In mammals, maintenance of energy and nutrient homeostasis during food deprivation is accomplished through an increase in mitochondrial fatty acid oxidation in peripheral tissues. An important component that drives this cellular oxidative process is the transcriptional coactivator PGC-1alpha. Here, we show that fasting induced PGC-1alpha deacetylation in skeletal muscle and that SIRT1 deacetylation of PGC-1alpha is required for activation of mitochondrial fatty acid oxidation genes. Moreover, expression of the acetyltransferase, GCN5, or the SIRT1 inhibitor, nicotinamide, induces PGC-1alpha acetylation and decreases expression of PGC-1alpha target genes in myotubes. Consistent with a switch from glucose to fatty acid oxidation that occurs in nutrient deprivation states, SIRT1 is required for induction and maintenance of fatty acid oxidation in response to low glucose concentrations. Thus, we have identified SIRT1 as a functional regulator of PGC-1alpha that induces a metabolic gene transcription program of mitochondrial fatty acid oxidation. These results have implications for understanding selective nutrient adaptation and how it might impact lifespan or metabolic diseases such as obesity and diabetes.

Hormonal and nutrient regulation of hepatic gluconeogenesis mainly occurs through modulation of the transcriptional coactivator PGC-1alpha. The identity of endogenous proteins and their enzymatic activities that regulate the functions and form part of PGC-1alpha complex are unknown. Here, we show that PGC-1alpha is in a multiprotein complex containing the acetyltransferase GCN5. PGC-1alpha is directly acetylated by GCN5 resulting in a transcriptionally inactive protein that relocalizes from promoter regions to nuclear foci. Adenoviral-mediated expression of GCN5 in cultured hepatocytes and in mouse liver largely represses activation of gluconeogenic enzymes and decreases hepatic glucose production. Thus, we have identified the endogenous PGC-1alpha protein complex and provided the molecular mechanism by which PGC-1alpha acetylation by GCN5 turns off the transcriptional and biological function of this metabolic coactivator. GCN5 might be a pharmacological target to regulate the activity of PGC-1alpha, providing a potential treatment for metabolic disorders in which hepatic glucose output is dysregulated.

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The reverse transcriptase (RT) of human immunodeficiency virus type-1 (HIV-1) converts the single-stranded (ϩ) viral RNA genome into a double-stranded proviral DNA prior to its integration into the host genomic DNA. The RT is a multifunctional enzyme with three recognized enzymatic activities of RNA-dependent DNA polymerase (RDDP), DNA-dependent DNA polymerase (DDDP), and ribonuclease H activities. HIV-1 protease is an aspartic protease required for the proteolytic processing of the large Gag and Gag-Pol viral polyprotein precursors into the mature virion structural proteins, as well as the virion enzymes. These two enzymes, HIV-1 RT and protease, have key roles in HIV replication and inhibition of these enzymes along with HIV-1 integrase has been a major target of acquired immunodeficiency syndrome (AIDS) therapy. 1)In addition to the well-known nucleoside RT inhibitors (NRTIs), zidovudine (AZT), didanosine (ddC), zalcitabine (ddT), stavudine (d4T), lamivudine (3TC), and abacavir (ABC), non-nucleoside RT inhibitors (NNRTIs), such as nevirapine, delavirdine, and efavirenz have been formally approved to treat HIV infection. On the other hand, saquinavir, ritonavir, and indinavir are the three main HIV protease inhibitors available today. A number of inhibitors interacting with RT have been isolated from plants (baicalin, avarol, avarone, and psychotrine) and marine resources (illimaquinone, peyssonol, and KM043). [2][3][4] In the case of HIV-1 protease, natural products, such as mangostin, ursolic, and maslinic acid, have been reported to show inhibitory activity against this enzyme. 5) We previously reported the results of screening inhibitory activities of 47 types of Korean seaweed on HIV-1 RT and found that the EtOAc fraction of Ecklonia cava strongly inhibited the RDDP activity of this enzyme. 6) In this study, we report the isolation of four phlorotannin compounds containing dibenzo [1,4]dioxin elements in common from E. cava and the kinetic study of HIV-1 RT by 8,8Ј-bieckol (2) that showed the most potent inhibitory effect on this enzyme. MATERIALS AND METHODS MaterialsThe thalli of E. cava KJELLMAN were collected from the coasts of Korea including Sungsanpo, Wando, and Namhaedo from January 1999 to June 2000. After cleaning the surface of the thalli with water to remove visible epiphytes and dirt, samples were dried at 60°C for 12 h in an oven and then ground in a coffee grinder. This seaweed was identified by Prof. S. M. Boo of the Department of Biology, Chungnam National University, Korea, and Prof. Y. S. Oh of the Department of Aquaculture, Gyeongsang National University, Korea. A voucher specimen (SSI-06) was deposited in the Herbarium of the Department of Biological Sciences, Sungkyunkwan University.Extraction and Isolation The dried thalli (1 kg) of E. cava were extracted three times with 100% MeOH and evaporated in vacuo. The MeOH extract (180 g) was dissolved in water and partitioned with n-hexane. After the H 2 O layer was further partitioned with ethyl acetate, the organic solvent fraction was c...

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CD13/aminopeptidase N (APN) is a membrane-bound, zinc-dependent metalloproteinase that plays a key role in tumor invasion and angiogenesis. Here, we show that curcumin, a phenolic natural product, binds to APN and irreversibly inhibits its activity. The direct interaction between curcumin with APN was confirmed both in vitro and in vivo by surface plasmon resonance analysis and an APN-specific antibody competition assay, respectively. Moreover, curcumin and other known APN inhibitors strongly inhibited APN-positive tumor cell invasion and basic fibroblast growth factor-induced angiogenesis. However, curcumin did not inhibit the invasion of APN-negative tumor cells, suggesting that the antiinvasive activity of curcumin against tumor cells is attributable to the inhibition of APN. Taken together, our study revealed that curcumin is a novel irreversible inhibitor of APN that binds to curcumin resulting in inhibition of angiogenesis.

The bioassay-directed isolation of Terminalia chebula fruits afforded four human immunodeficiency virus type 1 (HIV-1) integrase inhibitors, gallic acid ( 1) and three galloyl glucoses ( 2 - 4). In addition, four flavonol glycoside gallates ( 5 - 8) from Euphorbia pekinensis containing the galloyl moiety also showed the inhibitory activity at a level comparable to those of 2 - 4. By comparison with the activities of the compounds not bearing this moiety, it is proposed that the galloyl moiety plays a major role for inhibition against the 3'-processing of HIV-1 integrase of these compounds.

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