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Sirt3 promotes the urea cycle and fatty acid oxidation during dietary restriction.

ABSTRACT: Emerging evidence suggests that protein acetylation is a broad-ranging regulatory mechanism. Here we utilize acetyl-peptide arrays and metabolomic analyses to identify substrates of mitochondrial deacetylase Sirt3. We identified ornithine transcarbamoylase (OTC) from the urea cycle, and enzymes involved in ?-oxidation. Metabolomic analyses of fasted mice lacking Sirt3 (sirt3(-/-)) revealed alterations in ?-oxidation and the urea cycle. Biochemical analysis demonstrated that Sirt3 directly deacetylates OTC and stimulates its activity. Mice under caloric restriction (CR) increased Sirt3 protein levels, leading to deacetylation and stimulation of OTC activity. In contrast, sirt3(-/-) mice failed to deacetylate OTC in response to CR. Inability to stimulate OTC under CR led to a failure to reduce orotic acid levels, a known outcome of OTC deficiency. Thus, Sirt3 directly regulates OTC activity and promotes the urea cycle during CR, and the results suggest that under low energy input, Sirt3 modulates mitochondria by promoting amino acid catabolism and ?-oxidation.

SUBMITTER: Hallows WC

PROVIDER: S-EPMC3101115 | biostudies-literature | 2011 Jan

REPOSITORIES: biostudies-literature

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Sirt3 promotes the urea cycle and fatty acid oxidation during dietary restriction.

Hallows William C WC Yu Wei W Smith Brian C BC Devries Mark K MK Ellinger James J JJ Someya Shinichi S Shortreed Michael R MR Prolla Tomas T Markley John L JL Smith Lloyd M LM Zhao Shimin S Guan Kun-Liang KL Denu John M JM

Molecular cell 20110101 2

Emerging evidence suggests that protein acetylation is a broad-ranging regulatory mechanism. Here we utilize acetyl-peptide arrays and metabolomic analyses to identify substrates of mitochondrial deacetylase Sirt3. We identified ornithine transcarbamoylase (OTC) from the urea cycle, and enzymes involved in β-oxidation. Metabolomic analyses of fasted mice lacking Sirt3 (sirt3(-/-)) revealed alterations in β-oxidation and the urea cycle. Biochemical analysis demonstrated that Sirt3 directly deacet ...[more]

PMID: 21255725

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Project description:BackgroundPatients with phenylketonuria (PKU) have to follow a lifelong phenylalanine restricted diet. This type of diet markedly reduces the intake of saturated and unsaturated fatty acids especially long chain polyunsaturated fatty acids (LC-PUFA). Long-chain saturated fatty acids are substrates of mitochondrial fatty acid oxidation for acetyl-CoA production. LC-PUFA are discussed to affect inflammatory and haemostaseological processes in health and disease. The influence of the long term PKU diet on fatty acid metabolism with a special focus on platelet eicosanoid metabolism has been investigated in the study presented here.Methodology/principal findings12 children with PKU under good metabolic control and 8 healthy controls were included. Activated fatty acids (acylcarnitines C6-C18) in dried blood and the cholesterol metabolism in serum were analyzed by liquid chromatographic tandem mass spectrometry (LC-MS/MS). Fatty acid composition of plasma glycerophospholipids was determined by gas chromatography. LC-PUFA metabolites were analyzed in supernatants by LC-MS/MS before and after platelet activation and aggregation using a standardized protocol. Patients with PKU had significantly lower free carnitine and lower activated fatty acids in dried blood compared to controls. Phytosterols as marker of cholesterol (re-) absorption were not influenced by the dietary fatty acid restriction. Fatty acid composition in glycerophospholipids was comparable to that of healthy controls. However, patients with PKU showed significantly increased concentrations of y-linolenic acid (C18:3n-6) a precursor of arachidonic acid. In the PKU patients significantly higher platelet counts were observed. After activation with collagen platelet aggregation and thromboxane B(2) and thromboxane B(3) release did not differ from that of healthy controls.Conclusion/significanceLong-term dietary fatty acid restriction influenced the intermediates of mitochondrial beta-oxidation. No functional influence on unsaturated fatty acid metabolism and platelet aggregation in patients with PKU was detected.

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Sirt3 promotes the urea cycle and fatty acid oxidation during dietary restriction.

Publications

Sirt3 promotes the urea cycle and fatty acid oxidation during dietary restriction.

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