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1.  SREBP-1c/MicroRNA 33b Genomic Loci Control Adipocyte Differentiation 
Molecular and Cellular Biology  2016;36(7):1180-1193.
White adipose tissue (WAT) is essential for maintaining metabolic function, especially during obesity. The intronic microRNAs miR-33a and miR-33b, located within the genes encoding sterol regulatory element-binding protein 2 (SREBP-2) and SREBP-1, respectively, are transcribed in concert with their host genes and function alongside them to regulate cholesterol, fatty acid, and glucose metabolism. SREBP-1 is highly expressed in mature WAT and plays a critical role in promoting in vitro adipocyte differentiation. It is unknown whether miR-33b is induced during or involved in adipogenesis. This is in part due to loss of miR-33b in rodents, precluding in vivo assessment of the impact of miR-33b using standard mouse models. This work demonstrates that miR-33b is highly induced upon differentiation of human preadipocytes, along with SREBP-1. We further report that miR-33b is an important regulator of adipogenesis, as inhibition of miR-33b enhanced lipid droplet accumulation. Conversely, overexpression of miR-33b impaired preadipocyte proliferation and reduced lipid droplet formation and the induction of peroxisome proliferator-activated receptor γ (PPARγ) target genes during differentiation. These effects may be mediated by targeting of HMGA2, cyclin-dependent kinase 6 (CDK6), and other predicted miR-33b targets. Together, these findings demonstrate a novel role of miR-33b in the regulation of adipocyte differentiation, with important implications for the development of obesity and metabolic disease.
doi:10.1128/MCB.00745-15
PMCID: PMC4800797  PMID: 26830228
2.  Resveratrol improves health and survival of mice on a high-calorie diet 
Nature  2006;444(7117):337-342.
Resveratrol (3,5,4′-trihydroxystilbene) extends the lifespan of diverse species including Saccharomyces cerevisiae, Caenorhabditis elegans and Drosophila melanogaster. In these organisms, lifespan extension is dependent on Sir2, a conserved deacetylase proposed to underlie the beneficial effects of caloric restriction. Here we show that resveratrol shifts the physiology of middle-aged mice on a high-calorie diet towards that of mice on a standard diet and significantly increases their survival. Resveratrol produces changes associated with longer lifespan, including increased insulin sensitivity, reduced insulin-like growth factor-1 (IGF-I) levels, increased AMP-activated protein kinase (AMPK) and peroxisome proliferator-activated receptor- γ coactivator 1α (PGC-1α) activity, increased mitochondrial number, and improved motor function. Parametric analysis of gene set enrichment revealed that resveratrol opposed the effects of the high-calorie diet in 144 out of 153 significantly altered pathways. These data show that improving general health in mammals using small molecules is an attainable goal, and point to new approaches for treating obesity-related disorders and diseases of ageing.
doi:10.1038/nature05354
PMCID: PMC4990206  PMID: 17086191
3.  Novel role of miR-33 in regulating of mitochondrial function 
Circulation research  2015;117(3):225-228.
doi:10.1161/CIRCRESAHA.117.306949
PMCID: PMC4643669  PMID: 26185207
miR-33; ATP; mitochondrial function; cholesterol efflux
4.  Caloric restriction induces heat shock response and inhibits B16F10 cell tumorigenesis both in vitro and in vivo 
Aging (Albany NY)  2015;7(4):233-239.
Caloric restriction (CR) without malnutrition is one of the most consistent strategies for increasing mean and maximal lifespan and delaying the onset of age-associated diseases. Stress resistance is a common trait of many long-lived mutants and life-extending interventions, including CR. Indeed, better protection against heat shock and other genotoxic insults have helped explain the pro-survival properties of CR. In this study, both in vitro and in vivo responses to heat shock were investigated using two different models of CR. Murine B16F10 melanoma cells treated with serum from CR-fed rats showed lower proliferation, increased tolerance to heat shock and enhanced HSP-70 expression, compared to serum from ad libitum-fed animals. Similar effects were observed in B16F10 cells implanted subcutaneously in male C57BL/6 mice subjected to CR. Microarray analysis identified a number of genes and pathways whose expression profile were similar in both models. These results suggest that the use of an in vitro model could be a good alternative to study the mechanisms by which CR exerts its anti-tumorigenic effects.
