New data from diet restricted Lepob (ob/ob) mutant C57BL/6J mice-our DR-OB model-challenge the paradigm that benefits of diet restriction (DR) require insulin sensitivity, low insulin, and low adiposity. DR-OB mice have severe insulin resistance, high insulin levels, as well as high adiposity, but live as long as diet restricted controls (DR +/?) that are insulin sensitive with low insulin and low adiposity. This model will be used to test three categories of mechanisms proposed to produce the beneficial effects of DR: 1) the insulin, IGF-1, mTOR, and nutrient signaling transduction pathways, 2) fuel utilization pathways, 3) adipose tissue function. Five groups of mice will be compared at 6, 12, and 22 months of age: DR-OB, partially restricted ob/ob (partial DR-OB), ad lib fed ob/ob (AL-OB), diet restricted and ad lib fed genetic controls (DR +/?) and (AL +/?). Signal transduction, fuel utilization, and adipose tissue markers that differ between DR-OB and DR +/? will identify candidate mechanisms that correlate with low insulin and low adiposity but do not increase lifespan. Markers that are similar in DR-OB and DR +/?, and that correlate with lifespan in DR-OB, partial DR-OB and AL-OB, will specify candidate mechanisms by which DR may increase lifespan, which will be further tested later. The current project is unique in that it distinguishes features of DR-associated hypoinsulinemia and leanness that extend lifespan from features that do not. This work will specify the set of candidate mechanisms comprising those critical for DR-mediated, extended lifespan by testing the following hypotheses:
Aim 1. That, in DR-OB mice, critical branches of the mTOR, AMP-kinase, and insulin/IGF-1 signal transduction pathways shift from patterns typical of insulin resistance, hyperinsulinemia and obesity to patterns typical of DR and extended longevity. Key intermediates of these pathways will be tested in liver and gastrocnemius muscle, using western blots to compare protein pool and site-specific phosphorylation levels.
Aim 2. That, in DR-OB mice, fuel utilization pathways shift-at or before a critical point necessary to extend lifespan-from patterns typical of metabolic syndrome to patterns typical of DR that reduce mitochondrial free radical production. In vivo tests to identify this point will include short-term fasting glucose and insulin levels, glucose tolerance, insulin sensitivity, gluconeogenesis, glycogenolysis, beta-oxidation, glucose utilization, lipid utilization, and 24-hr respiratory exchange ratio. Collaborators will test free radical damage to proteins of the electron transport chains for liver and muscle mitochondria.
Aim 3. That, in DR-OB mice, critical aspects of adipose tissue reflect the lean state of DR +/? mice rather than the obese state of AL-OB mice. The following will be determined: body composition and subcutaneous/visceral fat tissue distribution (using computerized tomography imaging);circulating adipokines (adiponectin, resistin, IL-6, and TNF-alpha);circulating and tissue levels of free fatty acids, triglyceride and cholesterol;and fat cell size distribution in mesenteric and subcutaneous fat tissue.

Public Health Relevance

In the US, the continuing increase in childhood and adult obesity is expected to increase such ailments as type 2 diabetes, hypertension, and metabolic syndrome as the population ages. This study will suggest treatments to retard deleterious changes with age, especially those related to high insulin levels and adiposity. Effects of DR that extend life spans in both normal control and ob/ob mice in this study are likely targets for interventions to retard aging and extend healthy lifespan in human beings.

National Institute of Health (NIH)
National Institute on Aging (NIA)
Research Project (R01)
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Cellular Mechanisms in Aging and Development Study Section (CMAD)
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Finkelstein, David B
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Jackson Laboratory
Bar Harbor
United States
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Jiang, Zixuan; Harrison, David E; Parsons, Makayla E et al. (2016) Heritability of in vitro phenotypes exhibited by murine adipose-derived stromal cells. Mamm Genome 27:460-8
Thompson, Airlia C S; Bruss, Matthew D; Price, John C et al. (2016) Reduced in vivo hepatic proteome replacement rates but not cell proliferation rates predict maximum lifespan extension in mice. Aging Cell 15:118-27
Reifsnyder, Peter C; Doty, Rosalinda; Harrison, David E (2014) Rapamycin ameliorates nephropathy despite elevating hyperglycemia in a polygenic mouse model of type 2 diabetes, NONcNZO10/LtJ. PLoS One 9:e114324
Zhou, Yang; Harrison, David E; Love-Myers, Kimberly et al. (2014) Genetic analysis of tissue glutathione concentrations and redox balance. Free Radic Biol Med 71:157-64
Harrison, David E; Astle, Clinton M; Niazi, M Khalid Khan et al. (2014) Genetically diverse mice are novel and valuable models of age-associated susceptibility to Mycobacterium tuberculosis. Immun Ageing 11:24
Pazdro, Robert; Harrison, David E (2013) Murine adipose tissue-derived stromal cell apoptosis and susceptibility to oxidative stress in vitro are regulated by genetic background. PLoS One 8:e61235
Yuan, Rong; Flurkey, Kevin; Meng, Qingying et al. (2013) Genetic regulation of life span, metabolism, and body weight in Pohn, a new wild-derived mouse strain. J Gerontol A Biol Sci Med Sci 68:27-35
Ye, Lei; Zhang, Eric Yang; Xiong, Qiang et al. (2012) Aging Kit mutant mice develop cardiomyopathy. PLoS One 7:e33407
Berndt, Annerose; Cario, Clinton L; Silva, Kathleen A et al. (2011) Identification of fat4 and tsc22d1 as novel candidate genes for spontaneous pulmonary adenomas. Cancer Res 71:5779-91
Flurkey, Kevin; Astle, Clinton M; Harrison, David E (2010) Life extension by diet restriction and N-acetyl-L-cysteine in genetically heterogeneous mice. J Gerontol A Biol Sci Med Sci 65:1275-84