Aging
Abstract
The maintenance of functional independence is the top priority of patients with chronic kidney disease (CKD). Defects in mitochondrial energetics may compromise physical performance and independence. We investigated associations of the presence and severity of kidney disease with in vivo muscle energetics and the association of muscle energetics with physical performance. We performed measures of in vivo leg and hand muscle mitochondrial capacity (ATPmax) and resting ATP turnover (ATPflux) using 31phosphorus magnetic resonance spectroscopy and oxygen uptake (O2 uptake) by optical spectroscopy in 77 people (53 participants with CKD and 24 controls). We measured physical performance using the 6-minute walk test. Participants with CKD had a median estimated glomerular filtration rate (eGFR) of 33 ml/min per 1.73 m2. Participants with CKD had a –0.19 mM/s lower leg ATPmax compared with controls but no difference in hand ATPmax. Resting O2 uptake was higher in CKD compared with controls, despite no difference in ATPflux. ATPmax correlated with eGFR and serum bicarbonate among participants with GFR <60. ATPmax of the hand and leg correlated with 6-minute walking distance. The presence and severity of CKD associate with muscle mitochondrial capacity. Dysfunction of muscle mitochondrial energetics may contribute to reduced physical performance in CKD.
Authors
Bryan Kestenbaum, Jorge Gamboa, Sophia Liu, Amir S. Ali, Eric Shankland, Thomas Jue, Cecilia Giulivi, Lucas R. Smith, Jonathan Himmelfarb, Ian H. de Boer, Kevin Conley, Baback Roshanravan
Abstract
Clonal hematopoiesis of indeterminate potential is prevalent in elderly individuals and associated with increased risks of all-cause mortality and cardiovascular disease. However, mouse models to study the dynamics of clonal hematopoiesis and its consequences on the cardiovascular system under homeostatic conditions are lacking. We employed a model of clonal hematopoiesis using adoptive transfer of unfractionated ten-eleven translocation 2 (Tet2)-deficient bone marrow cells into non-irradiated mice. Consistent with age-related clonal hematopoiesis observed in humans, these mice displayed a progressive expansion of Tet2-deficient cells in multiple hematopoietic stem and progenitor cell fractions and blood cell linages. The expansion of the Tet2 mutant fraction was also observed in bone marrow-derived CCR2+ myeloid cell populations within the heart, but there was negligible impact on the yolk sac-derived CCR2– cardiac-resident macrophage population. Transcriptome profiling revealed an enhanced inflammatory signature in the donor-derived macrophages isolated from the heart. Mice receiving Tet2-deficient bone marrow cells spontaneously developed age-related cardiac dysfunction characterized by greater hypertrophy and fibrosis. Altogether we show that Tet2-deficient hematopoiesis contributes to cardiac dysfunction in a non-conditioned setting that faithfully models the human clonal hematopoiesis in unperturbed bone marrow. Our data support clinical findings that clonal hematopoiesis per se may contribute to diminished health span.
Authors
Ying Wang, Soichi Sano, Yoshimitsu Yura, Zhonghe Ke, Miho Sano, Kosei Oshima, Hayato Ogawa, Keita Horitani, Kyung-Duk Min, Emiri Miura-Yura, Anupreet Kour, Megan A. Evans, María A. Zuriaga, Karen K. Hirschi, Jose J. Fuster, Eric M. Pietras, Kenneth Walsh
Abstract
Aging is a major risk factor for cardiovascular disease. Although the impact of aging has been extensively studied, little is known regarding the aging processes in cells of the heart. Here we analyzed the transcriptomes of hearts of 12-week-old and 18-month-old mice by single-nucleus RNA-sequencing. Among all cell types, aged fibroblasts showed most significant differential gene expression, increased RNA dynamics, and network entropy. Aged fibroblasts exhibited significantly changed expression patterns of inflammatory, extracellular matrix organization angiogenesis, and osteogenic genes. Functional analyses indicated deterioration of paracrine signatures between fibroblasts and endothelial cells in old hearts. Aged heart-derived fibroblasts had impaired endothelial cell angiogenesis and autophagy and augmented proinflammatory response. In particular, expression of Serpine1 and Serpine2 were significantly increased and secreted by old fibroblasts to exert antiangiogenic effects on endothelial cells, an effect that could be significantly prevented by using neutralizing antibodies. Moreover, we found an enlarged subpopulation of aged fibroblasts expressing osteoblast genes in the epicardial layer associated with increased calcification. Taken together this study provides system-wide insights and identifies molecular changes of aging cardiac fibroblasts, which may contribute to declined heart function.