PMCID: PMC4429088  PMID: 25948793
caloric restriction; heat shock; stress response; tumorigenesis; aging
5.  Role of Sirtuins in Lifespan Regulation is Linked to Methylation of Nicotinamide 
Nature chemical biology  2013;9(11):693-700.
Sirtuins, a family of histone deacetylases, have a fiercely debated role in regulating lifespan. Contrasting recent observations, we here find that overexpression of sir-2.1, the orthologue of mammalian SirT1, does extend C. elegans lifespan. Sirtuins mandatorily convert NAD+ into nicotinamide (NAM). We here find that NAM and its metabolite, 1-methylnicotinamide (MNA), extend C. elegans lifespan, even in the absence of sir-2.1. We identify anmt-1 to encode a C. elegans orthologue of nicotinamide-N-methyltransferase (NNMT), the enzyme that methylates NAM to generate MNA. Disruption and overexpression of anmt-1 have opposing effects on lifespan independent of sirtuins, with loss of anmt-1 fully inhibiting sir-2.1-mediated lifespan extension. MNA serves as a substrate for a newly identified aldehyde oxidase, GAD-3, to generate hydrogen peroxide acting as a mitohormetic ROS signal to promote C. elegans longevity. Taken together, sirtuin-mediated lifespan extension depends on methylation of NAM, providing an unexpected mechanistic role for sirtuins beyond histone deacetylation.
doi:10.1038/nchembio.1352
PMCID: PMC4076143  PMID: 24077178
6.  Declining NAD+ Induces a Pseudohypoxic State Disrupting Nuclear-Mitochondrial Communication during Aging 
Cell  2013;155(7):1624-1638.
SUMMARY
Ever since eukaryotes subsumed the bacterial ancestor of mitochondria, the nuclear and mitochondrial genomes have had to closely coordinate their activities, as each encode different subunits of the oxidative phosphorylation (OXPHOS) system. Mitochondrial dysfunction is a hallmark of aging, but its causes are debated. We show that, during aging, there is a specific loss of mitochondrial, but not nuclear, encoded OXPHOS subunits. We trace the cause to an alternate PGC-1α/β-independent pathway of nuclear-mitochondrial communication that is induced by a decline in nuclear NAD+ and the accumulation of HIF-1α under normoxic conditions, with parallels to Warburg reprogramming. Deleting SIRT1 accelerates this process, whereas raising NAD+ levels in old mice restores mitochondrial function to that of a young mouse in a SIRT1-dependent manner. Thus, a pseudohypoxic state that disrupts PGC-1α/β-independent nuclear-mitochondrial communication contributes to the decline in mitochondrial function with age, a process that is apparently reversible.
doi:10.1016/j.cell.2013.11.037
PMCID: PMC4076149  PMID: 24360282
7.  Flavonoid Apigenin Is an Inhibitor of the NAD+ase CD38 
Diabetes  2013;62(4):1084-1093.
Metabolic syndrome is a growing health problem worldwide. It is therefore imperative to develop new strategies to treat this pathology. In the past years, the manipulation of NAD+ metabolism has emerged as a plausible strategy to ameliorate metabolic syndrome. In particular, an increase in cellular NAD+ levels has beneficial effects, likely because of the activation of sirtuins. Previously, we reported that CD38 is the primary NAD+ase in mammals. Moreover, CD38 knockout mice have higher NAD+ levels and are protected against obesity and metabolic syndrome. Here, we show that CD38 regulates global protein acetylation through changes in NAD+ levels and sirtuin activity. In addition, we characterize two CD38 inhibitors: quercetin and apigenin. We show that pharmacological inhibition of CD38 results in higher intracellular NAD+ levels and that treatment of cell cultures with apigenin decreases global acetylation as well as the acetylation of p53 and RelA-p65. Finally, apigenin administration to obese mice increases NAD+ levels, decreases global protein acetylation, and improves several aspects of glucose and lipid homeostasis. Our results show that CD38 is a novel pharmacological target to treat metabolic diseases via NAD+-dependent pathways.
