion size and restoring vascular reactivity, resulting in improved cognitive outcomes. mTOR inhibitors such as rapamycin, an FDA-approved drug, may have promise for the treatment of AD and potentially other dementias that have vascular dysfunction as a common etiology.

Analysis of the mouse lens glutathione-responsive transcriptome and proteome: implications for age-related cataract

Jeremy Whitson, Vincent M. Monnier, Xiang Zhang, Benlian Wang, Xingjun Fan

1Department of Pathology Case Western Reserve University, Cleveland, OH, USA

2Department of Biochemistry Case Western Reserve University, Cleveland, OH, USA

3Department of Environmental Health Cincinnati University, Cincinnati, OH, USA

4Center for Proteomics and Bioinformatics Case Western Reserve University, Cleveland, OH, USA

*Correspondence to: Jeremy Whitson, Department of Pathology, Case Western Reserve University, Cleveland, OH, USA, Email: jeremy.whitson@case.edu

To date, cataract remains the leading cause of blindness worldwide and no preventative treatment yet exists. As aging is the major risk factor for cataractogenesis, older populations in regions without easy access to cataract surgery are heavily affected. Glutathione is an essential antioxidant for protecting long-lived lens proteins from post-translational modification that can lead to their aggregation and, therefore, cataract. With advanced age, glutathione synthesis is greatly reduced in the lens, leading to deficiency in glutathione and an increase in post-translational modification of lens proteins. To determine gene products with a potentially protective role in the lens under conditions of depleted glutathione, we examined the transcriptome, using RNA-Seq technology, and proteome, using spectral count analysis, of engineered mice that lack glutathione synthesis in their lenses. Among the many gene expression changes measured between the knockout mice and wild-type mice, there were significant changes in several genes relating to detoxification and antioxidant defense including aldehyde dehydrogenases, metallothioneins, urea transporter UT-B, carboxylesterase, and a glutathione S-transferase. This indicates that these proteins may be of particular importance for protecting aging lenses from developing cataract. Future research will go into determining whether these proteins are linked to cataract development in humans.

A life course fall in plasma cortisol accompanied by decreased hypothalamus–pituitary–adrenal axis activity begins soon after puberty in female baboons

Shanshan Yang, Peter W. Nathanielsz, Cun Li

1Department of Neurology Harbin Medical University, Harbin, Heilongjiang, China

2Department of Animal Sciences Texas Pregnancy & Life-course Health Research Center, University of Wyoming, Laramie, WY, USA

*Correspondence to: Shanshan Yang, Department of Animal Sciences, Texas Pregnancy & Life-course Health Research Center, University of Wyoming, Laramie, WY, USA, Email: syang2@uwyo.edu

Introduction: Conflicting data exist on life course hypothalamus–pituitary–adrenal axis (HPAA) activity changes. We showed decreasing circulating rat corticosterone beginning at mid-life. (1) A similar plasma cortisol fall from early as 6 years (life span 25–30 years) has been recently reported, and (2) in the baboon which we have confirmed. To address the mechanisms involved in this age-related fall, we hypothesized that commensurate with the cortisol fall: (1) paraventricular nuclear (PVN) content of the hypothalamic secretagogues CRH and AVP would fall, and (2) regulators responsible for negative feedback on HPAA production of cortisol would increase.

Methods: We measured circulating fasting early morning cortisol. Following necropsy, we determined PVN-immunopositive AVP, CRH, GR, p-GR, 11β hydroxysteroid dehydrogenase 1 and 2 (11βHSD1/2), and pituitary pro-opiomelanocortin (POMC) in female baboons (n=14; 6–13 years).

Results: We observed (1) a negative correlation of PVN AVP but not CRH expression with age (p<0.05), (2) strong positive correlations of PVN glucocorticoid (GR) and mineralocorticoid receptors (MR), 11βHSD1 and 11βHSD2 and negative correlation of pituitary POMC with age (p<0.05).

Conclusions: We conclude over the early adult period in the baboon and into early aging that (1) AVP, not CRH, is the major drive to HPAA basal function; (2) components of negative feedback mechanisms on the HPAA increase; and (3) these changes may contribute to the aging-associated fall in circulating cortisol.