Authors
Ramon Vidal, Julian Uwe Gabriel Wagner, Caroline Braeuning, Cornelius Fischer, Ralph Patrick, Lukas Tombor, Marion Muhly-Reinholz, David John, Magdalena Kliem, Thomas Conrad, Nuno Guimarães-Camboa, Richard Harvey, Stefanie Dimmeler, Sascha Sauer
Abstract
With increased life expectancy worldwide, there is an urgent need for improving preventive measures that delay the development of age-related degenerative diseases. Here, we report evidence from mouse and human studies that this goal can be achieved by maintaining optimal hydration throughout life. We demonstrate that restricting the amount of drinking water shortens mouse lifespan with no major warning signs up to 14 months of life, followed by sharp deterioration. Mechanistically, water restriction yields stable metabolism remodeling toward metabolic water production with greater food intake and energy expenditure, an elevation of markers of inflammation and coagulation, accelerated decline of neuromuscular coordination, renal glomerular injury, and the development of cardiac fibrosis. In humans, analysis of data from the Atherosclerosis Risk in Communities (ARIC) study revealed that hydration level, assessed at middle age by serum sodium concentration, is associated with markers of coagulation and inflammation and predicts the development of many age-related degenerative diseases 24 years later. The analysis estimates that improving hydration throughout life may greatly decrease the prevalence of degenerative diseases, with the most profound effect on dementia, heart failure (HF), and chronic lung disease (CLD), translating to the development of these diseases in 3 million fewer people in the United States alone.
Authors
Michele D. Allen, Danielle A. Springer, Maurice B. Burg, Manfred Boehm, Natalia I. Dmitrieva
Abstract
Abnormalities in purine availability or purinergic receptor density are commonly seen in patients with lower urinary tract symptoms (LUTS), but the underlying mechanisms relating altered receptor function to LUTS are unknown. Here we provide extensive evidence for the reciprocal interplay of multiple receptors responding to ATP, ADP (adenosine diphosphate), and adenosine, agonists that regulate bladder function significantly. ADP stimulated P2Y12 receptors, causing bladder smooth muscle (BSM) contraction, whereas adenosine signaling through potentially newly defined A2b receptors, actively inhibited BSM purinergic contractility. The modulation of adenylyl cyclase-cAMP signaling via A2b and P2Y12 interaction actively regulated bladder contractility by modulating intracellular calcium levels. KO mice lacking the receptors display diametrically opposed bladder phenotypes, with P2Y12-KO mice exhibiting an underactive bladder (UAB) phenotype with increased bladder capacity and reduced voiding frequency, whereas A2b-KO mice have an overactive bladder (OAB), with decreased capacity and increased voiding frequency. The opposing phenotypes in P2Y12-KO and A2b-KO mice not only resulted from dysregulated BSM contractility, but also from abnormal BSM cell growth. Finally, we demonstrate that i.p. administration of drugs targeting P2Y12 or A2b receptor rescues these abnormal phenotypes in both KO mice. These findings strongly indicate that P2Y12 and A2b receptors are attractive therapeutic targets for human patients with LUTS.
