Our long-term objectives in this proposal are to understand the physiological significance of a novel metabolic network comprised of systemic NAD biosynthesis as a driver and Sirt1 as a mediator in the regulation of metabolism and aging in mammals. We have focused particularly on the role of Sirt1 in pancreatic b cells and demonstrated that Sirt1 promotes glucose-stimulated insulin secretion in b cells by analyzing pancreatic beta cell-specific Sirt1-overexpressing (BESTO) transgenic mice. Interestingly, this Sirt1-mediated enhancement of b cell function is blunted in aged BESTO mice, partly due to an age-associated decline in NAD biosynthesis. Furthermore, our extensive expression profiling performed in islets from BESTO and calorically restricted mice suggests that CR enhances Sirt1 activity in b cells, possibly due to augmented NAD biosynthesis at a systemic level. These findings set the stage for a novel avenue of exciting research concerning the connection between NAD biosynthesis and Sirt1 in the regulation of metabolism and aging. We have previously demonstrated that nicotinamide phosphoribosyltransferase (Nampt), the rate-limiting enzyme in the NAD biosynthetic pathway from nicotinamide (a form of vitamin B3), plays an important role in the regulation of Sirt1 activity and glucose-stimulated insulin secretion in 2 cells. Together, these findings led us to the hypothesis that a dynamic alteration in Nampt-mediated NAD biosynthesis in aging and caloric restriction (CR) causes significant changes in Sirt1 activity at a systemic level and thereby induces age-associated and CR-responsive metabolic changes in multiple tissues, such as 2 cells and hepatocytes. To address this hypothesis, we propose the following specific aims: 1) To further establish the physiological significance of Nampt-mediated NAD biosynthesis in the regulation of Sirt1 activity in b cells and hepatocytes, NAD content, Sirt1 target gene expression, and physiological functions will be examined in primary islets and hepatocytes by manipulating Nampt and Sirt1 activities genetically and pharmacologically, 2) to investigate whether Nampt-mediated NAD biosynthesis and Sirt1 activity decline with age in b cells and hepatocytes, Nampt protein levels, Nampt and Sirt1 activities, and b cell and hepatic functions will be examined in the process of aging, and 3) to analyze whether CR augments Nampt-mediated NAD biosynthesis and Sirt1 activity in b cells and hepatocytes, the metabolic effects of CR on Nampt-mediated NAD biosynthesis and Sirt1 activity will be analyzed in various genetic and pharmacological models. These studies should provide new insight into the physiological significance and therapeutic applications of this novel metabolic network comprised of systemic NAD biosynthesis and Sirt1 for age-associated complications in humans. Public Health Relevance: The proposed study should provide the following important outcomes: First, this study will identify a previously unrecognized metabolic network that plays a critical role in the regulation of metabolism and aging in mammals. Second, this study will provide insights into the mechanisms for age-associated changes in tissue function, especially in pancreatic b cells and liver, and anti-aging effects of caloric restriction. Lastly, the anticipated outcome of this study will provide important insight into the development of new preventive/therapeutic interventions for important age-associated metabolic complications, such as impaired glucose tolerance and type 2 diabetes in humans.

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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Washington University
Other Basic Sciences
Schools of Medicine
Saint Louis
United States
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Stein, Liana Roberts; Wozniak, David F; Dearborn, Joshua T et al. (2014) Expression of Nampt in hippocampal and cortical excitatory neurons is critical for cognitive function. J Neurosci 34:5800-15
Imai, Shin-ichiro; Guarente, Leonard (2014) NAD+ and sirtuins in aging and disease. Trends Cell Biol 24:464-71
Stein, Liana R; Imai, Shin-ichiro (2014) Specific ablation of Nampt in adult neural stem cells recapitulates their functional defects during aging. EMBO J 33:1321-40
Satoh, Akiko; Imai, Shin-ichiro (2014) Systemic regulation of mammalian ageing and longevity by brain sirtuins. Nat Commun 5:4211
Imai, S; Yoshino, J (2013) The importance of NAMPT/NAD/SIRT1 in the systemic regulation of metabolism and ageing. Diabetes Obes Metab 15 Suppl 3:26-33
Satoh, Akiko; Brace, Cynthia S; Rensing, Nick et al. (2013) Sirt1 extends life span and delays aging in mice through the regulation of Nk2 homeobox 1 in the DMH and LH. Cell Metab 18:416-30
Satoh, Akiko; Stein, Liana; Imai, Shin (2011) The role of mammalian sirtuins in the regulation of metabolism, aging, and longevity. Handb Exp Pharmacol 206:125-62
Imai, Shin-ichiro (2011) Dissecting systemic control of metabolism and aging in the NAD World: the importance of SIRT1 and NAMPT-mediated NAD biosynthesis. FEBS Lett 585:1657-62
Grimm, Andrew A; Brace, Cynthia S; Wang, Ting et al. (2011) A nutrient-sensitive interaction between Sirt1 and HNF-1? regulates Crp expression. Aging Cell 10:305-17
Satoh, Akiko; Brace, Cynthia S; Ben-Josef, Gal et al. (2010) SIRT1 promotes the central adaptive response to diet restriction through activation of the dorsomedial and lateral nuclei of the hypothalamus. J Neurosci 30:10220-32

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