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SIRT4 KO livers microarray

ABSTRACT: Sirtuins are a family of protein deacetylases, deacylases, and ADP-ribosyltransferases that regulate life span, control the onset of numerous age-associated diseases, and mediate metabolic homeostasis. We have uncovered a novel role for the mitochondrial sirtuin SIRT4 in the regulation of hepatic lipid metabolism during changes in nutrient availability. We show that SIRT4 levels decrease in the liver during fasting and that SIRT4 null mice display increased expression of hepatic peroxisome proliferator activated receptor (PPAR ) target genes associated with fatty acid catabolism. Accordingly, primary hepatocytes from SIRT4 knockout (KO) mice exhibit higher rates of fatty acid oxidation than wild-type hepatocytes, and SIRT4 overexpression decreases fatty acid oxidation rates. The enhanced fatty acid oxidation observed in SIRT4 KO hepatocytes requires functional SIRT1, demonstrating a clear cross talk between mitochondrial and nuclear sirtuins. Thus, SIRT4 is a new component of mitochondrial signaling in the liver and functions as an important regulator of lipid metabolism.

ORGANISM(S): Mus musculus

PROVIDER: GSE56321 | GEO | 2014/03/28

SECONDARY ACCESSION(S): PRJNA242909

REPOSITORIES: GEO

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SIRT4 KO livers microarray

Project description:Sirtuins are a family of protein deacetylases, deacylases, and ADP-ribosyltransferases that regulate life span, control the onset of numerous age-associated diseases, and mediate metabolic homeostasis. We have uncovered a novel role for the mitochondrial sirtuin SIRT4 in the regulation of hepatic lipid metabolism during changes in nutrient availability. We show that SIRT4 levels decrease in the liver during fasting and that SIRT4 null mice display increased expression of hepatic peroxisome proliferator activated receptor (PPAR ) target genes associated with fatty acid catabolism. Accordingly, primary hepatocytes from SIRT4 knockout (KO) mice exhibit higher rates of fatty acid oxidation than wild-type hepatocytes, and SIRT4 overexpression decreases fatty acid oxidation rates. The enhanced fatty acid oxidation observed in SIRT4 KO hepatocytes requires functional SIRT1, demonstrating a clear cross talk between mitochondrial and nuclear sirtuins. Thus, SIRT4 is a new component of mitochondrial signaling in the liver and functions as an important regulator of lipid metabolism. SIRT4 knockout (KO) and wild-type (WT) littermates (male; n 6 per genotype; 7- to 8-month-old littermates) were sacrificed after a 16-h overnight fast. Samples were individually hybridized on Affymetrix Mouse Genome 430 2.0 GeneChips by the Biopolymers Facility (Harvard Medical School).

2014-03-28 | E-GEOD-56321 | biostudies-arrayexpress

Downregulation of miR-15b is associated with increased SIRT4 expression in premature senescence and photoaging of the skin

Project description:Sirtuins are deacetylases or ADP-ribosyltransferases which are implicated in multiple pathways involved in metabolism and life-span regulation. Here, we link the mitochondrial sirtuin SIRT4, which overexpression negatively impacts on mitochondrial oxidative capacity, with premature senescence and skin aging. Accordingly, SIRT4 mRNA levels were significantly increased in vitro in human dermal fibroblasts after repetitive UVB exposure or in senescence triggered by mitotic spindle stress or ionizing radiation. Similarly, analysis of SIRT4 expression in vivo in human skin revealed upregulation of SIRT4 mRNA levels in the dermal compartment of photaged skin as compared with the dermis of intrinsically aged skin. In all our in vitro models, upregulation of SIRT4 expression was associated with decreased levels of miR-15b. Also, in human skin, highest copy numbers of miR-15b mRNA were detected in the epidermis, and epidermal expression was significantly reduced in photoaged skin as compared with intrinsically aged skin. Reduced miR-15b expression is most likely causally linked to increased SIRT4 expression because we found that (i) miR-15b displays a conserved and direct binding site within the 3'-untranslated region of the SIRT4 gene as demonstrated by luciferase reporter assays and (ii) transfection of oligonucleotides mimicking miR-15b function was sufficient to prevent SIRT4 upregulation in senescent cells in vitro. Thus, we propose that miR-15b acts as a negative regulator of SIRT4 expression to antagonize mitochondrial dysfunction and hence cellular senescence as well as tissue aging, in particular photoaging of the skin.

2016-06-08 | GSE45729 | GEO

SIRT4 Is a Lysine Deacylase that Controls Leucine Metabolism and Insulin Secretion

Project description:Sirtuins are NAD+-dependent protein deacylases that regulate several aspects of metabolism and aging. In contrast to the other mammalian sirtuins, the primary enzymatic activity of mitochondrial sirtuin 4 (SIRT4) and its overall role in metabolic control has remained enigmatic. Using a combination of phylogenetics, structural biology, and enzymology, we show that SIRT4 removes three acyl moieties from lysine residues – methylglutaryl(MG)-, hydroxymethylglutaryl(HMG)-, and 3-methylglutaconyl(MGc)-lysine. The metabolites leading to these post-translational modifications are intermediates in leucine oxidation, and we show a primary role for SIRT4 in controlling this pathway in mice. Furthermore, we find that dysregulated leucine metabolism in SIRT4KO mice leads to elevated basal and stimulated insulin secretion, which progressively develops into glucose intolerance and insulin resistance. These findings identify a robust enzymatic activity for SIRT4, uncover a mechanism controlling branched-chain amino acid flux, and position SIRT4 as a crucial player maintaining insulin secretion and glucose homeostasis during aging. From Anderson et. al. Cell Metabolism, 2017.