Authors
Yuan Hao, Lu Wang, Huan Chen, Warren G. Hill, Simon C. Robson, Mark L. Zeidel, Weiqun Yu
Abstract
Calorie restriction (CR) improved healthspan in two longitudinal studies in nonhuman primates (NHPs), yet only the University of Wisconsin (UW) study demonstrated an increase in survival in CR monkeys relative to controls; the National Institute on Aging (NIA) study did not. Here, analysis of left ventricle samples showed that CR did not reduce cardiac fibrosis relative to controls. However, there was a 5.9-fold increase of total fibrosis in UW hearts, compared to NIA. Diet composition was a prominent difference between the studies; therefore, we used the NHP diets to characterize diet-associated molecular and functional changes in the hearts of mice. Consistent with the findings from the NHP samples, mice fed UW or a modified NIA diet with increased sucrose and fat developed greater cardiac fibrosis compared to the NIA diet, and transcriptomics analysis revealed diet-induced activation of myocardial oxidative phosphorylation and cardiac muscle contraction pathways.
Authors
Niranjana Natarajan, Ana Vujic, Jishnu Das, Annie C. Wang, Krystal K. Phu, Spencer H. Kiehm, Elisabeth M. Ricci-Blair, Anthony Y. Zhu, Kelli L. Vaughan, Ricki J. Colman, Julie A. Mattison, Richard T. Lee
Abstract
Background: There is growing evidence to suggest that the brain is an important target for insulin action, and that states of insulin resistance may extend to the CNS with detrimental effects on cognitive functioning. Although the effect of systemic insulin resistance on peripheral organs is well-studied, the degree to which insulin impacts brain function in vivo remains unclear. Methods: This randomized, single-blinded, 2-way-crossover, sham-controlled, pilot study determined the effects of hyperinsulinemia on fMRI brain activation during a 2-back working memory task in 9 healthy older adults (aged 57-79 years). Each participant underwent two clamp procedures (an insulin infusion and a saline placebo infusion, with normoglycemia maintained during both conditions), to examine the effects of hyperinsulinemia on task performance and associated blood-oxygen-level dependent (BOLD) signal using fMRI. Results: Hyperinsulinemia (compared to saline control) was associated with an increase in both the spatial extent and relative strength of task-related BOLD signal during the 2-back task. Further, the degree of increased task-related activation in select brain regions correlated with greater systemic insulin sensitivity, as well as decreased reaction times and performance accuracy between experimental conditions. Conclusion: Together, these findings provide evidence of insulin action in the CNS among older adults during periods of sustained cognitive demand, with the greatest effects noted for individuals with highest systemic insulin sensitivity. Funding: This work was funded by the National Institutes of Health (5R21AG051958, 2016).
Authors
Victoria J. Williams, Bianca A. Trombetta, Rabab Z. Jafri, Aaron M. Koenig, Chase D. Wennick, Becky C. Carlyle, Laya Ekhlaspour, Rexford S. Ahima, Steven J. Russell, David H. Salat, Steven E. Arnold
Abstract
Cellular senescence is a tumor suppressive mechanism that can paradoxically contribute to aging pathologies. Despite evidence of immune clearance in mouse models, it is not known how senescent cells (SnCs) persist and accumulate with age or in tumors in individuals. Here, we identify cooperative mechanisms that orchestrate the immunoevasion and persistence of normal and cancer human SnCs through extracellular targeting of natural killer receptor signaling. Damaged SnCs avoid immune recognition through MMPs-dependent shedding of NKG2D-ligands reinforced via paracrine suppression of NKG2D receptor-mediated immunosurveillance. These coordinated immunoediting processes are evident in residual, drug-resistant tumors from cohorts of >700 prostate and breast cancer patients treated with senescence-inducing genotoxic chemotherapies. Unlike in mice, these reversible senescence-subversion mechanisms are independent of p53/p16 and exacerbated in oncogenic RAS-induced senescence. Critically, the p16INK4A tumor suppressor can disengage the senescence growth arrest from the damage-associated immune senescence program, which is manifest in benign nevi lesions where indolent SnCs accumulate over time and preserve a non-pro-inflammatory tissue microenvironment maintaining NKG2D-mediated immunosurveillance. Our study shows how subpopulations of SnCs elude immunosurveillance, and reveals secretome-targeted therapeutic strategies to selectively eliminate –and restore the clearance of– the detrimental SnCs that actively persist after chemotherapy and accumulate at sites of aging pathologies.
