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Shi Feng, Laura Reuss, Yu Wang
Obesity is a global health problem characterized as an increase in the mass of adipose tissue. Adipogenesis is one of the key pathways that increases the mass of adipose tissue, by which preadipocytes mature into adipocytes through cell differentiation. Peroxisome proliferator-activated receptor γ (PPARγ), the chief regulator of adipogenesis, has been acutely investigated as a molecular target for natural products in the development of anti-obesity treatments. In this review, the regulation of PPARγ expression by natural products through inhibition of CCAAT/enhancer-binding protein β (C/EBPβ) and the farnesoid X receptor (FXR), increased expression of GATA-2 and GATA-3 and activation of the Wnt/β-catenin pathway were analyzed...
2016: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Supriya R Kulkarni, Carol J Soroka, Lee R Hagey, James L Boyer
Sirtuin1 (Sirt1, mammalian homolog of S. Cerevisiae enzyme Sir2) is a transcriptional and transactivational regulator of murine Fxr, which is the primary bile acid (BA) sensor, and critical regulator of BA metabolism in physiological and pathophysiological conditions. Previous studies have suggested compromised Sirt1 expression in rodent models of cholestatic liver injury. We hypothesized that Sirt1 could be potentially targeted to alleviate cholestatic liver injury. In cultured primary human hepatocytes, SIRT1 mRNA was downregulated after GCA treatment, potentially via induction of miR-34a, whereas TUDCA induced SIRT1 expression without affecting miR-34a expression...
September 17, 2016: Hepatology: Official Journal of the American Association for the Study of Liver Diseases
Denis Arsenijevic, Jean-François Cajot, Abdul G Dulloo, Jean-Pierre Montani
The role of mild kidney dysfunction in altering lipid metabolism and promoting inflammation was investigated in uninephrectomized rats (UniNX) compared to Sham-operated controls rats. The impact of UniNX was studied 1, 2, and 4 weeks after UniNX under mild food restriction at 90% of ad libitum intake to ensure the same caloric intake in both groups. UniNX resulted in the reduction of fat pad weight. UniNX was associated with increased circulating levels of beta-hydroxybutyrate and glycerol, as well as increased fat pad mRNA of hormone sensitive lipase and adipose triglyceride lipase, suggesting enhanced lipolysis...
2015: Frontiers in Physiology
Jingling Jin, Il-Hwa Hong, Kyle Lewis, Polina Iakova, Meghan Breaux, Yanjun Jiang, Emily Sullivan, Nicole Jawanmardi, Lubov Timchenko, Nikolai A Timchenko
UNLABELLED: Liver cancer is the fifth most common cancer. A highly invasive surgical resection of the liver tumor is the main approach used to eliminate the tumor. Mechanisms that terminate liver regeneration when the liver reaches the original size are not known. The aims of this work were to generate an animal model that fails to stop liver regeneration after surgical resections and elucidate mechanisms that are involved in termination of liver regeneration. Because epigenetic control of liver function has been previously implicated in the regulation of liver proliferation, we generated C/EBPα-S193A knockin mice, which have alterations in formation of complexes of C/EBP family proteins with chromatin remodeling proteins...
January 2015: Hepatology: Official Journal of the American Association for the Study of Liver Diseases
Nevzat Kazgan, Mallikarjuna R Metukuri, Aparna Purushotham, Jing Lu, Anuradha Rao, Sangkyu Lee, Matthew Pratt-Hyatt, Andrew Lickteig, Iván L Csanaky, Yingming Zhao, Paul A Dawson, Xiaoling Li
BACKGROUND & AIMS: Sirtuin 1 (SIRT1), the most conserved mammalian oxidized nicotinamide adenine dinucleotide-dependent protein deacetylase, is an important metabolic sensor in many tissues. However, little is known about its role in the small intestine, which absorbs and senses nutrients. We investigated the functions of intestinal SIRT1 in systemic bile acid and cholesterol metabolism in mice. METHODS: SIRT1 was specifically deleted from the intestines of mice using the flox-Villin-Cre system (SIRT1 iKO mice)...
April 2014: Gastroenterology
Juan L García-Rodríguez, Lucía Barbier-Torres, Sara Fernández-Álvarez, Virginia Gutiérrez-de Juan, María J Monte, Emina Halilbasic, Daniel Herranz, Luis Álvarez, Patricia Aspichueta, Jose J G Marín, Michael Trauner, Jose M Mato, Manuel Serrano, Naiara Beraza, María Luz Martínez-Chantar
UNLABELLED: Sirtuin1 (SIRT1) regulates central metabolic functions such as lipogenesis, protein synthesis, gluconeogenesis, and bile acid (BA) homeostasis through deacetylation. Here we describe that SIRT1 tightly controls the regenerative response of the liver. We performed partial hepatectomy (PH) to transgenic mice that overexpress SIRT1 (SIRT). SIRT mice showed increased mortality, impaired hepatocyte proliferation, BA accumulation, and profuse liver injury after surgery. The damaging phenotype in SIRT mice correlated with impaired farnesoid X receptor (FXR) activity due to persistent deacetylation and lower protein expression that led to decreased FXR-target gene expression; small heterodimer partner (SHP), bile salt export pump (BSEP), and increased Cyp7A1...