Exercise-induced protein secretion from muscle

You Zhou, Ji Li, Sammy Pardo, Dana Molleur, Caleb Emmons, Susan T. Weintraub, Nicolas Musi

1Department of Cellular and Structural Biology University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

2Sam and Ann Barshop Institute for Aging and Longevity Studies University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

3Department of Biochemistry University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

4Proteome Software University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

5Diabetes Division Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

6Geriatric Research Education and Clinical Center, South Texas Veterans Health Care System, San Antonio, TX, USA

*Correspondence to: You Zhou, Department of Cellular and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: zhouy3@livemail.uthscsa.edu

Exercise has been shown to play an important role in prevention and treatment of a variety of diseases, and some of these benefits are thought to be induced by myokines – proteins and peptides that are produced and released from muscle fibers. The goal of this study is to identify exercise-induced myokines, as well as evaluate the dynamics of muscle myokine secretion postexercise. In this study, 3-month-old female C57BL/6 mice (three per group) were used for the study in the following groups: exercise and 2-hour postexercise, treadmill for 1 hour, 22 m/min, 15-degree incline; sedentary, cage-only control. After sacrifice, soleus and extensor digitorum longus (EDL) muscles were removed and incubated separately for 2 hours. Then, the solutions were sent for mass spectrometry. A surprisingly large number of proteins were found to be secreted from the muscles: soleus, 287 proteins in 246 clusters; and EDL, 350 proteins in 239 clusters. One-way ANOVA revealed that there was a significant difference in at least one experimental group for 103 soleus proteins but only 12 EDL proteins. Among the significantly changed secreted soleus proteins, 83 exhibited the highest relative quantity at 2-hour postexercise, 16 in the exercise group, and 4 in sedentary group, indicating that the quantities of many of the secreted soleus proteins increase with exercise.

Tyrosine activates p38 MAPK and innate immunity in C. elegans

Maruf H. Khan, Alfred L. Fisher

1Department of Medicine University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

2Center for Healthy Aging University of Texas Health Science Center at San Antonio, San Antonio, TX, USA

3GRECC, South Texas VA Healthcare System, San Antonio, TX, USA

*Correspondence to: Maruf H. Khan, Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA, Email: khanm3@uthscsa.edu

Obese individuals have higher circulating levels of aromatic amino acids including tyrosine. High level of tyrosine is correlated with the development of diabetes and heart disease. One of the underlying pathologies of obesity, diabetes, and heart disease is chronic inflammation. Whether there is a causal relationship between increased tyrosine, inflammation, and diabetes is not known. Using the model organism Caenorhabditis elegans, we have found that increased tyrosine levels in the worm can activate the p38 MAPK pathway and lead to increased innate immunity against pathogenic bacteria. In humans, p38 MAPK pathway is involved in inflammation and plays important roles in diseases such as diabetes and cancer. Understanding the effect of tyrosine on the p38 pathway and the mechanism by which it does so is thus important in the context of inflammation, aging, and age-related diseases. In our study, we have utilized the model organism C. elegans to study the mechanism by which tyrosine activates the p38 pathway. We have shown that the effect of tyrosine on p38 pathway activation is dependent on the MAPK signaling cascade tir-1, nsy-1, and pmk-1, and the transcription factor atf-7, which lies downstream of pmk-1. The activation is also partially dependent on the important nutrient sensor AMPK. In addition to increased immune resistance to pathogenic bacteria, mutant worm strains with increased levels of tyrosine also have increased lifespan; however, this increase in lifespan is not dependent on the p38 pathway. Currently, we are in the process of translating our findings to a mammalian system by looking at the effect of tyrosine on p38 activation and activation of inflammatory pathways in mammalian monocyte cell culture.

https://www.researchpad.co/tools/openurl?pubtype=article&doi=10.3402/pba.v6.34153&title=Promoting healthy aging: intervening with diet, drugs, or exercise&author=&keyword=&subject=Proceedings: Promoting healthy aging: intervening with diet, drugs, or exercise. 2016 meeting abstracts,