doi:10.2337/db12-1139
PMCID: PMC3609577  PMID: 23172919
8.  SIRT1 is required for AMPK activation and the beneficial effects of resveratrol on mitochondrial function 
Cell metabolism  2012;15(5):675-690.
SUMMARY
Resveratrol induces mitochondrial biogenesis and protects against metabolic decline but whether SIRT1 mediates these benefits is the subject of debate. To circumvent the developmental defects of germ-line SIRT1 knockouts, we have developed the first inducible system that permits whole-body deletion of SIRT1 in adult mice. Mice treated with a moderate dose of resveratrol showed increased mitochondrial biogenesis and function, AMPK activation and increased NAD+ levels in skeletal muscle, whereas SIRT1 knockouts displayed none of these benefits. A mouse overexpressing SIRT1 mimicked these effects. A high dose of resveratrol activated AMPK in a SIRT1-independent manner, demonstrating that resveratrol dosage is a critical factor. Importantly, at both doses of resveratrol no improvements in mitochondrial function were observed in animals lacking SIRT1. Together these data indicate that SIRT1 plays an essential role in the ability of moderate doses of resveratrol to stimulate AMPK and improve mitochondrial function both in vitro and in vivo.
doi:10.1016/j.cmet.2012.04.003
PMCID: PMC3545644  PMID: 22560220
10.  SRT1720 improves survival and healthspan of obese mice 
Scientific Reports  2011;1:70.
Sirt1 is an NAD+-dependent deacetylase that extends lifespan in lower organisms and improves metabolism and delays the onset of age-related diseases in mammals. Here we show that SRT1720, a synthetic compound that was identified for its ability to activate Sirt1 in vitro, extends both mean and maximum lifespan of adult mice fed a high-fat diet. This lifespan extension is accompanied by health benefits including reduced liver steatosis, increased insulin sensitivity, enhanced locomotor activity and normalization of gene expression profiles and markers of inflammation and apoptosis, all in the absence of any observable toxicity. Using a conditional SIRT1 knockout mouse and specific gene knockdowns we show SRT1720 affects mitochondrial respiration in a Sirt1- and PGC-1α-dependent manner. These findings indicate that SRT1720 has long-term benefits and demonstrate for the first time the feasibility of designing novel molecules that are safe and effective in promoting longevity and preventing multiple age-related diseases in mammals.
doi:10.1038/srep00070
PMCID: PMC3216557  PMID: 22355589
11.  Resveratrol delays age-related deterioration and mimics transcriptional aspects of dietary restriction without extending lifespan 
Cell metabolism  2008;8(2):157-168.
SUMMARY
A small molecule that safely mimics the ability of dietary restriction (DR) to delay age-related diseases in laboratory animals is greatly sought after. We and others have shown that resveratrol mimics effects of DR in lower organisms. In mice, we find that resveratrol induces gene expression patterns in multiple tissues that parallel those induced by DR and every-other-day feeding. Moreover, resveratrol-fed elderly mice show a marked reduction in signs of aging including reduced albuminuria, decreased inflammation and apoptosis in the vascular endothelium, increased aortic elasticity, greater motor coordination, reduced cataract formation, and preserved bone mineral density. However, mice fed a standard diet did not live longer when treated with resveratrol beginning at 12 months of age. Our findings indicate that resveratrol treatment has a range of beneficial effects in mice but does not increase the longevity of ad libitum-fed animals when started mid-life.
doi:10.1016/j.cmet.2008.06.011
PMCID: PMC2538685  PMID: 18599363

Results 1-11 (11)