May 2014: Hepatology: Official Journal of the American Association for the Study of Liver Diseases
Claire Curtil, Liviu S Enache, Pauline Radreau, Anne-Gaëlle Dron, Caroline Scholtès, Alexandre Deloire, Didier Roche, Vincent Lotteau, Patrice André, Christophe Ramière
Hepatitis B virus (HBV) genome transcription is highly dependent on liver-enriched, metabolic nuclear receptors (NRs). Among others, NR farnesoid X receptor α (FXRα) enhances HBV core promoter activity and pregenomic RNA synthesis. Interestingly, two food-withdrawal-induced FXRα modulators, peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) and deacetylase SIRT1, have been found to be associated with HBV genomes ex vivo. Whereas PGC-1α induction was shown to increase HBV replication, the effect of SIRT1 on HBV transcription remains unknown...
March 2014: FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology
Sung-E Choi, Ting Fu, Sunmi Seok, Dong-Hyun Kim, Eunkyung Yu, Kwan-Woo Lee, Yup Kang, Xiaoling Li, Byron Kemper, Jongsook K Kemper
SIRT1 is an NAD(+)-dependent deacetylase that is implicated in prevention of many age-related diseases including metabolic disorders. As SIRT1 deacetylase activity is dependent on NAD(+) levels and the development of compounds that directly activate SIRT1 has been controversial, indirectly activating SIRT1 through enhancing NAD(+) bioavailability has received increasing attention. NAD(+) levels are reduced in obesity and the aged, but the underlying mechanisms remain unclear. We recently showed that hepatic microRNA-34a (miR-34a), which is elevated in obesity, directly targets and decreases SIRT1 expression...
December 2013: Aging Cell
Shiying Shao, Yan Yang, Gang Yuan, Muxun Zhang, Xuefeng Yu
The increasing incidence of type 2 diabetes mellitus is partially due to the rising obesity rates and the elevated levels of free fatty acids (FFAs). It is known that FFAs are putative mediators of beta-cell dysfunction, which is characterized with impaired glucose-stimulated insulin secretion and increased apoptosis, being defined as lipotoxicity. To date, many factors and their related signal pathways have been reported to be involved in FFA-induced beta-cell dysfunction. However, the entire blueprint is still not obtained...
February 2013: DNA and Cell Biology
Aparna Purushotham, Qing Xu, Jing Lu, Julie F Foley, Xingjian Yan, Dong-Hyun Kim, Jongsook Kim Kemper, Xiaoling Li
SIRT1, a highly conserved NAD(+)-dependent protein deacetylase, is a key metabolic sensor that directly links nutrient signals to animal metabolic homeostasis. Although SIRT1 has been implicated in a number of hepatic metabolic processes, the mechanisms by which hepatic SIRT1 modulates bile acid metabolism are still not well understood. Here we report that deletion of hepatic SIRT1 reduces the expression of farnesoid X receptor (FXR), a nuclear receptor that regulates bile acid homeostasis. We provide evidence that SIRT1 regulates the expression of FXR through hepatocyte nuclear factor 1α (HNF1α)...
April 2012: Molecular and Cellular Biology
Jiyoung Lee, Jongsook Kim Kemper
SIRT1 is a NAD+-dependent deacetylase implicated in longevity and diverse physiological processes. SIRT1, as a key mediator of beneficial effects of caloric restriction, regulates lipid and glucose metabolism by deacetylating metabolic regulators, as well as histones, in response to nutritional deprivation. Here we discuss how SIRT1 levels are regulated by microRNAs (miRs) which are emerging as important metabolic regulators; the recently identified nuclear receptor FXR/SHP cascade pathway that controls the expression of miR-34a and its target SIRT1; and a FXR/SIRT1 positive feedback regulatory loop, which is deregulated in metabolic disease states...
August 2010: Aging
Jiyoung Lee, Amruta Padhye, Abhilasha Sharma, Guisheng Song, Ji Miao, Yin-Yuan Mo, Li Wang, Jongsook Kim Kemper
Sirtuin 1 (SIRT1) is a NAD-dependent deacetylase that is critically involved in diverse cellular processes including metabolic disease, cancer, and possibly aging. Despite extensive studies on SIRT1 function, how SIRT1 levels are regulated remains relatively unknown. Here, we report that the nuclear bile acid receptor farnesoid X receptor (FXR) inhibits microRNA-34a (miR-34a) in the liver, which results in a positive regulation of SIRT1 levels. Activation of FXR by the synthetic agonist GW4064 decreases hepatic miR-34a levels in normal mice, and consistently, hepatic miR-34a levels are elevated in FXR-null mice...
April 23, 2010: Journal of Biological Chemistry
Jongsook Kim Kemper, Zhen Xiao, Bhaskar Ponugoti, Ji Miao, Sungsoon Fang, Deepthi Kanamaluru, Stephanie Tsang, Shwu-Yuan Wu, Cheng-Ming Chiang, Timothy D Veenstra
The nuclear bile acid receptor FXR is critical for regulation of lipid and glucose metabolism. Here, we report that FXR is a target of SIRT1, a deacetylase that mediates nutritional and hormonal modulation of hepatic metabolism. Lysine 217 of FXR is the major acetylation site targeted by p300 and SIRT1. Acetylation of FXR increases its stability but inhibits heterodimerization with RXRalpha, DNA binding, and transactivation activity. Downregulation of hepatic SIRT1 increased FXR acetylation with deleterious metabolic outcomes...
November 2009: Cell Metabolism
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