Authors
Denise P. Muñoz, Steve M. Yannone, Anneleen Daemen, Yu Sun, Funda Vakar-Lopez, Misako Kawahara, Adam M. Freund, Francis Rodier, Jennifer D. Wu, Pierre-Yves Desprez, David H. Raulet, Peter S. Nelson, Laura J. van 't Veer, Judith Campisi, Jean-Philippe Coppé
Abstract
The bone marrow microenvironment (BMME) contributes to the regulation of hematopoietic stem cell (HSC) function, though its role in age-associated lineage skewing is poorly understood. Here we show that dysfunction of aged marrow macrophages (Mφs) directs HSC platelet-bias. Mφs from the marrow of aged mice and humans exhibited an activated phenotype, with increased expression of inflammatory signals. Aged marrow Mφs also displayed decreased phagocytic function. Senescent neutrophils, typically cleared by marrow Mφs, were markedly increased in aged mice, consistent with functional defects in Mφ phagocytosis and efferocytosis. In aged mice, Interleukin 1B (IL1B) was elevated in the bone marrow and caspase 1 activity, which can process pro-IL1B, was increased in marrow Mφs and neutrophils. Mechanistically, IL1B signaling was necessary and sufficient to induce a platelet bias in HSCs. In young mice, depletion of phagocytic cell populations or loss of the efferocytic receptor Axl expanded platelet-biased HSCs. Our data support a model wherein increased inflammatory signals and decreased phagocytic function of aged marrow Mφs induce the acquisition of platelet bias in aged HSCs. This work highlights the instructive role of Mφs and IL1B in the age-associated lineage-skewing of HSCs, and reveals the therapeutic potential of their manipulation as antigeronic targets.
Authors
Benjamin J. Frisch, Corey M. Hoffman, Sarah E. Latchney, Mark W. LaMere, Jason Myers, John Ashton, Allison J. Li, Jerry Saunders, James Palis, Archibald S. Perkins, Amanda McCabe, Julianne N. Smith, Kathleen E. McGrath, Fatima Rivera-Escalera, Andrew McDavid, Jane L. Liesveld, Vyacheslav A. Korshunov, Michael R. Elliott, Katherine C. MacNamara, Michael W. Becker, Laura M. Calvi
Abstract
Senescent cells (SnCs) are increasingly recognized as central effector cells in age-related pathologies. Extracellular vesicles (EVs) are potential cellular communication tools through which SnCs exert central effector functions in the local tissue environment. To test this hypothesis in a medical indication that could be validated clinically, we evaluated EV production from SnCs enriched from chondrocytes isolated from human arthritic cartilage. EV production increased in a dose-responsive manner as the concentration of SnCs increased. The EVs were capable of transferring senescence to nonsenescent chondrocytes and inhibited cartilage formation by non-SnCs. microRNA (miR) profiles of EVs isolated from human arthritic synovial fluid did not fully overlap with the senescent chondrocyte EV profiles. The effect of SnC clearance was tested in a murine model of posttraumatic osteoarthritis. miR and protein profiles changed after senolytic treatment but varied depending on age. In young animals, senolytic treatment altered expression of miR-34a, -30c, -125a, -24, -92a, -150, and -186, and this expression correlated with cartilage production. The primary changes in EV contents in aged mice after senolytic treatment, which only reduced pain and degeneration, were immune related. In sum, EV contents found in synovial fluid may serve as a diagnostic for arthritic disease and indicator for therapeutic efficacy of senolytic treatment.
Authors
Ok Hee Jeon, David R. Wilson, Cristina C. Clement, Sona Rathod, Christopher Cherry, Bonita Powell, Zhenghong Lee, Ahmad M. Khalil, Jordan J. Green, Judith Campisi, Laura Santambrogio, Kenneth W. Witwer, Jennifer H. Elisseeff
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