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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

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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.

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

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

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

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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

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