For humans, frailty constitutes of one of the most prominent and consistent features of aging and represents the summation of the effects of muscle atrophy and weakness. For the elderly, physical frailty contributes to impaired mobility, a high risk of falling, an increased incidence of muscle injury, and a decreased quality of life. Despite considerable effort over the past decade, little progress has been made in lessening the magnitude of the problem. During our first five years of support, research on a dozen or more varieties of knockout and transgenic mice, this Program Project identified the Sodl^'mouse as a highly promising model to test the working hypothesis of Project 1 that age-related skeletal muscle atrophy results from a decrease in the total number of motor units caused by increased superoxide-mediated oxidative stress in neurons and muscles, such that: (i) oxidative stress in neurons initiates a loss of motor neurons, impairs axonal sprouting from surviving motor neurons, and inhibits nerve regeneration;and (ii) oxidative stress in muscles fibers inhibits reinnervation and contributes to decreased contractility of innervated muscle fibers. The working hypothesis will be tested through experiments on SodfA and Sod1+/+ mice, transgenic Socf7v" mice with Sod1 expression rescued only in nerves (Soc/fA(N+) mice) or muscles (Soc(7~/~(M+) mice), and tissue-specific knockout mice that lack CuZnSOD activity only in nerves (Sod1A3,4N)N) or muscles (Sod 1 A3,4^). These models allow us to test hypotheses regarding the contribution of systemic oxidative stress, as well as tissue-specific oxidative stress on the structure and function of motor nerves, muscles, motor units and muscle fibers. Genetically modified mice will be studied at 6-8 months and 18-20 months, whereas Sod1+/+ mice will be studied at 6-8, 18-20, and 28-30 months. Unique aspects of the proposed studies are the determination of motor unit properties and contractility of permeabilized single fibers from Soc/f/"mice,, null mice with tissue-specific rescue, and tissue-specific Sodl knockout mice. Furthermore, studies of the relative timing of changes in nerves and muscles that have not been undertaken previously in the same animals will be particularly illuminating for establishing cause-effect relationships of age-related changes in the neuromuscular system. Along with Projects 2 and 3, studies utilizing the very powerful mouse models listed above will determine the mechanistic role of superoxide-induced oxidative stress in muscles and nerves in age-related skeletal muscle atrophy. The Public Health significance is the necessity to understand the mechanisms underlying age-associated skeletal muscle atrophy and weakness to provide the basis for health professionals to design and implement scientifically based strategies to ensure 'successful aging'by reducing and perhaps even eliminating physical frailty in the elderly population.

Public Health Relevance

It is known that human exposure to air pollution particulates is associated with increased hospitalization due to lung infections. However, the potential effects of inhaled ENPs on innate immune function has received surprisingly little attention. This research will determine the doses and physicochemical types of ENPs that affect innate immune function in macrophages, with a focus on developing dose-response data needed for risk analysis..

Agency
National Institute of Health (NIH)
Institute
National Institute on Aging (NIA)
Type
Research Program Projects (P01)
Project #
5P01AG020591-10
Application #
8375558
Study Section
Special Emphasis Panel (ZAG1-ZIJ-5)
Project Start
Project End
2014-04-30
Budget Start
2012-05-01
Budget End
2013-04-30
Support Year
10
Fiscal Year
2012
Total Cost
$323,958
Indirect Cost
$110,829
Name
University of Michigan Ann Arbor
Department
Type
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Sakellariou, Giorgos K; Pearson, Timothy; Lightfoot, Adam P et al. (2016) Mitochondrial ROS regulate oxidative damage and mitophagy but not age-related muscle fiber atrophy. Sci Rep 6:33944
Sloboda, Darcée D; Brooks, Susan V (2016) Treatment with selectin blocking antibodies after lengthening contractions of mouse muscle blunts neutrophil accumulation but does not reduce damage. Physiol Rep 4:
Sakellariou, Giorgos K; Pearson, Timothy; Lightfoot, Adam P et al. (2016) Long-term administration of the mitochondria-targeted antioxidant mitoquinone mesylate fails to attenuate age-related oxidative damage or rescue the loss of muscle mass and function associated with aging of skeletal muscle. FASEB J 30:3771-3785
Vasilaki, Aphrodite; Pollock, Natalie; Giakoumaki, Ifigeneia et al. (2016) The effect of lengthening contractions on neuromuscular junction structure in adult and old mice. Age (Dordr) 38:259-272
Zhang, Yiqiang; Unnikrishnan, Archana; Deepa, Sathyaseelan S et al. (2016) A new role for oxidative stress in aging: The accelerated aging phenotype in Sod1(-/)(-) mice is correlated to increased cellular senescence. Redox Biol 11:30-37
Zhang, Yiqiang; Liu, Yuhong; Walsh, Michael et al. (2016) Liver specific expression of Cu/ZnSOD extends the lifespan of Sod1 null mice. Mech Ageing Dev 154:1-8
Claflin, Dennis R; Jackson, Malcolm J; Brooks, Susan V (2015) Age affects the contraction-induced mitochondrial redox response in skeletal muscle. Front Physiol 6:21
Walsh, Michael E; Bhattacharya, Arunabh; Sataranatarajan, Kavithalakshmi et al. (2015) The histone deacetylase inhibitor butyrate improves metabolism and reduces muscle atrophy during aging. Aging Cell 14:957-70
Roche, Stuart M; Gumucio, Jonathan P; Brooks, Susan V et al. (2015) Measurement of Maximum Isometric Force Generated by Permeabilized Skeletal Muscle Fibers. J Vis Exp :e52695
Ivannikov, Maxim V; Van Remmen, Holly (2015) Sod1 gene ablation in adult mice leads to physiological changes at the neuromuscular junction similar to changes that occur in old wild-type mice. Free Radic Biol Med 84:254-62

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