2017-04-05 | PXD005896 | Pride

Amino Acids Downregulate SIRT4 to Detoxify Ammonia through the Urea Cycle

Project description:Ammonia production via glutamate dehydrogenase is inhibited by SIRT4, a sirtuin that displays both amidase and non-amidase activities. The processes underlying the regulation of ammonia removal by amino acids remain unclear. Here, we report that SIRT4 acts as a decarbamylase that responds to amino acid sufficiency and regulates ammonia removal. Amino acids promote lysine 307 carbamylation (OTCCP-K307) of ornithine transcarbamylase (OTC), which activates OTC and the urea cycle. Proteomic and interactome screening identified OTC as a substrate of SIRT4. SIRT4 decarbamylates OTCCP-K307 and inactivates OTC in a NAD+-dependent manner. SIRT4 expression was transcriptionally upregulated by the amino acid insufficiency-activated GCN2–eIF2a–ATF4 axis. SIRT4 knockout in cultured cells caused higher OTCCP-K307 levels, activated OTC, elevated urea cycle intermediates, and urea production via amino acid catabolism. Sirt4 ablation decreased mouse blood ammonia levels and ameliorated CCl4-induced hepatic encephalopathy phenotypes. We reveal that SIRT4 safeguards cellular ammonia toxicity during amino acid catabolism.

2023-03-29 | PXD037101 | Pride

PPARM-NM-4 activation in human myotubes increases mitochondrial fatty acid oxidative capacity and reduces glucose utilization by a switch in substrate preference.

Project description:The role of peroxisome proliferator-activated receptor M-NM-4 (PPARM-NM-4) activation on global gene expression and mitochondrial fuel utilization were investigated in human myotubes. Only 21 genes were up-regulated and 3 genes were down-regulated after activation by the PPARM-NM-4 agonist GW501516. Pathway analysis showed up-regulated mitochondrial fatty acid oxidation, TCA cycle and cholesterol biosynthesis. GW501516 increased oleic acid oxidation and mitochondrial oxidative capacity by 2-fold. Glucose uptake and oxidation were reduced, but total substrate oxidation was not affected, indicating a fuel switch from glucose to fatty acid. Cholesterol biosynthesis was increased, but lipid biosynthesis and mitochondrial content were not affected. This study confirmed that the principal effect of PPARM-NM-4 activation was to increase mitochondrial fatty acid oxidative capacity. Our results further suggest that PPARM-NM-4 activation reduced glucose utilization through a switch in mitochondrial substrate preference by up-regulating pyruvate dehydrogenase kinase isozyme 4 and genes involved in lipid metabolism and fatty acid oxidation. Keywords: Expression profiling by array Human myotubes from four donors were exposed to a PPARM-NM-4 agonist or control for 96 h after which gene expression was profiled.

2014-05-23 | E-GEOD-40789 | biostudies-arrayexpress

AP-MS analysis of sirtuin-4 interactions in human fibroblasts

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2015-01-05 | PXD001447 | Pride

Effect of deletion of Carnitine Palmitoyltransferase2 in hepatocytes on liver gene expression upon a 24 hour fast

Project description:The liver is critical for maintaining systemic energy balance during starvation. To understand the role of hepatic fatty acid Î²-oxidation on this process, we generated mice with a liver-specific knockout of carnitine palmitoyltransferase 2 (Cpt2L-/-), an obligate step in mitochondrial long-chain fatty acid Î²-oxidation. Surprisingly, Cpt2L-/- mice survived the perinatal period and a 24hr fast with sufficient blood glucose. The loss of hepatic fatty acid oxidation resulted in a significant loss in circulating ketones that remained unaltered by fasting. Fasting induced serum dyslipidemia, hepatic steatosis and adaptations in hepatic and systemic oxidative gene expression in Cpt2L-/- mice to maintain systemic energy homeostasis. Alternatively, feeding a ketogenic diet resulted in severe hepatomegaly, liver damage and death within one week with a complete absence of adipose triglyceride stores. These data show that hepatic fatty acid oxidation is not required for survival during acute food deprivation but essential for constraining adipocyte lipolysis and regulating systemic catabolism when glucose is limiting. In this dataset, we include the expression data obtained from dissected mouse liver from mice fasted for 24 hours with and without the deletion of carnitine palmitoyltransferase 2 (i.e. hepatocytes unable to beta-oxidize long chain fatty acids in mitochondria). WildType and KnockOut mice were fasted for 24 hours. Three biologic replicates were compared per class, thus six mice.

2016-06-16 | E-GEOD-76079 | biostudies-arrayexpress

PPARδ activation in human myotubes increases mitochondrial fatty acid oxidative capacity and reduces glucose utilization by a switch in substrate preference.

Project description:The role of peroxisome proliferator-activated receptor δ (PPARδ) activation on global gene expression and mitochondrial fuel utilization were investigated in human myotubes. Only 21 genes were up-regulated and 3 genes were down-regulated after activation by the PPARδ agonist GW501516. Pathway analysis showed up-regulated mitochondrial fatty acid oxidation, TCA cycle and cholesterol biosynthesis. GW501516 increased oleic acid oxidation and mitochondrial oxidative capacity by 2-fold. Glucose uptake and oxidation were reduced, but total substrate oxidation was not affected, indicating a fuel switch from glucose to fatty acid. Cholesterol biosynthesis was increased, but lipid biosynthesis and mitochondrial content were not affected. This study confirmed that the principal effect of PPARδ activation was to increase mitochondrial fatty acid oxidative capacity. Our results further suggest that PPARδ activation reduced glucose utilization through a switch in mitochondrial substrate preference by up-regulating pyruvate dehydrogenase kinase isozyme 4 and genes involved in lipid metabolism and fatty acid oxidation. Keywords: Expression profiling by array

2014-05-23 | GSE40789 | GEO

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